Simultaneous optical coherence tomography and lipofuscin autofluorescence imaging of the retina with a single broadband light source at 480nm.

PubMed

Jiang, Minshan; Liu, Tan; Liu, Xiaojing; Jiao, Shuliang

2014-12-01

We accomplished spectral domain optical coherence tomography and auto-fluorescence microscopy for imaging the retina with a single broadband light source centered at 480 nm. This technique is able to provide simultaneous structural imaging and lipofuscin molecular contrast of the retina. Since the two imaging modalities are provided by the same group of photons, their images are intrinsically registered. To test the capabilities of the technique we periodically imaged the retinas of the same rats for four weeks. The images successfully demonstrated lipofuscin accumulation in the retinal pigment epithelium with aging. The experimental results showed that the dual-modal imaging system can be a potentially powerful tool in the study of age-related degenerative retinal diseases.

Multipoint sensing with a low-coherence source using single-arm frequency-shifted interferometry

DOE PAGES

Zhang, Yiwei; Ye, Fei; Qi, Bing; ...

2016-07-12

We demonstrate that multiple-site sensing along an optical fiber can be done with incoherent continuous-wave light. Here, using a broadband low-coherence noise source, a slow detector, and an optical modulator, we construct a single-arm frequency-shifted interferometer (SA-FSI) capable of simultaneously sensing multiple weak-reflection sites distributed either in parallel or in series along fiber links. By scanning the driving frequency of an electro-optic amplitude modulator in the range of 2.7–3.2 GHz at steps of 41.7 KHz, we demonstrate a spatial resolution of 0.3 m and a measurement range of over 1 km.

Birefringence and vascular imaging of in vivo human skin by Jones-matrix optical coherence tomography

NASA Astrophysics Data System (ADS)

Li, En; Makita, Shuichi; Hong, Young-Joo; Kasaragod, Deepa; Yasuno, Yoshiaki

2017-02-01

A customized 1310-nm Jones-matrix optical coherence tomography (JM-OCT) for dermatological investigation was constructed and used for in vivo normal human skin tissue imaging. This system can simultaneously measure the threedimensional depth-resolved local birefringence, complex-correlation based OCT angiography (OCT-A), degree-ofpolarization- uniformity (DOPU) and scattering OCT intensity. By obtaining these optical properties of tissue, the morphology, vasculature, and collagen content of skin can be deduced and visualized. Structures in the deep layers of the epithelium were observed with depth-resolved local birefringence and polarization uniformity images. These results suggest high diagnostic and investigative potential of JM-OCT for dermatology.

Multispectral scanning laser ophthalmoscopy combined with optical coherence tomography for simultaneous in vivo mouse retinal imaging

NASA Astrophysics Data System (ADS)

Zhang, Pengfei; Zam, Azhar; Jian, Yifan; Wang, Xinlei; Burns, Marie E.; Sarunic, Marinko V.; Pugh, Edward N.; Zawadzki, Robert J.

2015-03-01

A compact, non-invasive multi-modal system has been developed for in vivo mouse retina imaging. It is configured for simultaneously detecting green and red fluorescent protein signals with scanning laser ophthalmoscopy (SLO) back-scattered light from the SLO illumination beam, and depth information about different retinal layers by means of Optical Coherence Tomography (OCT). Simultaneous assessment of retinal characteristics with different modalities can provide a wealth of information about the structural and functional changes in the retinal neural tissue and chorio-retinal vasculature in vivo. Additionally, simultaneous acquisition of multiple channels facilitates analysis of the data of different modalities by automatic temporal and structural co-registration. As an example of the instrument's performance we imaged the retina of a mouse with constitutive expression of GFP in microglia cells (Cx3cr1GFP/+), and which also expressed the red fluorescent protein mCherry in Müller glial cells by means of adeno-associated virus delivery (AAV2) of an mCherry cDNA driven by the GFAP (glial fibrillary acid protein) promoter.

Low-coherence interferometric tip-clearance probe

NASA Astrophysics Data System (ADS)

Kempe, Andreas; Schlamp, Stefan; Rösgen, Thomas; Haffner, Ken

2003-08-01

We propose an all-fiber, self-calibrating, economical probe that is capable of near-real-time, single-port, simultaneous blade-to-blade tip-clearance measurements with submillimeter accuracy (typically <100 μm, absolute) in the first stages of a gas turbine. Our probe relies on the interference between backreflected light from the blade tips during the 1-μs blade passage time and a frequency-shifted reference with variable time delay, making use of a low-coherence light source. A single optical fiber of arbitrary length connects the self-contained optics and electronics to the turbine.

Optimal spectral structure for simultaneous Stimulated Brillouin Scattering suppression and coherent property preservation in high power coherent beam combination system

NASA Astrophysics Data System (ADS)

Han, Kai; Xu, Xiaojun; Liu, Zejin

2013-05-01

Based on the spectral manipulation technique, the Stimulated Brillouin Scattering (SBS) suppression effect and the coherent beam combination (CBC) effect in multi-tone CBC system are researched theoretically and experimentally. To get satisfactory SBS suppression, the frequency interval of the multi-tone seed laser should be large enough, at least larger than the SBS gain bandwidth. In order to attain excellent CBC effect, the spectra of the multi-tone seed laser need to be matched with the optical path differences among the amplifier chains. Hence, a sufficiently separated matching spectrum is capable at both SBS mitigation and coherent property preservation. By comparing the SBS suppression effect and the CBC effect at various spectra, the optimal spectral structure for simultaneous SBS suppression and excellent CBC effect is found.

Coherent detection of position errors in inter-satellite laser communications

NASA Astrophysics Data System (ADS)

Xu, Nan; Liu, Liren; Liu, De'an; Sun, Jianfeng; Luan, Zhu

2007-09-01

Due to the improved receiver sensitivity and wavelength selectivity, coherent detection became an attractive alternative to direct detection in inter-satellite laser communications. A novel method to coherent detection of position errors information is proposed. Coherent communication system generally consists of receive telescope, local oscillator, optical hybrid, photoelectric detector and optical phase lock loop (OPLL). Based on the system composing, this method adds CCD and computer as position error detector. CCD captures interference pattern while detection of transmission data from the transmitter laser. After processed and analyzed by computer, target position information is obtained from characteristic parameter of the interference pattern. The position errors as the control signal of PAT subsystem drive the receiver telescope to keep tracking to the target. Theoretical deviation and analysis is presented. The application extends to coherent laser rang finder, in which object distance and position information can be obtained simultaneously.

Quantum-coherent coupling of a mechanical oscillator to an optical cavity mode.

PubMed

Verhagen, E; Deléglise, S; Weis, S; Schliesser, A; Kippenberg, T J

2012-02-01

Optical laser fields have been widely used to achieve quantum control over the motional and internal degrees of freedom of atoms and ions, molecules and atomic gases. A route to controlling the quantum states of macroscopic mechanical oscillators in a similar fashion is to exploit the parametric coupling between optical and mechanical degrees of freedom through radiation pressure in suitably engineered optical cavities. If the optomechanical coupling is 'quantum coherent'--that is, if the coherent coupling rate exceeds both the optical and the mechanical decoherence rate--quantum states are transferred from the optical field to the mechanical oscillator and vice versa. This transfer allows control of the mechanical oscillator state using the wide range of available quantum optical techniques. So far, however, quantum-coherent coupling of micromechanical oscillators has only been achieved using microwave fields at millikelvin temperatures. Optical experiments have not attained this regime owing to the large mechanical decoherence rates and the difficulty of overcoming optical dissipation. Here we achieve quantum-coherent coupling between optical photons and a micromechanical oscillator. Simultaneously, coupling to the cold photon bath cools the mechanical oscillator to an average occupancy of 1.7 ± 0.1 motional quanta. Excitation with weak classical light pulses reveals the exchange of energy between the optical light field and the micromechanical oscillator in the time domain at the level of less than one quantum on average. This optomechanical system establishes an efficient quantum interface between mechanical oscillators and optical photons, which can provide decoherence-free transport of quantum states through optical fibres. Our results offer a route towards the use of mechanical oscillators as quantum transducers or in microwave-to-optical quantum links.

Towards simultaneous Talbot bands based optical coherence tomography and scanning laser ophthalmoscopy imaging.

PubMed

Marques, Manuel J; Bradu, Adrian; Podoleanu, Adrian Gh

2014-05-01

We report a Talbot bands-based optical coherence tomography (OCT) system capable of producing longitudinal B-scan OCT images and en-face scanning laser ophthalmoscopy (SLO) images of the human retina in-vivo. The OCT channel employs a broadband optical source and a spectrometer. A gap is created between the sample and reference beams while on their way towards the spectrometer's dispersive element to create Talbot bands. The spatial separation of the two beams facilitates collection by an SLO channel of optical power originating exclusively from the retina, deprived from any contribution from the reference beam. Three different modes of operation are presented, constrained by the minimum integration time of the camera used in the spectrometer and by the galvo-scanners' scanning rate: (i) a simultaneous acquisition mode over the two channels, useful for small size imaging, that conserves the pixel-to-pixel correspondence between them; (ii) a hybrid sequential mode, where the system switches itself between the two regimes and (iii) a sequential "on-demand" mode, where the system can be used in either OCT or SLO regimes for as long as required. The two sequential modes present varying degrees of trade-off between pixel-to-pixel correspondence and independent full control of parameters within each channel. Images of the optic nerve and fovea regions obtained in the simultaneous (i) and in the hybrid sequential mode (ii) are presented.

Towards simultaneous Talbot bands based optical coherence tomography and scanning laser ophthalmoscopy imaging

PubMed Central

Marques, Manuel J.; Bradu, Adrian; Podoleanu, Adrian Gh.

2014-01-01

We report a Talbot bands-based optical coherence tomography (OCT) system capable of producing longitudinal B-scan OCT images and en-face scanning laser ophthalmoscopy (SLO) images of the human retina in-vivo. The OCT channel employs a broadband optical source and a spectrometer. A gap is created between the sample and reference beams while on their way towards the spectrometer’s dispersive element to create Talbot bands. The spatial separation of the two beams facilitates collection by an SLO channel of optical power originating exclusively from the retina, deprived from any contribution from the reference beam. Three different modes of operation are presented, constrained by the minimum integration time of the camera used in the spectrometer and by the galvo-scanners’ scanning rate: (i) a simultaneous acquisition mode over the two channels, useful for small size imaging, that conserves the pixel-to-pixel correspondence between them; (ii) a hybrid sequential mode, where the system switches itself between the two regimes and (iii) a sequential “on-demand” mode, where the system can be used in either OCT or SLO regimes for as long as required. The two sequential modes present varying degrees of trade-off between pixel-to-pixel correspondence and independent full control of parameters within each channel. Images of the optic nerve and fovea regions obtained in the simultaneous (i) and in the hybrid sequential mode (ii) are presented. PMID:24877006

Coherent control of flexural vibrations in dual-nanoweb fibers using phase-modulated two-frequency light

NASA Astrophysics Data System (ADS)

Koehler, J. R.; Noskov, R. E.; Sukhorukov, A. A.; Novoa, D.; Russell, P. St. J.

2017-12-01

Coherent control of the resonant response in spatially extended optomechanical structures is complicated by the fact that the optical drive is affected by the backaction from the generated phonons. Here we report an approach to coherent control based on stimulated Raman-like scattering, in which the optical pressure can remain unaffected by the induced vibrations even in the regime of strong optomechanical interactions. We demonstrate experimentally coherent control of flexural vibrations simultaneously along the whole length of a dual-nanoweb fiber, by imprinting steps in the relative phase between the components of a two-frequency pump signal, the beat frequency being chosen to match a flexural resonance. Furthermore, sequential switching of the relative phase at time intervals shorter than the lifetime of the vibrations reduces their amplitude to a constant value that is fully adjustable by tuning the phase modulation depth and switching rate. The results may trigger new developments in silicon photonics, since such coherent control uniquely decouples the amplitude of optomechanical oscillations from power-dependent thermal effects and nonlinear optical loss.

A linearly frequency-swept high-speed-rate multi-wavelength laser for optical coherence tomography

NASA Astrophysics Data System (ADS)

Wang, Qiyu; Wang, Zhaoying; Yuan, Quan; Ma, Rui; Du, Tao; Yang, Tianxin

2017-02-01

We proposed and demonstrated a linearly frequency-swept multi-wavelength laser source for optical coherence tomography (OCT) eliminating the need of wavenumber space resampling in the postprocessing progress. The source consists of a multi-wavelength fiber laser source (MFS) and an optical sweeping loop. In this novel laser source, an equally spaced multi-wavelength laser is swept simultaneously by a certain step each time in the frequency domain in the optical sweeping loop. The sweeping step is determined by radio frequency (RF) signal which can be precisely controlled. Thus the sweeping behavior strictly maintains a linear relationship between time and frequency. We experimentally achieved linear time-frequency sweeping at a sweeping rate of 400 kHz with our laser source.

Fraunhofer Diffraction and Polarization.

ERIC Educational Resources Information Center

Fortin, E.

1979-01-01

Describes an experiment for the intermediate undergraduate optics laboratory designed to illustrate simultaneously some aspects of the phenomena of diffraction; interference, coherence, apodization, the Fresnel-Arago law; as well as of the interrelations between these concepts. (HM)

Contrast-enhanced optical coherence microangiography with acoustic-actuated microbubbles

NASA Astrophysics Data System (ADS)

Liu, Yu-Hsuan; Zhang, Jia-Wei; Yeh, Chih-Kuang; Wei, Kuo-Chen; Liu, Hao-Li; Tsai, Meng-Tsan

2017-04-01

In this study, we propose to use gas-filled microbubbles (MBs) simultaneously actuated by the acoustic wave to enhance the imaging contrast of optical coherence tomography (OCT)-based angiography. In the phantom experiments, MBs can result in stronger backscattered intensity, enabling to enhance the contrast of OCT intensity image. Moreover, simultaneous application of low-intensity acoustic wave enables to temporally induce local vibration of particles and MBs in the vessels, resulting in time-variant OCT intensity which can be used for enhancing the contrast of OCT intensitybased angiography. Additionally, different acoustic modes and different acoustic powers to actuate MBs are performed and compared to investigate the feasibility of contrast enhancement. Finally, animal experiments are performed. The findings suggest that acoustic-actuated MBs can effectively enhance the imaging contrast of OCT-based angiography and the imaging depth of OCT angiography is also extended.

Practical implementation of spectral-intensity dispersion-canceled optical coherence tomography with artifact suppression

NASA Astrophysics Data System (ADS)

Shirai, Tomohiro; Friberg, Ari T.

2018-04-01

Dispersion-canceled optical coherence tomography (OCT) based on spectral intensity interferometry was devised as a classical counterpart of quantum OCT to enhance the basic performance of conventional OCT. In this paper, we demonstrate experimentally that an alternative method of realizing this kind of OCT by means of two optical fiber couplers and a single spectrometer is a more practical and reliable option than the existing methods proposed previously. Furthermore, we develop a recipe for reducing multiple artifacts simultaneously on the basis of simple averaging and verify experimentally that it works successfully in the sense that all the artifacts are mitigated effectively and only the true signals carrying structural information about the sample survive.

Bifocal optical coherenc refractometry of turbid media.

PubMed

Alexandrov, Sergey A; Zvyagin, Andrei V; Silva, K K M B Dilusha; Sampson, David D

2003-01-15

We propose and demonstrate a novel technique, which we term bifocal optical coherence refractometry, for the rapid determination of the refractive index of a turbid medium. The technique is based on the simultaneous creation of two closely spaced confocal gates in a sample. The optical path-length difference between the gates is measured by means of low-coherence interferometry and used to determine the refractive index. We present experimental results for the refractive indices of milk solutions and of human skin in vivo. As the axial scan rate determines the acquisition time, which is potentially of the order of tens of milliseconds, the technique has potential for in vivo refractive-index measurements of turbid biological media under dynamic conditions.

High responsivity coherent photonic receiver integrating an SOA, a 90° hybrid, and high speed UTC photodiodes.

PubMed

Santini, Guillaume; Caillaud, Christophe; Paret, Jean-François; Pommereau, Frederic; Mekhazni, Karim; Calo, Cosimo; Achouche, Mohand

2017-10-16

We demonstrate a single polarization monolithically integrated coherent receiver on an InP substrate with a SOA preamplifier, a 90° optical hybrid, and four 40 GHz UTC photodiodes. Record performances with responsivity above 4 A/W with low imbalance <1 dB and error free detection of 32 Gbaud QPSK signals were simultaneously demonstrated.

Parallel implementation of all-digital timing recovery for high-speed and real-time optical coherent receivers.

PubMed

Zhou, Xian; Chen, Xue

2011-05-09

The digital coherent receivers combine coherent detection with digital signal processing (DSP) to compensate for transmission impairments, and therefore are a promising candidate for future high-speed optical transmission system. However, the maximum symbol rate supported by such real-time receivers is limited by the processing rate of hardware. In order to cope with this difficulty, the parallel processing algorithms is imperative. In this paper, we propose a novel parallel digital timing recovery loop (PDTRL) based on our previous work. Furthermore, for increasing the dynamic dispersion tolerance range of receivers, we embed a parallel adaptive equalizer in the PDTRL. This parallel joint scheme (PJS) can be used to complete synchronization, equalization and polarization de-multiplexing simultaneously. Finally, we demonstrate that PDTRL and PJS allow the hardware to process 112 Gbit/s POLMUX-DQPSK signal at the hundreds MHz range. © 2011 Optical Society of America

Combined analysis of whole human blood parameters by Raman spectroscopy and spectral-domain low-coherence interferometry

NASA Astrophysics Data System (ADS)

Gnyba, M.; Wróbel, M. S.; Karpienko, K.; Milewska, D.; Jedrzejewska-Szczerska, M.

2015-07-01

In this article the simultaneous investigation of blood parameters by complementary optical methods, Raman spectroscopy and spectral-domain low-coherence interferometry, is presented. Thus, the mutual relationship between chemical and physical properties may be investigated, because low-coherence interferometry measures optical properties of the investigated object, while Raman spectroscopy gives information about its molecular composition. A series of in-vitro measurements were carried out to assess sufficient accuracy for monitoring of blood parameters. A vast number of blood samples with various hematological parameters, collected from different donors, were measured in order to achieve a statistical significance of results and validation of the methods. Preliminary results indicate the benefits in combination of presented complementary methods and form the basis for development of a multimodal system for rapid and accurate optical determination of selected parameters in whole human blood. Future development of optical systems and multivariate calibration models are planned to extend the number of detected blood parameters and provide a robust quantitative multi-component analysis.

In-vivo, real-time cross-sectional images of retina using a GPU enhanced master slave optical coherence tomography system

NASA Astrophysics Data System (ADS)

Bradu, Adrian; Kapinchev, Konstantin; Barnes, Frederick; Podoleanu, Adrian

2016-03-01

In our previous reports we demonstrated a novel Fourier domain optical coherence tomography method, Master Slave optical coherence tomography (MS-OCT), that does not require resampling of data and can deliver en-face images from several depths simultaneously. While ideally suited for delivering information from a selected depth, the MS-OCT has been so far inferior to the conventional FFT based OCT in terms of time of producing cross section images. Here, we demonstrate that by taking advantage of the parallel processing capabilities offered by the MS-OCT method, cross-sectional OCT images of the human retina can be produced in real-time by assembling several T-scans from different depths. We analyze the conditions that ensure a real-time B-scan imaging operation, and demonstrate in-vivo real-time images from human fovea and the optic nerve, of comparable resolution and sensitivity to those produced using the traditional Fourier domain based method.

Simultaneous wavelength and format conversion in SDN/NFV for flexible optical network based on FWM in SOA

NASA Astrophysics Data System (ADS)

Zhan, Yueying; Wang, Danshi; Zhang, Min

2018-04-01

We propose an all-optical wavelength and format conversion model (CM) for a dynamic data center interconnect node and coherent passive optical network (PON) optical network unit (ONU) in software-defined networking and network function virtualization system based on four-wave mixing in a semiconductor optical amplifier. Five wavelength converted DQPSK signals and two format converted DPSK signals are generated; the performances of the generated signals for two strategies of setting CM in the data center interconnect node and coherent PON ONU, which are over 10 km fiber transmission, have been verified. All of the converted signals are with a power penalty less than 2.2 dB at FEC threshold of 3.8 × 10 - 3, and the optimum bias current of SOA is 300 mA.

Optical superheterodyne receiver.

PubMed

Lucy, R F; Lang, K; Peters, C J; Duval, K

1967-08-01

Optical communications experiments at 6328 A, comparing the fading characteristics of coherent and noncoherent optical detection, have been performed over a 1-km real atmospheric path in different weather conditions. The results show that fading is less severe for noncoherent detection and that the fading characteristic for both types vary significantly with weather conditions. In addition, the similarity of optical FM to rf FM is demonstrated. The measurements were performed using a remote laser transmitter and an optical superheterodyne receiver operating simultaneously in both a coherent and noncoherent detection mode. The receiver, tunable over a frequency range of 1 GHz at the IF difference frequency of 30 MHz, has automatic frequency control and also uses a precision angle tracking servo to maintain receiver spatial alignment with a remote transmitter. The angle and frequency tracking capability permit operation between moving transmitter and receiver terminals.

Trends in optical coherence tomography applied to medical imaging

NASA Astrophysics Data System (ADS)

Podoleanu, Adrian G.

2014-01-01

The number of publications on optical coherence tomography (OCT) continues to double every three years. Traditionally applied to imaging the eye, OCT is now being extended to fields outside ophthalmology and optometry. Widening its applicability, progress in the core engine of the technology, and impact on development of novel optical sources, make OCT a very active and rapidly evolving field. Trends in the developments of different specific devices, such as optical sources, optical configurations and signal processing will be presented. Encompassing studies on both the configurations as well as on signal processing themes, current research in Kent looks at combining spectral domain with time domain imaging for long axial range and simultaneous imaging at several depths. Results of the collaborative work of the Applied Optics Group in Kent with organisers of this conference will be presented, with reference to 3D monitoring of abfraction.

Fast Acquisition and Reconstruction of Optical Coherence Tomography Images via Sparse Representation

PubMed Central

Li, Shutao; McNabb, Ryan P.; Nie, Qing; Kuo, Anthony N.; Toth, Cynthia A.; Izatt, Joseph A.; Farsiu, Sina

2014-01-01

In this paper, we present a novel technique, based on compressive sensing principles, for reconstruction and enhancement of multi-dimensional image data. Our method is a major improvement and generalization of the multi-scale sparsity based tomographic denoising (MSBTD) algorithm we recently introduced for reducing speckle noise. Our new technique exhibits several advantages over MSBTD, including its capability to simultaneously reduce noise and interpolate missing data. Unlike MSBTD, our new method does not require an a priori high-quality image from the target imaging subject and thus offers the potential to shorten clinical imaging sessions. This novel image restoration method, which we termed sparsity based simultaneous denoising and interpolation (SBSDI), utilizes sparse representation dictionaries constructed from previously collected datasets. We tested the SBSDI algorithm on retinal spectral domain optical coherence tomography images captured in the clinic. Experiments showed that the SBSDI algorithm qualitatively and quantitatively outperforms other state-of-the-art methods. PMID:23846467

Simultaneous transfer of optical frequency and time over 306 km long-haul optical fibre link

NASA Astrophysics Data System (ADS)

Hucl, Vaclav; Cizek, Martin; Pravdova, Lenka; Rerucha, Simon; Hrabina, Jan; Mikel, Bretislav; Smotlacha, Vladimir; Vojtech, Josef; Lazar, Josef; Cip, Ondrej

2016-12-01

Optical fibre links for distributing optical frequencies and time stamps were researched and experimentally tested in the past fifteen years. They have been used mainly for stability comparison of experimental optical clocks. But recent development puts demands on a technology transfer from laboratory experiments to the real industry. The remote calibration of interrogators of Fibre Bragg Grating strain sensory networks is one of important examples. The first step of the adoption the time and frequency broadcasting should be the drop-out free long-term operation of this technology between research laboratories connected via long-haul fibre links. We present a 306 km long-haul optical fibre link between the cities of Prague and Brno in the Czech Republic where a coherent transfer of stable optical frequency and a stable time signal has been firstly demonstrated. The link between ISI CAS Brno and CESNET Prague uses an internet communication fibre where a window of 1540-1546 nm is dedicated for the coherent transfer and 1PPS signal. The link is equipped with 6 bidirectional EDFA amplifiers. The optical frequency standard based on the highly-coherent laser Koheras Adjustik working at 1540.5 nm and stabilized with a saturation absorption spectroscopy technique was used for the coherent wave transfer. The suppression of the Doppler shift induced by the optical fibre was based on an accoustooptical modulator with a servo-loop including a fast PID controller processing the beat-note frequency given by mixing of the Adjustik laser (Brno) and the reflected frequency of this laser from the far end of 306 km long-haul fibre link (Prague). We verified the Doppler shift suppression for the coherent wave with a measuring method analysing the transport delay of the 1PPS signal.

Optical Coherence Tomography–Enhanced Microlaryngoscopy: Preliminary Report of a Noncontact Optical Coherence Tomography System Integrated With a Surgical Microscope

PubMed Central

Vokes, David E.; Jackson, Ryan; Guo, Shuguang; Perez, Jorge A.; Su, Jianping; Ridgway, James M.; Armstrong, William B.; Chen, Zhongping; Wong, Brian J. F.

2014-01-01

Objectives Optical coherence tomography (OCT) is a new imaging modality that uses near-infrared light to produce cross-sectional images of tissue with a resolution approaching that of light microscopy. We have previously reported use of OCT imaging of the vocal folds (VFs) during direct laryngoscopy with a probe held in contact or near-contact with the VFs. This aim of this study was to develop and evaluate a novel OCT system integrated with a surgical microscope to allow hands-free OCT imaging of the VFs, which could be performed simultaneously with microscopic visualization. Methods We performed a prospective evaluation of a new method of acquiring OCT images of the VFs. Results An OCT system was successfully integrated with a surgical microscope to permit noncontact OCT imaging of the VFs of 10 patients. With this novel device we were able to identify VF epithelium and lamina propria; however, the resolution was reduced compared to that achieved with the standard contact or near-contact OCT. Conclusions Optical coherence tomography is able to produce high-resolution images of vocal fold mucosa to a maximum depth of 1.6 mm. It may be used in the diagnosis of VF lesions, particularly early squamous cell carcinoma, in which OCT can show disruption of the basement membrane. Mounting the OCT device directly onto the operating microscope allows hands-free noncontact OCT imaging and simultaneous conventional microscopic visualization of the VFs. However, the lateral resolution of the OCT microscope system is 50 µm, in contrast to the conventional handheld probe system (10 µm). Although such images at this resolution are still useful clinically, improved resolution would enhance the system’s performance, potentially enabling real-time OCT-guided microsurgery of the larynx. PMID:18700431

Nonlinear characterization of elasticity using quantitative optical coherence elastography.

PubMed

Qiu, Yi; Zaki, Farzana R; Chandra, Namas; Chester, Shawn A; Liu, Xuan

2016-11-01

Optical coherence elastography (OCE) has been used to perform mechanical characterization on biological tissue at the microscopic scale. In this work, we used quantitative optical coherence elastography (qOCE), a novel technology we recently developed, to study the nonlinear elastic behavior of biological tissue. The qOCE system had a fiber-optic probe to exert a compressive force to deform tissue under the tip of the probe. Using the space-division multiplexed optical coherence tomography (OCT) signal detected by a spectral domain OCT engine, we were able to simultaneously quantify the probe deformation that was proportional to the force applied, and to quantify the tissue deformation. In other words, our qOCE system allowed us to establish the relationship between mechanical stimulus and tissue response to characterize the stiffness of biological tissue. Most biological tissues have nonlinear elastic behavior, and the apparent stress-strain relationship characterized by our qOCE system was nonlinear an extended range of strain, for a tissue-mimicking phantom as well as biological tissues. Our experimental results suggested that the quantification of force in OCE was critical for accurate characterization of tissue mechanical properties and the qOCE technique was capable of differentiating biological tissues based on the elasticity of tissue that is generally nonlinear.

Three years coherent space to ground links: performance results and outlook for the optical ground station equipped with adaptive optics

NASA Astrophysics Data System (ADS)

Gregory, M.; Troendle, D.; Muehlnikel, G.; Heine, F.; Meyer, R.; Lutzer, M.; Czichy, R.

2013-03-01

Tesat is performing inter-satellite links (ISLs) for over 5 years now. Besides the successful demonstration of the suitability of coherent laser communication for high speed data transmission in space, Tesat has also conducted two major satellite to ground link (SGL) campaigns during the last 3 years. A transportable ground station has been developed to measure the impact of atmospheric turbulence to the coherent system. The SGLs have been performed between the Tesat optical ground station and the two LEO satellites TerraSAR-X and NFIRE, both equipped with a Tesat LCT. The capability of the LCTs of measuring the signal intensity on a direct detection sensor and on a coherent sensor simultaneously makes the system unique for investigating the atmospheric distortion impacts. In this paper the main results of the SGL campaigns are presented, including BER performance for the uplink and downlink. Measured scintillation profiles versus elevation angles at different weather conditions are illustrated. Finally preliminary results of an adaptive optics system are presented that has been developed to be used in the transportable adaptive optical ground station (T-AOGS) acting as the counter terminal for the LCT mounted on Alphasat, a geostationary satellite of the European Space Agency (ESA), in autumn 2013.

In vivo time-serial evaluation of laser-induced choroidal neovascularization in rats simultaneously using photoacoustic microscopy and optical coherence tomography

NASA Astrophysics Data System (ADS)

Dai, Cuixia; Li, Lin; Liu, Wenlu; Wang, Fenghua; Zhou, Chuanqing

2018-02-01

Determination of the precise location and degree of condition of the Choroidal neovascularization (CNV) lesion is essential for diagnosation Neovascular age-related macular degeneration (AMD) and evaluation the efficacy of treatment. Given the complimentary contrast mechanisms of Photoacoustic microscopy (PAM) and Optical coherence tomography (OCT), the combination of PAM and OCT imaging could potentially provide much sensitive and specific detection of CNV. In this paper, we validated the opportunity to evaluate the information of laser-induced CNV and presented the in vivo time-serial evaluation of the CNV by simultaneously using PAM and OCT techniques. In vivo PAM and OCT examination was performed after laser photocoagulation applied to the rat fundus at days 1, 3, 5, 7, 14. Time-serial results showed that CNV in rats increased to its maximum at day 7 and decreased at day 14. Evolution of CNV information was given in PAM images with a high contrast and details of high axial resolution OCT images were simultaneously given to show the hyperreflective reaction progress.

Quantitative, simultaneous, and collinear eye-tracked, high dynamic range optical coherence tomography at 850 and 1060 nm

NASA Astrophysics Data System (ADS)

Mooser, Matthias; Burri, Christian; Stoller, Markus; Luggen, David; Peyer, Michael; Arnold, Patrik; Meier, Christoph; Považay, Boris

2017-07-01

Ocular optical coherence tomography at the wavelengths ranges of 850 and 1060 nm have been integrated with a confocal scanning laser ophthalmoscope eye-tracker as a clinical commercial-class system. Collinear optics enables an exact overlap of the different channels to produce precisely overlapping depth-scans for evaluating the similarities and differences between the wavelengths to extract additional physiologic information. A reliable segmentation algorithm utilizing Graphcuts has been implemented and applied to automatically extract retinal and choroidal shape in cross-sections and volumes. The device has been tested in normals and pathologies including a cross-sectional and longitudinal study of myopia progress and control with a duplicate instrument in Asian children.

Simultaneous measurement of tear film dynamics using wavefront sensor and optical coherence tomography.

PubMed

Koh, Shizuka; Tung, Cynthia; Aquavella, James; Yadav, Rahul; Zavislan, James; Yoon, Geunyoung

2010-07-01

PURPOSE. To investigate tear film dynamics using simultaneous measurements of ocular aberrations and lower tear meniscus. METHODS. Simultaneous measurements of wavefront aberration and lower tear meniscus were performed for 11 normal eyes and 7 eyes with short tear film break-up time (SBUT) dry eye, with a tear film break-up time shorter than 5 seconds, using a wavefront sensor and an anterior segment optical coherence tomography (OCT). During the measurement, the subjects were instructed to blink every 6 seconds for a total of 30 seconds. From the measured aberration, root mean square (RMS) wavefront error and volume modulation transfer function (vMTF) induced by changes in tear film dynamics were calculated for a 5-mm pupil. Lower tear meniscus height (TMH) and area (TMA) were estimated from the cross-sectional OCT images of lower tear meniscus. RESULTS. There was a positive correlation between RMS and tear meniscus dimensions and a negative correlation between vMTF and tear meniscus in both groups. There were moderate negative correlations between the postblink initial RMS change and baseline TMH (R = -0.61) and TMA (R = -0.54) in SBUT dry eyes that were stronger than in normal eyes (R = -0.37, R = -0.38). CONCLUSIONS. Tear meniscus dimensions increase with RMS over time, and tear quantity before blink has a significant role in maintaining initial optical integrity, especially in SBUT dry eye. Simultaneous measurement of optical quality and tear meniscus has the potential to improve understanding of tear stability in normal eyes and dry eyes.

Integrated adaptive optics optical coherence tomography and adaptive optics scanning laser ophthalmoscope system for simultaneous cellular resolution in vivo retinal imaging

PubMed Central

Zawadzki, Robert J.; Jones, Steven M.; Pilli, Suman; Balderas-Mata, Sandra; Kim, Dae Yu; Olivier, Scot S.; Werner, John S.

2011-01-01

We describe an ultrahigh-resolution (UHR) retinal imaging system that combines adaptive optics Fourier-domain optical coherence tomography (AO-OCT) with an adaptive optics scanning laser ophthalmoscope (AO-SLO) to allow simultaneous data acquisition by the two modalities. The AO-SLO subsystem was integrated into the previously described AO-UHR OCT instrument with minimal changes to the latter. This was done in order to ensure optimal performance and image quality of the AO- UHR OCT. In this design both imaging modalities share most of the optical components including a common AO-subsystem and vertical scanner. One of the benefits of combining Fd-OCT with SLO includes automatic co-registration between two acquisition channels for direct comparison between retinal structures imaged by both modalities (e.g., photoreceptor mosaics or microvasculature maps). Because of differences in the detection scheme of the two systems, this dual imaging modality instrument can provide insight into retinal morphology and potentially function, that could not be accessed easily by a single system. In this paper we describe details of the components and parameters of the combined instrument, including incorporation of a novel membrane magnetic deformable mirror with increased stroke and actuator count used as a single wavefront corrector. We also discuss laser safety calculations for this multimodal system. Finally, retinal images acquired in vivo with this system are presented. PMID:21698028

Advanced optical fiber communication systems

NASA Astrophysics Data System (ADS)

Kazovsky, Leonid G.

1994-03-01

Our research is focused on three major aspects of advanced optical fiber communication systems: dynamic wavelength division multiplexing (WDM) networks, fiber nonlinearities, and high dynamic range coherent analog optical links. In the area of WDM networks, we have designed and implemented two high-speed interface boards and measured their throughput and latency. Furthermore, we designed and constructed an experimental PSK/ASK transceiver that simultaneously transmits packet-switched ASK data and circuit-switched PSK data on the same optical carrier. In the area of fiber nonlinearities, we investigated the theoretical impact of modulation frequency on cross-phase modulation (XPM) in dispersive fibers. In the area of high dynamic range coherent analog optical links, we developed theoretical expressions for the RF power transfer ratio (or RF power gain) and the noise figure (NF) of angle-modulated links. We then compared the RF power gains and noise figures of these links to that of an intensity modulated direct detection (DD) link.

A multimodal imaging platform with integrated simultaneous photoacoustic microscopy, optical coherence tomography, optical Doppler tomography and fluorescence microscopy

NASA Astrophysics Data System (ADS)

Dadkhah, Arash; Zhou, Jun; Yeasmin, Nusrat; Jiao, Shuliang

2018-02-01

Various optical imaging modalities with different optical contrast mechanisms have been developed over the past years. Although most of these imaging techniques are being used in many biomedical applications and researches, integration of these techniques will allow researchers to reach the full potential of these technologies. Nevertheless, combining different imaging techniques is always challenging due to the difference in optical and hardware requirements for different imaging systems. Here, we developed a multimodal optical imaging system with the capability of providing comprehensive structural, functional and molecular information of living tissue in micrometer scale. This imaging system integrates photoacoustic microscopy (PAM), optical coherence tomography (OCT), optical Doppler tomography (ODT) and fluorescence microscopy in one platform. Optical-resolution PAM (OR-PAM) provides absorption-based imaging of biological tissues. Spectral domain OCT is able to provide structural information based on the scattering property of biological sample with no need for exogenous contrast agents. In addition, ODT is a functional extension of OCT with the capability of measurement and visualization of blood flow based on the Doppler effect. Fluorescence microscopy allows to reveal molecular information of biological tissue using autofluoresce or exogenous fluorophores. In-vivo as well as ex-vivo imaging studies demonstrated the capability of our multimodal imaging system to provide comprehensive microscopic information on biological tissues. Integrating all the aforementioned imaging modalities for simultaneous multimodal imaging has promising potential for preclinical research and clinical practice in the near future.

Laser tissue coagulation and concurrent optical coherence tomography through a double-clad fiber coupler.

PubMed

Beaudette, Kathy; Baac, Hyoung Won; Madore, Wendy-Julie; Villiger, Martin; Godbout, Nicolas; Bouma, Brett E; Boudoux, Caroline

2015-04-01

Double-clad fiber (DCF) is herein used in conjunction with a double-clad fiber coupler (DCFC) to enable simultaneous and co-registered optical coherence tomography (OCT) and laser tissue coagulation. The DCF allows a single channel fiber-optic probe to be shared: i.e. the core propagating the OCT signal while the inner cladding delivers the coagulation laser light. We herein present a novel DCFC designed and built to combine both signals within a DCF (>90% of single-mode transmission; >65% multimode coupling). Potential OCT imaging degradation mechanisms are also investigated and solutions to mitigate them are presented. The combined DCFC-based system was used to induce coagulation of an ex vivo swine esophagus allowing a real-time assessment of thermal dynamic processes. We therefore demonstrate a DCFC-based system combining OCT imaging with laser coagulation through a single fiber, thus enabling both modalities to be performed simultaneously and in a co-registered manner. Such a system enables endoscopic image-guided laser marking of superficial epithelial tissues or laser thermal therapy of epithelial lesions in pathologies such as Barrett's esophagus.

Laser tissue coagulation and concurrent optical coherence tomography through a double-clad fiber coupler

PubMed Central

Beaudette, Kathy; Baac, Hyoung Won; Madore, Wendy-Julie; Villiger, Martin; Godbout, Nicolas; Bouma, Brett E.; Boudoux, Caroline

2015-01-01

Double-clad fiber (DCF) is herein used in conjunction with a double-clad fiber coupler (DCFC) to enable simultaneous and co-registered optical coherence tomography (OCT) and laser tissue coagulation. The DCF allows a single channel fiber-optic probe to be shared: i.e. the core propagating the OCT signal while the inner cladding delivers the coagulation laser light. We herein present a novel DCFC designed and built to combine both signals within a DCF (>90% of single-mode transmission; >65% multimode coupling). Potential OCT imaging degradation mechanisms are also investigated and solutions to mitigate them are presented. The combined DCFC-based system was used to induce coagulation of an ex vivo swine esophagus allowing a real-time assessment of thermal dynamic processes. We therefore demonstrate a DCFC-based system combining OCT imaging with laser coagulation through a single fiber, thus enabling both modalities to be performed simultaneously and in a co-registered manner. Such a system enables endoscopic image-guided laser marking of superficial epithelial tissues or laser thermal therapy of epithelial lesions in pathologies such as Barrett’s esophagus. PMID:25909013

Broadband light generation by femtosecond pulse amplification with stimulated Raman scattering in a high-power erbium-doped fiber amplifier

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tamura, K.; Yoshida, E.; Sugawa, T.

1995-08-01

It is shown for the first time to our knowledge that short-pulse amplification in high-power erbium-doped fiber amplifiers, simultaneously accompanied by stimulated Raman scattering, generates a broadband optical spectrum at high output power (270 mW). At 20 dB down from the peak the continuum extended over 329 nm, from 1427 to 1756 nm. The FWHM bandwidth was 125 nm, centered at 1650 nm. The coherence was measured to be 15 fringes, which corresponds to a 25-{mu}m coherence length. {copyright} {ital 1995} {ital Optical} {ital Society} {ital of} {ital America}.

Noise-immune complex correlation for vasculature imaging based on standard and Jones-matrix optical coherence tomography

NASA Astrophysics Data System (ADS)

Makita, Shuichi; Kurokawa, Kazuhiro; Hong, Young-Joo; Li, En; Miura, Masahiro; Yasuno, Yoshiaki

2016-03-01

A new optical coherence angiography (OCA) method, called correlation mapping OCA (cmOCA), is presented by using the SNR-corrected complex correlation. An SNR-correction theory for the complex correlation calculation is presented. The method also integrates a motion-artifact-removal method for the sample motion induced decorrelation artifact. The theory is further extended to compute more reliable correlation by using multi- channel OCT systems, such as Jones-matrix OCT. The high contrast vasculature imaging of in vivo human posterior eye has been obtained. Composite imaging of cmOCA and degree of polarization uniformity indicates abnormalities of vasculature and pigmented tissues simultaneously.

Development of a phase-sensitive Fourier domain optical coherence tomography system to measure mouse organ of Corti vibrations in two cochlear turns

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramamoorthy, Sripriya; Zhang, Yuan; Jacques, Steven

In this study, we have developed a phase-sensitive Fourier-domain optical coherence tomography system to simultaneously measure the in vivo inner ear vibrations in the hook area and second turn of the mouse cochlea. This technical development will enable measurement of intra-cochlear distortion products at ideal locations such as the distortion product generation site and reflection site. This information is necessary to un-mix the complex mixture of intra-cochlear waves comprising the DPOAE and thus leads to the non-invasive identification of the local region of cochlear damage.

Spectroscopic optical coherence tomography based on wavelength de-multiplexing and smart pixel array detection

NASA Astrophysics Data System (ADS)

Laubscher, Markus; Bourquin, Stéphane; Froehly, Luc; Karamata, Boris; Lasser, Theo

2004-07-01

Current spectroscopic optical coherence tomography (OCT) methods rely on a posteriori numerical calculation. We present an experimental alternative for accessing spectroscopic information in OCT without post-processing based on wavelength de-multiplexing and parallel detection using a diffraction grating and a smart pixel detector array. Both a conventional A-scan with high axial resolution and the spectrally resolved measurement are acquired simultaneously. A proof-of-principle demonstration is given on a dynamically changing absorbing sample. The method's potential for fast spectroscopic OCT imaging is discussed. The spectral measurements obtained with this approach are insensitive to scan non-linearities or sample movements.

A dual-modality optical coherence tomography and selective plane illumination microscopy system for mouse embryonic imaging

NASA Astrophysics Data System (ADS)

Wu, Chen; Ran, Shihao; Le, Henry; Singh, Manmohan; Larina, Irina V.; Mayerich, David; Dickinson, Mary E.; Larin, Kirill V.

2017-02-01

Both optical coherence tomography (OCT) and selective plane illumination microscopy (SPIM) are frequently used in mouse embryonic research for high-resolution three-dimensional imaging. However, each of these imaging methods provide a unique and independent advantage: SPIM provides morpho-functional information through immunofluorescence and OCT provides a method for whole-embryo 3D imaging. In this study, we have combined rotational imaging OCT and SPIM into a single, dual-modality device to image E9.5 mouse embryos. The results demonstrate that the dual-modality setup is able to provide both anatomical and functional information simultaneously for more comprehensive tissue characterization.

Zero-field optical magnetic resonance study of phosphorus donors in 28-silicon

NASA Astrophysics Data System (ADS)

Morse, Kevin J.; Dluhy, Phillip; Huber, Julian; Salvail, Jeff Z.; Saeedi, Kamyar; Riemann, Helge; Abrosimov, Nikolay V.; Becker, Peter; Pohl, Hans-Joachim; Simmons, S.; Thewalt, M. L. W.

2018-03-01

Donor spins in silicon are some of the most promising qubits for upcoming solid-state quantum technologies. The nuclear spins of phosphorus donors in enriched silicon have among the longest coherence times of any solid-state system as well as simultaneous high fidelity qubit initialization, manipulation, and readout. Here we characterize the phosphorus in silicon system in the regime of "zero" magnetic field, where a singlet-triplet spin clock transition can be accessed, using laser spectroscopy and magnetic resonance methods. We show the system can be optically hyperpolarized and has ˜10 s Hahn echo coherence times, even for applied static magnetic fields below Earth's field.

CSI 2264: Simultaneous optical and X-ray variability in pre-main sequence stars. I. Time resolved X-ray spectral analysis during optical dips and accretion bursts in stars with disks

NASA Astrophysics Data System (ADS)

Guarcello, M. G.; Flaccomio, E.; Micela, G.; Argiroffi, C.; Sciortino, S.; Venuti, L.; Stauffer, J.; Rebull, L.; Cody, A. M.

2017-06-01

Context. Pre-main sequence stars are variable sources. The main mechanisms responsible for their variability are variable extinction, unsteady accretion, and rotational modulation of both hot and dark photospheric spots and X-ray-active regions. In stars with disks, this variability is related to the morphology of the inner circumstellar region (≤0.1 AU) and that of the photosphere and corona, all impossible to be spatially resolved with present-day techniques. This has been the main motivation for the Coordinated Synoptic Investigation of NGC 2264, a set of simultaneous observations of NGC 2264 with 15 different telescopes. Aims: In this paper, we focus on the stars with disks. We analyze the X-ray spectral properties extracted during optical bursts and dips in order to unveil the nature of these phenomena. Stars without disks are studied in a companion paper. Methods: We analyze simultaneous CoRoT and Chandra/ACIS-I observations to search for coherent optical and X-ray flux variability in stars with disks. Then, stars are analyzed in two different samples. In stars with variable extinction, we look for a simultaneous increase of optical extinction and X-ray absorption during the optical dips; in stars with accretion bursts, we search for soft X-ray emission and increasing X-ray absorption during the bursts. Results: We find evidence for coherent optical and X-ray flux variability among the stars with variable extinction. In 9 of the 24 stars with optical dips, we observe a simultaneous increase of X-ray absorption and optical extinction. In seven dips, it is possible to calculate the NH/AV ratio in order to infer the composition of the obscuring material. In 5 of the 20 stars with optical accretion bursts, we observe increasing soft X-ray emission during the bursts that we associate to the emission of accreting gas. It is not surprising that these properties are not observed in all the stars with dips and bursts, since favorable geometric configurations are required. Conclusions: The observed variable absorption during the dips is mainly due to dust-free material in accretion streams. In stars with accretion bursts, we observe, on average, a larger soft X-ray spectral component not observed in non-accreting stars.

Interferometer design and controls for pulse stacking in high power fiber lasers

NASA Astrophysics Data System (ADS)

Wilcox, Russell; Yang, Yawei; Dahlen, Dar; Xu, Yilun; Huang, Gang; Qiang, Du; Doolittle, Lawrence; Byrd, John; Leemans, Wim; Ruppe, John; Zhou, Tong; Sheikhsofla, Morteza; Nees, John; Galvanauskas, Almantas; Dawson, Jay; Chen, Diana; Pax, Paul

2017-03-01

In order to develop a design for a laser-plasma accelerator (LPA) driver, we demonstrate key technologies that enable fiber lasers to produce high energy, ultrafast pulses. These technologies must be scalable, and operate in the presence of thermal drift, acoustic noise, and other perturbations typical of an operating system. We show that coherent pulse stacking (CPS), which requires optical interferometers, can be made robust by image-relaying, multipass optical cavities, and by optical phase control schemes that sense pulse train amplitudes from each cavity. A four-stage pulse stacking system using image-relaying cavities is controlled for 14 hours using a pulse-pattern sensing algorithm. For coherent addition of simultaneous ultrafast pulses, we introduce a new scheme using diffractive optics, and show experimentally that four pulses can be added while a preserving pulse width of 128 fs.

Doppler Optical Coherence Tomography

NASA Astrophysics Data System (ADS)

Chen, Zhongping; Zhang, Jun

Noninvasive techniques for imaging in vivo blood flow are of great value to biomedical research and clinical diagnostics where many diseases have a vascular etiology or component. In ophthalmology, many diseases involve disturbances in ocular blood flow, including diabetic retinopathy, low tension glaucoma, anterior ischemic optic neuritis, and macular degeneration. Simultaneous imaging of tissue structure and blood flow could provide critical information for early diagnosis of ocular diseases.

Probing interactions of thermal Sr Rydberg atoms using simultaneous optical and ion detection

NASA Astrophysics Data System (ADS)

Hanley, Ryan K.; Bounds, Alistair D.; Huillery, Paul; Keegan, Niamh C.; Faoro, Riccardo; Bridge, Elizabeth M.; Weatherill, Kevin J.; Jones, Matthew P. A.

2017-06-01

We demonstrate a method for probing interaction effects in a thermal beam of strontium atoms using simultaneous measurements of Rydberg EIT and spontaneously created ions or electrons. We present a Doppler-averaged optical Bloch equation model that reproduces the optical signals and allows us to connect the optical coherences and the populations. We use this to determine that the spontaneous ionization process in our system occurs due to collisions between Rydberg and ground state atoms in the EIT regime. We measure the cross section of this process to be 0.6+/- 0.2 {σ }{geo}, where {σ }{geo} is the geometrical cross section of the Rydberg atom. This result adds complementary insight to a range of recent studies of interacting thermal Rydberg ensembles.

Coherent perfect absorption and laser modes in a cylindrical structure of conjugate metamaterials

NASA Astrophysics Data System (ADS)

Fu, Yangyang; Xu, Yadong; Chen, Huanyang; Cummer, Steven A.

2018-01-01

In this work, we theoretically find that coherent perfect absorption (CPA) and laser modes can be realized in a two-dimensional cylindrical structure composed of conjugate metamaterials (CMs). The required phase factors of CMs for achieving CPA and laser modes are determined by the geometric size of the CM cylinder, which is a unique feature compared with other non-Hermitian optical systems. Based on this property, we also demonstrate that CPA and laser modes can exist simultaneously in a CM cylinder with an extremely large size, where the excitations of CPA and laser modes depend on the angular momentum of coherent incident light. Therefore, compared with the well known parity time symmetry, our work opens up a brand-new path to obtaining CPA and laser modes, and is a significant advance in non-Hermitian optical systems.

Enhancing the performance of coherent OTDR systems with polarization diversity complementary codes.

PubMed

Dorize, Christian; Awwad, Elie

2018-05-14

Monitoring the optical phase change in a fiber enables a wide range of applications where fast phase variations are induced by acoustic signals or by vibrations in general. However, the quality of the estimated fiber response strongly depends on the method used to modulate the light sent to the fiber and capture the variations of the optical field. In this paper, we show that distributed optical fiber sensing systems can advantageously exploit techniques from the telecommunication domain, as those used in coherent optical transmission, to enhance their performance in detecting mechanical events, while jointly offering a simpler setup than widespread pulse-cloning or spectral-sweep based schemes with acousto-optic modulators. We periodically capture an overall fiber Jones matrix estimate thanks to a novel probing technique using two mutually orthogonal complementary (Golay) pairs of binary sequences applied simultaneously in phase and quadrature on two orthogonal polarization states. A perfect channel response estimation of the sensor array is achieved, subject to conditions detailed in the paper, thus enhancing the sensitivity and bandwidth of coherent ϕ-OTDR systems. High sensitivity, linear response, and bandwidth coverage up to 18 kHz are demonstrated with a sensor array composed of 10 fiber Bragg gratings (FBGs).

Enhancing the performance of coherent OTDR systems with polarization diversity complementary codes

NASA Astrophysics Data System (ADS)

Dorize, Christian; Awwad, Elie

2018-05-01

Monitoring the optical phase change in a fiber enables a wide range of applications where fast phase variations are induced by acoustic signals or vibrations in general. However, the quality of the estimated fiber response strongly depends on the method used to modulate the light sent to the fiber and capture the variations of the optical field. In this paper, we show that distributed optical fiber sensing systems can advantageously exploit techniques from the telecommunication domain, as those used in coherent optical transmission, to enhance their performance in detecting mechanical events, while jointly offering a simpler setup than widespread pulse-cloning or spectral-sweep based schemes with acousto-optic modulators. We periodically capture an overall fiber Jones matrix estimate thanks to a novel probing technique using two mutually orthogonal complementary (Golay) pairs of binary sequences applied simultaneously in phase and quadrature on two orthogonal polarization states. A perfect channel response estimation of the sensor array is achieved, subject to conditions detailed in the paper, thus enhancing the sensitivity and bandwidth of coherent phase-OTDR systems. High sensitivity, linear response, and bandwidth coverage up to 18 kHz are demonstrated with a sensor array composed of 10 fiber Bragg gratings (FBGs).

Layered Organization in the Coastal Ocean: 4-D Assessment of Thin Layer Structure, Dynamics and Impacts

DTIC Science & Technology

2009-09-30

maintenance and dissipation of layers; (2) to understand the spatial coherence and spatial properties of thin layers in the coastal ocean (especially in...ORCAS profilers at K1 South and K2 had a Nortek ADV (Acoustic Doppler Velocity meter) for simultaneously measuring centimeter- scale currents and...year will be used to (1) detect the presence, intensity, thickness, temporal persistence, and spatial coherence of thin optical and acoustical layers

Hybrid single-source online Fourier transform coherent anti-Stokes Raman scattering/optical coherence tomography.

PubMed

Kamali, Tschackad; Považay, Boris; Kumar, Sunil; Silberberg, Yaron; Hermann, Boris; Werkmeister, René; Drexler, Wolfgang; Unterhuber, Angelika

2014-10-01

We demonstrate a multimodal optical coherence tomography (OCT) and online Fourier transform coherent anti-Stokes Raman scattering (FTCARS) platform using a single sub-12 femtosecond (fs) Ti:sapphire laser enabling simultaneous extraction of structural and chemical ("morphomolecular") information of biological samples. Spectral domain OCT prescreens the specimen providing a fast ultrahigh (4×12  μm axial and transverse) resolution wide field morphologic overview. Additional complementary intrinsic molecular information is obtained by zooming into regions of interest for fast label-free chemical mapping with online FTCARS spectroscopy. Background-free CARS is based on a Michelson interferometer in combination with a highly linear piezo stage, which allows for quick point-to-point extraction of CARS spectra in the fingerprint region in less than 125 ms with a resolution better than 4  cm(-1) without the need for averaging. OCT morphology and CARS spectral maps indicating phosphate and carbonate bond vibrations from human bone samples are extracted to demonstrate the performance of this hybrid imaging platform.

Measurement of morphing wing deflection by a cross-coherence fiber optic interferometric technique

NASA Astrophysics Data System (ADS)

Tomić, Miloš C.; Djinović, Zoran V.; Scheerer, Michael; Petricevic, Slobodan J.

2018-01-01

A fiber-optic interferometric technique aimed at measuring the deflection of aircrafts’ morphing wings is presented. The wing deflection induces a strain in the sensing fiber optic coils that are firmly fixed onto the wing. A change of the phase angle of the light propagating through the fiber is measured by an ‘all-in-fiber’ Michelson interferometer based on a 3 × 3 fiber-optic coupler. Two light sources of different coherence lengths and wavelengths are simultaneously used to ensure a wide measurement range and high accuracy. A new technique for determination of the zero deflection point using the cross-correlation of the two interferograms is proposed. The experiments performed on a specimen made of a carbon-fiber-reinforced plastic honeycomb structure demonstrated a relative uncertainty <1% and a precision of about 0.06° in the measuring range ±5° of the morphing wing deflection.

Combining Optical Coherence Tomography with Fluorescence Molecular Imaging: Towards Simultaneous Morphology and Molecular Imaging

PubMed Central

Yuan, Shuai; Roney, Celeste A.; Wierwille, Jerry; Chen, Chao-Wei; Xu, Biying; Jiang, James; Ma, Hongzhou; Cable, Alex; Summers, Ronald M.; Chen, Yu

2010-01-01

Optical coherence tomography (OCT) provides high-resolution, cross-sectional imaging of tissue microstructure in situ and in real-time, while fluorescence molecular imaging (FMI) enables the visualization of basic molecular processes. There are great interests in combining these two modalities so that the tissue's structural and molecular information can be obtained simultaneously. This could greatly benefit biomedical applications such as detecting early diseases and monitoring therapeutic interventions. In this research, an optical system that combines OCT and FMI was developed. The system demonstrated that it could co-register en face OCT and FMI images with a 2.4 × 2.4 mm field of view. The transverse resolutions of OCT and FMI of the system are both ~10 μm. Capillary tubes filled with fluorescent dye Cy 5.5 in different concentrations under a scattering medium are used as the phantom. En face OCT images of the phantoms were obtained and successfully co-registered with FMI images that were acquired simultaneously. A linear relationship between FMI intensity and dye concentration was observed. The relationship between FMI intensity and target fluorescence tube depth measured by OCT images was also observed and compared with theoretical modeling. This relationship could help in correcting reconstructed dye concentration. Imaging of colon polyps of APCmin mouse model is presented as an example of biological applications of this co-registered OCT/FMI system. PMID:20009192

Optical coherence tomography using images of hair structure and dyes penetrating into the hair.

PubMed

Tsugita, Tetsuya; Iwai, Toshiaki

2014-11-01

Hair dyes are commonly evaluated by the appearance of the hair after dyeing. However, this approach cannot simultaneously assess how deep the dye has penetrated into hair. For simultaneous assessment of the appearance and the interior of hair, we developed a visible-range red, green, and blue (RGB) (three primary colors)-optical coherence tomography (OCT) using an RGB LED light source. We then evaluated a phantom model based on the assumption that the sample's absorbability in the vertical direction affects the tomographic imaging. Consistent with theory, our device showed higher resolution than conventional OCT with far-red light. In the experiment on the phantom model, we confirmed that the tomographic imaging is affected by absorbability unique to the sample. Furthermore, we verified that permeability can be estimated from this tomographic image. We also identified for the first time the relationship between penetration of the dye into hair and characteristics of wavelength by tomographic imaging of dyed hair. We successfully simultaneously assessed the appearance of dyed hair and inward penetration of the dye without preparing hair sections. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Dual-scanning optical coherence elastography for rapid imaging of two tissue volumes (Conference Presentation)

NASA Astrophysics Data System (ADS)

Fang, Qi; Frewer, Luke; Wijesinghe, Philip; Hamzah, Juliana; Ganss, Ruth; Allen, Wes M.; Sampson, David D.; Curatolo, Andrea; Kennedy, Brendan F.

2017-02-01

In many applications of optical coherence elastography (OCE), it is necessary to rapidly acquire images in vivo, or within intraoperative timeframes, over fields-of-view far greater than can be achieved in one OCT image acquisition. For example, tumour margin assessment in breast cancer requires acquisition over linear dimensions of 4-5 centimetres in under 20 minutes. However, the majority of existing techniques are not compatible with these requirements, which may present a hurdle to the effective translation of OCE. To increase throughput, we have designed and developed an OCE system that simultaneously captures two 3D elastograms from opposite sides of a sample. The optical system comprises two interferometers: a common-path interferometer on one side of the sample and a dual-arm interferometer on the other side. This optical system is combined with scanning mechanisms and compression loading techniques to realize dual-scanning OCE. The optical signals scattered from two volumes are simultaneously detected on a single spectrometer by depth-encoding the interference signal from each interferometer. To demonstrate dual-scanning OCE, we performed measurements on tissue-mimicking phantoms containing rigid inclusions and freshly isolated samples of murine hepatocellular carcinoma, highlighting the use of this technique to visualise 3D tumour stiffness. These findings indicate that our technique holds promise for in vivo and intraoperative applications.

Coherence Volume of an Optical Wave Field with Broad Frequency and Angular Spectra

NASA Astrophysics Data System (ADS)

Lyakin, D. V.; Mysina, N. Yu.; Ryabukho, V. P.

2018-03-01

We consider the sizes of a region in a three-dimensional space in which an optical wave field excites mutually coherent perturbations. We discuss the conditions under which the length of this region along the direction of propagation of the wave field and, correspondingly, its volume are determined either by the width of the frequency spectrum of the field or by the width of its angular spectrum, or by the parameters of these spectra simultaneously. We obtain expressions for estimating extremely small values of the coherence volume of the fields with a broad frequency spectrum and an extremely broad angular spectrum. Using the notion of instantaneous speckle-modulation of the wave field, we give a physical interpretation to the occurrence of a limited coherence volume of the field. The length of the spatiotemporal coherence region in which mutually coherent perturbations occur at different times is determined. The coherence volume of a wave field that illuminates an object in high-resolution microscopy with frequency broadband light is considered. The conditions for the dominant influence of the angular or frequency spectra on the longitudinal length of the coherence region are given, and the conditions for the influence of the frequency spectrum width on the transverse coherence of the wave field are examined. We show that, when using fields with broad and ultrabroad spectra in high-resolution microscopy, this influence should be taken into account.

Diagnostic blood-flow monitoring during therapeutic interventions using color Doppler optical coherence tomography

NASA Astrophysics Data System (ADS)

Yazdanfar, Siavash; Kulkarni, Manish D.; Wong, Richard C. K.; Sivak, Michael J., Jr.; Willis, Joseph; Barton, Jennifer K.; Welch, Ashley J.; Izatt, Joseph A.

1998-04-01

A recently developed modality for blood flow measurement holds high promise in the management of bleeding ulcers. Color Doppler optical coherence tomography (CDOCT) uses low- coherence interferometry and digital signal processing to obtain precise localization of tissue microstructure simultaneous with bi-directional quantitation of blood flow. We discuss CDOCT as a diagnostic tool in the management of bleeding gastrointestinal lesions. Common treatments for bleeding ulcers include local injection of a vasoconstrictor, coagulation of blood via thermal contact or laser treatment, and necrosis of surrounding tissue with a sclerosant. We implemented these procedures in a rat dorsal skin flap model, and acquired CDOCT images before and after treatment. In these studies, CDOCT succeeded in identifying cessation of flow before it could be determined visually. Hence, we demonstrate the diagnostic capabilities of CDOCT in the regulation of bleeding in micron-scale vessels.

Snapshot polarization-sensitive plug-in optical module for a Fourier-domain optical coherence tomography system

NASA Astrophysics Data System (ADS)

Marques, Manuel J.; Rivet, Sylvain; Bradu, Adrian; Podoleanu, Adrian

2018-02-01

In this communication, we present a proof-of-concept polarization-sensitive Optical Coherence Tomography (PS-OCT) which can be used to characterize the retardance and the axis orientation of a linear birefringent sample. This module configuration is an improvement from our previous work1, 2 since it encodes the two polarization channels on the optical path difference, effectively carrying out the polarization measurements simultaneously (snapshot measurement), whilst retaining all the advantages (namely the insensitivity to environmental parameters when using SM fibers) of these two previous configurations. Further progress consists in employing Master Slave OCT technology,3 which is used to automatically compensate for the dispersion mismatch introduced by the elements in the module. This is essential given the encoding of the polarization states on two different optical path lengths, each of them having dissimilar dispersive properties. By utilizing this method instead of the commonly used re-linearization and numerical dispersion compensation methods an improvement in terms of the calculation time required can be achieved.

Real time en face Fourier-domain optical coherence tomography with direct hardware frequency demodulation

PubMed Central

Biedermann, Benjamin R.; Wieser, Wolfgang; Eigenwillig, Christoph M.; Palte, Gesa; Adler, Desmond C.; Srinivasan, Vivek J.; Fujimoto, James G.; Huber, Robert

2009-01-01

We demonstrate en face swept source optical coherence tomography (ss-OCT) without requiring a Fourier transformation step. The electronic optical coherence tomography (OCT) interference signal from a k-space linear Fourier domain mode-locked laser is mixed with an adjustable local oscillator, yielding the analytic reflectance signal from one image depth for each frequency sweep of the laser. Furthermore, a method for arbitrarily shaping the spectral intensity profile of the laser is presented, without requiring the step of numerical apodization. In combination, these two techniques enable sampling of the in-phase and quadrature signal with a slow analog-to-digital converter and allow for real-time display of en face projections even for highest axial scan rates. Image data generated with this technique is compared to en face images extracted from a three-dimensional OCT data set. This technique can allow for real-time visualization of arbitrarily oriented en face planes for the purpose of alignment, registration, or operator-guided survey scans while simultaneously maintaining the full capability of high-speed volumetric ss-OCT functionality. PMID:18978919

Emerging Connections: Quantum & Classical Optics Incubator Program Book

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lesky, Marcia

The Emerging Connections: Quantum & Classical Optics Incubator was a scientific meeting held in Washington, DC on 6-8 November 2016. This Incubator provided unique and focused experiences and valuable opportunities to discuss advances, challenges and opportunities regarding this important area of research. Quantum optics and classical optics have coexisted for nearly a century as two distinct, but consistent descriptions of light in their respective domains. Recently, a number of detailed examinations of the structure of classical light beams have revealed that effects widely thought to be solely quantum in origin also have a place in classical optics. These new quantum-classicalmore » connections are informing classical optics in meaningful ways specifically by expanding understanding of optical coherence. Simultaneously, relationships discovered with classical light beams now also serve as a vehicle to illuminate concepts that no longer solely belong to the quantum realm. Interference, polarization, coherence, complementarity and entanglement are a partial list of elementary notions that now appear to belong to both quantum and classical optics. The goal of this meeting was to bring emerging quantum-classical links into wider view and to indicate directions in which forthcoming and future work would promote discussion and lead to a more unified understanding of optics.« less

Dynamic analysis of mental sweating of eccrine sweat gland of human fingertip by time-sequential piled-up en face optical coherence tomography images.

PubMed

Ohmi, Masato; Wada, Yuki

2016-08-01

In this paper, we demonstrate dynamic analysis of mental sweating for sound stimulus of a few tens of eccrine sweat glands by the time-sequential piled-up en face optical coherence tomography (OCT) images with the frame spacing of 3.3 sec. In the experiment, the amount of excess sweat can be evaluated simultaneously for a few tens of sweat glands by piling up of all the en face OCT images. Non-uniformity was observed in mental sweating where the amount of sweat in response to sound stimulus is different for each sweat gland. Furthermore, the amount of sweat is significantly increased in proportion to the strength of the stimulus.

In vivo imaging of middle-ear and inner-ear microstructures of a mouse guided by SD-OCT combined with a surgical microscope

PubMed Central

Cho, Nam Hyun; Jang, Jeong Hun; Jung, Woonggyu; Kim, Jeehyun

2014-01-01

We developed an augmented-reality system that combines optical coherence tomography (OCT) with a surgical microscope. By sharing the common optical path in the microscope and OCT, we could simultaneously acquire OCT and microscope views. The system was tested to identify the middle-ear and inner-ear microstructures of a mouse. Considering the probability of clinical application including otorhinolaryngology, diseases such as middle-ear effusion were visualized using in vivo mouse and OCT images simultaneously acquired through the eyepiece of the surgical microscope during surgical manipulation using the proposed system. This system is expected to realize a new practical area of OCT application. PMID:24787787

Molecular imaging needles: dual-modality optical coherence tomography and fluorescence imaging of labeled antibodies deep in tissue

PubMed Central

Scolaro, Loretta; Lorenser, Dirk; Madore, Wendy-Julie; Kirk, Rodney W.; Kramer, Anne S.; Yeoh, George C.; Godbout, Nicolas; Sampson, David D.; Boudoux, Caroline; McLaughlin, Robert A.

2015-01-01

Molecular imaging using optical techniques provides insight into disease at the cellular level. In this paper, we report on a novel dual-modality probe capable of performing molecular imaging by combining simultaneous three-dimensional optical coherence tomography (OCT) and two-dimensional fluorescence imaging in a hypodermic needle. The probe, referred to as a molecular imaging (MI) needle, may be inserted tens of millimeters into tissue. The MI needle utilizes double-clad fiber to carry both imaging modalities, and is interfaced to a 1310-nm OCT system and a fluorescence imaging subsystem using an asymmetrical double-clad fiber coupler customized to achieve high fluorescence collection efficiency. We present, to the best of our knowledge, the first dual-modality OCT and fluorescence needle probe with sufficient sensitivity to image fluorescently labeled antibodies. Such probes enable high-resolution molecular imaging deep within tissue. PMID:26137379

Full ocular biometry through dual-depth whole-eye optical coherence tomography

PubMed Central

Kim, Hyung-Jin; Kim, Minji; Hyeon, Min Gyu; Choi, Youngwoon; Kim, Beop-Min

2018-01-01

We propose a new method of determining the optical axis (OA), pupillary axis (PA), and visual axis (VA) of the human eye by using dual-depth whole-eye optical coherence tomography (OCT). These axes, as well as the angles “α” between the OA and VA and “κ” between PA and VA, are important in many ophthalmologic applications, especially in refractive surgery. Whole-eye images are reconstructed based on simultaneously acquired images of the anterior segment and retina. The light from a light source is split into two orthogonal polarization components for imaging the anterior segment and retina, respectively. The OA and PA are identified based on their geometric definitions by using the anterior segment image only, while the VA is detected through accurate correlation between the two images. The feasibility of our approach was tested using a model eye and human subjects. PMID:29552378

Cavity opto-mechanics using an optically levitated nanosphere

PubMed Central

Chang, D. E.; Regal, C. A.; Papp, S. B.; Wilson, D. J.; Ye, J.; Painter, O.; Kimble, H. J.; Zoller, P.

2010-01-01

Recently, remarkable advances have been made in coupling a number of high-Q modes of nano-mechanical systems to high-finesse optical cavities, with the goal of reaching regimes in which quantum behavior can be observed and leveraged toward new applications. To reach this regime, the coupling between these systems and their thermal environments must be minimized. Here we propose a novel approach to this problem, in which optically levitating a nano-mechanical system can greatly reduce its thermal contact, while simultaneously eliminating dissipation arising from clamping. Through the long coherence times allowed, this approach potentially opens the door to ground-state cooling and coherent manipulation of a single mesoscopic mechanical system or entanglement generation between spatially separate systems, even in room-temperature environments. As an example, we show that these goals should be achievable when the mechanical mode consists of the center-of-mass motion of a levitated nanosphere. PMID:20080573

Simultaneous X-Ray/Ultraviolet Timing of 4U 1626-67

NASA Technical Reports Server (NTRS)

Chakrabarty, Deepto

2003-01-01

The science results from our observation have been published (Chakrabarty et al. 2001, ApJ, 562, 985). We detected large-amplitude 0.3- 1.2 mHz quasi-periodic oscillations (QPOs) from the low-mass X-ray binary pulsar 4U 1626--67, using ultraviolet photometry from the Hubble Space Telescope and ground-based optical photometry. These 1 mHz QPOs, which have coherence (nu/Delta_nu) = 8, are entirely distinct from the 130 mHz pulsar spin frequency, a previously known 48 mHz QPO, and the 42 min binary period (independently confirmed here). Unlike the 48 mHz and 130 mHz oscillations which are present in both the optical/UV and the X-ray emission, the 1 mHz QPOs are not detected in simultaneous observations with the X-Ray Timing Explorer. The rms amplitude of the mHz QPO decreases from 15% in the far UV to 3% in the optical, while the upper limit on a corresponding X-ray QPO is as low as 0.8\\%. We suggest that the mHz oscillations are due to warping of the inner accretion disk. We also report the detection of coherent upper and lower sidebands of the 130 mHz optical pulsations, with unequal amplitude and a spacing of 1.93 mHz around the main pulsation. The origin of these sidebands remains unclear.

Noninvasive imaging of oral mucosae with optical coherence tomography

NASA Astrophysics Data System (ADS)

Lee, Cheng-Yu; Chen, Wei-Chuan; Tsai, Meng-Tsan

2017-04-01

In this study, a swept-source optical coherence tomography (OCT) system is developed for in vivo visualization of structural and vascular morphology oral mucosa. For simplification of optical probe fabrication, probe weight, and system setup, the body of the scanning probe is fabricated by a 3D printer to fix the optical components and the mechanical scanning device, and a partially reflective slide is attached at the output end of probe to achieve a common-path configuration. Aside from providing the ability of 3D structural imaging with the developed system, 3D vascular images of oral mucosa can be simultaneously obtained. Then, different locations of oral mucosa are scanned with common-path OCT. The results show that epithelium and lamina propria layers as well as fungiform papilla can be identified and microvascular images can be acquired. With the proposed probe, the system cost and volume can be greatly reduced. Experimental results indicate that such common-path OCT system could be further implemented for oral cancer diagnosis.

FIBRE AND INTEGRATED OPTICS. OPTICAL PROCESSING OF INFORMATION: Method for optical data processing based on a two-pulse photon echo

NASA Astrophysics Data System (ADS)

Zakharov, S. M.; Manykin, Eduard A.

1995-02-01

The principles of optical processing based on dynamic spatial—temporal properties of two-pulse photon echo signals are considered. The properties of a resonant medium as an on-line filter of temporal and spatial frequencies are discussed. These properties are due to the sensitivity of such a medium to the Fourier spectrum of the second exiting pulse. Degeneracy of quantum resonant systems, demonstrated by the coherent response dependence on the square of the amplitude of the second pulse, can be used for 'simultaneous' correlation processing of optical 'signals'. Various methods for the processing of the Fourier optical image are discussed.

Novel adaptive fiber-optics collimator for coherent beam combination.

PubMed

Zhi, Dong; Ma, Pengfei; Ma, Yanxing; Wang, Xiaolin; Zhou, Pu; Si, Lei

2014-12-15

In this manuscript, we experimentally validate a novel design of adaptive fiber-optics collimator (AFOC), which utilizes two levers to enlarge the movable range of the fiber end cap. The enlargement of the range makes the new AFOC possible to compensate the end-cap/tilt aberration in fiber laser beam combining system. The new AFOC based on flexible hinges and levers was fabricated and the performance of the new AFOC was tested carefully, including its control range, frequency response and control accuracy. Coherent beam combination (CBC) of two 5-W fiber amplifiers array with simultaneously end-cap/tilt control and phase-locking control was implemented successfully with the novel AFOC. Experimental results show that the average normalized power in the bucket (PIB) value increases from 0.311 to 0.934 with active phasing and tilt aberration compensation simultaneously, and with both controls on, the fringe contrast improves to more than 82% from 0% for the case with both control off. This work presents a promising structure for tilt aberration control in high power CBC system.

Electronic Holography with a Broad Spectrum Laser for Time Gated Imaging Through Highly Scattering Media.

NASA Astrophysics Data System (ADS)

Shih, Marian Pei-Ling

The problem of optical imaging through a highly scattering volume diffuser, in particular, biological tissue, has received renewed interest in recent years because of a search for alternative imaging diagnostics in the optical wavelengths for the early detection of human breast cancer. This dissertation discusses the optical imaging of objects obscured by diffusers that contribute an otherwise overwhelming degree of multiple scatter. Many optical imaging techniques are based on the first-arriving light principle. These methods usually combine a transilluminating optical short pulse with a time windowing gate in order to form a flat shadowgraph image of absorbing objects either embedded within or hidden behind a scattering medium. The gate selectively records an image of the first-arriving light, while simultaneously rejecting the later-arriving scattered light. One set of the many implementations of the first -arriving light principle relies on the gating property of holography. This thesis presents several holographic optical gating experiments that demonstrate the role that the temporal coherence function of the illumination source plays in the imaging of all objects with short coherence length holography, with special emphasis on the application to image through diffusers and its resolution capabilities. Previous researchers have already successfully combined electronic holography, holography in which the recording medium is a two dimensional detector array instead of photographic film, with light-in-flight holography into a short coherence length holography method that images through various types of multiply scattering random media, including chicken breast tissue and wax. This thesis reports further experimental exploration of the short coherence holography method for imaging through severely scattering diffusers. There is a study on the effectiveness of spatial filtering of the first-arriving light, as well as a report of the imaging, by means of the short coherence holographic method, of an absorber through a living human hand. This thesis also includes both theoretical analyses and experimental results of a spectral dispersion holography system which, instead of optically synthesizing the broad spectrum illumination source that is used for the short coherence holography method, digitally synthesizes a broad spectrum hologram from a collection of single frequency component holograms. This system has the time gating properties of short coherence length holography, as well as experimentally demonstrated applications for imaging through multiply scattering media.

Digital holographic interferometer using simultaneously three lasers and a single monochrome sensor for 3D displacement measurements.

PubMed

Saucedo-A, Tonatiuh; De la Torre-Ibarra, M H; Santoyo, F Mendoza; Moreno, Ivan

2010-09-13

The use of digital holographic interferometry for 3D measurements using simultaneously three illumination directions was demonstrated by Saucedo et al. (Optics Express 14(4) 2006). The technique records two consecutive images where each one contains three holograms in it, e.g., one before the deformation and one after the deformation. A short coherence length laser must be used to obtain the simultaneous 3D information from the same laser source. In this manuscript we present an extension of this technique now illuminating simultaneously with three different lasers at 458, 532 and 633 nm, and using only one high resolution monochrome CMOS sensor. This new configuration gives the opportunity to use long coherence length lasers allowing the measurement of large object areas. A series of digital holographic interferograms are recorded and the information corresponding to each laser is isolated in the Fourier spectral domain where the corresponding phase difference is calculated. Experimental results render the orthogonal displacement components u, v and w during a simple load deformation.

Globally Stable Microresonator Turing Pattern Formation for Coherent High-Power THz Radiation On-Chip

NASA Astrophysics Data System (ADS)

Huang, Shu-Wei; Yang, Jinghui; Yang, Shang-Hua; Yu, Mingbin; Kwong, Dim-Lee; Zelevinsky, T.; Jarrahi, Mona; Wong, Chee Wei

2017-10-01

In nonlinear microresonators driven by continuous-wave (cw) lasers, Turing patterns have been studied in the formalism of the Lugiato-Lefever equation with emphasis on their high coherence and exceptional robustness against perturbations. Destabilization of Turing patterns and the transition to spatiotemporal chaos, however, limit the available energy carried in the Turing rolls and prevent further harvest of their high coherence and robustness to noise. Here, we report a novel scheme to circumvent such destabilization, by incorporating the effect of local mode hybridizations, and we attain globally stable Turing pattern formation in chip-scale nonlinear oscillators with significantly enlarged parameter space, achieving a record-high power-conversion efficiency of 45% and an elevated peak-to-valley contrast of 100. The stationary Turing pattern is discretely tunable across 430 GHz on a THz carrier, with a fractional frequency sideband nonuniformity measured at 7.3 ×10-14 . We demonstrate the simultaneous microwave and optical coherence of the Turing rolls at different evolution stages through ultrafast optical correlation techniques. The free-running Turing-roll coherence, 9 kHz in 200 ms and 160 kHz in 20 minutes, is transferred onto a plasmonic photomixer for one of the highest-power THz coherent generations at room temperature, with 1.1% optical-to-THz power conversion. Its long-term stability can be further improved by more than 2 orders of magnitude, reaching an Allan deviation of 6 ×10-10 at 100 s, with a simple computer-aided slow feedback control. The demonstrated on-chip coherent high-power Turing-THz system is promising to find applications in astrophysics, medical imaging, and wireless communications.

A broadband chip-scale optical frequency synthesizer at 2.7 × 10−16 relative uncertainty

PubMed Central

Huang, Shu-Wei; Yang, Jinghui; Yu, Mingbin; McGuyer, Bart H.; Kwong, Dim-Lee; Zelevinsky, Tanya; Wong, Chee Wei

2016-01-01

Optical frequency combs—coherent light sources that connect optical frequencies with microwave oscillations—have become the enabling tool for precision spectroscopy, optical clockwork, and attosecond physics over the past decades. Current benchmark systems are self-referenced femtosecond mode-locked lasers, but Kerr nonlinear dynamics in high-Q solid-state microresonators has recently demonstrated promising features as alternative platforms. The advance not only fosters studies of chip-scale frequency metrology but also extends the realm of optical frequency combs. We report the full stabilization of chip-scale optical frequency combs. The microcomb’s two degrees of freedom, one of the comb lines and the native 18-GHz comb spacing, are simultaneously phase-locked to known optical and microwave references. Active comb spacing stabilization improves long-term stability by six orders of magnitude, reaching a record instrument-limited residual instability of 3.6mHz/τ. Comparing 46 nitride frequency comb lines with a fiber laser frequency comb, we demonstrate the unprecedented microcomb tooth-to-tooth relative frequency uncertainty down to 50 mHz and 2.7 × 10−16, heralding novel solid-state applications in precision spectroscopy, coherent communications, and astronomical spectrography. PMID:27152341

Implementation of biological tissue Mueller matrix for polarization-sensitive optical coherence tomography based on LabVIEW

NASA Astrophysics Data System (ADS)

Lin, Yongping; Zhang, Xiyang; He, Youwu; Cai, Jianyong; Li, Hui

2018-02-01

The Jones matrix and the Mueller matrix are main tools to study polarization devices. The Mueller matrix can also be used for biological tissue research to get complete tissue properties, while the commercial optical coherence tomography system does not give relevant analysis function. Based on the LabVIEW, a near real time display method of Mueller matrix image of biological tissue is developed and it gives the corresponding phase retardant image simultaneously. A quarter-wave plate was placed at 45 in the sample arm. Experimental results of the two orthogonal channels show that the phase retardance based on incident light vector fixed mode and the Mueller matrix based on incident light vector dynamic mode can provide an effective analysis method of the existing system.

Enhancing early bladder cancer detection with fluorescence-guided endoscopic optical coherence tomography

NASA Astrophysics Data System (ADS)

Pan, Y. T.; Xie, T. Q.; Du, C. W.; Bastacky, S.; Meyers, S.; Zeidel, M. L.

2003-12-01

We report an experimental study of the possibility of enhancing early bladder cancer diagnosis with fluorescence-image-guided endoscopic optical coherence tomography (OCT). After the intravesical instillation of a 10% solution of 5-aminolevulinic acid, simultaneous fluorescence imaging (excitation of 380-420 nm, emission of 620-700 nm) and OCT are performed on rat bladders to identify the photochemical and morphological changes associated with uroepithelial tumorigenesis. The preliminary results of our ex vivo study reveal that both fluorescence and OCT can identify early uroepithelial cancers, and OCT can detect precancerous lesions (e.g., hyperplasia) that fluorescence may miss. This suggests that a cystoscope combining 5-aminolevulinic acid fluorescence and OCT imaging has the potential to enhance the efficiency and sensitivity of early bladder cancer diagnosis.

Remote air lasing for trace detection

NASA Astrophysics Data System (ADS)

Dogariu, Arthur; Michael, James B.; Miles, Richard B.

2011-05-01

We demonstrate coherent light propagating backwards from a remotely generated high gain air laser. A short ultraviolet laser pulse tuned to a two-photon atomic oxygen electronic resonance at 226 nm simultaneously dissociates the oxygen molecules in air and excites the resulting atomic oxygen fragments. Due to the focal depth of the pumping laser, a millimeter long region of high gain is created in air for the atomic oxygen stimulated emission at 845nm. We demonstrate that the gain in excess of 60 cm-1 is responsible for both forward and backwards emission of a strong, collimated, coherent laser beam. We present evidence for coherent emission and characterize the backscattered laser beam while varying the pumping conditions. The optical gain and directional emission allows for six orders of magnitude enhancement for the backscattered emission when compared with the fluorescence emission collected into the same solid angle. . This opens new opportunities for the remote detection capabilities of trace species, and provides much greater range for the detection of optical molecular and atomic features from a distant target.

Joint OSNR monitoring and modulation format identification in digital coherent receivers using deep neural networks.

PubMed

Khan, Faisal Nadeem; Zhong, Kangping; Zhou, Xian; Al-Arashi, Waled Hussein; Yu, Changyuan; Lu, Chao; Lau, Alan Pak Tao

2017-07-24

We experimentally demonstrate the use of deep neural networks (DNNs) in combination with signals' amplitude histograms (AHs) for simultaneous optical signal-to-noise ratio (OSNR) monitoring and modulation format identification (MFI) in digital coherent receivers. The proposed technique automatically extracts OSNR and modulation format dependent features of AHs, obtained after constant modulus algorithm (CMA) equalization, and exploits them for the joint estimation of these parameters. Experimental results for 112 Gbps polarization-multiplexed (PM) quadrature phase-shift keying (QPSK), 112 Gbps PM 16 quadrature amplitude modulation (16-QAM), and 240 Gbps PM 64-QAM signals demonstrate OSNR monitoring with mean estimation errors of 1.2 dB, 0.4 dB, and 1 dB, respectively. Similarly, the results for MFI show 100% identification accuracy for all three modulation formats. The proposed technique applies deep machine learning algorithms inside standard digital coherent receiver and does not require any additional hardware. Therefore, it is attractive for cost-effective multi-parameter estimation in next-generation elastic optical networks (EONs).

PT-symmetric laser absorber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Longhi, Stefano

2010-09-15

In a recent work, Y. D. Chong et al. [Phys. Rev. Lett. 105, 053901 (2010)] proposed the idea of a coherent perfect absorber (CPA) as the time-reversed counterpart of a laser, in which a purely incoming radiation pattern is completely absorbed by a lossy medium. The optical medium that realizes CPA is obtained by reversing the gain with absorption, and thus it generally differs from the lasing medium. Here it is shown that a laser with an optical medium that satisfies the parity-time (PT) symmetry condition {epsilon}(-r)={epsilon}*(r) for the dielectric constant behaves simultaneously as a laser oscillator (i.e., it canmore » emit outgoing coherent waves) and as a CPA (i.e., it can fully absorb incoming coherent waves with appropriate amplitudes and phases). Such a device can thus be referred to as a PT-symmetric CPA laser. The general amplification or absorption features of the PT CPA laser below lasing threshold driven by two fields are determined.« less

In Vivo Near Infrared Virtual Intraoperative Surgical Photoacoustic Optical Coherence Tomography

PubMed Central

Lee, Donghyun; Lee, Changho; Kim, Sehui; Zhou, Qifa; Kim, Jeehyun; Kim, Chulhong

2016-01-01

Since its first implementation in otolaryngological surgery nearly a century ago, the surgical microscope has improved the accuracy and the safety of microsurgeries. However, the microscope shows only a magnified surface view of the surgical region. To overcome this limitation, either optical coherence tomography (OCT) or photoacoustic microscopy (PAM) has been independently combined with conventional surgical microscope. Herein, we present a near-infrared virtual intraoperative photoacoustic optical coherence tomography (NIR-VISPAOCT) system that combines both PAM and OCT with a conventional surgical microscope. Using optical scattering and absorption, the NIR-VISPAOCT system simultaneously provides surgeons with real-time comprehensive biological information such as tumor margins, tissue structure, and a magnified view of the region of interest. Moreover, by utilizing a miniaturized beam projector, it can back-project 2D cross-sectional PAM and OCT images onto the microscopic view plane. In this way, both microscopic and cross-sectional PAM and OCT images are concurrently displayed on the ocular lens of the microscope. To verify the usability of the NIR-VISPAOCT system, we demonstrate simulated surgeries, including in vivo image-guided melanoma resection surgery and in vivo needle injection of carbon particles into a mouse thigh. The proposed NIR-VISPAOCT system has potential applications in neurosurgery, ophthalmological surgery, and other microsurgeries. PMID:27731390

Real-time optical holographic tracking of multiple objects

NASA Technical Reports Server (NTRS)

Chao, Tien-Hsin; Liu, Hua-Kuang

1989-01-01

A coherent optical correlation technique for real-time simultaneous tracking of several different objects making independent movements is described, and experimental results are presented. An evaluation of this system compared with digital computing systems is made. The real-time processing capability is obtained through the use of a liquid crystal television spatial light modulator and a dichromated gelatin multifocus hololens. A coded reference beam is utilized in the separation of the output correlation plane associated with each input target so that independent tracking can be achieved.

A detailed X-ray investigation of ζ Puppis. IV. Further characterization of the variability

NASA Astrophysics Data System (ADS)

Nazé, Yaël; Ramiaramanantsoa, Tahina; Stevens, Ian R.; Howarth, Ian D.; Moffat, Anthony F. J.

2018-01-01

Context. One of the optically brightest and closest massive stars, ζ Pup, is also a bright X-ray source. Previously, its X-ray emission was found to be variable with light curves harbouring "trends" with a typical timescale longer than the exposure length, i.e. >1 d. The origin of these changes was proposed to be linked to large-scale structures in the wind of ζ Pup, but further characterization of the variability at high energies was needed to investigate this scenario. Aims: Since the previous papers of this series, a number of new X-ray observations have become available. Furthermore, a cyclic behaviour with a 1.78 d period was identified in long optical photometric runs, which is thought to be associated with the launching mechanism of large-scale wind structures. Methods: We analysed these new X-ray data, revisited the old data, and compared the X-ray light curves with the optical data, notably those taken simultaneously. Results: The behaviour of ζ Pup in X-rays cannot be explained in terms of a perfect clock because the amplitude and shape of its variations change with time. For example, ζ Pup was much more strongly variable between 2007 and 2011 than before and after this interval. Comparing the X-ray spectra of the star at maximum and minimum brightness yields no compelling difference beyond the overall flux change: the temperatures, absorptions, and line shapes seem to remain constant, well within errors. The only common feature between X-ray datasets is that the variation amplitudes appear maximum in the medium (0.6-1.2 keV) energy band. Finally, no clear and coherent correlation can be found between simultaneous X-ray and optical data. Only a subgroup of observations may be combined coherently with the optical period of 1.78 d, although the simultaneous optical behaviour is unknown. Conclusions: The currently available data do not reveal any obvious, permanent, and direct correlation between X-ray and optical variations. The origin of the X-ray variability therefore still needs to be ascertained, highlighting the need for long-term monitoring in multiwavelengths, i.e. X-ray, UV, and optical.

x-y curvature wavefront sensor.

PubMed

Cagigal, Manuel P; Valle, Pedro J

2015-04-15

In this Letter, we propose a new curvature wavefront sensor based on the principles of optical differentiation. The theoretically modeled setup consists of a diffractive optical mask placed at the intermediate plane of a classical two-lens coherent optical processor. The resulting image is composed of a number of local derivatives of the entrance pupil function whose proper combination provides the wavefront curvature. In contrast to the common radial curvature sensors, this one is able to provide the x and y wavefront curvature maps simultaneously. The sensor offers other additional advantages like having high spatial resolution, adjustable dynamic range, and not being sensitive to misalignment.

High resolution multiple excitation spot optical microscopy

NASA Astrophysics Data System (ADS)

Dilipkumar, Shilpa; Mondal, Partha Pratim

2011-06-01

We propose fundamental improvements in three-dimensional (3D) resolution of multiple excitation spot optical microscopy. The excitation point spread function (PSF) is generated by two interfering counter-propagating depth-of-focus beams along the optical axis. Detection PSF is obtained by coherently interfering the emitted fluorescent light (collected by both the objectives) at the detector. System PSF shows upto 14-fold reduction in focal volume as compared to confocal, and almost 2-fold improvement in lateral resolution. Proposed PSF has the ability to simultaneously excite multiple 3D-spots of sub-femtoliter volume. Potential applications are in fluorescence microscopy and nanobioimaging.

Phase-locking and coherent power combining of broadband linearly chirped optical waves.

PubMed

Satyan, Naresh; Vasilyev, Arseny; Rakuljic, George; White, Jeffrey O; Yariv, Amnon

2012-11-05

We propose, analyze and demonstrate the optoelectronic phase-locking of optical waves whose frequencies are chirped continuously and rapidly with time. The optical waves are derived from a common optoelectronic swept-frequency laser based on a semiconductor laser in a negative feedback loop, with a precisely linear frequency chirp of 400 GHz in 2 ms. In contrast to monochromatic waves, a differential delay between two linearly chirped optical waves results in a mutual frequency difference, and an acoustooptic frequency shifter is therefore used to phase-lock the two waves. We demonstrate and characterize homodyne and heterodyne optical phase-locked loops with rapidly chirped waves, and show the ability to precisely control the phase of the chirped optical waveform using a digital electronic oscillator. A loop bandwidth of ~ 60 kHz, and a residual phase error variance of < 0.01 rad(2) between the chirped waves is obtained. Further, we demonstrate the simultaneous phase-locking of two optical paths to a common master waveform, and the ability to electronically control the resultant two-element optical phased array. The results of this work enable coherent power combining of high-power fiber amplifiers-where a rapidly chirping seed laser reduces stimulated Brillouin scattering-and electronic beam steering of chirped optical waves.

Coherent Femtosecond Spectroscopy and Nonlinear Optical Imaging on the Nanoscale

NASA Astrophysics Data System (ADS)

Kravtsov, Vasily

Optical properties of many materials and macroscopic systems are defined by ultrafast dynamics of electronic, vibrational, and spin excitations localized on the nanoscale. Harnessing these excitations for material engineering, optical computing, and control of chemical reactions has been a long-standing goal in science and technology. However, it is challenging due to the lack of spectroscopic techniques that can resolve processes simultaneously on the nanometer spatial and femtosecond temporal scales. This thesis describes the fundamental principles, implementation, and experimental demonstration of a novel type of ultrafast microscopy based on the concept of adiabatic plasmonic nanofocusing. Simultaneous spatio-temporal resolution on a nanometer-femtosecond scale is achieved by using a near-field nonlinear optical response induced by ultrafast surface plasmon polaritons nanofocused on a metal tip. First, we study the surface plasmon response in metallic structures and evaluate its prospects and limitations for ultrafast near-field microscopy. Through plasmon emission-based spectroscopy, we investigate dephasing times and interplay between radiative and non-radiative decay rates of localized plasmons and their modification due to coupling. We identify a new regime of quantum plasmonic coupling, which limits the achievable spatial resolution to several angstroms but at the same time provides a potential channel for generating ultrafast electron currents at optical frequencies. Next, we study propagation of femtosecond wavepackets of surface plasmon polaritons on a metal tip. In time-domain interferometric measurements we detect group delays that correspond to slowing of the plasmon polaritons down to 20% of the speed of light at the tip apex. This provides direct experimental verification of the plasmonic nanofocusing mechanism and suggests enhanced nonlinear optical interactions at the tip apex. We then measure a plasmon-generated third-order nonlinear optical four-wave mixing response from the tip apex and investigate its microscopic mechanism. Our results reveal a significant contribution to the third order nonlinearity of plasmonic structures due to large near-field gradients associated with nanofocused plasmons. In combination with scanning probe imaging and femtosecond pulse shaping, the nanofocused four-wave mixing response provides a basis for a novel type of ultrafast optical microscopy on the nanoscale. We demonstrate its capabilities by nano-imaging the coherent dynamics of localized plasmonic modes in a rough gold film edge with simultaneous sub-50 nm spatial and sub-5 fs temporal resolution. We capture the coherent decay and extract the dephasing times of individual plasmonic modes. Lastly, we apply our technique to study nanoscale spatial heterogeneity of the nonlinear optical response in novel two-dimensional materials: monolayer and few-layer graphene. An enhanced four-wave mixing signal is revealed on the edges of graphene flakes. We investigate the mechanism of this enhancement by performing nano-imaging on a graphene field-effect transistor with the variable carrier density controlled by electrostatic gating.

Coherent cavity-enhanced dual-comb spectroscopy

PubMed Central

Fleisher, Adam J.; Long, David A.; Reed, Zachary D.; Hodges, Joseph T.; Plusquellic, David F.

2016-01-01

Dual-comb spectroscopy allows for the rapid, multiplexed acquisition of high-resolution spectra without the need for moving parts or low-resolution dispersive optics. This method of broadband spectroscopy is most often accomplished via tight phase locking of two mode-locked lasers or via sophisticated signal processing algorithms, and therefore, long integration times of phase coherent signals are difficult to achieve. Here we demonstrate an alternative approach to dual-comb spectroscopy using two phase modulator combs originating from a single continuous-wave laser capable of > 2 hours of coherent real-time averaging. The dual combs were generated by driving the phase modulators with step-recovery diodes where each comb consisted of > 250 teeth with 203 MHz spacing and spanned > 50 GHz region in the near-infrared. The step-recovery diodes are passive devices that provide low-phase-noise harmonics for efficient coupling into an enhancement cavity at picowatt optical powers. With this approach, we demonstrate the sensitivity to simultaneously monitor ambient levels of CO2, CO, HDO, and H2O in a single spectral region at a maximum acquisition rate of 150 kHz. Robust, compact, low-cost and widely tunable dual-comb systems could enable a network of distributed multiplexed optical sensors. PMID:27409866

Techniques of noninvasive optical tomographic imaging

NASA Astrophysics Data System (ADS)

Rosen, Joseph; Abookasis, David; Gokhler, Mark

2006-01-01

Recently invented methods of optical tomographic imaging through scattering and absorbing media are presented. In one method, the three-dimensional structure of an object hidden between two biological tissues is recovered from many noisy speckle pictures obtained on the output of a multi-channeled optical imaging system. Objects are recovered from many speckled images observed by a digital camera through two stereoscopic microlens arrays. Each microlens in each array generates a speckle image of the object buried between the layers. In the computer each image is Fourier transformed jointly with an image of the speckled point-like source captured under the same conditions. A set of the squared magnitudes of the Fourier-transformed pictures is accumulated to form a single average picture. This final picture is again Fourier transformed, resulting in the three-dimensional reconstruction of the hidden object. In the other method, the effect of spatial longitudinal coherence is used for imaging through an absorbing layer with different thickness, or different index of refraction, along the layer. The technique is based on synthesis of multiple peak spatial degree of coherence. This degree of coherence enables us to scan simultaneously different sample points on different altitudes, and thus decreases the acquisition time. The same multi peak degree of coherence is also used for imaging through the absorbing layer. Our entire experiments are performed with a quasi-monochromatic light source. Therefore problems of dispersion and inhomogeneous absorption are avoided.

Achromatic registration of quadrature components of the optical spectrum in spectral domain optical coherence tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shilyagin, P A; Gelikonov, G V; Gelikonov, V M

2014-07-31

We have thoroughly investigated the method of simultaneous reception of spectral components with the achromatised quadrature phase shift between two portions of a reference wave, designed for the effective suppression of the 'mirror' artefact in the resulting image obtained by means of spectral domain optical coherence tomography (SD OCT). We have developed and experimentally tested a phase-shifting element consisting of a beam divider, which splits the reference optical beam into the two beams, and of delay lines being individual for each beam, which create a mutual phase difference of π/2 in the double pass of the reference beam. The phasemore » shift achromatism over a wide spectral range is achieved by using in the delay lines the individual elements with different dispersion characteristics. The ranges of admissible adjustment parameters of the achromatised delay line are estimated for exact and inexact conformity of the geometric characteristics of its components to those calculated. A possibility of simultaneous recording of the close-to-quadrature spectral components with a single linear photodetector element is experimentally confirmed. The suppression of the artefact mirror peak in the OCT-signal by an additional 9 dB relative to the level of its suppression is experimentally achieved when the air delay line is used. Two-dimensional images of the surface positioned at an angle to the axis of the probe beam are obtained with the correction of the 'mirror' artefact while maintaining the dynamic range of the image. (laser biophotonics)« less

Optical coherence tomography angiography offers comprehensive evaluation of skin optical clearing in vivo by quantifying optical properties and blood flow imaging simultaneously

NASA Astrophysics Data System (ADS)

Guo, Li; Shi, Rui; Zhang, Chao; Zhu, Dan; Ding, Zhihua; Li, Peng

2016-08-01

Tissue optical clearing (TOC) is helpful for reducing scattering and enhancing the penetration depth of light, and shows promising potential in optimizing optical imaging performances. A mixture of fructose with PEG-400 and thiazone (FPT) is used as an optical clearing agent in mouse dorsal skin and evaluated with OCT angiography (Angio-OCT) by quantifying optical properties and blood flow imaging simultaneously. It is observed that FPT leads to an improved imaging performance for the deeper tissues. The imaging performance improvement is most likely caused by the FPT-induced dehydration of skin, and the reduction of scattering coefficient (more than ˜40.5%) and refractive-index mismatching (more than ˜25.3%) in the superficial (epidermal, dermal, and hypodermal) layers. A high correlation (up to ˜90%) between the relative changes in refractive-index mismatching and Angio-OCT signal strength is measured. The optical clearing rate is ˜5.83×10-5 cm/s. In addition, Angio-OCT demonstrates enhanced performance in imaging cutaneous hemodynamics with satisfactory spatiotemporal resolution and contrast when combined with TOC, which exhibits a powerful practical application in studying microcirculation.

Simultaneous real-time quantification of blood flow and vascular growth in the chick embryo using optical coherence tomography

NASA Astrophysics Data System (ADS)

Kowalski, William J.; Teslovich, Nikola C.; Chen, Chia-Yuan; Keller, Bradley B.; Pekkan, Kerem

2014-03-01

Experimental and clinical data indicate that hemodynamic forces within the embryo provide critical biomechanical cues for cardiovascular morphogenesis, growth, and remodeling and that perturbed flow is a major etiology of congenital heart disease. However, embryonic flow-growth relationships are largely qualitative and poorly defined. In this work, we provide a quantitative analysis of in vivo flow and growth trends in the chick embryo using optical coherence tomography (OCT) to acquire simultaneous velocity and structural data of the right vitelline artery continuously over a ten hour period beginning at stage 16 (hour 54). We obtained 3D vessel volumes (15 μm lateral, 4.3 μm axial resolutions, 6 μm slice spacing) at 60 minute intervals, taking a B-scan time series totaling one cardiac cycle at each slice. Embryos were maintained at a constant 37°C and 60% humidity during the entire acquisition period through an inhouse built chamber. The 3D vessel lumen geometries were reconstructed manually to assess growth. Blood flow velocity was computed from the central B-scan using red blood cell particle image velocimetry. The use of extended OCT imaging as a non-invasive method for continuous and simultaneous flow and structural data can enhance our understanding of the biomechanical regulation of critical events in morphogenesis. Data acquired will be useful to validate predictive finite-element 3D growth models.

Dispersion-based stimulated Raman scattering spectroscopy, holography, and optical coherence tomography

PubMed Central

Robles, Francisco E.; Fischer, Martin C.; Warren, Warren S.

2016-01-01

Stimulated Raman scattering (SRS) enables fast, high resolution imaging of chemical constituents important to biological structures and functional processes, both in a label-free manner and using exogenous biomarkers. While this technology has shown remarkable potential, it is currently limited to point scanning and can only probe a few Raman bands at a time (most often, only one). In this work we take a fundamentally different approach to detecting the small nonlinear signals based on dispersion effects that accompany the loss/gain processes in SRS. In this proof of concept, we demonstrate that the dispersive measurements are more robust to noise compared to amplitude-based measurements, which then permit spectral or spatial multiplexing (potentially both, simultaneously). Finally, we illustrate how this method may enable different strategies for biochemical imaging using phase microscopy and optical coherence tomography. PMID:26832279

In vivo imaging of human labial glands using advanced optical coherence tomography.

PubMed

Ozawa, Nobuyoshi; Sumi, Yasunori; Shimozato, Kazuo; Chong, Changho; Kurabayashi, Tohru

2009-09-01

Optical coherence tomography (OCT) has emerged as a high-resolution noninvasive clinical imaging application. The purpose of this study was to show OCT images of human labial glands obtained using a swept-source (SS) OCT system. Labial gland OCT imaging was carried out using our new SS-OCT system for 5 healthy volunteers using a hand-held in vivo OCT scanning probe. The labial tissue was scanned in a superior to inferior direction in 2 and 3 dimensions. The resulting 2- and 3-dimensional ultrahigh-resolution images of in vivo OCT human labial minor salivary glands revealed the epithelium, connective tissue, lobes, and duct. OCT was capable of providing simultaneous and noninvasive structural information with high resolution. This clinical imaging modality promises to have clinical impact in the diagnosis of such conditions as Sjögren syndrome and xerostomia.

Flexible needle with integrated optical coherence tomography probe for imaging during transbronchial tissue aspiration

NASA Astrophysics Data System (ADS)

Li, Jiawen; Quirk, Bryden C.; Noble, Peter B.; Kirk, Rodney W.; Sampson, David D.; McLaughlin, Robert A.

2017-10-01

Transbronchial needle aspiration (TBNA) of small lesions or lymph nodes in the lung may result in nondiagnostic tissue samples. We demonstrate the integration of an optical coherence tomography (OCT) probe into a 19-gauge flexible needle for lung tissue aspiration. This probe allows simultaneous visualization and aspiration of the tissue. By eliminating the need for insertion and withdrawal of a separate imaging probe, this integrated design minimizes the risk of dislodging the needle from the lesion prior to aspiration and may facilitate more accurate placement of the needle. Results from in situ imaging in a sheep lung show clear distinction between solid tissue and two typical constituents of nondiagnostic samples (adipose and lung parenchyma). Clinical translation of this OCT-guided aspiration needle holds promise for improving the diagnostic yield of TBNA.

All-diamond optical assemblies for a beam-multiplexing X-ray monochromator at the Linac Coherent Light Source

PubMed Central

Stoupin, S.; Terentyev, S. A.; Blank, V. D.; Shvyd’ko, Yu. V.; Goetze, K.; Assoufid, L.; Polyakov, S. N.; Kuznetsov, M. S.; Kornilov, N. V.; Katsoudas, J.; Alonso-Mori, R.; Chollet, M.; Feng, Y.; Glownia, J. M.; Lemke, H.; Robert, A.; Sikorski, M.; Song, S.; Zhu, D.

2014-01-01

A double-crystal diamond (111) monochromator recently implemented at the Linac Coherent Light Source (LCLS) enables splitting of the primary X-ray beam into a pink (transmitted) and a monochromatic (reflected) branch. The first monochromator crystal, with a thickness of ∼100 µm, provides sufficient X-ray transmittance to enable simultaneous operation of two beamlines. This article reports the design, fabrication and X-ray characterization of the first and second (300 µm-thick) crystals utilized in the monochromator and the optical assemblies holding these crystals. Each crystal plate has a region of about 5 × 2 mm with low defect concentration, sufficient for use in X-ray optics at the LCLS. The optical assemblies holding the crystals were designed to provide mounting on a rigid substrate and to minimize mounting-induced crystal strain. The induced strain was evaluated using double-crystal X-ray topography and was found to be small over the 5 × 2 mm working regions of the crystals. PMID:25242912

Label-free optical lymphangiography: development of an automatic segmentation method applied to optical coherence tomography to visualize lymphatic vessels using Hessian filters

PubMed Central

Yousefi, Siavash; Qin, Jia; Zhi, Zhongwei

2013-01-01

Abstract. Lymphatic vessels are a part of the circulatory system that collect plasma and other substances that have leaked from the capillaries into interstitial fluid (lymph) and transport lymph back to the circulatory system. Since lymph is transparent, lymphatic vessels appear as dark hallow vessel-like regions in optical coherence tomography (OCT) cross sectional images. We propose an automatic method to segment lymphatic vessel lumen from OCT structural cross sections using eigenvalues of Hessian filters. Compared to the existing method based on intensity threshold, Hessian filters are more selective on vessel shape and less sensitive to intensity variations and noise. Using this segmentation technique along with optical micro-angiography allows label-free noninvasive simultaneous visualization of blood and lymphatic vessels in vivo. Lymphatic vessels play an important role in cancer, immune system response, inflammatory disease, wound healing and tissue regeneration. Development of imaging techniques and visualization tools for lymphatic vessels is valuable in understanding the mechanisms and studying therapeutic methods in related disease and tissue response. PMID:23922124

Coherent Backscattering and Opposition Effects Observed in Some Atmosphereless Bodies of the Solar System

NASA Technical Reports Server (NTRS)

Dlugach, Zh. M.; Mishchenko, M. I.

2013-01-01

The results of photometric and polarimetric observations carried out for some bright atmosphere-less bodies of the Solar system near the zero phase angle reveal the simultaneous existence of two spectacular optical phenomena, the so-called brightness and polarization opposition effects. In a number of studies, these phenomena were explained by the influence of coherent backscattering. However, in general, the interference concept of coherent backscattering can be used only in the case where the particles are in the far-field zones of each other, i.e., when the scattering medium is rather rarefied. Because of this, it is important to prove rigorously and to demonstrate that the coherent backscattering effect may also exist in densely packed scattering media like regolith surface layers of celestial bodies. From the results of the computer modeling performed with the use of numerically exact solutions of the macroscopic Maxwell equations for discrete random media with different packing densities of particles, we studied the origin and evolution of all the opposition phenomena predicted by the coherent backscattering theory for low-packing-density media. It has been shown that the predictions of this theory remain valid for rather high-packing densities of particles that are typical, in particular, of regolith surfaces of the Solar system bodies. The results allow us to conclude that both opposition effects observed simultaneously in some high-albedo atmosphereless bodies of the Solar system are caused precisely by coherent backscattering of solar light in the regolith layers composed of microscopic particles.

On the possibility of producing true real-time retinal cross-sectional images using a graphics processing unit enhanced master-slave optical coherence tomography system.

PubMed

Bradu, Adrian; Kapinchev, Konstantin; Barnes, Frederick; Podoleanu, Adrian

2015-07-01

In a previous report, we demonstrated master-slave optical coherence tomography (MS-OCT), an OCT method that does not need resampling of data and can be used to deliver en face images from several depths simultaneously. In a separate report, we have also demonstrated MS-OCT's capability of producing cross-sectional images of a quality similar to those provided by the traditional Fourier domain (FD) OCT technique, but at a much slower rate. Here, we demonstrate that by taking advantage of the parallel processing capabilities offered by the MS-OCT method, cross-sectional OCT images of the human retina can be produced in real time. We analyze the conditions that ensure a true real-time B-scan imaging operation and demonstrate in vivo real-time images from human fovea and the optic nerve, with resolution and sensitivity comparable to those produced using the traditional FD-based method, however, without the need of data resampling.

In vivo oral imaging with integrated portable photoacoustic microscopy and optical coherence tomography

NASA Astrophysics Data System (ADS)

Qin, Wei; Qi, Weizhi; Jin, Tian; Guo, Heng; Xi, Lei

2017-12-01

Oral diseases, especially oral cancers, are becoming serious health problems in humans. To image vasculatures and structures simultaneously in the human oral cavity which are tightly associated with various oral diseases, we develop a dual-modality portable optical resolution photoacoustic microscopy (ORPAM) and optical coherence tomography (OCT) system. This system utilizes a new rotary scanning mechanism and a compact design of the imaging head, making it portable and free of translation of the imaging interface or samples. Through the phantom experiments, both modalities yield high lateral resolutions of 8.1 μm (ORPAM) and 8.56 μm (OCT), respectively. The axial resolutions are measured to be 116.5 μm for ORPAM and 6.1 μm for OCT. In vivo imaging of a mouse ear was carried out to evaluate the performance of the system in biological tissues. In addition, in vivo oral imaging of a healthy human lip and monitoring recovery progress of a lip ulcer demonstrate the clinical potential of this system.

Fluorescence-based surface magnifying chromoendoscopy and optical coherence tomography endoscope

NASA Astrophysics Data System (ADS)

Wall, R. Andrew; Barton, Jennifer K.

2012-02-01

A side-viewing, 2 mm diameter, surface magnifying chromoendoscopy (SMC)-optical coherence tomography (OCT) endoscope has been designed for simultaneous, non-destructive surface fluorescence visualization and cross-sectional imaging. We apply this endoscope to in vivo examination of mouse colon. A 30,000 element fiber bundle is combined with single mode fibers. The distal optics consist of a gradient-index lens and spacer to provide a magnification of 1 at a working distance of 1.58 mm in air, necessary to image the sample through a 0.23 mm thick outer glass envelope, and an aluminized right-angle prism fixed to the distal end of the GRIN lens assembly. The resulting 1:1 imaging system is capable of 3.9 μm lateral and 2.3 μm axial resolution in the OCT channel, and 125 lp/mm resolution across a 0.70 mm field of view in the SMC channel. The endoscope can perform high contrast crypt visualization, molecular imaging, and cross-sectional imaging of colon microstructure.

Spectral domain optical coherence tomography of multi-MHz A-scan rates at 1310 nm range and real-time 4D-display up to 41 volumes/second

PubMed Central

Choi, Dong-hak; Hiro-Oka, Hideaki; Shimizu, Kimiya; Ohbayashi, Kohji

2012-01-01

An ultrafast frequency domain optical coherence tomography system was developed at A-scan rates between 2.5 and 10 MHz, a B-scan rate of 4 or 8 kHz, and volume-rates between 12 and 41 volumes/second. In the case of the worst duty ratio of 10%, the averaged A-scan rate was 1 MHz. Two optical demultiplexers at a center wavelength of 1310 nm were used for linear-k spectral dispersion and simultaneous differential signal detection at 320 wavelengths. The depth-range, sensitivity, sensitivity roll-off by 6 dB, and axial resolution were 4 mm, 97 dB, 6 mm, and 23 μm, respectively. Using FPGAs for FFT and a GPU for volume rendering, a real-time 4D display was demonstrated at a rate up to 41 volumes/second for an image size of 256 (axial) × 128 × 128 (lateral) voxels. PMID:23243560

Early simultaneous fundus autofluorescence and optical coherence tomography features after pars plana vitrectomy for primary rhegmatogenous retinal detachment.

PubMed

Dell'Omo, Roberto; Mura, Marco; Lesnik Oberstein, Sarit Y; Bijl, Heico; Tan, H Stevie

2012-04-01

To describe fundus autofluorescence and optical coherence tomography (OCT) features of the macula after pars plana vitrectomy for rhegmatogenous retinal detachment. Thirty-three eyes of 33 consecutive patients with repaired rhegmatogenous retinal detachment with or without the involvement of the macula were prospectively investigated with simultaneous fundus autofluorescence and OCT imaging using the Spectralis HRA+OCT (Heidelberg Engineering, Heidelberg, Germany) within a few weeks after the operation. Fundus autofluorescence imaging of the macula showed lines of increased and decreased autofluorescence in 19 cases (57.6%). On OCT, these lines corresponded to the following abnormalities: outer retinal folds, inner retinal folds, and skip reflectivity abnormalities of the photoreceptor inner segment/outer segment band. Other OCT findings, not related to abnormal lines on fundus autofluorescence, consisted of disruption of photoreceptor inner segment/outer segment band and collection of intraretinal or subretinal fluid. The presence of outer retinal folds significantly related to metamorphopsia but did not relate to poor postoperative visual acuity. Partial-thickness retinal folds occur commonly after vitrectomy for rhegmatogenous retinal detachment repair and may represent an important anatomical substrate for postoperative metamorphopsia. Fundus autofluorescence and OCT are both sensitive techniques for the detection of these abnormalities.

Simultaneous confocal fluorescence microscopy and optical coherence tomography for drug distribution and tissue integrity assessment

NASA Astrophysics Data System (ADS)

Rinehart, Matthew T.; LaCroix, Jeffrey; Henderson, Marcus; Katz, David; Wax, Adam

2011-03-01

The effectiveness of microbicidal gels, topical products developed to prevent infection by sexually transmitted diseases including HIV/AIDS, is governed by extent of gel coverage, pharmacokinetics of active pharmaceutical ingredients (APIs), and integrity of vaginal epithelium. While biopsies provide localized information about drug delivery and tissue structure, in vivo measurements are preferable in providing objective data on API and gel coating distribution as well as tissue integrity. We are developing a system combining confocal fluorescence microscopy with optical coherence tomography (OCT) to simultaneously measure local concentrations and diffusion coefficients of APIs during transport from microbicidal gels into tissue, while assessing tissue integrity. The confocal module acquires 2-D images of fluorescent APIs multiple times per second allowing analysis of lateral diffusion kinetics. The custom Fourier domain OCT module has a maximum a-scan rate of 54 kHz and provides depth-resolved tissue integrity information coregistered with the confocal fluorescence measurements. The combined system is validated by imaging phantoms with a surrogate fluorophore. Time-resolved API concentration measured at fixed depths is analyzed for diffusion kinetics. This multimodal system will eventually be implemented in vivo for objective evaluation of microbicide product performance.

Nonlinear intermodulation distortion suppression in coherent analog fiber optic link using electro-optic polymeric dual parallel Mach-Zehnder modulator.

PubMed

Kim, Seong-Ku; Liu, Wei; Pei, Qibing; Dalton, Larry R; Fetterman, Harold R

2011-04-11

A linearized dual parallel Mach-Zehnder modulator (DPMZM) based on electro-optic (EO) polymer was both fabricated, and experimentally used to suppress the third-order intermodulation distortion (IMD3) in a coherent analog fiber optic link. This optical transmitter design was based on a new EO chromophore called B10, which was synthesized for applications dealing with the fiber-optic communication systems. The chromophore was mixed with amorphous polycarbonate (APC) to form the waveguide's core material. The DPMZM was configured with two MZMs, of different lengths in parallel, with unbalanced input and output couplers and a phase shifter in one arm. In this configuration each of the MZMs carried a different optical power, and imposed a different depth of optical modulation. When the two optical beams from the MZMs were combined to generate the transmitted signal it was possible to set the IMD3 produced by each modulator to be equal in amplitude but 180° out of phase from the other. Therefore, the resulting IMD3 of the DPMZM transmitter was effectively canceled out during two-tone experiments. A reduction of the IMD3 below the noise floor was observed while leaving fifth-order distortion (IMD5) as the dominant IMD product. This configuration has the capability of broadband operation and shot-noise limited operation simultaneously. © 2011 Optical Society of America

A Hierarchical Modulation Coherent Communication Scheme for Simultaneous Four-State Continuous-Variable Quantum Key Distribution and Classical Communication

NASA Astrophysics Data System (ADS)

Yang, Can; Ma, Cheng; Hu, Linxi; He, Guangqiang

2018-06-01

We present a hierarchical modulation coherent communication protocol, which simultaneously achieves classical optical communication and continuous-variable quantum key distribution. Our hierarchical modulation scheme consists of a quadrature phase-shifting keying modulation for classical communication and a four-state discrete modulation for continuous-variable quantum key distribution. The simulation results based on practical parameters show that it is feasible to transmit both quantum information and classical information on a single carrier. We obtained a secure key rate of 10^{-3} bits/pulse to 10^{-1} bits/pulse within 40 kilometers, and in the meantime the maximum bit error rate for classical information is about 10^{-7}. Because continuous-variable quantum key distribution protocol is compatible with standard telecommunication technology, we think our hierarchical modulation scheme can be used to upgrade the digital communication systems to extend system function in the future.

Reflective afocal broadband adaptive optics scanning ophthalmoscope

PubMed Central

Dubra, Alfredo; Sulai, Yusufu

2011-01-01

A broadband adaptive optics scanning ophthalmoscope (BAOSO) consisting of four afocal telescopes, formed by pairs of off-axis spherical mirrors in a non-planar arrangement, is presented. The non-planar folding of the telescopes is used to simultaneously reduce pupil and image plane astigmatism. The former improves the adaptive optics performance by reducing the root-mean-square (RMS) of the wavefront and the beam wandering due to optical scanning. The latter provides diffraction limited performance over a 3 diopter (D) vergence range. This vergence range allows for the use of any broadband light source(s) in the 450-850 nm wavelength range to simultaneously image any combination of retinal layers. Imaging modalities that could benefit from such a large vergence range are optical coherence tomography (OCT), multi- and hyper-spectral imaging, single- and multi-photon fluorescence. The benefits of the non-planar telescopes in the BAOSO are illustrated by resolving the human foveal photoreceptor mosaic in reflectance using two different superluminescent diodes with 680 and 796 nm peak wavelengths, reaching the eye with a vergence of 0.76 D relative to each other. PMID:21698035

Reflective afocal broadband adaptive optics scanning ophthalmoscope.

PubMed

Dubra, Alfredo; Sulai, Yusufu

2011-06-01

A broadband adaptive optics scanning ophthalmoscope (BAOSO) consisting of four afocal telescopes, formed by pairs of off-axis spherical mirrors in a non-planar arrangement, is presented. The non-planar folding of the telescopes is used to simultaneously reduce pupil and image plane astigmatism. The former improves the adaptive optics performance by reducing the root-mean-square (RMS) of the wavefront and the beam wandering due to optical scanning. The latter provides diffraction limited performance over a 3 diopter (D) vergence range. This vergence range allows for the use of any broadband light source(s) in the 450-850 nm wavelength range to simultaneously image any combination of retinal layers. Imaging modalities that could benefit from such a large vergence range are optical coherence tomography (OCT), multi- and hyper-spectral imaging, single- and multi-photon fluorescence. The benefits of the non-planar telescopes in the BAOSO are illustrated by resolving the human foveal photoreceptor mosaic in reflectance using two different superluminescent diodes with 680 and 796 nm peak wavelengths, reaching the eye with a vergence of 0.76 D relative to each other.

Advanced Instrumentation for Aero Engine Components: Conference Proceedings of the Propulsion and Energetics Panel Symposium (67th) Held in Philadelphia, Pennsylvania on 19-23 May 1986.

DTIC Science & Technology

1986-11-01

optical wave-mixing am., interact via the third order non linear susceptibility of the medium to produce a coherent laser-like signal beam at the higher...is the third order non- linear susceptibility of the medium and determines the shape of the CARS spectrum. It is the sum of a resonant contribution and...simultaneously using an appropriate spectrograph/optical multichannel detector; intensified linear diode array detectors are now used in most systems. The two

Coherent Raman detected electron spin resonance spectroscopy of metalloproteins: linking electron spin resonance and magnetic circular dichroism.

PubMed

Bingham, Stephen J; Wolverson, Daniel; Thomson, Andrew J

2008-12-01

The simultaneous excitation of paramagnetic molecules with optical (laser) and microwave radiation in the presence of a magnetic field can cause an amplitude, or phase, modulation of the transmitted light at the microwave frequency. The detection of this modulation indicates the presence of coupled optical and ESR transitions. The phenomenon can be viewed as a coherent Raman effect or, in most cases, as a microwave frequency modulation of the magnetic circular dichroism by the precessing magnetization. By allowing the optical and magnetic properties of a transition metal ion centre to be correlated, it becomes possible to deconvolute the overlapping optical or ESR spectra of multiple centres in a protein or of multiple chemical forms of a particular centre. The same correlation capability also allows the relative orientation of the magnetic and optical anisotropies of each species to be measured, even when the species cannot be obtained in a crystalline form. Such measurements provide constraints on electronic structure calculations. The capabilities of the method are illustrated by data from the dimeric mixed-valence Cu(A) centre of nitrous oxide reductase (N(2)OR) from Paracoccus pantotrophus.

Truly simultaneous SS-OCT of the anterior and posterior human eye with full anterior chamber and 50° retinal field of views (Conference Presentation)

NASA Astrophysics Data System (ADS)

McNabb, Ryan P.; Viehland, Christian; Keller, Brenton; Vann, Robin R.; Izatt, Joseph A.; Kuo, Anthony N.

2017-02-01

Optical coherence tomography (OCT) has revolutionized clinical observation of the eye and is an indispensable part of the modern ophthalmic practice. Unlike many other ophthalmic imaging techniques, OCT provides three-dimensional information about the imaged eye. However, conventional clinical OCT systems image only the anterior or the posterior eye during a single acquisition. Newer OCT systems have begun to image both during the same acquisition but with compromises such as limited field of view in the posterior eye or requiring rapid switching between the anterior and posterior eye during the scan. We describe here the development and demonstration of an OCT system with truly simultaneous imaging of both the anterior and posterior eye capable of imaging the full anterior chamber width and 50° on the retina (macula, optic nerve, and arcades). The whole eye OCT system was developed using custom optics and optomechanics. Polarization was utilized to separate the imaging channels. We utilized a 200kHz swept-source laser (Axsun Technologies) centered at 1040±50nm of bandwidth. The clock signal generated by the laser was interpolated 4x to generate 5504 samples per laser sweep. With the whole eye OCT system, we simultaneously acquired anterior and posterior segments with repeated B-scans as well as three-dimensional volumes from seven healthy volunteers (other than refractive error). On three of these volunteers, whole eye OCT and partial coherence interferometry (LenStar PCI, Haag-Streit) were used to measure axial eye length. We measured a mean repeatability of ±47µm with whole eye OCT and a mean difference from PCI of -68µm.

Coherent cavity-enhanced dual-comb spectroscopy.

PubMed

Fleisher, Adam J; Long, David A; Reed, Zachary D; Hodges, Joseph T; Plusquellic, David F

2016-05-16

Dual-comb spectroscopy allows for the rapid, multiplexed acquisition of high-resolution spectra without the need for moving parts or low-resolution dispersive optics. This method of broadband spectroscopy is most often accomplished via tight phase locking of two mode-locked lasers or via sophisticated signal processing algorithms, and therefore, long integration times of phase coherent signals are difficult to achieve. Here we demonstrate an alternative approach to dual-comb spectroscopy using two phase modulator combs originating from a single continuous-wave laser capable of > 2 hours of coherent real-time averaging. The dual combs were generated by driving the phase modulators with step-recovery diodes where each comb consisted of > 250 teeth with 203 MHz spacing and spanned > 50 GHz region in the near-infrared. The step-recovery diodes are passive devices that provide low-phase-noise harmonics for efficient coupling into an enhancement cavity at picowatt optical powers. With this approach, we demonstrate the sensitivity to simultaneously monitor ambient levels of CO₂, CO, HDO, and H₂O in a single spectral region at a maximum acquisition rate of 150 kHz. Robust, compact, low-cost and widely tunable dual-comb systems could enable a network of distributed multiplexed optical sensors.

Array-type miniature interferometer as the core optical microsystem of an optical coherence tomography device for tissue inspection

NASA Astrophysics Data System (ADS)

Passilly, Nicolas; Perrin, Stéphane; Lullin, Justine; Albero, Jorge; Bargiel, Sylwester; Froehly, Luc; Gorecki, Christophe; Krauter, Johann; Osten, Wolfgang; Wang, Wei-Shan; Wiemer, Maik

2016-04-01

Some of the critical limitations for widespread use in medical applications of optical devices, such as confocal or optical coherence tomography (OCT) systems, are related to their cost and large size. Indeed, although quite efficient systems are available on the market, e.g. in dermatology, they equip only a few hospitals and hence, are far from being used as an early detection tool, for instance in screening of patients for early detection of cancers. In this framework, the VIAMOS project aims at proposing a concept of miniaturized, batch-fabricated and lower-cost, OCT system dedicated to non-invasive skin inspection. In order to image a large skin area, the system is based on a full-field approach. Moreover, since it relies on micro-fabricated devices whose fields of view are limited, 16 small interferometers are arranged in a dense array to perform multi-channel simultaneous imaging. Gaps between each channel are then filled by scanning of the system followed by stitching. This approach allows imaging a large area without the need of large optics. It also avoids the use of very fast and often expensive laser sources, since instead of a single point detector, almost 250 thousands pixels are used simultaneously. The architecture is then based on an array of Mirau interferometers which are interesting for their vertical arrangement compatible with vertical assembly at the wafer-level. Each array is consequently a local part of a stack of seven wafers. This stack includes a glass lens doublet, an out-of-plane actuated micro-mirror for phase shifting, a spacer and a planar beam-splitter. Consequently, different materials, such as silicon and glass, are bonded together and well-aligned thanks to lithographic-based fabrication processes.

Towards combined optical coherence tomography and hyper-spectral imaging for gastrointestinal endoscopy

NASA Astrophysics Data System (ADS)

Attendu, Xavier; Crunelle, Camille; de Sivry-Houle, Martin Poinsinet; Maubois, Billie; Urbain, Joanie; Turrell, Chloe; Strupler, Mathias; Godbout, Nicolas; Boudoux, Caroline

2018-04-01

Previous works have demonstrated feasibility of combining optical coherence tomography (OCT) and hyper-spectral imaging (HSI) through a single double-clad fiber (DCF). In this proceeding we present the continued development of a system combining both modalities and capable of rapid imaging. We discuss the development of a rapidly scanning, dual-band, polygonal swept-source system which combines NIR (1260-1340 nm) and visible (450-800 nm) wavelengths. The NIR band is used for OCT imaging while visible light allows HSI. Scanning rates up to 24 kHz are reported. Furthermore, we present and discuss the fiber system used for light transport, delivery and collection, and the custom signal acquisition software. Key points include the use of a double-clad fiber coupler as well as important alignments and back-reflection management. Simultaneous and co-registered imaging with both modalities is presented in a bench-top system

Measurement of shear-induced diffusion of red blood cells using dynamic light scattering-optical coherence tomography

NASA Astrophysics Data System (ADS)

Tang, Jianbo; Erdener, Sefik Evren; Li, Baoqiang; Fu, Buyin; Sakadzic, Sava; Carp, Stefan A.; Lee, Jonghwan; Boas, David A.

2018-02-01

Dynamic Light Scattering-Optical Coherence Tomography (DLS-OCT) takes the advantages of using DLS to measure particle flow and diffusion within an OCT resolution-constrained 3D volume, enabling the simultaneous measurements of absolute RBC velocity and diffusion coefficient with high spatial resolution. In this work, we applied DLS-OCT to measure both RBC velocity and the shear-induced diffusion coefficient within penetrating venules of the somatosensory cortex of anesthetized mice. Blood flow laminar profile measurements indicate a blunted laminar flow profile, and the degree of blunting decreases with increasing vessel diameter. The measured shear-induced diffusion coefficient was proportional to the flow shear rate with a magnitude of 0.1 to 0.5 × 10-6 mm2 . These results provide important experimental support for the recent theoretical explanation for why DCS is dominantly sensitive to RBC diffusive motion.

Narrow linewidth comb realized with a mode-locked fiber laser using an intra-cavity waveguide electro-optic modulator for high-speed control.

PubMed

Iwakuni, Kana; Inaba, Hajime; Nakajima, Yoshiaki; Kobayashi, Takumi; Hosaka, Kazumoto; Onae, Atsushi; Hong, Feng-Lei

2012-06-18

We have developed an optical frequency comb using a mode-locked fiber ring laser with an intra-cavity waveguide electro-optic modulator controlling the optical length in the laser cavity. The mode-locking is achieved with a simple ring configuration and a nonlinear polarization rotation mechanism. The beat note between the laser and a reference laser and the carrier envelope offset frequency of the comb were simultaneously phase locked with servo bandwidths of 1.3 MHz and 900 kHz, respectively. We observed an out-of-loop beat between two identical combs, and obtained a coherent δ-function peak with a signal to noise ratio of 70 dB/Hz.

Plasmonic metasurface cavity for simultaneous enhancement of optical electric and magnetic fields in deep subwavelength volume.

PubMed

Hong, Jongwoo; Kim, Sun-Je; Kim, Inki; Yun, Hansik; Mun, Sang-Eun; Rho, Junsuk; Lee, Byoungho

2018-05-14

It has been hard to achieve simultaneous plasmonic enhancement of nanoscale light-matter interactions in terms of both electric and magnetic manners with easily reproducible fabrication method and systematic theoretical design rule. In this paper, a novel concept of a flat nanofocusing device is proposed for simultaneously squeezing both electric and magnetic fields in deep-subwavelength volume (~λ 3 /538) in a large area. Based on the funneled unit cell structures and surface plasmon-assisted coherent interactions between them, the array of rectangular nanocavity connected to a tapered nanoantenna, plasmonic metasurface cavity, is constructed by periodic arrangement of the unit cell. The average enhancement factors of electric and magnetic field intensities reach about 60 and 22 in nanocavities, respectively. The proposed outstanding performance of the device is verified numerically and experimentally. We expect that this work would expand methodologies involving optical near-field manipulations in large areas and related potential applications including nanophotonic sensors, nonlinear responses, and quantum interactions.

Experimental generation of optical coherence lattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Yahong; Cai, Yangjian, E-mail: serpo@dal.ca, E-mail: yangjiancai@suda.edu.cn; Key Lab of Advanced Optical Manufacturing Technologies of Jiangsu Province and Key Lab of Modern Optical Technologies of Education Ministry of China, Soochow University, Suzhou 215006

2016-08-08

We report experimental generation and measurement of recently introduced optical coherence lattices. The presented optical coherence lattice realization technique hinges on a superposition of mutually uncorrelated partially coherent Schell-model beams with tailored coherence properties. We show theoretically that information can be encoded into and, in principle, recovered from the lattice degree of coherence. Our results can find applications to image transmission and optical encryption.

Fizeau simultaneous phase-shifting interferometry based on extended source

NASA Astrophysics Data System (ADS)

Wang, Shanshan; Zhu, Qiudong; Hou, Yinlong; Cao, Zheng

2016-09-01

Coaxial Fizeau simultaneous phase-shifting interferometer plays an important role in many fields for its characteristics of long optical path, miniaturization, and elimination of reference surface high-frequency error. Based on the matching of coherence between extended source and interferometer, orthogonal polarization reference wave and measurement wave can be obtained by Fizeau interferometry with Michelson interferometer preposed. Through matching spatial coherence length between preposed interferometer and primary interferometer, high contrast interference fringes can be obtained and additional interference fringes can be eliminated. Thus, the problem of separation of measurement and reference surface in the common optical path Fizeau interferometer is solved. Numerical simulation and principle experiment is conducted to verify the feasibility of extended source interferometer. Simulation platform is established by using the communication technique of DDE (dynamic data exchange) to connect Zemax and Matlab. The modeling of the extended source interferometer is realized by using Zemax. Matlab codes are programmed to automatically rectify the field parameters of the optical system and conveniently calculate the visibility of interference fringes. Combined with the simulation, the experimental platform of the extended source interferometer is established. After experimental research on the influence law of scattering screen granularity to interference fringes, the granularity of scattering screen is determined. Based on the simulation platform and experimental platform, the impacts on phase measurement accuracy of the imaging system aberration and collimation system aberration of the interferometer are analyzed. Compared the visibility relation curves between experimental measurement and simulation result, the experimental result is in line with the theoretical result.

Label-free, multi-contrast optical coherence tomography for study of skin melanoma mice in vivo

NASA Astrophysics Data System (ADS)

Lai, Pei-Yu; Lin, Tim-Han; Chou, Ya-Shuan; Chang, Chung-Hsing; Kuo, Wen-Chuan

2018-02-01

The lymphatic system plays an important role in inflammation and cancer such as melanoma. Due to the limitations of current developed imaging techniques, visualization of lymphatic vessels within the tissue in vivo has been challenging. Optical imaging of lymphatic vessel is gaining increased interests because it does not involve any radiation and can achieve very high resolution. Here, we developed a multi-contrast, label-free optical coherence tomography (OCT) imaging technology with an axial resolution of 5 μm and lateral resolution of 7 μm, which is capable of providing microstructural information and microcirculatory system including blood and lymphatic vessels simultaneously. Using this technique, we observed the melanoma mice in vivo. Mice were treated topically on the ear with (Z)-4- Hydroxytamoxifen(4-OHT) to elicit BRAFV600E and to silence Pten expression. Also, to observing the structural information, angiogenesis and lymphangiogenesis in the ear of the induced melanoma mouse can be done. The advantage of using OCT over other imaging modalities is its ability to assess label-free blood flow along with lymphatic vessels simultaneously for imaging the microcirculatory system within tissue beds without any exogenous agents. Because the metastasis of melanoma is highly related to the lymphatic vessels, our findings can be a powerful tool to help the diagnosis of the metastasis melanoma. In the future, this may become a helpful tool for better understanding pathologic mechanisms and treatment technique development in some diseases.

Frequency set on systems

NASA Astrophysics Data System (ADS)

Wilby, W. A.; Brett, A. R. H.

Frequency set on techniques used in ECM applications include repeater jammers, frequency memory loops (RF and optical), coherent digital RF memories, and closed loop VCO set on systems. Closed loop frequency set on systems using analog phase and frequency locking are considered to have a number of cost and performance advantages. Their performance is discussed in terms of frequency accuracy, bandwidth, locking time, stability, and simultaneous signals. Some experimental results are presented which show typical locking performance. Future ECM systems might require a response to very short pulses. Acoustooptic and fiber-optic pulse stretching techniques can be used to meet such requirements.

Three-dimensional simultaneous optical coherence tomography and confocal fluorescence microscopy for investigation of lung tissue.

PubMed

Gaertner, Maria; Cimalla, Peter; Meissner, Sven; Kuebler, Wolfgang M; Koch, Edmund

2012-07-01

Although several strategies exist for a minimal-invasive treatment of patients with lung failure, the mortality rate of acute respiratory distress syndrome still reaches 30% at minimum. This striking number indicates the necessity of understanding lung dynamics on an alveolar level. To investigate the dynamical behavior on a microscale, we used three-dimensional geometrical and functional imaging to observe tissue parameters including alveolar size and length of embedded elastic fibers during ventilation. We established a combined optical coherence tomography (OCT) and confocal fluorescence microscopy system that is able to monitor the distension of alveolar tissue and elastin fibers simultaneously within three dimensions. The OCT system can laterally resolve a 4.9 μm line pair feature and has an approximately 11 μm full-width-half-maximum axial resolution in air. confocal fluorescence microscopy visualizes molecular properties of the tissue with a resolution of 0.75 μm (laterally), and 5.9 μm (axially) via fluorescence detection of the dye sulforhodamine B specifically binding to elastin. For system evaluation, we used a mouse model in situ to perform lung distension by application of different constant pressure values within the physiological regime. Our method enables the investigation of alveolar dynamics by helping to reveal basic processes emerging during artificial ventilation and breathing.

Fluorescence-based surface magnifying chromoendoscopy and optical coherence tomography endoscope

NASA Astrophysics Data System (ADS)

Wall, R. Andrew; Barton, Jennifer K.

2012-08-01

A side-viewing, 2.3-mm diameter, surface magnifying chromoendoscopy-optical coherence tomography (SMC-OCT) endoscope has been designed for simultaneous, nondestructive surface fluorescence visualization and cross-sectional imaging. We apply this endoscope to in vivo examination of the mouse colon. A 30,000 element fiber bundle is combined with single mode fibers, for SMC and OCT imaging, respectively. The distal optics consist of a gradient-index lens and spacer to provide a 1× magnification at a working distance of 1.58 mm in air, necessary to image the sample through a 0.23-mm thick outer glass envelope, and an aluminized right-angle prism fixed to the distal end of the gradient-index lens assembly. The resulting 1∶1 imaging system is capable of 3.9-μm lateral and 2.3-μm axial resolution in the OCT channel, and 125-lp/mm resolution across a 0.70-mm field of view in the SMC channel. The endoscope can perform high contrast crypt visualization, molecular imaging, and cross-sectional imaging of colon microstructure.

Fluorescence-based surface magnifying chromoendoscopy and optical coherence tomography endoscope

PubMed Central

Wall, R. Andrew

2012-01-01

Abstract. A side-viewing, 2.3-mm diameter, surface magnifying chromoendoscopy-optical coherence tomography (SMC-OCT) endoscope has been designed for simultaneous, nondestructive surface fluorescence visualization and cross-sectional imaging. We apply this endoscope to in vivo examination of the mouse colon. A 30,000 element fiber bundle is combined with single mode fibers, for SMC and OCT imaging, respectively. The distal optics consist of a gradient-index lens and spacer to provide a 1× magnification at a working distance of 1.58 mm in air, necessary to image the sample through a 0.23-mm thick outer glass envelope, and an aluminized right-angle prism fixed to the distal end of the gradient-index lens assembly. The resulting 1∶1 imaging system is capable of 3.9-µm lateral and 2.3-µm axial resolution in the OCT channel, and 125-lp/mm resolution across a 0.70-mm field of view in the SMC channel. The endoscope can perform high contrast crypt visualization, molecular imaging, and cross-sectional imaging of colon microstructure. PMID:23224190

Volumetric imaging of rod and cone photoreceptor structure with a combined adaptive optics-optical coherence tomography-scanning laser ophthalmoscope

NASA Astrophysics Data System (ADS)

Wells-Gray, Elaine M.; Choi, Stacey S.; Zawadzki, Robert J.; Finn, Susanna C.; Greiner, Cherry; Werner, John S.; Doble, Nathan

2018-03-01

We have designed and implemented a dual-mode adaptive optics (AO) imaging system that combines spectral domain optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO) for in vivo imaging of the human retina. The system simultaneously acquires SLO frames and OCT B-scans at 60 Hz with an OCT volume acquisition time of 4.2 s. Transverse eye motion measured from the SLO is used to register the OCT B-scans to generate three-dimensional (3-D) volumes. Key optical design considerations include: minimizing system aberrations through the use of off-axis relay telescopes, conjugate pupil plane requirements, and the use of dichroic beam splitters to separate and recombine the OCT and SLO beams around the nonshared horizontal scanning mirrors. To demonstrate system performance, AO-OCT-SLO images and measurements are taken from three normal human subjects ranging in retinal eccentricity from the fovea out to 15-deg temporal and 20-deg superior. Also presented are en face OCT projections generated from the registered 3-D volumes. The ability to acquire high-resolution 3-D images of the human retina in the midperiphery and beyond has clinical importance in diseases, such as retinitis pigmentosa and cone-rod dystrophy.

Ultra-narrow linewidth quantum dot coherent comb lasers with self-injection feedback locking.

PubMed

Lu, Z G; Liu, J R; Poole, P J; Song, C Y; Chang, S D

2018-04-30

We have used an external cavity self-injection feedback locking (SIFL) system to simultaneously reduce the optical linewidth of over 39 individual wavelength channels of an InAs/InP quantum dot (QD) coherent comb laser (CCL). Linewidth reduction from a few MHz to less than 200 kHz is observed. Measured phase noise spectra clearly indicate a significant decrease in phase noise in the frequency range above 2 kHz. The RF beating signal between two adjacent channels also shows a substantial reduction in 3-dB linewidth from 10 kHz to 300 Hz with the SIFL system, and a corresponding drop in baseline level (-27 dB to -50 dB).

Lineshape asymmetry for joint coherent population trapping and three-photon N resonances

NASA Astrophysics Data System (ADS)

Hancox, Cindy; Hohensee, Michael; Crescimanno, Michael; Phillips, David F.; Walsworth, Ronald L.

2008-06-01

We show that a characteristic two photon lineshape asymmetry arises in coherent population trapping (CPT) and three photon (N) resonances because both resonances are simultaneously induced by modulation sidebands in the interrogating laser light. The N resonance is a three-photon resonance in which a two-photon Raman excitation is combined with a resonant optical pumping field. This joint CPT and N resonance can be the dominant source of lineshape distortion, with direct relevance for the operation of miniaturized atomic frequency standards. We present the results of both an experimental study and theoretical treatment of the asymmetry of the joint CPT and N resonance under conditions typical to the operation of an N resonance clock.

Coherent/Noncoherent Detection of Coherent Optical Heterodyne DPSK-CDMA and MFSK-CDMA Signals

DTIC Science & Technology

1991-12-01

AD-A246 215 NAVAL POSTGRADUATE SCHOOL Monterey, Californla DTI THESIS COHERENT/ NONCOHERENT DETECTION OF COHERENT OPTICAL HETERODYNE DPSK-CDMA AND...NO ~ ACCESSION NO 11TILE(ncud S~riy ~a~fiat~r)COHERENT/ NONCOHERENT DETECTION OF COHERENT OPTICAL HETERODYNE DPSK-CDMA AND MFSK-CDMA SIGNALS 12 PERSONAL...early optical fiber communication systems. Gas lasers are also disregarded for practical systems due to size and safety considerations, even though

Study on image feature extraction and classification for human colorectal cancer using optical coherence tomography

NASA Astrophysics Data System (ADS)

Huang, Shu-Wei; Yang, Shan-Yi; Huang, Wei-Cheng; Chiu, Han-Mo; Lu, Chih-Wei

2011-06-01

Most of the colorectal cancer has grown from the adenomatous polyp. Adenomatous lesions have a well-documented relationship to colorectal cancer in previous studies. Thus, to detect the morphological changes between polyp and tumor can allow early diagnosis of colorectal cancer and simultaneous removal of lesions. OCT (Optical coherence tomography) has been several advantages including high resolution and non-invasive cross-sectional image in vivo. In this study, we investigated the relationship between the B-scan OCT image features and histology of malignant human colorectal tissues, also en-face OCT image and the endoscopic image pattern. The in-vitro experiments were performed by a swept-source optical coherence tomography (SS-OCT) system; the swept source has a center wavelength at 1310 nm and 160nm in wavelength scanning range which produced 6 um axial resolution. In the study, the en-face images were reconstructed by integrating the axial values in 3D OCT images. The reconstructed en-face images show the same roundish or gyrus-like pattern with endoscopy images. The pattern of en-face images relate to the stages of colon cancer. Endoscopic OCT technique would provide three-dimensional imaging and rapidly reconstruct en-face images which can increase the speed of colon cancer diagnosis. Our results indicate a great potential for early detection of colorectal adenomas by using the OCT imaging.

Coherent optical transients observed in rubidium atomic line filtered Doppler velocimetry experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fajardo, Mario E., E-mail: mario.fajardo@eglin.af.mil; Molek, Christopher D.; Vesely, Annamaria L.

2015-10-14

We report the first successful results from our novel Rubidium Atomic Line Filtered (RALF) Doppler velocimetry apparatus, along with unanticipated oscillatory signals due to coherent optical transients generated within pure Rb vapor cells. RALF is a high-velocity and high-acceleration extension of the well-known Doppler Global Velocimetry (DGV) technique for constructing multi-dimensional flow velocity vector maps in aerodynamics experiments [H. Komine, U.S. Patent No. 4,919,536 (24 April 1990)]. RALF exploits the frequency dependence of pressure-broadened Rb atom optical absorptions in a heated Rb/N{sub 2} gas cell to encode the Doppler shift of reflected near-resonant (λ{sub 0} ≈ 780.24 nm) laser light onto the intensitymore » transmitted by the cell. The present RALF apparatus combines fiber optic and free-space components and was built to determine suitable operating conditions and performance parameters for the Rb/N{sub 2} gas cells. It yields single-spot velocities of thin laser-driven-flyer test surfaces and incorporates a simultaneous Photonic Doppler Velocimetry (PDV) channel [Strand et al., Rev. Sci. Instrum. 77, 083108 (2006)] for validation of the RALF results, which we demonstrate here over the v = 0 to 1 km/s range. Both RALF and DGV presume the vapor cells to be simple Beer's Law optical absorbers, so we were quite surprised to observe oscillatory signals in experiments employing low pressure pure Rb vapor cells. We interpret these oscillations as interference between the Doppler shifted reflected light and the Free Induction Decay (FID) coherent optical transient produced within the pure Rb cells at the original laser frequency; this is confirmed by direct comparison of the PDV and FID signals. We attribute the different behaviors of the Rb/N{sub 2} vs. Rb gas cells to efficient dephasing of the atomic/optical coherences by Rb-N{sub 2} collisions. The minimum necessary N{sub 2} buffer gas density ≈0.3 amagat translates into a smallest useful velocity range of 0 to 2 km/s, which can readily be extended to cover the 0 to 10 km/s range, and beyond. The recognition that coherent optical transients can be produced within low pressure vapor cells during velocimetry experiments may offer new insights into some quantitative discrepancies reported in earlier DGV studies. Future plans include “line-RALF” experiments with streak camera detection, and two-dimensional surface velocity mapping using pulsed laser illumination and/or gated intensified CCD camera detection.« less

Demonstration of free space coherent optical communication using integrated silicon photonic orbital angular momentum devices.

PubMed

Su, Tiehui; Scott, Ryan P; Djordjevic, Stevan S; Fontaine, Nicolas K; Geisler, David J; Cai, Xinran; Yoo, S J B

2012-04-23

We propose and demonstrate silicon photonic integrated circuits (PICs) for free-space spatial-division-multiplexing (SDM) optical transmission with multiplexed orbital angular momentum (OAM) states over a topological charge range of -2 to +2. The silicon PIC fabricated using a CMOS-compatible process exploits tunable-phase arrayed waveguides with vertical grating couplers to achieve space division multiplexing and demultiplexing. The experimental results utilizing two silicon PICs achieve SDM mux/demux bit-error-rate performance for 1‑b/s/Hz, 10-Gb/s binary phase shifted keying (BPSK) data and 2-b/s/Hz, 20-Gb/s quadrature phase shifted keying (QPSK) data for individual and two simultaneous OAM states. © 2012 Optical Society of America

Simultaneously extracting multiple parameters via multi-distance and multi-exposure diffuse speckle contrast analysis

PubMed Central

Liu, Jialin; Zhang, Hongchao; Lu, Jian; Ni, Xiaowu; Shen, Zhonghua

2017-01-01

Recent advancements in diffuse speckle contrast analysis (DSCA) have opened the path for noninvasive acquisition of deep tissue microvasculature blood flow. In fact, in addition to blood flow index αDB, the variations of tissue optical absorption μa, reduced scattering coefficients μs′, as well as coherence factor β can modulate temporal fluctuations of speckle patterns. In this study, we use multi-distance and multi-exposure DSCA (MDME-DSCA) to simultaneously extract multiple parameters such as μa, μs′, αDB, and β. The validity of MDME-DSCA has been validated by the simulated data and phantoms experiments. Moreover, as a comparison, the results also show that it is impractical to simultaneously obtain multiple parameters by multi-exposure DSCA (ME-DSCA). PMID:29082083

Optical coherence tomography monitoring of vocal fold femtosecond laser microsurgery

NASA Astrophysics Data System (ADS)

Wisweh, Henning; Merkel, Ulrich; Hüller, Ann-Kristin; Lüerßen, Kathrin; Lubatschowski, Holger

2007-07-01

Surgery of benign pathological alterations of the vocal folds results in permanent disphonia if the bounderies of the vocal fold layers are disregarded. Precise cutting with a femtosecond laser (fs-laser) combined with simultanous imaging of the layered structure enables accurate resections with respect to the layer boundaries. Earlier works demonstrated the capability of optical coherence tomography (OCT) for utilization on vocal folds. The layered structure can be imaged with a spatial resolution of 10-20μm up to a depth of 1.5mm. The performance of fs-laser cutting was analyzed on extracted porcine vocal folds with OCT monitoring. Histopathological sections of the same processed samples could be well correlated with the OCT images. With adequate laser parameters thermal effects induced only negligable damage to the processed tissue. The dimensions of the thermal necrosis were determined to be smaller than 1μm. OCT contolled fs-laser cutting of porcine vocal fold tissue in the μm range with minimal tissue damage is presented.

In-vivo gingival sulcus imaging using full-range, complex-conjugate-free, endoscopic spectral domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Huang, Yong; Zhang, Kang; Yi, WonJin; Kang, Jin U.

2012-01-01

Frequent monitoring of gingival sulcus will provide valuable information for judging the presence and severity of periodontal disease. Optical coherence tomography, as a 3D high resolution high speed imaging modality is able to provide information for pocket depth, gum contour, gum texture, gum recession simultaneously. A handheld forward-viewing miniature resonant fiber-scanning probe was developed for in-vivo gingival sulcus imaging. The fiber cantilever driven by magnetic force vibrates at resonant frequency. A synchronized linear phase-modulation was applied in the reference arm by the galvanometer-driven reference mirror. Full-range, complex-conjugate-free, real-time endoscopic SD-OCT was achieved by accelerating the data process using graphics processing unit. Preliminary results showed a real-time in-vivo imaging at 33 fps with an imaging range of lateral 2 mm by depth 3 mm. Gap between the tooth and gum area was clearly visualized. Further quantification analysis of the gingival sulcus will be performed on the image acquired.

Coherent beam combining of collimated fiber array based on target-in-the-loop technique

NASA Astrophysics Data System (ADS)

Li, Xinyang; Geng, Chao; Zhang, Xiaojun; Rao, Changhui

2011-11-01

Coherent beam combining (CBC) of fiber array is a promising way to generate high power and high quality laser beams. Target-in-the-loop (TIL) technique might be an effective way to ensure atmosphere propagation compensation without wavefront sensors. In this paper, we present very recent research work about CBC of collimated fiber array using TIL technique at the Key Lab on Adaptive Optics (KLAO), CAS. A novel Adaptive Fiber Optics Collimator (AFOC) composed of phase-locking module and tip/tilt control module was developed. CBC experimental setup of three-element fiber array was established. Feedback control is realized using stochastic parallel gradient descent (SPGD) algorithm. The CBC based on TIL with piston and tip/tilt correction simultaneously is demonstrated. And the beam pointing to locate or sweep position of combined spot on target was achieved through TIL technique too. The goal of our work is achieve multi-element CBC for long-distance transmission in atmosphere.

Measurement of three-dimensional velocity profiles using forward scattering particle image velocimetry (FSPIV) and neural net pattern recognition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ovryn, B.; Wright, T.; Khaydarov, J.D.

1995-12-31

The authors employ Forward Scattering Particle Image Velocimetry (FSPIV) to measure all three components of the velocity of a buoyant polystyrene particle in oil. Unlike conventional particle image velocimetry (PIV) techniques, FSPIV employs coherent or partially coherent back illumination and collects the forward scattered wavefront; additionally, the field-of-view is microscopic. Using FSPIV, it is possible to easily identify the particle`s centroid and to simultaneously obtain the fluid velocity in different planes perpendicular to the viewing direction without changing the collection or imaging optics. The authors have trained a neural network to identify the scattering pattern as function of displacement alongmore » the optical axis (axial defocus) and determine the transverse velocity by tracking the centroid as function of time. They present preliminary results from Mie theory calculations which include the effect of the imaging system. To their knowledge, this is the first work of this kind; preliminary results are encouraging.« less

True color scanning laser ophthalmoscopy and optical coherence tomography handheld probe

PubMed Central

LaRocca, Francesco; Nankivil, Derek; Farsiu, Sina; Izatt, Joseph A.

2014-01-01

Scanning laser ophthalmoscopes (SLOs) are able to achieve superior contrast and axial sectioning capability compared to fundus photography. However, SLOs typically use monochromatic illumination and are thus unable to extract color information of the retina. Previous color SLO imaging techniques utilized multiple lasers or narrow band sources for illumination, which allowed for multiple color but not “true color” imaging as done in fundus photography. We describe the first “true color” SLO, handheld color SLO, and combined color SLO integrated with a spectral domain optical coherence tomography (OCT) system. To achieve accurate color imaging, the SLO was calibrated with a color test target and utilized an achromatizing lens when imaging the retina to correct for the eye’s longitudinal chromatic aberration. Color SLO and OCT images from volunteers were then acquired simultaneously with a combined power under the ANSI limit. Images from this system were then compared with those from commercially available SLOs featuring multiple narrow-band color imaging. PMID:25401032

Robust intravascular optical coherence elastography driven by acoustic radiation pressure

NASA Astrophysics Data System (ADS)

van Soest, Gijs; Bouchard, Richard R.; Mastik, Frits; de Jong, Nico; van der Steen, Anton F. W.

2007-07-01

High strain spots in the vessel wall indicate the presence of vulnerable plaques. The majority of acute cardiovascular events are preceded by rupture of such a plaque in a coronary artery. Intracoronary optical coherence tomography (OCT) can be extended, in principle, to an elastography technique, mapping the strain in the vascular wall. However, the susceptibility of OCT to frame-to-frame decorrelation, caused by tissue and catheter motion, inhibits reliable tissue displacement tracking and has to date obstructed the development of OCT-based intravascular elastography. We introduce a new technique for intravascular optical coherence elastography, which is robust against motion artifacts. Using acoustic radiation force, we apply a pressure to deform the tissue synchronously with the line scan rate of the OCT instrument. Radial tissue displacement can be tracked based on the correlation between adjacent lines, instead of subsequent frames in conventional elastography. The viability of the method is demonstrated with a simulation study. The root mean square (rms) error of the displacement estimate is 0.55 μm, and the rms error of the strain is 0.6%. It is shown that high-strain spots in the vessel wall, such as observed at the sites of vulnerable atherosclerotic lesions, can be detected with the technique. Experiments to realize this new elastographic method are presented. Simultaneous optical and ultrasonic pulse-echo tracking demonstrate that the material can be put in a high-frequency oscillatory motion with an amplitude of several micrometers, more than sufficient for accurate tracking with OCT. The resulting data are used to optimize the acoustic pushing sequence and geometry.

Objective assessment of multimodality optical coherence tomography and second-harmonic generation image quality of ex vivo mouse ovaries using human observers

NASA Astrophysics Data System (ADS)

Welge, Weston A.; DeMarco, Andrew T.; Watson, Jennifer M.; Rice, Photini S.; Barton, Jennifer K.; Kupinski, Matthew A.

2014-03-01

Ovarian cancer is particularly deadly because it is usually diagnosed after it has begun to spread. Transvaginal sonography (TVS) is the most common imaging screening technique. However, routine use of TVS has not reduced ovarian cancer mortality. The superior resolution of optical imaging techniques may make them attractive alternatives to TVS. We have previously identified features of ovarian cancer using optical coherence tomography (OCT) and secondharmonic generation (SHG) microscopy (with collagen as the targeted fluorophore). OCT provides a gross anatomical image of the ovary while SHG provides a closer look at a particular region. Knowing these anatomical features, we sought to investigate the diagnostic potential of OCT and SHG. We conducted a fully crossed, multi-reader, multi-case study using seven human observers. Each observer classified 44 ex vivo mouse ovaries as normal or abnormal from OCT, SHG, and simultaneous, co-registered OCT and SHG images and provided a confidence rating on a three-point ordinal scale. We determined the average receiver operating characteristic (ROC) curves, area under the ROC curves (AUC), and other quantitative figures of merit. The results show that OCT has diagnostic potential with an average AUC of 0.91 +/- 0.03. The average AUC for SHG was less promising at 0.71 +/- 0.06. Interestingly, the average AUC for simultaneous, co-registered OCT and SHG was not significantly different from OCT alone. This suggests that collagen may not be a useful fluorophore for ovarian cancer screening. The high performance of OCT warrants further investigation.

MULTIMODAL IMAGING OF ACUTE EXUDATIVE POLYMORPHOUS VITELLIFORM MACULOPATHY WITH OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY AND ADAPTIVE OPTICS SCANNING LASER OPHTHALMOSCOPY.

PubMed

Skondra, Dimitra; Nesper, Peter L; Fawzi, Amani A

2017-05-16

To report a case of acute exudative polymorphous vitelliform maculopathy including the findings of optical coherence tomography angiography and adaptive optics scanning laser ophthalmoscopy. Findings on clinical examination, color fundus photography, spectral-domain optical coherence tomography, infrared reflectance, autofluorescence, optical coherence tomography angiography, and adaptive optics scanning laser ophthalmoscopy. A 54-year-old white man with no significant medical history and history of smoking presented with bilateral multiple serous and vitelliform detachments consistent with acute exudative polymorphous vitelliform maculopathy. Extensive infectious, inflammatory, and malignancy workup was negative. Spectral-domain optical coherence tomography showed thickened, hyperreflective ellipsoid zone, subretinal fluid, and focal as well as diffuse subretinal hyperreflective material corresponding to the vitelliform lesions. Optical coherence tomography angiography showed normal retinal and choroidal vasculature, whereas adaptive optics scanning laser ophthalmoscopy showed circular focal "target" lesions at the level of the photoreceptors in the area of foveal detachment. Multimodal imaging is valuable in evaluating patients with acute exudative polymorphous vitelliform maculopathy.

Phase noise suppression for coherent optical block transmission systems: a unified framework.

PubMed

Yang, Chuanchuan; Yang, Feng; Wang, Ziyu

2011-08-29

A unified framework for phase noise suppression is proposed in this paper, which could be applied in any coherent optical block transmission systems, including coherent optical orthogonal frequency-division multiplexing (CO-OFDM), coherent optical single-carrier frequency-domain equalization block transmission (CO-SCFDE), etc. Based on adaptive modeling of phase noise, unified observation equations for different coherent optical block transmission systems are constructed, which lead to unified phase noise estimation and suppression. Numerical results demonstrate that the proposal is powerful in mitigating laser phase noise.

Coherent time-stretch transformation for real-time capture of wideband signals.

PubMed

Buckley, Brandon W; Madni, Asad M; Jalali, Bahram

2013-09-09

Time stretch transformation of wideband waveforms boosts the performance of analog-to-digital converters and digital signal processors by slowing down analog electrical signals before digitization. The transform is based on dispersive Fourier transformation implemented in the optical domain. A coherent receiver would be ideal for capturing the time-stretched optical signal. Coherent receivers offer improved sensitivity, allow for digital cancellation of dispersion-induced impairments and optical nonlinearities, and enable decoding of phase-modulated optical data formats. Because time-stretch uses a chirped broadband (>1 THz) optical carrier, a new coherent detection technique is required. In this paper, we introduce and demonstrate coherent time stretch transformation; a technique that combines dispersive Fourier transform with optically broadband coherent detection.

Coherence degree of the fundamental Bessel-Gaussian beam in turbulent atmosphere

NASA Astrophysics Data System (ADS)

Lukin, Igor P.

2017-11-01

In this article the coherence of a fundamental Bessel-Gaussian optical beam in turbulent atmosphere is analyzed. The problem analysis is based on the solution of the equation for the transverse second-order mutual coherence function of a fundamental Bessel-Gaussian optical beam of optical radiation. The behavior of a coherence degree of a fundamental Bessel-Gaussian optical beam depending on parameters of an optical beam and characteristics of turbulent atmosphere is examined. It was revealed that at low levels of fluctuations in turbulent atmosphere the coherence degree of a fundamental Bessel-Gaussian optical beam has the characteristic oscillating appearance. At high levels of fluctuations in turbulent atmosphere the coherence degree of a fundamental Bessel-Gaussian optical beam is described by an one-scale decreasing curve which in process of increase of level of fluctuations on a line of formation of a laser beam becomes closer to the same characteristic of a spherical optical wave.

Coherence of the vortex Bessel-Gaussian beam in turbulent atmosphere

NASA Astrophysics Data System (ADS)

Lukin, Igor P.

2017-11-01

In this paper the theoretical research of coherent properties of the vortex Bessel-Gaussian optical beams propagating in turbulent atmosphere are developed. The approach to the analysis of this problem is based on the analytical solution of the equation for the transverse second-order mutual coherence function of a field of optical radiation. The behavior of integral scale of coherence degree of vortex Bessel-Gaussian optical beams depending on parameters of an optical beam and characteristics of turbulent atmosphere is particularly considered. It is shown that the integral scale of coherence degree of a vortex Bessel-Gaussian optical beam essentially depends on value of a topological charge of a vortex optical beam. With increase in a topological charge of a vortex Bessel-Gaussian optical beam the value of integral scale of coherence degree of a vortex Bessel-Gaussian optical beam are decreased.

Simultaneous refraction measurement and OCT axial biometry of the eye during accommodation (Conference Presentation)

NASA Astrophysics Data System (ADS)

De Freitas, Carolina; Hernandez, Victor M.; Ruggeri, Marco; Durkee, Heather A.; Williams, Siobhan; Gregori, Giovanni; Ho, Arthur; Manns, Fabrice; Parel, Jean-Marie

2016-03-01

The purpose of this project is to design and evaluate a system that will enable objective assessment of the optical accommodative response in real-time while acquiring axial biometric information. The system combines three sub-systems which were integrated and mounted on a joystick x-y-z adjustable modified slit-lamp base to facilitate alignment and data acquisition: (1) a Shack-Hartmann wavefront sensor for dynamic refraction measurement, provided software calculates sphere, cylinder and axis values, (2) an extended-depth Optical Coherence Tomography (OCT) system using an optical switch records high-resolution cross-sectional images across the length of the eye, from which, dynamic axial biometry (corneal thickness, anterior chamber depth, crystalline lens thickness and vitreous depth) can be extracted, and (3) a modified dual-channel accommodation stimulus unit based on the Badal optometer for providing a step change in accommodative stimulus. The prototypal system is capable of taking simultaneous measurements of both the optical and the mechanical response of lens accommodation. These measurements can provide insight into correlating changes in lens shape with changes in lens power and ocular refraction and ultimately provide a more comprehensive understanding of accommodation, presbyopia and an objective assessment of presbyopia correction techniques.

Simultaneous distance measurement at multiple wavelengths using the intermode beats from a femtosecond laser coherent supercontinuum

NASA Astrophysics Data System (ADS)

Salido-Monzú, David; Wieser, Andreas

2018-04-01

The intermode beats generated by direct detection of a mode-locked femtosecond laser represent inherent high-quality and high-frequency modulations suitable for electro-optical distance measurement (EDM). This approach has already been demonstrated as a robust alternative to standard long-distance EDM techniques. However, we extend this idea to intermode beating of a wideband source obtained by spectral broadening of a femtosecond laser. We aim at establishing a technological basis for accurate and flexible multiwavelength distance measurement. Results are presented from experiments using beat notes at 1 GHz generated by two bandpass-filtered regions from both extremes of a coherent supercontinuum ranging from 550 to 1050 nm. The displacement measurements performed simultaneously on both colors on a short-distance setup show that noise and coherence of the wideband laser are adequate for achieving accuracies of about 0.01 mm on each channel with a potential improvement by accessing higher beat notes. Pointing and power instabilities have been identified as dominant sources of systematic deviations. Nevertheless, the results demonstrate the basic feasibility of the proposed technique. We consider this a promising starting point for the further development of multiwavelength EDM enabling increased accuracy over long distances through dispersion-based integral refractivity compensation and for remote surface material probing along with distance measurement in laser scanning.

The New Physical Optics Notebook: Tutorials in Fourier Optics.

ERIC Educational Resources Information Center

Reynolds, George O.; And Others

This is a textbook of Fourier optics for the classroom or self-study. Major topics included in the 38 chapters are: Huygens' principle and Fourier transforms; image formation; optical coherence theory; coherent imaging; image analysis; coherent noise; interferometry; holography; communication theory techniques; analog optical computing; phase…

Development of a parallel demodulation system used for extrinsic Fabry-Perot interferometer and fiber Bragg grating sensors.

PubMed

Jiang, Junfeng; Liu, Tiegen; Zhang, Yimo; Liu, Lina; Zha, Ying; Zhang, Fan; Wang, Yunxin; Long, Pin

2006-01-20

A parallel demodulation system for extrinsic Fabry-Perot interferometer (EFPI) and fiber Bragg grating (FBG) sensors is presented, which is based on a Michelson interferometer and combines the methods of low-coherence interference and a Fourier-transform spectrum. The parallel demodulation theory is modeled with Fourier-transform spectrum technology, and a signal separation method with an EFPI and FBG is proposed. The design of an optical path difference scanning and sampling method without a reference light is described. Experiments show that the parallel demodulation system has good spectrum demodulation and low-coherence interference demodulation performance. It can realize simultaneous strain and temperature measurements while keeping the whole system configuration less complex.

MOEMS optical delay line for optical coherence tomography

NASA Astrophysics Data System (ADS)

Choudhary, Om P.; Chouksey, S.; Sen, P. K.; Sen, P.; Solanki, J.; Andrews, J. T.

2014-09-01

Micro-Opto-Electro-Mechanical optical coherence tomography, a lab-on-chip for biomedical applications is designed, studied, fabricated and characterized. To fabricate the device standard PolyMUMPS processes is adopted. We report the utilization of electro-optic modulator for a fast scanning optical delay line for time domain optical coherence tomography. Design optimization are performed using Tanner EDA while simulations are performed using COMSOL. The paper summarizes various results and fabrication methodology adopted. The success of the device promises a future hand-held or endoscopic optical coherence tomography for biomedical applications.

Tri-band optical coherence tomography for lipid and vessel spectroscopic imaging

NASA Astrophysics Data System (ADS)

Yu, Luoqin; Kang, Jiqiang; Wang, Xie; Wei, Xiaoming; Chan, Kin-Tak; Lee, Nikki P.; Wong, Kenneth K. Y.

2016-03-01

Optical coherence tomography (OCT) has been utilized for various functional imaging applications. One of its highlights comes from spectroscopic imaging, which can simultaneously obtain both morphologic and spectroscopic information. Assisting diagnosis and therapeutic intervention of coronary artery disease is one of the major directions in spectroscopic OCT applications. Previously Tanaka et al. have developed a spectral domain OCT (SDOCT) to image lipid distribution within blood vessel [1]. In the meantime, Fleming et al. have demonstrated optical frequency domain imaging (OFDI) by a 1.3-μm swept source and quadratic discriminant analysis model [2]. However, these systems suffered from burdensome computation as the optical properties' variation was calculated from a single-band illumination that provided limited contrast. On the other hand, multi-band OCT facilitates contrast enhancement with separated wavelength bands, which further offers an easier way to distinguish different materials. Federici and Dubois [3] and Tsai and Chan [4] have demonstrated tri-band OCT systems to further enhance the image contrast. However, these previous work provided under-explored functional properties. Our group has reported a dual-band OCT system based on parametrically amplified Fourier domain mode-locked (FDML) laser with time multiplexing scheme [5] and a dual-band FDML laser OCT system with wavelength-division multiplexing [6]. Fiber optical parametric amplifier (OPA) can be ideally incorporated in multi-band spectroscopic OCT system as it has a broad amplification window and offers an additional output range at idler band, which is phase matched with the signal band. The sweeping ranges can thus overcome traditional wavelength bands that are limited by intra-cavity amplifiers in FDML lasers. Here, we combines the dual-band FDML laser together with fiber OPA, which consequently renders a simultaneous tri-band output at 1.3, 1.5, and 1.6 μm, for intravascular applications. Lipid and blood vessel distribution can be subsequently visualized with the tri-band OCT system by ex vivo experiments using porcine artery model with artificial lipid plaques.

Tissue-mimicking bladder wall phantoms for evaluating acoustic radiation force-optical coherence elastography systems.

PubMed

Ejofodomi, O'tega A; Zderic, Vesna; Zara, Jason M

2010-04-01

Acoustic radiation force-optical coherence elastography (ARF-OCE) systems are novel imaging systems that have the potential to simultaneously quantify and characterize the optical and mechanical properties of in vivo tissues. This article presents the construction of bladder wall phantoms for use in ARF-OCE systems. Mechanical, acoustic, and optical properties are reported and compared to published values for the urinary bladder. The phantom consisted of 0.2000 +/- 0.0089 and 6.0000 +/- 0.2830 microm polystyrene microspheres (Polysciences Inc., Warrington, PA, Catalog Nos. 07304 and 07312), 7.5 +/- 1.5 microm copolymer microspheres composed of acrylonitrile and vinylidene chloride, (Expancel, Duluth, GA, Catalog No. 461 DU 20), and bovine serum albumin within a gelatin matrix. Young's modulus was measured by successive compression of the phantom and obtaining the slope of the resulting force-displacement data. Acoustic measurements were performed using the transmission method. The phantoms were submerged in a water bath and placed between transmitting and receiving 13 mm diameter unfocused transducers operating at a frequency of 3.5 MHz. A MATLAB algorithm to extract the optical scattering coefficient from optical coherence tomography (OCT) images of the phantom was used. The phantoms possess a Young's modulus of 17.12 +/- 2.72 kPa, a mass density of 1.05 +/- 0.02 g/cm3, an acoustic attenuation coefficient of 0.66 +/- 0.08 dB/cm/MHz, a speed of sound of 1591 +/- 8.76 m/s, and an optical scattering coefficient of 1.80 +/- 0.23 mm(-1). Ultrasound and OCT images of the bladder wall phantom are presented. A material that mimics the mechanical, optical, and acoustic properties of healthy bladder wall has been developed. This tissue-mimicking bladder wall phantom was developed as a control tool to investigate the feasibility of using ARF-OCE to detect the mechanical and optical changes that may be indicative of the onset or development of cancer in the urinary bladder. By following the methods used in this article, phantoms matching the optical, acoustic, and mechanical properties of other biological tissues can also be constructed.

Generation and optimization of superpixels as image processing kernels for Jones matrix optical coherence tomography

PubMed Central

Miyazawa, Arata; Hong, Young-Joo; Makita, Shuichi; Kasaragod, Deepa; Yasuno, Yoshiaki

2017-01-01

Jones matrix-based polarization sensitive optical coherence tomography (JM-OCT) simultaneously measures optical intensity, birefringence, degree of polarization uniformity, and OCT angiography. The statistics of the optical features in a local region, such as the local mean of the OCT intensity, are frequently used for image processing and the quantitative analysis of JM-OCT. Conventionally, local statistics have been computed with fixed-size rectangular kernels. However, this results in a trade-off between image sharpness and statistical accuracy. We introduce a superpixel method to JM-OCT for generating the flexible kernels of local statistics. A superpixel is a cluster of image pixels that is formed by the pixels’ spatial and signal value proximities. An algorithm for superpixel generation specialized for JM-OCT and its optimization methods are presented in this paper. The spatial proximity is in two-dimensional cross-sectional space and the signal values are the four optical features. Hence, the superpixel method is a six-dimensional clustering technique for JM-OCT pixels. The performance of the JM-OCT superpixels and its optimization methods are evaluated in detail using JM-OCT datasets of posterior eyes. The superpixels were found to well preserve tissue structures, such as layer structures, sclera, vessels, and retinal pigment epithelium. And hence, they are more suitable for local statistics kernels than conventional uniform rectangular kernels. PMID:29082073

Simulated microsurgery monitoring using intraoperative multimodal surgical microscopy

NASA Astrophysics Data System (ADS)

Lee, Donghyun; Lee, Changho; Kim, Sehui; Zhou, Qifa; Kim, Jeehyun; Kim, Chulhong

2016-03-01

We have developed an intraoperative multimodal surgical microscopy system that provides simultaneous real-time enlarged surface views and subsurface anatomic information during surgeries by integrating spectral domain optical coherence tomography (SD-OCT), optical-resolution photoacoustic microscopy (OR-PAM), and conventional surgical microscopy. By sharing the same optical path, both OCT and PAM images were simultaneously acquired. Additionally, the custom-made needle-type transducer received the generated PA signals enabling convenient surgical operation without using a water bath. Using a simple augmented device, the OCT and PAM images were projected on the view plane of the surgical microscope. To quantify the performance of our system, we measured spatial resolutions of our system. Then, three microsurgery simulation and analysis were processed: (1) ex vivo needle tracking and monitoring injection of carbon particles in biological tissues, (2) in vivo needle tracking and monitoring injection of carbon particles in tumor-bearing mice, and (3) in vivo guiding of melanoma removal in melanoma-bearing mice. The results indicate that this triple modal system is useful for intraoperative purposes, and can potentially be a vital tool in microsurgeries.

Multichannel brain recordings in behaving Drosophila reveal oscillatory activity and local coherence in response to sensory stimulation and circuit activation

PubMed Central

Paulk, Angelique C.; Zhou, Yanqiong; Stratton, Peter; Liu, Li

2013-01-01

Neural networks in vertebrates exhibit endogenous oscillations that have been associated with functions ranging from sensory processing to locomotion. It remains unclear whether oscillations may play a similar role in the insect brain. We describe a novel “whole brain” readout for Drosophila melanogaster using a simple multichannel recording preparation to study electrical activity across the brain of flies exposed to different sensory stimuli. We recorded local field potential (LFP) activity from >2,000 registered recording sites across the fly brain in >200 wild-type and transgenic animals to uncover specific LFP frequency bands that correlate with: 1) brain region; 2) sensory modality (olfactory, visual, or mechanosensory); and 3) activity in specific neural circuits. We found endogenous and stimulus-specific oscillations throughout the fly brain. Central (higher-order) brain regions exhibited sensory modality-specific increases in power within narrow frequency bands. Conversely, in sensory brain regions such as the optic or antennal lobes, LFP coherence, rather than power, best defined sensory responses across modalities. By transiently activating specific circuits via expression of TrpA1, we found that several circuits in the fly brain modulate LFP power and coherence across brain regions and frequency domains. However, activation of a neuromodulatory octopaminergic circuit specifically increased neuronal coherence in the optic lobes during visual stimulation while decreasing coherence in central brain regions. Our multichannel recording and brain registration approach provides an effective way to track activity simultaneously across the fly brain in vivo, allowing investigation of functional roles for oscillations in processing sensory stimuli and modulating behavior. PMID:23864378

Real-time optical signal processors employing optical feedback: amplitude and phase control.

PubMed

Gallagher, N C

1976-04-01

The development of real-time coherent optical signal processors has increased the appeal of optical computing techniques in signal processing applications. A major limitation of these real-time systems is the. fact that the optical processing material is generally of a phase-only type. The result is that the spatial filters synthesized with these systems must be either phase-only filters or amplitude-only filters. The main concern of this paper is the application of optical feedback techniques to obtain simultaneous and independent amplitude and phase control of the light passing through the system. It is shown that optical feedback techniques may be employed with phase-only spatial filters to obtain this amplitude and phase control. The feedback system with phase-only filters is compared with other feedback systems that employ combinations of phase-only and amplitude-only filters; it is found that the phase-only system is substantially more flexible than the other two systems investigated.

Coherence transfer of subhertz-linewidth laser light via an optical fiber noise compensated by remote users.

PubMed

Wu, Lifei; Jiang, Yanyi; Ma, Chaoqun; Yu, Hongfu; Bi, Zhiyi; Ma, Longsheng

2016-09-15

We present a technique for the coherence transfer of laser light through a fiber link, where the optical phase noise induced by environmental perturbation via the fiber link is compensated by remote users. When compensating the fiber noise by remote users, the time base at the remote site independent from that at the local site does not destroy the performance of the fiber output light. Using this technique, we demonstrate the transfer of subhertz-linewidth laser light through a 25-km-long, lab-based spooled fiber. After being compensated, the relative linewidth between the fiber input and output light is 1 mHz, and the relative frequency instability is 4×10^-17 at 1 s averaging time and scales down to 2×10^-19 at 800 s averaging time. The frequency uncertainty of the light after transferring through the fiber relative to that of the input light is 3.0×10^-19. This system is suitable for the simultaneous transfer of an optical signal to a number of end users within a city.

Endoscopic Optical Coherence Tomography

NASA Astrophysics Data System (ADS)

Zhou, Chao; Fujimoto, James G.; Tsai, Tsung-Han; Mashimo, Hiroshi

New gastrointestinal (GI) cancers are expected to affect more than 290,200 new patients and will cause more than 144,570 deaths in the United States in 2013 [1]. When detected and treated early, the 5-year survival rate for colorectal cancer increases by a factor of 1.4 [1]. For esophageal cancer, the rate increases by a factor of 2 [1]. The majority of GI cancers begin as small lesions that are difficult to identify with conventional endoscopy. With resolutions approaching that of histopathology, optical coherence tomography (OCT) is well suited for detecting the changes in tissue microstructure associated with early GI cancers. Since the lesions are not endoscopically apparent, however, it is necessary to survey a relatively large area of the GI tract. Tissue motion is another limiting factor in the GI tract; therefore, in vivo imaging must be performed at extremely high speeds. OCT imaging can be performed using fiber optics and miniaturized lens systems, enabling endoscopic OCT inside the human body in conjunction with conventional video endoscopy. An OCT probe can be inserted through the working channel of a standard endoscope, thus enabling depth-resolved imaging of tissue microstructure in the GI tract with micron-scale resolution simultaneously with the endoscopic view (Fig. 68.1).

Coherent perfect rotation

NASA Astrophysics Data System (ADS)

Crescimanno, Michael; Dawson, Nathan J.; Andrews, James H.

2012-09-01

Two classes of conservative, linear, optical rotary effects (optical activity and Faraday rotation) are distinguished by their behavior under time reversal. Faraday rotation, but not optical activity, is capable of coherent perfect rotation, by which we mean the complete transfer of counterpropagating coherent light fields into their orthogonal polarization. Unlike coherent perfect absorption, however, this process is explicitly energy conserving and reversible. Our study highlights the necessity of time-reversal-odd processes (not just absorption) and coherence in perfect mode conversion and thus informs the optimization of active multiport optical devices.

Non-destructive geometric and refractive index characterization of single and multi-element lenses using optical coherence tomography

NASA Astrophysics Data System (ADS)

El-Haddad, Mohamed T.; Tao, Yuankai K.

2018-02-01

Design of optical imaging systems requires careful balancing of lens aberrations to optimize the point-spread function (PSF) and minimize field distortions. Aberrations and distortions are a result of both lens geometry and glass material. While most lens manufacturers provide optical models to facilitate system-level simulation, these models are often not reflective of true system performance because of manufacturing tolerances. Optical design can be further confounded when achromatic or proprietary lenses are employed. Achromats are ubiquitous in systems that utilize broadband sources due to their superior performance in balancing chromatic aberrations. Similarly, proprietary lenses may be custom-designed for optimal performance, but lens models are generally not available. Optical coherence tomography (OCT) provides non-contact, depth-resolved imaging with high axial resolution and sensitivity. OCT has been previously used to measure the refractive index of unknown materials. In a homogenous sample, the group refractive index is obtained as the ratio between the measured optical and geometric thicknesses of the sample. In heterogenous samples, a method called focus-tracking (FT) quantifies the effect of focal shift introduced by the sample. This enables simultaneous measurement of the thickness and refractive index of intermediate sample layers. Here, we extend the mathematical framework of FT to spherical surfaces, and describe a method based on OCT and FT for full characterization of lens geometry and refractive index. Finally, we validate our characterization method on commercially available singlet and doublet lenses.

Corneal thickness and elevation measurements using swept-source optical coherence tomography and slit scanning topography in normal and keratoconic eyes.

PubMed

Jhanji, Vishal; Yang, Bingzhi; Yu, Marco; Ye, Cong; Leung, Christopher K S

2013-11-01

To compare corneal thickness and corneal elevation using swept source optical coherence tomography and slit scanning topography. Prospective study. 41 normal and 46 keratoconus subjects. All eyes were imaged using swept source optical coherence tomography and slit scanning tomography during the same visit. Mean corneal thickness and best-fit sphere measurements were compared between the instruments. Agreement of measurements between swept source optical coherence tomography and scanning slit topography was analyzed. Intra-rater reproducibility coefficient and intraclass correlation coefficient were evaluated. In normal eyes, central corneal thickness measured by swept source optical coherence tomography was thinner compared with slit scanning topography (p < 0.0001) and ultrasound pachymetry (p = < .0001). Ultrasound pachymetry readings had better 95% limits of agreement with swept source optical coherence tomography than slit scanning topography. In keratoconus eyes, central corneal thickness was thinner on swept source optical coherence tomography than slit scanning topography (p = 0.081) and ultrasound pachymetry (p = 0.001). There were significant differences between thinnest corneal thickness, and, anterior and posterior best-fit sphere measurements between both instruments (p < 0.05 for all). Overall, reproducibility coefficients and intraclass correlation coefficients were significantly better with swept source optical coherence tomography for measurement of central corneal thickness, anterior best-fit sphere and, posterior best-fit sphere (all p < 0.001). Corneal thickness and elevation measurements were significantly different between swept source optical coherence tomography and slit scanning topography. With better reproducibility coefficients and intraclass correlation coefficients, swept source optical coherence tomography may provide a reliable alternative for measurement of corneal parameters. © 2013 The Authors. Clinical and Experimental Ophthalmology © 2013 Royal Australian and New Zealand College of Ophthalmologists.

SPECTRAL DOMAIN VERSUS SWEPT SOURCE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY OF THE RETINAL CAPILLARY PLEXUSES IN SICKLE CELL MACULOPATHY.

PubMed

Jung, Jesse J; Chen, Michael H; Frambach, Caroline R; Rofagha, Soraya; Lee, Scott S

2018-01-01

To compare the spectral domain and swept source optical coherence tomography angiography findings in two cases of sickle cell maculopathy. A 53-year-old man and a 24-year-old man both with sickle cell disease (hemoglobin SS) presented with no visual complaints; Humphrey visual field testing demonstrated asymptomatic paracentral scotomas that extended nasally in the involved eyes. Clinical examination and multimodal imaging including spectral domain and swept source optical coherence tomography, and spectral domain optical coherence tomography angiography and swept source optical coherence tomography angiography (Carl Zeiss Meditec Inc, Dublin, CA) were performed. Fundus examination of both patients revealed subtle thinning of the macula. En-face swept source optical coherence tomography confirmed the extent of the thinning correlating with the functional paracentral scotomas on Humphrey visual field. Swept source optical coherence tomography B-scan revealed multiple confluent areas of inner nuclear thinning and significant temporal retinal atrophy. En-face 6 × 6-mm spectral domain optical coherence tomography angiography of the macula demonstrated greater loss of the deep capillary plexus compared with the superficial capillary plexus. Swept source optical coherence tomography angiography 12 × 12-mm imaging captured the same macular findings and loss of both plexuses temporally outside the macula. In these two cases of sickle cell maculopathy, deep capillary plexus ischemia is more extensive within the macula, whereas both the superficial capillary plexus and deep capillary plexus are involved outside the macula likely due to the greater oxygen demands and watershed nature of these areas. Swept source optical coherence tomography angiography clearly demonstrates the angiographic extent of the disease correlating with the Humphrey visual field scotomas and confluent areas of inner nuclear atrophy.

Laser radar: from early history to new trends

NASA Astrophysics Data System (ADS)

Molebny, Vasyl; Kamerman, Gary; Steinvall, Ove

2010-10-01

The first steps of laser radar are discussed with the examples from range finding and designation. The followed successes in field tests and further fast development provided their wide use. Coherent laser radar, developed almost simultaneously, tried the ideas from microwaves including chirp technology for pulse compression, and Doppler mode of operation. This latter found a unique implementation in a cruise missile. In many applications, environmental studies very strongly rely upon the lidars sensing the wind, temperature, constituents, optical parameters. Lidars are used in the atmosphere and in the sea water measurements. Imaging and mapping is an important role prescribed to ladars. One of the prospective trends in laser radar development is incorporation of range and velocity data into the image information. Deep space program, even having not come to the finish, gave a lot for 3D imaging. Gated imaging, as one of the 3D techniques, demonstrated its prospects (seeing through scattering layers) for military and security usage. Synthetic aperture laser radar, which had a long incubation period, started to show first results, at least in modeling. Coherent laser radar baptized as the optical coherence tomography, along with the position sensitive laser radar, synthetic aperture laser radar, multispectral laser radar demonstrated very pragmatic results in the micro-scale applications.

Framework for computing the spatial coherence effects of polycapillary x-ray optics

PubMed Central

Zysk, Adam M.; Schoonover, Robert W.; Xu, Qiaofeng; Anastasio, Mark A.

2012-01-01

Despite the extensive use of polycapillary x-ray optics for focusing and collimating applications, there remains a significant need for characterization of the coherence properties of the output wavefield. In this work, we present the first quantitative computational method for calculation of the spatial coherence effects of polycapillary x-ray optical devices. This method employs the coherent mode decomposition of an extended x-ray source, geometric optical propagation of individual wavefield modes through a polycapillary device, output wavefield calculation by ray data resampling onto a uniform grid, and the calculation of spatial coherence properties by way of the spectral degree of coherence. PMID:22418154

Doppler optical coherence microscopy and tomography applied to inner ear mechanics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Page, Scott; Freeman, Dennis M.; Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts

While it is clear that cochlear traveling waves underlie the extraordinary sensitivity, frequency selectivity, and dynamic range of mammalian hearing, the underlying micromechanical mechanisms remain unresolved. Recent advances in low coherence measurement techniques show promise over traditional laser Doppler vibrometry and video microscopy, which are limited by low reflectivities of cochlear structures and restricted optical access. Doppler optical coherence tomography (DOCT) and Doppler optical coherence microscopy (DOCM) both utilize a broadband source to limit constructive interference of scattered light to a small axial depth called a coherence gate. The coherence gate can be swept axially to image and measure sub-nanometermore » motions of cochlear structures throughout the cochlear partition. The coherence gate of DOCT is generally narrower than the confocal gate of the focusing optics, enabling increased axial resolution (typically 15 μm) within optical sections of the cochlear partition. DOCM, frequently implemented in the time domain, centers the coherence gate on the focal plane, achieving enhanced lateral and axial resolution when the confocal gate is narrower than the coherence gate. We compare these two complementary systems and demonstrate their utility in studying cellular and micromechanical mechanisms involved in mammalian hearing.« less

Generation of various partially coherent beams and their propagation properties in turbulent atmosphere: a review

NASA Astrophysics Data System (ADS)

Cai, Yangjian

2011-03-01

Partially coherent beams, such as Gaussian Schell-model beam, partially coherent dark hollow beam, partially coherent flat-topped beam and electromagnetic Gaussian Schell-model beam, have important applications in free space optical communications, optical imaging, optical trapping, inertial confinement fusion and nonlinear optics. In this paper, experimental generations of various partially coherent beams are introduced. Furthermore, with the help of a tensor method, analytical formulae for such beams propagating in turbulent atmosphere are derived, and the propagation properties of such beams in turbulent atmosphere are reviewed.

Coherent Optical Communications: Historical Perspectives and Future Directions

NASA Astrophysics Data System (ADS)

Kikuchi, Kazuro

Coherent optical fiber communications were studied extensively in the 1980s mainly because high sensitivity of coherent receivers could elongate the unrepeated transmission distance; however, their research and development have been interrupted for nearly 20 years behind the rapid progress in high-capacity wavelength-division multiplexed (WDM) systems using erbium-doped fiber amplifiers (EDFAs). In 2005, the demonstration of digital carrier phase estimation in coherent receivers has stimulated a widespread interest in coherent optical communications again. This is due to the fact that the digital coherent receiver enables us to employ a variety of spectrally efficient modulation formats such as M-ary phase-shift keying (PSK) and quadrature amplitude modulation (QAM) without relying upon a rather complicated optical phase-locked loop. In addition, since the phase information is preserved after detection, we can realize electrical post-processing functions such as compensation for chromatic dispersion and polarization-mode dispersion in the digital domain. These advantages of the born-again coherent receiver have enormous potential for innovating existing optical communication systems. In this chapter, after reviewing the 20-year history of coherent optical communication systems, we describe the principle of operation of coherent detection, the concept of the digital coherent receiver, and its performance evaluation. Finally, challenges for the future are summarized.

Unidirectional, dual-comb lasing under multiple pulse formation mechanisms in a passively mode-locked fiber ring laser

NASA Astrophysics Data System (ADS)

Liu, Ya; Zhao, Xin; Hu, Guoqing; Li, Cui; Zhao, Bofeng; Zheng, Zheng

2016-09-01

Dual-comb lasers from which asynchronous ultrashort pulses can be simultaneously generated have recently become an interesting research subject. They could be an intriguing alternative to the current dual-laser optical-frequency-comb source with highly sophisticated electronic control systems. If generated through a common light path traveled by all pulses, the common-mode noises between the spectral lines of different pulse trains could be significantly reduced. Therefore, coherent dual-comb generation from a completely common-path, unidirectional lasing cavity would be an interesting territory to explore. In this paper, we demonstrate such a dual-comb lasing scheme based on a nanomaterial saturable absorber with additional pulse narrowing and broadening mechanisms concurrently introduced into a mode-locked fiber laser. The interactions between multiple soliton formation mechanisms result in unusual bifurcation into two-pulse states with quite different characteristics. Simultaneous oscillation of pulses with four-fold difference in pulsewidths and tens of Hz repetition rate difference is observed. The coherence between these spectral-overlapped, picosecond and femtosecond pulses is further verified by the corresponding asynchronous cross-sampling and dual-comb spectroscopy measurements.

3D interferometric shape measurement technique using coherent fiber bundles

NASA Astrophysics Data System (ADS)

Zhang, Hao; Kuschmierz, Robert; Czarske, Jürgen

2017-06-01

In-situ 3-D shape measurements with submicron shape uncertainty of fast rotating objects in a cutting lathe are expected, which can be achieved by simultaneous distance and velocity measurements. Conventional tactile methods, coordinate measurement machines, only support ex-situ measurements. Optical measurement techniques such as triangulation and conoscopic holography offer only the distance, so that the absolute diameter cannot be retrieved directly. In comparison, laser Doppler distance sensors (P-LDD sensor) enable simultaneous and in-situ distance and velocity measurements for monitoring the cutting process in a lathe. In order to achieve shape measurement uncertainties below 1 μm, a P-LDD sensor with a dual camera based scattered light detection has been investigated. Coherent fiber bundles (CFB) are employed to forward the scattered light towards cameras. This enables a compact and passive sensor head in the future. Compared with a photo detector based sensor, the dual camera based sensor allows to decrease the measurement uncertainty by the order of one magnitude. As a result, the total shape uncertainty of absolute 3-D shape measurements can be reduced to about 100 nm.

Compression and information recovery in ptychography

NASA Astrophysics Data System (ADS)

Loetgering, L.; Treffer, D.; Wilhein, T.

2018-04-01

Ptychographic coherent diffraction imaging (PCDI) is a scanning microscopy modality that allows for simultaneous recovery of object and illumination information. This ability renders PCDI a suitable technique for x-ray lensless imaging and optics characterization. Its potential for information recovery typically relies on large amounts of data redundancy. However, the field of view in ptychography is practically limited by the memory and the computational facilities available. We describe techniques that achieve robust ptychographic information recovery at high compression rates. The techniques are compared and tested with experimental data.

Laser Doppler measurement techniques for spacecraft

NASA Technical Reports Server (NTRS)

Kinman, Peter W.; Gagliardi, Robert M.

1986-01-01

Two techniques are proposed for using laser links to measure the relative radial velocity of two spacecraft. The first technique determines the relative radial velocity from a measurement of the two-way Doppler shift on a transponded radio-frequency subcarrier. The subcarrier intensity-modulates reciprocating laser beams. The second technique determines the relative radial velocity from a measurement of the two-way Doppler shift on an optical frequency carrier which is transponded between spacecraft using optical Costas loops. The first technique might be used in conjunction with noncoherent optical communications, while the second technique is compatible with coherent optical communications. The first technique simultaneously exploits the diffraction advantage of laser beams and the maturity of radio-frequency phase-locked loop technology. The second technique exploits both the diffraction advantage of laser beams and the large Doppler effect at optical frequencies. The second technique has the potential for greater accuracy; unfortunately, it is more difficult to implement since it involves optical Costas loops.

IQ imbalance tolerable parallel-channel DMT transmission for coherent optical OFDMA access network

NASA Astrophysics Data System (ADS)

Jung, Sang-Min; Mun, Kyoung-Hak; Jung, Sun-Young; Han, Sang-Kook

2016-12-01

Phase diversity of coherent optical communication provides spectrally efficient higher-order modulation for optical communications. However, in-phase/quadrature (IQ) imbalance in coherent optical communication degrades transmission performance by introducing unwanted signal distortions. In a coherent optical orthogonal frequency division multiple access (OFDMA) passive optical network (PON), IQ imbalance-induced signal distortions degrade transmission performance by interferences of mirror subcarriers, inter-symbol interference (ISI), and inter-channel interference (ICI). We propose parallel-channel discrete multitone (DMT) transmission to mitigate transceiver IQ imbalance-induced signal distortions in coherent orthogonal frequency division multiplexing (OFDM) transmissions. We experimentally demonstrate the effectiveness of parallel-channel DMT transmission compared with that of OFDM transmission in the presence of IQ imbalance.

Coherent optical modulation for antenna remoting

NASA Technical Reports Server (NTRS)

Fitzmartin, D. J.; Gels, R. G.; Balboni, E. J.

1991-01-01

A coherent fiber optic link employing wideband frequency modulation (FM) of the optical carrier is used to transfer radio frequency (RF) or microwave signals. This system is used to link a remotely located antenna to a conveniently located electronics processing site. The advantages of coherent analog fiber optic systems over non-coherent intensity modulated fiber optic analog transmission systems are described. An optical FM link employing an indirect transmitter to frequency modulate the optical carrier and a microwave delay line discriminator receiver is described. Measured performance data for a video signal centered at 60 MHz is presented showing the use of wideband FM in the link.

Detection of Biochemical Pathogens, Laser Stand-off Spectroscopy, Quantum Coherence, and Many Body Quantum Optics

DTIC Science & Technology

2012-02-24

AND SUBTITLE Detection of Biochemical Pathogens, Laser Stand-off Spectroscopy, Quantum Coherence, and Many Body Quantum Optics 6. AUTHORS Marian O...Maximum 200 words) Results of our earlier research in the realm of quantum optics were extended in order to solve the challenging technical problems of...efficient methods of generating UV light via quantum coherence. 14. SUBJECT TERMS Quantum coherence, quantum optics, lasers 15. NUMBER OF PAGES 15

Multimodal ophthalmic imaging using handheld spectrally encoded coherence tomography and reflectometry (SECTR)

NASA Astrophysics Data System (ADS)

Leeburg, Kelsey C.; El-Haddad, Mohamed T.; Malone, Joseph D.; Terrones, Benjamin D.; Tao, Yuankai K.

2018-02-01

Scanning laser ophthalmoscopy (SLO) provides high-speed, noninvasive en face imaging of the retinal fundus. Optical coherence tomography (OCT) is the current "gold-standard" for ophthalmic diagnostic imaging and enables depth-resolved visualization of ophthalmic structures and image-based surrogate biomarkers of disease. We present a compact optical and mechanical design for handheld spectrally encoded coherence tomography and reflectometry (SECTR) for multimodality en face spectrally encoded reflectometry (SER) and cross-sectional OCT imaging. We custom-designed a double-pass telecentric scan lens, which halves the size of 4-f optical relays and allowed us to reduce the footprint of our SECTR scan-head by a factor of >2.7x (volume) over our previous design. The double-pass scan lens was optimized for diffraction-limited performance over a +/-10° scan field. SECTR optics and optomechanics were combined in a compact rapid-prototyped enclosure with dimensions 87 x 141.8 x 137 mm (w x h x d). SECTR was implemented using a custom-built 400 kHz 1050 nm swept-source. OCT and SER were simultaneously digitized on dual input channels of a 4 GS/s digitizer at 1.4 GS/s per channel. In vivo human en face SER and cross-sectional OCT images were acquired at 350 fps. OCT volumes of 1000 B-scans were acquired in 2.86 s. We believe clinical translation of our compact handheld design will benefit point-of-care ophthalmic diagnostics in patients who are unable to be imaged on conventional slit-lamp based systems, such as infants and the bedridden. When combined with multi-volumetric registration methods, handheld SECTR will have advantages in motion-artifact free imaging over existing handheld technologies.

Detection of oral early cancerous lesion by using polarization-sensitive optical coherence tomography: mice model

NASA Astrophysics Data System (ADS)

Lee, Hong-Yi; Chen, Ping-Hsien; Lee, Tzu-Han; Chang, Kuo-Wei; Kuo, Wen-Chuan

2018-02-01

Oral cancer is the 11th most common cancer worldwide, especially in a male adult. The median age of death in oral cancer was 55 years, 10-20 years earlier than other cancers. Presently, oral cancer is often found in late stage, because the lesion is often flat in early stage and is difficult to diagnose under traditional white light imaging. The only definitive method for determining cancer is an invasive biopsy and then using histology examination. How to detect precancerous lesions or early malignant lesions is an important issue for improving prognosis of oral cancer. Optical coherence tomography (OCT) is a new optical tool for diagnosing early malignant lesions in the skin or gastrointestinal tract recently. Here we report a new method for detecting precancerous or early malignant oral lesions by using swept source polarization-sensitive optical coherence tomography (PS-OCT) with center-wavelength 1310 nm, bandwidth 110 nm and 100 kHz swept rate. We used all single-mode fiber design to detect the change of birefringence information in the epithelium structure. This system has an advantage that enables measurement of backscattered intensity and birefringence simultaneously with only one A-scan per transverse location. In preliminary result, we computed the slope of the every A-scan signal in tissue part using a linear-curve fitting in backscattered intensity and birefringence on the enface. In this research, we used an oral cancer mice model for observing the change of structure and birefringence properties in different stages of oral cancer mice. We presented the parametric enface imaging that can detect the early oral malignant lesions.

All-optical simultaneous multichannel quadrature phase shift keying signal regeneration based on phase-sensitive amplification

NASA Astrophysics Data System (ADS)

Wang, Hongxiang; Wang, Qi; Bai, Lin; Ji, Yuefeng

2018-01-01

A scheme is proposed to realize the all-optical phase regeneration of four-channel quadrature phase shift keying (QPSK) signal based on phase-sensitive amplification. By utilizing conjugate pump and common pump in a highly nonlinear optical fiber, degenerate four-wave mixing process is observed, and QPSK signals are regenerated. The number of waves is reduced to decrease the cross talk caused by undesired nonlinear interaction during the coherent superposition process. In addition, to avoid the effect of overlapping frequency, frequency spans between pumps and signals are set to be nonintegral multiples. Optical signal-to-noise ratio improvement is validated by bit error rate measurements. Compared with single-channel regeneration, multichannel regeneration brings 0.4-dB OSNR penalty when the value of BER is 10-3, which shows the cross talk in regeneration process is negligible.

Laser a balayage spectral double-bande pour l'imagerie biomedicale multimodale

NASA Astrophysics Data System (ADS)

Goulamhoussen, Nadir

A novel swept laser providing simultaneous dual-band (780nm and 1 300 nm) wavelength scanning has been designed for use in multimodal imaging systems. The swept laser is based on two gain media : a fibered semiconductor optical amplifier (SOA) centered at 1 300nm and a free-space laser diode centered at 780 nm. Simultaneous wavelength tuning for both bands is obtained by separate wavelength filters set up around the same rotating polygonal mirror. For each band, a telescope in an infinite conjugate setup converges the wavelengths dispersed by a grating on the polygon. The polygon reflects back a narrow band of wavelengths for amplification in the gain medium. Rotating the polygon enables wavelength tuning and imaging at a rate of 6 000 to 30 000 spectral lines/s, or A-lines/s in Optical Coherence Tomography (OCT). The 780nm source has a bandwidth of 37 nm, a fibered output power of 54 mW and a coherence length of 11 mm. The 1 300nm source has a bandwidth of 75 nm, a fibered output power of 17mW and a coherence length of 7.2 mm. Three multimodal systems were designed to test the potential of the swept laser in biomedical imaging. A two color OCT which allows three-dimensional in depth imaging of biological tissues with good morphological contrast was first designed, including a novel arrangement for balanced detection in both bands. A simultaneous OCT and SECM instrument was also built in which spectrally encoded confocal microscopy (SECM) provides en face images of subcellular features with high resolution on top of the 3D high penetration image obtained by OCT. Finally, a system combining OCT with fluorescence was designed, thus adding functional imaging to structural OCT images. There are many prospective paths for these three modalities, first among them the adaptation of the systems such that they may be used with imaging probes. One potential solution would be the development of novel fiber components to combine the illumination of theses modalities while demultiplexing their detection, and as would be the development of new optomechanics to enable 3D real-time in vivo imaging.

Methods, systems, and apparatus for storage, transfer and/or control of information via matter wave dynamics

NASA Technical Reports Server (NTRS)

Vestergaard Hau, Lene (Inventor)

2012-01-01

Methods, systems and apparatus for generating atomic traps, and for storing, controlling and transferring information between first and second spatially separated phase-coherent objects, or using a single phase-coherent object. For plural objects, both phase-coherent objects have a macroscopic occupation of a particular quantum state by identical bosons or identical BCS-paired fermions. The information may be optical information, and the phase-coherent object(s) may be Bose-Einstein condensates, superfluids, or superconductors. The information is stored in the first phase-coherent object at a first storage time and recovered from the second phase-coherent object, or the same first phase-coherent object, at a second revival time. In one example, an integrated silicon wafer-based optical buffer includes an electrolytic atom source to provide the phase-coherent object(s), a nanoscale atomic trap for the phase-coherent object(s), and semiconductor-based optical sources to cool the phase-coherent object(s) and provide coupling fields for storage and transfer of optical information.

Study on turbulence characteristics and sensitivity of quadrant analysis to threshold level in Lake Taihu.

PubMed

Weng, Shenglin; Li, Yiping; Wei, Jin; Du, Wei; Gao, Xiaomeng; Wang, Wencai; Wang, Jianwei; Acharya, Kumud; Luo, Liancong

2018-05-01

The identification of coherent structures is very important in investigating the sediment transport mechanism and controlling the eutrophication in shallow lakes. This study analyzed the turbulence characteristics and the sensitivity of quadrant analysis to threshold level. Simultaneous in situ measurements of velocities and suspended sediment concentration (SSC) were conducted in Lake Taihu with acoustic Doppler velocimeter (ADV) and optical backscatter sensor (OBS) instruments. The results show that the increase in hole size makes the difference between dominant and non-dominant events more distinct. Wind velocity determines the frequency of occurrence of sweep and ejection events, which provide dominant contributions to the Reynolds stress. The increase of wind velocity enlarges the magnitude of coherent events but has little impact on the events frequency with the same hole size. The events occurring within short periods provide large contributions to the momentum flux. Transportation and diffusion of sediment are in control of the intermittent coherent events to a large extent.

Conditions for space invariance in optical data processors used with coherent or noncoherent light.

PubMed

Arsenault, H R

1972-10-01

The conditions for space invariance in coherent and noncoherent optical processors are considered. All linear optical processors are shown to belong to one of two types. The conditions for space invariance are more stringent for noncoherent processors than for coherent processors, so that a system that is linear in coherent light may be nonlinear in noncoherent light. However, any processor that is linear in noncoherent light is also linear in the coherent limit.

A design of a high speed dual spectrometer by single line scan camera

NASA Astrophysics Data System (ADS)

Palawong, Kunakorn; Meemon, Panomsak

2018-03-01

A spectrometer that can capture two orthogonal polarization components of s light beam is demanded for polarization sensitive imaging system. Here, we describe the design and implementation of a high speed spectrometer for simultaneous capturing of two orthogonal polarization components, i.e. vertical and horizontal components, of light beam. The design consists of a polarization beam splitter, two polarization-maintain optical fibers, two collimators, a single line-scan camera, a focusing lens, and a reflection blaze grating. The alignment of two beam paths was designed to be symmetrically incident on the blaze side and reverse blaze side of reflection grating, respectively. The two diffracted beams were passed through the same focusing lens and focused on the single line-scan sensors of a CMOS camera. The two spectra of orthogonal polarization were imaged on 1000 pixels per spectrum. With the proposed setup, the amplitude and shape of the two detected spectra can be controlled by rotating the collimators. The technique for optical alignment of spectrometer will be presented and discussed. The two orthogonal polarization spectra can be simultaneously captured at a speed of 70,000 spectra per second. The high speed dual spectrometer can simultaneously detected two orthogonal polarizations, which is an important component for the development of polarization-sensitive optical coherence tomography. The performance of the spectrometer have been measured and analyzed.

Automated 3D segmentation of intraretinal layers from optic nerve head optical coherence tomography images

NASA Astrophysics Data System (ADS)

Antony, Bhavna J.; Abràmoff, Michael D.; Lee, Kyungmoo; Sonkova, Pavlina; Gupta, Priya; Kwon, Young; Niemeijer, Meindert; Hu, Zhihong; Garvin, Mona K.

2010-03-01

Optical coherence tomography (OCT), being a noninvasive imaging modality, has begun to find vast use in the diagnosis and management of ocular diseases such as glaucoma, where the retinal nerve fiber layer (RNFL) has been known to thin. Furthermore, the recent availability of the considerably larger volumetric data with spectral-domain OCT has increased the need for new processing techniques. In this paper, we present an automated 3-D graph-theoretic approach for the segmentation of 7 surfaces (6 layers) of the retina from 3-D spectral-domain OCT images centered on the optic nerve head (ONH). The multiple surfaces are detected simultaneously through the computation of a minimum-cost closed set in a vertex-weighted graph constructed using edge/regional information, and subject to a priori determined varying surface interaction and smoothness constraints. The method also addresses the challenges posed by presence of the large blood vessels and the optic disc. The algorithm was compared to the average manual tracings of two observers on a total of 15 volumetric scans, and the border positioning error was found to be 7.25 +/- 1.08 μm and 8.94 +/- 3.76 μm for the normal and glaucomatous eyes, respectively. The RNFL thickness was also computed for 26 normal and 70 glaucomatous scans where the glaucomatous eyes showed a significant thinning (p < 0.01, mean thickness 73.7 +/- 32.7 μm in normal eyes versus 60.4 +/- 25.2 μm in glaucomatous eyes).

Noncontact measurement of substrate temperature by optical low-coherence interferometry in high-power pulsed magnetron sputtering

NASA Astrophysics Data System (ADS)

Hattori, Katsuhiro; Ohta, Takayuki; Oda, Akinori; Kousaka, Hiroyuki

2018-01-01

Substrate temperature is one of the important parameters that affect the quality of deposited films. The monitoring of the substrate temperature is an important technique of controlling the deposition process precisely. In this study, the Si substrate temperature in high-power pulse magnetron sputtering (HPPMS) was measured by a noncontact method based on optical low-coherence interferometry (LCI). The measurement was simultaneously performed using an LCI system and a thermocouple (TC) as a contact measurement method. The difference in measured value between the LCI system and the TC was about 7.4 °C. The reproducibilities of measurement for the LCI system and TC were ±0.7 and ±2.0 °C, respectively. The heat influx from the plasma to the substrate was estimated using the temporal variation of substrate temperature and increased from 19.7 to 160.0 mW/cm2 with increasing target applied voltage. The major factor for the enhancement of the heat influx would be charged species such as ions and electrons owing to the high ionization degree of sputtered metal particles in HPPMS.

Joint aperture detection for speckle reduction and increased collection efficiency in ophthalmic MHz OCT

PubMed Central

Klein, Thomas; André, Raphael; Wieser, Wolfgang; Pfeiffer, Tom; Huber, Robert

2013-01-01

Joint-aperture optical coherence tomography (JA-OCT) is an angle-resolved OCT method, in which illumination from an active channel is simultaneously probed by several passive channels. JA-OCT increases the collection efficiency and effective sensitivity of the OCT system without increasing the power on the sample. Additionally, JA-OCT provides angular scattering information about the sample in a single acquisition, so the OCT imaging speed is not reduced. Thus, JA-OCT is especially suitable for ultra high speed in-vivo imaging. JA-OCT is compared to other angle-resolved techniques, and the relation between joint aperture imaging, adaptive optics, coherent and incoherent compounding is discussed. We present angle-resolved imaging of the human retina at an axial scan rate of 1.68 MHz, and demonstrate the benefits of JA-OCT: Speckle reduction, signal increase and suppression of specular and parasitic reflections. Moreover, in the future JA-OCT may allow for the reconstruction of the full Doppler vector and tissue discrimination by analysis of the angular scattering dependence. PMID:23577296

Stimulated penetrating keratoplasty using real-time virtual intraoperative surgical optical coherence tomography

PubMed Central

Lee, Changho; Kim, Kyungun; Han, Seunghoon; Kim, Sehui; Lee, Jun Hoon; Kim, Hong kyun; Kim, Chulhong; Jung, Woonggyu; Kim, Jeehyun

2014-01-01

Abstract. An intraoperative surgical microscope is an essential tool in a neuro- or ophthalmological surgical environment. Yet, it has an inherent limitation to classify subsurface information because it only provides the surface images. To compensate for and assist in this problem, combining the surgical microscope with optical coherence tomography (OCT) has been adapted. We developed a real-time virtual intraoperative surgical OCT (VISOCT) system by adapting a spectral-domain OCT scanner with a commercial surgical microscope. Thanks to our custom-made beam splitting and image display subsystems, the OCT images and microscopic images are simultaneously visualized through an ocular lens or the eyepiece of the microscope. This improvement helps surgeons to focus on the operation without distraction to view OCT images on another separate display. Moreover, displaying the OCT live images on the eyepiece helps surgeon’s depth perception during the surgeries. Finally, we successfully processed stimulated penetrating keratoplasty in live rabbits. We believe that these technical achievements are crucial to enhance the usability of the VISOCT system in a real surgical operating condition. PMID:24604471

Massively parallel sensing of trace molecules and their isotopologues with broadband subharmonic mid-infrared frequency combs

NASA Astrophysics Data System (ADS)

Muraviev, A. V.; Smolski, V. O.; Loparo, Z. E.; Vodopyanov, K. L.

2018-04-01

Mid-infrared spectroscopy offers supreme sensitivity for the detection of trace gases, solids and liquids based on tell-tale vibrational bands specific to this spectral region. Here, we present a new platform for mid-infrared dual-comb Fourier-transform spectroscopy based on a pair of ultra-broadband subharmonic optical parametric oscillators pumped by two phase-locked thulium-fibre combs. Our system provides fast (7 ms for a single interferogram), moving-parts-free, simultaneous acquisition of 350,000 spectral data points, spaced by a 115 MHz intermodal interval over the 3.1-5.5 µm spectral range. Parallel detection of 22 trace molecular species in a gas mixture, including isotopologues containing isotopes such as 13C, 18O, 17O, 15N, 34S, 33S and deuterium, with part-per-billion sensitivity and sub-Doppler resolution is demonstrated. The technique also features absolute optical frequency referencing to an atomic clock, a high degree of mutual coherence between the two mid-infrared combs with a relative comb-tooth linewidth of 25 mHz, coherent averaging and feasibility for kilohertz-scale spectral resolution.

Application of wearable optical coherence tomography (OCT) and loop-mediated isothermal amplification (LAMP) techniques for in situ real-time field inspection of apple Marssonina blotch disease

NASA Astrophysics Data System (ADS)

Wijesinghe, Ruchire Eranga; Lee, Seung-Yeol; Ravichandran, Naresh Kumar; Shirazi, Muhammad Faizan; Han, Sangyeop; Jeong, Hyosang; Kim, Pilun; Jung, Hee-Young; Jeon, Mansik; Kim, Jeehyun

2017-04-01

Here we describe the possible application of optical coherence tomography (OCT) to inspect Marssonina coronaria infected apple blotch disease of in situ apple leaves. To fulfill the in situ field inspection requirement, we developed a compact wearable OCT system. For the confirmation of OCT results, simultaneous experiment was performed in realtime using loop-mediated isothermal amplification (LAMP), which is frequently used in agriculture. LAMP method was developed as an alternative approach for the inspection of disease. We performed field inspection for 30 consecutive days, and all the acquired results from both OCT and lamp were compared to confirm the correlation. A clear identification between healthy specimens, apparently healthy but infected specimens, and infected specimens could be obtained through the real-time OCT images, and the correlation between OCT and lamp results was confirmed through the obtained realtime lamp results. Based on this feasibility study, we conclude that the combination of both these diagnosing modalities can be effective for various novel agricultural discoveries.

Accommodation-induced variations in retinal thickness measured by spectral domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Fan, Shanhui; Sun, Yong; Dai, Cuixia; Zheng, Haihua; Ren, Qiushi; Jiao, Shuliang; Zhou, Chuanqing

2014-09-01

To research retinal stretching or distortion with accommodation, accommodation-induced changes in retinal thickness (RT) in the macular area were investigated in a population of young adults (n=23) by using a dual-channel spectral domain optical coherence tomography (SD-OCT) system manufactured in-house for this study. This dual-channel SD-OCT is capable of imaging the cornea and retina simultaneously with an imaging speed of 24 kHz A-line scan rate, which can provide the anatomical dimensions of the eye, including the RT and axial length. Thus, the modification of the RT with accommodation can be calculated. A significant decrease in the RT (13.50±1.25 μm) was observed during maximum accommodation. In the 4 mm×4 mm macular area centered at the fovea, we did not find a significant quadrant-dependent difference in retinal volume change, which indicates that neither retinal stretching nor distortion was quadrant-dependent during accommodation. We speculate that the changes in RT with maximum accommodation resulted from accommodation-induced ciliary muscle contractions.

Three-dimensional calibration targets for optical coherence tomography

NASA Astrophysics Data System (ADS)

Gabriele Sandrian, Michelle; Tomlins, Pete; Woolliams, Peter; Rasakanthan, Janarthanan; Lee, Graham C.; Yang, Anna; Považay, Boris; Alex, Aneesh; Sugden, Kate; Drexler, Wolfgang

2012-03-01

The recent expansion of clinical applications for optical coherence tomography (OCT) is driving the development of approaches for consistent image acquisition. There is a simultaneous need for time-stable, easy-to-use imaging targets for calibration and standardization of OCT devices. We present calibration targets consisting of three-dimensional structures etched into nanoparticle-embedded resin. Spherical iron oxide nanoparticles with a predominant particle diameter of 400 nm were homogeneously dispersed in a two part polyurethane resin and allowed to harden overnight. These samples were then etched using a precision micromachining femtosecond laser with a center wavelength of 1026 nm, 100kHz repetition rate and 450 fs pulse duration. A series of lines in depth were etched, varying the percentage of inscription energy and speed of the translation stage moving the target with respect to the laser. Samples were imaged with a dual wavelength spectral-domain OCT system (λ=800nm, ▵λ~180nm, and λ=1325nm, ▵λ~100nm) and point-spread function of nanoparticles within the target was measured.

Simultaneous measurement of lipid and aqueous layers of tear film using optical coherence tomography and statistical decision theory

NASA Astrophysics Data System (ADS)

Huang, Jinxin; Clarkson, Eric; Kupinski, Matthew; Rolland, Jannick P.

2014-03-01

The prevalence of Dry Eye Disease (DED) in the USA is approximately 40 million in aging adults with about $3.8 billion economic burden. However, a comprehensive understanding of tear film dynamics, which is the prerequisite to advance the management of DED, is yet to be realized. To extend our understanding of tear film dynamics, we investigate the simultaneous estimation of the lipid and aqueous layers thicknesses with the combination of optical coherence tomography (OCT) and statistical decision theory. In specific, we develop a mathematical model for Fourier-domain OCT where we take into account the different statistical processes associated with the imaging chain. We formulate the first-order and second-order statistical quantities of the output of the OCT system, which can generate some simulated OCT spectra. A tear film model, which includes a lipid and aqueous layer on top of a rough corneal surface, is the object being imaged. Then we further implement a Maximum-likelihood (ML) estimator to interpret the simulated OCT data to estimate the thicknesses of both layers of the tear film. Results show that an axial resolution of 1 μm allows estimates down to nanometers scale. We use the root mean square error of the estimates as a metric to evaluate the system parameters, such as the tradeoff between the imaging speed and the precision of estimation. This framework further provides the theoretical basics to optimize the imaging setup for a specific thickness estimation task.

In vivo wide-field multispectral scanning laser ophthalmoscopy–optical coherence tomography mouse retinal imager: longitudinal imaging of ganglion cells, microglia, and Müller glia, and mapping of the mouse retinal and choroidal vasculature

PubMed Central

Zhang, Pengfei; Zam, Azhar; Jian, Yifan; Wang, Xinlei; Li, Yuanpei; Lam, Kit S.; Burns, Marie E.; Sarunic, Marinko V.; Pugh, Edward N.; Zawadzki, Robert J.

2015-01-01

Abstract. Scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) provide complementary views of the retina, with the former collecting fluorescence data with good lateral but relatively low-axial resolution, and the latter collecting label-free backscattering data with comparable lateral but much higher axial resolution. To take maximal advantage of the information of both modalities in mouse retinal imaging, we have constructed a compact, four-channel, wide-field (∼50  deg) system that simultaneously acquires and automatically coregisters three channels of confocal SLO and Fourier domain OCT data. The scanner control system allows “zoomed” imaging of a region of interest identified in a wide-field image, providing efficient digital sampling and localization of cellular resolution features in longitudinal imaging of individual mice. The SLO is equipped with a “flip-in” spectrometer that enables spectral “fingerprinting” of fluorochromes. Segmentation of retina layers and en face display facilitate spatial comparison of OCT data with SLO fluorescence patterns. We demonstrate that the system can be used to image an individual retinal ganglion cell over many months, to simultaneously image microglia and Müller glia expressing different fluorochromes, to characterize the distinctive spatial distributions and clearance times of circulating fluorochromes with different molecular sizes, and to produce unequivocal images of the heretofore uncharacterized mouse choroidal vasculature. PMID:26677070

Laser diode technology for coherent communications

NASA Technical Reports Server (NTRS)

Channin, D. J.; Palfrey, S. L.; Toda, M.

1989-01-01

The effect of diode laser characteristics on the overall performance capabilities of coherent communication systems is discussed. In particular, attention is given to optical performance issues for diode lasers in coherent systems, measurements of key performance parameters, and optical requirements for coherent single-channel and multichannel communication systems. The discussion also covers limitations imposed by diode laser optical performance on multichannel system capabilities and implications for future developments.

Propagation of a partially coherent hollow vortex Gaussian beam through a paraxial ABCD optical system in turbulent atmosphere.

PubMed

Zhou, Guoquan; Cai, Yangjian; Chu, Xiuxiang

2012-04-23

The propagation of a partially coherent hollow vortex Gaussian beam through a paraxial ABCD optical system in turbulent atmosphere has been investigated. The analytical expressions for the average intensity and the degree of the polarization of a partially coherent hollow vortex Gaussian beam through a paraxial ABCD optical system are derived in turbulent atmosphere, respectively. The average intensity distribution and the degree of the polarization of a partially coherent hollow vortex Gaussian beam in turbulent atmosphere are numerically demonstrated. The influences of the beam parameters, the topological charge, the transverse coherent lengths, and the structure constant of the atmospheric turbulence on the propagation of a partially coherent hollow vortex Gaussian beam in turbulent atmosphere are also examined in detail. This research is beneficial to the practical applications in free-space optical communications and the remote sensing of the dark hollow beams. © 2012 Optical Society of America

Increasing the information rates of optical communications via coded modulation: a study of transceiver performance

NASA Astrophysics Data System (ADS)

Maher, Robert; Alvarado, Alex; Lavery, Domaniç; Bayvel, Polina

2016-02-01

Optical fibre underpins the global communications infrastructure and has experienced an astonishing evolution over the past four decades, with current commercial systems transmitting data rates in excess of 10 Tb/s over a single fibre core. The continuation of this dramatic growth in throughput has become constrained due to a power dependent nonlinear distortion arising from a phenomenon known as the Kerr effect. The mitigation of fibre nonlinearities is an area of intense research. However, even in the absence of nonlinear distortion, the practical limit on the transmission throughput of a single fibre core is dominated by the finite signal-to-noise ratio (SNR) afforded by current state-of-the-art coherent optical transceivers. Therefore, the key to maximising the number of information bits that can be reliably transmitted over a fibre channel hinges on the simultaneous optimisation of the modulation format and code rate, based on the SNR achieved at the receiver. In this work, we use an information theoretic approach based on the mutual information and the generalised mutual information to characterise a state-of-the-art dual polarisation m-ary quadrature amplitude modulation transceiver and subsequently apply this methodology to a 15-carrier super-channel to achieve the highest throughput (1.125 Tb/s) ever recorded using a single coherent receiver.

Dual modality instrument for simultaneous optical coherence tomography imaging and fluorescence spectroscopy.

PubMed

Barton, Jennifer Kehlet; Guzman, Francisco; Tumlinson, Alexandre

2004-01-01

We develop a dual-modality device that combines the anatomical imaging capabilities of optical coherence tomography (OCT) with the functional capabilities of laser-induced fluorescence (LIF) spectroscopy. OCT provides cross-sectional images of tissue structure to a depth of up to 2 mm with approximately 10-microm resolution. LIF spectroscopy provides histochemical information in the form of emission spectra from a given tissue location. The OCT subsystem utilizes a superluminescent diode with a center wavelength of 1300 nm, whereas a helium cadmium laser provides the LIF excitation source at wavelengths of 325 and 442 nm. Preliminary data are obtained on eight postmortem aorta samples, each 10 mm in length. OCT images and LIF spectra give complementary information from normal and atherosclerotic portions of aorta wall. OCT images show structures such as intima, media, internal elastic lamina, and fibrotic regions. Emission spectra ratios of 520/490 (325-nm excitation) and 595/635 (442-nm excitation) could be used to identify normal and plaque regions with 97 and 91% correct classification rates, respectively. With miniaturization of the delivery probe and improvements in system speed, this dual-modality device could provide a valuable tool for identification and characterization of atherosclerotic plaques. (c) 2004 Society of Photo-Optical Instrumentation Engineers.

Application of maximum-likelihood estimation in optical coherence tomography for nanometer-class thickness estimation

NASA Astrophysics Data System (ADS)

Huang, Jinxin; Yuan, Qun; Tankam, Patrice; Clarkson, Eric; Kupinski, Matthew; Hindman, Holly B.; Aquavella, James V.; Rolland, Jannick P.

2015-03-01

In biophotonics imaging, one important and quantitative task is layer-thickness estimation. In this study, we investigate the approach of combining optical coherence tomography and a maximum-likelihood (ML) estimator for layer thickness estimation in the context of tear film imaging. The motivation of this study is to extend our understanding of tear film dynamics, which is the prerequisite to advance the management of Dry Eye Disease, through the simultaneous estimation of the thickness of the tear film lipid and aqueous layers. The estimator takes into account the different statistical processes associated with the imaging chain. We theoretically investigated the impact of key system parameters, such as the axial point spread functions (PSF) and various sources of noise on measurement uncertainty. Simulations show that an OCT system with a 1 μm axial PSF (FWHM) allows unbiased estimates down to nanometers with nanometer precision. In implementation, we built a customized Fourier domain OCT system that operates in the 600 to 1000 nm spectral window and achieves 0.93 micron axial PSF in corneal epithelium. We then validated the theoretical framework with physical phantoms made of custom optical coatings, with layer thicknesses from tens of nanometers to microns. Results demonstrate unbiased nanometer-class thickness estimates in three different physical phantoms.

Increasing the information rates of optical communications via coded modulation: a study of transceiver performance

PubMed Central

Maher, Robert; Alvarado, Alex; Lavery, Domaniç; Bayvel, Polina

2016-01-01

Optical fibre underpins the global communications infrastructure and has experienced an astonishing evolution over the past four decades, with current commercial systems transmitting data rates in excess of 10 Tb/s over a single fibre core. The continuation of this dramatic growth in throughput has become constrained due to a power dependent nonlinear distortion arising from a phenomenon known as the Kerr effect. The mitigation of fibre nonlinearities is an area of intense research. However, even in the absence of nonlinear distortion, the practical limit on the transmission throughput of a single fibre core is dominated by the finite signal-to-noise ratio (SNR) afforded by current state-of-the-art coherent optical transceivers. Therefore, the key to maximising the number of information bits that can be reliably transmitted over a fibre channel hinges on the simultaneous optimisation of the modulation format and code rate, based on the SNR achieved at the receiver. In this work, we use an information theoretic approach based on the mutual information and the generalised mutual information to characterise a state-of-the-art dual polarisation m-ary quadrature amplitude modulation transceiver and subsequently apply this methodology to a 15-carrier super-channel to achieve the highest throughput (1.125 Tb/s) ever recorded using a single coherent receiver. PMID:26864633

Measurement of in vivo basal-turn vibrations of the organ of Corti using phase-sensitive Fourier domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Ramamoorthy, Sripriya; Zhang, Yuan; Petrie, Tracy; Chen, Fangyi; Subhash, Hrebesh M.; Choudhury, Niloy; Wang, Ruikang; Jacques, Steven L.; Nuttall, Alfred L.

2013-03-01

A major reason we can perceive faint sounds and communicate in noisy environments is that the outer hair cells of the organ of Corti enhance the sound-evoked motions inside the cochlea. To understand how the organ of Corti works, we have built and tested the phase-sensitive Fourier domain optical coherence tomography (PSFDOCT) system. This system has key advantages over our previous time domain OCT system [1]. The PSFDOCT system has better signal to noise and simultaneously acquires vibration data from all points along the optical-axis [2]. Feasibility of this system to measure in vitro cochlear vibrations in the apex was demonstrated earlier [3]. In this study, we measure the in vivo vibrations of the organ of Corti via round window in live anaesthetized guinea pigs using PSFDOCT. This region of the guinea pig cochlea responds to very high frequencies (10 - 40 kHz). The current vibration noise floor for native organ of Corti tissue is 0.03 nm in this frequency range. Sound-induced vibrations of the stapes, which delivers input to the cochlea, are also measured. The measured vibrations of the organ of Corti demonstrate non-linear compression and active amplification characteristic of sensitive mammalian cochlea.

Full-Field Spectroscopy at Megahertz-frame-rates: Application of Coherent Time-Stretch Transform

NASA Astrophysics Data System (ADS)

DeVore, Peter Thomas Setsuda

Outliers or rogue events are found extensively in our world and have incredible effects. Also called rare events, they arise in the distribution of wealth (e.g., Pareto index), finance, network traffic, ocean waves, and e-commerce (selling less of more). Interest in rare optical events exploded after the sighting of optical rogue waves in laboratory experiments at UCLA. Detecting such tail events in fast streams of information necessitates real-time measurements. The Coherent Time-Stretch Transform chirps a pulsed source of radiation so that its temporal envelope matches its spectral profile (analogous to the far field regime of spatial diffraction), and the mapped spectral electric field is slow enough to be captured by a real-time digitizer. Combining this technique with spectral encoding, the time stretch technique has enabled a new class of ultra-high performance spectrometers and cameras (30+ MHz), and analog-to-digital converters that have led to the discovery of optical rogue waves and detection of cancer cells in blood with one in a million sensitivity. Conventionally, the Coherent Time-Stretch Transform maps the spectrum into the temporal electric field, but the time-dilation process along with inherent fiber losses results in reduction of peak power and loss of sensitivity, a problem exacerbated by extremely narrow molecular linewidths. The loss issue notwithstanding, in many cases the requisite dispersive optical device is not available. By extending the Coherent Time-Stretch Transform to the temporal near field, I have demonstrated, for the first time, phase-sensitive absorption spectroscopy of a gaseous sample at millions of frames per second. As the Coherent Time-Stretch Transform may capture both near and far field optical waves, it is a complete spectro-temporal optical characterization tool. This is manifested as an amplitude-dependent chirp, which implies the ability to measure the complex refractive index dispersion at megahertz frame rates. This technique is not only four orders of magnitude faster than even the fastest (kHz) spectrometers, but will also enable capture of real-time complex dielectric function dynamics of plasmas and chemical reactions (e.g. combustion). It also has applications in high-energy physics, biology, and monitoring fast high-throughput industrial processes. Adding an electro-optic modulator to the Time-Stretch Transform yields time-to-time mapping of electrical waveforms. Known as TiSER, it is an analog slow-motion processor that uses light to reduce the bandwidth of broadband RF signals for capture by high-sensitivity analog-to-digital converters (ADC). However, the electro-optic modulator limits the electrical bandwidth of TiSER. To solve this, I introduced Optical Sideband-only Amplification, wherein electro-optically generated modulation (containing the RF information) is amplified at the expense of the carrier, addressing the two most important problems plaguing electro-optic modulators: (1) low RF bandwidth and (2) high required RF drive voltages. I demonstrated drive voltage reductions of 5x at 10 GHz and 10x at 50 GHz, while simultaneously increasing the RF bandwidth.

A chip-integrated coherent photonic-phononic memory.

PubMed

Merklein, Moritz; Stiller, Birgit; Vu, Khu; Madden, Stephen J; Eggleton, Benjamin J

2017-09-18

Controlling and manipulating quanta of coherent acoustic vibrations-phonons-in integrated circuits has recently drawn a lot of attention, since phonons can function as unique links between radiofrequency and optical signals, allow access to quantum regimes and offer advanced signal processing capabilities. Recent approaches based on optomechanical resonators have achieved impressive quality factors allowing for storage of optical signals. However, so far these techniques have been limited in bandwidth and are incompatible with multi-wavelength operation. In this work, we experimentally demonstrate a coherent buffer in an integrated planar optical waveguide by transferring the optical information coherently to an acoustic hypersound wave. Optical information is extracted using the reverse process. These hypersound phonons have similar wavelengths as the optical photons but travel at five orders of magnitude lower velocity. We demonstrate the storage of phase and amplitude of optical information with gigahertz bandwidth and show operation at separate wavelengths with negligible cross-talk.Optical storage implementations based on optomechanical resonator are limited to one wavelength. Here, exploiting stimulated Brillouin scattering, the authors demonstrate a coherent optical memory based on a planar integrated waveguide, which can operate at different wavelengths without cross-talk.

Structure and symmetry in coherent perfect polarization rotation

NASA Astrophysics Data System (ADS)

Crescimanno, Michael; Zhou, Chuanhong; Andrews, James H.; Baker, Michael A.

2015-01-01

Theoretical investigations of different routes to coherent perfect polarization rotation illustrate its phenomenological connection with coherent perfect absorption. Our study of systems with broken parity, layering, combined Faraday rotation and optical activity, or a rotator-loaded optical cavity highlights their similarity and suggests alternate approaches to improving and miniaturizing optical devices.

Optical coherence tomography angiography in age-related macular degeneration: The game changer.

PubMed

Lupidi, Marco; Cerquaglia, Alessio; Chhablani, Jay; Fiore, Tito; Singh, Sumit Randhir; Cardillo Piccolino, Felice; Corbucci, Roberta; Coscas, Florence; Coscas, Gabriel; Cagini, Carlo

2018-04-01

Optical coherence tomography angiography is one of the biggest advances in ophthalmic imaging. It enables a depth-resolved assessment of the retinal and choroidal blood flow, far exceeding the levels of detail commonly obtained with dye angiographies. One of the first applications of optical coherence tomography angiography was in detecting the presence of choroidal neovascularization in age-related macular degeneration and establishing its position in relation to the retinal pigmented epithelium and Bruch's membrane, and thereby classifying the CNV as type 1, type 2, type 3, or mixed lesions. Optical coherence tomography angiograms, due to the longer wavelength used by optical coherence tomography, showed a more distinct choroidal neovascularization vascular pattern than fluorescein angiography, since there is less suffering from light scattering or is less obscured by overlying subretinal hemorrhages or exudation. Qualitative and quantitative assessments of optical coherence tomography angiography findings in exudative and nonexudative age-related macular degeneration have been largely investigated within the past 3 years both in clinical and experimental settings. This review constitutes an up-to-date of all the potential applications of optical coherence tomography angiography in age-related macular degeneration in order to better understand how to translate its theoretical usefulness into the current clinical practice.

Coherence rephasing combined with spin-wave storage using chirped control pulses

NASA Astrophysics Data System (ADS)

Demeter, Gabor

2014-06-01

Photon-echo based optical quantum memory schemes often employ intermediate steps to transform optical coherences to spin coherences for longer storage times. We analyze a scheme that uses three identical chirped control pulses for coherence rephasing in an inhomogeneously broadened ensemble of three-level Λ systems. The pulses induce a cyclic permutation of the atomic populations in the adiabatic regime. Optical coherences created by a signal pulse are stored as spin coherences at an intermediate time interval, and are rephased for echo emission when the ensemble is returned to the initial state. Echo emission during a possible partial rephasing when the medium is inverted can be suppressed with an appropriate choice of control pulse wave vectors. We demonstrate that the scheme works in an optically dense ensemble, despite control pulse distortions during propagation. It integrates conveniently the spin-wave storage step into memory schemes based on a second rephasing of the atomic coherences.

Scrambled coherent superposition for enhanced optical fiber communication in the nonlinear transmission regime.

PubMed

Liu, Xiang; Chandrasekhar, S; Winzer, P J; Chraplyvy, A R; Tkach, R W; Zhu, B; Taunay, T F; Fishteyn, M; DiGiovanni, D J

2012-08-13

Coherent superposition of light waves has long been used in various fields of science, and recent advances in digital coherent detection and space-division multiplexing have enabled the coherent superposition of information-carrying optical signals to achieve better communication fidelity on amplified-spontaneous-noise limited communication links. However, fiber nonlinearity introduces highly correlated distortions on identical signals and diminishes the benefit of coherent superposition in nonlinear transmission regime. Here we experimentally demonstrate that through coordinated scrambling of signal constellations at the transmitter, together with appropriate unscrambling at the receiver, the full benefit of coherent superposition is retained in the nonlinear transmission regime of a space-diversity fiber link based on an innovatively engineered multi-core fiber. This scrambled coherent superposition may provide the flexibility of trading communication capacity for performance in future optical fiber networks, and may open new possibilities in high-performance and secure optical communications.

Coherent phonon optics in a chip with an electrically controlled active device.

PubMed

Poyser, Caroline L; Akimov, Andrey V; Campion, Richard P; Kent, Anthony J

2015-02-05

Phonon optics concerns operations with high-frequency acoustic waves in solid media in a similar way to how traditional optics operates with the light beams (i.e. photons). Phonon optics experiments with coherent terahertz and sub-terahertz phonons promise a revolution in various technical applications related to high-frequency acoustics, imaging, and heat transport. Previously, phonon optics used passive methods for manipulations with propagating phonon beams that did not enable their external control. Here we fabricate a phononic chip, which includes a generator of coherent monochromatic phonons with frequency 378 GHz, a sensitive coherent phonon detector, and an active layer: a doped semiconductor superlattice, with electrical contacts, inserted into the phonon propagation path. In the experiments, we demonstrate the modulation of the coherent phonon flux by an external electrical bias applied to the active layer. Phonon optics using external control broadens the spectrum of prospective applications of phononics on the nanometer scale.

Multi-Aperture Digital Coherent Combining for Free-Space Optical Communication Receivers

DTIC Science & Technology

2016-04-21

Distribution A: Public Release; unlimited distribution 2016 Optical Society of America OCIS codes: (060.1660) Coherent communications; (070.2025) Discrete ...Coherent combining algorithm Multi-aperture coherent combining enables using many discrete apertures together to create a large effective aperture. A

Integrated InAs/InP quantum-dot coherence comb lasers (Conference Presentation)

NASA Astrophysics Data System (ADS)

Lu, Zhenguo; Liu, Jiaren; Poole, Philip J.; Song, Chun-Ying; Webber, John; Mao, Linda; Chang, Shoude; Ding, Heping; Barrios, Pedro J.; Poitras, Daniel; Janz, Siegfried

2017-02-01

Current communication networks needs to keep up with the exponential growth of today's internet traffic, and telecommunications industry is looking for radically new integrated photonics components for new generation optical networks. We at National Research Council (NRC) Canada have successfully developed nanostructure InAs/InP quantum dot (QD) coherence comb lasers (CCLs) around 1.55 μm. Unlike uniform semiconductor layers in most telecommunication lasers, in these QD CCLs light is emitted and amplified by millions of semiconductor QDs less than 60 nm in diameter. Each QD acts like an isolated light source acting independently of its neighbours, and each QD emits light at its own unique wavelength. The end result is a QD CCL is more stable and has ultra-low timing jitter. But most importantly, a single QD CCL can simultaneously produce 50 or more separate laser beams at distinct wavelengths over the telecommunications C-band. Utilizing those unique properties we have put considerable effort well to design, grow and fabricate InAs/InP QD gain materials. After our integrated packaging and using electrical feedback-loop control systems, we have successfully demonstrated ultra-low intensity and phase noise, frequency-stabilized integrated QD CCLs with the repetition rates from 10 GHz to 100 GHz and the total output power up to 60 mW at room temperature. We have investigated their relative intensity noises, phase noises, RF beating signals and other performance of both filtered individual channel and the whole CCLs. Those highly phase-coherence comb lasers are the promising candidates for flexible bandwidth terabit coherent optical networks and signal processing applications.

Multimodal nonlinear microscope based on a compact fiber-format laser source

NASA Astrophysics Data System (ADS)

Crisafi, Francesco; Kumar, Vikas; Perri, Antonio; Marangoni, Marco; Cerullo, Giulio; Polli, Dario

2018-01-01

We present a multimodal non-linear optical (NLO) laser-scanning microscope, based on a compact fiber-format excitation laser and integrating coherent anti-Stokes Raman scattering (CARS), stimulated Raman scattering (SRS) and two-photon-excitation fluorescence (TPEF) on a single platform. We demonstrate its capabilities in simultaneously acquiring CARS and SRS images of a blend of 6-μm poly(methyl methacrylate) beads and 3-μm polystyrene beads. We then apply it to visualize cell walls and chloroplast of an unprocessed fresh leaf of Elodea aquatic plant via SRS and TPEF modalities, respectively. The presented NLO microscope, developed in house using off-the-shelf components, offers full accessibility to the optical path and ensures its easy re-configurability and flexibility.

Method and apparatus for producing laser radiation following two-photon excitation of a gaseous medium

DOEpatents

Bischel, William K. [Menlo Park, CA; Jacobs, Ralph R. [Livermore, CA; Prosnitz, Donald [Hamden, CT; Rhodes, Charles K. [Palo Alto, CA; Kelly, Patrick J. [Fort Lewis, WA

1979-02-20

Method and apparatus for producing laser radiation by two-photon optical pumping of an atomic or molecular gaseous medium and subsequent lasing action. A population inversion is created as a result of two-photon absorption of the gaseous species. Stark tuning is utilized, if necessary, in order to tune the two-photon transition into exact resonance. In particular, gaseous ammonia (NH.sub.3) or methyl fluoride (CH.sub.3 F) is optically pumped by a pair of CO.sub.2 lasers to create a population inversion resulting from simultaneous two-photon excitation of a high-lying vibrational state, and laser radiation is produced by stimulated emission of coherent radiation from the inverted level.

Method and apparatus for producing laser radiation following two-photon excitation of a gaseous medium

DOEpatents

Bischel, W.K.; Jacobs, R.R.; Prosnitz, D.P.; Rhodes, C.K.; Kelly, P.J.

1979-02-20

Method and apparatus are disclosed for producing laser radiation by two-photon optical pumping of an atomic or molecular gaseous medium and subsequent lasing action. A population inversion is created as a result of two-photon absorption of the gaseous species. Stark tuning is utilized, if necessary, in order to tune the two-photon transition into exact resonance. In particular, gaseous ammonia (NH[sub 3]) or methyl fluoride (CH[sub 3]F) is optically pumped by a pair of CO[sub 2] lasers to create a population inversion resulting from simultaneous two-photon excitation of a high-lying vibrational state, and laser radiation is produced by stimulated emission of coherent radiation from the inverted level. 3 figs.

Atmospheric free-space coherent optical communications with adaptive optics

NASA Astrophysics Data System (ADS)

Ting, Chueh; Zhang, Chengyu; Yang, Zikai

2017-02-01

Free-space coherent optical communications have a potential application to offer last mile bottleneck solution in future local area networks (LAN) because of their information carrier, information security and license-free status. Coherent optical communication systems using orthogonal frequency division multiplexing (OFDM) digital modulation are successfully demonstrated in a long-haul tens Giga bits via optical fiber, but they are not yet available in free space due to atmospheric turbulence-induced channel fading. Adaptive optics is recognized as a promising technology to mitigate the effects of atmospheric turbulence in free-space optics. In this paper, a free-space coherent optical communication system using an OFDM digital modulation scheme and adaptive optics (FSO OFDM AO) is proposed, a Gamma-Gamma distribution statistical channel fading model for the FSO OFDM AO system is examined, and FSO OFDM AO system performance is evaluated in terms of bit error rate (BER) versus various propagation distances.

Individual bioaerosol particle discrimination by multi-photon excited fluorescence.

PubMed

Kiselev, Denis; Bonacina, Luigi; Wolf, Jean-Pierre

2011-11-21

Femtosecond laser induced multi-photon excited fluorescence (MPEF) from individual airborne particles is tested for the first time for discriminating bioaerosols. The fluorescence spectra, analysed in 32 channels, exhibit a composite character originating from simultaneous two-photon and three-photon excitation at 790 nm. Simulants of bacteria aggregates (clusters of dyed polystyrene microspheres) and different pollen particles (Ragweed, Pecan, Mulberry) are clearly discriminated by their MPEF spectra. This demonstration experiment opens the way to more sophisticated spectroscopic schemes like pump-probe and coherent control. © 2011 Optical Society of America

EN FACE IMAGING OF RETINAL ARTERY MACROANEURYSMS USING SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHY.

PubMed

Hanhart, Joel; Strassman, Israel; Rozenman, Yaakov

2017-01-01

To describe the advantages of en face view with swept-source optical coherence tomography in assessing the morphologic features of retinal arterial macroaneurysms, their consequences on adjacent retina, planning laser treatment, and evaluating its effects. Three eyes were treated for retinal arterial macroaneurysms and followed by swept-source optical coherence tomography in 2014-2015. En face images of the retina and choroid were obtained by EnView, a swept-source optical coherence tomography program. Retinal arterial macroaneurysms have a typical optical coherence tomography appearance. En face view allows delineation of the macroaneurysm wall, thrombotic components within the dilation, and lumen measurement. Hemorrhage, lipids, and fluids can be precisely described in terms of amount and extent over the macula and depth. This technique is also practical for planning focal laser treatment and determining its effects. En face swept-source optical coherence tomography is a rapid, noninvasive, high-resolution, promising technology, which allows excellent visualization of retinal arterial macroaneurysms and their consequences on surrounding tissues. It could make angiography with intravenous injection redundant in planning and assessing therapy.

Spectral domain optical coherence tomography findings in tamoxifen retinopathy--a case report.

PubMed

Nair, Sandhya Narayanan; Anantharaman, Giridhar; Gopalakrishnan, Mahesh; Vyas, Jyothiprakash

2013-01-01

To report spectral domain optical coherence tomography findings in a case of typical tamoxifen retinopathy. In this observational case report, a patient with tamoxifen retinopathy was imaged with spectral domain optical coherence tomography and fundus auto fluorescence. Spectral domain optical coherence tomography showed numerous hyperreflective spots within the retina, mainly in the inner retinal layers in both the eyes. The external limiting membrane, the Inner Segment-Outer Segment junction, and the photoreceptors were not discernable at the fovea in the right eye. In the left eye, there was foveal atrophy with total loss of photoreceptors. The autofluorescent images showed macular hypofluorescence with foveal hyperfluorescence. Spectral domain optical coherence tomography demonstrated abnormalities in the outer retinal layers in tamoxifen retinopathy. There were also characteristic alterations in the autofluorescence pattern at the macula in tamoxifen retinopathy.

Characterization of dynamic physiology of the bladder by optical coherence tomography

NASA Astrophysics Data System (ADS)

Yuan, Zhijia; Keng, Kerri; Pan, Rubin; Ren, Hugang; Du, Congwu; Kim, Jason; Pan, Yingtian

2012-03-01

Because of its high spatial resolution and noninvasive imaging capabilities, optical coherence tomography has been used to characterize the morphological details of various biological tissues including urinary bladder and to diagnose their alternations (e.g., cancers). In addition to static morphology, the dynamic features of tissue morphology can provide important information that can be used to diagnose the physiological and functional characteristics of biological tissues. Here, we present the imaging studies based on optical coherence tomography to characterize motion related physiology and functions of rat bladder detrusor muscles and compared the results with traditional biomechanical measurements. Our results suggest that optical coherence tomography is capable of providing quantitative evaluation of contractile functions of intact bladder (without removing bladder epithelium and connective tissue), which is potentially of more clinical relevance for future clinical diagnosis - if incorporated with cystoscopic optical coherence tomography.

Coherent Excitation of Optical Phonons in GaAs by Broadband Terahertz Pulses

PubMed Central

Fu, Zhengping; Yamaguchi, Masashi

2016-01-01

Coherent excitation and control of lattice motion by electromagnetic radiation in optical frequency range has been reported through variety of indirect interaction mechanisms with phonon modes. However, coherent phonon excitation by direct interaction of electromagnetic radiation and nuclei has not been demonstrated experimentally in terahertz (THz) frequency range mainly due to the lack of THz emitters with broad bandwidth suitable for the purpose. We report the experimental observation of coherent phonon excitation and detection in GaAs using ultrafast THz-pump/optical-probe scheme. From the results of THz pump field dependence, pump/probe polarization dependence, and crystal orientation dependence, we attributed THz wave absorption and linear electro-optic effect to the excitation and detection mechanisms of coherent polar TO phonons. Furthermore, the carrier density dependence of the interaction of coherent phonons and free carriers is reported. PMID:27905563

Coupling Photonics and Coherent Spintronics for Low-Loss Flexible Optical Logic

DTIC Science & Technology

2015-12-02

AFRL-AFOSR-VA-TR-2016-0055 Coupling photonics and coherent spintronics for low-loss flexible optical logic Jesse Berezovsky CASE WESTERN RESERVE UNIV...2012 - 14/06/2015 4. TITLE AND SUBTITLE Coupling photonics and coherent spintronics for low-loss flexible optical logic 5a. CONTRACT NUMBER 5b...into devices, ranging from macroscopic optical cavities, to arrays of microlens cavities, to quantum dot-impregnated integrated polymer waveguides

Performance verification of adaptive optics for satellite-to-ground coherent optical communications at large zenith angle.

PubMed

Chen, Mo; Liu, Chao; Rui, Daoman; Xian, Hao

2018-02-19

Although there is an urgent demand, it is still a tremendous challenge to use the coherent optical communication technology to the satellite-to-ground data transmission system especially at large zenith angle due to the influence of atmospheric turbulence. Adaptive optics (AO) is a considerable scheme to solve the problem. In this paper, we integrate the adaptive optics (AO) to the coherent laser communications and the performances of mixing efficiency as well as bit-error-rate (BER) at different zenith angles are studied. The analytical results show that the increasing of zenith angle can severely decrease the performances of the coherent detection, and increase the BER to higher than 10 -3 , which is unacceptable. The simulative results of coherent detection with AO compensation indicate that the larger mixing efficiency and lower BER can be performed by the coherent receiver with a high-mode AO compensation. The experiment of correcting the atmospheric turbulence wavefront distortion using a 249-element AO system at large zenith angles is carried out. The result demonstrates that the AO system has a significant improvement on satellite-to-ground coherent optical communication system at large zenith angle. It also indicates that the 249-element AO system can only meet the needs of coherent communication systems at zenith angle smaller than 65̊ for the 1.8m telescope under weak and moderate turbulence.

High-speed asynchronous optical sampling for high-sensitivity detection of coherent phonons

NASA Astrophysics Data System (ADS)

Dekorsy, T.; Taubert, R.; Hudert, F.; Schrenk, G.; Bartels, A.; Cerna, R.; Kotaidis, V.; Plech, A.; Köhler, K.; Schmitz, J.; Wagner, J.

2007-12-01

A new optical pump-probe technique is implemented for the investigation of coherent acoustic phonon dynamics in the GHz to THz frequency range which is based on two asynchronously linked femtosecond lasers. Asynchronous optical sampling (ASOPS) provides the performance of on all-optical oscilloscope and allows us to record optically induced lattice dynamics over nanosecond times with femtosecond resolution at scan rates of 10 kHz without any moving part in the set-up. Within 1 minute of data acquisition time signal-to-noise ratios better than 107 are achieved. We present examples of the high-sensitivity detection of coherent phonons in superlattices and of the coherent acoustic vibration of metallic nanoparticles.

Fiber optic system for deflection and damage detection in morphing wing structures

NASA Astrophysics Data System (ADS)

Scheerer, M.; Djinovic, Z.; Schüller, M.

2013-04-01

Within the EC Clean Sky - Smart Fixed Wing Aircraft initiative concepts for actuating morphing wing structures are under development. In order for developing a complete integrated system including the actuation, the structure to be actuated and the closed loop control unit a hybrid deflection and damage monitoring system is required. The aim of the project "FOS3D" is to develop and validate a fiber optic sensing system based on low-coherence interferometry for simultaneous deflection and damage monitoring. The proposed system uses several distributed and multiplexed fiber optic Michelson interferometers to monitor the strain distribution over the actuated part. In addition the same sensor principle will be used to acquire and locate the acoustic emission signals originated from the onset and growth of defects like impact damages, cracks and delamination's. Within this paper the authors present the concept, analyses and first experimental results of the mentioned system.

Electrically Injected UV-Visible Nanowire Lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, George T.; Li, Changyi; Li, Qiming

2015-09-01

There is strong interest in minimizing the volume of lasers to enable ultracompact, low-power, coherent light sources. Nanowires represent an ideal candidate for such nanolasers as stand-alone optical cavities and gain media, and optically pumped nanowire lasing has been demonstrated in several semiconductor systems. Electrically injected nanowire lasers are needed to realize actual working devices but have been elusive due to limitations of current methods to address the requirement for nanowire device heterostructures with high material quality, controlled doping and geometry, low optical loss, and efficient carrier injection. In this project we proposed to demonstrate electrically injected single nanowire lasersmore » emitting in the important UV to visible wavelengths. Our approach to simultaneously address these challenges is based on high quality III-nitride nanowire device heterostructures with precisely controlled geometries and strong gain and mode confinement to minimize lasing thresholds, enabled by a unique top-down nanowire fabrication technique.« less

In-vivo multi-nonlinear optical imaging of a living cell using a supercontinuum light source generated from a photonic crystal fiber

NASA Astrophysics Data System (ADS)

Kano, Hideaki; Hamaguchi, Hiro-O.

2006-04-01

A supercontinuum light source generated with a femtosecond Ti:Sapphire oscillator has been used to obtain both vibrational and two-photon excitation fluorescence (TPEF) images of a living cell simultaneously at different wavelengths. Owing to an ultrabroadband spectral profile of the supercontinuum, multiple vibrational resonances have been detected through coherent anti-Stokes Raman scattering (CARS) process. In addition to the multiplex CARS process, multiple electronic states can be excited due to the broadband electronic two-photon excitation using the supercontinuum, giving rise to a two-photon excitation fluorescence (TPEF) signal. Using a living yeast cell whose nucleus is labeled by green fluorescent protein (GFP), we have succeeded in visualizing organelles such as mitochondria, septum, and nucleus through the CARS and the TPEF processes. The supercontinuum enables us to perform unique multi-nonlinear optical imaging through two different nonlinear optical processes.

Multimodal ophthalmic imaging using swept source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography

NASA Astrophysics Data System (ADS)

Malone, Joseph D.; El-Haddad, Mohamed T.; Tye, Logan A.; Majeau, Lucas; Godbout, Nicolas; Rollins, Andrew M.; Boudoux, Caroline; Tao, Yuankai K.

2016-03-01

Scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) benefit clinical diagnostic imaging in ophthalmology by enabling in vivo noninvasive en face and volumetric visualization of retinal structures, respectively. Spectrally encoding methods enable confocal imaging through fiber optics and reduces system complexity. Previous applications in ophthalmic imaging include spectrally encoded confocal scanning laser ophthalmoscopy (SECSLO) and a combined SECSLO-OCT system for image guidance, tracking, and registration. However, spectrally encoded imaging suffers from speckle noise because each spectrally encoded channel is effectively monochromatic. Here, we demonstrate in vivo human retinal imaging using a swept source spectrally encoded scanning laser ophthalmoscope and OCT (SSSESLO- OCT) at 1060 nm. SS-SESLO-OCT uses a shared 100 kHz Axsun swept source, shared scanner and imaging optics, and are detected simultaneously on a shared, dual channel high-speed digitizer. SESLO illumination and detection was performed using the single mode core and multimode inner cladding of a double clad fiber coupler, respectively, to preserve lateral resolution while improving collection efficiency and reducing speckle contrast at the expense of confocality. Concurrent en face SESLO and cross-sectional OCT images were acquired with 1376 x 500 pixels at 200 frames-per-second. Our system design is compact and uses a shared light source, imaging optics, and digitizer, which reduces overall system complexity and ensures inherent co-registration between SESLO and OCT FOVs. En face SESLO images acquired concurrent with OCT cross-sections enables lateral motion tracking and three-dimensional volume registration with broad applications in multivolume OCT averaging, image mosaicking, and intraoperative instrument tracking.

Novel microscope-integrated stereoscopic heads-up display for intrasurgical optical coherence tomography

PubMed Central

Shen, Liangbo; Carrasco-Zevallos, Oscar; Keller, Brenton; Viehland, Christian; Waterman, Gar; Hahn, Paul S.; Kuo, Anthony N.; Toth, Cynthia A.; Izatt, Joseph A.

2016-01-01

Intra-operative optical coherence tomography (OCT) requires a display technology which allows surgeons to visualize OCT data without disrupting surgery. Previous research and commercial intrasurgical OCT systems have integrated heads-up display (HUD) systems into surgical microscopes to provide monoscopic viewing of OCT data through one microscope ocular. To take full advantage of our previously reported real-time volumetric microscope-integrated OCT (4D MIOCT) system, we describe a stereoscopic HUD which projects a stereo pair of OCT volume renderings into both oculars simultaneously. The stereoscopic HUD uses a novel optical design employing spatial multiplexing to project dual OCT volume renderings utilizing a single micro-display. The optical performance of the surgical microscope with the HUD was quantitatively characterized and the addition of the HUD was found not to substantially effect the resolution, field of view, or pincushion distortion of the operating microscope. In a pilot depth perception subject study, five ophthalmic surgeons completed a pre-set dexterity task with 50.0% (SD = 37.3%) higher success rate and in 35.0% (SD = 24.8%) less time on average with stereoscopic OCT vision compared to monoscopic OCT vision. Preliminary experience using the HUD in 40 vitreo-retinal human surgeries by five ophthalmic surgeons is reported, in which all surgeons reported that the HUD did not alter their normal view of surgery and that live surgical maneuvers were readily visible in displayed stereoscopic OCT volumes. PMID:27231616

Development of a miniature multiple reference optical coherence tomography imaging device

NASA Astrophysics Data System (ADS)

McNamara, Paul M.; O'Riordan, Colm; Collins, Seán.; O'Brien, Peter; Wilson, Carol; Hogan, Josh; Leahy, Martin J.

2016-03-01

Multiple reference optical coherence tomography (MR-OCT) is a new technology ideally suited to low-cost, compact OCT imaging. This modality is an extension of time-domain OCT with the addition of a partial mirror in front of the reference mirror. This enables extended, simultaneous depth scanning with the relatively short sweep of a miniature voice coil motor on which the scanning mirror is mounted. Applications of this technology include biometric security, ophthalmology, personal health monitoring and non-destructive testing. This work details early-stage development of the first iteration of a miniature MR-OCT device. This device utilizes a fiber-coupled input from an off-board superluminescent diode (SLD). Typical dimensions of the module are 40 × 57 mm, but future designs are expected to be more compact. Off-the-shelf miniature optical components, voice coil motors and photodetectors are used, with the complexity of design depending on specific applications. The photonic module can be configured as either polarized or non-polarized and can include balanced detection. The photodetectors are directly connected to a printed circuit board under the module containing a transimpedance amplifier with complimentary outputs. The results shown in this work are from the non-polarized device. Assembly of the photonic modules requires extensive planning. In choosing the optical components, Zemax simulations are performed to model the beam characteristics. The physical layout is modeled using Solidworks and each component is placed and aligned via a well-designed alignment procedure involving an active-alignment pick-and-place assembly system.

Scattering matrix analysis for evaluating the photocurrent in hydrogenated-amorphous-silicon-based thin film solar cells.

PubMed

Shin, Myunghun; Lee, Seong Hyun; Lim, Jung Wook; Yun, Sun Jin

2014-11-01

A scattering matrix (S-matrix) analysis method was developed for evaluating hydrogenated amorphous silicon (a-Si:H)-based thin film solar cells. In this approach, light wave vectors A and B represent the incoming and outgoing behaviors of the incident solar light, respectively, in terms of coherent wave and incoherent intensity components. The S-matrix determines the relation between A and B according to optical effects such as reflection and transmission, as described by the Fresnel equations, scattering at the boundary surfaces, or scattering within the propagation medium, as described by the Beer-Lambert law and the change in the phase of the propagating light wave. This matrix can be used to evaluate the behavior of angle-incident coherent and incoherent light simultaneously, and takes into account not only the light scattering process at material boundaries (haze effects) but also nonlinear optical processes within the material. The optical parameters in the S-matrix were determined by modeling both a 2%-gallium-doped zinc oxide transparent conducting oxide and germanium-compounded a-Si:H (a-SiGe:H). Using the S-matrix equations, the photocurrent for an a-Si:H/a-SiGe:H tandem cell and the optical loss in semitransparent a-Si:H solar cells for use in building-integrated photovoltaic applications were analyzed. The developed S-matrix method can also be used as a general analysis tool for various thin film solar cells.

Optical coherence tomography measurement of the retinal nerve fiber layer in normal and juvenile glaucomatous eyes.

PubMed

Mrugacz, Malgorzata; Bakunowicz-Lazarczyk, Alina

2005-01-01

The aim of this study was to quantitatively assess and compare the thickness of the retinal nerve fiber layer (RNFL) in normal and glaucomatous eyes of children using the optical coherence tomograph. The mean RNFL thickness of normal eyes (n=26) was compared with that of glaucomatous eyes (n=26). The eyes were classified into diagnostic groups based on conventional ophthalmological physical examination, Humphrey 30-2 visual fields, stereoscopic optic nerve head photography, and optical coherence tomography. The mean RNFL was significantly thinner in glaucomatous eyes than in normal eyes: 95+/-26.3 and 132+/-24.5 microm, respectively. More specifically, the RNFL was significantly thinner in glaucomatous eyes than in normal eyes in the inferior quadrant: 87+/-23.5 and 122+/-24.2 microm, respectively. The mean and inferior quadrant RFNL thicknesses as measured by the optical coherence tomograph showed a statistically significant correlation with glaucoma. Optical coherence tomography may contribute to tracking of juvenile glaucoma progression. Copyright (c) 2005 S. Karger AG, Basel.

Fundus autofluorescence and optical coherence tomography findings in thiamine responsive megaloblastic anemia.

PubMed

Ach, Thomas; Kardorff, Rüdiger; Rohrschneider, Klaus

2015-01-01

To report ophthalmologic fundus autofluorescence and spectral domain optical coherence tomography findings in a patient with thiamine responsive megaloblastic anemia (TRMA). A 13-year-old girl with genetically proven TRMA was ophthalmologically (visual acuity, funduscopy, perimetry, electroretinogram) followed up over >5 years. Fundus imaging also included autofluorescence and spectral domain optical coherence tomography. During a 5-year follow-up, visual acuity and visual field decreased, despite a special TRMA diet. Funduscopy revealed bull's eye appearance, whereas fundus autofluorescence showed central and peripheral hyperfluorescence and perifoveal hypofluorescence. Spectral domain optical coherence tomography revealed affected inner segment ellipsoid band and irregularities in the retinal pigment epithelium and choroidea. Autofluorescence and spectral domain optical coherence tomography findings in a patient with TRMA show retinitis pigmentosa-like retina, retinal pigment epithelium, and choroid alterations. These findings might progress even under special TRMA diet, indispensable to life. Ophthalmologist should consider TRMA in patients with deafness and ophthalmologic disorders.

Graphene-based carbon-layered electrode array technology for neural imaging and optogenetic applications

PubMed Central

Park, Dong-Wook; Schendel, Amelia A.; Mikael, Solomon; Brodnick, Sarah K.; Richner, Thomas J.; Ness, Jared P.; Hayat, Mohammed R.; Atry, Farid; Frye, Seth T.; Pashaie, Ramin; Thongpang, Sanitta; Ma, Zhenqiang; Williams, Justin C.

2014-01-01

Neural micro-electrode arrays that are transparent over a broad wavelength spectrum from ultraviolet to infrared could allow for simultaneous electrophysiology and optical imaging, as well as optogenetic modulation of the underlying brain tissue. The long-term biocompatibility and reliability of neural micro-electrodes also require their mechanical flexibility and compliance with soft tissues. Here we present a graphene-based, carbon-layered electrode array (CLEAR) device, which can be implanted on the brain surface in rodents for high-resolution neurophysiological recording. We characterize optical transparency of the device at >90% transmission over the ultraviolet to infrared spectrum and demonstrate its utility through optical interface experiments that use this broad spectrum transparency. These include optogenetic activation of focal cortical areas directly beneath electrodes, in vivo imaging of the cortical vasculature via fluorescence microscopy and 3D optical coherence tomography. This study demonstrates an array of interfacing abilities of the CLEAR device and its utility for neural applications. PMID:25327513

Single-shot measurement of phase and amplitude by using a heterodyne time-lens system and ultrafast digital time-holography

NASA Astrophysics Data System (ADS)

Tikan, Alexey; Bielawski, Serge; Szwaj, Christophe; Randoux, Stéphane; Suret, Pierre

2018-04-01

Temporal imaging systems are outstanding tools for single-shot observation of optical signals that have irregular and ultrafast dynamics. They allow long time windows to be recorded with femtosecond resolution, and do not rely on complex algorithms. However, simultaneous recording of amplitude and phase remains an open challenge for these systems. Here, we present a new heterodyne time-lens arrangement that efficiently records both the amplitude and phase of complex and random signals over large temporal windows (tens of picoseconds). Phase and time are encoded onto the two spatial dimensions of a camera. We implement this phase-sensitive time-lens system in two configurations: a time microscope and a digital temporal-holography device that enables single-shot measurement with a temporal resolution of 80 fs. We demonstrate direct application of our heterodyne time-lens to turbulent-like optical fields and optical rogue waves generated from nonlinear propagation of partially coherent waves inside optical fibres.

Diagnostic power of optic disc morphology, peripapillary retinal nerve fiber layer thickness, and macular inner retinal layer thickness in glaucoma diagnosis with fourier-domain optical coherence tomography.

PubMed

Huang, Jehn-Yu; Pekmezci, Melike; Mesiwala, Nisreen; Kao, Andrew; Lin, Shan

2011-02-01

To evaluate the capability of the optic disc, peripapillary retinal nerve fiber layer (P-RNFL), macular inner retinal layer (M-IRL) parameters, and their combination obtained by Fourier-domain optical coherent tomography (OCT) in differentiating a glaucoma suspect from perimetric glaucoma. Two hundred and twenty eyes from 220 patients were enrolled in this study. The optic disc morphology, P-RNFL, and M-IRL were assessed by the Fourier-domain OCT (RTVue OCT, Model RT100, Optovue, Fremont, CA). A linear discriminant function was generated by stepwise linear discriminant analysis on the basis of OCT parameters and demographic factors. The diagnostic power of these parameters was evaluated with receiver operating characteristic (ROC) curve analysis. The diagnostic power in the clinically relevant range (specificity ≥ 80%) was presented as the partial area under the ROC curve (partial AROC). The individual OCT parameter with the largest AROC and partial AROC in the high specificity (≥ 80%) range were cup/disc vertical ratio (AROC = 0.854 and partial AROC = 0.142) for the optic disc parameters, average thickness (AROC = 0.919 and partial AROC = 0.147) for P-RNFL parameters, inferior hemisphere thickness (AROC = 0.871 and partial AROC = 0.138) for M-IRL parameters, respectively. The linear discriminant function further enhanced the ability in detecting perimetric glaucoma (AROC = 0.970 and partial AROC = 0.172). Average P-RNFL thickness is the optimal individual OCT parameter to detect perimetric glaucoma. Simultaneous evaluation on disc morphology, P-RNFL, and M-IRL thickness can improve the diagnostic accuracy in diagnosing glaucoma.

Dental optical coherence domain reflectometry explorer

DOEpatents

Everett, Matthew J.; Colston, Jr., Billy W.; Sathyam, Ujwal S.; Da Silva, Luiz B.

2001-01-01

A hand-held, fiber optic based dental device with optical coherence domain reflectometry (OCDR) sensing capabilities provides a profile of optical scattering as a function of depth in the tissue at the point where the tip of the dental explorer touches the tissue. This system provides information on the internal structure of the dental tissue, which is then used to detect caries and periodontal disease. A series of profiles of optical scattering or tissue microstructure are generated by moving the explorer across the tooth or other tissue. The profiles are combined to form a cross-sectional, or optical coherence tomography (OCT), image.

PREFACE: XVIII International Youth Scientific School "Coherent Optics and Optical Spectroscopy"

NASA Astrophysics Data System (ADS)

Salakhov, M. Kh; Samartsev, V. V.; Gainutdinov, R. Kh

2015-05-01

Kazan Federal University has held the annual International Youth School "Coherent Optics and Optical Spectroscopy" since 1997. The choice of the topic is not accidental. Kazan is the home of photon echo which was predicted at Kazan Physical-Technical Institute in 1963 by Prof. U.G. Kopvil'em and V.R. Nagibarov and observed in Columbia University by N.A. Kurnit, I.D. Abella, and S.R. Hartmann in 1964. Since then, photon echo has become a powerful tool of coherent optical spectroscopy and optical information processing, which have been developed here in Kazan in close collaboration between Kazan Physical-Technical Institute and Kazan Federal University. The main subjects of the XVIII International Youth School are: Nonlinear and coherent optics; Atomic and molecular spectroscopy; Coherent laser spectroscopy; Problems of quantum optics; Quantum theory of radiation; and Nanophotonics and Scanning Probe Microscopy. The unchallenged organizers of that school are Kazan Federal University and Kazan E.K. Zavoisky Physical-Technical Institute. The rector of the School is Professor Myakzyum Salakhov, and the vice-rector is Professor Vitaly Samartsev. The International Youth Scientific School "Coherent Optics and Optical Spectroscopy" follows the global pattern of comprehensive studies of matter properties and their interaction with electromagnetic fields. Since 1997 more than 100 famous scientists from the USA, Germany, Ukraine, Belarus and Russia have given plenary lecture presentations. Here over 1000 young scientists had an opportunity to participate in lively discussions about the latest scientific news. Many young people have submitted interesting reports on photonics, quantum electronics, laser physics, quantum optics, traditional optical and laser spectroscopy, non-linear optics, material science and nanotechnology. Here we are publishing the fullsize papers prepared from the most interesting lectures and reports selected by the Program Committee of the School. The International Youth Scientific School "Coherent Optics and Optical Spectroscopy" was greatly supported by The Optical Society of America, the Russian Foundation for Basic Research, the non-profit Dynasty Foundation, the Tatarstan Academy of Science, and the Ministry of Education and Science of the Russian Federation. It is a pleasure to thank the sponsors and all the participants and contributors who made the International School meeting possible and interesting.

Synchrotron-based coherent scatter x-ray projection imaging using an array of monoenergetic pencil beams.

PubMed

Landheer, Karl; Johns, Paul C

2012-09-01

Traditional projection x-ray imaging utilizes only the information from the primary photons. Low-angle coherent scatter images can be acquired simultaneous to the primary images and provide additional information. In medical applications scatter imaging can improve x-ray contrast or reduce dose using information that is currently discarded in radiological images to augment the transmitted radiation information. Other applications include non-destructive testing and security. A system at the Canadian Light Source synchrotron was configured which utilizes multiple pencil beams (up to five) to create both primary and coherent scatter projection images, simultaneously. The sample was scanned through the beams using an automated step-and-shoot setup. Pixels were acquired in a hexagonal lattice to maximize packing efficiency. The typical pitch was between 1.0 and 1.6 mm. A Maximum Likelihood-Expectation Maximization-based iterative method was used to disentangle the overlapping information from the flat panel digital x-ray detector. The pixel value of the coherent scatter image was generated by integrating the radial profile (scatter intensity versus scattering angle) over an angular range. Different angular ranges maximize the contrast between different materials of interest. A five-beam primary and scatter image set (which had a pixel beam time of 990 ms and total scan time of 56 min) of a porcine phantom is included. For comparison a single-beam coherent scatter image of the same phantom is included. The muscle-fat contrast was 0.10 ± 0.01 and 1.16 ± 0.03 for the five-beam primary and scatter images, respectively. The air kerma was measured free in air using aluminum oxide optically stimulated luminescent dosimeters. The total area-averaged air kerma for the scan was measured to be 7.2 ± 0.4 cGy although due to difficulties in small-beam dosimetry this number could be inaccurate.

IMAGING WITH MULTIMODAL ADAPTIVE-OPTICS OPTICAL COHERENCE TOMOGRAPHY IN MULTIPLE EVANESCENT WHITE DOT SYNDROME: THE STRUCTURE AND FUNCTIONAL RELATIONSHIP.

PubMed

Labriola, Leanne T; Legarreta, Andrew D; Legarreta, John E; Nadler, Zach; Gallagher, Denise; Hammer, Daniel X; Ferguson, R Daniel; Iftimia, Nicusor; Wollstein, Gadi; Schuman, Joel S

2016-01-01

To elucidate the location of pathological changes in multiple evanescent white dot syndrome (MEWDS) with the use of multimodal adaptive optics (AO) imaging. A 5-year observational case study of a 24-year-old female with recurrent MEWDS. Full examination included history, Snellen chart visual acuity, pupil assessment, intraocular pressures, slit lamp evaluation, dilated fundoscopic exam, imaging with Fourier-domain optical coherence tomography (FD-OCT), blue-light fundus autofluorescence (FAF), fundus photography, fluorescein angiography, and adaptive-optics optical coherence tomography. Three distinct acute episodes of MEWDS occurred during the period of follow-up. Fourier-domain optical coherence tomography and adaptive-optics imaging showed disturbance in the photoreceptor outer segments (PR OS) in the posterior pole with each flare. The degree of disturbance at the photoreceptor level corresponded to size and extent of the visual field changes. All findings were transient with delineation of the photoreceptor recovery from the outer edges of the lesion inward. Hyperautofluorescence was seen during acute flares. Increase in choroidal thickness did occur with each active flare but resolved. Although changes in the choroid and RPE can be observed in MEWDS, Fourier-domain optical coherence tomography, and multimodal adaptive optics imaging localized the visually significant changes seen in this disease at the level of the photoreceptors. These transient retinal changes specifically occur at the level of the inner segment ellipsoid and OS/RPE line. En face optical coherence tomography imaging provides a detailed, yet noninvasive method for following the convalescence of MEWDS and provides insight into the structural and functional relationship of this transient inflammatory retinal disease.

Label-free imaging of trabecular meshwork cells using Coherent Anti-Stokes Raman Scattering (CARS) microscopy

PubMed Central

Lei, Tim C.; Ammar, David A.; Masihzadeh, Omid; Gibson, Emily A.

2011-01-01

Purpose To image the human trabecular meshwork (TM) using a non-invasive, non-destructive technique without the application of exogenous label. Methods Flat-mounted TM samples from a human cadaver eye were imaged using two nonlinear optical techniques: coherent anti-Stokes Raman scattering (CARS) and two-photon autofluorescence (TPAF). In TPAF, two optical photons are simultaneously absorbed and excite molecules in the sample that then emit a higher energy photon. The signal is predominately from collagen and elastin. The CARS technique uses two laser frequencies to specifically excite carbon-hydrogen bonds, allowing the visualization of lipid-rich cell membranes. Multiple images were taken along an axis perpendicular to the surface of the TM for subsequent analysis. Results Analysis of multiple TPAF images of the TM reveals the characteristic overlapping bundles of collagen of various sizes. Simultaneous CARS imaging revealed elliptical structures of ~7×10 µm in diameter populating the meshwork which were consistent with TM cells. Irregularly shaped objects of ~4 µm diameter appeared in both the TPAF and CARS channels, and are consistent with melanin granules. Conclusions CARS techniques were successful in imaging live TM cells in freshly isolated human TM samples. Similar images have been obtained with standard histological techniques, however the method described here has the advantage of being performed on unprocessed, unfixed tissue free from the potential distortions of the fine tissue morphology that can occur due to infusion of fixatives and treatment with alcohols. CARS imaging of the TM represents a new avenue for exploring details of aqueous outflow and TM cell physiology. PMID:22025898

Autofluorescence and spectral-domain optical coherence tomography of optic disk melanocytoma.

PubMed

Guerra, Ricardo Luz Leitão; Marback, Eduardo Ferrari; Silva, Igor Sandes Pessoa da; Maia Junior, Otacílio de Oliveira; Marback, Roberto Lorens

2014-01-01

The authors report fundus autofluorescence (FAF) and spectral-domain optical coherence tomography (OCT) findings of two consecutive patients who presented with optic disk melanocytoma (ODM). A retrospective study was performed by reviewing medical records and ophthalmic imaging examinations. Optical coherence tomography findings were sloped and brightly reflective anterior tumor surface, adjacent retinal desorganization and abrupt posterior optical shadowing. Vitreous seeds were found in one patient. Fundus autofluorescence revealed outstanding hypoautofluorescence at the tumor area and isoautofluorescence at the remaining retina. Optical coherence tomography findings of the reported cases are consistent with those reported in the reviewed literature. Fundus autofluorescence has been used in the assessment of choroidal melanocytic tumors, but not yet in melanocytomas. We assume that this is the first report of these findings and believe that when its pattern has become clearly defined, fundus autofluorescence will be a useful tool to avoid misdiagnosis in suspicious cases and for follow-up.

Spectrally Shaped DP-16QAM Super-Channel Transmission with Multi-Channel Digital Back-Propagation

PubMed Central

Maher, Robert; Xu, Tianhua; Galdino, Lidia; Sato, Masaki; Alvarado, Alex; Shi, Kai; Savory, Seb J.; Thomsen, Benn C.; Killey, Robert I.; Bayvel, Polina

2015-01-01

The achievable transmission capacity of conventional optical fibre communication systems is limited by nonlinear distortions due to the Kerr effect and the difficulty in modulating the optical field to effectively use the available fibre bandwidth. In order to achieve a high information spectral density (ISD), while simultaneously maintaining transmission reach, multi-channel fibre nonlinearity compensation and spectrally efficient data encoding must be utilised. In this work, we use a single coherent super-receiver to simultaneously receive a DP-16QAM super-channel, consisting of seven spectrally shaped 10GBd sub-carriers spaced at the Nyquist frequency. Effective nonlinearity mitigation is achieved using multi-channel digital back-propagation (MC-DBP) and this technique is combined with an optimised forward error correction implementation to demonstrate a record gain in transmission reach of 85%; increasing the maximum transmission distance from 3190 km to 5890 km, with an ISD of 6.60 b/s/Hz. In addition, this report outlines for the first time, the sensitivity of MC-DBP gain to linear transmission line impairments and defines a trade-off between performance and complexity. PMID:25645457

Potentials of radial partially coherent beams in free-space optical communication: a numerical investigation.

PubMed

Wang, Minghao; Yuan, Xiuhua; Ma, Donglin

2017-04-01

Nonuniformly correlated partially coherent beams (PCBs) have extraordinary propagation properties, making it possible to further improve the performance of free-space optical communications. In this paper, a series of PCBs with varying degrees of coherence in the radial direction, academically called radial partially coherent beams (RPCBs), are considered. RPCBs with arbitrary coherence distributions can be created by adjusting the amplitude profile of a spatial modulation function imposed on a uniformly correlated phase screen. Since RPCBs cannot be well characterized by the coherence length, a modulation depth factor is introduced as an indicator of the overall distribution of coherence. By wave optics simulation, free-space and atmospheric propagation properties of RPCBs with (inverse) Gaussian and super-Gaussian coherence distributions are examined in comparison with conventional Gaussian Schell-model beams. Furthermore, the impacts of varying central coherent areas are studied. Simulation results reveal that under comparable overall coherence, beams with a highly coherent core and a less coherent margin exhibit a smaller beam spread and greater on-axis intensity, which is mainly due to the self-focusing phenomenon right after the beam exits the transmitter. Particularly, those RPCBs with super-Gaussian coherence distributions will repeatedly focus during propagation, resulting in even greater intensities. Additionally, RPCBs also have a considerable ability to reduce scintillation. And it is demonstrated that those properties have made RPCBs very effective in improving the mean signal-to-noise ratio of small optical receivers, especially in relatively short, weakly fluctuating links.

Generation of coherent two-color pulses at two adjacent harmonics in a seeded free-electron laser

NASA Astrophysics Data System (ADS)

Zhao, Zhouyu; Li, Heting; Jia, Qika

2018-02-01

The growing requirements of pump-probe techniques and nonlinear optics experiments greatly promote the studies of two-color free-electron lasers (FELs). We propose a new method to generate coherent two-color pulses in a high-gain harmonic generation (HGHG) FEL. In this scheme, an initial tilted electron beam is sent though the modulator and dispersive section of an HGHG FEL to generate the bunching at harmonics of the seed laser. Then a transverse gradient undulator (TGU) is adopted as the radiator and in such radiator, only two separated fractions of the tilted beam will resonate at two adjacent harmonics of the seed laser and are enabled to emit the coherent two-color pulses simultaneously. The time separation between the two pulses are on the order of hundreds of femtoseconds, and can be precisely controlled by varying the tilted amplitude of the electron beam and/or the transverse gradient of the TGU radiator. Numerical simulations confirm the validity and feasibility of this scheme in the extreme ultraviolet waveband.

Dark and white lesions observed in central serous chorioretinopathy on optical coherence tomography angiography.

PubMed

De Bats, Flore; Cornut, Pierre-Loïc; Wolff, Benjamin; Kodjikian, Laurent; Mauget-Faÿsse, Martine

2018-03-01

To describe abnormal dark (hyposignal) and white (hypersignal) lesions observed on optical coherence tomography angiography in central serous chorioretinopathy. Prospective, multicenter, and descriptive study including patients with active or quiescent central serous chorioretinopathy. All patients had undergone a complete ophthalmic examination. Abnormal dark lesions were detected as "dark spots" and "dark areas" on optical coherence tomography angiography. A "dark spot" could correspond to six different abnormalities: pigment epithelium detachment, subretinal deposit, "Lucency" within surrounding subretinal fibrin, choroidal cavitation, choroidal excavation, and choroidal fluid. A "dark area" could be related to a serous retinal detachment or choriocapillary compression. Abnormal white lesions were also detected: A "white spot" could correspond with the leaking point on fluorescein angiography or with hyper-reflective dots; A "white filamentous pattern" at the Brüch's membrane level corresponded to abnormal choroidal neovascular vessels. A semiology is described using optical coherence tomography angiography in central serous chorioretinopathy as abnormal dark and white lesions. Multimodal imaging is mandatory in addition to optical coherence tomography angiography to diagnose non-neovascular retinal and choroidal central serous chorioretinopathy lesions. However, optical coherence tomography angiography alone is helpful in detecting choroidal neovascular membrane in central serous chorioretinopathy.

In-line optical fiber metallic mirror reflector for monolithic common path optical coherence tomography probes.

PubMed

Singh, Kanwarpal; Reddy, Rohith; Sharma, Gargi; Verma, Yogesh; Gardecki, Joseph A; Tearney, Guillermo

2018-03-01

Endoscopic optical coherence tomography probes suffer from various artifacts due to dispersion imbalance and polarization mismatch between reference and sample arm light. Such artifacts can be minimized using a common path approach. In this work, we demonstrate a miniaturized common path probe for optical coherence tomography using an inline fiber mirror. A common path optical fiber probe suitable for performing high-resolution endoscopic optical coherence tomography imaging was developed. To achieve common path functionality, an inline fiber mirror was fabricated using a thin gold layer. A commercially available swept source engine was used to test the designed probe in a cadaver human coronary artery ex vivo. We achieved a sensitivity of 104 dB for this probe using a swept source optical coherence tomography system. To test the probe, images of a cadaver human coronary artery were obtained, demonstrating the quality that is comparable to those obtained by OCT systems with separate reference arms. Additionally, we demonstrate recovery of ranging depth by use of a Michelson interferometer in the detection path. We developed a miniaturized monolithic inline fiber mirror-based common path probe for optical coherence tomography. Owing to its simplicity, our design will be helpful in endoscopic applications that require high-resolution probes in a compact form factor while reducing system complexity. Lasers Surg. Med. 50:230-235, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Non-Gaussian statistics and optical rogue waves in stimulated Raman scattering.

PubMed

Monfared, Yashar E; Ponomarenko, Sergey A

2017-03-20

We explore theoretically and numerically optical rogue wave formation in stimulated Raman scattering inside a hydrogen filled hollow core photonic crystal fiber. We assume a weak noisy Stokes pulse input and explicitly construct the input Stokes pulse ensemble using the coherent mode representation of optical coherence theory, thereby providing a link between optical coherence and rogue wave theories. We show that the Stokes pulse peak power probability distribution function (PDF) acquires a long tail in the limit of nearly incoherent input Stokes pulses. We demonstrate a clear link between the PDF tail magnitude and the source coherence time. Thus, the latter can serve as a convenient parameter to control the former. We explain our findings qualitatively using the concepts of statistical granularity and global degree of coherence.

Monte Carlo modeling of spatial coherence: free-space diffraction

PubMed Central

Fischer, David G.; Prahl, Scott A.; Duncan, Donald D.

2008-01-01

We present a Monte Carlo method for propagating partially coherent fields through complex deterministic optical systems. A Gaussian copula is used to synthesize a random source with an arbitrary spatial coherence function. Physical optics and Monte Carlo predictions of the first- and second-order statistics of the field are shown for coherent and partially coherent sources for free-space propagation, imaging using a binary Fresnel zone plate, and propagation through a limiting aperture. Excellent agreement between the physical optics and Monte Carlo predictions is demonstrated in all cases. Convergence criteria are presented for judging the quality of the Monte Carlo predictions. PMID:18830335

Spectroscopic Doppler analysis for visible-light optical coherence tomography

NASA Astrophysics Data System (ADS)

Shu, Xiao; Liu, Wenzhong; Duan, Lian; Zhang, Hao F.

2017-12-01

Retinal oxygen metabolic rate can be effectively measured by visible-light optical coherence tomography (vis-OCT), which simultaneously quantifies oxygen saturation and blood flow rate in retinal vessels through spectroscopic analysis and Doppler measurement, respectively. Doppler OCT relates phase variation between sequential A-lines to the axial flow velocity of the scattering medium. The detectable phase shift is between -π and π due to its periodicity, which limits the maximum measurable unambiguous velocity without phase unwrapping. Using shorter wavelengths, vis-OCT is more vulnerable to phase ambiguity since flow induced phase variation is linearly related to the center wavenumber of the probing light. We eliminated the need for phase unwrapping using spectroscopic Doppler analysis. We split the whole vis-OCT spectrum into a series of narrow subbands and reconstructed vis-OCT images to extract corresponding Doppler phase shifts in all the subbands. Then, we quantified flow velocity by analyzing subband-dependent phase shift using linear regression. In the phantom experiment, we showed that spectroscopic Doppler analysis extended the measurable absolute phase shift range without conducting phase unwrapping. We also tested this method to quantify retinal blood flow in rodents in vivo.

A new OTDR based on probe frequency multiplexing

NASA Astrophysics Data System (ADS)

Lu, Lidong; Liang, Yun; Li, Binglin; Guo, Jinghong; Zhang, Xuping

2013-12-01

Two signal multiplexing methods are proposed and experimentally demonstrated in optical time domain reflectometry (OTDR) for fault location of optical fiber transmission line to obtain high measurement efficiency. Probe signal multiplexing is individually obtained by phase modulation for generation of multi-frequency and time sequential frequency probe pulses. The backscattered Rayleigh light of the multiplexing probe signals is transferred to corresponding heterodyne intermediate frequency (IF) through heterodyning with the single frequency local oscillator (LO). Then the IFs are simultaneously acquired by use of a data acquisition card (DAQ) with sampling rate of 100Msps, and the obtained data are processed by digital band pass filtering (BPF), digital down conversion (DDC) and digital low pass filtering (BPF) procedure. For each probe frequency of the detected signals, the extraction of the time domain reflecting signal power is performed by parallel computing method. For a comprehensive performance comparison with conventional coherent OTDR on the probe frequency multiplexing methods, the potential for enhancement of dynamic range, spatial resolution and measurement time are analyzed and discussed. Experimental results show that by use of the probe frequency multiplexing method, the measurement efficiency of coherent OTDR can be enhanced by nearly 40 times.

Handheld optical coherence tomography-reflectance confocal microscopy probe for detection of basal cell carcinoma and delineation of margins

NASA Astrophysics Data System (ADS)

Iftimia, Nicusor; Yélamos, Oriol; Chen, Chih-Shan J.; Maguluri, Gopi; Cordova, Miguel A.; Sahu, Aditi; Park, Jesung; Fox, William; Alessi-Fox, Christi; Rajadhyaksha, Milind

2017-07-01

We present a hand-held implementation and preliminary evaluation of a combined optical coherence tomography (OCT) and reflectance confocal microscopy (RCM) probe for detecting and delineating the margins of basal cell carcinomas (BCCs) in human skin in vivo. A standard OCT approach (spectrometer-based) with a central wavelength of 1310 nm and 0.11 numerical aperture (NA) was combined with a standard RCM approach (830-nm wavelength and 0.9 NA) into a common path hand-held probe. Cross-sectional OCT images and enface RCM images are simultaneously displayed, allowing for three-dimensional microscopic assessment of tumor morphology in real time. Depending on the subtype and depth of the BCC tumor and surrounding skin conditions, OCT and RCM imaging are able to complement each other, the strengths of each helping overcome the limitations of the other. Four representative cases are summarized, out of the 15 investigated in a preliminary pilot study, demonstrating how OCT and RCM imaging may be synergistically combined to more accurately detect BCCs and more completely delineate margins. Our preliminary results highlight the potential benefits of combining the two technologies within a single probe to potentially guide diagnosis as well as treatment of BCCs.

3D optical coherence tomography image registration for guiding cochlear implant insertion

NASA Astrophysics Data System (ADS)

Cheon, Gyeong-Woo; Jeong, Hyun-Woo; Chalasani, Preetham; Chien, Wade W.; Iordachita, Iulian; Taylor, Russell; Niparko, John; Kang, Jin U.

2014-03-01

In cochlear implant surgery, an electrode array is inserted into the cochlear canal to restore hearing to a person who is profoundly deaf or significantly hearing impaired. One critical part of the procedure is the insertion of the electrode array, which looks like a thin wire, into the cochlear canal. Although X-ray or computed tomography (CT) could be used as a reference to evaluate the pathway of the whole electrode array, there is no way to depict the intra-cochlear canal and basal turn intra-operatively to help guide insertion of the electrode array. Optical coherent tomography (OCT) is a highly effective way of visualizing internal structures of cochlea. Swept source OCT (SSOCT) having center wavelength of 1.3 micron and 2D Galvonometer mirrors was used to achieve 7-mm depth 3-D imaging. Graphics processing unit (GPU), OpenGL, C++ and C# were integrated for real-time volumetric rendering simultaneously. The 3D volume images taken by the OCT system were assembled and registered which could be used to guide a cochlear implant. We performed a feasibility study using both dry and wet temporal bones and the result is presented.

Multispectral analog-mean-delay fluorescence lifetime imaging combined with optical coherence tomography

PubMed Central

Nam, Hyeong Soo; Kang, Woo Jae; Lee, Min Woo; Song, Joon Woo; Kim, Jin Won; Oh, Wang-Yuhl; Yoo, Hongki

2018-01-01

The pathophysiological progression of chronic diseases, including atherosclerosis and cancer, is closely related to compositional changes in biological tissues containing endogenous fluorophores such as collagen, elastin, and NADH, which exhibit strong autofluorescence under ultraviolet excitation. Fluorescence lifetime imaging (FLIm) provides robust detection of the compositional changes by measuring fluorescence lifetime, which is an inherent property of a fluorophore. In this paper, we present a dual-modality system combining a multispectral analog-mean-delay (AMD) FLIm and a high-speed swept-source optical coherence tomography (OCT) to simultaneously visualize the cross-sectional morphology and biochemical compositional information of a biological tissue. Experiments using standard fluorescent solutions showed that the fluorescence lifetime could be measured with a precision of less than 40 psec using the multispectral AMD-FLIm without averaging. In addition, we performed ex vivo imaging on rabbit iliac normal-looking and atherosclerotic specimens to demonstrate the feasibility of the combined FLIm-OCT system for atherosclerosis imaging. We expect that the combined FLIm-OCT will be a promising next-generation imaging technique for diagnosing atherosclerosis and cancer due to the advantages of the proposed label-free high-precision multispectral lifetime measurement. PMID:29675330

Dynamics of ultra-broadband terahertz quantum cascade lasers for comb operation.

PubMed

Li, Hua; Laffaille, Pierre; Gacemi, Djamal; Apfel, Marc; Sirtori, Carlo; Leonardon, Jeremie; Santarelli, Giorgio; Rösch, Markus; Scalari, Giacomo; Beck, Mattias; Faist, Jerome; Hänsel, Wolfgang; Holzwarth, Ronald; Barbieri, Stefano

2015-12-28

We present an experimental investigation of the multimode dynamics and the coherence of terahertz quantum cascade lasers emitting over a spectral bandwidth of ~1THz. The devices are studied in free-running and under direct RF modulation. Depending on the pump current we observe different regimes of operation, where RF spectra displaying single and multiple narrow beat-note signals alternate with spectra showing a single beat-note characterized by an intense phase-noise, extending over a bandwidth up to a few GHz. We investigate the relation between this phase-noise and the dynamics of the THz modes through the electro-optic sampling of the laser emission. We find that when the phase-noise is large, the laser operates in an unstable regime where the lasing modes are incoherent. Under RF modulation of the laser current such instability can be suppressed and the modes coherence recovered, while, simultaneously, generating a strong broadening of the THz emission spectrum.

Design and validation of a multiplexed low coherence interferometry instrument for in vivo clinical measurement of microbicide gel thickness distribution

PubMed Central

Drake, Tyler K.; DeSoto, Michael G.; Peters, Jennifer J.; Henderson, Marcus H.; Murtha, Amy P.; Katz, David F.; Wax, Adam

2011-01-01

We present a multiplexed, Fourier-domain low coherence interferometry (mLCI) instrument for in vivo measurement of intravaginal microbicide gel coating thickness distribution over the surface of the vaginal epithelium. The mLCI instrument uses multiple delivery fibers to acquire depth resolved reflection profiles across large scanned tissue areas. Here mLCI has been adapted into an endoscopic system with a custom imaging module for simultaneous, co-registered measurements with fluorimetric scans of the same surface. The resolution, optical signal-to-noise, and cross-talk of the mLCI instrument are characterized to evaluate performance. Validation measurements of gel thickness are made using a calibration socket. Initial results from a clinical study are presented to show the in vivo capability of the dual-modality system for assessing the distribution of microbicide gel vehicles in the lower human female reproductive tract. PMID:22025989

3-dB signal-ASE beat noise reduction of coherent multi-carrier signal utilizing phase sensitive amplification.

PubMed

Umeki, Takeshi; Takara, Hidehiko; Miyamoto, Yutaka; Asobe, Masaki

2012-10-22

We demonstrated the simultaneous amplification of a coherent multi-carrier signal using a χ(2)-based non-degenerate phase sensitive amplifier (PSA). The signal-to-noise ratio (SNR), which is degraded by the additional amplified spontaneous emission (ASE) noise, can be recovered due to the gain difference between a phase-correlated signal-idler pair and uncorrelated excess noise. Utilizing the second harmonic pumping of a χ(2)-based PSA enables us to observe the SNR recovery directly by comparing the SNR for the input with that for the PSA output. A 3-dB optical-SNR (OSNR) improvement was obtained as a result of the gain difference. We also achieved a 3-dB SNR improvement in the electric domain by reducing the signal-ASE beat noise. The receiver sensitivity for a 10 Gbit/s phase shift keying signal was clearly improved with the PSA.

Doublet Pulse Coherent Laser Radar for Tracking of Resident Space Objects

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Rudd, Van; Shald, Scott; Sandford, Stephen; Dimarcantonio, Albert

2014-01-01

In this paper, the development of a long range ladar system known as ExoSPEAR at NASA Langley Research Center for tracking rapidly moving resident space objects is discussed. Based on 100 W, nanosecond class, near-IR laser, this ladar system with coherent detection technique is currently being investigated for short dwell time measurements of resident space objects (RSOs) in LEO and beyond for space surveillance applications. This unique ladar architecture is configured using a continuously agile doublet-pulse waveform scheme coupled to a closed-loop tracking and control loop approach to simultaneously achieve mm class range precision and mm/s velocity precision and hence obtain unprecedented track accuracies. Salient features of the design architecture followed by performance modeling and engagement simulations illustrating the dependence of range and velocity precision in LEO orbits on ladar parameters are presented. Estimated limits on detectable optical cross sections of RSOs in LEO orbits are discussed.

Families of quantum fingerprinting protocols

NASA Astrophysics Data System (ADS)

Lovitz, Benjamin; Lütkenhaus, Norbert

2018-03-01

We introduce several families of quantum fingerprinting protocols to evaluate the equality function on two n -bit strings in the simultaneous message passing model. The original quantum fingerprinting protocol uses a tensor product of a small number of O (logn ) -qubit high-dimensional signals [H. Buhrman et al., Phys. Rev. Lett. 87, 167902 (2001), 10.1103/PhysRevLett.87.167902], whereas a recently proposed optical protocol uses a tensor product of O (n ) single-qubit signals, while maintaining the O (logn ) information leakage of the original protocol [J. M. Arazola and N. Lütkenhaus, Phys. Rev. A 89, 062305 (2014), 10.1103/PhysRevA.89.062305]. We find a family of protocols which interpolate between the original and optical protocols while maintaining the O (logn ) information leakage, thus demonstrating a tradeoff between the number of signals sent and the dimension of each signal. There has been interest in experimental realization of the recently proposed optical protocol using coherent states [F. Xu et al., Nat. Commun. 6, 8735 (2015), 10.1038/ncomms9735; J.-Y. Guan et al., Phys. Rev. Lett. 116, 240502 (2016), 10.1103/PhysRevLett.116.240502], but as the required number of laser pulses grows linearly with the input size n , eventual challenges for the long-time stability of experimental setups arise. We find a coherent state protocol which reduces the number of signals by a factor 1/2 while also reducing the information leakage. Our reduction makes use of a simple modulation scheme in optical phase space, and we find that more complex modulation schemes are not advantageous. Using a similar technique, we improve a recently proposed coherent state protocol for evaluating the Euclidean distance between two real unit vectors [N. Kumar et al., Phys. Rev. A 95, 032337 (2017), 10.1103/PhysRevA.95.032337] by reducing the number of signals by a factor 1/2 and also reducing the information leakage.

A coherent optical feedback system for optical information processing

NASA Technical Reports Server (NTRS)

Jablonowski, D. P.; Lee, S. H.

1975-01-01

A unique optical feedback system for coherent optical data processing is described. With the introduction of feedback, the well-known transfer function for feedback systems is obtained in two dimensions. Operational details of the optical feedback system are given. Experimental results of system applications in image restoration, contrast control and analog computation are presented.

Time-domain Brillouin scattering assisted by diffraction gratings

NASA Astrophysics Data System (ADS)

Matsuda, Osamu; Pezeril, Thomas; Chaban, Ievgeniia; Fujita, Kentaro; Gusev, Vitalyi

2018-02-01

Absorption of ultrashort laser pulses in a metallic grating deposited on a transparent sample launches coherent compression/dilatation acoustic pulses in directions of different orders of acoustic diffraction. Their propagation is detected by delayed laser pulses, which are also diffracted by the metallic grating, through the measurement of the transient intensity change of the first-order diffracted light. The obtained data contain multiple frequency components, which are interpreted by considering all possible angles for the Brillouin scattering of light achieved through multiplexing of the propagation directions of light and coherent sound by the metallic grating. The emitted acoustic field can be equivalently presented as a superposition of plane inhomogeneous acoustic waves, which constitute an acoustic diffraction grating for the probe light. Thus the obtained results can also be interpreted as a consequence of probe light diffraction by both metallic and acoustic gratings. The realized scheme of time-domain Brillouin scattering with metallic gratings operating in reflection mode provides access to wide range of acoustic frequencies from minimal to maximal possible values in a single experimental optical configuration for the directions of probe light incidence and scattered light detection. This is achieved by monitoring the backward and forward Brillouin scattering processes in parallel. Potential applications include measurements of the acoustic dispersion, simultaneous determination of sound velocity and optical refractive index, and evaluation of samples with a single direction of possible optical access.

Optical subcarrier processing for Nyquist SCM signals via coherent spectrum overlapping in four-wave mixing with coherent multi-tone pump.

PubMed

Lu, Guo-Wei; Luís, Ruben S; Mendinueta, José Manuel Delgado; Sakamoto, Takahide; Yamamoto, Naokatsu

2018-01-22

As one of the promising multiplexing and multicarrier modulation technologies, Nyquist subcarrier multiplexing (Nyquist SCM) has recently attracted research attention to realize ultra-fast and ultra-spectral-efficient optical networks. In this paper, we propose and experimentally demonstrate optical subcarrier processing technologies for Nyquist SCM signals such as frequency conversion, multicast and data aggregation of subcarriers, through the coherent spectrum overlapping between subcarriers in four-wave mixing (FWM) with coherent multi-tone pump. The data aggregation is realized by coherently superposing or combining low-level subcarriers to yield high-level subcarriers in the optical field. Moreover, multiple replicas of the data-aggregated subcarriers and the subcarriers carrying the original data are obtained. In the experiment, two 5 Gbps quadrature phase-shift keying (QPSK) subcarriers are coherently combined to generate a 10 Gbps 16 quadrature amplitude modulation (QAM) subcarrier with frequency conversions through the FWM with coherent multi-tone pump. Less than 1 dB optical signal-to-noise ratio (OSNR) penalty variation is observed for the synthesized 16QAM subcarriers after the data aggregation. In addition, some subcarriers are kept in the original formats, QPSK, with a power penalty of less than 0.4 dB with respect to the original input subcarriers. The proposed subcarrier processing technology enables flexibility for spectral management in future dynamic optical networks.

Efficient dynamic coherence transfer relying on offset locking using optical phase-locked loop

NASA Astrophysics Data System (ADS)

Xie, Weilin; Dong, Yi; Bretenaker, Fabien; Shi, Hongxiao; Zhou, Qian; Xia, Zongyang; Qin, Jie; Zhang, Lin; Lin, Xi; Hu, Weisheng

2018-01-01

We design and experimentally demonstrate a highly efficient coherence transfer based on composite optical phaselocked loop comprising multiple feedback servo loops. The heterodyne offset-locking is achieved by conducting an acousto-optic frequency shifter in combination with the current tuning and the temperature controlling of the semiconductor laser. The adaptation of the composite optical phase-locked loop enables the tight coherence transfer from a frequency comb to a semiconductor laser in a fully dynamic manner.

A first demonstration of audio-frequency optical coherence elastography of tissue

NASA Astrophysics Data System (ADS)

Adie, Steven G.; Alexandrov, Sergey A.; Armstrong, Julian J.; Kennedy, Brendan F.; Sampson, David D.

2008-12-01

Optical elastography is aimed at using the visco-elastic properties of soft tissue as a contrast mechanism, and could be particularly suitable for high-resolution differentiation of tumour from surrounding normal tissue. We present a new approach to measure the effect of an applied stimulus in the kilohertz frequency range that is based on optical coherence tomography. We describe the approach and present the first in vivo optical coherence elastography measurements in human skin at audio excitation frequencies.

T-2 in Coherent Optics: Collision, Dephasing Time, or Reciprocal Linewidth.

ERIC Educational Resources Information Center

Nettel, Stephen J.; Lempicki, Alexander

1979-01-01

Discusses how the frequency domain (line widths) and time domain (coherent optical transients) are related to the concept of transverse relaxation time in the study of high resolution optical spectroscopy. (HM)

Multi-contrast imaging of human posterior eye by Jones matrix optical coherence tomography

NASA Astrophysics Data System (ADS)

Yasuno, Yoshiaki

2017-04-01

A multi-contrast imaging of pathologic posterior eyes is demonstrated by Jones matrix optical coherence tomography (Jones matrix OCT). The Jones matrix OCT provides five tomographies, which includes scattering, local attenuation, birefringence, polarization uniformity, and optical coherence angiography, by a single scan. The hardware configuration, algorithms of the Jones matrix OCT as well as its application to ophthalmology is discussed.

High-speed polarization sensitive optical frequency domain imaging with frequency multiplexing

PubMed Central

Yun, S.H.; Vakoc, B.J.; Shishkov, M.; Desjardins, A.E.; Park, B.H.; de Boer, J.F.; Tearney, G.J.; Bouma, B.E.

2009-01-01

Polarization sensitive optical coherence tomography (PS-OCT) provides a cross-sectional image of birefringence in biological samples that is complementary in many applications to the standard reflectance-based image. Recent ex vivo studies have demonstrated that birefringence mapping enables the characterization of collagen and smooth muscle concentration and distribution in vascular tissues. Instruments capable of applying these measurements percutaneously in vivo may provide new insights into coronary atherosclerosis and acute myocardial infarction. We have developed a polarization sensitive optical frequency domain imaging (PS-OFDI) system that enables high-speed intravascular birefringence imaging through a fiber-optic catheter. The novel design of this system utilizes frequency multiplexing to simultaneously measure reflectance of two incident polarization states, overcoming concerns regarding temporal variations of the catheter fiber birefringence and spatial variations in the birefringence of the sample. We demonstrate circular cross-sectional birefringence imaging of a human coronary artery ex vivo through a flexible fiber-optic catheter with an A-line rate of 62 kHz and a ranging depth of 6.2 mm. PMID:18542183

Measuring the complex optical conductivity of graphene by Fabry-Pérot reflectance spectroscopy [Determination of the optical index for few-layer graphene by reflectivity spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghamsari, Behnood G.; Tosado, Jacob; Yamamoto, Mahito

Here, we have experimentally studied the optical refractive index of few-layer graphene through reflection spectroscopy at visible wavelengths. A laser scanning microscope (LSM) with a coherent supercontinuum laser source measured the reflectivity of an exfoliated graphene flake on a Si/SiO 2 substrate, containing monolayer, bilayer and trilayer areas, as the wavelength of the laser was varied from 545nm to 710nm. The complex refractive index of few-layer graphene, n-ik, was extracted from the reflectivity contrast to the bare substrate and the Fresnel reflection theory. Since the SiO 2 thickness enters to the modeling as a parameter, it was precisely measured atmore » the location of the sample. It was found that a common constant optical index cannot explain the wavelength-dependent reflectivity data for single-, double- and three-layer graphene simultaneously, but rather each individual few-layer graphene possesses a unique optical index whose complex values were precisely and accurately determined from the experimental data.« less

Measuring the complex optical conductivity of graphene by Fabry-Pérot reflectance spectroscopy [Determination of the optical index for few-layer graphene by reflectivity spectroscopy

DOE PAGES

Ghamsari, Behnood G.; Tosado, Jacob; Yamamoto, Mahito; ...

2016-09-29

Here, we have experimentally studied the optical refractive index of few-layer graphene through reflection spectroscopy at visible wavelengths. A laser scanning microscope (LSM) with a coherent supercontinuum laser source measured the reflectivity of an exfoliated graphene flake on a Si/SiO 2 substrate, containing monolayer, bilayer and trilayer areas, as the wavelength of the laser was varied from 545nm to 710nm. The complex refractive index of few-layer graphene, n-ik, was extracted from the reflectivity contrast to the bare substrate and the Fresnel reflection theory. Since the SiO 2 thickness enters to the modeling as a parameter, it was precisely measured atmore » the location of the sample. It was found that a common constant optical index cannot explain the wavelength-dependent reflectivity data for single-, double- and three-layer graphene simultaneously, but rather each individual few-layer graphene possesses a unique optical index whose complex values were precisely and accurately determined from the experimental data.« less

Differential phase optical coherence probe for depth-resolved detection of photothermal response in tissue.

PubMed

Telenkov, Sergey A; Dave, Digant P; Sethuraman, Shriram; Akkin, Taner; Milner, Thomas E

2004-01-07

We describe a differential phase low-coherence interferometric probe for non-invasive, quantitative imaging of photothermal phenomena in biological materials. Our detection method utilizes principles of optical coherence tomography with differential phase measurement of interference fringe signals. A dual-channel optical low-coherence probe is used to analyse laser-induced thermoelastic and thermorefractive effects in tissue with micrometre axial resolution and nanometre sensitivity. We demonstrate an application of the technique using tissue phantoms and ex-vivo tissue specimens of rodent dorsal skin.

Coherent startup of an infrared free-electron laser

NASA Astrophysics Data System (ADS)

Jaroszynski, D. A.; Bakker, R. J.; van der Meer, A. F. G.; Oepts, D.; van Amersfoort, P. W.

1993-12-01

Coherent enhancement of the spontaneous undulator radiation by several orders of magnitude has been observed in a free-electron laser at wavelengths from 40 to 100 μm. The coherent emission can be explained by details of the electron-beam micropulse structure. Furthermore, it has been found that the phase of the optical micropulses is fixed by the electron pulse structure and that the coherence extends over successive optical micropulses, which gives rise to interference effects as a function of the optical cavity length in a laser oscillator.

A landmark recognition and tracking experiment for flight on the Shuttle/Advanced Technology Laboratory (ATL)

NASA Technical Reports Server (NTRS)

Welch, J. D.

1975-01-01

The preliminary design of an experiment for landmark recognition and tracking from the Shuttle/Advanced Technology Laboratory is described. It makes use of parallel coherent optical processing to perform correlation tests between landmarks observed passively with a telescope and previously made holographic matched filters. The experimental equipment including the optics, the low power laser, the random access file of matched filters and the electro-optical readout device are described. A real time optically excited liquid crystal device is recommended for performing the input non-coherent optical to coherent optical interface function. A development program leading to a flight experiment in 1981 is outlined.

Coherent Amplification of Ultrafast Molecular Dynamics in an Optical Oscillator

NASA Astrophysics Data System (ADS)

Aharonovich, Igal; Pe'er, Avi

2016-02-01

Optical oscillators present a powerful optimization mechanism. The inherent competition for the gain resources between possible modes of oscillation entails the prevalence of the most efficient single mode. We harness this "ultrafast" coherent feedback to optimize an optical field in time, and show that, when an optical oscillator based on a molecular gain medium is synchronously pumped by ultrashort pulses, a temporally coherent multimode field can develop that optimally dumps a general, dynamically evolving vibrational wave packet, into a single vibrational target state. Measuring the emitted field opens a new window to visualization and control of fast molecular dynamics. The realization of such a coherent oscillator with hot alkali dimers appears within experimental reach.

Squeezed light in an optical parametric oscillator network with coherent feedback quantum control.

PubMed

Crisafulli, Orion; Tezak, Nikolas; Soh, Daniel B S; Armen, Michael A; Mabuchi, Hideo

2013-07-29

We present squeezing and anti-squeezing spectra of the output from a degenerate optical parametric oscillator (OPO) network arranged in different coherent quantum feedback configurations. One OPO serves as a quantum plant, the other as a quantum controller. The addition of coherent feedback enables shaping of the output squeezing spectrum of the plant, and is found to be capable of pushing the frequency of maximum squeezing away from the optical driving frequency and broadening the spectrum over a wider frequency band. The experimental results are in excellent agreement with the developed theory, and illustrate the use of coherent quantum feedback to engineer the quantum-optical properties of the plant OPO output.

Design and characterization of a handheld multimodal imaging device for the assessment of oral epithelial lesions

NASA Astrophysics Data System (ADS)

Higgins, Laura M.; Pierce, Mark C.

2014-08-01

A compact handpiece combining high resolution fluorescence (HRF) imaging with optical coherence tomography (OCT) was developed to provide real-time assessment of oral lesions. This multimodal imaging device simultaneously captures coregistered en face images with subcellular detail alongside cross-sectional images of tissue microstructure. The HRF imaging acquires a 712×594 μm2 field-of-view at the sample with a spatial resolution of 3.5 μm. The OCT images were acquired to a depth of 1.5 mm with axial and lateral resolutions of 9.3 and 8.0 μm, respectively. HRF and OCT images are simultaneously displayed at 25 fps. The handheld device was used to image a healthy volunteer, demonstrating the potential for in vivo assessment of the epithelial surface for dysplastic and neoplastic changes at the cellular level, while simultaneously evaluating submucosal involvement. We anticipate potential applications in real-time assessment of oral lesions for improved surveillance and surgical guidance.

Transmission and full-band coherent detection of polarization-multiplexed all-optical Nyquist signals generated by Sinc-shaped Nyquist pulses

PubMed Central

Zhang, Junwen; Yu, Jianjun; Chi, Nan

2015-01-01

All optical method is considered as a promising technique for high symbol rate Nyquist signal generation, which has attracted a lot of research interests for high spectral-efficiency and high-capacity optical communication system. In this paper, we extend our previous work and report the fully experimental demonstration of polarization-division multiplexed (PDM) all-optical Nyquist signal generation based on Sinc-shaped Nyquist pulse with advanced modulation formats, fiber-transmission and single-receiver full-band coherent detection. Using this scheme, we have successfully demonstrated the generation, fiber transmission and single-receiver full-band coherent detection of all-optical Nyquist PDM-QPSK and PDM-16QAM signals up to 125-GBaud. 1-Tb/s single-carrier PDM-16QAM signal generation and full-band coherent detection is realized, which shows the advantage and feasibility of the single-carrier all-optical Nyquist signals. PMID:26323238

Optical coherence of 166Er:7LiYF4 crystal below 1 K

NASA Astrophysics Data System (ADS)

Kukharchyk, N.; Sholokhov, D.; Morozov, O.; Korableva, S. L.; Kalachev, A. A.; Bushev, P. A.

2018-02-01

We explore optical coherence and spin dynamics of an isotopically purified 166Er:7LiYF4 crystal below 1 K and at weak magnetic fields < 0.3T. Crystals were grown in our lab and demonstrate narrow inhomogeneous optical broadening down to 16 MHz. Solid-state atomic ensembles with such narrow linewidths are very attractive for implementing of off-resonant Raman quantum memory and for the interfacing of superconducting quantum circuits and telecom C-band optical photons. Both applications require a low magnetic field of ∼10 mT. However, at conventional experimental temperatures T > 1.5 K, optical coherence of Er:LYF crystal attains ≃ 10 μ {{s}} time scale only at strong magnetic fields above 1.5 T. In the present work, we demonstrate that the deep freezing of Er:LYF crystal below 1 K results in the increase of optical coherence time to ≃ 100 μ {{s}} at weak fields.

Optical Coherence Elastography

NASA Astrophysics Data System (ADS)

Kennedy, Brendan F.; Kennedy, Kelsey M.; Oldenburg, Amy L.; Adie, Steven G.; Boppart, Stephen A.; Sampson, David D.

The mechanical properties of tissue are pivotal in its function and behavior, and are often modified by disease. From the nano- to the macro-scale, many tools have been developed to measure tissue mechanical properties, both to understand the contribution of mechanics in the origin of disease and to improve diagnosis. Optical coherence elastography is applicable to the intermediate scale, between that of cells and whole organs, which is critical in the progression of many diseases and not widely studied to date. In optical coherence elastography, a mechanical load is imparted to a tissue and the resulting deformation is measured using optical coherence tomography. The deformation is used to deduce a mechanical parameter, e.g., Young's modulus, which is mapped into an image, known as an elastogram. In this chapter, we review the development of optical coherence elastography and report on the latest developments. We provide a focus on the underlying principles and assumptions, techniques to measure deformation, loading mechanisms, imaging probes and modeling, including the inverse elasticity problem.

High-brightness laser imaging with tunable speckle reduction enabled by electroactive micro-optic diffusers.

PubMed

Farrokhi, Hamid; Rohith, Thazhe Madam; Boonruangkan, Jeeranan; Han, Seunghwoi; Kim, Hyunwoong; Kim, Seung-Woo; Kim, Young-Jin

2017-11-10

High coherence of lasers is desirable in high-speed, high-resolution, and wide-field imaging. However, it also causes unavoidable background speckle noise thus degrades the image quality in traditional microscopy and more significantly in interferometric quantitative phase imaging (QPI). QPI utilizes optical interference for high-precision measurement of the optical properties where the speckle can severely distort the information. To overcome this, we demonstrated a light source system having a wide tunability in the spatial coherence over 43% by controlling the illumination angle, scatterer's size, and the rotational speed of an electroactive-polymer rotational micro-optic diffuser. Spatially random phase modulation was implemented for the lower speckle imaging with over a 50% speckle reduction without a significant degradation in the temporal coherence. Our coherence control technique will provide a unique solution for a low-speckle, full-field, and coherent imaging in optically scattering media in the fields of healthcare sciences, material sciences and high-precision engineering.

All-optical control of long-lived nuclear spins in rare-earth doped nanoparticles.

PubMed

Serrano, D; Karlsson, J; Fossati, A; Ferrier, A; Goldner, P

2018-05-29

Nanoscale systems that coherently couple to light and possess spins offer key capabilities for quantum technologies. However, an outstanding challenge is to preserve properties, and especially optical and spin coherence lifetimes, at the nanoscale. Here, we report optically controlled nuclear spins with long coherence lifetimes (T 2 ) in rare-earth-doped nanoparticles. We detect spins echoes and measure a spin coherence lifetime of 2.9 ± 0.3 ms at 5 K under an external magnetic field of 9 mT, a T 2 value comparable to those obtained in bulk rare-earth crystals. Moreover, we achieve spin T 2 extension using all-optical spin dynamical decoupling and observe high fidelity between excitation and echo phases. Rare-earth-doped nanoparticles are thus the only nano-material in which optically controlled spins with millisecond coherence lifetimes have been reported. These results open the way to providing quantum light-atom-spin interfaces with long storage time within hybrid architectures.

Integrated Photoacoustic Ophthalmoscopy and Spectral-domain Optical Coherence Tomography

PubMed Central

Jiao, Shuliang; Zhang, Hao F.

2013-01-01

Both the clinical diagnosis and fundamental investigation of major ocular diseases greatly benefit from various non-invasive ophthalmic imaging technologies. Existing retinal imaging modalities, such as fundus photography1, confocal scanning laser ophthalmoscopy (cSLO)2, and optical coherence tomography (OCT)3, have significant contributions in monitoring disease onsets and progressions, and developing new therapeutic strategies. However, they predominantly rely on the back-reflected photons from the retina. As a consequence, the optical absorption properties of the retina, which are usually strongly associated with retinal pathophysiology status, are inaccessible by the traditional imaging technologies. Photoacoustic ophthalmoscopy (PAOM) is an emerging retinal imaging modality that permits the detection of the optical absorption contrasts in the eye with a high sensitivity4-7 . In PAOM nanosecond laser pulses are delivered through the pupil and scanned across the posterior eye to induce photoacoustic (PA) signals, which are detected by an unfocused ultrasonic transducer attached to the eyelid. Because of the strong optical absorption of hemoglobin and melanin, PAOM is capable of non-invasively imaging the retinal and choroidal vasculatures, and the retinal pigment epithelium (RPE) melanin at high contrasts 6,7. More importantly, based on the well-developed spectroscopic photoacoustic imaging5,8 , PAOM has the potential to map the hemoglobin oxygen saturation in retinal vessels, which can be critical in studying the physiology and pathology of several blinding diseases 9 such as diabetic retinopathy and neovascular age-related macular degeneration. Moreover, being the only existing optical-absorption-based ophthalmic imaging modality, PAOM can be integrated with well-established clinical ophthalmic imaging techniques to achieve more comprehensive anatomic and functional evaluations of the eye based on multiple optical contrasts6,10 . In this work, we integrate PAOM and spectral-domain OCT (SD-OCT) for simultaneously in vivo retinal imaging of rat, where both optical absorption and scattering properties of the retina are revealed. The system configuration, system alignment and imaging acquisition are presented. PMID:23354081

Applications of Optical Coherence Tomography in Pediatric Clinical Neuroscience

PubMed Central

Avery, Robert A.; Rajjoub, Raneem D.; Trimboli-Heidler, Carmelina; Waldman, Amy T.

2015-01-01

For nearly two centuries, the ophthalmoscope has permitted examination of the retina and optic nerve—the only axons directly visualized by the physician. The retinal ganglion cells project their axons, which travel along the innermost retina to form the optic nerve, marking the beginning of the anterior visual pathway. Both the structure and function of the visual pathway are essential components of the neurologic examination as it can be involved in numerous acquired, congenital and genetic central nervous system conditions. The development of optical coherence tomography now permits the pediatric neuroscientist to visualize and quantify the optic nerve and retinal layers with unprecedented resolution. As optical coherence tomography becomes more accessible and integrated into research and clinical care, the pediatric neuroscientist may have the opportunity to utilize and/or interpret results from this device. This review describes the basic technical features of optical coherence tomography and highlights its potential clinical and research applications in pediatric clinical neuroscience including optic nerve swelling, optic neuritis, tumors of the visual pathway, vigabatrin toxicity, nystagmus, and neurodegenerative conditions. PMID:25803824

Applications of optical coherence tomography in pediatric clinical neuroscience.

PubMed

Avery, Robert A; Rajjoub, Raneem D; Trimboli-Heidler, Carmelina; Waldman, Amy T

2015-04-01

For nearly two centuries, the ophthalmoscope has permitted examination of the retina and optic nerve-the only axons directly visualized by the physician. The retinal ganglion cells project their axons, which travel along the innermost retina to form the optic nerve, marking the beginning of the anterior visual pathway. Both the structure and function of the visual pathway are essential components of the neurologic examination as it can be involved in numerous acquired, congenital and genetic central nervous system conditions. The development of optical coherence tomography now permits the pediatric neuroscientist to visualize and quantify the optic nerve and retinal layers with unprecedented resolution. As optical coherence tomography becomes more accessible and integrated into research and clinical care, the pediatric neuroscientist may have the opportunity to utilize and/or interpret results from this device. This review describes the basic technical features of optical coherence tomography and highlights its potential clinical and research applications in pediatric clinical neuroscience including optic nerve swelling, optic neuritis, tumors of the visual pathway, vigabatrin toxicity, nystagmus, and neurodegenerative conditions. Georg Thieme Verlag KG Stuttgart · New York.

Multiplexed image storage by electromagnetically induced transparency in a solid

NASA Astrophysics Data System (ADS)

Heinze, G.; Rentzsch, N.; Halfmann, T.

2012-11-01

We report on frequency- and angle-multiplexed image storage by electromagnetically induced transparency (EIT) in a Pr3+:Y2SiO5 crystal. Frequency multiplexing by EIT relies on simultaneous storage of light pulses in atomic coherences, driven in different frequency ensembles of the inhomogeneously broadened solid medium. Angular multiplexing by EIT relies on phase matching of the driving laser beams, which permits simultaneous storage of light pulses propagating under different angles into the crystal. We apply the multiplexing techniques to increase the storage capacity of the EIT-driven optical memory, in particular to implement multiplexed storage of larger two-dimensional amounts of data (images). We demonstrate selective storage and readout of images by frequency-multiplexed EIT and angular-multiplexed EIT, as well as the potential to combine both multiplexing approaches towards further enhanced storage capacities.

Digitally enhanced homodyne interferometry.

PubMed

Sutton, Andrew J; Gerberding, Oliver; Heinzel, Gerhard; Shaddock, Daniel A

2012-09-24

We present two variations of a novel interferometry technique capable of simultaneously measuring multiple targets with high sensitivity. The technique performs a homodyne phase measurement by application of a four point phase shifting algorithm, with pseudo-random switching between points to allow multiplexed measurement based upon propagation delay alone. By multiplexing measurements and shifting complexity into signal processing, both variants realise significant complexity reductions over comparable methods. The first variant performs a typical coherent detection with a dedicated reference field and achieves a displacement noise floor 0.8 pm/√Hz above 50 Hz. The second allows for removal of the dedicated reference, resulting in further simplifications and improved low frequency performance with a 1 pm/√Hz noise floor measured down to 20 Hz. These results represent the most sensitive measurement performed using this style of interferometry whilst simultaneously reducing the electro-optic footprint.

OPTICAL PROCESSING OF INFORMATION: Potential applications of quasi-cw partially coherent radiation in optical data recording and processing

NASA Astrophysics Data System (ADS)

Volkov, L. V.; Larkin, A. I.

1994-04-01

Theoretical and experimental investigations are reported of the potential applications of quasi-cw partially coherent radiation in optical systems based on diffraction—interference principles. It is shown that the spectral characteristics of quasi-cw radiation influence the data-handling capabilities of a holographic correlator and of a partially coherent holographic system for data acquisition. Relevant experimental results are reported.

Developments in Coherent Perfect Polarization Rotation

NASA Astrophysics Data System (ADS)

Crescimanno, Michael; Andrews, James; Zhou, Chaunhong; Baker, Michael

2015-05-01

Coherent Perfect Polarization Rotation (CPR) is a useful technique akin to Coherent Perfect Absorption (CPA, also known as the anti-laser) but that results in very high efficiency optical mode conversion. We describe the analysis of recent experimental data from our CPR testbed, the use of CPR in miniaturizing optical isolators and CPR phenomena in non-linear optics. Work supported by the N.S.F. under Grant No. ECCS-1360725.

Developing single-laser sources for multimodal coherent anti-Stokes Raman scattering microscopy

NASA Astrophysics Data System (ADS)

Pegoraro, Adrian Frank

Coherent anti-Stokes Raman scattering (CARS) microscopy has developed rapidly and is opening the door to new types of experiments. This work describes the development of new laser sources for CARS microscopy and their use for different applications. It is specifically focused on multimodal nonlinear optical microscopy—the simultaneous combination of different imaging techniques. This allows us to address a diverse range of applications, such as the study of biomaterials, fluid inclusions, atherosclerosis, hepatitis C infection in cells, and ice formation in cells. For these applications new laser sources are developed that allow for practical multimodal imaging. For example, it is shown that using a single Ti:sapphire oscillator with a photonic crystal fiber, it is possible to develop a versatile multimodal imaging system using optimally chirped laser pulses. This system can perform simultaneous two photon excited fluorescence, second harmonic generation, and CARS microscopy. The versatility of the system is further demonstrated by showing that it is possible to probe different Raman modes using CARS microscopy simply by changing a time delay between the excitation beams. Using optimally chirped pulses also enables further simplification of the laser system required by using a single fiber laser combined with nonlinear optical fibers to perform effective multimodal imaging. While these sources are useful for practical multimodal imaging, it is believed that for further improvements in CARS microscopy sensitivity, new excitation schemes are necessary. This has led to the design of a new, high power, extended cavity oscillator that should be capable of implementing new excitation schemes for CARS microscopy as well as other techniques. Our interest in multimodal imaging has led us to other areas of research as well. For example, a fiber-coupling scheme for signal collection in the forward direction is demonstrated that allows for fluorescence lifetime imaging without significant temporal distortion. Also highlighted is an imaging artifact that is unique to CARS microscopy that can alter image interpretation, especially when using multimodal imaging. By combining expertise in nonlinear optics, laser development, fiber optics, and microscopy, we have developed systems and techniques that will be of benefit for multimodal CARS microscopy.

Optical amplifiers for coherent lidar

NASA Technical Reports Server (NTRS)

Fork, Richard

1996-01-01

We examine application of optical amplification to coherent lidar for the case of a weak return signal (a number of quanta of the return optical field close to unity). We consider the option that has been explored to date, namely, incorporation of an optical amplifier operated in a linear manner located after reception of the signal and immediately prior to heterodyning and photodetection. We also consider alternative strategies where the coherent interaction, the nonlinear processes, and the amplification are not necessarily constrained to occur in the manner investigated to date. We include the complications that occur because of mechanisms that occur at the level of a few, or one, quantum excitation. Two factors combine in the work to date that limit the value of the approach. These are: (1) the weak signal tends to require operation of the amplifier in the linear regime where the important advantages of nonlinear optical processing are not accessed, (2) the linear optical amplifier has a -3dB noise figure (SN(out)/SN(in)) that necessarily degrades the signal. Some improvement is gained because the gain provided by the optical amplifier can be used to overcome losses in the heterodyned process and photodetection. The result, however, is that introduction of an optical amplifier in a well optimized coherent lidar system results in, at best, a modest improvement in signal to noise. Some improvement may also be realized on incorporating more optical components in a coherent lidar system for purely practical reasons. For example, more compact, lighter weight, components, more robust alignment, or more rapid processing may be gained. We further find that there remain a number of potentially valuable, but unexplored options offered both by the rapidly expanding base of optical technology and the recent investigation of novel nonlinear coherent interference phenomena occurring at the single quantum excitation level. Key findings are: (1) insertion of linear optical amplifiers in well optimized conventional lidar systems offers modest improvements, at best, (2) the practical advantages of optical amplifiers, especially fiber amplifiers, such as ease of alignment, compactness, efficiency, lightweight, etc., warrant further investigation for coherent lidar, (3) the possibility of more fully optical lidar systems should be explored, (4) advantages gained by use of coherent interference of optical fields at the level of one, or a few, signal quanta should be explored, (5) amplification without inversion, population trapping, and use of electromagnetic induced transparency warrant investigation in connection with coherent lidar, (6) these new findings are probably more applicable to earth related NASA work, although applications to deep space should not be excluded, and (7) our own work in the Ultrafast Laboratory at UAH along some of the above lines of investigation, may be useful.

Development of a high-speed wavelength-agile CO2 local oscillator for heterodyne DIAL measurements

NASA Astrophysics Data System (ADS)

Senft, Daniel C.; Pierrottet, Diego F.

2002-06-01

A high repetition rate, wavelength agile CO2 laser has been developed at the Air Force Research Laboratory for use as a local oscillator in a heterodyne detection receiver. Fats wavelength selection is required for measurements of airborne chemical vapors using the differential absorption lidar (DIAL) technique. Acousto-optic modulator are used to tune between different wavelengths at high speeds without the need for moving mechanical parts. Other advantages obtained by the use of acousto-optic modulators are laser output power control per wavelength and rugged packaging for field applications. The local oscillator design is described, and the results from laboratory DIAL measurements are presented. The coherent remote optical sensor system is an internal research project being conducted by the Air Force Research Laboratory Directed Energy Directorate, Active Remote Sensing Branch. The objective of the project is to develop a new long-range standoff spectral sensor that takes advantage of the enhanced performance capabilities coherent detection can provide. Emphasis of the development is on a low cost, compact, and rugged active sensor exclusively designed for heterodyne detection using the differential absorption lidar technique. State of the art technologies in waveguide laser construction and acousto- optics make feasible the next generation of lasers capable of supporting coherent lidar system requirements. Issues addressed as part of the development include optoelectronic engineering of a low cost rugged system, and fast data throughput for real time chemical concentration measurements. All hardware used in this sensor are off-the- shelf items, so only minor hardware modifications were required for the system as it stands. This paper describes a high-speed heterodyne detection CO2 DIAL system that employs a wavelength agile, acousto-optically tuned local oscillator in the receiver. Sample experimental data collected in a controlled environment are presented as well. Chemical detection using 12 wavelengths at 200 pulses per second has been demonstrated. Initial progress on experiments to make a direct, simultaneous comparison of heterodyne and direct detection DIAL systems will also be described.

Low-cost coherent receiver for long-reach optical access network using single-ended detection.

PubMed

Zhang, Xuebing; Li, Zhaohui; Li, Jianping; Yu, Changyuan; Lau, Alan Pak Tao; Lu, Chao

2014-09-15

A low-cost coherent receiver using two 2×3 optical hybrids and single-ended detection is proposed for long-reach optical access network. This structure can detect the two polarization components of polarization division multiplexing (PDM) signals. Polarization de-multiplexing and signal-to-signal beat interference (SSBI) cancellation are realized by using only three photodiodes. Simulation results for 40 Gb/s PDM-OFDM transmissions indicate that the low-cost coherent receiver has 3.2 dB optical signal-to-noise ratio difference compared with the theoretical value.

Use of optical coherence topography for objective assessment of fundus torsion.

PubMed

Sophocleous, Sophocles

2017-02-23

Objective assessment of fundus torsion is currently performed with indirect ophthalmoscopy or fundus photography. Using the infrared image of the macular scan of the optical coherence tomography one can assess the presence and amount of fundus torsion. In addition, the line scan through the fovea can be used as a reference to confirm the position of the foveal pit in relation to the optic nerve head. Two cases are used to demonstrate how to assess fundus torsion with the use of the optical coherence tomography. 2017 BMJ Publishing Group Ltd.

Overlapped optics induced perfect coherent effects.

PubMed

Li, Jian Jie; Zang, Xiao Fei; Mao, Jun Fa; Tang, Min; Zhu, Yi Ming; Zhuang, Song Lin

2013-12-20

For traditional coherent effects, two separated identical point sources can be interfered with each other only when the optical path difference is integer number of wavelengths, leading to alternate dark and bright fringes for different optical path difference. For hundreds of years, such a perfect coherent condition seems insurmountable. However, in this paper, based on transformation optics, two separated in-phase identical point sources can induce perfect interference with each other without satisfying the traditional coherent condition. This shifting illusion media is realized by inductor-capacitor transmission line network. Theoretical analysis, numerical simulations and experimental results are performed to confirm such a kind of perfect coherent effect and it is found that the total radiation power of multiple elements system can be greatly enhanced. Our investigation may be applicable to National Ignition Facility (NIF), Inertial Confined Fusion (ICF) of China, LED lighting technology, terahertz communication, and so on.

Magneto-optical rotation in cavity QED with Zeeman coherence

NASA Astrophysics Data System (ADS)

Sun, Hui; Jia, Xiaohua; Fan, Shuangli; Zhang, Hongjun; Guo, Hong

2018-06-01

We investigate theoretically the magneto-optical rotation in cavity QED system with atomic Zeeman coherence, which is established via coherent population trapping. Owing to Zeeman coherence, the ultranarrow transmission spectrum less than 1 MHz with gain can be achieved with a flat-top Faraday rotation angle. By controlling the parameters appropriately, the input probe components within the flat-top regime rotate with almost the same angle, and transmit through the cavity perpendicularly to the other components outside the flat-top regime. The concepts discussed here provide an important tool for perfect ultranarrow Faraday optical filter and quantum information processing.

Multimodal swept-source spectrally encoded scanning laser ophthalmoscopy and optical coherence tomography at 400 kHz

NASA Astrophysics Data System (ADS)

El-Haddad, Mohamed T.; Joos, Karen M.; Patel, Shriji N.; Tao, Yuankai K.

2017-02-01

Multimodal imaging systems that combine scanning laser ophthalmoscopy (SLO) and optical coherence tomography (OCT) have demonstrated the utility of concurrent en face and volumetric imaging for aiming, eye tracking, bulk motion compensation, mosaicking, and contrast enhancement. However, this additional functionality trades off with increased system complexity and cost because both SLO and OCT generally require dedicated light sources, galvanometer scanners, relay and imaging optics, detectors, and control and digitization electronics. We previously demonstrated multimodal ophthalmic imaging using swept-source spectrally encoded SLO and OCT (SS-SESLO-OCT). Here, we present system enhancements and a new optical design that increase our SS-SESLO-OCT data throughput by >7x and field-of-view (FOV) by >4x. A 200 kHz 1060 nm Axsun swept-source was optically buffered to 400 kHz sweep-rate, and SESLO and OCT were simultaneously digitized on dual input channels of a 4 GS/s digitizer at 1.2 GS/s per channel using a custom k-clock. We show in vivo human imaging of the anterior segment out to the limbus and retinal fundus over a >40° FOV. In addition, nine overlapping volumetric SS-SESLO-OCT volumes were acquired under video-rate SESLO preview and guidance. In post-processing, all nine SESLO images and en face projections of the corresponding OCT volumes were mosaicked to show widefield multimodal fundus imaging with a >80° FOV. Concurrent multimodal SS-SESLO-OCT may have applications in clinical diagnostic imaging by enabling aiming, image registration, and multi-field mosaicking and benefit intraoperative imaging by allowing for real-time surgical feedback, instrument tracking, and overlays of computationally extracted image-based surrogate biomarkers of disease.

Coherent Optical Control of Electronic Excitations in Wide-Band-Gap Semiconductor Structures

DTIC Science & Technology

2015-05-01

ABSTRACT The main objective of this research is to study coherent quantum effects, such as Rabi oscillations in optical spectra of wide- band-gap...field corresponds to the rotation of the B vector about the pseudo field vector, Ω, with components determined by the effective Rabi frequency ( )e...to examine coherent quantum effects, such as Rabi oscillations and quantum entanglement in optical spectra of wide-band-gap materials, and to

Compound focusing mirror and X-ray waveguide optics for coherent imaging and nano-diffraction.

PubMed

Salditt, Tim; Osterhoff, Markus; Krenkel, Martin; Wilke, Robin N; Priebe, Marius; Bartels, Matthias; Kalbfleisch, Sebastian; Sprung, Michael

2015-07-01

A compound optical system for coherent focusing and imaging at the nanoscale is reported, realised by high-gain fixed-curvature elliptical mirrors in combination with X-ray waveguide optics or different cleaning apertures. The key optical concepts are illustrated, as implemented at the Göttingen Instrument for Nano-Imaging with X-rays (GINIX), installed at the P10 coherence beamline of the PETRA III storage ring at DESY, Hamburg, and examples for typical applications in biological imaging are given. Characteristic beam configurations with the recently achieved values are also described, meeting the different requirements of the applications, such as spot size, coherence or bandwidth. The emphasis of this work is on the different beam shaping, filtering and characterization methods.

Measuring finite-range phase coherence in an optical lattice using Talbot interferometry

PubMed Central

Santra, Bodhaditya; Baals, Christian; Labouvie, Ralf; Bhattacherjee, Aranya B.; Pelster, Axel; Ott, Herwig

2017-01-01

One of the important goals of present research is to control and manipulate coherence in a broad variety of systems, such as semiconductor spintronics, biological photosynthetic systems, superconducting qubits and complex atomic networks. Over the past decades, interferometry of atoms and molecules has proven to be a powerful tool to explore coherence. Here we demonstrate a near-field interferometer based on the Talbot effect, which allows us to measure finite-range phase coherence of ultracold atoms in an optical lattice. We apply this interferometer to study the build-up of phase coherence after a quantum quench of a Bose–Einstein condensate residing in a one-dimensional optical lattice. Our technique of measuring finite-range phase coherence is generic, easy to adopt and can be applied in practically all lattice experiments without further modifications. PMID:28580941

Physical-layer network coding in coherent optical OFDM systems.

PubMed

Guan, Xun; Chan, Chun-Kit

2015-04-20

We present the first experimental demonstration and characterization of the application of optical physical-layer network coding in coherent optical OFDM systems. It combines two optical OFDM frames to share the same link so as to enhance system throughput, while individual OFDM frames can be recovered with digital signal processing at the destined node.

Noise characterization of broadband fiber Cherenkov radiation as a visible-wavelength source for optical coherence tomography and two-photon fluorescence microscopy.

PubMed

Tu, Haohua; Zhao, Youbo; Liu, Yuan; Liu, Yuan-Zhi; Boppart, Stephen

2014-08-25

Optical sources in the visible region immediately adjacent to the near-infrared biological optical window are preferred in imaging techniques such as spectroscopic optical coherence tomography of endogenous absorptive molecules and two-photon fluorescence microscopy of intrinsic fluorophores. However, existing sources based on fiber supercontinuum generation are known to have high relative intensity noise and low spectral coherence, which may degrade imaging performance. Here we compare the optical noise and pulse compressibility of three high-power fiber Cherenkov radiation sources developed recently, and evaluate their potential to replace the existing supercontinuum sources in these imaging techniques.

Real-time high-velocity resolution color Doppler OCT

NASA Astrophysics Data System (ADS)

Westphal, Volker; Yazdanfar, Siavash; Rollins, Andrew M.; Izatt, Joseph A.

2001-05-01

Color Doppler optical coherence tomography (CDOCT), also called Optical Doppler Tomography) is a noninvasive optical imaging technique, which allows for micron-scale physiological flow mapping simultaneous with morphological OCT imaging. Current systems for real-time endoscopic optical coherence tomography (EOCT) would be enhanced by the capability to visualize sub-surface blood flow for applications in early cancer diagnosis and the management of bleeding ulcers. Unfortunately, previous implementations of CDOCT have either been sufficiently computationally expensive (employing Fourier or Hilbert transform techniques) to rule out real-time imaging of flow, or have been restricted to imaging of excessively high flow velocities when used in real time. We have developed a novel Doppler OCT signal-processing strategy capable of imaging physiological flow rates in real time. This strategy employs cross-correlation processing of sequential A-scans in an EOCT image, as opposed to autocorrelation processing as described previously. To measure Doppler shifts in the kHz range using this technique, it was necessary to stabilize the EOCT interferometer center frequency, eliminate parasitic phase noise, and to construct a digital cross correlation unit able to correlate signals of megahertz bandwidth by a fixed lag of up to a few ms. The performance of the color Doppler OCT system was demonstrated in a flow phantom, demonstrating a minimum detectable flow velocity of ~0.8 mm/s at a data acquisition rate of 8 images/second (with 480 A-scans/image) using a handheld probe. Dynamic flow as well as using it freehanded was shown. Flow was also detectable in a phantom in combination with a clinical usable endoscopic probe.

Complementary use of optical coherence tomography and 5-aminolevulinic acid induced fluorescent spectroscopy for diagnosis of neoplastic processes in cervix and vulva

NASA Astrophysics Data System (ADS)

Sapozhnikova, Veronika V.; Shakhova, Natalia M.; Kamensky, Vladislav A.; Kuranov, Roman V.; Loshenov, Victor B.; Petrova, Svetlana A.

2003-07-01

A new approach to improving the diagnostic value of optical methods is suggested, which is based on a complementary investigation of different optical parameters of biotissues. The aim of this paper is comparative study of the feasibility of two optical methods - fluorescence spectroscopy and optical coherence tomography - for visualization of borders of neoplastic processes in the uterine cervix and vulva. Fluorescence spectroscopy is based on the detection of biochemical and optical coherence tomography on backscattering properties in norm and pathological changes of tissues. By means of these optical methods changes in biochemical and morphological properties of tissues were investigated. A parallel analysis of these two optical methods and histology from the center of tumors and their optical borders was made. Thirteen female patients with neoplastic changes in uterine cervix and vulva were enrolled in this study. The borders of the tumor determined by optical methods (fluorescence spectroscopy and optical coherence tomography) are coinciding with the biopsy proved ones. In addition, OCT and fluorescence borders of tumor in the uterine cervix and vulva exceeds colposcopically detectable borders, the averaging difference 2 mm. In future optical methods would considerably enhance diagnostic accuracy of conventional methods used in oncogynecology.

Simultaneous SLO/OCT imaging of the human retina with axial eye motion correction.

PubMed

Pircher, Michael; Baumann, Bernhard; Götzinger, Erich; Sattmann, Harald; Hitzenberger, Christoph K

2007-12-10

It has been shown that transversal scanning (or en-face) optical coherence tomography (TS-OCT) represents an imaging modality capable to record high isotropic resolution images of the human retina in vivo. However, axial eye motion still remains a challenging problem of this technique. In this paper we introduce a novel method to compensate for this eye motion. An auxiliary spectral domain partial coherence interferometer (SD-PCI) was integrated into an existing TS-OCT system and used to measure accurately the position of the cornea. A light source emitting at 1310nm was used in the additional interferometer which enabled a nearly loss free coupling of the two measurement beams via a dichroic mirror. The recorded corneal position was used to drive an additional voice coil translation stage in the reference arm of the TS-OCT system to correct for axial eye motion. Currently, the correction can be performed with an update rate of ~200Hz. The TS-OCT instrument is operated with a line scan rate of 4000 transversal lines per second which enables simultaneous SLO/OCT imaging at a frame rate of 40fps. 3D data of the human retina with isotropic high resolution, that was sufficient to visualize the human cone mosaic in vivo, is presented.

Retinal nerve fiber layer thickness measured with optical coherence tomography is related to visual function in glaucomatous eyes.

PubMed

El Beltagi, Tarek A; Bowd, Christopher; Boden, Catherine; Amini, Payam; Sample, Pamela A; Zangwill, Linda M; Weinreb, Robert N

2003-11-01

To determine the relationship between areas of glaucomatous retinal nerve fiber layer thinning identified by optical coherence tomography and areas of decreased visual field sensitivity identified by standard automated perimetry in glaucomatous eyes. Retrospective observational case series. Forty-three patients with glaucomatous optic neuropathy identified by optic disc stereo photographs and standard automated perimetry mean deviations >-8 dB were included. Participants were imaged with optical coherence tomography within 6 months of reliable standard automated perimetry testing. The location and number of optical coherence tomography clock hour retinal nerve fiber layer thickness measures outside normal limits were compared with the location and number of standard automated perimetry visual field zones outside normal limits. Further, the relationship between the deviation from normal optical coherence tomography-measured retinal nerve fiber layer thickness at each clock hour and the average pattern deviation in each visual field zone was examined by using linear regression (R(2)). The retinal nerve fiber layer areas most frequently outside normal limits were the inferior and inferior temporal regions. The least sensitive visual field zones were in the superior hemifield. Linear regression results (R(2)) showed that deviation from the normal retinal nerve fiber layer thickness at optical coherence tomography clock hour positions 6 o'clock, 7 o'clock, and 8 o'clock (inferior and inferior temporal) was best correlated with standard automated perimetry pattern deviation in visual field zones corresponding to the superior arcuate and nasal step regions (R(2) range, 0.34-0.57). These associations were much stronger than those between clock hour position 6 o'clock and the visual field zone corresponding to the inferior nasal step region (R(2) = 0.01). Localized retinal nerve fiber layer thinning, measured by optical coherence tomography, is topographically related to decreased localized standard automated perimetry sensitivity in glaucoma patients.

Signal Coherence Recovery Using Acousto-Optic Fourier Transform Architectures

DTIC Science & Technology

1990-06-14

processing of data in ground- and space-based applications. We have implemented a prototype one-dimensional time-integrating acousto - optic (AO) Fourier...theory of optimum coherence recovery (CR) applicable in computation-limited environments. We have demonstrated direct acousto - optic implementation of CR

Optic flow detection is not influenced by visual-vestibular congruency.

PubMed

Holten, Vivian; MacNeilage, Paul R

2018-01-01

Optic flow patterns generated by self-motion relative to the stationary environment result in congruent visual-vestibular self-motion signals. Incongruent signals can arise due to object motion, vestibular dysfunction, or artificial stimulation, which are less common. Hence, we are predominantly exposed to congruent rather than incongruent visual-vestibular stimulation. If the brain takes advantage of this probabilistic association, we expect observers to be more sensitive to visual optic flow that is congruent with ongoing vestibular stimulation. We tested this expectation by measuring the motion coherence threshold, which is the percentage of signal versus noise dots, necessary to detect an optic flow pattern. Observers seated on a hexapod motion platform in front of a screen experienced two sequential intervals. One interval contained optic flow with a given motion coherence and the other contained noise dots only. Observers had to indicate which interval contained the optic flow pattern. The motion coherence threshold was measured for detection of laminar and radial optic flow during leftward/rightward and fore/aft linear self-motion, respectively. We observed no dependence of coherence thresholds on vestibular congruency for either radial or laminar optic flow. Prior studies using similar methods reported both decreases and increases in coherence thresholds in response to congruent vestibular stimulation; our results do not confirm either of these prior reports. While methodological differences may explain the diversity of results, another possibility is that motion coherence thresholds are mediated by neural populations that are either not modulated by vestibular stimulation or that are modulated in a manner that does not depend on congruency.

Evaluation of white-to-white distance and anterior chamber depth measurements using the IOL Master, slit-lamp adapted optical coherence tomography and digital photographs in phakic eyes.

PubMed

Wilczyński, Michał; Pośpiech-Zabierek, Aleksandra

2015-01-01

The accurate measurement of the anterior chamber internal diameter and depth is important in ophthalmic diagnosis and before some eye surgery procedures. The purpose of the study was to compare the white-to-white distance measurements performed using the IOL-Master and photography with internal anterior chamber diameter determined using slit lamp adapted optical coherence tomography in healthy eyes, and to compare anterior chamber depth measurements by IOL-Master and slit lamp adapted optical coherence tomography. The data were gathered prospectively from a non-randomized consecutive series of patients. The examined group consisted of 46 eyes of 39 patients. White-to-white was measured using IOL-Master and photographs of the eye were taken with a digital camera. Internal anterior chamber diameter was measured with slit-lamp adapted optical coherence tomography. Anterior chamber depth was measured using the IOL Master and slit-lamp adapted optical coherence tomography. Statistical analysis was performed using parametric tests. A Bland-Altman plot was drawn. White-to-white distance by the IOL Master was 11.8 +/- 0.40 mm, on photographs it was 11.29 +/- 0.58 mm and internal anterior chamber diameter by slit-lamp adapted optical coherence tomography was 11.34?0.54 mm. A significant difference was found between IOL-Master and slit-lamp adapted optical coherence tomography (p<0.01), as well as between IOL Master and digital photographs (p<0.01). There was no difference between SL-OCT and digital photographs (p>0.05). All measurements were correlated (Spearman p<0.001). Mean anterior chamber depth determined using the IOL-Master was 2.99 +/- 0.50 mm and by slit-lamp adapted optical coherence tomography was 2.56 +/- 0.46 mm. The difference was statistically significant (p<0.001). The correlation between the values was also statistically significant (Spearman, p<0.001). Automated measurements using IOL-Master yield constantly higher values than measurements based on direct eye visualization slit-lamp adapted optical coherence tomography and digital photographs. In order to obtain accurate measurements of the internal anterior chamber diameter and anterior chamber depth, a method involving direct visualization of intraocular structures should be used.

Real-time calibration-free C-scan images of the eye fundus using Master Slave swept source optical coherence tomography

NASA Astrophysics Data System (ADS)

Bradu, Adrian; Kapinchev, Konstantin; Barnes, Fred; Garway-Heath, David F.; Rajendram, Ranjan; Keane, Pearce; Podoleanu, Adrian G.

2015-03-01

Recently, we introduced a novel Optical Coherence Tomography (OCT) method, termed as Master Slave OCT (MS-OCT), specialized for delivering en-face images. This method uses principles of spectral domain interfereometry in two stages. MS-OCT operates like a time domain OCT, selecting only signals from a chosen depth only while scanning the laser beam across the eye. Time domain OCT allows real time production of an en-face image, although relatively slowly. As a major advance, the Master Slave method allows collection of signals from any number of depths, as required by the user. The tremendous advantage in terms of parallel provision of data from numerous depths could not be fully employed by using multi core processors only. The data processing required to generate images at multiple depths simultaneously is not achievable with commodity multicore processors only. We compare here the major improvement in processing and display, brought about by using graphic cards. We demonstrate images obtained with a swept source at 100 kHz (which determines an acquisition time [Ta] for a frame of 200×200 pixels2 of Ta =1.6 s). By the end of the acquired frame being scanned, using our computing capacity, 4 simultaneous en-face images could be created in T = 0.8 s. We demonstrate that by using graphic cards, 32 en-face images can be displayed in Td 0.3 s. Other faster swept source engines can be used with no difference in terms of Td. With 32 images (or more), volumes can be created for 3D display, using en-face images, as opposed to the current technology where volumes are created using cross section OCT images.

Evaluation of Time to Donor Lenticule Apposition Using Intraoperative Optical Coherence Tomography in Descemet Stripping Automated Endothelial Keratoplasty.

PubMed

Titiyal, Jeewan S; Kaur, Manpreet; Falera, Ruchita; Jose, Cijin P; Sharma, Namrata

2016-04-01

To evaluate the time to donor lenticule apposition in cases of Descemet stripping automated endothelial keratoplasty (DSAEK) using microscope-integrated intraoperative optical coherence tomography (iOCT). Thirty eyes of 27 patients planned to undergo Descemet stripping automated endothelial keratoplasty were enrolled in this prospective study. In group I (n = 10), continuous intracameral positive pressure was maintained for 8 minutes. In group II (n = 10) and group III (n = 10), external corneal massage was initiated simultaneously with positive intracameral air pressure. The external corneal massage was continued till complete resolution of interface fluid; the positive intracameral pressure was maintained for 8 minutes in group II and for 5 minutes in group III. The host-donor relationship was continuously monitored with the iOCT. The main outcome measure was time to complete donor lenticule apposition. In group I, the interface fluid persisted after 8 minutes of positive intracameral pressure in all eyes (10/10); hence an external corneal massage was required to achieve optimal donor adherence. In groups II and III, all eyes (20/20) had complete resolution of the interface fluid at the end of 3 minutes. In 100% of the eyes (30/30), the grafts were attached after anterior chamber decompression as seen on the iOCT. In all cases, the donor lenticules were adhered in the postoperative period. iOCT helps in understanding that the donor lenticule is well apposed within 1 to 3 minutes with the technique of simultaneous positive intracameral pressure and external corneal massage. This knowledge minimizes the waiting time for graft apposition and prevents prolonged intraocular pressure elevation.

A Miniature Forward-imaging B-scan Optical Coherence Tomography Probe to Guide Real-time Laser Ablation

PubMed Central

Li, Zhuoyan; Shen, Jin H.; Kozub, John A.; Prasad, Ratna; Lu, Pengcheng; Joos, Karen M.

2014-01-01

Background and Objective Investigations have shown that pulsed lasers tuned to 6.1 μm in wavelength are capable of ablating ocular and neural tissue with minimal collateral damage. This study investigated whether a miniature B-scan forward-imaging optical coherence tomography (OCT) probe can be combined with the laser to provide real-time visual feedback during laser incisions. Study Design/Methods and Materials A miniature 25-gauge B-scan forward-imaging OCT probe was developed and combined with a 250 μm hollow-glass waveguide to permit delivery of 6.1 μm laser energy. A gelatin mixture and both porcine corneal and retinal tissues were simultaneously imaged and lased (6.1 μm, 10 Hz, 0.4-0.7 mJ) through air. The ablation studies were observed and recorded in real time. The crater dimensions were measured using OCT imaging software (Bioptigen, Durham, NC). Histological analysis was performed on the ocular tissues. Results The combined miniature forward-imaging OCT and mid-infrared laser-delivery probe successfully imaged real-time tissue ablation in gelatin, corneal tissue, and retinal tissue. Application of a constant number of 60 pulses at 0.5 mJ/pulse to the gelatin resulted in a mean crater depth of 123 ± 15 μm. For the corneal tissue, there was a significant correlation between the number of pulses used and depth of the lased hole (Pearson correlation coefficient = 0.82; P = 0.0002). Histological analysis of the cornea and retina tissues showed discrete holes with minimal thermal damage. Conclusions A combined miniature OCT and laser -delivery probe can monitor real-time tissue laser ablation. With additional testing and improvements, this novel instrument has the future possibility of effectively guiding surgeries by simultaneously imaging and ablating tissue. PMID:24648326

Capacity of optical communications over a lossy bosonic channel with a receiver employing the most general coherent electro-optic feedback control

NASA Astrophysics Data System (ADS)

Chung, Hye Won; Guha, Saikat; Zheng, Lizhong

2017-07-01

We study the problem of designing optical receivers to discriminate between multiple coherent states using coherent processing receivers—i.e., one that uses arbitrary coherent feedback control and quantum-noise-limited direct detection—which was shown by Dolinar to achieve the minimum error probability in discriminating any two coherent states. We first derive and reinterpret Dolinar's binary-hypothesis minimum-probability-of-error receiver as the one that optimizes the information efficiency at each time instant, based on recursive Bayesian updates within the receiver. Using this viewpoint, we propose a natural generalization of Dolinar's receiver design to discriminate M coherent states, each of which could now be a codeword, i.e., a sequence of N coherent states, each drawn from a modulation alphabet. We analyze the channel capacity of the pure-loss optical channel with a general coherent-processing receiver in the low-photon number regime and compare it with the capacity achievable with direct detection and the Holevo limit (achieving the latter would require a quantum joint-detection receiver). We show compelling evidence that despite the optimal performance of Dolinar's receiver for the binary coherent-state hypothesis test (either in error probability or mutual information), the asymptotic communication rate achievable by such a coherent-processing receiver is only as good as direct detection. This suggests that in the infinitely long codeword limit, all potential benefits of coherent processing at the receiver can be obtained by designing a good code and direct detection, with no feedback within the receiver.

Optically controlled locking of the nuclear field via coherent dark-state spectroscopy.

PubMed

Xu, Xiaodong; Yao, Wang; Sun, Bo; Steel, Duncan G; Bracker, Allan S; Gammon, Daniel; Sham, L J

2009-06-25

A single electron or hole spin trapped inside a semiconductor quantum dot forms the foundation for many proposed quantum logic devices. In group III-V materials, the resonance and coherence between two ground states of the single spin are inevitably affected by the lattice nuclear spins through the hyperfine interaction, while the dynamics of the single spin also influence the nuclear environment. Recent efforts have been made to protect the coherence of spins in quantum dots by suppressing the nuclear spin fluctuations. However, coherent control of a single spin in a single dot with simultaneous suppression of the nuclear fluctuations has yet to be achieved. Here we report the suppression of nuclear field fluctuations in a singly charged quantum dot to well below the thermal value, as shown by an enhancement of the single electron spin dephasing time T(2)*, which we measure using coherent dark-state spectroscopy. The suppression of nuclear fluctuations is found to result from a hole-spin assisted dynamic nuclear spin polarization feedback process, where the stable value of the nuclear field is determined only by the laser frequencies at fixed laser powers. This nuclear field locking is further demonstrated in a three-laser measurement, indicating a possible enhancement of the electron spin T(2)* by a factor of several hundred. This is a simple and powerful method of enhancing the electron spin coherence time without use of 'spin echo'-type techniques. We expect that our results will enable the reproducible preparation of the nuclear spin environment for repetitive control and measurement of a single spin with minimal statistical broadening.

TOWARD QUANTITATIVE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY: Visualizing Blood Flow Speeds in Ocular Pathology Using Variable Interscan Time Analysis.

PubMed

Ploner, Stefan B; Moult, Eric M; Choi, WooJhon; Waheed, Nadia K; Lee, ByungKun; Novais, Eduardo A; Cole, Emily D; Potsaid, Benjamin; Husvogt, Lennart; Schottenhamml, Julia; Maier, Andreas; Rosenfeld, Philip J; Duker, Jay S; Hornegger, Joachim; Fujimoto, James G

2016-12-01

Currently available optical coherence tomography angiography systems provide information about blood flux but only limited information about blood flow speed. The authors develop a method for mapping the previously proposed variable interscan time analysis (VISTA) algorithm into a color display that encodes relative blood flow speed. Optical coherence tomography angiography was performed with a 1,050 nm, 400 kHz A-scan rate, swept source optical coherence tomography system using a 5 repeated B-scan protocol. Variable interscan time analysis was used to compute the optical coherence tomography angiography signal from B-scan pairs having 1.5 millisecond and 3.0 milliseconds interscan times. The resulting VISTA data were then mapped to a color space for display. The authors evaluated the VISTA visualization algorithm in normal eyes (n = 2), nonproliferative diabetic retinopathy eyes (n = 6), proliferative diabetic retinopathy eyes (n = 3), geographic atrophy eyes (n = 4), and exudative age-related macular degeneration eyes (n = 2). All eyes showed blood flow speed variations, and all eyes with pathology showed abnormal blood flow speeds compared with controls. The authors developed a novel method for mapping VISTA into a color display, allowing visualization of relative blood flow speeds. The method was found useful, in a small case series, for visualizing blood flow speeds in a variety of ocular diseases and serves as a step toward quantitative optical coherence tomography angiography.

Assessment of Sentinel Node Biopsies With Full-Field Optical Coherence Tomography.

PubMed

Grieve, Kate; Mouslim, Karima; Assayag, Osnath; Dalimier, Eugénie; Harms, Fabrice; Bruhat, Alexis; Boccara, Claude; Antoine, Martine

2016-04-01

Current techniques for the intraoperative analysis of sentinel lymph nodes during breast cancer surgery present drawbacks such as time and tissue consumption. Full-field optical coherence tomography is a novel noninvasive, high-resolution, fast imaging technique. This study investigated the use of full-field optical coherence tomography as an alternative technique for the intraoperative analysis of sentinel lymph nodes. Seventy-one axillary lymph nodes from 38 patients at Tenon Hospital were imaged minutes after excision with full-field optical coherence tomography in the pathology laboratory, before being handled for histological analysis. A pathologist performed a blind diagnosis (benign/malignant), based on the full-field optical coherence tomography images alone, which resulted in a sensitivity of 92% and a specificity of 83% (n = 65 samples). Regular feedback was given during the blind diagnosis, with thorough analysis of the images, such that features of normal and suspect nodes were identified in the images and compared with histology. A nonmedically trained imaging expert also performed a blind diagnosis aided by the reading criteria defined by the pathologist, which resulted in 85% sensitivity and 90% specificity (n = 71 samples). The number of false positives of the pathologist was reduced by 3 in a second blind reading a few months later. These results indicate that following adequate training, full-field optical coherence tomography can be an effective noninvasive diagnostic tool for extemporaneous sentinel node biopsy qualification. © The Author(s) 2015.

High frequency optical communications; Proceedings of the Meeting, Cambridge, MA, Sept. 23, 24, 1986

NASA Astrophysics Data System (ADS)

Ramer, O. Glenn; Sierak, Paul

Topics discussed in this volume include systems and applications, detectors, sources, and coherent communications. Papers are presented on RF fiber optic links for avionics applications, fiber optics and optoelectronics for radar and electronic warfare applications, symmetric coplanar electrodes for high-speed Ti:LiNbO3 devices, and surface wave electrooptic modulator. Attention is given to X-band RF fiber-optic links, fiber-optic links for microwave signal transmission, GaAs monolithic receiver and laser driver for GHz transmission rates, and monolithically integrable high-speed photodetectors. Additional papers are on irregular and chaotic behavior of semiconductor lasers under modulation, high-frequency laser package for microwave optical communications, receiver modeling for coherent light wave communications, and polarization sensors and controllers for coherent optical communication systems.

Coherent control of optical polarization effects in metamaterials

PubMed Central

Mousavi, Seyedmohammad A.; Plum, Eric; Shi, Jinhui; Zheludev, Nikolay I.

2015-01-01

Processing of photonic information usually relies on electronics. Aiming to avoid the conversion between photonic and electronic signals, modulation of light with light based on optical nonlinearity has become a major research field and coherent optical effects on the nanoscale are emerging as new means of handling and distributing signals. Here we demonstrate that in slabs of linear material of sub-wavelength thickness optical manifestations of birefringence and optical activity (linear and circular birefringence and dichroism) can be controlled by a wave coherent with the wave probing the polarization effect. We demonstrate this in proof-of-principle experiments for chiral and anisotropic microwave metamaterials, where we show that the large parameter space of polarization characteristics may be accessed at will by coherent control. Such control can be exerted at arbitrarily low intensities, thus arguably allowing for fast handling of electromagnetic signals without facing thermal management and energy challenges. PMID:25755071

Coherent optical processing using noncoherent light after source masking.

PubMed

Boopathi, V; Vasu, R M

1992-01-10

Coherent optical processing starting with spatially noncoherent illumination is described. Good spatial coherence is introduced in the far field by modulating a noncoherent source when masks with sharp autocorrelation are used. The far-field mutual coherence function of light is measured and it is seen that, for the masks and the source size used here, we get a fairly large area over which the mutual coherence function is high and flat. We demonstrate traditional coherent processing operations such as Fourier transformation and image deblurring when coherent light that is produced in the above fashion is used. A coherence-redundancy merit function is defined for this type of processing system. It is experimentally demonstrated that the processing system introduced here has superior blemish tolerance compared with a traditional processor that uses coherent illumination.

Retinal Evaluation Using Optical Coherence Tomography (OCT) During Deep Space Gateway Missions

NASA Astrophysics Data System (ADS)

Stenger, M. B.; Laurie, S. S.; Macias, B. R.; Barr, Y. R.

2018-02-01

Optical Coherence Tomography (OCT) imaging will be conducted before, during, and after Deep Space Gateway missions to evaluate changes in the retina and, in particular, the optic nerve head and surrounding structures. Additional parameters will be collected before and after flight.

Phase noise reduction by optical phase-locked loop for a coherent bichromatic laser based on the injection-locking technique.

PubMed

Wu, C F; Yan, X S; Huang, J Q; Zhang, J W; Wang, L J

2018-01-01

We present a coherent bichromatic laser system with low phase noise. An optical injection process is used to generate coherent laser beams with a frequency difference of 9.192 631 77 GHz using an electro-optical modulator. An optical phase-locked loop is then applied to reduce the phase noise. The phase noise of the beat note is -41, -81, -98, -83, and -95 dBrad 2 /Hz at the offset frequencies of 1 Hz, 100 Hz, 1 kHz, 10 kHz, and 1 MHz, respectively. Compared to a system that uses optical injection alone, the phase noise is reduced by up to 20-30 dB in the low-frequency range, and the intermodulation effect on the continuous atomic clock is reduced by an order of magnitude. This configuration can adjust the intensities and polarizations of the laser beams independently and reduce the phase noise caused by environmental disturbances and optical injection, which may be useful for application to atomic coherence experiments.

Phase noise reduction by optical phase-locked loop for a coherent bichromatic laser based on the injection-locking technique

NASA Astrophysics Data System (ADS)

Wu, C. F.; Yan, X. S.; Huang, J. Q.; Zhang, J. W.; Wang, L. J.

2018-01-01

We present a coherent bichromatic laser system with low phase noise. An optical injection process is used to generate coherent laser beams with a frequency difference of 9.192 631 77 GHz using an electro-optical modulator. An optical phase-locked loop is then applied to reduce the phase noise. The phase noise of the beat note is -41, -81, -98, -83, and -95 dBrad2/Hz at the offset frequencies of 1 Hz, 100 Hz, 1 kHz, 10 kHz, and 1 MHz, respectively. Compared to a system that uses optical injection alone, the phase noise is reduced by up to 20-30 dB in the low-frequency range, and the intermodulation effect on the continuous atomic clock is reduced by an order of magnitude. This configuration can adjust the intensities and polarizations of the laser beams independently and reduce the phase noise caused by environmental disturbances and optical injection, which may be useful for application to atomic coherence experiments.

Mitigation of Laser Beam Scintillation in Free-Space Optical Communication Systems Through Coherence-Reducing Optical Materials

NASA Technical Reports Server (NTRS)

Renner, Christoffer J.

2005-01-01

Free-space optical communication systems (also known as lasercom systems) offer several performance advantages over traditional radio frequency communication systems. These advantages include increased data rates and reduced operating power and system weight. One serious limiting factor in a lasercom system is Optical turbulence in Earth's atmosphere. This turbulence breaks up the laser beam used to transmit the information into multiple segments that interfere with each other when the beam is focused onto the receiver. This interference pattern at the receiver changes with time causing fluctuations in the received optical intensity (scintillation). Scintillation leads to intermittent losses of the signal and an overall reduction in the lasercom system's performance. Since scintillation is a coherent effect, reducing the spatial and temporal coherence of the laser beam will reduce the scintillation. Transmitting a laser beam through certain materials is thought to reduce its coherence. Materials that were tested included: sapphire, BK7 glass, fused silica and others. The spatial and temporal coherence of the laser beam was determined by examining the interference patterns (fringes) it formed when interacting with various interferometers and etalons.

Bilateral simultaneous central serous chorioretinopathy in a teenage girl with systemic arterial hypertension.

PubMed

Alwassia, Ahmad A; Adhi, Mehreen; Duker, Jay S

2013-02-01

We present a case of bilateral simultaneous central serous chorioretinopathy (CSCR) in a teenage girl with a history of systemic arterial hypertension. A 19-year-old Caucasian female, with a history of systemic arterial hypertension, presented with gradual decrease in her central vision for 1 month. She was diagnosed with bilateral simultaneous CSCR, based on the findings of spectral domain optical coherence tomography (SD-OCT), indocyanine green angiography (ICG), fundus auto-fluorescence, fluorescein angiography and color fundus photographs, which are described. Blood pressure was 134/95 mmHg at presentation. Systemic evaluation failed to reveal a cause for the high blood pressure, and included a panel of blood tests, which were all normal. Her best-corrected visual acuity was 20/30 OD and 20/25 OS. Dilated fundus examination showed normal optic discs and retinal vasculature, with no evidence of hypertensive retinopathy. However, shallow retinal fluid associated with pigmentary changes was noted in the center of both maculae. OCT and ICG findings were consistent with the diagnosis of bilateral CSCR. CSCR can manifest in patients with demographics outside the range of those previously reported. This is the first report of CSCR occurring in a teenage girl, with a history of systemic arterial hypertension. It is important to consider this disease in any patient who has a clinically compatible presentation.

Nonlocal Electron Coherence in MoS2 Flakes Correlated through Spatial Self Phase Modulation

NASA Astrophysics Data System (ADS)

Wu, Yanling; Wu, Qiong; Sun, Fei; Tian, Yichao; Zuo, Xu; Meng, Sheng; Zhao, Jimin

2015-03-01

Electron coherence among different flake domains of MoS2 has been generated using ultrafast or continuous wave laser beams. Such electron coherence generates characteristic far-field diffraction patterns through a purely coherent nonlinear optical effect--spatial self-phase modulation (SSPM). A wind-chime model is developed to describe the establishment of the electron coherence through correlating the photo-excited electrons among different flakes using coherent light. Owing to its finite gap band structure, we find different mechanisms, including two-photon processes, might be responsible for the SSPM in MoS2 [with a large nonlinear dielectric susceptibility χ (3) = 1.6 × 10-9 e.s.u. (SI: 2.23 × 10-17 m2/V2) per layer]. Finally, we realized all optical switching based on SSPM, demonstrating that the electron coherence generation we report here is a ubiquitous property of layered quantum materials, by which novel optical applications are accessible. National Natural Science Foundation of China (11274372).

Coherent and partially coherent dark hollow beams with rectangular symmetry and paraxial propagation properties

NASA Astrophysics Data System (ADS)

Cai, Yangjian; Zhang, Lei

2006-07-01

A theoretical model is proposed to describe coherent dark hollow beams (DHBs) with rectangular symmetry. The electric field of a coherent rectangular DHB is expressed as a superposition of a series of the electric field of a finite series of fundamental Gaussian beams. Analytical propagation formulas for a coherent rectangular DHB passing through paraxial optical systems are derived in a tensor form. Furthermore, for the more general case, we propose a theoretical model to describe a partially coherent rectangular DHB. Analytical propagation formulas for a partially coherent rectangular DHB passing through paraxial optical systems are derived. The beam propagation factor (M2 factor) for both coherent and partially coherent rectangular DHBs are studied. Numerical examples are given by using the derived formulas. Our models and method provide an effective way to describe and treat the propagation of coherent and partially coherent rectangular DHBs.

Femtosecond Timekeeping: Slip-Free Clockwork for Optical Timescales

NASA Astrophysics Data System (ADS)

Herman, D.; Droste, S.; Baumann, E.; Roslund, J.; Churin, D.; Cingoz, A.; Deschênes, J.-D.; Khader, I. H.; Swann, W. C.; Nelson, C.; Newbury, N. R.; Coddington, I.

2018-04-01

The generation of true optical time standards will require the conversion of the highly stable optical-frequency output of an optical atomic clock to a high-fidelity time output. We demonstrate a comb-based clockwork that phase-coherently integrates ˜7 ×1020 optical cycles of an input optical frequency to create a coherent time output. We verify the underlying stability of the optical timing system by comparing two comb-based clockworks with a common input optical frequency and show <20 fs total time drift over the 37-day measurement period. Both clockworks also generate traditional timing signals including an optical pulse per second and a 10-MHz rf reference. The optical pulse-per-second time outputs remain synchronized to 240 attoseconds (240 as) at 1000 s. The phase-coherent 10-MHz rf outputs are stable to near a part in 1019 . Fault-free timekeeping from an optical clock to femtosecond level over months is an important step in replacing the current microwave time standard by an optical standard.

Nonexponential Decoherence and Subdiffusion in Atom-Optics Kicked Rotor.

PubMed

Sarkar, Sumit; Paul, Sanku; Vishwakarma, Chetan; Kumar, Sunil; Verma, Gunjan; Sainath, M; Rapol, Umakant D; Santhanam, M S

2017-04-28

Quantum systems lose coherence upon interaction with the environment and tend towards classical states. Quantum coherence is known to exponentially decay in time so that macroscopic quantum superpositions are generally unsustainable. In this work, slower than exponential decay of coherences is experimentally realized in an atom-optics kicked rotor system subjected to nonstationary Lévy noise in the applied kick sequence. The slower coherence decay manifests in the form of quantum subdiffusion that can be controlled through the Lévy exponent. The experimental results are in good agreement with the analytical estimates and numerical simulations for the mean energy growth and momentum profiles of an atom-optics kicked rotor.

Optical Coherence Tomography

PubMed Central

Huang, David; Swanson, Eric A.; Lin, Charles P.; Schuman, Joel S.; Stinson, William G.; Chang, Warren; Hee, Michael R.; Flotte, Thomas; Gregory, Kenton; Puliafito, Carmen A.; Fujimoto, James G.

2015-01-01

A technique called optical coherence tomography (OCT) has been developed for noninvasive cross-sectional imaging in biological systems. OCT uses low-coherence interferometry to produce a two-dimensional image of optical scattering from internal tissue microstructures in a way that is analogous to ultrasonic pulse-echo imaging. OCT has longitudinal and lateral spatial resolutions of a few micrometers and can detect reflected signals as small as ~10−10 of the incident optical power. Tomographic imaging is demonstrated in vitro in the peripapillary area of the retina and in the coronary artery, two clinically relevant examples that are representative of transparent and turbid media, respectively. PMID:1957169

Coherent Perfect Rotation

NASA Astrophysics Data System (ADS)

Crescimanno, Michael; Dawson, Nathan; Andrews, James

2012-04-01

Two classes of conservative, linear, optical rotary effects (optical activity and Faraday rotation) are distinguished by their behavior under time reversal. In analogy with coherent perfect absorption, where counterpropagating light fields are controllably converted into other degrees of freedom, we show that in a linear-conservative medium only time-odd (Faraday) rotation is capable of coherent perfect rotation, by which we mean the complete transfer of counterpropagating coherent light fields into their orthogonal polarization. This highlights the necessity of time reversal odd processes (not just absorption) and coherence in perfect mode conversion and may inform device design.

Coherence properties and quantum state transportation in an optical conveyor belt.

PubMed

Kuhr, S; Alt, W; Schrader, D; Dotsenko, I; Miroshnychenko, Y; Rosenfeld, W; Khudaverdyan, M; Gomer, V; Rauschenbeutel, A; Meschede, D

2003-11-21

We have prepared and detected quantum coherences of trapped cesium atoms with long dephasing times. Controlled transport by an "optical conveyor belt" over macroscopic distances preserves the atomic coherence with slight reduction of coherence time. The limiting dephasing effects are experimentally identified, and we present an analytical model of the reversible and irreversible dephasing mechanisms. Our experimental methods are applicable at the single-atom level. Coherent quantum bit operations along with quantum state transport open the route towards a "quantum shift register" of individual neutral atoms.

Geometrical and wave optics of paraxial beams.

PubMed

Meron, M; Viccaro, P J; Lin, B

1999-06-01

Most calculational techniques used to evaluate beam propagation are geared towards either fully coherent or fully incoherent beams. The intermediate partial-coherence regime, while in principle known for a long time, has received comparably little attention so far. The resulting shortage of adequate calculational techniques is currently being felt in the realm of x-ray optics where, with the advent of third generation synchrotron light sources, partially coherent beams become increasingly common. The purpose of this paper is to present a calculational approach which, utilizing a "variance matrix" representation of paraxial beams, allows for a straightforward evaluation of wave propagation through an optical system. Being capable of dealing with an arbitrary degree of coherence, this approach covers the whole range from wave to ray optics, in a seamless fashion.

Natural motion of the optic nerve head revealed by high speed phase-sensitive OCT

NASA Astrophysics Data System (ADS)

OHara, Keith; Schmoll, Tilman; Vass, Clemens; Leitgeb, Rainer A.

2013-03-01

We use phase-sensitive optical coherence tomography (OCT) to measure the deformation of the optic nerve head during the pulse cycle, motivated by the possibility that these deformations might be indicative of the progression of glaucoma. A spectral-domain OCT system acquired 100k A-scans per second, with measurements from a pulse-oximeter recorded simultaneously, correlating OCT data to the subject's pulse. Data acquisition lasted for 2 seconds, to cover at least two pulse cycles. A frame-rate of 200-400 B-scans per second results in a sufficient degree of correlated speckle between successive frames that the phase-differences between fames can be extracted. Bulk motion of the entire eye changes the phase by several full cycles between frames, but this does not severely hinder extracting the smaller phase-changes due to differential motion within a frame. The central cup moves about 5 μm/s relative to the retinal-pigment-epithelium edge, with tissue adjacent to blood vessels showing larger motion.

A new multifunction acousto-optic signal processor

NASA Technical Reports Server (NTRS)

Berg, N. J.; Casseday, M. W.; Filipov, A. N.; Pellegrino, J. M.

1984-01-01

An acousto-optic architecture for simultaneously obtaining time integration correlation and high-speed power spectrum analysis was constructed using commercially available TeO2 modulators and photodiode detector-arrays. The correlator section of the processor uses coherent interferometry to attain maximum bandwidth and dynamic range while achieving a time-bandwidth product of 1 million. Two correllator outputs are achieved in this system configuration. One is optically filtered and magnified 2 : 1 to decrease the spatial frequency to a level where a 25-MHz bandwidth may be sampled by a 62-mm array with elements on 25-micro centers. The other output is magnified by a factor of 10 such that the center 4 microseconds of information is available for estimation of time-difference-of-arrival to within 10 ns. The Bragg cell spectrum-analyzer section, which also has two outputs, resolves a 25-MHz instantaneous bandwidth to 25 kHz and can determine discrete-frequency reception time to within 15 microseconds. A microprocessor combines spectrum analysis information with that obtained from the correlator.

Measuring Dilution of Microbicide Gels with Optical Imaging

PubMed Central

Drake, Tyler K.; Shah, Tejen; Peters, Jennifer J.; Wax, Adam; Katz, David F.

2013-01-01

We present a novel approach for measuring topical microbicide gel dilution using optical imaging. The approach compares gel thickness measurements from fluorimetry and multiplexed low coherence interferometry in order to calculate dilution of a gel. As a microbicide gel becomes diluted at fixed thickness, its mLCI thickness measurement remains constant, while the fluorimetry signal decreases in intensity. The difference between the two measurements is related to the extent of gel dilution. These two optical modalities are implemented in a single endoscopic instrument that enables simultaneous data collection. A preliminary validation study was performed with in vitro placebo gel measurements taken in a controlled test socket. It was found that change in slope of the regression line between fluorimetry and mLCI based measurements indicates dilution. A dilution calibration curve was then generated by repeating the test socket measurements with serial dilutions of placebo gel with vaginal fluid simulant. This methodology can provide valuable dilution information on candidate microbicide products, which could substantially enhance our understanding of their in vivo functioning. PMID:24340006

Directly Phase-Modulated Light Source

NASA Astrophysics Data System (ADS)

Yuan, Z. L.; Fröhlich, B.; Lucamarini, M.; Roberts, G. L.; Dynes, J. F.; Shields, A. J.

2016-07-01

The art of imparting information onto a light wave by optical signal modulation is fundamental to all forms of optical communication. Among many schemes, direct modulation of laser diodes stands out as a simple, robust, and cost-effective method. However, the simultaneous changes in intensity, frequency, and phase have prevented its application in the field of secure quantum communication. Here, we propose and experimentally demonstrate a directly phase-modulated light source which overcomes the main disadvantages associated with direct modulation and is suitable for diverse applications such as coherent communications and quantum cryptography. The source separates the tasks of phase preparation and pulse generation between a pair of semiconductor lasers leading to very pure phase states. Moreover, the cavity-enhanced electro-optic effect enables the first example of subvolt half-wave phase modulation at high signal rates. The source is compact, stable, and versatile, and we show its potential to become the standard transmitter for future quantum communication networks based on attenuated laser pulses.

Wave packet interferometry and quantum state reconstruction by acousto-optic phase modulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tekavec, Patrick F.; Dyke, Thomas R.; Marcus, Andrew H.

2006-11-21

Studies of wave packet dynamics often involve phase-selective measurements of coherent optical signals generated from sequences of ultrashort laser pulses. In wave packet interferometry (WPI), the separation between the temporal envelopes of the pulses must be precisely monitored or maintained. Here we introduce a new (and easy to implement) experimental scheme for phase-selective measurements that combines acousto-optic phase modulation with ultrashort laser excitation to produce an intensity-modulated fluorescence signal. Synchronous detection, with respect to an appropriately constructed reference, allows the signal to be simultaneously measured at two phases differing by 90 deg. Our method effectively decouples the relative temporal phasemore » from the pulse envelopes of a collinear train of optical pulse pairs. We thus achieve a robust and high signal-to-noise scheme for WPI applications, such as quantum state reconstruction and electronic spectroscopy. The validity of the method is demonstrated, and state reconstruction is performed, on a model quantum system - atomic Rb vapor. Moreover, we show that our measurements recover the correct separation between the absorptive and dispersive contributions to the system susceptibility.« less

Resonant optical spectroscopy and coherent control of Cr4+ spin ensembles in SiC and GaN

NASA Astrophysics Data System (ADS)

Koehl, William

Spins bound to point defects have emerged as an important resource in quantum information and spintronic technologies, especially as new materials systems have been developed that enable robust and precise quantum state control via optical, electronic, or mechanical degrees of freedom. In an effort to broaden the range of materials platforms available to such defect-based quantum technologies, we have recently begun exploring optically active transition metal ion spins doped into common wide-bandgap semiconductors. The spins of such ions are derived in part from unpaired d orbital electron states, suggesting in some cases that they may be portable across multiple materials systems. This in contrast to many vacancy-related defect spins such as the diamond nitrogen vacancy center or silicon carbide divacancy, which are formed primarily from the dangling bond states of the host. Here we demonstrate ensemble optical spin polarization and time-resolved optically detected magnetic resonance (ODMR) of the S = 1 electronic ground state of chromium (Cr4+) impurities in silicon carbide (SiC) and gallium nitride (GaN). We find that these impurities possess narrow optical linewidths (<8.5 GHz at cryogenic temperatures) that allow us to optically resolve the magnetic sublevels of the spins even when probing a large ensemble of many ions simultaneously. This enables us to directly polarize and probe the Cr4+ spins using straightforward optical techniques, which we then combine with coherent microwave excitation in order to characterize the dynamical properties of the ensemble. Significantly, these near-infrared emitters also possess exceptionally weak phonon sidebands, ensuring that >73% of the overall optical emission is contained within the defects' zero-phonon lines. These characteristics make the Cr4+ ion system a promising target for further study in the ongoing effort to integrate optically active quantum states within common optoelectronic materials. In collaboration with B. Diler, S. J. Whiteley, A. Bourassa, N. T. Son, E. Janzén, and D. D. Awschalom. This work supported by AFOSR, ARO, NSF MRSEC, the Argonne LDRD Program, LiLi-NFM, and the Knut and Alice Wallenberg Foundation.

Ultradispersive adaptive prism based on a coherently prepared atomic medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sautenkov, Vladimir A.; P. N. Lebedev Institute of Physics, Moscow 119991; Li Hebin

2010-06-15

We have experimentally demonstrated an ultra-dispersive optical prism made from a coherently driven Rb atomic vapor. The prism possesses spectral angular dispersion that is 6 orders of magnitude higher than that of a prism made of optical glass; such angular dispersion allows one to spatially resolve light beams with different frequencies separated by a few kilohertz. The prism operates near the resonant frequency of atomic vapor and its dispersion is optically controlled by a coherent driving field.

Demonstration of simultaneous experiments using thin crystal multiplexing at the Linac Coherent Light Source

DOE PAGES

Feng, Y.; Alonso-Mori, R.; Barends, T. R. M.; ...

2015-04-10

Multiplexing of the Linac Coherent Light Source beam was demonstrated for hard X-rays by spectral division using a near-perfect diamond thin-crystal monochromator operating in the Bragg geometry. The wavefront and coherence properties of both the reflected and transmitted beams were well preserved, thus allowing simultaneous measurements at two separate instruments. In this report, the structure determination of a prototypical protein was performed using serial femtosecond crystallography simultaneously with a femtosecond time-resolved XANES studies of photoexcited spin transition dynamics in an iron spin-crossover system. The results of both experiments using the multiplexed beams are similar to those obtained separately, using amore » dedicated beam, with no significant differences in quality.« less

Broadband high-resolution multi-species CARS in gas-filled hollow-core photonic crystal fiber.

PubMed

Trabold, Barbara M; Hupfer, Robert J R; Abdolvand, Amir; St J Russell, Philip

2017-09-01

We report the use of coherent anti-Stokes Raman spectroscopy (CARS) in gas-filled hollow-core photonic crystal fiber (HC-PCF) for trace gas detection. The long optical path-lengths yield a 60 dB increase in the signal level compared with free-space arrangements. This enables a relatively weak supercontinuum (SC) to be used as Stokes seed, along with a ns pump pulse, paving the way for broadband (>4000  cm -1 ) single-shot CARS with an unprecedented resolution of ∼100  MHz. A kagomé-style HC-PCF provides broadband guidance, and, by operating close to the pressure-tunable zero dispersion wavelength, we can ensure simultaneous phase-matching of all gas species. We demonstrate simultaneous measurement of the concentrations of multiple trace gases in a gas sample introduced into the core of the HC-PCF.

Axial resolution improvement in spectral domain optical coherence tomography using a depth-adaptive maximum-a-posterior framework

NASA Astrophysics Data System (ADS)

Boroomand, Ameneh; Tan, Bingyao; Wong, Alexander; Bizheva, Kostadinka

2015-03-01

The axial resolution of Spectral Domain Optical Coherence Tomography (SD-OCT) images degrades with scanning depth due to the limited number of pixels and the pixel size of the camera, any aberrations in the spectrometer optics and wavelength dependent scattering and absorption in the imaged object [1]. Here we propose a novel algorithm which compensates for the blurring effect of these factors of the depth-dependent axial Point Spread Function (PSF) in SDOCT images. The proposed method is based on a Maximum A Posteriori (MAP) reconstruction framework which takes advantage of a Stochastic Fully Connected Conditional Random Field (SFCRF) model. The aim is to compensate for the depth-dependent axial blur in SD-OCT images and simultaneously suppress the speckle noise which is inherent to all OCT images. Applying the proposed depth-dependent axial resolution enhancement technique to an OCT image of cucumber considerably improved the axial resolution of the image especially at higher imaging depths and allowed for better visualization of cellular membrane and nuclei. Comparing the result of our proposed method with the conventional Lucy-Richardson deconvolution algorithm clearly demonstrates the efficiency of our proposed technique in better visualization and preservation of fine details and structures in the imaged sample, as well as better speckle noise suppression. This illustrates the potential usefulness of our proposed technique as a suitable replacement for the hardware approaches which are often very costly and complicated.

Imaging the eye fundus with real-time en-face spectral domain optical coherence tomography

PubMed Central

Bradu, Adrian; Podoleanu, Adrian Gh.

2014-01-01

Real-time display of processed en-face spectral domain optical coherence tomography (SD-OCT) images is important for diagnosis. However, due to many steps of data processing requirements, such as Fast Fourier transformation (FFT), data re-sampling, spectral shaping, apodization, zero padding, followed by software cut of the 3D volume acquired to produce an en-face slice, conventional high-speed SD-OCT cannot render an en-face OCT image in real time. Recently we demonstrated a Master/Slave (MS)-OCT method that is highly parallelizable, as it provides reflectivity values of points at depth within an A-scan in parallel. This allows direct production of en-face images. In addition, the MS-OCT method does not require data linearization, which further simplifies the processing. The computation in our previous paper was however time consuming. In this paper we present an optimized algorithm that can be used to provide en-face MS-OCT images much quicker. Using such an algorithm we demonstrate around 10 times faster production of sets of en-face OCT images than previously obtained as well as simultaneous real-time display of up to 4 en-face OCT images of 200 × 200 pixels2 from the fovea and the optic nerve of a volunteer. We also demonstrate 3D and B-scan OCT images obtained from sets of MS-OCT C-scans, i.e. with no FFT and no intermediate step of generation of A-scans. PMID:24761303

Nonuniform Liouville transformers for quasi-homogeneous optical fields. Final technical report, September 25, 1989--January 22, 1993

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jannson, T.

1993-03-01

During the last two decades, there have been dramatic improvements in the development of optical sources. Examples of this development range from semiconductor laser diodes to free electron beam lasers and synchrotron radiation. Before these developments, standards for the measurement of basic optical parameters (quantities) were less demanding. Now, however, there is a fundamental need for new, reliable methods for providing fast quantitative results for a very broad variety of optical systems and sources. This is particularly true for partially coherent optical beams, since all optical sources are either fully or partially spatially coherent (including Lambertian sources). Until now, theremore » has been no satisfactory solution to this problem. During the last two decades, however, the foundations of physical radiometry have been developed by Walther, Wolf and co-workers. By integrating physical optics, statistical optics and conventional radiometry, this body of work provides necessary tools for the evaluation of radiometric quantities for partially coherent optical beams propagating through optical systems. In this program, Physical Optics Corporation (POC) demonstrated the viability of such a radiometric approach for the specific case of generalized energy concentrators called Liouville transformers. We believe that this radiometric approach is necessary to fully characterize any type of optical system since it takes into account the partial coherence of radiation. 90 refs., 57 figs., 4 tabs.« less

Elimination of coherent noise in a coherent light imaging system

NASA Technical Reports Server (NTRS)

Grebowsky, G. J.; Hermann, R. L.; Paull, H. B.; Shulman, A. R.

1970-01-01

Optical imaging systems using coherent light introduce objectionable noise into the output image plane. Dust and bubbles on and in lenses cause most of the noise in the output image. This noise usually appears as bull's-eye diffraction patterns in the image. By rotating the lens about the optical axis these diffraction patterns can be essentially eliminated. The technique does not destroy the spatial coherence of the light and permits spatial filtering of the input plane.

Design concepts for an on-board coherent optical image processor

NASA Technical Reports Server (NTRS)

Husain-Abidi, A. S.

1972-01-01

On-board spacecraft image data processing systems for transmitting processed data rather than raw data are discussed. A brief history of the development of the optical data processing techniques is presented along with the conceptual design of a coherent optical system with a noncoherent image input.

Intrinsic coherence time of trions in monolayer MoSe2 measured via two-dimensional coherent spectroscopy

NASA Astrophysics Data System (ADS)

Titze, Michael; Li, Bo; Zhang, Xiang; Ajayan, Pulickel M.; Li, Hebin

2018-05-01

Quantum coherence and its dynamics in monolayer transition metal dichalcogenides (TMDs) are essential information to fully control valley pseudospin for valleytronics applications. Experimental understanding of coherence dephasing dynamics has been limited for excitons and largely unexplored for trions in monolayer TMDs. Here we use optical two-dimensional coherent spectroscopy to measure the trion coherence dephasing time in monolayer MoSe2 by analyzing the homogeneous linewidth. An intrinsic coherence time of 182 fs is extrapolated from the excitation density and temperature dependence measurement. The results show that trion-trion and trion-phonon interactions strongly affect the coherence dephasing time, while the intrinsic coherence time at zero excitation and zero temperature is primarily limited by the pure dephasing due to defect states. Our experiment also confirms optical two-dimensional coherent spectroscopy as a reliable technique for studying valley quantum dynamics in two-dimensional layered materials.

Automatic detection and recognition of multiple macular lesions in retinal optical coherence tomography images with multi-instance multilabel learning

NASA Astrophysics Data System (ADS)

Fang, Leyuan; Yang, Liumao; Li, Shutao; Rabbani, Hossein; Liu, Zhimin; Peng, Qinghua; Chen, Xiangdong

2017-06-01

Detection and recognition of macular lesions in optical coherence tomography (OCT) are very important for retinal diseases diagnosis and treatment. As one kind of retinal disease (e.g., diabetic retinopathy) may contain multiple lesions (e.g., edema, exudates, and microaneurysms) and eye patients may suffer from multiple retinal diseases, multiple lesions often coexist within one retinal image. Therefore, one single-lesion-based detector may not support the diagnosis of clinical eye diseases. To address this issue, we propose a multi-instance multilabel-based lesions recognition (MIML-LR) method for the simultaneous detection and recognition of multiple lesions. The proposed MIML-LR method consists of the following steps: (1) segment the regions of interest (ROIs) for different lesions, (2) compute descriptive instances (features) for each lesion region, (3) construct multilabel detectors, and (4) recognize each ROI with the detectors. The proposed MIML-LR method was tested on 823 clinically labeled OCT images with normal macular and macular with three common lesions: epiretinal membrane, edema, and drusen. For each input OCT image, our MIML-LR method can automatically identify the number of lesions and assign the class labels, achieving the average accuracy of 88.72% for the cases with multiple lesions, which better assists macular disease diagnosis and treatment.

Fiber-based coherent polarization beam combining with cascaded phase-locking and polarization-transforming controls

NASA Astrophysics Data System (ADS)

Yang, Yan; Geng, Chao; Li, Feng; Huang, Guan; Li, Xinyang

2018-05-01

In this paper, the fiber-based coherent polarization beam combining (CPBC) with cascaded phase-locking (PL) and polarization-transforming (PT) controls was proposed to combine imbalanced input beams where the number of the input beams is not binary, in which the PL control was performed using the piezoelectric-ring fiber-optic phase compensator, and the PT control was realized by the dynamic polarization controller, simultaneously. The principle of the proposed CPBC was introduced. The performance of the proposed CPBC was analyzed in comparison with the CPBC based on PL control and the CPBC based on PT control. The basic experiment of CPBC of three laser beams was carried out to validate the feasibility of the proposed CPBC, where cascaded controls of PL and PT were implemented based on stochastic parallel gradient descent algorithm. Simulation and experimental results show that the proposed CPBC incorporates the advantages of the two previous CPBC schemes and performs well in the closed loop. Moreover, the expansibility and the application of the proposed CPBC were validated by scaling the CPBC to combine seven laser beams. We believe that the proposed fiber-based CPBC with cascaded PL and PT controls has great potential in free space optical communications employing the multi-aperture receiver with asymmetric structure.

Correlation of collagen synthesis with polarization-sensitive optical coherence tomography imaging of in vitro human atherosclerosis

NASA Astrophysics Data System (ADS)

Kuo, Wen-Chuan; Shyu, Jeou-Jong; Chou, Nai-Kuan; Lai, Chih-Ming; Tien, En-Kuang; Huang, Huan-Jang; Chou, Chien; Jan, Gwo-Jen

2005-04-01

Atherosclerosis is unquestionably the leading cause of morbidity and mortality in developed countries. In the mean time, the worldwide importance of acute vascular syndromes is increasing. Because collagen fiber is a critical component of atherosclerotic lesions; it constitutes up to 60% of the total atherosclerotic plaque protein. The uncontrolled collagen accumulation leads to arterial stenosis, whereas excessive collagen breakdown weakens plaques thereby making them prone to rupture finally. Thus, in this study, we present the first application, to our knowledge, of using polarization-sensitive optical coherence tomography (PS-OCT) in human atherosclerosis. We demonstrate this technique for imaging of intensity, birefringence, and fast-axis orientation simultaneously in atherosclerotic plaques. This in vitro study suggests that the birefringence change in plaque is due to the prominent deposition of collagen according to the correlation of PS-OCT images with histological counterpart. Moreover, we can acquire quantitative criteria based on the change of polarization of incident beam to estimate whether the collagen synthesized is "too much" or "not enough". Thus by combining of high resolution intensity imaging and birefringence detection makes PS-OCT could be a potentially powerful tool for early assessment of atherosclerosis appearance and the prediction of plaque rupture in clinic.

Optical coherence tomography-guided laser microsurgery for blood coagulation with continuous-wave laser diode.

PubMed

Chang, Feng-Yu; Tsai, Meng-Tsan; Wang, Zu-Yi; Chi, Chun-Kai; Lee, Cheng-Kuang; Yang, Chih-Hsun; Chan, Ming-Che; Lee, Ya-Ju

2015-11-16

Blood coagulation is the clotting and subsequent dissolution of the clot following repair to the damaged tissue. However, inducing blood coagulation is difficult for some patients with homeostasis dysfunction or during surgery. In this study, we proposed a method to develop an integrated system that combines optical coherence tomography (OCT) and laser microsurgery for blood coagulation. Also, an algorithm for positioning of the treatment location from OCT images was developed. With OCT scanning, 2D/3D OCT images and angiography of tissue can be obtained simultaneously, enabling to noninvasively reconstruct the morphological and microvascular structures for real-time monitoring of changes in biological tissues during laser microsurgery. Instead of high-cost pulsed lasers, continuous-wave laser diodes (CW-LDs) with the central wavelengths of 450 nm and 532 nm are used for blood coagulation, corresponding to higher absorption coefficients of oxyhemoglobin and deoxyhemoglobin. Experimental results showed that the location of laser exposure can be accurately controlled with the proposed approach of imaging-based feedback positioning. Moreover, blood coagulation can be efficiently induced by CW-LDs and the coagulation process can be monitored in real-time with OCT. This technology enables to potentially provide accurate positioning for laser microsurgery and control the laser exposure to avoid extra damage by real-time OCT imaging.

Discrepancy between fluorescein angiography and optical coherence tomography in detection of macular disease.

PubMed

Kozak, Igor; Morrison, Victoria L; Clark, Thomas M; Bartsch, Dirk-Uwe; Lee, Byung Ro; Falkenstein, Iryna; Tammewar, Ajay M; Mojana, Francesca; Freeman, William R

2008-04-01

To compare high-resolution optical coherence tomography (OCT) and fluorescein angiography (FA) in detection of macular edema (ME) of various etiologies. In a retrospective study over a 12-month period at one retina center, data for consecutive eyes that had undergone simultaneous conventional FA (HRA; Heidelberg Engineering, Vista, CA) and StratusOCT (Carl Zeiss Meditec, Dublin, CA) to rule out ME were reviewed. A subset of patients underwent additional examination with extremely high-resolution (6-microm)/ultrahigh-speed spectral OCT/scanning laser ophthalmoscopy (OTI, Inc., Toronto, Ontario, Canada). Of 1,272 eyes, 1,208 (94.97%) had the finding of ME or subretinal fluid confirmed by both techniques. There were 49 eyes (3.86%) for which FA showed dye leakage in the macular area and OCT showed normal foveal contour. Of 10 eyes in this group that underwent imaging with ultrahigh-speed spectral OCT/scanning laser ophthalmoscopy, 8 had subtle diffuse lucencies in the retina. For 15 eyes (1.17%), OCT showed intraretinal and subretinal fluid, which was missed by FA. Both FA and high-resolution OCT are highly sensitive techniques and correlate well in detection of ME. However, there is a small chance that when performed alone they might miss existing subtle ME.

Optical coherence tomography-guided laser microsurgery for blood coagulation with continuous-wave laser diode

NASA Astrophysics Data System (ADS)

Chang, Feng-Yu; Tsai, Meng-Tsan; Wang, Zu-Yi; Chi, Chun-Kai; Lee, Cheng-Kuang; Yang, Chih-Hsun; Chan, Ming-Che; Lee, Ya-Ju

2015-11-01

Blood coagulation is the clotting and subsequent dissolution of the clot following repair to the damaged tissue. However, inducing blood coagulation is difficult for some patients with homeostasis dysfunction or during surgery. In this study, we proposed a method to develop an integrated system that combines optical coherence tomography (OCT) and laser microsurgery for blood coagulation. Also, an algorithm for positioning of the treatment location from OCT images was developed. With OCT scanning, 2D/3D OCT images and angiography of tissue can be obtained simultaneously, enabling to noninvasively reconstruct the morphological and microvascular structures for real-time monitoring of changes in biological tissues during laser microsurgery. Instead of high-cost pulsed lasers, continuous-wave laser diodes (CW-LDs) with the central wavelengths of 450 nm and 532 nm are used for blood coagulation, corresponding to higher absorption coefficients of oxyhemoglobin and deoxyhemoglobin. Experimental results showed that the location of laser exposure can be accurately controlled with the proposed approach of imaging-based feedback positioning. Moreover, blood coagulation can be efficiently induced by CW-LDs and the coagulation process can be monitored in real-time with OCT. This technology enables to potentially provide accurate positioning for laser microsurgery and control the laser exposure to avoid extra damage by real-time OCT imaging.

Ground-based solar astrometric measurements during the PICARD mission

NASA Astrophysics Data System (ADS)

Irbah, A.; Meftah, M.; Corbard, T.; Ikhlef, R.; Morand, F.; Assus, P.; Fodil, M.; Lin, M.; Ducourt, E.; Lesueur, P.; Poiet, G.; Renaud, C.; Rouze, M.

2011-11-01

PICARD is a space mission developed mainly to study the geometry of the Sun. The satellite was launched in June 2010. The PICARD mission has a ground program which is based at the Calern Observatory (Observatoire de la C^ote d'Azur). It will allow recording simultaneous solar images from ground. Astrometric observations of the Sun using ground-based telescopes need however an accurate modelling of optical e®ects induced by atmospheric turbulence. Previous works have revealed a dependence of the Sun radius measurements with the observation conditions (Fried's parameter, atmospheric correlation time(s) ...). The ground instruments consist mainly in SODISM II, replica of the PICARD space instrument and MISOLFA, a generalized daytime seeing monitor. They are complemented by standard sun-photometers and a pyranometer for estimating a global sky quality index. MISOLFA is founded on the observation of Angle-of-Arrival (AA) °uctuations and allows us to analyze atmospheric turbulence optical e®ects on measurements performed by SODISM II. It gives estimations of the coherence parameters characterizing wave-fronts degraded by the atmospheric turbulence (Fried's parameter, size of the isoplanatic patch, the spatial coherence outer scale and atmospheric correlation times). This paper presents an overview of the ground based instruments of PICARD and some results obtained from observations performed at Calern observatory in 2011.

Stimuli-disassembling gold nanoclusters for diagnosis of early stage oral cancer by optical coherence tomography

NASA Astrophysics Data System (ADS)

Kim, Chang Soo; Ingato, Dominique; Wilder-Smith, Petra; Chen, Zhongping; Kwon, Young Jik

2018-01-01

A key design consideration in developing contrast agents is obtaining distinct, multiple signal changes in diseased tissue. Plasmonic gold nanoparticles (Au NPs) have been developed as contrast agents due to their strong surface plasmon resonance (SPR). This study aims to demonstrate that stimuli-responsive plasmonic Au nanoclusters (Au NCs) can be used as a contrast agent for optical coherence tomography (OCT) in detecting early-stage cancer. Au NPs were clustered via acid-cleavable linkers to synthesize Au NCs that disassemble under mildly acidic conditions into individual Au NPs, simultaneously diminishing SPR effect (quantified by scattering intensity) and increasing Brownian motion (quantified by Doppler variance). The acid-triggered morphological and accompanying optico-physical property changes of the acid-disassembling Au NCs were confirmed by TEM, DLS, UV/Vis, and OCT. Stimuli-responsive Au NCs were applied in a hamster check pouch model carrying early-stage squamous carcinoma tissue. The tissue was visualized by OCT imaging, which showed reduced scattering intensity and increased Doppler variance in the dysplastic tissue. This study demonstrates the promise of diagnosing early-stage cancer using molecularly programmable, inorganic nanomaterial-based contrast agents that are capable of generating multiple, stimuli-triggered diagnostic signals in early-stage cancer.[Figure not available: see fulltext.

Diagnostic accuracy of integrated intravascular ultrasound and optical coherence tomography (IVUS-OCT) system for coronary plaque characterization

NASA Astrophysics Data System (ADS)

Li, Jiawen; Ma, Teng; Mohar, Dilbahar; Correa, Adrian; Minami, Hataka; Jing, Joseph; Zhou, Qifa; Patel, Pranav M.; Chen, Zhongping

2014-03-01

Intravascular ultrasound (IVUS) imaging and optical coherence tomography (OCT), two commonly used intracoronary imaging modalities, play important roles in plaque evaluation. The combined use of IVUS (to visualize the entire plaque volume) and OCT (to quantify the thickness of the plaque cap, if any) is hypothesized to increase plaque diagnostic accuracy. Our group has developed a fully-integrated dual-modality IVUS-OCT imaging system and 3.6F catheter for simultaneous IVUS-OCT imaging with a high resolution and deep penetration depth. However, the diagnostic accuracy of an integrated IVUS-OCT system has not been investigated. In this study, we imaged 175 coronary artery sites (241 regions of interest) from 20 cadavers using our previous reported integrated IVUS-OCT system. IVUS-OCT images were read by two skilled interventional cardiologists. Each region of interest was classified as either calcification, lipid pool or fibrosis. Comparing the diagnosis by cardiologists using IVUSOCT images with the diagnosis by the pathologist, we calculated the sensitivity and specificity for characterization of calcification, lipid pool or fibrosis with this integrated system. In vitro imaging of cadaver coronary specimens demonstrated the complementary nature of these two modalities for plaques classification. A higher accuracy was shown than using a single modality alone.

Spectral optical coherence tomography for ophthalmologic applications

NASA Astrophysics Data System (ADS)

Targowski, Piotr; Bajraszewski, Tomasz; Gorczyńska, Iwona; Szkulmowska, Anna; Szkulmowski, Maciej; Wojtkowski, Maciej; Kowalczyk, Andrzej; Kaluzny, Jakub J.; Kaluzny, Bartłomiej J.

2006-09-01

The overview of the Spectral Optical Coherence Tomography an alternative method to more popular Time domain modality is given. Examples from medical practice utilizing high resolution, ultra fast SOCT device are presented.

Non-Hermitian optics in atomic systems

NASA Astrophysics Data System (ADS)

Zhang, Zhaoyang; Ma, Danmeng; Sheng, Jiteng; Zhang, Yiqi; Zhang, Yanpeng; Xiao, Min

2018-04-01

A wide class of non-Hermitian Hamiltonians can possess entirely real eigenvalues when they have parity-time (PT) symmetric potentials. Recently, this family of non-Hermitian systems has attracted considerable attention in diverse areas of physics due to their extraordinary properties, especially in optical systems based on solid-state materials, such as coupled gain-loss waveguides and microcavities. Considering the desired refractive index can be effectively manipulated through atomic coherence, it is important to realize such non-Hermitian optical potentials and further investigate their distinct properties in atomic systems. In this paper, we review the recent theoretical and experimental progress of non-Hermitian optics with coherently prepared multi-level atomic configurations. The realizations of (anti-) PT symmetry with different schemes have extensively demonstrated the special optical properties of non-Hermitian optical systems with atomic coherence.

Free-space coherent optical communication with orbital angular, momentum multiplexing/demultiplexing using a hybrid 3D photonic integrated circuit.

PubMed

Guan, Binbin; Scott, Ryan P; Qin, Chuan; Fontaine, Nicolas K; Su, Tiehui; Ferrari, Carlo; Cappuzzo, Mark; Klemens, Fred; Keller, Bob; Earnshaw, Mark; Yoo, S J B

2014-01-13

We demonstrate free-space space-division-multiplexing (SDM) with 15 orbital angular momentum (OAM) states using a three-dimensional (3D) photonic integrated circuit (PIC). The hybrid device consists of a silica planar lightwave circuit (PLC) coupled to a 3D waveguide circuit to multiplex/demultiplex OAM states. The low excess loss hybrid device is used in individual and two simultaneous OAM states multiplexing and demultiplexing link experiments with a 20 Gb/s, 1.67 b/s/Hz quadrature phase shift keyed (QPSK) signal, which shows error-free performance for 379,960 tested bits for all OAM states.

Role of many-body effects in the coherent dynamics of excitons in low-temperature-grown GaAs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Webber, D.; Hacquebard, L.; Hall, K. C.

2015-10-05

Femtosecond four-wave mixing experiments on low-temperature-grown (LT-) GaAs indicate a polarization-dependent nonlinear optical response at the exciton, which we attribute to Coulomb-mediated coupling between excitons and electron-hole pairs simultaneously excited by the broad-bandwidth laser pulses. Strong suppression of the exciton response through screening by carriers injected by a third pump pulse was observed, an effect that is transient due to rapid carrier trapping. Our findings highlight the need to account for the complex interplay of disorder and many-body effects in the design of ultrafast optoelectronic devices using this material.

Multiparameter thermo-mechanical OCT-based characterization of laser-induced cornea reshaping

NASA Astrophysics Data System (ADS)

Zaitsev, Vladimir Yu.; Matveyev, Alexandr L.; Matveev, Lev A.; Gelikonov, Grigory V.; Vitkin, Alex; Omelchenko, Alexander I.; Baum, Olga I.; Shabanov, Dmitry V.; Sovetsky, Alexander A.; Sobol, Emil N.

2017-02-01

Phase-sensitive optical coherence tomography (OCT) is used for visualizing dynamic and cumulative strains and corneashape changes during laser-produced tissue heating. Such non-destructive (non-ablative) cornea reshaping can be used as a basis of emerging technologies of laser vision correction. In experiments with cartilaginous samples, polyacrilamide phantoms and excised rabbit eyes we demonstrate ability of the developed OCT system to simultaneously characterize transient and cumulated strain distributions, surface displacements, scattering tissue properties and possibility of temperature estimation via thermal-expansion measurements. The proposed approach can be implemented in perspective real-time OCT systems for ensuring safety of new methods of laser reshaping of cornea.

Multimodal optical coherence tomography for in vivo imaging of brain tissue structure and microvascular network at glioblastoma

NASA Astrophysics Data System (ADS)

Yashin, Konstantin S.; Kiseleva, Elena B.; Gubarkova, Ekaterina V.; Matveev, Lev A.; Karabut, Maria M.; Elagin, Vadim V.; Sirotkina, Marina A.; Medyanik, Igor A.; Kravets, L. Y.; Gladkova, Natalia D.

2017-02-01

In the case of infiltrative brain tumors the surgeon faces difficulties in determining their boundaries to achieve total resection. The aim of the investigation was to evaluate the performance of multimodal OCT (MM OCT) for differential diagnostics of normal brain tissue and glioma using an experimental model of glioblastoma. The spectral domain OCT device that was used for the study provides simultaneously two modes: cross-polarization and microangiographic OCT. The comparative analysis of the both OCT modalities images from tumorous and normal brain tissue areas concurrently with histologic correlation shows certain difference between when accordingly to morphological and microvascular tissue features.

Cross polarization optical coherence tomography for diagnosis of oral soft tissues

NASA Astrophysics Data System (ADS)

Gladkova, Natalia; Karabut, Maria; Kiseleva, Elena; Robakidze, Natalia; Muraev, Alexander; Fomina, Julia

2011-03-01

We consider the capabilities of cross-polarization OCT (CP OCT) focused on comparison of images resulting from cross-polarization and co-polarization scattering simultaneously for diagnosis of oral soft tissues. CP OCT was done for 35 patients with dental implants and 30 patients with inflammatory intestine diseases. Our study showed good diagnostic capabilities of CP OCT for detecting soft tissue pathology in the oral cavity. The cross-polarized images demonstrate the ability of tissue to depolarize. CP OCT demonstrates clinical capabilities for early diagnosis of inflammatory intestine diseases by the state of oral cavity mucosa and for early detection of gingivitis in patients above implant.

Fully-resonant, tunable, monolithic frequency conversion as a coherent UVA source.

PubMed

Zielińska, Joanna A; Zukauskas, Andrius; Canalias, Carlota; Noyan, Mehmet A; Mitchell, Morgan W

2017-01-23

We demonstrate a monolithic frequency converter incorporating up to four tuning degrees of freedom, three temperature and one strain, allowing resonance of pump and generated wavelengths simultaneous with optimal phase-matching. With a Rb-doped periodically-poled potassium titanyl phosphate (KTP) implementation, we demonstrate efficient continuous-wave second harmonic generation from 795 to 397, with low-power efficiency of 72% and high-power slope efficiency of 4.5%. The measured performance shows good agreement with theoretical modeling of the device. We measure optical bistability effects, and show how they can be used to improve the stability of the output against pump frequency and amplitude variations.

Simultaneous multi-laser, multi-species trace-level sensing of gas mixtures by rapidly swept continuous-wave cavity-ringdown spectroscopy.

PubMed

He, Yabai; Kan, Ruifeng; Englich, Florian V; Liu, Wenqing; Orr, Brian J

2010-09-13

The greenhouse-gas molecules CO(2), CH(4), and H(2)O are detected in air within a few ms by a novel cavity-ringdown laser-absorption spectroscopy technique using a rapidly swept optical cavity and multi-wavelength coherent radiation from a set of pre-tuned near-infrared diode lasers. The performance of various types of tunable diode laser, on which this technique depends, is evaluated. Our instrument is both sensitive and compact, as needed for reliable environmental monitoring with high absolute accuracy to detect trace concentrations of greenhouse gases in outdoor air.

The Development, Commercialization, and Impact of Optical Coherence Tomography.

PubMed

Fujimoto, James; Swanson, Eric

2016-07-01

This review was written for the special issue of IOVS to describe the history of optical coherence tomography (OCT) and its evolution from a nonscientific, historic perspective. Optical coherence tomography has become a standard of care in ophthalmology, providing real-time information on structure and function - diagnosing disease, evaluating progression, and assessing response to therapy, as well as helping to understand disease pathogenesis and create new therapies. Optical coherence tomography also has applications in multiple clinical specialties, fundamental research, and manufacturing. We review the early history of OCT describing how research and development evolves and the important role of multidisciplinary collaboration and expertise. Optical coherence tomography had its origin in femtosecond optics, but used optical communications technologies and required advanced engineering for early OCT prototypes, clinical feasibility studies, entrepreneurship, and corporate development in order to achieve clinical acceptance and clinical impact. Critical advances were made by early career researchers, clinician scientists, engineering experts, and business leaders, which enabled OCT to have a worldwide impact on health care. We introduce the concept of an "ecosystem" consisting of research, government funding, collaboration and competition, clinical studies, innovation, entrepreneurship and industry, and impact - all of which must work synergistically. The process that we recount is long and challenging, but it is our hope that it might inspire early career professionals in science, engineering, and medicine, and that the clinical and research community will find this review of interest.

New Diamond Color Center for Quantum Communication

NASA Astrophysics Data System (ADS)

Huang, Ding; Rose, Brendon; Tyryshkin, Alexei; Sangtawesin, Sorawis; Srinivasan, Srikanth; Twitchen, Daniel; Markham, Matthew; Edmonds, Andrew; Gali, Adam; Stacey, Alastair; Wang, Wuyi; D'Haenens-Johansson, Ulrika; Zaitsev, Alexandre; Lyon, Stephen; de Leon, Nathalie

2017-04-01

Color centers in diamond are attractive for quantum communication applications because of their long electron spin coherence times and efficient optical transitions. Previous demonstrations of color centers as solid-state spin qubits were primarily focused on centers that exhibit either long coherence times or highly efficient optical interfaces. Recently, we developed a method to stabilize the neutral charge state of silicon-vacancy center in diamond (SiV0) with high conversion efficiency. We observe spin relaxation times exceeding 1 minute and spin coherence times of 1 ms for SiV0 centers. Additionally, the SiV0 center also has > 90 % of its emission into its zero-phonon line and a narrow inhomogeneous optical linewidth. The combination of a long spin coherence time and efficient optical interface make the SiV0 center a promising candidate for applications in long distance quantum communication.

Simple and versatile long range swept source for optical coherence tomography applications

NASA Astrophysics Data System (ADS)

Bräuer, Bastian; Lippok, Norman; Murdoch, Stuart G.; Vanholsbeeck, Frédérique

2015-12-01

We present a versatile long coherence length swept-source laser design for optical coherence tomography applications. This design consists of a polygonal spinning mirror and an optical gain chip in a modified Littman-Metcalf cavity. A narrowband intra-cavity filter is implemented through multiple passes off a diffraction grating set at grazing incidence. The key advantage of this design is that it can be readily adapted to any wavelength regions for which broadband gain chips are available. We demonstrate this by implementing sources at 1650 nm, 1550 nm, 1310 nm and 1050 nm. In particular, we present a 1310 nm swept source laser with 24 mm coherence length, 95 nm optical bandwidth, 2 kHz maximum sweep frequency and 7.5 mW average output power. These parameters make it a suitable source for the imaging of biological samples.

On the performance of joint iterative detection and decoding in coherent optical channels with laser frequency fluctuations

NASA Astrophysics Data System (ADS)

Castrillón, Mario A.; Morero, Damián A.; Agazzi, Oscar E.; Hueda, Mario R.

2015-08-01

The joint iterative detection and decoding (JIDD) technique has been proposed by Barbieri et al. (2007) with the objective of compensating the time-varying phase noise and constant frequency offset experienced in satellite communication systems. The application of JIDD to optical coherent receivers in the presence of laser frequency fluctuations has not been reported in prior literature. Laser frequency fluctuations are caused by mechanical vibrations, power supply noise, and other mechanisms. They significantly degrade the performance of the carrier phase estimator in high-speed intradyne coherent optical receivers. This work investigates the performance of the JIDD algorithm in multi-gigabit optical coherent receivers. We present simulation results of bit error rate (BER) for non-differential polarization division multiplexing (PDM)-16QAM modulation in a 200 Gb/s coherent optical system that includes an LDPC code with 20% overhead and net coding gain of 11.3 dB at BER = 10-15. Our study shows that JIDD with a pilot rate ⩽ 5 % compensates for both laser phase noise and laser frequency fluctuation. Furthermore, since JIDD is used with non-differential modulation formats, we find that gains in excess of 1 dB can be achieved over existing solutions based on an explicit carrier phase estimator with differential modulation. The impact of the fiber nonlinearities in dense wavelength division multiplexing (DWDM) systems is also investigated. Our results demonstrate that JIDD is an excellent candidate for application in next generation high-speed optical coherent receivers.

Single laser beam of spatial coherence from an array of GaAs lasers - Free-running mode

NASA Technical Reports Server (NTRS)

Philipp-Rutz, E. M.

1975-01-01

Spatially coherent radiation from a monolithic array of three GaAs lasers in a free-running mode is reported. The lasers, with their mirror faces antireflection coated, are operated in an external optical cavity built of spherical lenses and plane mirrors. The spatially coherent-beam formation makes use of the Fourier-transformation property of the internal lenses. Transverse mode control is accomplished by a spatial filter. The optical cavity is similar to that used for the phase-controlled mode of spatially coherent-beam formation; only the spatial filters are different. In the far field (when restored by an external lens), the intensities of the lasers in the array are concentrated in a single laser beam of spatial coherence, without any grating lobes. The far-field distribution of the laser array in the free-running mode differs significantly from the interference pattern of the phase-controlled mode. The modulation characteristics of the optical waveforms of the two modes are also quite different because modulation is related to the interaction of the spatial filter with the longitudinal modes of the laser array within the optical cavity. The modulation of the optical waveform of the free-running mode is nonperiodic, confirming that the fluctuations of the optical fields of the lasers are random.

Applications of Optical Coherent Transient Technology to Pulse Shaping, Spectral Filtering, Arbitrary Waveform Generation and RF Beamforming

DTIC Science & Technology

2006-04-15

was amplified by injection locking of a high power diode laser and further amplified to -300 mW with a semiconductor optical amplifier. This light...amplifiers at 793nm, cascaded injection locked amplifiers at 793nm, and frequency chirped lasers at 793nm. 15. SUBJECT TERMS Optical Coherent Transients...injection- locking for broadband optical signal amplification ................. 34 2.10. Tapered semiconductor optical amplifier

Extension of depth-resolved reconstruction of attenuation coefficients in optical coherence tomography for slim samples

NASA Astrophysics Data System (ADS)

Hohmann, Martin; Lengenfelder, B.; Kanawade, R.; Klämpfl, F.; Schmidt, Michael

2015-12-01

Coherent light propagating through turbid media is attenuated due to scattering and absorption. The decrease of the intensity of the coherent light is described by the attenuation coefficient. The measured decay of the coherent light through turbid media with optical coherence tomography (OCT) can be used to reconstruct the attenuation coefficient. Since most of the OCT systems work in the near-infrared region, they are the optical window from 800-1400 nm in tissue. Hence, the most part of the attenuation coefficient is caused due to the scattering. Therefore, deriving the attenuation coefficient is one way to get an approximation of the scattering coefficient which is difficult to access even up to day. Moreover, OCT measurements are one of the few possibilities to derive physical properties with micrometre resolution of the media under investigation.

GENERAL: Teleportation of a Bipartite Entangled Coherent State via a Four-Partite Cluster-Type Entangled State

NASA Astrophysics Data System (ADS)

Chen, Hui-Na; Liu, Jin-Ming

2009-10-01

We present an optical scheme to almost completely teleport a bipartite entangled coherent state using a four-partite cluster-type entangled coherent state as quantum channel. The scheme is based on optical elements such as beam splitters, phase shifters, and photon detectors. We also obtain the average fidelity of the teleportation process. It is shown that the average fidelity is quite close to unity if the mean photon number of the coherent state is not too small.

Electromagnetic-Optical Coherence Tomography Guidance of Transbronchial Solitary Pulmonary Nodule Biopsy

DTIC Science & Technology

2016-04-01

6 1. INTRODUCTION Lung cancer is the leading cause of cancer related death accounting for more deaths than breast , prostate and colon...the cancer has spread, at which time patients have little chance of cure. Macroscopic imaging modalities including CT and bronchoscopy have made...Electromagnetic Navigation , Biopsy Guidance, Optical Microscopy, Optical Coherence Tomography, Lung Cancer , Optical needle. 3. OVERALL PROJECT SUMMARY

Modulating the amplitude and phase of the complex spectral degree of coherence with plasmonic interferometry

NASA Astrophysics Data System (ADS)

Li, Dongfang; Pacifici, Domenico

The spectral degree of coherence describes the correlation of electromagnetic fields, which plays a key role in many applications, including free-space optical communications and speckle-free bioimaging. Recently, plasmonic interferometry, i.e. optical interferometry that employs surface plasmon polaritons (SPPs), has enabled enhanced light transmission and high-sensitivity biosensing, among other applications. It offers new ways to characterize and engineer electromagnetic fields using nano-structured thin metal films. Here, we employ plasmonic interferometry to demonstrate full control of spatial coherence at length scales comparable to the wavelength of the incident light. Specifically, by measuring the diffraction pattern of several double-slit plasmonic structures etched on a metal film, the amplitude and phase of the degree of spatial coherence is determined as a function of slit-slit separation distance and incident wavelength. When the SPP contribution is turned on (i.e., by changing the polarization of the incident light from TE to TM illumination mode), strong modulation of both amplitude and phase of the spatial coherence is observed. These findings may help design compact modulators of optical spatial coherence and other optical elements to shape the light intensity in the far-field.

Classical trajectories in polar-asymmetric laser fields: Synchronous THz and XUV emission

NASA Astrophysics Data System (ADS)

Gragossian, Aram; Seletskiy, Denis V.; Sheik-Bahae, Mansoor

2016-10-01

The interaction of intense near- and mid-infrared laser pulses with rare gases has produced bursts of radiation with spectral content extending into the extreme ultraviolet and soft x-ray region of electromagnetic spectrum. On the other end of the spectrum, laser-driven gas plasmas has been shown to produce coherent sub-harmonic optical waveforms, covering from terahertz (THz) to mid- and near-infrared frequency spectral band. Both processes can be enhanced via a combination of a driving field and its second harmonic. Despite this striking similarity, only limited experimental and theoretical attempts have been made to address these two regimes simultaneously. Here we present systematic experiments and a unifying picture of these processes, based on our extension of the semi-classical three-step model. Further understanding of the generation and coherent control of time-synchronized transients with photon energies from meV to 1 keV can lead to numerous technological advances and to an intriguing possibilities of ultra-broadband investigations into complex condensed matter systems.

Entangling atomic spins with a Rydberg-dressed spin-flip blockade

DOE PAGES

Jau, Y. -Y.; Hankin, A. M.; Keating, T.; ...

2015-10-05

Controlling the quantum entanglement between parts of a many-body system is key to unlocking the power of quantum technologies such as quantum computation, high-precision sensing, and the simulation of many-body physics. The spin degrees of freedom of ultracold neutral atoms in their ground electronic state provide a natural platform for such applications thanks to their long coherence times and the ability to control them with magneto-optical fields. However, the creation of strong coherent coupling between spins has been challenging. In this paper, we demonstrate a strong and tunable Rydberg-dressed interaction between spins of individually trapped caesium atoms with energy shiftsmore » of order 1 MHz in units of Planck’s constant. This interaction leads to a ground-state spin-flip blockade, whereby simultaneous hyperfine spin flips of two atoms are inhibited owing to their mutual interaction. Finally, we employ this spin-flip blockade to rapidly produce single-step Bell-state entanglement between two atoms with a fidelity ≥81(2)%.« less

Joint transform correlators with spatially incoherent illumination

NASA Astrophysics Data System (ADS)

Bykovsky, Yuri A.; Karpiouk, Andrey B.; Markilov, Anatoly A.; Rodin, Vladislav G.; Starikov, Sergey N.

1997-03-01

Two variants of joint transform correlators with monochromatic spatially incoherent illumination are considered. The Fourier-holograms of the reference and recognized images are recorded simultaneously or apart in a time on the same spatial light modulator directly by monochromatic spatially incoherent light. To create the signal of mutual correlation of the images it is necessary to execute nonlinear transformation when the hologram is illuminated by coherent light. In the first scheme of the correlator this aim was achieved by using double pas of a restoring coherent wave through the hologram. In the second variant of the correlator the non-linearity of the characteristic of the spatial light modulator for hologram recording was used. Experimental schemes and results on processing teste images by both variants of joint transform correlators with monochromatic spatially incoherent illumination. The use of spatially incoherent light on the input of joint transform correlators permits to reduce the requirements to optical quality of elements, to reduce accuracy requirements on elements positioning and to expand a number of devices suitable to input images in correlators.

Quantum measurement and orientation tracking of fluorescent nanodiamonds inside living cells

NASA Astrophysics Data System (ADS)

McGuinness, L. P.; Yan, Y.; Stacey, A.; Simpson, D. A.; Hall, L. T.; MacLaurin, D.; Prawer, S.; Mulvaney, P.; Wrachtrup, J.; Caruso, F.; Scholten, R. E.; Hollenberg, L. C. L.

2011-06-01

Fluorescent particles are routinely used to probe biological processes. The quantum properties of single spins within fluorescent particles have been explored in the field of nanoscale magnetometry, but not yet in biological environments. Here, we demonstrate optically detected magnetic resonance of individual fluorescent nanodiamond nitrogen-vacancy centres inside living human HeLa cells, and measure their location, orientation, spin levels and spin coherence times with nanoscale precision. Quantum coherence was measured through Rabi and spin-echo sequences over long (>10 h) periods, and orientation was tracked with effective 1° angular precision over acquisition times of 89 ms. The quantum spin levels served as fingerprints, allowing individual centres with identical fluorescence to be identified and tracked simultaneously. Furthermore, monitoring decoherence rates in response to changes in the local environment may provide new information about intracellular processes. The experiments reported here demonstrate the viability of controlled single spin probes for nanomagnetometry in biological systems, opening up a host of new possibilities for quantum-based imaging in the life sciences.

Single-shot observation of optical rogue waves in integrable turbulence using time microscopy

PubMed Central

Suret, Pierre; Koussaifi, Rebecca El; Tikan, Alexey; Evain, Clément; Randoux, Stéphane; Szwaj, Christophe; Bielawski, Serge

2016-01-01

Optical fibres are favourable tabletop laboratories to investigate both coherent and incoherent nonlinear waves. In particular, exact solutions of the one-dimensional nonlinear Schrödinger equation such as fundamental solitons or solitons on finite background can be generated by launching periodic, specifically designed coherent waves in optical fibres. It is an open fundamental question to know whether these coherent structures can emerge from the nonlinear propagation of random waves. However the typical sub-picosecond timescale prevented—up to now—time-resolved observations of the awaited dynamics. Here, we report temporal ‘snapshots' of random light using a specially designed ‘time-microscope'. Ultrafast structures having peak powers much larger than the average optical power are generated from the propagation of partially coherent waves in optical fibre and are recorded with 250 femtoseconds resolution. Our experiment demonstrates the central role played by ‘breather-like' structures such as the Peregrine soliton in the emergence of heavy-tailed statistics in integrable turbulence. PMID:27713416

Adaptive restoration of a partially coherent blurred image using an all-optical feedback interferometer with a liquid-crystal device.

PubMed

Shirai, Tomohiro; Barnes, Thomas H

2002-02-01

A liquid-crystal adaptive optics system using all-optical feedback interferometry is applied to partially coherent imaging through a phase disturbance. A theoretical analysis based on the propagation of the cross-spectral density shows that the blurred image due to the phase disturbance can be restored, in principle, irrespective of the state of coherence of the light illuminating the object. Experimental verification of the theory has been performed for two cases when the object to be imaged is illuminated by spatially coherent light originating from a He-Ne laser and by spatially incoherent white light from a halogen lamp. We observed in both cases that images blurred by the phase disturbance were successfully restored, in agreement with the theory, immediately after the adaptive optics system was activated. The origin of the deviation of the experimental results from the theory, together with the effect of the feedback misalignment inherent in our optical arrangement, is also discussed.

Probing myocardium biomechanics using quantitative optical coherence elastography

NASA Astrophysics Data System (ADS)

Wang, Shang; Lopez, Andrew L.; Morikawa, Yuka; Tao, Ge; Li, Jiasong; Larina, Irina V.; Martin, James F.; Larin, Kirill V.

2015-03-01

We present a quantitative optical coherence elastographic method for noncontact assessment of the myocardium elasticity. The method is based on shear wave imaging optical coherence tomography (SWI-OCT), where a focused air-puff system is used to induce localized tissue deformation through a low-pressure short-duration air stream and a phase-sensitive OCT system is utilized to monitor the propagation of the induced tissue displacement with nanoscale sensitivity. The 1-D scanning of M-mode OCT imaging and the application of optical phase retrieval and mapping techniques enable the reconstruction and visualization of 2-D depth-resolved shear wave propagation in tissue with ultra-high frame rate. The feasibility of this method in quantitative elasticity measurement is demonstrated on tissue-mimicking phantoms with the estimated Young's modulus compared with uniaxial compression tests. We also performed pilot experiments on ex vivo mouse cardiac muscle tissues with normal and genetically altered cardiomyocytes. Our results indicate this noncontact quantitative optical coherence elastographic method can be a useful tool for the cardiac muscle research and studies.

Coherent fluorescence emission by using hybrid photonic–plasmonic crystals

PubMed Central

Shi, Lei; Yuan, Xiaowen; Zhang, Yafeng; Hakala, Tommi; Yin, Shaoyu; Han, Dezhuan; Zhu, Xiaolong; Zhang, Bo; Liu, Xiaohan; Törmä, Päivi; Lu, Wei; Zi, Jian

2014-01-01

The spatial and temporal coherence of the fluorescence emission controlled by a quasi-two-dimensional hybrid photonic–plasmonic crystal structure covered with a thin fluorescent-molecular-doped dielectric film is investigated experimentally. A simple theoretical model to describe how a confined quasi-two-dimensional optical mode may induce coherent fluorescence emission is also presented. Concerning the spatial coherence, it is experimentally observed that the coherence area in the plane of the light source is in excess of 49 μm2, which results in enhanced directional fluorescence emission. Concerning temporal coherence, the obtained coherence time is 4 times longer than that of the normal fluorescence emission in vacuum. Moreover, a Young's double-slit interference experiment is performed to directly confirm the spatially coherent emission. This smoking gun proof of spatial coherence is reported here for the first time for the optical-mode-modified emission. PMID:25793015

Ultrafast acousto-optic mode conversion in optically birefringent ferroelectrics

NASA Astrophysics Data System (ADS)

Lejman, Mariusz; Vaudel, Gwenaelle; Infante, Ingrid C.; Chaban, Ievgeniia; Pezeril, Thomas; Edely, Mathieu; Nataf, Guillaume F.; Guennou, Mael; Kreisel, Jens; Gusev, Vitalyi E.; Dkhil, Brahim; Ruello, Pascal

2016-08-01

The ability to generate efficient giga-terahertz coherent acoustic phonons with femtosecond laser makes acousto-optics a promising candidate for ultrafast light processing, which faces electronic device limits intrinsic to complementary metal oxide semiconductor technology. Modern acousto-optic devices, including optical mode conversion process between ordinary and extraordinary light waves (and vice versa), remain limited to the megahertz range. Here, using coherent acoustic waves generated at tens of gigahertz frequency by a femtosecond laser pulse, we reveal the mode conversion process and show its efficiency in ferroelectric materials such as BiFeO3 and LiNbO3. Further to the experimental evidence, we provide a complete theoretical support to this all-optical ultrafast mechanism mediated by acousto-optic interaction. By allowing the manipulation of light polarization with gigahertz coherent acoustic phonons, our results provide a novel route for the development of next-generation photonic-based devices and highlight new capabilities in using ferroelectrics in modern photonics.

Access to long-term optical memories using photon echoes retrieved from electron spins in semiconductor quantum wells

NASA Astrophysics Data System (ADS)

Poltavtsev, S. V.; Langer, L.; Yugova, I. A.; Salewski, M.; Kapitonov, Y. V.; Yakovlev, D. R.; Karczewski, G.; Wojtowicz, T.; Akimov, I. A.; Bayer, M.

2016-10-01

We use spontaneous (two-pulse) and stimulated (three-pulse) photon echoes for studying the coherent evolution of optically excited ensemble of trions which are localized in semiconductor CdTe/CdMgTe quantum well. Application of transverse magnetic field leads to the Larmor precession of the resident electron spins, which shuffles optically induced polarization between optically accessible and inaccessible states. This results in several spectacular phenomena. First, magnetic field induces oscillations of spontaneous photon echo amplitude. Second, in three-pulse excitation scheme, the photon echo decay is extended by several orders of magnitude. In this study, short-lived optical excitation which is created by the first pulse is coherently transferred into a long-lived electron spin state using the second optical pulse. This coherent spin state of electron ensemble persists much longer than any optical excitation in the system, preserving information on initial optical field, which can be retrieved as a photon echo by means of third optical pulse.

Audio frequency in vivo optical coherence elastography

NASA Astrophysics Data System (ADS)

Adie, Steven G.; Kennedy, Brendan F.; Armstrong, Julian J.; Alexandrov, Sergey A.; Sampson, David D.

2009-05-01

We present a new approach to optical coherence elastography (OCE), which probes the local elastic properties of tissue by using optical coherence tomography to measure the effect of an applied stimulus in the audio frequency range. We describe the approach, based on analysis of the Bessel frequency spectrum of the interferometric signal detected from scatterers undergoing periodic motion in response to an applied stimulus. We present quantitative results of sub-micron excitation at 820 Hz in a layered phantom and the first such measurements in human skin in vivo.

Joint optimization of a partially coherent Gaussian beam for free-space optical communication over turbulent channels with pointing errors.

PubMed

Lee, It Ee; Ghassemlooy, Zabih; Ng, Wai Pang; Khalighi, Mohammad-Ali

2013-02-01

Joint beam width and spatial coherence length optimization is proposed to maximize the average capacity in partially coherent free-space optical links, under the combined effects of atmospheric turbulence and pointing errors. An optimization metric is introduced to enable feasible translation of the joint optimal transmitter beam parameters into an analogous level of divergence of the received optical beam. Results show that near-ideal average capacity is best achieved through the introduction of a larger receiver aperture and the joint optimization technique.

Perception of power modulation of light in conjunction with acoustic stimulation

NASA Astrophysics Data System (ADS)

Hahlweg, Cornelius F.; Weyer, Cornelia; Gercke-Hahn, Harald; Gutzmann, Holger L.; Brahmann, Andre; Rothe, Hendrik

2013-09-01

The present paper is derived from an ongoing study on the human perception of combined optical and acoustical periodical stimuli. Originating from problems of occupational medicine concerning artificial illumination and certain machinery with coherent optical and acoustical emissions there are effects which are interesting in the context of Optics and Music. Because of the difficulties in evaluation of physical and psychological effects of such coherent stimuli in a first step we questioned if such coherence is perceivable at all. Concept, experimental set-up and first results are discussed in short.

Optical coherence tomography findings of bilateral foveal leukemic infiltration.

PubMed

Le, John Q; Braich, Puneet S; Brar, Vikram S

2016-01-01

We report a case of a 59-year-old man with a history of atypical chronic myelogenous leukemia who presented with a several-week history of decreased vision in both eyes. His clinical examination revealed bilateral foveal infiltration, which was also demonstrated on optical coherence tomography. After a failed induction with imatinib (Gleevec(®)), he was treated with omacetaxine (Synribo(®)) with an appropriate hematologic response. As his leukemia improved with chemotherapy, his retinal lesions regressed as demonstrated by serial optical coherence tomography and fundus photographs, with near complete restoration of foveal architecture.

Digital phase demodulation for low-coherence interferometry-based fiber-optic sensors

NASA Astrophysics Data System (ADS)

Liu, Y.; Strum, R.; Stiles, D.; Long, C.; Rakhman, A.; Blokland, W.; Winder, D.; Riemer, B.; Wendel, M.

2018-03-01

We describe a digital phase demodulation scheme for low-coherence interferometry-based fiber-optic sensors by employing a simple generation of phase-shifted signals at the interrogation interferometer. The scheme allows a real-time calibration process and offers capability of measuring large variations (up to the coherence of the light source) at the bandwidth that is only limited by the data acquisition system. The proposed phase demodulation method is analytically derived and its validity and performance are experimentally verified using fiber-optic Fabry-Perot sensors for measurement of strains and vibrations.

High-resolution non-contact measurement of the electrical activity of plants in situ using optical recording

PubMed Central

Zhao, Dong-Jie; Chen, Yang; Wang, Zi-Yang; Xue, Lin; Mao, Tong-Lin; Liu, Yi-Min; Wang, Zhong-Yi; Huang, Lan

2015-01-01

The limitations of conventional extracellular recording and intracellular recording make high-resolution multisite recording of plant bioelectrical activity in situ challenging. By combining a cooled charge-coupled device camera with a voltage-sensitive dye, we recorded the action potentials in the stem of Helianthus annuus and variation potentials at multiple sites simultaneously with high spatial resolution. The method of signal processing using coherence analysis was used to determine the synchronization of the selected signals. Our results provide direct visualization of the phloem, which is the distribution region of the electrical activities in the stem and leaf of H. annuus, and verify that the phloem is the main action potential transmission route in the stems of higher plants. Finally, the method of optical recording offers a unique opportunity to map the dynamic bioelectrical activity and provides an insight into the mechanisms of long-distance electrical signal transmission in higher plants. PMID:26333536

Fast, noise-free memory for photon synchronization at room temperature.

PubMed

Finkelstein, Ran; Poem, Eilon; Michel, Ohad; Lahad, Ohr; Firstenberg, Ofer

2018-01-01

Future quantum photonic networks require coherent optical memories for synchronizing quantum sources and gates of probabilistic nature. We demonstrate a fast ladder memory (FLAME) mapping the optical field onto the superposition between electronic orbitals of rubidium vapor. Using a ladder-level system of orbital transitions with nearly degenerate frequencies simultaneously enables high bandwidth, low noise, and long memory lifetime. We store and retrieve 1.7-ns-long pulses, containing 0.5 photons on average, and observe short-time external efficiency of 25%, memory lifetime (1/ e ) of 86 ns, and below 10 -4 added noise photons. Consequently, coupling this memory to a probabilistic source would enhance the on-demand photon generation probability by a factor of 12, the highest number yet reported for a noise-free, room temperature memory. This paves the way toward the controlled production of large quantum states of light from probabilistic photon sources.

A Deep Learning Approach to Digitally Stain Optical Coherence Tomography Images of the Optic Nerve Head.

PubMed

Devalla, Sripad Krishna; Chin, Khai Sing; Mari, Jean-Martial; Tun, Tin A; Strouthidis, Nicholas G; Aung, Tin; Thiéry, Alexandre H; Girard, Michaël J A

2018-01-01

To develop a deep learning approach to digitally stain optical coherence tomography (OCT) images of the optic nerve head (ONH). A horizontal B-scan was acquired through the center of the ONH using OCT (Spectralis) for one eye of each of 100 subjects (40 healthy and 60 glaucoma). All images were enhanced using adaptive compensation. A custom deep learning network was then designed and trained with the compensated images to digitally stain (i.e., highlight) six tissue layers of the ONH. The accuracy of our algorithm was assessed (against manual segmentations) using the dice coefficient, sensitivity, specificity, intersection over union (IU), and accuracy. We studied the effect of compensation, number of training images, and performance comparison between glaucoma and healthy subjects. For images it had not yet assessed, our algorithm was able to digitally stain the retinal nerve fiber layer + prelamina, the RPE, all other retinal layers, the choroid, and the peripapillary sclera and lamina cribrosa. For all tissues, the dice coefficient, sensitivity, specificity, IU, and accuracy (mean) were 0.84 ± 0.03, 0.92 ± 0.03, 0.99 ± 0.00, 0.89 ± 0.03, and 0.94 ± 0.02, respectively. Our algorithm performed significantly better when compensated images were used for training (P < 0.001). Besides offering a good reliability, digital staining also performed well on OCT images of both glaucoma and healthy individuals. Our deep learning algorithm can simultaneously stain the neural and connective tissues of the ONH, offering a framework to automatically measure multiple key structural parameters of the ONH that may be critical to improve glaucoma management.

Coherent Doppler Wind Lidar Technology for Space Based Wind Measurements Including SPARCLE

NASA Technical Reports Server (NTRS)

Kavaya, Michael J.; Singh, Upendra N.

1999-01-01

It has been over 30 years since coherent lidar systems first measured wind velocity, and over 20 years since the "ultimate application" of measuring Earth's winds from space was conceived. Coherent or heterodyne optical detection involves the combination (or mixing) of the returned optical field with a local oscillator (LO) laser's optical field on the optical detector. This detection technique yields the benefits of dramatically improved signal-to-noise ratios; insensitivity to detector noise, background light and multiply scattered light; reduction of the returned signal's dynamic range; and preservation of the optical signal spectrum for electronic and computer processing. (Note that lidar systems are also referred to as optical radar, laser radar, and LADAR systems.) Many individuals, agencies, and countries have pursued the goal of space-based wind measurements through technology development, experiments, field campaigns and studies.

High efficiency coherent optical memory with warm rubidium vapour

PubMed Central

Hosseini, M.; Sparkes, B.M.; Campbell, G.; Lam, P.K.; Buchler, B.C.

2011-01-01

By harnessing aspects of quantum mechanics, communication and information processing could be radically transformed. Promising forms of quantum information technology include optical quantum cryptographic systems and computing using photons for quantum logic operations. As with current information processing systems, some form of memory will be required. Quantum repeaters, which are required for long distance quantum key distribution, require quantum optical memory as do deterministic logic gates for optical quantum computing. Here, we present results from a coherent optical memory based on warm rubidium vapour and show 87% efficient recall of light pulses, the highest efficiency measured to date for any coherent optical memory suitable for quantum information applications. We also show storage and recall of up to 20 pulses from our system. These results show that simple warm atomic vapour systems have clear potential as a platform for quantum memory. PMID:21285952

High efficiency coherent optical memory with warm rubidium vapour.

PubMed

Hosseini, M; Sparkes, B M; Campbell, G; Lam, P K; Buchler, B C

2011-02-01

By harnessing aspects of quantum mechanics, communication and information processing could be radically transformed. Promising forms of quantum information technology include optical quantum cryptographic systems and computing using photons for quantum logic operations. As with current information processing systems, some form of memory will be required. Quantum repeaters, which are required for long distance quantum key distribution, require quantum optical memory as do deterministic logic gates for optical quantum computing. Here, we present results from a coherent optical memory based on warm rubidium vapour and show 87% efficient recall of light pulses, the highest efficiency measured to date for any coherent optical memory suitable for quantum information applications. We also show storage and recall of up to 20 pulses from our system. These results show that simple warm atomic vapour systems have clear potential as a platform for quantum memory.

On important precursor of singular optics (tutorial)

NASA Astrophysics Data System (ADS)

Polyanskii, Peter V.; Felde, Christina V.; Bogatyryova, Halina V.; Konovchuk, Alexey V.

2018-01-01

The rise of singular optics is usually associated with the seminal paper by J. F. Nye and M. V. Berry [Proc. R. Soc. Lond. A, 336, 165-189 (1974)]. Intense development of this area of modern photonics has started since the early eighties of the XX century due to invention of the interfrence technique for detection and diagnostics of phase singularities, such as optical vortices in complex speckle-structured light fields. The next powerful incentive for formation of singular optics into separate area of the science on light was connectected with discovering of very practical technique for creation of singular optical beams of various kinds on the base of computer-generated holograms. In the eghties and ninetieth of the XX century, singular optics evolved, almost entirely, under the approximation of complete coherency of light field. Only at the threshold of the XXI century, it has been comprehended that the singular-optics approaches can be fruitfully expanded onto partially spatially coherent, partially polarized and polychromatic light fields supporting singularities of new kinds, that has been resulted in establishing of correlation singular optics. Here we show that correlation singular optics has much deeper roots, ascending to "pre-singular" and even pre-laser epoch and associated with the concept of partial coherence and polarization. It is remarcable that correlation singular optics in its present interpretation has forestalled the standard coherent singular optics. This paper is timed to the sixtieth anniversary of the most profound precursor of modern correlation singular optics [J. Opt. Soc. Am., 47, 895-902 (1957)].

Theoretical Investigation of Optical Detection and Recognition of Single Biological Molecules Using Coherent Dynamics of Exciton-Plasmon Coupling

PubMed Central

Sadeghi, S. M.; Hood, B.; Patty, K. D.; Mao, C.-B.

2013-01-01

We use quantum coherence in a system consisting of one metallic nanorod and one semi-conductor quantum dot to investigate a plasmonic nanosensor capable of digital optical detection and recognition of single biological molecules. In such a sensor the adsorption of a specific molecule to the nanorod turns off the emission of the system when it interacts with an optical pulse having a certain intensity and temporal width. The proposed quantum sensors can count the number of molecules of the same type or differentiate between molecule types with digital optical signals that can be measured with high certainty. We show that these sensors are based on the ultrafast upheaval of coherent dynamics of the system and the removal of coherent blockage of energy transfer from the quantum dot to the nanorod once the adsorption process has occurred. PMID:24040424

Combined spectral-domain optical coherence tomography and hyperspectral imaging applied for tissue analysis: Preliminary results

NASA Astrophysics Data System (ADS)

Dontu, S.; Miclos, S.; Savastru, D.; Tautan, M.

2017-09-01

In recent years many optoelectronic techniques have been developed for improvement and the development of devices for tissue analysis. Spectral-Domain Optical Coherence Tomography (SD-OCT) is a new medical interferometric imaging modality that provides depth resolved tissue structure information with resolution in the μm range. However, SD-OCT has its own limitations and cannot offer the biochemical information of the tissue. These data can be obtained with hyperspectral imaging, a non-invasive, sensitive and real time technique. In the present study we have combined Spectral-Domain Optical Coherence Tomography (SD-OCT) with Hyperspectral imaging (HSI) for tissue analysis. The Spectral-Domain Optical Coherence Tomography (SD-OCT) and Hyperspectral imaging (HSI) are two methods that have demonstrated significant potential in this context. Preliminary results using different tissue have highlighted the capabilities of this technique of combinations.

Coherent fiber supercontinuum for biophotonics

PubMed Central

Tu, Haohua; Boppart, Stephen A.

2013-01-01

Biophotonics and nonlinear fiber optics have traditionally been two independent fields. Since the discovery of fiber-based supercontinuum generation in 1999, biophotonics applications employing incoherent light have experienced a large impact from nonlinear fiber optics, primarily because of the access to a wide range of wavelengths and a uniform spatial profile afforded by fiber supercontinuum. However, biophotonics applications employing coherent light have not benefited from the most well-known techniques of supercontinuum generation for reasons such as poor coherence (or high noise), insufficient controllability, and inadequate portability. Fortunately, a few key techniques involving nonlinear fiber optics and femtosecond laser development have emerged to overcome these critical limitations. Despite their relative independence, these techniques are the focus of this review, because they can be integrated into a low-cost portable biophotonics source platform. This platform can be shared across many different areas of research in biophotonics, enabling new applications such as point-of-care coherent optical biomedical imaging. PMID:24358056

Improved measurement of vibration amplitude in dynamic optical coherence elastography

PubMed Central

Kennedy, Brendan F.; Wojtkowski, Maciej; Szkulmowski, Maciej; Kennedy, Kelsey M.; Karnowski, Karol; Sampson, David D.

2012-01-01

Abstract: Optical coherence elastography employs optical coherence tomography (OCT) to measure the displacement of tissues under load and, thus, maps the resulting strain into an image, known as an elastogram. We present a new improved method to measure vibration amplitude in dynamic optical coherence elastography. The tissue vibration amplitude caused by sinusoidal loading is measured from the spread of the Doppler spectrum, which is extracted using joint spectral and time domain signal processing. At low OCT signal-to-noise ratio (SNR), the method provides more accurate vibration amplitude measurements than the currently used phase-sensitive method. For measurements performed on a mirror at OCT SNR = 5 dB, our method introduces <3% error, compared to >20% using the phase-sensitive method. We present elastograms of a tissue-mimicking phantom and excised porcine tissue that demonstrate improvements, including a 50% increase in the depth range of reliable vibration amplitude measurement. PMID:23243565

Optical sectioning in induced coherence tomography with frequency-entangled photons

NASA Astrophysics Data System (ADS)

Vallés, Adam; Jiménez, Gerard; Salazar-Serrano, Luis José; Torres, Juan P.

2018-02-01

We demonstrate a different scheme to perform optical sectioning of a sample based on the concept of induced coherence [Zou et al., Phys. Rev. Lett. 67, 318 (1991), 10.1103/PhysRevLett.67.318]. This can be viewed as a different type of optical coherence tomography scheme where the varying reflectivity of the sample along the direction of propagation of an optical beam translates into changes of the degree of first-order coherence between two beams. As a practical advantage the scheme allows probing the sample with one wavelength and measuring photons with another wavelength. In a bio-imaging scenario, this would result in a deeper penetration into the sample because of probing with longer wavelengths, while still using the optimum wavelength for detection. The scheme proposed here could achieve submicron axial resolution by making use of nonlinear parametric sources with broad spectral bandwidth emission.

Probing coherence in microcavity frequency combs via optical pulse shaping

NASA Astrophysics Data System (ADS)

Ferdous, Fahmida; Miao, Houxun; Wang, Pei-Hsun; Leaird, Daniel E.; Srinivasan, Kartik; Chen, Lei; Aksyuk, Vladimir; Weiner, Andrew M.

2012-09-01

Recent investigations of microcavity frequency combs based on cascaded four-wave mixing have revealed a link between the evolution of the optical spectrum and the observed temporal coherence. Here we study a silicon nitride microresonator for which the initial four-wave mixing sidebands are spaced by multiple free spectral ranges (FSRs) from the pump, then fill in to yield a comb with single FSR spacing, resulting in partial coherence. By using a pulse shaper to select and manipulate the phase of various subsets of spectral lines, we are able to probe the structure of the coherence within the partially coherent comb. Our data demonstrate strong variation in the degree of mutual coherence between different groups of lines and provide support for a simple model of partially coherent comb formation.

SPECIAL ISSUE ON OPTICAL PROCESSING OF INFORMATION: Phase of an optical wave as an additional degree of freedom in optical information processing systems based on optical bistability

NASA Astrophysics Data System (ADS)

Basharov, Askhat M.

1995-10-01

It is shown theoretically that additional illumination by a squeezed field of a thin layer of two-level atoms, which interact with a resonant coherent electromagnetic wave, results in bistable transmission/reflection of this wave. This bistability depends strongly on the difference between the phases of the coherent and squeezed fields.

Free-space coherent optical communication receivers implemented with photorefractive optical beam combiners

NASA Technical Reports Server (NTRS)

Davidson, Frederic M.

1992-01-01

Performance measurements are reported concerning a coherent optical communication receiver that contained an iron doped indium phosphide photorefractive beam combiner, rather than a conventional optical beam splitter. The system obtained a bit error probability of 10(exp -6) at received signal powers corresponding to less than 100 detected photons per bit. The system used phase modulated Nd:YAG laser light at a wavelength of 1.06 microns.

Comparison of optic area measurement using fundus photography and optical coherence tomography between optic nerve head drusen and control subjects.

PubMed

Flores-Rodríguez, Patricia; Gili, Pablo; Martín-Ríos, María Dolores; Grifol-Clar, Eulalia

2013-03-01

To compare optic disc area measurement between optic nerve head drusen (ONHD) and control subjects using fundus photography, time-domain optical coherence tomography (TD-OCT) and spectral-domain optical coherence tomography (SD-OCT). We also made a comparison between each of the three techniques. We performed our study on 66 eyes (66 patients) with ONHD and 70 healthy control subjects (70 controls) with colour ocular fundus photography at 20º (Zeiss FF 450 IR plus), TD-OCT (Stratus OCT) with the Fast Optic Disc protocol and SD-OCT (Cirrus OCT) with the Optic Disc Cube 200 × 200 protocol for measurement of the optic disc area. The measurements were made by two observers and in each measurement a correction of the image magnification factor was performed. Measurement comparison using the Student's t-test/Mann-Whitney U test, the intraclass correlation coefficient, Pearson/Spearman rank correlation coefficient and the Bland-Altman plot was performed in the statistical analysis. Mean and standard deviation (SD) of the optic disc area in ONHD and in controls was 2.38 (0.54) mm(2) and 2.54 (0.42) mm(2), respectively with fundus photography; 2.01 (0.56) mm(2) and 1.66 (0.37) mm(2), respectively with TD-OCT, and 2.03 (0.49) mm(2) and 1.75 (0.38) mm(2), respectively with SD-OCT. In ONHD and controls, repeatability of optic disc area measurement was excellent with fundus photography and optical coherence tomography (TD-OCT and SD-OCT), but with a low degree of agreement between both techniques. Optic disc area measurement is smaller in ONHD compared to healthy subjects with fundus photography, unlike time-domain and spectral-domain optical coherence tomography in which the reverse is true. Both techniques offer good repeatability, but a low degree of correlation and agreement, which means that optic disc area measurement is not interchangeable or comparable between techniques. Ophthalmic & Physiological Optics © 2013 The College of Optometrists.

Conceptual design of a coherent optical system of modular imaging collectors (COSMIC). [telescope array deployed by space shuttle in 1990's

NASA Technical Reports Server (NTRS)

Nein, M. E.; Davis, B. G.

1982-01-01

The Coherent Optical System of Modular Imaging Collectors (COSMIC) is the design concept for a phase-coherent optical telescope array that may be placed in earth orbit by the Space Shuttle in the 1990s. The initial system module is a minimum redundancy array whose photon collecting area is three times larger than that of the Space Telescope, and possesses a one-dimensional resoution of better than 0.01 arcsec in the visible range. Thermal structural requirements are assessed. Although the coherent beam combination requirements will be met by an active control system, the COSMIC structural/thermal design must meet more stringent performance criteria than even those of the Space Telescope.

Optical communication with two-photon coherent stages. I - Quantum-state propagation and quantum-noise reduction

NASA Technical Reports Server (NTRS)

Yuen, H. P.; Shapiro, J. H.

1978-01-01

To determine the ultimate performance limitations imposed by quantum effects, it is also essential to consider optimum quantum-state generation. Certain 'generalized' coherent states of the radiation field possess novel quantum noise characteristics that offer the potential for greatly improved optical communications. These states have been called two-photon coherent states because they can be generated, in principle, by stimulated two-photon processes. The use of two-photon coherent state (TCS) radiation in free-space optical communications is considered. A simple theory of quantum state propagation is developed. The theory provides the basis for representing the free-space channel in a quantum-mechanical form convenient for communication analysis. The new theory is applied to TCS radiation.

Spatial coherence effect on layer thickness determination in narrowband full-field optical coherence tomography.

PubMed

Safrani, Avner; Abdulhalim, Ibrahim

2011-06-20

Longitudinal spatial coherence (LSC) is determined by the spatial frequency content of an optical beam. The use of lenses with a high numerical aperture (NA) in full-field optical coherence tomography and a narrowband light source makes the LSC length much shorter than the temporal coherence length, hence suggesting that high-resolution 3D images of biological and multilayered samples can be obtained based on the low LSC. A simplified model is derived, supported by experimental results, which describes the expected interference output signal of multilayered samples when high-NA lenses are used together with a narrowband light source. An expression for the correction factor for the layer thickness determination is found valid for high-NA objectives. Additionally, the method was applied to a strongly scattering layer, demonstrating the potential of this method for high-resolution imaging of scattering media.

Investigation of coherent receiver designs in high-speed optical inter-satellite links using digital signal processing

NASA Astrophysics Data System (ADS)

Schaefer, S.; Gregory, M.; Rosenkranz, W.

2017-09-01

Due to higher data rates, better data security and unlicensed spectral usage optical inter-satellite links (OISL) offer an attractive alternative to conventional RF-communication. However, the very high transmission distances necessitate an optical receiver design enabling high receiver sensitivity which requires careful carrier synchronization and a quasi-coherent detection scheme.

A Method of Assembling Compact Coherent Fiber-Optic Bundles

NASA Technical Reports Server (NTRS)

Martin, Stefan; Liu, Duncan; Levine, Bruce Martin; Shao, Michael; Wallace, James

2007-01-01

A method of assembling coherent fiber-optic bundles in which all the fibers are packed together as closely as possible is undergoing development. The method is based, straightforwardly, on the established concept of hexagonal close packing; hence, the development efforts are focused on fixtures and techniques for practical implementation of hexagonal close packing of parallel optical fibers.

The Development, Commercialization, and Impact of Optical Coherence Tomography

PubMed Central

Fujimoto, James; Swanson, Eric

2016-01-01

This review was written for the special issue of IOVS to describe the history of optical coherence tomography (OCT) and its evolution from a nonscientific, historic perspective. Optical coherence tomography has become a standard of care in ophthalmology, providing real-time information on structure and function – diagnosing disease, evaluating progression, and assessing response to therapy, as well as helping to understand disease pathogenesis and create new therapies. Optical coherence tomography also has applications in multiple clinical specialties, fundamental research, and manufacturing. We review the early history of OCT describing how research and development evolves and the important role of multidisciplinary collaboration and expertise. Optical coherence tomography had its origin in femtosecond optics, but used optical communications technologies and required advanced engineering for early OCT prototypes, clinical feasibility studies, entrepreneurship, and corporate development in order to achieve clinical acceptance and clinical impact. Critical advances were made by early career researchers, clinician scientists, engineering experts, and business leaders, which enabled OCT to have a worldwide impact on health care. We introduce the concept of an “ecosystem” consisting of research, government funding, collaboration and competition, clinical studies, innovation, entrepreneurship and industry, and impact – all of which must work synergistically. The process that we recount is long and challenging, but it is our hope that it might inspire early career professionals in science, engineering, and medicine, and that the clinical and research community will find this review of interest. PMID:27409459

Fundus autofluorescence and optical coherence tomography of congenital grouped albinotic spots.

PubMed

Kim, David Y; Hwang, John C; Moore, Anthony T; Bird, Alan C; Tsang, Stephen H

2010-09-01

The purpose of this study was to describe the findings of fundus autofluores-cence (FAF) and optical coherence tomography in a series of patients with congenital grouped albinotic spots. Three eyes of three patients with congenital grouped albinotic spots were evaluated with FAF and optical coherence tomography imaging to evaluate the nature of the albinotic spots. In all three eyes with congenital grouped albinotic spots, FAF imaging showed autofluorescent spots corresponding to the albinotic spots seen on stereo biomicroscopy. One eye also had additional spots detected on FAF imaging that were not visible on stereo biomicroscopy or color fundus photographs. Fundus autofluorescence imaging of the spots showed decreased general autofluorescence and decreased peripheral autofluorescence surrounding central areas of retained or increased autofluorescence. Optical coherence tomography showed a disruption in signal from the hyperreflective layer corresponding to the inner and outer segment junction and increased signal backscattering from the choroid in the area of the spots. Fluorescein angiography showed early and stable hyperfluorescence of the spots without leakage. In this case series, FAF showed decreased autofluorescence of the spots consistent with focal retinal pigment epithelium atrophy or abnormal material blocking normal autofluorescence and areas of increased autofluorescence suggesting retinal pigment epithelium dysfunction. The findings of optical coherence tomography and fluorescein angiography suggest photoreceptor and retinal pigment epithelium layer abnormalities. Fundus autofluorescence and optical coherence tomography are useful noninvasive diagnostic adjuncts that can aid in the diagnosis of congenital grouped albinotic spots, help determine extent of disease, and contribute to our understanding of its pathophysiology.

ULTRAHIGH SPEED SWEPT SOURCE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY OF RETINAL AND CHORIOCAPILLARIS ALTERATIONS IN DIABETIC PATIENTS WITH AND WITHOUT RETINOPATHY.

PubMed

Choi, WooJhon; Waheed, Nadia K; Moult, Eric M; Adhi, Mehreen; Lee, ByungKun; De Carlo, Talisa; Jayaraman, Vijaysekhar; Baumal, Caroline R; Duker, Jay S; Fujimoto, James G

2017-01-01

To investigate the utility of ultrahigh speed, swept source optical coherence tomography angiography in visualizing retinal microvascular and choriocapillaris (CC) changes in diabetic patients. The study was prospective and cross-sectional. A 1,050 nm wavelength, 400 kHz A-scan rate swept source optical coherence tomography prototype was used to perform volumetric optical coherence tomography angiography of the retinal and CC vasculatures in diabetic patients and normal subjects. Sixty-three eyes from 32 normal subjects, 9 eyes from 7 patients with proliferative diabetic retinopathy, 29 eyes from 16 patients with nonproliferative diabetic retinopathy, and 51 eyes from 28 diabetic patients without retinopathy were imaged. Retinal and CC microvascular abnormalities were observed in all stages of diabetic retinopathy. In nonproliferative diabetic retinopathy and proliferative diabetic retinopathy, optical coherence tomography angiography visualized a variety of vascular abnormalities, including clustered capillaries, dilated capillary segments, tortuous capillaries, regions of capillary dropout, reduced capillary density, abnormal capillary loops, and foveal avascular zone enlargement. In proliferative diabetic retinopathy, retinal neovascularization above the inner limiting membrane was visualized. Regions of CC flow impairment in patients with proliferative diabetic retinopathy and nonproliferative diabetic retinopathy were also observed. In 18 of the 51 of eyes from diabetic patients without retinopathy, retinal mircrovascular abnormalities were observed and CC flow impairment was found in 24 of the 51 diabetic eyes without retinopathy. The ability of optical coherence tomography angiography to visualize retinal and CC microvascular abnormalities suggests it may be a useful tool for understanding pathogenesis, evaluating treatment response, and earlier detection of vascular abnormalities in patients with diabetes.

Harmonic scalpel versus electrocautery for harvest of radial artery conduits: Reduced risk of spasm and intimal injury on optical coherence tomography

PubMed Central

Brazio, Philip S.; Laird, Patrick C.; Xu, Chenyang; Gu, Junyan; Burris, Nicholas S.; Brown, Emile N.; Kon, Zachary N.; Poston, Robert S.

2009-01-01

Objective Vasospasm is the primary obstacle to widespread adoption of the radial artery as a conduit in coronary artery bypass grafting. We used optical coherence tomography, a catheter-based intravascular imaging modality, to measure the degree of radial artery spasm induced by means of harvest with electrocautery or a harmonic scalpel in patients undergoing coronary artery bypass grafting. Methods Radial arteries were harvested from 44 consecutive patients with a harmonic scalpel (n = 15) or electrocautery (n = 29). Vessels were imaged before harvesting and after removal from the arm, with saphenous vein tracts serving as internal controls. Optical coherence tomographic findings for the degree of harvesting-induced injury were validated against histologic measures. Results Optical coherence tomographic measures of endovascular dimensions and injury correlated strongly with histologic findings. Mean luminal volume, a measure of vasospasm, decreased significantly less after harvesting with a harmonic scalpel (9% ± 7%) than with electrocautery (35% ± 6%, P = .015). Completely intact intima was present in 11 (73%) of 15 radial arteries harvested with a harmonic scalpel (73%) compared with 9 of 29 arteries harvested by means of electrocautery (31%, P = .011). Intraoperative flow measurements and patency rates at 5 days postoperatively were not significantly different among groups. Conclusions Optical coherence tomography provides a level of speed and accuracy for quantifying endothelial injury and vasospasm that has not been described for any other modality, suggesting potential as an intraoperative quality assurance tool. Our optical coherence tomographic findings suggest that the harmonic scalpel induces less spasm and intimal injury compared with electrocautery. PMID:19026820

The collagen structure of equine articular cartilage, characterized using polarization-sensitive optical coherence tomography

NASA Astrophysics Data System (ADS)

Ugryumova, Nadya; Attenburrow, Don P.; Winlove, C. Peter; Matcher, Stephen J.

2005-08-01

Optical coherence tomography and polarization-sensitive optical coherence tomography images of equine articular cartilage are presented. Measurements were made on intact joint surfaces. Significant (e.g. × 2) variations in the intrinsic birefringence were found over spatial scales of a few millimetres, even on samples taken from young (18 month) animals that appeared visually homogeneous. A comparison of data obtained on a control tissue (equine flexor tendon) further suggests that significant variations in the orientation of the collagen fibres relative to the plane of the joint surface exist. Images of visually damaged cartilage tissue show characteristic features both in terms of the distribution of optical scatterers and of the birefringent components.

General interference law for nonstationary, separable optical fields.

PubMed

Manea, Vladimir

2009-09-01

An approach to the theory of partial coherence for nonstationary optical fields is presented. Starting with a spectral representation, a favorable decomposition of the optical signals is discussed that supports a natural extension of the mathematical formalism. The coherence functions are redefined, but still as temporal correlation functions, allowing the obtaining of a more general form of the interference law for partially coherent optical signals. The general theory is applied in some relevant particular cases of nonstationary interference, namely, with quasi-monochromatic beams of different frequencies and with phase-modulated quasi-monochromatic beams of similar frequency spectra. All the results of the general treatment are reducible to the ones given in the literature for the case of stationary interference.

High speed, wide velocity dynamic range Doppler optical coherence tomography (Part III): in vivo endoscopic imaging of blood flow in the rat and human gastrointestinal tracts

NASA Astrophysics Data System (ADS)

Yang, Victor X. D.; Gordon, Maggie L.; Tang, Shou-Jiang; Marcon, Norman E.; Gardiner, Geoffrey; Qi, Bing; Bisland, Stuart; Seng-Yue, Emily; Lo, Stewart; Pekar, Julius; Wilson, Brian C.; Vitkin, I. Alex

2003-09-01

We previously described a fiber based Doppler optical coherence tomography system [1] capable of imaging embryo cardiac blood flow at 4~16 frames per second with wide velocity dynamic range [2]. Coupling this system to a linear scanning fiber optical catheter design that minimizes friction and vibrations, we report here the initial results of in vivo endoscopic Doppler optical coherence tomography (EDOCT) imaging in normal rat and human esophagus. Microvascular flow in blood vessels less than 100 µm diameter was detected using a combination of color-Doppler and velocity variance imaging modes, during clinical endoscopy using a mobile EDOCT system.

Prototype of a coherent tracking and detection receiver with wideband vibration compensation for free-space laser communications

NASA Astrophysics Data System (ADS)

Giggenbach, Dirk; Schex, Anton; Wandernoth, Bernhard

1996-04-01

The Optical Communications Group of the German Aerospace Research Establishment (DLR) has investigated the feasibility of a fiberless receiver telescope for high sensitive coherent optical space communication, resulting in an elegant pointing, acquisition and tracking (PAT) concept. To demonstrate the feasibility of this new concept, an optical receiver terminal that coherently obtains both the spatial error signal for tracking and the data signal with only one set of detectors has been built. The result is a very simple and compact setup with few optical surfaces. It does not require fibers for superpositioning and is capable to compensate for microaccelerations up to about one kilohertz.

Two improved coherent optical feedback systems for optical information processing

NASA Technical Reports Server (NTRS)

Lee, S. H.; Bartholomew, B.; Cederquist, J.

1976-01-01

Coherent optical feedback systems are Fabry-Perot interferometers modified to perform optical information processing. Two new systems based on plane parallel and confocal Fabry-Perot interferometers are introduced. The plane parallel system can be used for contrast control, intensity level selection, and image thresholding. The confocal system can be used for image restoration and solving partial differential equations. These devices are simpler and less expensive than previous systems. Experimental results are presented to demonstrate their potential for optical information processing.

High-resolution retinal imaging using adaptive optics and Fourier-domain optical coherence tomography

DOEpatents

Olivier, Scot S.; Werner, John S.; Zawadzki, Robert J.; Laut, Sophie P.; Jones, Steven M.

2010-09-07

This invention permits retinal images to be acquired at high speed and with unprecedented resolution in three dimensions (4.times.4.times.6 .mu.m). The instrument achieves high lateral resolution by using adaptive optics to correct optical aberrations of the human eye in real time. High axial resolution and high speed are made possible by the use of Fourier-domain optical coherence tomography. Using this system, we have demonstrated the ability to image microscopic blood vessels and the cone photoreceptor mosaic.

Ray-optical theory of broadband partially coherent emission

NASA Astrophysics Data System (ADS)

Epstein, Ariel; Tessler, Nir; Einziger, Pinchas D.

2013-04-01

We present a rigorous formulation of the effects of spectral broadening on emission of partially coherent source ensembles embedded in multilayered formations with arbitrarily shaped interfaces, provided geometrical optics is valid. The resulting ray-optical theory, applicable to a variety of optical systems from terahertz lenses to photovoltaic cells, quantifies the fundamental interplay between bandwidth and layer dimensions, and sheds light on common practices in optical analysis of statistical fields, e.g., disregarding multiple reflections or neglecting interference cross terms.

Fiber-optic-bundle-based optical coherence tomography.

PubMed

Xie, Tuqiang; Mukai, David; Guo, Shuguang; Brenner, Matthew; Chen, Zhongping

2005-07-15

A fiber-optic-bundle-based optical coherence tomography (OCT) probe method is presented. The experimental results demonstrate this multimode optical fiber-bundle-based OCT system can achieve a lateral resolution of 12 microm and an axial resolution of 10 microm with a superluminescent diode source. This novel OCT imaging approach eliminates any moving parts in the probe and has a primary advantage for use in extremely compact and safe OCT endoscopes for imaging internal organs and great potential to be combined with confocal endoscopic microscopy.

Two mode optical fiber in space optics communication

NASA Astrophysics Data System (ADS)

Hampl, Martin

2017-11-01

In our contribution we propose to use of a two-mode optical fiber as a primary source in a transmitting optical head instead of the laser diode. The distribution of the optical intensity and the complex degree of the coherence on the output aperture of the lens that is irradiated by a step-index weakly guiding optical fiber is investigated. In our treatment we take into account weakly guided modes with polarization corrections to the propagation constant and unified theory of second order coherence and polarization of electromagnetic beams.

Optical Communications Experiments at 6328 A and 10.6 micro.

PubMed

Lucy, R F; Lang, K

1968-10-01

Diagnostic optical communication experiments were performed comparing noncoherent and coherent detection techniques. Three different receiver-transmitter configurations with variable apertures were used during the experiments that were performed over a 1-km real atmospheric path. In every case, it was found that the coherent system fading, due to atmospheric turbulence, was considerably greater than the noncoherent system fading. This result shows the greater sensitivity of the coherent system to the time-varying wavefront breakup produced by atmospheric turbulence. A coherent homodyne experiment at 10.6 micro over a 2-km round-trip path was also performed. Its results indicated that a coherent system at 10.6 micro is less susceptible to atmospheric turbulence than a coherent system at 6328 A.

Emergence of electron coherence and two-color all-optical switching in MoS2 based on spatial self-phase modulation

PubMed Central

Wu, Yanling; Wu, Qiong; Sun, Fei; Cheng, Cai; Meng, Sheng; Zhao, Jimin

2015-01-01

Generating electron coherence in quantum materials is essential in optimal control of many-body interactions and correlations. In a multidomain system this signifies nonlocal coherence and emergence of collective phenomena, particularly in layered 2D quantum materials possessing novel electronic structures and high carrier mobilities. Here we report nonlocal ac electron coherence induced in dispersed MoS2 flake domains, using coherent spatial self-phase modulation (SSPM). The gap-dependent nonlinear dielectric susceptibility χ(3) measured is surprisingly large, where direct interband transition and two-photon SSPM are responsible for excitations above and below the bandgap, respectively. A wind-chime model is proposed to account for the emergence of the ac electron coherence. Furthermore, all-optical switching is achieved based on SSPM, especially with two-color intraband coherence, demonstrating that electron coherence generation is a ubiquitous property of layered quantum materials. PMID:26351696

Quantum-Fluctuation-Initiated Coherence in Multioctave Raman Optical Frequency Combs

NASA Astrophysics Data System (ADS)

Wang, Y. Y.; Wu, Chunbai; Couny, F.; Raymer, M. G.; Benabid, F.

2010-09-01

We show experimentally and theoretically that the spectral components of a multioctave frequency comb spontaneously created by stimulated Raman scattering in a hydrogen-filled hollow-core photonic crystal fiber exhibit strong self-coherence and mutual coherence within each 12 ns driving laser pulse. This coherence arises in spite of the field’s initiation being from quantum zero-point fluctuations, which causes each spectral component to show large phase and energy fluctuations. This points to the possibility of an optical frequency comb with nonclassical correlations between all comb lines.

Transient ultrafast coherent spectroscopy of 2-propanol

NASA Astrophysics Data System (ADS)

Meiselman, Seth; Decamp, Matthew; Lorenz, Virginia

We use transient coherent spontaneous Raman spectroscopy to measure the coherence lifetimes of vibrational states in liquid propanol. By creating single-photon-level collective excitations of the vibrational states in the system we observe coherence oscillations due to simultaneous excitation of the 2885 cm-1, 2938 cm-1, and 2976 cm-1 modes. These lifetimes and oscillation frequencies agree with frequency-domain lineshape measurements.

Adaptive-optics optical coherence tomography processing using a graphics processing unit.

PubMed

Shafer, Brandon A; Kriske, Jeffery E; Kocaoglu, Omer P; Turner, Timothy L; Liu, Zhuolin; Lee, John Jaehwan; Miller, Donald T

2014-01-01

Graphics processing units are increasingly being used for scientific computing for their powerful parallel processing abilities, and moderate price compared to super computers and computing grids. In this paper we have used a general purpose graphics processing unit to process adaptive-optics optical coherence tomography (AOOCT) images in real time. Increasing the processing speed of AOOCT is an essential step in moving the super high resolution technology closer to clinical viability.

LASER BIOLOGY AND MEDICINE: Combined application of optical methods to increase the information content of optical coherent tomography in diagnostics of neoplastic processes

NASA Astrophysics Data System (ADS)

Kuranov, R. V.; Sapozhnikova, V. V.; Shakhova, N. M.; Gelikonov, V. M.; Zagainova, E. V.; Petrova, S. A.

2002-11-01

A combined application of optical methods [optical coherent tomography (OCT), cross-polarisation optical coherent tomography, and fluorescence spectroscopy] is proposed for obtaining information on morphological and biochemical changes occurring in tissues in norm and pathology. It is shown that neoplastic and scar changes in esophagus can be distinguished using a combination of polarisation and standard OCT due to the difference between the depolarising properties of the tissues caused by the structural properties of collagenic fibres in stroma. It is shown that OCT combined with fluorescence spectroscopy with the use of 5-aminolevulinic acid is promising for determining the boundaries of carcinoma of the uterine cervix and vulva. It is found that the tumour boundary detected by optical methods coincides with the morphological boundary and extends beyond colposcopically determined boundary by about 2 mm.

Optical cryptography topology based on a three-dimensional particle-like distribution and diffractive imaging.

PubMed

Chen, Wen; Chen, Xudong

2011-05-09

In recent years, coherent diffractive imaging has been considered as a promising alternative for information retrieval instead of conventional interference methods. Coherent diffractive imaging using the X-ray light source has opened up a new research perspective for the measurement of non-crystalline and biological specimens, and can achieve unprecedentedly high resolutions. In this paper, we show how a three-dimensional (3D) particle-like distribution and coherent diffractive imaging can be applied for a study of optical cryptography. An optical multiple-random-phase-mask encoding approach is used, and the plaintext is considered as a series of particles distributed in a 3D space. A topology concept is also introduced into the proposed optical cryptosystem. During image decryption, a retrieval algorithm is developed to extract the plaintext from the ciphertexts. In addition, security and advantages of the proposed optical cryptography topology are also analyzed. © 2011 Optical Society of America

Optical characterization in wide spectral range by a coherent spectrophotometer

NASA Astrophysics Data System (ADS)

Sirutkaitis, Valdas; Eckardt, Robert C.; Balachninaite, Ona; Grigonis, Rimantas; Melninkaitis, A.; Rakickas, T.

2003-11-01

We report on the development and use of coherent spectrophotometers specialized for the unusual requirements of characterizing nonlinear optical materials and multilayer dielectric coatings used in laser systems. A large dynamic range is required to measure the linear properties of transmission, reflection and absorption and nonlinear properties of laser-induced damage threshold and nonlinear frequency conversion. Optical parametric oscillators generate coherent radiation that is widely tunable with instantaneous powers that can range from milliwatts to megawatts and are well matched to this application. As particular example a laser spectrophotometer based on optical parametric oscillators and a diode-pumped, Q-switched Nd:YAG laser and suitable for optical characterization in the spectral range 420-4500 nm is described. Measurements include reflectance and transmittance, absorption, scattering and laser-induced damage thresholds. Possibilities of a system based on a 130-fs Ti:sapphire laser and optical parametric generators are also discussed.

Combined application of optical methods to increase the information content of optical coherent tomography in diagnostics of neoplastic processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuranov, R V; Sapozhnikova, V V; Shakhova, N M

2002-11-30

A combined application of optical methods [optical coherent tomography (OCT), cross-polarisation optical coherent tomography, and fluorescence spectroscopy] is proposed for obtaining information on morphological and biochemical changes occurring in tissues in norm and pathology. It is shown that neoplastic and scar changes in esophagus can be distinguished using a combination of polarisation and standard OCT due to the difference between the depolarising properties of the tissues caused by the structural properties of collagenic fibres in stroma. It is shown that OCT combined with fluorescence spectroscopy with the use of 5-aminolevulinic acid is promising for determining the boundaries of carcinoma ofmore » the uterine cervix and vulva. It is found that the tumour boundary detected by optical methods coincides with the morphological boundary and extends beyond colposcopically determined boundary by about 2 mm. (laser biology and medicine)« less

High-speed spectral domain polarization- sensitive optical coherence tomography using a single camera and an optical switch at 1.3 microm.

PubMed

Lee, Sang-Won; Jeong, Hyun-Woo; Kim, Beop-Min

2010-01-01

We propose high-speed spectral domain polarization-sensitive optical coherence tomography (SD-PS-OCT) using a single camera and a 1x2 optical switch at the 1.3-microm region. The PS-low coherence interferometer used in the system is constructed using free-space optics. The reflected horizontal and vertical polarization light rays are delivered via an optical switch to a single spectrometer by turns. Therefore, our system costs less to build than those that use dual spectrometers, and the processes of timing and triggering are simpler from the viewpoints of both hardware and software. Our SD-PS-OCT has a sensitivity of 101.5 dB, an axial resolution of 8.2 microm, and an acquisition speed of 23,496 A-scans per second. We obtain the intensity, phase retardation, and fast axis orientation images of a rat tail tendon ex vivo.

Dosimetry control and monitoring of selective retina therapy using optical coherence tomography

NASA Astrophysics Data System (ADS)

Kaufmann, Daniel; Burri, Christian; Arnold, Patrik; Koch, Volker M.; Meier, Christoph; Považay, Boris; Justiz, Joern

2017-07-01

Selective retina therapy and optical coherence tomography have been combined to monitor laser-tissue interaction in real-time. An ex-vivo study of porcine eyes unveils mechanisms that enable automated and accurate dose-control during laser-therapy.

Polarization sensitive optical low-coherence reflectometry for blood glucose monitoring in human subjects

NASA Astrophysics Data System (ADS)

Solanki, Jitendra; Choudhary, Om Prakash; Sen, P.; Andrews, J. T.

2013-07-01

A device based on polarization sensitive optical low-coherence reflectometry is developed to monitor blood glucose levels in human subjects. The device was initially tested with tissue phantom. The measurements with human subjects for various glucose concentration levels are found to be linearly dependent on the ellipticity obtainable from the home-made phase-sensitive optical low-coherence reflectometry device. The linearity obtained between glucose concentration and ellipticity are explained with theoretical calculations using Mie theory. A comparison of results with standard clinical methods establishes the utility of the present device for non-invasive glucose monitoring.

Optical coherence tomography findings of bilateral foveal leukemic infiltration

PubMed Central

Le, John Q; Braich, Puneet S; Brar, Vikram S

2016-01-01

We report a case of a 59-year-old man with a history of atypical chronic myelogenous leukemia who presented with a several-week history of decreased vision in both eyes. His clinical examination revealed bilateral foveal infiltration, which was also demonstrated on optical coherence tomography. After a failed induction with imatinib (Gleevec®), he was treated with omacetaxine (Synribo®) with an appropriate hematologic response. As his leukemia improved with chemotherapy, his retinal lesions regressed as demonstrated by serial optical coherence tomography and fundus photographs, with near complete restoration of foveal architecture. PMID:27540313

Enhancement of the resolution of full-field optical coherence tomography by using a colour image sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalyanov, A L; Lychagov, V V; Smirnov, I V

2013-08-31

The influence of white balance in a colour image detector on the resolution of a full-field optical coherence tomograph (FFOCT) is studied. The change in the interference pulse width depending on the white balance tuning is estimated in the cases of a thermal radiation source (incandescent lamp) and a white light emitting diode. It is shown that by tuning white balance of the detector in a certain range, the FFOCT resolution can be increased by 20 % as compared to the resolution, attained with the use of a monochrome detector. (optical coherence tomography)

IN VIVO CHARACTERIZATION OF ORAL PEMPHIGUS VULGARIS BY OPTICAL COHERENCE TOMOGRAPHY.

PubMed

Di Stasio, D; Lauritano, D; Romano, A; Salerno, C; Minervini, G; Minervini, G; Gentile, E; Serpico, R; Lucchese, A

2015-01-01

Pemphigus vulgaris (PV) is an autoimmune disease that manifests as intraepithelial blisters in skin and mucous membranes. We report the case of a 62-year-old female patient with clinical picture of desquamative gingivitis and a histological and serological diagnosis of pemphigus vulgaris. The aim of this study is to analyse bollous oral diseases in order to evaluate the feasibility to image epithelial architecture of oral mucosae using in vivo optical coherence tomography. Optical coherence tomography seems to be a valid non-invasive auxiliary diagnostic device able to show in vivo the epithelial layers and basal membrane.

Digital phase demodulation for low-coherence interferometry-based fiber-optic sensors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Y.; Strum, R.; Stiles, D.

In this paper, we describe a digital phase demodulation scheme for low-coherence interferometry-based fiber-optic sensors by employing a simple generation of phase-shifted signals at the interrogation interferometer. The scheme allows a real-time calibration process and offers capability of measuring large variations (up to the coherence of the light source) at the bandwidth that is only limited by the data acquisition system. Finally, the proposed phase demodulation method is analytically derived and its validity and performance are experimentally verified using fiber-optic Fabry–Perot sensors for measurement of strains and vibrations.

Digital phase demodulation for low-coherence interferometry-based fiber-optic sensors

DOE PAGES

Liu, Y.; Strum, R.; Stiles, D.; ...

2017-11-20

In this paper, we describe a digital phase demodulation scheme for low-coherence interferometry-based fiber-optic sensors by employing a simple generation of phase-shifted signals at the interrogation interferometer. The scheme allows a real-time calibration process and offers capability of measuring large variations (up to the coherence of the light source) at the bandwidth that is only limited by the data acquisition system. Finally, the proposed phase demodulation method is analytically derived and its validity and performance are experimentally verified using fiber-optic Fabry–Perot sensors for measurement of strains and vibrations.

Ultrafast Coherent Dynamics of a Photonic Crystal All-Optical Switch.

PubMed

Colman, Pierre; Lunnemann, Per; Yu, Yi; Mørk, Jesper

2016-12-02

We present pump-probe measurements of an all-optical photonic crystal switch based on a nanocavity, resolving fast coherent temporal dynamics. The measurements demonstrate the importance of coherent effects typically neglected when considering nanocavity dynamics. In particular, we report the observation of an idler pulse and more than 10 dB parametric gain. The measurements are in good agreement with a theoretical model that ascribes the observation to oscillations of the free-carrier population in the nanocavity. The effect opens perspectives for the realization of new all-optical photonic crystal switches with unprecedented switching contrast.

Spontaneous closure of macular hole in a patient with x-linked juvenile retinoschisis.

PubMed

Gao, Hua; Province, William D; Peracha, Mohammed O

2010-01-01

To observe macular hole in a patient with juvenile retinoschisis. A 4-year-old boy with X-linked juvenile retinoschisis was examined and followed-up for 2 years. Optical coherence tomography was used to study his maculae. A full-thickness macular hole was detected by clinical examination and optical coherence tomography. Spontaneous closure of the macular hole was noticed and confirmed by optical coherence tomography 2 years later with visual improvement. Macular hole in patients with juvenile retinoschisis should be observed for at least a short period of time before a surgical repair is considered.

Fundus autofluorescence, optical coherence tomography, and electroretinogram findings in choroidal sclerosis.

PubMed

Hwang, John C; Kim, David Y; Chou, Chai Lin; Tsang, Stephen H

2010-01-01

The purpose of this study was to describe fundus autofluorescence (FAF), optical coherence tomography, and electroretinogram findings in choroidal sclerosis. This is a retrospective case series. Eight eyes of four patients with choroidal sclerosis were evaluated with FAF, optical coherence tomography, and electroretinogram testing. In all eight eyes, FAF imaging showed hypofluorescent placoid lesions corresponding to areas of chorioretinal atrophy seen on stereo biomicroscopy. Prominent hyperfluorescent linear markings underlying regions of atrophic disease were observed in all eyes, likely representative of normal choroidal vessel autofluorescence. In two eyes, FAF showed punctate hypofluorescent lesions in the fovea that were not visualized on biomicroscopy. In one eye, FAF identified a central island of preserved retinal pigment epithelium that was not realized on ophthalmoscopic examination. Optical coherence imaging was significant for loss of choroidal fine tubular structures, retinal pigment epithelium, and outer nuclear layer in regions of chorioretinal atrophy. Full-field electroretinogram testing showed generalized rod-cone dysfunction in all patients with a lower B- to A-wave ratio in two patients. Fundus autofluorescence and optical coherence tomography are nonin-vasive diagnostic adjuncts that can aid in the diagnosis of choroidal sclerosis. Fundus autofluorescence may be a more sensitive marker of disease extent and progression than clinical examination alone. Electroretinogram testing can result in an electronegative maximal response.

Quantum coherent optical phase modulation in an ultrafast transmission electron microscope.

PubMed

Feist, Armin; Echternkamp, Katharina E; Schauss, Jakob; Yalunin, Sergey V; Schäfer, Sascha; Ropers, Claus

2015-05-14

Coherent manipulation of quantum systems with light is expected to be a cornerstone of future information and communication technology, including quantum computation and cryptography. The transfer of an optical phase onto a quantum wavefunction is a defining aspect of coherent interactions and forms the basis of quantum state preparation, synchronization and metrology. Light-phase-modulated electron states near atoms and molecules are essential for the techniques of attosecond science, including the generation of extreme-ultraviolet pulses and orbital tomography. In contrast, the quantum-coherent phase-modulation of energetic free-electron beams has not been demonstrated, although it promises direct access to ultrafast imaging and spectroscopy with tailored electron pulses on the attosecond scale. Here we demonstrate the coherent quantum state manipulation of free-electron populations in an electron microscope beam. We employ the interaction of ultrashort electron pulses with optical near-fields to induce Rabi oscillations in the populations of electron momentum states, observed as a function of the optical driving field. Excellent agreement with the scaling of an equal-Rabi multilevel quantum ladder is obtained, representing the observation of a light-driven 'quantum walk' coherently reshaping electron density in momentum space. We note that, after the interaction, the optically generated superposition of momentum states evolves into a train of attosecond electron pulses. Our results reveal the potential of quantum control for the precision structuring of electron densities, with possible applications ranging from ultrafast electron spectroscopy and microscopy to accelerator science and free-electron lasers.

Quantum coherent optical phase modulation in an ultrafast transmission electron microscope

NASA Astrophysics Data System (ADS)

Feist, Armin; Echternkamp, Katharina E.; Schauss, Jakob; Yalunin, Sergey V.; Schäfer, Sascha; Ropers, Claus

2015-05-01

Coherent manipulation of quantum systems with light is expected to be a cornerstone of future information and communication technology, including quantum computation and cryptography. The transfer of an optical phase onto a quantum wavefunction is a defining aspect of coherent interactions and forms the basis of quantum state preparation, synchronization and metrology. Light-phase-modulated electron states near atoms and molecules are essential for the techniques of attosecond science, including the generation of extreme-ultraviolet pulses and orbital tomography. In contrast, the quantum-coherent phase-modulation of energetic free-electron beams has not been demonstrated, although it promises direct access to ultrafast imaging and spectroscopy with tailored electron pulses on the attosecond scale. Here we demonstrate the coherent quantum state manipulation of free-electron populations in an electron microscope beam. We employ the interaction of ultrashort electron pulses with optical near-fields to induce Rabi oscillations in the populations of electron momentum states, observed as a function of the optical driving field. Excellent agreement with the scaling of an equal-Rabi multilevel quantum ladder is obtained, representing the observation of a light-driven `quantum walk' coherently reshaping electron density in momentum space. We note that, after the interaction, the optically generated superposition of momentum states evolves into a train of attosecond electron pulses. Our results reveal the potential of quantum control for the precision structuring of electron densities, with possible applications ranging from ultrafast electron spectroscopy and microscopy to accelerator science and free-electron lasers.

Continuum generation in optical fibers for high-resolution holographic coherence domain imaging application

NASA Astrophysics Data System (ADS)

Li, Linghui; Gruzdev, Vitaly; Yu, Ping; Chen, J. K.

2009-02-01

High pulse energy continuum generation in conventional multimode optical fibers has been studied for potential applications to a holographic optical coherence imaging system. As a new imaging modality for the biological tissue imaging, high-resolution holographic optical coherence imaging requires a broadband light source with a high brightness, a relatively low spatial coherence and a high stability. A broadband femtosecond laser can not be used as the light source of holographic imaging system since the laser creates a lot of speckle patterns. By coupling high peak power femtosecond laser pulses into a multimode optical fiber, nonlinear optical effects cause a continuum generation that can be served as a super-bright and broadband light source. In our experiment, an amplified femtosecond laser was coupled into the fiber through a microscopic objective. We measured the FWHM of the continuum generation as a function of incident pulse energy from 80 nJ to 800 μJ. The maximum FWHM is about 8 times higher than that of the input pulses. The stability was analyzed at different pump energies, integration times and fiber lengths. The spectral broadening and peak position show that more than two processes compete in the fiber.

Coherent noise reduction in digital holographic microscopy by averaging multiple holograms recorded with a multimode laser.

PubMed

Pan, Feng; Yang, Lizhi; Xiao, Wen

2017-09-04

In digital holographic microscopy (DHM), it is undesirable to observe coherent noise in the reconstructed images. The sources of the noise are mainly the parasitic interference fringes caused by multiple reflections and the speckle pattern caused by the optical scattering on the object surface. Here we propose a noise reduction approach in DHM by averaging multiple holograms recorded with a multimode laser. Based on the periodicity of the temporal coherence of a multimode semiconductor laser, we acquire a series of holograms by changing the optical path length difference between the reference beam and object beam. Because of the use of low coherence light, we can remove the parasitic interference fringes caused by multiple reflections in the holograms. In addition, the coherent noise patterns change in this process due to the different optical paths. Therefore, the coherent noise can be reduced by averaging the multiple reconstructions with uncorrelated noise patterns. Several experiments have been carried out to validate the effectiveness of the proposed approach for coherent noise reduction in DHM. It is shown a remarkable improvement both in amplitude imaging quality and phase measurement accuracy.

Coherent spin control of a nanocavity-enhanced qubit in diamond

DOE PAGES

Li, Luozhou; Lu, Ming; Schroder, Tim; ...

2015-01-28

A central aim of quantum information processing is the efficient entanglement of multiple stationary quantum memories via photons. Among solid-state systems, the nitrogen-vacancy centre in diamond has emerged as an excellent optically addressable memory with second-scale electron spin coherence times. Recently, quantum entanglement and teleportation have been shown between two nitrogen-vacancy memories, but scaling to larger networks requires more efficient spin-photon interfaces such as optical resonators. Here we report such nitrogen-vacancy nanocavity systems in strong Purcell regime with optical quality factors approaching 10,000 and electron spin coherence times exceeding 200 µs using a silicon hard-mask fabrication process. This spin-photon interfacemore » is integrated with on-chip microwave striplines for coherent spin control, providing an efficient quantum memory for quantum networks.« less

Analysis of the Origin of Atypical Scanning Laser Polarimetry Patterns by Polarization-Sensitive Optical Coherence Tomography

PubMed Central

Götzinger, Erich; Pircher, Michael; Baumann, Bernhard; Hirn, Cornelia; Vass, Clemens; Hitzenberger, Christoph K.

2010-01-01

Purpose To analyze the physical origin of atypical scanning laser polarimetry (SLP) patterns. To compare polarization-sensitive optical coherence tomography (PS-OCT) scans to SLP images. To present a method to obtain pseudo-SLP images by PS-OCT that are free of atypical artifacts. Methods Forty-one eyes of healthy subjects, subjects with suspected glaucoma, and patients with glaucoma were imaged by SLP (GDx VCC) and a prototype spectral domain PS-OCT system. The PS-OCT system acquires three-dimensional (3D) datasets of intensity, retardation, and optic axis orientation simultaneously within 3 seconds. B-scans of intensity and retardation and en face maps of retinal nerve fiber layer (RNFL) retardation were derived from the 3D PS-OCT datasets. Results were compared with those obtained by SLP. Results Twenty-two eyes showed atypical retardation patterns, and 19 eyes showed normal patterns. From the 22 atypical eyes, 15 showed atypical patterns in both imaging modalities, five were atypical only in SLP images, and two were atypical only in PS-OCT images. In most (15 of 22) atypical cases, an increased penetration of the probing beam into the birefringent sclera was identified as the source of atypical patterns. In such cases, the artifacts could be eliminated in PS-OCT images by depth segmentation and exclusion of scleral signals. Conclusions PS-OCT provides deeper insight into the contribution of different fundus layers to SLP images. Increased light penetration into the sclera can distort SLP retardation patterns of the RNFL. PMID:19036999

Bubble velocity, diameter, and void fraction measurements in a multiphase flow using fiber optic reflectometer

NASA Astrophysics Data System (ADS)

Lim, Ho-Joon; Chang, Kuang-An; Su, Chin B.; Chen, Chi-Yueh

2008-12-01

A fiber optic reflectometer (FOR) technique featuring a single fiber probe is investigated for its feasibility of measuring the bubble velocity, diameter, and void fraction in a multiphase flow. The method is based on the interference of the scattered signal from the bubble surface with the Fresnel reflection signal from the tip of the optical fiber. Void fraction is obtained with a high accuracy if an appropriate correction is applied to compensate the underestimated measurement value. Velocity information is accurately obtained from the reflected signals before the fiber tip touches the bubble surface so that several factors affecting the traditional dual-tip probes such as blinding, crawling, and drifting effects due to the interaction between the probe and bubbles can be prevented. The coherent signals reflected from both the front and rear ends of a bubble can provide velocity information. Deceleration of rising bubbles and particles due to the presence of the fiber probe is observed when they are very close to the fiber tip. With the residence time obtained, the bubble chord length can be determined by analyzing the coherent signal for velocity determination before the deceleration starts. The bubble diameters are directly obtained from analyzing the signals of the bubbles that contain velocity information. The chord lengths of these bubbles measured by FOR represent the bubble diameters when the bubble shape is spherical or represent the minor axes when the bubble shape is ellipsoidal. The velocity and size of bubbles obtained from the FOR measurements are compared with those obtained simultaneously using a high speed camera.

Frequency accurate coherent electro-optic dual-comb spectroscopy in real-time.

PubMed

Martín-Mateos, Pedro; Jerez, Borja; Largo-Izquierdo, Pedro; Acedo, Pablo

2018-04-16

Electro-optic dual-comb spectrometers have proved to be a promising technology for sensitive, high-resolution and rapid spectral measurements. Electro-optic combs possess very attractive features like simplicity, reliability, bright optical teeth, and typically moderate but quickly tunable optical spans. Furthermore, in a dual-comb arrangement, narrowband electro-optic combs are generated with a level of mutual coherence that is sufficiently high to enable optical multiheterodyning without inter-comb stabilization or signal processing systems. However, this valuable tool still presents several limitations; for instance, on most systems, absolute frequency accuracy and long-term stability cannot be guaranteed; likewise, interferometer-induced phase noise restricts coherence time and limits the attainable signal-to-noise ratio. In this paper, we address these drawbacks and demonstrate a cost-efficient absolute electro-optic dual-comb instrument based on a frequency stabilization mechanism and a novel adaptive interferogram acquisition approach devised for electro-optic dual-combs capable of operating in real-time. The spectrometer, completely built from commercial components, provides sub-ppm frequency uncertainties and enables a signal-to-noise ratio of 10000 (intensity noise) in 30 seconds of integration time.

Optical Coherence Tomography Angiography of Retinal Cavernous Hemangioma.

PubMed

Pierro, Luisa; Marchese, Alessandro; Gagliardi, Marco; Bandello, Francesco

2017-08-01

Retinal cavernous hemangioma is a rare, benign, retinal tumor characterized by angiomatous proliferation of vessels within the inner retina or the optic disc.1 Here we report a case of retinal cavernous hemangioma on the margin of the optic disc in the right eye of a 61-year-old asymptomatic female. The lesion was studied with multimodal imaging which included structural optical coherence tomography, fluorescein angiography, blue fundus auto-fluorescence, optical coherence tomography angiography (OCTA) (DRI OCT Triton; Topcon, Tokyo, Japan) and visual field examination. Blood circulation inside retinal cavernous hemangioma lesion is typically low-stagnant.2 However, OCTA demonstrated blood flow inside the lesion, illustrating its vascular circulation.3 Visual field was within the normal limits, except from a slight enlargement of the blind spot. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:684-685.]. Copyright 2017, SLACK Incorporated.

Development of a coherent optical particle spectrometer for industrial applications: a feasibility investigation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, H.T.; Bachalo, W.D.

1984-10-01

The feasibility of developing a particle-sizing instrument for in-situ measurements in industrial environments, based on the method of optical heterodyne or coherent detection, was investigated. The instrument, a coherent optical particle spectrometer, or COPS, is potentially capable of measuring several important particle parameters, such as particle size, number density, and speed, because of the versatility of the optical heterodyne method. Water droplets generated by an aerosol/particle generator were used to test the performance of the COPS. Study findings have shown that the optical setup of the COPS is extremely sensitive to even minute mechanical or acoustic vibrations. At the optimalmore » setup, the COPS performs satisfactorily and has more than adequate signal-to-noise even with a 0.5 mW He-Ne laser.« less

Ultrafast acousto-optic mode conversion in optically birefringent ferroelectrics

PubMed Central

Lejman, Mariusz; Vaudel, Gwenaelle; Infante, Ingrid C.; Chaban, Ievgeniia; Pezeril, Thomas; Edely, Mathieu; Nataf, Guillaume F.; Guennou, Mael; Kreisel, Jens; Gusev, Vitalyi E.; Dkhil, Brahim; Ruello, Pascal

2016-01-01

The ability to generate efficient giga–terahertz coherent acoustic phonons with femtosecond laser makes acousto-optics a promising candidate for ultrafast light processing, which faces electronic device limits intrinsic to complementary metal oxide semiconductor technology. Modern acousto-optic devices, including optical mode conversion process between ordinary and extraordinary light waves (and vice versa), remain limited to the megahertz range. Here, using coherent acoustic waves generated at tens of gigahertz frequency by a femtosecond laser pulse, we reveal the mode conversion process and show its efficiency in ferroelectric materials such as BiFeO3 and LiNbO3. Further to the experimental evidence, we provide a complete theoretical support to this all-optical ultrafast mechanism mediated by acousto-optic interaction. By allowing the manipulation of light polarization with gigahertz coherent acoustic phonons, our results provide a novel route for the development of next-generation photonic-based devices and highlight new capabilities in using ferroelectrics in modern photonics. PMID:27492493

Coherent multi-dimensional spectroscopy at optical frequencies in a single beam with optical readout

NASA Astrophysics Data System (ADS)

Seiler, Hélène; Palato, Samuel; Kambhampati, Patanjali

2017-09-01

Ultrafast coherent multi-dimensional spectroscopies form a powerful set of techniques to unravel complex processes, ranging from light-harvesting, chemical exchange in biological systems to many-body interactions in quantum-confined materials. Yet these spectroscopies remain complex to implement at the high frequencies of vibrational and electronic transitions, thereby limiting their widespread use. Here we demonstrate the feasibility of two-dimensional spectroscopy at optical frequencies in a single beam. Femtosecond optical pulses are spectrally broadened to a relevant bandwidth and subsequently shaped into phase coherent pulse trains. By suitably modulating the phases of the pulses within the beam, we show that it is possible to directly read out the relevant optical signals. This work shows that one needs neither complex beam geometries nor complex detection schemes in order to measure two-dimensional spectra at optical frequencies. Our setup provides not only a simplified experimental design over standard two-dimensional spectrometers but its optical readout also enables novel applications in microscopy.

Optically Tunable Gratings Based on Coherent Population Oscillation.

PubMed

Zhang, Xiao-Jun; Wang, Hai-Hua; Wang, Lei; Wu, Jin-Hui

2018-05-01

We theoretically study the optically tunable gratings based on a L-type atomic medium using coherent population oscillations from the angle of reflection and transmission of the probe field. Adopting a standing-wave driving field, the refractive index of the medium as well as the absorption are periodically modified. Consequently, the Bragg scattering causes the effective reflection. We show that different intensities of the control field lead to three types of reflection profile which actually correspond to different absorption/amplification features of the medium. We present a detailed analyses about the influence of amplification on the reflection profile as well. The coherent population oscillation is robust to the dephasing effect, and such induced gratings could have promising applications in nonlinear optics and all-optical information processing.

Coherent transfer of orbital angular momentum to excitons by optical four-wave mixing.

PubMed

Ueno, Y; Toda, Y; Adachi, S; Morita, R; Tawara, T

2009-10-26

We demonstrate the coherent transfer of optical orbital angular momentum (OAM) to the center of mass momentum of excitons in semiconductor GaN using a four-wave mixing (FWM) process. When we apply the optical vortex (OV) as an excitation pulse, the diffracted FWM signal exhibits phase singularities that satisfy the OAM conservation law, which remain clear within the exciton dephasing time (approximately 1ps). We also demonstrate the arbitrary control of the topological charge in the output signal by changing the OAM of the input pulse. The results provide a way of controlling the optical OAM through carriers in solids. Moreover, the time evolution of the FWM with OAM leads to the study of the closed-loop carrier coherence in materials.

Coherent Pound-Drever-Hall technique for high resolution fiber optic strain sensor at very low light power

NASA Astrophysics Data System (ADS)

Wu, Mengxin; Liu, Qingwen; Chen, Jiageng; He, Zuyuan

2017-04-01

Pound-Drever-Hall (PDH) technique has been widely adopted for ultrahigh resolution fiber-optic sensors, but its performance degenerates seriously as the light power drops. To solve this problem, we developed a coherent PDH technique for weak optical signal detection, with which the signal-to-noise ratio (SNR) of demodulated PDH signal is dramatically improved. In the demonstrational experiments, a high resolution fiber-optic sensor using the proposed technique is realized, and n"-order strain resolution at a low light power down to -43 dBm is achieved, which is about 15 dB lower compared with classical PDH technique. The proposed coherent PDH technique has great potentials in longer distance and larger scale sensor networks.

Practical somewhat-secure quantum somewhat-homomorphic encryption with coherent states

NASA Astrophysics Data System (ADS)

Tan, Si-Hui; Ouyang, Yingkai; Rohde, Peter P.

2018-04-01

We present a scheme for implementing homomorphic encryption on coherent states encoded using phase-shift keys. The encryption operations require only rotations in phase space, which commute with computations in the code space performed via passive linear optics, and with generalized nonlinear phase operations that are polynomials of the photon-number operator in the code space. This encoding scheme can thus be applied to any computation with coherent-state inputs, and the computation proceeds via a combination of passive linear optics and generalized nonlinear phase operations. An example of such a computation is matrix multiplication, whereby a vector representing coherent-state amplitudes is multiplied by a matrix representing a linear optics network, yielding a new vector of coherent-state amplitudes. By finding an orthogonal partitioning of the support of our encoded states, we quantify the security of our scheme via the indistinguishability of the encrypted code words. While we focus on coherent-state encodings, we expect that this phase-key encoding technique could apply to any continuous-variable computation scheme where the phase-shift operator commutes with the computation.

Simultaneous Bistability of a Qubit and Resonator in Circuit Quantum Electrodynamics

NASA Astrophysics Data System (ADS)

Mavrogordatos, Th. K.; Tancredi, G.; Elliott, M.; Peterer, M. J.; Patterson, A.; Rahamim, J.; Leek, P. J.; Ginossar, E.; Szymańska, M. H.

2017-01-01

We explore the joint activated dynamics exhibited by two quantum degrees of freedom: a cavity mode oscillator which is strongly coupled to a superconducting qubit in the strongly coherently driven dispersive regime. Dynamical simulations and complementary measurements show a range of parameters where both the cavity and the qubit exhibit sudden simultaneous switching between two metastable states. This manifests in ensemble averaged amplitudes of both the cavity and qubit exhibiting a partial coherent cancellation. Transmission measurements of driven microwave cavities coupled to transmon qubits show detailed features which agree with the theory in the regime of simultaneous switching.

Bendable Focusing X-Ray Optics for the ALS and the LCLS/FEL: Design, Metrology, and Performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yashchuk, V. V.; Yuan, S.; Baker, S.

2010-06-02

We review the recent development of bendable x-ray optics used for focusing of beams of soft and hard x-rays at the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory and at the Linac Coherent Light Source (LCLS) x-ray free electron laser (FEL) at the Stanford Linear Accelerator Center (SLAC) National Accelerator Laboratory. For simultaneous focusing in the tangential and sagittal directions, two elliptically cylindrical reflecting elements, a Kirkpatrick-Baez (KB) pair, are used. Because fabrication of elliptical surfaces is complicated, the cost of directly fabricated tangential elliptical cylinders is often prohibitive. Moreover, such optics cannot be easily readjusted for usemore » in multiple, different experimental arrangements, e.g. at different focal distances. This is in contrast to flat optics that are simpler to manufacture and easier to measure by conventional interferometry. The tangential figure of a flat substrate is changed by placing torques (couples) at each end. Depending on the applied couples, one can tune the shape close to a desired tangential cylinder, ellipse or parabola. We review the nature of the bending, requirements and approaches to the mechanical design, describe original optical and at-wavelength techniques for optimal tuning of bendable optics and alignment on the beamline, and provide beamline performance of the bendable optics used for sub-micro and nano focusing of soft x-rays.« less

Comment on "Optical-fiber-based Mueller optical coherence tomography".

PubMed

Park, B Hyle; Pierce, Mark C; de Boer, Johannes F

2004-12-15

We comment on the recent Letter by Jiao et al. [Opt. Lett. 28, 1206 (2003)] in which a polarization-sensitive optical coherence tomography system was presented. Interrogating a sample with two orthogonal incident polarization states cannot always recover birefringence correctly. A previously presented fiber-based polarization-sensitive system was inaccurately characterized, and its method of eliminating the polarization distortion caused by single-mode optical fiber was presented earlier by Saxer et al. [Opt. Lett. 25, 1355 (2000)].

Multimodal Imaging of the Normal Eye.

PubMed

Kawali, Ankush; Pichi, Francesco; Avadhani, Kavitha; Invernizzi, Alessandro; Hashimoto, Yuki; Mahendradas, Padmamalini

2017-10-01

Multimodal imaging is the concept of "bundling" images obtained from various imaging modalities, viz., fundus photograph, fundus autofluorescence imaging, infrared (IR) imaging, simultaneous fluorescein and indocyanine angiography, optical coherence tomography (OCT), and, more recently, OCT angiography. Each modality has its pros and cons as well as its limitations. Combination of multiple imaging techniques will overcome their individual weaknesses and give a comprehensive picture. Such approach helps in accurate localization of a lesion and understanding the pathology in posterior segment. It is important to know imaging of normal eye before one starts evaluating pathology. This article describes multimodal imaging modalities in detail and discusses healthy eye features as seen on various imaging modalities mentioned above.

Witnessing effective entanglement over a 2 km fiber channel.

PubMed

Wittmann, Christoffer; Fürst, Josef; Wiechers, Carlos; Elser, Dominique; Häseler, Hauke; Lütkenhaus, Norbert; Leuchs, Gerd

2010-03-01

We present a fiber-based continuous-variable quantum key distribution system. In the scheme, a quantum signal of two non-orthogonal weak optical coherent states is sent through a fiber-based quantum channel. The receiver simultaneously measures conjugate quadratures of the light using two homodyne detectors. From the measured Q-function of the transmitted signal, we estimate the attenuation and the excess noise caused by the channel. The estimated excess noise originating from the channel and the channel attenuation including the quantum efficiency of the detection setup is investigated with respect to the detection of effective entanglement. The local oscillator is considered in the verification. We witness effective entanglement with a channel length of up to 2 km.

CAPILLARY NETWORK ANOMALIES IN BRANCH RETINAL VEIN OCCLUSION ON OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY.

PubMed

Rispoli, Marco; Savastano, Maria Cristina; Lumbroso, Bruno

2015-11-01

To analyze the foveal microvasculature features in eyes with branch retinal vein occlusion (BRVO) using optical coherence tomography angiography based on split spectrum amplitude decorrelation angiography technology. A total of 10 BRVO eyes (mean age 64.2 ± 8.02 range between 52 years and 76 years) were evaluated by optical coherence tomography angiography (XR-Avanti; Optovue). The macular angiography scan protocol covered a 3 mm × 3 mm area. The focus of angiography analysis were two retinal layers: superficial vascular network and deep vascular network. The following vascular morphological congestion parameters were assessed in the vein occlusion area in both the superficial and deep networks: foveal avascular zone enlargement, capillary non-perfusion occurrence, microvascular abnormalities appearance, and vascular congestion signs. Image analyses were performed by 2 masked observers and interobserver agreement of image analyses was 0.90 (κ = 0.225, P < 0.01). In both superficial and deep network of BRVO, a decrease in capillary density with foveal avascular zone enlargement, capillary non-perfusion occurrence, and microvascular abnormalities appearance was observed (P < 0.01). The deep network showed the main vascular congestion at the boundary between healthy and nonperfused retina. Optical coherence tomography angiography in BRVO allows to detect foveal avascular zone enlargement, capillary nonperfusion, microvascular abnormalities, and vascular congestion signs both in the superficial and deep capillary network in all eyes. Optical coherence tomography angiography technology is a potential clinical tool for BRVO diagnosis and follow-up, providing stratigraphic vascular details that have not been previously observed by standard fluorescein angiography. The normal retinal vascular nets and areas of nonperfusion and congestion can be identified at various retinal levels. Optical coherence tomography angiography provides noninvasive images of the retinal capillaries and vascular networks.

Image routing via atomic spin coherence

PubMed Central

Wang, Lei; Sun, Jia-Xiang; Luo, Meng-Xi; Sun, Yuan-Hang; Wang, Xiao-Xiao; Chen, Yi; Kang, Zhi-Hui; Wang, Hai-Hua; Wu, Jin-Hui; Gao, Jin-Yue

2015-01-01

Coherent storage of optical image in a coherently-driven medium is a promising method with possible applications in many fields. In this work, we experimentally report a controllable spatial-frequency routing of image via atomic spin coherence in a solid-state medium driven by electromagnetically induced transparency (EIT). Under the EIT-based light-storage regime, a transverse spatial image carried by the probe field is stored into atomic spin coherence. By manipulating the frequency and spatial propagation direction of the read control field, the stored image is transferred into a new spatial-frequency channel. When two read control fields are used to retrieve the stored information, the image information is converted into a superposition of two spatial-frequency modes. Through this technique, the image is manipulated coherently and all-optically in a controlled fashion. PMID:26658846

Demonstration of two-qubit algorithms with a superconducting quantum processor.

PubMed

DiCarlo, L; Chow, J M; Gambetta, J M; Bishop, Lev S; Johnson, B R; Schuster, D I; Majer, J; Blais, A; Frunzio, L; Girvin, S M; Schoelkopf, R J

2009-07-09

Quantum computers, which harness the superposition and entanglement of physical states, could outperform their classical counterparts in solving problems with technological impact-such as factoring large numbers and searching databases. A quantum processor executes algorithms by applying a programmable sequence of gates to an initialized register of qubits, which coherently evolves into a final state containing the result of the computation. Building a quantum processor is challenging because of the need to meet simultaneously requirements that are in conflict: state preparation, long coherence times, universal gate operations and qubit readout. Processors based on a few qubits have been demonstrated using nuclear magnetic resonance, cold ion trap and optical systems, but a solid-state realization has remained an outstanding challenge. Here we demonstrate a two-qubit superconducting processor and the implementation of the Grover search and Deutsch-Jozsa quantum algorithms. We use a two-qubit interaction, tunable in strength by two orders of magnitude on nanosecond timescales, which is mediated by a cavity bus in a circuit quantum electrodynamics architecture. This interaction allows the generation of highly entangled states with concurrence up to 94 per cent. Although this processor constitutes an important step in quantum computing with integrated circuits, continuing efforts to increase qubit coherence times, gate performance and register size will be required to fulfil the promise of a scalable technology.

Imaging separation of neuronal from vascular effects of cocaine on rat cortical brain in vivo

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuan, Z.; Du, C.; Yuan, Z.

MRI techniques to study brain function assume coupling between neuronal activity, metabolism and flow. However, recent evidence of physiological uncoupling between neuronal and cerebrovascular events highlights the need for methods to simultaneously measure these three properties. We report a multimodality optical approach that integrates dual-wavelength laser speckle imaging (measures changes in blood flow, blood volume and hemoglobin oxygenation), digital-frequency-ramping optical coherence tomography (images quantitative 3D vascular network) and Rhod2 fluorescence (images intracellular calcium for measure of neuronal activity) at high spatiotemporal resolutions (30 {micro}m, 10 Hz) and over a large field of view (3 x 5 mm{sup 2}). We applymore » it to assess cocaine's effects in rat cortical brain and show an immediate decrease 3.5 {+-} 0.9 min, phase (1) in the oxygen content of hemoglobin and the cerebral blood flow followed by an overshoot 7.1 {+-} 0.2 min, phase (2) lasting over 20 min whereas Ca{sup 2+} increased immediately (peaked at t = 4.1 {+-} 0.4 min) and remained elevated. This enabled us to identify a delay (2.9 {+-} 0.5 min) between peak neuronal and vascular responses in phase 2. The ability of this multimodality optical approach for simultaneous imaging at high spatiotemporal resolutions permits us to distinguish the vascular versus cellular changes of the brain, thus complimenting other neuroimaging modalities for brain functional studies (e. g., PET, fMRI).« less

Optical superheterodyne receiver.

NASA Technical Reports Server (NTRS)

Duval, K.; Lang, K.; Lucy, R. F.; Peters, C. J.

1967-01-01

Optical communication experiments to compare coherent and noncoherent optical detection fading characteristics in different weather conditions, using laser transmitter and optical superheterodyne receiver

Enhanced optical clearing of skin in vivo and optical coherence tomography in-depth imaging

NASA Astrophysics Data System (ADS)

Wen, Xiang; Jacques, Steven L.; Tuchin, Valery V.; Zhu, Dan

2012-06-01

The strong optical scattering of skin tissue makes it very difficult for optical coherence tomography (OCT) to achieve deep imaging in skin. Significant optical clearing of in vivo rat skin sites was achieved within 15 min by topical application of an optical clearing agent PEG-400, a chemical enhancer (thiazone or propanediol), and physical massage. Only when all three components were applied together could a 15 min treatment achieve a three fold increase in the OCT reflectance from a 300 μm depth and 31% enhancement in image depth Zthreshold.

Quantitative assessment of hyaline cartilage elasticity during optical clearing using optical coherence elastography

NASA Astrophysics Data System (ADS)

Liu, Chih-Hao; Singh, Manmohan; Li, Jiasong; Han, Zhaolong; Wu, Chen; Wang, Shang; Idugboe, Rita; Raghunathan, Raksha; Zakharov, Valery P.; Sobol, Emil N.; Tuchin, Valery V.; Twa, Michael; Larin, Kirill V.

2015-03-01

We report the first study on using optical coherence elastography (OCE) to quantitatively monitor the elasticity change of the hyaline cartilage during the optical clearing administrated by glucose solution. The measurement of the elasticity is verified using uniaxial compression test, demonstrating the feasibility of using OCE to quantify the Young's modulus of the cartilage tissue. As the results, we found that the stiffness of the hyaline cartilage increases during the optical clearing of the tissue. This study might be potentially useful for the early detection of osteoarthritis disease.

Fabrication of Fiber Optic Grating Apparatus and Method

NASA Technical Reports Server (NTRS)

Wang, Ying (Inventor); Sharma, Anup (Inventor); Grant, Joseph (Inventor)

2005-01-01

An apparatus and method for forming a Bragg grating on an optical fiber using a phase mask to diffract a beam of coherent energy and a lens combined with a pair of mirrors to produce two symmetrical virtual point sources of coherent energy in the plane of the optical fiber. The two virtual light sources produce an interference pattern along the optical fiber. In a further embodiment, the period of the pattern and therefore the Bragg wavelength grating applied to the fiber is varied with the position of the optical fiber relative the lens.

Elliptical As2Se3 filled core ultra-high-nonlinearity and polarization-maintaining photonic crystal fiber with double hexagonal lattice cladding

NASA Astrophysics Data System (ADS)

Li, Feng; He, Menghui; Zhang, Xuedian; Chang, Min; Wu, Zhizheng; Liu, Zheng; Chen, Hua

2018-05-01

A high birefringence and ultra-high nonlinearity photonic crystal fiber (PCF) is proposed, which is composed of an elliptical As2Se3-doped core and an inner cladding with hexagonal lattice. Optical properties of the PCF are simulated by the full-vector finite element method. The simulation results show that the high birefringence of ∼0.33, ultra-high-nonlinearity coefficient of 300757 W-1km-1 and the low confinement loss can be achieved in the proposed PCF simultaneously at the wavelength of 1.55 μm. Furthermore, by comparison with the other two materials (80PbO•20Ga2O3, As2S3) filled in the core, the As2Se3-doped PCF is found to have the highest birefringence and nonlinearity due to its higher refractive index and nonlinear refractive index. The flattened dispersion feature, as well as the low confinement loss of the proposed PCF structure make it suitable as a wide range of applications, such as the coherent optical communications, polarization-maintaining and nonlinear optics, etc.

Direct-phase and amplitude digitalization based on free-space interferometry

NASA Astrophysics Data System (ADS)

Kleiner, Vladimir; Rudnitsky, Arkady; Zalevsky, Zeev

2017-12-01

A novel ADC configuration that can be characterized as a photonic-domain flash analog-to-digital convertor operating based upon free-space interferometry is proposed and analysed. The structure can be used as the front-end of a coherent receiver as well as for other applications. Two configurations are considered: the first, ‘direct free-space interference’, allows simultaneous measuring of the optical phase and amplitude; the second, ‘extraction of the ac component of interference by means of pixel-by-pixel balanced photodetection’, allows only phase digitization but with significantly higher sensitivity. For both proposed configurations, we present Monte Carlo estimations of the performance limitations, due to optical noise and photo-current noise, at sampling rates of 60 giga-samples per second. In terms of bit resolution, we simulated multiple cases with growing complexity of up to 4 bits for the amplitude and up to 6 bits for the phase. The simulations show that the digitization errors in the optical domain can be reduced to levels close to the quantization noise limits. Preliminary experimental results validate the fundamentals of the proposed idea.

Simultaneous observations of electromagnetically induced transparency (EIT) and absorption (EIA) in a multi-level V-type system of 87Rb and theoretical simulation of the observed spectra using a multi-mode approach

NASA Astrophysics Data System (ADS)

Das, Bankim Chandra; Bhattacharyya, Dipankar; Das, Arpita; Chakrabarti, Shrabana; De, Sankar

2016-12-01

We report here simultaneous experimental observation of Electromagnetically Induced Transparency (EIT) and Electromagnetically Induced Absorption (EIA) in a multi-level V-type system in D2 transition of 87Rb, i.e., F =2 →F' with a strong pump and a weak probe beam. We studied the probe spectrum by locking the probe beam to the transition F =2 →F'=2 while the pump is scanned from F =2 →F' . EIA is observed for the open transition (F =2 →F'=2 ) whereas EIT is observed in the closed transition (F =2 →F'=3 ). Sub natural line-width is observed for the EIA. To simulate the observed spectra theoretically, Liouville equation for the three-level V-type system is solved analytically with a multi-mode approach for the density matrix elements. We assumed both the pump and the probe beams can couple the excited states. A multi-mode approach for the coherence terms facilitates the study of all the frequency contributions due to the pump and the probe fields. Since the terms contain higher harmonics of the pump and the probe frequencies, we expressed them in Fourier transformed forms. To simulate the probe spectrum, we have solved inhomogeneous difference equations for the coherence terms using the Green's function technique and continued fraction theory. The experimental line-widths of the EIT and the EIA are compared with our theoretical model. Our system can be useful in optical switching applications as it can be precisely tuned to render the medium opaque and transparent simultaneously.

Simultaneous observations of electromagnetically induced transparency (EIT) and absorption (EIA) in a multi-level V-type system of 87Rb and theoretical simulation of the observed spectra using a multi-mode approach.

PubMed

Das, Bankim Chandra; Bhattacharyya, Dipankar; Das, Arpita; Chakrabarti, Shrabana; De, Sankar

2016-12-14

We report here simultaneous experimental observation of Electromagnetically Induced Transparency (EIT) and Electromagnetically Induced Absorption (EIA) in a multi-level V-type system in D 2 transition of Rb87, i.e., F=2→F ' with a strong pump and a weak probe beam. We studied the probe spectrum by locking the probe beam to the transition F=2→F ' =2 while the pump is scanned from F=2→F ' . EIA is observed for the open transition (F=2→F ' =2) whereas EIT is observed in the closed transition (F=2→F ' =3). Sub natural line-width is observed for the EIA. To simulate the observed spectra theoretically, Liouville equation for the three-level V-type system is solved analytically with a multi-mode approach for the density matrix elements. We assumed both the pump and the probe beams can couple the excited states. A multi-mode approach for the coherence terms facilitates the study of all the frequency contributions due to the pump and the probe fields. Since the terms contain higher harmonics of the pump and the probe frequencies, we expressed them in Fourier transformed forms. To simulate the probe spectrum, we have solved inhomogeneous difference equations for the coherence terms using the Green's function technique and continued fraction theory. The experimental line-widths of the EIT and the EIA are compared with our theoretical model. Our system can be useful in optical switching applications as it can be precisely tuned to render the medium opaque and transparent simultaneously.

The Multi-Spectral Imaging Diagnostic on Alcator C-MOD and TCV

NASA Astrophysics Data System (ADS)

Linehan, B. L.; Mumgaard, R. T.; Duval, B. P.; Theiler, C. G.; TCV Team

2017-10-01

The Multi-Spectral Imaging (MSI) diagnostic is a new instrument that captures simultaneous spectrally filtered images from a common sight view while maintaining a large tendue and high spatial resolution. The system uses a polychromator layout where each image is sequentially filtered. This procedure yields a high transmission for each spectral channel with minimal vignetting and aberrations. A four-wavelength system was installed on Alcator C-Mod and then moved to TCV. The system uses industrial cameras to simultaneously image the divertor region at 95 frames per second at f/# 2.8 via a coherent fiber bundle (C-Mod) or a lens-based relay optic (TCV). The images are absolutely calibrated and spatially registered enabling accurate measurement of atomic line ratios and absolute line intensities. The images will be used to study divertor detachment by imaging impurities and Balmer series emissions. Furthermore, the large field of view and an ability to support many types of detectors opens the door for other novel approaches to optically measuring plasma with high temporal, spatial, and spectral resolution. Such measurements will allow for the study of Stark broadening and divertor turbulence. Here, we present the first measurements taken with this cavity imaging system. USDoE awards DE-FC02-99ER54512 and award DE-AC05-06OR23100, ORISE, administered by ORAU.

Correlation of morphological and molecular parameters for colon cancer

NASA Astrophysics Data System (ADS)

Yuan, Shuai; Roney, Celeste A.; Li, Qian; Jiang, James; Cable, Alex; Summers, Ronald M.; Chen, Yu

2010-02-01

Colorectal cancer (CRC) is the second leading cause of cancer death in the United States. There is great interest in studying the relationship among microstructures and molecular processes of colorectal cancer during its progression at early stages. In this study, we use our multi-modality optical system that could obtain co-registered optical coherence tomography (OCT) and fluorescence molecular imaging (FMI) images simultaneously to study CRC. The overexpressed carbohydrate α-L-fucose on the surfaces of polyps facilitates the bond of adenomatous polyps with UEA-1 and is used as biomarker. Tissue scattering coefficient derived from OCT axial scan is used as quantitative value of structural information. Both structural images from OCT and molecular images show spatial heterogeneity of tumors. Correlations between those values are analyzed and demonstrate that scattering coefficients are positively correlated with FMI signals in conjugated. In UEA-1 conjugated samples (8 polyps and 8 control regions), the correlation coefficient is ranged from 0.45 to 0.99. These findings indicate that the microstructure of polyps is changed gradually during cancer progression and the change is well correlated with certain molecular process. Our study demonstrated that multi-parametric imaging is able to simultaneously detect morphology and molecular information and it can enable spatially and temporally correlated studies of structure-function relationships during tumor progression.

Measurement accuracy of a stressed contact lens during its relaxation period

NASA Astrophysics Data System (ADS)

Compertore, David C.; Ignatovich, Filipp V.

2018-02-01

We examine the dioptric power and transmitted wavefront of a contact lens as it releases its handling stresses. Handling stresses are introduced as part of the contact lens loading process and are common across all contact lens measurement procedures and systems. The latest advances in vision correction require tighter quality control during the manufacturing of the contact lenses. The optical power of contact lenses is one of the critical characteristics for users. Power measurements are conducted in the hydrated state, where the lens is resting inside a solution-filled glass cuvette. In a typical approach, the contact lens must be subject to long settling times prior to any measurements. Alternatively, multiple measurements must be averaged. Apart from potential operator dependency of such approach, it is extremely time-consuming, and therefore it precludes higher rates of testing. Comprehensive knowledge about the settling process can be obtained by monitoring multiple parameters of the lens simultaneously. We have developed a system that combines co-aligned a Shack-Hartmann transmitted wavefront sensor and a time-domain low coherence interferometer to measure several optical and physical parameters (power, cylinder power, aberrations, center thickness, sagittal depth, and diameter) simultaneously. We monitor these parameters during the stress relaxation period and show correlations that can be used by manufacturers to devise methods for improved quality control procedures.

A comparison between using incoherent or coherent sources to align and test an adaptive optical telescope

NASA Technical Reports Server (NTRS)

Anderson, Richard

1994-01-01

The concept in the initial alignment of the segmented mirror adaptive optics telescope called the phased array mirror extendable large aperture telescope (Pamela) is to produce an optical transfer function (OTF) which closely approximates the diffraction limited value which would correspond to a system pupil function that is unity over the aperture and zero outside. There are differences in the theory of intensity measurements between coherent and incoherent radiation. As a result, some of the classical quantities which describe the performance of an optical system for incoherent radiation can not be defined for a coherent field. The most important quantity describing the quality of an optical system is the OTF and for a coherent source the OTF is not defined. Instead a coherent transfer function (CTF) is defined. The main conclusion of the paper is that an incoherent collimated source and not a collimated laser source is preferred to calibrate the Hartmann wavefront sensor (WFS) of an aligned adaptive optical system. A distant laser source can be used with minimum problems to correct the system for atmospheric turbulence. The collimation of the HeNe laser alignment source can be improved by using a very small pin hole in the spatial filter so only the central portion of the beam is transmitted and the beam from the filter is nearly constant in amplitude. The size of this pin hole will be limited by the sensitivity of the lateral effect diode (LEDD) elements.

Marginal adaptation of ceramic veneers investigated with en face optical coherence tomography

NASA Astrophysics Data System (ADS)

Sinescu, Cosmin; Negruţiu, Meda-Lavinia; Petrescu, Emanuela; Rominu, Mihai; Marcauteanu, Corina; Rominu, Roxana; Hughes, Michael; Bradu, Adrian; Dobre, George; Podoleanu, Adrian G.

2009-07-01

The aim of this study was to analyze the quality of marginal adaptation and gap width of Empress veneers using en-face optical coherence tomography. The results prove the necessity of investigating the marginal adaptation after each veneer bonding process.

Combined two-photon microscopy and optical coherence tomography using individually optimized sources

NASA Astrophysics Data System (ADS)

Jeong, Bosu; Lee, Byunghak; Jang, Min Seong; Nam, Hyoseok; Kim, Hae Koo; Yoon, Sang June; Doh, Junsang; Lee, Sang-Joon; Yang, Bo-Gie; Jang, Myoung Ho; Kim, Ki Hean

2011-03-01

Two-photon microscopy (TPM) and optical coherence tomography (OCT) are 3D tissue imaging techniques based on different contrast mechanisms. We developed a combined system of TPM and OCT to provide information of both imaging modalities for in-vivo tissue study. TPM and OCT were implemented by using separate light sources, a Ti-Sapphire laser and a wavelength-swept source centered at 1300 nm respectively, and scanners. Light from the two sources was combined for the simultaneous imaging of tissue samples. TPM provided molecular, cellular information of tissues in the region of a few hundred microns on one side at a sub-cellular resolution, and ran at approximately 40 frames per second. OCT provided structural information in the tissue region larger than TPM images at a sub-tenth micron resolution by using 0.1 numerical aperture. OCT had the field of view of 800 um × 800 um based on a 20x objective, the sensitivity of 97dB, and the imaging speed of 0.8 volumes per second. This combined system was tested with simple microsphere specimens, and then was applied to image the explanted intestine of a mouse model and the plant leaves. Morphology and micro-structures of the intestine villi and immune cells within the villi were shown in the intestine image, and chloroplasts and various microstructures of the maize leaves were visualized in 3D by the combined system.

In vivo imaging of the Drosophila Melanogaster heart using a novel optical coherence tomography microscope

NASA Astrophysics Data System (ADS)

Izatt, Susan D.; Choma, Michael A.; Israel, Steven; Wessells, Robert J.; Bodmer, Rolf; Izatt, Joseph A.

2005-03-01

Real time in vivo optical coherence tomography (OCT) imaging of the adult fruit fly Drosophila melanogaster heart using a newly designed OCT microscope allows accurate assessment of cardiac anatomy and function. D. melanogaster has been used extensively in genetic research for over a century, but in vivo evaluation of the heart has been limited by available imaging technology. The ability to assess phenotypic changes with micrometer-scale resolution noninvasively in genetic models such as D. melanogaster is needed in the advancing fields of developmental biology and genetics. We have developed a dedicated small animal OCT imaging system incorporating a state-of-the-art, real time OCT scanner integrated into a standard stereo zoom microscope which allows for simultaneous OCT and video imaging. System capabilities include A-scan, B-scan, and M-scan imaging as well as automated 3D volumetric acquisition and visualization. Transverse and sagittal B-mode scans of the four chambered D. melanogaster heart have been obtained with the OCT microscope and are consistent with detailed anatomical studies from the literature. Further analysis by M-mode scanning is currently under way to assess cardiac function as a function of age and sex by determination of shortening fraction and ejection fraction. These studies create control cardiac data on the wild type D. melanogaster, allowing subsequent evaluation of phenotypic cardiac changes in this model after regulated genetic mutation.

In vivo molecular imaging of colorectal cancer using quantum dots targeted to vascular endothelial growth factor receptor 2 and optical coherence tomography/laser-induced fluorescence dual-modality imaging

NASA Astrophysics Data System (ADS)

Carbary-Ganz, Jordan L.; Welge, Weston A.; Barton, Jennifer K.; Utzinger, Urs

2015-09-01

Optical coherence tomography/laser induced fluorescence (OCT/LIF) dual-modality imaging allows for minimally invasive, nondestructive endoscopic visualization of colorectal cancer in mice. This technology enables simultaneous longitudinal tracking of morphological (OCT) and biochemical (fluorescence) changes as colorectal cancer develops, compared to current methods of colorectal cancer screening in humans that rely on morphological changes alone. We have shown that QDot655 targeted to vascular endothelial growth factor receptor 2 (QD655-VEGFR2) can be applied to the colon of carcinogen-treated mice and provides significantly increased contrast between the diseased and undiseased tissue with high sensitivity and specificity ex vivo. QD655-VEGFR2 was used in a longitudinal in vivo study to investigate the ability to correlate fluorescence signal to tumor development. QD655-VEGFR2 was applied to the colon of azoxymethane (AOM-) or saline-treated control mice in vivo via lavage. OCT/LIF images of the distal colon were taken at five consecutive time points every three weeks after the final AOM injection. Difficulties in fully flushing unbound contrast agent from the colon led to variable background signal; however, a spatial correlation was found between tumors identified in OCT images, and high fluorescence intensity of the QD655 signal, demonstrating the ability to detect VEGFR2 expressing tumors in vivo.

Optical coherence tomography imaging of colonic crypts in a mouse model of colorectal cancer

NASA Astrophysics Data System (ADS)

Welge, Weston A.; Barton, Jennifer K.

2016-03-01

Aberrant crypt foci (ACF) are abnormal epithelial lesions that precede development of colonic polyps. As the earliest morphological change in the development of colorectal cancer, ACF is a highly studied phenomenon. The most common method of imaging ACF is chromoendoscopy using methylene blue as a contrast agent. Narrow- band imaging is a contrast-agent-free modality for imaging the colonic crypts. Optical coherence tomography (OCT) is an attractive alternative to chromoendoscopy and narrow-band imaging because it can resolve the crypt structure at sufficiently high sampling while simultaneously providing depth-resolved data. We imaged in vivo the distal 15 mm of colon in the azoxymethane (AOM) mouse model of colorectal cancer using a commercial swept-source OCT system and a miniature endoscope designed and built in-house. We present en face images of the colonic crypts and demonstrate that different patterns in healthy and adenoma tissue can be seen. These patterns correspond to those reported in the literature. We have previously demonstrated early detection of colon adenoma using OCT by detecting minute thickening of the mucosa. By combining mucosal thickness measurement with imaging of the crypt structure, OCT can be used to correlate ACF and adenoma development in space and time. These results suggest that OCT may be a superior imaging modality for studying the connection between ACF and colorectal cancer.

Development of an endoscopic fluorescence image-guided OCT probe for oral cancer detection

NASA Astrophysics Data System (ADS)

McNichols, Roger J.; Gowda, Ashok; Bell, Brent A.; Johnigan, Richard M.; Calhoun, Karen H.; Motamedi, Massoud

2001-06-01

Oral squamous cell carcinoma is a disease which progresses through a number of well-defined morphological and biochemical changes. Optical coherence tomography (OCT) is a rapidly-evolving, non-invasive imaging modality which allows detailed probing of subsurface tissue structures with resolution on the order of microns. While this technique offers tremendous potential as a diagnostic tool for detection and characterization of oral cancer, OCT imaging is presently associated with a field of view on the order of millimeters, and acquisition time on the order of seconds. Thus, OCT's utility as a rapid cancer screening technique is presently limited. On the other hand, imaging of tissue autofluorescence provides a very rapid, high-throughput method for cancer screening. However, while autofluorescence measures may be sensitive to cancer, they are often non- specific and lead to a large number of false positives. In the present work, we have developed a fluorescence image guided optical coherence tomographic (FIG-OCT) probe in which tissue autofluorescence images are simultaneously used to guide OCT image acquisition of suspicious regions in real time. We have begun pre-clinical pilot studies with this instrument in a DMBA-induced model of oral cancer in the hamster cheek pouch. Initial results indicate that the FIG- OCT approach shows promise as a rapid and effective tool for screening of oral cancer.

Atmospheric seeing measurements obtained with MISOLFA in the framework of the PICARD Mission

NASA Astrophysics Data System (ADS)

Ikhlef, R.; Corbard, T.; Irbah, A.; Morand, F.; Fodil, M.; Chauvineau, B.; Assus, P.; Renaud, C.; Meftah, M.; Abbaki, S.; Borgnino, J.; Cissé, E. M.; D'Almeida, E.; Hauchecorne, A.; Laclare, F.; Lesueur, P.; Lin, M.; Martin, F.; Poiet, G.; Rouzé, M.; Thuillier, G.; Ziad, A.

2012-09-01

PICARD is a space mission launched in June 2010 to study mainly the geometry of the Sun. The PICARD mission has a ground program consisting mostly in four instruments based at the Calern Observatory (Observatoire de la Côte d’Azur). They allow recording simultaneous solar images and various atmospheric data from ground. The ground instruments consist in the qualification model of the PICARD space instrument (SODISM II: Solar Diameter Imager and Surface Mapper), standard sun-photometers, a pyranometer for estimating a global sky quality index, and MISOLFA a generalized daytime seeing monitor. Indeed, astrometric observations of the Sun using ground-based telescopes need an accurate modeling of optical effects induced by atmospheric turbulence. MISOLFA is founded on the observation of Angle-of-Arrival (AA) fluctuations and allows us to analyze atmospheric turbulence optical effects on measurements performed by SODISM II. It gives estimations of the coherence parameters characterizing wave-fronts degraded by the atmospheric turbulence (Fried parameter r0, size of the isoplanatic patch, the spatial coherence outer scale L0 and atmospheric correlation times). We present in this paper simulations showing how the Fried parameter infered from MISOLFA records can be used to interpret radius measurements extracted from SODISM II images. We show an example of daily and monthly evolution of r0 and present its statistics over 2 years at Calern Observatory with a global mean value of 3.5cm.

Dual-wavelength multifrequency photothermal wave imaging combined with optical coherence tomography for macrophage and lipid detection in atherosclerotic plaques using gold nanoparticles

PubMed Central

Wang, Tianyi; Jacob Mancuso, J.; Sapozhnikova, Veronika; Dwelle, Jordan; Ma, Li L.; Willsey, Brian; Shams Kazmi, S. M.; Qiu, Jinze; Li, Xiankai; Asmis, Reto; Johnston, Keith P.; Feldman, Marc D.

2012-01-01

Abstract. The objective of this study was to assess the ability of combined photothermal wave (PTW) imaging and optical coherence tomography (OCT) to detect, and further characterize the distribution of macrophages (having taken up plasmonic gold nanorose as a contrast agent) and lipid deposits in atherosclerotic plaques. Aortas with atherosclerotic plaques were harvested from nine male New Zealand white rabbits divided into nanorose- and saline-injected groups and were imaged by dual-wavelength (800 and 1210 nm) multifrequency (0.1, 1 and 4 Hz) PTW imaging in combination with OCT. Amplitude PTW images suggest that lateral and depth distribution of nanorose-loaded macrophages (confirmed by two-photon luminescence microscopy and RAM-11 macrophage stain) and lipid deposits can be identified at selected modulation frequencies. Radiometric temperature increase and modulation amplitude of superficial nanoroses in response to 4 Hz laser irradiation (800 nm) were significantly higher than native plaque (P<0.001). Amplitude PTW images (4 Hz) were merged into a coregistered OCT image, suggesting that superficial nanorose-loaded macrophages are distributed at shoulders on the upstream side of atherosclerotic plaques (P<0.001) at edges of lipid deposits. Results suggest that combined PTW-OCT imaging can simultaneously reveal plaque structure and composition, permitting characterization of nanorose-loaded macrophages and lipid deposits in atherosclerotic plaques. PMID:22502567