Selection and amplification of a single optical frequency comb mode for laser cooling of the strontium atoms in an optical clock

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

Liu, Hui; School of Physics, University of Chinese Academy of Sciences, Beijing 100049; Yin, Mojuan

2015-10-12

In this paper, we report on the active filtering and amplification of a single mode from an optical femtosecond laser comb with mode spacing of 250 MHz by optical injection of two external-cavity diode lasers operating in cascade to build a narrow linewidth laser for laser cooling of the strontium atoms in an optical lattice clock. Despite the low injection of individual comb mode of approximately 50 nW, a single comb line at 689 nm could be filtered and amplified to reach as high as 10 mW with 37 dB side mode suppression and a linewidth of 240 Hz. This method could be appliedmore » over a broad spectral band to build narrow linewidth lasers for various applications.« less

Nonlinear dynamics of solitary and optically injected two-element laser arrays with four different waveguide structures: a numerical study.

PubMed

Li, Nianqiang; Susanto, H; Cemlyn, B R; Henning, I D; Adams, M J

2018-02-19

We study the nonlinear dynamics of solitary and optically injected two-element laser arrays with a range of waveguide structures. The analysis is performed with a detailed direct numerical simulation, where high-resolution dynamic maps are generated to identify regions of dynamic instability in the parameter space of interest. Our combined one- and two-parameter bifurcation analysis uncovers globally diverse dynamical regimes (steady-state, oscillation, and chaos) in the solitary laser arrays, which are greatly influenced by static design waveguiding structures, the amplitude-phase coupling factor of the electric field, i.e. the linewidth-enhancement factor, as well as the control parameter, e.g. the pump rate. When external optical injection is introduced to one element of the arrays, we show that the whole system can be either injection-locked simultaneously or display rich, different dynamics outside the locking region. The effect of optical injection is to significantly modify the nature and the regions of nonlinear dynamics from those found in the solitary case. We also show similarities and differences (asymmetry) between the oscillation amplitude of the two elements of the array in specific well-defined regions, which hold for all the waveguiding structures considered. Our findings pave the way to a better understanding of dynamic instability in large arrays of lasers.

Coherently wavelength injection-locking a 600-μm long cavity colorless laser diode for 16-QAM OFDM at 12 Gbit/s over 25-km SMF.

PubMed

Li, Yi-Cheng; Chi, Yu-Chieh; Cheng, Min-Chi; Lu, I-Cheng; Chen, Jason; Lin, Gong-Ru

2013-07-15

The coherent injection-locking and directly modulation of a long-cavity colorless laser diode with 1% end-facet reflectance and weak-resonant longitudinal modes is employed as an universal optical transmitter to demonstrated for optical 16-QAM OFDM transmission at 12 Gbit/s over 25 km in a DWDM-PON system. The optimized bias current of 30 mA (~1.5Ith) with corresponding extinction ratio (ER) of 6 dB and the external injection power of -9 dBm is (are) required for such a wavelength-locked universal transmitter to carry the 16-QAM and 122-subcarrier formatted OFDM and data-stream. By increasing external injection-locking from -9 dBm to 0 dBm, the peak-to-peak chirp of the OFDM data stream reduces from 7.7 to 5.4 GHz. The side mode suppression ratio (SMSR) of up to 50 dB is achieved with wider detuning range between -0.5 nm to 2.0 nm under an injection power of 0 dBm. By modulating such a colorless laser diode with an OFDM data stream of 122 subcarriers at a central carrier frequency of 1.5625 GHz and a total bandwidth of 3 GHz, the transmission data rate of up to 12 Gbit/s in standard single-mode fiber over 25 km is demonstrated to achieve an error vector magnitude (EVM) of 5.435%. Such a universal colorless DWDM-PON transmitter can deliver the optical OFDM data-stream at 12 Gbit/s QAM-OFDM data after 25-km transmission with a receiving power sensitivity of -7 dBm at BER of 3.6 × 10(-7) when pre-amplifying the OFDM data by 5 dB.

The LED and fiber based calibration system for the photomultiplier array of SNO+

NASA Astrophysics Data System (ADS)

Seabra, L.; Alves, R.; Andringa, S.; Bradbury, S.; Carvalho, J.; Clark, K.; Coulter, I.; Descamps, F.; Falk, L.; Gurriana, L.; Kraus, C.; Lefeuvre, G.; Maio, A.; Maneira, J.; Mottram, M.; Peeters, S.; Rose, J.; Sinclair, J.; Skensved, P.; Waterfield, J.; White, R.; Wilson, J.; SNO+ Collaboration

2015-02-01

A new external LED/fiber light injection calibration system was designed for the calibration and monitoring of the photomultiplier array of the SNO+ experiment at SNOLAB. The goal of the calibration system is to allow an accurate and regular measurement of the photomultiplier array's performance, while minimizing the risk of radioactivity ingress. The choice in SNO+ was to use a set of optical fiber cables to convey into the detector the light pulses produced by external LEDs. The quality control was carried out using a modified test bench that was used in QC of optical fibers for TileCal/ATLAS. The optical fibers were characterized for transmission, timing and angular dispersions. This article describes the setups used for the characterization and quality control of the system based on LEDs and optical fibers and their results.

High-accuracy self-mixing interferometer based on multiple reflections using a simple external reflecting mirror

NASA Astrophysics Data System (ADS)

Wang, Xiu-lin; Wei, Zheng; Wang, Rui; Huang, Wen-cai

2018-05-01

A self-mixing interferometer (SMI) with resolution twenty times higher than that of a conventional interferometer is developed by multiple reflections. Only by employing a simple external reflecting mirror, the multiple-pass optical configuration can be constructed. The advantage of the configuration is simple and easy to make the light re-injected back into the laser cavity. Theoretical analysis shows that the resolution of measurement is scalable by adjusting the number of reflections. The experiment shows that the proposed method has the optical resolution of approximate λ/40. The influence of displacement sensitivity gain ( G) is further analyzed and discussed in practical experiments.

Demonstration of L-band DP-QPSK transmission over FSO and fiber channels employing InAs/InP quantum-dash laser source

NASA Astrophysics Data System (ADS)

Shemis, M. A.; Khan, M. T. A.; Alkhazraji, E.; Ragheb, A. M.; Esmail, M. A.; Fathallah, H.; Qureshi, K. K.; Alshebeili, S.; Khan, M. Z. M.

2018-03-01

The next generation of optical access communication networks that support 100 Gbps and beyond, require advances in modulation schemes, spectrum utilization, new transmission bands, and efficient devices, particularly laser diodes. In this paper, we investigated the viability of new-class of InAs/InP Quantum-dash laser diode (Qdash-LD) exhibiting multiple longitudinal light modes in the L-band to carry high-speed data rate for access network applications. We exploited external and self injection-locking techniques on Qdash-LD to generate large number of stable and tunable locked modes, and compared them. To stem the capability of each locked mode as a potential subcarrier, data transmission is carried out over two mediums; single mode fiber (SMF) and free space optics (FSO) to emulate real deployment scenarios of optical networks. The results showed that with external-injection locking (EIL), an error-free transmission of 100 Gbps dual polarization quadrature phase shift keying (DP-QPSK) signal is demonstrated over 10 km SMF and 4 m indoor FSO channels, with capability of reaching up to 128 Gbps, demonstrated under back-to-back (BTB) configuration. On the other hand, using self-injection locking (SIL) scheme, a successful data transmission of 64 Gbps and 128 Gbps DP-QPSK signal over 20 km SMF and 10 m indoor FSO links, respectively, is achieved.

External control of semiconductor nanostructure lasers

NASA Astrophysics Data System (ADS)

Naderi, Nader A.

2011-12-01

Novel semiconductor nanostructure laser diodes such as quantum-dot and quantum-dash are key optoelectronic candidates for many applications such as data transmitters in ultra fast optical communications. This is mainly due to their unique carrier dynamics compared to conventional quantum-well lasers that enables their potential for high differential gain and modified linewidth enhancement factor. However, there are known intrinsic limitations associated with semiconductor laser dynamics that can hinder the performance including the mode stability, spectral linewidth, and direct modulation capabilities. One possible method to overcome these limitations is through the use of external control techniques. The electrical and/or optical external perturbations can be implemented to improve the parameters associated with the intrinsic laser's dynamics, such as threshold gain, damping rate, spectral linewidth, and mode selectivity. In this dissertation, studies on the impact of external control techniques through optical injection-locking, optical feedback and asymmetric current bias control on the overall performance of the nanostructure lasers were conducted in order to understand the associated intrinsic device limitations and to develop strategies for controlling the underlying dynamics to improve laser performance. In turn, the findings of this work can act as a guideline for making high performance nanostructure lasers for future ultra fast data transmitters in long-haul optical communication systems, and some can provide an insight into making a compact and low-cost terahertz optical source for future implementation in monolithic millimeter-wave integrated circuits.

Optical gain tuning within IR region in type-II In0.5Ga0.5As0.8P0.2/GaAs0.5Sb0.5 nano-scale heterostructure under external uniaxial strain

NASA Astrophysics Data System (ADS)

Singh, A. K.; Rathi, Amit; Riyaj, Md.; Bhardwaj, Garima; Alvi, P. A.

2017-11-01

Quaternary and ternary alloy semiconductors offer an extra degree of flexibility in terms of bandgap tuning. Modifications in the wave functions and alterations in optical transitions in quaternary and ternary QW (quantum well) heterostructures due to external uniaxial strain provide valuable insights on the characteristics of the heterostructure. This paper reports the optical gain in strained InGaAsP/GaAsSb type-II QW heterostructure (well width = 20 Å) under external uniaxial strain at room temperature (300 K). The entire heterostructure is supposed to be grown on InP substrate pseudomorphically. Band structure, wave functions, energy dispersion and momentum matrix elements of the heterostructure have been computed. 6 × 6 diagonalised k → ·p → Hamiltonian matrix of the system is evaluated and Luttinger-Kohn model has been applied for the band structure and wavefunction calculations. TE mode optical gain spectrum in the QW-heterostructure under uniaxial strain along [110] is calculated. Optical gain of the heterostructure as a function of 2D carrier density and temperature variation is investigated. The variation of the peak optical gain as a function of As and Sb fractions in InGaAsP as a barrier and GaAsSb as a well respectively is exhibited. For a charge carrier injection of 5 ×1012 /cm2 , the TE optical gain is 3952 cm-1 at room temperature under no external uniaxial strain. Significant increase in TE mode optical gain is observed under high external uniaxial strain (1, 5 and 10 GPa) along [110] within IR (Infrared region) region.

Intra-Cavity Total Reflection For High Sensitivity Measurement Of Optical Properties

DOEpatents

Pipino, Andrew Charles Rule

1999-11-16

An optical cavity resonator device is provided for conducting sensitive murement of optical absorption by matter in any state with diffraction-limited spatial resolution through utilization of total internal reflection within a high-Q (high quality, low loss) optical cavity. Intracavity total reflection generates an evanescent wave that decays exponentially in space at a point external to the cavity, thereby providing a localized region where absorbing materials can be sensitively probed through alteration of the Q-factor of the otherwise isolated cavity. When a laser pulse is injected into the cavity and passes through the evanescent state, an amplitude loss resulting from absorption is incurred that reduces the lifetime of the pulse in the cavity. By monitoring the decay of the injected pulse, the absorption coefficient of manner within the evanescent wave region is accurately obtained from the decay time measurement.

Intra-Cavity Total Reflection For High Sensitivity Measurement Of Optical Properties

DOEpatents

Pipino, Andrew C. R.; Hudgens, Jeffrey W.

1999-08-24

An optical cavity resonator device is provided for conducting sensitive murement of optical absorption by matter in any state with diffraction-limited spatial resolution through utilization of total internal reflection within a high-Q (high quality, low loss) optical cavity. Intracavity total reflection generates an evanescent wave that decays exponentially in space at a point external to the cavity, thereby providing a localized region where absorbing materials can be sensitively probed through alteration of the Q-factor of the otherwise isolated cavity. When a laser pulse is injected into the cavity and passes through the evanescent state, an amplitude loss resulting from absorption is incurred that reduces the lifetime of the pulse in the cavity. By monitoring the decay of the injected pulse, the absorption coefficient of manner within the evanescent wave region is accurately obtained from the decay time measurement.

Wideband and high-gain frequency stabilization of a 100-W injection-locked Nd:YAG laser for second-generation gravitational wave detectors.

PubMed

Ohmae, Noriaki; Moriwaki, Shigenori; Mio, Norikatsu

2010-07-01

Second-generation gravitational wave detectors require a highly stable laser with an output power greater than 100 W to attain their target sensitivity. We have developed a frequency stabilization system for a 100-W injection-locked Nd:YAG (yttrium aluminum garnet) laser. By placing an external wideband electro-optic modulator used as a fast-frequency actuator in the optical path of the slave output, we can circumvent a phase delay in the frequency control loop originating from the pole of an injection-locked slave cavity. Thus, we have developed an electro-optic modulator made of a MgO-doped stoichiometric LiNbO(3) crystal. Using this modulator, we achieve a frequency control bandwidth of 800 kHz and a control gain of 180 dB at 1 kHz. These values satisfy the requirement for a laser frequency control loop in second-generation gravitational wave detectors.

Polarization and dynamical properties of VCSELs-based photonic neuron subject to optical pulse injection

NASA Astrophysics Data System (ADS)

Xiang, Shuiying; Wen, Aijun; Zhang, Hao; Li, Jiafu; Guo, Xingxing; Shang, Lei; Lin, Lin

2016-11-01

The polarization-resolved nonlinear dynamics of vertical-cavity surface-emitting lasers (VCSELs) subject to orthogonally polarized optical pulse injection are investigated numerically based on the spin flip model. By extensive numerical bifurcation analysis, the responses dynamics of photonic neuron based on VCSELs under the arrival of external stimuli of orthogonally polarized optical pulse injection are mainly discussed. It is found that, several neuron-like dynamics, such as phasic spiking of a single abrupt large amplitude pulse followed with or without subthreshold oscillation, and tonic spiking with multiple periodic pulses, are successfully reproduced in the numerical model of VCSELs. Besides, the effects of stimuli strength, pump current, frequency detuning, as well as the linewidth enhancement factor on the neuron-like response dynamics are examined carefully. The operating parameters ranges corresponding to different neuron-like dynamics are further identified. Thus, the numerical model and simulation results are very useful and interesting for the ultrafast brain-inspired neuromorphic photonics systems based on VCSELs.

Real-time needle guidance with photoacoustic and laser-generated ultrasound probes

NASA Astrophysics Data System (ADS)

Colchester, Richard J.; Mosse, Charles A.; Nikitichev, Daniil I.; Zhang, Edward Z.; West, Simeon; Beard, Paul C.; Papakonstantinou, Ioannis; Desjardins, Adrien E.

2015-03-01

Detection of tissue structures such as nerves and blood vessels is of critical importance during many needle-based minimally invasive procedures. For instance, unintentional injections into arteries can lead to strokes or cardiotoxicity during interventional pain management procedures that involve injections in the vicinity of nerves. Reliable detection with current external imaging systems remains elusive. Optical generation and reception of ultrasound allow for depth-resolved sensing and they can be performed with optical fibers that are positioned within needles used in clinical practice. The needle probe developed in this study comprised separate optical fibers for generating and receiving ultrasound. Photoacoustic generation of ultrasound was performed on the distal end face of an optical fiber by coating it with an optically absorbing material. Ultrasound reception was performed using a high-finesse Fabry-Pérot cavity. The sensor data was displayed as an M-mode image with a real-time interface. Imaging was performed on a biological tissue phantom.

New functionalities of potassium tantalate niobate deflectors enabled by the coexistence of pre-injected space charge and composition gradient

NASA Astrophysics Data System (ADS)

Zhu, Wenbin; Chao, Ju-Hung; Chen, Chang-Jiang; Campbell, Adrian L.; Henry, Michael G.; Yin, Stuart Shizhuo; Hoffman, Robert C.

2017-10-01

In most beam steering applications such as 3D printing and in vivo imaging, one of the essential challenges has been high-resolution high-speed multi-dimensional optical beam scanning. Although the pre-injected space charge controlled potassium tantalate niobate (KTN) deflectors can achieve speeds in the nanosecond regime, they deflect in only one dimension. In order to develop a high-resolution high-speed multi-dimensional KTN deflector, we studied the deflection behavior of KTN deflectors in the case of coexisting pre-injected space charge and composition gradient. We find that such coexistence can enable new functionalities of KTN crystal based electro-optic deflectors. When the direction of the composition gradient is parallel to the direction of the external electric field, the zero-deflection position can be shifted, which can reduce the internal electric field induced beam distortion, and thus enhance the resolution. When the direction of the composition gradient is perpendicular to the direction of the external electric field, two-dimensional beam scanning can be achieved by harnessing only one single piece of KTN crystal, which can result in a compact, high-speed two-dimensional deflector. Both theoretical analyses and experiments are conducted, which are consistent with each other. These new functionalities can expedite the usage of KTN deflection in many applications such as high-speed 3D printing, high-speed, high-resolution imaging, and free space broadband optical communication.

20-Gbps optical LiFi transport system.

PubMed

Ying, Cheng-Ling; Lu, Hai-Han; Li, Chung-Yi; Cheng, Chun-Jen; Peng, Peng-Chun; Ho, Wen-Jeng

2015-07-15

A 20-Gbps optical light-based WiFi (LiFi) transport system employing vertical-cavity surface-emitting laser (VCSEL) and external light injection technique with 16-quadrature amplitude modulation (QAM)-orthogonal frequency-division multiplexing (OFDM) modulating signal is proposed. Good bit error rate (BER) performance and clear constellation map are achieved in our proposed optical LiFi transport systems. An optical LiFi transport system, delivering 16-QAM-OFDM signal over a 6-m free-space link, with a data rate of 20 Gbps, is successfully demonstrated. Such a 20-Gbps optical LiFi transport system provides the advantage of a free-space communication link for high data rates, which can accelerate the visible laser light communication (VLLC) deployment.

Electrically-pumped, broad-area, single-mode photonic crystal lasers.

PubMed

Zhu, Lin; Chak, Philip; Poon, Joyce K S; DeRose, Guy A; Yariv, Amnon; Scherer, Axel

2007-05-14

Planar broad-area single-mode lasers, with modal widths of the order of tens of microns, are technologically important for high-power applications and improved coupling efficiency into optical fibers. They may also find new areas of applications in on-chip integration with devices that are of similar size scales, such as for spectroscopy in microfluidic chambers or optical signal processing with micro-electromechanical systems. An outstanding challenge is that broad-area lasers often require external means of control, such as injection-locking or a frequency/spatial filter to obtain single-mode operation. In this paper, we propose and demonstrate effective index-guided, large-area, edge-emitting photonic crystal lasers driven by pulsed electrical current injection at the optical telecommunication wavelength of 1550 nm. By suitable design of the photonic crystal lattice, our lasers operate in a single mode with a 1/e(2) modal width of 25 microm and a length of 600 microm.

Excess spontaneous emission in non-Hermitian optical systems. I. Laser amplifiers

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

Siegman, A.E.

1989-02-01

Petermann first predicted in 1979 the existence of an excess-spontaneous-emission factor in gain-guided semiconductor lasers. We show that an excess spontaneous emission of this type, and also a correlation between the spontaneous emission into different cavity modes, will in fact be present in all open-sided laser resonators or optical lens guides. These properties arise from the non-self-adjoint or non-power-orthogonal nature of the optical resonator modes. The spontaneous-emission rate is only slightly enhanced in stable-resonator or index-guided structures, but can become very much larger than normal in gain-guided or geometrically unstable structures. Optical resonators or lens guides that have an excessmore » noise emission necessarily also exhibit an ''excess initial-mode excitation factor'' for externally injected signals. As a result, the excess spontaneous emission can be balanced out and the usual quantum-noise limit recovered in laser amplifiers and in injection-seeded laser oscillators, but not in free-running laser oscillators.« less

Generation of flat wideband chaos with suppressed time delay signature by using optical time lens.

PubMed

Jiang, Ning; Wang, Chao; Xue, Chenpeng; Li, Guilan; Lin, Shuqing; Qiu, Kun

2017-06-26

We propose a flat wideband chaos generation scheme that shows excellent time delay signature suppression effect, by injecting the chaotic output of general external cavity semiconductor laser into an optical time lens module composed of a phase modulator and two dispersive units. The numerical results demonstrate that by properly setting the parameters of the driving signal of phase modulator and the accumulated dispersion of dispersive units, the relaxation oscillation in chaos can be eliminated, wideband chaos generation with an efficient bandwidth up to several tens of GHz can be achieved, and the RF spectrum of generated chaotic signal is nearly as flat as uniform distribution. Moreover, the periodicity of chaos induced by the external cavity modes can be simultaneously destructed by the optical time lens module, based on this the time delay signature can be completely suppressed.

Theoretical analysis of a new class of optical bistability due to noncoherent coupling within a twin-laser system

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

Kuszelewicz, R.; Oudar, J.L.

1987-04-01

A new class of optical bistable devices, relying on the mutual quenching of two identical lasers, is theoretically analyzed. Conditions for achieving adequate competition between an external injected beam and the intracavity field through a noncoherent coupling (NCC) are discussed. Steady-state and transient behaviours are analyzed and lead to fast electrical or optical switching ( <100 ps ) and low commutation energy ( <10 pH). High efficiency, compactness, and technological compatibility with other integrated devices are expected. In addition, the emissive properties of these devices should considerably simplify their use in cascaded configurations.

V-shaped resonators for addition of broad-area laser diode arrays

DOEpatents

Liu, Bo; Liu, Yun; Braiman, Yehuda Y.

2012-12-25

A system and method for addition of broad-area semiconductor laser diode arrays are described. The system can include an array of laser diodes, a V-shaped external cavity, and grating systems to provide feedback for phase-locking of the laser diode array. A V-shaped mirror used to couple the laser diode emissions along two optical paths can be a V-shaped prism mirror, a V-shaped stepped mirror or include multiple V-shaped micro-mirrors. The V-shaped external cavity can be a ring cavity. The system can include an external injection laser to further improve coherence and phase-locking.

Dual-pumped nondegenerate four-wave mixing in semiconductor laser with a built-in external cavity

NASA Astrophysics Data System (ADS)

Wu, Jian-Wei; Qiu, Qi; Hyub Won, Yong

2017-04-01

In this paper, a semiconductor laser system consisting of a conventional multimode Fabry-Pérot laser diode with a built-in external cavity is presented and demonstrated. More than two resonance modes, whose peak levels are significantly higher than other residual modes, are simultaneously supported and output by adjusting the bias current and operating temperature of the active region. Based on this device, dual-pumped nondegenerate four-wave mixing—in which two pump waves and a single signal wave are simultaneously fed into the laser, and the injection power and wavelength of the injected pump and signal waves are changed—is observed and discussed thoroughly. The results show that while the wavelengths of pump wave A and signal wave S are kept constant, the other pump wave B jumps from about 1535 nm to 1578 nm, generating conversion signals with changed wavelengths. The achieved conversion bandwidth between the primary signal and the converted signal waves is broadly tunable in the range of several terahertz frequencies. Both the conversion efficiency and optical signal-to-noise ratio of the newly generated conversion signals are adopted to evaluate the performance of the proposed four-wave mixing process, and are strongly dependent on the wavelength and power of the injected waves. Here, the attained maximum conversion efficiency and optical signal-to-noise ratio are close to -22 dB and 15 dB, respectively.

Phase compensation with fiber optic surface profile acquisition and reconstruction system

NASA Astrophysics Data System (ADS)

Bo, En; Duan, Fajie; Feng, Fan; Lv, Changrong; Xiao, Fu; Huang, Tingting

2015-02-01

A fiber-optic sinusoidal phase modulating (SPM) interferometer was proposed for the acquisition and reconstruction of three-dimensional (3-D) surface profile. Sinusoidal phase modulation was induced by controlling the injection current of light source. The surface profile was constructed on the basis of fringe projection. Fringe patterns are vulnerable to external disturbances such as mechanical vibration and temperature fluctuation, which cause phase drift in the interference signal and decrease measuring accuracy. A closed-loop feedback phase compensation system was built. In the subsystem, the initial phase of the interference signal, which was caused by the initial optical path difference between interference arms, could be demodulated using phase generated carrier (PGC) method and counted out using coordinated rotation digital computer (CORDIC) , then a compensation voltage was generated for the PZT driver. The bias value of external disturbances superimposed on fringe patterns could be reduced to about 50 mrad, and the phase stability for interference fringes was less than 6 mrad. The feasibility for real-time profile measurement has been verified.

Optical Imaging of Ionizing Radiation from Clinical Sources

PubMed Central

Shaffer, Travis M.; Drain, Charles Michael

2016-01-01

Nuclear medicine uses ionizing radiation for both in vivo diagnosis and therapy. Ionizing radiation comes from a variety of sources, including x-rays, beam therapy, brachytherapy, and various injected radionuclides. Although PET and SPECT remain clinical mainstays, optical readouts of ionizing radiation offer numerous benefits and complement these standard techniques. Furthermore, for ionizing radiation sources that cannot be imaged using these standard techniques, optical imaging offers a unique imaging alternative. This article reviews optical imaging of both radionuclide- and beam-based ionizing radiation from high-energy photons and charged particles through mechanisms including radioluminescence, Cerenkov luminescence, and scintillation. Therapeutically, these visible photons have been combined with photodynamic therapeutic agents preclinically for increasing therapeutic response at depths difficult to reach with external light sources. Last, new microscopy methods that allow single-cell optical imaging of radionuclides are reviewed. PMID:27688469

Impact of optical feedback on current-induced polarization behavior of 1550 nm vertical-cavity surface-emitting lasers.

PubMed

Deng, Tao; Wu, Zheng-Mao; Xie, Yi-Yuan; Wu, Jia-Gui; Tang, Xi; Fan, Li; Panajotov, Krassimir; Xia, Guang-Qiong

2013-06-01

Polarization switching (PS) between two orthogonal linearly polarized fundamental modes is experimentally observed in commercial free-running 1550 nm vertical-cavity surface-emitting lasers (VCSELs) (Raycan). The characteristics of this PS are strongly modified after introducing a polarization-preserved (PP) or polarization-orthogonal (PO) optical feedback. Under the case that the external cavity is approximately 30 cm, the PP optical feedback results in the PS point shifting toward a lower injection current, and the region within which the two polarization modes coexist is enlarged with the increase of the PP feedback strength. Under too-strong PP feedback levels, the PS disappears. The impact of PO optical feedback on VCSEL polarization behavior is quite similar to that of PP optical feedback, but larger feedback strength is needed to obtain similar results.

A 16 element quasi-optical FET oscillator power combining array with external injection locking

NASA Astrophysics Data System (ADS)

Birkeland, Joel; Itoh, Tatsuo

1992-03-01

The authors present analysis, design and experimental results of a 16 element planar oscillator array for quasi-optical power combining. Each element in the array consists of a single FET oscillator with an input port for injection of the locking signal, and an output port which is connected to a patch radiator. The array is synchronized using a 16-way power dividing network which distributes the locking signal to the oscillating elements. The array is constructed using a two-sided microstrip configuration, with the oscillators and feed network on one side of a ground plane, and the patch radiators on the opposite side. An effective radiated power (ERP) of 28.2 W CW with an isotropic conversion gain of 9.9 dB was measured at 6 GHz. For an injected power of 10.3 dBm, a locking range of 453 MHz at a center frequency of 6.015 GHz was obtained; a bandwidth of 7.5 percent. Because of the simple nature of the individual oscillator elements, this approach is well suited to MMIC implementation.

Injection locking of a high power ultraviolet laser diode for laser cooling of ytterbium atoms

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

Hosoya, Toshiyuki; Miranda, Martin; Inoue, Ryotaro

2015-07-15

We developed a high-power laser system at a wavelength of 399 nm for laser cooling of ytterbium atoms with ultraviolet laser diodes. The system is composed of an external cavity laser diode providing frequency stabilized output at a power of 40 mW and another laser diode for amplifying the laser power up to 220 mW by injection locking. The systematic method for optimization of our injection locking can also be applied to high power light sources at any other wavelengths. Our system does not depend on complex nonlinear frequency-doubling and can be made compact, which will be useful for providing light sources formore » laser cooling experiments including transportable optical lattice clocks.« less

GRB 110530A: Peculiar Broad Bump and Delayed Plateau in Early Optical Afterglows

NASA Astrophysics Data System (ADS)

Zhong, Shu-Qing; Xin, Li-Ping; Liang, En-Wei; Wei, Jian-Yan; Urata, Yuji; Huang, Kui-Yun; Qiu, Yu-Lei; Deng, Can-Min; Wang, Yuan-Zhu; Deng, Jin-Song

2016-11-01

We report our very early optical observations of GRB 110530A and investigate its jet properties together with its X-ray afterglow data. A peculiar broad onset bump followed by a plateau is observed in its early R band afterglow light curve. The optical data in the other bands and the X-ray data are well consistent with the temporal feature of the R band light curve. Our joint spectral fits of the optical and X-ray data show that they are in the same regime, with a photon index of ∼1.70. The optical and X-ray afterglow light curves are well fitted with the standard external shock model by considering a delayed energy injection component. Based on our modeling results, we find that the radiative efficiency of the gamma-ray burst jet is ∼ 1 % and the magnetization parameter of the afterglow jet is \\lt 0.04 with a derived extremely low {ε }B (the ratio of shock energy to the magnetic field) of (1.64+/- 0.25)× {10}-6. These results indicate that the jet may be matter dominated. A discussion on delayed energy injection from the accretion of the late fall-back material of its pre-supernova star is also presented.

Optical Imaging of Ionizing Radiation from Clinical Sources.

PubMed

Shaffer, Travis M; Drain, Charles Michael; Grimm, Jan

2016-11-01

Nuclear medicine uses ionizing radiation for both in vivo diagnosis and therapy. Ionizing radiation comes from a variety of sources, including x-rays, beam therapy, brachytherapy, and various injected radionuclides. Although PET and SPECT remain clinical mainstays, optical readouts of ionizing radiation offer numerous benefits and complement these standard techniques. Furthermore, for ionizing radiation sources that cannot be imaged using these standard techniques, optical imaging offers a unique imaging alternative. This article reviews optical imaging of both radionuclide- and beam-based ionizing radiation from high-energy photons and charged particles through mechanisms including radioluminescence, Cerenkov luminescence, and scintillation. Therapeutically, these visible photons have been combined with photodynamic therapeutic agents preclinically for increasing therapeutic response at depths difficult to reach with external light sources. Last, new microscopy methods that allow single-cell optical imaging of radionuclides are reviewed. © 2016 by the Society of Nuclear Medicine and Molecular Imaging, Inc.

Single-frequency diode-pumped lasers for free-space optical communication

NASA Technical Reports Server (NTRS)

Kane, Thomas J.; Cheng, Emily A. P.; Gerstenberger, David C.; Wallace, Richard W.

1990-01-01

Recent advances in laser technology for intersatellite optical communication systems are reviewed and illustrated with graphs and diagrams. Topics addressed include (1) single-frequency diode-pumped Nd:YAG lasers of monolithic ring configuration (yielding 368-384 mW output power with 1-W pumping), (2) injection chaining of up to 10 monolithic resonators to achieve redundancy and/or higher output power, (3) 2-kHz-linewidth 5-mW versions of (1) which are tunable over a 30-MHz range for use as local oscillators in coherent communication, (4) resonant external modulation and doubling or resonant phase modulation of diode-pumped lasers, and (5) wavelength multiplexing.

Carbon particles

DOEpatents

Hunt, Arlon J.

1984-01-01

A method and apparatus whereby small carbon particles are made by pyrolysis of a mixture of acetylene carried in argon. The mixture is injected through a nozzle into a heated tube. A small amount of air is added to the mixture. In order to prevent carbon build-up at the nozzle, the nozzle tip is externally cooled. The tube is also elongated sufficiently to assure efficient pyrolysis at the desired flow rates. A key feature of the method is that the acetylene and argon, for example, are premixed in a dilute ratio, and such mixture is injected while cool to minimize the agglomeration of the particles, which produces carbon particles with desired optical properties for use as a solar radiant heat absorber.

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).

Carbon-particle generator

DOEpatents

Hunt, A.J.

1982-09-29

A method and apparatus whereby small carbon particles are made by pyrolysis of a mixture of acetylene carried in argon. The mixture is injected through a nozzle into a heated tube. A small amount of air is added to the mixture. In order to prevent carbon build-up at the nozzle, the nozzle tip is externally cooled. The tube is also elongated sufficiently to assure efficient pyrolysis at the desired flow rates. A key feature of the method is that the acetylene and argon, for example, are premixed in a dilute ratio, and such mixture is injected while cool to minimize the agglomeration of the particles, which produces carbon particles with desired optical properties for use as a solar radiant heat absorber.

External Shock in a Multi-bursting Gamma-Ray Burst: Energy Injection Phase Induced by the Later Launched Ejecta

NASA Astrophysics Data System (ADS)

Lin, Da-Bin; Huang, Bao-Quan; Liu, Tong; Gu, Wei-Min; Mu, Hui-Jun; Liang, En-Wei

2018-01-01

Central engines of gamma-ray bursts (GRBs) may be intermittent and launch several episodes of ejecta separated by a long quiescent interval. In this scenario, an external shock is formed due to the propagation of the first launched ejecta into the circum-burst medium and the later launched ejecta may interact with the external shock at a later period. Owing to the internal dissipation, the later launched ejecta may be observed at a later time (t jet). In this paper, we study the relation of t b and t jet, where t b is the collision time of the later launched ejecta with the formed external shock. It is found that the relation of t b and t jet depends on the bulk Lorentz factor (Γjet) of the later launched ejecta and the density (ρ) of the circum-burst medium. If the value of Γjet or ρ is low, the t b would be significantly larger than t jet. However, the t b ∼ t jet can be found if the value of Γjet or ρ is significantly large. Our results can explain the large lag of the optical emission relative to the γ-ray/X-ray emission in GRBs, e.g., GRB 111209A. For GRBs with a precursor, our results suggest that the energy injection into the external shock and thus more than one external-reverse shock may appear in the main prompt emission phase. According to our model, we estimate the Lorentz factor of the second launched ejecta in GRB 160625B.

Flexible deep-ultraviolet light-emitting diodes for significant improvement of quantum efficiencies by external bending

NASA Astrophysics Data System (ADS)

Shervin, Shahab; Oh, Seung Kyu; Park, Hyun Jung; Lee, Keon-Hwa; Asadirad, Mojtaba; Kim, Seung-Hwan; Kim, Jeomoh; Pouladi, Sara; Lee, Sung-Nam; Li, Xiaohang; Kwak, Joon Seop; Ryou, Jae-Hyun

2018-03-01

We report a new route to improve quantum efficiencies of AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) using mechanical flexibility of recently developed bendable thin-film structures. Numerical studies show that electronic band structures of AlGaN heterostructures and resulting optical and electrical characteristics of the devices can be significantly modified by external bending through active control of piezoelectric polarization. Internal quantum efficiency is enhanced higher than three times, when the DUV LEDs are moderately bent with concave curvatures. Furthermore, an efficiency droop at high injection currents is mitigated and turn-on voltage of diodes decreases with the same bending condition. The concept of bendable DUV LEDs with a controlled external strain can provide a new path for high-output-power and high-efficiency devices.

Ultralong time response of magnetic fluid based on fiber-optic evanescent field.

PubMed

Du, Bobo; Yang, Dexing; Bai, Yang; Yuan, Yuan; Xu, Jian; Jiang, Yajun; Wang, Meirong

2016-07-20

The ultralong time (a few hours) response properties of magnetic fluid using etched optical fiber are visualized and investigated experimentally. The operating structure is made by injecting magnetic fluid into a capillary tube that contains etched single-mode fiber. An interesting extreme asymmetry is observed, in which the transmitted light intensity after the etched optical fiber cannot reach the final steady value when the external magnetic field is turned on (referred to as the falling process), while it can reach the stable state quickly once the magnetic field is turned off (referred to as the rising process). The relationship between the response times/loss rates of the transmitted light and the strength of the applied magnetic field is obtained. The physical mechanisms of two different processes are discussed qualitatively.

Qualitative and quantitative changes in detrital reservoir rocks caused by CO2-brine-rock interactions during first injection phases (Utrillas sandstones, northern Spain)

NASA Astrophysics Data System (ADS)

Berrezueta, E.; Ordóñez-Casado, B.; Quintana, L.

2016-01-01

The aim of this article is to describe and interpret qualitative and quantitative changes at rock matrix scale of lower-upper Cretaceous sandstones exposed to supercritical (SC) CO2 and brine. The effects of experimental injection of CO2-rich brine during the first injection phases were studied at rock matrix scale, in a potential deep sedimentary reservoir in northern Spain (Utrillas unit, at the base of the Cenozoic Duero Basin).

Experimental CO2-rich brine was exposed to sandstone in a reactor chamber under realistic conditions of deep saline formations (P ≈ 7.8 MPa, T ≈ 38 °C and 24 h exposure time). After the experiment, exposed and non-exposed equivalent sample sets were compared with the aim of assessing possible changes due to the effect of the CO2-rich brine exposure. Optical microscopy (OpM) and scanning electron microscopy (SEM) aided by optical image analysis (OIA) were used to compare the rock samples and get qualitative and quantitative information about mineralogy, texture and pore network distribution. Complementary chemical analyses were performed to refine the mineralogical information and to obtain whole rock geochemical data. Brine composition was also analyzed before and after the experiment.

The petrographic study of contiguous sandstone samples (more external area of sample blocks) before and after CO2-rich brine injection indicates an evolution of the pore network (porosity increase ≈ 2 %). It is probable that these measured pore changes could be due to intergranular quartz matrix detachment and partial removal from the rock sample, considering them as the early features produced by the CO2-rich brine. Nevertheless, the whole rock and brine chemical analyses after interaction with CO2-rich brine do not present important changes in the mineralogical and chemical configuration of the rock with respect to initial conditions, ruling out relevant precipitation or dissolution at these early stages to rock-block scale. These results, simulating the CO2 injection near the injection well during the first phases (24 h) indicate that, in this environment where CO2 enriches the brine, the mixture principally generates local mineralogical/textural re-adjustments on the external area of the samples studied.

The application of OpM, SEM and optical image analysis have allowed an exhaustive characterization of the sandstones studied. The procedure followed, the porosity characterization and the chemical analysis allowed a preliminary approximation of the CO2-brine-rock interactions and could be applied to similar experimental injection tests.

Dynamical regimes and intracavity propagation delay in external cavity semiconductor diode lasers

NASA Astrophysics Data System (ADS)

Jayaprasath, E.; Sivaprakasam, S.

2017-11-01

Intracavity propagation delay, a delay introduced by a semiconductor diode laser, is found to significantly influence synchronization of multiple semiconductor diode lasers, operated either in stable or in chaotic regime. Two diode lasers coupled in unidirectional scheme is considered in this numerical study. A diode laser subjected to an optical feedback, also called an external cavity diode laser, acts as the transmitter laser (TL). A solitary diode laser acts as the receiver laser (RL). The optical output of the TL is coupled to the RL and laser operating parameters are optimized to achieve synchronization in their output intensities. The time-of-flight between the TL and RL introduces an intercavity time delay in the dynamics of RL. In addition to this, an intracavity propagation delay arises as the TL's field propagated within the RL. This intracavity propagation delay is evaluated by cross-correlation analysis between the output intensities of the lasers. The intracavity propagation delay is found to increase as the external cavity feedback rate of TL is increased, while an increment in the injection rate between the two lasers resulted in a reduction of intracavity propagation delay.

GRB 081029: A Gamma-Ray Burst with a Multi-Component Afterglow

NASA Technical Reports Server (NTRS)

Holland, Stephen T.; De Pasquale, Massimiliano; Mao, Jirong; Sakamoto, Takanori; Schady, Patricia; Covino, Stefano; Fan, Yi-Zhong; Jin, Zhi-Ping; D'Avanzo, Paolo; Antonelli, Angelo;

Complex-enhanced chaotic signals with time-delay signature suppression based on vertical-cavity surface-emitting lasers subject to chaotic optical injection

NASA Astrophysics Data System (ADS)

Chen, Jianjun; Duan, Yingni; Zhong, Zhuqiang

2018-06-01

A chaotic system is constructed on the basis of vertical-cavity surface-emitting lasers (VCSELs), where a slave VCSEL subject to chaotic optical injection (COI) from a master VCSEL with the external feedback. The complex degree (CD) and time-delay signature (TDS) of chaotic signals generated by this chaotic system are investigated numerically via permutation entropy (PE) and self-correlation function (SF) methods, respectively. The results show that, compared with master VCSEL subject to optical feedback, complex-enhanced chaotic signals with TDS suppression can be achieved for S-VCSEL subject to COI. Meanwhile, the influences of several controllable parameters on the evolution maps of CD of chaotic signals are carefully considered. It is shown that the CD of chaotic signals for S-VCSEL is always higher than that for M-VCSEL due to the CIO effect. The TDS of chaotic signals can be significantly suppressed by choosing the reasonable parameters in this system. Furthermore, TDS suppression and high CD chaos can be obtained simultaneously in the specific parameter ranges. The results confirm that this chaotic system may effectively improve the security of a chaos-based communication scheme.

Complex-enhanced chaotic signals with time-delay signature suppression based on vertical-cavity surface-emitting lasers subject to chaotic optical injection

NASA Astrophysics Data System (ADS)

Chen, Jianjun; Duan, Yingni; Zhong, Zhuqiang

2018-03-01

A chaotic system is constructed on the basis of vertical-cavity surface-emitting lasers (VCSELs), where a slave VCSEL subject to chaotic optical injection (COI) from a master VCSEL with the external feedback. The complex degree (CD) and time-delay signature (TDS) of chaotic signals generated by this chaotic system are investigated numerically via permutation entropy (PE) and self-correlation function (SF) methods, respectively. The results show that, compared with master VCSEL subject to optical feedback, complex-enhanced chaotic signals with TDS suppression can be achieved for S-VCSEL subject to COI. Meanwhile, the influences of several controllable parameters on the evolution maps of CD of chaotic signals are carefully considered. It is shown that the CD of chaotic signals for S-VCSEL is always higher than that for M-VCSEL due to the CIO effect. The TDS of chaotic signals can be significantly suppressed by choosing the reasonable parameters in this system. Furthermore, TDS suppression and high CD chaos can be obtained simultaneously in the specific parameter ranges. The results confirm that this chaotic system may effectively improve the security of a chaos-based communication scheme.

Detection of macrophages in atherosclerotic tissue using magnetic nanoparticles and differential phase optical coherence tomography.

PubMed

Oh, Junghwan; Feldman, Marc D; Kim, Jihoon; Sanghi, Pramod; Do, Dat; Mancuso, J Jacob; Kemp, Nate; Cilingiroglu, Mehmet; Milner, Thomas E

2008-01-01

We demonstrate the detection of iron oxide nanoparticles taken up by macrophages in atherosclerotic plaque with differential phase optical coherence tomography (DP-OCT). Magneto mechanical detection of nanoparticles is demonstrated in hyperlipidemic Watanabe and balloon-injured fat-fed New Zealand white rabbits injected with monocrystalline iron oxide nanoparticles (MIONs) of < 40 nm diam. MIONs taken up by macrophages was excited by an oscillating magnetic flux density and resulting nanometer tissue surface displacement was detected by DP-OCT. Frequency response of tissue surface displacement in response to an externally applied magnetic flux density was twice the stimulus frequency as expected from the equations of motion for the nanoparticle cluster.

Hybrid WDM/TDM-PON With Wavelength-Selection-Free Transmitters

NASA Astrophysics Data System (ADS)

Shin, Dong Jae; Jung, Dae Kwang; Shin, Hong Seok; Kwon, Jin Wook; Hwang, Seongtaek; Oh, Yunje; Shim, Changsup

2005-01-01

A hybrid wavelength-division-multiplexed/time-division-multiplexed passive optical network serving 128 subscribers with wavelength-selection-free transmitters is presented by cascading 1x16 arrayed-waveguide gratings (AWGs) and 1x8 splitters. The wavelength-selection-free transmitter is an uncooled Fabry-Pérot laser diode (FP-LD) wavelength-locked to an externally injected narrow-band amplified spontaneous emission (ASE). Bit-error rates better than 10^-9 over temperature ranging from 0 to 60 °C are achieved in all 16 wavelength channels using a single FP-LD with an ASE injection of about -15 and -2 dBm in 622-Mb/s upstream and 1.25-Gb/s downstream transmissions over a 10-km feeder fiber, respectively. It is also reported that the ASE injection does not exert penalty upon burst-mode operations of the FP-LDs in the upstream.

Frequency chirped light at large detuning with an injection-locked diode laser

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

Teng, K.; Disla, M.; Dellatto, J.

2015-04-15

We have developed a laser system to generate frequency-chirped light at rapid modulation speeds (∼100 MHz) with a large frequency offset. Light from an external cavity diode laser with its frequency locked to an atomic resonance is passed through a lithium niobate electro-optical phase modulator. The phase modulator is driven by a ∼6 GHz signal whose frequency is itself modulated with a RF MHz signal (<200 MHz). A second injection locked diode laser is used to filter out all of the light except the frequency-chirped ±1 order by more than 30 dB. Using this system, it is possible to generatemore » a 1 GHz frequency chirp in 5 ns.« less

Optical light curve of GRB 121011A: a textbook for the onset of GRB afterglow in a mixture of ISM and wind-type medium

NASA Astrophysics Data System (ADS)

Xin, Li-Ping; Wei, Jian-Yan; Qiu, Yu-Lei; Deng, Jin-Song; Wang, Jing; Han, Xu-Hui

2016-01-01

We report the optical observations of GRB 121011A by the 0.8m TNT facility at Xinglong observatory, China. The light curve of the optical afterglow shows a smooth and featureless bump during the epoch of ˜130 s and ˜5000 s with a rising index of 1.57 ± 0.28 before the break time of 539 ± 44 s, and a decaying index of about 1.29 ± 0.07 up to the end of our observations. Moreover, the X-ray light curve decays in a single power-law with a slope of about 1.51 ± 0.03 observed by XRT onboard Swift from 100 s to about 10 000 s after the burst trigger. The featureless optical light curve could be understood as an onset process under the external-shock model. The typical frequency has been below or near the optical one before the deceleration time, and the cooling frequency is located between the optical and X-ray wavelengths. The external medium density has a transition from a mixed stage of ISM and wind-type medium before the peak time to the ISM at the later phase. The joint-analysis of X-ray and optical light curves shows that the emissions from both frequencies are consistent with the prediction of the standard afterglow model without any energy injections, indicating that the central engine has stopped its activity and does not restart anymore after the prompt phase.

Boltzmann sampling for an XY model using a non-degenerate optical parametric oscillator network

NASA Astrophysics Data System (ADS)

Takeda, Y.; Tamate, S.; Yamamoto, Y.; Takesue, H.; Inagaki, T.; Utsunomiya, S.

2018-01-01

We present an experimental scheme of implementing multiple spins in a classical XY model using a non-degenerate optical parametric oscillator (NOPO) network. We built an NOPO network to simulate a one-dimensional XY Hamiltonian with 5000 spins and externally controllable effective temperatures. The XY spin variables in our scheme are mapped onto the phases of multiple NOPO pulses in a single ring cavity and interactions between XY spins are implemented by mutual injections between NOPOs. We show the steady-state distribution of optical phases of such NOPO pulses is equivalent to the Boltzmann distribution of the corresponding XY model. Estimated effective temperatures converged to the setting values, and the estimated temperatures and the mean energy exhibited good agreement with the numerical simulations of the Langevin dynamics of NOPO phases.

Short-pulse controlled optical switch using external cavity based single mode Fabry-Pérot laser diode.

PubMed

Nakarmi, Bikash; Hoai, Tran Quoc; Won, Yong-Hyub; Zhang, Xuping

2014-06-30

We propose and demonstrate a novel scheme for short pulse controlled all-optical switch using external cavity based single mode Fabry- Pérot laser diode (SMFP-LD). The proposed scheme consists of control unit and switching unit as two essential blocks. The basic principle of the proposed scheme is the optical bistability property of SMFP-LD for the control unit and the suppression of the dominant beam of SMFP-LD with injection locking for the switching unit. We also present the analysis of hysteresis width and rising/falling time with change in wavelength detuning which helps to find the optimum wavelength detuning value and power of light beams at different stages of the proposed scheme that gives wide input dynamic power range, high ON/OFF contrast ratio, and low rising/falling time. Input data of 10 Gb/s Non Return to Zero (NRZ) signal is switched at output ports depending upon the control signal generated by the control unit, which comprises of optical SR latch. Output waveforms, clear eye diagrams with extinction ratio of about 11 dB, rising/falling time of about 30 ps and 40 ps, and bit error rate (BER) are measured to validate proposed scheme. No noise floor is observed at output ports up to BER of 10-(12) and the maximum power penalty recorded is about 1.7 dB at a BER of 10-(9) which shows good performance of the proposed short pulse controlled optical switch using SMFP-LDs.

2.5 Gbit/s Optical Receiver Front-End Circuit with High Sensitivity and Wide Dynamic Range

NASA Astrophysics Data System (ADS)

Zhu, Tiezhu; Mo, Taishan; Ye, Tianchun

2017-12-01

An optical receiver front-end circuit is designed for passive optical network and fabricated in a 0.18 um CMOS technology. The whole circuit consists of a transimpedance amplifier (TIA), a single-ended to differential amplifier and an output driver. The TIA employs a cascode stage as the input stage and auxiliary amplifier to reduce the miller effect. Current injecting technique is employed to enlarge the input transistor's transconductance, optimize the noise performance and overcome the lack of voltage headroom. To achieve a wide dynamic range, an automatic gain control circuit with self-adaptive function is proposed. Experiment results show an optical sensitivity of -28 dBm for a bit error rate of 10-10 at 2.5 Gbit/s and a maxim input optical power of 2 dBm using an external photodiode. The chip occupies an area of 1×0.9 mm2 and consumes around 30 mW from single 1.8 V supply. The front-end circuit can be used in various optical receivers.

The electro-optic mechanism and infrared switching dynamic of the hybrid multilayer VO2/Al:ZnO heterojunctions.

PubMed

Zhang, Peng; Zhang, Wu; Wang, Junyong; Jiang, Kai; Zhang, Jinzhong; Li, Wenwu; Wu, Jiada; Hu, Zhigao; Chu, Junhao

2017-06-30

Active and widely controllable phase transition optical materials have got rapid applications in energy-efficient electronic devices, field of meta-devices and so on. Here, we report the optical properties of the vanadium dioxide (VO 2 )/aluminum-doped zinc oxide (Al:ZnO) hybrid n-n type heterojunctions and the corresponding electro-optic performances of the devices. Various structures are fabricated to compare the discrepancy of the optical and electrical characteristics. It was found that the reflectance spectra presents the wheel phenomenon rather than increases monotonically with temperature at near-infrared region range. The strong interference effects was found in the hybrid multilayer heterojunction. In addition, the phase transition temperature decreases with increasing the number of the Al:ZnO layer, which can be ascribed to the electron injection to the VO 2 film from the Al:ZnO interface. Affected by the double layer Al:ZnO, the abnormal Raman vibration mode was presented in the insulator region. By adding the external voltage on the Al 2 O 3 /Al:ZnO/VO 2 /Al:ZnO, Al 2 O 3 /Al:ZnO/VO 2 and Al 2 O 3 /VO 2 /Al:ZnO thin-film devices, the infrared optical spectra of the devices can be real-time manipulated by an external voltage. The main effect of joule heating and assistant effect of electric field are illustrated in this work. It is believed that the results will add a more thorough understanding in the application of the VO 2 /transparent conductive film device.

1.55-μm mode-locked quantum-dot lasers with 300 MHz frequency tuning range

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

Sadeev, T., E-mail: tagir@mailbox.tu-berlin.de; Arsenijević, D.; Bimberg, D.

2015-01-19

Passive mode-locking of two-section quantum-dot mode-locked lasers grown by metalorganic vapor phase epitaxy on InP is reported. 1250-μm long lasers exhibit a wide tuning range of 300 MHz around the fundamental mode-locking frequency of 33.48 GHz. The frequency tuning is achieved by varying the reverse bias of the saturable absorber from 0 to −2.2 V and the gain section current from 90 to 280 mA. 3 dB optical spectra width of 6–7 nm leads to ex-facet optical pulses with full-width half-maximum down to 3.7 ps. Single-section quantum-dot mode-locked lasers show 0.8 ps broad optical pulses after external fiber-based compression. Injection current tuning from 70 tomore » 300 mA leads to 30 MHz frequency tuning.« less

Optical sideband generation up to room temperature with mid-infrared quantum cascade lasers.

PubMed

Houver, S; Cavalié, P; St-Jean, M Renaudat; Amanti, M I; Sirtori, C; Li, L H; Davies, A G; Linfield, E H; Pereira, T A S; Lebreton, A; Tignon, J; Dhillon, S S

2015-02-23

Mid-infrared (MIR) sideband generation on a near infrared (NIR) optical carrier is demonstrated within a quantum cascade laser (QCL). By employing an externally injected NIR beam, E(NIR), that is resonant with the interband transitions of the quantum wells in the QCL, the nonlinear susceptibility is enhanced, leading to both frequency mixing and sideband generation. A GaAs-based MIR QCL (E(QCL) = 135 meV) with an aluminum-reinforced waveguide was utilized to overlap the NIR and MIR modes with the optical nonlinearity of the active region. The resulting difference sideband (E(NIR) - E(QCL)) shows a resonant behavior as a function of NIR pump wavelength and a maximum second order nonlinear susceptibility, χ((2)), of ~1 nm/V was obtained. Further, the sideband intensity showed little dependence with the operating temperature of the QCL, allowing sideband generation to be realized at room temperature.

Improving hole injection efficiency by manipulating the hole transport mechanism through p-type electron blocking layer engineering.

PubMed

Zhang, Zi-Hui; Ju, Zhengang; Liu, Wei; Tan, Swee Tiam; Ji, Yun; Kyaw, Zabu; Zhang, Xueliang; Hasanov, Namig; Sun, Xiao Wei; Demir, Hilmi Volkan

2014-04-15

The p-type AlGaN electron blocking layer (EBL) is widely used in InGaN/GaN light-emitting diodes (LEDs) for electron overflow suppression. However, a typical EBL also reduces the hole injection efficiency, because holes have to climb over the energy barrier generated at the p-AlGaN/p-GaN interface before entering the quantum wells. In this work, to address this problem, we report the enhancement of hole injection efficiency by manipulating the hole transport mechanism through insertion of a thin GaN layer of 1 nm into the p-AlGaN EBL and propose an AlGaN/GaN/AlGaN-type EBL outperforming conventional AlGaN EBLs. Here, the position of the inserted thin GaN layer relative to the p-GaN region is found to be the key to enhancing the hole injection efficiency. InGaN/GaN LEDs with the proposed p-type AlGaN/GaN/AlGaN EBL have demonstrated substantially higher optical output power and external quantum efficiency.

Cycles of self-pulsations in a photonic integrated circuit.

PubMed

Karsaklian Dal Bosco, Andreas; Kanno, Kazutaka; Uchida, Atsushi; Sciamanna, Marc; Harayama, Takahisa; Yoshimura, Kazuyuki

2015-12-01

We report experimentally on the bifurcation cascade leading to the appearance of self-pulsation in a photonic integrated circuit in which a laser diode is subjected to delayed optical feedback. We study the evolution of the self-pulsing frequency with the increase of both the feedback strength and the injection current. Experimental observations show good qualitative accordance with numerical results carried out with the Lang-Kobayashi rate equation model. We explain the mechanism underlying the self-pulsations by a phenomenon of beating between successive pairs of external cavity modes and antimodes.

Injection locked coupled opto-electronic oscillator for optical frequency comb generation

NASA Astrophysics Data System (ADS)

Williams, Charles; Mandridis, Dimitrios; Davila-Rodriguez, Josue; Delfyett, Peter J.

2011-06-01

A CW injection locked Coupled Opto-Electronic Oscillator (COEO) is presented with a 10.24 GHz spaced optical frequency comb output as well as a low noise RF output. A modified Pound-Drever-Hall scheme is employed to ensure long-term stability of the injection lock, feeding back into the cavity length to compensate for cavity resonance drifts relative to the injection seed frequency. Error signal comparison to an actively mode-locked injection locked laser is presented. High optical signal-to-noise ratio of ~35 dB is demonstrated with >20 comblines of useable bandwidth. The optical linewidth, in agreement with injection locking theory, reduces to that of the injection seed frequency, <5 kHz. Low amplitude and absolute phase noise are presented from the optical output of the laser system. The integrated pulse-to-pulse energy fluctuation was found to be reduced by up to a factor of two due to optical injection. Additional decreases were shown for varying injection powers.

Externally controlled pressure and temperature microreactor for in situ x-ray diffraction, visual and spectroscopic reaction investigations under supercritical and subcritial conditions

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

Diefenbacher, J.; McKelvy, M.; Chizemeshya, A.V.

2010-07-13

A microreactor has been developed for in situ, spectroscopic investigations of materials and reaction processes with full external pressure and temperature control from ambient conditions to 400 C and 310 bar. The sample chamber is in direct contact with an external manifold, whereby gases, liquids or fluids can be injected and their activities controlled prior to and under investigation conditions. The microreactor employs high strength, single crystal moissanite windows which allow direct probe beam interaction with a sample to investigate in situ reaction processes and other materials properties. The relatively large volume of the cell, along with full optical accessibilitymore » and external temperature and pressure control, make this reaction cell well suited for experimental investigations involving any combination of gas, fluid, and solid interactions. The microreactor's capabilities are demonstrated through an in situ x-ray diffraction study of the conversion of a meta-serpentine sample to magnesite under high pressure and temperature. Serpentine is one of the mineral candidates for the implementation of mineral carbonation, an intriguing carbon sequestration candidate technology.« less

Tissue expansion and fluid absorption by skin tissue following intradermal injections through hollow microneedles

NASA Astrophysics Data System (ADS)

Shrestha, Pranav; Stoeber, Boris

2017-11-01

Hollow microneedles provide a promising alternative to conventional drug delivery techniques due to improved patient compliance and the dose sparing effect. The dynamics of fluid injected through hollow microneedles into skin, which is a heterogeneous and deformable porous medium, have not been investigated extensively in the past. We have introduced the use of Optical Coherence Tomography (OCT) for real-time visualization of fluid injections into excised porcine tissue. The results from ex-vivo experiments, including cross-sectional tissue images from OCT and pressure/flow-rate measurements, show a transient mode of high flow-rate into the tissue followed by a lower steady-state infusion rate. The injected fluid expands the underlying tissue and causes the external free surface of the skin to rise, forming a characteristic intradermal wheal. We have used OCT to visualize the evolution of tissue and free surface deformation, and advancement of the boundary between regions of expanding and stationary tissue. We will show the effect of different injection parameters such as fluid pressure, viscosity and microneedle retraction on the injected volume. This work has been supported through funding from the Collaborative Health Research Program by the Natural Science and Engineering Research Council of Canada and the Canadian Health Research Institute, and through the Canada Research Chairs program.

Study on the characteristic and application of DFB semiconductor lasers under optical injection for microwave photonics

NASA Astrophysics Data System (ADS)

Pu, Tao; Wang, Wei wei

2018-01-01

In order to apply optical injection effect in Microwave Photonics system, The red-shift effect of the cavity mode of the DFB semiconductor laser under single-frequency optical injection is studied experimentally, and the red-shift curve of the cavity mode is measured. The wavelength-selective amplification property of the DFB semiconductor laser under multi-frequency optical injection is also investigated, and the gain curves for the injected signals in different injection ratios are measured in the experiment. A novel and simple structure to implement a single-passband MPF with wideband tunability based on the wavelength-selective amplification of a DFB semiconductor laser under optical injection is proposed and experimentally demonstrated. MPFs with center frequency tuned from 13 to 41 GHz are realized in the experiment. A wideband and frequency-tunable optoelectronic oscillator based on a directly modulated distributed feedback (DFB) semiconductor laser under optical injection is proposed and experimentally demonstrated. By optical injection, the relaxation oscillation frequency of the DFB laser is enhanced and its high modulation efficiency makes the loop oscillate without the necessary of the electrical filter. An experiment is performed; microwave signals with frequency tuned from 5.98 to 15.22 GHz are generated by adjusting the injection ratio and frequency detuning between the master and slave lasers.

Precision injection molding of freeform optics

NASA Astrophysics Data System (ADS)

Fang, Fengzhou; Zhang, Nan; Zhang, Xiaodong

2016-08-01

Precision injection molding is the most efficient mass production technology for manufacturing plastic optics. Applications of plastic optics in field of imaging, illumination, and concentration demonstrate a variety of complex surface forms, developing from conventional plano and spherical surfaces to aspheric and freeform surfaces. It requires high optical quality with high form accuracy and lower residual stresses, which challenges both optical tool inserts machining and precision injection molding process. The present paper reviews recent progress in mold tool machining and precision injection molding, with more emphasis on precision injection molding. The challenges and future development trend are also discussed.

Optical-microwave interactions in semiconductor devices

NASA Astrophysics Data System (ADS)

Figueroa, L.; Slayman, C. W.; Yen, H. W.

1981-03-01

The results of an extensive characterization of microwave-optical devices is presented. The study has concentrated in the optical injection locking of IMPATT oscillators, high-speed analog modulation of (GaAl)As injection laser, mode-locking of (GaAl)As injection laser, and high-speed optical detectors.

Photonic generation of polarization-resolved wideband chaos with time-delay concealment in three-cascaded vertical-cavity surface-emitting lasers.

PubMed

Liu, Huijie; Li, Nianqiang; Zhao, Qingchun

2015-05-10

Optical chaos generated by chaotic lasers has been widely used in several important applications, such as chaos-based communications and high-speed random-number generators. However, these applications are susceptible to degradation by the presence of time-delay (TD) signature identified from the chaotic output. Here we propose to achieve the concealment of TD signature, along with the enhancement of chaos bandwidth, in three-cascaded vertical-cavity surface-emitting lasers (VCSELs). The cascaded system is composed of an external-cavity master VCSEL, a solitary intermediate VCSEL, and a solitary slave VCSEL. Through mapping the evolutions of TD signature and chaos bandwidth in the parameter space of the injection strength and frequency detuning, photonic generation of polarization-resolved wideband chaos with TD concealment is numerically demonstrated for wide regions of the injection parameters.

Dynamic chirp control of all-optical format-converted pulsed data from a multi-wavelength inverse-optical-comb injected semiconductor optical amplifier.

PubMed

Lin, Gong-Ru; Pan, Ci-Ling; Yu, Kun-Chieh

2007-10-01

By spectrally and temporally reshaping the gain-window of a traveling-wave semiconductor optical amplifier (TWSOA) with a backward injected multi- or single-wavelength inverse-optical-comb, we theoretically and experimentally investigate the dynamic frequency chirp of the all-optical 10GBit/s Return-to-Zero (RZ) data-stream format-converted from the TWSOA under strong cross-gain depletion scheme. The multi-wavelength inverse-optical-comb injection effectively depletes the TWSOA gain spectrally and temporally, remaining a narrow gain-window and a reduced spectral linewidth and provide a converted RZ data with a smaller peak-to-peak frequency chirp of 6.7 GHz. Even at high inverse-optical-comb injection power and highly biased current condition for improving the operational bit-rate, the chirp of the multi-wavelength-injection converted RZ pulse is still 2.1-GHz smaller than that obtained by using single-wavelength injection at a cost of slight pulse-width broadening by 1 ps.

Quasi-stable injection channels in a wakefield accelerator

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

Wiltshire-Turkay, Mara; Farmer, John P.; Pukhov, Alexander

2016-05-15

The influence of initial position on the acceleration of externally injected electrons in a plasma wakefield is investigated. Test-particle simulations show previously unobserved complex structure in the parameter space, with quasi-stable injection channels forming for particles injected in narrow regions away from the wake centre. Particles injected into these channels remain in the wake for a considerable time after dephasing and as a result achieve significantly higher energy than their neighbours. The result is relevant to both the planning and optimisation of experiments making use of external injection.

Watt-level widely tunable single-mode emission by injection-locking of a multimode Fabry-Perot quantum cascade laser

NASA Astrophysics Data System (ADS)

Chevalier, Paul; Piccardo, Marco; Anand, Sajant; Mejia, Enrique A.; Wang, Yongrui; Mansuripur, Tobias S.; Xie, Feng; Lascola, Kevin; Belyanin, Alexey; Capasso, Federico

2018-02-01

Free-running Fabry-Perot lasers normally operate in a single-mode regime until the pumping current is increased beyond the single-mode instability threshold, above which they evolve into a multimode state. As a result of this instability, the single-mode operation of these lasers is typically constrained to few percents of their output power range, this being an undesired limitation in spectroscopy applications. In order to expand the span of single-mode operation, we use an optical injection seed generated by an external-cavity single-mode laser source to force the Fabry-Perot quantum cascade laser into a single-mode state in the high current range, where it would otherwise operate in a multimode regime. Utilizing this approach, we achieve single-mode emission at room temperature with a tuning range of 36 cm-1 and stable continuous-wave output power exceeding 1 W at 4.5 μm. Far-field measurements show that a single transverse mode is emitted up to the highest optical power, indicating that the beam properties of the seeded Fabry-Perot laser remain unchanged as compared to free-running operation.

Pain during external dacryocystorhinostomy with local anesthesia.

PubMed

Knežević, Miroslav M; Stojković, Milenko Ž; Vlajković, Gordana P; Jovanović, Miloš B; Rašić, Dejan M

2011-06-01

External dacryocystorhinostomy (DCR) is often performed under local anesthesia (LA) without adequate knowledge of the pain experienced by the patient. We subdivided our surgical technique into stages easily understood by the patients (introducing cotton tipped applicators, performing parabulbar injection, creating the incision, bone cracking (opening the ostium), manipulating the nose, intubating, closing the wound, and packing with gauze). A total of 50 patients ranging in age from 31 to 83 years of age (63.64±9.64) underwent external DCR. Each patient was asked 30 minutes after surgery to indicate the intensity of pain experienced at each stage of the surgery and during intramuscular (i.m.) injection of an antibiotic using a visual analog scale (VAS). Analysis of the VAS-based pain scores indicated 3 statistically equal occurrences of pain coinciding with the opening of the ostium, and receiving both parabulbar anesthetic and i.m. antibiotic injections. The level of pain experienced during the most unpleasant stage of external DCR (ostium opening) was similar to the pain experienced from an i.m. injection. Patients can be informed that pain during external DCR with local anesthesia is comparable to receiving an i.m. gluteal injection.

Design and evaluation of an intraocular B-scan OCT-guided 36-gauge needle

NASA Astrophysics Data System (ADS)

Shen, Jin H.; Joos, Karen M.

2015-03-01

Optical coherence tomography imaging is widely used in ophthalmology and optometry clinics for diagnosing retinal disorders. External microscope-mounted OCT operating room systems have imaged retinal changes immediately following surgical manipulations. However, the goal is to image critical surgical maneuvers in real time. External microscope-mounted OCT systems have some limitations with problems tracking constantly moving intraocular surgical instruments, and formation of absolute shadows by the metallic surgical instruments upon the underlying tissues of interest. An intraocular OCT-imaging probe was developed to resolve these problems. A disposable 25-gauge probe tip extended beyond the handpiece, with a 36-gauge needle welded to a disposable tip with its end extending an additional 3.5 mm. A sealed 0.35 mm diameter GRIN lens protected the fiber scanner and focused the scanning beam at a 3 to 4 mm distance. The OCT engine was a very high-resolution spectral-domain optical coherence tomography (SDOCT) system (870 nm, Bioptigen, Inc. Durham, NC) which produced 2000 A-scan lines per B-scan image at a frequency of 5 Hz with the fiber optic oscillations matched to this frequency. Real-time imaging of the needle tip as it touched infrared paper was performed. The B-scan OCT-needle was capable of real-time performance and imaging of the phantom material. In the future, the B-scan OCT-guided needle will be used to perform sub-retinal injections.

Efficient Color-Stable Inverted White Organic Light-Emitting Diodes with Outcoupling-Enhanced ZnO Layer.

PubMed

Zhao, Xin-Dong; Li, Yan-Qing; Xiang, Heng-Yang; Zhang, Yi-Bo; Chen, Jing-De; Xu, Lu-Hai; Tang, Jian-Xin

2017-01-25

Inverted organic light-emitting diode (OLED) has attracted extensive attention due to the demand in active-matrix OLED display panels as its geometry enables the direct connection with n-channel transistor backplane on the substrate. One key challenge of high-performance inverted OLED is an efficient electron-injection layer with superior electrical and optical properties to match the indium tin oxide cathode on substrate. We here propose a synergistic electron-injection architecture using surface modification of ZnO layer to simultaneously promote electron injection into organic emitter and enhance out-coupling of waveguided light. An efficient inverted white OLED is realized by introducing the nanoimprinted aperiodic nanostructure of ZnO for broadband and angle-independent light out-coupling and inserting an n-type doped interlayer for energy level tuning and injection barrier lowering. As a result, the optimized inverted white OLEDs have an external quantum efficiency of 42.4% and a power efficiency of 85.4 lm W 1- , which are accompanied by the superiority of angular color stability over the visible wavelength range. Our results may inspire a promising approach to fabricate high-efficiency inverted OLEDs for large-scale display panels.

Efficient optical injection locking of electronic oscillators

NASA Astrophysics Data System (ADS)

Cochran, S. R.; Wang, S. Y.

1989-05-01

The paper presents techniques for direct optical injection locking of electronic oscillators and analyzes the problem of direct optical injection locking of a common-source FET oscillator using a high impedance optoelectronic transducer. A figure-of-merit for optically injection locked oscillators is defined, and an experimental oscillator based on the design criteria was fabricated. The oscillator achieved efficient, high power operation and moderate locking bandwidth with small locking signal magnitude. The experimental results are consistent with the theoretical model.

Optical re-injection in cavity-enhanced absorption spectroscopy

PubMed Central

Leen, J. Brian; O’Keefe, Anthony

2014-01-01

Non-mode-matched cavity-enhanced absorption spectrometry (e.g., cavity ringdown spectroscopy and integrated cavity output spectroscopy) is commonly used for the ultrasensitive detection of trace gases. These techniques are attractive for their simplicity and robustness, but their performance may be limited by the reflection of light from the front mirror and the resulting low optical transmission. Although this low transmitted power can sometimes be overcome with higher power lasers and lower noise detectors (e.g., in the near-infrared), many regimes exist where the available light intensity or photodetector sensitivity limits instrument performance (e.g., in the mid-infrared). In this article, we describe a method of repeatedly re-injecting light reflected off the front mirror of the optical cavity to boost the cavity's circulating power and deliver more light to the photodetector and thus increase the signal-to-noise ratio of the absorption measurement. We model and experimentally demonstrate the method's performance using off-axis cavity ringdown spectroscopy (OA-CRDS) with a broadly tunable external cavity quantum cascade laser. The power coupled through the cavity to the detector is increased by a factor of 22.5. The cavity loss is measured with a precision of 2 × 10−10 cm−1/\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$\\sqrt {{\\rm Hz;}}$\\end{document} Hz ; an increase of 12 times over the standard off-axis configuration without reinjection and comparable to the best reported sensitivities in the mid-infrared. Finally, the re-injected CRDS system is used to measure the spectrum of several volatile organic compounds, demonstrating the improved ability to resolve weakly absorbing spectroscopic features. PMID:25273701

Modulation response characteristics of optical injection-locked cascaded microring laser

NASA Astrophysics Data System (ADS)

Yu, Shaowei; Pei, Li; Liu, Chao; Wang, Yiqun; Weng, Sijun

2014-09-01

Modulation bandwidth and frequency chirping of the optical injection-locked (OIL) microring laser (MRL) in the cascaded configuration are investigated. The unidirectional operation of the MRL under strong injection allows simple and cost-saving monolithic integration of the OIL system on one chip as it does not need the use of isolators between the master and slave lasers. Two cascading schemes are discussed in detail by focusing on the tailorable modulation response. The chip-to-power ratio of the cascaded optical injection-locked configuration has decreased by up to two orders of magnitude, compared with the single optical injection-locked configuration.

Dynamic stability analysis for a self-mixing interferometry system.

PubMed

Fan, Yuanlong; Yu, Yanguang; Xi, Jiangtao; Guo, Qinghua

2014-11-17

A self-mixing interferometry (SMI) system is a laser diode (LD) with an external cavity formed by a moving external target. The behavior of an SMI system is governed by the injection current J to the LD and the parameters associated with the external cavity mainly including optical feedback factor C, the initial external cavity length (L₀) and the light phase (ϕ₀) which is mapped to the movement of the target. In this paper, we investigate the dynamic behavior of an SMI system by using the Lang-Kobayashi model. The stability boundary of such system is presented in the plane of (C, ϕ₀), from which a critical C (denoted as C(critical)) is derived. Both simulations and experiments show that the stability can be enhanced by increasing either L₀ or J. Furthermore, three regions on the plane of (C, ϕ₀) are proposed to characterize the behavior of an SMI system, including stable, semi-stable and unstable regions. We found that the existing SMI model is only valid for the stable region, and the semi-stable region has potential applications on sensing and measurement but needs re-modeling the system by considering the bandwidth of the detection components.

Characterisation of acoustic energy content in an experimental combustion chamber with and without external forcing

NASA Astrophysics Data System (ADS)

Webster, S.; Hardi, J.; Oschwald, M.

2015-03-01

The influence of injection conditions on rocket engine combustion stability is investigated for a sub-scale combustion chamber with shear coaxial injection elements and the propellant combination hydrogen-oxygen. The experimental results presented are from a series of tests conducted at subcritical and supercritical pressures for oxygen and for both ambient and cryogenic temperature hydrogen. The stability of the system is characterised by the root mean squared amplitude of dynamic combustion chamber pressure in the upper part of the acoustic spectrum relevant for high frequency combustion instabilities. Results are presented for both unforced and externally forced combustion chamber configurations. It was found that, for both the unforced and externally forced configurations, the injection velocity had the strongest influence on combustion chamber stability. Through the use of multivariate linear regression the influence of hydrogen injection temperature and hydrogen injection mass flow rate were best able to explain the variance in stability for dependence on injection velocity ratio. For unforced tests turbulent jet noise from injection was found to dominate the energy content of the signal. For the externally forced configuration a non-linear regression model was better able to predict the variance, suggesting the influence of non-linear behaviour. The response of the system to variation of injection conditions was found to be small; suggesting that the combustion chamber investigated in the experiment is highly stable.

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

Electrical and Optical Enhancement in Internally Nanopatterned Organic Light-Emitting Diodes

NASA Astrophysics Data System (ADS)

Fina, Michael Dane

Organic light-emitting diodes (OLEDs) have made tremendous technological progress in the past two decades and have emerged as a top competitor for next generation light-emitting displays and lighting. State-of-the-art OLEDs have been reported in literature to approach, and even surpass, white fluorescent tube efficiency. However, despite rapid technological progress, efficiency metrics must be improved to compete with traditional inorganic light-emitting diode (LED) technology. Organic materials possess specialized traits that permit manipulations to the light-emitting cavity. Overall, as demonstrated within, these modifications can be used to improve electrical and optical device efficiencies. This work is focused at analyzing the effects that nanopatterned geometric modifications to the organic active layers play on device efficiency. In general, OLED efficiency is complicated by the complex, coupled processes which contribute to spontaneous dipole emission. A composite of three sub-systems (electrical, exciton and optical) ultimately dictate the OLED device efficiency. OLED electrical operation is believed to take place via a low-mobility-modified Schottky injection process. In the injection-limited regime, geometric effects are expected to modify the local electric field leading to device current enhancement. It is shown that the patterning effect can be used to enhance charge carrier parity, thereby enhancing overall recombination. Current density and luminance characteristics are shown to be improved by OLED nanopatterning from both the model developed within and experimental techniques. Next, the optical enhancement effects produced by the nanopatterned array are considered. Finite-difference time-domain (FDTD) simulations are used to determine positional, spectral optical enhancement for the nanopatterned device. The results show beneficial effects to the device performance. The optical enhancements are related to the reduction in internal radiative quenching (improved internal quantum efficiency) and improvement in light extraction (improved outcoupling efficiency). Furthermore, the electrical model is used to construct a positional radiative efficiency map that when combined with the optical enhancement reveals the overall external quantum efficiency enhancement.

DETECTING WATER FLOW BEHIND PIPE IN INJECTION WELLS

EPA Science Inventory

Regulations of the Environmental Protection Agency require that an injection well exhibit both internal and external mechanical integrity. The external mechanical integrity consideration is that there is no significant fluid movement into an underground source of drinking water ...

Bilateral Deep Peroneal Nerve Paralysis Following Kerosene Self-Injection into External Hemorrhoids

PubMed Central

Rostami, Khalil; Farzaneh, Esmaeil; Abolhassani, Hassan

2010-01-01

Along with conventional therapies, some abrogated traditional treatment had been used for hemorrhoids like local Kerosene injection especially for extremely irritated external hemorrhoids. We report a rare case of Kerosene self-injection into the hemorrhoid. Despite antibiotics therapy, extent debridement, and colostomy, the patient died after 24 hours because of heart attack. Moreover, we discuss here the case with contact or injection of hydrocarbon materials and early care action to decrease the extensions of injury and side effects. PMID:20936130

Spectral domain optical coherence tomography imaging of spectacular ecdysis in the royal python (Python regius).

PubMed

Tusler, Charlotte A; Maggs, David J; Kass, Philip H; Paul-Murphy, Joanne R; Schwab, Ivan R; Murphy, Christopher J

2015-01-01

To describe using spectral domain optical coherence tomography (SD-OCT), digital slit-lamp biomicroscopy, and external photography, changes in the ophidian cuticle, spectacle, and cornea during ecdysis. Four normal royal pythons (Python regius). Snakes were assessed once daily throughout a complete shed cycle using nasal, axial, and temporal SD-OCT images, digital slit-lamp biomicroscopy, and external photography. Spectral domain optical coherence tomography (SD-OCT) images reliably showed the spectacular cuticle and stroma, subcuticular space (SCS), cornea, anterior chamber, iris, and Schlemm's canal. When visible, the subspectacular space (SSS) was more distended peripherally than axially. Ocular surface changes throughout ecdysis were relatively conserved among snakes at all three regions imaged. From baseline (7 days following completion of a full cycle), the spectacle gradually thickened before separating into superficial cuticular and deep, hyper-reflective stromal components, thereby creating the SCS. During spectacular separation, the stroma regained original reflectivity, and multiple hyper-reflective foci (likely fragments from the cuticular-stromal interface) were noted within the SCS. The cornea was relatively unchanged in character or thickness throughout all stages of ecdysis. Slit-lamp images did not permit observation of these changes. Spectral domain optical coherence tomography (SD-OCT) provided excellent high-resolution images of the snake anterior segment, and especially the cuticle, spectacle, and cornea of manually restrained normal snakes at all stages of ecdysis and warrants investigation in snakes with anterior segment disease. The peripheral spectacle may be the preferred entry point for diagnostic or therapeutic injections into the SSS and for initiating spectacular surgery. © 2014 American College of Veterinary Ophthalmologists.

Route to broadband chaos in a chaotic laser diode subject to optical injection.

PubMed

Wang, An-Bang; Wang, Yun-Cai; Wang, Juan-Fen

2009-04-15

We experimentally and numerically demonstrate a route to bandwidth-enhanced chaos that is induced by an additional optical injection for a chaotic laser diode with optical feedback. The measured and calculated optical spectra consistently reveal that the mechanism of bandwidth enhancement is the interaction between the injection and chaotic laser field via beating. The bandwidth can be maximized only when the injected light is detuned into the edge of the optical spectrum of the chaotic laser field and the beating frequency exceeds the original bandwidth. The simulated dynamics maps indicate that 20 GHz broadband chaos can be obtained by commonly used laser diodes.

Investigation of charge injection and transport behavior in multilayer structure consisted of ferromagnetic metal and organic polymer under external fields

NASA Astrophysics Data System (ADS)

Zhao, Hua; Meng, Wei-Feng

2017-10-01

In this paper a five layer organic electronic device with alternately placed ferromagnetic metals and organic polymers: ferromagnetic metal/organic layer/ferromagnetic metal/organic layer/ferromagnetic metal, which is injected a spin-polarized electron from outsides, is studied theoretically using one-dimensional tight binding model Hamiltonian. We calculated equilibrium state behavior after an electron with spin is injected into the organic layer of this structure, charge density distribution and spin polarization density distribution of this injected spin-polarized electron, and mainly studied possible transport behavior of the injected spin polarized electron in this multilayer structure under different external electric fields. We analyze the physical process of the injected electron in this multilayer system. It is found by our calculation that the injected spin polarized electron exists as an electron-polaron state with spin polarization in the organic layer and it can pass through the middle ferromagnetic layer from the right-hand organic layer to the left-hand organic layer by the action of increasing external electric fields, which indicates that this structure may be used as a possible spin-polarized charge electronic device and also may provide a theoretical base for the organic electronic devices and it is also found that in the boundaries between the ferromagnetic layer and the organic layer there exist induced interface local dipoles due to the external electric fields.

Tunable Oscillations in Optically Injected Semiconductor Lasers With Reduced Sensitivity to Perturbations - Postprint

DTIC Science & Technology

2014-09-01

Squeezed light from injection- locked quantum well lasers ,” Phys. Rev. Lett., vol. 71, pp. 3951–3954, 1993. [30] A. E. Siegman , Lasers , 1st ed...AFRL-RY-WP-TP-2014-0297 TUNABLE OSCILLATIONS IN OPTICALLY INJECTED SEMICONDUCTOR LASERS WITH REDUCED SENSITIVITY TO PERTURBATIONS -POSTPRINT...OSCILLATIONS IN OPTICALLY INJECTED SEMICONDUCTOR LASERS WITH REDUCED SENSITIVITY TO PERTURBATIONS - POSTPRINT 5a. CONTRACT NUMBER In-House 5b. GRANT NUMBER

INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Electrical response of InGaAsP/InP heterolasers

NASA Astrophysics Data System (ADS)

Luc, Vu V.; Eliseev, P. G.; Man'ko, Margarita A.; Tsotsorya, M. V.

1988-11-01

An investigation was made of the change in the voltage across laser diodes emitting in the 1.3 μm range as a result of introduction of an external optical feedback in the form of an electrical response to interruption of the feedback ("optoelectronic" signal). Measurements were made on single-mode buried stripe heterostructures, using both unpackaged laboratory lasers and also serially manufactured ILPN-202 devices with radiation coupled out via a fiber waveguide. The optoelectronic signal reached 10-16 mV, but when a fiber waveguide was used, it was only 0.1-0.8 mV, depending on the quality of the contact between the laser and the fiber. Experiments showed that the ILPN-202 lasers could be used without any additional optics as sensors capable of detection of submicron displacements with a sensitivity in excess of 10 kV/m.

INJECTION OPTICS FOR THE JLEIC ION COLLIDER RING

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

Morozov, Vasiliy; Derbenev, Yaroslav; Lin, Fanglei

2016-05-01

The Jefferson Lab Electron-Ion Collider (JLEIC) will accelerate protons and ions from 8 GeV to 100 GeV. A very low beta function at the Interaction Point (IP) is needed to achieve the required luminosity. One consequence of the low beta optics is that the beta function in the final focusing (FF) quadrupoles is extremely high. This leads to a large beam size in these magnets as well as strong sensitivity to errors which limits the dynamic aperture. These effects are stronger at injection energy where the beam size is maximum, and therefore very large aperture FF magnets are required tomore » allow a large dynamic aperture. A standard solution is a relaxed injection optics with IP beta function large enough to provide a reasonable FF aperture. This also reduces the effects of FF errors resulting in a larger dynamic aperture at injection. We describe the ion ring injection optics design as well as a beta-squeeze transition from the injection to collision optics.« less

Targeted Drug Delivery in the Suprachoroidal Space by Swollen Hydrogel Pushing.

PubMed

Jung, Jae Hwan; Desit, Patcharin; Prausnitz, Mark R

2018-04-01

The purpose is to target model drug particles to the posterior region of the suprachoroidal space (SCS) of the eye controlled via pushing by hydrogel swelling. A particle formulation containing 1% hyaluronic acid (HA) with fluorescent polymer particles and a hydrogel formulation containing 4% HA were introduced in a single syringe as two layers without mixing, and injected sequentially into the SCS of the rabbit eye ex vivo and in vivo using a microneedle. Distribution of particles in the eye was determined by microscopy. During injection, the particle formulation was pushed toward the middle of the SCS by the viscous hydrogel formulation, but less than 12% of particles reached the posterior SCS. After injection, the particle formulation was pushed further toward the macula and optic nerve in the posterior SCS by hydrogel swelling and spreading. Heating the eye to 37°C, or injecting in vivo decreased viscosity and mechanical strength of the hydrogel, thereby allowing it to swell and flow further in the SCS. A high salt concentration (9% NaCl) in the hydrogel formulation further increased hydrogel swelling due to osmotic flow into the hydrogel. In this way, up to 76% of particles were delivered to the posterior SCS from an injection made near the limbus. This study shows that model drug particles can be targeted to the posterior SCS by HA hydrogel swelling and pushing without particle functionalization or administering external driving forces.

Effect of additional optical pumping injection into the ground-state ensemble on the gain and the phase recovery acceleration of quantum-dot semiconductor optical amplifiers

NASA Astrophysics Data System (ADS)

Kim, Jungho

2014-02-01

The effect of additional optical pumping injection into the ground-state ensemble on the ultrafast gain and the phase recovery dynamics of electrically-driven quantum-dot semiconductor optical amplifiers is numerically investigated by solving 1088 coupled rate equations. The ultrafast gain and the phase recovery responses are calculated with respect to the additional optical pumping power. Increasing the additional optical pumping power can significantly accelerate the ultrafast phase recovery, which cannot be done by increasing the injection current density.

Phase-locked Optical Signal Recovery

DTIC Science & Technology

2009-01-01

detection . However, implementing an optical phase lock loop ( OPLL ) to generate the synchronised carrier for the homodyne technique requires... Loop (OIPLL) in which a narrow bandwidth optical phase lock loop ( OPLL ) is used to control the free -running frequency of an optically injection...receiver uses an Optical Injection Phase Lock Loop (OIPLL) for carrier recovery,

Phase-locked Optical Signal Recovery

DTIC Science & Technology

2009-01-01

detection . However, implementing an optical phase lock loop ( OPLL ) to generate the synchronised carrier for the homodyne technique requires... Loop (OIPLL) in which a narrow bandwidth optical phase lock loop ( OPLL ) is used to control the free -running frequency of an optically injection...The receiver uses an Optical Injection Phase Lock Loop (OIPLL) for carrier

All-Optical Logic Gates and Wavelength Conversion Via the Injection-Locking of a Fabry-Perot Semiconductor Laser

DTIC Science & Technology

2013-03-21

be modified to create a non -inverting output as well. The probe beam is initially injected at a slightly higher frequency than the slave mode so...input signal(s) is (are) in the on state, injection locking, and thus the suppression of the non -injected Fabry–Perot modes, is induced, yielding a...laser diode), SLD (slave laser diode), EOM (electro-optic modulator), P (polarizer), OI (optical isolator), G (grating), L (lens), BE ( beam expander

Computational analysis of the effectiveness of blood flushing with saline injection from an intravascular diagnostic catheter

PubMed Central

Ghata, Narugopal; Aldredge, Ralph C.; Bec, Julien; Marcu, Laura

2015-01-01

SUMMARY Optical techniques including fluorescence lifetime spectroscopy have demonstrated potential as a tool for study and diagnosis of arterial vessel pathologies. However, their application in the intravascular diagnostic procedures has been hampered by the presence of blood hemoglobin that affects the light delivery to and the collection from the vessel wall. We report a computational fluid dynamics model that allows for the optimization of blood flushing parameters in a manner that minimizes the amount of saline needed to clear the optical field of view and reduces any adverse effects caused by the external saline jet. A 3D turbulence (k−ω) model was employed for Eulerian–Eulerian two-phase flow to simulate the flow inside and around a side-viewing fiber-optic catheter. Current analysis demonstrates the effects of various parameters including infusion and blood flow rates, vessel diameters, and pulsatile nature of blood flow on the flow structure around the catheter tip. The results from this study can be utilized in determining the optimal flushing rate for given vessel diameter, blood flow rate, and maximum wall shear stress that the vessel wall can sustain and subsequently in optimizing the design parameters of optical-based intravascular catheters. PMID:24953876

Computational modeling of the effect of external electron injection into a direct-current microdischarge

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

Panneer Chelvam, Prem Kumar; Raja, Laxminarayan L.

2015-12-28

Electron emission from the electrode surface plays an important role in determining the structure of a direct-current microdischarge. Here we have developed a computational model of a direct-current microdischarge to study the effect of external electron injection from the cathode surface into the discharge to manipulate its properties. The model provides a self-consistent, multi-species, multi-temperature fluid representation of the plasma. A microdischarge with a metal-insulator-metal configuration is chosen for this study. The effect of external electron injection on the structure and properties of the microdischarge is described. The transient behavior of the microdischarge during the electron injection is examined. Themore » nonlinearities in the dynamics of the plasma result in a large increase of conduction current after active electron injection. For the conditions simulated a switching time of ∼100 ns from a low-current to high-current discharge state is realized.« less

Interband optical pulse injection locking of quantum dot mode-locked semiconductor laser.

PubMed

Kim, Jimyung; Delfyett, Peter J

2008-07-21

We experimentally demonstrate optical clock recovery from quantum dot mode-locked semiconductor lasers by interband optical pulse injection locking. The passively mode-locked slave laser oscillating on the ground state or the first excited state transition is locked through the injection of optical pulses generated via the opposite transition bands, i.e. the first excited state or the ground state transition from the hybridly mode-locked master laser, respectively. When an optical pulse train generated via the first excited state from the master laser is injected to the slave laser oscillating via ground state, the slave laser shows an asymmetric locking bandwidth around the nominal repetition rate of the slave laser. In the reverse injection case of, i.e. the ground state (master laser) to the first excited state (slave laser), the slave laser does not lock even though both lasers oscillate at the same cavity frequency. In this case, the slave laser only locks to higher injection rates as compared to its own nominal repetition rate, and also shows a large locking bandwidth of 6.7 MHz.

Optical injection locking-based amplification in phase-coherent transfer of optical frequencies.

PubMed

Kim, Joonyoung; Schnatz, Harald; Wu, David S; Marra, Giuseppe; Richardson, David J; Slavík, Radan

2015-09-15

We demonstrate the use of an optical injection phase locked loop (OIPLL) as a regenerative amplifier for optical frequency transfer applications. The optical injection locking provides high gain within a narrow bandwidth (<100  MHz) and is capable of preserving the fractional frequency stability of the incoming carrier to better than 10(-18) at 1000 s. The OIPLL was tested in the field as a mid-span amplifier for the transfer of an ultrastable optical carrier, stabilized to an optical frequency standard, over a 292 km long installed dark fiber link. The transferred frequency at the remote end reached a fractional frequency instability of less than 1×10(-19) at averaging time of 3200 s.

Design and fabrication of optical homogenizer with micro structure by injection molding process

NASA Astrophysics Data System (ADS)

Chen, C.-C. A.; Chang, S.-W.; Weng, C.-J.

2008-08-01

This paper is to design and fabricate an optical homogenizer with hybrid design of collimator, toroidal lens array, and projection lens for beam shaping of Gaussian beam into uniform cylindrical beam. TracePro software was used to design the geometry of homogenizer and simulation of injection molding was preceded by Moldflow MPI to evaluate the mold design for injection molding process. The optical homogenizer is a cylindrical part with thickness 8.03 mm and diameter 5 mm. The micro structure of toroidal array has groove height designed from 12 μm to 99 μm. An electrical injection molding machine and PMMA (n= 1.4747) were selected to perform the experiment. Experimental results show that the optics homogenizer has achieved the transfer ratio of grooves (TRG) as 88.98% and also the optical uniformity as 68% with optical efficiency as 91.88%. Future study focuses on development of an optical homogenizer for LED light source.

Mode stabilization in quantum cascade lasers via an intra-cavity cascaded nonlinearity.

PubMed

St-Jean, M Renaudat; Amanti, M I; Bismuto, A; Beck, M; Faist, J; Sirtori, C

2017-02-06

We present self-stabilization of the inter-mode separation of a quantum cascade laser (QCL) emitting at 9 μm via cascaded second order nonlinearity. This effect has been observed in lasers that have the optical cavity embedded into a microwave strip-line. The intermodal beat note spectra narrow with increasing laser output power, up to less than 100 kHz. A flat frequency response to direct modulation up to 14 GHz is reported for these microstrip QCLs. The laser inter-mode spacing can be locked to an external RF signal and tuned by more than 1 MHz from the free-running spacing. A parallel study on the same laser material in a non-microstrip line waveguide shows superior performances of the microstrip QCL in terms of the intermodal spectral locking and stability. Finally by analyzing our results with the theory of the injection locking of coupled oscillators, we deduce that the microwave power injected in the microstrip QCL is 2 orders of magnitude higher than in the reference laser.

Combined Optical Coherence and Fluorescence Microscopy to assess dynamics and specificity of pancreatic beta-cell tracers

PubMed Central

Berclaz, Corinne; Pache, Christophe; Bouwens, Arno; Szlag, Daniel; Lopez, Antonio; Joosten, Lieke; Ekim, Selen; Brom, Maarten; Gotthardt, Martin; Grapin-Botton, Anne; Lasser, Theo

2015-01-01

The identification of a beta-cell tracer is a major quest in diabetes research. However, since MRI, PET and SPECT cannot resolve individual islets, optical techniques are required to assess the specificity of these tracers. We propose to combine Optical Coherence Microscopy (OCM) with fluorescence detection in a single optical platform to facilitate these initial screening steps from cell culture up to living rodents. OCM can image islets and vascularization without any labeling. Thereby, it alleviates the need of both genetically modified mice to detect islets and injection of external dye to reveal vascularization. We characterized Cy5.5-exendin-3, an agonist of glucagon-like peptide 1 receptor (GLP1R), for which other imaging modalities have been used and can serve as a reference. Cultured cells transfected with GLP1R and incubated with Cy5.5-exendin-3 show full tracer internalization. We determined that a dose of 1 μg of Cy5.5-exendin-3 is sufficient to optically detect in vivo the tracer in islets with a high specificity. In a next step, time-lapse OCM imaging was used to monitor the rapid and specific tracer accumulation in murine islets and its persistence over hours. This optical platform represents a versatile toolbox for selecting beta-cell specific markers for diabetes research and future clinical diagnosis. PMID:25988507

GRB 081029: A Gamma-Ray Burst with a Multi-Component Afterglow

NASA Technical Reports Server (NTRS)

Holland, Stephen T.; DePasquale, Massimiliano; Mao, Jirong; Sakamoto, Taka; Shady, Patricia; Covino, Stefano; Yi-Zhong, Fan; Zhi-Ping, Jin; D'Avanzo, Paolo; Antonelli, Angelo;

A tunable optofluidic circular liquid fiber

NASA Astrophysics Data System (ADS)

Li, Lei; Wu, Wei; Shi, Yang; Gong, Enze; Yang, Yi

2016-01-01

This paper presents a tunable optofluidic circular liquid fiber through the numerical simulation. Fiber is a significant optical device and has been widely applied on optical fiber communication. But the fiber based solid has limited tunability. Compared to solid fiber, the fiber based liquid material is relatively infrequent. Cause for the liquid optical device has more freedom tunable properties than solid counterpart, it has attracted more interest. The traditional optofluidic waveguide is designed like a sandwich in planar channel. This two-dimensional (2D) structure liquid waveguide will face huge transmission loss in the perpendicular direction of the flow streams. In this paper, a curving microchannel is designed inside the microchip to produce centrifugal effect. Two different liquids are injected into the chip by external pumps. In a particular situation, the core flow will be totally surrounded by the cladding flow. So the liquid can form an optical waveguide. Its structure is similar to an optical fiber which high refractive index (RI) liquid is core of the waveguide and the low RI liquid is cladding of the waveguide. Profit from the reconfigurability of liquid material, this liquid fiber has excellent tunability. The diameter of the core flow can be tuned in a wider range by changing the volume ratio of the flows through the finite element analysis. It is predictable that such a tunable liquid fiber may find wider applications in lab-on-a-chip systems and integrated optical devices.

External Cavity Coherent Transmitter Modules

DTIC Science & Technology

1990-11-01

Lasers 141 Tunability Aspects of DFB External Cavity Semiconductor Lasers Harish R. D. Sunak & Clark P. Engert Fiber Optical Communications Laboratory...Linewidth Considerations for DFB External Cavity Semiconductor Lasers Harish R. D. Sunak & Clark P. Engert Fiber Optical Communications Laboratory

Flexible Near-Field Wireless Optoelectronics as Subdermal Implants for Broad Applications in Optogenetics.

PubMed

Shin, Gunchul; Gomez, Adrian M; Al-Hasani, Ream; Jeong, Yu Ra; Kim, Jeonghyun; Xie, Zhaoqian; Banks, Anthony; Lee, Seung Min; Han, Sang Youn; Yoo, Chul Jong; Lee, Jong-Lam; Lee, Seung Hee; Kurniawan, Jonas; Tureb, Jacob; Guo, Zhongzhu; Yoon, Jangyeol; Park, Sung-Il; Bang, Sang Yun; Nam, Yoonho; Walicki, Marie C; Samineni, Vijay K; Mickle, Aaron D; Lee, Kunhyuk; Heo, Seung Yun; McCall, Jordan G; Pan, Taisong; Wang, Liang; Feng, Xue; Kim, Tae-Il; Kim, Jong Kyu; Li, Yuhang; Huang, Yonggang; Gereau, Robert W; Ha, Jeong Sook; Bruchas, Michael R; Rogers, John A

2017-02-08

In vivo optogenetics provides unique, powerful capabilities in the dissection of neural circuits implicated in neuropsychiatric disorders. Conventional hardware for such studies, however, physically tethers the experimental animal to an external light source, limiting the range of possible experiments. Emerging wireless options offer important capabilities that avoid some of these limitations, but the current size, bulk, weight, and wireless area of coverage is often disadvantageous. Here, we present a simple but powerful setup based on wireless, near-field power transfer and miniaturized, thin, flexible optoelectronic implants, for complete optical control in a variety of behavioral paradigms. The devices combine subdermal magnetic coil antennas connected to microscale, injectable light-emitting diodes (LEDs), with the ability to operate at wavelengths ranging from UV to blue, green-yellow, and red. An external loop antenna allows robust, straightforward application in a multitude of behavioral apparatuses. The result is a readily mass-producible, user-friendly technology with broad potential for optogenetics applications. Copyright © 2017 Elsevier Inc. All rights reserved.

Flexible near field wireless optoelectronics as subdermal implants for broad applications in optogenetics

PubMed Central

Shin, Gunchul; Gomez, Adrian M.; Al-Hasani, Ream; Jeong, Yu Ra; Kim, Jeonghyun; Xie, Zhaoqian; Banks, Anthony; Lee, Seung Min; Han, Sang Youn; Yoo, Chul Jong; Lee, Jong-Lam; Lee, Seung Hee; Kurniawan, Jonas; Tureb, Jacob; Guo, Zhongzhu; Yoon, Jangyeol; Park, Sung-Il; Bang, Sang Yun; Nam, Yoonho; Walicki, Marie C.; Samineni, Vijay K.; Mickle, Aaron D.; Lee, Kunhyuk; Heo, Seung Yun; McCall, Jordan G.; Pan, Taisong; Wang, Liang; Feng, Xue; Kim, Taeil; Kim, Jong Kyu; Li, Yuhang; Huang, Yonggang; Gereau, Robert W.; Ha, Jeong Sook; Bruchas, Michael R.; Rogers, John A.

2017-01-01

Summary In vivo optogenetics provides unique, powerful capabilities in the dissection of neural circuits implicated in neuropsychiatric disorders. Conventional hardware for such studies, however, physically tethers the experimental animal to an external light source limiting the range of possible experiments. Emerging wireless options offer important capabilities that avoid some of these limitations, but the current size, bulk, weight, and wireless area of coverage is often disadvantageous. Here, we present a simple but powerful setup based on wireless, near-field power transfer and miniaturized, thin flexible optoelectronic implants, for complete optical control in a variety of behavioral paradigms. The devices combine subdermal magnetic coil antennas connected to microscale, injectable LEDs, with the ability to operate at wavelengths ranging from ultraviolet to blue, green/yellow, and red. An external loop antenna allows robust, straightforward application in a multitude of behavioral apparatuses. The result is a readily mass-producible, user-friendly technology with broad potential for optogenetics applications. PMID:28132830

Plasmonic nanobubbles for target cell-specific gene and drug delivery and multifunctional processing of heterogeneous cell systems

NASA Astrophysics Data System (ADS)

Lukianova-Hleb, Ekaterina Y.; Huye, Leslie E.; Brenner, Malcolm K.; Lapotko, Dmitri O.

2014-03-01

Cell and gene cancer therapies require ex vivo cell processing of human grafts. Such processing requires at least three steps - cell enrichment, cell separation (destruction), and gene transfer - each of which requires the use of a separate technology. While these technologies may be satisfactory for research use, they are of limited usefulness in the clinical treatment setting because they have a low processing rate, as well as a low transfection and separation efficacy and specificity in heterogeneous human grafts. Most problematic, because current technologies are administered in multiple steps - rather than in a single, multifunctional, and simultaneous procedure - they lengthen treatment process and introduce an unnecessary level of complexity, labor, and resources into clinical treatment; all these limitations result in high losses of valuable cells. We report a universal, high-throughput, and multifunctional technology that simultaneously (1) inject free external cargo in target cells, (2) destroys unwanted cells, and (3) preserve valuable non-target cells in heterogeneous grafts. Each of these functions has single target cell specificity in heterogeneous cell system, processing rate > 45 mln cell/min, injection efficacy 90% under 96% viability of the injected cells, target cell destruction efficacy > 99%, viability of not-target cells >99% The developed technology employs novel cellular agents, called plasmonic nanobubbles (PNBs). PNBs are not particles, but transient, intracellular events, a vapor nanobubbles that expand and collapse in mere nanoseconds under optical excitation of gold nanoparticles with short picosecond laser pulses. PNBs of different, cell-specific, size (1) inject free external cargo with small PNBs, (2) Destroy other target cells mechanically with large PNBs and (3) Preserve non-target cells. The multi-functionality, precision, and high throughput of all-in-one PNB technology will tremendously impact cell and gene therapies and other clinical applications that depend on ex vivo processing of heterogeneous cell systems.

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

Afonenko, A A; Dorogush, E S; Malyshev, S A

Using a system of coupled travelling wave equations, in the small-signal regime we analyse frequency and noise characteristics of index- or absorption-coupled distributed feedback laser diodes, as well as of Fabry – Perot (FP) laser diodes. It is shown that the weakest dependence of the direct modulation efficiency on the locking frequency in the regime of strong external optical injection locking is exhibited by a FP laser diode formed by highly reflective and antireflective coatings on the end faces of a laser structure. A reduction in the dependence of output characteristics of the laser diode on the locking frequency canmore » be attained by decreasing the reflection coefficient of the antireflective FP mirror. (control of laser radiation parameters)« less

Wavelength-resonant surface-emitting semiconductor laser

DOEpatents

Brueck, Steven R. J.; Schaus, Christian F.; Osinski, Marek A.; McInerney, John G.; Raja, M. Yasin A.; Brennan, Thomas M.; Hammons, Burrell E.

1989-01-01

A wavelength resonant semiconductor gain medium is disclosed. The essential feature of this medium is a multiplicity of quantum-well gain regions separated by semiconductor spacer regions of higher bandgap. Each period of this medium consisting of one quantum-well region and the adjacent spacer region is chosen such that the total width is equal to an integral multiple of 1/2 the wavelength in the medium of the radiation with which the medium is interacting. Optical, electron-beam and electrical injection pumping of the medium is disclosed. This medium may be used as a laser medium for single devices or arrays either with or without reflectors, which may be either semiconductor or external.

Modulation properties of optically injection-locked quantum cascade lasers.

PubMed

Wang, Cheng; Grillot, Fédéric; Kovanis, Vassilios I; Bodyfelt, Joshua D; Even, Jacky

2013-06-01

A rate equation analysis on the modulation response of an optical injection-locked quantum cascade laser is outlined. It is found that the bifurcation diagram exhibits both bistable and unstable locked regions. In addition, the stable locked regime widens as the linewidth enhancement factor increases. It is also shown that both positive and negative optical detunings as well as strong injection strength enhance the 3 dB modulation bandwidth by as much as 30 GHz. Finally, the peak in the modulation response is significantly influenced by the optical frequency detuning.

Width-tunable pulse laser via optical injection induced gain modulation of semiconductor optical amplifiers

NASA Astrophysics Data System (ADS)

Pan, Honggang; Zhang, Ailing; Tong, Zhengrong; Zhang, Yue; Song, Hongyun; Yao, Yuan

2018-03-01

A width-tunable pulse laser via an optical injection induced gain modulation of a semiconductor optical amplifier (SOA) is demonstrated. When the pump current of the SOA is 330 mA or 400 mA and a continuous wave is injected into the laser cavity with different powers, bright or dark pulses with different pulse widths and frequency repetition rates are obtained. The bright and dark pulses are formed by the effect of gain dispersion and cross-gain modulation of the SOA.

"Who has ever loved a drug addict? It's a lie. They think a 'teja' is as bad person": multiple stigmas faced by women who inject drugs in coastal Kenya.

PubMed

Mburu, Gitau; Ayon, Sylvia; Tsai, Alexander C; Ndimbii, James; Wang, Bangyuan; Strathdee, Steffanie; Seeley, Janet

2018-05-25

A tenth of all people who inject drugs in Kenya are women, yet their social contexts and experiences remain poorly understood. This paper reports how multiple forms of stigma are experienced by women who inject drugs in coastal Kenya and the impact that they have on their ability to access essential health services. In 2015, in-depth interviews and focus group discussions were held with 45 women who inject drugs in two coastal towns. These data were supplemented with in-depth interviews with five individual stakeholders involved in service provision to this population. Data were analyzed thematically using NVivo. Women who inject drugs experience multiple stigmas, often simultaneously. These included the external stigma and self-stigma of injection drug use, external gender-related stigma of being a female injecting drug user, and the external stigma of being HIV positive (i.e., among those living with HIV). Stigma led to rejection, social exclusion, low self-esteem, and delay or denial of services at health facilities. HIV and harm reduction programs should incorporate interventions that address different forms of stigma among women who inject drugs in coastal Kenya. Addressing stigma will require a combination of individual, social, and structural interventions, such as collective empowerment of injecting drug users, training of healthcare providers on issues and needs of women who inject drugs, peer accompaniment to health facilities, addressing wider social determinants of stigma and discrimination, and expansion of harm reduction interventions to change perceptions of communities towards women who inject drugs.

All-optical NRZ-to-RZ data format conversion with optically injected laser diode or semiconductor optical amplifier

NASA Astrophysics Data System (ADS)

Lin, Gong-Ru; Chang, Yung-Cheng; Yu, Kun-Chieh

2006-09-01

By injecting the optical NRZ data into a Fabry-Perot laser diode (FPLD) synchronously modulated at below threshold condition or a semiconductor optical amplifier (SOA) gain-depleted with a backward injected clock stream, the all-optical non-return to zero (NRZ) to return-to-zero (RZ) format conversion of a STM-64 date-stream for synchronous digital hierarchy (SDH) or an OC-192 data stream for synchronous optical network (SONET) in high-speed fiber-optic communication link can be performed. Without the assistance of any complicated RF electronic circuitry, the output RZ data-stream at bit rate of up to 10 Gbit/s is successfully transformed in the optically NRZ injection-locked FPLD, in which the incoming NRZ data induces gain-switching of the FPLD without DC driving current or at below threshold condition. A power penalty of 1.2 dB is measured after NRZ-to-RZ transformation in the FPLD. Alternatively, the all-optical 10Gbits/s NRZ-to-RZ format conversion can also be demonstrated in a semiconductor optical amplifier under a backward dark-optical-comb injection with its duty-cycle 70%, which is obtained by reshaping from the received data clock at 10 GHz. The incoming optical NRZ data-stream is transformed into a pulsed RZ data-stream with its duty-cycle, rms timing jitter, and conversion gain of 15%, 4ps, and 3dB, respectively. In contrast to the FPLD, the SOA based NRZ-to-RZ converter exhibits an enhanced extinction ratio from 7 to 13 dB, and BER of 10 -13 at -18.5 dBm. In particular, the power penalty of the received RZ data-stream has greatly improved by 5 dB as compared to that obtained from FPLD.

Targeted Drug Delivery in the Suprachoroidal Space by Swollen Hydrogel Pushing

PubMed Central

Jung, Jae Hwan; Desit, Patcharin; Prausnitz, Mark R.

2018-01-01

Purpose The purpose is to target model drug particles to the posterior region of the suprachoroidal space (SCS) of the eye controlled via pushing by hydrogel swelling. Methods A particle formulation containing 1% hyaluronic acid (HA) with fluorescent polymer particles and a hydrogel formulation containing 4% HA were introduced in a single syringe as two layers without mixing, and injected sequentially into the SCS of the rabbit eye ex vivo and in vivo using a microneedle. Distribution of particles in the eye was determined by microscopy. Results During injection, the particle formulation was pushed toward the middle of the SCS by the viscous hydrogel formulation, but less than 12% of particles reached the posterior SCS. After injection, the particle formulation was pushed further toward the macula and optic nerve in the posterior SCS by hydrogel swelling and spreading. Heating the eye to 37°C, or injecting in vivo decreased viscosity and mechanical strength of the hydrogel, thereby allowing it to swell and flow further in the SCS. A high salt concentration (9% NaCl) in the hydrogel formulation further increased hydrogel swelling due to osmotic flow into the hydrogel. In this way, up to 76% of particles were delivered to the posterior SCS from an injection made near the limbus. Conclusions This study shows that model drug particles can be targeted to the posterior SCS by HA hydrogel swelling and pushing without particle functionalization or administering external driving forces. PMID:29677369

Photonic jet: key role of injection for etchings with a shaped optical fiber tip.

PubMed

Pierron, Robin; Zelgowski, Julien; Pfeiffer, Pierre; Fontaine, Joël; Lecler, Sylvain

2017-07-15

We demonstrate the key role of the laser injection into a multimode fiber to obtain a photonic jet (PJ). PJ, a high concentrated propagating beam with a full width at half-maximum smaller than the diffraction limit, is here generated with a shaped optical fiber tip using a pulsed laser source (1064 nm, 100 ns, 35 kHz). Three optical injection systems of light are compared. For similar etched marks on silicon with diameters around 1 μm, we show that the required ablation energy is minimum when the injected light beam is close to the fundamental mode diameter of the fiber. Thus, we confirm experimentally that to obtain a PJ out of an optical fiber, light injection plays a role as important as that of the tip shape and, therefore, the role of the fundamental mode in the process.

High average power scaling of optical parametric amplification through cascaded difference-frequency generators

DOEpatents

Jovanovic, Igor; Comaskey, Brian J.

2004-09-14

A first pump pulse and a signal pulse are injected into a first optical parametric amplifier. This produces a first amplified signal pulse. At least one additional pump pulse and the first amplified signal pulse are injected into at least one additional optical parametric amplifier producing an increased power coherent optical pulse.

Compensation of power drops in reflective semiconductor optical amplifier-based passive optical network with upstream data rate adjustment

NASA Astrophysics Data System (ADS)

Yeh, Chien-Hung; Chow, Chi-Wai; Chiang, Ming-Feng; Shih, Fu-Yuan; Pan, Ci-Ling

2011-09-01

In a wavelength division multiplexed-passive optical network (WDM-PON), different fiber lengths and optical components would introduce different power budgets to different optical networking units (ONUs). Besides, the power decay of the distributed optical carrier from the optical line terminal owing to aging of the optical transmitter could also reduce the injected power into the ONU. In this work, we propose and demonstrate a carrier distributed WDM-PON using a reflective semiconductor optical amplifier-based ONU that can adjust its upstream data rate to accommodate different injected optical powers. The WDM-PON is evaluated at standard-reach (25 km) and long-reach (100 km). Bit-error rate measurements at different injected optical powers and transmission lengths show that by adjusting the upstream data rate of the system (622 Mb/s, 1.25 and 2.5 Gb/s), error-free (<10-9) operation can still be achieved when the power budget drops.

Power- or frequency-driven hysteresis for continuous-wave optically injected distributed-feedback semiconductor lasers.

PubMed

Blin, Stéphane; Vaudel, Olivier; Besnard, Pascal; Gabet, Renaud

2009-05-25

Bistabilities between a steady (or pulsating, chaotic) and different pulsating regimes are investigated for an optically injected semi-conductor laser. Both numerical and experimental studies are reported for continuous-wave single-mode semiconductor distributed-feedback lasers emitting at 1.55 microm. Hysteresis are driven by either changing the optically injected power or the frequency difference between both lasers. The effect of the injected laser pumping rate is also examined. Systematic mappings of the possible laser outputs (injection locking, bimodal, wave mixing, chaos or relaxation oscillations) are carried out. At small pumping rates (1.2 times threshold), only locking and bimodal regimes are observed. The extent of the bistable area is either 11 dB or 35 GHz, depending on the varying parameters. At high pumping rates (4 times threshold), numerous injection regimes are observed. Injection locking and its bistabilities are also reported for secondary longitudinal modes.

Intravitreal gas injection without vitrectomy for macular detachment associated with an optic disk pit.

PubMed

Akiyama, Hideo; Shimoda, Yukitoshi; Fukuchi, Mariko; Kashima, Tomoyuki; Mayuzumi, Hideyasu; Shinohara, Yoichiro; Kishi, Shoji

2014-02-01

To evaluate the clinical outcomes after gas tamponade without vitrectomy for retinal detachment associated with an optic disk pit using optical coherence tomography. Intravitreal gas injection was performed on 8 consecutive patients (mean age, 35.0 years; range, 15-74 years) with unilateral macular detachment associated with an optic disk pit. A 0.3-mL injection of 100% sulfur hexafluoride 6 gas was carried out without an anterior chamber tap. Patients treated with gas injection were instructed to remain facedown for 5 days. Complete retinal reattachment after only gas tamponade was achieved in four out of eight eyes. The mean number of gas injections was 1.8. The mean best-corrected visual acuity before and after the treatment with gas tamponade was approximately 30/100 and 20/20, respectively. The period required for reattachment after final gas treatment was 12 months. There were no incidences of recurrence after complete reattachment by gas tamponade in any of the cases during the 94-month average follow-up period (range, 64-132 months). Gas tamponade appears to be an effective alternative method for macular detachment associated with an optic disk pit, even though the mechanisms of optic disk pit maculopathy are still unknown.

Recent Electrochemical and Optical Sensors in Flow-Based Analysis

PubMed Central

Chailapakul, Orawon; Ngamukot, Passapol; Yoosamran, Alongkorn; Siangproh, Weena; Wangfuengkanagul, Nattakarn

2006-01-01

Some recent analytical sensors based on electrochemical and optical detection coupled with different flow techniques have been chosen in this overview. A brief description of fundamental concepts and applications of each flow technique, such as flow injection analysis (FIA), sequential injection analysis (SIA), all injection analysis (AIA), batch injection analysis (BIA), multicommutated FIA (MCFIA), multisyringe FIA (MSFIA), and multipumped FIA (MPFIA) were reviewed.

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.

International Space Station External Contamination Status

NASA Technical Reports Server (NTRS)

Mikatarian, Ron; Soares, Carlos

2000-01-01

PResentation slides examine external contamination requirements; International Space Station (ISS) external contamination sources; ISS external contamination sensitive surfaces; external contamination control; external contamination control for pre-launch verification; flight experiments and observations; the Space Shuttle Orbiter waste water dump, materials outgassing, active vacuum vents; example of molecular column density profile, modeling and analysis tools; sources of outgassing induced contamination analyzed to date, quiescent sources, observations on optical degradation due to induced external contamination in LEO; examples of typical contaminant and depth profiles; and status of the ISS system, material outgassing, thruster plumes, and optical degradation.

System for testing optical fibers

DOEpatents

Golob, John E. [Olathe, KS; Looney, Larry D. [Los Alamos, NM; Lyons, Peter B. [Los Alamos, NM; Nelson, Melvin A. [Santa Barbara, CA; Davies, Terence J. [Santa Barbara, CA

1980-07-15

A system for measuring a combination of optical transmission properties of fiber optic waveguides. A polarized light pulse probe is injected into one end of the optical fiber. Reflections from discontinuities within the fiber are unpolarized whereas reflections of the probe pulse incident to its injection remain polarized. The polarized reflections are prevented from reaching a light detector whereas reflections from the discontinuities reaches the detector.

Self-Raman Nd:YVO4 laser and electro-optic technology for space-based sodium lidar instrument

NASA Astrophysics Data System (ADS)

Krainak, Michael A.; Yu, Anthony W.; Janches, Diego; Jones, Sarah L.; Blagojevic, Branimir; Chen, Jeffrey

2014-02-01

We are developing a laser and electro-optic technology to remotely measure Sodium (Na) by adapting existing lidar technology with space flight heritage. The developed instrumentation will serve as the core for the planning of an Heliophysics mission targeted to study the composition and dynamics of Earth's mesosphere based on a spaceborne lidar that will measure the mesospheric Na layer. We present performance results from our diode-pumped tunable Q-switched self-Raman c-cut Nd:YVO4 laser with intra-cavity frequency doubling that produces multi-watt 589 nm wavelength output. The c-cut Nd:YVO4 laser has a fundamental wavelength that is tunable from 1063-1067 nm. A CW External Cavity diode laser is used as a injection seeder to provide single-frequency grating tunable output around 1066 nm. The injection-seeded self-Raman shifted Nd:VO4 laser is tuned across the sodium vapor D2 line at 589 nm. We will review technologies that provide strong leverage for the sodium lidar laser system with strong heritage from the Ice Cloud and Land Elevation Satellite-2 (ICESat-2) Advanced Topographic Laser Altimeter System (ATLAS). These include a space-qualified frequency-doubled 9W @ 532 nm wavelength Nd:YVO4 laser, a tandem interference filter temperature-stabilized fused-silica-etalon receiver and high-bandwidth photon-counting detectors.

Self-Raman Nd:YVO4 Laser and Electro-Optic Technology for Space-Based Sodium Lidar Instrument

NASA Technical Reports Server (NTRS)

Krainak, Michael A.; Yu, Anthony W.; Janches, Diego; Jones, Sarah L.; Blagojevic, Branimir; Chen, Jeffrey

2014-01-01

We are developing a laser and electro-optic technology to remotely measure Sodium (Na) by adapting existing lidar technology with space flight heritage. The developed instrumentation will serve as the core for the planning of an Heliophysics mission targeted to study the composition and dynamics of Earth's mesosphere based on a spaceborne lidar that will measure the mesospheric Na layer. We present performance results from our diode-pumped tunable Q-switched self-Raman c-cut Nd:YVO4 laser with intra-cavity frequency doubling that produces multi-watt 589 nm wavelength output. The c-cut Nd:YVO4 laser has a fundamental wavelength that is tunable from 1063-1067 nanometers. A CW (Continuous Wave) External Cavity diode laser is used as a injection seeder to provide single-frequency grating tunable output around 1066 nanometers. The injection-seeded self-Raman shifted Nd:VO4 laser is tuned across the sodium vapor D2 line at 589 nanometers. We will review technologies that provide strong leverage for the sodium lidar laser system with strong heritage from the Ice Cloud and Land Elevation Satellite-2 (ICESat-2) Advanced Topographic Laser Altimeter System (ATLAS). These include a space-qualified frequency-doubled 9 watts-at-532-nanometer wavelength Nd:YVO4 laser, a tandem interference filter temperature-stabilized fused-silica-etalon receiver and high-bandwidth photon-counting detectors.

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

Zhang, H. D.; Fiorito, R. B.; Corbett, J.

The 3GeV SPEAR3 synchrotron light source operates in top-up injection mode with up to 500 mA circulating in the storage ring (equivalently 392 nC). Each injection pulse contains 40–80 pC producing a contrast ratio between total stored charge and injected charge of about 6500:1. In order to study transient injected beam dynamics during user operations, it is desirable to optically image the injected pulse in the presence of the bright stored beam. In the present work this is done by imaging the visible component of the synchrotron radiation onto a digital micro-mirror-array device (DMD), which is then used as anmore » optical mask to block out light from the bright central core of the stored beam. The physical masking, together with an asynchronously-gated, ICCD imaging camera, makes it possible to observe the weak injected beam component on a turn-by-turn basis. The DMD optical masking system works similar to a classical solar coronagraph but has some distinct practical advantages: i.e. rapid adaption to changes in the shape of the stored beam, a high extinction ratio for unwanted light and minimum scattering from the primary beam into the secondary optics. In this paper we describe the DMD masking method, features of the high dynamic range point spread function for the SPEAR3 optical beam line and measurements of the injected beam in the presence of the stored beam.« less

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

Zhang, Hao; Fiorito, Ralph; Corbett, Jeff

The 3GeV SPEAR3 synchrotron light source operates in top-up injection mode with up to 500mA circulating in the storage ring (equivalently 392nC). Each injection pulse contains only 40-80 pC producing a contrast ratio between total stored charge and injected charge of about 6500:1. In order to study transient injected beam dynamics during User operations, it is desirable to optically image the injected pulse in the presence of the bright stored beam. In the present work this is done by re-imaging visible synchrotron radiation onto a digital micro-mirror-array device (DMD), which is then used as an optical mask to block outmore » light from the bright central core of the stored beam. The physical masking, together with an asynchronously-gated, ICCD imaging camera makes it is possible to observe the weak injected beam component on a turn-by-turn basis. The DMD optical masking system works similar to a classical solar coronagraph but has some distinct practical advantages: i.e. rapid adaption to changes in the shape of the stored beam, high extinction ratio for unwanted light and minimum scattering from the primary beam into the secondary optics. In this paper we describe the DMD masking method, features of the high dynamic range point spread function for the SPEAR3 optical beam line and measurements of the injected beam in the presence of the stored beam.« less

Direct solar pumping of semiconductor lasers: A feasibility study

NASA Technical Reports Server (NTRS)

Anderson, Neal G.

1991-01-01

The primary goals of the feasibility study are the following: (1) to provide a preliminary assessment of the feasibility of pumping semiconductor lasers in space directly focused sunlight; and (2) to identify semiconductor laser structures expected to operate at the lowest possible focusing intensities. It should be emphasized that the structures under consideration would provide direct optical-to-optical conversion of sunlight into laser light in a single crystal, in contrast to a configuration consisting of a solar cell or battery electrically pumping a current injection laser. With external modulation, such lasers may prove to be efficient sources for intersatellite communications. We proposed to develop a theoretical model of semiconductor quantum-well lasers photopumped by a broadband source, test it against existing experimental data where possible, and apply it to estimating solar pumping requirements and identifying optimum structures for operation for operation at low pump intensities. This report outlines our progress toward these goals. Discussion of several technical details are left to the attached summary abstract.

Exceptional points in anisotropic photonic structures: from non-Hermitian physics to possible device applications

NASA Astrophysics Data System (ADS)

Grundmann, Marius; Richter, Steffen; Michalsky, Tom; Sturm, Chris; Zúñiga-Pérez, Jesús; Schmidt-Grund, Rüdiger

2017-02-01

We demonstrate that exceptional points exist in fully transparent, optically "effectively" biaxial, anisotropic micro-cavities, fabricated using an uniaxial cavity material with its axis inclined to the Bragg mirror growth direction. This is similar to the existence of singular (optic) axes in absorbing biaxial crystals, but the lack of time reversal symmetry is mediated by the mode broadening, i.e. the photon escape from the - in principle - open cavity system. As a consequence the eigenmodes are generally elliptically polarized, and completely circularly polarized eigenmodes are expected in certain directions. Via geometric and chemical composition design degrees of freedom, the spectral and angular position of these chiral modes can be rationally designed. Possible applications arise from the use of such directions for circularly polarized emission without the use of spin injection or internal or external magnetic fields. Also the coupling of such modes to excitons, adding oscillator strength to the system, seems a promising avenue of research.

Process influences and correction possibilities for high precision injection molded freeform optics

NASA Astrophysics Data System (ADS)

Dick, Lars; Risse, Stefan; Tünnermann, Andreas

2016-08-01

Modern injection molding processes offer a cost-efficient method for manufacturing high precision plastic optics for high volume applications. Besides form deviation of molded freeform optics, internal material stress is a relevant influencing factor for the functionality of a freeform optics in an optical system. This paper illustrates dominant influence parameters of an injection molding process relating to form deviation and internal material stress based on a freeform demonstrator geometry. Furthermore, a deterministic and efficient way for 3D mold correcting of systematic, asymmetrical shrinkage errors is shown to reach micrometer range shape accuracy at diameters up to 40 mm. In a second case, a stress-optimized parameter combination using unusual molding conditions was 3D corrected to reach high precision and low stress freeform polymer optics.

Fast, externally triggered, digital phase controller for an optical lattice

NASA Astrophysics Data System (ADS)

Sadgrove, Mark; Nakagawa, Ken'ichi

2011-11-01

We present a method to control the phase of an optical lattice according to an external trigger signal. The method has a latency of less than 30 μs. Two phase locked digital synthesizers provide the driving signal for two acousto-optic modulators which control the frequency and phase of the counter-propagating beams which form a standing wave (optical lattice). A micro-controller with an external interrupt function is connected to the desired external signal, and updates the phase register of one of the synthesizers when the external signal changes. The standing wave (period λ/2 = 390 nm) can be moved by units of 49 nm with a mean jitter of 28 nm. The phase change is well known due to the digital nature of the synthesizer, and does not need calibration. The uses of the scheme include coherent control of atomic matter-wave dynamics.

Single-element optical injection locking of diode-laser arrays

DOEpatents

Hadley, G. Ronald; Hohimer, John P.; Owyoung, Adelbert

1988-01-01

By optically injecting a single end-element of a semiconductor laser array, both the spatial and spectral emission characteristics of the entire laser array is controlled. With the output of the array locked, the far-field emission angle of the array is continuously scanned over several degrees by varying the injection frequency.

Thermally insensitive determination of the linewidth broadening factor in nanostructured semiconductor lasers using optical injection locking

PubMed Central

Wang, Cheng; Schires, Kevin; Osiński, Marek; Poole, Philip J.; Grillot, Frédéric

2016-01-01

In semiconductor lasers, current injection not only provides the optical gain, but also induces variation of the refractive index, as governed by the Kramers-Krönig relation. The linear coupling between the changes of the effective refractive index and the modal gain is described by the linewidth broadening factor, which is responsible for many static and dynamic features of semiconductor lasers. Intensive efforts have been made to characterize this factor in the past three decades. In this paper, we propose a simple, flexible technique for measuring the linewidth broadening factor of semiconductor lasers. It relies on the stable optical injection locking of semiconductor lasers, and the linewidth broadening factor is extracted from the residual side-modes, which are supported by the amplified spontaneous emission. This new technique has great advantages of insensitivity to thermal effects, the bias current, and the choice of injection-locked mode. In addition, it does not require the explicit knowledge of optical injection conditions, including the injection strength and the frequency detuning. The standard deviation of the measurements is less than 15%. PMID:27302301

Applications of Optical Coherent Transient Technology to Pulse Shaping, Spectral Filtering Arbitrary Waveform Generation and RF Beamforming

DTIC Science & Technology

2006-04-14

the EOPM (~1 mW) was amplified by injection locking of a high power diode laser and further amplified to ~300 mW with a semiconductor optical ...The spectra of 8 GHz CW phase modulated signals in cascaded injection locking system from (a) master laser ; (b) the first slave, and (c) the second...cascaded injection locked amplifiers at 793nm, and frequency chirped lasers at 793nm. 15. SUBJECT TERMS Optical Coherent Transients, Spatial

System for testing optical fibers

DOEpatents

Golob, J.E.; Looney, L.D.; Lyons, P.B.; Nelson, M.A.; Davies, T.J.

1980-07-15

A system for measuring a combination of optical transmission properties of fiber optic waveguides. A polarized light pulse probe is injected into one end of the optical fiber. Reflections from discontinuities within the fiber are unpolarized whereas reflections of the probe pulse incident to its injection remain polarized. The polarized reflections are prevented from reaching a light detector whereas reflections from the discontinuities reaches the detector. 2 figs.

Optical Microwave Interactions in Semiconductor Devices.

DTIC Science & Technology

1980-11-01

geometry can be used in microwave-optical analog T signal processing systems. A theoretical and experimental study of mode locking in (GaAI)As injection... STUDY OF MODE-LOCKING IN (GaAl)As INJECTION LASER .......... ......................... ... 55 A. Experimental Set-Up and DC Characteristics...modulation and 4 detection of optical beams at microwave frequencies. Our approach for modulating the optical beam has been to study the modulation capability

Optical Injection Locking of Vertical Cavity Surface-Emitting Lasers: Digital and Analog Applications

NASA Astrophysics Data System (ADS)

Parekh, Devang

With the rise of mobile (cellphones, tablets, notebooks, etc.) and broadband wireline communications (Fiber to the Home), there are increasing demands being placed on transmitters for moving data from device to device and around the world. Digital and analog fiber-optic communications have been the key technology to meet this challenge, ushering in ubiquitous Internet and cable TV over the past 20 years. At the physical layer, high-volume low-cost manufacturing of semiconductor optoelectronic devices has played an integral role in allowing for deployment of high-speed communication links. In particular, vertical cavity surface emitting lasers (VCSEL) have revolutionized short reach communications and are poised to enter more markets due to their low cost, small size, and performance. However, VCSELs have disadvantages such as limited modulation performance and large frequency chirp which limits fiber transmission speed and distance, key parameters for many fiber-optic communication systems. Optical injection locking is one method to overcome these limitations without re-engineering the VCSEL at the device level. By locking the frequency and phase of the VCSEL by the direct injection of light from another laser oscillator, improved device performance is achieved in a post-fabrication method. In this dissertation, optical injection locking of VCSELs is investigated from an applications perspective. Optical injection locking of VCSELs can be used as a pathway to reduce complexity, cost, and size of both digital and analog fiber-optic communications. On the digital front, reduction of frequency chirp via bit pattern inversion for large-signal modulation is experimentally demonstrated showing up to 10 times reduction in frequency chirp and over 90 times increase in fiber transmission distance. Based on these results, a new reflection-based interferometric model for optical injection locking was established to explain this phenomenon. On the analog side, the resonance frequency enhancement was exploited for millimeter-wave radio over fiber communications. Experimental demonstration of 4 Gb/s data transmission over 20 km of fiber and 3 m of wireless transmission at a 60 GHz carrier frequency was achieved. Additionally, optical injection of multi-transverse mode (MM) VCSELs was investigated showing record resonance frequency enhancement of > 54 GHz and 3-dB bandwidth of 38 GHz. Besides these applications, a number of other intriguing applications are also discussed, including an optoelectronic oscillator (OEO) and wavelength-division multiplexed passive optical networks (WDM-PON). Finally, the future of optical injection locking and its direction going forward will be discussed.

Architectural Considerations of Fiber-Radio Millimeter-Wave Wireless Access Systems

NASA Astrophysics Data System (ADS)

Kitayama, Ken-Ichi

The architecture of fiber-radio mm-wave wireless access systems critically depends upon the optical mm-wave generation and transport techniques. Four optical mm-wave generation and transport techniques: 1) optical self-heterodyning, 2) external modulation, 3) up- and downconversion, and 4) optical transceiver, will be assessed. From the technical viewpoints, their advantages and disadvantages are discussed. The economical assessment, focusing on the cost of a base station BS ( ), will suggest that the optical transceiver looks the most promising in the long run, but in the near future, however, the external modulation will be cost-effective. The experimental results of 60 GHz testbeds using the external modulation will support the conclusion.

Quantum correlation in degenerate optical parametric oscillators with mutual injections

NASA Astrophysics Data System (ADS)

Takata, Kenta; Marandi, Alireza; Yamamoto, Yoshihisa

2015-10-01

We theoretically and numerically study the quantum dynamics of two degenerate optical parametric oscillators with mutual injections. The cavity mode in the optical coupling path between the two oscillator facets is explicitly considered. Stochastic equations for the oscillators and mutual injection path based on the positive P representation are derived. The system of two gradually pumped oscillators with out-of-phase mutual injections is simulated, and its quantum state is investigated. When the incoherent loss of the oscillators other than the mutual injections is small, the squeezed quadratic amplitudes p ̂ in the oscillators are positively correlated near the oscillation threshold. It indicates finite quantum correlation, estimated via Gaussian quantum discord, and the entanglement between the intracavity subharmonic fields. When the loss in the injection path is low, each oscillator around the phase transition point forms macroscopic superposition even under a small pump noise. It suggests that the squeezed field stored in the low-loss injection path weakens the decoherence in the oscillators.

Numerical investigation into the injection-locking phenomena of gain switched lasers for optical frequency comb generation

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

Ó Dúill, Sean P., E-mail: sean.oduill@dcu.ie; Anandarajah, Prince M.; Zhou, Rui

2015-05-25

We present detailed numerical simulations of the laser dynamics that describe optical frequency comb formation by injection-locking a gain-switched laser. The typical rate equations for semiconductor lasers including stochastic carrier recombination and spontaneous emission suffice to show the injection-locking behavior of gain switched lasers, and we show how the optical frequency comb evolves starting from the free-running state, right through the final injection-locked state. Unlike the locking of continuous wave lasers, we show that the locking range for gain switched lasers is considerably greater because injection locking can be achieved by injecting at frequencies close to one of the combmore » lines. The quality of the comb lines is formally assessed by calculating the frequency modulation (FM)-noise spectral density and we show that under injection-locking conditions the FM-noise spectral density of the comb lines tend to that of the maser laser.« less

Determination of injection molding process windows for optical lenses using response surface methodology.

PubMed

Tsai, Kuo-Ming; Wang, He-Yi

2014-08-20

This study focuses on injection molding process window determination for obtaining optimal imaging optical properties, astigmatism, coma, and spherical aberration using plastic lenses. The Taguchi experimental method was first used to identify the optimized combination of parameters and significant factors affecting the imaging optical properties of the lens. Full factorial experiments were then implemented based on the significant factors to build the response surface models. The injection molding process windows for lenses with optimized optical properties were determined based on the surface models, and confirmation experiments were performed to verify their validity. The results indicated that the significant factors affecting the optical properties of lenses are mold temperature, melt temperature, and cooling time. According to experimental data for the significant factors, the oblique ovals for different optical properties on the injection molding process windows based on melt temperature and cooling time can be obtained using the curve fitting approach. The confirmation experiments revealed that the average errors for astigmatism, coma, and spherical aberration are 3.44%, 5.62%, and 5.69%, respectively. The results indicated that the process windows proposed are highly reliable.

Forward-biased nanophotonic detector for ultralow-energy dissipation receiver

NASA Astrophysics Data System (ADS)

Nozaki, Kengo; Matsuo, Shinji; Fujii, Takuro; Takeda, Koji; Shinya, Akihiko; Kuramochi, Eiichi; Notomi, Masaya

2018-04-01

Generally, reverse-biased photodetectors (PDs) are used for high-speed optical receivers. The forward voltage region is only utilized in solar-cells, and this photovoltaic operation would not be concurrently obtained with high efficiency and high speed operation. Here we report that photonic-crystal waveguide PDs enable forward-biased high-speed operation at 40 Gbit/s with keeping high responsivity (0.88 A/W). Within our knowledge, this is the first demonstration of the forward-biased PDs with high responsivity. This achievement is attributed to the ultracompactness of our PD and the strong light confinement within the absorber and depleted regions, thereby enabling efficient photo-carrier generation and fast extraction. This result indicates that it is possible to construct a high-speed and ultracompact photo-receiver without an electrical amplifier nor an external bias circuit. Since there is no electrical energy required, our estimation shows that the consumption energy is just the optical energy of the injected signal pulse which is about 1 fJ/bit. Hence, it will lead to an ultimately efficient and highly integrable optical-to-electrical converter in a chip, which will be a key ingredient for dense nanophotonic communication and processors.

Optics of ion beams for the neutral beam injection system on HL-2A Tokamak.

PubMed

Zou, G Q; Lei, G J; Cao, J Y; Duan, X R

2012-07-01

The ion beam optics for the neutral beam injection system on HL-2A Tokomak is studied by two- dimensional numerical simulation program firstly, where the emitting surface is taken at 100 Debye lengths from the plasma electrode. The mathematical formulation, computation techniques are described. Typical ion orbits, equipotential contours, and emittance diagram are shown. For a fixed geometry electrode, the effect of plasma density, plasma potential and plasma electron temperature on ion beam optics is examined, and the calculation reliability is confirmed by experimental results. In order to improve ion beam optics, the application of a small pre-acceleration voltage (∼100 V) between the plasma electrode and the arc discharge anode is reasonable, and a lower plasma electron temperature is desired. The results allow optimization of the ion beam optics in the neutral beam injection system on HL-2A Tokomak and provide guidelines for designing future neutral beam injection system on HL-2M Tokomak.

Mutual Injection Locking of Monolithically Integrated Coupled-Cavity DBR Lasers

DOE PAGES

Tauke-Pedretti, Anna; Vawter, G. Allen; Skogen, Erik J.; ...

2011-07-01

We present a photonic integrated circuit (PIC) composed of two strongly coupled distributed Bragg reflector (DBR) lasers. This PIC utilizes the dynamics of mutual injection locking to increase the relaxation resonance frequency from 3 GHz to beyond 30 GHz. Mutual injection-locking and external injection-locking operation are then compared.

Integrated Nanoscale Antenna-LED for On-Chip Optical Communication

NASA Astrophysics Data System (ADS)

Fortuna, Seth

Traditional semiconductor light emitting diodes (LEDs) have low modulation speed because of long spontaneous emission lifetime. Spontaneous emission in semiconductors (and indeed most light emitters) is an inherently slow process owing to the size mismatch between the dipole length of the optical dipole oscillators responsible for light emission and the wavelength of the emitted light. More simply stated: semiconductors behave as a poor antenna for its own light emission. By coupling a semiconductor at the nanoscale to an external antenna, the spontaneous emission rate can be dramatically increased alluding to the exciting possibility of an antenna-LED that can be directly modulated faster than the laser. Such an antenna-LED is well-suited as a light source for on-chip optical communication where small size, fast speed, and high efficiency are needed to achieve the promised benefit of reduced power consumption of on-chip optical interconnect links compared with less efficient electrical interconnect links. Despite the promise of the antenna-LED, significant challenges remain to implement an antenna-coupled device in a monolithically integrated manner. Notably, most demonstrations of antenna-enhanced spontaneous emission have relied upon optical pumping of the light emitting material which is useful for fundamental studies; however, an electrical injection scheme is required for practical implementation of an antenna-LED. In this dissertation, demonstration of an electrically-injected III-V antenna-LED is reported: an important milestone toward on-chip optical interconnects. In the first part of this dissertation, the general design principles of enhancing the spontaneous emission rate of a semiconductor with an optical antenna is discussed. The cavity-backed slot antenna is shown to be uniquely suited for an electrically-injected antenna-LED because of large spontaneous emission enhancement, simple fabrication, and directional emission of light. The design, fabrication, and experimental results of the electrically-injected III-V antenna-LED is then presented. Clear evidence of antenna-enhanced electroluminescence is demonstrated including a large increase in the emitted light intensity with respect to an LED without antenna. Furthermore, it is shown that the active region emission wavelength is influenced by the antenna resonance and the emitted light is polarized; consistent with the expected behavior of the cavity-backed slot antenna. An antenna-LED consisting of a InGaAs quantum well active region is shown to have a large 200-fold enhancement of the spontaneous emission rate. In the last half of this dissertation, the performance of the antenna-LED is discussed. Remarkably, despite the high III-V surface recombination velocity, it is shown that an efficient antenna-LED consisting of an InGaAs active region is possible with an antenna-enhanced spontaneous emission rate. This is true provided the active region surface quality is preserved through the entire device process. A novel technique to preserve and clean InGaAs surfaces is reported. Finally, a rate-equation analysis shows that the optimized antenna-LED with cavity-backed slot antenna is fundamentally capable of achieving greater than 100 GHz direct modulation rate at high efficiency thus showing that an antenna-LED faster than the laser is achievable with this device architecture.

Optical gain in 1.3-μm electrically driven dilute nitride VCSOAs

PubMed Central

2014-01-01

We report the observation of room-temperature optical gain at 1.3 μm in electrically driven dilute nitride vertical cavity semiconductor optical amplifiers. The gain is calculated with respect to injected power for samples with and without a confinement aperture. At lower injected powers, a gain of almost 10 dB is observed in both samples. At injection powers over 5 nW, the gain is observed to decrease. For nearly all investigated power levels, the sample with confinement aperture gives slightly higher gain. PMID:24417791

Effect of carrier doping and external electric field on the optical properties of graphene quantum dots

NASA Astrophysics Data System (ADS)

Basak, Tista; Basak, Tushima

2018-02-01

In this paper, we demonstrate that the optical properties of finite-sized graphene quantum dots can be effectively controlled by doping it with different types of charge carriers (electron/hole). In addition, the role played by a suitably directed external electric field on the optical absorption of charge-doped graphene quantum dots have also been elucidated. The computations have been performed on diamond-shaped graphene quantum dot (DQD) within the framework of the Pariser-Parr-Pople (PPP) model Hamiltonian, which takes into account long-range Coulomb interactions. Our results reveal that the energy band-gap increases when the DQD is doped with holes while it decreases on doping it with electrons. Further, the optical absorption spectra of DQD exhibits red/blue-shift on doping with electrons/holes. Our computations also indicate that the application of external transverse electric field results in a substantial blue-shift of the optical spectrum for charge-doped DQD. However, it is observed that the influence of charge-doping is more prominent in tuning the optical properties of finite-sized graphene quantum dots as compared to externally applied electric field. Thus, tailoring the optical properties of finite-sized graphene quantum dots by manipulative doping with charge carriers and suitably aligned external electric field can greatly enhance its potential application in designing nano-photonic devices.

Transpiration purged optical probe

DOEpatents

VanOsdol, John; Woodruff, Steven

2004-01-06

An optical apparatus for clearly viewing the interior of a containment vessel by applying a transpiration fluid to a volume directly in front of the external surface of the optical element of the optical apparatus. The fluid is provided by an external source and transported by means of an annular tube to a capped end region where the inner tube is perforated. The perforation allows the fluid to stream axially towards the center of the inner tube and then axially away from an optical element which is positioned in the inner tube just prior to the porous sleeve. This arrangement draws any contaminants away from the optical element keeping it free of contaminants. In one of several embodiments, the optical element can be a lens, a viewing port or a laser, and the external source can provide a transpiration fluid having either steady properties or time varying properties.

Hairlike Percutaneous Photochemical Sensors

NASA Technical Reports Server (NTRS)

George, Thomas; Loeb, Gerald

2004-01-01

Instrumentation systems based on hairlike fiber-optic photochemical sensors have been proposed as minimally invasive means of detecting biochemicals associated with cancer and other diseases. The fiber-optic sensors could be mass-produced as inexpensive, disposable components. The sensory tip of a fiber-optic sensor would be injected through the patient's skin into subcutaneous tissue. A biosensing material on the sensory tip would bind or otherwise react with the biochemical(s) of interest [the analyte(s)] to produce a change in optical properties that would be measured by use of an external photonic analyzer. After use, a fiber-optic sensor could be simply removed by plucking it out with tweezers. A fiber-optic sensor according to the proposal would be of the approximate size and shape of a human hair, and its sensory tip would resemble a follicle. Once inserted into a patient's subcutaneous tissue, the sensor would even more closely resemble a hair growing from a follicle (see Figure 1). The biosensing material on the sensory tip could consist of a chemical and/or cells cultured and modified for the purpose. The biosensing material would be contained within a membrane that would cover the tip. If the membrane were not permeable by an analyte, then it would be necessary to create pores in the membrane that would be large enough to allow analyte molecules to diffuse to the biosensing material, but not so large as to allow cells (if present as part of the biosensing material) to diffuse out. The end of the fiber-optic sensor opposite the sensory tip would be inserted in a fiberoptic socket in the photonic analyzer.

Focal Activation of Cells by Plasmon Resonance Assisted Optical Injection of Signaling Molecules

PubMed Central

2015-01-01

Experimental methods for single cell intracellular delivery are essential for probing cell signaling dynamics within complex cellular networks, such as those making up the tumor microenvironment. Here, we show a quantitative and general method of interrogation of signaling pathways. We applied highly focused near-infrared laser light to optically inject gold-coated liposomes encapsulating bioactive molecules into single cells for focal activation of cell signaling. For this demonstration, we encapsulated either inositol trisphosphate (IP3), an endogenous cell signaling second messenger, or adenophostin A (AdA), a potent analogue of IP, within 100 nm gold-coated liposomes, and injected these gold-coated liposomes and their contents into the cytosol of single ovarian carcinoma cells to initiate calcium (Ca2+) release from intracellular stores. Upon optical injection of IP3 or AdA at doses above the activation threshold, we observed increases in cytosolic Ca2+ concentration within the injected cell initiating the propagation of a Ca2+ wave throughout nearby cells. As confirmed by octanol-induced inhibition, the intercellular Ca2+ wave traveled via gap junctions. Optical injection of gold-coated liposomes represents a quantitative method of focal activation of signaling cascades of broad interest in biomedical research. PMID:24877558

Regimes of external optical feedback in 5.6 μm distributed feedback mid-infrared quantum cascade lasers

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

Jumpertz, L., E-mail: louise.jumpertz@telecom-paristech.fr; Alcatel Thales III-V Lab, Campus de Polytechnique, 1 avenue Augustin Fresnel, 91767 Palaiseau; Carras, M.

2014-09-29

External optical feedback is studied experimentally in mid-infrared quantum cascade lasers. These structures exhibit a dynamical response close to that observed in interband lasers, with threshold reduction and optical power enhancement when increasing the feedback ratio. The study of the optical spectrum proves that the laser undergoes five distinct regimes depending on the phase and amplitude of the reinjected field. These regimes are mapped in the plane of external cavity length and feedback strength, revealing unstable behavior only for a very narrow range of operation, making quantum cascade lasers much more stable than their interband counterparts.

Demonstration of the spin solar cell and spin photodiode effect

PubMed Central

Endres, B.; Ciorga, M.; Schmid, M.; Utz, M.; Bougeard, D.; Weiss, D.; Bayreuther, G.; Back, C.H.

2013-01-01

Spin injection and extraction are at the core of semiconductor spintronics. Electrical injection is one method of choice for the creation of a sizeable spin polarization in a semiconductor, requiring especially tailored tunnel or Schottky barriers. Alternatively, optical orientation can be used to generate spins in semiconductors with significant spin-orbit interaction, if optical selection rules are obeyed, typically by using circularly polarized light at a well-defined wavelength. Here we introduce a novel concept for spin injection/extraction that combines the principle of a solar cell with the creation of spin accumulation. We demonstrate that efficient optical spin injection can be achieved with unpolarized light by illuminating a p-n junction where the p-type region consists of a ferromagnet. The discovered mechanism opens the window for the optical generation of a sizeable spin accumulation also in semiconductors without direct band gap such as Si or Ge. PMID:23820766

Optical bistability in erbium-doped yttrium aluminum garnet crystal combined with a laser diode.

PubMed

Maeda, Y

1994-01-10

Optical bistability was observed in a simple structure of an injection laser diode combined with an erbium-doped yttrium aluminum garnet crystal. Since a hysteresis characteristic exists in the relationship between the wavelength and the injection current of a laser diode, an optical memory function capable of holding the output status is confirmed. In addition, an optical signal inversion was caused by the decrease of transmission of the erbium-doped yttrium aluminum garnet crystal against the red shift (principally mode hopping) of the laser diode. It is suggested that the switching time of this phenomenon is the time necessary for a mode hopping by current injection.

Optical double-locked semiconductor lasers

NASA Astrophysics Data System (ADS)

AlMulla, Mohammad

2018-06-01

Self-sustained period-one (P1) nonlinear dynamics of a semiconductor laser are investigated when both optical injection and modulation are applied for stable microwave frequency generation. Locking the P1 oscillation through modulation on the bias current, injection strength, or detuning frequency stabilizes the P1 oscillation. Through the phase noise variance, the different modulation types are compared. It is demonstrated that locking the P1 oscillation through optical modulation on the output of the master laser outperforms bias-current modulation of the slave laser. Master laser modulation shows wider P1-oscillation locking range and lower phase noise variance. The locking characteristics of the P1 oscillation also depend on the operating conditions of the optical injection system

Chirp and error rate analyses of an optical-injection gain-switching VCSEL based all-optical NRZ-to-PRZ converter.

PubMed

Lin, Chia-Chi; Kuo, Hao-Chung; Peng, Peng-Chun; Lin, Gong-Ru

2008-03-31

Optically injection-locked single-wavelength gain-switching VCSEL based all-optical converter is demonstrated to generate RZ data at 2.5 Gbit/s with bit-error-rate of 10(-9) under receiving power of -29.3 dBm. A modified rate equation model is established to elucidate the optical injection induced gain-switching and NRZ-to-RZ data conversion in the VCSEL. The peak-to-peak frequency chirp of the VCSEL based NRZ-to-RZ is 4.5 GHz associated with a reduced frequency chirp rate of 178 MHz/ps at input optical NRZ power of -21 dBm, which is almost decreasing by a factor of 1/3 comparing with chirp on the SOA based NRZ-to-RZ converter reported previously. The power penalty of the BER measured back-to-back is about 2 dB from 1 Gbit/s to 2.5 Gbit/s.

Using quantum dot photoluminescence for load detection

NASA Astrophysics Data System (ADS)

Moebius, M.; Martin, J.; Hartwig, M.; Baumann, R. R.; Otto, T.; Gessner, T.

2016-08-01

We propose a novel concept for an integrable and flexible sensor capable to visualize mechanical impacts on lightweight structures by quenching the photoluminescence (PL) of CdSe quantum dots. Considering the requirements such as visibility, storage time and high optical contrast of PL quenching with low power consumption, we have investigated a symmetrical and an asymmetrical layer stack consisting of semiconductor organic N,N,N',N'-Tetrakis(3-methylphenyl)-3,3'-dimethylbenzidine (HMTPD) and CdSe quantum dots with elongated CdS shell. Time-resolved series of PL spectra from layer stacks with applied voltages of different polarity and simultaneous observation of power consumption have shown that a variety of mechanisms such as photo-induced charge separation and charge injection, cause PL quenching. However, mechanisms such as screening of external field as well as Auger-assisted charge ejection is working contrary to that. Investigations regarding the influence of illumination revealed that the positive biased asymmetrical layer stack is the preferred sensor configuration, due to a charge carrier injection at voltages of 10 V without the need of coincident illumination.

Optical microwave interactions in semiconductor devices

NASA Astrophysics Data System (ADS)

Figueroa, L.; Slayman, C. W.; Yen, H. W.

1980-11-01

The results of an extensive characterization of high speed analog modulation of (GaAl)As injection lasers, high speed optical detectors, and mode locking of (GaAl)As injection lasers are presented. Commercial injection lasers were successfully modulated up to 5 GHz. The 5 GHz value represents a practical upper limit to the modulation bandwith of existing commercial lasers. The laser equivalent circuit was characterized and the parasitics were found to play a significant role in the high speed modulation of the injection laser.

On finding the analytic dependencies of the external field potential on the control function when optimizing the beam dynamics

NASA Astrophysics Data System (ADS)

Ovsyannikov, A. D.; Kozynchenko, S. A.; Kozynchenko, V. A.

2017-12-01

When developing a particle accelerator for generating the high-precision beams, the injection system design is of importance, because it largely determines the output characteristics of the beam. At the present paper we consider the injection systems consisting of electrodes with given potentials. The design of such systems requires carrying out simulation of beam dynamics in the electrostatic fields. For external field simulation we use the new approach, proposed by A.D. Ovsyannikov, which is based on analytical approximations, or finite difference method, taking into account the real geometry of the injection system. The software designed for solving the problems of beam dynamics simulation and optimization in the injection system for non-relativistic beams has been developed. Both beam dynamics and electric field simulations in the injection system which use analytical approach and finite difference method have been made and the results presented in this paper.

Distal Hemorrhoidectomy With ALTA Injection: A New Method for Hemorrhoid Surgery

PubMed Central

Abe, Tatsuya; Hachiro, Yoshikazu; Ebisawa, Yoshiaki; Hishiyama, Houhei; Kunimoto, Masao

2014-01-01

Aluminum potassium sulfate and tannic acid injection (ALTA) is a useful and less-invasive treatment for internal hemorrhoids. However, it is not a treatment option for external hemorrhoidal diseases, including mixed hemorrhoids. Distal hemorrhoidectomy with ALTA injection involves surgical resection of external piles, followed by injection therapy on internal piles. We report technical details and the short-term results of this procedure in patients with mixed hemorrhoids. Seventy-two patients with mixed hemorrhoids treated between 2010 and 2011 were included. The main outcome measures were the short-term response and complication rates. At 28 days after surgery, the disappearance rate of prolapse was 100%. Three patients (4%) had postoperative complications, all minor in nature. No prolapse recurrence was observed within a median follow-up period of 6 months. Distal hemorrhoidectomy with ALTA injection appears to be a promising treatment option for patients with mixed hemorrhoids. PMID:24833156

Latching micro optical switch

DOEpatents

Garcia, Ernest J; Polosky, Marc A

2013-05-21

An optical switch reliably maintains its on or off state even when subjected to environments where the switch is bumped or otherwise moved. In addition, the optical switch maintains its on or off state indefinitely without requiring external power. External power is used only to transition the switch from one state to the other. The optical switch is configured with a fixed optical fiber and a movable optical fiber. The movable optical fiber is guided by various actuators in conjunction with a latching mechanism that configure the switch in one position that corresponds to the on state and in another position that corresponds to the off state.

1.2-ps mode-locked semiconductor optical amplifier fiber laser pulses generated by 60-ps backward dark-optical comb injection and soliton compression.

PubMed

Lin, Gong-Ru; Chiu, I-Hsiang; Wu, Ming-Chung

2005-02-07

Optically harmonic mode-locking of a semiconductor optical amplifier fiber laser (SOAFL) induced by backward injecting a dark-optical comb is demonstrated for the first time. The dark-optical comb with 60-ps pulsewidth is generated from a Mach-Zehnder modulator, which is driven by an electrical comb at a DC offset of 0.3Vn. Theoretical simulation indicates that the backward injection of dark-optical comb results in a narrow gain window of 60 ps within one modulating period, providing a cross-gainmodulation induced mode-locking in the SOAFL with a shortest pulsewidth of 15 ps at repetition frequency of 1 GHz. The mode-locked SOAFL pulsewidth can be slightly shortened to 10.8 ps with a 200m-long dispersion compensating fiber. After nonlinearly soliton compression in a 5km-long single mode fiber, the pulsewidth, linewidth and time-bandwidth product become 1.2 ps, 2.06 nm and 0.31, respectively.

Optical mm-wave generation by using external modulator based on optical carrier suppression

NASA Astrophysics Data System (ADS)

Ma, Jianxin; Yu, Chongxiu; Zhou, Zhen; Yu, Jianjun

2006-12-01

In this paper, we have theoretically investigated the transmission performance of the optical millimeter (mm)-wave generated by using an external modulator based on optical carrier suppression for the first time. According to our theory, the data signals carried by the optical mm-wave are transmitted in the dispersion fiber without fading but are degraded greatly because of the time shift of the code edges, which still limits the transmission distance. The experimental results agree well with our theory.

Frequency division multiplexed radio-over-fiber transmission using an optically injected laser diode

NASA Astrophysics Data System (ADS)

Chan, Sze-Chun

2008-04-01

Nonlinear dynamics of semiconductor lasers have recently attracted much attention in the area of microwave photonics. By invoking the nonlinear dynamics of an optically injected laser diode, high-speed microwave oscillation can be generated using the period-one oscillation state. The oscillation is harnessed for application as a photonic microwave source in radio-over-fiber (RoF) systems. It is advantageous over conventional direct current modulation because it alleviates the modulation bandwidth limitation and naturally generates single sideband signals. The method is thus applicable to wireless communication systems even when the subcarrier frequency increases to 60 GHz. Because RoF is usually incorporated with standard wireless schemes that involve frequency division multiplexing (FDM), we investigate the performance of the optical injection system under simultaneous current injection of multiple data streams. Frequency mixings and competition for locking among subcarriers result in intermodulation distortion (IMD). The relative weightings of different channels should be optimized to ensure acceptable signal qualities. The results illustrate the feasibility of applying the optical injection system for FDM RoF transmission at high subcarrier frequencies.

External optical imaging of freely moving mice with green fluorescent protein-expressing metastatic tumors

NASA Astrophysics Data System (ADS)

Yang, Meng; Baranov, Eugene; Shimada, Hiroshi; Moossa, A. R.; Hoffman, Robert M.

2000-04-01

We report here a new approach to genetically engineering tumors to become fluorescence such that they can be imaged externally in freely-moving animals. We describe here external high-resolution real-time fluorescent optical imaging of metastatic tumors in live mice. Stable high-level green flourescent protein (GFP)-expressing human and rodent cell lines enable tumors and metastasis is formed from them to be externally imaged from freely-moving mice. Real-time tumor and metastatic growth were quantitated from whole-body real-time imaging in GFP-expressing melanoma and colon carcinoma models. This GFP optical imaging system is highly appropriate for high throughput in vivo drug screening.

Pulse-amplitude modulation of optical injection-locked quantum-dot lasers

NASA Astrophysics Data System (ADS)

Zhou, Yue-Guang; Wang, Cheng

2018-02-01

This work theoretically investigates the four-level pulse-amplitude modulation characteristics of quantum dot lasers subject to optical injection. The rate equation model takes into account carrier dynamics in the carrier reservoir, in the excited state, and in the ground state, as well as photon dynamics and phase dynamics of the electric field. It is found that the optical injection significantly improves the eye diagram quality through suppressing the relaxation oscillation, while the extinction ratio is reduced as well. In addition, both the adiabatic chirp and the transient chirp of the signal are substantially suppressed.

Demonstration of ultra-wideband (UWB) over fiber based on optical pulse-injected semiconductor laser.

PubMed

Juan, Yu-Shan; Lin, Fan-Yi

2010-04-26

We experimentally demonstrated the ultra-wideband (UWB) signal generation utilizing nonlinear dynamics of an optical pulse-injected semiconductor laser. The UWB signals generated are fully in compliant with the FCC mask for indoor radiation, while a large fractional bandwidth of 93% is achieved. To show the feasibility of UWB-over-fiber, transmission over a 2 km single-mode fiber and a wireless channel utilizing a pair of broadband antennas are examined. Moreover, proof of concept experiment on data encoding and decoding with 250 Mb/s in the optical pulse-injected laser is successfully demonstrated.

PARACENTRAL ACUTE MIDDLE MACULOPATHY ASSOCIATED WITH RETINAL ARTERY OCCLUSION AFTER COSMETIC FILLER INJECTION.

PubMed

Sridhar, Jayanth; Shahlaee, Abtin; Shieh, Wen-Shi; Rahimy, Ehsan

2017-01-01

To report a single case of paracentral acute middle maculopathy in association with retinal artery occlusion in the setting of ipsilateral facial cosmetic filler injection. Case report. A 35-year-old woman presenting with sudden vision loss to finger count vision immediately after left nasal fat pad cosmetic filler injection. Dilated funduscopic examination revealed a swollen optic disc with multiple branch arterial occlusions with visible embolic material. Fluorescein angiography confirmed multiple branch arterial occlusions in addition to a focal choroidal infarction in the macula. Spectral-domain optical coherence tomography revealed middle retinal hyperreflectivity in the superotemporal macula consistent with paracentral acute middle maculopathy. En face optical coherence tomography demonstrated a superotemporal area of whitening at the level of the deep capillary plexus corresponding to the paracentral acute middle maculopathy lesion seen on spectral-domain optical coherence tomography. On twelve-month follow-up, final visual acuity was 20/100 due to optic neuropathy. Emboli from cosmetic facial filler injections may rarely result in ipsilateral arterial occlusions and now have a novel association with paracentral acute middle maculopathy likely due to deep capillary plexus feeder vessel occlusion.

Effect of temperature and ridge-width on the lasing characteristics of InAs/InP quantum-dash lasers: A thermal analysis view

NASA Astrophysics Data System (ADS)

Alkhazraji, E.; Khan, M. T. A.; Ragheb, A. M.; Fathallah, H.; Qureshi, K. K.; Alshebeili, S.; Khan, M. Z. M.

2018-01-01

We investigate the thermal characteristics of multi-stack chirped barrier thickness InAs/InGaAlAs/InP quantum-dash-in-a-well lasers of different ridge widths 2, 3, 4 and 15 μm. The effect of varying this geometrical parameter on the extracted thermal resistance and characteristic temperature, and their stability with temperature are examined. The results show an inverse relation of ridge-width with junction temperature with 2 μm device exhibiting the largest junction temperature buildup owing to an associated high thermal resistance of ∼45 °C/W. Under the light of this thermal analysis, lasing behavior of different ridge-width quantum-dash (Qdash) lasers with injection currents and operating temperatures, is investigated. Thermionic carrier escape and phonon-assisted tunneling are found to be the dominant carrier transport mechanisms resulting in wide thermal spread of carriers across the available transition states of the chirped active region. An emission coverage of ∼75 nm and 3 dB bandwidth of ∼55 nm is exhibited by the 2 μm device, thus possibly exploiting the inhomogeneous optical transitions to the fullest. Furthermore, successful external modulation of a single Qdash Fabry-Perot laser mode via injection locking is demonstrated with eye diagrams at bit rates of 2-12 Gbit/s incorporating various modulation schemes. These devices are being considered as potential light sources for future high-speed wavelength-division multiplexed optical communication systems.

Monolayer semiconductor nanocavity lasers with ultralow thresholds.

PubMed

Wu, Sanfeng; Buckley, Sonia; Schaibley, John R; Feng, Liefeng; Yan, Jiaqiang; Mandrus, David G; Hatami, Fariba; Yao, Wang; Vučković, Jelena; Majumdar, Arka; Xu, Xiaodong

2015-04-02

Engineering the electromagnetic environment of a nanometre-scale light emitter by use of a photonic cavity can significantly enhance its spontaneous emission rate, through cavity quantum electrodynamics in the Purcell regime. This effect can greatly reduce the lasing threshold of the emitter, providing a low-threshold laser system with small footprint, low power consumption and ultrafast modulation. An ultralow-threshold nanoscale laser has been successfully developed by embedding quantum dots into a photonic crystal cavity (PCC). However, several challenges impede the practical application of this architecture, including the random positions and compositional fluctuations of the dots, extreme difficulty in current injection, and lack of compatibility with electronic circuits. Here we report a new lasing strategy: an atomically thin crystalline semiconductor--that is, a tungsten diselenide monolayer--is non-destructively and deterministically introduced as a gain medium at the surface of a pre-fabricated PCC. A continuous-wave nanolaser operating in the visible regime is thereby achieved with an optical pumping threshold as low as 27 nanowatts at 130 kelvin, similar to the value achieved in quantum-dot PCC lasers. The key to the lasing action lies in the monolayer nature of the gain medium, which confines direct-gap excitons to within one nanometre of the PCC surface. The surface-gain geometry gives unprecedented accessibility and hence the ability to tailor gain properties via external controls such as electrostatic gating and current injection, enabling electrically pumped operation. Our scheme is scalable and compatible with integrated photonics for on-chip optical communication technologies.

Monolayer semiconductor nanocavity lasers with ultralow thresholds

NASA Astrophysics Data System (ADS)

Wu, Sanfeng; Buckley, Sonia; Schaibley, John R.; Feng, Liefeng; Yan, Jiaqiang; Mandrus, David G.; Hatami, Fariba; Yao, Wang; Vučković, Jelena; Majumdar, Arka; Xu, Xiaodong

2015-04-01

Engineering the electromagnetic environment of a nanometre-scale light emitter by use of a photonic cavity can significantly enhance its spontaneous emission rate, through cavity quantum electrodynamics in the Purcell regime. This effect can greatly reduce the lasing threshold of the emitter, providing a low-threshold laser system with small footprint, low power consumption and ultrafast modulation. An ultralow-threshold nanoscale laser has been successfully developed by embedding quantum dots into a photonic crystal cavity (PCC). However, several challenges impede the practical application of this architecture, including the random positions and compositional fluctuations of the dots, extreme difficulty in current injection, and lack of compatibility with electronic circuits. Here we report a new lasing strategy: an atomically thin crystalline semiconductor--that is, a tungsten diselenide monolayer--is non-destructively and deterministically introduced as a gain medium at the surface of a pre-fabricated PCC. A continuous-wave nanolaser operating in the visible regime is thereby achieved with an optical pumping threshold as low as 27 nanowatts at 130 kelvin, similar to the value achieved in quantum-dot PCC lasers. The key to the lasing action lies in the monolayer nature of the gain medium, which confines direct-gap excitons to within one nanometre of the PCC surface. The surface-gain geometry gives unprecedented accessibility and hence the ability to tailor gain properties via external controls such as electrostatic gating and current injection, enabling electrically pumped operation. Our scheme is scalable and compatible with integrated photonics for on-chip optical communication technologies.

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.

Ultrafast optical pulse convertor caused by oscillations of the energy level structure in the conjugated polymer poly(p-phenylenevinylene).

PubMed

Zhang, Yusong; Chen, Weikang; Lin, Zhe; Li, Sheng; George, Thomas F

2017-08-21

For a conjugated polymer irradiated by two optical pulses, the whole process of excitation, involving lattice oscillations, oscillations of the energy level structure, and evolution of the electron cloud, is investigated. Localization of the electron cloud appears in the first 100 fs of irradiation, which in turn induces vibrations of lattice of the polymer chain as well as oscillations of the band gap. These oscillations filter the absorption of the external optical field inversely and convert the original optical field to an ultrafast light field whose intensity varies with a certain period. Based on the mechanism, oscillations of the energy level structure, induced by the external excitation, can be designed as an ultrafast response optical convertor that is able to change the external optical pulse into a new effective light field with a certain oscillation period. This helps provide new insight into designing nanostructures for polymeric optoelectronics.

Simultaneous frequency stabilization and high-power dense wavelength division multiplexing (HP-DWDM) using an external cavity based on volume Bragg gratings (VBGs)

NASA Astrophysics Data System (ADS)

Hengesbach, Stefan; Klein, Sarah; Holly, Carlo; Witte, Ulrich; Traub, Martin; Hoffmann, Dieter

2016-03-01

Multiplexing technologies enable the development of high-brightness diode lasers for direct industrial applications. We present a High-Power Dense Wavelength Division Multiplexer (HP-DWDM) with an average channel spacing of 1.7 (1.5) nm and a subsequent external cavity mirror to provide feedback for frequency stabilization and multiplexing in one step. The "self-optimizing" multiplexing unit consists of four reflective Volume Bragg Gratings (VBGs) with 99% diffraction efficiency and seven dielectric mirrors to overlay the radiation of five input channels with an adjustable channel spacing of 1-2 nm. In detail, we focus on the analysis of the overall optical efficiency, the change of the beam parameter product and the spectral width. The performance is demonstrated using five 90 μm multimode 9xx single emitters with M2<=17. Because of the feedback the lateral (multimodal) spatial and angular intensity distribution changes strongly and the beam parameter product decreases by a factor of 1.2 to 1.9. Thereby the angular intensity distribution is more affected than the width of the beam waist. The spectral width per emitter decreases to 3-200 pm (FWHM) depending on the injection current and the reflectance of the feedback mirror (0.75%, 1.5%, 4%, 6% or 8%). The overall optical multiplexing efficiency ranges between 77% and 86%. With some modifications (e.g. enhanced AR-coatings) we expect 90-95%.

Modern trends in industrial technology of production of optical polymeric components for night vision devices

NASA Astrophysics Data System (ADS)

Goev, A. I.; Knyazeva, N. A.; Potelov, V. V.; Senik, B. N.

2005-06-01

The present paper represents in detail the complex approach to creating industrial technology of production of polymeric optical components: information has been given on optical polymeric materials, automatic machines for injection moulding, the possibilities of the Moldflow system (the AB "Universal" company) used for mathematical simulation of the technological process of injection moulding and making the moulds.

Apparatus for injecting high power laser light into a fiber optic cable

DOEpatents

Sweatt, William C.

1997-01-01

High intensity laser light is evenly injected into an optical fiber by the combination of a converging lens and a multisegment kinoform (binary optical element). The segments preferably have multi-order gratings on each which are aligned parallel to a radial line emanating from the center of the kinoform and pass through the center of the element. The grating in each segment causes circumferential (lateral) dispersion of the light, thereby avoiding detrimental concentration of light energy within the optical fiber.

Sustained neuroprotection from a single intravitreal injection of PGJ2 in a rodent model of anterior ischemic optic neuropathy.

PubMed

Touitou, Valerie; Johnson, Mary A; Guo, Yan; Miller, Neil R; Bernstein, Steven L

2013-11-11

Nonarteritic anterior ischemic optic neuropathy (NAION) is the most common cause of sudden optic nerve-related vision loss in persons older than 50 in the United States. There currently is no treatment for this disorder. We previously showed that systemic administration of 15-deoxy, delta (12, 14) prostaglandin J2 (PGJ2) is neuroprotective in our rodent model of AION (rAION). In this study, we determined if a single intravitreal (IVT) injection of PGJ2 is neuroprotective after rAION, and if this method of administration is toxic to the retina, optic nerve, or both. TOXICITY was assessed after a single IVT injection of PGJ2 in one eye and PBS in the contralateral eye of normal, adult Long-Evans rats. EFFICACY was assessed by inducing rAION in one eye and injecting either PGJ2 or vehicle immediately following induction, with the fellow eye serving as naïve control. Visual evoked potentials (VEPs) and ERGs were performed before induction and at specific intervals thereafter. Animals were euthanized 30 days after induction, after which immunohistochemistry, transmission electron microscopy, and quantitative stereology of retinal ganglion cell (RGC) numbers were performed. IVT PGJ2 did not alter the VEP or ERG compared with PBS-injected control eyes, and neither IVT PGJ2 nor PBS reduced overall RGC numbers. IVT PGJ2 preserved VEP amplitude, reduced optic nerve edema, and resulted in significant preservation of RGCs and axons in eyes with rAION. A single IVT injection of PGJ2 is nontoxic to the retina and optic nerve and neuroprotective when given immediately after rAION induction.

High-power microwave generation using optically activated semiconductor switches

NASA Astrophysics Data System (ADS)

Nunnally, William C.

1990-12-01

The two prominent types of optically controlled switches, the optically controlled linear (OCL) switch and the optically initiated avalanche (OIA) switch, are described, and their operating parameters are characterized. Two transmission line approaches, one using a frozen-wave generator and the other using an injected-wave generator, for generation of multiple cycles of high-power microwave energy using optically controlled switches are discussed. The point design performances of the series-switch, frozen-wave generator and the parallel-switch, injected-wave generator are compared. The operating and performance limitations of the optically controlled switch types are discussed, and additional research needed to advance the development of the optically controlled, bulk, semiconductor switches is indicated.

Optical Injection Locking of a VCSEL in an OEO

NASA Technical Reports Server (NTRS)

Strekalov, Dmitry; Matsko, Andrey; Savchenkov, Anatoliy; Yu, Nan; Maleki, Lute

2009-01-01

Optical injection locking has been demonstrated to be effective as a means of stabilizing the wavelength of light emitted by a vertical-cavity surface- emitting laser (VCSEL) that is an active element in the frequency-control loop of an opto-electronic oscillator (OEO) designed to implement an atomic clock based on an electromagnetically- induced-transparency resonance. This particular optical-injection- locking scheme is expected to enable the development of small, low-power, high-stability atomic clocks that would be suitable for use in applications involving precise navigation and/or communication. In one essential aspect of operation of an OEO of the type described above, a microwave modulation signal is coupled into the VCSEL. Heretofore, it has been well known that the wavelength of light emitted by a VCSEL depends on its temperature and drive current, necessitating thorough stabilization of these operational parameters. Recently, it was discovered that the wavelength also depends on the microwave power coupled into the VCSEL. Inasmuch as the microwave power circulating in the frequency-control loop is a dynamic frequency-control variable (and, hence, cannot be stabilized), there arises a need for another means of stabilizing the wavelength. The present optical-injection-locking scheme satisfies the need for a means to stabilize the wavelength against microwave- power fluctuations. It is also expected to afford stabilization against temperature and current fluctuations. In an experiment performed to demonstrate this scheme, wavelength locking was observed when about 200 W of the output power of a commercial tunable diode laser was injected into a commercial VCSEL, designed to operate in the wavelength range of 795+/-3 nm, that was generating about 200 microW of optical power. (The use of relatively high injection power levels is a usual practice in injection locking of VCSELs.)

A novel approach to photonic generate microwave signals based on optical injection locking and four-wave mixing

NASA Astrophysics Data System (ADS)

Zhu, Huatao; Wang, Rong; Xiang, Peng; Pu, Tao; Fang, Tao; Zheng, Jilin; Li, Yuandong

2017-10-01

In this paper, a novel approach for photonic generation of microwave signals based on frequency multiplication using an injected distributed-feedback (DFB) semiconductor laser is proposed and demonstrated by a proof-of-concept experiment. The proposed system is mainly made up of a dual-parallel Mach-Zehnder modulator (DPMZM) and an injected DFB laser. By properly setting the bias voltage of the DPMZM, ±2-order sidebands with carrier suppression are generated, which are then injected into the slave laser. Due to the optical sideband locking and four-wave mixing (FWM) nonlinearity in the slave laser, new sidebands are generated. Then these sidebands are sent to an optical notch filter where all the undesired sidebands are removed. Finally, after photodetector detection, frequency multiplied microwave signals can be generated. Thanks to the flexibility of the optical sideband locking and FWM, frequency octupling, 12-tupling, 14-tupling and 16-tupling can be obtained.

All-optical regeneration using SOA-based polarization-discriminated switch injected by transparent assist light

NASA Astrophysics Data System (ADS)

Usami, Masashi; Tsurusawa, Munefumi; Inohara, Ryo; Nishimura, Kohsuke

2003-08-01

All optical regenerations or wavelength conversions using SOA-based polarization discriminated switch injected by a transparent assist light are reviewed. First, the reduction of a gain recovery time in SOA by injection of a transparent assist light wass discussed. A simple measurement technique of cross gain modulation (XGM) and cross phase modulation (XPM) in SOA was shown to confirm that the injection of transparent cw assist light reduced a gain recovery time without significant reduction in the amount of XGM and XPM. All optical regeneration operation 40Gbit/s as well as bit-rate tunable operation from 10Gbit/s to 80Gbit/s were presented. Simultaneous demultiplexing from 80Gbit/s to 2 channels of 40Gbit/s signals with little loss was also demonstrated. Finally, tolerance to amplitude noise and timing jitter was discussed. Those results indicate that the SOA-based polarization discriminated switch is a promising candidate for all-optical regenerator from the practical point of view.

40-Gb/s directly-modulated photonic crystal lasers under optical injection-locking

NASA Astrophysics Data System (ADS)

Chen, Chin-Hui; Takeda, Koji; Shinya, Akihiko; Nozaki, Kengo; Sato, Tomonari; Kawaguchi, Yoshihiro; Notomi, Masaya; Matsuo, Shinji

2011-08-01

CMOS integrated circuits (IC) usually requires high data bandwidth for off-chip input/output (I/O) data transport with sufficiently low power consumption in order to overcome pin-count limitation. In order to meet future requirements of photonic network interconnect, we propose an optical output device based on an optical injection-locked photonic crystal (PhC) laser to realize low-power and high-speed off-chip interconnects. This device enables ultralow-power operation and is suitable for highly integrated photonic circuits because of its strong light-matter interaction in the PhC nanocavity and ultra-compact size. High-speed operation is achieved by using the optical injection-locking (OIL) technique, which has been shown as an effective means to enhance modulation bandwidth beyond the relaxation resonance frequency limit. In this paper, we report experimental results of the OIL-PhC laser under various injection conditions and also demonstrate 40-Gb/s large-signal direct modulation with an ultralow energy consumption of 6.6 fJ/bit.

Sensitivity of a fibre scattered-light interferometer to external phase perturbations in an optical fibre

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

Alekseev, A E; Potapov, V T; Gorshkov, B G

2015-10-31

Sensitivity of a fibre scattered-light interferometer to external phase perturbations is studied for the first time. An expression is derived for an average power of a useful signal at the interferometer output under external harmonic perturbations in a signal fibre of the interferometer. It is shown that the maximum sensitivity of the scattered-light interferometer depends on the dispersion of the interferogram intensity. An average signal-to-noise ratio is determined theoretically and experimentally at the output of the interferometer at different amplitudes of external perturbations. Using the measured dependences of the signal-to-noise ratio, the threshold sensitivity of the fibre scattered-light interferometer tomore » external phase perturbations is found. The results obtained can be used to optimise characteristics of optical time-domain reflectometers and to design individual phase-sensitive fibre-optic sensors. (laser applications and other topics in quantum electronics)« less

Optical Variability of BL Lacertae During the Major Outburst of 1997

NASA Technical Reports Server (NTRS)

Ghosh, K. K.; Ramsey, B. D.; Sadun, A. C.; Soundararajaperumal, S.; Wang, J.

2000-01-01

We have undertaken an investigation of recent flux variability in BL Lac. We present optical observations taken over 22 nights documenting major as well as minor outbursts. This has been combined, for purposes of multifrequency analysis, with published X-ray and T-ray data taken for an additional single night, On two nights in particular, including the night of the X-ray observations, a major outburst of about a full magnitude of variation was recorded. All the data have been analyzed with theoretical models. Attempts were made to use synchrotron self-Compton and external Comptonization models to explain the data; however, both classes of models were found lacking. More satisfactory results were obtained using an analytical model proposed by Wang et al. that involves the evolution of synchrotron spectra in a homogeneous jet due to the injection of relativistic electrons, taking into account radiation losses during the outbursts. It is hoped that the results of this study of BL Lac, an archetype for the class of blazars in general, represent a more generic phenomenon applicable to the entire class.

Optical Variability of BL Lacertae During the Major Outburst of 1997

NASA Technical Reports Server (NTRS)

Ghosh, K. K.; Ramsey, B. D.; Sadun, A. C.; Soundarajaperumal, S.; Wang, J.

1999-01-01

We have undertaken an investigation of recent flux variability in BL Lac. We present optical observations taken over 12 nights documenting major as well as minor outbursts. This has been combined, for purposes of multifrequency analysis, with published X-ray and gamma ray data taken for an additional single night. On two nights in particular, which includes the night of the X-ray observations, a major outburst of about a full magnitude of variation was recorded. All the data have been analyzed with theoretical models. Attempts were made to use synchrotron self-Compton and external Comptonization models to explain the data; however both classes of models were found lacking. More satisfactory results were obtained using an analytical model proposed by Wang et al. that involves the evolution of synchrotron spectra in a homogeneous jet due to the injection of relativistic electrons, taking into account radiation losses during the outbursts. It is hoped that the results of this study of BL Lac, an archetype for the class of blazars in general, represent a more generic phenomenon applicable to the entire class.

Implementation of light extraction improvements of GaN-based light-emitting diodes with specific textured sidewalls

NASA Astrophysics Data System (ADS)

Chen, Chun-Yen; Chen, Wei-Cheng; Chang, Ching-Hong; Lee, Yu-Lin; Liu, Wen-Chau

2018-05-01

Textured-sidewall GaN-based light-emitting diodes (LEDs) with various sidewall angles (15-90°) and convex or concave sidewalls prepared using an inductively-coupled-plasma approach are comprehensively fabricated and studied. The device with 45° sidewalls (Device F) and that with convex sidewalls (Device B) show significant improvements in optical properties. Experiments show that, at an injection current of 350 mA, the light output power, external quantum efficiency, wall-plug efficiency, and luminous flux of Device F (Device B) are greatly improved by 18.3% (18.2%), 18.2% (18.2%), 17.3% (19.8%), and 16.6% (18.4%), respectively, compared to those of a conventional LED with flat sidewalls. In addition, negligible degradation in electrical properties is found. The enhanced optical performance is mainly attributed to increased light extraction in the horizontal direction due to a significant reduction in total internal reflection at the textured sidewalls. Therefore, the reported specific textured-sidewall structures (Devices B and F) are promising for high-power GaN-based LED applications.

Integration of polarization-multiplexing and phase-shifting in nanometric two dimensional self-mixing measurement.

PubMed

Tao, Yufeng; Xia, Wei; Wang, Ming; Guo, Dongmei; Hao, Hui

2017-02-06

Integration of phase manipulation and polarization multiplexing was introduced to self-mixing interferometry (SMI) for high-sensitive measurement. Light polarizations were used to increase measuring path number and predict manifold merits for potential applications. Laser source was studied as a microwave-photonic resonator optically-injected by double reflected lights on a two-feedback-factor analytical model. Independent external paths exploited magnesium-oxide doped lithium niobate crystals at perpendicular polarizations to transfer interferometric phases into amplitudes of harmonics. Theoretical resolutions reached angstrom level. By integrating two techniques, this SMI outperformed the conventional single-path SMIs by simultaneous dual-targets measurement on single laser tube with high sensitivity and low speckle noise. In experimental demonstration, by nonlinear filtering method, a custom-made phase-resolved algorithm real-time figured out instantaneous two-dimensional displacements with nanometer resolution. Experimental comparisons to lock-in technique and a commercial Ploytec-5000 laser Doppler velocity meter validated this two-path SMI in micron range without optical cross-talk. Moreover, accuracy subjected to slewing rates of crystals could be flexibly adjusted.

The SPARC_LAB femtosecond synchronization for electron and photon pulsed beams

NASA Astrophysics Data System (ADS)

Bellaveglia, M.; Gallo, A.; Piersanti, L.; Pompili, R.; Gatti, G.; Anania, M. P.; Petrarca, M.; Villa, F.; Chiadroni, E.; Biagioni, A.; Mostacci, A.

2015-05-01

The SPARC LAB complex hosts a 150 MeV electron photo-injector equipped with an undulator for FEL production (SPARC) together with a high power TW laser (FLAME). Recently the synchronization system reached the performance of < 100 fsRMS relative jitter between lasers, electron beam and RF accelerating fields. This matches the requirements for next future experiments: (i) the production of X-rays by means of Thomson scattering (first collisions achieved in 2014) and (ii) the particle driven PWFA experiment by means of multiple electron bunches. We report about the measurements taken during the machine operation using BAMs (Bunch Arrival Monitors) and EOS (Electro-Optical Sampling) system. A new R and D activity concerning the LWFA using the external injection of electron bunches in a plasma generated by the FLAME laser pulse is under design. The upgrade of the synchronization system is under way to guarantee the < 30 fs RMS jitter required specification. It foresees the transition from electrical to optical architecture that mainly affects the reference signal distribution and the time of arrival detection performances. The new system architecture is presented together with the related experimental data.

Electrical and Optical Properties of Green Polymer Light Emitting Diodes with Various Structures of Au Nanoparticles.

PubMed

Park, Byung Min; Kim, Gi Ppeum; Mun, Sae Chan; Chang, Ho Jung

2015-10-01

The green polymer light emitting diodes (PLEDs) were fabricated using the solution precursor synthesis method. To improve the device's electrical. and optical properties, gold (Au) nanoparticles (NPs) were added to the hole injection layer (HIL) with poly(3,4-ethylene- dioxythiophene):poly(styrenesulfolnate) ( PSS) organic material. The green PLED devices with a structure of glass/ITO/PEDOT:PSS+Au NPs/PVK:Ir(ppy)3/TPBi/LiF/Al were prepared by conventional spin-coating and thermal evaporation methods. Various concentrations of Au NPs were doped to the HILs to optimize the device's light emitting characteristic. The effects of Au NPs concentrations on the properties of PLEDs were investigated. The doping concentrations of Au NPs were changed ranging from 0.0 to 1.0 vol%. At the optimized Au NPs concentration of 0.5 vol%, we also studied the effects of various film layers with and without Au NPs on the properties of PLEDs. The maximum luminance and external quantum efficiency of the devices were found to be 20,430 cd/m2 and 7.49%, respectively.

SU-F-T-10: Validation of ELP Dosimetry Using PRESAGE Dosimeter: Feasibility Test and Practical Considerations

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

Lambson, K; Lafata, K; Miles, D

Purpose: To validate the use of a PRESAGE dosimeter as a method to quantitatively measure dose distributions of injectable brachytherapy based on elastin-like polypeptide (ELP) nanoparticles. PRESAGE is a solid, transparent polyurethane-based dosimeter whose dose is proportional to a change in optical density, making it useful for visualizing the dose from a radionuclide-tagged-ELP injection. Methods: A PRESAGE dosimeter was designed to simulate an ELP injection. To calibrate, cuvette samples from the batch of PRESAGE were exposed to varying levels of radiation from 0–35.9Gy applied via a linear accelerator, then placed into a spectrophotometer to obtain the optical density change asmore » a function of dose. A pre-optical-CT scan was acquired of the phantom to obtain a baseline tomographic optical density. A 1cc saline solution of I-125 tagged-ELP with and activity concentration of 1mCi/cc was injected into the phantom and left for five days. After five days, the ELP was removed and the cavity cleaned of all remaining radioactive material. Post tomographic optical images were acquired to obtain a differential optical density dataset. Results: Initial results after the 5-day exposure revealed an opaque white film that resembled the volume of the ELP solution injected into the phantom. We think this is possibly due to the saline solution diffusing into the PRESAGE and causing a change in the index of refraction at this shallow depth. Therefore, initially the optical scanner yielded inconclusive results. After several more days, the saline seemed to have evaporated out of the injection site and the ELP dose distribution was visible via color change in the dosimeter. Conclusion: We have created the first experimental design to measure the dose distribution of I-125-tagged-ELP. The PRESAGE formulation proves to be a feasible option for such measurements. Future experimental measurements need to be obtained to further characterize ELP dosimetry.« less

Adaptive upstream rate adjustment by RSOA-ONU depending on different injection power of seeding light in standard-reach and long-reach PON systems

NASA Astrophysics Data System (ADS)

Yeh, C. H.; Chow, C. W.; Shih, F. Y.; Pan, C. L.

2012-08-01

The wavelength division multiplexing-time division multiplexing (WDM-TDM) passive optical network (PON) using reflective semiconductor optical amplifier (RSOA)-based colorless optical networking units (ONUs) is considered as a promising candidate for the realization of fiber-to-the-home (FTTH). And this architecture is actively considered by Industrial Technology Research Institute (ITRI) for the realization of FTTH in Taiwan. However, different fiber distances and optical components would introduce different power budgets to different ONUs in the PON. Besides, due to the aging of optical transmitter (Tx), the power decay of the distributed optical carrier from the central office (CO) could also reduce the injection power into each ONU. The situation will be more severe in the long-reach (LR) PON, which is considered as an option for the future access. In this work, we investigate a WDM-TDM PON using RSOA-based ONU for upstream data rate adjustment depending on different continuous wave (CW) injection powers. Both standard-reach (25 km) and LR (100 km) transmissions are evaluated. Moreover, a detail analysis of the upstream signal bit-error rate (BER) performances at different injection powers, upstream data rates, PON split-ratios under stand-reach and long-reach is presented.

Micro-optical fabrication by ultraprecision diamond machining and precision molding

NASA Astrophysics Data System (ADS)

Li, Hui; Li, Likai; Naples, Neil J.; Roblee, Jeffrey W.; Yi, Allen Y.

2017-06-01

Ultraprecision diamond machining and high volume molding for affordable high precision high performance optical elements are becoming a viable process in optical industry for low cost high quality microoptical component manufacturing. In this process, first high precision microoptical molds are fabricated using ultraprecision single point diamond machining followed by high volume production methods such as compression or injection molding. In the last two decades, there have been steady improvements in ultraprecision machine design and performance, particularly with the introduction of both slow tool and fast tool servo. Today optical molds, including freeform surfaces and microlens arrays, are routinely diamond machined to final finish without post machining polishing. For consumers, compression molding or injection molding provide efficient and high quality optics at extremely low cost. In this paper, first ultraprecision machine design and machining processes such as slow tool and fast too servo are described then both compression molding and injection molding of polymer optics are discussed. To implement precision optical manufacturing by molding, numerical modeling can be included in the future as a critical part of the manufacturing process to ensure high product quality.

Modular separation-based fiber-optic sensors for remote in situ monitoring.

PubMed

Dickens, J; Sepaniak, M

2000-02-01

A modular separation-based fiber-optic sensor (SBFOS) with an integrated electronically controlled injection device is described for potential use in remote environmental monitoring. An SBFOS is a chemical monitor that integrates the separation selectivity and versatility afforded by capillary electrophoresis with the remote and high sensitivity capabilities of fiber-optic-based laser-induced fluorescence sensing. The detection module of the SBFOS accommodates all essential sensing components for dual-optical fiber, on-capillary fluorescence detection. An injection module, similar to injection platforms on micro-analysis chips, is also integrated to the SBFOS. The injection module allows for electronically controlled injection of the sample onto the separation capillary. The design and operational characteristics of the modular SBFOS are discussed in this paper. A micellar electrokinetic capillary chromatography mode of separation is employed to evaluate the potential of the sensor for in situ monitoring of neutral toxins (aflatoxins). The analytical figures of merit for the modular SBFOS include analysis times of between 5 and 10 min, separation efficiencies of approximately 10(4) theoretical plates, detection limits for aflatoxins in the mid-to-low nanomolar range, and controllable operation that results in sensor performance that is largely immune to sample matrix effects.

High-sensitivity detection of biological amines using fast Hadamard transform CE coupled with photolytic optical gating.

PubMed

Braun, Kevin L; Hapuarachchi, Suminda; Fernandez, Facundo M; Aspinwall, Craig A

2007-08-01

Here, we report the first utilization of Hadamard transform CE (HTCE), a high-sensitivity, multiplexed CE technique, with photolytic optical gating sample injection of caged fluorescent labels for the detection of biologically important amines. Previous implementations of HTCE have relied upon photobleaching optical gating sample injection of fluorescent dyes. Photolysis of caged fluorescent labels reduces the fluorescence background, providing marked enhancements in sensitivity compared to photobleaching. Application of fast Hadamard transform CE (fHTCE) for fluorescein-based dyes yields a ten-fold higher sensitivity for photolytic injections compared to photobleaching injections, due primarily to the reduced fluorescent background provided by caged fluorescent dyes. Detection limits as low as 5 pM (ca. 18 molecules per injection event) were obtained with on-column LIF detection using fHTCE in less than 25 s, with the capacity for continuous, online separations. Detection limits for glutamate and aspartate below 150 pM (1-2 amol/injection event) were obtained using photolytic sample injection, with separation efficiencies exceeding 1 x 10(6) plates/m and total multiplexed separation times as low as 8 s. These results strongly support the feasibility of this approach for high-sensitivity dynamic chemical monitoring applications.

Manufacturing plastic injection optical molds

NASA Astrophysics Data System (ADS)

Bourque, David

2008-08-01

ABCO Tool & Die, Inc. is a mold manufacturer specializing in the manufacturing of plastic injection molds for molded optical parts. The purpose of this presentation is to explain the concepts and procedures required to build a mold that produces precision optical parts. Optical molds can produce a variety of molded parts ranging from safety eyewear to sophisticated military lens parts, which must meet precise optical specifications. The manufacturing of these molds begins with the design engineering of precision optical components. The mold design and the related optical inserts are determined based upon the specific optical criteria and optical surface geometry. The mold manufacturing techniques will be based upon the optical surface geometry requirements and specific details. Manufacturing processes used will be specific to prescribed geometrical surface requirements of the molded part. The combined efforts result in a robust optical mold which can produce molded parts that meet the most precise optical specifications.

X-Ray Spectral Variability Signatures of Flares in BL Lac Objects

NASA Technical Reports Server (NTRS)

Boettcher, Markus; Chiang, James; White, Nicholas E. (Technical Monitor)

2002-01-01

We are presenting a detailed parameter study of the time-dependent electron injection and kinematics and the self-consistent radiation transport in jets of intermediate and low-frequency peaked BL Lac objects. Using a time-dependent, combined synchrotron-self-Compton and external-Compton jet model, we study the influence of variations of several essential model parameters, such as the electron injection compactness, the relative contribution of synchrotron to external soft photons to the soft photon compactness, the electron- injection spectral index, and the details of the time profiles of the electron injection episodes giving rise to flaring activity. In the analysis of our results, we focus on the expected X-ray spectral variability signatures in a region of parameter space particularly well suited to reproduce the broadband spectral energy distributions of intermediate and low-frequency peaked BL Lac objects. We demonstrate that SSC- and external-Compton dominated models for the gamma-ray emission from blazars are producing significantly different signatures in the X-ray variability, in particular in the soft X-ray light curves and the spectral hysteresis at soft X-ray energies, which can be used as a powerful diagnostic to unveil the nature of the high-energy emission from BL Lac objects.

A Single Intravitreal Injection of Ranibizumab Provides No Neuroprotection in a Nonhuman Primate Model of Moderate-to-Severe Nonarteritic Anterior Ischemic Optic Neuropathy.

PubMed

Miller, Neil R; Johnson, Mary A; Nolan, Theresa; Guo, Yan; Bernstein, Steven L

2015-12-01

Ranibizumab, a vascular endothelial growth factor-antagonist, is said to be neuroprotective when injected intravitreally in patients with nonarteritic anterior ischemic optic neuropathy (NAION). We evaluated the efficacy of a single intravitreal (IVT) injection of ranibizumab in a nonhuman primate model of NAION (pNAION). We induced pNAION in one eye of four adult male rhesus monkeys using a laser-activated rose Bengal induction method. We then immediately injected the eye with either ranibizumab or normal saline (NS) intravitreally. We performed a clinical assessment, optical coherence tomography, electrophysiological testing, fundus photography, and fluorescein angiography in three of the animals (one animal developed significant retinal hemorrhages and, therefore, could not be analyzed completely) prior to induction, 1 day and 1, 2, and 4 weeks thereafter. Following the 4-week analysis of the first eye, we induced pNAION in the contralateral eye and then injected either ranibizumab or NS, whichever substance had not been injected in the first eye. We euthanized all animals 5 to 12 weeks after the final assessment of the second eye and performed both immunohistochemical and light and electron microscopic analyses of the retina and optic nerves of both eyes. A single IVT dose of ranibizumab administered immediately after induction of pNAION resulted in no significant reduction of clinical, electrophysiological, or histologic damage compared with vehicle-injected eyes. A single IVT dose of ranibizumab is not neuroprotective when administered immediately after induction of pNAION.

All plastic ultra-small size imaging lens unit fabrication and evaluation for endoscope

NASA Astrophysics Data System (ADS)

Ishii, Kenta; Okamoto, Dai; Ushio, Makoto; Tai, Hidetoshi; Nishihara, Atsuhiko; Tokuda, Kimio; Kawai, Shinsuke; Kitagawa, Seiichiro

2017-02-01

There is demand for small-size lens units for endoscope and industrial applications. Polished glass lenses with a diameter of 1 - 2mm exist, however plastic lenses similar in size are not commonplace. For low-cost, light-weight, and mass production, plastic lens fabrication is extremely beneficial. Especially, in the medical field, there is strong demand for disposable lens unit for endoscopes which prevent contamination due to reuse of the lens. Therefore, high mass producible and low cost becomes increasingly important. This paper reports our findings on injection-molded ultra-small size plastic lens units with a diameter of 1.3mm and total thickness of 1.4mm. We performed optical design, injection molding, and lens unit assembly for injection moldable, high imaging performance ultra-small sized lens units. We prioritize a robust product design, considering injection molding properties and lens unit assembly, with feedback from molding simulations reflected into the optical design. A mold capable of high precision lens positioning is used to fabricate the lenses and decrease the variability of the assembly. The geometric dimensions of the resulting lenses, are measured and used in the optical simulation to validate the optical performance, and a high agreement is reported. The injection molding of the lens and the assembly of the lens unit is performed with high precision, and results in high optical performance.

Non-intrusive optical study of gas and its exchange in human maxillary sinuses

NASA Astrophysics Data System (ADS)

Persson, L.; Andersson, M.; Svensson, T.; Cassel-Engquist, M.; Svanberg, K.; Svanberg, S.

2007-07-01

We demonstrate a novel non-intrusive technique based on tunable diode laser absorption spectroscopy to investigate human maxillary sinuses in vivo. The technique relies on the fact that free gases have much sharper absorption features (typical a few GHz) than the surrounding tissue. Molecular oxygen was detected at 760 nm. Volunteers have been investigated by injecting near-infrared light fibre-optically in contact with the palate inside the mouth. The multiply scattered light was detected externally by a handheld probe on and around the cheek bone. A significant signal difference in oxygen imprint was observed when comparing volunteers with widely different anamnesis regarding maxillary sinus status. Control measurements through the hand and through the cheek below the cheekbone were also performed to investigate any possible oxygen offset in the setup. These provided a consistently non-detectable signal level. The passages between the nasal cavity and the maxillary sinuses were also non-intrusively optically studied, to the best of our knowledge for the first time. These measurements provide information on the channel conductivity which may prove useful in facial sinus diagnostics. The results suggest that a clinical trial together with an ear-nose-throat (ENT) clinic should be carried out to investigate the clinical use of the new technique.

Electrical Tuning of Exciton-Plasmon Polariton Coupling in Monolayer MoS2 Integrated with Plasmonic Nanoantenna Lattice.

PubMed

Lee, Bumsu; Liu, Wenjing; Naylor, Carl H; Park, Joohee; Malek, Stephanie C; Berger, Jacob S; Johnson, A T Charlie; Agarwal, Ritesh

2017-07-12

Active control of light-matter interactions in semiconductors is critical for realizing next generation optoelectronic devices with real-time control of the system's optical properties and hence functionalities via external fields. The ability to dynamically manipulate optical interactions by applied fields in active materials coupled to cavities with fixed geometrical parameters opens up possibilities of controlling the lifetimes, oscillator strengths, effective mass, and relaxation properties of a coupled exciton-photon (or plasmon) system. Here, we demonstrate electrical control of exciton-plasmon coupling strengths between strong and weak coupling limits in a two-dimensional semiconductor integrated with plasmonic nanoresonators assembled in a field-effect transistor device by electrostatic doping. As a result, the energy-momentum dispersions of such an exciton-plasmon coupled system can be altered dynamically with applied electric field by modulating the excitonic properties of monolayer MoS 2 arising from many-body effects. In addition, evidence of enhanced coupling between charged excitons (trions) and plasmons was also observed upon increased carrier injection, which can be utilized for fabricating Fermionic polaritonic and magnetoplasmonic devices. The ability to dynamically control the optical properties of a coupled exciton-plasmonic system with electric fields demonstrates the versatility of the coupled system and offers a new platform for the design of optoelectronic devices with precisely tailored responses.

Experimental characterization of an all-optical wavelength converter of OFDM signals using two-mode injection-locking in a Fabry-Pérot laser.

PubMed

Dang, Juntao; Yi, Xingwen; Zhang, Jing; Ye, Taiping; Xu, Bo; Qiu, Kun

2016-07-25

While optical OFDM has been demonstrated for superior transmission performance, its analogue waveform in the time domain challenges many conventional all-optical wavelength converters (AOWC) that are needed for future flexible optical networks. There only exist a few reports on AOWC of OFDM signals, which are mainly based on the low-efficient four-wave mixing. In this paper, we propose an AOWC for OFDM signals by using two-mode injection-locking in a low-cost Fabry-Pérot laser. The control signal and the probe signal at a milliwatt power level are combined and injected into the FP laser. By a proper control, they can be injection-locked to two longitudinal modes in the FP laser and subsequently, the transmission of the probe signal is conditioned by the control signal. We conduct an experimental study on various aspects of this AOWC. Despite a vendor-specified electrical-to-optical (E/O) modulation bandwidth of 2.5 GHz, we find that the optical-to-optical (O/O) modulation bandwidth of AOWC is free from this limit and can be much wider. We examine the linear transfer curve of the AOWC by simply using the OFDM waveforms as the stimulus. The performance tolerance to the wavelength detuning and injected power ratio is also measured. The proposed AOWC can provide a linear transfer function from the control signal to the probe signal to support the random-fluctuated OFDM waveform. We also investigate the maximum capacity of the AOWC by using the adaptive bit-loading OFDM. Finally, we measure the power penalty after the AOWC at two different bit rates to show the tradeoff between the penalty and capacity.

GRB 120729A: External Shock Origin for Both the Prompt Gamma-Ray Emission and Afterglow

NASA Astrophysics Data System (ADS)

Huang, Li-Ye; Wang, Xiang-Gao; Zheng, WeiKang; Liang, En-Wei; Lin, Da-bin; Zhong, Shu-Qing; Zhang, Hai-Ming; Huang, Xiao-Li; Filippenko, Alexei V.; Zhang, Bing

2018-06-01

Gamma-ray burst (GRB) 120729A was detected by Swift/BAT and Fermi/GBM, and then rapidly observed by Swift/XRT, Swift/UVOT, and ground-based telescopes. It had a single long and smooth γ-ray emission pulse, which extends continuously to the X-rays. We report Lick/KAIT observations of the source, and make temporal and spectral joint fits of the multiwavelength light curves of GRB 120729A. It exhibits achromatic light-curve behavior, consistent with the predictions of the external shock model. The light curves are decomposed into four typical phases: onset bump (Phase I), normal decay (Phase II), shallow decay (Phase III), and post-jet break (Phase IV). The spectral energy distribution (SED) evolves from prompt γ-ray emission to the afterglow with a photon index from Γ γ = 1.36 to Γ ≈ 1.75. There is no obvious evolution of the SED during the afterglow. The multiwavelength light curves from γ-ray to optical can be well modeled with an external shock by considering energy injection, and a time-dependent microphysics model with {ε }B\\propto {t}{α B} for the emission at early times, T< {T}0+157 {{s}}. Therefore, we conclude that both the prompt γ-ray emission and afterglow of GRB 120729A have the same external shock physical origin. Our model indicates that the ɛ B evolution can be described as a broken power-law function with α B,1 = 0.18 ± 0.04 and α B,2 = 0.84 ± 0.04. We also systematically investigate single-pulse GRBs in the Swift era, finding that only a small fraction of GRBs (GRBs 120729A, 051111, and 070318) are likely to originate from an external shock for both the prompt γ-ray emission and afterglow.

Effect of systemic nitric oxide synthase inhibition on optic disc oxygen partial pressure in normoxia and in hypercapnia.

PubMed

Petropoulos, Ioannis K; Pournaras, Jean-Antoine C; Stangos, Alexandros N; Pournaras, Constantin J

2009-01-01

To investigate the effect of systemic nitric oxide synthase (NOS) inhibition on optic disc oxygen partial pressure (PO(2)) in normoxia and hypercapnia. Intervascular optic disc PO(2) was measured in 12 anesthetized minipigs by using oxygen-sensitive microelectrodes placed <50 microm from the optic disc. PO(2) was measured continuously during 10 minutes under normoxia, hyperoxia (100% O(2)), carbogen breathing (95% O(2), 5% CO(2)), and hypercapnia (increased inhaled CO(2)). Measurements were repeated after intravenous injection of N(omega)-nitro-L-arginine methyl ester (L-NAME) 100 mg/kg. Intravenous L-arginine 100 mg/kg was subsequently given to three animals. Before L-NAME injection, an increase was observed in optic disc PO(2) during hypercapnia (DeltaPO(2) = 3.2 +/- 1.7 mm Hg; 18%; P = 0.001) and carbogen breathing (DeltaPO(2) = 12.8 +/- 5.1 mm Hg; 69%; P < 0.001). Optic disc PO(2) in normoxia remained stable for 30 minutes after L-NAME injection (4% decrease from baseline; P > 0.1), despite a 21% increase of mean arterial pressure. Optic disc PO(2) increase under hypercapnia was blunted after L-NAME injection (DeltaPO(2) = 0.6 +/- 1.1 mm Hg; 3%; P > 0.1), and this effect was reversible by L-arginine. Moreover, L-NAME reduced the response to carbogen by 29% (DeltaPO(2) = 9.1 +/- 4.4 mm Hg; 49%; P = 0.01 versus before L-NAME). The response to hyperoxia was not affected. Whereas systemic NOS inhibition did not affect optic disc PO(2) in normoxia, a blunting effect was noted on the CO(2)-induced optic disc PO(2) increase. Nitric oxide appears to mediate the hypercapnic optic disc PO(2) increase.

Computational study of single-expansion-ramp nozzles with external burning

NASA Astrophysics Data System (ADS)

Yungster, Shaye; Trefny, Charles J.

1992-04-01

A computational investigation of the effects of external burning on the performance of single expansion ramp nozzles (SERN) operating at transonic speeds is presented. The study focuses on the effects of external heat addition and introduces a simplified injection and mixing model based on a control volume analysis. This simplified model permits parametric and scaling studies that would have been impossible to conduct with a detailed CFD analysis. The CFD model is validated by comparing the computed pressure distribution and thrust forces, for several nozzle configurations, with experimental data. Specific impulse calculations are also presented which indicate that external burning performance can be superior to other methods of thrust augmentation at transonic speeds. The effects of injection fuel pressure and nozzle pressure ratio on the performance of SERN nozzles with external burning are described. The results show trends similar to those reported in the experimental study, and provide additional information that complements the experimental data, improving our understanding of external burning flowfields. A study of the effect of scale is also presented. The results indicate that combustion kinetics do not make the flowfield sensitive to scale.

Computational study of single-expansion-ramp nozzles with external burning

NASA Technical Reports Server (NTRS)

Yungster, Shaye; Trefny, Charles J.

1992-01-01

A computational investigation of the effects of external burning on the performance of single expansion ramp nozzles (SERN) operating at transonic speeds is presented. The study focuses on the effects of external heat addition and introduces a simplified injection and mixing model based on a control volume analysis. This simplified model permits parametric and scaling studies that would have been impossible to conduct with a detailed CFD analysis. The CFD model is validated by comparing the computed pressure distribution and thrust forces, for several nozzle configurations, with experimental data. Specific impulse calculations are also presented which indicate that external burning performance can be superior to other methods of thrust augmentation at transonic speeds. The effects of injection fuel pressure and nozzle pressure ratio on the performance of SERN nozzles with external burning are described. The results show trends similar to those reported in the experimental study, and provide additional information that complements the experimental data, improving our understanding of external burning flowfields. A study of the effect of scale is also presented. The results indicate that combustion kinetics do not make the flowfield sensitive to scale.

Frequency characterization of a swept- and fixed-wavelength external-cavity quantum cascade laser by use of a frequency comb.

PubMed

Knabe, Kevin; Williams, Paul A; Giorgetta, Fabrizio R; Armacost, Chris M; Crivello, Sam; Radunsky, Michael B; Newbury, Nathan R

2012-05-21

The instantaneous optical frequency of an external-cavity quantum cascade laser (QCL) is characterized by comparison to a near-infrared frequency comb. Fluctuations in the instantaneous optical frequency are analyzed to determine the frequency-noise power spectral density for the external-cavity QCL both during fixed-wavelength and swept-wavelength operation. The noise performance of a near-infrared external-cavity diode laser is measured for comparison. In addition to providing basic frequency metrology of external-cavity QCLs, this comb-calibrated swept QCL system can be applied to rapid, precise broadband spectroscopy in the mid-infrared spectral region.

Tunable negative-tap photonic microwave filter based on a cladding-mode coupler and an optically injected laser of large detuning.

PubMed

Chan, Sze-Chun; Liu, Qing; Wang, Zhu; Chiang, Kin Seng

2011-06-20

A tunable negative-tap photonic microwave filter using a cladding-mode coupler together with optical injection locking of large wavelength detuning is demonstrated. Continuous and precise tunability of the filter is realized by physically sliding a pair of bare fibers inside the cladding-mode coupler. Signal inversion for the negative tap is achieved by optical injection locking of a single-mode semiconductor laser. To couple light into and out of the cladding-mode coupler, a pair of matching long-period fiber gratings is employed. The large bandwidth of the gratings requires injection locking of an exceptionally large wavelength detuning that has never been demonstrated before. Experimentally, injection locking with wavelength detuning as large as 27 nm was achieved, which corresponded to locking the 36-th side mode. Microwave filtering with a free-spectral range tunable from 88.6 MHz to 1.57 GHz and a notch depth larger than 35 dB was obtained.

All-optical pulse data generation in a semiconductor optical amplifier gain controlled by a reshaped optical clock injection

NASA Astrophysics Data System (ADS)

Lin, Gong-Ru; Chang, Yung-Cheng; Yu, Kun-Chieh

2006-05-01

Wavelength-maintained all-optical pulse data pattern transformation based on a modified cross-gain-modulation architecture in a strongly gain-depleted semiconductor optical amplifier (SOA) is investigated. Under a backward dark-optical-comb injection with 70% duty-cycle reshaping from the received data clock at 10GHz, the incoming optical data stream is transformed into a pulse data stream with duty cycle, rms timing jitter, and conversion gain of 15%, 4ps, and 3dB, respectively. The high-pass filtering effect of the gain-saturated SOA greatly improves the extinction ratio of data stream by 8dB and reduces its bit error rate to 10-12 at -18dBm.

Conversion from non-orthogonally to orthogonally polarized optical single-sideband modulation using optically injected semiconductor lasers.

PubMed

Hung, Yu-Han; Tseng, Chin-Hao; Hwang, Sheng-Kwang

2018-06-01

This Letter investigates an optically injected semiconductor laser for conversion from non-orthogonally to orthogonally polarized optical single-sideband modulation. The underlying mechanism relies solely on nonlinear laser characteristics and, thus, only a typical semiconductor laser is required as the key conversion unit. This conversion can be achieved for a broadly tunable frequency range up to at least 65 GHz. After conversion, the microwave phase quality, including linewidth and phase noise, is mostly preserved, and simultaneous microwave amplification up to 23 dB is feasible.

Optoelectronic device with nanoparticle embedded hole injection/transport layer

DOEpatents

Wang, Qingwu [Chelmsford, MA; Li, Wenguang [Andover, MA; Jiang, Hua [Methuen, MA

2012-01-03

An optoelectronic device is disclosed that can function as an emitter of optical radiation, such as a light-emitting diode (LED), or as a photovoltaic (PV) device that can be used to convert optical radiation into electrical current, such as a photovoltaic solar cell. The optoelectronic device comprises an anode, a hole injection/transport layer, an active layer, and a cathode, where the hole injection/transport layer includes transparent conductive nanoparticles in a hole transport material.

Optical coherence tomography for image-guided dermal filler injection and biomechanical evaluation

NASA Astrophysics Data System (ADS)

Singh, Manmohan; Wang, Shang; Yee, Richard W.; Han, Zhaolong; Aglyamov, Salavat R.; Larin, Kirill V.

2017-02-01

Dermal fillers are a very popular anti-ag ing treatment with estimated sales in the billions of dollars and millions of procedures performed. As the aging population continues to grow, these figures are only e xpected to increase. Dermal fillers have various compositions depending on their intended applicati on. Reactions to dermal fillers can be severe, such as ischemic events and filler migration to the eyes. Howe ver, these adverse reactions are rare. Nevertheless, the capability to perform imag e-guided filler injections would minimize th e risk of such reacti ons. In addition, the biomechanical properties of various fillers have been evalua ted, but there has been no investigation on the effects of filler on the biomechanical properties of skin. In this work, we utilize optical cohe rence tomography (OCT) for visualizing dermal filler injections with micrometer-scale sp atial resolution. In addition, we utilize noncontact optical coherence elastography (OCE) to quantify the changes in the biomechan ical properties of pig skin after the dermal filler injections. OCT was successfully able to visualize the dermal filler injecti on process, and OCE showed that the viscoelasticity of the pig skin was increased locally at the filler injection sites. OCT may be able to provide real-time image guidance in 3D, and when combined with functional OCT techniques such as optical microangiography, could be used to avoid blood vessels during the injection.

The effects of a geometrical size, external electric fields and impurity on the optical gain of a quantum dot laser with a semi-parabolic spherical well potential

NASA Astrophysics Data System (ADS)

Owji, Erfan; Keshavarz, Alireza; Mokhtari, Hosein

2017-03-01

In this paper, a GaAs / Alx Ga1-x As quantum dot laser with a semi-parabolic spherical well potential is assumed. By using Runge-Kutta method the eigenenergies and the eigenstates of valence and conduct bands are obtained. The effects of geometrical sizes, external electric fields and hydrogen impurity on the different electronic transitions of the optical gain are studied. The results show that the optical gain peak increases and red-shifts, by increasing the width of well or barrier, while more increasing of the width causes blue-shift and decreases it. The hydrogen impurity decreases the optical gain peak and blue-shifts it. Also, the increasing of the external electric fields cause to increase the peak of the optical gain, and (blue) red shift it. Finally, the optical gain for 1s-1s and 2s-1s transitions is prominent, while it is so weak for other transitions.

The relative roles of external and internal CO(2) versus H(+) in eliciting the cardiorespiratory responses of Salmo salar and Squalus acanthias to hypercarbia.

PubMed

Perry, S F; McKendry, J E

2001-11-01

Fish breathing hypercarbic water encounter externally elevated P(CO(2)) and proton levels ([H(+)]) and experience an associated internal respiratory acidosis, an elevation of blood P(CO(2)) and [H(+)]. The objective of the present study was to assess the potential relative contributions of CO(2) versus H(+) in promoting the cardiorespiratory responses of dogfish (Squalus acanthias) and Atlantic salmon (Salmo salar) to hypercarbia and to evaluate the relative contributions of externally versus internally oriented receptors in dogfish. In dogfish, the preferential stimulation of externally oriented branchial chemoreceptors using bolus injections (50 ml kg(-1)) of CO(2)-enriched (4 % CO(2)) sea water into the buccal cavity caused marked cardiorespiratory responses including bradycardia (-4.1+/-0.9 min(-1)), a reduction in cardiac output (-3.2+/-0.6 ml min(-1) kg(-1)), an increase in systemic vascular resistance (+0.3+/-0.2 mmHg ml min(-1) kg(-1)), arterial hypotension (-1.6+/-0.2 mmHg) and an increase in breathing amplitude (+0.3+/-0.09 mmHg) (means +/- S.E.M., N=9-11). Similar injections of CO(2)-free sea water acidified to the corresponding pH of the hypercarbic water (pH 6.3) did not significantly affect any of the measured cardiorespiratory variables (when compared with control injections). To preferentially stimulate putative internal CO(2)/H(+) chemoreceptors, hypercarbic saline (4 % CO(2)) was injected (2 ml kg(-1)) into the caudal vein. Apart from an increase in arterial blood pressure caused by volume loading, internally injected CO(2) was without effect on any measured variable. In salmon, injection of hypercarbic water into the buccal cavity caused a bradycardia (-13.9+/-3.8 min(-1)), a decrease in cardiac output (-5.3+/-1.2 ml min(-1) kg(-1)), an increase in systemic resistance (0.33+/-0.08 mmHg ml min(-1) kg(-1)) and increases in breathing frequency (9.7+/-2.2 min(-1)) and amplitude (1.2+/-0.2 mmHg) (means +/- S.E.M., N=8-12). Apart from a small increase in breathing amplitude (0.4+/-0.1 mmHg), these cardiorespiratory responses were not observed after injection of acidified water. These results demonstrate that, in dogfish and salmon, the external chemoreceptors linked to the initiation of cardiorespiratory responses during hypercarbia are predominantly stimulated by the increase in water P(CO(2)) rather than by the accompanying decrease in water pH. Furthermore, in dogfish, the cardiorespiratory responses to hypercarbia are probably exclusively derived from the stimulation of external CO(2) chemoreceptors, with no apparent contribution from internally oriented receptors.

Active stabilization of a diode laser injection lock.

PubMed

Saxberg, Brendan; Plotkin-Swing, Benjamin; Gupta, Subhadeep

2016-06-01

We report on a device to electronically stabilize the optical injection lock of a semiconductor diode laser. Our technique uses as discriminator the peak height of the laser's transmission signal on a scanning Fabry-Perot cavity and feeds back to the diode current, thereby maintaining maximum optical power in the injected mode. A two-component feedback algorithm provides constant optimization of the injection lock, keeping it robust to slow thermal drifts and allowing fast recovery from sudden failures such as temporary occlusion of the injection beam. We demonstrate the successful performance of our stabilization method in a diode laser setup at 399 nm used for laser cooling of Yb atoms. The device eases the requirements on passive stabilization and can benefit any diode laser injection lock application, particularly those where several such locks are employed.

Stability of aerosol droplets in Bessel beam optical traps under constant and pulsed external forces

NASA Astrophysics Data System (ADS)

David, Grégory; Esat, Kıvanç; Hartweg, Sebastian; Cremer, Johannes; Chasovskikh, Egor; Signorell, Ruth

2015-04-01

We report on the dynamics of aerosol droplets in optical traps under the influence of additional constant and pulsed external forces. Experimental results are compared with simulations of the three-dimensional droplet dynamics for two types of optical traps, the counter-propagating Bessel beam (CPBB) trap and the quadruple Bessel beam (QBB) trap. Under the influence of a constant gas flow (constant external force), the QBB trap is found to be more stable compared with the CPBB trap. By contrast, under pulsed laser excitation with laser pulse durations of nanoseconds (pulsed external force), the type of trap is of minor importance for the droplet stability. It typically needs pulsed laser forces that are several orders of magnitude higher than the optical forces to induce escape of the droplet from the trap. If the droplet strongly absorbs the pulsed laser light, these escape forces can be strongly reduced. The lower stability of absorbing droplets is a result of secondary thermal processes that cause droplet escape.

Stability of aerosol droplets in Bessel beam optical traps under constant and pulsed external forces.

PubMed

David, Grégory; Esat, Kıvanç; Hartweg, Sebastian; Cremer, Johannes; Chasovskikh, Egor; Signorell, Ruth

2015-04-21

We report on the dynamics of aerosol droplets in optical traps under the influence of additional constant and pulsed external forces. Experimental results are compared with simulations of the three-dimensional droplet dynamics for two types of optical traps, the counter-propagating Bessel beam (CPBB) trap and the quadruple Bessel beam (QBB) trap. Under the influence of a constant gas flow (constant external force), the QBB trap is found to be more stable compared with the CPBB trap. By contrast, under pulsed laser excitation with laser pulse durations of nanoseconds (pulsed external force), the type of trap is of minor importance for the droplet stability. It typically needs pulsed laser forces that are several orders of magnitude higher than the optical forces to induce escape of the droplet from the trap. If the droplet strongly absorbs the pulsed laser light, these escape forces can be strongly reduced. The lower stability of absorbing droplets is a result of secondary thermal processes that cause droplet escape.

Targeted endomyocardial injections of therapeutic cells using x-ray fused with MRI guidance

NASA Astrophysics Data System (ADS)

Gutiérrez, Luis F.; de Silva, Ranil; McVeigh, Elliot R.; Ozturk, Cengizhan; Lederman, Robert J.

2006-03-01

The utility of X-ray fused with MRI (XFM) using external fiducial markers to perform targeted endomyocardial injections in infarcted hearts of swine was tested. Endomyocardial injections of feridex-labeled mesenchymal stromal cells (Fe-MSC) were performed in the previously infarcted hearts of 12 Yucatan miniswine (33-67 kg). Animals had pre-injection cardiac MRI, XFM-guided endomyocardial injection of Fe-MSC suspension spiked with tissue dye, and post-injection MRI. 24 hours later, after euthanasia, the hearts were excised, sliced and stained with TTC. During the injection procedure, operators were provided with 3D surfaces of endocardium, epicardium, myocardial wall thickness and infarct registered with live XF images to facilitate device navigation and choice of injection location. 130 injections were performed in hearts where diastolic wall thickness ranged from 2.6 to 17.7 mm. Visual inspection of the pattern of dye staining on TTC stained heart slices correlated (r=0.98) with XFM-derived injection locations mapped onto delayed hyperenhancement MRI and the susceptibility artifacts seen on the post-injection T2*-weighted gradient echo MRI. The in vivo target registration error was 3.17+/-2.61 mm (n=64) and 75% of injections were within 4 mm of the predicted location. 3D to 2D registration of XF and MR images using external fiducial markers enables accurate targeted endomyocardial injection in a swine model of myocardial infarction. The present data suggest that the safety and efficacy of this approach for performing targeted endomyocardial delivery should be evaluated further clinically.

Safety assessment of a new single-use small-incision injector for intraocular lens implantation.

PubMed

Satanovsky, Alexandra; Ben-Eliahu, Shmuel; Apple, David J; Kleinmann, Guy

2011-07-01

To evaluate the safety of a new injector, the Raysert R-INJ-04/18, for implantation of the C-flex intraocular lens (IOL). Ophthalmology Department, Kaplan Medical Center, Rehovot, Israel. Experimental study. Sixty IOLs were subdivided into 2 equally sized groups. Group A IOLs were injected using the established R-INJ-04 injector, and those in Group B were injected with the new injector. The IOLs were injected into a Petri dish. Subsequently, all IOLs and injectors were evaluated macroscopically and microscopically and then photographed under light microscopy (LM). Two IOLs in each group were randomly chosen and sent for evaluation by scanning electron microscopy (SEM) and energy dispersive analysis of x-ray. All remaining IOLs were sent for power and modulation transfer function (MTF) analysis. All Group B IOLs were successfully injected without evident signs of scratching, cracks, or deposits on LM and SEM examination. In Group A, findings were confined to a singular incidence of a small deposit detected on the periphery of the posterior optical surface of the IOL, with corresponding findings detected on the injector nozzle. No signs of scratching, cracks, or deposits were found in the rest of the IOLs or injectors. The power and MTF analyses were within the normal range for all IOLs. The new 1.8 mm external diameter soft-tipped injector for 2.4 to 2.2 mm incisions was shown to be safe for the implantation of the C-flex 21.0 diopter IOL. Copyright © 2011 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

Recent Development in Optical Chemical Sensors Coupling with Flow Injection Analysis

PubMed Central

Ojeda, Catalina Bosch; Rojas, Fuensanta Sánchez

2006-01-01

Optical techniques for chemical analysis are well established and sensors based on these techniques are now attracting considerable attention because of their importance in applications such as environmental monitoring, biomedical sensing, and industrial process control. On the other hand, flow injection analysis (FIA) is advisable for the rapid analysis of microliter volume samples and can be interfaced directly to the chemical process. The FIA has become a widespread automatic analytical method for more reasons; mainly due to the simplicity and low cost of the setups, their versatility, and ease of assembling. In this paper, an overview of flow injection determinations by using optical chemical sensors is provided, and instrumentation, sensor design, and applications are discussed. This work summarizes the most relevant manuscripts from 1980 to date referred to analysis using optical chemical sensors in FIA.

Hole-cyclotron instability in semiconductor quantum plasmas

NASA Astrophysics Data System (ADS)

Areeb, F.; Rasheed, A.; Jamil, M.; Siddique, M.; Sumera, P.

2018-01-01

The excitation of electrostatic hole-cyclotron waves generated by an externally injected electron beam in semiconductor plasmas is examined using a quantum hydrodynamic model. The quantum effects such as tunneling potential, Fermi degenerate pressure, and exchange-correlation potential are taken care of. The growth rate of the wave is analyzed on varying the parameters normalized by hole-plasma frequency, like the angle θ between propagation vector and B0∥z ̂ , speed of the externally injected electron beam v0∥k , thermal temperature of the electron beam τ, external magnetic field B0∥z ̂ that modifies the hole-cyclotron frequency, and finally, the semiconductor electron number density. The instability of the hole-cyclotron wave seeks its applications in semiconductor devices.

Optical-microwave interactions in semiconductor devices

NASA Astrophysics Data System (ADS)

Figueroa, L.; Slayman, C.; Yen, H. W.

1980-02-01

GaAs FETs with built-in optical waveguides are being developed. The purpose is to allow optical signals to be coupled into the active region of the devices efficiently. These FETs will be useful for optical mixing, optical injection locking, and optical detection purposes.

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

Dorogush, E S; Afonenko, A A

The distributed resonator model is used to show the presence of several resonance responses on the modulation characteristic of optically injection-locked Fabry–Perot lasers. The positions of the resonance peaks on the modulation characteristic are determined by the resonator length and frequency detuning of optical injection. It is shown that an appropriate choice of the resonator length and injection locking conditions allows one to obtain efficient modulation in two ranges near 40 – 60 GHz or to increase the direct modulation bandwidth up to 50 GHz. (control of laser radiation parameters)

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

A Single Intravitreal Injection of Ranibizumab Provides No Neuroprotection in a Nonhuman Primate Model of Moderate-to-Severe Nonarteritic Anterior Ischemic Optic Neuropathy

PubMed Central

Miller, Neil R.; Johnson, Mary A.; Nolan, Theresa; Guo, Yan; Bernstein, Steven L.

2015-01-01

Purpose Ranibizumab, a vascular endothelial growth factor-antagonist, is said to be neuroprotective when injected intravitreally in patients with nonarteritic anterior ischemic optic neuropathy (NAION). We evaluated the efficacy of a single intravitreal (IVT) injection of ranibizumab in a nonhuman primate model of NAION (pNAION). Methods We induced pNAION in one eye of four adult male rhesus monkeys using a laser-activated rose Bengal induction method. We then immediately injected the eye with either ranibizumab or normal saline (NS) intravitreally. We performed a clinical assessment, optical coherence tomography, electrophysiological testing, fundus photography, and fluorescein angiography in three of the animals (one animal developed significant retinal hemorrhages and, therefore, could not be analyzed completely) prior to induction, 1 day and 1, 2, and 4 weeks thereafter. Following the 4-week analysis of the first eye, we induced pNAION in the contralateral eye and then injected either ranibizumab or NS, whichever substance had not been injected in the first eye. We euthanized all animals 5 to 12 weeks after the final assessment of the second eye and performed both immunohistochemical and light and electron microscopic analyses of the retina and optic nerves of both eyes. Results A single IVT dose of ranibizumab administered immediately after induction of pNAION resulted in no significant reduction of clinical, electrophysiological, or histologic damage compared with vehicle-injected eyes. Conclusions A single IVT dose of ranibizumab is not neuroprotective when administered immediately after induction of pNAION. PMID:26624498

Alternative laser system for cesium magneto-optical trap via optical injection locking to sideband of a 9-GHz current-modulated diode laser.

PubMed

Diao, Wenting; He, Jun; Liu, Zhi; Yang, Baodong; Wang, Junmin

2012-03-26

By optical injection of an 852-nm extended-cavity diode laser (master laser) to lock the + 1-order sideband of a ~9-GHz-current-modulated diode laser (slave laser), we generate a pair of phase-locked lasers with a frequency difference up to ~9-GHz for a cesium (Cs) magneto-optical trap (MOT) with convenient tuning capability. For a cesium MOT, the master laser acts as repumping laser, locked to the Cs 6S₁/₂ (F = 3) - 6P₃/₂ (F' = 4) transition. When the + 1-order sideband of the 8.9536-GHz-current-modulated slave laser is optically injection-locked, the carrier operates on the Cs 6S₁/₂ (F = 4) - 6P₃/₂ (F' = 5) cooling cycle transition with -12 MHz detuning and acts as cooling/trapping laser. When carrying a 9.1926-GHz modulation signal, this phase-locked laser system can be applied in the fields of coherent population trapping and coherent manipulation of Cs atomic ground states.

Clinical trials of a new chlorin photosensitizer for photodynamic therapy of malignant tumors

NASA Astrophysics Data System (ADS)

Privalov, Valeriy A.; Lappa, Alexander V.; Seliverstov, Oleg V.; Faizrakhmanov, Alexey B.; Yarovoy, Nicolay N.; Kochneva, Elena V.; Evnevich, Michail V.; Anikina, Alla S.; Reshetnicov, Andrey V.; Zalevsky, Igor D.; Kemov, Yuriy V.

2002-06-01

Photodynamic therapy (PDT) was performed with a new photosensitizer, a water soluble form of chlorins (Radachlorin, Russia) possessing an absorption peak around 662 nm. As light source there was used the diode laser (ML-662-SP, Russia) with 662 nm wavelength and 2.5 W optical power. The sensitizer had passed broad pre-clinical in vitro and in vivo studies, which showed safety and efficiency of it. PDT was applied to 51 patients with basal cell cancer of the skin (about 60% of all cases), breast cancer, lip cancer, melanoma, cancer of esophagus, stomach, and rectum, cancer and leucoplacia of vulva, malignant ganglioneuroma, sarcoma of soft tissue, cancer and reticular sarcoma of thyroid gland, cancer of ductus choledochus. Most of non-basalioma patients had either forth stage or recurrence of disease. The sensitizer was injected intravenously or applied externally (Radachlorin gel). There were used surface, endoscopic, and interstitial ways of irradiation. Full tumor regression with excellent cosmetic effect was reached in 100% cases of 1-3 stage basal cell cancer patients treated with intravenous Radachlorin injection. In most other (non-basalioma) cases significant regression of tumors and improvement of life quality of patients (recanalization and regain of conductivity) was obtained.

Hybrid electronic/optical synchronized chaos communication system.

PubMed

Toomey, J P; Kane, D M; Davidović, A; Huntington, E H

2009-04-27

A hybrid electronic/optical system for synchronizing a chaotic receiver to a chaotic transmitter has been demonstrated. The chaotic signal is generated electronically and injected, in addition to a constant bias current, to a semiconductor laser to produce an optical carrier for transmission. The optical chaotic carrier is photodetected to regenerate an electronic signal for synchronization in a matched electronic receiver The system has been successfully used for the transmission and recovery of a chaos masked message that is added to the chaotic optical carrier. Past demonstrations of synchronized chaos based, secure communication systems have used either an electronic chaotic carrier or an optical chaotic carrier (such as the chaotic output of various nonlinear laser systems). This is the first electronic/optical hybrid system to be demonstrated. We call this generation of a chaotic optical carrier by electronic injection.

Effects of 5,7-DHT Injection into the Optic Lobe on the Circadian Locomotor Rhythm in the Cricket, Gryllus bimaculatus.

PubMed

Germ, M; Tomioka, K

1998-06-01

The effect of direct 5,7-dihydroxytryptamine (5,7-DHT) injection into the medulla region of the optic lobe on the locomotor activity was investigated in the adult male cricket, Gryllus bimaculatus. After a 6 hr phase advance of a light-dark cycle, the 5,7-DHT injected animals needed significantly longer time for resynchronization to the new cycle (6.55 +/- 0.62 days) than the control, Ringer's solution injected animals (3.17 +/- 0.15 days; P < 0.001, t-test). Light induced a bout of activity (i.e., masking effect) when light-dark cycle was phase advanced by 6 hr and the duration of the masking effect was significantly longer in 5,7-DHT injected animals. An initial bout of the nocturnal activity was significantly greater in the 5,7-DHT injected animal. Under constant darkness, the freerunning periods of both groups were not significantly different. Under constant light, a significantly higher percentage of 5,7-DHT injected animals showed arrhythmicity compared with the control group. An analysis carried by high-pressure liquid chromatography with electro-chemical detection (HPLC-ECD) revealed that the serotonin content in the optic lobe was significantly reduced to less than 50% in the 5,7-DHT injected animals, even one month after the injection. These results suggest that serotonin plays important roles in the regulation of circadian locomotor rhythms of the cricket mainly by regulating the sensitivity of the photoreceptive system.

Optical Rogue Waves in Vortex Turbulence.

PubMed

Gibson, Christopher J; Yao, Alison M; Oppo, Gian-Luca

2016-01-29

We present a spatiotemporal mechanism for producing 2D optical rogue waves in the presence of a turbulent state with creation, interaction, and annihilation of optical vortices. Spatially periodic structures with bound phase lose stability to phase unbound turbulent states in complex Ginzburg-Landau and Swift-Hohenberg models with external driving. When the pumping is high and the external driving is low, synchronized oscillations are unstable and lead to spatiotemporal vortex-mediated turbulence with high excursions in amplitude. Nonlinear amplification leads to rogue waves close to turbulent optical vortices, where the amplitude tends to zero, and to probability density functions (PDFs) with long tails typical of extreme optical events.

Generation of a CW local oscillator signal using a stabilized injection locked semiconductor laser

NASA Astrophysics Data System (ADS)

Pezeshki, Jonah Massih

In high speed-communications, it is desirable to be able to detect small signals while maintaining a low bit-error rate. Conventional receivers for high-speed fiber optic networks are Amplified Direct Detectors (ADDs) that use erbium-doped fiber amplifiers (EDFAs) before the detector to achieve a suitable sensitivity. In principle, a better method for obtaining the maximum possible signal to noise ratio is through the use of homodyne detection. The major difficulty in implementing a homodyne detection system is the generation of a suitable local oscillator signal. This local oscillator signal must be at the same frequency as the received data signal, as well as be phase coherent with it. To accomplish this, a variety of synchronization techniques have been explored, including Optical Phase-Lock Loops (OPLL), Optical Injection Locking (OIL) with both Fabry-Perot and DFB lasers, and an Optical Injection Phase-Lock Loop (OIPLL). For this project I have implemented a method for regenerating a local oscillator from a portion of the received optical signal. This regenerated local oscillator is at the same frequency, and is phase coherent with, the received optical signal. In addition, we show that the injection locking process can be electronically stabilized by using the modulation transfer ratio of the slave laser as a monitor, given either a DFB or Fabry-Perot slave laser. We show that this stabilization technique maintains injection lock (given a locking range of ˜1GHz) for laser drift much greater than what is expected in a typical transmission system. In addition, we explore the quality of the output of the slave laser, and analyze its suitability as a local oscillator signal for a homodyne receiver.

Tunnel-injected sub 290 nm ultra-violet light emitting diodes with 2.8% external quantum efficiency

NASA Astrophysics Data System (ADS)

Zhang, Yuewei; Jamal-Eddine, Zane; Akyol, Fatih; Bajaj, Sanyam; Johnson, Jared M.; Calderon, Gabriel; Allerman, Andrew A.; Moseley, Michael W.; Armstrong, Andrew M.; Hwang, Jinwoo; Rajan, Siddharth

2018-02-01

We report on the high efficiency tunnel-injected ultraviolet light emitting diodes (UV LEDs) emitting at 287 nm. Deep UV LED performance has been limited by the severe internal light absorption in the p-type contact layers and low electrical injection efficiency due to poor p-type conduction. In this work, a polarization engineered Al0.65Ga0.35N/In0.2Ga0.8N tunnel junction layer is adopted for non-equilibrium hole injection to replace the conventionally used direct p-type contact. A reverse-graded AlGaN contact layer is further introduced to realize a low resistance contact to the top n-AlGaN layer. This led to the demonstration of a low tunnel junction resistance of 1.9 × 10-3 Ω cm2 obtained at 1 kA/cm2. Light emission at 287 nm with an on-wafer peak external quantum efficiency of 2.8% and a wall-plug efficiency of 1.1% was achieved. The measured power density at 1 kA/cm2 was 54.4 W/cm2, confirming the efficient hole injection through interband tunneling. With the benefits of the minimized internal absorption and efficient hole injection, a tunnel-injected UV LED structure could enable future high efficiency UV emitters.

Experimental Investigation of Centrifugal Compressor Stabilization Techniques

NASA Technical Reports Server (NTRS)

Skoch, Gary J.

2003-01-01

Results from a series of experiments to investigate techniques for extending the stable flow range of a centrifugal compressor are reported. The research was conducted in a high-speed centrifugal compressor at the NASA Glenn Research Center. The stabilizing effect of steadily flowing air-streams injected into the vaneless region of a vane-island diffuser through the shroud surface is described. Parametric variations of injection angle, injection flow rate, number of injectors, injector spacing, and injection versus bleed were investigated for a range of impeller speeds and tip clearances. Both the compressor discharge and an external source were used for the injection air supply. The stabilizing effect of flow obstructions created by tubes that were inserted into the diffuser vaneless space through the shroud was also investigated. Tube immersion into the vaneless space was varied in the flow obstruction experiments. Results from testing done at impeller design speed and tip clearance are presented. Surge margin improved by 1.7 points using injection air that was supplied from within the compressor. Externally supplied injection air was used to return the compressor to stable operation after being throttled into surge. The tubes, which were capped to prevent mass flux, provided 9.3 points of additional surge margin over the baseline surge margin of 11.7 points.

Far infrared pump injection using an alumina waveguide

NASA Astrophysics Data System (ADS)

Nedvidek, F. J.; Kucerovsky, Z.; Brannen, Eric

1987-01-01

An alumina waveguide extension is employed to channel infrared radiation from a CO2 waveguide laser into an optically pumped far IR waveguide laser resonator in order to obtain far IR lasing with methyl alcohol and other media. Low pump transmission losses and efficient free space coupling are possible with proper choice of waveguide bore. The technique compares favorably with other injection schemes using refractive optics, and it offers greater flexibility, easier alignment, and less expense than optical arrangements using lenses.

Methods for determining optical power, for power-normalizing laser measurements, and for stabilizing power of lasers via compliance voltage sensing

DOEpatents

Taubman, Matthew S; Phillips, Mark C

2015-04-07

A method is disclosed for power normalization of spectroscopic signatures obtained from laser based chemical sensors that employs the compliance voltage across a quantum cascade laser device within an external cavity laser. The method obviates the need for a dedicated optical detector used specifically for power normalization purposes. A method is also disclosed that employs the compliance voltage developed across the laser device within an external cavity semiconductor laser to power-stabilize the laser mode of the semiconductor laser by adjusting drive current to the laser such that the output optical power from the external cavity semiconductor laser remains constant.

Effect of injection current and temperature on signal strength in a laser diode optical feedback interferometer.

PubMed

Al Roumy, Jalal; Perchoux, Julien; Lim, Yah Leng; Taimre, Thomas; Rakić, Aleksandar D; Bosch, Thierry

2015-01-10

We present a simple analytical model that describes the injection current and temperature dependence of optical feedback interferometry signal strength for a single-mode laser diode. The model is derived from the Lang and Kobayashi rate equations, and is developed both for signals acquired from the monitoring photodiode (proportional to the variations in optical power) and for those obtained by amplification of the corresponding variations in laser voltage. The model shows that both the photodiode and the voltage signal strengths are dependent on the laser slope efficiency, which itself is a function of the injection current and the temperature. Moreover, the model predicts that the photodiode and voltage signal strengths depend differently on injection current and temperature. This important model prediction was proven experimentally for a near-infrared distributed feedback laser by measuring both types of signals over a wide range of injection currents and temperatures. Therefore, this simple model provides important insight into the radically different biasing strategies required to achieve optimal sensor sensitivity for both interferometric signal acquisition schemes.

Semiconductor ring lasers subject to both on-chip filtered optical feedback and external conventional optical feedback

NASA Astrophysics Data System (ADS)

Khoder, Mulham; Van der Sande, Guy; Danckaert, Jan; Verschaffelt, Guy

2016-05-01

It is well known that the performance of semiconductor lasers is very sensitive to external optical feedback. This feedback can lead to changes in lasing characteristics and a variety of dynamical effects including chaos and coherence collapse. One way to avoid this external feedback is by using optical isolation, but these isolators and their packaging will increase the cost of the total system. Semiconductor ring lasers nowadays are promising sources in photonic integrated circuits because they do not require cleaved facets or mirrors to form a laser cavity. Recently, some of us proposed to combine semiconductor ring lasers with on chip filtered optical feedback to achieve tunable lasers. The feedback is realized by employing two arrayed waveguide gratings to split/recombine light into different wavelength channels. Semiconductor optical amplifier gates are used to control the feedback strength. In this work, we investigate how such lasers with filtered feedback are influenced by an external conventional optical feedback. The experimental results show intensity fluctuations in the time traces in both the clockwise and counterclockwise directions due to the conventional feedback. We quantify the strength of the conventional feedback induced dynamics be extracting the standard deviation of the intensity fluctuations in the time traces. By using filtered feedback, we can shift the onset of the conventional feedback induced dynamics to larger values of the feedback rate [ Khoder et al, IEEE Photon. Technol. Lett. DOI: 10.1109/LPT.2016.2522184]. The on-chip filtered optical feedback thus makes the semiconductor ring laser less senstive to the effect of (long) conventional optical feedback. We think these conclusions can be extended to other types of lasers.

Stability of aerosol droplets in Bessel beam optical traps under constant and pulsed external forces

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

David, Grégory; Esat, Kıvanç; Hartweg, Sebastian

We report on the dynamics of aerosol droplets in optical traps under the influence of additional constant and pulsed external forces. Experimental results are compared with simulations of the three-dimensional droplet dynamics for two types of optical traps, the counter-propagating Bessel beam (CPBB) trap and the quadruple Bessel beam (QBB) trap. Under the influence of a constant gas flow (constant external force), the QBB trap is found to be more stable compared with the CPBB trap. By contrast, under pulsed laser excitation with laser pulse durations of nanoseconds (pulsed external force), the type of trap is of minor importance formore » the droplet stability. It typically needs pulsed laser forces that are several orders of magnitude higher than the optical forces to induce escape of the droplet from the trap. If the droplet strongly absorbs the pulsed laser light, these escape forces can be strongly reduced. The lower stability of absorbing droplets is a result of secondary thermal processes that cause droplet escape.« less

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

Saxberg, Brendan; Plotkin-Swing, Benjamin; Gupta, Subhadeep

We report on a device to electronically stabilize the optical injection lock of a semiconductor diode laser. Our technique uses as discriminator the peak height of the laser’s transmission signal on a scanning Fabry-Perot cavity and feeds back to the diode current, thereby maintaining maximum optical power in the injected mode. A two-component feedback algorithm provides constant optimization of the injection lock, keeping it robust to slow thermal drifts and allowing fast recovery from sudden failures such as temporary occlusion of the injection beam. We demonstrate the successful performance of our stabilization method in a diode laser setup at 399more » nm used for laser cooling of Yb atoms. The device eases the requirements on passive stabilization and can benefit any diode laser injection lock application, particularly those where several such locks are employed.« less

INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Influence of spontaneous fluctuations on the emission spectrum of an injection semiconductor laser

NASA Astrophysics Data System (ADS)

Gulyaev, Yurii V.; Suris, Robert A.; Tager, A. A.; Élenkrig, B. B.

1988-11-01

A theoretical investigation is made of fluctuation-induced excitation of side longitudinal modes in the emission spectra of semiconductor lasers, including those with an external mirror. It is shown that nonlinear refraction of light in the active region of a semiconductor laser may result in a noise redistribution of the radiation between longitudinal resonator modes and can be responsible for the multimode nature of the average emission spectrum. An analysis is made of the influence of selectivity of an external mirror on the stability of cw operation, minimum line width, and mode composition of the emission spectra of semiconductor lasers. The conditions for maximum narrowing of the emission spectrum of a semiconductor laser with an external selective mirror are identified.

Effect of post injections on mixture preparation and unburned hydrocarbon emissions in a heavy-duty diesel engine

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

O'Connor, Jacqueline; Musculus, Mark P. B.; Pickett, Lyle M.

This work explores the mechanisms by which a post injection can reduce unburned hydrocarbon (UHC) emissions in heavy-duty diesel engines operating at low-temperature combustion conditions. Post injections, small, close-coupled injections of fuel after the main injection, have been shown to reduce UHC in the authors’ previous work. In this work, we analyze optical data from laser-induced fluorescence of both CH 2O and OH and use chemical reactor modeling to better understand the mechanism by which post injections reduce UHC emissions. The results indicate that post-injection efficacy, or the extent to which a post injection reduces UHC emissions, is a strongmore » function of the cylinder pressure variation during the post injection. However, the data and analysis indicate that the pressure and temperature rise from the post injection combustion cannot solely explain the UHC reduction measured by both engine-out and optical diagnostics. In conclusion, the fluid-mechanic, thermal, and chemical interaction of the post injection with the main-injection mixture is a key part of UHC reduction; the starting action of the post jet and the subsequent entrainment of surrounding gases are likely both important processes in reducing UHC with a post injection.« less

Effect of post injections on mixture preparation and unburned hydrocarbon emissions in a heavy-duty diesel engine

DOE PAGES

O'Connor, Jacqueline; Musculus, Mark P. B.; Pickett, Lyle M.

2016-05-30

This work explores the mechanisms by which a post injection can reduce unburned hydrocarbon (UHC) emissions in heavy-duty diesel engines operating at low-temperature combustion conditions. Post injections, small, close-coupled injections of fuel after the main injection, have been shown to reduce UHC in the authors’ previous work. In this work, we analyze optical data from laser-induced fluorescence of both CH 2O and OH and use chemical reactor modeling to better understand the mechanism by which post injections reduce UHC emissions. The results indicate that post-injection efficacy, or the extent to which a post injection reduces UHC emissions, is a strongmore » function of the cylinder pressure variation during the post injection. However, the data and analysis indicate that the pressure and temperature rise from the post injection combustion cannot solely explain the UHC reduction measured by both engine-out and optical diagnostics. In conclusion, the fluid-mechanic, thermal, and chemical interaction of the post injection with the main-injection mixture is a key part of UHC reduction; the starting action of the post jet and the subsequent entrainment of surrounding gases are likely both important processes in reducing UHC with a post injection.« less

Optical sampling by laser cavity tuning.

PubMed

Hochrein, Thomas; Wilk, Rafal; Mei, Michael; Holzwarth, Ronald; Krumbholz, Norman; Koch, Martin

2010-01-18

Most time-resolved optical experiments rely either on external mechanical delay lines or on two synchronized femtosecond lasers to achieve a defined temporal delay between two optical pulses. Here, we present a new method which does not require any external delay lines and uses only a single femtosecond laser. It is based on the cross-correlation of an optical pulse with a subsequent pulse from the same laser. Temporal delay between these two pulses is achieved by varying the repetition rate of the laser. We validate the new scheme by a comparison with a cross-correlation measurement carried out with a conventional mechanical delay line.

Internal-illumination photoacoustic computed tomography

NASA Astrophysics Data System (ADS)

Li, Mucong; Lan, Bangxin; Liu, Wei; Xia, Jun; Yao, Junjie

2018-03-01

We report a photoacoustic computed tomography (PACT) system using a customized optical fiber with a cylindrical diffuser to internally illuminate deep targets. The traditional external light illumination in PACT usually limits the penetration depth to a few centimeters from the tissue surface, mainly due to strong optical attenuation along the light propagation path from the outside in. By contrast, internal light illumination, with external ultrasound detection, can potentially detect much deeper targets. Different from previous internal illumination PACT implementations using forward-looking optical fibers, our internal-illumination PACT system uses a customized optical fiber with a 3-cm-long conoid needle diffuser attached to the fiber tip, which can homogeneously illuminate the surrounding space and substantially enlarge the field of view. We characterized the internal illumination distribution and PACT system performance. We performed tissue phantom and in vivo animal studies to further demonstrate the superior imaging depth using internal illumination over external illumination. We imaged a 7.5-cm-deep leaf target embedded in optically scattering medium and the beating heart of a mouse overlaid with 3.7-cm-thick chicken tissue. Our results have collectively demonstrated that the internal light illumination combined with external ultrasound detection might be a useful strategy to improve the penetration depth of PACT in imaging deep organs of large animals and humans.

In vivo fiber-optic confocal reflectance microscope with an injection-molded plastic miniature objective lens.

PubMed

Carlson, Kristen; Chidley, Matthew; Sung, Kung-Bin; Descour, Michael; Gillenwater, Ann; Follen, Michele; Richards-Kortum, Rebecca

2005-04-01

For in vivo optical diagnostic technologies to be distributed to the developed and developing worlds, optical imaging systems must be constructed of inexpensive components. We present a fiber-optic confocal reflectance microscope with a cost-effective injection-molded plastic miniature objective lens for in vivo imaging of human tissues in near real time. The measured lateral resolution is less than 2.2 microm, and the measured axial resolution is 10 microm. Confocal images of ex vivo cervical tissue biopsies and in vivo human lip taken at 15 frames/s demonstrate the microscope's capability of imaging cell morphology and tissue architecture.

Analysis of all-optical temporal integrator employing phased-shifted DFB-SOA.

PubMed

Jia, Xin-Hong; Ji, Xiao-Ling; Xu, Cong; Wang, Zi-Nan; Zhang, Wei-Li

2014-11-17

All-optical temporal integrator using phase-shifted distributed-feedback semiconductor optical amplifier (DFB-SOA) is investigated. The influences of system parameters on its energy transmittance and integration error are explored in detail. The numerical analysis shows that, enhanced energy transmittance and integration time window can be simultaneously achieved by increased injected current in the vicinity of lasing threshold. We find that the range of input pulse-width with lower integration error is highly sensitive to the injected optical power, due to gain saturation and induced detuning deviation mechanism. The initial frequency detuning should also be carefully chosen to suppress the integration deviation with ideal waveform output.

40 CFR 146.92 - Injection well plugging.

Code of Federal Regulations, 2011 CFR

2011-07-01

... operator must flush each Class VI injection well with a buffer fluid, determine bottomhole reservoir... for determining bottomhole reservoir pressure; (2) Appropriate testing methods to ensure external... accurate by the owner or operator and by the person who performed the plugging operation (if other than the...

Attosecond optical-field-enhanced carrier injection into the GaAs conduction band

NASA Astrophysics Data System (ADS)

Schlaepfer, F.; Lucchini, M.; Sato, S. A.; Volkov, M.; Kasmi, L.; Hartmann, N.; Rubio, A.; Gallmann, L.; Keller, U.

2018-06-01

Resolving the fundamental carrier dynamics induced in solids by strong electric fields is essential for future applications, ranging from nanoscale transistors1,2 to high-speed electro-optical switches3. How fast and at what rate can electrons be injected into the conduction band of a solid? Here, we investigate the sub-femtosecond response of GaAs induced by resonant intense near-infrared laser pulses using attosecond transient absorption spectroscopy. In particular, we unravel the distinct role of intra- versus interband transitions. Surprisingly, we found that despite the resonant driving laser, the optical response during the light-matter interaction is dominated by intraband motion. Furthermore, we observed that the coupling between the two mechanisms results in a significant enhancement of the carrier injection from the valence into the conduction band. This is especially unexpected as the intraband mechanism itself can accelerate carriers only within the same band. This physical phenomenon could be used to control ultrafast carrier excitation and boost injection rates in electronic switches in the petahertz regime.

Injection moulding of plastic parts with laser textured surfaces with optical applications

NASA Astrophysics Data System (ADS)

Pina-Estany, J.; García-Granada, A. A.; Corull-Massana, E.

2018-05-01

The purpose of this work is to manufacture micro and nanotextured surfaces on plastic injection moulds with the aim of replicating them and obtaining plastic parts with optical applications. Different patterns are manufactured with nanosecond and femtosecond lasers in order to obtain three different optical applications: (i) homogeneous light diffusion (ii) 1D light directionality and (iii) 2D light directionality. Induction heating is used in the injections in order to improve the textures degree of replication. The steel mould and the plastic parts are analyzed with a confocal/focus variation microscope and with a surface roughness tester. A mock-up and a luminance camera are used to evaluate the homogeneity and luminance of the homogeneous light diffusion application in comparison with the current industrial solutions.

A magneto-electro-optical effect in a plasmonic nanowire material

PubMed Central

Valente, João; Ou, Jun-Yu; Plum, Eric; Youngs, Ian J.; Zheludev, Nikolay I.

2015-01-01

Electro- and magneto-optical phenomena play key roles in photonic technology enabling light modulators, optical data storage, sensors and numerous spectroscopic techniques. Optical effects, linear and quadratic in external electric and magnetic field are widely known and comprehensively studied. However, optical phenomena that depend on the simultaneous application of external electric and magnetic fields in conventional media are barely detectable and technologically insignificant. Here we report that a large reciprocal magneto-electro-optical effect can be observed in metamaterials. In an artificial chevron nanowire structure fabricated on an elastic nano-membrane, the Lorentz force drives reversible transmission changes on application of a fraction of a volt when the structure is placed in a fraction-of-tesla magnetic field. We show that magneto-electro-optical modulation can be driven to hundreds of thousands of cycles per second promising applications in magneto-electro-optical modulators and field sensors at nano-tesla levels. PMID:25906761

Live Imaging of Cell Motility and Actin Cytoskeleton of Individual Neurons and Neural Crest Cells in Zebrafish Embryos

PubMed Central

Andersen, Erica; Asuri, Namrata; Clay, Matthew; Halloran, Mary

2010-01-01

The zebrafish is an ideal model for imaging cell behaviors during development in vivo. Zebrafish embryos are externally fertilized and thus easily accessible at all stages of development. Moreover, their optical clarity allows high resolution imaging of cell and molecular dynamics in the natural environment of the intact embryo. We are using a live imaging approach to analyze cell behaviors during neural crest cell migration and the outgrowth and guidance of neuronal axons. Live imaging is particularly useful for understanding mechanisms that regulate cell motility processes. To visualize details of cell motility, such as protrusive activity and molecular dynamics, it is advantageous to label individual cells. In zebrafish, plasmid DNA injection yields a transient mosaic expression pattern and offers distinct benefits over other cell labeling methods. For example, transgenic lines often label entire cell populations and thus may obscure visualization of the fine protrusions (or changes in molecular distribution) in a single cell. In addition, injection of DNA at the one-cell stage is less invasive and more precise than dye injections at later stages. Here we describe a method for labeling individual developing neurons or neural crest cells and imaging their behavior in vivo. We inject plasmid DNA into 1-cell stage embryos, which results in mosaic transgene expression. The vectors contain cell-specific promoters that drive expression of a gene of interest in a subset of sensory neurons or neural crest cells. We provide examples of cells labeled with membrane targeted GFP or with a biosensor probe that allows visualization of F-actin in living cells1. Erica Andersen, Namrata Asuri, and Matthew Clay contributed equally to this work. PMID:20130524

Covisualization in living onion cells of putative integrin, putative spectrin, actin, putative intermediate filaments, and other proteins at the cell membrane and in an endomembrane sheath

NASA Technical Reports Server (NTRS)

Reuzeau, C.; Doolittle, K. W.; McNally, J. G.; Pickard, B. G.; Evans, M. L. (Principal Investigator)

1997-01-01

Covisualizations with wide-field computational optical-sectioning microscopy of living epidermal cells of the onion bulb scale have evidenced two major new cellular features. First, a sheath of cytoskeletal elements clads the endomembrane system. Similar elements clad the inner faces of punctate plasmalemmal sites interpreted as plasmalemmal control centers. One component of the endomembrane sheath and plasmalemmal control center cladding is anti-genicity-recognized by two injected antibodies against animal spectrin. Immunoblots of separated epidermal protein also showed bands recognized by these antibodies. Injected phalloidin identified F-actin with the same cellular distribution pattern, as did antibodies against intermediate-filament protein and other cytoskeletal elements known from animal cells. Injection of general protein stains demonstrated the abundance of endomembrane sheath protein. Second, the endomembrane system, like the plasmalemmal puncta, contains antigen recognized by an anti-beta 1 integrin injected into the cytoplasm. Previously, immunoblots of separated epidermal protein were shown to have a major band recognized both by this antibody prepared against a peptide representing the cytosolic region of beta 1 integrin and an antibody against the matrix region of beta 1 integrin. The latter antiboby also identified puncta at the external face of protoplasts. It is proposed that integrin and associated transmembrane proteins secure the endomembrane sheath and transmit signals between it and the lumen or matrix of the endoplasmic reticulum and organellar matrices. This function is comparable to that proposed for such transmembrane linkers in the plasmalemmal control centers, which also appear to bind cytoskeleton and a host of related molecules and transmit signals between them and the wall matrix. It is at the plasmalemmal control centers that the endoplasmic reticulum, a major component of the endomembrane system, attaches to the plasma membrane.

Phase Recovery Acceleration of Quantum-Dot Semiconductor Optical Amplifiers by Optical Pumping to Quantum-Well Wetting Layer

NASA Astrophysics Data System (ADS)

Kim, Jungho

2013-11-01

We theoretically investigate the phase recovery acceleration of quantum-dot (QD) semiconductor optical amplifiers (SOAs) by means of the optical pump injection to the quantum-well (QW) wetting layer (WL). We compare the ultrafast gain and phase recovery responses of QD SOAs in either the electrical or the optical pumping scheme by numerically solving 1088 coupled rate equations. The ultrafast gain recovery responses on the order of sub-picosecond are nearly the same for the two pumping schemes. The ultrafast phase recovery is not significantly accelerated by increasing the electrical current density, but greatly improved by increasing the optical pumping power to the QW WL. Because the phase recovery time of QD SOAs with the optical pumping scheme can be reduced down to several picoseconds, the complete phase recovery can be achieved when consecutive pulse signals with a repetition rate of 100 GHz is injected.

Measuring optical fiber length by use of a short-pulse optical fiber ring laser in a self-injection seeding scheme.

PubMed

Wang, Yi-Ping; Wang, Dong Ning; Jin, Wei

2006-09-01

A method for measuring the length of an optical fiber by use of an optical fiber ring laser pulse source is proposed and demonstrated. The key element of the optical fiber ring laser is a gain-switched Fabry-Perot laser diode operated in a self-injection seeding scheme. This method is especially suitable for measuring a medium or long fiber, and a resolution of 0.1 m is experimentally achieved. The measurement is implemented by accurately determining the pulse frequency that can maximize the output power of the fiber ring laser. The measurement results depend only on the refractive index of the fiber corresponding to this single wavelength, instead of the group index of the fiber, which represents a great advantage over both optical time-domain reflectometry and optical low-coherence reflectometry methods.

Bistable optical devices with laser diodes coupled to absorbers of narrow spectral bandwidth.

PubMed

Maeda, Y

1994-06-20

An optical signal inverter was demonstrated with a combination of the following two effects: One is the decrease of the transmission of an Er-doped YAG crystal with increasing red shift of a laser diode resulting from an increase in the injection current, and the other is a negative nonlinear absorption in which the transmission decreases inversely with increasing laser intensity. Because a hysteresis characteristic exists in the relationship between the wavelength and the injection current of the laser diode, an optical bistability was observed in this system.

Features of a Self-Mixing Laser Diode Operating Near Relaxation Oscillation.

PubMed

Liu, Bin; Yu, Yanguang; Xi, Jiangtao; Fan, Yuanlong; Guo, Qinghua; Tong, Jun; Lewis, Roger A

2016-09-21

When a fraction of the light reflected by an external cavity re-enters the laser cavity, both the amplitude and the frequency of the lasing field can be modulated. This phenomenon is called the self-mixing effect (SME). A self-mixing laser diode (SM-LD) is a sensor using the SME. Usually, such LDs operate below the stability boundary where no relaxation oscillation happens. The boundary is determined by the operation condition including the injection current, optical feedback strength and external cavity length. This paper discovers the features of an SM-LD where the LD operates beyond the stability boundary, that is, near the relaxation oscillation (RO) status. We call the signals from such a SM-LD as RO-SM signals to differentiate them from the conventional SM signals reported in the literature. Firstly, simulations are made based on the well-known Lang and Kobayashi (L-K) equations. Then the experiments are conducted on different LDs to verify the simulation results. It shows that a RO-SM signal exhibits high frequency oscillation with its amplitude modulated by a slow time varying envelop which corresponds to the movement of the external target. The envelope has same fringe structure (half-wavelength displacement resolution) with the conventional SM signals. However, the amplitudes of the RO-SM signals are much higher compared to conventional SM signals. The results presented reveal that an SM-LD operating near the RO has potential for achieving sensing with improved sensitivity.

Features of a Self-Mixing Laser Diode Operating Near Relaxation Oscillation

PubMed Central

Liu, Bin; Yu, Yanguang; Xi, Jiangtao; Fan, Yuanlong; Guo, Qinghua; Tong, Jun; Lewis, Roger A.

2016-01-01

When a fraction of the light reflected by an external cavity re-enters the laser cavity, both the amplitude and the frequency of the lasing field can be modulated. This phenomenon is called the self-mixing effect (SME). A self-mixing laser diode (SM-LD) is a sensor using the SME. Usually, such LDs operate below the stability boundary where no relaxation oscillation happens. The boundary is determined by the operation condition including the injection current, optical feedback strength and external cavity length. This paper discovers the features of an SM-LD where the LD operates beyond the stability boundary, that is, near the relaxation oscillation (RO) status. We call the signals from such a SM-LD as RO-SM signals to differentiate them from the conventional SM signals reported in the literature. Firstly, simulations are made based on the well-known Lang and Kobayashi (L-K) equations. Then the experiments are conducted on different LDs to verify the simulation results. It shows that a RO-SM signal exhibits high frequency oscillation with its amplitude modulated by a slow time varying envelop which corresponds to the movement of the external target. The envelope has same fringe structure (half-wavelength displacement resolution) with the conventional SM signals. However, the amplitudes of the RO-SM signals are much higher compared to conventional SM signals. The results presented reveal that an SM-LD operating near the RO has potential for achieving sensing with improved sensitivity. PMID:27657077

External electro-optic sampling utilizing a poled polymer asymmetric Fabry Perot cavity as an electro-optical probe tip

NASA Astrophysics Data System (ADS)

Chen, Kaixin; Zhang, Hongbo; Zhang, Daming; Yang, Han; Yi, Maobin

2002-09-01

External electro-optic sampling utilizing a poled polymer asymmetry Fabry-Perot cavity as electro-optic probe tip has been demonstrated. Electro-optical polymer spin coated on the high-reflectivity mirror (HRM) was corona poled. Thus, an asymmetric F-P cavity was formed based on the different reflectivity of the polymer and HRM and it converted the phase modulation that originates from electro-optic effect of the poled polymer to amplitude modulation, so only one laser beam is needed in this system. The principle of the sampling was analyzed by multiple reflection and index ellipsoid methods. A 1.2 GHz microwave signal propagating on coplanar waveguide transmission line was sampled, and the voltage sensitivity about 0.5 mV/ Hz was obtained.

Designing optically pumped InGaN quantum wells with long wavelength emission for a phosphor-free device with polarized white-light emission

NASA Astrophysics Data System (ADS)

Kowsz, Stacy J.; Pynn, Christopher D.; Wu, Feng; Farrell, Robert M.; Speck, James S.; DenBaars, Steven P.; Nakamura, Shuji

2016-02-01

We report a semipolar III-nitride device in which an electrically injected blue light emitting diode optically pumps monolithic long wavelength emitting quantum wells (QWs) to create polarized white light. We have demonstrated an initial device with emission peaks at 440 nm and 560 nm from the electrically injected and optically pumped QWs, respectively. By tuning the ratio of blue to yellow, white light was measured with a polarization ratio of 0.40. High indium content InGaN is required for long wavelength emission but is difficult to achieve because it requires low growth temperatures and has a large lattice mismatch with GaN. This device design incorporates optically pumped QWs for long wavelength emission because they offer advantages over using electrically injected QWs. Optically pumped QWs do not have to be confined within a p-n junction, and carrier transport is not a concern. Thus, thick GaN barriers can be incorporated between multiple InGaN QWs to manage stress. Optically pumping long wavelength emitting QWs also eliminates high temperature steps that degrade high indium content InGaN but are required when growing p-GaN for an LED structure. Additionally, by eliminating electrical injection, the doping profile can instead be engineered to affect the emission wavelength. We discuss ongoing work focused on improving polarized white light emission by optimizing the optically pumped QWs. We consider the effects of growth conditions, including: trimethylindium (TMI) flow rate, InGaN growth rate, and growth temperature. We also examine the effects of epitaxial design, including: QW width, number of QWs, and doping.

Charge transfer through amino groups-small molecules interface improving the performance of electroluminescent devices

NASA Astrophysics Data System (ADS)

Havare, Ali Kemal; Can, Mustafa; Tozlu, Cem; Kus, Mahmut; Okur, Salih; Demic, Şerafettin; Demirak, Kadir; Kurt, Mustafa; Icli, Sıddık

2016-05-01

A carboxylic group functioned charge transporting was synthesized and self-assembled on an indium tin oxide (ITO) anode. A typical electroluminescent device [modified ITO/TPD (50 nm)/Alq3 (60 nm)/LiF (2 nm)/(120 nm)] was fabricated to investigate the effect of the amino groups-small molecules interface on the characteristics of the device. The increase in the surface work function of ITO is expected to facilitate the hole injection from the ITO anode to the Hole Transport Layer (HTL) in electroluminescence. The modified electroluminescent device could endure a higher current and showed a much higher luminance than the nonmodified one. For the produced electroluminescent devices, the I-V characteristics, optical characterization and quantum yields were performed. The external quantum efficiency of the modified electroluminescent device is improved as the result of the presence of the amino groups-small molecules interface.

Influences of point defects on electrical and optical properties of InGaN light-emitting diodes at cryogenic temperature

NASA Astrophysics Data System (ADS)

Tu, Yi; Ruan, Yujiao; Zhu, Lihong; Tu, Qingzhen; Wang, Hongwei; Chen, Jie; Lu, Yijun; Gao, Yulin; Shih, Tien-Mo; Chen, Zhong; Lin, Yue

2018-04-01

We investigate the cryogenic external quantum efficiency (EQE) for some InGaN light-emitting diodes with different indium contents. We observe a monotonic decrease in EQE with the increasing forward current before the "U-turn" point, beyond which the thermal effect increases the EQE. We discover positive dependences among the droop rate (χ), differential electrical resistance (Rd), and indium content. Also, χ and Rd of individual green samples shift correspondingly during the aging test, when the Mg ions are activated at high injection density and diffuse into the active region. Considering the fact that both In and Mg ions would introduce point defects (PDs), we proposed a model that reveals the mechanism of interplay between PDs and carriers. PDs serve as both energy traps and non-radiative recombination centers. They attract and confine carriers, leading to an increase in Rd and a decrease in EQE.

Signal-to-noise optimization and evaluation of a home-made visible diode-array spectrophotometer

PubMed Central

Raimundo, Jr., Ivo M.; Pasquini, Celio

1993-01-01

This paper describes a simple low-cost multichannel visible spectrophotometer built with an RL512G EGG-Reticon photodiode array. A symmetric Czerny-Turner optical design was employed; instrument control was via a single-board microcomputer based on the 8085 Intel microprocessor. Spectral intensity data are stored in the single-board's RAM and then transferred to an IBM-AT 3865X compatible microcomputer through a RS-232C interface. This external microcomputer processes the data to recover transmittance, absorbance or relative intensity of the spectra. The signal-to-noise ratio and dynamic range were improved by using variable integration times, which increase during the same scan; and by the use of either weighted or unweighted sliding average of consecutive diodes. The instrument is suitable for automatic methods requiring quasi-simultaneous multiwavelength detections, such as multivariative calibration and flow-injection gradient scan techniques. PMID:18924979

Achievement of two logical states through a polymer/silicon interface for organic-inorganic hybrid memory

NASA Astrophysics Data System (ADS)

Chen, Jianhui; Chen, Bingbing; Shen, Yanjiao; Guo, Jianxin; Liu, Baoting; Dai, Xiuhong; Xu, Ying; Mai, Yaohua

2017-11-01

A hysteresis loop of minority carrier lifetime vs voltage is found in polystyrenesulfonate (PSS)/Si organic-inorganic hybrid heterojunctions, implying an interfacial memory effect. Capacitance-voltage and conductance-voltage hysteresis loops are observed and reveal a memory window. A switchable interface state, which can be controlled by charge transfer based on an electrochemical oxidation/deoxidation process, is suggested to be responsible for this hysteresis effect. We perform first-principle total-energy calculations on the influence of external electric fields and electrons or holes, which are injected into interface states on the adsorption energy of PSS on Si. It is demonstrated that the dependence of the interface adsorption energy difference on the electric field is the origin of this two-state switching. These results offer a concept of organic-inorganic hybrid interface memory being optically or electrically readable, low-cost, and compatible with the flexible organic electronics.

Adjustable Powder Injector For Vacuum Plasma Sprayer

NASA Technical Reports Server (NTRS)

Burns, D. H.; Woodford, W. H.; Mckechnie, T. N.; Mcferrin, D. C.; Davis, W. M.; Beason, G. P., Jr.

1993-01-01

Attachment for plasma spray gun provides four degrees of freedom for adjustment of position and orientation at which powder injected externally into plasma flame. Manipulator provides for adjustment of pitch angle of injection tube: set to inject powder at any angle ranging from perpendicular to parallel to cylindrical axis. Scribed lines on extension bar and manipulator indicate pitch angle of extension tube. Collar changed to adapt injector to different gun.

Demonstration of frequency control and CW diode laser injection control of a titanium-doped sapphire ring laser with no internal optical elements

NASA Technical Reports Server (NTRS)

Bair, Clayton H.; Brockman, Philip; Hess, Robert V.; Modlin, Edward A.

1988-01-01

Theoretical and experimental frequency narrowing studies of a Ti:sapphire ring laser with no intracavity optical elements are reported. Frequency narrowing has been achieved using a birefringent filter between a partially reflecting reverse wave suppressor mirror and the ring cavity output mirror. Results of CW diode laser injection seeding are reported.

Tunable radio-frequency photonic filter based on an actively mode-locked fiber laser.

PubMed

Ortigosa-Blanch, A; Mora, J; Capmany, J; Ortega, B; Pastor, D

2006-03-15

We propose the use of an actively mode-locked fiber laser as a multitap optical source for a microwave photonic filter. The fiber laser provides multiple optical taps with an optical frequency separation equal to the external driving radio-frequency signal of the laser that governs its repetition rate. All the optical taps show equal polarization and an overall Gaussian apodization, which reduces the sidelobes. We demonstrate continuous tunability of the filter by changing the external driving radio-frequency signal of the laser, which shows good fine tunability in the operating range of the laser from 5 to 10 GHz.

DFB laser - External modulator fiber optic delay line for radar applications

NASA Astrophysics Data System (ADS)

Newberg, I. L.; Gee, C. M.; Thurmond, G. D.; Yen, H. W.

1989-09-01

A new application of a long fiber-optic delay line as a radar repeater in a radar test set is described. The experimental 31.6-kilometer fiber-optic link includes an external modulator operating with a distributed-feedback laser and low-loss single-mode fiber matched to the laser wavelength to obtain low dispersion for achieving large bandwidth-length performance. The successful tests, in which pulse compression peak sidelobe measurements are used to confirm the link RF phase linearity and SNR performance, show that fiber-optic links can meet the stringent phase and noise requirements of modern radars at high microwave frequencies.

1300 nm optically pumped quantum dot spin vertical external-cavity surface-emitting laser

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

Alharthi, S. S., E-mail: ssmalh@essex.ac.uk; Henning, I. D.; Adams, M. J.

We report a room temperature optically pumped Quantum Dot-based Spin-Vertical-External-Cavity Surface-Emitting laser (QD Spin-VECSEL) operating at the telecom wavelength of 1.3 μm. The active medium was composed of 5 × 3 QD layers; each threefold group was positioned at an antinode of the standing wave of the optical field. Circularly polarized lasing in the QD-VECSEL under Continuous-Wave optical pumping has been realized with a threshold pump power of 11 mW. We further demonstrate at room temperature control of the QD-VECSEL output polarization ellipticity via the pump polarization.

Chaotic oscillation and random-number generation based on nanoscale optical-energy transfer.

PubMed

Naruse, Makoto; Kim, Song-Ju; Aono, Masashi; Hori, Hirokazu; Ohtsu, Motoichi

2014-08-12

By using nanoscale energy-transfer dynamics and density matrix formalism, we demonstrate theoretically and numerically that chaotic oscillation and random-number generation occur in a nanoscale system. The physical system consists of a pair of quantum dots (QDs), with one QD smaller than the other, between which energy transfers via optical near-field interactions. When the system is pumped by continuous-wave radiation and incorporates a timing delay between two energy transfers within the system, it emits optical pulses. We refer to such QD pairs as nano-optical pulsers (NOPs). Irradiating an NOP with external periodic optical pulses causes the oscillating frequency of the NOP to synchronize with the external stimulus. We find that chaotic oscillation occurs in the NOP population when they are connected by an external time delay. Moreover, by evaluating the time-domain signals by statistical-test suites, we confirm that the signals are sufficiently random to qualify the system as a random-number generator (RNG). This study reveals that even relatively simple nanodevices that interact locally with each other through optical energy transfer at scales far below the wavelength of irradiating light can exhibit complex oscillatory dynamics. These findings are significant for applications such as ultrasmall RNGs.

Externally-Modulated Electro-Optically Coupled Detector Architecture for Nuclear Physics Instrumentation

NASA Astrophysics Data System (ADS)

Xi, Wenze; McKisson, J. E.; Weisenberger, Andrew G.; Zhang, Shukui; Zorn, Carl

2014-06-01

A new laser-based externally-modulated electro-optically coupled detector (EOCD) architecture is being developed to enable high-density readout for radiation detectors with accurate analog radiation pulse shape and timing preservation. Unlike digital conversion before electro-optical modulation, the EOCD implements complete analog optical signal modulation and multiplexing in its detector front-end. The result is a compact, high performance detector readout that can be both radiation tolerant and immune to magnetic fields. In this work, the feasibility of EOCD was explored by constructing a two-wavelength laser-based externally-modulated EOCD, and testing analog pulse shape preservation and wavelength-division multiplexing (WDM) crosstalk. Comparisons were first made between the corresponding initial pulses and the electro-optically coupled analog pulses. This confirmed an excellent analog pulse preservation over 29% of the modulator's switching voltage range. Optical spectrum analysis revealed less than -14 dB crosstalk with 1.2 nm WDM wavelength bandgap, and provided insight on experimental conditions that could lead to increased inter-wavelength crosstalk. Further discussions and previous research on the radiation tolerance and magnetic field immunity of the candidate materials were also given, and quantitative device testing is proposed in the future.

Integrated Optics for Planar imaging and Optical Signal Processing

NASA Astrophysics Data System (ADS)

Song, Qi

Silicon photonics is a subject of growing interest with the potential of delivering planar electro-optical devices with chip scale integration. Silicon-on-insulator (SOI) technology has provided a marvelous platform for photonics industry because of its advantages in integration capability in CMOS circuit and countless nonlinearity applications in optical signal processing. This thesis is focused on the investigation of planar imaging techniques on SOI platform and potential applications in ultra-fast optical signal processing. In the first part, a general review and background introduction about integrated photonics circuit and planar imaging technique are provided. In chapter 2, planar imaging platform is realized by a silicon photodiode on SOI chip. Silicon photodiode on waveguide provides a high numerical aperture for an imaging transceiver pixel. An erbium doped Y2O3 particle is excited by 1550nm Laser and the fluorescent image is obtained with assistance of the scanning system. Fluorescence image is reconstructed by using image de-convolution technique. Under photovoltaic mode, we use an on-chip photodiode and an external PIN photodiode to realize similar resolution as 5μm. In chapter 3, a time stretching technique is developed to a spatial domain to realize a 2D imaging system as an ultrafast imaging tool. The system is evaluated based on theoretical calculation. The experimental results are shown for a verification of system capability to imaging a micron size particle or a finger print. Meanwhile, dynamic information for a moving object is also achieved by correlation algorithm. In chapter 4, the optical leaky wave antenna based on SOI waveguide has been utilized for imaging applications and extensive numerical studied has been conducted. and the theoretical explanation is supported by leaky wave theory. The highly directive radiation has been obtained from the broadside with 15.7 dB directivity and a 3dB beam width of ΔØ 3dB ≈ 1.65° in free space environment when β -1 = 2.409 × 105/m, α=4.576 ×103/m. At the end, electronics beam-steering principle has been studied and the comprehensive model has been built to explain carrier transformation behavior in a PIN junction as individual silicon perturbation. Results show that 1019/cm3 is possible obtained with electron injection mechanism. Although the radiation modulation based on carrier injection of 1019/cm3 gives 0.5dB variation, resonant structure, such as Fabry Perrot Cavity, can be integrated with LOWAs to enhance modulation effect.

Frequency-doubled vertical-external-cavity surface-emitting laser

DOEpatents

Raymond, Thomas D.; Alford, William J.; Crawford, Mary H.; Allerman, Andrew A.

2002-01-01

A frequency-doubled semiconductor vertical-external-cavity surface-emitting laser (VECSEL) is disclosed for generating light at a wavelength in the range of 300-550 nanometers. The VECSEL includes a semiconductor multi-quantum-well active region that is electrically or optically pumped to generate lasing at a fundamental wavelength in the range of 600-1100 nanometers. An intracavity nonlinear frequency-doubling crystal then converts the fundamental lasing into a second-harmonic output beam. With optical pumping with 330 milliWatts from a semiconductor diode pump laser, about 5 milliWatts or more of blue light can be generated at 490 nm. The device has applications for high-density optical data storage and retrieval, laser printing, optical image projection, chemical-sensing, materials processing and optical metrology.

Injection-seeded optical parametric oscillator and system

DOEpatents

Lucht, Robert P.; Kulatilaka, Waruna D.; Anderson, Thomas N.; Bougher, Thomas L.

2007-10-09

Optical parametric oscillators (OPO) and systems are provided. The OPO has a non-linear optical material located between two optical elements where the product of the reflection coefficients of the optical elements are higher at the output wavelength than at either the pump or idler wavelength. The OPO output may be amplified using an additional optical parametric amplifier (OPA) stage.

76 FR 57905 - Implantation or Injectable Dosage Form New Animal Drugs; Ivermectin

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-19

... solution for treatment and control of various internal and external parasites in cattle, swine, reindeer...: John K. Harshman, Center for Veterinary Medicine (HFV-170), Food and Drug Administration, 7500 Standish... of BIMECTIN (ivermectin) Injection for Cattle and Swine for treatment and control of various internal...

Scintillating Balloon-Enabled Fiber-Optic System for Radionuclide Imaging of Atherosclerotic Plaques

PubMed Central

Zaman, Raiyan T.; Kosuge, Hisanori; Carpenter, Colin; Sun, Conroy; McConnell, Michael V.; Xing, Lei

2015-01-01

Atherosclerosis underlies coronary artery disease, the leading cause of death in the United States and worldwide. Detection of coronary plaque inflammation remains challenging. In this study, we developed a scintillating balloon-enabled fiber-optic radio-nuclide imaging (SBRI) system to improve the sensitivity and resolution of plaque imaging using 18F-FDG, a marker of vascular inflammation, and tested it in a murine model. Methods The fiber-optic system uses a Complementary Metal-Oxide Silicon (CMOS) camera with a distal ferrule terminated with a wide-angle lens. The novelty of this system is a scintillating balloon in the front of the wide-angle lens to image light from the decay of 18F-FDG emission signal. To identify the optimal scintillating materials with respect to resolution, we calculated the modulation transfer function of yttrium–aluminum–garnet doped with cerium, anthracene, and calcium fluoride doped with europium (CaF2:Eu) phosphors using an edge pattern and a thin-line optical phantom. The scintillating balloon was then fabricated from 10 mL of silicone RTV catalyst mixed with 1 mL of base and 50 mg of CaF2:Eu per mL. The addition of a lutetium oxyorthosilicate scintillating crystal (500 μm thick) to the balloon was also investigated. The SBRI system was tested in a murine atherosclerosis model: carotid-ligated mice (n = 5) were injected with 18F-FDG, followed by ex vivo imaging of the macrophage-rich carotid plaques and nonligated controls. Confirmatory imaging of carotid plaques and controls was also performed by an external optical imaging system and autoradiography. Results Analyses of the different phosphors showed that CaF2:Eu enabled the best resolution of 1.2 μm. The SBRI system detected almost a 4-fold-higher radioluminescence signal from the ligated left carotid artery than the nonligated right carotid: 1.63 × 102 ± 4.01 × 101 vs. 4.21 × 101 ± 2.09 × 100 (photon counts), P = 0.006. We found no significant benefit to adding a scintillating crystal to the balloon: 1.65 × 102 ± 4.07 × 101 vs. 4.44 × 101 ± 2.17 × 100 (photon counts), P = 0.005. Both external optical imaging and autoradiography confirmed the high signal from the 18F-FDG in carotid plaques versus controls. Conclusion This SBRI system provides high-resolution and sensitive detection of 18F-FDG uptake by murine atherosclerotic plaques. PMID:25858046

Theoretical analysis of a method for extracting the phase of a phase-amplitude modulated signal generated by a direct-modulated optical injection-locked semiconductor laser

NASA Astrophysics Data System (ADS)

Lee, Hwan; Cho, Jun-Hyung; Sung, Hyuk-Kee

2017-05-01

The phase modulation (PM) and amplitude modulation (AM) of optical signals can be achieved using a direct-modulated (DM) optical injection-locked (OIL) semiconductor laser. We propose and theoretically analyze a simple method to extract the phase component of a PM signal produced by a DM-OIL semiconductor laser. The pure AM component of the combined PM-AM signal can be isolated by square-law detection in a photodetector and can then be used to compensate for the PM-AM signal based on an optical homodyne method. Using the AM compensation technique, we successfully developed a simple and cost-effective phase extraction method applicable to the PM-AM optical signal of a DM-OIL semiconductor laser.

Improving upstream transmission performance using a receiver with decision threshold level adjustment in a loopback WDM-PON

NASA Astrophysics Data System (ADS)

Cho, Seung-Hyun; Lee, Sang-Soo; Shin, Dong-Wook

2010-06-01

We have experimentally demonstrated that the use of an optical receiver with decision threshold level adjustment (DTLA) improved the performance of an upstream transmission in reflective semiconductor optical amplifier (RSOA)-based loopback wavelength division multiplexing-passive optical network (WDM-PON). Even though the extinction ratio (ER) of the downstream signal was as much as 9 dB and the injection power into the RSOA at the optical network unit was about -24 dBm, we successfully obtained error-free transmission results for the upstream signal through careful control of the decision threshold value in the optical receiver located at optical line terminal (OLT). Using an optical receiver with DTLA for upstream signal detection overcame significant obstacles related to the injection power into the RSOA and the ER of the downstream signal, which were previously considered limitations of the wavelength remodulation scheme. This technique is expected to provide flexibility for the optical link design in the practical deployment of a WDM-PON.

75 FR 26647 - Implantation or Injectable Dosage Form New Animal Drugs; Ivermectin

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-12

... solution in cattle and swine for treatment and control of various internal and external parasites. DATES... Veterinary Medicine (HFV-170), Food and Drug Administration, 7500 Standish Pl., Rockville, MD 20855, 240-276... and swine for treatment and control of various internal and external parasites. Sparhawk Laboratories...

Drilling and completion of the three CO2SINK boreholes in Europe's pilot CO2 storage and verification project in an onshore saline aquifer

NASA Astrophysics Data System (ADS)

Prevedel, P.,; Wohlgemuth, L.; Legarth, B.; Henninges, J.; Schütt, H.; Schmidt-Hattenberger, C.; Norden, B.; Förster, A.; Hurter, S.

2009-04-01

This paper reports the CO2SINK drilling and permanent monitoring completions, as well as the well testing techniques applied in Europe's first scientific carbon dioxide onshore storage test in a saline aquifer near the town of Ketzin, 40 km east of Berlin/Germany. Three boreholes, one injection and two observation wells have been drilled in 2007 to a total depth of about 800 m. The wells were completed as "smart" wells containing a variety of permanently installed down-hole sensors, which have successfully proven their functionality during over their first injection year and are the key instruments for the continuous monitoring of the CO2 inside the reservoir during the storage phase. Constructing three wells in close proximity of 50 to 100m distance to each other with a dense sensor and monitoring cable population requires detailed planning and employment of high-end project management tools. All wells were cased with stainless final casings equipped with pre-perforated sand filters in the pay-zone and wired on the outside with two fibre-optical, one multi-conductor copper, and a PU-heating cable to the surface. The reservoir casing section is externally coated with a fibre-glass-resin wrap for electrical insulation of the 15 geo-electrical toroid antennas in the open hole section. A staged cementation program was selected in combination with the application of a newly developed swellable rubber packer technology and specialized cementation down-hole tools. This technology was given preference over perforation work inside the final casing at the reservoir face, which would have created unmanageable risks of potential damage of the outside casing cables. Prior to the start of the injection phase, an extensive production and injection well test program as well as well-to-well interference tests were performed in order to determine the optimum CO2 injection regime.

Optical properties of monolayer polystyrene microspheres driven by a direct current

NASA Astrophysics Data System (ADS)

Jiao, Xinbing; Pan, Qian; Zhao, Xinwei; Hao, Ruirui; Bai, Xue

2018-04-01

Polystyrene microspheres (PSMs) with diameters of 5 μm and 10 μm are prepared on garnet by a self-assembly method. The pressure generated by quartz sheet/PSM/garnet/graphite is measured by a resistance strain sensor as a function of the external direct current (DC) voltage. The surface morphology of the PSMs are observed by optical microscopy. The polarization properties of the linearly and circularly polarized laser beams with a wavelength of 1550 nm reflected from the different PSMs are researched by a Thorlabs PAX 5710 IR3 Polarization Analyzing System as a function of the external DC voltage. The results show that the PSMs with different sizes can be damaged when the external pressure exceeds its critical value of 3.0 MPa, but the critical DC voltages are different. The optical polarization properties of the circularly polarized laser beam can be changed with the external DC voltage, whereas the linearly polarized laser beam cannot be changed.

Miniaturized flow injection analysis system

DOEpatents

Folta, James A.

1997-01-01

A chemical analysis technique known as flow injection analysis, wherein small quantities of chemical reagents and sample are intermixed and reacted within a capillary flow system and the reaction products are detected optically, electrochemically, or by other means. A highly miniaturized version of a flow injection analysis system has been fabricated utilizing microfabrication techniques common to the microelectronics industry. The microflow system uses flow capillaries formed by etching microchannels in a silicon or glass wafer followed by bonding to another wafer, commercially available microvalves bonded directly to the microflow channels, and an optical absorption detector cell formed near the capillary outlet, with light being both delivered and collected with fiber optics. The microflow system is designed mainly for analysis of liquids and currently measures 38.times.25.times.3 mm, but can be designed for gas analysis and be substantially smaller in construction.

Pseudorandom binary injection of levitons for electron quantum optics

NASA Astrophysics Data System (ADS)

Glattli, D. C.; Roulleau, P.

2018-03-01

The recent realization of single-electron sources lets us envision performing electron quantum optics experiments, where electrons can be viewed as flying qubits propagating in a ballistic conductor. To date, all electron sources operate in a periodic electron injection mode, leading to energy spectrum singularities in various physical observables which sometimes hide the bare nature of physical effects. To go beyond this, we propose a spread-spectrum approach where electron flying qubits are injected in a nonperiodic manner following a pseudorandom binary bit pattern. Extending the Floquet scattering theory approach from periodic to spread-spectrum drive, the shot noise of pseudorandom binary sequences of single-electron injection can be calculated for leviton and nonleviton sources. Our new approach allows us to disentangle the physics of the manipulated excitations from that of the injection protocol. In particular, the spread-spectrum approach is shown to provide better knowledge of electronic Hong-Ou-Mandel correlations and to clarify the nature of the pulse train coherence and the role of the dynamical orthogonality catastrophe for noninteger charge injection.

Liquid metal ion source assembly for external ion injection into an electron string ion source (ESIS)

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

Segal, M. J., E-mail: mattiti@gmail.com; University of Cape Town, Rondebosch, Cape Town 7700; Bark, R. A.

An assembly for a commercial Ga{sup +} liquid metal ion source in combination with an ion transportation and focusing system, a pulse high-voltage quadrupole deflector, and a beam diagnostics system has been constructed in the framework of the iThemba LABS (Cape Town, South Africa)—JINR (Dubna, Russia) collaboration. First, results on Ga{sup +} ion beam commissioning will be presented. Outlook of further experiments for measurements of charge breeding efficiency in the electron string ion source with the use of external injection of Ga{sup +} and Au{sup +} ion beams will be reported as well.

External and Intraparticle Diffusion of Coumarin 102 with Surfactant in the ODS-silica Gel/water System by Single Microparticle Injection and Confocal Fluorescence Microspectroscopy.

PubMed

Nakatani, Kiyoharu; Matsuta, Emi

2015-01-01

The release mechanism of coumarin 102 from a single ODS-silica gel microparticle into the water phase in the presence of Triton X-100 was investigated by confocal fluorescence microspectroscopy combined with the single microparticle injection technique. The release rate significantly depended on the Triton X-100 concentration in the water phase and was not limited by diffusion in the pores of the microparticle. The release rate constant was inversely proportional to the microparticle radius squared, indicating that the rate-determining step is the external diffusion between the microparticle and the water phase.

Control of runaway electron energy using externally injected whistler waves

NASA Astrophysics Data System (ADS)

Guo, Zehua; McDevitt, Christopher J.; Tang, Xian-Zhu

2018-03-01

One way of mitigating runaway damage of the plasma-facing components in a tokamak fusion reactor is by limiting the runaway electron energy under a few MeV, while not necessarily reducing the runaway current appreciably. Here, we describe a physics mechanism by which such momentum space engineering of the runaway distribution can be facilitated by externally injected high-frequency electromagnetic waves such as whistler waves. The drastic impact that wave-induced scattering can have on the runaway energy distribution is fundamentally the result of its ability to control the runaway vortex in the momentum space. The runaway vortex, which is a local circulation of runaways in momentum space, is the outcome of the competition between Coulomb collisions, synchrotron radiation damping, and runaway acceleration by the parallel electric field. By introducing a wave that resonantly interacts with runaways in a particular range of energies which is mildly relativistic, the enhanced scattering would reshape the vortex by cutting off the part that is highly relativistic. The efficiency of resonant scattering accentuates the requirement that the wave amplitude can be small so the power requirement from external wave injection is practical for the mitigation scheme.

Controlling runaway vortex via externally injected high-frequency electromagnetic waves

NASA Astrophysics Data System (ADS)

Guo, Zehua; McDevitt, Chris; Tang, Xianzhu

2017-10-01

One way of mitigating runaway damage of the plasma-facing components in a tokamak fusion reactor is by limiting the runaway electron energy under a few MeV, while not necessarily reducing the runaway current appreciably. Here we describe a physics mechanism by which such momentum space engineering of the runaway distribution can be facilitated by externally injected high-frequency electromagnetic waves such as the whistler waves. The drastic impact that wave-induced scattering can have on the runaway energy distribution is fundamentally the result of its ability to control the runaway vortex in the momentum space. The runaway vortex, which is a local circulation of runaways in momentum space, is the outcome of the competition between Coulomb collisions, synchrotron radiation damping, and runaway acceleration by parallel electric field. By introducing a wave that resonantly interacts with runaways at a particular range of energy that is mildly relativistic, the enhanced scattering would reshape the vortex by cutting off the part that is highly relativistic. The efficiency of resonant scattering accentuates the requirement that the wave amplitude can be small so the power requirement from external wave injection is practical for the mitigation scheme.

Electrically injected visible vertical cavity surface emitting laser diodes

DOEpatents

Schneider, Richard P.; Lott, James A.

1994-01-01

Visible laser light output from an electrically injected vertical cavity surface emitting laser (VSCEL) diode is enabled by the addition of phase-matching spacer layers on either side of the active region to form the optical cavity. The spacer layers comprise InAlP which act as charge carrier confinement means. Distributed Bragg reflector layers are formed on either side of the optical cavity to act as mirrors.

Electrically injected visible vertical cavity surface emitting laser diodes

DOEpatents

Schneider, R.P.; Lott, J.A.

1994-09-27

Visible laser light output from an electrically injected vertical cavity surface emitting laser (VSCEL) diode is enabled by the addition of phase-matching spacer layers on either side of the active region to form the optical cavity. The spacer layers comprise InAlP which act as charge carrier confinement means. Distributed Bragg reflector layers are formed on either side of the optical cavity to act as mirrors. 5 figs.

Injection locking of optomechanical oscillators via acoustic waves

NASA Astrophysics Data System (ADS)

Huang, Ke; Hossein-Zadeh, Mani

2018-04-01

Injection locking is a powerful technique for synchronization of oscillator networks and controlling the phase and frequency of individual oscillators using similar or other types of oscillators. Here, we present the first demonstration of injection locking of a radiation-pressure driven optomechanical oscillator (OMO) via acoustic waves. As opposed to previously reported techniques (based on pump modulation or direct application of a modulated electrostatic force), injection locking of OMO via acoustic waves does not require optical power modulation or physical contact with the OMO and it can easily be implemented on various platforms. Using this approach we have locked the phase and frequency of two distinct modes of a microtoroidal silica OMO to a piezoelectric transducer (PZT). We have characterized the behavior of the injection locked OMO with three acoustic excitation configurations and showed that even without proper acoustic impedance matching the OMO can be locked to the PZT and tuned over 17 kHz with only -30 dBm of RF power fed to the PZT. The high efficiency, simplicity and scalability of the proposed approach paves the road toward a new class of photonic systems that rely on synchronization of several OMOs to a single or multiple RF oscillators with applications in optical communication, metrology and sensing. Beyond its practical applications, injection locking via acoustic waves can be used in fundamental studies in quantum optomechanics where thermal and optical isolation of the OMO are critical.

Applying simulation to optimize plastic molded optical parts

NASA Astrophysics Data System (ADS)

Jaworski, Matthew; Bakharev, Alexander; Costa, Franco; Friedl, Chris

2012-10-01

Optical injection molded parts are used in many different industries including electronics, consumer, medical and automotive due to their cost and performance advantages compared to alternative materials such as glass. The injection molding process, however, induces elastic (residual stress) and viscoelastic (flow orientation stress) deformation into the molded article which alters the material's refractive index to be anisotropic in different directions. Being able to predict and correct optical performance issues associated with birefringence early in the design phase is a huge competitive advantage. This paper reviews how to apply simulation analysis of the entire molding process to optimize manufacturability and part performance.

Modeling of magnetic particle orientation in magnetic powder injection molding

NASA Astrophysics Data System (ADS)

Doo Jung, Im; Kang, Tae Gon; Seul Shin, Da; Park, Seong Jin

2018-03-01

The magnetic micro powder orientation under viscous shear flow has been analytically understood and characterized into a new analytical orientation model for a powder injection molding process. The effects of hydrodynamic force from the viscous flow, external magnetic force and internal dipole-dipole interaction were considered to predict the orientation under given process conditions. Comparative studies with a finite element method proved the calculation validity with a partial differential form of the model. The angular motion, agglomeration and magnetic chain formation have been simulated, which shows that the effect of dipole-dipole interaction among powders on the orientation state becomes negligible at a high Mason number condition and at a low λ condition (the ratio of external magnetic field strength and internal magnetic moment of powder). Our developed model can be very usefully employed in the process analysis and design of magnetic powder injection molding.

Semi-monolithic cavity for external resonant frequency doubling and method of performing the same

NASA Technical Reports Server (NTRS)

Hemmati, Hamid (Inventor)

1999-01-01

The fabrication of an optical cavity for use in a laser, in a frequency doubling external cavity, or any other type of nonlinear optical device, can be simplified by providing the nonlinear crystal in combination with a surrounding glass having an index of refraction substantially equal to that of the nonlinear crystal. The closed optical path in this cavity is formed in the surrounding glass and through the nonlinear crystal which lies in one of the optical segments of the light path. The light is transmitted through interfaces between the surrounding glass in the nonlinear crystal through interfaces which are formed at the Brewster-angle to minimize or eliminate reflection.

Albedo of an irradiated plane-parallel atmosphere with finite optical depth

NASA Astrophysics Data System (ADS)

Fukue, Jun

2018-03-01

We analytically derive albedo for a plane-parallel atmosphere with finite optical depth, irradiated by an external source, under the local thermodynamic equilibrium approximation. Albedo is expressed as a function of the photon destruction probability ɛ and optical depth τ, with several parameters such as dilution factors of the external source. In the particular case of the infinite optical depth, albedo A is expressed as A=[1 + (1-W_J/W_H)√{3ɛ}/3]/(1+√{3ɛ}), where WJ and WH are the dilution factors for the mean intensity and Eddington flux, respectively. An example of a model atmosphere is also presented under a gray approximation.

Silicon photonic dynamic optical channel leveler with external feedback loop.

PubMed

Doylend, J K; Jessop, P E; Knights, A P

2010-06-21

We demonstrate a dynamic optical channel leveler composed of a variable optical attenuator (VOA) integrated monolithically with a defect-mediated photodiode in a silicon photonic waveguide device. An external feedback loop mimics an analog circuit such that the photodiode directly controls the VOA to provide blind channel leveling within +/-1 dB across a 7-10 dB dynamic range for wavelengths from 1530 nm to 1570 nm. The device consumes approximately 50 mW electrical power and occupies a 6 mm x 0.1 mm footprint per channel. Dynamic leveling is accomplished without tapping optical power from the output path to the photodiode and thus the loss penalty is minimized.

Optical and magneto-optical properties of one-dimensional magnetized coupled resonator plasma photonic crystals

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

Hamidi, S. M.

2012-01-15

In this paper, the optical and magneto-optical properties of one-dimensional magnetized coupled resonator plasma photonic crystals have been investigated. We use transfer matrix method to solve our magnetized coupled resonator plasma photonic crystals consist of dielectric and magnetized plasma layers. The results of the change in the optical and magneto-optical properties of structure as a result of the alteration in the structural properties such as thickness, plasma frequency and collision frequency, plasma filling factor, number of resonators and dielectric constant of dielectric layers and external magnetic field have been reported. The main feature of this structure is a good magneto-opticalmore » rotation that takes place at the defect modes and the edge of photonic band gap of our proposed optical magnetized plasma waveguide. Our outcomes demonstrate the potential applications of the device for tunable and adjustable filters or reflectors and active magneto-optic in microwave devices under structural parameter and external magnetic field.« less

All optical coherent receiver for self-homodyne detection of digitally phase modulated optical signals

NASA Astrophysics Data System (ADS)

Kiasaleh, Kamran

1994-02-01

A novel optical phase-locked loop (OPLL) system for the self-homodyne detection of digitally phase modulated optical signals is introduced. A Mach-Zehnder type interferometer is used to self-homodyne binary phase-modulated optical signals with an external phase modulator inserted in the control arm of the interferometer.

Direct link of a mid-infrared QCL to a frequency comb by optical injection.

PubMed

Borri, S; Galli, I; Cappelli, F; Bismuto, A; Bartalini, S; Cancio, P; Giusfredi, G; Mazzotti, D; Faist, J; De Natale, P

2012-03-15

A narrow-linewidth comb-linked nonlinear source is used as master radiation to injection lock a room-temperature mid-infrared quantum cascade laser (QCL). This process leads to a direct lock of the QCL to the optical frequency comb, providing the unique features of narrow linewidth, absolute frequency, higher output power, and wide mode-hop-free tunability. The QCL reproduces the injected radiation within more than 94%, with a reduction of the frequency-noise spectral density by 3 to 4 orders of magnitude up to about 100 kHz, and a linewidth narrowing from a few MHz to 20 kHz.

Development of devices for self-injection: using tribological analysis to optimize injection force

PubMed Central

Lange, Jakob; Urbanek, Leos; Burren, Stefan

2016-01-01

This article describes the use of analytical models and physical measurements to characterize and optimize the tribological behavior of pen injectors for self-administration of biopharmaceuticals. One of the main performance attributes of this kind of device is its efficiency in transmitting the external force applied by the user on to the cartridge inside the pen in order to effectuate an injection. This injection force characteristic is heavily influenced by the frictional properties of the polymeric materials employed in the mechanism. Standard friction tests are available for characterizing candidate materials, but they use geometries and conditions far removed from the actual situation inside a pen injector and thus do not always generate relevant data. A new test procedure, allowing the direct measurement of the coefficient of friction between two key parts of a pen injector mechanism using real parts under simulated use conditions, is presented. In addition to the absolute level of friction, the test method provides information on expected evolution of friction over lifetime as well as on expected consistency between individual devices. Paired with an analytical model of the pen mechanism, the frictional data allow the expected overall injection system force efficiency to be estimated. The test method and analytical model are applied to a range of polymer combinations with different kinds of lubrication. It is found that material combinations used without lubrication generally have unsatisfactory performance, that the use of silicone-based internal lubricating additives improves performance, and that the best results can be achieved with external silicone-based lubricants. Polytetrafluoroethylene-based internal lubrication and external lubrication are also evaluated but found to provide only limited benefits unless used in combination with silicone. PMID:27274319

Microwave fiber optics delay line

NASA Astrophysics Data System (ADS)

Slayman, C.; Yen, H. W.

1980-01-01

A microwave delay line is one of the devices used in EW systems for preserving the frequency and phase contents of RF signals. For such applications, delay lines are required to have large dynamic range, wide bandwidth, low insertion loss, and a linear response. The basic components of a fiber-optics delay line are: an optical source, a wideband optical modulator, a spool of single-mode fiber with appropriate length to provide a given microwave signal delay, and a high-speed photodetector with an RF amplifier. This contract program is to study the feasibility of such a fiber-optic delay line in the frequency range of 4.0 to 6.5 GHz. The modulation scheme studied is the direct modulation of injection lasers. The most important issue identified is the frequency response of the injection laser and the photodetector.

Towards optical brain imaging: getting light through a bone

NASA Astrophysics Data System (ADS)

Thompson, J. V.; Hokr, B. H.; Nodurft, D. T.; Yakovlev, V. V.

2018-06-01

Optical imaging and detection in biological samples is severely limited by scattering effects. In particular, optical techniques for measuring conditions beneath the skull and within the bone marrow hold significant promise when it comes to speed, sensitivity and specificity. However, the strong optical scattering due to bone hinders the realization of these methods. In this article, we propose a technique to enhance the transmittance of light through bone. This is achieved by injecting light below the top surface of the bone and utilizing multiple scattering to increase transmittance. This technique suggests that enhancements of 2-6 times may be realized by injection of light 1 mm below the surface of the bone. By enhancing the transmittance of light through bone, we will greatly improve our ability to utilize optical methods to better understand and diagnose conditions within biological media.

Physics of the current injection process during localized helicity injection

NASA Astrophysics Data System (ADS)

Hinson, Edward Thomas

An impedance model has been developed for the arc-plasma cathode electron current source used in localized helicity injection tokamak startup. According to this model, a potential double layer (DL) is established between the high-density arc plasma (narc ˜ 1021 m-3) in the electron source, and the less-dense external tokamak edge plasma (nedge ˜ 10 18 m-3) into which current is injected. The DL launches an electron beam at the applied voltage with cross-sectional area close to that of the source aperture: Ainj ≈ 2 cm 2. The injected current, Iinj, increases with applied voltage, Vinj, according to the standard DL scaling, Iinj ˜ V(3/2/ inj), until the more restrictive of two limits to beam density nb arises, producing Iinj ˜ V(1/2/inj), a scaling with beam drift velocity. For low external tokamak edge density nedge, space-charge neutralization of the intense electron beam restricts the injected beam density to nb ˜ nedge. At high Jinj and sufficient edge density, the injected current is limited by expansion of the DL sheath, which leads to nb ˜ narc. Measurements of narc, Iinj , nedge, Vinj, support these predicted scalings, and suggest narc as a viable control actuator for the source impedance. Magnetic probe signals ≈ 300 degrees toroidally from the injection location are consistent with expectations for a gyrating, coherent electron beam with a compact areal cross-section. Technological development of the source has allowed an extension of the favorable Iinj ˜ V(1/2/inj) to higher power without electrical breakdown.

Highly sensitive protein detection by combination of atomic force microscopy fishing with charge generation and mass spectrometry analysis.

PubMed

Ivanov, Yuri D; Pleshakova, Tatyana; Malsagova, Krystina; Kozlov, Andrey; Kaysheva, Anna; Kopylov, Arthur; Izotov, Alexander; Andreeva, Elena; Kanashenko, Sergey; Usanov, Sergey; Archakov, Alexander

2014-10-01

An approach combining atomic force microscopy (AFM) fishing and mass spectrometry (MS) analysis to detect proteins at ultra-low concentrations is proposed. Fishing out protein molecules onto a highly oriented pyrolytic graphite surface coated with polytetrafluoroethylene film was carried out with and without application of an external electric field. After that they were visualized by AFM and identified by MS. It was found that injection of solution leads to charge generation in the solution, and an electric potential within the measuring cell is induced. It was demonstrated that without an external electric field in the rapid injection input of diluted protein solution the fishing is efficient, as opposed to slow fluid input. The high sensitivity of this method was demonstrated by detection of human serum albumin and human cytochrome b5 in 10(-17) -10(-18) m water solutions. It was shown that an external negative voltage applied to highly oriented pyrolytic graphite hinders the protein fishing. The efficiency of fishing with an external positive voltage was similar to that obtained without applying any voltage. © 2014 FEBS.

50 Mb/s, 220-mW Laser-Array Transmitter

NASA Technical Reports Server (NTRS)

Cornwell, Donald M., Jr.

1992-01-01

Laser transmitter based on injection locking produces single-wavelength, diffraction-limited, single-lobe beam. Output stage is array of laser diodes producing non-diffraction-limited, multi-mode beam in absence of injection locking. Suitable for both free-space and optical-fiber communication systems. Because beam from transmitter focused to spot as small as 5 micrometers, devices usable for reading and writing optical disks at increased information densities. Application also in remote sensing and ranging.

Optical Measurements in a Combustor Using a 9-Point Swirl-Venturi Fuel Injector

NASA Technical Reports Server (NTRS)

Hicks, Yolanda R.; Anderson, Robert C.; Locke, Randy J.

2007-01-01

This paper highlights the use of two-dimensional data to characterize a multipoint swirl-venturi injector. The injector is based on a NASA-conceived lean direct injection concept. Using a variety of advanced optical diagnostic techniques, we examine the flows resultant from multipoint, lean-direct injectors that have nine injection sites arranged in a 3 x 3 grid. The measurements are made within an optically-accessible, jet-A-fueled, 76-mm by 76-mm flame tube combustor. Combustion species mapping and velocity measurements are obtained using planar laser-induced fluorescence of OH and fuel, planar laser scatter of liquid fuel, chemiluminescence from CH*, NO*, and OH*, and particle image velocimetry of seeded air (non-fueled). These measurements are used to study fuel injection, mixedness, and combustion processes and are part of a database of measurements that will be used for validating computational combustion models.

A novel photonic oscillator

NASA Technical Reports Server (NTRS)

Yao, X. S.; Maleki, L.

1995-01-01

We report a novel oscillator for photonic RF systems. This oscillator is capable of generating high-frequency signals up to 70 GHz in both electrical and optical domains and is a special voltage-controlled oscillator with an optical output port. It can be used to make a phase-locked loop (PLL) and perform all functions that a PLL is capable of for photonic systems. It can be synchronized to a reference source by means of optical injection locking, electrical injection locking, and PLL. It can also be self-phase locked and self-injection locked to generate a high-stability photonic RF reference. Its applications include high-frequency reference regeneration and distribution, high-gain frequency multiplication, comb-frequecy and square-wave generation, carrier recovery, and clock recovery. We anticipate that such photonic voltage-controlled oscillators (VCOs) will be as important to photonic RF systems as electrical VCOs are to electrical RF systems.

Miniaturized flow injection analysis system

DOEpatents

Folta, J.A.

1997-07-01

A chemical analysis technique known as flow injection analysis is described, wherein small quantities of chemical reagents and sample are intermixed and reacted within a capillary flow system and the reaction products are detected optically, electrochemically, or by other means. A highly miniaturized version of a flow injection analysis system has been fabricated utilizing microfabrication techniques common to the microelectronics industry. The microflow system uses flow capillaries formed by etching microchannels in a silicon or glass wafer followed by bonding to another wafer, commercially available microvalves bonded directly to the microflow channels, and an optical absorption detector cell formed near the capillary outlet, with light being both delivered and collected with fiber optics. The microflow system is designed mainly for analysis of liquids and currently measures 38{times}25{times}3 mm, but can be designed for gas analysis and be substantially smaller in construction. 9 figs.

Injection locking of optomechanical oscillators via acoustic waves.

PubMed

Huang, Ke; Hossein-Zadeh, Mani

2018-04-02

Injection locking is an effective technique for synchronization of oscillator networks and controlling the phase and frequency of individual oscillators. As such, exploring new mechanisms for injection locking of emerging oscillators is important for their usage in various systems. Here, we present the first demonstration of injection locking of a radiation pressure driven optomechanical oscillator (OMO) via acoustic waves. As opposed to previously reported techniques (based on pump modulation or direct application of a modulated electrostatic force), injection locking of OMO via acoustic waves does not require optical power modulation or physical contact with the OMO and it can be easily implemented on various platforms to lock different types of OMOs independent of their size and structure. Using this approach we have locked the phase and frequency of two distinct modes of a microtoroidal silica OMO to a piezoelectric transducer (PZT). We have characterized the behavior of the injection locked OMO with three acoustic excitation configurations and showed that even without proper acoustic impedance, matching the OMO can be locked to the PZT and tuned over 17 kHz with only -30 dBm of RF power fed to the PZT. The high efficiency, simplicity, and scalability of the proposed approach paves the road toward a new class of photonic systems that rely on synchronization of several OMOs to a single or multiple RF oscillators with applications in optical communication, metrology, and sensing. Beyond its practical applications, injection locking via acoustic waves can be used in fundamental studies in quantum optomechanics where thermal and optical isolation of the OMO are critical.

Crisis route to chaos in semiconductor lasers subjected to external optical feedback

NASA Astrophysics Data System (ADS)

Wishon, Michael J.; Locquet, Alexandre; Chang, C. Y.; Choi, D.; Citrin, D. S.

2018-03-01

Semiconductor lasers subjected to optical feedback have been intensively used as archetypical testbeds for high-speed (sub-ns) and high-dimensional nonlinear dynamics. By simultaneously extracting all the dynamical variables, we demonstrate that for larger current, the commonly named "quasiperiodic" route is in fact based on mixed external-cavity solutions that lock the oscillation frequency of the intensity, voltage, and separation in optical frequency through a mechanism involving successive rejections along the unstable manifold of an antimode. We show that chaos emerges from a crisis resulting from the inability to maintain locking as the unstable manifold becomes inaccessible.

Phase noise analysis of a 10-GHz optical injection-locked vertical-cavity surface-emitting laser-based optoelectronic oscillator

NASA Astrophysics Data System (ADS)

Coronel, Juan; Varón, Margarita; Rissons, Angélique

2016-09-01

The optical injection locking (OIL) technique is proposed to reduce the phase noise of a carrier generated for a vertical-cavity surface-emitting laser (VCSEL)-based optoelectronic oscillator. The OIL technique permits the enhancement of the VCSEL direct modulation bandwidth as well as the stabilization of the optical noise of the laser. A 2-km delay line, 10-GHz optical injection-locked VCSEL-based optoelectronic oscillator (OILVBO) was implemented. The internal noise sources of the optoelectronic oscillator components were characterized and analyzed to understand the noise conversion of the system into phase noise in the oscillator carrier. The implemented OILVBO phase noise was -105.7 dBc/Hz at 10 kHz from the carrier; this value agrees well with the performed simulated analysis. From the computed and measured phase noise curves, it is possible to infer the noise processes that take place inside the OILVBO. As a second measurement of the oscillation quality, a time-domain analysis was done through the Allan's standard deviation measurement, reported for first time for an optoelectronic oscillator using the OIL technique.

An analytical method for predicting the geometrical and optical properties of the human lens under accommodation

PubMed Central

Sheil, Conor J.; Bahrami, Mehdi; Goncharov, Alexander V.

2014-01-01

We present an analytical method to describe the accommodative changes in the human crystalline lens. The method is based on the geometry-invariant lens model, in which the gradient-index (GRIN) iso-indicial contours are coupled to the external shape. This feature ensures that any given number of iso-indicial contours does not change with accommodation, which preserves the optical integrity of the GRIN structure. The coupling also enables us to define the GRIN structure if the radii and asphericities of the external lens surfaces are known. As an example, the accommodative changes in lenticular radii and central thickness were taken from the literature, while the asphericities of the external surfaces were derived analytically by adhering to the basic physical conditions of constant lens volume and its axial position. The resulting changes in lens geometry are consistent with experimental data, and the optical properties are in line with expected values for optical power and spherical aberration. The aim of the paper is to provide an anatomically and optically accurate lens model that is valid for 3 mm pupils and can be used as a new tool for better understanding of accommodation. PMID:24877022

An analytical method for predicting the geometrical and optical properties of the human lens under accommodation.

PubMed

Sheil, Conor J; Bahrami, Mehdi; Goncharov, Alexander V

2014-05-01

We present an analytical method to describe the accommodative changes in the human crystalline lens. The method is based on the geometry-invariant lens model, in which the gradient-index (GRIN) iso-indicial contours are coupled to the external shape. This feature ensures that any given number of iso-indicial contours does not change with accommodation, which preserves the optical integrity of the GRIN structure. The coupling also enables us to define the GRIN structure if the radii and asphericities of the external lens surfaces are known. As an example, the accommodative changes in lenticular radii and central thickness were taken from the literature, while the asphericities of the external surfaces were derived analytically by adhering to the basic physical conditions of constant lens volume and its axial position. The resulting changes in lens geometry are consistent with experimental data, and the optical properties are in line with expected values for optical power and spherical aberration. The aim of the paper is to provide an anatomically and optically accurate lens model that is valid for 3 mm pupils and can be used as a new tool for better understanding of accommodation.

Human umbilical cord blood mononuclear cells and chorionic plate-derived mesenchymal stem cells promote axon survival in a rat model of optic nerve crush injury

PubMed Central

CHUNG, SOKJOONG; RHO, SEUNGSOO; KIM, GIJIN; KIM, SO-RA; BAEK, KWANG-HYUN; KANG, MYUNGSEO; LEW, HELEN

2016-01-01

The use of mesenchymal stem cells (MSCs) in cell therapy in regenerative medicine has great potential, particularly in the treatment of nerve injury. Umbilical cord blood (UCB) reportedly contains stem cells, which have been widely used as a hematopoietic source and may have therapeutic potential for neurological impairment. Although ongoing research is dedicated to the management of traumatic optic nerve injury using various measures, novel therapeutic strategies based on the complex underlying mechanisms responsible for optic nerve injury, such as inflammation and/or ischemia, are required. In the present study, a rat model of optic nerve crush (ONC) injury was established in order to examine the effects of transplanting human chorionic plate-derived MSCs (CP-MSCs) isolated from the placenta, as well as human UCB mononuclear cells (CB-MNCs) on compressed rat optic nerves. Expression markers for inflammation, apoptosis, and optic nerve regeneration were analyzed, as well as the axon survival rate by direct counting. Increased axon survival rates were observed following the injection of CB-MNCs at at 1 week post-transplantation compared with the controls. The levels of growth-associated protein-43 (GAP-43) were increased after the injection of CB-MNCs or CP-MSCs compared with the controls, and the expression levels of hypoxia-inducible factor-1α (HIF-1α) were also significantly increased following the injection of CB-MNCs or CP-MSCs. ERM-like protein (ERMN) and SLIT-ROBO Rho GTPase activating protein 2 (SRGAP2) were found to be expressed in the optic nerves of the CP-MSC-injected rats with ONC injury. The findings of our study suggest that the administration of CB-MNCs or CP-MSCs may promote axon survival through systemic concomitant mechanisms involving GAP-43 and HIF-1α. Taken together, these findings provide further understanding of the mechanisms repsonsible for optic nerve injury and may aid in the development of novel cell-based therapeutic strategies with future applications in regenerative medicine, particularly in the management of optic nerve disorders. PMID:26986762

Mass Manufacturing Challenges For CPV Primary And Secondary Optics

NASA Astrophysics Data System (ADS)

Luce, Thomas; Cohen, Joel

2010-10-01

Crucial for the performance and longevity of CPV installations is the efficiency of the optics used. Low production cost and high performance are key for the economical success of a CPV concept. To be able to compete with existing energy sources, proven mass production methods as well as high performance materials have to be employed. The injection molding process is the ideal serial production process capable to deliver at the same time high part quantities, excellent part precision and repeatable part quality at low manufacturing cost. Primary and secondary optics require different materials to be applied. The Pros and Cons of these materials in terms of production properties and achievable part precision will be discussed. We will show quality results for primary Fresnel optics using PMMA and, alternatively Silicone on Glass. For secondary optics we will demonstrate the use of optical silicone lenses widely used for high power LED applications today. Optical grade silicone has an excellent environmental stability even when encountering high energy density levels. The experience of Eschenbach Optik in injection molding silicone optics shows that this material is a very cost competitive alternative for glass secondary optics providing both highest optical performance and precision.

Design, assembly, and optical bench testing of a high-numerical-aperture miniature injection-molded objective for fiber-optic confocal reflectance microscopy.

PubMed

Chidley, Matthew D; Carlson, Kristen D; Richards-Kortum, Rebecca R; Descour, Michael R

2006-04-10

The design, analysis, assembly methods, and optical-bench test results for a miniature injection-molded plastic objective lens used in a fiber-optic confocal reflectance microscope are presented. The five-lens plastic objective was tested as a stand-alone optical system before its integration into a confocal microscope for in vivo imaging of cells and tissue. Changing the spacing and rotation of the individual optical elements can compensate for fabrication inaccuracies and improve performance. The system performance of the miniature objective lens is measured by use of an industry-accepted slanted-edge modulation transfer function (MTF) metric. An estimated Strehl ratio of 0.61 and a MTF value of 0.66 at the fiber-optic bundle Nyquist frequency have been obtained. The optical bench testing system is configured to permit interactive optical alignment during testing to optimize performance. These results are part of an effort to demonstrate the manufacturability of low-cost, high-performance biomedical optics for high-resolution in vivo imaging. Disposable endoscopic microscope objectives could help in vivo confocal microscopy technology mature to permit wide-scale clinical screening and detection of early cancers and precancerous lesions.

Boundary Layer Measurements in a Supersonic Wind Tunnel Using Doppler Global Velocimetry

NASA Technical Reports Server (NTRS)

Meyers, James F.; Lee, Joseph W.; Cavone, Angelo A.

2010-01-01

A modified Doppler Global Velocimeter (DGV) was developed to measure the velocity within the boundary layer above a flat plate in a supersonic flow. Classic laser velocimetry (LV) approaches could not be used since the model surface was composed of a glass-ceramic insulator in support of heat-transfer measurements. Since surface flare limited the use of external LV techniques and windows placed in the model would change the heat transfer characteristics of the flat plate, a novel approach was developed. The input laser beam was divided into nine equal power beams and each transmitted through optical fibers to a small cavity within the model. The beams were then directed through 1.6-mm diameter orifices to form a series of orthogonal beams emitted from the model and aligned with the tunnel centerline to approximate a laser light sheet. Scattered light from 0.1-micron diameter water condensation ice crystals was collected by four 5-mm diameter lenses and transmitted by their respective optical fiber bundles to terminate at the image plane of a standard two-camera DGV receiver. Flow measurements were made over a range from 0.5-mm above the surface to the freestream at Mach 3.51 in steady state and heat pulse injected flows. This technique provides a unique option for measuring boundary layers in supersonic flows where seeding the flow is problematic or where the experimental apparatus does not provide the optical access required by other techniques.

Injectable microstimulator for functional electrical stimulation.

PubMed

Loeb, G E; Zamin, C J; Schulman, J H; Troyk, P R

1991-11-01

A family of digitally controlled devices is constructed for functional electrical stimulation in which each module is an hermetically sealed glass capsule that is small enough to be injected through the lumen of a hypodermic needle. The overall design and component characteristics of microstimulators that receive power and command signals by inductive coupling from a single, externally worn coil are described. Each device stores power between stimulus pulses by charging an electrolytic capacitor formed by its two electrodes, made of sintered, anodised tantalum and electrochemically activated iridium, respectively. Externally, a highly efficient class E amplifier provides power and digitally encoded command signals to control the amplitude, duration and timing of pulses from up to 256 such microstimulators.

Simultaneous signal transmission of different data-rates in a DWDM system employing external injection locking technique

NASA Astrophysics Data System (ADS)

Das, Anindya Sundar; Patra, Ardhendu Sekhar

2014-12-01

A novel architecture of DWDM-PON is proposed and demonstrated for downlink transmission of different data-rates of 622 Mbps, 1 Gbps, 1.25 Gbps and 2.5 Gbps simultaneously over a long-haul single mode fiber (SMF). The data rates are directly modulated by Fabry-Pérot laser diodes (FPLD), which are externally injection locked by asynchronous spontaneous emission (ASE) source. The transmission performances are checked by the bit error rate (BER), Quality (Q) factor and clear eye-diagrams. Since this proposed system consists of one ASE source, FPLDs and depends on the direct modulation technique, it reveals a prominent alternative with advantages in simplicity and cost.

Ultra-low power fiber-coupled gallium arsenide photonic crystal cavity electro-optic modulator.

PubMed

Shambat, Gary; Ellis, Bryan; Mayer, Marie A; Majumdar, Arka; Haller, Eugene E; Vučković, Jelena

2011-04-11

We demonstrate a gallium arsenide photonic crystal cavity injection-based electro-optic modulator coupled to a fiber taper waveguide. The fiber taper serves as a convenient and tunable waveguide for cavity coupling with minimal loss. Localized electrical injection of carriers into the cavity region via a laterally doped p-i-n diode combined with the small mode volume of the cavity enable ultra-low energy modulation at sub-fJ/bit levels. Speeds of up to 1 GHz are demonstrated with photoluminescence lifetime measurements revealing that the ultimate limit goes well into the tens of GHz. © 2011 Optical Society of America

1030-nm diode-laser-based light source delivering pulses with nanojoule energies and picosecond duration adjustable by mode locking or pulse gating operation

NASA Astrophysics Data System (ADS)

Klehr, A.; Liero, A.; Wenzel, H.; Bugge, F.; Brox, O.; Fricke, J.; Ressel, P.; Knigge, A.; Heinrich, W.; Tränkle, G.

2017-02-01

A new compact 1030 nm picosecond light source which can be switched between pulse gating and mode locking operation is presented. It consists of a multi-section distributed Bragg reflector (DBR) laser, an ultrafast multisection optical gate and a flared power amplifier (PA), mounted together with high frequency electronics and optical elements on a 5×4 cm micro bench. The master oscillator (MO) is a 10 mm long ridge wave-guide (RW) laser consisting of 200 μm long saturable absorber, 1500 μm long gain, 8000 μm long cavity, 200 μm long DBR and 100 μm long monitor sections. The 2 mm long optical gate consisting of several RW sections is monolithically integrated with the 4 mm long gain-guided tapered amplifier on a single chip. The light source can be switched between pulse gating and passive mode locking operation. For pulse gating all sections of the MO (except of the DBR and monitor sections) are forward biased and driven by a constant current. By injecting electrical pulses into one section of the optical gate the CW beam emitted by the MO is converted into a train of optical pulses with adjustable widths between 250 ps and 1000 ps. Peak powers of 20 W and spectral linewidths in the MHz range are achieved. Shorter pulses with widths between 4 ps and 15 ps and peak powers up to 50 W but larger spectral widths of about 300 pm are generated by mode locking where the saturable absorber section of the MO is reversed biased. The repetition rate of 4.2 GHz of the pulse train emitted by the MO can be reduced to values between 1 kHz and 100 MHz by utilizing the optical gate as pulse picker. The pulse-to-pulse distance can be controlled by an external trigger source.

Plasmon enhanced heterogeneous electron transfer with continuous band energy model

NASA Astrophysics Data System (ADS)

Zhao, Dandan; Niu, Lu; Wang, Luxia

2017-08-01

Photoinduced charge injection from a perylene dye molecule into the conduction band of a TiO2 system decorated by a metal nanoparticles (MNP) is studied theoretically. Utilizing the density matrix theory the charge transfer dynamics is analyzed. The continuous behavior of the TiO2 conduction band is accounted for by a Legendre polynomials expansion. The simulations consider optical excitation of the dye molecule coupled to the MNP and the subsequent electron injection into the TiO2 semiconductor. Due to the energy transfer coupling between the molecule and the MNP optical excitation and subsequent charge injection into semiconductor is strongly enhanced. The respective enhancement factor can reach values larger than 103. Effects of pulse duration, coupling strength and energetic resonances are also analyzed. The whole approach offers an efficient way to increase charge injection in dye-sensitized solar cells.

Microvascular complications associated with injection of cosmetic facelift dermal fillers

NASA Astrophysics Data System (ADS)

Yousefi, Siavash; Prendes, Mark; Chang, Shu-Hong; Wang, Ruikang K.

2015-02-01

Minimally-invasive cosmetic surgeries such as injection of subdermal fillers have become very popular in the past decade. Although rare, some complications may follow injections such as tissue necrosis and even blindness. There exist two hypothesis regarding source of these complications both of which include microvasculature. The first hypothesis is that fillers in between the tissue structures and compress microvasculature that causes blockage of tissue neutrition and oxygen exchange in the tissue. In another theory, it is hypothesized that fillers move inside major arteries and block the arteries/veins. In this paper, we study these hypotheses using optical coherence tomography and optical microangiography technologies with different hyaluronic-acid fillers in a mouse ear model. Based on our observations, the fillers eventually block arteries/veins if injected directly into them that eventually causes tissue necrosis.

Common-signal-induced synchronization in photonic integrated circuits and its application to secure key distribution.

PubMed

Sasaki, Takuma; Kakesu, Izumi; Mitsui, Yusuke; Rontani, Damien; Uchida, Atsushi; Sunada, Satoshi; Yoshimura, Kazuyuki; Inubushi, Masanobu

2017-10-16

We experimentally achieve common-signal-induced synchronization in two photonic integrated circuits with short external cavities driven by a constant-amplitude random-phase light. The degree of synchronization can be controlled by changing the optical feedback phase of the two photonic integrated circuits. The change in the optical feedback phase leads to a significant redistribution of the spectral energy of optical and RF spectra, which is a unique characteristic of PICs with the short external cavity. The matching of the RF and optical spectra is necessary to achieve synchronization between the two PICs, and stable synchronization can be obtained over an hour in the presence of optical feedback. We succeed in generating information-theoretic secure keys and achieving the final key generation rate of 184 kb/s using the PICs.

Sustained neuroprotection from a single intravitreal injection of PGJ₂ in a nonhuman primate model of nonarteritic anterior ischemic optic neuropathy.

PubMed

Miller, Neil R; Johnson, Mary A; Nolan, Theresa; Guo, Yan; Bernstein, Alexander M; Bernstein, Steven L

2014-10-08

Prostaglandin J₂ (PGJ₂) is neuroprotective in a murine model of nonarteritic anterior ischemic optic neuropathy (NAION). After assessing for potential toxicity, we evaluated the efficacy of a single intravitreal (IVT) injection of PGJ₂ in a nonhuman primate model of NAION (pNAION). We assessed PGJ₂ toxicity by administering it as a single high-dose intravenous (IV) injection, consecutive daily high-dose IV injections, or a single IVT injection in one eye of five adult rhesus monkeys. To assess efficacy, we induced pNAION in one eye of five adult male rhesus monkeys using a laser-activated rose bengal induction method. We then injected the eye with either PGJ₂ or phosphate-buffered saline (PBS) intravitreally immediately or 5 hours post induction. We performed a clinical assessment, optical coherence tomography, electrophysiological testing, fundus photography, and fluorescein angiography in all animals prior to induction and at 1 day, 1 week, 2 weeks, and 4 weeks after induction. Following analysis of the first eye, we induced pNAION in the contralateral eye and then injected either PGJ₂ or PBS. We euthanized all animals 5 weeks after final assessment of the fellow eye and performed both immunohistochemical and light and electron microscopic analyses of the retina and optic nerves. PGJ₂ caused no permanent systemic toxicity regardless of the amount injected or route of delivery, and there was no evidence of any ocular toxicity with the dose of PGJ₂ used in efficacy studies. Transient reduction in the amplitudes of the visual evoked potentials and the N95 component of the pattern electroretinogram (PERG) occurred after both IV and IVT administration of high doses of PGJ₂; however, the amplitudes returned to normal in all animals within 1 week. In all eyes, a single IVT dose of PGJ₂ administered immediately or shortly after induction of pNAION resulted in a significant reduction of clinical, electrophysiological, and histological damage compared with vehicle-injected eyes (P = 0.03 for both VEP and PERG; P = 0.05 for axon counts). In nonhuman primates, PGJ₂ administered either intravenously or intravitreally produces no permanent toxicity at even four times the dose given for neuroprotection. Additionally, a single IVT dose of PGJ₂ is neuroprotective when administered up to 5 hours after induction of pNAION. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

Injection molding of high precision optics for LED applications made of liquid silicone rubber

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

Hopmann, Christian; Röbig, Malte

Light Emitting Diodes (LED) conquer the growing global market of lighting technologies. Due to their advantages, they are increasingly used in consumer products, in lighting applications in the home and in the mobility sector as well as in industrial applications. Particularly, with regard to the increasing use of high-power LED (HP-LED) the materials in the surrounding area of the light emitting semiconductor chip are of utmost importance. While the materials behind the semiconductor chip are optimized for maximum heat dissipation, the materials currently used for the encapsulation of the semiconductor chip (primary optics) and the secondary optics encounter their limitsmore » due to the high temperatures. In addition certain amounts of blue UV radiation degrade the currently used materials such as epoxy resins or polyurethanes for primary optics. In the context of an ongoing joint research project with various partners from the industry, an innovative manufacturing method for high precision optics for LED applications made of liquid silicone rubber (LSR) is analyzed at the Institut of Plastics Processing (IKV), Aachen. The aim of this project is to utilize the material-specific advantages of high transparent LSR, especially the excellent high temperature resistance and the great freedom in design. Therefore, a high integrated injection molding process is developed. For the production of combined LED primary and secondary optics a LED board is placed in an injection mold and overmolded with LSR. Due to the integrated process and the reduction of subcomponents like the secondary optics the economics of the production process can be improved significantly. Furthermore combined LED optics offer an improved effectiveness, because there are no losses of the light power at the transition of the primary and secondary optics.« less

Optical trapping and binding of particles in an optofluidic stable Fabry-Pérot resonator with single-sided injection.

PubMed

Gaber, Noha; Malak, Maurine; Marty, Frédéric; Angelescu, Dan E; Richalot, Elodie; Bourouina, Tarik

2014-07-07

In this article, microparticles are manipulated inside an optofluidic Fabry-Pérot cylindrical cavity embedding a fluidic capillary tube, taking advantage of field enhancement and multiple reflections within the optically-resonant cavity. This enables trapping of suspended particles with single-side injection of light and with low optical power. A Hermite-Gaussian standing wave is developed inside the cavity, forming trapping spots at the locations of the electromagnetic field maxima with a strong intensity gradient. The particles get arranged in a pattern related to the mechanism affecting them: either optical trapping or optical binding. This is proven to eventually translate into either an axial one dimensional (1D) particle array or a cluster of particles. Numerical simulations are performed to model the field distributions inside the cavity allowing a behavioral understanding of the phenomena involved in each case.

Investigation on nonautonomous soliton management in generalized external potentials via dispersion and nonlinearity

NASA Astrophysics Data System (ADS)

Vijayalekshmi, S.; Mani Rajan, M. S.; Mahalingam, A.; Uthayakumar, A.

2015-09-01

We investigate the controllable behavior of nonautonomous soliton in external potentials with variable dispersion and nonlinearity management functions, which describes the propagation of optical pulses in an inhomogeneous fiber system. We derive the Lax pair with a variable spectral parameter and the exact multi-soliton solution is generated via Darboux transformation. Based on these solutions, several novel optical solitons are constructed by selecting appropriate functions and the main evolution features of these waves are shown by some interesting figures with computer simulation. As few examples, breathers in periodic potential, soliton compression in an exponentially dispersion decreasing fiber and interaction of boomerang solitons are discussed. The presented results have applications in the study of nonautonomous soliton birefringence-managed switching architecture. These results are potentially useful in the management of nonautonomous soliton with external potentials in the optical soliton communications and long-haul telecommunication networks.

Analysis and demonstration of vibration waveform reconstruction in distributed optical fiber vibration sensing system

NASA Astrophysics Data System (ADS)

Zhu, Hui; Shan, Xuekang; Sun, Xiaohan

2017-10-01

A method for reconstructing the vibration waveform from the optical time-domain backscattering pulses in the distributed optical fiber sensing system (DOFSS) is proposed, which allows for extracting and recovering the external vibration signal from the tested pulses by analog signal processing, so that can obtain vibration location and waveform simultaneously. We establish the response model of DOFSS to the external vibration and analyze the effects of system parameters on the operational performance. The main parts of the DOFSS are optimized, including delay fiber length and wavelength, to improve the sensitivity of the system. The experimental system is set up and the vibration amplitudes and reconstructed waveforms are fit well with the original driving signal. The experimental results demonstrate that the performance of vibration waveform reconstruction is good with SNR of 15 dB whenever the external vibrations with different intensities and frequencies exert on the sensing fiber.

Kerr electro-optic field mapping study of the effect of charge injection on the impulse breakdown strength of transformer oil

NASA Astrophysics Data System (ADS)

Zhang, X.; Zahn, M.

2013-10-01

The smart use of charge injection to improve breakdown strength in transformer oil is demonstrated in this paper. Hypothetically, bipolar homo-charge injection with reduced electric field at both electrodes may allow higher voltage operation without insulation failure, since electrical breakdown usually initiates at the electrode-dielectric interfaces. To find experimental evidence, the applicability and limitation of the hypothesis is first analyzed. Impulse breakdown tests and Kerr electro-optic field mapping measurements are then conducted with different combinations of parallel-plate aluminum and brass electrodes stressed by millisecond duration impulse. It is found that the breakdown voltage of brass anode and aluminum cathode is ˜50% higher than that of aluminum anode and brass cathode. This can be explained by charge injection patterns from Kerr measurements under a lower voltage, where aluminum and brass electrodes inject negative and positive charges, respectively. This work provides a feasible approach to investigating the effect of electrode material on breakdown strength.

Experimental verification of a theoretical model of an active cladding optical fiber fluorosensor

NASA Technical Reports Server (NTRS)

Albin, Sacharia; Briant, Alvin L.; Egalon, Claudio O.; Rogowski, Robert S.; Nankung, Juock S.

1993-01-01

Experiments were conducted to verify a theoretical model on the injection efficiency of sources in the cladding of an optical fiber. The theoretical results predicted an increase in the injection efficiency for higher differences in refractive indices between the core and cladding. The experimental apparatus used consisted of a glass rod 50 cm long, coated at one end with a thin film of fluorescent substance. The fluorescent substance was excited with side illumination, perpendicular to the rod axis, using a 476 nm Argon-ion laser. Part of the excited fluorescence was injected into the core and guided to a detector. The signal was measured for several different cladding refractive indices. The cladding consisted of sugar dissolved in water and the refractive index was changed by varying the sugar concentration in the solution. The results indicate that the power injected into the rod, due to evanescent wave injection, increases with the difference in refractive index which is in qualitative agreement with theory.

Feedback effects in optical communication systems: characteristic curve for single-mode InGaAsP lasers.

PubMed

Brivio, F; Reverdito, C; Sacchi, G; Chiaretti, G; Milani, M

1992-08-20

An experimental analysis of InGaAsP injection lasers shows an unexpected decrease of the differential quantum efficiency as a function of injected current when optical power is fed back into the active cavity of a diode inserted into a long transmission line. To investigate the response of laser diodes to optical feedback, we base our analysis on a microscopic model, resulting in a set of coupled equations that include the microscopic parameters that characterize the material and the device. This description takes into account the nonlinear dependence of the interband carrier lifetime on the level of optical feedback. Good agreement between the analytical description and experimental data is obtained for threshold current and differential quantum efficiency as functions of the feedback ratio.

Coherent radio-frequency detection for narrowband direct comb spectroscopy.

PubMed

Anstie, James D; Perrella, Christopher; Light, Philip S; Luiten, Andre N

2016-02-22

We demonstrate a scheme for coherent narrowband direct optical frequency comb spectroscopy. An extended cavity diode laser is injection locked to a single mode of an optical frequency comb, frequency shifted, and used as a local oscillator to optically down-mix the interrogating comb on a fast photodetector. The high spectral coherence of the injection lock generates a microwave frequency comb at the output of the photodiode with very narrow features, enabling spectral information to be further down-mixed to RF frequencies, allowing optical transmittance and phase to be obtained using electronics commonly found in the lab. We demonstrate two methods for achieving this step: a serial mode-by-mode approach and a parallel dual-comb approach, with the Cs D1 transition at 894 nm as a test case.

Feasibility of Leadless Cardiac Pacing Using Injectable Magnetic Microparticles

PubMed Central

Rotenberg, Menahem Y.; Gabay, Hovav; Etzion, Yoram; Cohen, Smadar

2016-01-01

A noninvasive, effective approach for immediate and painless heart pacing would have invaluable implications in several clinical scenarios. Here we present a novel strategy that utilizes the well-known mechano-electric feedback of the heart to evoke cardiac pacing, while relying on magnetic microparticles as leadless mechanical stimulators. We demonstrate that after localizing intravenously-injected magnetic microparticles in the right ventricular cavity using an external electromagnet, the application of magnetic pulses generates mechanical stimulation that provokes ventricular overdrive pacing in the rat heart. This temporary pacing consistently managed to revert drug-induced bradycardia, but could only last up to several seconds in the rat model, most likely due to escape of the particles between the applied pulses using our current experimental setting. In a pig model with open chest, MEF-based pacing was induced by banging magnetic particles and has lasted for a longer time. Due to overheating of the electromagnet, we intentionally terminated the experiments after 2 min. Our results demonstrate for the first time the feasibility of external leadless temporary pacing, using injectable magnetic microparticles that are manipulated by an external electromagnet. This new approach can have important utilities in clinical settings in which immediate and painless control of cardiac rhythm is required. PMID:27091192

High-Performance, Solution-Processed Quantum Dot Light-Emitting Field-Effect Transistors with a Scandium-Incorporated Indium Oxide Semiconductor.

PubMed

He, Penghui; Jiang, Congbiao; Lan, Linfeng; Sun, Sheng; Li, Yizhi; Gao, Peixiong; Zhang, Peng; Dai, Xingqiang; Wang, Jian; Peng, Junbiao; Cao, Yong

2018-05-22

Light-emitting field-effect transistors (LEFETs) have attained great attention due to their special characteristics of both the switching capacity and the electroluminescence capacity. However, high-performance LEFETs with high mobility, high brightness, and high efficiency have not been realized due to the difficulty in developing high electron and hole mobility materials with suitable band structures. In this paper, quantum dot hybrid LEFETs (QD-HLEFETs) combining high-luminous-efficiency quantum dots (QDs) and a solution-processed scandium-incorporated indium oxide (Sc:In 2 O 3 ) semiconductor were demonstrated. The red QD-HLEFET showed high electrical and optical performance with an electron mobility of 0.8 cm 2 V -1 s -1 , a maximum brightness of 13 400 cd/m 2 , and a maximum external quantum efficiency of 8.7%. The high performance of the QD-HLEFET is attributed to the good energy band matching between Sc:In 2 O 3 and QDs and the balanced hole and electron injection (less exciton nonradiative recombination). In addition, incorporation of Sc into In 2 O 3 can suppress the oxygen vacancy and free carrier generation and brings about excellent current and optical modulation (the on/off current ratio is 10 5 and the on/off brightness ratio is 10 6 ).

External corrosion and leakage detection of oil and gas pipeline using FBG fiber optics and a trigger

NASA Astrophysics Data System (ADS)

Ge, Yaomou

Oil and gas pipelines play a critical role in delivering the energy resources from producing fields to power communities around the world. However, there are many threats to pipeline integrity, which may lead to significant incidents, causing safety, environmental and economic problems. Corrosion has been a big threat to oil and gas pipelines for a long time, which has attributed to approximately 18% of the significant incidents in oil and gas pipelines. In addition, external corrosion of pipelines accounts for a significant portion (more than 25%) of pipeline failure. External corrosion detection is the research area of this thesis. In this thesis, a review of existing corrosion detection or monitoring methods is presented, and optical fiber sensors show a great promise in corrosion detection of oil and gas pipelines. Several scenarios of optical fiber corrosion sensors are discussed, and two of them are selected for future research. A new corrosion and leakage detection sensor, consisting of a custom designed trigger and a FBG optical fiber, will be presented. This new device has been experimentally tested and it shows great promise.

Optical injection phase-lock loops

NASA Astrophysics Data System (ADS)

Bordonalli, Aldario Chrestani

Locking techniques have been widely applied for frequency synchronisation of semiconductor lasers used in coherent communication and microwave signal generation systems. Two main locking techniques, the optical phase-lock loop (OPLL) and optical injection locking (OIL) are analysed in this thesis. The principal limitations on OPLL performance result from the loop propagation delay, which makes difficult the implementation of high gain and wide bandwidth loops, leading to poor phase noise suppression performance and requiring the linewidths of the semiconductor laser sources to be less than a few megahertz for practical values of loop delay. The OIL phase noise suppression is controlled by the injected power. The principal limitations of the OIL implementation are the finite phase error under locked conditions and the narrow stable locking range the system provides at injected power levels required to reduce the phase noise output of semiconductor lasers significantly. This thesis demonstrates theoretically and experimentally that it is possible to overcome the limitations of OPLL and OIL systems by combining them, to form an optical injection phase-lock loop (OIPLL). The modelling of an OIPLL system is presented and compared with the equivalent OPLL and OIL results. Optical and electrical design of an homodyne OIPLL is detailed. Experimental results are given which verify the theoretical prediction that the OIPLL would keep the phase noise suppression as high as that of the OIL system over a much wider stable locking range, even with wide linewidth lasers and long loop delays. The experimental results for lasers with summed linewidth of 36 MHz and a loop delay of 15 ns showed measured phase error variances as low as 0.006 rad2 (500 MHz bandwidth) for locking bandwidths greater than 26 GHz, compared with the equivalent OPLL phase error variance of around 1 rad2 (500 MHz bandwidth) and the equivalent OIL locking bandwidth of less than 1.2 GHz.

Effects of Ultrasound-guided intra-articular ketorolac injection with capsular distension.

PubMed

Ahn, Jae Ki; Kim, Jongwoo; Lee, Sang Jae; Park, Yongbum; Bae, Byung; Lee, Woo

2015-01-01

Frozen shoulder is a painful condition with gradual onset and loss of range of motion in the glenohumeral joint. To investigate the efficacy of ultrasound(US)-guided intra-articular (IA) ketorolac injection with capsular distension compared with steroid injection alone in patients with frozen shoulder by assessing pain relief, functional improvements, and range of motion at 1,3 and 6 months after the last injections. Between January 2009 and December 2012, 121 patient were treated with US-guided IA steroid injection or IA ketorolac injection with capsular distension for frozen shoulder. Patients (n= 57) of US-guided IA steroid injection group were administered with a mixture of 0.5% lidocaine (4 ml) plus triamcinolone (40 mg/ml; 1 ml) and patients (n= 64) of US-guided IA ketorolac injection with capsular distension group were administered by using 0.5% lidocaine (19 mL) plus ketorolac (30 mg/ml; 1 mL) for capsular distension. Outcome measurement was assessed by Shoulder Pain and Disability Index (SPADI), Verbal Numeric pain Scale (VNS) and passive range of motion (ROM) before injections and at 1, 3 and 6 months after the last injections. We regarded the outcomes as a success if patients obtained significant pain relief (as measured by > 50% improvement in the VNS score and 20 point improvement in the SPASI) at 1, 3 and 6 months after the last injections. SPADI, VNS and passive ROM were improved 1, 3 and 6 months after the last injections in both groups. The statistical differences were not observed in SPADI, VNS between groups (p< 0.05). Successful treatment rate were not significantly different between the groups as well as in 1, 3 and 6 month outcomes. However, greater improvement was found in a matter of range of motion in patients receiving IA ketorolac injection with capsular distension than participants receiving US-guided IA steroid injection alone. Significant differences in improvement at 3 and 6 months were observed for shoulder passive abduction and external rotation (p< 0.05). IA ketorolac injection with capsular distension was shown to be a treatment method as effective as the steroid injection alone in pain relief and functional improvement in patient with frozen shoulder and more improvement in passive abduction and external rotation than steroid injection alone at 3 and 6 months.

Analytical modeling and numerical simulation of the short-wave infrared electron-injection detectors

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

Movassaghi, Yashar; Fathipour, Morteza; Fathipour, Vala

2016-03-21

This paper describes comprehensive analytical and simulation models for the design and optimization of the electron-injection based detectors. The electron-injection detectors evaluated here operate in the short-wave infrared range and utilize a type-II band alignment in InP/GaAsSb/InGaAs material system. The unique geometry of detectors along with an inherent negative-feedback mechanism in the device allows for achieving high internal avalanche-free amplifications without any excess noise. Physics-based closed-form analytical models are derived for the detector rise time and dark current. Our optical gain model takes into account the drop in the optical gain at high optical power levels. Furthermore, numerical simulation studiesmore » of the electrical characteristics of the device show good agreement with our analytical models as well experimental data. Performance comparison between devices with different injector sizes shows that enhancement in the gain and speed is anticipated by reducing the injector size. Sensitivity analysis for the key detector parameters shows the relative importance of each parameter. The results of this study may provide useful information and guidelines for development of future electron-injection based detectors as well as other heterojunction photodetectors.« less

Successful treatment of toxoplasmosis-associated choroidal neovascular lesions with bevacizumab and antiparasitic therapy.

PubMed

Lin, Chun-Ju; Chen, San-Ni; Hwang, Jiunn-Feng; Hu, Pei-Shin

2011-01-01

To report the effects of oral trimethoprim/sulfamethoxazole and intravitreal bevacizumab injection in the treatment of ocular toxoplasmosis-associated choroidal neovascular lesions (CNV). This was a noncomparative, nonrandomized, consecutive case series. All eyes with ocular toxoplasmosis-associated CNV received one intravitreal bevacizumab injection under the coverage of oral trimethoprim/sulfamethoxazole. The changes in best-corrected visual acuity were recorded. Serial fundus photography, fluorescein angiography, optical coherence tomography, and indocyanine green angiography were performed to measure the treatment efficacy. Three eyes of two patients with a history of ocular toxoplasmosis had active CNV demonstrated by fluorescein angiography and optical coherence tomography. Each was treated with oral trimethoprim/sulfamethoxazole and one intravitreal bevacizumab injection. Best-corrected visual acuity, fundus photographs, fluorescein angiography, optical coherence tomography, and indocyanine green angiography all showed favorable results. No ocular or systemic complications were noted. In all three eyes, the CNV subsided and vision improved. Oral trimethoprim/sulfamethoxazole is an effective and less expensive antibiotic against Toxoplasma gondii. Intravitreal bevacizumab injection appears to be a well-tolerated treatment for toxoplasmosis-associated CNV and has the potential as an adjuvant therapy to improve final vision. More cases and further studies are required.

Image-guided intraocular injection using multimodality optical coherence tomography and fluorescence confocal scanning laser ophthalmoscopy in rodent ophthalmological models

NASA Astrophysics Data System (ADS)

Terrones, Benjamin D.; Benavides, Oscar R.; Leeburg, Kelsey C.; Mehanathan, Sankarathi B.; Levine, Edward M.; Tao, Yuankai K.

2018-02-01

Intraocular injections are routinely performed for delivery of anti-VEGF and anti-inflammatory therapies in humans. While these injections are also performed in mice to develop novel models of ophthalmic diseases and screen novel therapeutics, the injection location and volume are not well-controlled and reproducible. We overcome limitations of conventional injections methods by developing a multimodality, long working distance, non-contact optical coherence tomography (OCT) and fluorescence confocal scanning laser ophthalmoscopy (cSLO) system for retinal imaging before and after injections. Our OCT+cSLO system combines a custom-built spectraldomain OCT engine (875+/-85 nm) with 125 kHz line-rate with a modified commercial cSLO with a maximum frame-rate of 30 fps (512 x 512 pix.). The system was designed for an overlapping OCT+cSLO field-of-view of 1.1 mm with a 7.76 mm working distance to the pupil. cSLO excitation light sources and filters were optimized for simultaneous GFP and tdTomato imaging. Lateral resolution was 3.02 µm for OCT and 2.74 μm for cSLO. Intravitreal injections of 5%, 10%, and 20% intralipid with Alex Fluor 488 were manually injected intraocularly in C57BL/6 mice. Post-injection imaging showed structural changes associated with retinal puncture, including the injection track, a retinal elevation, and detachment of the posterior hyaloid. OCT enables quantitative analysis of injection location and volumes whereas complementary cSLO improves specificity for identifying fluorescently labeled injected compounds and transgenic cells. The long working distance of our non-contact OCT+cSLO system is uniquely-suited for concurrent imaging with intraocular injections and may be applied for imaging of ophthalmic surgical dynamics and real-time image-guided injections.

Whole-body optical imaging of green fluorescent protein-expressing tumors and metastases

PubMed Central

Yang, Meng; Baranov, Eugene; Jiang, Ping; Sun, Fang-Xian; Li, Xiao-Ming; Li, Lingna; Hasegawa, Satoshi; Bouvet, Michael; Al-Tuwaijri, Maraya; Chishima, Takashi; Shimada, Hiroshi; Moossa, A. R.; Penman, Sheldon; Hoffman, Robert M.

2000-01-01

We have imaged, in real time, fluorescent tumors growing and metastasizing in live mice. The whole-body optical imaging system is external and noninvasive. It affords unprecedented continuous visual monitoring of malignant growth and spread within intact animals. We have established new human and rodent tumors that stably express very high levels of the Aequorea victoria green fluorescent protein (GFP) and transplanted these to appropriate animals. B16F0-GFP mouse melanoma cells were injected into the tail vein or portal vein of 6-week-old C57BL/6 and nude mice. Whole-body optical images showed metastatic lesions in the brain, liver, and bone of B16F0-GFP that were used for real time, quantitative measurement of tumor growth in each of these organs. The AC3488-GFP human colon cancer was surgically implanted orthotopically into nude mice. Whole-body optical images showed, in real time, growth of the primary colon tumor and its metastatic lesions in the liver and skeleton. Imaging was with either a trans-illuminated epifluorescence microscope or a fluorescence light box and thermoelectrically cooled color charge-coupled device camera. The depth to which metastasis and micrometastasis could be imaged depended on their size. A 60-μm diameter tumor was detectable at a depth of 0.5 mm whereas a 1,800-μm tumor could be visualized at 2.2-mm depth. The simple, noninvasive, and highly selective imaging of growing tumors, made possible by strong GFP fluorescence, enables the detailed imaging of tumor growth and metastasis formation. This should facilitate studies of modulators of cancer growth including inhibition by potential chemotherapeutic agents. PMID:10655509

Holographic interferometry with an injection seeded Nd:YAG laser and two reference beams

NASA Technical Reports Server (NTRS)

Decker, Arthur J.

1989-01-01

The performance of twin injection seeded Nd:YAG lasers is compared with the performance of an argon-ion laser for recording dual-reference-beam holograms in AGFA 8E56 emulsion. Optical heterodyning is used to measure interference, and the results are expressed in terms of heterodyning signal level and intensity signal-to-noise. The Nd:YAG laser system is to be used for optical inspections of structures for cracks, defects, gas leaks, and structural changes.

Chirped laser dispersion spectroscopy using a directly modulated quantum cascade laser

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

Hangauer, Andreas, E-mail: hangauer@princeton.edu; Nikodem, Michal; Wysocki, Gerard, E-mail: gwysocki@princeton.edu

2013-11-04

Chirped laser dispersion spectroscopy (CLaDS) utilizing direct modulation of a quantum cascade laser (QCL) is presented. By controlling the laser bias nearly single- and dual-sideband CLaDS operation can be realized in an extremely simplified optical setup with no external optical modulators. Capability of direct single-sideband modulation is a unique feature of QCLs that exhibit a low linewidth enhancement factor. The developed analytical model shows excellent agreement with the experimental, directly modulated CLaDS spectra. This method overcomes major technical limitations of mid-infrared CLaDS systems by allowing significantly higher modulation frequencies and eliminating optical fringes introduced by external modulators.

Investigation of a tripropylene-glycol monomethyl ether and diesel blend for soot-free combustion in an optical direct-injection diesel engine

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

Dumitrescu, Cosmin E.; Mueller, Charles J.; Kurtz, Eric

Natural luminosity and chemiluminescence imaging diagnostics were employed to investigate if a 50/50 blend by volume of tripropylene-glycol monomethyl ether (TPGME) and ultra-low sulfur #2 diesel certification fuel (CF) could enable leaner-lifted flame combustion (LLFC), a non-sooting mode of mixing-controlled combustion associated with equivalence ratios below approximately 2. The experiments were performed in a singlecylinder heavy-duty optical compression-ignition engine at three injection pressures and three dilution levels. Results indicate that TPGME addition effectively eliminated engine-out smoke emissions by curtailing soot production and/or increasing soot oxidation during and after the end of fuel injection. TPGME greatly reduced soot luminosity when compared with neat CF, but did not enable LLFC because the equivalence ratios at the lift-off length,more » $$\\phi$$(H), never reached the non-sooting limit. Nevertheless, this study showed that TPGME addition has the potential to enable LLFC under different experimental conditions that would further decrease $$\\phi$$(H) to ~ 2 and below. Concerning other engine-out emissions, injection pressure influenced the effects of TPGME addition on NO x emissions. Finally, HC and CO emissions were higher compared to baseline fuel likely due to the lower net heat of combustion of TPGME and the need to limit fuel-injection duration for valid optical measurements.« less

Investigation of a tripropylene-glycol monomethyl ether and diesel blend for soot-free combustion in an optical direct-injection diesel engine

DOE PAGES

Dumitrescu, Cosmin E.; Mueller, Charles J.; Kurtz, Eric

2015-12-31

Natural luminosity and chemiluminescence imaging diagnostics were employed to investigate if a 50/50 blend by volume of tripropylene-glycol monomethyl ether (TPGME) and ultra-low sulfur #2 diesel certification fuel (CF) could enable leaner-lifted flame combustion (LLFC), a non-sooting mode of mixing-controlled combustion associated with equivalence ratios below approximately 2. The experiments were performed in a singlecylinder heavy-duty optical compression-ignition engine at three injection pressures and three dilution levels. Results indicate that TPGME addition effectively eliminated engine-out smoke emissions by curtailing soot production and/or increasing soot oxidation during and after the end of fuel injection. TPGME greatly reduced soot luminosity when compared with neat CF, but did not enable LLFC because the equivalence ratios at the lift-off length,more » $$\\phi$$(H), never reached the non-sooting limit. Nevertheless, this study showed that TPGME addition has the potential to enable LLFC under different experimental conditions that would further decrease $$\\phi$$(H) to ~ 2 and below. Concerning other engine-out emissions, injection pressure influenced the effects of TPGME addition on NO x emissions. Finally, HC and CO emissions were higher compared to baseline fuel likely due to the lower net heat of combustion of TPGME and the need to limit fuel-injection duration for valid optical measurements.« less

Experiments in DIII-D Toward Achieving Rapid Shutdown with Runaway Electron Suppression

NASA Astrophysics Data System (ADS)

Hollmann, E. M.

2009-11-01

For safe discharge shutdown in future large tokamaks in the event of an unavoidable disruption, it is important to develop rapid (˜ several ms)shutdown methods to avoid large runaway electron currents, which pose a serious threat to plasma facing components. Prevention of runaway current formation has been proposed by either increasing electron-electron collisionality with massive particle injection, or magnetically by using externally applied non-axisymmetric fields to increase radial diffusive losses of a runaway seed population. Experiments studying both approaches have been pursued in the DIII-D tokamak. For collisional suppression, three different rapid shutdown methods are being investigated: massive gas injection, massive shattered cryogenic pellet injection, and polystyrene shell pellet injection. First-of-kind demonstrations of fast shutdowns were produced by 3000 Torr-l (0.8-g) shattered D2 pellets and large, 10-mm diameter, 0.3-g polystyrene shell pellets filled with boron powder. The application of external magnetic perturbations shows promising preliminary results in suppressing seed runaway electrons, although lack of repeatability in the runaway seed term made these results challenging to interpret. Experiments have been performed to help understand how runaways form and are transported during rapid shutdown. These experiments confirm that the commonly used 0D loop voltage + Dreicer evaporation picture of runaway seed formation is not applicable here, with relativistic E > 0.5,MeV electrons forming before any external loop voltage appears. Present applications of 0D, 1D, and 2D models to the rapid shutdown and runaway confinement experiments, as well as preliminary extrapolations to ITER, will be discussed.

Injection molding of iPP samples in controlled conditions and resulting morphology

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

Sessa, Nino, E-mail: ninosessa.ns@gmail.com; De Santis, Felice, E-mail: fedesantis@unisa.it; Pantani, Roberto, E-mail: rpantani@unisa.it

2015-12-17

Injection molded parts are driven down in size and weight especially for electronic applications. In this work, an investigation was carried out on the process of injection molding of thin iPP samples and on the morphology of these parts. Melt flow in the mold cavity was analyzed and described with a mathematical model. Influence of mold temperature and injection pressure was analyzed. Samples orientation was studied using optical microscopy.

Microinjected magnetic beads induce curvature in Chara rhizoids

NASA Astrophysics Data System (ADS)

Scherp, P.; Hasenstein, K.

The gravitropic response of the Chara rhizoid is based on the interaction between the statoliths and the actin network located in the rhizoid apex. The rhizoid represents a model system for the study of gravitropism, because its apical cell contains the gravity sensing and response mechanism. In order to study the function of the statoliths and the cytoskeleton, we supplemented the naturally occurring statoliths with magnetic beads. These beads can be moved by an external magnetic field and they can be coated to interact with the cytoskeleton. The magnetic beads (1μm diameter) were injected close to the tip of the rhizoid in the presence of an external osmoticum to offset turgor pressure. The injection caused the formation of a noticeable plug of dense material at the site of impalement. After a recovery period of ca. 2 - 4 hours, the whole plant was mounted on the rotatable stage of a custom- built horizontal microscope, equipped with a long-working distance objective and a video camera. This stage is designed to reorientate the cell and/or the injected beads. In order to study the effect of the displacement of magnetic beads, an external magnetic field was applied. This external field was capable of displacing the magnetic particles but did not affect the natural statoliths. Work is in progress to quantify the response, to study the effect of microinjection on wall formation, and utilize coating of the beads to investigate their possible interaction with the original statoliths and with the microfilament network. Supported by NASA grant NAG 2- 1423.

Anatomy of the Cervicomental Region: Insights From an Anatomy Laboratory and Roundtable Discussion.

PubMed

Kenkel, Jeffrey M; Jones, Derek H; Fagien, Steven; Glaser, Dee Anna; Monheit, Gary D; Stauffer, Karen; Sykes, Jonathan M

2016-11-01

In 2015, ATX-101 (deoxycholic acid injection; Kybella in the United States and Belkyra in Canada; Kythera Biopharmaceuticals, Inc., Westlake Village, CA [an affiliate of Allergan plc, Dublin, Ireland]) was approved as a first-in-class injectable drug for reduction of submental fat. Use of a pharmacologic/injectable therapy within the submental region requires a thorough understanding of cervicomental anatomy to ensure proper injection technique and safe administration. To this end, an anatomy laboratory was conducted to review key external landmarks and important internal anatomic structures that characterize the lower face and anterior neck. External landmarks that define the boundaries of the cervicomental and submental regions were identified including the inferior mandibular border, the anterior border of the sternocleidomastoid muscle, the antegonial notch, the submental crease, the thyroid notch, and the hyoid bone. Relevant internal anatomic structures, including preplatysmal submental fat (the target tissue for ATX-101) and the platysma muscle as well as critical neurovascular and glandular tissues were revealed by dissection. Of particular interest was the marginal mandibular branch of the facial nerve because it typically courses along the inferior mandibular border near the proposed treatment area for ATX-101.

The changing phenomenology of drug death over the years.

PubMed

Bohnert, M; Hafezi, M; Pollak, S

2001-12-27

When inspecting the scene the circumstances under which a body is found and the findings on the body surface may give first clues to premortal drug abuse. Besides fresh and/or old injection marks tattoos, underweight and signs of physical neglect, especially after long-term abuse, are mentioned in literature. The incidence of such externally visible physical signs of drug abuse was systematically investigated in 100 consecutive drug deaths occurring from 1995 to 1997. Sixty-eight percent of the bodies were found in the apartments of the deceased or those of friends, 11% in public restrooms or the washrooms of restaurants. The so-called body dumping was seen in three cases. In 61% externally visible, fresh injection marks were found; on dissection of the subcutaneous veins, residues of previous injections were found in 95% of the cases. Tattoos were present in 63%. In 8% there was clear evidence of physical neglect. Eighty-six percent of the drug victims had a normal nutritional status.

Nonlinear and Nonequilibrium Spin Injection in Magnetic Tunneling Junctions

NASA Astrophysics Data System (ADS)

Guo, Hong

2007-03-01

Quantitative analysis of charge and spin quantum transport in spintronic devices requires an atomistic first principles approach that can handle nonlinear and nonequilibrium transport conditions. We have developed an approach for this purpose based on real space density functional theory (DFT) carried out within the Keldysh nonequilibrium Green's function formalism (NEGF). We report theoretical analysis of nonlinear and nonequilibrium spin injection and quantum transport in Fe/MgO/Fe trilayer structures as a function of external bias voltage. Devices with well relaxed atomic structures and with FeO oxidization layers are investigated as a function of external bias voltage. We also report calculations of nonequilibrium spin injection into molecular layers and graphene. Comparisons to experimental data will be presented. Work in collaborations with: Derek Waldron, Vladimir Timochevski (McGill University); Ke Xia (Institute of Physics, Chinese Academy of Science, Beijing, China); Eric Zhu, Jian Wang (University of Hong Kong); Paul Haney, and Allan MacDonald (University of Texas at Austin).

Characterization of ultrafast devices using novel optical techniques

NASA Astrophysics Data System (ADS)

Ali, Md Ershad

Optical techniques have been extensively used to examine the high frequency performance of a number of devices including High Electron Mobility Transistors (HEMTs), Heterojunction Bipolar Phototransistors (HPTs) and Low Temperature GaAs (LT-GaAs) Photoconductive Switches. To characterize devices, frequency and time domain techniques, namely optical heterodyning and electro-optic sampling, having measurement bandwidths in excess of 200 GHz, were employed. Optical mixing in three-terminal devices has been extended for the first time to submillimeter wave frequencies. Using a new generation of 50-nm gate pseudomorphic InP-based HEMTs, optically mixed signals were detected to 552 GHz with a signal-to-noise ratio of approximately 5 dB. To the best of our knowledge, this is the highest frequency optical mixing obtained in three- terminal devices to date. A novel harmonic three-wave detection scheme was used for the detection of the optically generated signals. The technique involved downconversion of the signal in the device by the second harmonic of a gate-injected millimeter wave local oscillator. Measurements were also conducted up to 212 GHz using direct optical mixing and up to 382 GHz using a fundamental three-wave detection scheme. New interesting features in the bias dependence of the optically mixed signals have been reported. An exciting novel development from this work is the successful integration of near-field optics with optical heterodyning. The technique, called near-field optical heterodyning (NFOH), allows for extremely localized injection of high-frequency stimulus to any arbitrary point of an ultrafast device or circuit. Scanning the point of injection across the sample provides details of the high frequency operation of the device with high spatial resolution. For the implementation of the technique, fiber-optic probes with 100 nm apertures were fabricated. A feedback controlled positioning system was built for accurate placement and scanning of the fiber probe with nanometric precision. The applicability of the NFOH technique was first confirmed by measurements on heterojunction phototransistors at 100 GHz. Later NFOH scans were performed at 63 GHz on two other important devices, HEMTs and LT-GaAs Photoconductive Switches. Spatially resolved response characteristics of these devices revealed interesting details of their operation.

FIBER AND INTEGRATED OPTICS: Integrated optical passive ring resonator for optical gyroscopes

NASA Astrophysics Data System (ADS)

Baĭborodin, Yu V.; Dyadin, S. S.; Lyadenko, A. F.; Mashchenko, A. I.; Ul'yanov, I. A.; Fatin, Yu L.

1992-02-01

A passive ring resonator based on channel waveguides, formed in a K8 glass substrate by diffusion ion exchange in molten potassium nitrate, was made and investigated. The waveguide structure of the resonator included a ring waveguide as well as two Y-type couplers, whose symmetric arms were coupled to the ring waveguide, whereas homogeneous arms were coupled to an external laser and a photodetector. The coupling of the external devices to the channel waveguides was implemented by prisms and butt (end face) contacts. The transfer function of the ring resonator was determined experimentally in order to illustrate its resonant properties and sharpness. Estimates were obtained of the ultimate sensitivity of an optical gyroscope utilizing a ring resonator with the properties described above and ways of improving this sensitivity were analyzed.

Measurements of high impedance two-terminal device with SMU NI PXIe-4139

NASA Astrophysics Data System (ADS)

Bogdanov, S. V.; Lelekov, E. T.; Kovalev, I. V.; Zelenkov, P. V.; Lelekov, A. T.

2016-11-01

To measure high-frequency and low-frequency impedance of betavoltaic power sources (it can be represented as two-terminal device), measurement stand was created. To measure high-frequency part need to inject external test signal through the current transformer with waveform generator and need to use external high-frequency current sensor, because of SMU PXIe-4139 current channel limitations.

Application of an Externally Applied Rotating Magnetic Field for Control of MHD Relaxation Phenomena in the HIST Spherical Torus Device

NASA Astrophysics Data System (ADS)

Kikuchi, Yusuke; Yoshikawa, Tatsuya; Nishioka, Tsutomu; Hashimoto, Shotaro; Fukumoto, Naoyuki; Nagata, Masayoshi

Application of an externally applied rotating magnetic field (RMF) for control of MHD relaxation phenomena driven by a coaxial helicity injection has been proposed in the HIST spherical torus device. In this letter, the plasma responses to the RMF evaluated by magnetic fields inside the plasma in HIST are shown.

A Piezoelectroluminescent Fiber-Optical Sensor for Diagnostics of the 3D Stress State in Composite Structures

NASA Astrophysics Data System (ADS)

Pan'kov, A. A.

2018-05-01

The mathematical model of a piezoelectroluminescent fiber-optical sensor is developed for diagnostics of the 3D stress state of composite structures. The sensor model is a coaxial sector-compound layered cylinder consisting of a central optical fiber with electroluminescent and piezoelectric layers and an external uniform elastic buffer layer. The electroluminescent and piezoelectric layers are separated by radial-longitudinal boundaries, common for both layers, into geometrically equal six "measuring elements" — cylindrical two-layered sectors. The directions of 3D polarization of the piezoelectric phases and the frequencies of luminous efficacy of the electroluminescent phases are different in each sector. In the sensor, a thin translucent "internal" controlling electrode is located between the optical fiber and the electroluminescent layer, and the piezoelectric layer is coated by a thin "external" controlling electrode. The results of numerical modeling of the nonuniform coupled electroelastic fields of the piezoelectroluminescent fiber-optical sensor in the loaded "representative volume" of a composite, taking into account the action of the controlling voltage on the internal and external electrodes, of a numerical calculation of "informative and controlling coefficients" of the sensor, and of testing of an arbitrary 3D stress of state of a unidirectional glass-fiber plastic by the finite-element method are presented.

Memory and Spin Injection Devices Involving Half Metals

DOE PAGES

Shaughnessy, M.; Snow, Ryan; Damewood, L.; ...

2011-01-01

We suggest memory and spin injection devices fabricated with half-metallic materials and based on the anomalous Hall effect. Schematic diagrams of the memory chips, in thin film and bulk crystal form, are presented. Spin injection devices made in thin film form are also suggested. These devices do not need any external magnetic field but make use of their own magnetization. Only a gate voltage is needed. The carriers are 100% spin polarized. Memory devices may potentially be smaller, faster, and less volatile than existing ones, and the injection devices may be much smaller and more efficient than existing spin injectionmore » devices.« less

Observations on the site and mode of action of pyrogens in the rabbit brain

PubMed Central

Cooper, K. E.; Cranston, W. I.; Honour, A. J.

1967-01-01

1. Leucocyte pyrogen has been injected bilaterally into various parts of the rabbit brain. It caused fever when injected into the pre-optic area and the anterior hypothalamus, but not when injected into the posterior hypothalamus, the mid-brain, the pons, the cerebellum or the cerebral cortex. 2. The mean time which elapsed between a leucocyte pyrogen injection into the anterior hypothalamus and the onset of fever was 7·8 min. For similar injections of bacterial pyrogen the time lag was 24·8 min. The mean time lag between bilateral injections of noradrenaline into the anterior hypothalamus and the onset of fever was 7·4 min. 3. The amount of leucocyte pyrogen required to cause fever when injected into the anterior hypothalamus was less than 1/100 of that required to cause a similar fever on intravenous injection. The quantity of bacterial pyrogen injected into the hypothalamus was of the same order as that which would cause a similar fever on intravenous injection. 4. Control injections of saline, plasma, cerebrospinal fluid, heated leucocyte pyrogen and red cells into the anterior hypothalamus did not cause fever. 5. After attempts to deplete the hypothalamus of its monoamine stores by intraventricular injections of reserpine, the rabbit had fever as a result of an intravenous injection of bacterial pyrogen. 6. We conclude that the anterior hypothalamus and the pre-optic area are sites at which leucocyte pyrogen acts to cause fever in the rabbit. The mechanism of this febrile response is not clear, but it appears that part, at least, of the response could be mediated by a mechanism other than release of noradrenaline or failure to release 5-HT. ImagesPlate 1 PMID:6050108

[Angioscanning in the diagnosis of breast neoplasms].

PubMed

Trishkin, V A; Fadeev, N P; Tetel'baum, B I; Dymarskiĭ, L Iu

1976-01-01

Angioscanning with macroalbumin J131 was performed in 30 patients with different mammary gland diseases (breast cancer--in 22, breast sarcoma--in 1, cystic fibroadenomatosis--in 6 and one patients without any breast pathology). Twenty eight of thirty patients were subjected to surgery, and the diagnosis was supported histologically. Injection of macroalbumin J131 in the subclavian artery enabled the authors to visualize malignant neoplasms, located mainly in the external quadrants of the mammary gland. The least size of the tumor, revealed by angioscanning, was 1.5 cm in diameter. The method of isotope injection directly in the subclavian artery, employed by the authors, may be recommended for patients, whose primary tumor is localized in the external half of the gland and in the axillary process.

Transport Simulations of DIII-D Discharges with Impurity Injection

NASA Astrophysics Data System (ADS)

Mandrekas, J.; Stacey, W. M.; Murakami, M.

2001-10-01

Several recent DIII-D discharges with external impurity injection into L-mode plasmas are analyzed with a coupled main plasma and multi-charge state 1frac 12-D impurity transport code. These discharges exhibit various degrees of confinement improvement, which has been attributed to the synergistic effects of impurity induced enhancement of the E×B shearing rate and reduction of the drift wave turbulence growth rate (M. Murakami, et. al., Nucl. Fusion 41) (2001) 317.. Impurity transport is described by empirical and neoclassical transport models. Both the standard neoclassical theory as well as an enhanced theory which takes into account the effects of external momentum input and radial momentum transport (W.M. Stacey, Phys. Plasmas 8) (2001) 158. have been considered.

Sample holder with optical features

DOEpatents

Milas, Mirko; Zhu, Yimei; Rameau, Jonathan David

2013-07-30

A sample holder for holding a sample to be observed for research purposes, particularly in a transmission electron microscope (TEM), generally includes an external alignment part for directing a light beam in a predetermined beam direction, a sample holder body in optical communication with the external alignment part and a sample support member disposed at a distal end of the sample holder body opposite the external alignment part for holding a sample to be analyzed. The sample holder body defines an internal conduit for the light beam and the sample support member includes a light beam positioner for directing the light beam between the sample holder body and the sample held by the sample support member.

Transmission electron microscope sample holder with optical features

DOEpatents

Milas, Mirko [Port Jefferson, NY; Zhu, Yimei [Stony Brook, NY; Rameau, Jonathan David [Coram, NY

2012-03-27

A sample holder for holding a sample to be observed for research purposes, particularly in a transmission electron microscope (TEM), generally includes an external alignment part for directing a light beam in a predetermined beam direction, a sample holder body in optical communication with the external alignment part and a sample support member disposed at a distal end of the sample holder body opposite the external alignment part for holding a sample to be analyzed. The sample holder body defines an internal conduit for the light beam and the sample support member includes a light beam positioner for directing the light beam between the sample holder body and the sample held by the sample support member.

Cavitation Inside High-Pressure Optically Transparent Fuel Injector Nozzles

NASA Astrophysics Data System (ADS)

Falgout, Z.; Linne, M.

2015-12-01

Nozzle-orifice flow and cavitation have an important effect on primary breakup of sprays. For this reason, a number of studies in recent years have used injectors with optically transparent nozzles so that orifice flow cavitation can be examined directly. Many of these studies use injection pressures scaled down from realistic injection pressures used in modern fuel injectors, and so the geometry must be scaled up so that the Reynolds number can be matched with the industrial applications of interest. A relatively small number of studies have shown results at or near the injection pressures used in real systems. Unfortunately, neither the specifics of the design of the optical nozzle nor the design methodology used is explained in detail in these papers. Here, a methodology demonstrating how to prevent failure of a finished design made from commonly used optically transparent materials will be explained in detail, and a description of a new design for transparent nozzles which minimizes size and cost will be shown. The design methodology combines Finite Element Analysis with relevant materials science to evaluate the potential for failure of the finished assembly. Finally, test results imaging a cavitating flow at elevated pressures are presented.

Quantitative evaluation of reduction of plaque-like hard exudates in diabetic macular edema after intravitreal triamcinolone injection.

PubMed

Cekiç, Osman; Bardak, Yavuz; Tiğ, U Sahin; Yildizoğlu, Uzeyir; Bardak, Handan

2008-04-01

To describe a new method of quantifying the amount of plaque-like hard exudates after intravitreal triamcinolone acetonide injection in diabetic macular edema. This study included 22 eyes of 14 patients (mean age, 63 years) with chronic diabetic macular edema and plaque-like hard exudates. The patients were injected with a single dose of 4 mg intravitreal triamcinolone acetonide. The optic disc size as relative size unit was taken to quantify the hard exudates: Total areas of exudates and the optic nerve head were computed from fundus pictures with a digital analysis program on magnified images. The former was divided by the latter, and the results were expressed as a percentage value. The ratio was used to track improvements in a given eye over 6 months. Average ratio of hard exudates to optic nerve head area reduced to 81% of its initial value at 1 month (P=0.007), to 54% at 3 months (P<0.001) and to 41% at 6 months (P<0.001). The new method allowed detection of a significant reduction of ratio of hard exudates to optic disc area of diabetic plaque-like hard exudates following 4 mg intravitreal triamcinolone.

Electron-Focus Adjustment for Photo-Optical Imagers

NASA Technical Reports Server (NTRS)

Fowler, Walter B.; Flemming, Keith; Ziegler, Michael M.

1987-01-01

Internal electron focus made independent of optical focus. Procedure enables fine tuning of internal electron-focusing system of photo-optical imager, without complication by imperfections of associated external optics. Applicable to imager in which electrons emitted from photocathode in optical focal plane, then electrostatically and/or magnetically focused to replica of image in second focal plane containing photodiodes, phototransistorss, charge-coupled devices, multiple-anode outputs, or other detectors.

Optical implementation of neural learning algorithms based on cross-gain modulation in a semiconductor optical amplifier

NASA Astrophysics Data System (ADS)

Li, Qiang; Wang, Zhi; Le, Yansi; Sun, Chonghui; Song, Xiaojia; Wu, Chongqing

2016-10-01

Neuromorphic engineering has a wide range of applications in the fields of machine learning, pattern recognition, adaptive control, etc. Photonics, characterized by its high speed, wide bandwidth, low power consumption and massive parallelism, is an ideal way to realize ultrafast spiking neural networks (SNNs). Synaptic plasticity is believed to be critical for learning, memory and development in neural circuits. Experimental results have shown that changes of synapse are highly dependent on the relative timing of pre- and postsynaptic spikes. Synaptic plasticity in which presynaptic spikes preceding postsynaptic spikes results in strengthening, while the opposite timing results in weakening is called antisymmetric spike-timing-dependent plasticity (STDP) learning rule. And synaptic plasticity has the opposite effect under the same conditions is called antisymmetric anti-STDP learning rule. We proposed and experimentally demonstrated an optical implementation of neural learning algorithms, which can achieve both of antisymmetric STDP and anti-STDP learning rule, based on the cross-gain modulation (XGM) within a single semiconductor optical amplifier (SOA). The weight and height of the potentitation and depression window can be controlled by adjusting the injection current of the SOA, to mimic the biological antisymmetric STDP and anti-STDP learning rule more realistically. As the injection current increases, the width of depression and potentitation window decreases and height increases, due to the decreasing of recovery time and increasing of gain under a stronger injection current. Based on the demonstrated optical STDP circuit, ultrafast learning in optical SNNs can be realized.

Diffractive optics in industry and research: novel components for optical security systems

NASA Astrophysics Data System (ADS)

Laakkonen, Pasi; Turunen, Jari; Pietarinen, Juha; Siitonen, Samuli; Laukkanen, Janne; Jefimovs, Konstantins; Orava, Joni; Ritala, Mikko; Pilvi, Tero; Tuovinen, Hemmo; Ventola, Kalle; Vallius, Tuomas; Kaipiainen, Matti; Kuittinen, Markku

2005-09-01

Design and manufacturing of diffractive optical elements (DOEs) are presented. Mass replication methods for DOEs are explained including UV-replication, micro-injection moulding and reel-to-reel production. Novel applications of diffractive optics including spectroscopic surface relief gratings, antireflection surfaces, infrared light rejection gratings, light incoupling into thin waveguides, and additive diffractive colour mixing are presented.

Progress to a Gallium-Arsenide Deep-Center Laser

PubMed Central

Pan, Janet L.

2009-01-01

Although photoluminescence from gallium-arsenide (GaAs) deep-centers was first observed in the 1960s, semiconductor lasers have always utilized conduction-to-valence-band transitions. Here we review recent materials studies leading to the first GaAs deep-center laser. First, we summarize well-known properties: nature of deep-center complexes, Franck-Condon effect, photoluminescence. Second, we describe our recent work: insensitivity of photoluminescence with heating, striking differences between electroluminescence and photoluminescence, correlation between transitions to deep-states and absence of bandgap-emission. Room-temperature stimulated-emission from GaAs deep-centers was observed at low electrical injection, and could be tuned from the bandgap to half-the-bandgap (900–1,600 nm) by changing the electrical injection. The first GaAs deep-center laser was demonstrated with electrical injection, and exhibited a threshold of less than 27 mA/cm2 in continuous-wave mode at room temperature at the important 1.54 μm fiber-optic wavelength. This small injection for laser action was explained by fast depopulation of the lower state of the optical transition (fast capture of free holes onto deep-centers), which maintains the population inversion. The evidence for laser action included: superlinear L-I curve, quasi-Fermi level separations satisfying Bernard-Duraffourg’s criterion, optical gains larger than known significant losses, clamping of the optical-emission from lossy modes unable to reach laser action, pinning of the population distribution during laser action.

Design of the central region for axial injection in the VINCY cyclotron

NASA Astrophysics Data System (ADS)

Milinković, Ljiljana; Toprek, Dragan

1996-02-01

This paper describes the design of the central region for h = 1, h = 2 and h = 4 modes of acceleration in the VINCY cyclotron. The result which is worth reported in that the central region is unique and compatible with the three above mentioned harmonic modes of operation. Only one spiral type inflector will be used. The central region is designed to operate with two external ion sources: (a) an ECR ion source with the maximum extraction voltage of 25 kV for heavy ions, and (b) a multicusp ion source with the maximum extraction voltage of 30 kV for H - and D - ions. Heavy ions will be accelerated by the second and fourth harmonics, D - ions by the second harmonic and H - ions by the first harmonic of the RF field. The central region is equipped with an axial injection system. The electric field distribution in the inflector and in the four acceleration gaps has been numerically calculated from an electric potential map produced by the program RELAX3D. The geometry of the central region has been tested with the computations of orbits carried out by means of the computer code CYCLONE. The optical properties of the spiral inflector and the central region were studied by using the programs CASINO and CYCLONE respectively. We have also made an effort to minimize the inflector fringe field using the RELAX3D program.

[Clinical randomized controlled trial on ultrashort wave and magnetic therapy for the treatment of early stage distal radius fractures].

PubMed

Wang, Guan-Jie; Liu, Jia

2012-07-01

To explore the effect of application of ultrashort wave and magnetic therapy instrument on the swelling regression in distal radius fractures treated by splint external fixation in initial stage. From March 2007 to May 2010,90 patients with distal radial fracture were treated by manual reduction and splint external fixation. After manual reduction and small splints external fixation, these patients were randomly divided into electrical physical therapy group, western medicine group and the control group by the order of calling number, with 30 cases each group. In control group, there were 9 males and 21 females with an average age of (61.29 +/- 1.97) years, the patients raised and exercise the limb and fingers only. The other two groups also carried out this treatment. In electrical physical therapy group, there were 9 males and 21 females with an average age of (62.37 +/- 2.48) years, the patients were treated with ultrashort wave and magnetic therapy instrument for early intervention, once a day, 5 days for a course of treatment and three cycle were operated. In western medicine group,there were 8 males and 22 females with an average age of (60.12 +/- 2.87) years, the patients were injected with beta-aescin (20 mg, intravenous injection,once a day) for 5 days, followed by Danshen injection (20 ml, intravenous injection, once a day) for 10 days. The limb swelling of patients were assessed every day for 20 days after manual reduction and small splints external fixation. The time of swelling regression in electrical physical therapy group, western medicine group and the control group were respectively (9.62 +/- 3.32), (10.05 +/- 3.05) and (14.57 +/- 2.93) days. Both of that in electrical physical therapy group and western medicine group were shorter than that in the control group (P<0.05), then there were not statistical difference between electrical physical therapy group and western medicine group (P>0.05). The effective rate of swelling regression in electrical physical therapy group, western medicine group and the control group were 86.67%, 80.00%, 46.66% respectively. There was no significant differences between electrical physical therapy group and western medicine group in the curative effect, but both of them had advantage over the control group. Application of ultrashort wave and magnetic therapy instrument for treatment of distal radial fractures in initial stage can promote the regression of limb swelling evidently, which is similar to the intravenous infusion of beta-aescin injection and Danshen injection in curative effect.

Theory of Magnetic Bipolar Transistors

NASA Astrophysics Data System (ADS)

Zutic, Igor; Fabian, Jaroslav; Das Sarma, S.

2003-03-01

We introduce the concept of a magnetic bipolar transistor (MBT) (J. Fabian, I. Zutic, S. Das Sarma, cond-mat/0211639.), which can be realized using already available materials. The transistor has at least one magnetic region (emitter, base, or collector) characterized by spin-splitting of the carrier bands. In addition, nonequilibrium (source) spin in MBTs can be induced by external means (electrically or optically). The theory of ideal MBTs is developed and discussed in the forward active regime where the transistors can amplify signals. It is shown that source spin can be injected from the emitter to the collector. It is predicted that electrical current gain (amplification) can be controlled effectively by magnetic field and source spin. If a base is a ferromagnetic semiconductor we suggest several methods for using spin-polarized bipolar transport (I. Zutic, J. Fabian, S. Das Sarma, Phys. Rev. Lett. f 88, 066603 (2002); J. Fabian, I. Zutic, S. Das Sarma, Phys. Rev. B f 66, 165301 (2002).) to manipulate semiconductor ferromagnetism.

Effect of external magnetic field on locking range of spintronic feedback nano oscillator

NASA Astrophysics Data System (ADS)

Singh, Hanuman; Konishi, K.; Bose, A.; Bhuktare, S.; Miwa, S.; Fukushima, A.; Yakushiji, K.; Yuasa, S.; Kubota, H.; Suzuki, Y.; Tulapurkar, A. A.

2018-05-01

In this work we have studied the effect of external applied magnetic field on the locking range of spintronic feedback nano oscillator. Injection locking of spintronic feedback nano oscillator at integer and fractional multiple of its auto oscillation frequency was demonstrated recently. Here we show that the locking range increases with increasing external magnetic field. We also show synchronization of spintronic feedback nano oscillator at integer (n=1,2,3) multiples of auto oscillation frequency and side band peaks at higher external magnetic field values. We have verified experimental results with macro-spin simulation using similar conditions as used for the experimental study.

Tracking Stripped Proton Particles in SNS Ring Injection Momentum Dump Line

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

Wang, Jian-Guang

3D computer simulations are performed to study magnetic field distributions and particle trajectories along the SNS ring injection momentum dump line. Optical properties and transfer maps along the dump line are calculated. The stripped proton particle distributions on the dump window are analyzed. The study has provided useful information for the redesign of the SNS ring injection beam dump.

Self-similar relativistic blast waves with energy injection

NASA Astrophysics Data System (ADS)

van Eerten, Hendrik

2014-08-01

A sufficiently powerful astrophysical source with power-law luminosity in time will give rise to a self-similar relativistic blast wave with a reverse shock travelling into the ejecta and a forward shock moving into the surrounding medium. Once energy injection ceases and the last energy is delivered to the shock front, the blast wave will transit into another self-similar stage depending only on the total amount of energy injected. I describe the effect of limited duration energy injection into environments with density depending on radius as a power law, emphasizing optical/X-ray Gamma-ray Burst afterglows as applications. The blast wave during injection is treated analytically, the transition following last energy injection with one-dimensional simulations. Flux equations for synchrotron emission from the forward and reverse shock regions are provided. The reverse shock emission can easily dominate, especially with different magnetizations for both regions. Reverse shock emission is shown to support both the reported X-ray and optical correlations between afterglow plateau duration and end time flux, independently of the luminosity power-law slope. The model is demonstrated by application to bursts 120521A and 090515, and can accommodate their steep post-plateau light-curve slopes.

Wavelength-controlled external-cavity laser with a silicon photonic crystal resonant reflector

NASA Astrophysics Data System (ADS)

Gonzalez-Fernandez, A. A.; Liles, Alexandros A.; Persheyev, Saydulla; Debnath, Kapil; O'Faolain, Liam

2016-03-01

We report the experimental demonstration of an alternative design of external-cavity hybrid lasers consisting of a III-V Semiconductor Optical Amplifier with fiber reflector and a Photonic Crystal (PhC) based resonant reflector on SOI. The Silicon reflector comprises a polymer (SU8) bus waveguide vertically coupled to a PhC cavity and provides a wavelength-selective optical feedback to the laser cavity. This device exhibits milliwatt-level output power and sidemode suppression ratio of more than 25 dB.

Intracavity dispersion effect on timing jitter of ultralow noise mode-locked semiconductor based external-cavity laser.

PubMed

Gee, S; Ozharar, S; Plant, J J; Juodawlkis, P W; Delfyett, P J

2009-02-01

We report the generation of optical pulse trains with 380 as of residual timing jitter (1 Hz-1 MHz) from a mode-locked external-cavity semiconductor laser, through a combination of optimizing the intracavity dispersion and utilizing a high-power, low-noise InGaAsP quantum-well slab-coupled optical waveguide amplifier gain medium. This is, to our knowledge, the lowest residual timing jitter reported to date from an actively mode-locked laser.

Reconfigurable dynamic all-optical chaotic logic operations in an optically injected VCSEL

NASA Astrophysics Data System (ADS)

Zhong, Dong-Zhou; Xu, Ge-Liang; Luo, Wei; Xiao, Zhen-Zhen

2017-12-01

Not Available Project supported by the National Natural Science Foundation of China (Grant No. 61475120) and the Innovative Projects in Guangdong Colleges and Universities, China (Grant No. 2015KTSCX146).

Rational harmonic mode-locking pulse quality of the dark-optical-comb injected semiconductor optical amplifier fiber ring laser.

PubMed

Lin, Gong-Ru; Lee, Chao-Kuei; Kang, Jung-Jui

2008-06-09

We study the rational harmonic mode-locking (RHML) order dependent pulse shortening force and dynamic chirp characteristics of a gain-saturated semiconductor optical amplifier fiber laser (SOAFL) under dark-optical-comb injection, and discuss the competition between mode-locking mechanisms in the SOAFL at high-gain and strong optical injection condition at higher RHML orders. The evolutions of spectra, mode-locking and continuous lasing powers by measuring the ratio of DC/pulse amplitude and the pulse shortening force (I(pulse)/P(avg)(2) ) are performed to determine the RHML capability of SOAFL. As the rational harmonic order increases up to 20, the spectral linewidth shrinks from 12 to 3 nm, the ratio of DC/pulse amplitude enlarges from 0.025 to 2.4, and the pulse-shortening force reduces from 0.9 to 0.05. At fundamental and highest RHML condition, we characterize the frequency detuning range to realize the mode-locking quality, and measure the dynamic frequency chirp of the RHML-SOAFL to distinguish the linear and nonlinear chirp after dispersion compensation. With increasing RHML order, the pulsewidth is broadened from 4.2 to 26.4 ps with corresponding chirp reducing from 0.7 to 0.2 GHz and linear/nonlinear chirp ratio changes from 4.3 to 1.3, which interprets the high-order chirp becomes dominates at higher RHML orders.

Querectin improves myelin repair of optic chiasm in lyolecithin-induced focal demyelination model.

PubMed

Naeimi, Reza; Baradaran, Saeideh; Ashrafpour, Manouchehr; Moghadamnia, Ali Akbar; Ghasemi-Kasman, Maryam

2018-05-01

Although the beneficial effects of quercetin on oligodendrocyte precursor cell (OPCs) population has been evaluated in-vitro, there are few studies about the effects of quercetin on myelin repair in the context of demyelination. The aim of this study was to investigate the effects of querectin on functional recovery and myelin repair of optic chiasm in lysolecithin (LPC)-induced demyelination model. Demyelination was induced by local injection of LPC 1% (2 μl) into rat optic chiasm. Querectin at doses 25 or 50 mg/kg was administrated daily by oral gavage for 7 or 14 days post LPC. Visual evoked potential (VEPs) recordings were used to assess the functional property of the optic pathway. Immunostaining and myelin staining were performed on brain sections 7 or 14 days post lesion. Electrophysiological data indicated that LPC injection increased the latency of VEPs waves and quercetin effectively reduced the delay of visual signals. The level of glial activation was alleviated in animals under treatment of quercetin compared to vehicle group. Furthermore, quercetin treatment decreased the extent of demyelination areas and increased the remyelination process following LPC injection. Overall, our findings indicate that quercetin could remarkably improve the functional recovery of the optic pathway by its protective effects on myelin sheath and attenuation of glial activation. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Femtosecond wavelength tunable semiconductor optical amplifier fiber laser mode-locked by backward dark-optical-comb injection at 10 GHz.

PubMed

Lin, Gong-Ru; Chiu, I-Hsiang

2005-10-31

Femtosecond nonlinear pulse compression of a wavelength-tunable, backward dark-optical-comb injection harmonic-mode-locked semiconductor optical amplifier based fiber laser (SOAFL) is demonstrated for the first time. Shortest mode-locked SOAFL pulsewidth of 15 ps at 1 GHz is generated, which can further be compressed to 180 fs after linear chirp compensation, nonlinear soliton compression, and birefringent filtering. A maximum pulsewidth compression ratio for the compressed eighth-order SOAFL soliton of up to 80 is reported. The pedestal-free eighth-order soliton can be obtained by injecting the amplified pulse with peak power of 51 W into a 107.5m-long single-mode fiber (SMF), providing a linewidth and time-bandwidth product of 13.8 nm and 0.31, respectively. The tolerance in SMF length is relatively large (100-300 m) for obtaining <200fs SOAFL pulsewidth at wavelength tuning range of 1530-1560 nm. By extending the repetition frequency of dark-optical-comb up to 10 GHz, the mode-locked SOAFL pulsewidth can be slightly shortened from 5.4 ps to 3.9 ps after dispersion compensating, and further to 560 fs after second-order soliton compression. The lasing linewidth, time-bandwidth product and pulsewidth suppressing ratio of the SOAFL soliton become 4.5 nm, 0.33, and 10, respectively.

Sustained Neuroprotection From a Single Intravitreal Injection of PGJ2 in a Nonhuman Primate Model of Nonarteritic Anterior Ischemic Optic Neuropathy

PubMed Central

Miller, Neil R.; Johnson, Mary A.; Nolan, Theresa; Guo, Yan; Bernstein, Alexander M.; Bernstein, Steven L.

2014-01-01

Purpose. Prostaglandin J2 (PGJ2) is neuroprotective in a murine model of nonarteritic anterior ischemic optic neuropathy (NAION). After assessing for potential toxicity, we evaluated the efficacy of a single intravitreal (IVT) injection of PGJ2 in a nonhuman primate model of NAION (pNAION). Methods. We assessed PGJ2 toxicity by administering it as a single high-dose intravenous (IV) injection, consecutive daily high-dose IV injections, or a single IVT injection in one eye of five adult rhesus monkeys. To assess efficacy, we induced pNAION in one eye of five adult male rhesus monkeys using a laser-activated rose bengal induction method. We then injected the eye with either PGJ2 or phosphate-buffered saline (PBS) intravitreally immediately or 5 hours post induction. We performed a clinical assessment, optical coherence tomography, electrophysiological testing, fundus photography, and fluorescein angiography in all animals prior to induction and at 1 day, 1 week, 2 weeks, and 4 weeks after induction. Following analysis of the first eye, we induced pNAION in the contralateral eye and then injected either PGJ2 or PBS. We euthanized all animals 5 weeks after final assessment of the fellow eye and performed both immunohistochemical and light and electron microscopic analyses of the retina and optic nerves. Results. Toxicity: PGJ2 caused no permanent systemic toxicity regardless of the amount injected or route of delivery, and there was no evidence of any ocular toxicity with the dose of PGJ2 used in efficacy studies. Transient reduction in the amplitudes of the visual evoked potentials and the N95 component of the pattern electroretinogram (PERG) occurred after both IV and IVT administration of high doses of PGJ2; however, the amplitudes returned to normal in all animals within 1 week. Efficacy: In all eyes, a single IVT dose of PGJ2 administered immediately or shortly after induction of pNAION resulted in a significant reduction of clinical, electrophysiological, and histological damage compared with vehicle-injected eyes (P = 0.03 for both VEP and PERG; P = 0.05 for axon counts). Conclusions. In nonhuman primates, PGJ2 administered either intravenously or intravitreally produces no permanent toxicity at even four times the dose given for neuroprotection. Additionally, a single IVT dose of PGJ2 is neuroprotective when administered up to 5 hours after induction of pNAION. PMID:25298416

Navigation-guided optic canal decompression for traumatic optic neuropathy: Two case reports.

PubMed

Bhattacharjee, Kasturi; Serasiya, Samir; Kapoor, Deepika; Bhattacharjee, Harsha

2018-06-01

Two cases of traumatic optic neuropathy presented with profound loss of vision. Both cases received a course of intravenous corticosteroids elsewhere but did not improve. They underwent Navigation guided optic canal decompression via external transcaruncular approach, following which both cases showed visual improvement. Postoperative Visual Evoked Potential and optical coherence technology of Retinal nerve fibre layer showed improvement. These case reports emphasize on the role of stereotactic navigation technology for optic canal decompression in cases of traumatic optic neuropathy.

The Dirac-Moshinsky oscillator coupled to an external field and its connection to quantum optics

NASA Astrophysics Data System (ADS)

Torres, Juan Mauricio; Sadurní, Emerson; Seligman, Thomas H.

2010-12-01

The Dirac-Moshinsky oscillator is an elegant example of an exactly solvable quantum relativistic model that under certain circumstances can be mapped onto the Jaynes-Cummings model in quantum optics. In this work we show, how to do this in detail. Then we extend it by considering its coupling with an external (isospin) field and find the conditions that maintain solvability. We use this extended system to explore entanglement in relativistic systems and then identify its quantum optical analog: two different atoms interacting with an electromagnetic mode. We show different aspects of entanglement which gain relevance in this last system, which can be used to emulate the former.

Analytic Optimization of Near-Field Optical Chirality Enhancement

PubMed Central

2017-01-01

We present an analytic derivation for the enhancement of local optical chirality in the near field of plasmonic nanostructures by tuning the far-field polarization of external light. We illustrate the results by means of simulations with an achiral and a chiral nanostructure assembly and demonstrate that local optical chirality is significantly enhanced with respect to circular polarization in free space. The optimal external far-field polarizations are different from both circular and linear. Symmetry properties of the nanostructure can be exploited to determine whether the optimal far-field polarization is circular. Furthermore, the optimal far-field polarization depends on the frequency, which results in complex-shaped laser pulses for broadband optimization. PMID:28239617

Single-mode, narrow-linewidth external cavity quantum cascade laser through optical feedback from a partial-reflector.

PubMed

Cendejas, Richard A; Phillips, Mark C; Myers, Tanya L; Taubman, Matthew S

2010-12-06

An external-cavity (EC) quantum cascade (QC) laser using optical feedback from a partial-reflector is reported. With this configuration, the otherwise multi-mode emission of a Fabry-Perot QC laser was made single-mode with optical output powers exceeding 40 mW. A mode-hop free tuning range of 2.46 cm(-1) was achieved by synchronously tuning the EC length and QC laser current. The linewidth of the partial-reflector EC-QC laser was measured for integration times from 100 μs to 4 seconds, and compared to a distributed feedback QC laser. Linewidths as small as 480 kHz were recorded for the EC-QC laser.

BRAZILIAN BOOTY RETINOPATHY: PURTSCHER-LIKE RETINOPATHY WITH PARACENTRAL ACUTE MIDDLE MACULOPATHY ASSOCIATED WITH PMMA INJECTION INTO BUTTOCKS.

PubMed

Khatibi, Azadeh

2018-01-01

To report a case of Purtscher-like retinopathy with paracentral acute middle maculopathy preceded by febrile illness after filler injection into the buttock muscles bilaterally for cosmesis to achieve a "Brazilian booty." Retrospective case report. A 35-year-old female presented with febrile illness and then decreased vision after repeat polymethyl methacrylate injections into her buttock muscles in Mexico. Examination was significant for retinal whitening, especially in the perifoveal areas, and intraretinal hemorrhages. Optical coherence tomography and fluorescein angiography imaging were consistent with small-vessel ischemic disease in the retina and choroid. Once systemic infection was ruled out, patient was treated with high-dose intravenous and then oral steroids. Vision recovery was good, with retinal atrophy on optical coherence tomography in the previous areas of retinal whitening. A Purtscher-like retinopathy with paracentral acute middle maculopathy and loss of vision may occur after filler injection below the neck, not just the face. This is the first report of vision loss caused by filler injected outside the face.

Advanced processing methods to introduce and preserve dipole orientation in organic electro-optic materials for next generation photonic devices

NASA Astrophysics Data System (ADS)

Huang, Su

Organic electro-optic (E-O) materials have attracted considerable research attention in the past 20 years due to their rising potentials in a lot of novel photonic applications, such as high-speed telecommunication, terahertz generation and ultra-fast optical interconnections. Chapter 2 of this dissertation focuses on a barrier layer approach to improve the poling efficiency of electro-optic polymers. First of all, high conduction current from excessive charge injection is identified as a fundamental challenge of effective poling. After analyzing the conduction mechanism, we introduce a sol-gel derived thin titanium dioxide (TiO2) layer that can significantly block excessive charge injection and reduce the leakage current during high field poling. Ultralarge E-O coefficients, up to 160-350 pm/V at 1310 nm have been achieved by poling with such a barrier, which are 26%-40% higher than the results poled without such a TiO2 layer. This enhancement is explained by the suppressed charge injection and space charge accumulation by the insertion of the high injection barrier from the TiO2 barrier layer. In Chapter 3, the impact of the inserted barrier layer on the temporal alignment stability of E-O polymers is discussed. Considerable stability enhancement is confirmed using both standard 500-hour temporal alignment stability test at 85 °C and thermally stimulated discharge method. We suggest that the enhancement comes from improved stability of the screening charge. During poling the additional barrier layer helps to lower the injection and thus the space charge accumulation. And this reduced space charge accumulation further helps to replace the space charge part in the total formulation of screening charge with more stable interface trapped charge. We thus expand this knowledge to a group of other materials that can also block excessive charge injection and suppressed space charge accumulation, including dielectric polymers polyvinyl alcohol (PVA), poly(4-vinylphenol) (PVP) and TOPAS as well as ferroelectric polymer poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE), 65/35 copolymer), which differ largely from the others in dielectric constant, conductivity and surface properties. The only common feature of them is that they all lowered the charge injection and leakage current for 1-2 orders during poling. On every buffer layer we tried, similar trend of stability enhancement is found. These results suggest that the observed temporal stability enhancement is indeed an effect from the abovementioned mechanism. Chapter 4 focuses on the development of an innovative new poling method, which utilizes pyroelectric effect instead of external power sources to overcome the limitations of conventional contact poling and corona poling. With careful theory assisted design, we developed a reliable protocol to efficiently introduce dipole orientation in organic E-O materials by heating and cooling them with detachable pyroelectric crystals. This new method can potentially improve the process adaptability of organic E-O materials in a variety of photonic devices. Large Pockels coefficients (up to 81 pm/V at 1.3 micron) have been successfully achieved in thin films poled using this method. The effective fields in these experiments are estimated to be around 0.5 to 0.9 MV/cm, which agree well with the electrostatics analysis using an idealized model. The same method is directly applied to surface modified hybrid polymer silicon slot waveguide ring-resonator modulators devices. A 25 pm/V tunability of resonance peak wavelength shift has been realized, which was higher than any reported results in similar devices. Chapter 5 discusses about the possible application of the pyroelectric poling in a multi-stack waveguide device architecture. A long-existing challenge to pole E-O polymer based photonic devices is how to effectively drop the poling voltage to the core layer, which is usually sandwiched between two dielectric claddings. In the past, this was done by using relatively conductive claddings, which on the other hand can bring larger optical loss and dielectric loss to the waveguide. Thus careful engineering compromise must be made between better poling efficiency and lower loss. Pyroelectric poling as discussed in Chapter 4 opens up new possibilities. In this chapter, it is demonstrated that E-O polymer films can be poled even with 3 orders thicker dielectric layer in circuit using pyroelectric poling. The theoretical analysis matches well with the experimental results. (Abstract shortened by UMI.).

Injection molding lens metrology using software configurable optical test system

NASA Astrophysics Data System (ADS)

Zhan, Cheng; Cheng, Dewen; Wang, Shanshan; Wang, Yongtian

2016-10-01

Optical plastic lens produced by injection molding machine possesses numerous advantages of light quality, impact resistance, low cost, etc. The measuring methods in the optical shop are mainly interferometry, profile meter. However, these instruments are not only expensive, but also difficult to alignment. The software configurable optical test system (SCOTS) is based on the geometry of the fringe refection and phase measuring deflectometry method (PMD), which can be used to measure large diameter mirror, aspheric and freeform surface rapidly, robustly, and accurately. In addition to the conventional phase shifting method, we propose another data collection method called as dots matrix projection. We also use the Zernike polynomials to correct the camera distortion. This polynomials fitting mapping distortion method has not only simple operation, but also high conversion precision. We simulate this test system to measure the concave surface using CODE V and MATLAB. The simulation results show that the dots matrix projection method has high accuracy and SCOTS has important significance for on-line detection in optical shop.

Investigation of numerical simulation on all-optical flip-flop stability maps of 1550nm vertical-cavity surface-emitting laser

NASA Astrophysics Data System (ADS)

Li, Jun; Xia, Qing; Wang, Xiaofa

2017-10-01

Based on the extended spin-flip model, the all-optical flip-flop stability maps of the 1550nm vertical-cavity surface-emitting laser have been studied. Theoretical results show that excellent agreement is found between theoretical and the reported experimental results in polarization switching point current which is equal to 1.95 times threshold. Furthermore, the polarization bistable region is wide which is from 1.05 to 1.95 times threshold. A new method is presented that uses power difference between two linear polarization modes as the judging criterion of trigger degree and stability maps of all-optical flip-flop operation under different injection parameters are obtained. By alternately injecting set and reset pulse with appropriate parameters, the mutual conversion switching between two polarization modes is realized, the feasibility of all-optical flip-flop operation is checked theoretically. The results show certain guiding significance on the experimental study on all optical buffer technology.

Isolating the effects of reactivity stratification in reactivity-controlled compression ignition with iso-octane and n-heptane on a light-duty multi-cylinder engine

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

Wissink, Martin L.; Curran, Scott J.; Roberts, Greg

Reactivity-controlled compression ignition (RCCI) is a dual-fuel variant of low-temperature combustion that uses in-cylinder fuel stratification to control the rate of reactions occurring during combustion. Using fuels of varying reactivity (autoignition propensity), gradients of reactivity can be established within the charge, allowing for control over combustion phasing and duration for high efficiency while achieving low NO x and soot emissions. In practice, this is typically accomplished by premixing a low-reactivity fuel, such as gasoline, with early port or direct injection, and by direct injecting a high-reactivity fuel, such as diesel, at an intermediate timing before top dead center. Both themore » relative quantity and the timing of the injection(s) of high-reactivity fuel can be used to tailor the combustion process and thereby the efficiency and emissions under RCCI. While many combinations of high- and low-reactivity fuels have been successfully demonstrated to enable RCCI, there is a lack of fundamental understanding of what properties, chemical or physical, are most important or desirable for extending operation to both lower and higher loads and reducing emissions of unreacted fuel and CO. This is partly due to the fact that important variables such as temperature, equivalence ratio, and reactivity change simultaneously in both a local and a global sense with changes in the injection of the high-reactivity fuel. This study uses primary reference fuels iso-octane and n-heptane, which have similar physical properties but much different autoignition properties, to create both external and in-cylinder fuel blends that allow for the effects of reactivity stratification to be isolated and quantified. This study is part of a collaborative effort with researchers at Sandia National Laboratories who are investigating the same fuels and conditions of interest in an optical engine. Furthermore, this collaboration aims to improve our fundamental understanding of what fuel properties are required to further develop advanced combustion modes.« less

Isolating the effects of reactivity stratification in reactivity-controlled compression ignition with iso-octane and n-heptane on a light-duty multi-cylinder engine

DOE PAGES

Wissink, Martin L.; Curran, Scott J.; Roberts, Greg; ...

2017-10-09

Reactivity-controlled compression ignition (RCCI) is a dual-fuel variant of low-temperature combustion that uses in-cylinder fuel stratification to control the rate of reactions occurring during combustion. Using fuels of varying reactivity (autoignition propensity), gradients of reactivity can be established within the charge, allowing for control over combustion phasing and duration for high efficiency while achieving low NO x and soot emissions. In practice, this is typically accomplished by premixing a low-reactivity fuel, such as gasoline, with early port or direct injection, and by direct injecting a high-reactivity fuel, such as diesel, at an intermediate timing before top dead center. Both themore » relative quantity and the timing of the injection(s) of high-reactivity fuel can be used to tailor the combustion process and thereby the efficiency and emissions under RCCI. While many combinations of high- and low-reactivity fuels have been successfully demonstrated to enable RCCI, there is a lack of fundamental understanding of what properties, chemical or physical, are most important or desirable for extending operation to both lower and higher loads and reducing emissions of unreacted fuel and CO. This is partly due to the fact that important variables such as temperature, equivalence ratio, and reactivity change simultaneously in both a local and a global sense with changes in the injection of the high-reactivity fuel. This study uses primary reference fuels iso-octane and n-heptane, which have similar physical properties but much different autoignition properties, to create both external and in-cylinder fuel blends that allow for the effects of reactivity stratification to be isolated and quantified. This study is part of a collaborative effort with researchers at Sandia National Laboratories who are investigating the same fuels and conditions of interest in an optical engine. Furthermore, this collaboration aims to improve our fundamental understanding of what fuel properties are required to further develop advanced combustion modes.« less

Photonic Arbitrary Waveform Generation Technology

DTIC Science & Technology

2006-06-01

locked external- cavity semiconductor diode ring laser “, Optics Letters, Vol. 27, No. 9 , 719-721, (2002). [22] S. Gee, F. Quinlan, S. Ozharar... optical pulses that one is accustomed to. Modelocked semiconductor lasers are used to generate a set of phase locked optical frequencies on a periodic...The corresponding optical spectrum of the laser consists of a comb of periodically spaced, phase - locked

Electroforming of optical tooling in high-strength Ni-Co alloy

NASA Astrophysics Data System (ADS)

Stein, Berl

2003-05-01

Plastic optics are often mass produced by injection, compression or injection-compression molding. Optical quality molds can be directly machined in appropriate materials (tool steels, electroless nickel, aluminum, etc.), but much greater cost efficiency can be achieved with electroformed modl inserts. Traditionally, electroforming of optical quality mold inserts has been carried out in nickel, a material much softer than tool steels which, when hardened to 45 - 50 HRc usually exhibit high wear resistance and long service life (hundreds of thousands of impressions per mold). Because of their low hardness (< 20 HRc), nickel molds can produce only tens of thousands of parts before they are scrapped due to wear or accidental damage. This drawback prevented their wider usage in general plastic and optical mold making. Recently, NiCoForm has developed a proprietary Ni-CO electroforming bath combining the high strength and wear resistance of the alloy with the low stress and high replication fidelity typical of pure nickel electroforming. This paper will outline the approach to electroforming of optical quality tooling in low stress, high strength Ni-Co alloy and present several examples of electroformed NiColoy mold inserts.

Prescription, Dispensation, and Generic Medicine Replacement Ratios: Influence on Japanese Medicine Costs

PubMed Central

Yokoi, Masayuki; Tashiro, Takao

2016-01-01

This study used publicly available data to examine the effect of the separation of dispensing and prescribing medicines between pharmacists in pharmacies and doctors in medical institutions (the separation system) and the generic medicine replacement ratio on the cost of various medicines in Japanese prefectures. For Japanese medical institutions, participation in the separation system is optional. Consequently, the expansion rate of the separation system for each administrative district is highly variable. In our multiple regression analysis, the dependent variables were the costs of daily medicines, specifically, total, internal, external, and injection medicines, as well as medical devices, and the independent variables were the expansion rate of the separation system and generic medicine replacement ratio. The expansion rate of the separation system showed a significant negative partial correlation with the daily costs of total, internal, and injection medicines as well as medical devices. Moreover, the rate of replacing brand name medicines with generic medicines showed a significant negative partial correlation with the daily costs of total and internal medicines. However, external and injection medicines and medical devices did not because only a few or no generic products of these types were sold in the Japanese market. Otherwise, expansion of the separation system was effective in reducing medicine costs, except in the case of external medicines. This suggests that the cost efficiency effect of the separation system does not function all the time. PMID:26234979

Optical tweezers with 2.5 kHz bandwidth video detection for single-colloid electrophoresis

NASA Astrophysics Data System (ADS)

Otto, Oliver; Gutsche, Christof; Kremer, Friedrich; Keyser, Ulrich F.

2008-02-01

We developed an optical tweezers setup to study the electrophoretic motion of colloids in an external electric field. The setup is based on standard components for illumination and video detection. Our video based optical tracking of the colloid motion has a time resolution of 0.2ms, resulting in a bandwidth of 2.5kHz. This enables calibration of the optical tweezers by Brownian motion without applying a quadrant photodetector. We demonstrate that our system has a spatial resolution of 0.5nm and a force sensitivity of 20fN using a Fourier algorithm to detect periodic oscillations of the trapped colloid caused by an external ac field. The electrophoretic mobility and zeta potential of a single colloid can be extracted in aqueous solution avoiding screening effects common for usual bulk measurements.

Fabrication of Long Period Gratings by Periodically Removing the Coating of Cladding-Etched Single Mode Optical Fiber Towards Optical Fiber Sensor Development.

PubMed

Ascorbe, Joaquin; Corres, Jesus M; Del Villar, Ignacio; Matias, Ignacio R

2018-06-07

Here, we present a novel method to fabricate long period gratings using standard single mode optical fibers (SMF). These optical devices were fabricated in a three-step process, which consisted of etching the SMF, then coating it with a thin-film and, the final step, which involved removing sections of the coating periodically by laser ablation. Tin dioxide was chosen as the material for this study and it was sputtered using a pulsed DC sputtering system. Theoretical simulations were performed in order to select the appropriate parameters for the experiments. The responses of two different devices to different external refractive indices was studied, and the maximum sensitivity obtained was 6430 nm/RIU for external refractive indices ranging from 1.37 to 1.39.

Protective shield for an instrument probe

DOEpatents

Johnsen, Howard A.; Ross, James R.; Birtola, Sal R.

2004-10-26

A shield is disclosed that is particularly useful for protecting exposed optical elements at the end of optical probes used in the analysis of hazardous emissions in and around an industrial environment from the contaminating effects of those emissions. The instant invention provides a hood or cowl in the shape of a right circular cylinder that can be fitted over the end of such optical probes. The hood provides a clear aperture through which the probe can perform unobstructed analysis. The probe optical elements are protected from the external environment by passing a dry gas through the interior of the hood and out through the hood aperture in sufficient quantity and velocity to prevent any significant mixing between the internal and external environments. Additionally, the hood is provided with a cooling jacket to lessen the potential for damaging the probe due to temperature excursions.

Dynamics of shaping ultrashort optical dissipative solitary pulses in the actively mode-locked semiconductor laser with an external long-haul single-mode fiber cavity

NASA Astrophysics Data System (ADS)

Shcherbakov, Alexandre S.; Moreno Zarate, Pedro

2010-02-01

We describe the conditions of shaping regular trains of optical dissipative solitary pulses, excited by multi-pulse sequences of periodic modulating signals, in the actively mode-locked semiconductor laser heterostructure with an external long-haul single-mode silicon fiber exhibiting square-law dispersion, cubic Kerr nonlinearity, and linear optical losses. The presented model for the analysis includes three principal contributions associated with the modulated gain, optical losses, as well as linear and nonlinear phase shifts. In fact, the trains of optical dissipative solitary pulses appear within simultaneous presenting and a balance of mutually compensating interactions between the second-order dispersion and cubic-law Kerr nonlinearity as well as between active medium gain and linear optical losses in the combined cavity. Within such a model, a contribution of the nonlinear Ginzburg-Landau operator to shaping the parameters of optical dissipative solitary pulses is described via exploiting an approximate variational procedure involving the technique of trial functions. Finally, the results of the illustrating proof-of-principle experiments are briefly presented and discussed in terms of optical dissipative solitary pulses.

Photovoltaic dependence of photorefractive grating on the externally applied dc electric field

NASA Astrophysics Data System (ADS)

Maurya, M. K.; Yadav, R. A.

2013-04-01

Photovoltaic dependence of photorefractive grating (i.e., space-charge field and phase-shift of the index grating) on the externally applied dc electric field in photovoltaic-photorefractive materials has been investigated. The influence of photovoltaic field (EPhN), diffusion field and carrier concentration ratio r (donor/acceptor impurity concentration ratio) on the space-charge field (SCF) and phase-shift of the index grating in the presence and absence of the externally applied dc electric field have also been studied in details. Our results show that, for a given value of EPhN and r, the magnitude of the SCF and phase-shift of the index grating can be enhanced significantly by employing the lower dc electric field (EON<10) across the photovoltaic-photorefractive crystal and higher value of diffusion field (EDN>40). Such an enhancement in the magnitude of the SCF and phase-shift of the index grating are responsible for the strongest beam coupling in photovoltaic-photorefractive materials. This sufficiently strong beam coupling increases the two-beam coupling gain that may be exceed the absorption and reflection losses of the photovoltaic-photorefractive sample, and optical amplification can occur. The higher value of optical amplification in photovoltaic-photorefractive sample is required for the every applications of photorefractive effect so that technology based on the photorefractive effect such as holographic storage devices, optical information processing, acousto-optic tunable filters, gyro-sensors, optical modulators, optical switches, photorefractive-photovoltaic solitons, biomedical applications, and frequency converters could be improved.

Controlled Asymmetry of Einstein-Podolsky-Rosen Steering with an Injected Nondegenerate Optical Parametric Oscillator

NASA Astrophysics Data System (ADS)

Olsen, M. K.

2017-10-01

We propose and analyze a nonlinear optical apparatus in which the direction of asymmetric steering is controllable within the apparatus, rather than by adding noise to measurements. Using a nondegenerate parametric oscillator with an injected signal field, we show how the directionality and extent of the steering can be readily controlled for output modes that can be up to one octave apart. The two down-converted modes, which exhibit the greater violations of the steering inequalities, can also be controlled to exhibit asymmetric steering in some regimes.

Optical path design of phase contrast imaging on HL-2A tokamak

NASA Astrophysics Data System (ADS)

Qiyun, CHENG; Yi, YU; Shaobo, GONG; Min, XU; Tao, LAN; Wei, JIANG; Boda, YUAN; Yifan, WU; Lin, NIE; Rui, KE; Ting, LONG; Dong, GUO; Minyou, YE; Xuru, DUAN

2017-12-01

A phase contrast imaging (PCI) diagnostic has recently been developed on HL-2A tokamak. It can diagnose plasma density fluctuations with maximum wave number of 15 cm-1 and wave number resolution of 2 cm-1. The time resolution reaches 2 μs. A 10.6 μm CO2 laser is expanded to a beam with a diameter of 30 mm and injected into the plasma as an incident beam, injecting into plasma. The emerging scattered and unscattered beams are contrasted by a phase plate. The ideas of optical path design are presented in this paper, together with the parameters of the main optical components. The whole optical path of PCI is not only carefully designed, but also constructed on HL-2A. First calibration results show the ability of this system to catch plasma turbulence in a wide frequency domain.

Reset Tree-Based Optical Fault Detection

PubMed Central

Lee, Dong-Geon; Choi, Dooho; Seo, Jungtaek; Kim, Howon

2013-01-01

In this paper, we present a new reset tree-based scheme to protect cryptographic hardware against optical fault injection attacks. As one of the most powerful invasive attacks on cryptographic hardware, optical fault attacks cause semiconductors to misbehave by injecting high-energy light into a decapped integrated circuit. The contaminated result from the affected chip is then used to reveal secret information, such as a key, from the cryptographic hardware. Since the advent of such attacks, various countermeasures have been proposed. Although most of these countermeasures are strong, there is still the possibility of attack. In this paper, we present a novel optical fault detection scheme that utilizes the buffers on a circuit's reset signal tree as a fault detection sensor. To evaluate our proposal, we model radiation-induced currents into circuit components and perform a SPICE simulation. The proposed scheme is expected to be used as a supplemental security tool. PMID:23698267

Proton Injection into the Fermilab Integrable Optics Test Accelerator (IOTA)

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

Prebys, Eric; Antipov, Sergey; Piekarz, Henryk

The Integrable Optics Test Accelerator (IOTA) is an experimental synchrotron being built at Fermilab to test the concept of non-linear "integrable optics". These optics are based on a lattice including non-linear elements that satisfies particular conditions on the Hamiltonian. The resulting particle motion is predicted to be stable but without a unique tune. The system is therefore insensitive to resonant instabilities and can in principle store very intense beams, with space charge tune shifts larger than those which are possible in conventional linear synchrotrons. The ring will initially be tested with pencil electron beams, but this poster describes the ultimatemore » plan to install a 2.5 MeV RFQ to inject protons, which will produce tune shifts on the order of unity. Technical details will be presented, as well as simulations of protons in the ring.« less

Electrically tunable negative refraction in core/shell-structured nanorod fluids.

PubMed

Su, Zhaoxian; Yin, Jianbo; Guan, Yanqing; Zhao, Xiaopeng

2014-10-21

We theoretically investigate optical refraction behavior in a fluid system which contains silica-coated gold nanorods dispersed in silicone oil under an external electric field. Because of the formation of a chain-like or lattice-like structure of dispersed nanorods along the electric field, the fluid shows a hyperbolic equifrequency contour characteristic and, as a result, all-angle broadband optical negative refraction for transverse magnetic wave propagation can be realized. We calculate the effective permittivity tensor of the fluid and verify the analysis using finite element simulations. We also find that the negative refractive index can vary with the electric field strength and external field distribution. Under a non-uniform external field, the gradient refraction behavior can be realized.

ON THE ORIGIN OF THE {gamma}-RAY/OPTICAL LAGS IN LUMINOUS BLAZARS

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

Janiak, Mateusz; Sikora, Marek; Moderski, Rafal

2012-12-01

Blazars are strongly variable sources that occasionally show spectacular flares visible in various energy bands. These flares are often, but not always, correlated. In a number of cases, the peaks of optical flares are found to be somewhat delayed with respect to the {gamma}-ray peaks. One notable example of such a delay was found in 3C 279 by Hayashida et al. and interpreted as a result of steeper drop with a distance of the energy density of an external radiation field than of the magnetic energy density. In this paper, we demonstrate that, in general, depending on the respective energymore » density profile along the jet, such lags can have both signs and that they can take place for any ratio of these energy densities. We study the dependence of such lags on the ratio of these energy densities at a distance of a maximal energy dissipation in a jet, on their gradients, as well as on the time profile of the relativistic electron injection within the moving source. We show how prominent such lags can be, and their expected timescales. We suggest that studies of such lags can provide a powerful tool to resolve the structure of relativistic jets and their radiative environment. As an example we model the lag observed in 3C 279, showing that in this object the flare is produced at a distance of a few parsecs from the central black hole, consistent with our previous inferences based on the spectra and optical polarization properties.« less

Discharge-pumped cw gas lasers utilizing 'dressed-atom' gain media

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

Sorokin, P.P.; Glownia, J.H.; Hodgson, R.T.

The possibility of realizing an efficient gaseous laser-beam-generating medium that utilizes {lambda}-type coherently phased (i.e., 'dressed') atoms for the active laser species, but that does not inherently require the use of external laser beams for pumping, is explored. Specifically, it is investigated if multiphoton stimulated hyper-Raman scattering (SHRS) processes driven by fluorescence radiation generated in a continuous electrical discharge present within the vapor-containing cell could produce continuous-wave (cw) optical gain at the {lambda}-atom resonance frequencies {omega}{sub o} and {omega}{sub o}{sup '}. It is deduced that such gain could result from n-photon (n{>=}4) SHRS processes only if absorption of fluorescence pumpmore » light occurs in the first three transitions of the n-photon sequence representing the process unit step. Estimates of the amount of optical gain that could be produced in such a system indicate that it should be sufficient to allow multiwatt cw laser operation to occur on one set of {lambda} transitions connecting levels in a 'double-{lambda}' structure, with the pump light being discharge-produced fluorescence centered about the transitions of the other {lambda} pair. However, to initiate operation of such a device would require injection into the laser optical cavity of intense 'starter' laser pulses at both lasing frequencies. What should be an optimal experimental configuration for determining feasibility of the proposed laser device is described. In the suggested configuration, Cs-atom 6S{sub 1/2}-6P{sub 1/2} transitions form the double-{lambda} structure.« less

The Role of Dopant Ions on Charge Injection and Transport in Electrochemically Doped Quantum Dot Films.

PubMed

Gudjonsdottir, Solrun; van der Stam, Ward; Kirkwood, Nicholas; Evers, Wiel H; Houtepen, Arjan J

2018-05-16

Control over the charge density is very important for implementation of colloidal semiconductor nanocrystals into various optoelectronic applications. A promising approach to dope nanocrystal assemblies is charge injection by electrochemistry, in which the charge compensating electrolyte ions can be regarded as external dopant ions. To gain insight into the doping mechanism and the role of the external dopant ions, we investigate charge injection in ZnO nanocrystal assemblies for a large series of charge compensating electrolyte ions with spectroelectrochemical and electrochemical transistor measurements. We show that charge injection is limited by the diffusion of cations in the nanocrystal films as their diffusion coefficient are found to be ∼7 orders of magnitude lower than those of electrons. We further show that the rate of charge injection depends strongly on the cation size and cation concentration. Strikingly, the onset of electron injection varies up to 0.4 V, depending on the size of the electrolyte cation. For the small ions Li + and Na + the onset is at significantly less negative potentials. For larger ions (K + , quaternary ammonium ions) the onset is always at the same, more negative potential, suggesting that intercalation may take place for Li + and Na + . Finally, we show that the nature of the charge compensating cation does not affect the source-drain electronic conductivity and mobility, indicating that shallow donor levels from intercalating ions fully hybridize with the quantum confined energy levels and that the reorganization energy due to intercalating ions does not strongly affect electron transport in these nanocrystal assemblies.

The Role of Dopant Ions on Charge Injection and Transport in Electrochemically Doped Quantum Dot Films

PubMed Central

2018-01-01

Control over the charge density is very important for implementation of colloidal semiconductor nanocrystals into various optoelectronic applications. A promising approach to dope nanocrystal assemblies is charge injection by electrochemistry, in which the charge compensating electrolyte ions can be regarded as external dopant ions. To gain insight into the doping mechanism and the role of the external dopant ions, we investigate charge injection in ZnO nanocrystal assemblies for a large series of charge compensating electrolyte ions with spectroelectrochemical and electrochemical transistor measurements. We show that charge injection is limited by the diffusion of cations in the nanocrystal films as their diffusion coefficient are found to be ∼7 orders of magnitude lower than those of electrons. We further show that the rate of charge injection depends strongly on the cation size and cation concentration. Strikingly, the onset of electron injection varies up to 0.4 V, depending on the size of the electrolyte cation. For the small ions Li+ and Na+ the onset is at significantly less negative potentials. For larger ions (K+, quaternary ammonium ions) the onset is always at the same, more negative potential, suggesting that intercalation may take place for Li+ and Na+. Finally, we show that the nature of the charge compensating cation does not affect the source-drain electronic conductivity and mobility, indicating that shallow donor levels from intercalating ions fully hybridize with the quantum confined energy levels and that the reorganization energy due to intercalating ions does not strongly affect electron transport in these nanocrystal assemblies. PMID:29718666

Computation of H2/air reacting flowfields in drag-reduction external combustion

NASA Technical Reports Server (NTRS)

Lai, H. T.

1992-01-01

Numerical simulation and analysis of the solution are presented for a laminar reacting flowfield of air and hydrogen in the case of external combustion employed to reduce base drag in hypersonic vehicles operating at transonic speeds. The flowfield consists of a transonic air stream at a Mach number of 1.26 and a sonic transverse hydrogen injection along a row of 26 orifices. Self-sustained combustion is computed over an expansion ramp downstream of the injection and a flameholder, using the recently developed RPLUS code. Measured data is available only for surface pressure distributions and is used for validation of the code in practical 3D reacting flowfields. Pressure comparison shows generally good agreements, and the main effects of combustion are also qualitatively consistent with experiment.

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

Chen, S. L., E-mail: shuch@ist.hokudai.ac.jp; Takayama, J.; Murayama, A.

Time-resolved optical spin orientation spectroscopy was employed to investigate the temperature-dependent electron spin injection in In{sub 0.1}Ga{sub 0.9}As quantum well (QW) and In{sub 0.5}Ga{sub 0.5}As quantum dots (QDs) tunnel-coupled nanostructures with 4, 6, and 8 nm-thick GaAs barriers. The fast picosecond-ranged spin injection from QW to QD excited states (ES) was observed to speed up with temperature, as induced by pronounced longitudinal-optical (LO)-phonon-involved multiple scattering process, which contributes to a thermally stable and almost fully spin-conserving injection within 5–180 K. The LO-phonon coupling was also found to cause accelerated electron spin relaxation of QD ES at elevated temperature, mainly via hyperfine interactionmore » with random nuclear field.« less

Atmospheric Signatures and Effects of Space-based Relativistic Electron Beam Injection

NASA Astrophysics Data System (ADS)

Marshall, R. A.; Sanchez, E. R.; Kero, A.; Turunen, E. S.; Marsh, D. R.

2017-12-01

Future relativistic electron beam injection experiments have the potential to provide groundbreaking insights into the physics of wave-particle interactions and beam-neutral interactions, relevant to space physics and to fundamental plasma physics. However, these experiments are only useful if their signatures can be detected. In this work, we use a physics-based forward modeling framework to investigate the observable signatures of a relativistic beam interacting with the upper atmosphere. The modeling framework is based around the Electron Precipitation Monte Carlo (EPMC) model, used to simulate electron precipitation in the upper atmosphere. That model is coupled to physics-based models of i) optical emission production; ii) bremsstrahlung photon production and propagation; iii) D-region ion chemistry; and iv) VLF wave propagation in the Earth-ionosphere waveguide. Using these modeling tools, we predict the optical, X-ray, chemical, radar, and VLF signatures of a realistic beam injection, based on recent space-based accelerator designs. In particular, we inject a beam pulse of 10 mA for a duration of 500 μs at an energy of 1 MeV, providing a total pulse energy of 5 J. We further investigate variations in these parameters, in particular the total energy and the electron energy. Our modeling shows that for this 5 J pulse injection at 1 MeV electron energy, the optical signal is easily detectable from the ground in common emission bands, but the X-ray signal is likely too weak to be seen from either balloons or LEO orbiting spacecraft. We further predict the optical signal-to-noise ratio that would be expected in different optical systems. Chemical signatures such as changes to NOx and HOx concentrations are too short-lived to be detectable; however our modeling provides a valuable estimate of the total chemical response. Electron density perturbations should be easily measurable from ground-based high-power radars and via VLF subionospheric remote sensing. However, the VLF diagnostic is complicated by the geometry of the problem, in that the perturbation in the upper atmosphere is much smaller than the VLF wavelength, so wide-angle scattering needs to be taken into account.

Injection molded polymer optics in the 21st Century

NASA Astrophysics Data System (ADS)

Beich, William S.

2005-08-01

Precision polymer optics, manufactured by injection molding techniques, has been a key enabling technology for several decades now. The technology, which can be thought of as a subset of the wider field of precision optics manufacturing, was pioneered in the United States by companies such as Eastman Kodak, US Precision Lens, and Polaroid. In addition to suppliers in the U.S. there are several companies worldwide that design and manufacture precision polymer optics, for example Philips High Tech Plastics in Europe and Fujinon in Japan. Designers who are considering using polymer optics need a fundamental understanding of exactly how the optics are created. This paper will survey the technology and processes that are employed in the successful implementation of a polymer optic solution from a manufacturer's perspective. Special emphasis will be paid to the unique relationship between the molds and the optics that they produce. We will discuss the key elements of production: molding resins, molds and molding equipment, and metrology. Finally we will offer a case study to illustrate just how the optics designer carries a design concept through to production. The underlying theme throughout the discussion of polymer optics is the need for the design team to work closely with an experienced polymer optics manufacturer with a solid track record of success in molded optics. As will be seen shortly, the complex interaction between thermoplastics, molds, and molding machines dictates the need for working closely with a supplier who has the critical knowledge needed to manage all aspects of the program.

Clinical experience of external -route retinal detachment surgery under a surgical microscope.

PubMed

Xu, Hui

2014-03-01

To evaluate the efficacy of external-route retinal reattachment surgery under a surgical microscope. A total of 86 patients (86 eyes) with rhegmatogenous retinal detachment underwent external-route retinal detachment surgery under a surgical microscope. Drainage of subretinal fluid, transscleral cryotherapy, scleral buckling, and intravitreal injection of gas were performed intraoperatively. Among 85 patients, 81 achieved postoperative retinal re-attachment after the first surgery and 5 after two surgeries. The visual acuity was elevated in 67 patients, unchanged in 15, and decreased in 4. External-route retinal reattachment surgery under a surgical microscope is a convenient procedure for physicians to master and worthy of widespread application in clinical settings.

Tunable optical limiting optofluidic device filled with graphene oxide dispersion in ethanol

PubMed Central

Fang, Chaolong; Dai, Bo; Hong, Ruijin; Tao, Chunxian; Wang, Qi; Wang, Xu; Zhang, Dawei; Zhuang, Songlin

2015-01-01

An optofluidic device with tunable optical limiting property is proposed and demonstrated. The optofluidic device is designed for adjusting the concentration of graphene oxide (GO) in the ethanol solution and fabricated by photolithography technique. By controlling the flow rate ratio of the injection, the concentration of GO can be precisely adjusted so that the optical nonlinearity can be changed. The nonlinear optical properties and dynamic excitation relaxation of the GO/ethanol solution are investigated by using Z-scan and pump-probe measurements in the femtosecond regime within the 1.5 μm telecom band. The GO/ethanol solution presents ultrafast recovery time. Besides, the optical limiting property is in proportion to the concentration of the solution. Thus, the threshold power and the saturated power of the optical limiting property can be simply and efficiently manipulated by controlling the flow rate ratio of the injection. Furthermore, the amplitude regeneration is demonstrated by employing the proposed optofluidic device. The signal quality of intensity-impaired femtosecond pulse is significantly improved. The optofluidic device is compact and has long interaction length of optical field and nonlinear material. Heat can be dissipated in the solution and nonlinear material is isolated from other optical components, efficiently avoiding thermal damage and mechanical damage. PMID:26477662

Microfluidic Flows and Heat Transfer and Their Influence on Optical Modes in Microstructure Fibers

PubMed Central

Davies, Edward; Christodoulides, Paul; Florides, George; Kalli, Kyriacos

2014-01-01

A finite element analysis (FEA) model has been constructed to predict the thermo-fluidic and optical properties of a microstructure optical fiber (MOF) accounting for changes in external temperature, input water velocity and optical fiber geometry. Modeling a water laminar flow within a water channel has shown that the steady-state temperature is dependent on the water channel radius while independent of the input velocity. There is a critical channel radius below which the steady-state temperature of the water channel is constant, while above, the temperature decreases. However, the distance required to reach steady state within the water channel is dependent on both the input velocity and the channel radius. The MOF has been found capable of supporting multiple modes. Despite the large thermo-optic coefficient of water, the bound modes’ response to temperature was dominated by the thermo-optic coefficient of glass. This is attributed to the majority of the light being confined within the glass, which increased with increasing external temperature due to a larger difference in the refractive index between the glass core and the water channel. PMID:28788263

Non-local opto-electrical spin injection and detection in germanium at room temperature

NASA Astrophysics Data System (ADS)

Jamet, Matthieu; Rortais, Fabien; Zucchetti, Carlo; Ghirardini, Lavinia; Ferrari, Alberto; Vergnaud, Celine; Widiez, Julie; Marty, Alain; Attane, Jean-Philippe; Jaffres, Henri; George, Jean-Marie; Celebrano, Michele; Isella, Giovanni; Ciccacci, Franco; Finazzi, Marco; Bottegoni, Federico

Non-local charge carriers injection/detection schemes lie at the foundation of information manipulation in integrated systems. The next generation electronics may operate on the spin instead of the charge and germanium appears as the best hosting material to develop such spintronics for its compatibility with mainstream silicon technology and long spin lifetime at room temperature. Moreover, the energy proximity between the direct and indirect bandgaps allows for optical spin orientation. In this presentation, we demonstrate injection of pure spin currents in Ge, combined with non-local spin detection blocks at room temperature. Spin injection is performed either electrically through a magnetic tunnel junction (MTJ) or optically, by using lithographed nanostructures to diffuse the light and create an in-plane polarized electron spin population. Pure spin current detection is achieved using either a MTJ or the inverse spin-Hall effect across a Pt stripe. Supported by the ANR project SiGeSPIN #ANR-13-BS10-0002 and the CARIPLO project SEARCH-IV (Grant 2013-0623).

Influence of misalignments on the performance of externally occulted solar coronagraphs. Application to PROBA-3/ASPIICS

NASA Astrophysics Data System (ADS)

Shestov, S. V.; Zhukov, A. N.

2018-05-01

Context. The ASPIICS instrument is a novel externally occulted coronagraph that will be launched on board the PROBA-3 mission of the European Space Agency. The external occulter will be placed on one satellite 150 m ahead of the second satellite that will carry an optical instrument. During 6 h out of 19.38 h of orbit, the satellites will fly in a precise (accuracy around a few millimeters) formation, constituting a giant externally occulted coronagraph. The large distance between the external occulter and the primary objective will allow observations of the white-light solar corona starting from extremely low heights 1.1R⊙. Aims: We intend to analyze influence of shifts of the satellites and misalignments of optical elements on the ASPIICS performance in terms of diffracted light. Based on the quantitative influence of misalignments on diffracted light, we provide a recipe for choosing the size of the internal occulter (IO) to achieve a trade-off between the minimal height of observations and sustainability to possible misalignments. Methods: We considered different types of misalignments and analyzed their influence from optical and computational points of view. We implemented a numerical model of the diffracted light and its propagation through the optical system and computed intensities of diffracted light throughout the instrument. Our numerical approach is based on a model from the literature that considered the axisymmetrical case. Here we extend the model to include nonsymmetrical cases and possible misalignments. Results: The numerical computations fully confirm the main properties of the diffracted light that we obtained from semi-analytical consideration. We obtain that relative influences of various misalignments are significantly different. We show that the internal occulter with RIO = 1.694 mm = 1.1R⊙ is large enough to compensate possible misalignments expected to occur in PROBA-3/ASPIICS. Besides that we show that apodizing the edge of the internal occulter leads to additional suppression of the diffracted light. Conclusions: We conclude that the most important misalignment is the tilt of the telescope with respect to the line connecting the center of the external occulter and the entrance aperture. Special care should be taken to co-align the external occulter and the coronagraph, which means co-aligning the diffraction fringe from the external occulter and the internal occulter. We suggest that the best orientation strategy is to point the coronagraph to the center of the external occulter.

An electro-optical and electron injection study of benzothiazole-based squaraine dyes as efficient dye-sensitized solar cell materials: a first principles study.

PubMed

Al-Fahdan, Najat Saeed; Asiri, Abdullah M; Irfan, Ahmad; Basaif, Salem A; El-Shishtawy, Reda M

2014-12-01

Squaraine dyes have attracted significant attention in many areas of daily life from biomedical imaging to semiconducting materials. Moreover, these dyes are used as photoactive materials in the field of solar cells. In the present study, we investigated the structural, electronic, photophysical, and charge transport properties of six benzothiazole-based squaraine dyes (Cis-SQ1-Cis-SQ3 and Trans-SQ1-Trans-SQ3). The effect of electron donating (-OCH3) and electron withdrawing (-COOH) groups was investigated intensively. Ground state geometry and frequency calculations were performed by applying density functional theory (DFT) at B3LYP/6-31G** level of theory. Absorption spectra were computed in chloroform at the time-dependent DFT/B3LYP/6-31G** level of theory. The driving force of electron injection (ΔG (inject)), relative driving force of electron injection (ΔG r (inject)), electronic coupling constants (|VRP|) and light harvesting efficiency (LHE) of all six compounds were calculated and compared with previously studied sensitizers. The ΔG (inject), ΔG r (inject) and |VRP| of all six compounds revealed that these sensitizers would be efficient dye-sensitized solar cell materials. Cis/Trans-SQ3 exhibited superior LHE as compared to other derivatives. The Cis/Trans geometric effect was studied and discussed with regard to electro-optical and charge transport properties.

Effect of electron beam cooling on transversal and longitudinal emittance of an external proton beam

NASA Astrophysics Data System (ADS)

Kilian, K.; Machner, H.; Magiera, A.; Prasuhn, D.; von Rossen, P.; Siudak, R.; Stein, H. J.; Stockhorst, H.

2018-02-01

Benefits of electron cooling to the quality of extracted ion beams from storage rings are discussed. The transversal emittances of an external proton beam with and without electron cooling at injection energy are measured with the GEM detector assembly. While the horizontal emittance remains the vertical emittance shrinks by the cooling process. The longitudinal momentum variance is also reduced by cooling.

Analysis of heat-transfer measurements from 2 AEDC wind tunnels on the Shuttle external tank

NASA Technical Reports Server (NTRS)

Nutt, K. W.

1984-01-01

Previous aerodynamic heating tests have been conducted in the AEDC/VKF Supersonic Wind Tunnel (A) to aid in defining the design thermal environment for the space shuttle external tank. The quality of these data has been under discussion because of the effects of low tunnel enthalpy and slow model injection rates. Recently the AEDC/VKF Hypersonic Wind Tunnel (C) has been modified to provide a Mach 4 capability that has significantly higher tunnel enthalpy with more rapid model injection rates. Tests were conducted in Tunnel C at Mach 4 to obtain data on the external tank for comparison with Tunnel A results. Data were obtained on a 0.0175 scale model of the Space Shuttle Integrated Vehicle at Re/ft = 4 x 10 to the 6th power with the tunnel stagnation temperature varying from 740 to 1440 R. Model attitude varied from an angle of attack of -5 to 5 deg and an angle of sideslip of -3 to 3 deg. One set of data was obtained in Tunnel C at Re/ft = 6.9 x 10 to the 6th for comparison with flight data. Data comparisons between the two tunnels for numerous regions on the external tank are given.

Electro-optic harmonic conversion to switch a laser beam out of a cavity

DOEpatents

Haas, Roger A.; Henesian, Mark A.

1987-01-01

The invention is a switch to permit a laser beam to escape a laser cavity through the use of an externally applied electric field across a harmonic conversion crystal. Amplification takes place in the laser cavity, and then the laser beam is switched out by the laser light being harmonically converted with dichroic or polarization sensitive elements present to alter the optical path of the harmonically converted laser light. Modulation of the laser beam can also be accomplished by varying the external electric field.

Lithographic wavelength control of an external cavity laser with a silicon photonic crystal cavity-based resonant reflector.

PubMed

Liles, Alexandros A; Debnath, Kapil; O'Faolain, Liam

2016-03-01

We report the experimental demonstration of a new design for external cavity hybrid lasers consisting of a III-V semiconductor optical amplifier (SOA) with fiber reflector and a photonic crystal (PhC)-based resonant reflector on SOI. The silicon reflector is composed of an SU8 polymer bus waveguide vertically coupled to a PhC cavity and provides a wavelength-selective optical feedback to the laser cavity. This device exhibits milliwatt-level output power and side-mode suppression ratios of more than 25 dB.

Exciton-phonon bound complex in single-walled carbon nanotubes revealed by high-field magneto-optical spectroscopy

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

Zhou, Weihang; Nakamura, Daisuke; Takeyama, Shojiro, E-mail: takeyama@issp.u-tokyo.ac.jp

2013-12-02

High-field magneto-optical spectroscopy was performed on highly enriched (6,5) single-walled carbon nanotubes. Spectra of phonon sidebands in both 1st and 2nd sub-bands were unchanged by an external magnetic field up to 52 T. The dark K-momentum singlet (D-K-S) exciton, which plays an important role for the external quantum efficiency of the system for both sub-bands in the near-infrared and the visible light region, respectively, was clarified to be the origin of the phonon sidebands.

The Dirac-Moshinsky oscillator coupled to an external field and its connection to quantum optics

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

Torres, Juan Mauricio; Sadurni, Emerson; Seligman, Thomas H.

2010-12-23

The Dirac-Moshinsky oscillator is an elegant example of an exactly solvable quantum relativistic model that under certain circumstances can be mapped onto the Jaynes-Cummings model in quantum optics. In this work we show, how to do this in detail. Then we extend it by considering its coupling with an external (isospin) field and find the conditions that maintain solvability. We use this extended system to explore entanglement in relativistic systems and then identify its quantum optical analog: two different atoms interacting with an electromagnetic mode. We show different aspects of entanglement which gain relevance in this last system, which canmore » be used to emulate the former.« less

Investigation of optical pump on dielectric tunability in PZT/PT thin film by THz spectroscopy.

PubMed

Ji, Jie; Luo, Chunya; Rao, Yunkun; Ling, Furi; Yao, Jianquan

2016-07-11

The dielectric spectra of single-layer PbTiO₃ (PT), single-layer PbZr_xTi_1-xO₃ (PZT) and multilayer PZT/PT thin films under an external optical field were investigated at room temperature by time-domain terahertz (THz) spectroscopy. Results showed that the real part of permittivity increased upon application of an external optical field, which could be interpreted as hardening of the soft mode and increasing of the damping coefficient and oscillator strength. Furthermore, the central mode was observed in the three films. Among the dielectric property of the three thin films studied, the tunability of the PZT/PT superlattice was the largest.

Nine-channel mid-power bipolar pulse generator based on a field programmable gate array

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

Haylock, Ben, E-mail: benjamin.haylock2@griffithuni.edu.au; Lenzini, Francesco; Kasture, Sachin

Many channel arbitrary pulse sequence generation is required for the electro-optic reconfiguration of optical waveguide networks in Lithium Niobate. Here we describe a scalable solution to the requirement for mid-power bipolar parallel outputs, based on pulse patterns generated by an externally clocked field programmable gate array. Positive and negative pulses can be generated at repetition rates up to 80 MHz with pulse width adjustable in increments of 1.6 ns across nine independent outputs. Each channel can provide 1.5 W of RF power and can be synchronised with the operation of other components in an optical network such as light sourcesmore » and detectors through an external clock with adjustable delay.« less

Method for optical pumping of thin laser media at high average power

DOEpatents

Zapata, Luis E [Livermore, CA; Beach, Raymond J [Livermore, CA; Honea, Eric C [Sunol, CA; Payne, Stephen A [Castro Valley, CA

2004-07-13

A thin, planar laser material is bonded to a light guide of an index-matched material forming a composite disk. Diode array or other pump light is introduced into the composite disk through the edges of the disk. Pump light trapped within the composite disk depletes as it multi-passes the laser medium before reaching an opposing edge of the disk. The resulting compound optical structure efficiently delivers concentrated pump light and to a laser medium of minimum thickness. The external face of the laser medium is used for cooling. A high performance cooler attached to the external face of the laser medium rejects heat. Laser beam extraction is parallel to the heat flux to minimize optical distortions.

Characterization of the hyperfine interaction of the excited D50 state of Eu3 +:Y2SiO5

NASA Astrophysics Data System (ADS)

Cruzeiro, Emmanuel Zambrini; Etesse, Jean; Tiranov, Alexey; Bourdel, Pierre-Antoine; Fröwis, Florian; Goldner, Philippe; Gisin, Nicolas; Afzelius, Mikael

2018-03-01

We characterize the europium (Eu3 +) hyperfine interaction of the excited state (D50) and determine its effective spin Hamiltonian parameters for the Zeeman and quadrupole tensors. An optical free induction decay method is used to measure all hyperfine splittings under a weak external magnetic field (up to 10 mT) for various field orientations. On the basis of the determined Hamiltonian, we discuss the possibility to predict optical transition probabilities between hyperfine levels for the F70⟷D50 transition. The obtained results provide necessary information to realize an optical quantum memory scheme which utilizes long spin coherence properties of 3 + 151Eu :Y2SiO5 material under external magnetic fields.

Fiber optic sensors

NASA Technical Reports Server (NTRS)

Hesse, J.; Sohler, W.

1984-01-01

A survey of the developments in the field of fiber optics sensor technology is presented along with a discussion of the advantages of optical measuring instruments as compared with electronic sensors. The two primary types of fiber optics sensors, specifically those with multiwave fibers and those with monowave fibers, are described. Examples of each major sensor type are presented and discussed. Multiwave detectors include external and internal fiber optics sensors. Among the monowave detectors are Mach-Zender interferometers, Michelson interferometers, Sagnac interferometers (optical gyroscopes), waveguide resonators, and polarimeter sensors. Integrated optical sensors and their application in spectroscopy are briefly discussed.

A theoretical analysis of the electromagnetic environment of the AS330 super Puma helicopter external and internal coupling

NASA Technical Reports Server (NTRS)

Flourens, F.; Morel, T.; Gauthier, D.; Serafin, D.

1991-01-01

Numerical techniques such as Finite Difference Time Domain (FDTD) computer programs, which were first developed to analyze the external electromagnetic environment of an aircraft during a wave illumination, a lightning event, or any kind of current injection, are now very powerful investigative tools. The program called GORFF-VE, was extended to compute the inner electromagnetic fields that are generated by the penetration of the outer fields through large apertures made in the all metallic body. Then, the internal fields can drive the electrical response of a cable network. The coupling between the inside and the outside of the helicopter is implemented using Huygen's principle. Moreover, the spectacular increase of computer resources, as calculations speed and memory capacity, allows the modellization structures as complex as these of helicopters with accuracy. This numerical model was exploited, first, to analyze the electromagnetic environment of an in-flight helicopter for several injection configurations, and second, to design a coaxial return path to simulate the lightning aircraft interaction with a strong current injection. The E field and current mappings are the result of these calculations.

Analysis of roll-stamped light guide plate fabricated with laser-ablated stamper

NASA Astrophysics Data System (ADS)

Na, Hyunjun; Hong, Seokkwan; Kim, Jongsun; Hwang, Jeongho; Joo, Byungyun; Yoon, Kyunghwan; Kang, Jeongjin

2017-12-01

LGP (light guide plate) is one of the major components of LCD (liquid crystal display), and it makes surface illumination for LCD backlit. LGP is a transparent plastic plate usually produced by injection molding process. On the back of LGP there are micron size patterns for extraction of light. Recently a roll-stamping process has achieved the high mass productivity of thinner LGPs. In order to fabricate optical patterns on LGPs, a fabricating tool called as a stamper is used. Micro patterns on metallic stampers are made by several micro machining processes such as chemical etching, LIGA-reflow, and laser ablation. In this study, a roll-stamping process by using a laser ablated metallic stamper was dealt with in consideration of the compatibility with the roll-stamping process. LGP fabricating tests were performed using a roll-stamping process with four different roll pressures. Pattern shapes on the stamper fabricated by laser ablation and transcription ratios of the roll-stamping process were analyzed, and LGP luminance was evaluated. Based on the evaluation, optical simulation model for LGP was made and simulation accuracy was evaluated. Simulation results showed good agreements with optical performance of LGPs in the brightness and uniformity. It was also shown that the roll-stamped LGP has the possibility of better optical performance than the conventional injection molded LGP. It was also shown that the roll-stamped LGP with the laser ablated stamper is potential to have better optical performance than the conventional injection molded LGP.

A Novel, Real-Time, In Vivo Mouse Retinal Imaging System.

PubMed

Butler, Mark C; Sullivan, Jack M

2015-11-01

To develop an efficient, low-cost instrument for robust real-time imaging of the mouse retina in vivo, and assess system capabilities by evaluating various animal models. Following multiple disappointing attempts to visualize the mouse retina during a subretinal injection using commercially available systems, we identified the key limitation to be inadequate illumination due to off axis illumination and poor optical train optimization. Therefore, we designed a paraxial illumination system for Greenough-type stereo dissecting microscope incorporating an optimized optical launch and an efficiently coupled fiber optic delivery system. Excitation and emission filters control spectral bandwidth. A color coupled-charged device (CCD) camera is coupled to the microscope for image capture. Although, field of view (FOV) is constrained by the small pupil aperture, the high optical power of the mouse eye, and the long working distance (needed for surgical manipulations), these limitations can be compensated by eye positioning in order to observe the entire retina. The retinal imaging system delivers an adjustable narrow beam to the dilated pupil with minimal vignetting. The optic nerve, vasculature, and posterior pole are crisply visualized and the entire retina can be observed through eye positioning. Normal and degenerative retinal phenotypes can be followed over time. Subretinal or intraocular injection procedures are followed in real time. Real-time, intravenous fluorescein angiography for the live mouse has been achieved. A novel device is established for real-time viewing and image capture of the small animal retina during subretinal injections for preclinical gene therapy studies.

In Vivo Imaging of the Human Retinal Pigment Epithelial Mosaic Using Adaptive Optics Enhanced Indocyanine Green Ophthalmoscopy

PubMed Central

Tam, Johnny; Liu, Jianfei; Dubra, Alfredo; Fariss, Robert

2016-01-01

Purpose The purpose of this study was to establish that retinal pigment epithelial (RPE) cells take up indocyanine green (ICG) dye following systemic injection and that adaptive optics enhanced indocyanine green ophthalmoscopy (AO-ICG) enables direct visualization of the RPE mosaic in the living human eye. Methods A customized adaptive optics scanning light ophthalmoscope (AOSLO) was used to acquire high-resolution retinal fluorescence images of residual ICG dye in human subjects after intravenous injection at the standard clinical dose. Simultaneously, multimodal AOSLO images were also acquired, which included confocal reflectance, nonconfocal split detection, and darkfield. Imaging was performed in 6 eyes of three healthy subjects with no history of ocular or systemic diseases. In addition, histologic studies in mice were carried out. Results The AO-ICG channel successfully resolved individual RPE cells in human subjects at various time points, including 20 minutes and 2 hours after dye administration. Adaptive optics-ICG images of RPE revealed detail which could be correlated with AO dark-field images of the same cells. Interestingly, there was a marked heterogeneity in the fluorescence of individual RPE cells. Confirmatory histologic studies in mice corroborated the specific uptake of ICG by the RPE layer at a late time point after systemic ICG injection. Conclusions Adaptive optics-enhanced imaging of ICG dye provides a novel way to visualize and assess the RPE mosaic in the living human eye alongside images of the overlying photoreceptors and other cells. PMID:27564519

In Vivo Imaging of the Human Retinal Pigment Epithelial Mosaic Using Adaptive Optics Enhanced Indocyanine Green Ophthalmoscopy.

PubMed

Tam, Johnny; Liu, Jianfei; Dubra, Alfredo; Fariss, Robert

2016-08-01

The purpose of this study was to establish that retinal pigment epithelial (RPE) cells take up indocyanine green (ICG) dye following systemic injection and that adaptive optics enhanced indocyanine green ophthalmoscopy (AO-ICG) enables direct visualization of the RPE mosaic in the living human eye. A customized adaptive optics scanning light ophthalmoscope (AOSLO) was used to acquire high-resolution retinal fluorescence images of residual ICG dye in human subjects after intravenous injection at the standard clinical dose. Simultaneously, multimodal AOSLO images were also acquired, which included confocal reflectance, nonconfocal split detection, and darkfield. Imaging was performed in 6 eyes of three healthy subjects with no history of ocular or systemic diseases. In addition, histologic studies in mice were carried out. The AO-ICG channel successfully resolved individual RPE cells in human subjects at various time points, including 20 minutes and 2 hours after dye administration. Adaptive optics-ICG images of RPE revealed detail which could be correlated with AO dark-field images of the same cells. Interestingly, there was a marked heterogeneity in the fluorescence of individual RPE cells. Confirmatory histologic studies in mice corroborated the specific uptake of ICG by the RPE layer at a late time point after systemic ICG injection. Adaptive optics-enhanced imaging of ICG dye provides a novel way to visualize and assess the RPE mosaic in the living human eye alongside images of the overlying photoreceptors and other cells.

Exciton center-of-mass localization and dielectric environment effect in monolayer WS2

NASA Astrophysics Data System (ADS)

Hichri, Aïda; Ben Amara, Imen; Ayari, Sabrine; Jaziri, Sihem

2017-06-01

The ultrathin transition metal dichalcogenides (TMDs) have emerged as promising materials for various applications using two dimensional semiconductors. They have attracted increasing attention due to their unique optical properties originate from neutral and charged excitons. In this paper, we study the strong localization of exciton center-of-mass motion within random potential fluctuations caused by the monolayer defects. Here, we report negatively charged exciton formation in monolayer TMDs, notably tungsten disulfide WS2. Our theory is based on an effective mass model of neutral and charged excitons, parameterized by ab-initio calculations. Taking into the account the strong correlation between the monolayer WS2 and the surrounding dielectric environment, our theoretical results are in good agreement with one-photon photoluminescence (PL) and reflectivity measurements. We also show that the exciton state with p-symmetry, experimentally observed by two-photon PL emission, is energetically below the 2s-state. We use the equilibrium mass action law, to quantify the relative weight of exciton and trion PL. We show that exciton and trion emission can be tuned and controlled by external parameters like temperature, pumping, and injection electrons. Finally, in comparison with experimental measurements, we show that exciton emission in monolayer tungsten dichalcogenides is substantially reduced. This feature suggests that free exciton can be trapped in disordered potential wells to form a localized exciton and therefore offers a route toward novel optical properties.

Double-cross hydrostatic pressure sample injection for chip CE: variable sample plug volume and minimum number of electrodes.

PubMed

Luo, Yong; Wu, Dapeng; Zeng, Shaojiang; Gai, Hongwei; Long, Zhicheng; Shen, Zheng; Dai, Zhongpeng; Qin, Jianhua; Lin, Bingcheng

2006-09-01

A novel sample injection method for chip CE was presented. This injection method uses hydrostatic pressure, generated by emptying the sample waste reservoir, for sample loading and electrokinetic force for dispensing. The injection was performed on a double-cross microchip. One cross, created by the sample and separation channels, is used for formation of a sample plug. Another cross, formed by the sample and controlling channels, is used for plug control. By varying the electric field in the controlling channel, the sample plug volume can be linearly adjusted. Hydrostatic pressure takes advantage of its ease of generation on a microfluidic chip, without any electrode or external pressure pump, thus allowing a sample injection with a minimum number of electrodes. The potential of this injection method was demonstrated by a four-separation-channel chip CE system. In this system, parallel sample separation can be achieved with only two electrodes, which is otherwise impossible with conventional injection methods. Hydrostatic pressure maintains the sample composition during the sample loading, allowing the injection to be free of injection bias.

Vertical-Cavity Surface-Emitting Laser Diodes: Design, Growth, Mode Control and Integration by Fluidic Self-Assembly

NASA Astrophysics Data System (ADS)

Hadley, Mark Alfred

Some important problems to overcome in the design and fabrication of vertical-cavity surface-emitting laser diodes (VCSELs) are: narrow design tolerances, molecular beam epitaxy growth control and multiple transverse modes. This dissertation addresses each of these problems. First, optical, electrical and thermal design issues are discussed in detail. Second, a new growth method using the thermal emission from the substrate during growth is described which is used to accurately control the growth of multilayer structures. The third problem addressed is that of multiple transverse modes. For many applications it is desirable for a VCSEL to lase in the lowest-order transverse mode. In most structures, this only occurs at low powers. It is shown that an external cavity can be used to force a VCSEL to lase in a single transverse mode at all power levels. A new type of VCSEL, grown on a p-doped substrate in order to increase injection uniformity, is designed specifically for use in an external cavity. There are two types of external cavities used to control modes: a long external "macro-cavity" and a short external "micro-cavity." These external cavities have been used to obtain peak powers of over 100 mW while remaining in the fundamental mode under pulsed operation. Finally, a more general topic is researched. This topic, called fluidic self-assembly (FSA), is a new integration technique that can be used not only to integrate VCSELs on a separate substrate, but to integrate many different material systems and devices together on the same substrate. The basic concept of FSA is to make a large number of objects of a particular shape. On a separate substrate, holes that match the shape of the objects are also fabricated. By placing the substrate in an inert fluid containing the objects, and recirculating the fluid and the objects over the substrate, it is possible to fill the holes with correctly oriented objects. Results of a FSA study are reported in which 100% fill factors are obtained. Specifically, FSA was used to assemble two different sizes of silicon blocks into holes in a silicon substrate. Fabrication techniques as well as FSA results are included.

Optical coatings on polymers

NASA Astrophysics Data System (ADS)

Bauer, Thomas

2005-09-01

Optical transparent polymers are used for technical optics for more than 50 years and currently replace glass as optical material in several application fields. Optical functional coatings like mirrors, filters, beam splitters and anti-reflection coatings gain increasingly in importance. New light sources and head mounted systems need light and effective reflector designs. The paper gives an overview about vacuum coating technologies for metal and dielectric layers on polymers for technical optics. Especially for polymers controlling the complete process chain from injection moulding to storing, coating and shipping decides on the technological and commercial success.

Method for the protection of extreme ultraviolet lithography optics

DOEpatents

Grunow, Philip A.; Clift, Wayne M.; Klebanoff, Leonard E.

2010-06-22

A coating for the protection of optical surfaces exposed to a high energy erosive plasma. A gas that can be decomposed by the high energy plasma, such as the xenon plasma used for extreme ultraviolet lithography (EUVL), is injected into the EUVL machine. The decomposition products coat the optical surfaces with a protective coating maintained at less than about 100 .ANG. thick by periodic injections of the gas. Gases that can be used include hydrocarbon gases, particularly methane, PH.sub.3 and H.sub.2S. The use of PH.sub.3 and H.sub.2S is particularly advantageous since films of the plasma-induced decomposition products S and P cannot grow to greater than 10 .ANG. thick in a vacuum atmosphere such as found in an EUVL machine.

Circular polarization switching and bistability in an optically injected 1300 nm spin-vertical cavity surface emitting laser

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

Alharthi, S. S., E-mail: ssmalh@essex.ac.uk; Henning, I. D.; Adams, M. J.

We report the experimental observation of circular polarization switching (PS) and polarization bistability (PB) in a 1300 nm dilute nitride spin-vertical cavity surface emitting laser (VCSEL). We demonstrate that the circularly polarized optical signal at 1300 nm can gradually or abruptly switch the polarization ellipticity of the spin-VCSEL from right-to-left circular polarization and vice versa. Moreover, different forms of PS and PB between right- and left-circular polarizations are observed by controlling the injection strength and the initial wavelength detuning. These results obtained at the telecom wavelength of 1300 nm open the door for novel uses of spin-VCSELs in polarization sensitive applications in futuremore » optical systems.« less

Plasmonic gold nanostars as optical nano-additives for injection molded polymer composites

NASA Astrophysics Data System (ADS)

Boyne, Devon A.; Orlicki, Joshua A.; Walck, Scott D.; Savage, Alice M.; Li, Thomas; Griep, Mark H.

2017-10-01

Nanoscale engineering of noble metal particles has provided numerous material configurations to selectively confine and manipulate light across the electromagnetic spectrum. Transitioning these materials to a composite form while maintaining the desired resonance properties has proven challenging. In this work, the successful integration of plasmon-focusing gold nanostars (GNSs) into polymer nanocomposites (PNCs) is demonstrated. Tailored GNSs are produced with over a 90% yield and methods to control the branching structures are shown. A protective silica capping shell is employed on the nanomaterials to facilitate survivability in the high temperate/high shear processing parameters to create optically-tuned injection molded PNCs. The developed GNS PNCs possess dichroic scattering and absorption behavior, opening up potential applications in the fields of holographic imaging, optical filtering and photovoltaics.

Some engineering aspects of insulin delivery systems.

PubMed

Spencer, W J; Bair, R E; Carlson, G A; Love, J T; Urenda, R S; Eaton, R P; Schade, D S

1980-01-01

The characteristics of electronically controlled insulin delivery systems are presented. Early experiments with an external system have shown promise in providing improved glycemic control over conventional methods of single or multiple subcutaneous insulin injections. The encouraging results with external insulin delivery systems have led to the development and early testing in dogs of an implantable system with remote controls to permit variable insulin flow rates. A number of questions remain to be answered before widespread experimentation with external and implanted insulin delivery systems is possible. There appears to be no major development problems with the engineering aspects of such systems.

The research on surface characteristics of optical lens by 3D printing technique and precise diamond turning technique

NASA Astrophysics Data System (ADS)

Huang, Chien-Yao; Chang, Chun-Ming; Ho, Cheng-Fong; Lee, Tai-Wen; Lin, Ping-Hung; Hsu, Wei-Yao

2017-06-01

The advantage of 3D printing technique is flexible in design and fabrication. Using 3D printing technique, the traditional manufacturing limitations are not considered. The optical lens is the key component in an optical system. The traditional process to manufacture optical plastic lens is injection molding. However injection molding is only suitable for plastics lens, it cannot fabricate optical and mechanical components at same time. The assembly error of optical system can be reduced effectively with fabricating optical and mechanical components at same time. The process of printing optical and mechanical components simultaneously is proposed in previous papers, but the optical surface of printing components is not transparent. If we increase the transmittance of the optical surface, the printing components which fabricated by 3D printing process could be high transmission. Therefore, precise diamond turning technique has been used to turning the surface of 3D printing optical lens in this paper. The precise diamond turning techniques could process surfaces of components to meet the requirements of optical system. A 3D printing machine, Stratasys Connex 500, and a precise diamond turning machine, Precitech Freeform705XG, have been used in this paper, respectively. The dimension, roughness, transmission and printing types of 3D printing components have been discussed in this paper. After turning and polishing process, the roughness of 3D printing component is below 0.05 μm and the transmittance increase above 80 %. This optical module can be used in hand-held telescope and other system which need lens and special mechanical structure fabricated simultaneously.

125-mJ diode-pumped injection-seeded Ho:Tm:YLF laser.

PubMed

Yu, J; Singh, U N; Barnes, N P; Petros, M

1998-05-15

We describe a diode-pumped, room-temperature Ho:Tm:YLF power oscillator with an optical-to-optical efficiency of 0.03. A Q -switched output energy of as much as 125 mJ at 6 Hz with a pulse width of 170 ns was obtained. Single-frequency, nearly transform-limited operation of the laser was achieved by injection seeding. Laser performance as a function of laser rod temperature and pump intensity was also investigated. The high power and high beam quality of this laser make it well suited for use as a coherent wind lidar transmitter on a space platform.

Study of phase-locked diode laser array and DFB/DBR surface emitting laser diode

NASA Astrophysics Data System (ADS)

Hsin, Wei

New types of phased-array and surface-emitting lasers are designed. The importance and approaches (or structures) of different phased array and surface emitting laser diodes are reviewed. The following are described: (1) a large optical cavity channel substrate planar laser array with layer thickness chirping; (2) a vertical cavity surface emitter with distributed feedback (DFB) optical cavity and a transverse junction buried heterostructure; (3) a microcavity distributed Bragg reflector (DBR) surface emitter; and (4) two surface emitting laser structures which utilized lateral current injection schemes to overcome the problems occurring in the vertical injection scheme.

Compact surface plasmon resonance biosensor utilizing an injection-molded prism

NASA Astrophysics Data System (ADS)

Chen, How-Foo; Chen, Chih-Han; Chang, Yun-Hsiang; Chuang, Hsin-Yuan

2016-05-01

Targeting at a low cost and accessible diagnostic device in clinical practice, a compact surface plasmon resonance (SPR) biosensor with a large dynamic range in high sensitivity is designed to satisfy commercial needs in food safety, environmental bio-pollution monitoring, and fast clinical diagnosis. The core component integrates an optical coupler, a sample-loading plate, and angle-tuning reflectors is injection-molded as a free-from prism made of plastic optics. This design makes a matching-oil-free operation during operation. The disposability of this low-cost component ensures testing or diagnosis without cross contamination in bio-samples.

Tunable microwave signal generator with an optically-injected 1310 nm QD-DFB laser.

PubMed

Hurtado, Antonio; Mee, Jesse; Nami, Mohsen; Henning, Ian D; Adams, Michael J; Lester, Luke F

2013-05-06

Tunable microwave signal generation with frequencies ranging from below 1 GHz to values over 40 GHz is demonstrated experimentally with a 1310 nm Quantum Dot (QD) Distributed-Feedback (DFB) laser. Microwave signal generation is achieved using the period 1 dynamics induced in the QD DFB under optical injection. Continuous tuning in the positive detuning frequency range of the quantum dot's unique stability map is demonstrated. The simplicity of the experimental configuration offers promise for novel uses of these nanostructure lasers in Radio-over-Fiber (RoF) applications and future mobile networks.

A RSOA based full-duplex 80 channel CATV signal with 1.25 Gbps data-stream transmission system using optical carrier suppression and injection-locked FPLDs

NASA Astrophysics Data System (ADS)

Das, Anindya Sundar; Kuiri, Probodh Kumar; Patra, Ardhendu Sekhar

2015-06-01

In this paper a novel architecture has been proposed and developed for full-duplex transmission of 80 channel CATV signal over 80 km single mode fiber (SMF) using various techniques such as mutually injection locking, optical carrier suppression (OCS) and remodulation etc. The up/downlink transmission performances are observed by the low bit error rate (BER) values and impressive eye diagrams. The satisfactory values of CNR, CBT and CSO verify the successful transmission of CATV signals through our proposed configuration.

All optical logic for optical pattern recognition and networking applications

NASA Astrophysics Data System (ADS)

Khoury, Jed

2017-05-01

In this paper, we propose architectures for the implementation 16 Boolean optical gates from two inputs using externally pumped phase- conjugate Michelson interferometer. Depending on the gate to be implemented, some require single stage interferometer and others require two stages interferometer. The proposed optical gates can be used in several applications in optical networks including, but not limited to, all-optical packet routers switching, and all-optical error detection. The optical logic gates can also be used in recognition of noiseless rotation and scale invariant objects such as finger prints for home land security applications.

Picosecond ballistic imaging of diesel injection in high-temperature and high-pressure air

NASA Astrophysics Data System (ADS)

Duran, Sean P.; Porter, Jason M.; Parker, Terence E.

2015-04-01

The first successful demonstration of picosecond ballistic imaging using a 15-ps-pulse-duration laser in diesel sprays at temperature and pressure is reported. This technique uses an optical Kerr effect shutter constructed from a CS2 liquid cell and a 15-ps pulse at 532 nm. The optical shutter can be adjusted to produce effective imaging pulses between 7 and 16 ps. This technique is used to image the near-orifice region (first 3 mm) of diesel sprays from a high-pressure single-hole fuel injector. Ballistic imaging of dodecane and methyl oleate sprays injected into ambient air and diesel injection at preignition engine-like conditions are reported. Dodecane was injected into air heated to 600 °C and pressurized to 20 atm. The resulting images of the near-orifice region at these conditions reveal dramatic shedding of the liquid near the nozzle, an effect that has been predicted, but to our knowledge never before imaged. These shedding structures have an approximate spatial frequency of 10 mm-1 with lengths from 50 to 200 μm. Several parameters are explored including injection pressure, liquid fuel temperature, air temperature and pressure, and fuel type. Resulting trends are summarized with accompanying images.

Fiber optic cables for transmission of high-power laser pulses in spaceflight applications

NASA Astrophysics Data System (ADS)

Thomes, W. J.; Ott, M. N.; Chuska, R. F.; Switzer, R. C.; Blair, D. E.

2017-11-01

Lasers with high peak power pulses are commonly used in spaceflight missions for a wide range of applications, from LIDAR systems to optical communications. Due to the high optical power needed, the laser has to be located on the exterior of the satellite or coupled through a series of free space optics. This presents challenges for thermal management, radiation resistance, and mechanical design. Future applications will require multiple lasers located close together, which further complicates the design. Coupling the laser energy into a fiber optic cable allows the laser to be relocated to a more favorable position on the spacecraft. Typical fiber optic termination procedures are not sufficient for injection of these high-power laser pulses without catastrophic damage to the fiber endface. In the current study, we will review the causes of fiber damage during high-power injection and discuss our new manufacturing procedures that overcome these issues to permit fiber use with high reliability in these applications. We will also discuss the proper methods for launching the laser pulses into the fiber to avoid damage and how this is being implemented for current spaceflight missions.

Fiber Optic Cables for Transmission of High-Power Laser Pulses in Spaceflight Applications

NASA Technical Reports Server (NTRS)

Thomes, W. J., Jr.; Ott, M. N.; Chuska, R. F.; Switzer, R. C.; Blair, D. E.

2010-01-01

Lasers with high peak power pulses are commonly used in spaceflight missions for a wide range of applications, from LIDAR systems to optical communications. Due to the high optical power needed, the laser has to be located on the exterior of the satellite or coupled through a series of free space optics. This presents challenges for thermal management, radiation resistance, and mechanical design. Future applications will require multiple lasers located close together, which further complicates the design. Coupling the laser energy into a fiber optic cable allows the laser to be relocated to a more favorable position on the spacecraft. Typical fiber optic termination procedures are not sufficient for injection of these high-power laser pulses without catastrophic damage to the fiber endface. In the current study, we will review the causes of fiber damage during high-power injection and discuss our new manufacturing procedures that overcome these issues to permit fiber use with high reliability in these applications. We will also discuss the proper methods for launching the laser pulses into the fiber to avoid damage and how this is being implemented for current spaceflight missions.

Keloid scar (image)

MedlinePlus

... tissue at the site of a healed skin injury. They often create a thick, puckered effect simulating a tumor. Keloids may be reduced in size by freezing (cryotherapy), external pressure, corticosteroid injections, laser treatments, radiation, or surgical removal.

Superluminescence from an optically pumped molecular tunneling junction by injection of plasmon induced hot electrons

PubMed Central

Braun, Kai; Wang, Xiao; Kern, Andreas M; Adler, Hilmar; Peisert, Heiko; Chassé, Thomas; Zhang, Dai

2015-01-01

Summary Here, we demonstrate a bias-driven superluminescent point light-source based on an optically pumped molecular junction (gold substrate/self-assembled molecular monolayer/gold tip) of a scanning tunneling microscope, operating at ambient conditions and providing almost three orders of magnitude higher electron-to-photon conversion efficiency than electroluminescence induced by inelastic tunneling without optical pumping. A positive, steadily increasing bias voltage induces a step-like rise of the Stokes shifted optical signal emitted from the junction. This emission is strongly attenuated by reversing the applied bias voltage. At high bias voltage, the emission intensity depends non-linearly on the optical pump power. The enhanced emission can be modelled by rate equations taking into account hole injection from the tip (anode) into the highest occupied orbital of the closest substrate-bound molecule (lower level) and radiative recombination with an electron from above the Fermi level (upper level), hence feeding photons back by stimulated emission resonant with the gap mode. The system reflects many essential features of a superluminescent light emitting diode. PMID:26171286

Two-phase SLIPI for instantaneous LIF and Mie imaging of transient fuel sprays.

PubMed

Storch, Michael; Mishra, Yogeshwar Nath; Koegl, Matthias; Kristensson, Elias; Will, Stefan; Zigan, Lars; Berrocal, Edouard

2016-12-01

We report in this Letter a two-phase structured laser illumination planar imaging [two-pulse SLIPI (2p-SLIPI)] optical setup where the "lines structure" is spatially shifted by exploiting the birefringence property of a calcite crystal. By using this optical component and two cross-polarized laser pulses, the shift of the modulated pattern is not "time-limited" anymore. Consequently, two sub-images with spatially mismatched phases can be recorded within a few hundred of nanoseconds only, freezing the motion of the illuminated transient flow. In comparison with previous setups for instantaneous imaging based on structured illumination, the current optical design presents the advantage of having a single optical path, greatly simplifying its complexity. Due to its virtue of suppressing the effects from multiple light scattering, the 2p-SLIPI technique is applied here in an optically dense multi-jet direct-injection spark-ignition (DISI) ethanol spray. The fast formation of polydispersed droplets and appearance of voids after fuel injection are investigated by simultaneous detection of Mie scattering and liquid laser-induced fluorescence. The results allow for significantly improved analysis of the spray structure.

InGaAsP Mach-Zehnder interferometer optical modulator monolithically integrated with InGaAs driver MOSFET on a III-V CMOS photonics platform.

PubMed

Park, Jin-Kown; Takagi, Shinichi; Takenaka, Mitsuru

2018-02-19

We demonstrated the monolithic integration of a carrier-injection InGaAsP Mach-Zehnder interferometer (MZI) optical modulator and InGaAs metal-oxide-semiconductor field-effect transistor (MOSFET) on a III-V-on-insulator (III-V-OI) wafer. A low-resistivity lateral PIN junction was formed along an InGaAsP rib waveguide by Zn diffusion and Ni-InGaAsP alloy, enabling direct driving of the InGaAsP optical modulator by the InGaAs MOSFET. A π phase shift of the InGaAsP optical modulator was obtained through the injection of a drain current from the InGaAs MOSFET with a gate voltage of approximately 1 V. This proof-of-concept demonstration of the monolithic integration of the InGaAsP optical modulator and InGaAs driver MOSFET will enable us to develop high-performance and low-power electronic-photonic integrated circuits on a III-V CMOS photonics platform.

Optical arbitrary waveform generation based on multi-wavelength semiconductor fiber ring laser

NASA Astrophysics Data System (ADS)

Li, Peili; Ma, Xiaolu; Shi, Weihua; Xu, Enming

2017-09-01

A new scheme of generating optical arbitrary waveforms based on multi-wavelength semiconductor fiber ring laser (SFRL) is proposed. In this novel scheme, a wide and flat optical frequency comb (OFC) is provided directly by multi-wavelength SFRL, whose central frequency and comb spacing are tunable. OFC generation, de-multiplexing, amplitude and phase modulation, and multiplexing are implementing in an intensity and phase tunable comb filter, as induces the merits of high spectral coherence, satisfactory waveform control and low system loss. By using the mode couple theory and the transfer matrix method, the theoretical model of the scheme is established. The impacts of amplitude control, phase control, number of spectral line, and injection current of semiconductor optical amplifier (SOA) on the waveform similarity are studied using the theoretical model. The results show that, amplitude control and phase control error should be smaller than 1% and 0.64% respectively to achieve high similarity. The similarity of the waveform is improved with the increase of the number of spectral line. When the injection current of SOA is in a certain range, the optical arbitrary waveform reaches a high similarity.

Constraints on Smoke Injection Height, Source Strength, and Transports from MISR and MODIS

NASA Technical Reports Server (NTRS)

Kahn, Ralph A.; Petrenko, Mariya; Val Martin, Maria; Chin, Mian

2014-01-01

The AeroCom BB (Biomass Burning) Experiment AOD (Aerosol Optical Depth) motivation: We have a substantial set of satellite wildfire plume AOD snapshots and injection heights to help calibrate model/inventory performance; We are 1) adding more fire source-strength cases 2) using MISR to improve the AOD constrains and 3) adding 2008 global injection heights; We selected GFED3-daily due to good overall source strength performance, but any inventory can be tested; Joint effort to test multiple, global models, to draw robust BB injection height and emission strength conclusions. We provide satellite-based injection height and smoke plume AOD climatologies.

New optical frequency domain differential mode delay measurement method for a multimode optical fiber.

PubMed

Ahn, T; Moon, S; Youk, Y; Jung, Y; Oh, K; Kim, D

2005-05-30

A novel mode analysis method and differential mode delay (DMD) measurement technique for a multimode optical fiber based on optical frequency domain reflectometry has been proposed for the first time. We have used a conventional OFDR with a tunable external cavity laser and a Michelson interferometer. A few-mode optical multimode fiber was prepared to test our proposed measurement technique. We have also compared the OFDR measurement results with those obtained using a traditional time-domain measurement method.

Asymmetric photon transport in organic semiconductor nanowires through electrically controlled exciton diffusion

PubMed Central

Cui, Qiu Hong; Peng, Qian; Luo, Yi; Jiang, Yuqian; Yan, Yongli; Wei, Cong; Shuai, Zhigang; Sun, Cheng; Yao, Jiannian; Zhao, Yong Sheng

2018-01-01

The ability to steer the flow of light toward desired propagation directions is critically important for the realization of key functionalities in optical communication and information processing. Although various schemes have been proposed for this purpose, the lack of capability to incorporate an external electric field to effectively tune the light propagation has severely limited the on-chip integration of photonics and electronics. Because of the noninteractive nature of photons, it is only possible to electrically control the flow of light by modifying the refractive index of materials through the electro-optic effect. However, the weak optical effects need to be strongly amplified for practical applications in high-density photonic integrations. We show a new strategy that takes advantage of the strong exciton-photon coupling in active waveguides to effectively manipulate photon transport by controlling the interaction between excitons and the external electric field. Single-crystal organic semiconductor nanowires were used to generate highly stable Frenkel exciton polaritons with strong binding and diffusion abilities. By making use of directional exciton diffusion in an external electric field, we have realized an electrically driven asymmetric photon transport and thus directional light propagation in a single nanowire. With this new concept, we constructed a dual-output single wire–based device to build an electrically controlled single-pole double-throw optical switch with fast temporal response and high switching frequency. Our findings may lead to the innovation of concepts and device architectures for optical information processing. PMID:29556529

A fluorescence model of the murine lung for optical detection of pathogenic bacteria

NASA Astrophysics Data System (ADS)

Durkee, Madeleine S.; Cirillo, Jeffrey D.; Maitland, Kristen C.

2017-07-01

We present a computer model of intravital excitation and external fluorescence detection in the murine lungs validated with a three-dimensional lung tissue phantom. The model is applied to optical detection of pulmonary tuberculosis infection.

Performance Enhancement of Organic Light-Emitting Diodes Using Electron-Injection Materials of Metal Carbonates

NASA Astrophysics Data System (ADS)

Shin, Jong-Yeol; Kim, Tae Wan; Kim, Gwi-Yeol; Lee, Su-Min; Shrestha, Bhanu; Hong, Jin-Woong

2016-05-01

Performance of organic light-emitting diodes was investigated depending on the electron-injection materials of metal carbonates (Li2CO3 and Cs2CO3 ); and number of layers. In order to improve the device efficiency, two types of devices were manufactured by using the hole-injection material (Teflon-amorphous fluoropolymer -AF) and electron-injection materials; one is a two-layer reference device ( ITO/Teflon-AF/Alq3/Al ) and the other is a three-layer device (ITO/Teflon-AF/Alq3/metal carbonate/Al). From the results of the efficiency for the devices with hole-injection layer and electron-injection layer, it was found that the electron-injection layer affects the electrical properties of the device more than the hole-injection layer. The external-quantum efficiency for the three-layer device with Li2CO3 and Cs2CO3 layer is improved by approximately six and eight times, respectively, compared with that of the two-layer reference device. It is thought that a use of electron-injection layer increases recombination rate of charge carriers by the active injection of electrons and the blocking of holes.

Phase difference in modulated signals of two orthogonally polarized outputs of a Nd:YAG microchip laser with anisotropic optical feedback.

PubMed

Zhang, Peng; Tan, Yi-Dong; Liu, Ning; Wu, Yun; Zhang, Shu-Lian

2013-11-01

We present an experimental observation of the output responses of a Nd:YAG microchip laser with an anisotropic external cavity under weak optical feedback. The feedback mirror is stationary during the experiments. A pair of acousto-optic modulators is used to produce a frequency shift in the feedback light with respect to the initial light. The laser output is a beat signal with 40 kHz modulation frequency and is separated into two orthogonal directions by a Wollaston prism. Phase differences between the two intensity curves are observed as the laser works in two orthogonal modes, and vary with the external birefringence element and the pump power. Theoretical analyses are given, and the simulated results are consistent with the experimental phenomena.

Impulsive Injection for Compressor Stator Separation Control

NASA Technical Reports Server (NTRS)

Culley, Dennis E.; Braunscheidel, Edward P.; Bright, Michelle M.

2005-01-01

Flow control using impulsive injection from the suction surface of a stator vane has been applied in a low speed axial compressor. Impulsive injection is shown to significantly reduce separation relative to steady injection for vanes that were induced to separate by an increase in vane stagger angle of 4 degrees. Injected flow was applied to the airfoil suction surface using spanwise slots pitched in the streamwise direction. Injection was limited to the near-hub region, from 10 to 36 percent of span, to affect the dominant loss due to hub leakage flow. Actuation was provided externally using high-speed solenoid valves closely coupled to the vane tip. Variations in injected mass, frequency, and duty cycle are explored. The local corrected total pressure loss across the vane at the lower span region was reduced by over 20 percent. Additionally, low momentum fluid migrating from the hub region toward the tip was effectively suppressed resulting in an overall benefit which reduced corrected area averaged loss through the passage by 4 percent. The injection mass fraction used for impulsive actuation was typically less than 0.1 percent of the compressor through flow.

Selective ion accumulation in an ICP/ITMS using a filtered noise field

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

Eiden, G.C.; Barinaga, C.J.; Koppenaal, D.W.

1995-12-31

Selective accumulation of ions in an ion trap mass spectrometer (ITMS) has been characterized using both single frequency and broadband resonant excitation. The goal of this work is to enhance selective accumulation of ions from plasmas and other external ion sources. The charge capacity of the ITMS is 10{sup 6} to 10{sup 7} ions, although the mass spectrum is distorted at much lower space charge. Detection of trace ions necessitates selective detection schemes such as selective trapping or optical detection. The authors report results of selective trapping studies for Sr, Y, and Zr solutions (100 ppb Y and 1 ppbmore » each Sr, Zr). {open_quotes}Background{close_quotes} ions in mass channels adjacent to the channel of interest is a worst case situation with respect to selective ejection and abundance sensitivity. Real samples will often have matrix ion m/z values much further removed from the m/z of the ions of interest. Thus, the authors also give results for a multielement solution. Ions from an inductively coupled plasma ion source are endcap injected into the ITMS. Broadband waveforms were generated by an HST-1000 (Teledyne MEC) instrument, using the filtered noise field (FNF) method. The experiment is controlled by the ITMS electronics and ICMS software. The sequence of experimental events is: ion injection at q{sub z} = 0.4 (typical), collisionally cool ions, set trapping potential for resonant excitation (q{sub z} = 0.2 to 0.6), analysis rf ramp.« less

INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Simple pulsed semiconductor lasers

NASA Astrophysics Data System (ADS)

Hulicius, E.; Abrahám, A.; Sĭmeček, T.

1988-11-01

A brief review is given of the main characteristics of pulsed GaAlAs/GaAs lasers made in Czechoslovakia. A description is given of laser structures with large optical cavities and their electrical, optical, and service life characteristics are reported.

Visualisation of distribution of gold nanoparticles in liver tissues ex vivo and in vitro using the method of optical coherence tomography

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

Genina, Elina A; Terentyuk, G S; Khlebtsov, B N

2012-06-30

The possibility of visualising the distribution of gold nanoparticles in liver by means of the method of optical coherence tomography is studied experimentally in model samples of beef liver in vitro and rat liver ex vivo. In the experiments we used the gold nanoparticles in the form of nanocages with resonance absorption in the near-IR spectral region. In the model studies the suspension of nanoparticles was applied to the surface of the sample, which then was treated with ultrasound. In the ex vivo studies the suspension of nanoparticles was injected to the laboratory rats intravenously. The image contrast and themore » optical depth of detection of blood vessels and liver structure components are calculated, as well as the depth of liver optical probing before and after the injection of nanoparticles. It was shown that the administration of the nanoparticle increases significantly the imaging contrast of liver blood vessels owing to the localisation of the nanoparticles therein.« less

Influences of external vs. core-shell mixing on aerosol optical properties at various relative humidities.

PubMed

Ramachandran, S; Srivastava, Rohit

2013-05-01

Aerosol optical properties of external and core-shell mixtures of aerosol species present in the atmosphere are calculated in this study for different relative humidities. Core-shell Mie calculations are performed using the values of radii, refractive indices and densities of aerosol species that act as core and shell, and the core-shell radius ratio. The single scattering albedo (SSA) is higher when the absorbing species (black carbon, BC) is the core, while for a sulfate core SSA does not vary significantly as the BC in the shell dominates the absorption. Absorption gets enhanced in core-shell mixing of absorbing and scattering aerosols when compared to their external mixture. Thus, SSA is significantly lower for a core-shell mixture than their external mixture. SSA is more sensitive to core-shell ratio than mode radius when BC is the core. The extinction coefficient, SSA and asymmetry parameter are higher for external mixing when compared to BC (core)-water soluble aerosol (shell), and water soluble aerosol (core)-BC (shell) mixtures in the relative humidity range of 0 to 90%. Spectral SSA exhibits the behaviour of the species which acts as a shell in core-shell mixing. The asymmetry parameter for an external mixture of water soluble aerosol and BC is higher than BC (core)-water soluble aerosol (shell) mixing and increases as function of relative humidity. The asymmetry parameter for the water soluble aerosol (core)-BC (shell) is independent of relative humidity as BC is hydrophobic. The asymmetry parameter of the core-shell mixture decreases when BC aerosols are involved in mixing, as the asymmetry parameter of BC is lower. Aerosol optical depth (AOD) of core-shell mixtures increases at a higher rate when the relative humidity exceeds 70% in continental clean and urban aerosol models, whereas AOD remains the same when the relative humidity exceeds 50% in maritime aerosol models. The SSA for continental aerosols varies for core-shell mixing of water soluble aerosol (core)-shell (BC) when compared to their external mixture, while the SSA for maritime aerosols does not vary significantly for different mixing scenarios because of the dominance of sea salt aerosols. Thus, these results confirm that aerosol mixing can modify the physical and optical characteristics of aerosols, which vary as a function of relative humidity. These calculations will be useful in parameterising the effect of core-shell vs. external mixing of aerosols in global climate models, and in the evaluation of aerosol radiative effects.

Multimodality optical coherence tomography and fluorescence confocal scanning laser ophthalmoscopy for image-guided feedback of intraocular injections in mouse models

NASA Astrophysics Data System (ADS)

Benavides, Oscar R.; Terrones, Benjamin D.; Leeburg, Kelsey C.; Mehanathan, Sankarathi B.; Levine, Edward M.; Tao, Yuankai K.

2018-02-01

Rodent models are robust tools for understanding human retinal disease and function because of their similarities with human physiology and anatomy and availability of genetic mutants. Optical coherence tomography (OCT) has been well-established for ophthalmic imaging in rodents and enables depth-resolved visualization of structures and image-based surrogate biomarkers of disease. Similarly, fluorescence confocal scanning laser ophthalmoscopy (cSLO) has demonstrated utility for imaging endogenous and exogenous fluorescence and scattering contrast in the mouse retina. Complementary volumetric scattering and en face fluorescence contrast from OCT and cSLO, respectively, enables cellular-resolution longitudinal imaging of changes in ophthalmic structure and function. We present a non-contact multimodal OCT+cSLO small animal imaging system with extended working distance to the pupil, which enables imaging during and after intraocular injection. While injections are routinely performed in mice to develop novel models of ophthalmic diseases and screen novel therapeutics, the location and volume delivered is not precisely controlled and difficult to reproduce. Animals were imaged using a custom-built OCT engine and scan-head combined with a modified commercial cSLO scan-head. Post-injection imaging showed structural changes associated with retinal puncture, including the injection track, a retinal elevation, and detachment of the posterior hyaloid. When combined with imagesegmentation, we believe OCT can be used to precisely identify injection locations and quantify injection volumes. Fluorescence cSLO can provide complementary contrast for either fluorescently labeled compounds or transgenic cells for improved specificity. Our non-contact OCT+cSLO system is uniquely-suited for concurrent imaging with intraocular injections, which may be used for real-time image-guided injections.

Pulsed-incoherent-light-injected Fabry-Perot laser diode for WDM passive optical networks.

PubMed

Kim, Hoon

2010-01-18

We propose and demonstrate a pulsed-incoherent-light-injected Fabry-Perot laser diode (FP-LD) which generates incoherent return-to-zero (RZ) signals for wavelength-division-multiplexing passive optical networks. For the generation of the RZ signals, we first convert the continuous-wave (CW) amplified spontaneous emission (ASE) into an ASE pulse train with a pulse carver, spectrum-slice it into multiple channels with a waveguide grating router, and then inject them into FP-LDs for data modulation. Thanks to a wide slicing bandwidth of the injected incoherent light, the spectral linewidth of the generated RZ signals is determined by the slicing bandwidth, without being affected by the use of the RZ format. Thus, compared to incoherent non-return-to-zero (NRZ) signals generated with CW-ASE-injected FP-LDs, the RZ signals have a similar spectral linewidth but a wide timing margin between adjacent bits. Thus, the proposed transmitter can offer better dispersion tolerance than the NRZ signals. For example, our experimental demonstration performed at 1.25 Gb/s shows approximately 50% higher dispersion tolerance than the NRZ signals generated with CW ASE-injected FP-LDs. Despite the large slicing bandwidth of 0.67 nm for the injected ASE, we were able to transmit 1.25-Gb/s signals over 45-km standard single-mode fiber without dispersion compensation. The receiver sensitivity is also improved by 1.5 dB by using the RZ format.

Multistate intermittency on the route to chaos of a semiconductor laser subjected to optical feedback from a long external cavity.

PubMed

Choi, Daeyoung; Wishon, Michael J; Chang, C Y; Citrin, D S; Locquet, A

2018-01-01

We observe experimentally two regimes of intermittency on the route to chaos of a semiconductor laser subjected to optical feedback from a long external cavity as the feedback level is increased. The first regime encountered corresponds to multistate intermittency involving two or three states composed of several combinations of periodic, quasiperiodic, and subharmonic dynamics. The second regime is observed for larger feedback levels and involves intermittency between period-doubled and chaotic regimes. This latter type of intermittency displays statistical properties similar to those of on-off intermittency.

Emergence of resonant mode-locking via delayed feedback in quantum dot semiconductor lasers.

PubMed

Tykalewicz, B; Goulding, D; Hegarty, S P; Huyet, G; Erneux, T; Kelleher, B; Viktorov, E A

2016-02-22

With conventional semiconductor lasers undergoing external optical feedback, a chaotic output is typically observed even for moderate levels of the feedback strength. In this paper we examine single mode quantum dot lasers under strong optical feedback conditions and show that an entirely new dynamical regime is found consisting of spontaneous mode-locking via a resonance between the relaxation oscillation frequency and the external cavity repetition rate. Experimental observations are supported by detailed numerical simulations of rate equations appropriate for this laser type. The phenomenon constitutes an entirely new mode-locking mechanism in semiconductor lasers.

Optical feedback in dfb quantum cascade laser for mid-infrared cavity ring-down spectroscopy

NASA Astrophysics Data System (ADS)

Terabayashi, Ryohei; Sonnenschein, Volker; Tomita, Hideki; Hayashi, Noriyoshi; Kato, Shusuke; Jin, Lei; Yamanaka, Masahito; Nishizawa, Norihiko; Sato, Atsushi; Nozawa, Kohei; Hashizume, Kenta; Oh-hara, Toshinari; Iguchi, Tetsuo

2017-11-01

A simple external optical feedback system has been applied to a distributed feedback quantum cascade laser (DFB QCL) for cavity ring-down spectroscopy (CRDS) and a clear effect of feedback was observed. A long external feedback path length of up to 4m can decrease the QCL linewidth to around 50kHz, which is of the order of the transmission linewidth of our high finesse ring-down cavity. The power spectral density of the transmission signal from high finesse cavity reveals that the noise at frequencies above 20kHz is reduced dramatically.

Development of an embedded Fabry Perot Fiber Optic Strain Rosette Sensor (FP-FOSRS)

NASA Technical Reports Server (NTRS)

Carman, Gregory P.; Lesko, John J.; Case, Scott W.; Fogg, Brian; Claus, Richard O.

1992-01-01

We investigate the feasibility of utilizing a Fabry-Perot Fiber Optic Strain Rosette Sensor (FP-FOSRS) for the evaluation of the internal strain state of a material system. We briefly describe the manufacturing process for this sensor and point out some potential problem areas. Results of an embedded FP-FOSRS in an epoxy matrix with external resistance strain gauges applied for comparative purposes are presented. We show that the internal and external strain measurements are in close agreement. This work lays the foundation for embedding this sensor in actual composite laminas.

Pigment-dispersing factor sets the night state of the medulla bilateral neurons in the optic lobe of the cricket, Gryllus bimaculatus.

PubMed

Saifullah, A S M; Tomioka, Kenji

2003-03-01

Pigment-dispersing factor (PDF) is an octadeca-neuropeptide widely distributed in the insect brain and suggested to be involved in the insect circadian systems. We have examined its effects on the neuronal activity of the brain efferents in the optic stalk including medulla bilateral neurons (MBNs) in the cricket, Gryllus bimaculatus. The MBNs are visually responding interneurons connecting the bilateral medulla, which show a clear day/night change in their light responsiveness that is greater during the night. Microinjection of PDF into the optic lobe induced a significant increase in the spontaneous activity of the brain efferents and the photo-responsiveness of the MBNs during the day, while little change was induced during the night. The enhancing effects began to occur about 20 min after the injection and another 10 min was necessary to reach the maximal level. The effects of PDF were dose-dependent. When 22 nl of anti-Gryllus-PDF (1:200) IgG was injected into the medulla, the photo-responsiveness of the MBNs was suppressed in both the day and the night with greater magnitude during the night. No significant suppression was induced by injection of the same amount of IgG from normal rabbit serum. These results suggest that in the cricket optic lobe, PDF is released during the night and enhances MBNs' photo-responsiveness to set their night state.

Optical modulation in silicon waveguides via charge state control of deep levels.

PubMed

Logan, D F; Jessop, P E; Knights, A P; Wojcik, G; Goebel, A

2009-10-12

The control of defect mediated optical absorption at a wavelength of 1550 nm via charge state manipulation is demonstrated using optical absorption measurements of indium doped Silicon-On-Insulator (SOI) rib waveguides. These measurements introduce the potential for modulation of waveguide transmission by using the local depletion and injection of free-carriers to change deep-level occupancy. The extinction ratio and modulating speed are simulated for a proposed device structure. A 'normally-off' depletion modulator is described with an extinction coefficient limited to 5 dB/cm and switching speeds in excess of 1 GHz. For a carrier injection modulator a fourfold enhancement in extinction ratio is provided relative to free carrier absorption alone. This significant improvement in performance is achieved with negligible increase in driving power but slightly degraded switching speed.

On the Hole Injection for III-Nitride Based Deep Ultraviolet Light-Emitting Diodes.

PubMed

Li, Luping; Zhang, Yonghui; Xu, Shu; Bi, Wengang; Zhang, Zi-Hui; Kuo, Hao-Chung

2017-10-24

The hole injection is one of the bottlenecks that strongly hinder the quantum efficiency and the optical power for deep ultraviolet light-emitting diodes (DUV LEDs) with the emission wavelength smaller than 360 nm. The hole injection efficiency for DUV LEDs is co-affected by the p-type ohmic contact, the p-type hole injection layer, the p-type electron blocking layer and the multiple quantum wells. In this report, we review a large diversity of advances that are currently adopted to increase the hole injection efficiency for DUV LEDs. Moreover, by disclosing the underlying device physics, the design strategies that we can follow have also been suggested to improve the hole injection for DUV LEDs.

On the Hole Injection for III-Nitride Based Deep Ultraviolet Light-Emitting Diodes

PubMed Central

Li, Luping; Zhang, Yonghui; Kuo, Hao-Chung

2017-01-01

The hole injection is one of the bottlenecks that strongly hinder the quantum efficiency and the optical power for deep ultraviolet light-emitting diodes (DUV LEDs) with the emission wavelength smaller than 360 nm. The hole injection efficiency for DUV LEDs is co-affected by the p-type ohmic contact, the p-type hole injection layer, the p-type electron blocking layer and the multiple quantum wells. In this report, we review a large diversity of advances that are currently adopted to increase the hole injection efficiency for DUV LEDs. Moreover, by disclosing the underlying device physics, the design strategies that we can follow have also been suggested to improve the hole injection for DUV LEDs. PMID:29073738

Design and development of an injection-molded demultiplexer for optical communication systems in the visible range.

PubMed

Höll, S; Haupt, M; Fischer, U H P

2013-06-20

Optical simulation software based on the ray-tracing method offers easy and fast results in imaging optics. This method can also be applied in other fields of light propagation. For short distance communications, polymer optical fibers (POFs) are gradually gaining importance. This kind of fiber offers a larger core diameter, e.g., the step index POF features a core diameter of 980 μm. Consequently, POFs have a large number of modes (>3 million modes) in the visible range, and ray tracing could be used to simulate the propagation of light. This simulation method is applicable not only for the fiber itself but also for the key components of a complete POF network, e.g., couplers or other key elements of the transmission line. In this paper a demultiplexer designed and developed by means of ray tracing is presented. Compared to the classical optical design, requirements for optimal design differ particularly with regard to minimizing the insertion loss (IL). The basis of the presented key element is a WDM device using a Rowland spectrometer setup. In this approach the input fiber carries multiple wavelengths, which will be divided into multiple output fibers that transmit only one wavelength. To adapt the basic setup to POF, the guidance of light in this element has to be changed fundamentally. Here, a monolithic approach is presented with a blazed grating using an aspheric mirror to minimize most of the aberrations. In the simulations the POF is represented by an area light source, while the grating is analyzed for different orders and the highest possible efficiency. In general, the element should be designed in a way that it can be produced with a mass production technology like injection molding in order to offer a reasonable price. However, designing the elements with regard to injection molding leads to some inherent challenges. The microstructure of an optical grating and the thick-walled 3D molded parts both result in high demands on the injection molding process. This also requires complex machining of the molding tool. Therefore, different experiments are done to optimize the process parameter, find the best molding material, and find a suitable machining method for the molding tool. The paper will describe the development of the demultiplexer by means of ray-tracing simulations step by step. Also, the process steps and the realized solutions for the injection molding are described.

Fiber optic hydrogen sensor

DOEpatents

Buchanan, B.R.; Prather, W.S.

1991-01-01

Apparatus and method for detecting a chemical substance by exposing an optic fiber having a core and a cladding to the chemical substance so that the chemical substance can be adsorbed onto the surface of the cladding. The optic fiber is coiled inside a container having a pair of valves for controlling the entrance and exit of the substance. Light from a light source is received by one end of the optic fiber, preferably external to the container, and carried by the core of the fiber. Adsorbed substance changes the transmissivity of the fiber as measured by a spectrophotometer at the other end, also preferably external to the container. Hydrogen is detected by the absorption of infrared light carried by an optic fiber with a silica cladding. Since the adsorption is reversible, a sensor according to the present invention can be used repeatedly. Multiple positions in a process system can be monitored using a single container that can be connected to each location to be monitored so that a sample can be obtained for measurement, or, alternatively, containers can be placed near each position and the optic fibers carrying the partially-absorbed light can be multiplexed for rapid sequential reading, by a single spectrophotometer.

Fiber optic hydrogen sensor

DOEpatents

Buchanan, B.R.; Prather, W.S.

1992-10-06

An apparatus and method are described for detecting a chemical substance by exposing an optic fiber having a core and a cladding to the chemical substance so that the chemical substance can be adsorbed onto the surface of the cladding. The optic fiber is coiled inside a container having a pair of valves for controlling the entrance and exit of the substance. Light from a light source is received by one end of the optic fiber, preferably external to the container, and carried by the core of the fiber. Adsorbed substance changes the transmissivity of the fiber as measured by a spectrophotometer at the other end, also preferably external to the container. Hydrogen is detected by the absorption of infrared light carried by an optic fiber with a silica cladding. Since the adsorption is reversible, a sensor according to the present invention can be used repeatedly. Multiple positions in a process system can be monitored using a single container that can be connected to each location to be monitored so that a sample can be obtained for measurement, or, alternatively, containers can be placed near each position and the optic fibers carrying the partially-absorbed light can be multiplexed for rapid sequential reading by a single spectrophotometer. 4 figs.

Fiber optic hydrogen sensor

DOEpatents

Buchanan, Bruce R.; Prather, William S.

1992-01-01

An apparatus and method for detecting a chemical substance by exposing an optic fiber having a core and a cladding to the chemical substance so that the chemical substance can be adsorbed onto the surface of the cladding. The optic fiber is coiled inside a container having a pair of valves for controlling the entrance and exit of the substance. Light from a light source is received by one end of the optic fiber, preferably external to the container, and carried by the core of the fiber. Adsorbed substance changes the transmissivity of the fiber as measured by a spectrophotometer at the other end, also preferably external to the container. Hydrogen is detected by the absorption of infrared light carried by an optic fiber with a silica cladding. Since the adsorption is reversible, a sensor according to the present invention can be used repeatedly. Multiple positions in a process system can be monitored using a single container that can be connected to each location to be monitored so that a sample can be obtained for measurement, or, alternatively, containers can be placed near each position and the optic fibers carrying the partially-absorbed light can be multiplexed for rapid sequential reading by a single spectrophotometer.

Novel Applications of High Speed Optical-Injection Locked Lasers

DTIC Science & Technology

2010-07-31

transimpedance amplifiers (TIAs) and optical hybrids. We have also demonstrated digital communications on a 60 GHz optical subcarrier using directly modulated...of the devices. Also included on the mask are both single ended as well as differential transimpedance amplifiers (TIAs). These circuits have a... transimpedance amplifiers with the photo-transistors as the input stage. Simulations predict a transimpedance bandwidth of 120 GHz for the single

Turnable Blue-Green LIDAR Transmitter Demonstration: Injection Laser Technology

DTIC Science & Technology

1990-08-30

5-1 5.2 Baseline Requirements ............................................. 5-1 5.3 Optical Parametric Oscillator Using Beta Barium Borate... optical parametric oscillators , and organic dye lasers. Tunable solid state lasers such as Ti: sapphire operate in the infrared and would have to be...The same is true of I frequency mixing schemes. Optical parametric oscillators (OPOs) are attractive because of their extremely wide potential tuning

High-power quantum-dot tapered tunable external-cavity lasers based on chirped and unchirped structures.

PubMed

Haggett, Stephanie; Krakowski, Michel; Montrosset, Ivo; Cataluna, Maria Ana

2014-09-22

A high-power tunable external cavity laser configuration with a tapered quantum-dot semiconductor optical amplifier at its core is presented, enabling a record output power for a broadly tunable semiconductor laser source in the 1.2 - 1.3 µm spectral region. Two distinct optical amplifiers are investigated, using either chirped or unchirped quantum-dot structures, and their merits are compared, considering the combination of tunability and high output power generation. At 1230 nm, the chirped quantum-dot laser achieved a maximum power of 0.62 W and demonstrated nearly 100-nm tunability. The unchirped laser enabled a tunability range of 32 nm and at 1254 nm generated a maximum power of 0.97 W, representing a 22-fold increase in output power compared with similar narrow-ridge external-cavity lasers at the same current density.

Pulse evolution and mode selection characteristics in a TEA-CO2 laser perturbed by injection of external radiation

NASA Technical Reports Server (NTRS)

Flamant, P. H.; Menzies, R. T.; Kavaya, M. J.; Oppenheim, U. P.

1983-01-01

A grating-tunable TEA-CO2 laser with an unstable resonator cavity, modified to allow injection of CW CO2 laser radiation at the resonant transition line by means of an intracavity NaCl window, has been used to study the coupling requirements for generation of single frequency pulses. The width and shape of the mode selection region, and the dependence of the gain-switched spike buildup time and the pulse shapes on the intensity and detuning frequency of the injected radiation are reported. Comparisons of the experimental results with previously reported mode selection behavior are discussed.

An Automated Mouse Tail Vascular Access System by Vision and Pressure Feedback.

PubMed

Chang, Yen-Chi; Berry-Pusey, Brittany; Yasin, Rashid; Vu, Nam; Maraglia, Brandon; Chatziioannou, Arion X; Tsao, Tsu-Chin

2015-08-01

This paper develops an automated vascular access system (A-VAS) with novel vision-based vein and needle detection methods and real-time pressure feedback for murine drug delivery. Mouse tail vein injection is a routine but critical step for preclinical imaging applications. Due to the small vein diameter and external disturbances such as tail hair, pigmentation, and scales, identifying vein location is difficult and manual injections usually result in poor repeatability. To improve the injection accuracy, consistency, safety, and processing time, A-VAS was developed to overcome difficulties in vein detection noise rejection, robustness in needle tracking, and visual servoing integration with the mechatronics system.

Phase-locking of annular-combination CO2 laser

NASA Astrophysics Data System (ADS)

Qi, Tingxiang; Chen, Mei; Zhang, Rongzhu; Xiao, Qianyi

2015-07-01

A new annular-combination resonator structure adopting the external-injection phase-locking technology is presented theoretically for that the beam quality of stable annular resonator is not satisfying. The phase-locking principle and feasibility are characterized by energy density of injection beam and coupling coefficient. Based on the diffraction theory, output mode of the resonator with phase-locking is deduced and simulated. Results also confirm that injection beam have a good control effect on output mode. The intensity distributions of output beam are studied briefly and indicate that this new resonator which is adaptable to annular gain media can produce high-power laser beam with high quality.

Investigation of the spreading of diesel injection jets using a new high-speed 3D drum camera

NASA Astrophysics Data System (ADS)

Eisfeld, Fritz

1997-05-01

To improve the combustion of the diesel engine it is important that the combustion chamber is equally filled with fuel and vapor of fuel. The investigation of the spatial spreading of the injection jet is possible with optical methods. Therefore a drum camera for 3D was developed to take this spatial event. The camera and the first results of the investigations of different injection nozzles are described.

A Novel, Real-Time, In Vivo Mouse Retinal Imaging System

PubMed Central

Butler, Mark C.; Sullivan, Jack M.

2015-01-01

Purpose To develop an efficient, low-cost instrument for robust real-time imaging of the mouse retina in vivo, and assess system capabilities by evaluating various animal models. Methods Following multiple disappointing attempts to visualize the mouse retina during a subretinal injection using commercially available systems, we identified the key limitation to be inadequate illumination due to off axis illumination and poor optical train optimization. Therefore, we designed a paraxial illumination system for Greenough-type stereo dissecting microscope incorporating an optimized optical launch and an efficiently coupled fiber optic delivery system. Excitation and emission filters control spectral bandwidth. A color coupled-charged device (CCD) camera is coupled to the microscope for image capture. Although, field of view (FOV) is constrained by the small pupil aperture, the high optical power of the mouse eye, and the long working distance (needed for surgical manipulations), these limitations can be compensated by eye positioning in order to observe the entire retina. Results The retinal imaging system delivers an adjustable narrow beam to the dilated pupil with minimal vignetting. The optic nerve, vasculature, and posterior pole are crisply visualized and the entire retina can be observed through eye positioning. Normal and degenerative retinal phenotypes can be followed over time. Subretinal or intraocular injection procedures are followed in real time. Real-time, intravenous fluorescein angiography for the live mouse has been achieved. Conclusions A novel device is established for real-time viewing and image capture of the small animal retina during subretinal injections for preclinical gene therapy studies. PMID:26551329

The influence of different black carbon and sulfate mixing methods on their optical and radiative properties

NASA Astrophysics Data System (ADS)

Zhang, Hua; Zhou, Chen; Wang, Zhili; Zhao, Shuyun; Li, Jiangnan

2015-08-01

Three different internal mixing methods (Core-Shell, Maxwell-Garnett, and Bruggeman) and one external mixing method are used to study the impact of mixing methods of black carbon (BC) with sulfate aerosol on their optical properties, radiative flux, and heating rate. The optical properties of a mixture of BC and sulfate aerosol particles are considered for three typical bands. The results show that mixing methods, the volume ratio of BC to sulfate, and relative humidity have a strong influence on the optical properties of mixed aerosols. Compared to internal mixing, external mixing underestimates the particle mass absorption coefficient by 20-70% and the particle mass scattering coefficient by up to 50%, whereas it overestimates the particle single scattering albedo by 20-50% in most cases. However, the asymmetry parameter is strongly sensitive to the equivalent particle radius, but is only weakly sensitive to the different mixing methods. Of the internal methods, there is less than 2% difference in all optical properties between the Maxwell-Garnett and Bruggeman methods in all bands; however, the differences between the Core-Shell and Maxwell-Garnett/Bruggeman methods are usually larger than 15% in the ultraviolet and visible bands. A sensitivity test is conducted with the Beijing Climate Center Radiation transfer model (BCC-RAD) using a simulated BC concentration that is typical of east-central China and a sulfate volume ratio of 75%. The results show that the internal mixing methods could reduce the radiative flux more effectively because they produce a higher absorption. The annual mean instantaneous radiative force due to BC-sulfate aerosol is about -3.18 W/m2 for the external method and -6.91 W/m2 for the internal methods at the surface, and -3.03/-1.56/-1.85 W/m2 for the external/Core-Shell/(Maxwell-Garnett/Bruggeman) methods, respectively, at the tropopause.