Amplified emission and modified spectral features in an opal hetero-structure mediated by passive defect mode localization

NASA Astrophysics Data System (ADS)

Rout, Dipak; Kumar, Govind; Vijaya, R.

2018-01-01

A photonic crystal hetero-structure consisting of a passive planar defect of SiO2 thin film sandwiched between two identical opals grown by inward growing self-assembly method using Rhodamine-B dye-doped polystyrene microspheres is studied for the characteristics of dye emission. The optical properties and the defect mode characteristics of the hetero-structure are studied from the reflection and transmission measurements. Laser-induced fluorescence from the hetero-structure showed amplified and spectrally narrowed emission compared to the photonic crystal emphasizing the role of the defect mode and distributed feedback. The enhanced emission is also complemented by the reduction in fluorescence decay time in the case of the hetero-structure in comparison to the 3D photonic crystals.

Random lasing in dye-doped polymer dispersed liquid crystal film

NASA Astrophysics Data System (ADS)

Wu, Rina; Shi, Rui-xin; Wu, Xiaojiao; Wu, Jie; Dai, Qin

2016-09-01

A dye-doped polymer-dispersed liquid crystal film was designed and fabricated, and random lasing action was studied. A mixture of laser dye, nematic liquid crystal, chiral dopant, and PVA was used to prepare the dye-doped polymer-dispersed liquid crystal film by means of microcapsules. Scanning electron microscopy analysis showed that most liquid crystal droplets in the polymer matrix ranged from 30 μm to 40 μm, the size of the liquid crystal droplets was small. Under frequency doubled 532 nm Nd:YAG laser-pumped optical excitation, a plurality of discrete and sharp random laser radiation peaks could be measured in the range of 575-590 nm. The line-width of the lasing peak was 0.2 nm and the threshold of the random lasing was 9 mJ. Under heating, the emission peaks of random lasing disappeared. By detecting the emission light spot energy distribution, the mechanism of radiation was found to be random lasing. The random lasing radiation mechanism was then analyzed and discussed. Experimental results indicated that the size of the liquid crystal droplets is the decisive factor that influences the lasing mechanism. The surface anchor role can be ignored when the size of the liquid crystal droplets in the polymer matrix is small, which is beneficial to form multiple scattering. The transmission path of photons is similar to that in a ring cavity, providing feedback to obtain random lasing output. Project supported by the National Natural Science Foundation of China (Grant No. 61378042), the Colleges and Universities in Liaoning Province Outstanding Young Scholars Growth Plans, China (Grant No. LJQ2015093), and Shenyang Ligong University Laser and Optical Information of Liaoning Province Key Laboratory Open Funds, China.

Airborne water vapor DIAL system and measurements of water and aerosol profiles

NASA Technical Reports Server (NTRS)

Higdon, Noah S.; Browell, Edward V.

1991-01-01

The Lidar Applications Group at NASA Langley Research Center has developed a differential absorption lidar (DIAL) system for the remote measurement of atmospheric water vapor (H2O) and aerosols from an aircraft. The airborne H2O DIAL system is designed for extended flights to perform mesoscale investigations of H2O and aerosol distributions. This DIAL system utilizes a Nd:YAG-laser-pumped dye laser as the off-line transmitter and a narrowband, tunable Alexandrite laser as the on-line transmitter. The dye laser has an oscillator/amplifier configuration which incorporates a grating and prism in the oscillator cavity to narrow the output linewidth to approximately 15 pm. This linewidth can be maintained over the wavelength range of 725 to 730 nm, and it is sufficiently narrow to satisfy the off-line spectral requirements. In the Alexandrite laser, three intracavity tuning elements combine to produce an output linewidth of 1.1 pm. These spectral devices include a five-plate birefringent tuner, a 1-mm thick solid etalon and a 1-cm air-spaced etalon. A wavelength stability of +/- 0.35 pm is achieved by active feedback control of the two Fabry-Perot etalons using a frequency stabilized He-Ne laser as a wavelength reference. The three tuning elements can be synchronously scanned over a 150 pm range with microprocessor-based scanning electronics. Other aspects of the DIAL system are discussed.

Electrically tunable laser based on heliconical cholesteric (Conference Presentation)

NASA Astrophysics Data System (ADS)

Xiang, Jie; Varanytsia, Andrii; Minkowski, Fred; Paterson, Daniel A.; Imrie, Corrie T.; Lavrentovich, Oleg D.; Palffy-Muhoray, Peter

2016-09-01

STUDENT CONTRIBUTION: Cholesteric liquid crystals (CLC) self-assemble into a periodic supramolecular helical structure with properties of a one-dimensional photonic crystal. The CLCs doped with a fluorescent dye and optical pump enable a distributed feedback cavity and lasing [1]. Although lasing was observed in range of wavelength from near UV to near IR, a practical method of tuning of emission wavelength from a dye-doped CLC without structural destruction of a helix is not demonstrated yet. In this work, we demonstrate an electrically tunable dye-doped CLC laser based on the so-called oblique helicoidal, or heliconical, CLC state [2,3]. In this state, the molecules twist around the helicoidal axis, making an angle smaller than 90 degrees with the axis. Molecular tilt makes the heliconical structure different from the regular CLC (in which the molecules are perpendicular to the axis) and enable electric tunability [2,3]. An electric field applied parallel to the heliconical axis changes the pitch but does not realign the axis. When the field increases, the pitch decreases. As a result, the selective reflection band and a lasing wavelength move towards shorter wavelength. Using heliconical CLC and two laser dyes DCM and LD688, we demonstrate effective tuning of the laser emission wavelength from 574 nm to 722 nm. With appropriate laser dyes, the spectrum can be extended from near UV to near IR. Efficient electric tuning in the broad spectral range and small size of the heliconical cholesteric lasers makes them potentially useful for optical and biomedical applications. [1] P. Palffy-Muhoay, W.Y. Cao, M. Moreira, B. Taheri, A. Munoz, Photonics and lasing in liquid crystal [2] J. Xiang, S.V. Shiyanovskii, C.T. Imrie, O.D. Lavrentovich, Electrooptic Response of Chiral Nematic Liquid Crystals with Oblique Helicoidal Director, Phys Rev Lett, 112 (2014) 217801. [3] J. Xiang, Y.N. Li, Q. Li, D.A. Paterson, J.M.D. Storey, C.T. Imrie, O.D. Lavrentovich, Electrically Tunable Selective Reflection of Light from Ultraviolet to Visible and Infrared by Heliconical Cholesterics, Adv Mater, 27 (2015) 3014-3018.

Construction of a Visible Diode Laser Source for Free Radical Photochemistry and Spectroscopy Experiments

NASA Technical Reports Server (NTRS)

Newman, Bronjelyn; Halpern, Joshua B.

1997-01-01

Tunable diode lasers are reliable sources of narrow-band light and comparatively cheap. Optical feedback simplifies frequency tuning of the laser diodes. We are building an inexpensive diode laser system incorporating optical feedback from a diffraction grating. The external optical cavity can be used with lasers that emit between 2 and 100 mW, and will also work if they are pulsed, although this will significantly degrade the bandwidth. The diode laser output power and bandwidth are comparable to CW dye lasers used in kinetics and dynamics experiments. However, their cost and maintenance will be much less as will alignment time. We intend to use the diode lasers to investigate CN and C2 kinetics as well as to study dissociation dynamics of atmospherically important molecules.

Feedback quantum control of molecular electronic population transfer

NASA Astrophysics Data System (ADS)

Bardeen, Christopher J.; Yakovlev, Vladislav V.; Wilson, Kent R.; Carpenter, Scott D.; Weber, Peter M.; Warren, Warren S.

1997-11-01

Feedback quantum control, where the sample `teaches' a computer-controlled arbitrary lightform generator to find the optimal light field, is experimentally demonstrated for a molecular system. Femtosecond pulses tailored by a computer-controlled acousto-optic pulse shaper excite fluorescence from laser dye molecules in solution. Fluorescence and laser power are monitored, and the computer uses the experimental data and a genetic algorithm to optimize population transfer from ground to first excited state. Both efficiency (the ratio of excited state population to laser energy) and effectiveness (total excited state population) are optimized. Potential use as an `automated theory tester' is discussed.

Transversely bounded DFB lasers. [bounded distributed-feedback lasers

NASA Technical Reports Server (NTRS)

Elachi, C.; Evans, G.; Yeh, C.

1975-01-01

Bounded distributed-feedback (DFB) lasers are studied in detail. Threshold gain and field distribution for a number of configurations are derived and analyzed. More specifically, the thin-film guide, fiber, diffusion guide, and hollow channel with inhomogeneous-cladding DFB lasers are considered. Optimum points exist and must be used in DFB laser design. Different-modes feedback and the effects of the transverse boundaries are included. A number of applications are also discussed.

The pulsed dye laser versus the Q-switched Nd:YAG laser in laser-induced shock-wave lithotripsy.

PubMed

Thomas, S; Pensel, J; Engelhardt, R; Meyer, W; Hofstetter, A G

1988-01-01

To date, there are two fairly well-established alternatives for laser-induced shock-wave lithotripsy in clinical practice. The Q-switched Nd:YAG laser is distinguished by the high-stone selectivity of its coupler systems. The necessity of a coupler system and its fairly small conversion rate of light energy into mechanical energy present serious drawbacks. Furthermore, the minimal outer diameter of the transmission system is 1.8 mm. The pulsed-dye laser can be used with a highly flexible and uncomplicated 200-micron fiber. However, the laser system itself is more complicated than the Q-switched Nd:YAG laser and requires a great deal of maintenance. Biological evaluation of damage caused by direct irradiation shows that both laser systems produce minor damage of different degrees. YAG laser lithotripsy with the optomechanical coupler was assessed in 31 patients with ureteral calculi. The instability and limited effectiveness of the fiber application system necessitated auxiliary lithotripsy methods in 14 cases. Dye-laser lithotripsy is currently being tested in clinical application. Further development, such as systems for blind application or electronic feedback mechanisms to limit adverse tissue effects, have yet to be optimized. Nevertheless, laser-induced shock-wave lithotripsy has the potential to become a standard procedure in the endourologic management of stone disease.

High-reflective colorful films fabricated by all-solid multi-layer cholesteric structures

NASA Astrophysics Data System (ADS)

Li, Y.; Luo, D.

2018-02-01

We demonstrate all-solid-state film with high-reflectivity based on cholesteric template. The adhesive (NOA81) is both filler and an adhesive, which can be avoids interfacial losses. The reflected right- and left-circularly polarized light has been developed by roll-to-roll method, and the reflectance of the films is more than 78%. Here, the all-solid film was used in distribute feedback laser with dye-doped. In addition, this films also used in include flexible reflective display, color pixels in digital photographs, printing and colored cladding of variety of objects.

Random lasing action in a polydimethylsiloxane wrinkle induced disordered structure

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

Shen, Zhenhua; Wu, Leilei; Zhu, Shu

This paper presents a chip-scale random lasing action utilizing polydimethylsiloxane (PDMS) wrinkles with random periods as disordered medium. Nanoscale wrinkles with long range disorder structures are formed on the oxidized surface of a PDMS slab and confirmed by atomic force microscopy. Light multiply scattered at each PDMS wrinkle-dye interfaces is optically amplified in the presence of pump gain. The shift of laser emission wavelength when pumping at different regions indicates the randomness of the winkle period. In addition, a relatively low threshold of about 27 μJ/mm{sup 2} is realized, which is comparable with traditional optofluidic dye laser. This is due tomore » the unique sinusoidal Bragg-grating-like random structure. Contrast to conventional microfluidic dye laser that inevitably requires the accurate design and implementation of microcavity to provide optical feedback, the convenience in both fabrication and operation makes PDMS wrinkle based random laser a promising underlying element in lab-on-a-chip systems and integrated microfluidic networks.« less

Apparatus For Linewidth Reduction in Distributed Feedback or Distributed Bragg Reflector Semiconductor Lasers Using Vertical Emission

NASA Technical Reports Server (NTRS)

Cook, Anthony L. (Inventor); Hendricks, Herbert D. (Inventor)

2000-01-01

The linewidth of a distributed feedback semiconductor laser or a distributed Bragg reflector laser having one or more second order gratings is reduced by using an external cavity to couple the vertical emission back into the laser. This method and device prevent disturbance of the main laser beam, provide unobstructed access to laser emission for the formation of the external cavity, and do not require a very narrow heat sink. Any distributed Bragg reflector semiconductor laser or distributed feedback semiconductor laser that can produce a vertical emission through the epitaxial material and through a window in the top metallization can be used. The external cavity can be formed with an optical fiber or with a lens and a mirror or grating.

Method and Apparatus for Linewidth Reduction in Distributed Feedback or Distributed Bragg Reflector Semiconductor Lasers using Vertical Emission

NASA Technical Reports Server (NTRS)

Cook, Anthony L. (Inventor); Hendricks, Herbert D. (Inventor)

1998-01-01

The linewidth of a distributed feedback semiconductor laser or a distributed Bragg reflector laser having one or more second order gratings is reduced by using an external cavity to couple the vertical emission back into the laser. This method and device prevent disturbance of the main laser beam. provide unobstructed access to laser emission for the formation of the external cavity. and do not require a very narrow heat sink. Any distributed Bragg reflector semiconductor laser or distributed feedback semiconductor laser that can produce a vertical emission through the epitaxial material and through a window in the top metallization can be used. The external cavity can be formed with an optical fiber or with a lens and a mirror of grating.

Co-extruded mechanically tunable multilayer elastomer laser

NASA Astrophysics Data System (ADS)

Crescimanno, Michael; Mao, Guilin; Andrews, James; Singer, Kenneth; Baer, Eric; Hiltner, Anne; Song, Hyunmin; Shakya, Bijayandra

2011-04-01

We have fabricated and studied mechanically tunable elastomer dye lasers constructed in large area sheets by a single-step layer-multiplying co-extrusion process. The laser films consist of a central dye-doped (Rhodamine-6G) elastomer layer between two 128-layer distributed Bragg reflector (DBR) films comprised of alternating elastomer layers with different refractive indices. The central gain layer is formed by folding the coextruded DBR film to enclose a dye-doped skin layer. By mechanically stretching the elastomer laser film from 0% to 19%, a tunable miniature laser source was obtained with ˜50 nm continuous tunability from red to green.

Single-Mode, Distributed Feedback Interband Cascade Lasers

NASA Technical Reports Server (NTRS)

Frez, Clifford F. (Inventor); Borgentun, Carl E. (Inventor); Briggs, Ryan M. (Inventor); Bagheri, Mahmood (Inventor); Forouhar, Siamak (Inventor)

2016-01-01

Single-mode, distributed feedback interband cascade lasers (ICLs) using distributed-feedback gratings (e.g., lateral Bragg gratings) and methods of fabricating such ICLs are provided. The ICLs incorporate distributed-feedback gratings that are formed above the laser active region and adjacent the ridge waveguide (RWG) of the ICL. The ICLs may incorporate a double-ridge system comprising an optical confinement structure (e.g., a RWG) disposed above the laser active region that comprises the first ridge of the double ridge system, a DFB grating (e.g., lateral Bragg grating) disposed above the laser active region and adjacent the optical confinement structure, and an electric confinement structure that passes at least partially through the laser active region and that defines the boundary of the second ridge comprises and the termination of the DFB grating.

High Power Dye Lasers

DTIC Science & Technology

1975-09-30

sphere is greatly reduced when compared to the axial flow dye cell. This is because the focusing optics can only direct light from a limited angle into...Distribution in Flashlamp . . . „ [ [ TTIH Flashlamp Cooling and Thermal Limits [ [ [ ii~ik Optical Characteristics ’,,: •*••••••••••• il-ib...Tracing Program e Dye Pumping System Laser Tests ! 1 i * * TTT’I Laser Output Fall Off !!!.’!!!" ’ TTT’H Single Shot Optical Distortion TTT’I

Nearly-octave wavelength tuning of a continuous wave fiber laser

PubMed Central

Zhang, Lei; Jiang, Huawei; Yang, Xuezong; Pan, Weiwei; Cui, Shuzhen; Feng, Yan

2017-01-01

The wavelength tunability of conventional fiber lasers are limited by the bandwidth of gain spectrum and the tunability of feedback mechanism. Here a fiber laser which is continuously tunable from 1 to 1.9 μm is reported. It is a random distributed feedback Raman fiber laser, pumped by a tunable Yb doped fiber laser. The ultra-wide wavelength tunability is enabled by the unique property of random distributed feedback Raman fiber laser that both stimulated Raman scattering gain and Rayleigh scattering feedback are available at any wavelength. The dispersion property of the gain fiber is used to control the spectral purity of the laser output. PMID:28198414

Narrow-band generation in random distributed feedback fiber laser.

PubMed

Sugavanam, Srikanth; Tarasov, Nikita; Shu, Xuewen; Churkin, Dmitry V

2013-07-15

Narrow-band emission of spectral width down to ~0.05 nm line-width is achieved in the random distributed feedback fiber laser employing narrow-band fiber Bragg grating or fiber Fabry-Perot interferometer filters. The observed line-width is ~10 times less than line-width of other demonstrated up to date random distributed feedback fiber lasers. The random DFB laser with Fabry-Perot interferometer filter provides simultaneously multi-wavelength and narrow-band (within each line) generation with possibility of further wavelength tuning.

Lasing in a nematic liquid crystal cell with an interdigitated electrode system

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

Shtykov, N M; Palto, S P; Umanskii, B A

2015-04-30

Waveguide lasing in a layer of a dye-doped nematic liquid crystal has been observed. The liquid-crystal layer was sandwiched between a quartz substrate and a glass cover plate on whose surface was deposited an interdigitated electrode system. This system had a period of 3.75 μm and played a dual role, namely, it created a spatial periodicity of the waveguide medium refractive index (thus creating distributed feedback) and served as a diffraction grating coupling out a part of waveguide radiation into the glass cover plate. The distributed feedback ensured lasing in the 18th diffraction order for the TE modes and inmore » the 19th order for the TM modes of the waveguide. The generated radiation was observed at the exit from the glass plate end face at the angles to the waveguide plane of 33.1 ± 1.5° for TM modes and 21.8 ± 1.8° for TE modes. The intensity and position of the TE emission line showed no regular dependence on the voltage on the electrodes. In the case of TM radiation, an increase in the voltage led to a short-wavelength shift of the laser line and to a decrease in its intensity. (lasers)« less

Random distributed feedback fiber laser at 2.1  μm.

PubMed

Jin, Xiaoxi; Lou, Zhaokai; Zhang, Hanwei; Xu, Jiangming; Zhou, Pu; Liu, Zejin

2016-11-01

We demonstrate a random distributed feedback fiber laser at 2.1 μm. A high-power pulsed Tm-doped fiber laser operating at 1.94 μm with a temporal duty ratio of 30% was employed as a pump laser to increase the equivalent incident pump power. A piece of 150 m highly GeO₂-doped silica fiber that provides a strong Raman gain and random distributed feedbacks was used to act as the gain medium. The maximum output power reached 0.5 W with the optical efficiency of 9%, which could be further improved by more pump power and optimized fiber length. To the best of our knowledge, this is the first demonstration of random distributed feedback fiber laser at 2 μm band based on Raman gain.

Effect of Rayleigh-scattering distributed feedback on multiwavelength Raman fiber laser generation.

PubMed

El-Taher, A E; Harper, P; Babin, S A; Churkin, D V; Podivilov, E V; Ania-Castanon, J D; Turitsyn, S K

2011-01-15

We experimentally demonstrate a Raman fiber laser based on multiple point-action fiber Bragg grating reflectors and distributed feedback via Rayleigh scattering in an ~22-km-long optical fiber. Twenty-two lasing lines with spacing of ~100 GHz (close to International Telecommunication Union grid) in the C band are generated at the watt level. In contrast to the normal cavity with competition between laser lines, the random distributed feedback cavity exhibits highly stable multiwavelength generation with a power-equalized uniform distribution, which is almost independent on power.

Surface-plasmon distributed-feedback quantum cascade lasers operating pulsed, room temperature

NASA Astrophysics Data System (ADS)

Bousseksou, A.; Chassagneux, Y.; Coudevylle, J. R.; Colombelli, R.; Sirtori, C.; Patriarche, G.; Beaudoin, G.; Sagnes, I.

2009-08-01

We report distributed-feedback surface-plasmon quantum cascade lasers operating at λ ≈7.6μm. The distributed feedback is obtained by the sole patterning of the top metal contact on a surface plasmon waveguide. Single mode operation with more than 30dB side mode suppression ratio is obtained in pulsed mode and at room temperature. A careful experimental study confirms that by varying the grating duty cycle, one can reduce the waveguide losses with respect to standard, unpatterned surface-plasmon devices. This allows one to reduce the laser threshold current of more than a factor of 2 in the 200-300K temperature range. This approach may lead to a fabrication technology for midinfrared distributed-feedback lasers based on a very simple processing.

Physical and chemical investigations on natural dyes

NASA Astrophysics Data System (ADS)

Acquaviva, S.; D'Anna, E.; de Giorgi, M. L.; Della Patria, A.; Baraldi, P.

2010-09-01

Natural dyes have been used extensively in the past for many purposes, such us to colour fibers and to produce inks, watercolours and paints, but their use declined rapidly after the discovery of synthetic colours. Nowadays we witness a renewed interest, as natural dyes are neither toxic nor polluting. In this work, physical and chemical properties of four selected dyes, namely red (Madder), yellow (Weld and Turmeric) and blue (Woad) colours, produced by means of traditional techniques at the Museo dei Colori Naturali (Lamoli, Italy), have been investigated. The chromatic properties have been studied through the reflectance spectroscopy, a non-invasive technique for the characterisation of chromaticity. Reflection spectra both from powders and egg-yolk tempera models have been acquired to provide the typical features of the dyes in the UV-vis spectral range. Moreover, to assess the feasibility of laser cleaning procedures, tempera layers were investigated after irradiation with an excimer laser. Micro Raman spectroscopy, Scanning Electron Microscopy and Energy Dispersive X-Ray analyses have complemented the survey, returning compositional and morphological information as well. Efforts have been made to give scientific feedback to the production processes and to support the research activity in the restoration of the artworks where these dyes were employed.

Random bit generation at tunable rates using a chaotic semiconductor laser under distributed feedback.

PubMed

Li, Xiao-Zhou; Li, Song-Sui; Zhuang, Jun-Ping; Chan, Sze-Chun

2015-09-01

A semiconductor laser with distributed feedback from a fiber Bragg grating (FBG) is investigated for random bit generation (RBG). The feedback perturbs the laser to emit chaotically with the intensity being sampled periodically. The samples are then converted into random bits by a simple postprocessing of self-differencing and selecting bits. Unlike a conventional mirror that provides localized feedback, the FBG provides distributed feedback which effectively suppresses the information of the round-trip feedback delay time. Randomness is ensured even when the sampling period is commensurate with the feedback delay between the laser and the grating. Consequently, in RBG, the FBG feedback enables continuous tuning of the output bit rate, reduces the minimum sampling period, and increases the number of bits selected per sample. RBG is experimentally investigated at a sampling period continuously tunable from over 16 ns down to 50 ps, while the feedback delay is fixed at 7.7 ns. By selecting 5 least-significant bits per sample, output bit rates from 0.3 to 100 Gbps are achieved with randomness examined by the National Institute of Standards and Technology test suite.

Photoactive dye-enhanced tissue ablation for endoscopic laser prostatectomy.

PubMed

Ahn, Minwoo; Hau, Nguyen Trung; Van Phuc, Nguyen; Oh, Junghwan; Kang, Hyun Wook

2014-11-01

Laser light has been widely used as a surgical tool to treat benign prostate hyperplasia (BPH) over 20 years. Recently, application of high laser power up to 200 W was often reported to swiftly remove a large amount of prostatic tissue. The purpose of this study was to validate the feasibility of photoactive dye injection to enhance light absorption and eventually to facilitate tissue vaporization with low laser power. Chicken breast tissue was selected as a target tissue due to minimal optical absorption at the visible wavelength. Four biocompatible photoactive dyes, including amaranth (AR), black dye (BD), hemoglobin powder (HP), and endoscopic marker (EM), were selected and tested in vitro with a customized 532 nm laser system with radiant exposure ranging from 0.9 to 3.9 J/cm(2) . Light absorbance and ablation threshold were measured with UV-Vis spectrometer and Probit analysis, respectively, and compared to feature the function of the injected dyes. Ablation performance with dye-injection was evaluated in light of radiant exposure, dye concentration, and number of injection. Higher light absorption by injected dyes led to lower ablation threshold as well as more efficient tissue removal in the order of AR, BD, HP, and EM. Regardless of the injected dyes, ablation efficiency principally increased with radiant exposure, dye concentration, and number of injection. Among the dyes, AR created the highest ablation rate of 44.2 ± 0.2 µm/pulse due to higher absorbance and lower ablation threshold. High aspect ratios up to 7.1 ± 0.4 entailed saturation behavior in the tissue ablation injected with AR and BD, possibly resulting from plume shielding and increased scattering due to coagulation. Preliminary tests on canine prostate with a hydraulic injection system demonstrated that 80 W with dye injection yielded comparable ablation efficiency to 120 W with no injection, indicating 33% reduced laser power with almost equivalent performance. Due to efficient coupling of optical energy, pre-injection of photoactive dyes promoted the degree of tissue removal during laser irradiation. Further studies will investigate spatial distribution of dyes and optimal injecting pressure to govern the extent of dye-assisted ablation in a predictable manner. In-depth comprehension on photoactive dye-enhanced tissue ablation can help accomplish efficient and safe laser vaporization for BPH with low power application. © 2014 Wiley Periodicals, Inc.

Photonic generation of stable microwave signals from a dual-wavelength Al2O3:Yb3+ distributed-feedback waveguide laser.

PubMed

Bernhardi, E H; Khan, M R H; Roeloffzen, C G H; van Wolferen, H A G M; Wörhoff, K; de Ridder, R M; Pollnau, M

2012-01-15

We report the fabrication and characterization of a dual-wavelength distributed-feedback channel waveguide laser in ytterbium-doped aluminum oxide. Operation of the device is based on the optical resonances that are induced by two local phase shifts in the distributed-feedback structure. A stable microwave signal at ~15 GHz with a -3 dB width of 9 kHz was subsequently created via the heterodyne photodetection of the two laser wavelengths. The long-term frequency stability of the microwave signal produced by the free-running laser is better than ±2.5 MHz, while the power of the microwave signal is stable within ±0.35 dB.

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.

Distributed feedback imprinted electrospun fiber lasers.

PubMed

Persano, Luana; Camposeo, Andrea; Del Carro, Pompilio; Fasano, Vito; Moffa, Maria; Manco, Rita; D'Agostino, Stefania; Pisignano, Dario

2014-10-01

Imprinted, distributed feedback lasers are demonstrated on individual, active electrospun polymer nanofibers. In addition to advantages related to miniaturization, optical confinement and grating nanopatterning lead to a significant threshold reduction compared to conventional thin-film lasers. The possibility of imprinting arbitrary photonic crystal geometries on electrospun lasing nanofibers opens new opportunities for realizing optical circuits and chips. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High resolution imaging of intracellular oxygen concentration by phosphorescence lifetime

PubMed Central

Kurokawa, Hiromi; Ito, Hidehiro; Inoue, Mai; Tabata, Kenji; Sato, Yoshifumi; Yamagata, Kazuya; Kizaka-Kondoh, Shinae; Kadonosono, Tetsuya; Yano, Shigenobu; Inoue, Masahiro; Kamachi, Toshiaki

2015-01-01

Optical methods using phosphorescence quenching by oxygen are suitable for sequential monitoring and non-invasive measurements for oxygen concentration (OC) imaging within cells. Phosphorescence intensity measurement is widely used with phosphorescent dyes. These dyes are ubiquitously but heterogeneously distributed inside the whole cell. The distribution of phosphorescent dye is a major disadvantage in phosphorescence intensity measurement. We established OC imaging system for a single cell using phosphorescence lifetime and a laser scanning confocal microscope. This system had improved spatial resolution and reduced the measurement time with the high repetition rate of the laser. By the combination of ubiquitously distributed phosphorescent dye with this lifetime imaging microscope, we can visualize the OC inside the whole cell and spheroid. This system uses reversible phosphorescence quenching by oxygen, so it can measure successive OC changes from normoxia to anoxia. Lower regions of OC inside the cell colocalized with mitochondria. The time-dependent OC change in an insulin-producing cell line MIN6 by the glucose stimulation was successfully visualized. Assessing the detailed distribution and dynamics of OC inside cells achieved by the presented system will be useful to understanding a physiological and pathological oxygen metabolism. PMID:26065366

Laterally Coupled Distributed-Feedback GaSb-Based Diode Lasers for Atmospheric Gas Detection at 2 Microns

NASA Technical Reports Server (NTRS)

Briggs, Ryan M.; Frez, Clifford; Ksendzov, Alexander; Franz, Kale J.; Bagheri, Mahmood; Forouhar, Siamak

2012-01-01

We demonstrate single-mode laterally coupled distributed-feedback diode lasers at 2.05 microns employing low-loss etched gratings. Single-facet CW output exceeds 50 mW near room temperature with linewidth below 1 MHz over 10-ms observation times

High-power ultralong-wavelength Tm-doped silica fiber laser cladding-pumped with a random distributed feedback fiber laser

PubMed Central

Jin, Xiaoxi; Du, Xueyuan; Wang, Xiong; Zhou, Pu; Zhang, Hanwei; Wang, Xiaolin; Liu, Zejin

2016-01-01

We demonstrated a high-power ultralong-wavelength Tm-doped silica fiber laser operating at 2153 nm with the output power exceeding 18 W and the slope efficiency of 25.5%. A random distributed feedback fiber laser with the center wavelength of 1173 nm was employed as pump source of Tm-doped fiber laser for the first time. No amplified spontaneous emissions or parasitic oscillations were observed when the maximum output power reached, which indicates that employing 1173 nm random distributed feedback fiber laser as pump laser is a feasible and promising scheme to achieve high-power emission of long-wavelength Tm-doped fiber laser. The output power of this Tm-doped fiber laser could be further improved by optimizing the length of active fiber, reflectivity of FBGs, increasing optical efficiency of pump laser and using better temperature management. We also compared the operation of 2153 nm Tm-doped fiber lasers pumped with 793 nm laser diodes, and the maximum output powers were limited to ~2 W by strong amplified spontaneous emission and parasitic oscillation in the range of 1900–2000 nm. PMID:27416893

High-power ultralong-wavelength Tm-doped silica fiber laser cladding-pumped with a random distributed feedback fiber laser.

PubMed

Jin, Xiaoxi; Du, Xueyuan; Wang, Xiong; Zhou, Pu; Zhang, Hanwei; Wang, Xiaolin; Liu, Zejin

2016-07-15

We demonstrated a high-power ultralong-wavelength Tm-doped silica fiber laser operating at 2153 nm with the output power exceeding 18 W and the slope efficiency of 25.5%. A random distributed feedback fiber laser with the center wavelength of 1173 nm was employed as pump source of Tm-doped fiber laser for the first time. No amplified spontaneous emissions or parasitic oscillations were observed when the maximum output power reached, which indicates that employing 1173 nm random distributed feedback fiber laser as pump laser is a feasible and promising scheme to achieve high-power emission of long-wavelength Tm-doped fiber laser. The output power of this Tm-doped fiber laser could be further improved by optimizing the length of active fiber, reflectivity of FBGs, increasing optical efficiency of pump laser and using better temperature management. We also compared the operation of 2153 nm Tm-doped fiber lasers pumped with 793 nm laser diodes, and the maximum output powers were limited to ~2 W by strong amplified spontaneous emission and parasitic oscillation in the range of 1900-2000 nm.

Distributed Feedback Laser Based on Single Crystal Perovskite

NASA Astrophysics Data System (ADS)

Sun, Shang; Xiao, Shumin; Song, Qinghai

2017-06-01

We demonstrate a single crystal perovskite based, with grating-structured photoresist on top, highly polarized distributed feedback laser. A lower laser threshold than the Fabry-Perot mode lasers from the same single crystal CH3NH3PbBr3 microplate was obtained. Single crystal CH3NH3PbBr3 microplates was synthesized with one-step solution processed precipitation method. Once the photoresist on top of the microplate was patterned with electron beam, the device was realized. This one-step fabrication process utilized the advantage of single crystal to the greatest extend. The ultra-low defect density in single crystalline microplate offer an opportunity for lower threshold lasing action compare with poly-crystal perovskite films. In the experiment, the lasing action based on the distributed feedback grating design was found with lower threshold and higher intensity than the Fabry-Perot mode lasers supported by the flat facets of the same microplate.

Multi-peak structure of generation spectrum of random distributed feedback fiber Raman lasers.

PubMed

Vatnik, I D; Zlobina, E A; Kablukov, S I; Babin, S A

2017-02-06

We study spectral features of the generation of random distributed feedback fiber Raman laser arising from two-peak shape of the Raman gain spectral profile realized in the germanosilicate fibers. We demonstrate that number of peaks can be calculated using power balance model considering different subcomponents within each Stokes component.

Hundred-watt-level high power random distributed feedback Raman fiber laser at 1150 nm and its application in mid-infrared laser generation.

PubMed

Zhang, Hanwei; Zhou, Pu; Wang, Xiong; Du, Xueyuan; Xiao, Hu; Xu, Xiaojun

2015-06-29

Two kinds of hundred-watt-level random distributed feedback Raman fiber have been demonstrated. The optical efficiency can reach to as high as 84.8%. The reported power and efficiency of the random laser is the highest one as we know. We have also demonstrated that the developed random laser can be further used to pump a Ho-doped fiber laser for mid-infrared laser generation. Finally, 23 W 2050 nm laser is achieved. The presented laser can obtain high power output efficiently and conveniently and opens a new direction for high power laser sources at designed wavelength.

A 12 GHz wavelength spacing multi-wavelength laser source for wireless communication systems

NASA Astrophysics Data System (ADS)

Peng, P. C.; Shiu, R. K.; Bitew, M. A.; Chang, T. L.; Lai, C. H.; Junior, J. I.

2017-08-01

This paper presents a multi-wavelength laser source with 12 GHz wavelength spacing based on a single distributed feedback laser. A light wave generated from the distributed feedback laser is fed into a frequency shifter loop consisting of 50:50 coupler, dual-parallel Mach-Zehnder modulator, optical amplifier, optical filter, and polarization controller. The frequency of the input wavelength is shifted and then re-injected into the frequency shifter loop. By re-injecting the shifted wavelengths multiple times, we have generated 84 optical carriers with 12 GHz wavelength spacing and stable output power. For each channel, two wavelengths are modulated by a wireless data using the phase modulator and transmitted through a 25 km single mode fiber. In contrast to previously developed schemes, the proposed laser source does not incur DC bias drift problem. Moreover, it is a good candidate for radio-over-fiber systems to support multiple users using a single distributed feedback laser.

Fiber distributed feedback laser

NASA Technical Reports Server (NTRS)

Elachi, C.; Evans, G. A.; Yeh, C. (Inventor)

1976-01-01

Utilizing round optical fibers as communication channels in optical communication networks presents the problem of obtaining a high efficiency coupling between the optical fiber and the laser. A laser is made an integral part of the optical fiber channel by either diffusing active material into the optical fiber or surrounding the optical fiber with the active material. Oscillation within the active medium to produce lasing action is established by grating the optical fiber so that distributed feedback occurs.

LASER BIOLOGY: Visualisation of the distributions of melanin and indocyanine green in biological tissues

NASA Astrophysics Data System (ADS)

Genina, E. A.; Fedosov, I. V.; Bashkatov, A. N.; Zimnyakov, D. A.; Altshuler, G. B.; Tuchin, V. V.

2008-03-01

A double-wavelength laser scanning microphotometer with the high spectral and spatial resolutions is developed for studying the distribution of endogenic and exogenic dyes in biological tissues. Samples of hair and skin biopsy with hair follicles stained with indocyanine green are studied. The spatial distribution of indocyanine green and melanin in the biological tissue is determined from the measured optical transmittance.

Visualisation of the distributions of melanin and indocyanine green in biological tissues

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

Genina, E A; Fedosov, I V; Bashkatov, A N

2008-03-31

A double-wavelength laser scanning microphotometer with the high spectral and spatial resolutions is developed for studying the distribution of endogenic and exogenic dyes in biological tissues. Samples of hair and skin biopsy with hair follicles stained with indocyanine green are studied. The spatial distribution of indocyanine green and melanin in the biological tissue is determined from the measured optical transmittance. (laser biology)

Enhancement of the static extinction ratio by using a dual-section distributed feedback laser integrated with an electro-absorption modulator

NASA Astrophysics Data System (ADS)

Cho, Chun-Hyung; Kim, Jongseong; Sung, Hyuk-Kee

2016-09-01

We report on the enhancement of the static extinction ratio by using a dual-section distributed feedback laser diode integrated with an electro-absorption modulator. A directly- modulated dual-section laser can provide improved modulation performance under a low bias level ( i.e., below the threshold level) compared with a standard directly-modulated laser. By combining the extinction ratio from a dual-section laser with that from an electro-absorption modulator section, a total extinction ratio of 49.6. dB are successfully achieved.

Characteristics of a Broadband Dye Laser Using Pyrromethene and Rhodamine Dyes

NASA Technical Reports Server (NTRS)

Tedder, Sarah A.; Danehy, Paul M.; Wheeler, Jeffrey L.

2011-01-01

A broadband dye laser pumped by a frequency-doubled Nd:YAG laser with a full-width half-maximum (FWHM) from 592 to 610 nm was created for the use in a dual-pump broadband CARS system called WIDECARS. The desired broadband dye laser was generated with a mixture of Pyrromethene dyes as an oscillator gain medium and a spectral selective optic in the oscillator cavity. A mixture of Rhodamine dyes were used in the amplifier dye cell. To create this laser a study was performed to characterize the spectral behavior of broadband dye lasers created with Rhodamine dyes 590, 610, and 640, Pyrromethene dyes 597 and 650 as well as mixture of these dyes.

INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Continuous-wave distributed-feedback InGaAsP (λ = 1.55 μm) injection heterolasers

NASA Astrophysics Data System (ADS)

Baryshev, V. I.; Golikova, E. G.; Duraev, V. P.; Kuchinskiĭ, V. I.; Kizhaev, K. Yu; Kuksenkov, D. V.; Portnoĭ, E. L.; Smirnitskiĭ, V. B.

1988-11-01

A study was made of stimulated emission from mesa-stripe distributed-feedback lasers in the form of double heterostructures with separate electron and optical confinement. A diffraction grating with a period Λ = 0.46 μm, formed on the surface of the upper waveguide layer by holographic lithography, ensured distributed feedback in the second order. The threshold current for cw operation at room temperature was 35-70 mA, the shift of the emission wavelength with temperature was ~ 0.08 nm/K, and the feedback coefficient deduced from the width of a "Bragg gap" was 110-150 cm- 1.

Plasmon-polariton distributed-feedback laser pumped by a fast drift current in graphene

NASA Astrophysics Data System (ADS)

Zolotovskii, Igor O.; Dadoenkova, Yuliya S.; Moiseev, Sergey G.; Kadochkin, Aleksei S.; Svetukhin, Vyacheslav V.; Fotiadi, Andrei A.

2018-05-01

We propose a model of a slow surface plasmon-polariton distributed-feedback laser with pump by drift current. The amplification in the dielectric-semiconducting film-dielectric waveguide structure is created by fast drift current in the graphene layer, placed at the semiconductor/dielectric interface. The feedback is provided due to a periodic change in the thickness of the semiconducting film. We have shown that in such a system it is possible to achieve surface plasmon-polariton generation in the terahertz region.

Dye-impregnated polymer-filled porous glass: a new composite material for solid state dye lasers and laser beam control optical elements (Abstract Only)

NASA Astrophysics Data System (ADS)

Koldunov, M. F.; Manenkov, Alexander A.; Sitnikov, N. M.; Dolotov, S. M.

1994-07-01

Polymer-filled microporous glass (PFMG) composite materials have been recently proposed as a proper host for dyes to create solid-state dye lasers and laser beam control elements (Q-switchers, etc.) [1,2]. In this paper we report investigation of some laser-related properties of Polymethilmethacrylate (PMAA) - filled porous glass doped with Rhodamine 6G perchiorate (active lasing dye) and 1055 dye (passive bleachable dye): laser induced damage threshold, lasmg efficiency, bleaching efficiency, and microhardness have been measured. All these characteristics have been found to be rather high indicating that PFMG composite materials are perspective hosts for dye impregnation and fabrication highly effective solid-state dye lasers and other laser related elements (Q-switchers, mode-lockers, modeselectors, spatial filters).

Distributed feedback laser diode integrated with distributed Bragg reflector for continuous-wave terahertz generation.

PubMed

Kim, Namje; Han, Sang-Pil; Ryu, Han-Cheol; Ko, Hyunsung; Park, Jeong-Woo; Lee, Donghun; Jeon, Min Yong; Park, Kyung Hyun

2012-07-30

A widely tunable dual mode laser diode with a single cavity structure is demonstrated. This novel device consists of a distributed feedback (DFB) laser diode and distributed Bragg reflector (DBR). Micro-heaters are integrated on the top of each section for continuous and independent wavelength tuning of each mode. By using a single gain medium in the DFB section, an effective common optical cavity and common modes are realized. The laser diode shows a wide tunability of the optical beat frequency, from 0.48 THz to over 2.36 THz. Continuous wave THz radiation is also successfully generated with low-temperature grown InGaAs photomixers from 0.48 GHz to 1.5 THz.

Laterally Coupled Quantum-Dot Distributed-Feedback Lasers

NASA Technical Reports Server (NTRS)

Qui, Yueming; Gogna, Pawan; Muller, Richard; Maker, paul; Wilson, Daniel; Stintz, Andreas; Lester, Luke

2003-01-01

InAs quantum-dot lasers that feature distributed feedback and lateral evanescent- wave coupling have been demonstrated in operation at a wavelength of 1.3 m. These lasers are prototypes of optical-communication oscillators that are required to be capable of stable single-frequency, single-spatial-mode operation. A laser of this type (see figure) includes an active layer that comprises multiple stacks of InAs quantum dots embedded within InGaAs quantum wells. Distributed feedback is provided by gratings formed on both sides of a ridge by electron lithography and reactive-ion etching on the surfaces of an AlGaAs/GaAs waveguide. The lateral evanescent-wave coupling between the gratings and the wave propagating in the waveguide is strong enough to ensure operation at a single frequency, and the waveguide is thick enough to sustain a stable single spatial mode. In tests, the lasers were found to emit continuous-wave radiation at temperatures up to about 90 C. Side modes were found to be suppressed by more than 30 dB.

Multiwavelength generation in a random distributed feedback fiber laser using an all fiber Lyot filter.

PubMed

Sugavanam, S; Yan, Z; Kamynin, V; Kurkov, A S; Zhang, L; Churkin, D V

2014-02-10

Multiwavelength lasing in the random distributed feedback fiber laser is demonstrated by employing an all fiber Lyot filter. Stable multiwavelength generation is obtained, with each line exhibiting sub-nanometer line-widths. A flat power distribution over multiple lines is obtained, which indicates that the power between lines is redistributed in nonlinear mixing processes. The multiwavelength generation is observed both in first and second Stokes waves.

Organic Lasers: Recent Developments on Materials, Device Geometries, and Fabrication Techniques.

PubMed

Kuehne, Alexander J C; Gather, Malte C

2016-11-09

Organic dyes have been used as gain medium for lasers since the 1960s, long before the advent of today's organic electronic devices. Organic gain materials are highly attractive for lasing due to their chemical tunability and large stimulated emission cross section. While the traditional dye laser has been largely replaced by solid-state lasers, a number of new and miniaturized organic lasers have emerged that hold great potential for lab-on-chip applications, biointegration, low-cost sensing and related areas, which benefit from the unique properties of organic gain materials. On the fundamental level, these include high exciton binding energy, low refractive index (compared to inorganic semiconductors), and ease of spectral and chemical tuning. On a technological level, mechanical flexibility and compatibility with simple processing techniques such as printing, roll-to-roll, self-assembly, and soft-lithography are most relevant. Here, the authors provide a comprehensive review of the developments in the field over the past decade, discussing recent advances in organic gain materials, which are today often based on solid-state organic semiconductors, as well as optical feedback structures, and device fabrication. Recent efforts toward continuous wave operation and electrical pumping of solid-state organic lasers are reviewed, and new device concepts and emerging applications are summarized.

All-Fiber Configuration Laser Self-Mixing Doppler Velocimeter Based on Distributed Feedback Fiber Laser.

PubMed

Wu, Shuang; Wang, Dehui; Xiang, Rong; Zhou, Junfeng; Ma, Yangcheng; Gui, Huaqiao; Liu, Jianguo; Wang, Huanqin; Lu, Liang; Yu, Benli

2016-07-27

In this paper, a novel velocimeter based on laser self-mixing Doppler technology has been developed for speed measurement. The laser employed in our experiment is a distributed feedback (DFB) fiber laser, which is an all-fiber structure using only one Fiber Bragg Grating to realize optical feedback and wavelength selection. Self-mixing interference for optical velocity sensing is experimentally investigated in this novel system, and the experimental results show that the Doppler frequency is linearly proportional to the velocity of a moving target, which agrees with the theoretical analysis commendably. In our experimental system, the velocity measurement can be achieved in the range of 3.58 mm/s-2216 mm/s with a relative error under one percent, demonstrating that our novel all-fiber configuration velocimeter can implement wide-range velocity measurements with high accuracy.

Characteristics of a broadband dye laser using Pyrromethene and Rhodamine dyes.

PubMed

Tedder, Sarah A; Wheeler, Jeffrey L; Danehy, Paul M

2011-02-20

A broadband dye laser pumped by a frequency-doubled Nd:YAG laser with a full width at half-maximum from 592 to 610 nm was created for the use in a dual-pump broadband coherent anti-Stokes Raman spectroscopy (CARS) system called width increased dual-pump enhanced CARS (WIDECARS). The desired broadband dye laser was generated with a mixture of Pyrromethene dyes as an oscillator gain medium and a spectral selective optic in the oscillator cavity. A mixture of Rhodamine dyes was used in the amplifier dye cell. To create this laser, a study was performed to characterize the spectral behavior of broadband dye lasers created with Rhodamine dyes 590, 610, and 640 and Pyrromethene dyes 597 and 650, as well as mixtures of these dyes.

Nanoimprinted polymer lasers with threshold below 100 W/cm2 using mixed-order distributed feedback resonators.

PubMed

Wang, Yue; Tsiminis, Georgios; Kanibolotsky, Alexander L; Skabara, Peter J; Samuel, Ifor D W; Turnbull, Graham A

2013-06-17

Organic semiconductor lasers were fabricated by UV-nanoimprint lithography with thresholds as low as 57 W/cm(2) under 4 ns pulsed operation. The nanoimprinted lasers employed mixed-order distributed feedback resonators, with second-order gratings surrounded by first-order gratings, combined with a light-emitting conjugated polymer. They were pumped by InGaN LEDs to produce green-emitting lasers, with thresholds of 208 W/cm(2) (102 nJ/pulse). These hybrid lasers incorporate a scalable UV-nanoimprint lithography process, compatible with high-performance LEDs, therefore we have demonstrated a coherent, compact, low-cost light source.

Construction and Characterization of External Cavity Diode Lasers for Atomic Physics

PubMed Central

Hardman, Kyle S.; Bennetts, Shayne; Debs, John E.; Kuhn, Carlos C. N.; McDonald, Gordon D.; Robins, Nick

2014-01-01

Since their development in the late 1980s, cheap, reliable external cavity diode lasers (ECDLs) have replaced complex and expensive traditional dye and Titanium Sapphire lasers as the workhorse laser of atomic physics labs1,2. Their versatility and prolific use throughout atomic physics in applications such as absorption spectroscopy and laser cooling1,2 makes it imperative for incoming students to gain a firm practical understanding of these lasers. This publication builds upon the seminal work by Wieman3, updating components, and providing a video tutorial. The setup, frequency locking and performance characterization of an ECDL will be described. Discussion of component selection and proper mounting of both diodes and gratings, the factors affecting mode selection within the cavity, proper alignment for optimal external feedback, optics setup for coarse and fine frequency sensitive measurements, a brief overview of laser locking techniques, and laser linewidth measurements are included. PMID:24796259

Construction and characterization of external cavity diode lasers for atomic physics.

PubMed

Hardman, Kyle S; Bennetts, Shayne; Debs, John E; Kuhn, Carlos C N; McDonald, Gordon D; Robins, Nick

2014-04-24

Since their development in the late 1980s, cheap, reliable external cavity diode lasers (ECDLs) have replaced complex and expensive traditional dye and Titanium Sapphire lasers as the workhorse laser of atomic physics labs. Their versatility and prolific use throughout atomic physics in applications such as absorption spectroscopy and laser cooling makes it imperative for incoming students to gain a firm practical understanding of these lasers. This publication builds upon the seminal work by Wieman, updating components, and providing a video tutorial. The setup, frequency locking and performance characterization of an ECDL will be described. Discussion of component selection and proper mounting of both diodes and gratings, the factors affecting mode selection within the cavity, proper alignment for optimal external feedback, optics setup for coarse and fine frequency sensitive measurements, a brief overview of laser locking techniques, and laser linewidth measurements are included.

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.

Design and Construction of Simple, Nitrogen-Laser-Pumped, Tunable Dye Lasers

ERIC Educational Resources Information Center

Hilborn, Robert C.

1978-01-01

The basic physical principles of dye lasers are discussed and used to analyze the design and operation of tunable dye lasers pumped by pulsed nitrogen lasers. Details of the design and construction of these dye lasers are presented. Some simple demonstration experiments are described. (BB)

Thermo-spectral properties of plastic lasers

NASA Astrophysics Data System (ADS)

Dawson, Nathan J.; Aviles, Michael; Andrews, James H.; Crescimanno, Michael; Petrus, Joshua B.; Mazzocco, Anthony; Singer, Kenneth D.; Baer, Eric; Song, Hyunmin

2013-09-01

We study the effects of temperature changes on the operating wavelength of all-polymer microresonator lasers, particularly on multilayered defect distributed feedback and distributed Bragg reflector lasers. The parameters that change the operating wavelength are discussed with comparisons between experiments and simulations.

All-Fiber Configuration Laser Self-Mixing Doppler Velocimeter Based on Distributed Feedback Fiber Laser

PubMed Central

Wu, Shuang; Wang, Dehui; Xiang, Rong; Zhou, Junfeng; Ma, Yangcheng; Gui, Huaqiao; Liu, Jianguo; Wang, Huanqin; Lu, Liang; Yu, Benli

2016-01-01

In this paper, a novel velocimeter based on laser self-mixing Doppler technology has been developed for speed measurement. The laser employed in our experiment is a distributed feedback (DFB) fiber laser, which is an all-fiber structure using only one Fiber Bragg Grating to realize optical feedback and wavelength selection. Self-mixing interference for optical velocity sensing is experimentally investigated in this novel system, and the experimental results show that the Doppler frequency is linearly proportional to the velocity of a moving target, which agrees with the theoretical analysis commendably. In our experimental system, the velocity measurement can be achieved in the range of 3.58 mm/s–2216 mm/s with a relative error under one percent, demonstrating that our novel all-fiber configuration velocimeter can implement wide-range velocity measurements with high accuracy. PMID:27472342

High laser efficiency and photostability of pyrromethene dyes mediated by nonpolar solvent.

PubMed

Gupta, Monika; Kamble, Priyadarshini; Rath, M C; Naik, D B; Ray, Alok K

2015-08-10

Many pyrromethene (PM) dyes have been shown to outperform established rhodamine dyes in terms of laser efficiency in the green-yellow spectral region, but their rapid photochemical degradation in commonly used ethanol or methanol solvents continues to limit its use in high average power liquid dye lasers. A comparative study on narrowband laser efficiency and photostability of commercially available PM567 and PM597 dyes, using nonpolar n-heptane and 1,4-dioxane and polar ethanol solvents, was carried out by a constructed pulsed dye laser, pumped by the second harmonic (532 nm) radiation of a Q-switched Nd:YAG laser. Interestingly, both nonpolar solvents showed a significantly higher laser photostability (∼100 times) as well as peak efficiency (∼5%) of these PM dyes in comparison to ethanol. The different photostability of the PM dyes was rationalized by determining their triplet-state spectra and capability to generate reactive singlet oxygen (O₂1) by energy transfer to dissolved oxygen in these solvents using pulse radiolysis. Heptane is identified as a promising solvent for these PM dyes for use in high average power dye lasers, pumped by copper vapor lasers or diode-pumped solid-state green lasers.

Experimental demonstration of a multi-wavelength distributed feedback semiconductor laser array with an equivalent chirped grating profile based on the equivalent chirp technology.

PubMed

Li, Wangzhe; Zhang, Xia; Yao, Jianping

2013-08-26

We report, to the best of our knowledge, the first realization of a multi-wavelength distributed feedback (DFB) semiconductor laser array with an equivalent chirped grating profile based on equivalent chirp technology. All the lasers in the laser array have an identical grating period with an equivalent chirped grating structure, which are realized by nonuniform sampling of the gratings. Different wavelengths are achieved by changing the sampling functions. A multi-wavelength DFB semiconductor laser array is fabricated and the lasing performance is evaluated. The results show that the equivalent chirp technology is an effective solution for monolithic integration of a multi-wavelength laser array with potential for large volume fabrication.

Development of New Laser Protective Dyes. Phase 2.

DTIC Science & Technology

DYE LASERS, PROTECTION, LASERS, DYES , HAZARDS, SYNTHESIS, EYE SAFETY, OPTICAL MATERIALS, PLASTICS, LENSES, THERMAL STABILITY, CYANINE DYES , POLYCARBONATES, INJECTION MOLDING, NEAR INFRARED RADIATION, FLUORENES.

Experimental demonstration of distributed feedback semiconductor lasers based on reconstruction-equivalent-chirp technology.

PubMed

Li, Jingsi; Wang, Huan; Chen, Xiangfei; Yin, Zuowei; Shi, Yuechun; Lu, Yanqing; Dai, Yitang; Zhu, Hongliang

2009-03-30

In this paper we report, to the best of our knowledge, the first experimental realization of distributed feedback (DFB) semiconductor lasers based on reconstruction-equivalent-chirp (REC) technology. Lasers with different lasing wavelengths are achieved simultaneously on one chip, which shows a potential for the REC technology in combination with the photonic integrated circuits (PIC) technology to be a possible method for monolithic integration, in that its fabrication is as powerful as electron beam technology and the cost and time-consuming are almost the same as standard holographic technology.

Heterogeneously integrated III-V/silicon dual-mode distributed feedback laser array for terahertz generation.

PubMed

Shao, Haifeng; Keyvaninia, Shahram; Vanwolleghem, Mathias; Ducournau, Guillaume; Jiang, Xiaoqing; Morthier, Geert; Lampin, Jean-Francois; Roelkens, Gunther

2014-11-15

We demonstrate an integrated distributed feedback (DFB) laser array as a dual-wavelength source for narrowband terahertz (THz) generation. The laser array is composed of four heterogeneously integrated III-V-on-silicon DFB lasers with different lengths enabling dual-mode lasing tolerant to process variations, bias fluctuations, and ambient temperature variations. By optical heterodyning the two modes emitted by the dual-wavelength DFB laser in the laser array using a THz photomixer composed of an uni-traveling carrier photodiode (UTC-PD), a narrow and stable carrier signal with a frequency of 0.357 THz is generated. The central operating frequency and the emitted terahertz wave linewidth are analyzed, along with their dependency on the bias current applied to the laser diode and ambient temperature.

Highly efficient single-pass frequency doubling of a continuous-wave distributed feedback laser diode using a PPLN waveguide crystal at 488 nm.

PubMed

Jechow, Andreas; Schedel, Marco; Stry, Sandra; Sacher, Joachim; Menzel, Ralf

2007-10-15

A continuous-wave distributed feedback diode laser emitting at 976 nm was frequency doubled by the use of a periodically poled lithium niobate waveguide crystal with a channel size of 3 microm x 5 microm and an interaction length of 10 mm. A laser to waveguide coupling efficiency of 75% could be achieved resulting in 304 mW of incident infrared light inside the waveguide. Blue laser light emission of 159 mW at 488 nm has been generated, which equals to a conversion efficiency of 52%. The resulting wall plug efficiency was 7.4%.

Temperature dependence of spectral linewidth of InAs/InP quantum dot distributed feedback lasers

NASA Astrophysics Data System (ADS)

Duan, J.; Huang, H.; Schires, K.; Poole, P. J.; Wang, C.; Grillot, F.

2018-02-01

In this paper, we investigate the temperature dependence of spectral linewidth of InAs/InP quantum dot distributed feedback lasers. In comparison with their quantum well counterparts, results show that quantum dot lasers have spectral linewidths rather insensitive to the temperature with minimum values below 200 kHz in the range of 283K to 303K. The experimental results are also well confirmed by numerical simulations. Overall, this work shows that quantum dot lasers are excellent candidates for various applications such as coherent communication systems, high-resolution spectroscopy, high purity photonic microwave generation and on-chip atomic clocks.

Calculation of photonic bandgap for 2D hexagonal and square structure base on hybrid polymer material

NASA Astrophysics Data System (ADS)

Hidayat, S.; Riveli, N.

2018-05-01

We have calculated 2D photonic crystal band gap using plane-wave expansion method. The studied model of structures is hexagonal lattice and square lattice of rod cylinder in air. We have simulated the dispersion relation of it structure using hybrid polymer as rod material. The parameter structures are nrod = 1.5, nhole = 1, and rrod = 0.25a, where a is lattice constant. We found the distributed feedback occurs at the edge of upper band or frequency at 0.66 (a/λ). In our experimental work, we have successfully fabricated the 2D photonic crystal from hybrid polymer incorporated with organic dye laser. The lasing characteristics ware investigated using strip-line excitation light of SHG Nd-YAG laser (λ=532 nm). The lasing wavelengths for hexagonal structure are observed at 606 nm and 621 nm for photonic crystal period of 400 nm and 410 nm, respectively. λ=532 nm). Whereas the square structure, the lasing wavelengths are observed at (588 nm ± 2) and (606 nm ± 2 nm) for grating period of 391 nm and 405 nm.

Non-Shilnikov cascades of spikes and hubs in a semiconductor laser with optoelectronic feedback.

PubMed

Freire, Joana G; Gallas, Jason A C

2010-09-01

Incomplete homoclinic scenarios were recently measured in a semiconductor laser with optoelectronic feedback. We show here that such a laser contains cascades of spirals of periodic oscillations and hubs which look identical to the familiar ones observed in complete homoclinic scenarios. This means that hubs are far more general than presumed so far, being not limited by Shilnikov's theorem. Laser hubs open the possibility of measuring complex distributions of non-Shilnikov laser oscillations, and we briefly discuss how to do it.

Study of gain-coupled distributed feedback laser based on high order surface gain-coupled gratings

NASA Astrophysics Data System (ADS)

Gao, Feng; Qin, Li; Chen, Yongyi; Jia, Peng; Chen, Chao; Cheng, LiWen; Chen, Hong; Liang, Lei; Zeng, Yugang; Zhang, Xing; Wu, Hao; Ning, Yongqiang; Wang, Lijun

2018-03-01

Single-longitudinal-mode, gain-coupled distributed feedback (DFB) lasers based on high order surface gain-coupled gratings are achieved. Periodic surface metal p-contacts with insulated grooves realize gain-coupled mechanism. To enhance gain contrast in the quantum wells without the introduction of effective index-coupled effect, groove length and depth were well designed. Our devices provided a single longitudinal mode with the maximum CW output power up to 48.8 mW/facet at 971.31 nm at 250 mA without facet coating, 3dB linewidth (<3.2 pm) and SMSR (>39 dB). Optical bistable characteristic was observed with a threshold current difference. Experimentally, devices with different cavity lengths were contrasted on power-current and spectrum characteristics. Due to easy fabrication technique and stable performance, it provides a method of fabricating practical gain-coupled distributed feedback lasers for commercial applications.

Influence of the UV-induced fiber loss on the distributed feedback fiber lasers

NASA Astrophysics Data System (ADS)

Fan, Wei; Chen, Bai; Qiao, Qiquan; Chen, Jialing; Lin, Zunqi

2003-06-01

It was found that the output power of the distributed feedback fiber lasers would be improved after annealing or left unused for several days after the laser had been fabricated, and the output of the fundamental mode would not increase but be clamped while the ±1 order modes would be predominant with the enhancement of the coupling coefficient during the fabrication. The paper discussed the influence of UV-induced fiber loss on the fiber phase-shifted DFB lasers. Due to the gain saturation and fiber internal loss, which included the temperament loss and permanent loss, there was an optimum coupling coefficient for the DFB fiber lasers that the higher internal fiber loss corresponded to the lower optimum values of coupling coefficient.

Review on recent Developments on Fabrication Techniques of Distributed Feedback (DFB) Based Organic Lasers

NASA Astrophysics Data System (ADS)

Azrina Talik, Noor; Boon Kar, Yap; Noradhlia Mohamad Tukijan, Siti; Wong, Chuan Ling

2017-10-01

To date, the state of art organic semiconductor distributed feedback (DFB) lasers gains tremendous interest in the organic device industry. This paper presents a short reviews on the fabrication techniques of DFB based laser by focusing on the fabrication method of DFB corrugated structure and the deposition of organic gain on the nano-patterned DFB resonator. The fabrication techniques such as Laser Direct Writing (LDW), ultrafast photo excitation dynamics, Laser Interference Lithography (LIL) and Nanoimprint Lithography (NIL) for DFB patterning are presented. In addition to that, the method for gain medium deposition method is also discussed. The technical procedures of the stated fabrication techniques are summarized together with their benefits and comparisons to the traditional fabrication techniques.

Continuous-wave dual-wavelength operation of a distributed feedback laser diode with an external cavity using a volume Bragg grating

NASA Astrophysics Data System (ADS)

Zheng, Yujin; Sekine, Takashi; Kurita, Takashi; Kato, Yoshinori; Kawashima, Toshiyuki

2018-03-01

We demonstrate continuous-wave dual-wavelength operation of a broad-area distributed feedback (DFB) laser diode with a single external-cavity configuration. This high-power DFB laser has a narrow bandwidth (<0.29 nm) and was used as a single-wavelength source. A volume Bragg grating was used as an output coupler for the external-cavity DFB laser to output another stable wavelength beam with a narrow bandwidth of 0.27 nm. A frequency difference for dual-wavelength operation of 0.88 THz was achieved and an output power of up to 415 mW was obtained. The external-cavity DFB laser showed a stable dual-wavelength operation over the practical current and temperature ranges.

Measurement of Zeta-Potential at Microchannel Wall by a Nanoscale Laser Induced Fluorescence Imaging

NASA Astrophysics Data System (ADS)

Kazoe, Yutaka; Sato, Yohei

A nanoscale laser induced fluorescence imaging was proposed by using fluorescent dye and the evanescent wave with total internal reflection of a laser beam. The present study focused on the two-dimensional measurement of zeta-potential at the microchannel wall, which is an electrostatic potential at the wall surface and a dominant parameter of electroosmotic flow. The evanescent wave, which decays exponentially from the wall, was used as an excitation light of the fluorescent dye. The fluorescent intensity detected by a CCD camera is closely related to the zeta-potential. Two kinds of fluorescent dye solution at different ionic concentrations were injected into a T-shaped microchannel, and formed a mixing flow field in the junction area. The two-dimensional distribution of zeta-potential at the microchannel wall in the pressure-driven flow field was measured. The obtained zeta-potential distribution has a transverse gradient toward the mixing flow field and was changed by the difference in the averaged velocity of pressure-driven flow. To understand the ion motion in the mixing flow field, the three-dimensional flow structure was analyzed by the velocity measurement using micron-resolution particle image velocimetry and the numerical simulation. It is concluded that the two-dimensional distribution of zeta-potential at the microchannel wall was dependent on the ion motion in the flow field, which was governed by the convection and molecular diffusion.

Narrow spectral linewidth in InAs/InP quantum dot distributed feedback lasers

NASA Astrophysics Data System (ADS)

Duan, J.; Huang, H.; Lu, Z. G.; Poole, P. J.; Wang, C.; Grillot, F.

2018-03-01

This paper reports on the spectral linewidth of InAs/InP quantum dot distributed feedback lasers. Owing to a low inversion factor and a low linewidth enhancement factor, a narrow spectral linewidth of 160 kHz (80 kHz intrinsic linewidth) with a low sensitivity to temperature is demonstrated. When using anti-reflection coatings on both facets, narrow linewidth operation is extended to high powers, believed to be due to a reduction in the longitudinal spatial hole burning. These results confirm the high potential of quantum dot lasers for increasing transmission capacity in future coherent communication systems.

Hybrid Multilayered Plasmonic Nanostars for Coherent Random Lasing.

PubMed

Munkhbat, Battulga; Ziegler, Johannes; Pöhl, Hannes; Wörister, Christian; Sivun, Dmitry; Scharber, Markus C; Klar, Thomas A; Hrelescu, Calin

2016-10-20

Here, we report that hybrid multilayered plasmonic nanostars can be universally used as feedback agents for coherent random lasing in polar or nonpolar solutions containing gain material. We show that silver-enhancement of gold nanostars reduces the pumping threshold for coherent random lasing substantially for both a typical dye (R6G) and a typical fluorescent polymer (MEH-PPV). Further, we reveal that the lasing intensity and pumping threshold of random lasers based on silver-enhanced gold nanostars are not influenced by the silica coating, in contrast to gold nanostar-based random lasers, where silica-coated gold nanostars support only amplified spontaneous emission but no coherent random lasing.

Single mode pulsed dye laser oscillator

DOEpatents

Hackel, Richard P.

1992-01-01

A single mode pulsed dye laser oscillator is disclosed. The dye laser oscillator provides for improved power efficiency by reducing the physical dimensions of the overall laser cavity, which improves frequency selection capability.

Monolithic dual-mode distributed feedback semiconductor laser for tunable continuous-wave terahertz generation.

PubMed

Kim, Namje; Shin, Jaeheon; Sim, Eundeok; Lee, Chul Wook; Yee, Dae-Su; Jeon, Min Yong; Jang, Yudong; Park, Kyung Hyun

2009-08-03

We report on a monolithic dual-mode semiconductor laser operating in the 1550-nm range as a compact optical beat source for tunable continuous-wave (CW) terahertz (THz) generation. It consists of two distributed feedback (DFB) laser sections and one phase section between them. Each wavelength of the two modes can be independently tuned by adjusting currents in micro-heaters which are fabricated on the top of the each DFB section. The continuous tuning of the CW THz emission from Fe(+)-implanted InGaAs photomixers is successfully demonstrated using our dual-mode laser as the excitation source. The CW THz frequency is continuously tuned from 0.17 to 0.49 THz.

Photophysical properties, photodegradation characteristics, and lasing action for coumarin dye C540A in polymeric media

NASA Astrophysics Data System (ADS)

Jones, Guilford, II; Huang, Zhennian; Pacheco, Dennis P., Jr.; Russell, Jeffrey A.

2004-07-01

Tunable solid-state dye lasers operating in the blue-green spectral region are attractive for a variety of applications. An important consideration in assessing the viability of this technology is the service life of the gain medium, which is presently limited by dye photodegradation. In this study, solid polymeric samples consisting of the coumarin dye C540A in modified PMMA were subjected to controlled photodegradation tests. The excitation laser was a flashlamp-pumped dye laser operating at 440 nm with a pulse duration of 1 μs. A complementary set of data was obtained for dye in solution phase for comparison purposes. Photophysical properties of C540A in water solution of polymethacrylic acid (PMAA) have been investigated with a view to assess the suitability of the sequestering polymer (PMAA) as an effective additive to facilitate use of a water medium for highly efficient blue-green dye lasers. Lasing action of C540A in aqueous PMAA has been realized using flashlamp-pumped laser system, yielding excellent laser efficiencies superior to that achieved in ethanolic solutions with the same dye. Laser characterization of dye in media included measurement of laser threshold, slope efficiency, pulse duration and output wavelength.

Argon dye photocoagulator for microsurgery of the interior structure of the eye

NASA Astrophysics Data System (ADS)

Wolinski, Wieslaw L.; Kazmirowski, Antoni; Kesik, Jerzy; Korobowicz, Witold; Spytkowski, Wojciech

1991-08-01

Argon-dye laser photocoagulator for the microsurgery of the interior structure of the eye is described. Some technical specifications like power stability shape of the spots and the dependence of the power on the tissue vs. wavelenght for dye laser are given. Argon-dye photocoagulator was designed and constructed including argon laser tube and dye laser in Institute of Microelectronics and Optoelectronics Technical University of Warsaw.

Single mode pulsed dye laser oscillator

DOEpatents

Hackel, R.P.

1992-11-24

A single mode pulsed dye laser oscillator is disclosed. The dye laser oscillator provides for improved power efficiency by reducing the physical dimensions of the overall laser cavity, which improves frequency selection capability. 6 figs.

Solvent-free fluidic organic dye lasers.

PubMed

Choi, Eun Young; Mager, Loic; Cham, Tran Thi; Dorkenoo, Kokou D; Fort, Alain; Wu, Jeong Weon; Barsella, Alberto; Ribierre, Jean-Charles

2013-05-06

We report on the demonstration of liquid organic dye lasers based on 9-(2-ethylhexyl)carbazole (EHCz), so-called liquid carbazole, doped with green- and red-emitting laser dyes. Both waveguide and Fabry-Perot type microcavity fluidic organic dye lasers were prepared by capillary action under solvent-free conditions. Cascade Förster-type energy transfer processes from liquid carbazole to laser dyes were employed to achieve color-variable amplified spontaneous emission and lasing. Overall, this study provides the first step towards the development of solvent-free fluidic organic semiconducting lasers and demonstrates a new kind of optoelectronic applications for liquid organic semiconductors.

MQW Optical Feedback Modulators And Phase Shifters

NASA Technical Reports Server (NTRS)

Jackson, Deborah J.

1995-01-01

Laser diodes equipped with proposed multiple-quantum-well (MQW) optical feedback modulators prove useful in variety of analog and digital optical-communication applications, including fiber-optic signal-distribution networks and high-speed, low-crosstalk interconnections among super computers or very-high-speed integrated circuits. Development exploits accompanying electro-optical aspect of QCSE - variation in index of refraction with applied electric field. Also exploits sensitivity of laser diodes to optical feedback. Approach is reverse of prior approach.

Mode switching in a multi-wavelength distributed feedback quantum cascade laser using an external micro-cavity

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

Sidler, Meinrad; Institute for Quantum Electronics, ETH Zurich, Wolfgang-Pauli-Strasse 16, 8093 Zurich; Rauter, Patrick

2014-02-03

We demonstrate a multi-wavelength distributed feedback (DFB) quantum cascade laser (QCL) operating in a lensless external micro-cavity and achieve switchable single-mode emission at three distinct wavelengths selected by the DFB grating, each with a side-mode suppression ratio larger than 30 dB. Discrete wavelength tuning is achieved by modulating the feedback experienced by each mode of the multi-wavelength DFB QCL, resulting from a variation of the external cavity length. This method also provides a post-fabrication control of the lasing modes to correct for fabrication inhomogeneities, in particular, related to the cleaved facets position.

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.

Tunable terahertz wave generation through a bimodal laser diode and plasmonic photomixer.

PubMed

Yang, S-H; Watts, R; Li, X; Wang, N; Cojocaru, V; O'Gorman, J; Barry, L P; Jarrahi, M

2015-11-30

We demonstrate a compact, robust, and stable terahertz source based on a novel two section digital distributed feedback laser diode and plasmonic photomixer. Terahertz wave generation is achieved through difference frequency generation by pumping the plasmonic photomixer with two output optical beams of the two section digital distributed feedback laser diode. The laser is designed to offer an adjustable terahertz frequency difference between the emitted wavelengths by varying the applied currents to the laser sections. The plasmonic photomixer is comprised of an ultrafast photoconductor with plasmonic contact electrodes integrated with a logarithmic spiral antenna. We demonstrate terahertz wave generation with 0.15-3 THz frequency tunability, 2 MHz linewidth, and less than 5 MHz frequency stability over 1 minute, at useful power levels for practical imaging and sensing applications.

Organic holographic polymer dispersed liquid crystal distributed feedback laser from different diffraction orders

NASA Astrophysics Data System (ADS)

Liu, Minghuan; Liu, Yonggang; Zhang, Guiyang; Peng, Zenghui; Li, Dayu; Ma, Ji; Xuan, Li

2016-11-01

Holographic polymer dispersed liquid crystal (HPDLC) based distributed feedback (DFB) lasers were prepared with poly (-methoxy-5-(2‧-ethyl-hexyloxy)-1,4-phenylene-vinylene) (MEH-PPV) film as the active medium layer. The HPDLC grating film was fabricated via holographic induced photopolymerization. The pure film spectra of MEH-PPV and the amplified spontaneous emission (ASE) spectrum were investigated. The laser device was single-longitudinal mode operation. The tunability of the HPDLC DFB laser was achieved by selecting different grating periods. The lasing performances were also characterized and compared from different diffraction orders. The lasing threshold increased with the diffraction order and the third order laser possessed the largest conversion efficiency in this device. The experimental results were in good agreement with the theoretical calculations.

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

Koch, T.H.

Coumarin laser dyes upon excitation degrade to produce products that absorb at the lasing wavelength. This results in attenuation of dye laser output through interference of stimulated emission. The roles of singlet oxygen and excitation intensity on dye degradation were explored. Singlet oxygen is formed but its reactions with the dye do not appear to be a major cause of dye laser output deterioration. High light intensity results in dye-sensitized, solvent oligomerization to yield materials that interfere with dye-stimulated emission. 1, 4-Diazabicyclo2,2,2octane (DABCO)inhibits this oligomerization.

Dye laser amplifier including a dye cell contained within a support vessel

DOEpatents

Davin, James

1992-01-01

A large (high flow rate) dye laser amplifier in which a continous replenished supply of dye is excited by a first light beam, specifically a copper vapor laser beam, in order to amplify the intensity of a second different light beam, specifically a dye beam, passing through the dye is disclosed herein. This amplifier includes a dye cell defining a dye chamber through which a continuous stream of dye is caused to pass at a flow rate of greater than 30 gallons/minute at a static pressure greater than 150 pounds/square inch and a specifically designed support vessel for containing the dye cell.

Stabilizing operation point technique based on the tunable distributed feedback laser for interferometric sensors

NASA Astrophysics Data System (ADS)

Mao, Xuefeng; Zhou, Xinlei; Yu, Qingxu

2016-02-01

We describe a stabilizing operation point technique based on the tunable Distributed Feedback (DFB) laser for quadrature demodulation of interferometric sensors. By introducing automatic lock quadrature point and wavelength periodically tuning compensation into an interferometric system, the operation point of interferometric system is stabilized when the system suffers various environmental perturbations. To demonstrate the feasibility of this stabilizing operation point technique, experiments have been performed using a tunable-DFB-laser as light source to interrogate an extrinsic Fabry-Perot interferometric vibration sensor and a diaphragm-based acoustic sensor. Experimental results show that good tracing of Q-point was effectively realized.

Cascaded Raman lasing in a PM phosphosilicate fiber with random distributed feedback

NASA Astrophysics Data System (ADS)

Lobach, Ivan A.; Kablukov, Sergey I.; Babin, Sergey A.

2018-02-01

We report on the first demonstration of a linearly polarized cascaded Raman fiber laser based on a simple half-open cavity with a broadband composite reflector and random distributed feedback in a polarization maintaining phosphosilicate fiber operating beyond zero dispersion wavelength ( 1400 nm). With increasing pump power from a Yb-doped fiber laser at 1080 nm, the random laser generates subsequently 8 W at 1262 nm and 9 W at 1515 nm with polarization extinction ratio of 27 dB. The generation linewidths amount to about 1 nm and 3 nm, respectively, being almost independent of power, in correspondence with the theory of a cascaded random lasing.

Pattern dependence in high-speed Q-modulated distributed feedback laser.

PubMed

Zhu, Hongli; Xia, Yimin; He, Jian-Jun

2015-05-04

We investigate the pattern dependence in high speed Q-modulated distributed feedback laser based on its complete physical structure and material properties. The structure parameters of the gain section as well as the modulation and phase sections are all taken into account in the simulations based on an integrated traveling wave model. Using this model, we show that an example Q-modulated DFB laser can achieve an extinction ratio of 6.8dB with a jitter of 4.7ps and a peak intensity fluctuation of less than 15% for 40Gbps RZ modulation signal. The simulation method is proved very useful for the complex laser structure design and high speed performance optimization, as well as for providing physical insight of the operation mechanism.

GaInAsP/InP lateral-current-injection distributed feedback laser with a-Si surface grating.

PubMed

Shindo, Takahiko; Okumura, Tadashi; Ito, Hitomi; Koguchi, Takayuki; Takahashi, Daisuke; Atsumi, Yuki; Kang, Joonhyun; Osabe, Ryo; Amemiya, Tomohiro; Nishiyama, Nobuhiko; Arai, Shigehisa

2011-01-31

We fabricated a novel lateral-current-injection-type distributed feedback (DFB) laser with amorphous-Si (a-Si) surface grating as a step to realize membrane lasers. This laser consists of a thin GaInAsP core layer grown on a semi-insulating InP substrate and a 30-nm-thick a-Si surface layer for DFB grating. Under a room-temperature continuous-wave condition, a low threshold current of 7.0 mA and high efficiency of 43% from the front facet were obtained for a 2.0-μm stripe width and 300-μm cavity length. A small-signal modulation bandwidth of 4.8 GHz was obtained at a bias current of 30 mA.

Laser dye DCM: CW, synchronously pumped, cavity pumped and single-frequency performance

NASA Astrophysics Data System (ADS)

Marason, E. G.

1981-04-01

Laser dye DCM exhibits a tuning range of 605 to 725 nm with a lasing efficiency as high as 34% when pumped by the 488 nm line of the argon ion laser, placing it among the most efficient and broadly tunable dyes known. Performance of the dye is characterized for four laser systems: 1) continuous wave, 2) synchronously pumped (SP), 3) cavity dumped synchrompously pumped (SPCD) and 4) single-frequency ring dye laser. Pulse peak powers were as high as 520 W and 2.8 kW for SP and SPCD systems respectively.

GaAs/GaAlAs distributed Bragg reflector laser with a focused ion beam, low dose dopant implanted grating

NASA Technical Reports Server (NTRS)

Wu, M. C.; Boenke, M. M.; Wang, S.; Clark, W. M., Jr.; Stevens, E. H.

1988-01-01

The performance of a GaAs/GaAlAs distributed Bragg reflector (DBR) laser using a focused ion beam implanted grating (FIB-DBR) is reported for the first time. Stripes of Si(2+) with a period of 2300 A and a dose about 10 to the 14th/sq cm are directly implanted into the passive large optical cavity layer to provide the distributed feedback. Surface-emitting light from the second-order grating is observed. Threshold current of 110 mA and single DBR mode operation from 20 to 40 C are obtained. The wavelength tuning rate with temperature is 0.8 A/C. The coupling coefficient is estimated to be 15/cm. The results show that FIB technology is practical for distributed feedback and DBR lasers and optoelectronic integrated circuits.

Dye laser amplifier including a low turbulence, stagnation-free dye flow configuration

DOEpatents

Davin, J.

1992-12-01

A large (high flow rate) dye laser amplifier in which a continuous replenished supply of dye is excited by a first light beam, specifically a copper vapor laser beam, in order to amplify the intensity of a second different light beam, specifically a dye beam, passing through the dye is disclosed herein. This amplifier includes a dye cell defining a dye chamber through which a continuous stream of dye is caused to pass at a flow rate of for example 30 gallons/minute, a specifically designed support vessel for containing the dye cell and a screen device for insuring that the dye stream passes into the dye cell in a substantially turbulent free, stagnation-free manner. 9 figs.

Measurements of the linewidth enhancement factor of mid-infrared quantum cascade lasers by different optical feedback techniques

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

Jumpertz, L., E-mail: louise.jumpertz@telecom-paristech.fr; MirSense, 8 avenue de la Vauve, F-91120 Palaiseau; Michel, F.

2016-01-15

Precise knowledge of the linewidth enhancement factor of a semiconductor laser under actual operating conditions is of prime importance since this parameter dictates various phenomena such as linewidth broadening or optical nonlinearities enhancement. The above-threshold linewidth enhancement factor of a mid-infrared quantum cascade laser structure operated at 10{sup ∘}C is determined experimentally using two different methods based on optical feedback. Both Fabry-Perot and distributed feedback quantum cascade lasers based on the same active area design are studied, the former by following the wavelength shift as a function of the feedback strength and the latter by self-mixing interferometry. The results aremore » consistent and unveil a clear pump current dependence of the linewidth enhancement factor, with values ranging from 0.8 to about 3.« less

Fundamental characteristics of degradation-recoverable solid-state DFB polymer laser.

PubMed

Yoshioka, Hiroaki; Yang, Yu; Watanabe, Hirofumi; Oki, Yuji

2012-02-13

A novel solid-state dye laser with degradation recovery was proposed and demonstrated. Polydimethylsiloxane was used as a nanoporous solid matrix to enable the internal circulation of dye molecules in the solid state. An internal circulation model for the dye molecules was also proposed and verified numerically by assuming molecular mobility and using a proposed diffusion equation. The durability of the laser was increased 20.5-fold compared with that of a conventional polymethylmethacrylate laser. This novel laser solves the low-durability problem of dye-doped polymer lasers.

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.

Distributed feedback fiber laser based on a fiber Bragg grating inscribed using the femtosecond point-by-point technique

NASA Astrophysics Data System (ADS)

Skvortsov, M. I.; Wolf, A. A.; Dostovalov, A. V.; Vlasov, A. A.; Akulov, V. A.; Babin, S. A.

2018-03-01

A distributed feedback (DFB) fiber laser based on a 32-mm long pi-phase-shifted fiber Bragg grating inscribed using the femtosecond point-by-point technique in a single-mode erbium-doped optical fiber (CorActive EDF-L 1500) is demonstrated. The lasing power of the DFB laser reaches 0.7 mW at a wavelength of 1550 nm when pumped with a laser diode at a wavelength of 976 nm and power of 525 mW. The width of the lasing spectrum is 17 kHz. It is shown that the pi-phase-shifted fiber Bragg grating fs-inscribed in a non-PM fiber provides the selection of the single polarization mode of the DFB laser. DFB laser formation in a highly doped non-photosensitive optical fiber (CoreActive SCF-ER60-8/125-12) is also demonstrated.

Feasibility of solar-pumped dye lasers

NASA Technical Reports Server (NTRS)

Lee, Ja H.; Kim, Kyung C.; Kim, Kyong H.

1987-01-01

Dye laser gains were measured at various pump-beam irradiances on a dye cell in order to evaluate the feasibility of solar pumping. Rhodamine 6G dye was considered as a candidate for the solar-pumped laser because of its high utilization of the solar spectrum and high quantum efficiency. Measurements show that a solar concentration of 20,000 is required to reach the threshold of the dye.

Hair ignition by dye laser for port-wine stain: risk factors evaluated.

PubMed

Molin, L; Hallgren, S

1999-04-01

Flashlamp-pumped pulsed dye laser is the preferred treatment for port-wine stain. Vascular hemoglobin and epidermal melanin are competing sites for dye laser absorption and damage. The case presented illustrates the potential hazard of ignition induced by dye laser treatment on the face of a patient receiving inhalation anesthesia. A 6-year-old girl with almost black hair was treated for a port-wine stain covering most of the right half of her face. She was treated with dye laser under general anesthesia administered by mask. A laser pulse close to the upper part of the eyebrow induced a blaze and the eyebrow was instantly destroyed by the fire. Regrowth of the eyebrow was complete after a few months. Hair specimens of various colors were exposed experimentally to dye laser irradiation in room and oxygen-saturated atmospheres. Risk factors of ignition are high laser dosage, a high oxygen level, repeated pulses and dark colored hair.

Preparation of 6-hydroxyindolines and their use for preparation of novel laser dyes

DOEpatents

Field, George F.; Hammond, Peter R.

1993-01-01

A novel method for the synthesis of 6-hydroxyindolines and new fluorescent dyes produced therefrom, which dyes are ring-constrained indoline-based rhodamine class dyes. These dyes have absorption and emission spectra which make them particularly useful in certain dye laser applications.

Heterogeneous distribution of dye-labelled biomineralizaiton proteins in calcite crystals

NASA Astrophysics Data System (ADS)

Liu, Chuang; Xie, Liping; Zhang, Rongqing

2015-12-01

Biominerals are highly ordered crystals mediated by organic matters especially proteins in organisms. However, how specific proteins are distributed inside biominerals are not well understood. In the present study, we use fluorescein isothiocyanate (FITC) to label extracted proteins from the shells of bivalve Pinctada fucata. By confocal laser scanning microscopy (CLSM), we observe a heterogeneous distribution of dye-labelled proteins inside synthetic calcite at the microscale. Proteins from the prismatic calcite layers accumulate at the edge of crystals while proteins from the nacreous aragonite layers accumulate at the center of crystals. Raman and X-ray powder diffraction show that both the proteins cannot alter the crystal phase. Scanning electron microscope demonstrates both proteins are able to affect the crystal morphology. This study may provide a direct approach for the visualization of protein distributions in crystals by small-molecule dye-labelled proteins as the additives in the crystallization process and improve our understanding of intracrystalline proteins distribution in biogenic calcites.

Laser head for simultaneous optical pumping of several dye lasers. [with single flash lamp

NASA Technical Reports Server (NTRS)

Mumola, P. B.; Mcalexander, B. T. (Inventor)

1975-01-01

The invention is a laser head for simultaneous pumping several dye lasers with a single flash lamp. The laser head includes primarily a multi-elliptical cylinder cavity with a single flash lamp placed along the common focal axis of the cavity and with capillary tube dye cells placed along each of the other focal axes of the cavity. The inside surface of the cavity is polished. Hence, the single flash lamp supplies the energy to the several dye cells.

Holographic injection locking of a broad area laser diode via a photorefractive thin-film device.

PubMed

van Voorst, P D; de Wit, M R; Offerhaus, H L; Tay, S; Thomas, J; Peyghambarian, N; Boller, K-J

2007-12-24

We demonstrate locking of a high power broad area laser diode to a single frequency using holographic feedback from a photorefractive polymer thin-film device for the first time. A four-wave mixing setup is used to generate feedback for the broad area diode at the wavelength of the single frequency source (Ti:Sapphire laser) while the spatial distribution adapts to the preferred profile of the broad area diode. The result is an injection-locked broad area diode emitting with a linewidth comparable to the Ti:Sapphire laser.

Laser Radar Study Using Resonance Absorption for Remote Detection Of Air Pollutants

NASA Technical Reports Server (NTRS)

Igarashi, Takashi

1973-01-01

A laser radar using resonance absorption has an advantage of increased detection range and sensitivity compared with that achieved by Raman or resonance back scattering. In this paper, new laser radar system using resonance absorption is proposed and results obtained from this laser radar system are discussed. NO2, SO2 gas has an absorption spectrum at 4500 A and 3000 A respectively as shown in Fig. 1. A laser light including at least a set of an absorption peak (lambda)1 and a valley (lambda)2 is emitted into a pollutant atmosphere. The light reflected with a topographical reflector or an atmospheric Mie scattering as distributed reflectors is received and divided into two wavelength components (lambda)1 and (lambda)2. The laser radar system used in the investigation is shown in Fig', 2 and consists of a dye laser transmitter, an optical receiver with a special monochrometer and a digital processer. Table 1 shows the molecular constants of NO2, and SO2 and the dye laser used in this experiment. In this system, the absolute concentration of the pollutant gas can be measured in comparison with a standard gas cell. The concentration of NO2, SO2 as low as 0.1 ppm have been measured at 100 m depth resolution. For a 1 mJ laser output, the observable range of this system achieved up to 300 m using the distributed Mie reflector. The capability and technical limitation of the system will be discussed in detail.

Precise measurement of single-mode fiber lengths using a gain-switched distributed feedback laser with delayed optical feedback.

PubMed

Wada, Kenji; Matsukura, Satoru; Tanaka, Amaka; Matsuyama, Tetsuya; Horinaka, Hiromichi

2015-09-07

A simple method to measure single-mode optical fiber lengths is proposed and demonstrated using a gain-switched 1.55-μm distributed feedback laser without a fast photodetector or an optical interferometer. From the variation in the amplified spontaneous emission noise intensity with respect to the modulation frequency of the gain switching, the optical length of a 1-km single-mode fiber immersed in water is found to be 1471.043915 m ± 33 μm, corresponding to a relative standard deviation of 2.2 × 10(-8). This optical length is an average value over a measurement time of one minute under ordinary laboratory conditions.

DBR and DFB Lasers in Neodymium- and Ytterbium-Doped Photothermorefractive Glasses

NASA Technical Reports Server (NTRS)

Ryasnyanskiy, Aleksandr; Vorobiev, N.; Smirnov, V.; Lumeau, J.; Glebov, A.; Mokhun, O..; Spiegelberg, Ch.; Krainak, Michael A.; Glebov, A.; Glebov, L.

2014-01-01

The first demonstration, to the best of our knowledge, of distributed Bragg reflector (DBR) and monolithic distributed feedback (DFB) lasers in photothermorefractive glass doped with rare-earth ions is reported. The lasers were produced by incorporation of the volume Bragg gratings into the laser gain elements. A monolithic single-frequency solid-state laser with a line width of 250 kHz and output power of 150 mW at 1066 nm is demonstrated.

Shape memory polymer (SMP) gripper with a release sensing system

DOEpatents

Maitland, Duncan J.; Lee, Abraham P.; Schumann, Daniel L.; Silva, Luiz Da

2000-01-01

A system for releasing a target material, such as an embolic coil from an SMP located at the end of a catheter utilizing an optical arrangement for releasing the material. The system includes a laser, laser driver, display panel, photodetector, fiber optics coupler, fiber optics and connectors, a catheter, and an SMP-based gripper, and includes a release sensing and feedback arrangement. The SMP-based gripper is heated via laser light through an optic fiber causing the gripper to release a target material (e.g., embolic coil for therapeutic treatment of aneurysms). Various embodiments are provided for coupling the laser light into the SMP, which includes specific positioning of the coils, removal of the fiber cladding adjacent the coil, a metal coating on the SMP, doping the SMP with a gradient absorbing dye, tapering the fiber optic end, coating the SMP with low refractive index material, and locating an insert between the fiber optic and the coil.

Preparation of 6-hydroxyindolines and their use for preparation of novel laser dyes

DOEpatents

Field, G.F.; Hammond, P.R.

1993-10-26

A novel method is described for the synthesis of 6-hydroxyindolines and new fluorescent dyes produced therefrom, which dyes are ring-constrained indoline-based rhodamine class dyes. These dyes have absorption and emission spectra which make them particularly useful in certain dye laser applications.

Absolute tracer dye concentration using airborne laser-induced water Raman backscatter

NASA Technical Reports Server (NTRS)

Hoge, F. E.; Swift, R. N.

1981-01-01

The use of simultaneous airborne-laser-induced dye fluorescence and water Raman backscatter to measure the absolute concentration of an ocean-dispersed tracer dye is discussed. Theoretical considerations of the calculation of dye concentration by the numerical comparison of airborne laser-induced fluorescence spectra with laboratory spectra for known dye concentrations using the 3400/cm OH-stretch water Raman scatter as a calibration signal are presented which show that minimum errors are obtained and no data concerning water mass transmission properties are required when the laser wavelength is chosen to yield a Raman signal near the dye emission band. Results of field experiments conducted with an airborne conical scan lidar over a site in New York Bight into which rhodamine dye had been injected in a study of oil spill dispersion are then indicated which resulted in a contour map of dye concentrations, with a minimum detectable dye concentration of approximately 2 ppb by weight.

Tunable random lasing behavior in plasmonic nanostructures

NASA Astrophysics Data System (ADS)

Yadav, Ashish; Zhong, Liubiao; Sun, Jun; Jiang, Lin; Cheng, Gary J.; Chi, Lifeng

2017-01-01

Random lasing is desired in plasmonics nanostructures through surface plasmon amplification. In this study, tunable random lasing behavior was observed in dye molecules attached with Au nanorods (NRs), Au nanoparticles (NPs) and Au@Ag nanorods (NRs) respectively. Our experimental investigations showed that all nanostructures i.e., Au@AgNRs, AuNRs & AuNPs have intensive tunable spectral effects. The random lasing has been observed at excitation wavelength 532 nm and varying pump powers. The best random lasing properties were noticed in Au@AgNRs structure, which exhibits broad absorption spectrum, sufficiently overlapping with that of dye Rhodamine B (RhB). Au@AgNRs significantly enhance the tunable spectral behavior through localized electromagnetic field and scattering. The random lasing in Au@AgNRs provides an efficient coherent feedback for random lasers.

Distributed-feedback Terahertz Quantum-cascade Lasers with Laterally Corrugated Metal Waveguides

NASA Technical Reports Server (NTRS)

Williams, Benjamin S.; Kumar, Sushil; Hu, Qing; Reno, John L.

2005-01-01

We report the demonstration of distributed-feedback terahertz quantum-cascade lasers based on a first-order grating fabricated via a lateral corrugation in a double-sided metal ridge waveguide. The phase of the facet reflection was precisely set by lithographically defined facets by dry etching. Single-mode emission was observed at low to moderate injection currents, although multimode emission was observed far beyond threshold owing to spatial hole burning. Finite-element simulations were used to calculate the modal and threshold characteristics for these devices, with results in good agreement with experiments.

Linearly polarized cascaded Raman fiber laser with random distributed feedback operating beyond 1.5  μm.

PubMed

Lobach, Ivan A; Kablukov, Sergey I; Babin, Sergey A

2017-09-15

We report on, to the best of our knowledge, the first demonstration of a linearly polarized cascaded Raman fiber laser based on a simple half-open cavity with a broadband composite reflector and random distributed feedback in a polarization-maintaining phosphosilicate fiber with a zero dispersion wavelength at ∼1400  nm. Pumped by a 1080 nm Yb-doped fiber laser, the random laser delivers more than 8 W at 1262 nm and 9 W at 1515 nm with a polarization extinction ratio of 27 dB. The generation linewidths amount to about 1 and 3 nm, respectively, being almost independent of power, in correspondence with the theory of a cascaded random fiber lasing.

Stable Single-Mode Operation of Distributed Feedback Quantum Cascade Laser by Optimized Reflectivity Facet Coatings

NASA Astrophysics Data System (ADS)

Wang, Dong-Bo; Zhang, Jin-Chuan; Cheng, Feng-Min; Zhao, Yue; Zhuo, Ning; Zhai, Shen-Qiang; Wang, Li-Jun; Liu, Jun-Qi; Liu, Shu-Man; Liu, Feng-Qi; Wang, Zhan-Guo

2018-02-01

In this work, quantum cascade lasers (QCLs) based on strain compensation combined with two-phonon resonance design are presented. Distributed feedback (DFB) laser emitting at 4.76 μm was fabricated through a standard buried first-order grating and buried heterostructure (BH) processing. Stable single-mode emission is achieved under all injection currents and temperature conditions without any mode hop by the optimized antireflection (AR) coating on the front facet. The AR coating consists of a double layer dielectric of Al2O3 and Ge. For a 2-mm laser cavity, the maximum output power of the AR-coated DFB-QCL was more than 170 mW at 20 °C with a high wall-plug efficiency (WPE) of 4.7% in a continuous-wave (CW) mode.

Single transverse mode protein laser

NASA Astrophysics Data System (ADS)

Dogru, Itir Bakis; Min, Kyungtaek; Umar, Muhammad; Bahmani Jalali, Houman; Begar, Efe; Conkar, Deniz; Firat Karalar, Elif Nur; Kim, Sunghwan; Nizamoglu, Sedat

2017-12-01

Here, we report a single transverse mode distributed feedback (DFB) protein laser. The gain medium that is composed of enhanced green fluorescent protein in a silk fibroin matrix yields a waveguiding gain layer on a DFB resonator. The thin TiO2 layer on the quartz grating improves optical feedback due to the increased effective refractive index. The protein laser shows a single transverse mode lasing at the wavelength of 520 nm with the threshold level of 92.1 μJ/ mm2.

Theoretical studies of solar-pumped lasers

NASA Technical Reports Server (NTRS)

Harries, W. L.

1983-01-01

Possible types of lasers were surveyed for solar power conversion. The types considered were (1) liquid dye lasers, (2) vapor dye lasers, and (3) nondissociative molecular lasers. These are discussed.

A switchable digital microfluidic droplet dye-laser.

PubMed

Kuehne, Alexander J C; Gather, Malte C; Eydelnant, Irwin A; Yun, Seok-Hyun; Weitz, David A; Wheeler, Aaron R

2011-11-07

Digital microfluidic devices allow the manipulation of droplets between two parallel electrodes. These electrodes can act as mirrors generating a micro-cavity, which can be exploited for a droplet dye-laser. Three representative laser-dyes with emission wavelengths spanning the whole visible spectrum are chosen to show the applicability of this concept. Sub-microlitre droplets of laser-dye solution are moved in and out of a lasing site on-chip to down-convert the UV-excitation light into blue, green and red laser-pulses. This journal is © The Royal Society of Chemistry 2011

Photoactive dye enhanced tissue ablation for endoscopic laser prostatectomy

NASA Astrophysics Data System (ADS)

Ahn, Minwoo; Nguyen, Trung Hau; Nguyen, Van Phuc; Oh, Junghwan; Kang, Hyun Wook

2015-02-01

Laser light has been widely used as a surgical tool to treat benign prostate hyperplasia with high laser power. The purpose of this study was to validate the feasibility of photoactive dye injection to enhance light absorption and eventually to facilitate tissue ablation with low laser power. The experiment was implemented on chicken breast due to minimal optical absorption Amaranth (AR), black dye (BD), hemoglobin powder (HP), and endoscopic marker (EM), were selected and tested in vitro with a customized 532-nm laser system with radiant exposure ranging from 0.9 to 3.9 J/cm2. Light absorbance and ablation threshold were measured with UV-VIS spectrometer and Probit analysis, respectively, and compared to feature the function of the injected dyes. Ablation performance with dye-injection was evaluated in light of radiant exposure, dye concentration, and number of injection. Higher light absorption by injected dyes led to lower ablation threshold as well as more efficient tissue removal in the order of AR, BD, HP, and EM. Regardless of the injected dyes, ablation efficiency principally increased with input parameter. Among the dyes, AR created the highest ablation rate of 44.2+/-0.2 μm/pulse due to higher absorbance and lower ablation threshold. Preliminary tests on canine prostate with a hydraulic injection system demonstrated that 80 W with dye injection yielded comparable ablation efficiency to 120 W with no injection, indicating 33 % reduced laser power with almost equivalent performance. In-depth comprehension on photoactive dye-enhanced tissue ablation can help accomplish efficient and safe laser treatment for BPH with low power application.

Intense excitation source of blue-green laser

NASA Astrophysics Data System (ADS)

Han, Kwang S.

1986-10-01

An intense and efficient source for blue green laser useful for the space-based satellite laser applications, underwater strategic communication, and measurement of ocean bottom profile is being developed. The source in use, the hypocycloidal pinch plasma (HCP), and the dense plasma focus (DPF) can produce intense uv photons (200 to 400nm) which match the absorption spectra of both near UV and blue green dye lasers (300 to 400nm). As a result of optimization of the DPF light at 355nm, the blue green dye (LD490) laser output exceeding 4mJ was obtained at the best cavity tunning of the laser system. With the HCP pumped system a significant enhancement of the blue green laser outputs with dye LD490 and coumarin 503 has been achieved through the spectrum conversion of the pumping light by mixing a converter dye BBQ. The maximum increase of laser output with the dye mixture of LD490+BBQ and coumarin 503+BBQ was greater than 80%. In addition, the untunned near UV lasers were also obtained. The near UV laser output energy of P-terphenyl dye was 0.5mJ at lambda sub C=337nm with the bandwidth of 3n m for the pulse duration of 0.2us. Another near UV laser output energy obtained with BBQ dye was 25 mJ at lambda sub C=383nm with the bandwidth of 3nm for the pulse duration of 0.2us. Another near UV laser output energy obtained with BBQ dye was 25 mJ at lambda sub C=383nm with the bandwidth of 3nm for the pulse duration of 0.2microsec.

Free-standing membrane polymer laser on the end of an optical fiber

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

Zhai, Tianrui, E-mail: trzhai@bjut.edu.cn, E-mail: zhangxinping@bjut.edu.cn; Li, Songtao; Hu, Yujie

2016-01-25

One- and two-dimensional distributed feedback cavities were constructed on free-standing polymer membranes using spin-coating and lift-off techniques. Low threshold lasing was generated through feedback amplification when the 290-nm membrane device was optically pumped, which was attributed to the strong confinement mechanism provided by the active waveguide layer without a substrate. The free-standing membrane polymer laser is flexible and can be transplanted. Single- and dual-wavelength fiber lasers were achieved by directly attaching the membrane polymer laser on the optical fiber end face. This technique provides potential to fabricate polymer lasers on surfaces with arbitrary shapes.

Application of LIF technique for the space- and time-resolved monitoring of pollutant gas decomposition in nonthermal plasma reactors

NASA Astrophysics Data System (ADS)

Mizeraczyk, Jerzy; Ohkubo, Toshikazu; Kanazawa, Seiji; Kocik, Marek

2003-10-01

Laser-induced fluorescence (LIF) technique aided by intensified CCD light signal detection and fast digital image processing is demonstrated to be a useful diagnostic method for in-situ observation of the discharge-induced plasma-chemistry processes responsible for NOx(NO + NO2) decomposition occurring in non-thermal plasma reactors. In this paper a method and results of the LIF measurement of two-dimensional distribution of the ground-state NO molecule density inside a DC positive streamer corona reactor during NO removal from a flue gas simulator [air/NO(up to 300 ppm)] are presented. Either a needle-to-plate or nozzle-to-plate electrode system, having an electrode gap of 30-50 mm was used for generating the corona discharge in the reactor. The LIF monitoring of NO molecules was carried out under the steady-state DC corona discharge condition. The laser-induced fluorescence on the transition NO X2Π(v"=0)<--A2Σ+(v'=0) at λ=226nm was chosen for monitoring ground-state NO molecules in the reactor. This transition was induced by irradiation of the NO molecules with UV laser pulses generated by a laser system consisted of a XeF excimer laser, dye laser and BBO crystal. The laser pulses from the XeF excimer laser (Lambda Physik, Complex 150, λ=351 nm) pumped the dye laser (Lambda Physik, Scanmate) with Coumarin 47 as a dye, which generated the laser beam of a wavelength turned around λ=450 nm. Then, the tuned dye laser beam pumped the BBO crystal in which the second harmonic radiation of a wavelength correspondingly tuned around λ=226 nm was generated. The 226-nm UV laser pulses of energy of 0.8-2 mJ and duration of about 20 ns were transformed into the form of the so-called laser sheet (width of 1 mm, height of 30-50 mm) which passed between the electrodes through the operating gas. The obtained results, presented in the form of images, which illustrated the two-dimensional distributions of NO molecule concentration in the non-thermal reactor, showed that the corona discharge-induced removal of NO molecules occurred not only in the vicinity of the plasma region formed by the corona discharge-induced removal of NO molecules occurred not only in the vicinity of the plasma region formed by the corona streamers and in the downstream region of the reactor but also in the upstream region of the reactor, i.e. before the flue gas simulator has entered the plasma region. This information obtained owing to the LIF technique, is important for the understanding of the plasma-chemistry processes responsible for NOx decomposition in non-thermal plasma reactors and for optimising their performance.

Excimer Pumped Pulsed Tunable Dye Laser

NASA Astrophysics Data System (ADS)

Littman, Michael G.

1988-06-01

It has been recently shown and reported for the first time at this meeting, that Excimer pumping of a single-mode, short-cavity, grazing-incidence, longitudinally-pumped pulsed dye laser is feasible. In this paper the key concepts upon which this latest development is based are presented and are in a somewhat unusual form. This manuscript describes five specific dye laser examples. The five examples represent a progression from the simplest type of dye laser to the single-mode version mentioned above. The examples thus serve as a tutorial introduction to potential users of dye lasers. The article is organized into five sections or STEPS, each of which describes a different pulsed dye laser. Since the subtle points about dye lasers are best appreciated only after one actually attempts to build a working model, a PROCEDURES category is included in which details about the construction of the particular form of laser are given. As one reads through this category, think of it as looking over the shoulder of the laser builder. The NOTES category which follows is a brief but essential discussion explaining why various components and procedures are used, as well as how laser performance specifications are obtained. This subsection can he viewed as a discussion with the laser builder concerning the reasons for specific actions and choices made in the assembly of the example laser. The last category contains COMMENTS which provide additional related information pertaining to the example laser that goes beyond the earlier annotated discussion. If you like, these are the narrator's comments. At the end of the article, after the five sequential forms of the laser have been presented, there is a brief summation.

Identification Of Natural Dyes On Archaeological Textile Objects Using Laser Induced Fluorescent Technique

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

Abdel-Kareem, O.; Eltokhy, A.; Harith, M. A.

2011-09-22

This study aims to evaluate the use of Laser Fluorescent as a non-destructive technique for identification of natural dyes on archaeological textile objects. In this study wool textile samples were dyed with 10 natural dyes such as cochineal, cutch, henna, indigo, Lac, madder, safflower, saffron, sumac and turmeric. These dyes common present on archaeological textile objects to be used as standard dyed textile samples. These selected natural dyes will be used as known references that can be used a guide to identify unknown archaeological dyes. The dyed textile samples were investigated with laser radiation in different wavelengths to detect themore » best wavelengths for identification each dye. This study confirms that Laser Florescent is very useful and a rapid technique can be used as a non-destructive technique for identification of natural dyes on archaeological textile objects. The results obtained with this study can be a guide for all conservators in identification of natural organic dyes on archaeological textile objects.« less

Identification Of Natural Dyes On Archaeological Textile Objects Using Laser Induced Fluorescent Technique

NASA Astrophysics Data System (ADS)

Abdel-Kareem, O.; Eltokhy, A.; Harith, M. A.

2011-09-01

This study aims to evaluate the use of Laser Fluorescent as a non-destructive technique for identification of natural dyes on archaeological textile objects. In this study wool textile samples were dyed with 10 natural dyes such as cochineal, cutch, henna, indigo, Lac, madder, safflower, saffron, sumac and turmeric. These dyes common present on archaeological textile objects to be used as standard dyed textile samples. These selected natural dyes will be used as known references that can be used a guide to identify unknown archaeological dyes. The dyed textile samples were investigated with laser radiation in different wavelengths to detect the best wavelengths for identification each dye. This study confirms that Laser Florescent is very useful and a rapid technique can be used as a non-destructive technique for identification of natural dyes on archaeological textile objects. The results obtained with this study can be a guide for all conservators in identification of natural organic dyes on archaeological textile objects.

The waveguide laser - A review

NASA Technical Reports Server (NTRS)

Degnan, J. J.

1976-01-01

The present article reviews the fundamental physical principles essential to an understanding of waveguide gas and liquid lasers, and the current technological state of these devices. At the present time, waveguide laser transitions span the visible through submillimeter regions of the wavelength spectrum. The introduction discusses the many applications of waveguide lasers and the wide variety of laser configurations that are possible. Section 1 summarizes the properties of modes in hollow dielectric waveguides of circular, rectangular, and planar cross section. Section 2 considers various approaches to optical feedback including internal and external mirror Fabry-Perot type resonators, hollow waveguide distributed feedback structures, and ring-resonant configurations. Section 3 discusses those aspects of molecular kinetic and laser theory pertinent to the design and optimization of waveguide gas lasers.

Threshold pump power of a solar-pumped dye laser

NASA Technical Reports Server (NTRS)

Lee, Ja H.; Kim, Kyung C.; Kim, Kyong H.

1988-01-01

Threshold solar power for dye laser pumping has been determined by measuring the gain of a rhodamine 6G dye laser amplifier at various solar-simulated irradiances on an amplifier cell. The measured threshold was 20,000 solar constants (2.7 kW/sq cm) for the dye volume of 2 x 5 x 40 cu mm and the optimum dye concentration of 0.001 M. The threshold is about one-third of that achievable with a high-intensity solar concentrator.

Experimental characterization of the transition to coherence collapse in a semiconductor laser with optical feedback

NASA Astrophysics Data System (ADS)

Panozzo, M.; Quintero-Quiroz, C.; Tiana-Alsina, J.; Torrent, M. C.; Masoller, C.

2017-11-01

Semiconductor lasers with time-delayed optical feedback display a wide range of dynamical regimes, which have found various practical applications. They also provide excellent testbeds for data analysis tools for characterizing complex signals. Recently, several of us have analyzed experimental intensity time-traces and quantitatively identified the onset of different dynamical regimes, as the laser current increases. Specifically, we identified the onset of low-frequency fluctuations (LFFs), where the laser intensity displays abrupt dropouts, and the onset of coherence collapse (CC), where the intensity fluctuations are highly irregular. Here we map these regimes when both, the laser current and the feedback strength vary. We show that the shape of the distribution of intensity fluctuations (characterized by the standard deviation, the skewness, and the kurtosis) allows to distinguish among noise, LFFs and CC, and to quantitatively determine (in spite of the gradual nature of the transitions) the boundaries of the three regimes. Ordinal analysis of the inter-dropout time intervals consistently identifies the three regimes occurring in the same parameter regions as the analysis of the intensity distribution. Simulations of the well-known time-delayed Lang-Kobayashi model are in good qualitative agreement with the observations.

Photodegradation and Photophysics of Laser Dyes

DTIC Science & Technology

1994-06-30

research. "The Photophysics and Photochem istry of’ Orgainic Laser Dyecs uander Conditions oit Binding to Polymethacrylic Acid in Water** thcsis...c 13. ABSTRACT (Maximum 200 wotrds) 6 The solubilization of laser dyes in water with the aid of the polyelectrolyte, poly(methacr,-- lic acid ) (PMAA...moderately acidic pH. Polymer-bound dyes in water display markedly enhanced emission yield, lifetime, and polarization. Dye materials are also less

Tunable microwave generation of a monolithic dual-wavelength distributed feedback laser.

PubMed

Lo, Yen-Hua; Wu, Yu-Chang; Hsu, Shun-Chieh; Hwang, Yi-Chia; Chen, Bai-Ci; Lin, Chien-Chung

2014-06-02

The dynamic behavior of a monolithic dual-wavelength distributed feedback laser was fully investigated and mapped. The combination of different driving currents for master and slave lasers can generate a wide range of different operational modes, from single mode, period 1 to chaos. Both the optical and microwave spectrum were recorded and analyzed. The detected single mode signal can continuously cover from 15GHz to 50GHz, limited by photodetector bandwidth. The measured optical four-wave-mixing pattern indicates that a 70GHz signal can be generated by this device. By applying rate equation analysis, the important laser parameters can be extracted from the spectrum. The extracted relaxation resonant frequency is found to be 8.96GHz. With the full operational map at hand, the suitable current combination can be applied to the device for proper applications.

Stable Single-Mode Operation of Distributed Feedback Quantum Cascade Laser by Optimized Reflectivity Facet Coatings.

PubMed

Wang, Dong-Bo; Zhang, Jin-Chuan; Cheng, Feng-Min; Zhao, Yue; Zhuo, Ning; Zhai, Shen-Qiang; Wang, Li-Jun; Liu, Jun-Qi; Liu, Shu-Man; Liu, Feng-Qi; Wang, Zhan-Guo

2018-02-02

In this work, quantum cascade lasers (QCLs) based on strain compensation combined with two-phonon resonance design are presented. Distributed feedback (DFB) laser emitting at ~ 4.76 μm was fabricated through a standard buried first-order grating and buried heterostructure (BH) processing. Stable single-mode emission is achieved under all injection currents and temperature conditions without any mode hop by the optimized antireflection (AR) coating on the front facet. The AR coating consists of a double layer dielectric of Al 2 O 3 and Ge. For a 2-mm laser cavity, the maximum output power of the AR-coated DFB-QCL was more than 170 mW at 20 °C with a high wall-plug efficiency (WPE) of 4.7% in a continuous-wave (CW) mode.

Surface normal velocity distribution of sputtered Zr-atoms for light-ion irradiation

NASA Astrophysics Data System (ADS)

Bay, H. L.; Berres, W.; Hintz, E.

1982-03-01

The velocity distribution of sputtered Zr-atoms has been measured for 8 keV Ar + and He + ions and 2.5 keV D + ion irradiation at normal incidence. The measurements were performed with the aid of laser induced fluorescence spectroscopy (LIFS) using a CW-laser pumped dye-laser. The influence of the measuring geometry was investigated and found to be in good agreement with calculation. For light-ion sputtering the collision-cascade theory is no longer applicable. Here a distinct shift in the velocity distributions towards lower velocities compared with the Ar results was found. The shift can be correlated to anisotropic effects in connection with the change in the maximum recoil energy Tm in the cascade.

Time-resolved spectral characterization of ring cavity surface emitting and ridge-type distributed feedback quantum cascade lasers by step-scan FT-IR spectroscopy.

PubMed

Brandstetter, Markus; Genner, Andreas; Schwarzer, Clemens; Mujagic, Elvis; Strasser, Gottfried; Lendl, Bernhard

2014-02-10

We present the time-resolved comparison of pulsed 2nd order ring cavity surface emitting (RCSE) quantum cascade lasers (QCLs) and pulsed 1st order ridge-type distributed feedback (DFB) QCLs using a step-scan Fourier transform infrared (FT-IR) spectrometer. Laser devices were part of QCL arrays and fabricated from the same laser material. Required grating periods were adjusted to account for the grating order. The step-scan technique provided a spectral resolution of 0.1 cm(-1) and a time resolution of 2 ns. As a result, it was possible to gain information about the tuning behavior and potential mode-hops of the investigated lasers. Different cavity-lengths were compared, including 0.9 mm and 3.2 mm long ridge-type and 0.97 mm (circumference) ring-type cavities. RCSE QCLs were found to have improved emission properties in terms of line-stability, tuning rate and maximum emission time compared to ridge-type lasers.

Compact Ozone Differential Absorption Lidar (DIAL) Transmitter Using Solid-State Dye Polymers

NASA Technical Reports Server (NTRS)

Jones, Alton L., Jr.; DeYoung, Russell J.; Elsayid-Ele, Hani

2001-01-01

A new potential DIAL laser transmitter is described that uses solid-state dye laser materials to make a simpler, more compact, lower mass laser system. Two solid-state dye laser materials were tested to evaluate their performance in a laser oscillator cavity end pumped by a pulsed Nd:YAG laser at 532 nm. The polymer host polymethyl-methacrylate was injected with a pyrromethene laser dye, PM 580, or PM 597. A narrowband laser oscillator cavity was constructed to produce visible wavelengths of 578 and 600 nm which were frequency doubled into the UV region (299 or 300 nm) by using a BBO crystal, resulting in a maximum energy of 11 mJ at a wavelength of 578 nm when pumped by the Nd:YAG laser at an energy of 100 mJ (532 nm). A maximum output energy of 378 microJ was achieved in the UV region at a wavelength of 289 nm but lasted only 2000 laser shots at a repetition rate of 10 Hz. The results are promising and show that a solid-state dye laser based ozone DIAL system is possible with improvements in the design of the laser transmitter.

Sub-5-ps optical pulse generation from a 1.55-µm distributed-feedback laser diode with nanosecond electric pulse excitation and spectral filtering.

PubMed

Chen, Shaoqiang; Sato, Aya; Ito, Takashi; Yoshita, Masahiro; Akiyama, Hidefumi; Yokoyama, Hiroyuki

2012-10-22

This paper reports generation of sub-5-ps Fourier-transform limited optical pulses from a 1.55-µm gain-switched single-mode distributed-feedback laser diode via nanosecond electric excitation and a simple spectral-filtering technique. Typical damped oscillations of the whole lasing spectrum were observed in the time-resolved waveform. Through a spectral-filtering technique, the initial relaxation oscillation pulse and the following components in the output pulse can be well separated, and the initial short pulse can be selectively extracted by filtering out the short-wavelength components in the spectrum. Short pulses generated by this simple method are expected to have wide potential applications comparable to mode-locking lasers.

A 16-Channel Distributed-Feedback Laser Array with a Monolithic Integrated Arrayed Waveguide Grating Multiplexer for a Wavelength Division Multiplex-Passive Optical Network System Network

NASA Astrophysics Data System (ADS)

Zhao, Jian-Yi; Chen, Xin; Zhou, Ning; Huang, Xiao-Dong; Cao, Ming-De; Liu, Wen

2014-07-01

A 16-channel distributed-feedback (DFB) laser array with a monolithic integrated arrayed waveguide grating multiplexer for a wavelength division multiplex-passive optical network system is fabricated by using the butt-joint metal organic chemical vapor deposition technology and nanoimpirnt technology. The results show that the threshold current is about 20-30 mA at 25°C. The DFB laser side output power is about 16 mW with a 150 mA injection current. The lasing wavelength is from 1550 nm to 1575 nm covering a more than 25 nm range with 200 GHz channel space. A more than 55 dB sidemode suppression ratio is obtained.

Chaotic optical time-domain reflectometry using a distributed feedback laser diode modulated by an improved Colpitts oscillator

NASA Astrophysics Data System (ADS)

Li, Jing Xia; Xu, Hang; Liu, Li; Su, Peng Cheng; Zhang, Jian Guo

2015-05-01

We report a chaotic optical time-domain reflectometry for fiber fault location, where a chaotic probe signal is generated by driving a distributed feedback laser diode with an improved Colpitts chaotic oscillator. The results show that the unterminated fiber end, the loose connector, and the mismatch connector can be precisely located. A measurement range of approximately 91 km and a range independent resolution of 6 cm are achieved. This implementation method is easy to integrate and is cost effective, which gives it great potential for commercial applications.

Transforming Benzophenoxazine Laser Dyes into Chromophores for Dye-Sensitized Solar Cells: A Molecular Engineering Approach

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

Schröder, Florian A. Y. N.; Cole, Jacqueline M.; Waddell, Paul G.

2015-02-03

The re-functionalization of a series of four well-known industrial laser dyes, based on benzophenoxazine, is explored with the prospect of molecularly engineering new chromophores for dye-sensitized solar cell (DSC) applications. Such engineering is important since a lack of suitable dyes is stifling the progress of DSC technology. The conceptual idea involves making laser dyes DSC-active by chemical modification, while maintaining their key property attributes that are attractive to DSC applications. This molecular engineering follows a step-wise approach. Firstly, molecular structures and optical absorption properties are determined for the parent laser dyes: Cresyl Violet (1); Oxazine 170 (2); Nile Blue Amore » (3), Oxazine 750 (4). These reveal structure-property relationships which define the prerequisites for computational molecular design of DSC dyes; the nature of their molecular architecture (D-π-A) and intramolecular charge transfer. Secondly, new DSC dyes are computationally designed by the in silico addition of a carboxylic acid anchor at various chemical substitution points in the parent laser dyes. A comparison of the resulting frontier molecular orbital energy levels with the conduction band edge of a TiO2 DSC photoanode and the redox potential of two electrolyte options I-/I3- and Co(II/III)tris(bipyridyl) suggests promise for these computationally designed dyes as co-sensitizers for DSC applications.« less

Composition and method of preparation of solid state dye laser rods

DOEpatents

Hermes, Robert E.

1992-01-01

The present invention includes solid polymeric-host laser rods prepared using bulk polymerization of acrylic acid ester comonomers which, when admixed with dye(s) capable of supporting laser oscillation and polymerized with a free radical initiator under mild thermal conditions, produce a solid product having the preferred properties for efficient lasing. Unsaturated polymerizable laser dyes can also be employed as one of the comonomers. Additionally, a method is disclosed which alleviates induced optical stress without having to anneal the polymers at elevated temperatures (>85.degree. C.).

Continuous-wave organic dye lasers and methods

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

Shapira, Ofer; Chua, Song-Liang; Zhen, Bo

2014-09-16

An organic dye laser produces a continuous-wave (cw) output without any moving parts (e.g., without using flowing dye streams or spinning discs of solid-state dye media to prevent photobleaching) and with a pump beam that is stationary with respect to the organic dye medium. The laser's resonant cavity, organic dye medium, and pump beam are configured to excite a lasing transition over a time scale longer than the associated decay lifetimes in the organic dye medium without photobleaching the organic dye medium. Because the organic dye medium does not photobleach when operating in this manner, it may be pumped continuouslymore » so as to emit a cw output beam. In some examples, operation in this manner lowers the lasing threshold (e.g., to only a few Watts per square centimeter), thereby facilitating electrical pumping for cw operation.« less

Laser-induced fluorescence spectroscopy in tissue local necrosis detection

NASA Astrophysics Data System (ADS)

Cip, Ondrej; Buchta, Zdenek; Lesundak, Adam; Randula, Antonin; Mikel, Bretislav; Lazar, Josef; Veverkova, Lenka

2014-03-01

The recent effort leads to reliable imaging techniques which can help to a surgeon during operations. The fluorescence spectroscopy was selected as very useful online in vivo imaging method to organics and biological materials analysis. The presented work scopes to a laser induced fluorescence spectroscopy technique to detect tissue local necrosis in small intestine surgery. In first experiments, we tested tissue auto-fluorescence technique but a signal-to-noise ratio didn't express significant results. Then we applied a contrast dye - IndoCyanine Green (ICG) which absorbs and emits wavelengths in the near IR. We arranged the pilot experimental setup based on highly coherent extended cavity diode laser (ECDL) used for stimulating of some critical areas of the small intestine tissue with injected ICG dye. We demonstrated the distribution of the ICG exciter with the first file of shots of small intestine tissue of a rabbit that was captured by high sensitivity fluorescent cam.

Multi-wavelength laser from dye-doped cholesteric polymer films.

PubMed

Huang, Yuhua; Wu, Shin-Tson

2010-12-20

A multi-wavelength laser is demonstrated using a dye-doped cholesteric polymer film whose reflection bandwidth is broadened with several oscillations. Due to the abrupt change of the density of state between oscillation peak and valley, each oscillation functions as a photonic band gap for generating a laser wavelength under the excitation of a pumping laser. As a result, a multiple wavelength laser is generated. Results indicate that the dye-doped cholesteric liquid crystal polymer film is a good candidate for fabricating broadband lasers such as white light lasers. Potential applications include experimental testing of laser materials, identification markers, information displays, and inertial confinement laser fusion.

Open-cavity fiber laser with distributed feedback based on externally or self-induced dynamic gratings.

PubMed

Lobach, Ivan A; Drobyshev, Roman V; Fotiadi, Andrei A; Podivilov, Evgeniy V; Kablukov, Sergey I; Babin, Sergey A

2017-10-15

Dynamic population inversion gratings induced in an active medium by counter-propagating optical fields may have a reverse effect on writing laser radiation via feedback they provide. In this Letter we report, to the best of our knowledge, on the first demonstration of an open-cavity fiber laser in which the distributed feedback is provided by a dynamic grating "written" in a Yb-doped active fiber, either by an external source or self-induced via a weak (∼0.1%) reflection from an angle-cleaved fiber end. It has been shown that meters-long dynamic grating is formed with a narrow bandwidth (<50  MHz) and a relatively high-reflection coefficient (>7%) securing single-frequency operation, but the subsequent hole-burning effects accompanied by new grating formation lead to the switching from one longitudinal mode to another. providing a regular pulse-mode dynamics. As a result, periodically generated pulse trains cover a spectrum range of several terahertz delivering millions of cavity modes in sequent pulses.

Distributed feedback interband cascade lasers with top grating and corrugated sidewalls

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

Xie, Feng; Stocker, Michael; Pham, John

Distributed feedback (DFB) interband cascade lasers (ICLs) with a 1st order top surface grating were designed and fabricated. Partially corrugated sidewalls were implemented to suppress high order lateral modes. The DFB ICLs have 4 mm long and 4.5 mu m wide ridge waveguides and are mounted epi-up on AlN submounts. We demonstrated a continuous-wave (CW) DFB ICL, from a first wafer which has a large detuning of the gain peak from the DFB wavelength, with a side mode suppression ratio of 30 dB. With proper matching of grating feedback and the gain peak wavelength for the second wafer, a DFBmore » ICL was demonstrated with a maximum CW output power and a maximum wall plug efficiency reaching 42 mW and 2%, respectively, at 25 degrees C. The lasing wavelengths of both lasers are around 3.3 mu m at 25 degrees C. Published by AIP Publishing.« less

Fiber Optic Laser Accelerometer

DTIC Science & Technology

2007-11-06

embodiment of a fiber laser accelerometer 10. The fiber laser accelerometer 10 includes a fiber laser 12. Fiber laser 12 can be either a Fabry - Perot type...cavity fiber laser or a distributed feedback fiber laser. In a 4 Attorney Docket No. 97966 Fabry - Perot type fiber laser, the laser cavity is a length...type of signal. A receiver 26 receives the phase shifted signal. Receiver 26 is capable of demodulating and detecting the signal from the fiber laser by

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.

Acceleration Strain Transducer with Increased Sensitivity

DTIC Science & Technology

2009-09-22

utilizing a fiber laser sensor. The fiber laser accelerometer 10 includes a fiber laser 12. Fiber laser 12 can be either a Fabry - Perot type cavity...fiber laser or a distributed feedback fiber laser. In a Fabry - Perot type fiber laser, the laser cavity is a length of erbium- doped optical fiber...designs can produce the same type of signal. A receiver 26 receives the phase shifted signal. Receiver 26 is capable of demodulating and detecting

Intracavity optical trapping with Ytterbium doped fiber ring laser

NASA Astrophysics Data System (ADS)

Sayed, Rania; Kalantarifard, Fatemeh; Elahi, Parviz; Ilday, F. Omer; Volpe, Giovanni; Maragò, Onofrio M.

2013-09-01

We propose a novel approach for trapping micron-sized particles and living cells based on optical feedback. This approach can be implemented at low numerical aperture (NA=0.5, 20X) and long working distance. In this configuration, an optical tweezers is constructed inside a ring cavity fiber laser and the optical feedback in the ring cavity is controlled by the light scattered from a trapped particle. In particular, once the particle is trapped, the laser operation, optical feedback and intracavity power are affected by the particle motion. We demonstrate that using this configuration is possible to stably hold micron-sized particles and single living cells in the focal spot of the laser beam. The calibration of the optical forces is achieved by tracking the Brownian motion of a trapped particle or cell and analysing its position distribution.

Spectroscopic properties and amplified spontaneous emission of fluorescein laser dye in ionic liquids as green media

NASA Astrophysics Data System (ADS)

AL-Aqmar, Dalal M.; Abdelkader, H. I.; Abou Kana, Maram T. H.

2015-09-01

The use of ionic liquids (ILs) as milieu materials for laser dyes is a promising field and quite competitive with volatile organic solvents and solid state-dye laser systems. This paper investigates some photo-physical parameters of fluorescein dye incorporated into ionic liquids; 1-Butyl-3-methylimidazolium chloride (BMIM Cl), 1-Butyl-3-methylimidazolium tetrachloroaluminate (BMIM AlCl4) and 1-Butyl-3-methylimidazolium tetrafluoroborate (BMIM BF4) as promising host matrix in addition to ethanol as reference. These parameters are: absorption and emission cross-sections, fluorescence lifetime and quantum yield, in addition to the transition dipole moment, the attenuation length and oscillator strength were also investigated. Lasing characteristics such as amplified spontaneous emission (ASE), the gain, and the photostability of fluorescein laser dye dissolved in different host materials were assessed. The composition and properties of the matrix of ILs were found that it has great interest in optimizing the laser performance and photostability of the investigated laser dye. Under transverse pumping of fluorescein dye by blue laser diode (450 nm) of (400 mW), the initial ASE for dye dissolved in BMIM AlCl4 and ethanol were decreased to 39% and 36% respectively as time progressed 132 min. Relatively high efficiency and high fluorescence quantum yield (11.8% and 0.82% respectively) were obtained with good photostability in case of fluorescein in BMIM BF4 that was decreased to ∼56% of the initial ASE after continuously pumping with 400 mW for 132 min.

Methodology for detection of carbon monoxide in hot, humid media by telecommunication distributed feedback laser-based tunable diode laser absorption spectrometry.

PubMed

Lathdavong, Lemthong; Shao, Jie; Kluczynski, Pawel; Lundqvist, Stefan; Axner, Ove

2011-06-10

Detection of carbon monoxide (CO) in combustion gases by tunable diode laser spectrometry is often hampered by spectral interferences from H2O and CO2. A methodology for assessment of CO in hot, humid media using telecommunication distributed feedback lasers is presented. By addressing the R14 line at 6395.4  cm(-1), and by using a dual-species-fitting technique that incorporates the fitting of both a previously measured water background reference spectrum and a 2f-wavelength modulation lineshape function, percent-level concentrations of CO can be detected in media with tens of percent of water (c(H2O)≤40%) at T≤1000 °C with an accuracy of a few percent by the use of a single reference water spectrum for background correction.

Preparation of certain m-aminophenols and the use thereof for preparation of laser dyes

DOEpatents

Hammond, P.R.

1983-12-29

Methods are provided for making certain m-aminophenols using a sulfonation/alkali fusion procedure. The aminophenols are key intermediates in the synthesis of dyes, particularly efficient, stable dyes for laser application. Preparations of some rhodamine and phenoxazone dyes from the m-aminophenols are described.

Preparation of certain m-aminophenols and the use thereof for preparation of laser dyes

DOEpatents

Hammond, Peter R.

1986-01-01

Methods are provided for making certain m-aminophenols using a sulfonation/alkali fusion procedure. The aminophenols are key intermediates in the synthesis of dyes, particularly efficient, stable dyes for laser application. Preparations of some rhodamine and phenoxazone dyes from the m-aminophenols are described.

Invasive leg vein treatment with 1064/1319 Nd:YAG laser: combination with dye laser treatment

NASA Astrophysics Data System (ADS)

Smucler, Roman; Horak, Ladislav; Mazanek, Jiri

1999-06-01

More than 2 500 leg veins patients were treated with dye laser / ScleroPlus, Candela, USA / successfully in our clinic and we use this therapy as the basic cosmetics treatment. But especially diameter of leg vein is limiting factor. Very often we have to treat some cases that are not ideal for classical surgical or for dye laser method. We decided to make invasive perivenous laser coagulation. We adapted original Czech 1064/1319 nm Nd:YAG laser / US patent pending /, which is new combine tool, for invasive application. Principe: After we have penetrated the cutis with laser fiber we coagulate leg veins during slowly perivenous motion. Perfect preoperative examination is a condition of success. After 15 months we have very interesting results. Some patients / 15%/ were perfect treated only with this possibility but excellent results are acquired from combination with dye laser.

Monolithically integrated distributed feedback laser array wavelength-selectable light sources for WDM-PON application

NASA Astrophysics Data System (ADS)

Chen, Xin; Zhao, Jianyi; Zhou, Ning; Huang, Xiaodong; Cao, Mingde; Wang, Lei; Liu, Wen

2015-01-01

The monolithic integration of 1.5-μm four channels phase shift distributed feedback lasers array (DFB-LD array) with 4×1 multi-mode interference (MMI) optical combiner is demonstrated. A home developed process mainly consists of butt-joint regrowth (BJR) and simultaneous thermal and ultraviolet nanoimprint lithography (STU-NIL) is implemented to fabricate gratings and integrated devices. The threshold currents of the lasers are less than 10 mA and the side mode suppression ratios (SMSR) are better than 40 dB for all channels. Quasi-continuous tuning is realized over 7.5 nm wavelength region with the 30 °C temperature variation. The results indicate that the integration device we proposed can be used in wavelength division multiplexing passive optical networks (WDM-PON).

Stimulated Brillouin scattering in ultra-long distributed feedback Bragg gratings in standard optical fiber.

PubMed

Loranger, Sébastien; Lambin-Iezzi, Victor; Wahbeh, Mamoun; Kashyap, Raman

2016-04-15

Distributed feedback (DFB) fiber Bragg gratings (FBG) are widely used as narrow-band filters and single-mode cavities for lasers. Recently, a nonlinear generation has been shown in 10-20 cm DFB gratings in a highly nonlinear fiber. First, we show in this Letter a novel fabrication technique of ultra-long DFBs in a standard fiber (SMF-28). Second, we demonstrate nonlinear generation in such gratings. A particular inscription technique was used to fabricate all-in-phase ultra-long FBG and to implement reproducible phase shift to form a DFB mode. We demonstrate stimulated Brillouin scattering (SBS) emission from this DFB mode and characterize the resulting laser. It seems that such a SBS based DFB laser stabilizes a pump's jittering and reduces its linewidth.

Peculiarities of spike multimode generation of a superradiant distributed feedback laser

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

Kocharovskaya, E R; Ginzburg, N S; Sergeev, A S

2011-08-31

Using one-dimensional semiclassical Maxwell - Bloch equations with account for the coherent polarisation dynamics, we have studied spike generation regimes of a superradiant distributed feedback laser in the case of inhomogeneous broadening of the spectral line of an active medium. By analysing the dynamic spectra of inversion of the active medium and laser radiation, we have revealed the relationship of individual spikes of radiation and their modulation with specific parts in the spectral line of the active medium and mode beatings. It has been shown that the broadening and shift of the lasing spectrum with respect to the initial electromagneticmore » Bragg-cavity modes is accompanied by a strong spectral gradient of inversion that is typical of the superradiant regimes. (control of radiation parameters)« less

Intensity-Stabilized Fast-Scanned Direct Absorption Spectroscopy Instrumentation Based on a Distributed Feedback Laser with Detection Sensitivity down to 4 × 10−6

PubMed Central

Zhao, Gang; Tan, Wei; Jia, Mengyuan; Hou, Jiajuan; Ma, Weiguang; Dong, Lei; Zhang, Lei; Feng, Xiaoxia; Wu, Xuechun; Yin, Wangbao; Xiao, Liantuan; Axner, Ove; Jia, Suotang

2016-01-01

A novel, intensity-stabilized, fast-scanned, direct absorption spectroscopy (IS-FS-DAS) instrumentation, based on a distributed feedback (DFB) diode laser, is developed. A fiber-coupled polarization rotator and a fiber-coupled polarizer are used to stabilize the intensity of the laser, which significantly reduces its relative intensity noise (RIN). The influence of white noise is reduced by fast scanning over the spectral feature (at 1 kHz), followed by averaging. By combining these two noise-reducing techniques, it is demonstrated that direct absorption spectroscopy (DAS) can be swiftly performed down to a limit of detection (LOD) (1σ) of 4 × 10−6, which opens up a number of new applications. PMID:27657082

Direct solar-pumped iodine laser amplifier

NASA Technical Reports Server (NTRS)

Han, Kwang S.; Kim, K. H.; Stock, L. V.

1986-01-01

In order to evaluate the feasibility of the solar pumped dye laser, the parametric study of a dye laser amplifier pumped by a solar simulator and flashlamp was carried out, and the amplifier gains were measured at various pump beam irradiances on the dye cell. Rhodamine 6G was considered as a candidate for the solar pumped laser because of its good utilization of the solar spectrum and high quantum efficiency. The measurement shows that a solar concentration of 20,000 is required to reach the threshold of the dye. The work to construct a kinetic model algorithm which predicts the output parameter of laser was progressed. The kinetic model was improved such that there is good agreement between the theoretical model and experimental data for the systems defined previously as flashlamp pumped laser oscillator, and the long path length solar pumped laser.

Photodynamic therapy: a synergy between light and colors

NASA Astrophysics Data System (ADS)

Merigo, Elisabetta; Sozzi, Michele; Ciociola, Tecla; Conti, Stefania; Fornaini, Carlo; Vescovi, Paolo; Selleri, Stefano; Cucinotta, Annamaria

2015-02-01

In this work the application of different laser wavelengths, in combination with different photosensitizing dyes, to bacterial cultures, in liquid or solid mean, has been investigated. Two types of Streptococcus mutans cultures have been used for the experiments, inside agar and saline solution. Three different laser wavelengths have been applied to the bacterial cultures together with a photosensitizing dye: red diode (650 nm) on cultures stained with Toluidine Blue, blueviolet diode (450 nm) on cultures stained with Curcumin and KTP laser (532 nm) on cultures stained with Erythrosine. The choice of the dye has been made considering the color affinity with the used wavelength. Tests without dyes have also been performed. Experimental results show that the maximum inhibition of bacterial growth with the blue laser has been obtained in a saline solution with a growth of 40.77%. While the combination with Curcumin lead to an inhibition growth of about 99.1%, for a laser fluence of 30J/cm2. No inhibition has been observed using the red laser in saline solution without dye, while the combination with Toluidine Blue resulted in a 100% inhibition growth for 20 and 30 J/cm2 fluences. An inhibition growth of just 16.26% has been obtained with the use of KTP laser in saline solution without dye. The use of Erythrosine had the effect of a complete inhibition growth. From the obtained results it is possible to observe that the combination of laser wavelength with a particular photosensitizing dye can dramatically increase the bacterial growth.

KrF laser-induced OH fluorescence imaging in a supersonic combustion tunnel

NASA Technical Reports Server (NTRS)

Quagliaroli, T. M.; Laufer, G.; Hollo, S. D.; Krauss, R. H.; Whitehurst, R. B., III; Mcdaniel, J. C., Jr.

1992-01-01

Planar fluorescence images of OH in a continuous-flow, electrical-resistively heated, high enthalpy, hydrogen-air combustion tunnel, induced by a tunable KrF laser, were recorded. These images were compared to previously recorded fluorescence images induced by a doubled-dye laser under similar conditions. Images induced by the doubled-dye laser system demonstrated a severe distortion caused by absorption and fluorescence trapping. By contrast, images of the fluorescence induced by the tunable KrF laser retained the symmetry properties of the flow. Based on signal-to-noise ratio measurements the yield of the fluorescence induced by the doubled-dye laser is larger than the fluorescence yield induced by the KrF laser. The measurements in the present facility of OH fluorescence induced by the KrF laser were limited by the photon-statistical noise. Based 2 on this result, doubled-dye laser systems are recommended for OH imaging in small and OH lean (less than 10 exp 15/cu cm) facilities. KrF lasers should be selected otherwise.

Two Wavelength Ti:sapphire Laser for Ozone DIAL Measurements from Aircraft

NASA Technical Reports Server (NTRS)

Situ, Wen; DeYoung, Russel J.

1998-01-01

Laser remote sensing of ozone from aircraft has proven to be a valuable technique for understanding the distribution and dynamics of ozone in the atmosphere. Presently the differential absorption lidar (DIAL) technique, using dual ND:YAG lasers that are doubled to pump dye lasers which in turn are doubled into the UV for the "on" and "off' line lasers, is used on either the NASA DC-8 or P-3 aircraft. Typically, the laser output for each line is 40-mJ and this is split into two beams, one looking up and the other downward, each beam having about 20-mJ. The residual ND:YAG (1.06 micron) and dye laser energies are also transmitted to obtain information on the atmospheric aerosols. While this system has operated well, there are several system characteristics that make the system less than ideal for aircraft operations. The system, which uses separate "on" and "off" line lasers, is quite large and massive requiring valuable aircraft volume and weight. The dye slowly degrades with time requiring replacement. The laser complexity requires a number of technical people to maintain the system performance. There is also the future interest in deploying an ozone DIAL system in an Unpiloted Atmospheric Vehicle (UAV) which would require a total payload mass of less than 150 kg and power requirement of less than 1500 W. A laser technology has emerged that could potentially provide significant enhancements over the present ozone DIAL system. The flashlamp pumped Ti:sapphire laser system is an emerging technology that could reduce the mass and volume over the present system and also provide a system with fewer conversion steps, reducing system complexity. This paper will discuss preliminary results from a flashlamp-pumped Ti:sapphire laser constructed as a radiation source for a UV DIAL system to measure ozone.

Feasibility of surveying pesticide coverage with airborne fluorometer

NASA Technical Reports Server (NTRS)

Stoertz, G. E.; Hemphill, W. R.

1970-01-01

Response of a Fraunhofer line discriminator (FLD) to varying distributions of granulated corncobs stained with varying concentrations of Rhodamine WT dye was tested on the ground and from an H-19 helicopter. The granules are used as a vehicle for airborne emplacement of poison to control fire ants in the eastern and southeastern United States. Test results showed that the granules are detectable by FLD but that the concentration must be too great to be practical with the present apparatus. Possible methods for enhancement of response may include: (1) increasing dye concentration; (2) incorporating with the poisoned granules a second material to carry the dye alone; (3) use of a more strongly fluorescent substance (at 5890 A); (4) modifying the time interval after dyeing, or modifying the method of dyeing; (5) modifying the FLD for greater efficiency, increased field of view or larger optics; or (6) experimenting with laser-stimulated fluorescence.

Modulation of distributed feedback (DFB) laser diode with the autonomous Chua's circuit: Theory and experiment

NASA Astrophysics Data System (ADS)

Talla Mbé, Jimmi Hervé; Woafo, Paul

2018-03-01

We report on a simple way to generate complex optical waveforms with very cheap and accessible equipments. The general idea consists in modulating a laser diode with an autonomous electronic oscillator, and in the case of this study, we use a distributed feedback (DFB) laser diode pumped with an electronic Chua's circuit. Based on the adiabatic P-I characteristics of the laser diode at low frequencies, we show that when the total pump is greater than the laser threshold, it is possible to convert the electrical waveforms of the Chua's circuit into optical carriers. But, if that is not the case, the on-off dynamical behavior of the laser permits to obtain many other optical waveform signals, mainly pulses. Our numerical results are consistent with experimental measurements. The work presents the advantage of extending the range of possible chaotic dynamics of the laser diodes in the time domains (millisecond) where it is not usually expected with conventional modulation techniques. Moreover, this new technique of laser diodes modulation brings a general benefit in the physical equipment, reduces their cost and congestion so that, it can constitute a step towards photonic integrated circuits.

Clean Photothermal Heating and Controlled Release from Near-Infrared Dye Doped Nanoparticles without Oxygen Photosensitization.

PubMed

Guha, Samit; Shaw, Scott K; Spence, Graeme T; Roland, Felicia M; Smith, Bradley D

2015-07-21

The photothermal heating and release properties of biocompatible organic nanoparticles, doped with a near-infrared croconaine (Croc) dye, were compared with analogous nanoparticles doped with the common near-infrared dyes ICG and IR780. Separate formulations of lipid-polymer hybrid nanoparticles and liposomes, each containing Croc dye, absorbed strongly at 808 nm and generated clean laser-induced heating (no production of (1)O2 and no photobleaching of the dye). In contrast, laser-induced heating of nanoparticles containing ICG or IR780 produced reactive (1)O2, leading to bleaching of the dye and also decomposition of coencapsulated payload such as the drug doxorubicin. Croc dye was especially useful as a photothermal agent for laser-controlled release of chemically sensitive payload from nanoparticles. Solution state experiments demonstrated repetitive fractional release of water-soluble fluorescent dye from the interior of thermosensitive liposomes. Additional experiments used a focused laser beam to control leakage from immobilized liposomes with very high spatial and temporal precision. The results indicate that fractional photothermal leakage from nanoparticles doped with Croc dye is a promising method for a range of controlled release applications.

Clean Photothermal Heating and Controlled Release From Near Infrared Dye Doped Nanoparticles Without Oxygen Photosensitization

PubMed Central

Guha, Samit; Shaw, Scott K.; Spence, Graeme T.; Roland, Felicia M.; Smith, Bradley D.

2015-01-01

The photothermal heating and release properties of biocompatible organic nanoparticles, doped with a near-infrared croconaine (Croc) dye, were compared with analogous nanoparticles doped with the common near-infrared dyes ICG and IR780. Separate formulations of lipid-polymer-hybrid nanoparticles and liposomes, each containing Croc dye, absorbed strongly at 808 nm and generated clean laser-induced heating (no production of 1O2 and no photobleaching of the dye). In contrast, laser-induced heating of nanoparticles containing ICG or IR780 produced reactive 1O2 leading to bleaching of the dye and also decomposition of co-encapsulated payload such as the drug Doxorubicin. Croc dye was especially useful as a photothermal agent for laser controlled release of chemically sensitive payload from nanoparticles. Solution state experiments demonstrated repetitive fractional release of water soluble fluorescent dye from the interior of thermosensitive liposomes. Additional experiments used a focused laser beam to control leakage from immobilized liposomes with very high spatial and temporal precision. The results indicate that fractional photothermal leakage from nanoparticles doped with Croc dye is a promising method for a range of controlled release applications. PMID:26149326

Characterization and Dynamic Analysis of Long-Cavity Multi-Section Gain- Levered Quantum-Dot Lasers

DTIC Science & Technology

2013-03-01

test setup .................................................................... 8 Figure 5: Comparison of a Fabry – Perot and distributed feedback...for example Fabry – Perot and distributed-feedback designs), with each possessing advantages and disadvantages that will be discussed in detail in...contrast to Fabry – Perot cavities (two discrete mirrors) that result in lasing over multiple longitudinal modes supported by the cavity. Figure 5 shows

CO.sub.2 optically pumped distributed feedback diode laser

DOEpatents

Rockwood, Stephen D.

1980-01-01

A diode laser optically pumped by a CO.sub.2 coherent source. Interference fringes generated by feeding the optical pumping beam against a second beam, periodically alter the reflectivity of the diode medium allowing frequency variation of the output signal by varying the impingent angle of the CO.sub.2 laser beams.

Laser lithotripsy of gallstones: alexandrite and rhodamine-6G versus coumarin dye laser: fragmentation and fiber burn-off in vitro

NASA Astrophysics Data System (ADS)

Hochberger, Juergen; Bredt, Marion; Mueller, Gudrun; Hahn, Eckhart G.; Ell, Christian

1993-05-01

In the following study three different pulsed laser lithotripsy systems were compared for the fine fragmentation of identical sets of natural and synthetic gallstones `in vitro.' Using a pulsed coumarin dye laser (504 nm), a pulsed rhodamine 6G dye laser (595 nm), and a pulsed Alexandrite laser (755 nm) a total of 184 concrements of known chemical composition, size, and weight were disintegrated to a fragment size of

Optimal parameters for laser tissue soldering: II. Premixed versus separate dye-solder techniques.

PubMed

McNally, K M; Sorg, B S; Chan, E K; Welch, A J; Dawes, J M; Owen, E R

2000-01-01

Laser tissue soldering by using an indocyanine green (ICG)-doped protein solder applied topically to the tissue surface and denatured with a diode laser was investigated in Part I of this study. The depth of light absorption was predominantly determined by the concentration of the ICG dye added to the solder. This study builds on that work with an in vitro investigation of the effects of limiting the zone of heat generation to the solder-tissue interface to determine whether more stable solder-tissue fusion can be achieved. An alternative laser tissue soldering technique was investigated, which increased light absorption at the vital solder-tissue interface. A thin layer of ICG dye was smeared over the surface to be treated, the protein solder was then placed directly on top of the dye, and the solder was denatured with an 808-nm diode laser. Because laser light at approximately 800 nm is absorbed primarily by the ICG dye, this thin layer of ICG solution restricted the heat source to the space between the solder and the tissue surfaces. A tensile strength analysis was conducted to compare the separate dye-solder technique with conventional techniques of laser tissue soldering for which a premixed dye-solder is applied directly to the tissue surface. The effect of hydration on bond stability of repairs formed by using both techniques was also investigated using tensile strength and scanning electron microscopy analysis. Equivalent results in terms of tensile strength were obtained for the premixed dye-solder technique using protein solders containing 0.25 mg/ml ICG (liquid solder, 220 +/- 35 N/cm(2); solid solder, 602 +/- 32 N/cm(2)) and for the separate dye-solder technique (liquid solder, 228 +/- 41 N/cm(2); solid solder, 578 +/- 29 N/cm(2)). The tensile strength of native bovine thoracic aorta was 596 +/- 31 N/cm(2). Repairs created by using the separate dye-solder technique were more stable during hydration than their premixed dye-solder counterparts. The conventional premixed dye-solder was simpler and approximately twice as fast to apply. The separate dye-solder technique, however, increased the shelf-life of the solder, because the dye was mixed at the time of the experiment, thus conserving its spectral absorbency properties. Two laser-assisted tissue soldering techniques have been evaluated for repairing aorta incisions in vitro. The advantages and disadvantages of each of these techniques are discussed. Copyright 2000 Wiley-Liss, Inc.

Dye foils with increased durability for passive Q-switching in a 1064 nm laser

NASA Astrophysics Data System (ADS)

Mierczyk, Z.; Kwasny, M.; Czeszko, J.

The results of spectral gel permeation chromatography and differential thermal analysis investigations of structures of dye foils consisting of bis-(4-dimethyl-amino-dithio-benzil)-nickel dye suspended in polymethylmethacrylate matrix, to be used for passive Q-switching in a 1064 nm laser, are reported. Results of experimental measurements and of numerical calculations of thermal and generating properties, and of the endurance of passive foil type Q-switches in the resonator of YAG:Nd(3+) laser are also presented. Optimization of polymerization conditions has enabled the production of dye foils with high thermal and photochemical resistance, which give stable operation of a giant pulsed laser.

Oxazine laser dyes

DOEpatents

Hammond, Peter R.; Field, George F.

1992-01-01

New oxazine compounds useful as dye laser media in solution, are superiior to prior art materials. The oxazine dyes useful when pumped by the 578.2 nm copper line to operate in the 700-800 nm range are described by formula I ##STR1##

On-chip tunable optofluidic dye laser

NASA Astrophysics Data System (ADS)

Cai, Zengyan; Shen, Zhenhua; Liu, Haigang; Yue, Huan; Zou, Yun; Chen, Xianfeng

2016-11-01

We demonstrate a chip-scale tunable optofluidic dye laser with Au-coated fibers as microcavity. The chip is fabricated by soft lithography. When the active region is pumped, a relatively low threshold of 6.7 μJ/mm2 is realized with multimode emission due to good confinement of the cavity mirrors, long active region, as well as total reflectivity. It is easy to tune the lasing emission wavelength by changing the solvent of laser dye. In addition, the various intensity ratios of multicolor lasing can be achieved by controlling flow rates of two fluid streams carried with different dye molecules. Furthermore, the convenience in fabrication and directional lasing emission outcoupled by the fiber make the tunable optofluidic dye laser a promising underlying coherent light source in the integrated optofluidic systems.

Acceleration Strain Transducer

DTIC Science & Technology

2007-11-05

accelerometer 10 includes a fiber laser 12. Fiber laser 12 can be either a Fabry - Perot type cavity fiber laser or a distributed feedback fiber laser. In a... Fabry - Perot type fiber laser, the laser cavity is a length of erbium- doped optical fiber with a Bragg grating written in the fiber core at either end of...the phase shifted signal. Receiver 26 is capable of demodulating and detecting the signal from the fiber laser by various methods well known in the

Porous Silicon Covered with Silver Nanoparticles as Surface-Enhanced Raman Scattering (SERS) Substrate for Ultra-Low Concentration Detection.

PubMed

Kosović, Marin; Balarin, Maja; Ivanda, Mile; Đerek, Vedran; Marciuš, Marijan; Ristić, Mira; Gamulin, Ozren

2015-12-01

Microporous and macro-mesoporous silicon templates for surface-enhanced Raman scattering (SERS) substrates were produced by anodization of low doped p-type silicon wafers. By immersion plating in AgNO3, the templates were covered with silver metallic film consisting of different silver nanostructures. Scanning electron microscopy (SEM) micrographs of these SERS substrates showed diverse morphology with significant difference in an average size and size distribution of silver nanoparticles. Ultraviolet-visible-near-infrared (UV-Vis-NIR) reflection spectroscopy showed plasmonic absorption at 398 and 469 nm, which is in accordance with the SEM findings. The activity of the SERS substrates was tested using rhodamine 6G (R6G) dye molecules and 514.5 nm laser excitation. Contrary to the microporous silicon template, the SERS substrate prepared from macro-mesoporous silicon template showed significantly broader size distribution of irregular silver nanoparticles as well as localized surface plasmon resonance closer to excitation laser wavelength. Such silver morphology has high SERS sensitivity that enables ultralow concentration detection of R6G dye molecules up to 10(-15) M. To our knowledge, this is the lowest concentration detected of R6G dye molecules on porous silicon-based SERS substrates, which might even indicate possible single molecule detection.

PicoGreen dye as an active medium for plastic lasers

NASA Astrophysics Data System (ADS)

Pradeep, C.; Vallabhan, C. P. G.; Radhakrishnan, P.; Nampoori, V. P. N.

2015-08-01

Deoxyribonucleic acid lipid complex thin films are used as a host material for laser dyes. We tested PicoGreen dye, which is commonly used for the quantification of single and double stranded DNA, for its applicability as lasing medium. PicoGreen dye exhibits enhanced fluorescence on intercalation with DNA. This enormous fluorescence emission is amplified in a planar microcavity to achieve yellow lasing. Here the role of DNA is not only a host medium, but also as a fluorescence dequencher. With the obtained results we have ample reasons to propose PicoGreen dye as a lasing medium, which can lead to the development of DNA based bio-lasers.

Intense excitation source of blue-green laser

NASA Astrophysics Data System (ADS)

Han, K. S.

1985-10-01

An intense and efficient excitation source for blue-green lasers useful for the space-based satellite laser applications, underwater strategic communication, and measurement of ocean bottom profile is being developed. The source in use, hypocycloidal pinch plasma (HCP), and a newly designed dense-plasma focus (DPF) can produce intense UV photons (200 to 300 nm) which match the absorption spectra of both near UV and blue green dye lasers (300 to 400 nm). During the current project period, the successful enhancement of blue-green laser output of both Coumarin 503 and LD490 dye through the spectral conversion of the HCP pumping light has been achieved with a converter dye BBQ. The factor of enhancement in the blue-green laser output energy of both Coumarin 503 and LD490 is almost 73%. This enhancement will definitely be helpful in achieving the direct high power blue-green laser (> 1 MW) with the existing blue green dye laser. On the other hand the dense-plasma focus (DPF) with new optical coupling has been designed and constructed. For the optimization of the DPF device as the UV pumping light source, the velocity of current sheath and the formation of plasma focus have been measured as function of argon or argon-deuterium fill gas pressure. Finally, the blue-green dye laser (LD490) has been pumped with the DPF device for preliminary tests. Experimental results with the DPF device show that the velocity of the current sheath follows the inverse relation of sq st. of pressure as expected. The blue-green dye (LD490) laser output exceeded 3.1 m at the best cavity tuning of laser system. This corresponds to 3J/1 cu cm laser energy extraction.

All optical mode controllable Er-doped random fiber laser with distributed Bragg gratings.

PubMed

Zhang, W L; Ma, R; Tang, C H; Rao, Y J; Zeng, X P; Yang, Z J; Wang, Z N; Gong, Y; Wang, Y S

2015-07-01

An all-optical method to control the lasing modes of Er-doped random fiber lasers (RFLs) is proposed and demonstrated. In the RFL, an Er-doped fiber (EDF) recoded with randomly separated fiber Bragg gratings (FBG) is used as the gain medium and randomly distributed reflectors, as well as the controllable element. By combining random feedback of the FBG array and Fresnel feedback of a cleaved fiber end, multi-mode coherent random lasing is obtained with a threshold of 14 mW and power efficiency of 14.4%. Moreover, a laterally-injected control light is used to induce local gain perturbation, providing additional gain for certain random resonance modes. As a result, active mode selection of the RFL is realized by changing locations of the laser cavity that is exposed to the control light.

New ultra-high resolution dye laser spectrometer utilizing a non-tunable reference resonator

NASA Astrophysics Data System (ADS)

Helmcke, J.; Snyder, J. J.; Morinaga, A.; Mensing, F.; Gläser, M.

1987-06-01

A new dye laser spectrometer utilizing a non-tunable reference resonator is described. The resonator consists of two Zerodur mirrors optically contacted to a Zerodur spacer. Frequency scanning of the laser is provided by acoustooptic modulation. Residual drifts of the resonator frequency — measured on line — are compensated automatically by corresponding corrections of the modulation frequency. The stability during several hours and the resettability of the dye laser frequency are±2.5 kHz and±10 kHz, respectively.

Picosecond pulse measurements using the active laser medium

NASA Technical Reports Server (NTRS)

Bernardin, James P.; Lawandy, N. M.

1990-01-01

A simple method for measuring the pulse lengths of synchronously pumped dye lasers which does not require the use of an external nonlinear medium, such as a doubling crystal or two-photon fluorescence cell, to autocorrelate the pulses is discussed. The technique involves feeding the laser pulses back into the dye jet, thus correlating the output pulses with the intracavity pulses to obtain pulse length signatures in the resulting time-averaged laser power. Experimental measurements were performed using a rhodamine 6G dye laser pumped by a mode-locked frequency-doubled Nd:YAG laser. The results agree well with numerical computations, and the method proves effective in determining lengths of picosecond laser pulses.

Method for obtaining a collimated near-unity aspect ratio output beam from a DFB-GSE laser with good beam quality.

PubMed

Liew, S K; Carlson, N W

1992-05-20

A simple method for obtaining a collimated near-unity aspect ratio output beam from laser sources with extremely large (> 100:1) aspect ratios is demonstrated by using a distributed-feedback grating-surfaceemitting laser. Far-field power-in-the-bucket measurements of the laser indicate good beam quality with a high Strehl ratio.

Characteristics research on self-amplified distributed feedback fiber laser

NASA Astrophysics Data System (ADS)

Song, Zhiqiang; Qi, Haifeng; Guo, Jian; Wang, Chang; Peng, Gangding

2014-09-01

A distributed feedback (DFB) fiber laser with a ratio of the backward to forward output power of 1:100 was composed by a 45-mm-length asymmetrical phase-shifted fiber grating fabricated on the 50-mm erbium-doped photosensitive fiber. Forward output laser was amplified using a certain length of Nufern EDFL-980-Hp erbium-doped fiber to absorb the surplus pump power after the active phase-shifted fiber grating and get population inversion. By using OptiSystem software, the best fiber length of the EDFL to get the highest gain was simulated. In order to keep the amplified laser with the narrow line-width and low noise, a narrow-band light filter consisting of a fiber Bragg grating (FBG) with the same Bragg wavelength as the laser and an optical circulator was used to filter the amplified spontaneous emission (ASE) noise of the out-cavity erbium-doped fiber. The designed laser structure sufficiently utilized the pump power, and a DFB fiber laser with the 32.5-mW output power, 11.5-kHz line width, and -87-dB/Hz relative intensity noise (RIN) at 300 mW of 980 nm pump power was brought out.

Dye system for dye laser applications

DOEpatents

Hammond, Peter R.

1991-01-01

A dye of the DCM family, [2-methyl-6-[2-(1,2,3,4-tetrahydro-1-methyl-6-quinolinyl)ethenyl]-4H-pyran -4-ylidene]-propanedinitrile, dissolved in 2-phenoxyethanol, is non-mutagenic, stable and efficient, particularly in a pumped continuous wave laser system.

Fluorescence lifetime imaging microscopy using near-infrared contrast agents.

PubMed

Nothdurft, R; Sarder, P; Bloch, S; Culver, J; Achilefu, S

2012-08-01

Although single-photon fluorescence lifetime imaging microscopy (FLIM) is widely used to image molecular processes using a wide range of excitation wavelengths, the captured emission of this technique is confined to the visible spectrum. Here, we explore the feasibility of utilizing near-infrared (NIR) fluorescent molecular probes with emission >700 nm for FLIM of live cells. The confocal microscope is equipped with a 785 nm laser diode, a red-enhanced photomultiplier tube, and a time-correlated single photon counting card. We demonstrate that our system reports the lifetime distributions of NIR fluorescent dyes, cypate and DTTCI, in cells. In cells labelled separately or jointly with these dyes, NIR FLIM successfully distinguishes their lifetimes, providing a method to sort different cell populations. In addition, lifetime distributions of cells co-incubated with these dyes allow estimate of the dyes' relative concentrations in complex cellular microenvironments. With the heightened interest in fluorescence lifetime-based small animal imaging using NIR fluorophores, this technique further serves as a bridge between in vitro spectroscopic characterization of new fluorophore lifetimes and in vivo tissue imaging. © 2012 The Author Journal of Microscopy © 2012 Royal Microscopical Society.

Dye Foils With Increased Durability For Passive Q-Switching In A 1064 Nm Laser.

NASA Astrophysics Data System (ADS)

Mierczyk, Z.; Kwasny, M.; Czeszko, J.

1987-10-01

The results of spectral (IR, UV-VIS, H NMR) , gel permeation chromatography and differential thermal analysis investigations of structures of dye foils consisting of bis-(4-dimethyl-amino-dithio-benzil)-nickel dye suspended in polymethylmethacrylate matrix, to be used for passive Q-switching in a 1064 nm laser, are reported. Results of experimental measurements and of numerical calculations of thermal and generating properties, and of the endurance of passive foil type Q-switches in the resona-tor of YAG:Nd3+ laser are also presented. Optimization of polymerization conditions has enabled the production of dye foils with high thermal and photochemical resistance, which give stable operation of a giant pulsed laser.

Coupled ridge waveguide distributed feedback quantum cascade laser arrays

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

Liu, Ying-Hui; Zhang, Jin-Chuan, E-mail: zhangjinchuan@semi.ac.cn; Yan, Fang-Liang

2015-04-06

A coupled ridge waveguide quantum cascade laser (QCL) array consisting of fifteen elements with parallel integration was presented. In-phase fundamental mode operation in each element is secured by both the index-guided nature of the ridge and delicate loss management by properly designed geometries of the ridges and interspaces. Single-lobe lateral far-field with a nearly diffraction limited beam pattern was obtained. By incorporating a one-dimensional buried distributed feedback grating, the in-phase-operating coupled ridge waveguide QCL design provides an efficient solution to obtaining high output power and stable single longitudinal mode emission. The simplicity of this structure and fabrication process makes thismore » approach attractive to many practical applications.« less

An All-Solid-State High Repetiton Rate Titanium:Sapphire Laser System For Resonance Ionization Laser Ion Sources

NASA Astrophysics Data System (ADS)

Mattolat, C.; Rothe, S.; Schwellnus, F.; Gottwald, T.; Raeder, S.; Wendt, K.

2009-03-01

On-line production facilities for radioactive isotopes nowadays heavily rely on resonance ionization laser ion sources due to their demonstrated unsurpassed efficiency and elemental selectivity. Powerful high repetition rate tunable pulsed dye or Ti:sapphire lasers can be used for this purpose. To counteract limitations of short pulse pump lasers, as needed for dye laser pumping, i.e. copper vapor lasers, which include high maintenance and nevertheless often only imperfect reliability, an all-solid-state Nd:YAG pumped Ti:sapphire laser system has been constructed. This could complement or even replace dye laser systems, eliminating their disadvantages but on the other hand introduce shortcomings on the side of the available wavelength range. Pros and cons of these developments will be discussed.

Performance of a nonlaser light source for photodynamic therapy

NASA Astrophysics Data System (ADS)

Whitehurst, Colin; Byrne, Karen T.; Morton, Colin; Moore, James V.

1995-03-01

Advances in short arc technology and optical filter coatings led to the design and construction of a table-top light source in 1989; the first viable and cost-effective alternative to a laser. The device can deliver over 3 W within a 30 nm band centered at any wavelength from 200 nm to 1200 nm at fluence rates of over 1 W cm-2. Its relative biological effectiveness (RBE) in vitro has been proven alongside an argon pumped dye laser and a copper vapor pumped dye laser. These in vitro tests showed an efficiency of hematoporphyrin derivative (HPD) induced cellular photoinactivation close to that of the argon/dye laser (RBE 100%), with a mean RBE for the lamp of 87 +/- 3% (p < 0.05). The lamp proved to be superior to that of the copper/dye laser system with an RBE of up to 150% at fluence rates above 50 mWcm-2. In vivo tests show that the extent and depth of tumor necrosis are comparable to that of an argon/dye laser. An in situ bioassay using tumor regrowth delay is currently underway. Early clinical trials show clearance of Bowen's disease and actinic keratosis using the same light fluences as costly PDT lasers.

Excitation/Detection Strategies for OH Planar Laser-Induced Fluorescence Measurements in the Presence of Interfering Fuel Signal and Absorption Effects

NASA Technical Reports Server (NTRS)

Heath, Christopher M.; Anderson, Robert C.; Hicks, Yolanda R.

2011-01-01

Planar laser-induced fluorescence (PLIF) excitation/detection methods have been applied to obtain spatial distributions of the hydroxyl [OH] reacting intermediary and hydrocarbon [HC] primary species in laminar and turbulent combustion reactions. In this report, broadband and narrowband excitation/filtering techniques are explored to identify an optimal experimental configuration yielding significant fluorescent signal with low absorption losses. The combustion environments analyzed include 1) a laminar non-premixed methane/air flame and 2) a turbulent, non-premixed Jet-A/air fueled flame within a lean flame tube combustor. Hydrocarbon-based fuel and OH were excited via the R1 (1), R1(10) and R2(7) transitions of the A(sup 2)Epsilon(+) X(sup 2)pi(1,0) band using a broadband Nd:YAG pumped optical parametric oscillator (OPO) and narrowband Nd:YAG/dye laser with ultraviolet frequency extension (UVX) package. Variables tested for influence on fluorescent signal and absorption characteristics were excitation line, laser energy, exciting linewidth, combustion reactants, and test flow conditions. Results are intended to guide the transition from a dye/UVX laser to an OPO system for performing advanced diagnostics of low-emission combustion concepts.

Toward continuous-wave operation of organic semiconductor lasers

PubMed Central

Sandanayaka, Atula S. D.; Matsushima, Toshinori; Bencheikh, Fatima; Yoshida, Kou; Inoue, Munetomo; Fujihara, Takashi; Goushi, Kenichi; Ribierre, Jean-Charles; Adachi, Chihaya

2017-01-01

The demonstration of continuous-wave lasing from organic semiconductor films is highly desirable for practical applications in the areas of spectroscopy, data communication, and sensing, but it still remains a challenging objective. We report low-threshold surface-emitting organic distributed feedback lasers operating in the quasi–continuous-wave regime at 80 MHz as well as under long-pulse photoexcitation of 30 ms. This outstanding performance was achieved using an organic semiconductor thin film with high optical gain, high photoluminescence quantum yield, and no triplet absorption losses at the lasing wavelength combined with a mixed-order distributed feedback grating to achieve a low lasing threshold. A simple encapsulation technique greatly reduced the laser-induced thermal degradation and suppressed the ablation of the gain medium otherwise taking place under intense continuous-wave photoexcitation. Overall, this study provides evidence that the development of a continuous-wave organic semiconductor laser technology is possible via the engineering of the gain medium and the device architecture. PMID:28508042

Toward continuous-wave operation of organic semiconductor lasers.

PubMed

Sandanayaka, Atula S D; Matsushima, Toshinori; Bencheikh, Fatima; Yoshida, Kou; Inoue, Munetomo; Fujihara, Takashi; Goushi, Kenichi; Ribierre, Jean-Charles; Adachi, Chihaya

2017-04-01

The demonstration of continuous-wave lasing from organic semiconductor films is highly desirable for practical applications in the areas of spectroscopy, data communication, and sensing, but it still remains a challenging objective. We report low-threshold surface-emitting organic distributed feedback lasers operating in the quasi-continuous-wave regime at 80 MHz as well as under long-pulse photoexcitation of 30 ms. This outstanding performance was achieved using an organic semiconductor thin film with high optical gain, high photoluminescence quantum yield, and no triplet absorption losses at the lasing wavelength combined with a mixed-order distributed feedback grating to achieve a low lasing threshold. A simple encapsulation technique greatly reduced the laser-induced thermal degradation and suppressed the ablation of the gain medium otherwise taking place under intense continuous-wave photoexcitation. Overall, this study provides evidence that the development of a continuous-wave organic semiconductor laser technology is possible via the engineering of the gain medium and the device architecture.

Turbulence hierarchy in a random fibre laser

PubMed Central

González, Iván R. Roa; Lima, Bismarck C.; Pincheira, Pablo I. R.; Brum, Arthur A.; Macêdo, Antônio M. S.; Vasconcelos, Giovani L.; de S. Menezes, Leonardo; Raposo, Ernesto P.; Gomes, Anderson S. L.; Kashyap, Raman

2017-01-01

Turbulence is a challenging feature common to a wide range of complex phenomena. Random fibre lasers are a special class of lasers in which the feedback arises from multiple scattering in a one-dimensional disordered cavity-less medium. Here we report on statistical signatures of turbulence in the distribution of intensity fluctuations in a continuous-wave-pumped erbium-based random fibre laser, with random Bragg grating scatterers. The distribution of intensity fluctuations in an extensive data set exhibits three qualitatively distinct behaviours: a Gaussian regime below threshold, a mixture of two distributions with exponentially decaying tails near the threshold and a mixture of distributions with stretched-exponential tails above threshold. All distributions are well described by a hierarchical stochastic model that incorporates Kolmogorov’s theory of turbulence, which includes energy cascade and the intermittence phenomenon. Our findings have implications for explaining the remarkably challenging turbulent behaviour in photonics, using a random fibre laser as the experimental platform. PMID:28561064

Skin closure with dye-enhanced laser welding and fibrinogen.

PubMed

Wider, T M; Libutti, S K; Greenwald, D P; Oz, M C; Yager, J S; Treat, M R; Hugo, N E

1991-12-01

The topical application of wavelength-specific dye and fibrinogen has been used to enhance laser closure of vascular anastomoses. We compared the closure of skin incisions by two different dye-enhanced, fibrinogen-based laser welding systems [argon laser (power density 4.78 W/cm2) with fluorescein isothiocyanate dye (n = 32) and diode laser (power density 9.55 W/cm2) with indocyanine green dye (n = 32)] with closure by interrupted 5-0 nylon suture (n = 64) and examined tensile strength, hydroxyproline production, histology, and cosmesis. Two 3-cm full-thickness incisions were made on the shaved backs of 64 rats. One incision was closed with suture, whereas the other, after treatment with the appropriate dye, was welded with either argon- or diode-lasered fibrinogen. At postoperative days 5, 10, 15, and 28, the closure sites were harvested and sectioned for analysis. Initially, wounds closed with argon-lasered fibrinogen showed less inflammatory response, greater collagen production (34.61 +/- 0.74 mg/gm), and greater mean peak stress at rupture (64.85 lbs/in2) than those closed with suture (16.42 +/- 3.20 mg/gm, 26.68 lbs/in2) (p less than 0.05). By 15 days, both argon and diode laser closures are superior in strength and collagen production to suture closure (p less than 0.05). At 28 days, diode laser closures (1315.60 lbs/in2) are stronger than suture closures (998.09 lbs/in2), whereas both are stronger than argon laser closures (813.16 lbs/in2) (p less than 0.05). Cosmetically, argon-welded wounds consistently appeared finer and lacked cross-hatched suture scars.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro photoacoustic measurement of hemoglobin oxygen saturation using a single pulsed broadband supercontinuum laser source.

PubMed

Lee, Changho; Jeon, Mansik; Jeon, Min Yong; Kim, Jeehyun; Kim, Chulhong

2014-06-20

We have utilized a single pulsed broadband supercontinuum laser source to photoacoustically sense total hemoglobin concentration (HbT) and oxygen saturation of hemoglobin (SO2) in bloods in vitro. Unlike existing expensive and bulky laser systems typically used for functional photoacoustic imaging (PAI), our laser system is relatively cost-effective and compact. Instead of using two single wavelengths, two wavelength bands were applied to distinguish the concentrations of two different chromophores in the mixture. In addition, we have successfully extracted the total dye concentration and the ratio of the red dye concentration to the total dye concentration in mixed red and blue dye solutions in phantoms. The results indicate that PAI with a cheap and compact fiber based laser source can potentially provide HbT and SO2 in live animals in vivo.

Distributed feedback InGaN/GaN laser diodes

NASA Astrophysics Data System (ADS)

Slight, Thomas J.; Watson, Scott; Yadav, Amit; Grzanka, Szymon; Stanczyk, Szymon; Docherty, Kevin E.; Rafailov, Edik; Perlin, Piotr; Najda, Steve; Leszczyński, Mike; Kelly, Anthony E.

2018-02-01

We have realised InGaN/GaN distributed feedback laser diodes emitting at a single wavelength in the 42X nm wavelength range. Laser diodes based on Gallium Nitride (GaN) are useful devices in a wide range of applications including atomic spectroscopy, data storage and optical communications. To fully exploit some of these application areas there is a need for a GaN laser diode with high spectral purity, e.g. in atomic clocks, where a narrow line width blue laser source can be used to target the atomic cooling transition. Previously, GaN DFB lasers have been realised using buried or surface gratings. Buried gratings require complex overgrowth steps which can introduce epi-defects. Surface gratings designs, can compromise the quality of the p-type contact due to dry etch damage and are prone to increased optical losses in the grating regions. In our approach the grating is etched into the sidewall of the ridge. Advantages include a simpler fabrication route and design freedom over the grating coupling strength.Our intended application for these devices is cooling of the Sr+ ion and for this objective the laser characteristics of SMSR, linewidth, and power are critical. We investigate how these characteristics are affected by adjusting laser design parameters such as grating coupling coefficient and cavity length.

Optical frequency stabilization in infrared region using improved dual feed-back loop

NASA Astrophysics Data System (ADS)

Ružička, B.; Číp, O.; Lazar, J.

2007-03-01

Modern technologies such as DWDM (Dense Wavelength Division Multiplex) need precise stability of laser frequencies. According to this fact, requirements of new etalons of optical frequencies in the telecommunication band is rapidly growing. Lasers working in near infrared telecommunication band (1500-1600 nm) can be stabilized to 12C IIH II or 13C IIH II (acetylene) gas absorption lines. The acetylene gas absorption has been widely studied and accepted by international bodies of standardization as a primary wavelength reference in the near infrared band around 1550 nm. Our aim was to design and develop a compact fibre optics laser system generating coherent light in near-IR band with high frequency stability (at least 1.10 -8). This system should become a base for realization of a primary frequency standard for optical communications in the Czech Republic. Such an etalon will be needed for calibration of wavelengthmeters and spectral analysers for DWDM communication systems. We are co-operating with CMI (Czech Metrology Institute) on this project. We present stabilized laser system based on a single frequency DFB (Distributed Feedback) laser diode with a narrow spectral profile. The laser is pre-stabilized by means of the FM-spectroscopy on a passive resonator. Thanks to a fast feed-back loop we are able to improve spectral characteristics of the laser. The laser frequency is locked by a relatively slow second feed-back loop on an absorption line of acetylene vapour which is sealed in a cell under the optimised pressure.

Numerical investigation of vessel heating using a copper vapor laser and a pulsed dye laser in treating vascular skin lesions

NASA Astrophysics Data System (ADS)

Pushkareva, A. E.; Ponomarev, I. V.; Isaev, A. A.; Klyuchareva, S. V.

2018-02-01

A computer simulation technique was employed to study the selective heating of a tissue vessel using emission from a pulsed copper vapor laser and a pulsed dye laser. The depth and size of vessels that could be selectively and safely removed were determined for the lasers under examination.

Fiber optics interface for a dye laser oscillator and method

DOEpatents

Johnson, Steve A.; Seppala, Lynn G.

1986-01-01

A dye laser oscillator in which one light beam is used to pump a continuous tream of dye within a cooperating dye chamber for producing a second, different beam is generally disclosed herein along with a specific arrangement including an optical fiber and a fiber optics interface for directing the pumping beam into the dye chamber. The specific fiber optics interface illustrated includes three cooperating lenses which together image one particular dimension of the pumping beam into the dye chamber from the output end of the optical fiber in order to insure that the dye chamber is properly illuminated by the pumping beam.

Fiber optics interface for a dye laser oscillator and method

DOEpatents

Johnson, S.A.; Seppala, L.G.

1984-06-13

A dye laser oscillator in which one light beam is used to pump a continuous stream of dye within a cooperating dye chamber for producing a second, different beam is generally disclosed herein along with a specific arrangement including an optical fiber and a fiber optics interface for directing the pumping beam into the dye chamber. The specific fiber optics interface illustrated includes three cooperating lenses which together image one particular dimension of the pumping beam into the dye chamber from the output end of the optical fiber in order to insure that the dye chamber is properly illuminated by the pumping beam.

CW Performance of an InGaAs-GaAs-AlGaAs Laterally-Coupled Distributed Feedback (LC-DFB) Ridge Laser Diode

NASA Technical Reports Server (NTRS)

Martin, R. D.; Forouhar, S.; Keo, S.; Lang, R. J.; Hunsperger, R. G.; Tiberio, R. C.; Chapman, P. F.

1995-01-01

Single-mode distributed feedback (DFB) laser diodes typically require a two-step epitaxial growth or use of a corrugated substrate. We demonstrate InGaAs-GaAs-AlGaAs DFB lasers fabricated from a single epitaxial growth using lateral evanescent coupling of the optical field to a surface grating etehed along the sides of the ridge. A CW threshold current of 25 mA and external quantum efficiency of 0.48 mW/mA per facet were measured for a 1 mm cavity length device with anti-reflection coated facets. Single-mode output powers as high as 11 mW per facet at 935 nm wavelength were attained. A coupling coefficient of at least 5.8/cm was calculated from the subthreshold spectrum taking into account the 2% residual facet reflectivity.

Time-Delayed Two-Step Selective Laser Photodamage of Dye-Biomolecule Complexes

NASA Astrophysics Data System (ADS)

Andreoni, A.; Cubeddu, R.; de Silvestri, S.; Laporta, P.; Svelto, O.

1980-08-01

A scheme is proposed for laser-selective photodamage of biological molecules, based on time-delayed two-step photoionization of a dye molecule bound to the biomolecule. The validity of the scheme is experimentally demonstrated in the case of the dye Proflavine, bound to synthetic polynucleotides.

Intensity calibration of a laser scanning confocal microscope based on concentrated dyes.

PubMed

Model, Michael A; Blank, James L

2006-10-01

To find water-soluble fluorescent dyes with absorption in various regions of the spectrum and investigate their utility as standards for laser scanning confocal microscopy. Several dyes were found to have characteristics required for fluorescence microscopy standards. The intensity of biological fluorescent specimens was measured against the emission of concentrated dyes. Results using different optics and different microscopes were compared. Slides based on concentrated dyes can be prepared in a highly reproducible manner and are stable under laser scanning. Normalized fluorescence of biological specimens remains consistent with different objective lenses and is tolerant to some mismatch in optical filters or imperfect pinhole alignment. Careful choice of scanning parameters is necessary to ensure linearity of intensity measurements. Concentrated dyes provide a robust and inexpensive intensity standard that can be used in basic research or clinical studies.

Comparison of pulsed dye laser versus combined pulsed dye laser and Nd:YAG laser in the treatment of inflammatory acne vulgaris.

PubMed

Salah El Din, Manal Mohamed; Samy, Nevien Ahmed; Salem, Amira Eid

2017-06-01

Both pulsed dye laser and combined 585/1064-nm (sequential dual-wavelength PDL and Nd:YAG) laser improves inflammatory skin disorders including acne vulgaris. To compare the efficacy of 585-nm pulsed dye laser versus sequential dual-wavelength PDL and Nd:YAG in treatment of acne vulgaris. Thirty patients with acne vulgaris were treated by PDL alone on half of the face while contra lateral half was treated by combined 585/1064 nm laser. The study showed that inflammatory acne lesions count was significantly reduced by 82.5% (p 0.0001) on PDL sides and by 83.5% (p 0.00001) on combined 585/1064-nm side after 8 weeks, while reduction of non-inflammatory acne lesions was observed at 8 weeks by 58.4% and 71.5% respectively. However, difference between the two modalities was not statistically significant. PDL and combined PDL/Nd:YAG laser treatment were found to be an effective, safe and well-tolerated treatment option for inflammatory and non-inflammatory acne vulgaris.

Gold nanoparticle-based plasmonic random fiber laser

NASA Astrophysics Data System (ADS)

Hu, Zhijia; Liang, Yunyun; Xie, Kang; Gao, Pengfei; Zhang, Douguo; Jiang, Haiming; Shi, Fan; Yin, Leicheng; Gao, Jiangang; Ming, Hai; Zhang, Qijin

2015-03-01

We have reported the realization of a plasmonic random fiber laser based on the localized surface plasmonic resonance of gold nanoparticles (NPs) in the liquid core optical fiber. The liquid core material contains a dispersive solution of gold NPs and laser dye pyrromethene 597 in toluene. It was experimentally proved that the fluorescence quenching of the dye is restrained in the optical fiber, which is considered one of the main sources of loss in the traditional laser system. Meanwhile, the random lasing can be more easily obtained in the random laser system with more overlap between the plasmonic resonance of the gold NPs and the photoluminescence spectrum of the dye molecules.

Direct Analysis of Textile Fabrics and Dyes Using IR Matrix-Assisted Laser Desorption Electrospray Ionization (MALDESI) Mass Spectrometry

PubMed Central

Cochran, Kristin H.; Barry, Jeremy A.; Muddiman, David C.; Hinks, David

2012-01-01

The forensic analysis of textile fibers uses a variety of techniques from microscopy to spectroscopy. One such technique that is often used to identify the dye(s) within the fiber is mass spectrometry (MS). In the traditional MS method, the dye must be extracted from the fabric and the dye components are separated by chromatography prior to mass spectrometric analysis. Direct analysis of the dye from the fabric allows the omission of the lengthy sample preparation involved in extraction, thereby significantly reducing the overall analysis time. Herein, a direct analysis of dyed textile fabric was performed using the infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) source for MS. In MALDESI, an IR laser with wavelength tuned to 2.94 μm is used to desorb the dye from the fabric sample with the aid of water as the matrix. The desorbed dye molecules are then post-ionized by electrospray ionization (ESI). A variety of dye classes were analyzed from various fabrics with little to no sample preparation allowing for the identification of the dye mass and in some cases the fiber polymer. Those dyes that were not detected using MALDESI were also not observed by direct infusion ESI of the dye standard. PMID:23237031

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Study of relaxation times of polymethine dyes used for passive mode locking of solid-state lasers emitting between 750 and 850 nm

NASA Astrophysics Data System (ADS)

Grigonis, R.; Derevyanko, Nadezhda A.; Ishchenko, Aleksandr A.; Sirutkaitis, V. A.

2001-11-01

The relaxation times τ of the bleached states of polymethine dyes absorbing light in the 750 — 850-nm are determined by the direct pump — probe method. The effect of the dye structure and the solvent type on the relaxation time is discussed. The role of different intra- and intermolecular interactions in the relaxation of excited electronic states of the dyes is analysed. Polymethine dyes are found (with τ=11 — 75 ps) that are promising for passive mode locking in Cr3+:LiCaAlF6, Cr3+:KZnF3, and Cr3+:LiSrAlF6 crystal lasers.

Terahertz plasmonic laser radiating in an ultra-narrow beam

DOE PAGES

Wu, Chongzhao; Khanal, Sudeep; Reno, John L.; ...

2016-07-07

Plasmonic lasers (spasers) generate coherent surface plasmon polaritons (SPPs) and could be realized at subwavelength dimensions in metallic cavities for applications in nanoscale optics. Plasmonic cavities are also utilized for terahertz quantum-cascade lasers (QCLs), which are the brightest available solid-state sources of terahertz radiation. A long standing challenge for spasers that are utilized as nanoscale sources of radiation, is their poor coupling to the far-field radiation. Unlike conventional lasers that could produce directional beams, spasers have highly divergent radiation patterns due to their subwavelength apertures. Here, we theoretically and experimentally demonstrate a new technique for implementing distributed feedback (DFB) thatmore » is distinct from any other previously utilized DFB schemes for semiconductor lasers. The so-termed antenna-feedback scheme leads to single-mode operation in plasmonic lasers, couples the resonant SPP mode to a highly directional far-field radiation pattern, and integrates hybrid SPPs in surrounding medium into the operation of the DFB lasers. Experimentally, the antenna-feedback method, which does not require the phase matching to a well-defined effective index, is implemented for terahertz QCLs, and single-mode terahertz QCLs with a beam divergence as small as 4°×4° are demonstrated, which is the narrowest beam reported for any terahertz QCL to date. Moreover, in contrast to a negligible radiative field in conventional photonic band-edge lasers, in which the periodicity follows the integer multiple of half-wavelengths inside the active medium, antenna-feedback breaks this integer limit for the first time and enhances the radiative field of the lasing mode. Terahertz lasers with narrow-beam emission will find applications for integrated as well as standoff terahertz spectroscopy and sensing. Furthermore, the antenna-feedback scheme is generally applicable to any plasmonic laser with a Fabry–Perot cavity irrespective of its operating wavelength and could bring plasmonic lasers closer to practical applications.« less

Suppression of thermal frequency noise in erbium-doped fiber random lasers.

PubMed

Saxena, Bhavaye; Bao, Xiaoyi; Chen, Liang

2014-02-15

Frequency and intensity noise are characterized for erbium-doped fiber (EDF) random lasers based on Rayleigh distributed feedback mechanism. We propose a theoretical model for the frequency noise of such random lasers using the property of random phase modulations from multiple scattering points in ultralong fibers. We find that the Rayleigh feedback suppresses the noise at higher frequencies by introducing a Lorentzian envelope over the thermal frequency noise of a long fiber cavity. The theoretical model and measured frequency noise agree quantitatively with two fitting parameters. The random laser exhibits a noise level of 6  Hz²/Hz at 2 kHz, which is lower than what is found in conventional narrow-linewidth EDF fiber lasers and nonplanar ring laser oscillators (NPROs) by a factor of 166 and 2, respectively. The frequency noise has a minimum value for an optimum length of the Rayleigh scattering fiber.

Optical feedback cavity-enhanced absorption spectroscopy with a 3.24 μm interband cascade laser

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

Manfred, K. M.; Ritchie, G. A. D.; Lang, N.

2015-06-01

The development of interband cascade lasers (ICLs) has made the strong C-H transitions in the 3 μm spectral region increasingly accessible. We present the demonstration of a single mode distributed feedback ICL coupled to a V-shaped optical cavity in an optical feedback cavity-enhanced absorption spectroscopy (OF-CEAS) experiment. We achieved a minimum detectable absorption coefficient, α{sub min}, of (7.1±0.2)×10{sup −8} cm{sup −1} for a spectrum of CH{sub 4} at 3.24 μm with a two second acquisition time (100 scans averaged). This corresponds to a detection limit of 3 ppb CH{sub 4} at atmospheric pressure, which is comparable to previously reported OF-CEAS instruments with diodemore » lasers or quantum cascade lasers. The ability to frequency lock an ICL source in the important 3 μm region to an optical cavity holds great promise for future spectroscopic applications.« less

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.

Single-mode SOA-based 1kHz-linewidth dual-wavelength random fiber laser.

PubMed

Xu, Yanping; Zhang, Liang; Chen, Liang; Bao, Xiaoyi

2017-07-10

Narrow-linewidth multi-wavelength fiber lasers are of significant interests for fiber-optic sensors, spectroscopy, optical communications, and microwave generation. A novel narrow-linewidth dual-wavelength random fiber laser with single-mode operation, based on the semiconductor optical amplifier (SOA) gain, is achieved in this work for the first time, to the best of our knowledge. A simplified theoretical model is established to characterize such kind of random fiber laser. The inhomogeneous gain in SOA mitigates the mode competition significantly and alleviates the laser instability, which are frequently encountered in multi-wavelength fiber lasers with Erbium-doped fiber gain. The enhanced random distributed feedback from a 5km non-uniform fiber provides coherent feedback, acting as mode selection element to ensure single-mode operation with narrow linewidth of ~1kHz. The laser noises are also comprehensively investigated and studied, showing the improvements of the proposed random fiber laser with suppressed intensity and frequency noises.

Hemangiomas

MedlinePlus

... grow. The flash-lamp pulse dye, pump dye, diode, and sclero-laser are the primary lasers used ... go through several trials of dosing-tapering. The current protocol is to put them on the initial ...

Plasmonic distributed feedback lasers at telecommunications wavelengths.

PubMed

Marell, Milan J H; Smalbrugge, Barry; Geluk, Erik Jan; van Veldhoven, Peter J; Barcones, Beatrix; Koopmans, Bert; Nötzel, Richard; Smit, Meint K; Hill, Martin T

2011-08-01

We investigate electrically pumped, distributed feedback (DFB) lasers, based on gap-plasmon mode metallic waveguides. The waveguides have nano-scale widths below the diffraction limit and incorporate vertical groove Bragg gratings. These metallic Bragg gratings provide a broad bandwidth stop band (~500 nm) with grating coupling coefficients of over 5000/cm. A strong suppression of spontaneous emission occurs in these Bragg grating cavities, over the stop band frequencies. This strong suppression manifests itself in our experimental results as a near absence of spontaneous emission and significantly reduced lasing thresholds when compared to similar length Fabry-Pérot waveguide cavities. Furthermore, the reduced threshold pumping requirements permits us to show strong line narrowing and super linear light current curves for these plasmon mode devices even at room temperature.

Quartz-enhanced photoacoustic spectroscopy sensor for ethylene detection with a 3.32 μm distributed feedback laser diode

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

Nguyen Ba, T.; Triki, M.; Vicet, A., E-mail: a.vicet@univ-montp2.fr

2015-02-15

An antimonide distributed feedback quantum wells diode laser operating at 3.32 μm at near room temperature in the continuous wave regime has been used to perform ethylene detection based on quartz enhanced photoacoustic spectroscopy. An absorption line centered at 3007.52 cm{sup −1} was investigated and a normalized noise equivalent absorption coefficient (1σ) of 3.09 10{sup −7} cm{sup −1} W Hz{sup −1/2} was obtained. The linearity and the stability of the detection have been evaluated. Biological samples’ respiration has been measured to validate the feasibility of the detection setup in an agronomic environment, especially on ripening apples.

Interface module for transverse energy input to dye laser modules

DOEpatents

English, R.E. Jr.; Johnson, S.A.

1994-10-11

An interface module for transverse energy input to dye laser modules is provided particularly for the purpose of delivering enhancing transverse energy beams in the form of illumination bar to the lasing zone of a dye laser device, in particular to a dye laser amplifier. The preferred interface module includes an optical fiber array having a plurality of optical fibers arrayed in a co-planar fashion with their distal ends receiving coherent laser energy from an enhancing laser source, and their proximal ends delivered into a relay structure. The proximal ends of the optical fibers are arrayed so as to be coplanar and to be aimed generally at a common point. The transverse energy beam array delivered from the optical fiber array is acted upon by an optical element array to produce an illumination bar which has a cross section in the form of a elongated rectangle at the position of the lasing window. The illumination bar is selected to have substantially uniform intensity throughout. 5 figs.

Laser desorption/ionization mass spectrometry of dye-sensitized solar cells: identification of the dye-electrolyte interaction.

PubMed

Ellis, Hanna; Leandri, Valentina; Hagfeldt, Anders; Boschloo, Gerrit; Bergquist, Jonas; Shevchenko, Denys

2015-05-01

Dye-sensitized solar cells (DSCs) have great potential to provide sustainable electricity from sunlight. The photoanode in DSCs consists of a dye-sensitized metal oxide film deposited on a conductive substrate. This configuration makes the photoanode a perfect sample for laser desorption/ionization mass spectrometry (LDI-MS). We applied LDI-MS for the study of molecular interactions between a dye and electrolyte on the surface of a TiO2 photoanode. We found that a dye containing polyoxyethylene groups forms complexes with alkali metal cations from the electrolyte, while a dye substituted with alkoxy groups does not. Guanidinium ion forms adducts with neither of the two dyes. Copyright © 2015 John Wiley & Sons, Ltd.

Laterally coupled distributed feedback lasers emitting at 2 μm with quantum dash active region and high-duty-cycle etched semiconductor gratings

NASA Astrophysics Data System (ADS)

Papatryfonos, Konstantinos; Saladukha, Dzianis; Merghem, Kamel; Joshi, Siddharth; Lelarge, Francois; Bouchoule, Sophie; Kazazis, Dimitrios; Guilet, Stephane; Le Gratiet, Luc; Ochalski, Tomasz J.; Huyet, Guillaume; Martinez, Anthony; Ramdane, Abderrahim

2017-02-01

Single-mode diode lasers on an InP(001) substrate have been developed using InAs/In0.53Ga0.47As quantum dash (Qdash) active regions and etched lateral Bragg gratings. The lasers have been designed to operate at wavelengths near 2 μm and exhibit a threshold current of 65 mA for a 600 μm long cavity, and a room temperature continuous wave output power per facet >5 mW. Using our novel growth approach based on the low ternary In0.53Ga0.47As barriers, we also demonstrate ridge-waveguide lasers emitting up to 2.1 μm and underline the possibilities for further pushing the emission wavelength out towards longer wavelengths with this material system. By introducing experimentally the concept of high-duty-cycle lateral Bragg gratings, a side mode suppression ratio of >37 dB has been achieved, owing to an appreciably increased grating coupling coefficient of κ ˜ 40 cm-1. These laterally coupled distributed feedback (LC-DFB) lasers combine the advantage of high and well-controlled coupling coefficients achieved in conventional DFB lasers, with the regrowth-free fabrication process of lateral gratings, and exhibit substantially lower optical losses compared to the conventional metal-based LC-DFB lasers.

Development of high-power dye laser chain

NASA Astrophysics Data System (ADS)

Konagai, Chikara; Kimura, Hironobu; Fukasawa, Teruichiro; Seki, Eiji; Abe, Motohisa; Mori, Hideo

2000-01-01

Copper vapor laser (CVL) pumped dye laser (DL) system, both in a master oscillator power amplifier (MOPA) configuration, has been developed for Atomic Vapor Isotope Separation program in Japan. Dye laser output power of about 500 W has been proved in long-term operations over 200 hours. High power fiber optic delivery system is utilized in order to efficiently transport kilowatt level CVL beams to the DL MOPA. Single model CVL pumped DL oscillator has been developed and worked for 200 hours within +/- 0.1 pm wavelength stability. Phase modulator for spreading spectrum to the linewidth of hyperfine structure has been developed and demonstrated.

Atraumatic laser treatment for laryngeal papillomatosis

NASA Astrophysics Data System (ADS)

McMillan, Kathleen; Pankratov, Michail M.; Wang, Zhi; Bottrill, Ian; Rebeiz, Elie E.; Shapshay, Stanley M.

1994-09-01

Ten to fifteen thousand new cases of recurrent respiratory papillomatosis (RRP) are diagnosed each year in the United States. RRP is caused by the human papillomavirus (HPV) and is characterized by recurrent, non-malignant, proliferative lesions of the larynx. Patients with RRP undergo numerous microsurgical procedures to remove laryngeal papilloma threatening airway patency and interfering with phonation. The standard surgical technique involves CO2 laser vaporization of laryngeal epithelium affected by the lesions, and requires general anesthesia. The pulsed dye laser operating at 585 nm has previously been demonstrated to be effective in clearing HPV lesions of the skin (verrucae). For treatment of RRP, the fiber- compatible pulsed dye laser radiation may be delivered under local anesthesia using a flexible intranasal laryngoscope. Potential advantages of the pulsed dye laser treatment over CO2 laser surgery include (1) reduced morbidity, especially a lower risk of laryngeal scarring; (2) lower cost; (3) reduced technical difficulty; and (4) reduced risk of viral dissemination or transmission. In vivo studies are underway to determine the effect of pulsed dye laser radiation on normal canine laryngeal tissue.

QUANTITATIVE DETECTION OF ENVIRONMENTALLY IMPORTANT DYES USING DIODE LASER/FIBER-OPTIC RAMAN

EPA Science Inventory

A compact diode laser/fiber-optic Raman spectrometer is used for quantitative detection of environmentally important dyes. This system is based on diode laser excitation at 782 mm, fiber optic probe technology, an imaging spectrometer, and state-of-the-art scientific CCD camera. ...

Fractional Resurfacing Aiding Photodynamic Therapy of a Recalcitrant Plantar Verruca

PubMed Central

Pope, Amy

2008-01-01

Fractional resurfacing has become a very popular laser modality in recent years, and photodynamic therapy (PDT) has become a mainstay of many practices treating a wide array of clinical entities. In this case report, we describe a recalcitrant verrucous lesion on the foot that is unresponsive to cryotherapy, pulsed dye laser, and pulsed dye laser with PDT. The lesion did, however, respond very well to the use of a fractional laser to enhance the penetration of the PDT photosensitizer and then responded to pulsed dye laser with PDT. Fractional resurfacing prior to PDT may be a novel dermatologic treatment approach, making PDT an even better treatment option in the future. PMID:21103307

Emission lifetimes of a fluorescent dye under shock compression

DOE PAGES

Liu, Wei-long; Bassett, Will P.; Christensen, James M.; ...

2015-10-15

The emission lifetimes of rhodamine 6G (R6G), were measured under shock compression to 9.1 GPa, with the dual intent of better understanding molecular photophysics in extreme environments and assessing the usefulness of fluorescence lifetime microscopy to measure spatially-dependent pressure distributions in shocked microstructured media. R6G was studied as free dye dissolved in poly-methyl methacrylate (PMMA), or dye encapsulated in silica microparticles suspended in PMMA. Thin layers of these materials in impedance-matched geometries were subjected to planar single-stage shocks created by laser-driven flyer plates. A synchronized femtosecond laser excited the dye at selected times relative to flyer plate arrival and themore » emission lifetimes were measured with a streak camera. Lifetimes decreased when shocks arrived. The lifetime decrease was attributed to a shock-induced enhancement of R6G nonradiative relaxation. At least part of the relaxation involved shock-enhanced intersystem crossing. For free dye in PMMA, the lifetime decrease during the shock was shown to be a linear function of shock pressure from 0-9 GPa, with a slope of -0.22 ns·GPa -1. Furthermore, the linear relationship makes it simple to convert lifetimes into pressures. Lifetime measurements in shocked microenvironments may be better than emission intensity measurements, since lifetimes are sensitive to the surrounding environment, but insensitive to intensity variations associated with the motion and optical properties of a dynamically changing structure.« less

Measuring the Dispersion Curve of a PMMA-Fibre Optic Cable Using a Dye Laser

ERIC Educational Resources Information Center

Zorba, Serkan; Farah, Constantine; Pant, Ravi

2010-01-01

An advanced undergraduate laboratory experiment is outlined which uses a dye laser to map out the chromatic dispersion curve of a polymethyl methacrylate (PMMA) optical fibre. Seven different wavelengths across the visible spectrum are employed using five different dyes. The light pulse is split into two pulses, one to a nearby photodetector and…

Ultrafast Laser Techniques

DTIC Science & Technology

1991-06-05

2 Prism Dye Amplifiers .................................................................................. 2 Axicon...carried out under this project. PRISM DYE AMPLIFIERS A first effort was devoted to setting up an amplifier system for the output of a short pulse dye laser...For amplification up to pulse energies of approximately 500 p.J/pulse we chose three stages of prism amplifier cells, with diameters of 1 m, 3 mm

In vitro study of bactericidal effect of low-level laser therapy in the presence of photosensitizer on cariogenic bacteria

NASA Astrophysics Data System (ADS)

Zanin, Iriana C. J.; Brugnera, Aldo, Jr.; Goncalves, Reginaldo B.

2002-06-01

The aim of this in vitro study was to determine whether low-level laser light in the presence of a photosensitizer could kill Streptococcus mutans and Streptococcus sobrinus. Suspensions of these microorganisms were exposed to a gallium-aluminium-arsenide laser light (660 nm) in the presence of photosensitizer toluidine blue O. Viable microorganisms were counted on brain heart agar plates after incubation at 37 degree(s)C in partial atmosphere of 10% CO2 for 48 hours. Their exposure to the laser light in the absence of the dye or the dye in the absence of the laser light presented no significant effect on the viability of the microorganisms. However, a decrease in the number of viable microorganisms was only verified when they were exposed to both the laser light and the dye at the same time. Their total growth inhibition was achieved with a dye concentration of 100 mg/mL and a light energy density of 28.8 J/cm2, after being exposed to laser light for 900 seconds. In conclusion, these results imply that these bacteria can be killed by low-power laser light in the presence of the photosensitizer.

Field-programmable gate array-controlled sweep velocity-locked laser pulse generator

NASA Astrophysics Data System (ADS)

Chen, Zhen; Hefferman, Gerald; Wei, Tao

2017-05-01

A field-programmable gate array (FPGA)-controlled sweep velocity-locked laser pulse generator (SV-LLPG) design based on an all-digital phase-locked loop (ADPLL) is proposed. A distributed feedback laser with modulated injection current was used as a swept-frequency laser source. An open-loop predistortion modulation waveform was calibrated using a feedback iteration method to initially improve frequency sweep linearity. An ADPLL control system was then implemented using an FPGA to lock the output of a Mach-Zehnder interferometer that was directly proportional to laser sweep velocity to an on-board system clock. Using this system, linearly chirped laser pulses with a sweep bandwidth of 111.16 GHz were demonstrated. Further testing evaluating the sensing utility of the system was conducted. In this test, the SV-LLPG served as the swept laser source of an optical frequency-domain reflectometry system used to interrogate a subterahertz range fiber structure (sub-THz-FS) array. A static strain test was then conducted and linear sensor results were observed.

Continuous wave dye-laser technique for simultaneous, spatially resolved measurements of temperature, pressure, and velocity of NO in an underexpanded free jet

NASA Technical Reports Server (NTRS)

Di Rosa, Michael D.; Chang, Albert Y.; Hanson, Ronald K.

1993-01-01

Gas dynamic quantities within an underexpanded nitrogen free jet, seeded with 0.5 percent NO, were measured nonintrusively by using an intracavity-doubled, rapid-tuning, CW ring dye laser. The UV beam passed obliquely through the jet axis, and its frequency repetitively scanned across adjacent rotational lines in the NO gamma band near 225 nm at a rate of 4 kHz. Spatially resolved excitation scans were obtained by monitoring the induced broadband fluoresence. Modeling the Doppler-shifted excitation scans with Voigt profiles permitted simultaneous determinations of NO velocity, rotational temperature, and pressure. Zero Doppler shift was referenced to an absorption trace obtained across a static cell and recorded concurrently with the excitation scan. Typically, the measured and predicted axial distributions agreed within 10 percent. At high Mach numbers there was evidence of rotational freezing of NO.

Pulsed dye laser application in ablation of vascular ectasias of the larynx: a preliminary animal study

NASA Astrophysics Data System (ADS)

Woo, Peak; Wang, Zhi; Perrault, Donald F., Jr.; McMillan, Kathleen; Pankratov, Michail M.

1995-05-01

Vascular ectasias (dilatation) and vascular lesions of the larynx are difficult to treat with exciting modalities. Varix (enlarged vessel) of the vocal folds, vocal fold hemorrhage, vascular polyp, hemangioma, intubation or contact granuloma are common problems which disturb voice. Current applications of CO2 laser and cautery often damage the delicate vocal fold cover. The 585 nm dermatologic pulsed dye laser may be an ideal substitute. Two adult canines were examined under anesthesia via microlaryngoscopy technique. Pulsed dye laser (SPTL-1a, Candela Laser Corp., Wayland, MA) energy was delivered via the micromanipulator with the 3.1-mm spot size in single pulses of 6, 8, and 10 Joules/cm2 and applied to the vessels of the vocal folds, epiglottis, and arytenoid cartilage. Endoscopic examination was carried out immediately after the treatment and at 4 weeks postoperatively. The animals were sacrificed at 3 weeks, larynges excised, and whole organ laryngeal section were prepared for histology. Pulsed dye laser thrombosed vessels of the vocal fold using 6 or 8 Joules/cm2. Vascular break and leakage occurred at 10 Joules/cm2. Follow up examination showed excellent vessel obliteration or thrombosis without scarring or injury to the overlying tissues. Histologic examination shows vascular thrombosis without inflammation and fibrosis in the vocal fold cover. Pulsed dye laser may have promise in treatment of vascular lesions of the larynx and upper airway.

1310 nm quantum dot DFB lasers with high dot density and ultra-low linewidth-power product

NASA Technical Reports Server (NTRS)

Qiu, Y.; Lester, L. F.; Gray, A. L.; Newell, T. C.; Hains, C.; Gogna, P.; Muller, R.; Maker, P.; Su, H.; Stintz, A.

2002-01-01

Laterally coupled distributed feedback lasers using high-density InAs quantum dots-in-a-well (DWELL) active region demonstrate a nominal wavelength of 1310 nm, a linewidth as small as 68 kHz, and a linewidth-power product of 100 kHz-mW.

Electro-optic device having a laterally varying region

NASA Technical Reports Server (NTRS)

Andrews, James T. (Inventor); Ladany, Ivan (Inventor)

1989-01-01

A distributed feedback laser comprising a semiconductor body having a channel which varies in width in the laterial direction and is periodic in the longitudinal direction. When the laser is electrically excited constructive interference of reflected light gives rise to a stable single wavelength output due to the periodic variations in the channel.

Laterally coupled distributed feedback type-I quantum well cascade diode lasers emitting near 3.22  μm.

PubMed

Feng, Tao; Hosoda, Takashi; Shterengas, Leon; Kipshidze, Gela; Stein, Aaron; Lu, Ming; Belenky, Gregory

2017-11-01

The laterally coupled distributed feedback (LC-DFB) GaSb-based type-I quantum well cascade diode lasers using the second- and the sixth-order gratings to stabilize the output spectrum near 3.22 μm were designed and fabricated. The laser heterostructure contained three cascades. The devices were manufactured using a single dry etching step defining the ∼5-μm-wide ridge with ∼5-μm-wide gratings sections adjacent to the ridge sides. The grating coupling coefficients were estimated to be about 1  cm -1 . The stability of the single-frequency operation was ensured by alignment of the DFB mode to the relatively wide gain peak. The 2-mm-long second-order LC-DFB lasers generated above 10 mW of continuous-wave (CW) output power at 20°C in epi-side-up configuration and demonstrated power conversion efficiency above 2%. The sixth-order LC-DFB lasers showed lower efficiency but still generated several milliwatts of CW output power. The devices demonstrated a CW current tuning range of about 3.5 nm at the temperature of 20°C.

Laterally coupled distributed feedback type-I quantum well cascade diode lasers emitting near 3.22 μm

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

Feng, Tao; Hosoda, Takashi; Shterengas, Leon

The laterally coupled distributed feedback (LC-DFB) GaSb-based type-I quantum well cascade diode lasers using the second- and the sixth-order gratings to stabilize the output spectrum near 3.22 μm were designed and fabricated in this paper. The laser heterostructure contained three cascades. The devices were manufactured using a single dry etching step defining the ~5-μm-wide ridge with ~5-μm-wide gratings sections adjacent to the ridge sides. The grating coupling coefficients were estimated to be about 1 cm -1. The stability of the single-frequency operation was ensured by alignment of the DFB mode to the relatively wide gain peak. The 2-mm-long second-order LC-DFBmore » lasers generated above 10 mW of continuous-wave (CW) output power at 20°C in epi-side-up configuration and demonstrated power conversion efficiency above 2%. The sixth-order LC-DFB lasers showed lower efficiency but still generated several milliwatts of CW output power. Finally, the devices demonstrated a CW current tuning range of about 3.5 nm at the temperature of 20°C.« less

Laterally coupled distributed feedback type-I quantum well cascade diode lasers emitting near 3.22 μm

DOE PAGES

Feng, Tao; Hosoda, Takashi; Shterengas, Leon; ...

2017-10-18

The laterally coupled distributed feedback (LC-DFB) GaSb-based type-I quantum well cascade diode lasers using the second- and the sixth-order gratings to stabilize the output spectrum near 3.22 μm were designed and fabricated in this paper. The laser heterostructure contained three cascades. The devices were manufactured using a single dry etching step defining the ~5-μm-wide ridge with ~5-μm-wide gratings sections adjacent to the ridge sides. The grating coupling coefficients were estimated to be about 1 cm -1. The stability of the single-frequency operation was ensured by alignment of the DFB mode to the relatively wide gain peak. The 2-mm-long second-order LC-DFBmore » lasers generated above 10 mW of continuous-wave (CW) output power at 20°C in epi-side-up configuration and demonstrated power conversion efficiency above 2%. The sixth-order LC-DFB lasers showed lower efficiency but still generated several milliwatts of CW output power. Finally, the devices demonstrated a CW current tuning range of about 3.5 nm at the temperature of 20°C.« less

Linearization of microwave photonic link based on nonlinearity of distributed feedback laser

NASA Astrophysics Data System (ADS)

Kang, Zi-jian; Gu, Yi-ying; Zhu, Wen-wu; Fan, Feng; Hu, Jing-jing; Zhao, Ming-shan

2016-02-01

A microwave photonic link (MPL) with spurious-free dynamic range (SFDR) improvement utilizing the nonlinearity of a distributed feedback (DFB) laser is proposed and demonstrated. First, the relationship between the bias current and nonlinearity of a semiconductor DFB laser is experimentally studied. On this basis, the proposed linear optimization of MPL is realized by the combination of the external intensity Mach-Zehnder modulator (MZM) modulation MPL and the direct modulation MPL with the nonlinear operation of the DFB laser. In the external modulation MPL, the MZM is biased at the linear point to achieve the radio frequency (RF) signal transmission. In the direct modulation MPL, the third-order intermodulation (IMD3) components are generated for enhancing the SFDR of the external modulation MPL. When the center frequency of the input RF signal is 5 GHz and the two-tone signal interval is 10 kHz, the experimental results show that IMD3 of the system is effectively suppressed by 29.3 dB and the SFDR is increased by 7.7 dB.

Acoustic Emission Source Location Using a Distributed Feedback Fiber Laser Rosette

PubMed Central

Huang, Wenzhu; Zhang, Wentao; Li, Fang

2013-01-01

This paper proposes an approach for acoustic emission (AE) source localization in a large marble stone using distributed feedback (DFB) fiber lasers. The aim of this study is to detect damage in structures such as those found in civil applications. The directional sensitivity of DFB fiber laser is investigated by calculating location coefficient using a method of digital signal analysis. In this, autocorrelation is used to extract the location coefficient from the periodic AE signal and wavelet packet energy is calculated to get the location coefficient of a burst AE source. Normalization is processed to eliminate the influence of distance and intensity of AE source. Then a new location algorithm based on the location coefficient is presented and tested to determine the location of AE source using a Delta (Δ) DFB fiber laser rosette configuration. The advantage of the proposed algorithm over the traditional methods based on fiber Bragg Grating (FBG) include the capability of: having higher strain resolution for AE detection and taking into account two different types of AE source for location. PMID:24141266

Comparison of distributed Bragg reflector ridge waveguide diode lasers and monolithic master oscillator power amplifiers

NASA Astrophysics Data System (ADS)

Werner, Nils; Wegemund, Jan; Gerke, Sebastian; Feise, David; Bugge, Frank; Paschke, Katrin; Tränkle, Günther

2018-02-01

Diode lasers with ridge waveguide structures and wavelength stabilization by a distributed Bragg-reflector (DBR) are key components for many different applications. These lasers provide diffraction limited laser emission in a single spectral mode, while an arbitrary emission wavelength can be chosen as long as the semiconductor allows for amplification. Furthermore, the DBR grating can be fabricated during the lateral structuring of the device which makes them well suited for mass production. A variety of different concepts can be used for the actual realization of the laser. While standard DBR ridge waveguide lasers (DBR-RWL) with a DBR as reflection grating provide up to 1W optical output power, the DBR can be also used as transmission grating for improved efficiency. Furthermore, more complex structures like monolithic master oscillator power amplifiers (MOPA), which show less spectral mode hops than DBR-RWLs, have been fabricated. The wide range of possible applications have different requirements on the emission characteristic of the used lasers. While the lasers can fulfill the requirements on the emission spectrum and the optical output power, the effects due to optical feedback from optical elements of the setup may limit their practical use in the respective application. Thus, it is of high importance to analyze the emission behavior of the different laser designs at various operation conditions with and without optical feedback. Here, the detailed investigation of the emission characteristics of lasers at an exemplary emission wavelength of 1120 nm is be presented.

Characterization of a liquid crystal/dye cell for a future application in display-integrated photovoltaics

NASA Astrophysics Data System (ADS)

Fujieda, Ichiro; Itaya, Shunsuke; Ohta, Masamichi; Ozawa, Shintaro; Azmi, Nada Dianah Binti M.

2016-04-01

One can convert a luminescent solar concentrator to a display by scanning a laser beam on it. When a guest-host system of liquid crystal (LC) and dye materials are incorporated, absorption of excitation light and the radiation pattern of photoluminescence (PL) can be adjusted to changes in lighting condition. The resolution of a displayed image can be degraded by PL spreading in the LC/dye layer. Its contrast can be limited by the PL induced by ambient light. In the experiment, we fabricated a 22×25 mm2 cell that contained 0.5 wt. % coumarin 6 in a nematic LC host. The alignment was antiparallel and the gap was 6 μm. Using a blue laser beam of 0.04 mm FWHM, the PL intensity distribution was measured to be 0.20 mm FWHM at zero bias. It became slightly wider at 10 V. For contrast evaluation, we measured PL spectra under two conditions. First, the center of the cell was irradiated by a 1.7-mW blue laser beam. Second, the whole cell was uniformly exposed to light from a fluorescent lamp at illuminance of 800lx. The contrast of luminance was calculated to be 1.4×105. The optical power reaching its edge surfaces was measured and roughly agreed with the prediction by a simple model.

Sub-wavelength plasmon laser

DOEpatents

Bora, Mihail; Bond, Tiziana C.

2016-04-19

A plasmonic laser device has resonant nanocavities filled with a gain medium containing an organic dye. The resonant plasmon frequencies of the nanocavities are tuned to align with both the absorption and emission spectra of the dye. Variables in the system include the nature of the dye and the wavelength of its absorption and emission, the wavelength of the pumping radiation, and the resonance frequencies of the nanocavities. In addition the pumping frequency of the dye is selected to be close to the absorption maximum.

Light-driven phase shifter

DOEpatents

Early, James W.

1990-01-01

A light-driven phase shifter is provided for modulating a transmission light beam. A gaseous medium such as argon is provided with electron energy states excited to populate a metastable state. A tunable dye laser is selected with a wavelength effective to deplete the metastable electron state and may be intensity modulated. The dye laser is directed through the gaseous medium to define a first optical path having an index of refraction determined by the gaseous medium having a depleted metastable electron state. A transmission laser beam is also directed through the gaseous medium to define a second optical path at least partially coincident with the first optical path. The intensity of the dye laser beam may then be varied to phase modulate the transmission laser beam.

X-Ray Radiation Measurements With Photodiodes In Plasmas Generated By 1017 W/Cm2 Intensity Krf Excimer Laser Pulses

NASA Astrophysics Data System (ADS)

Rácz, E.; Földes, I. B.; Ryć, L.

2006-01-01

Experiments were carried out using a prepulse-free hybrid KrF excimer-dye laser system (700fs pulse duration, 248nm wavelength, 15mJ pulse energy). The intensity of the p-polarized, focused laser beam was 1.5ṡ1017 W/cm2. Vacuum ultraviolet (VUV) and x-rays from solid state laser plasmas were generated in the laser-plasma interaction of subpicosecond laser pulses of nonrelativistic laser intensities. An x-ray sensitive FLM photodiode (ITE, Warsaw) was used to detect x-rays between 1-19 keV in front of the targets. The diode was filtered by a 4μm Al foil. The dependence of the x-ray flux on laser intensity and the angular distribution of x-rays for aluminum and copper targets in the half space of the front side of the targets were investigated.

Dynamics of short-pulse generation via spectral filtering from intensely excited gain-switched 1.55-μm distributed-feedback laser diodes.

PubMed

Chen, Shaoqiang; Yoshita, Masahiro; Sato, Aya; Ito, Takashi; Akiyama, Hidefumi; Yokoyama, Hiroyuki

2013-05-06

Picosecond-pulse-generation dynamics and pulse-width limiting factors via spectral filtering from intensely pulse-excited gain-switched 1.55-μm distributed-feedback laser diodes were studied. The spectral and temporal characteristics of the spectrally filtered pulses indicated that the short-wavelength component stems from the initial part of the gain-switched main pulse and has a nearly linear down-chirp of 5.2 ps/nm, whereas long-wavelength components include chirped pulse-lasing components and steady-state-lasing components. Rate-equation calculations with a model of linear change in refractive index with carrier density explained the major features of the experimental results. The analysis of the expected pulse widths with optimum spectral widths was also consistent with the experimental data.

Large depth high-precision FMCW tomography using a distributed feedback laser array

NASA Astrophysics Data System (ADS)

DiLazaro, Thomas; Nehmetallah, George

2018-02-01

Swept-source optical coherence tomography (SS-OCT) has been widely employed in the medical industry for the high resolution imaging of subsurface biological structures. SS-OCT typically exhibits axial resolutions on the order of tens of microns at speeds of hundreds of kilohertz. Using the same coherent heterodyne detection technique, frequency modulated continuous wave (FMCW) ladar has been used for highly precise ranging for distances up to kilometers. Distributed feedback lasers (DFBs) have been used as a simple and inexpensive source for FMCW ranging. Here, we use a bandwidth-combined DFB array for sub-surface volume imaging at a 27 μm axial resolution over meters of distance. 2D and 3D tomographic images of several semi-transparent and diffuse objects at distances up to 10 m will be presented.

Dynamics of a gain-switched distributed feedback ridge waveguide laser in nanoseconds time scale under very high current injection conditions.

PubMed

Klehr, A; Wenzel, H; Brox, O; Schwertfeger, S; Staske, R; Erbert, G

2013-02-11

We present detailed experimental investigations of the temporal, spectral and spatial behavior of a gain-switched distributed feedback (DFB) laser emitting at a wavelength of 1064 nm. Gain-switching is achieved by injecting nearly rectangular shaped current pulses having a length of 50 ns and a very high amplitude up to 2.5 A. The repetition frequency is 200 kHz. The laser has a ridge waveguide (RW) for lateral waveguiding with a ridge width of 3 µm and a cavity length of 1.5 mm. Time resolved investigations show, depending on the amplitude of the current pulses, that the optical power exhibits different types of oscillatory behavior during the pulses, accompanied by changes in the lateral near field intensity profiles and optical spectra. Three different types of instabilities can be distinguished: mode beating with frequencies between 25 GHz and 30 GHz, switching between different lateral intensity profiles with a frequency of 0.4 GHz and self-sustained oscillations with a frequency of 4 GHz. The investigations are of great relevance for the utilization of gain-switched DFB-RW lasers as seed lasers for fiber laser systems and in other applications, which require a high optical power.

Dye laser traveling wave amplifier

NASA Technical Reports Server (NTRS)

Davidson, F.; Hohman, J.

1985-01-01

Injection locking was applied to a cavity-dumped coaxial flashlamp pumped dye laser in an effort to obtain nanosecond duration pulses which have both high energy and narrow-linewidth. In the absence of an injected laser pulse, the cavity-dumped dye laser was capable of generating high energy (approx. 60mJ) nanosecond duration output pulses. These pulses, however, had a fixed center wavelength and were extremely broadband (approx. 6nm FWHM). Experimental investigations were performed to determine if the spectral properties of these outputs could be improved through the use of injection-locking techniques. A parametric study to determine the specific conditions under which the laser could be injection-locked was also carried out. Significant linewidth reduction to 0.0015nm) of the outputs was obtained through injection-locking but only at wavelengths near the peak lasing wavelength of the dye. It was found, however; that by inserting weakly dispersive tuning elements in the laser cavity, these narrow-linewidth outputs could be obtained over a wide (24nm) tuning range. Since the tuning elements had low insertion losses, the tunability of the output was obtained without sacrificing output pulse energy.

Interface module for transverse energy input to dye laser modules

DOEpatents

English, Jr., Ronald E.; Johnson, Steve A.

1994-01-01

An interface module (10) for transverse energy input to dye laser modules is provided particularly for the purpose of delivering enhancing transverse energy beams (36) in the form of illumination bar (54) to the lasing zone (18) of a dye laser device, in particular to a dye laser amplifier (12). The preferred interface module (10) includes an optical fiber array (30) having a plurality of optical fibers (38) arrayed in a co-planar fashion with their distal ends (44) receiving coherent laser energy from an enhancing laser source (46), and their proximal ends (4) delivered into a relay structure (3). The proximal ends (42) of the optical fibers (38) are arrayed so as to be coplanar and to be aimed generally at a common point. The transverse energy beam array (36) delivered from the optical fiber array (30) is acted upon by an optical element array (34) to produce an illumination bar (54) which has a cross section in the form of a elongated rectangle at the position of the lasing window (18). The illumination bar (54) is selected to have substantially uniform intensity throughout.

Understanding temperature tuning of the all polymer co-extruded laser

NASA Astrophysics Data System (ADS)

Crescimanno, Michael; Andrews, Jim; Aviles, Michael; Dawson, Nathan; Petrus, Joshua; Mazzocco, Anthony; Singer, Ken; Baer, Eric; Song, Hyunmin

2012-10-01

We investigate the effects of elevated temperatures on a few types of all-polymer multilayer films that were fabricated using a co-extrusion melt-process technique. We report on the anisotropic thermal expansion of the multilayer films, which affects the photonic crystal structure via constituent wise induced anisotropic strains and a change in the relative refractive indices. In addition to the characterization of these films in the temperature range of approximately 20-95 degrees C, we show the application to non-contact temperature sensing and wavelength tuning of all polymer Distributed FeedBack (DFB) lasers and Distributed Bragg Reflector (DBR) lasers.

Thin film DNA-complex-based dye lasers fabricated by immersion and conventional processes

NASA Astrophysics Data System (ADS)

Kawabe, Yutaka; Suzuki, Yuki

2017-08-01

DNA based thin film dye laser is one of promising optical devices for future technology. Laser oscillation and amplified spontaneous emission (ASE) were demonstrated by hemicyanine-doped DNA complex films prepared with `immersion method' as well as those made by a conventional way. In the immersion process, DNA-surfactant complex films were stained by immersion into an acetone solution including the dyes. In this study, three types of hemicyanines were incorporated with both methods, and laser oscillation was achieved with optically induced population grating formed in all of the complex films. The laser threshold values for six cases ranged in 0.07 - 0.18 mJ/cm2 , which was close to the best values made in DNA complex matrices. Continual pumping showed that laser oscillation persisted for 4 - 10 minutes. Immersion process gave superior laser capability especially for output efficiency over the conventional counterparts.

Development of New Laser Protective Dyes

DTIC Science & Technology

1993-07-31

Science’s Phase I research, the feasibility of thermally stabilizing cyanine and squarylium dyes for simulated polycarbonate injection-molding... SQUARYLIUM & CROCONIUM FIUORENE DYE SYNTHESIS SYNTHESIS OF NEW DYES DYE SYNTHESES IENGFICA TION ASYNTHESIS OF SUSSTITUTED DYES EVELOP OH TECHNOLOGIES...region, three dyes were successfully extruded into PETG and/or PC: (a.) the croconium dye SS-1044 (,%max = 834 um in PETG). (b.) the squarylium dye

Liquid-phase epitaxy grown PbSnTe distributed feedback laser diodes with broad continuous single-mode tuning range

NASA Technical Reports Server (NTRS)

Hsieh, H.-H.; Fonstad, C. G.

1980-01-01

Distributed feedback (DFB) pulsed laser operation has been demonstrated in stripe geometry Pb(1-x)Sn(x)Te double-heterostructures grown by liquid-phase epitaxy. The grating structure of 0.79 micron periodicity operates in first order near 12.8 microns and was fabricated prior to the liquid-phase epitaxial growth using holographic exposure techniques. These DFB lasers had moderate thresholds, 3.6 kA/sq cm, and the output power versus current curves exhibited a sharp turn-on free of kinks. Clean, single-mode emission spectra, continuously tunable over a range in excess of 20 per cm, centered about 780 per cm (12.8 microns), and at an average rate of 1.2 per cm-K from 9 to 26 K, were observed. While weaker modes could at times be seen in the spectrum, substantially single-mode operation was obtained over the entire operating range and to over 10 times threshold.

Diode-Pumped Organo-Lead Halide Perovskite Lasing in a Metal-Clad Distributed Feedback Resonator.

PubMed

Jia, Yufei; Kerner, Ross A; Grede, Alex J; Brigeman, Alyssa N; Rand, Barry P; Giebink, Noel C

2016-07-13

Organic-inorganic lead halide perovskite semiconductors have recently reignited the prospect of a tunable, solution-processed diode laser, which has the potential to impact a wide range of optoelectronic applications. Here, we demonstrate a metal-clad, second-order distributed feedback methylammonium lead iodide perovskite laser that marks a significant step toward this goal. Optically pumping this device with an InGaN diode laser at low temperature, we achieve lasing above a threshold pump intensity of 5 kW/cm(2) for durations up to ∼25 ns at repetition rates exceeding 2 MHz. We show that the lasing duration is not limited by thermal runaway and propose instead that lasing ceases under continuous pumping due to a photoinduced structural change in the perovskite that reduces the gain on a submicrosecond time scale. Our results indicate that the architecture demonstrated here could provide the foundation for electrically pumped lasing with a threshold current density Jth < 5 kA/cm(2) under sub-20 ns pulsed drive.

Open-path spectroscopic methane detection using a broadband monolithic distributed feedback-quantum cascade laser array.

PubMed

Michel, Anna P M; Kapit, Jason; Witinski, Mark F; Blanchard, Romain

2017-04-10

Methane is a powerful greenhouse gas that has both natural and anthropogenic sources. The ability to measure methane using an integrated path length approach such as an open/long-path length sensor would be beneficial in several environments for examining anthropogenic and natural sources, including tundra landscapes, rivers, lakes, landfills, estuaries, fracking sites, pipelines, and agricultural sites. Here a broadband monolithic distributed feedback-quantum cascade laser array was utilized as the source for an open-path methane sensor. Two telescopes were utilized for the launch (laser source) and receiver (detector) in a bistatic configuration for methane sensing across a 50 m path length. Direct-absorption spectroscopy was utilized with intrapulse tuning. Ambient methane levels were detectable, and an instrument precision of 70 ppb with 100 s averaging and 90 ppb with 10 s averaging was achieved. The sensor system was designed to work "off the grid" and utilizes batteries that are rechargeable with solar panels and wind turbines.

Surface-Emitting Distributed Feedback Terahertz Quantum-Cascade Lasers in Metal-Metal Waveguides

NASA Technical Reports Server (NTRS)

Kumar, Sushil; Williams, Benjamin S.; Qin, Qi; Lee, Alan W. M.; Hu, Qing; Reno, John L.

2007-01-01

Single-mode surface-emitting distributed feedback terahertz quantumcascade lasers operating around 2.9 THz are developed in metal-metal waveguides. A combination of techniques including precise control of phase of reflection at the facets, and u e of metal on the sidewalls to eliminate higher-order lateral modes allow robust single-mode operation over a range of approximately 0.35 THz. Single-lobed far-field radiation pattern is obtained using a pi phase-shift in center of the second-order Bragg grating. A grating device operating at 2.93 THz lased up to 149 K in pulsed mode and a temperature tuning of 19 .7 GHz was observed from 5 K to 147 K. The same device lased up to 78 K in continuous-wave (cw) mode emitting more than 6 m W of cw power at 5 K. ln general, maximum temperature of pulsed operation for grating devices was within a few Kelvin of that of multi-mode Fabry-Perot ridge lasers

Nanoimprinted organic semiconductor laser pumped by a light-emitting diode.

PubMed

Tsiminis, Georgios; Wang, Yue; Kanibolotsky, Alexander L; Inigo, Anto R; Skabara, Peter J; Samuel, Ifor D W; Turnbull, Graham A

2013-05-28

An organic semiconductor laser, simply fabricated by UV-nanoimprint lithography (UV-NIL), that is pumped with a pulsed InGaN LED is demonstrated. Molecular weight optimization of the polymer gain medium on a nanoimprinted polymer distributed feedback resonator enables the lowest reported UV-NIL laser threshold density of 770 W cm(-2) , establishing the potential for scalable organic laser fabrication compatible with mass-produced LEDs. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Laser generation in opal-like single-crystal and heterostructure photonic crystals

NASA Astrophysics Data System (ADS)

Kuchyanov, A. S.; Plekhanov, A. I.

2016-11-01

This study describes the laser generation of a 6Zh rhodamine in artificial opals representing single-crystal and heterostructure films. The spectral and angular properties of emission and the threshold characteristics of generation are investigated. In the case where the 6Zh rhodamine was in a bulk opal, the so-called random laser generation was observed. In contrast to this, the laser generation caused by a distributed feedback inside the structure of the photonic bandgap was observed in photonic-crystal opal films.

Bibliography of Soviet Laser Developments Number 57, January-February 1982.

DTIC Science & Technology

1983-03-02

1 3. Crystal: Miscellaneous ............. 2 4. Semiconductor a. InP..............................................3 b . Pbl...Nd...........................................6 6. Glass: Miscellaneous................................7 B . Liquid Lasers I. Organic Dyes a. Rhodamine...8 b . Miscellaneous Dyes...............................8 2. Incrganic Liquids

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

Liu, Wei-long; Bassett, Will P.; Christensen, James M.

The emission lifetimes of rhodamine 6G (R6G), were measured under shock compression to 9.1 GPa, with the dual intent of better understanding molecular photophysics in extreme environments and assessing the usefulness of fluorescence lifetime microscopy to measure spatially-dependent pressure distributions in shocked microstructured media. R6G was studied as free dye dissolved in poly-methyl methacrylate (PMMA), or dye encapsulated in silica microparticles suspended in PMMA. Thin layers of these materials in impedance-matched geometries were subjected to planar single-stage shocks created by laser-driven flyer plates. A synchronized femtosecond laser excited the dye at selected times relative to flyer plate arrival and themore » emission lifetimes were measured with a streak camera. Lifetimes decreased when shocks arrived. The lifetime decrease was attributed to a shock-induced enhancement of R6G nonradiative relaxation. At least part of the relaxation involved shock-enhanced intersystem crossing. For free dye in PMMA, the lifetime decrease during the shock was shown to be a linear function of shock pressure from 0-9 GPa, with a slope of -0.22 ns·GPa -1. Furthermore, the linear relationship makes it simple to convert lifetimes into pressures. Lifetime measurements in shocked microenvironments may be better than emission intensity measurements, since lifetimes are sensitive to the surrounding environment, but insensitive to intensity variations associated with the motion and optical properties of a dynamically changing structure.« less

Differential carrier phase recovery for QPSK optical coherent systems with integrated tunable lasers.

PubMed

Fatadin, Irshaad; Ives, David; Savory, Seb J

2013-04-22

The performance of a differential carrier phase recovery algorithm is investigated for the quadrature phase shift keying (QPSK) modulation format with an integrated tunable laser. The phase noise of the widely-tunable laser measured using a digital coherent receiver is shown to exhibit significant drift compared to a standard distributed feedback (DFB) laser due to enhanced low frequency noise component. The simulated performance of the differential algorithm is compared to the Viterbi-Viterbi phase estimation at different baud rates using the measured phase noise for the integrated tunable laser.

Terahertz plasmonic lasers with narrow beams and large tunability

NASA Astrophysics Data System (ADS)

Jin, Yuan; Wu, Chongzhao; Reno, John L.; Kumar, Sushil

2017-02-01

Plasmonic lasers generate coherent long-range or localized surface-plasmon-polaritons (SPPs), where the SPP mode exists at the interface of the metal (or a metallic nanoparticle) and a dielectric. Metallic-cavities sup- porting SPP modes are also utilized for terahertz quantum-cascade lasers (QCLs). Due to subwavelength apertures, plasmonic lasers have highly divergent radiation patterns. Recently, we theoretically and experimentally demonstrated a new technique for implementing distributed-feedback (DFB), which is termed as an antenna- feedback scheme, to establish a hybrid SPP mode in the surrounding medium of a plasmonic laser's cavity with a large wavefront. This technique allows such lasers to radiate in narrow beams without requirement of any specific design considerations for phase-matching. Experimental demonstration is done for terahertz QCLs that show beam-divergence as small as 4-degrees. The antenna-feedback scheme has a characteristic feature in that refractive-index of the laser's surrounding medium affects its radiative frequency in the same vein as refractive- index of the cavity. Hence, any perturbations in the refractive-index of the surrounding medium could lead to large modulation in the laser's emission frequency. Along this line, we report 57 GHz reversible, continuous, and mode-hop-free tuning of such QCLs operating at 78 K based on post-process deposition/etching of a dielectric on an already mounted QCL chip. This is the largest tuning range achieved for terahertz QCLs when operating much above the temperature of liquid-Helium. We review the aforementioned experimental results and discuss methods to increase optical power output from terahertz QCLs with antenna-feedback. Peak power output of 13 mW is realized for a 3.3 THz QCL operating in a Stirling cooler at 54 K. A new dual-slit photonic structure based on antenna-feedback scheme is proposed to further improve output power as well as provide enhanced tunability.

Thermally and optically tunable lasing properties from dye-doped holographic polymer dispersed liquid crystal in capillaries

NASA Astrophysics Data System (ADS)

Chen, Maozhou; Dai, Haitao; Wang, Dongshuo; Yang, Yue; Luo, Dan; Zhang, Xiaodong; Liu, Changlong

2018-03-01

In this paper, we investigated tunable lasing properties from the dye-doped holographic polymer dispersed liquid crystal (HPDLC) gratings in capillaries with thermal and optical manners. The thermally tunable range of the lasing from the dye-doped HPDLC reached 8.60 nm with the temperature ranging from 23 °C to 50 °C. The optically tunable laser emission was achieved by doping azo-dye in HPDLC. The transition of azo-dye from trans- to cis-state could induce the reorientation of LC molecules after UV light irradiation, which resulted in the variation of refractive index contrast of LC-rich/polymer-rich layer in HPDLC. Experimentally, the emission wavelength of lasing showed a blueshift (about 2 nm) coupled with decreasing output intensities. The tunable laser based on HPDLC may enable more applications in laser displays, optical communication, biosensors, etc.

[Therapeutic indications for percutaneous laser in patients with vascular malformations and tumors].

PubMed

Labau, D; Cadic, P; Ouroussoff, G; Ligeron, C; Laroche, J-P; Guillot, B; Dereure, O; Quéré, I; Galanaud, J-P

2014-12-01

Lasers are increasingly used to treat vascular abnormalities. Indeed, this technique is non-invasive and allows a specific treatment. The aim of this review is to present some biophysical principles of the lasers, to describe the different sorts of lasers available for treatment in vascular medicine indications. Three principal lasers exist in vascular medicine: the pulsed-dye laser, for the treatment of superficial pink lesions, the NdYAG-KTP laser for purple and bigger lesions, and the NdYAG long pulse laser for even deeper and bigger vascular lesions. In vascular malformations, port wine stains can also be treated by pulsed-dye laser, KTP or NdYAG when they are old and thick. Telangiectasias are good indications for the three sorts of lasers, depending on their depth, color and size. Microcystic lymphatic malformations can be improved by laser treatment. Arterio-venous malformations constitute a contraindication of laser treatment. In vascular tumors, involuted infantile hemangiomas constitute an excellent indication of pulsed-dye laser treatment. Controlled studies are necessary to evaluate and to compare the efficacy of each laser, in order to determine their optimal indications and optimal parameters for each machine. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Conversion of the luminescence of laser dyes in opal matrices to stimulated emission

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

Alimov, O K; Basiev, T T; Orlovskii, Yu V

The luminescence and laser characteristics of a synthetic opal matrix filled with organic dyes are studied upon excitation by nanosecond laser pulses. The appearance of stimulated emission in a partially ordered scattering medium is investigated. It is shown that if the luminescence spectrum of a dye (oxazine-17) is located far outside the photonic bandgap of the opal matrix, stimulated emission along a preferential direction in the (111) plane is observed when pumping exceeds a threshold even without an external optical cavity. The stimulated emission spectrum is considerably narrower than the luminescence spectrum and consists of several narrow lines located withinmore » the dye luminescence band. If the luminescence spectrum of a dye (rhodamine 6G) overlaps with the photonic bandgap of the opal matrix, a different picture is observed. The loss of radiation in the matrix leads to the red shift of the luminescence spectrum, while the stimulated emission as in the case of oxazine-17 lies is observed within the luminescence band. (active media, lasers, and amplifiers)« less

A frequency doubled pressure-tunable oscillator-amplifier dye laser system

NASA Technical Reports Server (NTRS)

Moriarty, A.; Heaps, W.; Davis, D. D.

1976-01-01

A tunable high-repetition-rate oscillator-amplifier dye-laser system is reported. The dye laser described was longitudinally pumped with the second harmonic of a Nd-YAG laser operating at 10 Hz. Using three Faraday-Perot etalons and pressure tuning, a maximum fundamental output power of the order of 6 MW with a corresponding spectral width of less than 0.003 nm at 564 nm was obtained. The fundamental at 564 nm was frequency doubled to give a maximum power level of 0.6 MW of second-harmonic output power with a spectral width less than 0.0015 nm at 282 nm. Frequency stability could be maintained to within approximately 15% of the line-width.

Pulsed dye laser treatment of rosacea using a novel 15 mm diameter treatment beam.

PubMed

Bernstein, Eric F; Schomacker, Kevin; Paranjape, Amit; Jones, Christopher J

2018-04-10

The pulsed-dye laser has been used to treat facial redness and rosacea for decades. Recent advances in dye laser technology enable 50% higher output energies supporting 50% larger treatment areas, and beam-diameters up to 15 mm with clinically-relevant fluences. In this study, we investigate this novel pulsed-dye laser using a 15 mm diameter beam for treatment of rosacea. Twenty subjects with erythemato-telangiectatic rosacea were enrolled in the study. A total of 4 monthly treatments were administered, first treating linear vessels with a 3 × 10 mm elliptical beam, then diffuse redness with a 15-mm diameter circular beam. Blinded assessment of digital, cross-polarized photographs taken 2 months following the last treatment was performed using an 11-point clearance scale. Nineteen subjects completed the study. Blinded reviewers correctly identified baseline photos in 55 out of the total of 57 images (96.5%). The blinded reviewers scored 17 of the 19 subjects with an improvement greater than 40%, and 11 of the 19 subjects greater than 50%. The average improvement was 53.9%. Side effects were limited to mild edema, mild to moderate erythema, and mild to moderate bruising. This study demonstrates that a newly designed pulsed-dye laser having a novel 15-mm diameter treatment beam improves the appearance of rosacea with a favorable safety profile. Lasers Surg. Med. 9999:1-5, 2018. © 2018 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc. © 2018 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.

Near-ultraviolet laser diodes for brilliant ultraviolet fluorophore excitation.

PubMed

Telford, William G

2015-12-01

Although multiple lasers are now standard equipment on most modern flow cytometers, ultraviolet (UV) lasers (325-365 nm) remain an uncommon excitation source for cytometry. Nd:YVO4 frequency-tripled diode pumped solid-state lasers emitting at 355 nm are now the primary means of providing UV excitation on multilaser flow cytometers. Although a number of UV excited fluorochromes are available for flow cytometry, the cost of solid-state UV lasers remains prohibitively high, limiting their use to all but the most sophisticated multilaser instruments. The recent introduction of the brilliant ultraviolet (BUV) series of fluorochromes for cell surface marker detection and their importance in increasing the number of simultaneous parameters for high-dimensional analysis has increased the urgency of including UV sources in cytometer designs; however, these lasers remain expensive. Near-UV laser diodes (NUVLDs), a direct diode laser source emitting in the 370-380 nm range, have been previously validated for flow cytometric analysis of most UV-excited probes, including quantum nanocrystals, the Hoechst dyes, and 4',6-diamidino-2-phenylindole. However, they remain a little-used laser source for cytometry, despite their significantly lower cost. In this study, the ability of NUVLDs to excite the BUV dyes was assessed, along with their compatibility with simultaneous brilliant violet (BV) labeling. A NUVLD emitting at 375 nm was found to excite most of the available BUV dyes at least as well as a UV 355 nm source. This slightly longer wavelength did produce some unwanted excitation of BV dyes, but at sufficiently low levels to require minimal additional compensation. NUVLDs are compact, relatively inexpensive lasers that have higher power levels than the newest generation of small 355 nm lasers. They can, therefore, make a useful, cost-effective substitute for traditional UV lasers in multicolor analysis involving the BUV and BV dyes. Published 2015 Wiley Periodicals Inc. on behalf of ISAC.

The optical biomedical sensors for DNA detection and imaging based on two-photon excited luminescent styryl dyes: phototoxic influence on the DNA

NASA Astrophysics Data System (ADS)

Yashchuk, Valeriy M.; Kudrya, Vladislav Yu.; Losytskyy, Mykhaylo Yu.; Tokar, Valentyna P.; Yarmoluk, Sergiy M.; Dmytruk, Igor M.; Prokopets, Vadym M.; Kovalska, Vladyslava B.; Balanda, Anatoliy O.; Kryvorotenko, Dmytro V.; Ogul'chansky, Tymish Yu.

2007-06-01

The optical absorption, fluorescence and phosphorescence of the novel styryl dyes developed for the fluorescent detection of DNA were investigated. The energy structures of dye molecules as well as spectral manifestations of the dyes aggregate formation and interaction with DNA were studied. The dramatic increase (up to 1000 times) of the fluorescence intensity of dyes in the presence of DNA was observed. The photostability and phototoxic influence on the DNA of several styryl dyes were studied by analyzing absorption, fluorescence and phosphorescence spectra of these dyes and dye-DNA systems. Changes of the optical density value of dye-DNA solutions caused by the visible light irradiation were fixed in the wavelength regions of the DNA absorption and of the dye absorption. Fluorescence emission of dye-DNA complexes upon two-photon excitation (TPE) at wavelength 1064 nm with the 20 ns pulsed YAG: Nd3+ laser and at 840 nm with the 90 fs pulsed Ti:sapphire laser was registered. The values of two-photon absorption cross-sections of dye-DNA complexes were evaluated.

Radio-Frequency Down-Conversion via Sampled Analog Optical Links

DTIC Science & Technology

2010-08-09

temporal intensity Popt(ω) includes intensity noise quantities arising from the optical source (e.g. laser intensity noise, amplified spontaneous emission...nm distributed feedback laser RF Down-Conversion via Sampled Links 5 (DFB, EM4, Inc.) the output of which is modulated via a low-biased Mach-Zehnder...Figure 5 (a). For comparison purposes the RF gain of one arm of the balanced link (utilizing a continuous- wave laser source) is measured and

Pulsed mononode dye laser developed for a geophysical application

NASA Technical Reports Server (NTRS)

Jegou, J. P.; Pain, T.; Megie, G.

1986-01-01

Following the extension of the lidar technique in the study of the atmosphere, the necessity of having a high power pulsed laser beam with a narrowed bandwidth and the possibility of selecting a particular wavelength within a certain spectral region arises. With the collaboration of others, a laser cavity using the multiwave Fizeau wedge (MWFW) was developed. Using the classical method of beam amplification with the aid of different stages, a new pulsed dye laser device was designed. The originality resides in the use of reflecting properties of the MFWF. Locally a plan wave coming with a particular angular incidence is reflected with a greater than unity coefficient; this is the consequence of the wedge angle which doubles the participation of every ray in the interferometric process. This dye laser operation and advantages are discussed. The feasibility of different geophysical applications envisageable with this laser is discussed.

Monolithically, widely tunable quantum cascade lasers based on a heterogeneous active region design.

PubMed

Zhou, Wenjia; Bandyopadhyay, Neelanjan; Wu, Donghai; McClintock, Ryan; Razeghi, Manijeh

2016-06-08

Quantum cascade lasers (QCLs) have become important laser sources for accessing the mid-infrared (mid-IR) spectral range, achieving watt-level continuous wave operation in a compact package at room temperature. However, up to now, wavelength tuning, which is desirable for most applications, has relied on external cavity feedback or exhibited a limited monolithic tuning range. Here we demonstrate a widely tunable QCL source over the 6.2 to 9.1 μm wavelength range with a single emitting aperture by integrating an eight-laser sampled grating distributed feedback laser array with an on-chip beam combiner. The laser gain medium is based on a five-core heterogeneous QCL wafer. A compact tunable laser system was built to drive the individual lasers within the array and produce any desired wavelength within the available spectral range. A rapid, broadband spectral measurement (520 cm(-1)) of methane using the tunable laser source shows excellent agreement to a measurement made using a standard low-speed infrared spectrometer. This monolithic, widely tunable laser technology is compact, with no moving parts, and will open new opportunities for MIR spectroscopy and chemical sensing.

Monolithically, widely tunable quantum cascade lasers based on a heterogeneous active region design

PubMed Central

Zhou, Wenjia; Bandyopadhyay, Neelanjan; Wu, Donghai; McClintock, Ryan; Razeghi, Manijeh

2016-01-01

Quantum cascade lasers (QCLs) have become important laser sources for accessing the mid-infrared (mid-IR) spectral range, achieving watt-level continuous wave operation in a compact package at room temperature. However, up to now, wavelength tuning, which is desirable for most applications, has relied on external cavity feedback or exhibited a limited monolithic tuning range. Here we demonstrate a widely tunable QCL source over the 6.2 to 9.1 μm wavelength range with a single emitting aperture by integrating an eight-laser sampled grating distributed feedback laser array with an on-chip beam combiner. The laser gain medium is based on a five-core heterogeneous QCL wafer. A compact tunable laser system was built to drive the individual lasers within the array and produce any desired wavelength within the available spectral range. A rapid, broadband spectral measurement (520 cm−1) of methane using the tunable laser source shows excellent agreement to a measurement made using a standard low-speed infrared spectrometer. This monolithic, widely tunable laser technology is compact, with no moving parts, and will open new opportunities for MIR spectroscopy and chemical sensing. PMID:27270634

Fabrication of Ocular Protective Devices against Laser Radiation and Ballistic Fragments for Evaluation in Military Scenarios

DTIC Science & Technology

1992-09-30

19 3.4.5 High Energy Laser ..... .............. .. 20 3.4.6 Solar ..................................... 21 3.4.7 Humidity...57 4.5.6 Solar ...................................... 57 4.5.7 Humidity... . .................. ...o.. ....57 4.5.8 Temperature...coated AO-ET dye 12. Effect of solar exposure on AO-ET dyeD 13. Spectral transmittance molded B-401 dye 14. Visible transmittance of typical two

Implementing Audio Digital Feedback Loop Using the National Instruments RIO System

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

Huang, G.; Byrd, J. M.

2006-11-20

Development of system for high precision RF distribution and laser synchronization at Berkeley Lab has been ongoing for several years. Successful operation of these systems requires multiple audio bandwidth feedback loops running at relatively high gains. Stable operation of the feedback loops requires careful design of the feedback transfer function. To allow for flexible and compact implementation, we have developed digital feedback loops on the National Instruments Reconfigurable Input/Output (RIO) platform. This platform uses an FPGA and multiple I/Os that can provide eight parallel channels running different filters. We present the design and preliminary experimental results of this system.

Low-threshold ablation of enamel and dentin using Nd:YAG laser assisted with chromophore with different pulse shapes

NASA Astrophysics Data System (ADS)

Bonora, Stefano; Benazzato, Paolo; Stefani, Alessandro; Villoresi, Paolo

2004-05-01

Neodimium laser treatment has several drawbacks when used in the hard tissue cutting, because of the low absorption of the dental tissues at its wavelength. This investigation proved that the Nd:YAG radiation is a powerful ablation tool if it is used with the dye assisted method. Several in vitro tests on enamel and dentin were accomplished changing some laser parameters to have different pulse shapes and durations from 125μs up to 1.4ms. The importance of short time high power peaks, typical of crystal lasers, in the ablation process was investigated. The pulse shapes were analyzed by their intensity in space and time profiles. A first set of results found the optimum dye concentration be used in all the following tests. Furthermore the ablation threshold for this technique was found for each different pulse shapes and durations. A low energy ablation method was found to avoid temperature increase and surface cracks formation. In vitro temperature analysis was reported comparing the differences between no dye application laser treatment and with a dye spray applied. A strong reduction of the temperature increase was found in the dye assisted method. A discussion on the general findings and their possible clinical applications is presented.

Fluorescence Lifetime Imaging Microscopy Using Near-Infrared Contrast Agents

PubMed Central

Nothdurft, Ralph; Sarder, Pinaki; Bloch, Sharon; Culver, Joseph; Achilefu, Samuel

2013-01-01

Although single-photon fluorescence lifetime imaging microscopy (FLIM) is widely used to image molecular processes using a wide range of excitation wavelengths, the captured emission of this technique is confined to the visible spectrum. Here, we explore the feasibility of utilizing near-infrared (NIR) fluorescent molecular probes with emission >700 nm for FLIM of live cells. The confocal microscope is equipped with a 785 nm laser diode, a red-enhanced photomultiplier tube, and a time-correlated single photon counting card. We demonstrate that our system reports the lifetime distributions of NIR fluorescent dyes, cypate and DTTCI, in cells. In cells labeled separately or jointly with these dyes, NIR FLIM successfully distinguishes their lifetimes, providing a method to sort different cell populations. In addition, lifetime distributions of cells co-incubated with these dyes allow estimate of the dyes’ relative concentrations in complex cellular microenvironments. With the heightened interest in fluorescence lifetime-based small animal imaging using NIR fluorophores, this technique further serves as a bridge between in vitro spectroscopic characterization of new fluorophore lifetimes and in vivo tissue imaging. PMID:22788550

[Mid-infrared distributed-feedback quantum cascade laser-based photoacoustic detection of trace methane gas].

PubMed

Tan, Song; Liu, Wan-feng; Wang, Li-jun; Zhang, Jin-chuan; Li, Lu; Liu, Jun-qi; Liu, Feng-qi; Wang, Zhan-guo

2012-05-01

There have been considerable interests in methane detection based on infrared absorption spectroscopy for industrial and environment monitoring. The authors report on the realization of photoacoustic detection of methane (CH4) using mid-infrared distributed-feedback quantum cascade laser (DFB-QCL). The absorption line at 1316.83 cm(-1) was selected for CH4 detection, which can be reached by the self-manufactured DFB-QCL source operating in pulsed mode near 7.6 microm at room-temperature. The CH4 gas is filled to a Helmholtz resonant photoacoustic cell, which was equipped with a commercial electret microphone. The DFB-QCL was operated at 234 Hz with an 80 mW optical peak power. A detection limit of 189 parts per billion in volume was derived when the signal-to-noise ratio equaled 1.

DBR laser with nondynamic plasma grating formed by focused ion beam implanted dopants

NASA Technical Reports Server (NTRS)

Boenke, Myra M.; Wu, M. C.; Wang, Shyh; Clark, William M., Jr.; Stevens, Eugene H.

1989-01-01

A static plasma grating has been demonstrated experimentally (Wu et al., 1988) in a large-optical-cavity focused-ion-beam-distributed-Bragg-reflector (FIB-DBR) GaAlAs/GaAs laser diode. The grating is formed by implanting stripes of dopants with a focused ion beam. The dopants ionize to form periodic fluctuations in the carrier concentration which, through the Kramers-Kronig relations, form an index grating. A model of the grating strength for optimizaton of the laser design is developed and presented. The computed results show that the coupling coefficient k can be increased by more than an order of magnitude over the 15/cm experimentally. Therefore, FIB-DBR or FIB-distributed-feedback (DFB) lasers with performance comparable to that of conventional DBR (or DFB) lasers can be expected.

Dye-sensitized solar cells using laser processing techniques

NASA Astrophysics Data System (ADS)

Kim, Heungsoo; Pique, Alberto; Kushto, Gary P.; Auyeung, Raymond C. Y.; Lee, S. H.; Arnold, Craig B.; Kafafi, Zakia H.

2004-07-01

Laser processing techniques, such as laser direct-write (LDW) and laser sintering, have been used to deposit mesoporous nanocrystalline TiO2 (nc-TiO2) films for use in dye-sensitized solar cells. LDW enables the fabrication of conformal structures containing metals, ceramics, polymers and composites on rigid and flexible substrates without the use of masks or additional patterning techniques. The transferred material maintains a porous, high surface area structure that is ideally suited for dye-sensitized solar cells. In this experiment, a pulsed UV laser (355nm) is used to forward transfer a paste of commercial TiO2 nanopowder (P25) onto transparent conducting electrodes on flexible polyethyleneterephthalate (PET) and rigid glass substrates. For the cells based on flexible PET substrates, the transferred TiO2 layers were sintered using an in-situ laser to improve electron paths without damaging PET substrates. In this paper, we demonstrate the use of laser processing techniques to produce nc-TiO2 films (~10 μm thickness) on glass for use in dye-sensitized solar cells (Voc = 690 mV, Jsc = 8.7 mA/cm2, ff = 0.67, η = 4.0 % at 100 mW/cm2). This work was supported by the Office of Naval Research.

Photodynamic tumor therapy and on-line fluorescence spectroscopy after aminolevulinic acid administration using 633-nm light as therapeutic and fluorescence excitation radiation

NASA Astrophysics Data System (ADS)

Koenig, Karsten; Kienle, Alwin; Boehncke, Wolf-Henning; Kaufmann, Roland; Rueck, Angelika C.; Meier, Thomas H.; Steiner, Rudolf W.

1994-03-01

PDT and on-line fluorescence spectroscopy were carried out on human tumors after ALA- administration using 633 nm-light of a dye laser as therapeutic radiation and as fluorescence excitation radiation. This has the following advantages: (1) use of one laser for PDT and fluorescence diagnosis only, (2) the possibility of on-line fluorescence measurements, and (3) excitation of protoporphyrin molecules in deep tissue layers. Monte Carlo calculations were carried out to determine the excitation and fluorescence photon distribution in the case of red and violet excitation radiation. The results show the possibility of depth-resolved measurements on the fluorophore distribution by variation of the excitation wavelength. The influence of remitted excitation light and of the spontaneous radiation from the laser as well as the possible excitation of food-based degradation products of chlorophyll has to be considered in high-sensitive fluorescence measurements.

Tapered fiber based Brillouin random fiber laser and its application for linewidth measurement.

PubMed

Gao, Song; Zhang, Liang; Xu, Yanping; Lu, Ping; Chen, Liang; Bao, Xiaoyi

2016-12-12

A one-end pumping Brillouin random fiber laser (BRFL) based on a 5-km tapered fiber (TF) is demonstrated. The enhanced Rayleigh scattering and the increased power density from tapering in the TF provide good directionality and a high degree of coherent feedback. Both the transmitting and TF enhanced Rayleigh scattered pump lights formed effective bi-direction pumping for the Brillouin gain in the standing cavity configuration in the distributed way as the gain and random feedback in the same fiber. The linewidth of the laser shows ~1.17 kHz while the relative intensity noise (RIN) has been verified to be suppressed comparing with that of the two-end pumping of the standard single mode fiber (SMF). Furthermore, utilizing the proposed laser, a high-resolution (~kHz) linewidth measurement method is demonstrated without long delay fiber (>100km) and extra frequency shifter thanks to the acoustic frequency shift from fiber itself.

Simple analytical model for low-frequency frequency-modulation noise of monolithic tunable lasers.

PubMed

Huynh, Tam N; Ó Dúill, Seán P; Nguyen, Lim; Rusch, Leslie A; Barry, Liam P

2014-02-10

We employ simple analytical models to construct the entire frequency-modulation (FM)-noise spectrum of tunable semiconductor lasers. Many contributions to the laser FM noise can be clearly identified from the FM-noise spectrum, such as standard Weiner FM noise incorporating laser relaxation oscillation, excess FM noise due to thermal fluctuations, and carrier-induced refractive index fluctuations from stochastic carrier generation in the passive tuning sections. The contribution of the latter effect is identified by noting a correlation between part of the FM-noise spectrum with the FM-modulation response of the passive sections. We pay particular attention to the case of widely tunable lasers with three independent tuning sections, mainly the sampled-grating distributed Bragg reflector laser, and compare with that of a distributed feedback laser. The theoretical model is confirmed with experimental measurements, with the calculations of the important phase-error variance demonstrating excellent agreement.

Tracheal anastomosis using indocyanine green dye enhanced fibrinogen with a near-infrared diode laser

NASA Astrophysics Data System (ADS)

Auteri, Joseph S.; Jeevanandam, Valluvan; Oz, Mehmet C.; Libutti, Steven K.; Kirby, Thomas J.; Smith, Craig R.; Treat, Michael R.

1990-06-01

A major obstacle to lung transplantation and combined heart- lung transplantation is dehiscence of the tracheobronchial anastomosis. We explored the possibility of laser welded anastomoses in canine tracheas in vivo. Laser anastomoses were performed on three-quarter circumferential anterior tracheotomies. A continous wave diode laser (808 +1 nm) at a power density of 9.6 watts/cm was used. Human fibrinogen was mixed with indocyanine green dye (ICG, max absorbance 805 nm) and applied to the anastomosis site prior to laser exposure. Animals were sacrificed at 0, 21 and 28 days post-operatively. At sacrifice weld bursting pressures were measured by raising intratracheal pressure using forced ventilation via an endotracheal tube. Sutured and laser welded anastomoses had similar bursting pressures, and exhibited satisfactory histologic evidence of healing. However, compared to polypropylene sutured controls, the laser welded anastomoses exhibited less peritracheal inflammatory reaction and showed visibly smoother luminal surfaces at 21 and 28 days post- operatively. Tracheal anastomosis using ICG dye enhanced fibrinogen combined with the near-infrared diode laser is a promising extension of the technology of laser tissue fusion and deserves further study.

Measurement technology based on laser internal/external cavity tuning

NASA Astrophysics Data System (ADS)

Zhang, Shulian

2011-08-01

For an ordinary laser with two cavity mirrors, if the length of laser cavity changes half wavelength the laser frequency changes one longitudinal mode separation. For a laser with three cavity mirrors, in which a feedback mirror is used to feed part of the laser output beam back into the laser cavity, the external cavity length changes half wavelength the laser intensity fluctuates one period. This presentation gives some research results in measurement field based on changing (tuning) the length of laser internal/external cavity, including 1) HeNe laser cavity-tuning nanometer displacement measurement instruments (laser nanometer rulers), 2) HeNe laser feedback displacement measurement, 3) Nd:YAG laser feedback nanometer displacement measurement, 4) benchmark of waveplate phase retardation measurement based on laser frequency splitting, 5) in-site waveplate phase retardation measurement instruments based on laser feedback and polarization hopping, 6) quasi-common-path microchip Nd:YAG laser feedback interferometer, 7) non-contact Nd:YAG laser feedback surface profile measurement. Some of these instruments have been put into application and display some irreplaceable advantages.

Experimental and computational laser tissue welding using a protein patch.

PubMed

Small, W; Heredia, N J; Maitland, D J; Eder, D C; Celliers, P M; Da Silva, L B; London, R A; Matthews, D L

1998-01-01

An in vitro study of laser tissue welding mediated with a dye-enhanced protein patch was conducted. Fresh sections of porcine aorta were used for the experiments. Arteriotomies were treated using an indocyanine green dye-enhanced collagen patch activated by an 805-nm continuous-wave fiber-delivered diode laser. Temperature histories of the surface of the weld site were obtained using a hollow glass optical fiber-based two-color infrared thermometer. The experimental effort was complemented by simulations with the LATIS (LAser-TISsue) computer code, which uses coupled Monte Carlo, thermal transport, and mass transport models. Comparison of simulated and experimental thermal data indicated that evaporative cooling clamped the surface temperature of the weld site below 100 °C. For fluences of approximately 200 J/cm2, peak surface temperatures averaged 74°C and acute burst strengths consistently exceeded 0.14×106 dyn/cm (hoop tension). The combination of experimental and simulation results showed that the inclusion of water transport and evaporative losses in the computer code has a significant impact on the thermal distributions and hydration levels throughout the tissue volume. The solid-matrix protein patch provided a means of controllable energy delivery and yielded consistently strong welds. © 1998 Society of Photo-Optical Instrumentation Engineers.

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.

Effects of vacuum exposure on stress and spectral shift of high reflective coatings

NASA Astrophysics Data System (ADS)

Stolz, C. J.; Taylor, J. R.; Eickelberg, W. K.; Lindh, J. D.

1992-06-01

The Atomic Vapor Laser Isotope Laser Separation (AVLIS) program operates the world's largest average power dye laser; the dye laser beams are combined, formatted, and transported in vacuum. The optical system is aligned at atmosphere, while the system must meet requirements in vacuum. Therefore, coating performance must be characterized in both atmosphere and vacuum. Changes in stress and spectral shift in ambient and vacuum environments are reported for conventional and dense multilayer dielectric coatings.

Direct and comprehensive analysis of dyes based on integrated molecular and structural information via laser desorption laser postionization mass spectrometry.

PubMed

Liu, Rong; Yin, Zhibin; Leng, Yixin; Hang, Wei; Huang, Benli

2018-01-01

Laser desorption laser postionization time-of-flight mass spectrometry (LDPI-TOFMS) was employed for direct analysis and determination of typical basic dyes. It was also used for the analysis and comprehensive understanding of complex materials such as blue ballpoint pen inks. Simultaneous emergences of fragmental and molecular information largely simplify and facilitate unambiguous identification of dyes via variable energy of 266nm postionization laser. More specifically, by optimizing postionization laser energy with the same energy of desorption laser, the structurally significant results show definite differences in the fragmentation patterns, which offer opportunities for discrimination of isomeric species with identical molecular weight. Moreover, relatively high spectra resolution can be acquired without the expense of sensitivity. In contrast to laser desorption/ionization mass spectrometry (LDI-MS), LDPI-MS simultaneously offers valuable molecular information about dyes in traces, solvents and additives about inks, thereby offering direct determination and comprehensive understanding of blue ballpoint inks and giving a high level of confidence to discriminate the complicated evidentiary samples. In addition, direct analysis of the inks not only allows the avoidance of the tedious sample preparation processes, significantly shortening the overall analysis time and improving throughput, but allows minimized sample consumption which is important for rare and precious samples. Copyright © 2017 Elsevier B.V. All rights reserved.

LASERS, ACTIVE MEDIA: The aqueous-polyelectrolyte dye solution as an active laser medium

NASA Astrophysics Data System (ADS)

Akimov, A. I.; Saletskii, A. M.

2000-11-01

The spectral, luminescent, and lasing properties of aqueous solutions of a cationic dye rhodamine 6G with additions of anion polyelectrolytes — polyacrylic and polymethacrylic acids — are studied. It is found that the energy and spectral properties of lasing of these solutions depend on the ratio of concentrations of polyelectrolyte and molecules. It is also found that the lasing parameters of aqueous-polyelectrolyte dye solutions can be controlled by changing the structure of the molecular system. The variation in the structure of aqueous-polyelectrolyte dye solutions of rhodamine 6G resulted in an almost five-fold increase in the lasing efficiency compared to that in aqueous dye solutions.

A cost-effective measurement-device-independent quantum key distribution system for quantum networks

NASA Astrophysics Data System (ADS)

Valivarthi, Raju; Zhou, Qiang; John, Caleb; Marsili, Francesco; Verma, Varun B.; Shaw, Matthew D.; Nam, Sae Woo; Oblak, Daniel; Tittel, Wolfgang

2017-12-01

We experimentally realize a measurement-device-independent quantum key distribution (MDI-QKD) system. It is based on cost-effective and commercially available hardware such as distributed feedback lasers and field-programmable gate arrays that enable time-bin qubit preparation and time-tagging, and active feedback systems that allow for compensation of time-varying properties of photons after transmission through deployed fiber. We examine the performance of our system, and conclude that its design does not compromise performance. Our demonstration paves the way for MDI-QKD-based quantum networks in star-type topology that extend over more than 100 km distance.

Theoretical studies on a new pattern of laser-driven systems: towards elucidation of direct photo-injection in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Mishima, Kenji; Yamashita, Koichi

2011-03-01

We theoretically and numerically investigated a new type of analytically solvable laser-driven systems inspired by electron-injection dynamics in dye-sensitized solar cells. The simple analytical expressions were found to be useful for understanding the difference between dye excitation and direct photo-injection occurring between dye molecule and semiconductor nanoparticles. More importantly, we propose a method for discriminating experimentally dye excitation and direct photo-injection by using time-dependent fluorescence. We found that dye excitation shows no significant quantum beat whereas the direct photo-injection shows a significant quantum beat. This work was supported by Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST) ``Development of Organic Photovoltaics toward a Low-Carbon Society,'' Cabinet Office, Japan.

Monolithically integrated mid-infrared sensor using narrow mode operation and temperature feedback

NASA Astrophysics Data System (ADS)

Ristanic, Daniela; Schwarz, Benedikt; Reininger, Peter; Detz, Hermann; Zederbauer, Tobias; Andrews, Aaron Maxwell; Schrenk, Werner; Strasser, Gottfried

2015-01-01

A method to improve the sensitivity and selectivity of a monolithically integrated mid-infrared sensor using a distributed feedback laser (DFB) is presented in this paper. The sensor is based on a quantum cascade laser/detector system built from the same epitaxial structure and with the same fabrication approach. The devices are connected via a dielectric-loaded surface plasmon polariton waveguide with a twofold function: it provides high light coupling efficiency and a strong interaction of the light with the environment (e.g., a surrounding fluid). The weakly coupled DFB quantum cascade laser emits narrow mode light with a FWHM of 2 cm-1 at 1586 cm-1. The room temperature laser threshold current density is 3 kA/cm2 and a pulsed output power of around 200 mW was measured. With the superior laser noise performance, due to narrow mode emission and the compensation of thermal fluctuations, the lower limit of detection was expanded by one order of magnitude to the 10 ppm range.

Fluorescence lifetime imaging with near-infrared dyes

NASA Astrophysics Data System (ADS)

Becker, Wolfgang; Shcheslavskiy, Vladislav

2013-02-01

Near-infrared (NIR) dyes are used as fluorescence markers in small-animal imaging and in diffuse optical tomography of the human brain. In these applications it is important to know whether the dyes bind to proteins or other tissue constituents, and whether their fluorescence lifetimes depend on the targets they are bound to. Unfortunately, neither the lasers nor the detectors of commonly used confocal and multiphoton laser scanning microscopes allow for excitation and detection of NIR fluorescence. We therefore upgraded existing confocal TCSPC FLIM systems with NIR lasers and NIR sensitive detectors. In multiphoton systems we used the Ti:Sa laser as a one-photon excitation source in combination with an NIR-sensitive detector in the confocal beam path. We tested a number of NIR dyes in biological tissue. Some of them showed clear lifetime changes depending on the tissue structures they are bound to. We therefore believe that NIR FLIM can deliver supplementary information on the tissue constitution and on local biochemical parameters.

Laser performance of Coumarin 540A dye molecules in polymeric host media with different viscosities: From liquid solution to solid polymer matrix

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

Costela, A.; Garcia-Moreno, I.; Barroso, J.

1998-01-01

Photophysical parameters and lasing properties of Coumarin 540A dye molecules are studied in solutions of increasing viscosity, from liquid solutions in 1,4-dioxane to solid solutions in poly(methyl methacrylate). The fluorescence quantum yield and lasing efficiencies decrease as the viscosity of the solution increases, reflecting the strong influence of the rigidity of the medium on the radiative processes. The photodegradation mechanisms acting on the fluorophores are analyzed by following the dependence of laser induced fluorescence and laser output on the number of pump laser pulses. The fluorescence redistribution after pattern photobleaching technique is used, and Fick{close_quote}s second law is applied tomore » study the diffusion of dye molecules in the highly viscous polymer solutions. The diffusion coefficients of the dye molecules as a function of the increased viscosity of the medium are determined. {copyright} {ital 1998 American Institute of Physics.}« less

Controlling Brownian motion of single protein molecules and single fluorophores in aqueous buffer.

PubMed

Cohen, Adam E; Moerner, W E

2008-05-12

We present an Anti-Brownian Electrokinetic trap (ABEL trap) capable of trapping individual fluorescently labeled protein molecules in aqueous buffer. The ABEL trap operates by tracking the Brownian motion of a single fluorescent particle in solution, and applying a time-dependent electric field designed to induce an electrokinetic drift that cancels the Brownian motion. The trapping strength of the ABEL trap is limited by the latency of the feedback loop. In previous versions of the trap, this latency was set by the finite frame rate of the camera used for video-tracking. In the present system, the motion of the particle is tracked entirely in hardware (without a camera or image-processing software) using a rapidly rotating laser focus and lock-in detection. The feedback latency is set by the finite rate of arrival of photons. We demonstrate trapping of individual molecules of the protein GroEL in buffer, and we show confinement of single fluorophores of the dye Cy3 in water.

Development of Advanced Seed Laser Modules for Lidar and Spectroscopy Applications

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Rosiewicz, Alex; Coleman, Steven M.

2013-01-01

We report on recent progress made in the development of highly compact, single mode, distributed feedback laser (DFB) seed laser modules for lidar and spectroscopy applications from space based platforms. One of the intended application of this technology is in the NASA's Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission. The DFB laser modules operating at 1571 nm and 1262 nm have advanced current and temperature drivers built into them. A combination of temperature and current tuning allows coarse and fine adjustment of the diode wavelengths.

An Ambipolar BODIPY Derivative for a White Exciplex OLED and Cholesteric Liquid Crystal Laser toward Multifunctional Devices.

PubMed

Chapran, Marian; Angioni, Enrico; Findlay, Neil J; Breig, Benjamin; Cherpak, Vladyslav; Stakhira, Pavlo; Tuttle, Tell; Volyniuk, Dmytro; Grazulevicius, Juozas V; Nastishin, Yuriy A; Lavrentovich, Oleg D; Skabara, Peter J

2017-02-08

A new interface engineering method is demonstrated for the preparation of an efficient white organic light-emitting diode (WOLED) by embedding an ultrathin layer of the novel ambipolar red emissive compound 4,4-difluoro-2,6-di(4-hexylthiopen-2-yl)-1,3,5,7,8-pentamethyl-4-bora-3a,4a-diaza-s-indacene (bThBODIPY) in the exciplex formation region. The compound shows a hole and electron mobility of 3.3 × 10 -4 and 2 × 10 -4 cm 2 V -1 s -1 , respectively, at electric fields higher than 5.3 × 10 5 V cm -1 . The resulting WOLED exhibited a maximum luminance of 6579 cd m -2 with CIE 1931 color coordinates (0.39; 0.35). The bThBODIPY dye is also demonstrated to be an effective laser dye for a cholesteric liquid crystal (ChLC) laser. New construction of the ChLC laser, by which a flat capillary with an optically isotropic dye solution is sandwiched between two dye-free ChLC cells, provides photonic lasing at a wavelength well matched with that of a dye-doped planar ChLC cell.

Comparison of different laser systems in the treatment of hypertrophic and atrophic scars and keloids

NASA Astrophysics Data System (ADS)

Scharschmidt, D.; Algermissen, Bernd; Willms-Jones, J.-C.; Philipp, Carsten M.; Berlien, Hans-Peter

1997-12-01

Different laser systems and techniques are used for the treatment of hypertrophic scars, keloids and acne scars. Significant criteria in selecting a suitable laser system are the scar's vascularization, age and diameter. Flashlamp- pumped dye-lasers, CO2-lasers with scanner, Argon and Nd:YAG-lasers are used. Telangiectatic scars respond well to argon lasers, erythematous scars and keloids to dye-laser treatment. Using interstitial Nd:YAG-laser vaporization, scars with a cross-section over 1 cm can generally be reduced. For the treatment of atrophic and acne scars good cosmetic results are achieved with a CO2-laser/scanner system, which allows a precise ablation of the upper dermis with low risk of side-effects.

Narrow-stripe broad-area lasers with distributed-feedback surface gratings as brilliant sources for high power spectral beam combining systems

NASA Astrophysics Data System (ADS)

Decker, J.; Crump, P.; Fricke, J.; Wenzel, H.; Maaβdorf, A.; Erbert, G.; Tränkle, G.

2014-03-01

Laser systems based on spectral beam combining (SBC) of broad-area (BA) diode lasers are promising tools for material processing applications. However, the system brightness is limited by the in-plane beam param- eter product, BPP, of the BA lasers, which operate with a BPP of < 3mm-mrad. The EU project BRIDLE (www.bridle.eu) is developing novel diode laser sources for such systems, and several technological advances are sought. For increased system brightness and optimal ber-coupling the diode lasers should operate with reduced BPP and vertical far eld angle (95% power content), μV 95. The resulting diode lasers are fabricated as mini- bars for reduced assembly costs. Gratings are integrated into the mini-bar, with each laser stripe emitting at a different wavelength. In this way, each emitter can be directed into a single bre via low-cost dielectric filters. Distributed-feedback narrow-stripe broad-area (DFB-NBA) lasers are promising candidates for these SBC sys- tems. We review here the design process and performance achieved, showing that DFB-NBA lasers with stripe width, W = 30 μm, successfully cut of higher-order lateral modes, improving BPP. Uniform, surface-etched, 80th-order Bragg gratings are used, with weak gratings essential for high e ciency. To date, such DFB-NBA sources operate with < 50% effciency at output power, Pout < 6 W, with BPP < 1.8 mm-mrad and offV 95 36 . The emission wavelength is about 970 nm and the spectral width is < 0.7 nm (95% power). The BPP is half that of a DFB-BA lasers with W = 90 um. We conclude with a review of options for further performance improvements.

Flow and thermal characteristics of high Reynolds number (2800-17,000) dye cell: simulation and experiment.

PubMed

Mishra, G K; Kumar, Abhay; Prakash, O; Biswal, R; Dixit, S K; Nakhe, S V

2015-04-10

This paper presents computational and experimental studies on wavelength/frequency fluctuation characteristics of a high pulse repetition rate (18 kHz) dye laser pumped by a frequency-doubled Nd:YAG laser (532 nm). The temperature gradient in the dye solution is found to be responsible for wavelength fluctuations of the dye laser at low flow rates (2800

Variations in thermo-optical properties of neutral red dye with laser ablated gold nanoparticles

NASA Astrophysics Data System (ADS)

Prakash, Anitha; Pathrose, Bini P.; Mathew, S.; Nampoori, V. P. N.; Radhakrishnan, P.; Mujeeb, A.

2018-05-01

We have investigated the thermal and optical properties of neutral red dye incorporated with different weight percentage of gold nanoparticles prepared by laser ablation method. Optical absorption studies confirmed the production of spherical nanoparticles and also the interactions of the dye molecules with gold nanoparticles. The quenching of fluorescence and the reduction in the lifetime of gold incorporated samples were observed and was due to the non-radiative energy transfer between the dye molecules and gold nanoparticles. Dual beam thermal lens technique has been employed to measure the heat diffusion in neutral red with various weight percentage of gold nano sol dispersed in ethanol. The significant outcome of the experiment is that, the overall heat diffusion is slower in the presence of gold nano sol compared to that of dye alone sample. Brownian motion is suggested to be the main mechanism of heat transfer under the present conditions. The thermal diffusivity variations of samples with respect to different excitation power of laser were also studied.

Intracavity absorption with a continuous wave dye laser - Quantification for a narrowband absorber

NASA Technical Reports Server (NTRS)

Brobst, William D.; Allen, John E., Jr.

1987-01-01

An experimental investigation of the dependence of intracavity absorption on factors including transition strength, concentration, absorber path length, and pump power is presented for a CW dye laser with a narrow-band absorber (NO2). A Beer-Lambert type relationship is found over a small but useful range of these parameters. Quantitative measurement of intracavity absorption from the dye laser spectral profiles showed enhancements up to 12,000 (for pump powers near lasing threshold) when compared to extracavity measurements. The definition of an intracavity absorption coefficient allowed the determination of accurate transition strength ratios, demonstrating the reliability of the method.

Single-mode surface plasmon distributed feedback lasers.

PubMed

Karami Keshmarzi, Elham; Tait, R Niall; Berini, Pierre

2018-03-29

Single-mode surface plasmon distributed feedback (DFB) lasers are realized in the near infrared using a two-dimensional non-uniform long-range surface plasmon polariton structure. The surface plasmon mode is excited onto a 20 nm-thick, 1 μm-wide metal stripe (Ag or Au) on a silica substrate, where the stripe is stepped in width periodically, forming a 1st order Bragg grating. Optical gain is provided by optically pumping a 450 nm-thick IR-140 doped PMMA layer as the top cladding, which covers the entire length of the Bragg grating, thus creating a DFB laser. Single-mode lasing peaks of very narrow linewidth were observed for Ag and Au DFBs near 882 nm at room temperature. The narrow linewidths are explained by the low spontaneous emission rate into the surface plasmon lasing mode as well as the high quality factor of the DFB structure. The lasing emission is exclusively TM polarized. Kinks in light-light curves accompanied by spectrum narrowing were observed, from which threshold pump power densities can be clearly identified (0.78 MW cm-2 and 1.04 MW cm-2 for Ag and Au DFB lasers, respectively). The Schawlow-Townes linewidth for our Ag and Au DFB lasers is estimated and very narrow linewidths are predicted for the lasers. The lasers are suitable as inexpensive, recyclable and highly coherent sources of surface plasmons, or for integration with other surface plasmon elements of similar structure.

Experimental study of cavity configurations for dye lasers pumped by a copper vapor laser

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

Tang Chaunshun; Sun Wei

1988-04-01

Four cavity configurations are considered for dye lasers pumped transversely by a CuBr laser at high pulse repetition frequencies. Their operating characteristics are compared. Optimum performance is found for a double-prism expander cavity equipped with a Littrow mounted grating. A single longitudinal mode lasing in the 598--640 nm range was achieved with a linewidth of 0.0012 nm and a conversion of efficiency of 7.5%, respectively. The amplified spontaneous emission was 1.5%.

Fiber optic laser rod

DOEpatents

Erickson, G.F.

1988-04-13

A laser rod is formed from a plurality of optical fibers, each forming an individual laser. Synchronization of the individual fiber lasers is obtained by evanescent wave coupling between adjacent optical fiber cores. The fiber cores are dye-doped and spaced at a distance appropriate for evanescent wave coupling at the wavelength of the selected dye. An interstitial material having an index of refraction lower than that of the fiber core provides the optical isolation for effective lasing action while maintaining the cores at the appropriate coupling distance. 2 figs.

Bichromatic emission in a ring dye laser

NASA Technical Reports Server (NTRS)

Lawandy, N. M.; Sohrab Afzal, R.; Rabinovich, W. S.

1987-01-01

An experimental study of a high-Q Rhodamine 6G ring dye laser has been performed, and bichromatic emission (BE) with wavelength spacings as large as 110 A when the laser operated bidirectionally has been measured. The BE vanished at all excitations when the laser was forced into unidirectional operation using a Faraday isolator. However, when a weak reflected beam was allowed to make a single pass in the direction opposite to that allowed by the Faraday device, BE is recovered at the higher pump powers.

Near-IR laser frequency standard stabilized using FM-spectroscopy

NASA Astrophysics Data System (ADS)

Ružička, Bohdan; Číp, Ondřej; Lazar, Josef

2006-02-01

At the present time fiber-optics and optical communication are in rapid progress. Modern technologies such as DWDM (Dense Wavelength Division Multiplex) need precise stability of laser frequencies. According to this fact, requirements of new etalons of optical frequencies in the telecommunication band is rapidly growing. Lasers working in near infrared telecommunication band (1500-1600 nm) can be stabilized to 12C IIH II or 13C IIH II (acetylene) gas absorption lines. The acetylene gas absorption has been widely studied and accepted by international bodies of standardization as a primary wavelength reference in the near infrared band around 1550nm. Our aim was to design and develop a compact fibre optics laser system generating coherent light in near-JR band with high frequency stability (at least 1.10 -8). This system should become a base for realization of a primary frequency standard for optical communications in the Czech Republic. Such an etalon will be needed for calibration of wavelength-meters and spectral analysers for DWDM communication systems. We are co-operating with CMI (Czech Metrology Institute) on this project. We present stabilized laser system based on a single frequency DFB (Distributed Feedback) laser diode with a narrow spectral profile. The laser is pre-stabilized by means of the FM-spectroscopy on a passive resonator. Thanks to a fast feed-back loop we are able to improve spectral characteristics of the laser. The laser frequency is locked by a relatively slow second feed-back loop on an absorption line of acetylene vapour which is sealed in a cell under the optimised pressure.

Self-assembled dye-doped polymer microspheres as whispering gallery mode lasers

NASA Astrophysics Data System (ADS)

Chen, Xiaogang; Sun, Hongyi; Yang, Hongqin; Wu, Xiang; Xie, Shusen

2016-10-01

Microlasers based on high-Q whispering-gallery-mode (WGM) resonances are promising low-threshold laser sources for bio-sensing and imaging applications. In this talk, we demonstrate a cost effective approach to obtain size-controllable polymer microspheres, which can be served as good WGM microcavities. By injecting SU-8 solution into low-refractiveindex UV polymer, self-assembled spherical droplet with smooth surface can be created inside the elastic medium and then solidified by UV exposure. The size of the microspheres can be tuned from several to hundreds of microns. WGM Lasing has been achieved by optically pumping the dye-doped microspheres with ns lasers. Experimental results show that the microsphere lasers have high quality factors and low lasing thresholds. The self-assembled dye-doped polymer microspheres would provide an excellent platform for the micro-laser sources in on-chip biosensing and imaging systems.

Random lasing from dye-doped negative liquid crystals using ZnO nanoparticles as tunable scatters

NASA Astrophysics Data System (ADS)

Li, Long-Wu; Shang, Zhen-Zhen; Deng, Luogen

2016-09-01

This work demonstrates the realization of a lasing in scattering media, which contains dispersive solution of ZnO nanoparticles (NPs) and laser dye 4-dicyanomethylene-2-methyle-6-(p-dimethylaminostyryl)-4H-pyran(DCM) in negative liquid crystals (LCs) that was injected into a cell. The lasing intensity of the dye-doped negative LC laser can be tuned from low to high if the NPs concentration is increased. The tunability of the laser is attributable to the clusters-sensitive feature in effective refractive index of the negative LCs. Such a tunable negative liquid crystal laser can be used in the fabrication of new optical sources, optical communication, and liquid crystal laser displays. Project supported by the Doctoral Science Research Start-up Funding of Guizhou Normal University, China (Grant No. 11904-0514162) and the National Natural Science Foundation of China (Grant No. 11474021).

Photophysics of Laser Dye-Doped Polymer Membranes for Laser-Induced Fluorescence Photogrammetry

NASA Technical Reports Server (NTRS)

Dorrington, Adrian A.; Jones, Thomas W.; Danehy, Paul M.

2004-01-01

Laser-induced fluorescence target generation in dye-doped polymer films has recently been introduced as a promising alternative to more traditional photogrammetric targeting techniques for surface profiling of highly transparent or reflective membrane structures. We investigate the photophysics of these dye-doped polymers to help determine their long-term durability and suitability for laser-induced fluorescence photogrammetric targeting. These investigations included experimental analysis of the fluorescence emission pattern, spectral content, temporal lifetime, linearity, and half-life. Results are presented that reveal an emission pattern wider than normal Lambertian diffuse surface scatter, a fluorescence time constant of 6.6 ns, a pump saturation level of approximately 20 micro J/mm(exp 2), and a useful lifetime of more than 300,000 measurements. Furthermore, two demonstrations of photogrammetric measurements by laser-induced fluorescence targeting are presented, showing agreement between photogrammetric and physically measured dimensions within the measurement scatter of 100 micron.

Characterization of Fluorescent Polystyrene Microspheres for Advanced Flow Diagnostics

NASA Technical Reports Server (NTRS)

Maisto, Pietro M. F.; Lowe, K. Todd; Byun, Guibo; Simpson, Roger; Vercamp, Max; Danley, Jason E.; Koh, Brian; Tiemsin, Pacita; Danehy, Paul M.; Wohl, Christopher J.

2013-01-01

Fluorescent dye-doped polystyrene latex microspheres (PSLs) are being developed for velocimetry and scalar measurements in variable property flows. Two organic dyes, Rhodamine B (RhB) and dichlorofluorescence (DCF), are examined to assess laser-induced fluorescence (LIF) properties for flow imaging applications and single-shot temperature measurements. A major interest in the current research is the application of safe dyes, thus DCF is of particular interest, while RhB is used as a benchmark. Success is demonstrated for single-point laser Doppler velocimetry (LDV) and also imaging fluorescence, excited via a continuous wave 2 W laser beam, for exposures down to 10 ms. In contrast, when exciting with a pulsed Nd:YAG laser at 200 mJ/pulse, no fluorescence was detected, even when integrating tens of pulses. We show that this is due to saturation of the LIF signal at relatively low excitation intensities, 4-5 orders of magnitude lower than the pulsed laser intensity. A two-band LIF technique is applied in a heated jet, indicating that the technique effectively removes interfering inputs such as particle diameter variation. Temperature measurement uncertainties are estimated based upon the variance measured for the two-band LIF intensity ratio and the achievable dye temperature sensitivity, indicating that particles developed to date may provide about +/-12.5 C precision, while future improvements in dye temperature sensitivity and signal quality may enable single-shot temperature measurements with sub-degree precision.

Violet laser diodes as light sources for cytometry.

PubMed

Shapiro, H M; Perlmutter, N G

2001-06-01

Violet laser diodes have recently become commercially available. These devices emit 5-25 mW in the range of 395-415 nm, and are available in systems that incorporate the diodes with collimating optics and regulated power supplies in housing incorporating thermoelectric coolers, which are necessary to maintain stable output. Such systems now cost several thousand dollars, but are expected to drop substantially in price. Materials and Methods A 4-mW, 397-nm violet diode system was used in a laboratory-built flow cytometer to excite fluorescence of DAPI and Hoechst dyes in permeabilized and intact cells. Forward and orthogonal light scattering were also measured. DNA content histograms with good precision (G(0)/G(1) coefficient of variation 1.7%) were obtained with DAPI staining; precision was lower using Hoechst 33342. Hoechst 34580, with an excitation maximum nearer 400 nm, yielded the highest fluorescence intensity, but appeared to decompose after a short time in solution. Scatter signals exhibited relatively broad distributions. Violet laser diodes are relatively inexpensive, compact, efficient, and quiet light sources for DNA fluorescence measurement using DAPI and Hoechst dyes; they can also excite several other fluorescent probes. Copyright 2001 Wiley-Liss, Inc.

Monolithic dye laser amplifier

DOEpatents

Kuklo, T.C.

1993-03-30

A fluid dye laser amplifier for amplifying a dye beam by pump beams has a channel structure defining a channel through which a laseable fluid flows and the dye and pump beams pass transversely to one another through a lasing region. The channel structure is formed with two pairs of mutually spaced-apart and mutually confronting glass windows, which are interlocked and make surface-contacts with one another and surround the lasing region. One of the glass window pairs passes the dye beam and the other passes the pump beams therethrough and through the lasing region. Where these glass window pieces make surface-contacts, glue is used to join the pieces together to form a monolithic structure so as to prevent the dye in the fluid passing through the channel from entering the space between the mutually contacting glass window pieces.

Monolithic dye laser amplifier

DOEpatents

Kuklo, Thomas C.

1993-01-01

A fluid dye laser amplifier for amplifying a dye beam by pump beams has a channel structure defining a channel through which a laseable fluid flows and the dye and pump beams pass transversely to one another through a lasing region. The channel structure is formed with two pairs of mutually spaced-apart and mutually confronting glass windows, which are interlocked and make surface-contacts with one another and surround the lasing region. One of the glass window pairs passes the dye beam and the other passes the pump beams therethrough and through the lasing region. Where these glass window pieces make surface-contacts, glue is used to join the pieces together to form a monolithic structure so as to prevent the dye in the fluid passing through the channel from entering the space between the mutually contacting glass window pieces.

Master dye laser oscillator including a specific grating assembly for use therein

DOEpatents

Davin, James M.

1992-01-01

A dye laser oscillator for producing a tuned dye beam is disclosed herein and includes, among other components, a beam output coupling assembly, a dye cell assembly, a beam expander assembly, an etalon assembly, and a grating assembly. Each of three assemblies is vertically supported from a horizontal base so as to be readily removable from the base without interference from or interfering with the other assemblies. The particular grating assembly disclosed is specifically designed for proper optical alignment with the intended path of the dye beam to be produced and for accurate pivotal movement relative to the beam path in order to function as a coarse tuning mechanism in the production of the ultimately tuned beam.

Master dye laser oscillator including a specific grating assembly for use therein

DOEpatents

Davin, J.M.

1992-09-01

A dye laser oscillator for producing a tuned dye beam is disclosed herein and includes, among other components, a beam output coupling assembly, a dye cell assembly, a beam expander assembly, an etalon assembly, and a grating assembly. Each of three assemblies is vertically supported from a horizontal base so as to be readily removable from the base without interference from or interfering with the other assemblies. The particular grating assembly disclosed is specifically designed for proper optical alignment with the intended path of the dye beam to be produced and for accurate pivotal movement relative to the beam path in order to function as a coarse tuning mechanism in the production of the ultimately tuned beam. 5 figs.

Distributed feedback lasers

NASA Technical Reports Server (NTRS)

Ladany, I.; Andrews, J. T.; Evans, G. A.

1988-01-01

A ridge waveguide distributed feedback laser was developed in InGaAsP. These devices have demonstrated CW output powers over 7 mW with threshold currents as low as 60 mA at 25 C. Measurements of the frequency response of these devices show a 3 dB bandwidth of about 2 GHz, which may be limited by the mount. The best devices have a single mode spectra over the entire temperature range tested with a side mode suppression of about 20 dB in both CW and pulsed modes. The design of this device, including detailed modeling of the ridge guide structure, effective index calculations, and a discussion of the grating configuration are presented. Also, the fabrication of the devices is presented in some detail, especially the fabrication of and subsequent growth over the grating. In addition, a high frequency fiber pigtailed package was designed and tested, which is a suitable prototype for a commercial package.

Efficient Third-Order Distributed Feedback Laser with Enhanced Beam Pattern

NASA Technical Reports Server (NTRS)

Hu, Qing (Inventor); Lee, Alan Wei Min (Inventor); Kao, Tsung-Yu (Inventor)

2015-01-01

A third-order distributed feedback laser has an active medium disposed on a substrate as a linear array of segments having a series of periodically spaced interstices therebetween and a first conductive layer disposed on a surface of the active medium on each of the segments and along a strip from each of the segments to a conductive electrical contact pad for application of current along a path including the active medium. Upon application of a current through the active medium, the active medium functions as an optical waveguide, and there is established an alternating electric field, at a THz frequency, both in the active medium and emerging from the interstices. Spacing of adjacent segments is approximately half of a wavelength of the THz frequency in free space or an odd integral multiple thereof, so that the linear array has a coherence length greater than the length of the linear array.

Frequency locking and monitoring based on Bi-directional terahertz radiation of a 3 rd-order distributed feedback quantum cascade laser

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

van Marrewijk, N.; Mirzaei, B.; Hayton, D.

2015-10-07

In this study, we have performed frequency locking of a dual, forward reverse emitting third-order distributed feedback quantum cascade laser (QCL) at 3.5 THz. By using both directions of THz emission in combination with two gas cells and two power detectors, we can for the first time perform frequency stabilization, while monitor the frequency locking quality independently. We also characterize how the use of a less sensitive pyroelectric detector can influence the quality of frequency locking, illustrating experimentally that the sensitivity of the detectors is crucial. Using both directions of terahertz (THz) radiation has a particular advantage for the applicationmore » of a QCL as a local oscillator, where radiation from one side can be used for frequency/phase stabilization, leaving the other side to be fully utilized as a local oscillator to pump a mixer.« less

Studies of third-order optical nonlinearities and optical limiting properties of azo dyes.

PubMed

Gayathri, C; Ramalingam, A

2008-03-01

In order to protect optical sensors and human eyes from debilitating laser effects, the intensity of the incoming laser light has to be opportunely reduced. Here, we report our results on the third-order optical nonlinearity and optical limiting properties of three azo dyes exposed to a 532nm continuous wave laser. We have observed low power optical limiting based on nonlinear refraction in our samples.

Photophysical parameters and laser performance of 3-(4‧-dimethylaminophenyl)-1-(2-furanyl)prop-2-en-1-one (DMAFP): A new laser dye

NASA Astrophysics Data System (ADS)

El-Daly, S. A.; Gaber, M.; El-Sayed, Y. S.

2009-09-01

The spectral properties such as singlet absorption, molar absorptivity, emission spectra, fluorescence quantum yield and excited state lifetime of 3-(4'-dimethylaminophenyl)-1-(2-furanyl)prop-2-en-1-one (DMAFP) have been determined in different solvents. DMAFP dye exhibits a large red shift in both electronic absorption and emission spectra as the solvent polarity increases, indicating a large change in the dipole moment of molecules upon excitation. A crystalline solid of DMAFP gives an excimer like emission at 566 nm due to the excitation of molecular aggregates. This is expected from the idealized crystal structure of the dye that belongs to the B-type class of Steven's classification. The ground and excited state protonation constants of DMAFP are calculated and amounted to 1.71 and 8.3, respectively. DMAFP acts as a good laser dye upon pumping with nitrogen laser ( λex=337.1 nm) in chloroform, methylene chloride and dioxane and gives laser emission in the range 460-590 nm. The laser parameters such as the tuning range, gain coefficient ( α), emission cross section ( σ e) and half-life energy ( E1/2) are calculated. The photoreactivity and net photochemical quantum yield of DMAFP in chloromethane solvents are also studied.

Combined pulsed dye and CO2 lasers in the treatment of angiolymphoid hyperplasia with eosinophilia.

PubMed

Sagi, Lior; Halachmi, Shlomit; Levi, Assi; Amitai, Dan Ben; Enk, Claes D; Lapidoth, Moshe

2016-08-01

Angiolymphoid hyperplasia with eosinophilia (ALHE) is an uncommon dermatosis of unknown etiology that manifests as characteristic red nodules and papules with a predilection for the scalp and periauricular region. Treatment is required for both esthetic and functional reasons, as lesions may ulcerate and bleed. Many treatment approaches have been reported, including excision, systemic medical approaches, topical or intralesional therapies, and non-invasive modalities including cryotherapy, electrosurgery, and laser. Treatments have exhibited variable efficacy, and the recurrence rate is 100 %. We report the combination of pulsed dye laser and CO2 laser in the treatment of ALHE in 14 patients. All patients exhibited clinical response after a mean of 2.4 ± 0.4 treatment sessions. The clinical efficacy of the combined treatment, together with its well-tolerated nature, render the use of pulsed dye laser in combination with CO2 laser, a viable treatment for debulking ALHE lesions. Ongoing maintenance treatments are needed to due to the high degree of relapse.

Superradiant laser emission from rhodamine 6G and rhodamine B using a coaxial flashpump.

NASA Technical Reports Server (NTRS)

Mumola, P. B.

1972-01-01

Superradiant laser emission has been observed from ethanol solutions of rhodamine 6G and rhodamine B using a coaxial flashlamp pump. The dependence of input threshold energy on dye concentration is examined. The possibility of exciting other dyes to superradiance is discussed.

Convenient Microscale Synthesis of a Coumarin Laser Dye Analog

ERIC Educational Resources Information Center

Aktoudianakis, Evangelos; Dicks, Andrew P.

2006-01-01

Coumarin (2H-1-benzopyran-2-one) and its derivatives constitute a fascinating class of organic substances that are utilized industrially in areas such as cosmetics, food preservatives, insecticides and fluorescent laser dyes. The product can be synthesized, purified, and characterized within two hours with benefits of microscale reactivity being…

Tissue temperature distribution measurement by MRI and laser immunology for cancer treatment

NASA Astrophysics Data System (ADS)

Chen, Yichao; Gnyawali, Surya C.; Wu, Feng; Liu, Hong; Tesiram, Yasvir A.; Abbott, Andrew; Towner, Rheal A.; Chen, Wei R.

2007-02-01

In cancer treatment and immune response enhancement research, Magnetic Resonance Imaging (MRI) is an ideal method for non-invasive, three-dimensional temperature measurement. We used a 7.1-Tesla magnetic resonance imager for ex vivo tissues and small animal to determine temperature distribution of target tissue during laser irradiation. The feasibility of imaging is approved with high spatial resolution and high signal-noise- ratio. Tissue-simulating gel phantom gel, biological tissues, and tumor-bearing animals were used in the experiments for laser treatment and MR imaging. Thermal couple measurement of temperature in target samples was used for system calibration. An 805-nm laser was used to irradiate the samples with a laser power in the range of 1 to 2.5 watts. Using the MRI system and a specially developed processing algorithm, a clear temperature distribution matrix in the target tissue and surrounding tissue was obtained. The temperature profiles show that the selective laser photothermal effect could result in tissue temperature elevation in a range of 10 to 45 °C. The temperature resolution of the measurement was about 0.37°C including the total system error. The spatial resolution was 0.4 mm (128x128 pixels with field of view of 5.5x5.5 cm). The temperature distribution provided in vivo thermal information and future reference for optimizing dye concentration and irradiation parameters to achieve optimal thermal effects in cancer treatment.

Direct writing of tunable multi-wavelength polymer lasers on a flexible substrate.

PubMed

Zhai, Tianrui; Wang, Yonglu; Chen, Li; Zhang, Xinping

2015-08-07

Tunable multi-wavelength polymer lasers based on two-dimensional distributed feedback structures are fabricated on a transparent flexible substrate using interference ablation. A scalene triangular lattice structure was designed to support stable tri-wavelength lasing emission and was achieved through multiple exposure processes. Three wavelengths were controlled by three periods of the compound cavity. Mode competition among different cavity modes was observed by changing the pump fluence. Both a redshift and blueshift of the laser wavelength could be achieved by bending the soft substrate. These results not only provide insight into the physical mechanisms behind co-cavity polymer lasers but also introduce new laser sources and laser designs for white light lasers.

Unidirectional photonic wire laser

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

Khalatpour, Ali; Reno, John L.; Kherani, Nazir P.

Photonic wire lasers are a new genre of lasers that have a transverse dimension much smaller than the wavelength. Unidirectional emission is highly desirable as most of the laser power will be in the desired direction. Owing to their small lateral dimension relative to the wavelength, however, the mode mostly propagates outside the solid core. Consequently, conventional approaches to attach a highly reflective element to the rear facet, whether a thin film or a distributed Bragg reflector, are not applicable. In this paper, we propose a simple and effective technique to achieve unidirectionality. Terahertz quantum-cascade lasers with distributed feedback (DFB)more » were chosen as the platform of the photonic wire lasers. Unidirectionality is achieved with a power ratio of the forward/backward of about eight, and the power of the forward-emitting laser is increased by a factor of 1.8 compared with a reference bidirectional DFB laser. Finally and furthermore, we achieved a wall plug power efficiency of ~1%.« less

Unidirectional photonic wire laser

DOE PAGES

Khalatpour, Ali; Reno, John L.; Kherani, Nazir P.; ...

2017-08-07

Photonic wire lasers are a new genre of lasers that have a transverse dimension much smaller than the wavelength. Unidirectional emission is highly desirable as most of the laser power will be in the desired direction. Owing to their small lateral dimension relative to the wavelength, however, the mode mostly propagates outside the solid core. Consequently, conventional approaches to attach a highly reflective element to the rear facet, whether a thin film or a distributed Bragg reflector, are not applicable. In this paper, we propose a simple and effective technique to achieve unidirectionality. Terahertz quantum-cascade lasers with distributed feedback (DFB)more » were chosen as the platform of the photonic wire lasers. Unidirectionality is achieved with a power ratio of the forward/backward of about eight, and the power of the forward-emitting laser is increased by a factor of 1.8 compared with a reference bidirectional DFB laser. Finally and furthermore, we achieved a wall plug power efficiency of ~1%.« less

Digitally controlled chirped pulse laser for sub-terahertz-range fiber structure interrogation.

PubMed

Chen, Zhen; Hefferman, Gerald; Wei, Tao

2017-03-01

This Letter reports a sweep velocity-locked laser pulse generator controlled using a digital phase-locked loop (DPLL) circuit. This design is used for the interrogation of sub-terahertz-range fiber structures for sensing applications that require real-time data collection with millimeter-level spatial resolution. A distributed feedback laser was employed to generate chirped laser pulses via injection current modulation. A DPLL circuit was developed to lock the optical frequency sweep velocity. A high-quality linearly chirped laser pulse with a frequency excursion of 117.69 GHz at an optical communication band was demonstrated. The system was further adopted to interrogate a continuously distributed sub-terahertz-range fiber structure (sub-THz-fs) for sensing applications. A strain test was conducted in which the sub-THz-fs showed a linear response to longitudinal strain change with predicted sensitivity. Additionally, temperature testing was conducted in which a heat source was used to generate a temperature distribution along the fiber structure to demonstrate its distributed sensing capability. A Gaussian temperature profile was measured using the described system and tracked in real time, as the heat source was moved.

High performance organic distributed Bragg reflector lasers fabricated by dot matrix holography.

PubMed

Wan, Wenqiang; Huang, Wenbin; Pu, Donglin; Qiao, Wen; Ye, Yan; Wei, Guojun; Fang, Zongbao; Zhou, Xiaohong; Chen, Linsen

2015-12-14

We report distributed Bragg reflector (DBR) polymer lasers fabricated using dot matrix holography. Pairs of distributed Bragg reflector mirrors with variable mirror separations are fabricated and a novel energy transfer blend consisting of a blue-emitting conjugated polymer and a red-emitting one is spin-coated onto the patterned substrate to complete the device. Under optical pumping, the device emits sing-mode lasing around 622 nm with a bandwidth of 0.41 nm. The working threshold is as low as 13.5 μJ/cm² (~1.68 kW/cm²) and the measured slope efficiency reaches 5.2%. The distributed feedback (DFB) cavity and the DBR cavity resonate at the same lasing wavelength while the DFB laser shows a much higher threshold. We further show that flexible DBR lasers can be conveniently fabricated through the UV-imprinting technique by using the patterned silica substrate as the mold. Dot matrix holography represents a versatile approach to control the number, the size, the location and the orientation of DBR mirrors, thus providing great flexibility in designing DBR lasers.

Efficient sintering of nanocrystalline titanium dioxide films for dye solar cells via raster scanning laser

NASA Astrophysics Data System (ADS)

Mincuzzi, Girolamo; Vesce, Luigi; Reale, Andrea; Di Carlo, Aldo; Brown, Thomas M.

2009-09-01

By identifying the right combination of laser parameters, in particular the integrated laser fluence Φ, we fabricated dye solar cells (DSCs) with UV laser-sintered TiO2 films exhibiting a power conversion efficiency η =5.2%, the highest reported for laser-sintered devices. η is dramatically affected by Φ and a clear trend is reported. Significantly, DSCs fabricated by raster scanning the laser beam to sinter the TiO2 films are made as efficient as those with oven-sintered ones. These results, confirmed on three batches of cells, demonstrate the remarkable potential (noncontact, local, low cost, rapid, selective, and scalable) of scanning laser processing applied to DSC technology.

Direct solar-pumped iodine laser amplifier

NASA Technical Reports Server (NTRS)

Han, K. S.

1986-01-01

During this period the parametric studies of the iodine laser oscillator pumped by a Vortek simulator were carried out before amplifier studies. The amplifier studies are postponed to the extended period after completing the parametric studies. In addition, the kinetic modeling of a solar-pumped iodine laser amplifier, and the experimental work for a solar pumped dye laser amplifier are in progress. This report contains three parts: (1) a 10 W CW iodine laser pumped by a Vortek solar simulator; (2) kinetic modeling to predict the time to lasing threshold, lasing time, and energy output of solar-pumped iodine laser; and (3) the study of the dye laser amplifier pumped by a Tamarack solar simulator.

High-repetition-rate, narrow-band dye lasers with water as a solvent for dyes

NASA Astrophysics Data System (ADS)

Ray, Alok K.; Sinha, Sucharita; Kundu, Soumitra; Kumar, Sasi; Nair, Sivagiriyal Karunakaran Sreenivasan; Pal, Tamal; Dasgupta, Kamalesh

2002-03-01

The performance of a copper vapor laser-pumped narrow-band dye laser in oscillator-amplifier configuration with water-based binary mixture solvents is described. Although oscillator efficiency in water-surfactant (sodium lauryl sulfate) solvent was comparable with that that employed pure ethanolic solvent, amplifier efficiency was found to be lower. Experiments that were carried out with vertically polarized pump beams and either horizontally or vertically polarized signal beams show that, in case of both the pump and signal having orthogonal polarization (horizontal) and same polarization (vertical), the extraction efficiency for both ethanolic and water-micelle media increased substantially from 15.7% to 18.5% and from 10% to 12.5%, respectively. However, the relative difference remained nearly the same, indicating that a slower orientational diffusion of excited dye molecules in a micellar medium is not responsible for a decrease in amplifier efficiency. Amplifier efficiency comparable with that containing ethanolic dye solutions could be obtained with a binary solvent that comprises a mixture of water and about 30% n-propanol. The performances of two efficient dyes, Rhodamine-6G and Kiton Red S, using water-based solvents were studied.

Picosecond transient backward stimulated Raman scattering and pumping of femtosecond dye lasers

NASA Astrophysics Data System (ADS)

Arrivo, Steven M.; Spears, Kenneth G.; Sipior, Jeffrey

1995-02-01

We report studies of transient, backward stimulated, Raman scattering (TBSRS) in solvents with a 10 Hz, 27 ps, 532 nm pump laser. The TBSRS effect was used to create pulses at 545 nm and 630 nm with durations of 2-3 ps and 5-10 μJ of energy. The duration, energy and fluctuations of the Raman pulse were studied as a function of pump energy and focal parameters. A 5 μJ Raman pulse was amplified in either a Raman amplifier or two stage dye amplifier to 1 mJ levels. A 545 nm pulse of 3 ps duration was generated in CCl 4 and was then used to pump a short cavity dye laser (SCDL). The SCDL oscillator and a 5 stage dye amplifier provided a pulse of 700 fs and 400 μJ that was tunable near 590 nm.

Dye lasing arrangement including an optical assembly for altering the cross-section of its pumping beam and method

DOEpatents

O'Neil, Richard W.; Sweatt, William C.

1992-01-01

An optical assembly is disclosed herein along with a method of operation for use in a dye lasing arrangement, for example a dye laser oscillator or a dye amplifier, in which a continuous stream of dye is caused to flow through a given zone in a cooperating dye chamber while the zone is being illuminated by light from a pumping beam which is directed into the given zone. This in turn causes the dye therein to lase and thereby produce a new dye beam in the case of a dye laser oscillator or amplify a dye beam in the case of a dye amplifier. The optical assembly so disclosed is designed to alter the pump beam such that the beam enters the dye chamber with a different cross-sectional configuration, preferably one having a more uniform intensity profile, than its initially produced cross-sectional configuration. To this end, the assembly includes a network of optical components which first act on the beam while the latter retains its initially produced cross-sectional configuration for separating it into a plurality of predetermined segments and then recombines the separated components in a predetermined way which causes the recombined beam to have the different cross-sectional configuration.

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

D'yachkov, Aleksei B; Labozin, Valerii P

The results of experiments on the 510 {yields} 578-nm conversion of high-power radiation from a copper vapour laser (CVL) in a dye cell are presented. The use of the efficient laser dye Pyrromethane 597 (PM-597) made it possible to convert the 120-W CVL radiation (72 W at 510 nm + 48 W at 578 nm) into 102-W radiation at 578 nm, which is equivalent to a conversion efficiency of 85%. Photostability of the dye in various solvents is studied. The photostability (more than 45 GJ mole{sup -1}) of PM-597 in n-heptane is found to be higher than that of Rhmore » 6G in ethanol. (control of laser radiation parameters)« less

Laser optogalvanic wavelength calibration with a commercial hollow cathode iron - neon discharge lamp

NASA Technical Reports Server (NTRS)

Zhu, Xinming; Nur, Abdullahi H.; Misra, Prabhakar

1994-01-01

351 optogalvanic transitions have been observed in the 337 - 598 nm wavelength region using an iron - neon hollow cathode discharge lamp and a pulsed tunable dye laser. 223 of these have been identified as transitions associated with neon energy levels. These optogalvanic transitions have allowed, in conjunction with interference fringes recorded concomitantly with an etalon, the calibration of the dye laser wavelength with 0.3/cm accuracy.

Mirrorless Optical Parametric Oscillation with Tunable Threshold in Cold Atoms.

PubMed

Mei, Yefeng; Guo, Xianxin; Zhao, Luwei; Du, Shengwang

2017-10-13

We report the demonstration of a mirrorless optical parametric oscillator with a tunable threshold in laser-cooled atoms with four-wave mixing (FWM) using electromagnetically induced transparency. Driven by two classical laser beams, the generated Stokes and anti-Stokes fields counterpropagate and build up efficient intrinsic feedback through the nonlinear FWM process. This feedback does not involve any cavity or spatially distributed microstructures. We observe the transition of photon correlation properties from the biphoton quantum regime (below the threshold) to the oscillation regime (above the threshold). The pump threshold can be tuned by varying the operating parameters. We achieve the oscillation with a threshold as low as 15  μW.

2-dimensional ion velocity distributions measured by laser-induced fluorescence above a radio-frequency biased silicon wafer

NASA Astrophysics Data System (ADS)

Moore, Nathaniel B.; Gekelman, Walter; Pribyl, Patrick; Zhang, Yiting; Kushner, Mark J.

2013-08-01

The dynamics of ions traversing sheaths in low temperature plasmas are important to the formation of the ion energy distribution incident onto surfaces during microelectronics fabrication. Ion dynamics have been measured using laser-induced fluorescence (LIF) in the sheath above a 30 cm diameter, 2.2 MHz-biased silicon wafer in a commercial inductively coupled plasma processing reactor. The velocity distribution of argon ions was measured at thousands of positions above and radially along the surface of the wafer by utilizing a planar laser sheet from a pulsed, tunable dye laser. Velocities were measured both parallel and perpendicular to the wafer over an energy range of 0.4-600 eV. The resulting fluorescence was recorded using a fast CCD camera, which provided resolution of 0.4 mm in space and 30 ns in time. Data were taken at eight different phases during the 2.2 MHz cycle. The ion velocity distributions (IVDs) in the sheath were found to be spatially non-uniform near the edge of the wafer and phase-dependent as a function of height. Several cm above the wafer the IVD is Maxwellian and independent of phase. Experimental results were compared with simulations. The experimental time-averaged ion energy distribution function as a function of height compare favorably with results from the computer model.

Third-order nonlinear optical properties of organic azo dyes by using strength of nonlinearity parameter and Z-scan technique

NASA Astrophysics Data System (ADS)

Motiei, H.; Jafari, A.; Naderali, R.

2017-02-01

In this paper, two chemically synthesized organic azo dyes, 2-(2,5-Dichloro-phenyazo)-5,5-dimethyl-cyclohexane-1,3-dione (azo dye (i)) and 5,5-Dimethyl-2-tolylazo-cyclohexane-1,3-dione (azo dye (ii)), have been studied from optical Kerr nonlinearity point of view. These materials were characterized by Ultraviolet-visible spectroscopy. Experiments were performed using a continous wave diode-pumped laser at 532 nm wavelength in three intensities of the laser beam. Nonlinear absorption (β), refractive index (n2) and third-order susceptibility (χ (3)) of dyes, were calculated. Nonlinear absorption coefficient of dyes have been calculated from two methods; 1) using theoretical fits and experimental data in the Z-scan technique, 2) using the strength of nonlinearity curves. The values of β obtained from both of the methods were approximately the same. The results demonstrated that azo dye (ii) displays better nonlinearity and has a lower two-photon absorption threshold than azo dye (i). Calculated parameter related to strength of nonlinearity for azo dye (ii) was higher than azo dye (i), It may be due to presence of methyl in azo dye (ii) instead of chlorine in azo dye (i). Furthermore, The measured values of third order susceptibility of azo dyes were from the order of 10-9 esu . These azo dyes can be suitable candidate for optical switching devices.

Rose bengal in poly(2-hydroxyethyl methacrylate) thin films: self-quenching by photoactive energy traps

NASA Astrophysics Data System (ADS)

Ezquerra Riega, Sergio D.; Rodríguez, Hernán B.; San Román, Enrique

2017-03-01

The effect of dye concentration on the fluorescence,ΦF, and singlet molecular oxygen,ΦΔ, quantum yields of rose bengal loaded poly(2-hydroxyethyl methacrylate) thin films (∼200 nm thick) was investigated, with the aim of understanding the effect of molecular interactions on the photophysical properties of dyes in crowded constrained environments. Films were characterized by absorption and fluorescence spectroscopy, singlet molecular oxygen (1O2) production was quantified using a chemical monitor, and the triplet decay was determined by laser flash-photolysis. For the monomeric dilute dye, ΦF = 0.05 ± 0.01 and ΦΔ = 0.76 ± 0.14. The effect of humidity and the photostability of the dye were also investigated. Spectral changes in absorption and fluorescence in excess of 0.05 M and concentration self-quenching after 0.01 M are interpreted in the context of a quenching radius model. Calculations of energy migration and trapping rates were performed assuming random distribution of the dye. Best fits of fluorescence quantum yields with concentration are obtained in the whole concentration range with a quenching radius r Q = 1.5 nm, in the order of molecular dimensions. Agreement is obtained only if dimeric traps are considered photoactive, with an observed fluorescence quantum yield ratio ΦF,trap/ΦF,monomer ≈ 0.35. Fluorescent traps are capable of yielding triplet states and 1O2. Results show that the excited state generation efficiency, calculated as the product between the absorption factor and the fluorescence quantum yield, is maximized at around 0.15 M, a very high concentration for random dye distributions. Relevant information for the design of photoactive dyed coatings is provided.

[First clinical results using a pulsed dye laser Rhodamine 590 lithotripter in treatment of ureteral calculi].

PubMed

Jichlinski, P; Bonard, M; von Niederhäusern, W; Delacrétaz, G; Rink, K; Lambelet, P; Klohn, M; Bolle, J F; Graber, P

1991-09-01

A collaborative study about a pulsed dye laser Rhodamin 590 was undergone, 2 years ago, between the laser application center of EPFL and both urological departments of the university of Geneva and the university of Lausanne. First clinical results are presented. Ten patients have been treated for various ureteral stones, mainly calcium oxalate stones. Laser fragmentation was successful in seven cases. No serious complication was noted. Fragmentation efficiency seems better with a 320 microns fiber than with a 200 microns fiber.

Exciton Hybridisation in Organic-Inorganic Semiconductor Microcavities

DTIC Science & Technology

2002-02-01

hybridizing organic and inorganic semiconductors in microcavities to produce a highly efficient light source that could be either a laser or a very efficient...such process may also have an important effect on the spectral distribution of photoluminescence from the microcavity and can be considered as a...Absorption (solid dots) and photoluminescence emission (open circles) of a thin film of J-aggregated cyanine dyes in a PVA matrix. Note, the chemical

Tri-channel single-mode terahertz quantum cascade laser.

PubMed

Wang, Tao; Liu, Jun-Qi; Liu, Feng-Qi; Wang, Li-Jun; Zhang, Jin-Chuan; Wang, Zhan-Guo

2014-12-01

We report on a compact THz quantum cascade laser source emitting at, individually controllable, three different wavelengths (92.6, 93.9, and 95.1 μm). This multiwavelength laser array can be used as a prototype of the emission source of THz wavelength division multiplex (WDM) wireless communication system. The source consists of three tapered single-mode distributed feedback (DFB) terahertz quantum cascade lasers fabricated monolithically on a single chip. All array elements feature longitudinal as well as lateral single-mode in the entire injection range. The peak output powers of individual lasers are 42, 73, and 37 mW at 10 K, respectively.

Design of bent waveguide semiconductor lasers using nonlinear equivalent chirp

NASA Astrophysics Data System (ADS)

Li, Lianyan; Shi, Yuechun; Zhang, Yunshan; Chen, Xiangfei

2018-01-01

Reconstruction equivalent chirp (REC) technique is widely used in the design and fabrication of semiconductor laser arrays and tunable lasers with low cost and high wavelength accuracy. Bent waveguide is a promising method to suppress the zeroth order resonance, which is an intrinsic problem in REC technique. However, it may introduce basic grating chirp and deteriorate the single longitudinal mode (SLM) property of the laser. A nonlinear equivalent chirp pattern is proposed in this paper to compensate the grating chirp and improve the SLM property. It will benefit the realization of low-cost Distributed feedback (DFB) semiconductor laser arrays with accurate lasing wavelength.

[Gas pipeline leak detection based on tunable diode laser absorption spectroscopy].

PubMed

Zhang, Qi-Xing; Wang, Jin-Jun; Liu, Bing-Hai; Cai, Ting-Li; Qiao, Li-Feng; Zhang, Yong-Ming

2009-08-01

The principle of tunable diode laser absorption spectroscopy and harmonic detection technique was introduced. An experimental device was developed by point sampling through small multi-reflection gas cell. A specific line near 1 653. 7 nm was targeted for methane measurement using a distributed feedback diode laser as tunable light source. The linearity between the intensity of second harmonic signal and the concentration of methane was determined. The background content of methane in air was measured. The results show that gas sensors using tunable diode lasers provide a high sensitivity and high selectivity method for city gas pipeline leak detection.

Bonding of human meniscal and articular cartilage with photoactive 1,8-naphthalimide dyes

NASA Astrophysics Data System (ADS)

Judy, Millard M.; Nosir, Hany R.; Jackson, Robert W.; Matthews, James Lester; Lewis, David E.; Utecht, Ronald E.; Yuan, Dongwu

1996-05-01

This study focused on meniscal cartilage repair by using the laser-activated photoactive 1,8- naphthalimide dye N,N'-bis-{6-[2-(2-(2- aminoethoxy)ethoxy)ethoxyethyl]amino-1H-benz (de)isoquinolin-1,3(2H)-dion-2- yl}-1,11-diamino-3,6,9-trioxaundecane. Harvested cadaveric human menisci were debrided and carved into strips 1 mm thick, 10 mm long, and 3 mm wide. Each strip was divided into two flaps, the surface painted with photoactive dye, the painted surfaces overlapped, the sample wrapped in Saran film, and the composite sandwiched between two glass slides at a pressure of approximately 3 kg/cm2. The sample then was transilluminated by argon ion laser light of 457.9-nm wavelength at a power density of 200 mW/cm2 with exposure times up to 5 h (3902 J/cm2 energy density). Essentially, the same procedures were performed for human femoral articular cartilage samples. Control experiments were conducted with laser irradiation alone and with dye alone. All the specimens were stored in isotonic saline solution for 2 h after irradiation to ensure hydration. The bond shear-strength was then tested and samples prepared for optical and electron transmission microscopy. Shear strength values of up to 1.8 kg/cm2 for meniscal tissues and 1.2 kg/cm2 for articular cartilaginous tissues were obtained for exposures of 3902 J/cm2. Shear strength values of approximately 0.9 kg/cm2 and 0.4 kg/cm2, respectively, for meniscus and cartilage were obtained with 459 J/cm2 exposure. Dye- and light-only controls exhibited 0 kg/cm2 shear strength values. Microscopy revealed close contact at the bonded surface in the laser-activated, dye-treated-specimens. This study shows that the laser-activated photoactive dyes have the capability of athermally bonding the meniscal and articular cartilage surfaces.

Strong intensity variations of laser feedback interferometer caused by atmospheric turbulence

NASA Astrophysics Data System (ADS)

Sun, Yiyi; Li, Zhiping

2003-05-01

The significant variation of the laser output can be caused by feedback of a small part of laser beam, which is reflected or backscattered by a target at a long distance from laser source, into the laser cavity. This paper describes and analyzes theoretically and experimentally the influence of atmospheric turbulence on interference caused by laser feedback. The influence depends upon both the energy of feedback into the laser cavity and the strength of turbulence over a laser propagation path in the atmosphere. In the case of stronger energy of feedback and weak turbulence variance of fluctuation of the laser output can be enhanced by hundreds to thousands times. From our measurements and theoretical analysis it shows thatthese significant enhancements can result from the change of laser-cavity-modes which can be stimulated simultaneously and from beat oscillations between a variety of frequencies of laser modes. This also can result from optical chaos inside the laser resonator because a non-separable distorted external cavity can become a prerequisite for optical chaos.

Multicolor fluorescence enhancement from a photonics crystal surface

NASA Astrophysics Data System (ADS)

Pokhriyal, A.; Lu, M.; Huang, C. S.; Schulz, S.; Cunningham, B. T.

2010-09-01

A photonic crystal substrate exhibiting resonant enhancement of multiple fluorophores has been demonstrated. The device, fabricated uniformly from plastic materials over a ˜3×5 in.2 surface area by nanoreplica molding, utilizes two distinct resonant modes to enhance electric field stimulation of a dye excited by a λ =632.8 nm laser (cyanine-5) and a dye excited by a λ =532 nm laser (cyanine-3). Resonant coupling of the laser excitation to the photonic crystal surface is obtained for each wavelength at a distinct incident angle. Compared to detection of a dye-labeled protein on an ordinary glass surface, the photonic crystal surface exhibited a 32× increase in fluorescent signal intensity for cyanine-5 conjugated streptavidin labeling, while a 25× increase was obtained for cyanine-3 conjugated streptavidin labeling. The photonic crystal is capable of amplifying the output of any fluorescent dye with an excitation wavelength in the 532 nm<λ<633 nm range by selection of an appropriate incident angle. The device is designed for biological assays that utilize multiple fluorescent dyes within a single imaged area, such as gene expression microarrays.

Multicolor fluorescence enhancement from a photonics crystal surface

PubMed Central

Pokhriyal, A.; Lu, M.; Huang, C. S.; Schulz, S.; Cunningham, B. T.

2010-01-01

A photonic crystal substrate exhibiting resonant enhancement of multiple fluorophores has been demonstrated. The device, fabricated uniformly from plastic materials over a ∼3×5 in.2 surface area by nanoreplica molding, utilizes two distinct resonant modes to enhance electric field stimulation of a dye excited by a λ=632.8 nm laser (cyanine-5) and a dye excited by a λ=532 nm laser (cyanine-3). Resonant coupling of the laser excitation to the photonic crystal surface is obtained for each wavelength at a distinct incident angle. Compared to detection of a dye-labeled protein on an ordinary glass surface, the photonic crystal surface exhibited a 32× increase in fluorescent signal intensity for cyanine-5 conjugated streptavidin labeling, while a 25× increase was obtained for cyanine-3 conjugated streptavidin labeling. The photonic crystal is capable of amplifying the output of any fluorescent dye with an excitation wavelength in the 532 nm<λ<633 nm range by selection of an appropriate incident angle. The device is designed for biological assays that utilize multiple fluorescent dyes within a single imaged area, such as gene expression microarrays. PMID:20957067

Multiperiod-grating surface-emitting lasers

NASA Technical Reports Server (NTRS)

Lang, Robert J. (Inventor)

1992-01-01

Surface-emitting distributed feedback (DFB) lasers are disclosed with hybrid gratings. A first-order grating is provided at one or both ends of the active region of the laser for retroreflection of light back into the active region, and a second-order or nonresonant grating is provided at the opposite end for coupling light out perpendicular to the surfaces of the laser or in some other selected direction. The gratings may be curved to focus light retroreflected into the active region and to focus light coupled out to a point. When so focused to a point, the DFB laser may be part of a monolithic read head for a laser recorded disk, or an optical coupler into an optical fiber.

Continuously tunable solution-processed organic semiconductor DFB lasers pumped by laser diode.

PubMed

Klinkhammer, Sönke; Liu, Xin; Huska, Klaus; Shen, Yuxin; Vanderheiden, Sylvia; Valouch, Sebastian; Vannahme, Christoph; Bräse, Stefan; Mappes, Timo; Lemmer, Uli

2012-03-12

The fabrication and characterization of continuously tunable, solution-processed distributed feedback (DFB) lasers in the visible regime is reported. Continuous thin film thickness gradients were achieved by means of horizontal dipping of several conjugated polymer and blended small molecule solutions on cm-scale surface gratings of different periods. We report optically pumped continuously tunable laser emission of 13 nm in the blue, 16 nm in the green and 19 nm in the red spectral region on a single chip respectively. Tuning behavior can be described with the Bragg-equation and the measured thickness profile. The laser threshold is low enough that inexpensive laser diodes can be used as pump sources.

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

Pulsed laser-induced damage of metals at 492 nm.

PubMed

Marrs, C D; Faith, W N; Dancy, J H; Porteus, J O

1982-11-15

A triaxial flashlamp-pumped dye laser has been used to perform laser damage testing of metal surfaces in the blue-green spectral region. Using LD490 laser dye, the laser produces 0.18-J, 0.5-microsec pulses at 492 nm. The spatial profile of the focused beam is measured in orthogonal directions in the plane of the sample surface. The orthogonal profiles are flat-topped Gaussians with 1/e(2) widths of 270 microm. Multithreshold laser damage test results are presented for polished Mo, diamond-turned high-purity Al alloy, diamond-turned bulk Cu, and diamond-turned electrodeposits of Ag and Au on Cu. Comparisons are made between calculated and experimentally measured slip and melt thresholds.

A Plasma Ultraviolet Source for Short Wavelength Lasers.

DTIC Science & Technology

1988-04-15

plasma focus (DPF) device was evaluated for the feasibility of blue-green and near ultraviolet laser pumping. As the result of optimizing the operating conditions of DPF and laser system, the maximum untuned laser output exceeded 4.0mJ corresponding to the energy density 8.3J/liter which is much higher than the typical flashlamp dye laser. The spectral irradiance of DPF at the absorption bands for LD390 and LD490 were 5.5W/sq cm-nm, 0.3W.sq cm-nm, respectively. Due to the lower pump power of DPF at 355nm than the threshold of LD390, the laser pumping of LD390 dye was not

GaSb-based single-mode distributed feedback lasers for sensing (Conference Presentation)

NASA Astrophysics Data System (ADS)

Gupta, James A.; Bezinger, Andrew; Lapointe, Jean; Poitras, Daniel; Aers, Geof C.

2017-02-01

GaSb-based tunable single-mode diode lasers can enable rapid, highly-selective and highly-sensitive absorption spectroscopy systems for gas sensing. In this work, single-mode distributed feedback (DFB) laser diodes were developed for the detection of various trace gases in the 2-3.3um range, including CO2, CO, HF, H2S, H2O and CH4. The lasers were fabricated using an index-coupled grating process without epitaxial regrowth, making the process significantly less expensive than conventional DFB fabrication. The devices are based on InGaAsSb/AlGaAsSb separate confinement heterostructures grown on GaSb by molecular beam epitaxy. DFB lasers were produced using a two step etch process. Narrow ridge waveguides were first defined by optical lithography and etched into the semiconductor. Lateral gratings were then defined on both sides of the ridge using electron-beam lithography and etched to produce the index-grating. Effective index modeling was used to optimize the ridge width, etch depths and the grating pitch to ensure single-lateral-mode operation and adequate coupling strength. The effective index method was further used to simulate the DFB laser emission spectrum, based on a transfer matrix model for light transmission through the periodic structure. The fabricated lasers exhibit single-mode operation which is tunable through the absorption features of the various target gases by adjustment of the drive current. In addition to the established open-path sensing applications, these devices have great potential for optoelectronic integrated gas sensors, making use of integrated photodetectors and possibly on-chip Si photonics waveguide structures.

High-speed off-axis holographic cinematography with a copper-vapor-pumped dye laser.

PubMed

Lauterborn, W; Judt, A; Schmitz, E

1993-01-01

A series of coherent light pulses is generated by pumping a dye laser with the pulsed output of a copper-vapor laser at rates of as much as 20 kHz. Holograms are recorded at this pulse rate on a rotating holographic plate. This technique of high-speed holographic cinematography is demonstrated by viewing the bubble filaments that appear in water under the action of a sound field of high intensity.

DNA-based dye lasers: progress in this half a decade

NASA Astrophysics Data System (ADS)

Kawabe, Yutaka

2016-09-01

After the invention of DNA-surfactant films and the proposal of dye doping into them by Ogata, many applications were demonstrated. Among them tunable thin film laser is one of the most attractive functional devices. Development and progress in DNA based lasers after the first observation of amplified spontaneous emission (ASE) by us has been reviewed in a former paper published in 2011.1 In this proceeding, progresses in the subsequent half a decade are described.

Intense Excitation Source of Blue-Green Laser.

DTIC Science & Technology

1985-10-15

plasma focus (DPF) can produce intense uv photons (200-300nm) which match the absorption spectra of both near uv and blue green dye lasers (300-400nm...existing blue green dye laser. On the other hand the dense- plasma focus (DPF) with new optical coupling has been designed and constructed. For the...optimization of the DPF device as the uv pumping light source, the velocity of current sheath and the formation of plasma focus have been measured as

Dye-enhanced laser welding for skin closure.

PubMed

DeCoste, S D; Farinelli, W; Flotte, T; Anderson, R R

1992-01-01

The use of a laser to weld tissue in combination with a topical photosensitizing dye permits selective delivery of energy to the target tissue. A combination of indocyanine green (IG), absorption peak 780 nm, and the near-infrared (IR) alexandrite laser was studied with albino guinea pig skin. IG was shown to bind to the outer 25 microns of guinea pig dermis and appeared to be bound to collagen. The optical transmittance of full-thickness guinea pig skin in the near IR was 40% indicating that the alexandrite laser should provide adequate tissue penetration. Laser "welding" of skin in vivo was achieved at various concentrations of IG from 0.03 to 3 mg/cc using the alexandrite at 780 nm, 250-microseconds pulse duration, 8 Hz, and a 4-mm spot size. A spectrum of welds was obtained from 1- to 20-W/cm2 average irradiance. Weak welds occurred with no thermal damage obtained at lower irradiances: stronger welds with thermal damage confined to the weld site occurred at higher irradiances. At still higher irradiances, local vaporization occurred with failure to "weld." Thus, there was an optimal range of irradiances for "welding," which varied inversely with dye concentration. Histology confirmed the thermal damage results that were evident clinically. IG dye-enhanced laser welding is possible in skin and with further optimization may have practical application.

Repetitively Mode-Locked Cavity-Enhanced Absorption Spectroscopy (RML-CEAS) for Near-Infrared Gas Sensing

PubMed Central

Zheng, Chuantao; Wang, Yiding

2017-01-01

A Pound-Drever-Hall (PDH)-based mode-locked cavity-enhanced sensor system was developed using a distributed feedback diode laser centered at 1.53 µm as the laser source. Laser temperature scanning, bias control of the piezoelectric ceramic transducer (PZT) and proportional-integral-derivative (PID) feedback control of diode laser current were used to repetitively lock the laser modes to the cavity modes. A gas absorption spectrum was obtained by using a series of absorption data from the discrete mode-locked points. The 15 cm-long Fabry-Perot cavity was sealed using an enclosure with an inlet and outlet for gas pumping and a PZT for cavity length tuning. The performance of the sensor system was evaluated by conducting water vapor measurements. A linear relationship was observed between the measured absorption signal amplitude and the H2O concentration. A minimum detectable absorption coefficient of 1.5 × 10–8 cm–1 was achieved with an averaging time of 700 s. This technique can also be used for the detection of other trace gas species by targeting the corresponding gas absorption line. PMID:29207470

Monolithically integrated mid-infrared sensor using narrow mode operation and temperature feedback

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

Ristanic, Daniela; Schwarz, Benedikt, E-mail: benedikt.schwarz@tuwien.ac.at; Reininger, Peter

A method to improve the sensitivity and selectivity of a monolithically integrated mid-infrared sensor using a distributed feedback laser (DFB) is presented in this paper. The sensor is based on a quantum cascade laser/detector system built from the same epitaxial structure and with the same fabrication approach. The devices are connected via a dielectric-loaded surface plasmon polariton waveguide with a twofold function: it provides high light coupling efficiency and a strong interaction of the light with the environment (e.g., a surrounding fluid). The weakly coupled DFB quantum cascade laser emits narrow mode light with a FWHM of 2 cm{sup −1} atmore » 1586 cm{sup −1}. The room temperature laser threshold current density is 3 kA∕cm{sup 2} and a pulsed output power of around 200 mW was measured. With the superior laser noise performance, due to narrow mode emission and the compensation of thermal fluctuations, the lower limit of detection was expanded by one order of magnitude to the 10 ppm range.« less

Evaluation of OH laser-induced fluorescence techniques for supersonic combustion diagnostics

NASA Technical Reports Server (NTRS)

Quagliaroli, T. M.; Laufer, G.; Krauss, R. H.; Mcdaniel, J. C., Jr.

1992-01-01

The limitations on application of dye laser and narrowband tunable KrF excimer laser systems to planar OH fluorescence measurements in supersonic combustion test facilities are examined. Included in the analysis are effects of collisional quenching, beam absorption, fluorescence trapping, and signal strengths on achievable measurement accuracy using several excitation and detection options for either of the two laser systems. Dye-based laser systems are found to be the method of choice for imaging OH concentrations less than 10 exp 15 per cu cm, while the KrF based systems provide significant reduction in measurement ambiguity for concentrations in excess of 10 exp 15 per cu cm.

Digital DNA detection based on a compact optofluidic laser with ultra-low sample consumption.

PubMed

Lee, Wonsuk; Chen, Qiushu; Fan, Xudong; Yoon, Dong Ki

2016-11-29

DNA lasers self-amplify optical signals from a DNA analyte as well as thermodynamic differences between sequences, allowing quasi-digital DNA detection. However, these systems have drawbacks, such as relatively large sample consumption and complicated dye labelling. Moreover, although the lasing signal can detect the target DNA, it is superimposed on an unintended fluorescence background, which persists for non-target DNA samples as well. From an optical point of view, it is thus not truly digital detection and requires spectral analysis to identify the target. In this work, we propose and demonstrate an optofluidic laser that has a single layer of DNA molecules as the gain material. A target DNA produces intensive laser emission comparable to existing DNA lasers, while any unnecessary fluorescence background is successfully suppressed. As a result, the target DNA can be detected with a single laser pulse, in a truly digital manner. Since the DNA molecules cover only a single layer on the surface of the laser microcavity, the DNA sample consumption is a few orders of magnitude lower than that of existing DNA lasers. Furthermore, the DNA molecules are stained by simply immersing the microcavity in the intercalating dye solution, and thus the proposed DNA laser is free of any complex dye-labelling process prior to analysis.

Electrically controllable liquid crystal random lasers below the Fréedericksz transition threshold.

PubMed

Lee, Chia-Rong; Lin, Jia-De; Huang, Bo-Yuang; Lin, Shih-Hung; Mo, Ting-Shan; Huang, Shuan-Yu; Kuo, Chie-Tong; Yeh, Hui-Chen

2011-01-31

This investigation elucidates for the first time electrically controllable random lasers below the threshold voltage in dye-doped liquid crystal (DDLC) cells with and without adding an azo-dye. Experimental results show that the lasing intensities and the energy thresholds of the random lasers can be decreased and increased, respectively, by increasing the applied voltage below the Fréedericksz transition threshold. The below-threshold-electric-controllability of the random lasers is attributable to the effective decrease of the spatial fluctuation of the orientational order and thus of the dielectric tensor of LCs by increasing the electric-field-aligned order of LCs below the threshold, thereby increasing the diffusion constant and decreasing the scattering strength of the fluorescence photons in their recurrent multiple scattering. This can result in the decrease in the lasing intensity of the random lasers and the increase in their energy thresholds. Furthermore, the addition of an azo-dye in DDLC cell can induce the range of the working voltage below the threshold for the control of the random laser to reduce.

Techniques for reducing and/or eliminating secondary modes in a dye laser oscillator

DOEpatents

Hackel, Richard P.

1988-01-01

A dye laser master oscillator is disclosed herein. This oscillator is intended to provide a single mode output, that is, a primary beam of light of a specific wavelength, but also has the tendency to provide secondary modes, that is, secondary beams of light at different wavelengths and slightly off-axis with respect to the primary beam as a result of grazing incident reflections within the dye cell forming part of the master oscillator. Also disclosed herein are a number of different techniques for reducing or eliminating these secondary modes.

Efficient 7-J flashlamp-pumped dye laser at 500-nm wavelength

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

Everett, P.N.; Aldag, H.R.; Ehrlich, J.J.

1986-07-01

An existing transverse flow flashlamp-pumped dye laser capable of operation at 500 pps for extended periods of time has been modified and optimized for operation at 502 nm using coumarin 504. Energies of over 7 J/ pulse and efficiencies of over 1% have been demonstrated in single-shot operation. This has been achieved by using a spectral transfer dye in the flashlamp coolant to increase the useful output of the flashlamps. Flashlamps were tested at up to 400-J input per lamp for extended periods to develop lamp life data.

On the possibility of measuring atmospheric OH using intracavity laser spectroscopy

NASA Technical Reports Server (NTRS)

Mcmanus, J. Barry; Kolb, C. E.

1994-01-01

Intracavity laser spectroscopy (ILS) has been demonstrated to be useful for measuring extremely weak absorption produced by gases in air. ILS is based on the observation that when there are spectrally narrow losses within the cavity of a broadband laser, the laser output has corresponding spectral holes where the laser oscillation is partially quenched. The depth of the laser output dips can be enhanced by a factor of 10(exp 5) over the depth of the initial cavity loss, and absorptivities of 10(exp -8) cm(exp -1) have been measured in lasers only one meter long. With ILS, one can achieve in a compact space a spectral contrast that would otherwise require kilometers of pathlength. ILS systems typically use quasi-continuous wave dye lasers operating close to threshold. The pump laser is modulated from just below to just above the threshold level for the dye laser, and the dye laser output is spectroscopically observed during a well defined time interval after the onset of lasing (the generation time). The spectral contrast of an intracavity absorber is equivalent to that produced by absorption through a path length equal to the generation time multiplied by the speed of light (assuming the cavity is completely filed with the absorber) up to some limiting time. Thus, if one measures the spectrum after 33 microseconds, the effective path length is 10,000 meters.

Three-dimensional dynamics of temperature fields in phantoms and biotissue under IR laser photothermal therapy using gold nanoparticles and ICG dye

NASA Astrophysics Data System (ADS)

Akchurin, Georgy G.; Garif, Akchurin G.; Maksimova, Irina L.; Skaptsov, Alexander A.; Terentyuk, Georgy S.; Khlebtsov, Boris N.; Khlebtsov, Nikolai G.; Tuchin, Valery V.

2010-02-01

We describe applications of silica (core)/gold (shell) nanoparticles and ICG dye to photothermal treatment of phantoms, biotissue and spontaneous tumor of cats and dogs. The laser irradiation parameters were optimized by preliminary experiments with laboratory rats. Three dimensional dynamics of temperature fields in tissue and solution samples was measured with a thermal imaging system. It is shown that the temperature in the volume region of nanoparticles localization can substantially exceed the surface temperature recorded by the thermal imaging system. We have demonstrated effective optical destruction of cancer cells by local injection of plasmon-resonant gold nanoshells and ICG dye followed by continuous wave (CW) diode laser irradiation at wavelength 808 nm.

Cellular dye lasers: lasing thresholds and sensing in a planar resonator

PubMed Central

Humar, Matjaž; Gather, Malte C.; Yun, Seok-Hyun

2015-01-01

Biological cell lasers are promising novel building blocks of future biocompatible optical systems and offer new approaches to cellular sensing and cytometry in a microfluidic setting. Here, we demonstrate a simple method for providing optical gain by using a variety of standard fluorescent dyes. The dye gain medium can be located inside or outside a cell, or in both, which gives flexibility in experimental design and makes the method applicable to all cell types. Due to the higher refractive index of the cytoplasm compared to the surrounding medium, a cell acts as a convex lens in a planar Fabry-Perot cavity. Its effect on the stability of the laser cavity is analyzed and utilized to suppress lasing outside cells. The resonance modes depend on the shape and internal structure of the cell. As proof of concept, we show how the laser output modes are affected by the osmotic pressure. PMID:26480446

Application of Raman spectroscopy and surface-enhanced Raman scattering to the analysis of synthetic dyes found in ballpoint pen inks.

PubMed

Geiman, Irina; Leona, Marco; Lombardi, John R

2009-07-01

The applicability of Raman spectroscopy and surface-enhanced Raman scattering (SERS) to the analysis of synthetic dyes commonly found in ballpoint inks was investigated in a comparative study. Spectra of 10 dyes were obtained using a dispersive system (633 nm, 785 nm lasers) and a Fourier transform system (1064 nm laser) under different analytical conditions (e.g., powdered pigments, solutions, thin layer chromatography [TLC] spots). While high fluorescence background and poor spectral quality often characterized the normal Raman spectra of the dyes studied, SERS was found to be generally helpful. Additionally, dye standards and a single ballpoint ink were developed on a TLC plate following a typical ink analysis procedure. SERS spectra were successfully collected directly from the TLC plate, thus demonstrating a possible forensic application for the technique.

Imaging of acoustic fields using optical feedback interferometry.

PubMed

Bertling, Karl; Perchoux, Julien; Taimre, Thomas; Malkin, Robert; Robert, Daniel; Rakić, Aleksandar D; Bosch, Thierry

2014-12-01

This study introduces optical feedback interferometry as a simple and effective technique for the two-dimensional visualisation of acoustic fields. We present imaging results for several pressure distributions including those for progressive waves, standing waves, as well as the diffraction and interference patterns of the acoustic waves. The proposed solution has the distinct advantage of extreme optical simplicity and robustness thus opening the way to a low cost acoustic field imaging system based on mass produced laser diodes.

1983 Annual Report on Laser Dyes.

DTIC Science & Technology

1984-04-01

Dye II). lThe laser portitm f 1327 11982) 311 the work was sLpp orted b , the National Aerollautics 10 (; II. \\s , .K. Jack-1 amnd AMI . ialpern. (hem...to be the longest-lived. ni)lciatc iu,pui , laser dive solution ol ami that hawe been reported. 1. Introduction We itade a tnore lhiirough evaluation...J. E. Colbert 01) E. White (1) I Riverside Research Institute. Arlington, VA (Suite 714. R. Pamst) 2 Riverside Research Institute. New York, NY Dr. M

Thermal damage control of dye-assisted laser tissue welding: effect of dye concentration

NASA Astrophysics Data System (ADS)

Xie, Hua; Buckley, Lisa A.; Prahl, Scott A.; Shaffer, Brian S.; Gregory, Kenton W.

2001-05-01

Successful laser-assisted tissue welding was implemented to provide proper weld strength with minimized tissue thermal injury. We investigated and compared the weld strengths and morphologic changes in porcine small intestinal submucose (SIS) and porcine ureteral tissues with various concentration of indocyanine green (ICG) and with a solid albumin sheet. The study showed that the tissues were welded at lower ICG concentration (0.05 mM) with minimized tissue thermal damage using an 800-nm wavelength diode laser.

Period locking due to delayed feedback in a laser with saturable absorber.

PubMed

Carr, T W

2003-08-01

We consider laser with saturable absorber operating in the pulsating regime that is subject to delayed feedback. Alone, both the saturable absorber and delayed feedback cause the clockwise output to become unstable to periodic output via Hopf bifurcations. The delay feedback causes the laser pulse period to lock to an integer fraction of the feedback time. We derive a map from the original model to describe the periodic pulsations of the laser. Equations for the period of the laser predict the occurrence of the different locking states as well as the value of the pump when there is a switch between the locked states.

Annual Technical Report, Materials Research Laboratory, July 1, 1980-June 30, 1981,

DTIC Science & Technology

1981-06-30

stress pulses (-- 100 i sec duration) has shown qualitative differences between the response of annealed and irradiated crystals (Elbaum, Hikata...wave which propa- gates in the sample before, during and after the stress pulse . Preliminary experiments have been carried out on irradiated and on...pressure seeded beams produced in a short pulse (50 Ips) valve. Rotational distributions are measured by focusing the output from a tunable dye laser

Advances in solid state laser technology for space and medical applications

NASA Technical Reports Server (NTRS)

Byvik, C. E.; Buoncristiani, A. M.

1988-01-01

Recent developments in laser technology and their potential for medical applications are discussed. Gas discharge lasers, dye lasers, excimer lasers, Nd:YAG lasers, HF and DF lasers, and other commonly used lasers are briefly addressed. Emerging laser technology is examined, including diode-pumped lasers and other solid state lasers.

Using the ultra-long pulse width pulsed dye laser and elliptical spot to treat resistant nasal telangiectasia.

PubMed

Madan, Vishal; Ferguson, Janice

2010-01-01

Thick linear telangiectasia on the ala nasi and nasolabial crease can be resistant to treatment with the potassium-titanyl-phosphate (KTP) laser and the traditional round spot on a pulsed dye laser (PDL). We evaluated the efficacy of a 3 mm x 10 mm elliptical spot using the ultra-long pulse width on a Candela Vbeam(R) PDL for treatment of PDL- and KTP laser-resistant nasal telangiectasia. Nasal telangiectasia resistant to PDL (12 patients) and KTP laser (12 patients) in 18 patients were treated with a 3 mm x 10 mm elliptical spot on the ultra-long pulse pulsed dye laser (ULPDL) utilising long pulse width [595 nm, 40 ms, double pulse, 30:20 dynamic cooling device (DCD)]. Six patients had previously received treatment with both PDL and KTP laser prior to ULPDL (40 treatments, range1-4, mean 2.2). Complete clearance was seen in ten patients, and eight patients displayed more than 80% improvement after ULPDL treatment. Self-limiting purpura occurred with round spot PDL and erythema with KTP laser and ULPDL. Subtle linear furrows along the treatment sites were seen in three patients treated with the KTP laser. ULPDL treatment delivered using a 3 mm x 10 mm elliptical spot was non-purpuric and highly effective in the treatment of nasal telangiectasia resistant to KTP laser and PDL.

Development of high sensitivity eight-element multiplexed fiber laser acoustic pressure hydrophone array and interrogation system

NASA Astrophysics Data System (ADS)

Li, Ming; Sun, Zhihui; Zhang, Xiaolei; Li, Shujuan; Song, Zhiqiang; Wang, Meng; Guo, Jian; Ni, Jiasheng; Wang, Chang; Peng, Gangding; Xu, Xiangang

2017-09-01

Fiber laser hydrophones have got widespread concerns due to the unique advantages and broad application prospects. In this paper, the research results of the eight-element multiplexed fiber laser acoustic pressure array and the interrogation system are introduced, containing low-noise distributed feedback fiber laser (DFB-FL) fabrication, sensitivity enhancement packaging, and interferometric signal demodulation. The frequency response range of the system is 10Hz-10kHz, the laser frequency acoustic pressure sensitivity reaches 115 dB re Hz/Pa, and the equivalent noise acoustic pressure is less than 60μPa/Hz1/2. The dynamic range of the system is greater than 120 dB.

Red and far-red fluorescent dyes for the characterization of head and neck cancer at the cellular level.

PubMed

Abbaci, Muriel; Casiraghi, Odile; Temam, Stephane; Ferchiou, Malek; Bosq, Jacques; Dartigues, Peggy; De Leeuw, Frederic; Breuskin, Ingrid; Laplace-Builhé, Corinne

2015-11-01

Primary upper aerodigestive tract malignancy remains a cancer having a poor prognosis, despite current progress in treatment, due to a generally late diagnosis. We conducted a preliminary assessment of five dyes approved for human use for the imaging of head and neck tissues at the cellular level, which could be considered for clinical examination. We investigated fluorescence endomicroscopic images on fresh samples obtained from head and neck surgeries after staining with hypericin, methylene blue, toluidine blue, patent blue or indocyanine green to provide a preliminary consideration as to whether these images contain enough information for identification of non-pathologic and pathologic tissues. The distribution pattern of dye has been examined using probe-based confocal laser endomicroscopy (pCLE) in ex vivo specimens and compared with corresponding histology. In most samples, the image quality provided by pCLE with both dyes allowed pathologists to recognize histological characteristics to identify the tissues. The combination of pCLE imaging with these dyes provides interpretable images close to conventional histology; a promising clinical tool to assist physicians in examination of upper aerodigestive tract, as long as depth imaging issues can be overcome. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Direct solar-pumped iodine laser amplifier

NASA Technical Reports Server (NTRS)

Han, K. S.

1985-01-01

This semiannual progress report covers the period from April 1, 1985 to Sept. 30, 1985 under NASA grant NAS1-441 entitled direct solar pumped iodine laser amplifier. During this period the parametric studies of the iodine laser oscillator pumped by a Vortek simulator was carried out before the amplifier studies. The amplifier studies are postponed to the extended period following completion of the parametric studies. In addition, the kinetic modeling of a solar pumped iodine laser amplifier, and the experimental work for a solar pumped dye laser amplifier are in progress. This report contains three parts: (1) the radiation characteristics of solar simulator and the parametric characteristics of photodissociation iodine laser continuously pumped by a Vortek solar simulator; (2) kinetic modeling of a solar pumped iodine laser amplifier; and (3) the study of the dye laser amplifier pumped by a Tamarack solar simulator.

Lidar stratospheric ozone measurements at the observatoire de Haute Provence (France)

NASA Technical Reports Server (NTRS)

Godin, S.; Pelon, J.; Megie, G.

1986-01-01

Strastospheric ozone monitoring is of particular importance to confirm present day theories predicting a maximal ozone depletion, due to chlorofluorocarbon emission, in the 35 to 45 km altitude range. Measurements presently rely on both ground based and satellite-borne passive experiments. Such systems have been recently shown to have intrinsic limitations mainly due to atmospheric aerosol presence and calibration problems. During the last few years, active lidar profiling of the ozone vertical distribution by the Differential Absorption Laser technique (DIAL) in the UV wavelength range has been developed using two different laser sources: a Nd-YAG pumped dye laser which enables a large tuning range of the UV emitted wavelengths; and exciplex laser sources using xenon chloride as an active medium and emitting at 308 nm, the off wavelength being usually generated by Raman shifting techniques. Advantages and limitations of using both of these systems are briefly discussed.

Drug delivery with microsecond laser pulses into gelatin

NASA Astrophysics Data System (ADS)

Shangguan, Hanqun; Casperson, Lee W.; Shearin, Alan; Gregory, Kenton W.; Prahl, Scott A.

1996-07-01

Photoacoustic drug delivery is a technique for localized drug delivery by laser-induced hydrodynamic pressure following cavitation bubble expansion and collapse. Photoacoustic drug delivery was investigated on gelatin-based thrombus models with planar and cylindrical geometries by use of one microsecond laser pulses. Solutions of a hydrophobic dye in mineral oil permitted monitoring of delivered colored oil into clear gelatin-based thrombus models. Cavitation bubble development and photoacoustic drug delivery were visualized with flash photography. This study demonstrated that cavitation is the governing mechanism for photoacoustic drug delivery, and the deepest penetration of colored oil in gels followed the bubble collapse. Spatial distribution measurements revealed that colored oil could be driven a few millimeters into the gels in both axial and radial directions, and the penetration was less than 500 mu m when the gelatin structure was not fractured. localized drug delivery, cavitation bubble, laser thrombolysis.

Bibliography of Soviet Laser Developments, Number 28, March - April 1977.

DTIC Science & Technology

1978-02-24

Dyes " a. Rhodamine 25. Makogon, M.M. and V.B. Sukhanov (0). Dye laser with a partially se- lective resonator. ZhPS, v.26, no.4, 1977, 622-625. b...medium. KE, no.4, 1977, 751-757. 105. Bel’tyugov, V.N., I.I. Sukhanov , and Yu.V. Troitskiy (0). Thermal dis- tortions in intraresonator optical

Reconfigurable Solid-state Dye-doped Polymer Ring Resonator Lasers

NASA Astrophysics Data System (ADS)

Chandrahalim, Hengky; Fan, Xudong

2015-12-01

This paper presents wavelength configurable on-chip solid-state ring lasers fabricated by a single-mask standard lithography. The single- and coupled-ring resonator hosts were fabricated on a fused-silica wafer and filled with 3,3‧-Diethyloxacarbocyanine iodide (CY3), Rhodamine 6G (R6G), and 3,3‧-Diethylthiadicarbocyanine iodide (CY5)-doped polymer as the reconfigurable gain media. The recorded lasing threshold was ~220 nJ/mm2 per pulse for the single-ring resonator laser with R6G, marking the lowest threshold shown by solid-state dye-doped polymer lasers fabricated with a standard lithography process on a chip. A single-mode lasing from a coupled-ring resonator system with the lasing threshold of ~360 nJ/mm2 per pulse was also demonstrated through the Vernier effect. The renewability of the dye-doped polymer was examined by removing and redepositing the dye-doped polymer on the same resonator hosts for multiple cycles. We recorded consistent emissions from the devices for all trials, suggesting the feasibility of employing this technology for numerous photonic and biochemical sensing applications that entail for sustainable, reconfigurable, and low lasing threshold coherent light sources on a chip.

Reconfigurable Solid-state Dye-doped Polymer Ring Resonator Lasers

PubMed Central

Chandrahalim, Hengky; Fan, Xudong

2015-01-01

This paper presents wavelength configurable on-chip solid-state ring lasers fabricated by a single-mask standard lithography. The single- and coupled-ring resonator hosts were fabricated on a fused-silica wafer and filled with 3,3′-Diethyloxacarbocyanine iodide (CY3), Rhodamine 6G (R6G), and 3,3′-Diethylthiadicarbocyanine iodide (CY5)-doped polymer as the reconfigurable gain media. The recorded lasing threshold was ~220 nJ/mm2 per pulse for the single-ring resonator laser with R6G, marking the lowest threshold shown by solid-state dye-doped polymer lasers fabricated with a standard lithography process on a chip. A single-mode lasing from a coupled-ring resonator system with the lasing threshold of ~360 nJ/mm2 per pulse was also demonstrated through the Vernier effect. The renewability of the dye-doped polymer was examined by removing and redepositing the dye-doped polymer on the same resonator hosts for multiple cycles. We recorded consistent emissions from the devices for all trials, suggesting the feasibility of employing this technology for numerous photonic and biochemical sensing applications that entail for sustainable, reconfigurable, and low lasing threshold coherent light sources on a chip. PMID:26674508

Reconfigurable Solid-state Dye-doped Polymer Ring Resonator Lasers.

PubMed

Chandrahalim, Hengky; Fan, Xudong

2015-12-17

This paper presents wavelength configurable on-chip solid-state ring lasers fabricated by a single-mask standard lithography. The single- and coupled-ring resonator hosts were fabricated on a fused-silica wafer and filled with 3,3'-Diethyloxacarbocyanine iodide (CY3), Rhodamine 6G (R6G), and 3,3'-Diethylthiadicarbocyanine iodide (CY5)-doped polymer as the reconfigurable gain media. The recorded lasing threshold was ~220 nJ/mm(2) per pulse for the single-ring resonator laser with R6G, marking the lowest threshold shown by solid-state dye-doped polymer lasers fabricated with a standard lithography process on a chip. A single-mode lasing from a coupled-ring resonator system with the lasing threshold of ~360 nJ/mm(2) per pulse was also demonstrated through the Vernier effect. The renewability of the dye-doped polymer was examined by removing and redepositing the dye-doped polymer on the same resonator hosts for multiple cycles. We recorded consistent emissions from the devices for all trials, suggesting the feasibility of employing this technology for numerous photonic and biochemical sensing applications that entail for sustainable, reconfigurable, and low lasing threshold coherent light sources on a chip.

Two-dimensional dissipative rogue waves due to time-delayed feedback in cavity nonlinear optics.

PubMed

Tlidi, Mustapha; Panajotov, Krassimir

2017-01-01

We demonstrate a way to generate two-dimensional rogue waves in two types of broad area nonlinear optical systems subject to time-delayed feedback: in the generic Lugiato-Lefever model and in the model of a broad-area surface-emitting laser with saturable absorber. The delayed feedback is found to induce a spontaneous formation of rogue waves. In the absence of delayed feedback, spatial pulses are stationary. The rogue waves are exited and controlled by the delay feedback. We characterize their formation by computing the probability distribution of the pulse height. The long-tailed statistical contribution, which is often considered as a signature of the presence of rogue waves, appears for sufficiently strong feedback. The generality of our analysis suggests that the feedback induced instability leading to the spontaneous formation of two-dimensional rogue waves is a universal phenomenon.

Analysis of in vivo penetration of textile dyes causing allergic reactions

NASA Astrophysics Data System (ADS)

Lademann, J.; Patzelt, A.; Worm, M.; Richter, H.; Sterry, W.; Meinke, M.

2009-10-01

Contact allergies to textile dyes are common and can cause severe eczema. In the present study, we investigated the penetration of a fluorescent textile dye, dissolved from a black pullover, into the skin of one volunteer during perspiration and nonperspiration. Previously, wearing this pullover had induced a severe contact dermatitis in an 82-year old woman, who was not aware of her sensitization to textile dyes. The investigations were carried out by in vivo laser scanning microscopy. It could be demonstrated that the dye was eluted from the textile material by sweat. Afterwards, the dye penetrated into the stratum corneum and into the hair follicles. Inside the hair follicles, the fluorescent signal was still detectable after 24 h, whereas it was not verifiable anymore in the stratum corneum, Laser scanning microscopy represents an efficient tool for in vivo investigation of the penetration and storage of topically applied substances and allergens into the human skin and reveals useful hints for the development and optimization of protection strategies.

Solar generation and storage of O2 (a 1 delta g)

NASA Technical Reports Server (NTRS)

Twarowski, Allen J.; Dao, Phan; Good, Lisa A.

1988-01-01

An investigation was performed of the technical steps required to design a solar powered oxygen-iodine laser. Singlet delta oxygen is formed upon transfer of energy from selected photoexcited dye molecules to ground state molecular oxygen and then is concentrated and stored as an endoperoxide by reaction with an aromatic hydrocarbon. The endoperoxide, when heated, releases singlet oxygen in high yield thus providing a regenerable source of laser fuel. Energy transfer from dye molecules to molecular oxygen was investigated. When dye molecules were adsorbed to polymer substrates it was observed that the dye became embedded in the polymer matrix. Porphin dyes were incorporated into films of 1,4-dimethyl-2-poly(vinylnaphthalene), 2PVN. An endoperoxide was formed when porphin-doped 2PVN was exposed to visible radiation. This demonstrates the possibility of generating singlet oxygen using solar energy and concentrating and storing it in one simple step. Transport of energy by exciton migration in polycrystalline dye films was also investigated.

Water soluble laser dyes

DOEpatents

Hammond, Peter R.; Feeman, James F.; Field, George F.

1998-01-01

Novel water soluble dyes of the formula I are provided ##STR1## wherein R.sup.1 and R.sup.4 are alkyl of 1 to 4 carbon atoms or hydrogen; or R.sup.1 -R.sup.2 or R.sup.2 -R.sup.4 form part of aliphatic heterocyclic rings; R.sup.2 is hydrogen or joined with R.sup.1 or R.sup.4 as described above; R.sup.3 is --(CH.sub.2).sub.m --SO.sub.3.sup.-, where m is 1 to 6; X is N, CH or ##STR2## where Y is 2 --SO.sub.3.sup.- ; Z is 3, 4, 5 or 6 --SO.sub.3.sup.-. The novel dyes are particularly useful as the active media in water solution dye lasers.

Parity–time-symmetric circular Bragg lasers: a proposal and analysis

PubMed Central

Gu, Jiahua; Xi, Xiang; Ma, Jingwen; Yu, Zejie; Sun, Xiankai

2016-01-01

We propose a new type of semiconductor lasers by implementing the concept of parity–time symmetry in a two-dimensional circular Bragg grating structure, where both the real and imaginary parts of the refractive index are modulated along the radial direction. The laser modal properties are analyzed with a transfer-matrix method and are verified with numerical simulation of a practical design. Compared with conventional distributed-feedback lasers with modulation of only the real part of refractive index, the parity–time-symmetric circular Bragg lasers feature reduced threshold and enhanced modal discrimination, which in combination with the intrinsic circularly symmetric, large emission aperture are clear advantages in applications that require mode-hop-free, high-power, single-mode laser operation. PMID:27892933

High power and single mode quantum cascade lasers.

PubMed

Bismuto, Alfredo; Bidaux, Yves; Blaser, Stéphane; Terazzi, Romain; Gresch, Tobias; Rochat, Michel; Muller, Antoine; Bonzon, Christopher; Faist, Jerome

2016-05-16

We present a single mode quantum cascade laser with nearly 1 W optical power. A buried distributed feedback reflector is used on the back section for wavelength selection. The laser is 6 mm long, 3.5 μm wide, mounted episide-up and the laser facets are left uncoated. Laser emission is centered at 4.68 μm. Single-mode operation with a side mode suppression ratio of more than 30 dB is obtained in whole range of operation. Farfield measurements prove a symmetric, single transverse-mode emission in TM00-mode with typical divergences of 41° and 33° in the vertical and horizontal direction respectively. This work shows the potential for simple fabrication of high power lasers compatible with standard DFB processing.

Nike Facility Diagnostics and Data Acquisition System

NASA Astrophysics Data System (ADS)

Chan, Yung; Aglitskiy, Yefim; Karasik, Max; Kehne, David; Obenschain, Steve; Oh, Jaechul; Serlin, Victor; Weaver, Jim

2013-10-01

The Nike laser-target facility is a 56-beam krypton fluoride system that can deliver 2 to 3 kJ of laser energy at 248 nm onto targets inside a two meter diameter vacuum chamber. Nike is used to study physics and technology issues related to laser direct-drive ICF fusion, including hydrodynamic and laser-plasma instabilities, material behavior at extreme pressures, and optical and x-ray diagnostics for laser-heated targets. A suite of laser and target diagnostics are fielded on the Nike facility, including high-speed, high-resolution x-ray and visible imaging cameras, spectrometers and photo-detectors. A centrally-controlled, distributed computerized data acquisition system provides robust data management and near real-time analysis feedback capability during target shots. Work supported by DOE/NNSA.

Fabrication of redox-responsive magnetic protein microcapsules from hen egg white by the sonochemical method.

PubMed

Zhong, Shuangling; Cui, Xuejun; Tian, Fangyuan

2015-01-01

Redox-responsive magnetic protein microcapsules with Fe3O4 magnetic nanoparticles (MNPs) encapsulated inside have been obtained using a facile, cost-effective and fast sonochemical method from hen egg white proteins. Such prepared redox-responsive magnetic hen egg white protein microcapsules (MHEWPMCs) could be easily manipulated to do magnetic-guided targeting delivery. The synchronous loading of the hydrophobic dye Coumarin 6 as a model of drug into MHEWPMCs was readily achieved during the fabrication of MHEWPMCs by dissolving them into the oil phase before ultrasonication. TEM images indicated that Fe3O4 MNPs were encapsulated in MHEWPMCs. Confocal laser scanning microscopic images indicated that the dye was distributed evenly in the MHEWPMCs and no leakage of dye from the MHEWPMCs was observed due to the protection of protein shells. The MHEWPMCs are potential candidates as attractive carriers for drug targeting delivery and stimuli-responsive release due to their magnetic and redox responsiveness of the disulfide in the microcapsule shells.

Co2/Erbium:YAG/Dye laser combination: an effective and successful treatment for angiofibromas in tuberous sclerosis.

PubMed

Fioramonti, Paolo; De Santo, Liliana; Ruggieri, Martina; Carella, Sara; Federico, Lo Torto; Onesti, Maria Giuseppina; Scuderi, Nicolò

2014-02-01

Tuberous sclerosis, an autosomal dominant neurocutaneous syndrome seen in approximately 1 in 6,000 people worldwide, is characterized by the appearance of hamartomas in multiple organs. The classic clinical triad consists of angiofibromas, epilepsy, and developmental delay. Dermatologic disorder is one of the main characteristics. Angiofibromas, a common form of presentation, causes significant cosmetic and medical problems. The current treatment for skin lesions is laser therapy. The carbon dioxide (CO2) laser has been used satisfactorily in treating these lesions, but several studies have demonstrated a high percentage of recurrences. Erbium:yttrium-aluminum-garnet (YAG) laser treatment has been used to resurface skin abnormalities in patients with dermatologic conditions. The dye laser as an alternative uses the principles of selective photothermolysis and is very effective in treating the vascular component of tuberous sclerosis. The use of all these lasers to treat skin lesions in patients affected by tuberous sclerosis has never been described in the literature. A retrospective study, conducted from 2007 to May 2013, investigated 13 patients who had tuberous sclerosis treated with an erbium:YAG/CO2/dye laser combination. All the patients showed great improvement of their skin lesions. The results were evident immediately after the first treatment. No patient experienced complications or recurrence. The combined use of the erbium:YAG/Dye/CO2 laser is a safe and effective treatment for skin lesions in patients affected by tuberous sclerosis. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

High-power, fixed, and tunable wavelength, grating-free cascaded Raman fiber lasers

NASA Astrophysics Data System (ADS)

Balaswamy, V.; Arun, S.; Aparanji, Santosh; Choudhury, Vishal; Supradeepa, V. R.

2018-04-01

Cascaded Raman lasers enable high powers at various wavelength bands inaccessible with conventional rare-earth doped lasers. The input and output wavelengths of conventional implementations are fixed by the constituent fiber gratings necessary for cascaded Raman conversion. We demonstrate here, a simple architecture for high power, fixed and wavelength tunable, grating-free, cascaded Raman conversion between different wavelength bands. The architecture is based on the recently proposed distributed feedback Raman lasers. Here, we implement a module which converts the Ytterbium band to the eye-safe 1.5micron region. We demonstrate pump-limited output powers of over 30W in fixed and continuously wavelength tunable configurations.

Progress of the volume FEL (VFEL) experiments in millimeter range

NASA Astrophysics Data System (ADS)

Baryshevsky, V. G.; Batrakov, K. G.; Gurinovich, A. A.; Ilienko, I. I.; Lobko, A. S.; Molchanov, P. V.; Moroz, V. I.; Sofronov, P. F.; Stolyarsky, V. I.

2003-07-01

Use of non-one-dimensional distributed feedback in Volume Free Electron Laser gives possibility of frequency tuning in wide range. In present work, dependence of lasing process on the angle between resonant diffraction grating grooves and direction of electron beam velocity is discussed.

Estimation of ground and excited state dipole moment of laser dyes C504T and C521T using solvatochromic shifts of absorption and fluorescence spectra.

PubMed

Basavaraja, Jana; Suresh Kumar, H M; Inamdar, S R; Wari, M N

2016-02-05

The absorption and fluorescence spectra of laser dyes: coumarin 504T (C504T) and coumarin 521T (C521T) have been recorded at room temperature in a series of non-polar and polar solvents. The spectra of these dyes showed bathochromic shift with increasing in solvent polarity indicating the involvement of π→π⁎ transition. Kamlet-Taft and Catalan solvent parameters were used to analyze the effect of solvents on C504T and C521T molecules. The study reveals that both general solute-solvent interactions and specific interactions are operative in these two systems. The ground state dipole moment was estimated using Guggenheim's method and also by quantum mechanical calculations. The solvatochromic data were used to determine the excited state dipole moment (μ(e)). It is observed that dipole moment value of excited state (μ(e)) is higher than that of the ground state in both the laser dyes indicating that these dyes are more polar in nature in the excited state than in the ground state. Copyright © 2015. Published by Elsevier B.V.

Strong coupling between surface plasmon polariton and laser dye rhodamine 800

NASA Astrophysics Data System (ADS)

Valmorra, Federico; Bröll, Markus; Schwaiger, Stephan; Welzel, Nadine; Heitmann, Detlef; Mendach, Stefan

2011-08-01

We report on strong coupling between surface plasmon polaritons on a thin silver film and laser dye Rhodamine 800. Attenuated total reflection measurements reveal that the pure surface plasmon polaritons interact with the Rhodamine 800 absorption lines exhibiting pronounced anticrossings in the dispersion relation. We show that the corresponding energy gap can be tailored by the concentration of dye molecules in the dielectric matrix between 50 meV and 70 meV. We can well model our data by a classical transfer matrix approach as well as by a quantum mechanical coupled oscillator ansatz.

Adaptive optics in multiphoton microscopy: comparison of two, three and four photon fluorescence

PubMed Central

Sinefeld, David; Paudel, Hari P.; Ouzounov, Dimitre G.; Bifano, Thomas G.; Xu, Chris

2015-01-01

We demonstrate adaptive optics system based on nonlinear feedback from 3- and 4-photon fluorescence. The system is based on femtosecond pulses created by soliton self-frequency shift of a 1550-nm fiber-based femtosecond laser together with micro-electro-mechanical system (MEMS) phase spatial light modulator (SLM). We perturb the 1020-segment SLM using an orthogonal Walsh sequence basis set with a modified version of three-point phase shifting interferometry. We show the improvement after aberrations correction in 3-photon signal from fluorescent beads. In addition, we compare the improvement obtained in the same adaptive optical system for 2-, 3- and 4-photon fluorescence using dye pool. We show that signal improvement resulting from aberration correction grows exponentially as a function of the order of nonlinearity. PMID:26698772

Wideband tunable laser phase noise reduction using single sideband modulation in an electro-optical feed-forward scheme.

PubMed

Aflatouni, Firooz; Hashemi, Hossein

2012-01-15

A wideband laser phase noise reduction scheme is introduced where the optical field of a laser is single sideband modulated with an electrical signal containing the discriminated phase noise of the laser. The proof-of-concept experiments on a commercially available 1549 nm distributed feedback laser show linewidth reduction from 7.5 MHz to 1.8 kHz without using large optical cavity resonators. This feed-forward scheme performs wideband phase noise cancellation independent of the light source and, as such, it is compatible with the original laser source tunability without requiring tunable optical components. By placing the proposed phase noise reduction system after a commercial tunable laser, a tunable coherent light source with kilohertz linewidth over a tuning range of 1530-1570 nm is demonstrated.

Extended-bandwidth frequency sweeps of a distributed feedback laser using combined injection current and temperature modulation

NASA Astrophysics Data System (ADS)

Hefferman, Gerald; Chen, Zhen; Wei, Tao

2017-07-01

This article details the generation of an extended-bandwidth frequency sweep using a single, communication grade distributed feedback (DFB) laser. The frequency sweep is generated using a two-step technique. In the first step, injection current modulation is employed as a means of varying the output frequency of a DFB laser over a bandwidth of 99.26 GHz. A digital optical phase lock loop is used to lock the frequency sweep speed during current modulation, resulting in a linear frequency chirp. In the second step, the temperature of the DFB laser is modulated, resulting in a shifted starting laser output frequency. A laser frequency chirp is again generated beginning at this shifted starting frequency, resulting in a frequency-shifted spectrum relative to the first recorded data. This process is then repeated across a range of starting temperatures, resulting in a series of partially overlapping, frequency-shifted spectra. These spectra are then aligned using cross-correlation and combined using averaging to form a single, broadband spectrum with a total bandwidth of 510.9 GHz. In order to investigate the utility of this technique, experimental testing was performed in which the approach was used as the swept-frequency source of a coherent optical frequency domain reflectometry system. This system was used to interrogate an optical fiber containing a 20 point, 1-mm pitch length fiber Bragg grating, corresponding to a period of 100 GHz. Using this technique, both the periodicity of the grating in the frequency domain and the individual reflector elements of the structure in the time domain were resolved, demonstrating the technique's potential as a method of extending the sweeping bandwidth of semiconductor lasers for frequency-based sensing applications.

Extended-bandwidth frequency sweeps of a distributed feedback laser using combined injection current and temperature modulation.

PubMed

Hefferman, Gerald; Chen, Zhen; Wei, Tao

2017-07-01

This article details the generation of an extended-bandwidth frequency sweep using a single, communication grade distributed feedback (DFB) laser. The frequency sweep is generated using a two-step technique. In the first step, injection current modulation is employed as a means of varying the output frequency of a DFB laser over a bandwidth of 99.26 GHz. A digital optical phase lock loop is used to lock the frequency sweep speed during current modulation, resulting in a linear frequency chirp. In the second step, the temperature of the DFB laser is modulated, resulting in a shifted starting laser output frequency. A laser frequency chirp is again generated beginning at this shifted starting frequency, resulting in a frequency-shifted spectrum relative to the first recorded data. This process is then repeated across a range of starting temperatures, resulting in a series of partially overlapping, frequency-shifted spectra. These spectra are then aligned using cross-correlation and combined using averaging to form a single, broadband spectrum with a total bandwidth of 510.9 GHz. In order to investigate the utility of this technique, experimental testing was performed in which the approach was used as the swept-frequency source of a coherent optical frequency domain reflectometry system. This system was used to interrogate an optical fiber containing a 20 point, 1-mm pitch length fiber Bragg grating, corresponding to a period of 100 GHz. Using this technique, both the periodicity of the grating in the frequency domain and the individual reflector elements of the structure in the time domain were resolved, demonstrating the technique's potential as a method of extending the sweeping bandwidth of semiconductor lasers for frequency-based sensing applications.

Vegetation effects on event water dynamics - Insights from in-situ stable isotope observations and dye patterns

NASA Astrophysics Data System (ADS)

Volkmann, Till; Haberer, Kristine; Gessler, Arthur; Weiler, Markus

2014-05-01

The predicted changes of climate and land-use could have drastic effects on the water balance of ecosystems, particularly under frequent drought and subsequent rewetting conditions. Yet, inference of these effects and related consequences for the structure and functioning of ecosystems, groundwater recharge, leaching of nutrients and pollutants, drinking water availability, and the water cycle is currently impeded by gaps in our understanding of the manifold interactions between vegetation and soil water dynamics. While plants require water and nutrients, they also exert, for instance, important below-ground controls on the distribution and movement of water and chemicals in the rooted soil horizons via uptake and redistribution of water, modification of soil hydraulic properties, and formation of conduits for rapid preferential water flow. This work aims to contribute to fill existing gaps by assessing the effects of different plant types and their rooting systems on the soil water dynamics. Therefore, we conducted artificial drought and subsequent rewetting experiments using isotopically and dye (Brilliant Blue FCF) labeled water on plots of various surface cover (bare soil, grass, beech, oak, vine) established on relatively homogeneous luvisol on loess in southwestern Germany. Detailed insight into the short-term dynamics of event water infiltration and root uptake during the field experiments was facilitated by the application of novel techniques for high-frequency in-situ monitoring of stable isotope signatures in pore and transpiration water using commercial laser-based spectrometers, augmenting conventional observations of soil physicochemical states (soil water content, matric potential, electrical conductivity). The temporal point information is complemented by dye staining profiles, providing a detailed picture of spatial infiltration patterns, and by root density observations. The results of the experiments allow for a comprehensive spatiotemporal characterization of the effects of differing vegetation cover and rooting systems on infiltration, preferential flow path characteristics, and water storage in the rooted soil horizons. This will contribute to an improved ability to estimate environmental change impacts on the fate of water, nutrients, and pollutants in this critical zone and associated feedbacks within the soil-vegetation-atmosphere system.

IV INTERNATIONAL CONFERENCE ON ATOM AND MOLECULAR PULSED LASERS (AMPL'99): Radiative and photochemical properties of organic compounds excited by high-power XeCl laser radiation

NASA Astrophysics Data System (ADS)

Kopylova, T. N.; Kuznetsova, Rimma T.; Svetlichnyi, Valerii A.; Sergeev, A. K.; Tel'minov, E. N.; Filinov, D. N.

2000-06-01

Radiative and photochemical properties of a number of laser dyes excited by focused radiation of a XeCl laser with intensity up to 200 MW cm-2 were studied. A method for measuring the gain of organic molecules under high-power excitation is proposed. The dependence of the dye transmittance for the pump radiation on its intensity was studied. It is shown that changes in energy, spectral, and time characteristics of radiation and the photostability of compounds under high-power excitation are associated with the formation of superluminescence.

Comparison of the effect of the carbon dioxide laser and the bipolar coagulator on the cat brain

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

Cozzens, J.W.; Cerullo, L.J.

The carbon dioxide laser has recently received clinical acceptance in neurosurgical practice. There are, however, few studies reported in the neurosurgical literature, either clinical or experimental, concerning its safety or efficacy on a physiological level by comparison to a more conventional tool. This study is not a description of a surgical technique, but is rather a basic physiological comparison of two surgical instruments. In this study, 11 cats were pretreated with the protein-bound dye, Evans blue. A corticotomy was performed in one hemisphere with the carbon dioxide laser and in the other with a microbipolar coagulator and a sharp blade.more » The subsequent extravasation of dye was presumed to be proportional to the amount of blood-brain barrier disruption associated with each lesion. When effective power settings for the two devices were compared, the laser lesions had significantly less extravasation of blue dye. This indicated that there was less damage to the blood-brain barrier surrounding laser corticotomy than surrounding conventional bipolar coagulation and sharp dissection at comparable power settings for each modality.« less

Laser velocimetry with fluorescent dye-doped polystyrene microspheres.

PubMed

Lowe, K Todd; Maisto, Pietro; Byun, Gwibo; Simpson, Roger L; Verkamp, Max; Danehy, Paul M; Tiemsin, Pacita I; Wohl, Christopher J

2013-04-15

Simultaneous Mie scattering and laser-induced fluorescence (LIF) signals are obtained from individual polystyrene latex microspheres dispersed in an air flow. Microspheres less than 1 μm mean diameter were doped with two organic fluorescent dyes, Rhodamine B (RhB) and dichlorofluorescein (DCF), intended either to provide improved particle-based flow velocimetry in the vicinity of surfaces or to provide scalar flow information (e.g., marking one of two fluid streams). Both dyes exhibit measureable fluorescence signals that are on the order of 10(-3) to 10(-4) times weaker than the simultaneously measured Mie signals. It is determined that at the conditions measured, 95.5% of RhB LIF signals and 32.2% of DCF signals provide valid laser-Doppler velocimetry measurements compared with the Mie scattering validation rate with 6.5 W of 532 nm excitation, while RhB excited with 1.0 W incident laser power still exhibits 95.4% valid velocimetry signals from the LIF channel. The results suggest that the method is applicable to wind tunnel measurements near walls where laser flare can be a limiting factor and monodisperse particles are essential.

Single bead near-infrared random laser based on silica-gel infiltrated with Rhodamine 640

NASA Astrophysics Data System (ADS)

Moura, André L.; Barbosa-Silva, Renato; Dominguez, Christian T.; Pecoraro, Édison; Gomes, Anderson S. L.; de Araújo, Cid B.

2018-04-01

Photoluminescence properties of single bead silica-gel (SG) embedded with a laser-dye were studied aiming at the operation of near-infrared (NIR) Random Lasers (RLs). The operation of RLs in the NIR spectral region is especially important for biological applications since the optical radiation has deep tissue penetration with negligible damage. Since laser-dyes operating in the NIR have poor stability and are poor emitters, ethanol solutions of Rhodamine 640 (Rh640) infiltrated in SG beads were used. The Rh640 concentrations in ethanol varied from 10-5 to 10-2 M and the excitation at 532 nm was made by using a 7 ns pulsed laser. The proof-of-principle RL scheme herein presented was adopted in order to protect the dye-molecules from the environment and to favor formation of aggregates. The RL emission from ≈650 nm to 720 nm, beyond the typical Rh640 monomer and dimer wavelengths emissions range, was attributed to the trade-off between reabsorption and reemission processes along the light pathways inside the SG bead and the contribution of Rh640 aggregates.

Spectroscopy and laser action of the "red perylimide dye" in various solvents

NASA Astrophysics Data System (ADS)

Gvishi, R.; Reisfeld, R.; Burshtein, Z.

1993-10-01

Optical properties of the red perylimide laser dye in various solvents are studied. The absorption spectrum exhibits two main bands, in the ranges 480-600 and 400-460 nm, due to the S 0-S 1 and S 0-S 2 transition. The fluorescence spectrum is a mirror image of the S 0-S 1 absorption (shift of ˜ 30-50 nm). The Stokes shift increases with solvent polarity. Such dye-solvent interactions are compared to theoretical predictions. The fluorescence quantum yields approaches unity in all the solvents studied. Laser tunability around 30 nm was obtained each time, covering the spectral range 580-640 nm. This interval is important for medical applications in photodynamic therapy and fluorescence diagnostics. The laser threshold energy varied from 0.35 mJ/pulse in cyclohexane to 1.87 mJ/pulse in methanol, and the slope efficiency from about 6.6% in methanol to 14% in xylenes. The laser output was stable for several hours of operation under an average pump energy of about 20 mJ/pulse at 1 Hz repetition rate, without flow.

Diagnosis of NMOS DRAM functional performance as affected by a picosecond dye laser

NASA Technical Reports Server (NTRS)

Kim, Q.; Schwartz, H. R.; Edmonds, L. D.; Zoutendyk, J. A.

1992-01-01

A picosec pulsed dye laser beam was at selected wavelengths successfully used to simulate heavy-ion single-event effects (SEEs) in negative channel NMOS DRAMs. A DRAM was used to develop the test technique because bit-mapping capability and previous heavy-ion upset data were available. The present analysis is the first to establish such a correlation between laser and heavy-ion data for devices, such as the NMOS DRAM, where charge collection is dominated by long-range diffusion, which is controlled by carrier density at remote distances from a depletion region. In the latter case, penetration depth is an important parameter and is included in the present analysis. A single-pulse picosecond dye laser beam (1.5 microns diameter) focused onto a single cell component can upset a single memory cell; clusters of memory cell upsets (multiple errors) were observed when the laser energy was increased above the threshold energy. The multiple errors were analyzed as a function of the bias voltage and total energy of a single pulse. A diffusion model to distinguish the multiple upsets from the laser-induced charge agreed well with previously reported heavy ion data.

Comparison of microleakages of photo-cured composites using three different light sources: halogen lamp, LED and argon laser: an in vitro study.

PubMed

Tielemans, M; Compere, Ph; Geerts, S O; Lamy, M; Limme, M; De Moor, R J G; Delmé, K I M; Bertrand, M F; Rompen, E; Nammour, S

2009-01-01

In this study, we compared the microleakage of composite fillings cured with halogen bulb, LED and argon ion laser (488 nm). Twenty-four extracted human molars were divided randomly in three groups. Six cavities were prepared on the coronal part of each tooth. Standard cavities (1.7 x 2 mm) were prepared. Cavities were acid etched, sealed with Scotch Bond 1 and filled by a hybrid composite. Cavities were exposed to one light source, thermocycled and immersed in a 2% methylene blue dye solution. Dye penetration in the leakage of cavities was recorded using a digital optical microscope. Mean values of percentage of dye penetrations in microleakages of cavities were 49.303 +/- 5.178% for cavities cured with LED, 44.486 +/- 6.075% with halogen bulb and 36.647 +/- 5.936% for those cured by argon laser. Statistically significant difference exists between cavities cured by halogen vs LED (P < 0.01), halogen vs laser (P < 0.001) and LED vs laser (P < 0.001). The lowest microleakage was observed in the cavities and composites cured with argon ion laser.

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.

Dye laser traveling wave amplifier

NASA Technical Reports Server (NTRS)

Davidson, F.; Hohman, J.

1984-01-01

A flashlamp pumped dye laser suitable for use as a single stage amplifier is described. Particular emphasis is placed on the efforts to increase output pulse energy and improve the temporal profile of the injected pulse. By using high power thin film polarizers, output energies reach from 4 to 45 mJ. Various dispersive elements are used to develop an amplified pulse with an extremely clean temporal profile.

Simultaneous sampling technique for two spectral sources

NASA Technical Reports Server (NTRS)

Jarrett, Olin, Jr.

1987-01-01

A technique is described that uses a bundle of fiber optics to simultaneously sample a dye laser and a spectral lamp. By the use of a real-time display with this technique, the two signals can be superimposed, and the effect of any spectral adjustments can be immediately accessed. In the NASA's CARS system used for combustion diagnostics, the dye laser mixes with a simultaneously pulsed Nd:YAG laser at 532 nm to probe the vibrational levels of nitrogen. An illustration of the oscilloscopic display of the system is presented.

Development of New Laser-Protective Dyes. Phase 1.

DTIC Science & Technology

1990-10-30

technology to stabilize cyanine and squarylium dyes . This accomplishment will justify continued research on the synthesis and process development of...beyond. This is the subject of a proposed Phase II program. RESULTS AND DISCUSSION THERMAL STABILITY: In Phase I, dyes of the cyanine and squarylium ...Test in Appendix 1). Table 1 shows that the squarylium dyes are inherently more thermally stable than the cyanines. This observation supports

Nanocrystal waveguide (NOW) laser

DOEpatents

Simpson, John T.; Simpson, Marcus L.; Withrow, Stephen P.; White, Clark W.; Jaiswal, Supriya L.

2005-02-08

A solid state laser includes an optical waveguide and a laser cavity including at least one subwavelength mirror disposed in or on the optical waveguide. A plurality of photoluminescent nanocrystals are disposed in the laser cavity. The reflective subwavelength mirror can be a pair of subwavelength resonant gratings (SWG), a pair of photonic crystal structures (PC), or a distributed feedback structure. In the case of a pair of mirrors, a PC which is substantially transmissive at an operating wavelength of the laser can be disposed in the laser cavity between the subwavelength mirrors to improve the mode structure, coherence and overall efficiency of the laser. A method for forming a solid state laser includes the steps of providing an optical waveguide, creating a laser cavity in the optical waveguide by disposing at least one subwavelength mirror on or in the waveguide, and positioning a plurality of photoluminescent nanocrystals in the laser cavity.

Long pulsed dye laser treatment of facial wrinkles.

PubMed

Tay, Yong-Kwang; Khoo, Boo-Peng; Tan, Eileen; Kwok, Colin

2004-11-01

The flashlamp pulsed dye laser has been used in the treatment of rhytids. To evaluate the efficacy of the long pulsed dye laser in the treatment of mild to moderate wrinkles in Asian patients. Wrinkles on one half of the face in 10 subjects were treated with the long pulsed dye laser (595 nm, 10 mm spot size, 10 ms, 7 J/cm2, 40 ms spray, 40 ms delay, single-pass, 30% overlap) with the other side serving as a control. A total of three treatments were given at 2 monthly intervals. The following sites were treated: periorbital area, six patients; forehead, two patients; cheek, two patients. No preoperative anesthesia or postoperative treatment were used. Clinical photographs were taken before and after each treatment, and analysis was undertaken through photographic evaluation by non-treating physicians. At 2 months after the last treatment, the clinical improvement of rhytids was noted in all patients compared with baseline. Four subjects had mild improvement (< or = 25%), five had moderate improvement (26-50%) and one had marked improvement (51-75%). The periorbital area was more responsive to treatment compared with the other sites. No clinical changes were noted in the control areas. No adverse effects were reported except for transient mild erythema in two patients which lasted for up to an hour. Nine patients were somewhat satisfied with the treatment and one was highly satisfied. All wanted the other half of the face to be treated. Treatment with a non-ablative 595 nm flashlamp pulsed dye laser can lead to mild to moderate clinical improvement in class I-II rhytids with minimal to no side effects in patients with darker skin types.

Water soluble laser dyes

DOEpatents

Hammond, P.R.; Feeman, J.F.; Field, G.F.

1998-08-11

Novel water soluble dyes of the formula 1 are provided by the formula described in the paper wherein R{sup 1} and R{sup 4} are alkyl of 1 to 4 carbon atoms or hydrogen; or R{sup 1}--R{sup 2} or R{sup 2}--R{sup 4} form part of aliphatic heterocyclic rings; R{sup 2} is hydrogen or joined with R{sup 1} or R{sup 4} as described above; R{sup 3} is --(CH{sub 2}){sub m}--SO{sub 3}{sup {minus}}, where m is 1 to 6; X is N, CH or formula 2 given in paper where Y is 2 --SO{sub 3}{sup {minus}} ; Z is 3, 4, 5 or 6 --SO{sub 3}{sup {minus}}. The novel dyes are particularly useful as the active media in water solution dye lasers.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Influence of the layer thickness and concentration of dye molecules on the emission amplification in cholesteric liquid crystals

NASA Astrophysics Data System (ADS)

Alaverdyan, R. B.; Gevorgyan, A. A.; Chilingaryan, A. D.; Chilingaryan, Yu S.

2008-05-01

The propagation of light through a planar layer of a cholesteric liquid crystal doped with dye molecules is considered. The features of the emission spectra of the crystal are studied both in the absence and presence of dielectric boundaries. The increase in the emission intensity is investigated for different layer thicknesses and different concentrations of dye molecules. It is shown that an anomalously strong increase in the emission intensity with the diffraction intrinsic polarisation takes place in the case of a comparatively small crystal thickness and a relatively low concentration of dye molecules. The obtained results can be used for the development of miniature lasers with the circular polarisation of the fundamental radiation mode.

Generation of wideband chaos with suppressed time-delay signature by delayed self-interference.

PubMed

Wang, Anbang; Yang, Yibiao; Wang, Bingjie; Zhang, Beibei; Li, Lei; Wang, Yuncai

2013-04-08

We demonstrate experimentally and numerically a method using the incoherent delayed self-interference (DSI) of chaotic light from a semiconductor laser with optical feedback to generate wideband chaotic signal. The results show that, the DSI can eliminate the domination of laser relaxation oscillation existing in the chaotic laser light and therefore flatten and widen the power spectrum. Furthermore, the DSI depresses the time-delay signature induced by external cavity modes and improves the symmetry of probability distribution by more than one magnitude. We also experimentally show that this DSI signal is beneficial to the random number generation.

Short cavity DFB fiber laser based vector hydrophone for low frequency signal detection

NASA Astrophysics Data System (ADS)

Zhang, Xiaolei; Zhang, Faxiang; Jiang, Shaodong; Min, Li; Li, Ming; Peng, Gangding; Ni, Jiasheng; Wang, Chang

2017-12-01

A short cavity distributed feedback (DFB) fiber laser is used for low frequency acoustic signal detection. Three DFB fiber lasers with different central wavelengths are chained together to make three-element vector hydrophone with proper sensitivity enhancement design, which has extensive and significant applications to underwater acoustic monitoring for the national defense, oil, gas exploration, and so on. By wavelength-phase demodulation, the lasing wavelength changes under different frequency signals can be interpreted, and the sensitivity is tested about 33 dB re pm/g. The frequency response range is rather flat from 5 Hz to 300 Hz.

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.

Multiwavelength ytterbium-Brillouin random Rayleigh feedback fiber laser

NASA Astrophysics Data System (ADS)

Wu, Han; Wang, Zinan; Fan, Mengqiu; Li, Jiaqi; Meng, Qingyang; Xu, Dangpeng; Rao, Yunjiang

2018-03-01

In this letter, we experimentally demonstrate the multiwavelength ytterbium-Brillouin random fiber laser for the first time, in the half-open cavity formed by a fiber loop mirror and randomly distributed Rayleigh mirrors. With a cladding-pumped ytterbium-doped fiber and a long TrueWave fiber, the narrow linewidth Brillouin pump can generate multiple Brillouin Stokes lines with hybrid ytterbium-Brillouin gain. Up to six stable channels with a spacing of about 0.06 nm are obtained. This work extends the operation wavelength of the multiwavelength Brillouin random fiber laser to the 1 µm band, and has potential in various applications.

Peculiarities of the statistics of spectrally selected fluorescence radiation in laser-pumped dye-doped random media

NASA Astrophysics Data System (ADS)

Yuvchenko, S. A.; Ushakova, E. V.; Pavlova, M. V.; Alonova, M. V.; Zimnyakov, D. A.

2018-04-01

We consider the practical realization of a new optical probe method of the random media which is defined as the reference-free path length interferometry with the intensity moments analysis. A peculiarity in the statistics of the spectrally selected fluorescence radiation in laser-pumped dye-doped random medium is discussed. Previously established correlations between the second- and the third-order moments of the intensity fluctuations in the random interference patterns, the coherence function of the probe radiation, and the path difference probability density for the interfering partial waves in the medium are confirmed. The correlations were verified using the statistical analysis of the spectrally selected fluorescence radiation emitted by a laser-pumped dye-doped random medium. Water solution of Rhodamine 6G was applied as the doping fluorescent agent for the ensembles of the densely packed silica grains, which were pumped by the 532 nm radiation of a solid state laser. The spectrum of the mean path length for a random medium was reconstructed.

Advances in high power linearly polarized fiber laser and its application

NASA Astrophysics Data System (ADS)

Zhou, Pu; Huang, Long; Ma, Pengfei; Xu, Jiangming; Su, Rongtao; Wang, Xiaolin

2017-10-01

Fiber lasers are now attracting more and more research interest due to their advantages in efficiency, beam quality and flexible operation. Up to now, most of the high power fiber lasers have random distributed polarization state. Linearlypolarized (LP) fiber lasers, which could find wide application potential in coherent detection, coherent/spectral beam combining, nonlinear frequency conversion, have been a research focus in recent years. In this paper, we will present a general review on the achievements of various kinds of high power linear-polarized fiber laser and its application. The recent progress in our group, including power scaling by using power amplifier with different mechanism, high power linearly polarized fiber laser with diversified properties, and various applications of high power linear-polarized fiber laser, are summarized. We have achieved 100 Watt level random distributed feedback fiber laser, kilowatt level continuous-wave (CW) all-fiber polarization-maintained fiber amplifier, 600 watt level average power picosecond polarization-maintained fiber amplifier and 300 watt level average power femtosecond polarization-maintained fiber amplifier. In addition, high power linearly polarized fiber lasers have been successfully applied in 5 kilowatt level coherent beam combining, structured light field and ultrasonic generation.

Optimization of Nanocomposite Solar Cell/Liquid Crystal Matrix to Diminish High Intensity Laser Light Relevant to Aviation Safety Applications

NASA Astrophysics Data System (ADS)

Hofmann, James A.

An increasing threat to the aviation industry is laser light illumination on airplanes during critical phases of flight. If a laser hits the cockpit, it not only distracts the pilots, but it can cause flash blindness or permanently damage the vision of the pilots. This research attempts to mitigate these lasers illuminations through the application of both liquid crystal (LC's) technologies and dye sensitized solar cell (DSSC) technologies. The LC of choice is N-(4-Methoxybenzylidene)-4-butylaniline, or MBBA, because it has special optical properties including the ability to undergo phase transitions when exposed to an electric field. By applying an external electric field, MBBA switches from its transparent nematic phase, to its non-transparent crystalline phase, blocking the laser light. This research optimized the application of MBBA by reducing the triggering voltage and relaxation time of the LC using spacer thicknesses and scratching techniques. The liquid to solid phase transition was reduced to a 3V differential, and the time required for the crystals to relax into its transparent liquid phase was reduced to less than ten seconds. The phase transition was studied using an external electric field generated by DSSCs constructed from a titanium dioxide (TiO2) nanocomposite layer coated with dye. To maximize the voltage output by the DSSCs, layer thickness and dye sensitizer were studied to investigate their impact on the performance of the DSSC when illuminated by solar lamps and green light (532nm). Three different layer thicknesses and five different dyes were tested: Eosin Y, Eriochrome Black, Congo Red, Fast Green, and Alizarine Yellow. The experimental results showed a thin layer of nanocomposite sensitized with Eosin Y dye produced the most efficient DSSCs for the scope of this research. Experimental testing showed the DSSCs can generate 381 +/- 10mV under solar lamp exposure, 356 +/- 10mV under laser light exposure, and a voltage increase of 60 +/- 16mV when exposed to both light sources. Additionally, the performance of the DSSCs were correlated to molecular modeling predictions using Spartan software. The stability of TiO2-dye interactions indicated that dye adsorption to the surface of the nanocomposite directly impacted the performance of the DSSCs. Implementation of a LC and DSSC system forces the LCs to transition between its nematic and crystalline phases depending on the wavelength of light that is illuminating the DSSC. This research explores the practicality of using LCs and DSSCs as a preliminary approach to mitigating green laser light illumination on aircraft. Experimental results have shown that DSSCs alone are not capable of forcing a phase transitions in LCs which can entirely mitigate incoming laser light. The intense laser light required to generate substantial voltage (3V) from the DSSCs penetrates the crystalline phase of the LC with minimal attenuation of 5%.

Photonic integrated circuits unveil crisis-induced intermittency.

PubMed

Karsaklian Dal Bosco, Andreas; Akizawa, Yasuhiro; Kanno, Kazutaka; Uchida, Atsushi; Harayama, Takahisa; Yoshimura, Kazuyuki

2016-09-19

We experimentally investigate an intermittent route to chaos in a photonic integrated circuit consisting of a semiconductor laser with time-delayed optical feedback from a short external cavity. The transition from a period-doubling dynamics to a fully-developed chaos reveals a stage intermittently exhibiting these two dynamics. We unveil the bifurcation mechanism underlying this route to chaos by using the Lang-Kobayashi model and demonstrate that the process is based on a phenomenon of attractor expansion initiated by a particular distribution of the local Lyapunov exponents. We emphasize on the crucial importance of the distribution of the steady-state solutions introduced by the time-delayed feedback on the existence of this intermittent dynamics.

Effects of diode laser welding with dye-enhanced glue on tensile strength of sutures commonly used in urology.

PubMed

Kirsch, A J; Chang, D T; Kayton, M L; Libutti, S K; Connor, J P; Hensle, T W

1996-01-01

Tissue welding using laser-activated protein solders may soon become an alternative to sutured tissue approximation. In most cases, approximating sutures are used both to align tissue edges and provide added tensile strength. Collateral thermal injury, however, may cause disruption of tissue alignment and weaken the tensile strength of sutures. The objective of this study was to evaluate the effect of laser welding on the tensile strength of suture materials used in urologic surgery. Eleven types of sutures were exposed to diode laser energy (power density = 15.9 W/cm2) for 10, 30, and 60 seconds. Each suture was compared with and without the addition of dye-enhanced albumin-based solder. After exposure, each suture material was strained (2"/min) until ultimate breakage on a tensometer and compared to untreated sutures using ANOVA. The strength of undyed sutures were not significantly affected; however, violet and green-dyed sutures were in general weakened by laser exposure in the presence of dye-enhanced glue. Laser activation of the smallest caliber, dyed sutures (7-0) in the presence of glue caused the most significant loss of tensile strength of all sutures tested. These results indicate that the thermal effects of laser welding using our technique decrease the tensile strength of dyed sutures. A thermally resistant suture material (undyed or clear) may prevent disruption of wounds closed by laser welding techniques.

A comparative study of pulsed dye laser versus long pulsed Nd:YAG laser treatment in recalcitrant viral warts.

PubMed

Shin, Yo Sup; Cho, Eun Byul; Park, Eun Joo; Kim, Kwang Ho; Kim, Kwang Joong

2017-08-01

Viral warts are common infectious skin disease induced by human papillomavirus (HPV). But the treatment of recalcitrant warts is still challenging. In this study, we compared the effectiveness of pulsed dye laser (PDL) and long pulsed Nd:YAG (LPNY) laser in the treatment of recalcitrant viral warts. We retrospectively analyzed the medical records of patients with recalcitrant warts treated with laser therapy between January 2013 and February 2016. Seventy-two patients with recalcitrant warts were evaluated. Thirty-nine patients were treated with pulsed dye laser and thirty-three patients were treated with LPNY laser. The following parameters were used: PDL (spot size, 7 mm; pulse duration, 1.5 ms; and fluence, 10-14 J/cm 2 ) and LPNY (spot size, 5 mm; pulse duration, 20 ms; and fluence, 240-300 J/cm 2 ). Complete clearance of two patients (5.1%) in PDL group, and three patients (9.1%) in LPNY group were observed without significant side effects. The patients who achieved at least 50% improvement from baseline were 20 (51.3%) in PDL and 22 (66.7%) in LPNY, respectively. This research is meaningful because we compared the effectiveness of the PDL and LPNY in the recalcitrant warts. Both PDL and LPNY laser could be used as a safe and alternative treatment for recalcitrant warts.

Near-field analysis of metallic DFB lasers at telecom wavelengths.

PubMed

Greusard, L; Costantini, D; Bousseksou, A; Decobert, J; Lelarge, F; Duan, G-H; De Wilde, Y; Colombelli, R

2013-05-06

We image in near-field the transverse modes of semiconductor distributed feedback (DFB) lasers operating at λ ≈ 1.3 μm and employing metallic gratings. The active region is based on tensile-strained InGaAlAs quantum wells emitting transverse magnetic polarized light and is coupled via an extremely thin cladding to a nano-patterned gold grating integrated on the device surface. Single mode emission is achieved, which tunes with the grating periodicity. The near-field measurements confirm laser operation on the fundamental transverse mode. Furthermore--together with a laser threshold reduction observed in the DFB lasers--it suggests that the patterning of the top metal contact can be a strategy to reduce the high plasmonic losses in this kind of systems.

Drug delivery with microsecond laser pulses into gelatin.

PubMed

Shangguan, H; Casperson, L W; Shearin, A; Gregory, K W; Prahl, S A

1996-07-01

Photo acoustic drug delivery is a technique for localized drug delivery by laser-induced hydrodynamic pressure following cavitation bubble expansion and collapse. Photoacoustic drug delivery was investigated on gelatin-based thrombus models with planar and cylindrical geometries by use of one microsecond laser pulses. Solutions of a hydrophobic dye in mineral oil permitted monitoring of delivered colored oil into clear gelatin-based thrombus models. Cavitation bubble development and photoacoustic drug delivery were visualized with flash photography. This study demonstrated that cavitation is the governing mechanism for photoacoustic drug delivery, and the deepest penetration of colored oil in gels followed the bubble collapse. Spatial distribution measurements revealed that colored oil could be driven a few millimeters into the gels in both axial and radial directions, and the penetration was less than 500 µm when the gelatin structure was not fractured.

Modulation of frequency doubled DFB-tapered diode lasers for medical treatment

NASA Astrophysics Data System (ADS)

Christensen, Mathias; Hansen, Anders K.; Noordegraaf, Danny; Jensen, Ole B.; Skovgaard, Peter M. W.

2017-02-01

The use of visible lasers for medical treatments is on the rise, and together with this comes higher expectations for the laser systems. For many medical treatments, such as ophthalmology, doctors require pulse on demand operation together with a complete extinction of the light between pulses. We have demonstrated power modulation from 0.1 Hz to 10 kHz at 532 nm with a modulation depth above 97% by wavelength detuning of the laser diode. The laser diode is a 1064 nm monolithic device with a distributed feedback (DFB) laser as the master oscillator (MO), and a tapered power amplifier (PA). The MO and PA have separate electrical contacts and the modulation is achieved with wavelength tuning by adjusting the current through the MO 40 mA.

Rapid and efficient formation of propagation invariant shaped laser beams.

PubMed

Chriki, Ronen; Barach, Gilad; Tradosnky, Chene; Smartsev, Slava; Pal, Vishwa; Friesem, Asher A; Davidson, Nir

2018-02-19

A rapid and efficient all-optical method for forming propagation invariant shaped beams by exploiting the optical feedback of a laser cavity is presented. The method is based on the modified degenerate cavity laser (MDCL), which is a highly incoherent cavity laser. The MDCL has a very large number of degrees of freedom (320,000 modes in our system) that can be coupled and controlled, and allows direct access to both the real space and Fourier space of the laser beam. By inserting amplitude masks into the cavity, constraints can be imposed on the laser in order to obtain minimal loss solutions that would optimally lead to a superposition of Bessel-Gauss beams forming a desired shaped beam. The resulting beam maintains its transverse intensity distribution for relatively long propagation distances.

Quantum cascade lasers, systems, and applications in Europe

NASA Astrophysics Data System (ADS)

Lambrecht, Armin

2005-03-01

Since the invention of the Quantum Cascade Laser (QCL) a decade ago an impressive progress has been achieved from first low temperature pulsed laser emission to continuous wave operation at room temperature. Distributed feedback (DFB) lasers working in pulsed mode at ambient temperatures and covering a broad spectral range in the mid infrared (MIR) are commercially available now. For many industrial applications e.g. automotive exhaust control and process monitoring, laser spectroscopy is an established technique, generally using near infrared (NIR) diode lasers. However, the mid infrared (MIR) spectral region is of special interest because of much stronger absorption lines compared to NIR. The status of QCL devices, system development and applications is reviewed. Special emphasis is given to the situation in Europe where a remarkable growth of QCL related R&D can be observed.

IN SITU COMBUSTION MEASUREMENTS OF CO2 USING A DISTRIBUTED FEEDBACK DIODE LASER SENSOR NEAR 2.0 MM. (R827123)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

Passive mode lockers for lasers generating at a wavelength of 1.06 micron

NASA Astrophysics Data System (ADS)

Mikhailov, V. P.; Demchuk, M. I.; Lugovskii, A. P.; Sosnovskii, G. M.; Iumashev, K. V.

1983-04-01

New polymethine dyes that can be used for the passive mode locking of lasers generating at 1.06 micron are investigated using YAG:Nd as the active element. The effect of introducing various substituents into the heterocyclic nuclei of the end groups of polymethine dyes is discussed. It is shown that substituents generally increase the energy of the ultrashort pulse while also increasing its length.

Laser inhibited diffusion in rhodamine-ethanol solutions

NASA Technical Reports Server (NTRS)

Lawandy, N. M.; Fuhr, P. L.; Robinson, D. W.

1981-01-01

The diffusion of rhodamine-6G dye in ethanol is observed to be inhibited by optical pumping by a cadmium laser. The diffusion process is observed as a function of the solution temperature. The relative difference in diffusion coefficients with and without optical pumping is calculated. The effect is interpreted as being due to a stronger solvent-dye interaction in the first excited singlet state of rhodamine-6G.

Topical timolol maleate 0.5% for infantile hemangioma; it's effectiveness and/or adjunctive pulsed dye laser - single center experience of 102 cases in Korea.

PubMed

Park, Kyung Hea; Jang, Yong Hyun; Chung, Ho Yun; Lee, Weon Ju; Kim, Do Won; Lee, Seok-Jong

2015-01-01

Although oral beta-blocker, propranolol, was shown excellent outcome for infantile hemangioma (IH) up to date, concern of side effects and reluctance of treatment-related cumbersome evaluations are major obstacles to employ. Instead, topical beta-blockers were recently introduced as an effective alternative, but few studies are reported. So we performed a retrospective study of IH treated with topical beta-blockers, timolol maleate 0.5%, and adjunctive role of pulsed dye laser from 2011 to 2014. Among 102 IH enrolled, 61 patients (59.8%) treated with only timolol maleate and 41 (40.2%) patients treated with combination of pulsed dye laser. A clinical review of medical records and evaluation at 4-8 weeks intervals using the physicians' Global Assessment Scores (GAS) and patients' parents' GAS at the latest visit. Physicians' GAS was used to grade the lesions compared with the baseline photo by two physicians' evaluation. And parents' GAS was assessed by direct or telephone interview. In the only timolol treatment group, mean change was within 47.0% improvement from baseline by physicians. In addition, adjunctive treatment of pulsed dye laser group showed 66.5% improvement. No side effects were found on both groups, and mean change was 54.5% improvement by overall parent assessments.

Pulsed Dye Laser Therapy in the Treatment of Warts: A Review of the Literature.

PubMed

Veitch, David; Kravvas, Georgios; Al-Niaimi, Firas

2017-04-01

Warts or verrucae vulgaris are common cutaneous infections with currently no definitive curative treatments available. To determine the efficacy of pulsed dye laser (PDL) in the treatment of warts. A literature search was performed using the PubMed and MEDLINE databases. A search using {(Wart[s], verruca or condylomata)} AND [(Pulsed dye laser)] was used. Forty-four articles were identified as relevant to this review. Simple warts were very responsive to PDL, being treated successfully in over 95% of patients. Facial and anogenital warts also demonstrated excellent outcomes. Recalcitrant warts, displayed significant variability in their response, ranging between 50% and 100% across all articles. The response rates seen in peripheral warts (involving the hands and feet) were also very variable, ranging between 48% and 95%. Recurrence rates at 4 months of follow-up were documented as 0% to 15%. Complications have been described as very few and rare, the main ones being topical discomfort and erythema. Pulsed dye laser is a safe and effective modality in the treatment of warts that can be applied to most body parts. Cost and availability remain a limitation to the use of PDL; however, this modality can be used when other more traditional and accessible treatments have failed.

Studies on the optogalvanic effect and isotope-selective excitation of ytterbium in a hollow cathode discharge lamp using a pulsed dye laser.

PubMed

Kumar, Pankaj; Kumar, Jitendra; Prakash, Om; Saini, Vinod K; Dixit, Sudhir K; Nakhe, Shankar V

2013-09-01

This paper presents studies on the pulsed optogalvanic effect and isotope-selective excitation of Yb 555.648 nm (0 cm(-1) → 17 992.007 cm(-1)) and 581.067 nm (17 992.007 cm(-1) → 35 196.98 cm(-1)) transitions, in a Yb/Ne hollow cathode lamp. The Yb atoms were excited by narrow linewidth (500-1000 MHz) Rh110 and Rh6G dye based pulsed lasers. Optogalvanic signal inversion for ground state transition at 555.648 nm was observed beyond a hollow cathode discharge current of 8.5 mA, in contrast to normal optogalvanic signal at 581.067 nm up to maximum current of 14 mA. The isotope-selective excitation studies of Yb were carried out by recording Doppler limited optogalvanic signals as a function of dye laser wavelength. For the 581.067 nm transition, three even isotopes, (172)Yb, (174)Yb, and (176)Yb, and one odd isotope, (171)Yb, were clearly resolved. These data were compared with selective isotope excitation by 10 MHz linewidth continuous-wave dye laser. For 555.648 nm transition, isotopes were not clearly resolved, although isotope peaks of low modulation were observed.

Model for a pulsed terahertz quantum cascade laser under optical feedback.

PubMed

Agnew, Gary; Grier, Andrew; Taimre, Thomas; Lim, Yah Leng; Bertling, Karl; Ikonić, Zoran; Valavanis, Alexander; Dean, Paul; Cooper, Jonathan; Khanna, Suraj P; Lachab, Mohammad; Linfield, Edmund H; Davies, A Giles; Harrison, Paul; Indjin, Dragan; Rakić, Aleksandar D

2016-09-05

Optical feedback effects in lasers may be useful or problematic, depending on the type of application. When semiconductor lasers are operated using pulsed-mode excitation, their behavior under optical feedback depends on the electronic and thermal characteristics of the laser, as well as the nature of the external cavity. Predicting the behavior of a laser under both optical feedback and pulsed operation therefore requires a detailed model that includes laser-specific thermal and electronic characteristics. In this paper we introduce such a model for an exemplar bound-to-continuum terahertz frequency quantum cascade laser (QCL), illustrating its use in a selection of pulsed operation scenarios. Our results demonstrate significant interplay between electro-optical, thermal, and feedback phenomena, and that this interplay is key to understanding QCL behavior in pulsed applications. Further, our results suggest that for many types of QCL in interferometric applications, thermal modulation via low duty cycle pulsed operation would be an alternative to commonly used adiabatic modulation.

High-power, fixed, and tunable wavelength, grating-free cascaded Raman fiber lasers.

PubMed

Balaswamy, V; Arun, S; Aparanji, Santosh; Choudhury, Vishal; Supradeepa, V R

2018-04-01

Cascaded Raman lasers enable high powers at various wavelength bands inaccessible with conventional rare-earth-doped lasers. The input and output wavelengths of conventional implementations are fixed by the constituent fiber gratings necessary for cascaded Raman conversion. We demonstrate here a simple architecture for high-power, fixed, and wavelength tunable, grating-free, cascaded Raman conversion between different wavelength bands. The architecture is based on the recently proposed distributed feedback Raman lasers. Here, we implement a module which converts the ytterbium band to the eye-safe 1.5 μm region. We demonstrate pump-limited output powers of over 30 W in fixed and continuously wavelength tunable configurations.

Ultra-broad gain quantum cascade lasers tunable from 6.5 to 10.4 μm.

PubMed

Xie, Feng; Caneau, C; Leblanc, H; Ho, M-T; Zah, C

2015-09-01

We present a quantum cascade laser structure with an ultra-broad gain profile that covers the wavelength range from 6.5 to 10.4 μm. In a grating-tuned external cavity, we demonstrated continuous tuning from 1027  cm(-1) to 1492  cm(-1) with this broad gain laser chip. We also fabricated distributed feedback quantum cascade laser arrays with this active region design and varied grating periods. We demonstrated single wavelength lasing from 962 (10.4) to 1542  cm(-1) (6.5 μm). The frequency coverage (580  cm(-1)) is about 46% of center frequency.

Gain compression and its dependence on output power in quantum dot lasers

NASA Astrophysics Data System (ADS)

Zhukov, A. E.; Maximov, M. V.; Savelyev, A. V.; Shernyakov, Yu. M.; Zubov, F. I.; Korenev, V. V.; Martinez, A.; Ramdane, A.; Provost, J.-G.; Livshits, D. A.

2013-06-01

The gain compression coefficient was evaluated by applying the frequency modulation/amplitude modulation technique in a distributed feedback InAs/InGaAs quantum dot laser. A strong dependence of the gain compression coefficient on the output power was found. Our analysis of the gain compression within the frame of the modified well-barrier hole burning model reveals that the gain compression coefficient decreases beyond the lasing threshold, which is in a good agreement with the experimental observations.

1310nm VCSELs in 1-10Gb/s commercial applications

NASA Astrophysics Data System (ADS)

Jewell, Jack; Graham, Luke; Crom, Max; Maranowski, Kevin; Smith, Joseph; Fanning, Tom

2006-02-01

Beginning with 4 Gigabit/sec Fibre-Channel, 1310nm vertical-cavity surface-emitting lasers (VCSELs) are now entering the marketplace. Such VCSELs perform like distributed feedback lasers but have drive currents and heat dissipation like 850nm VCSELs, making them ideal for today's high-performance interconnects and the only choice for the next step in increased interconnection density. Transceiver performances at 4 and 10 Gigabits/sec over fiber lengths 10-40km are presented. The active material is extremely robust, resulting in excellent reliability.

Applications of lasers and electro-optics

NASA Astrophysics Data System (ADS)

Tan, B. C.; Low, K. S.; Chen, Y. H.; Ahmad, Harith; Tou, T. Y.

Supported by the IRPA Programme on Laser Technology and Applications, many types of lasers have been designed, constructed and applied in various areas of science, medicine and industries. Amongst these lasers constructed were high power carbon dioxide lasers, rare gas halide excimer lasers, solid state Neodymium-YAG lasers, nitrogen lasers, flashlamp pumped dye lasers and nitrogen and excimer laser pumped dye lasers. These lasers and the associated electro-optics system, some with computer controlled, are designed and developed for the following areas of applications: (1) industrial applications of high power carbon dioxide lasers for making of i.c. components and other materials processing purposes -- prototype operational systems have been developed; (2) Medical applications of lasers for cancer treatment using the technique of photodynamic therapy -- a new and more effective treatment protocol has been proposed; (3) agricultural applications of lasers in palm oil and palm fruit-fluorescence diagnostic studies -- fruit ripeness signature has been developed and palm oil oxidation level were investigated; (4) development of atmospheric pollution monitoring systems using laser lidar techniques -- laboratory scale systems were developed; and (5) other applications of lasers including laser holographic and interferometric methods for the non destructive testing of materials.

Portable IR dye laser optofluidic microresonator as a temperature and chemical sensor.

PubMed

Lahoz, F; Martín, I R; Gil-Rostra, J; Oliva-Ramirez, M; Yubero, F; Gonzalez-Elipe, A R

2016-06-27

A compact and portable optofluidic microresonator has been fabricated and characterized. It is based on a Fabry-Perot microcavity consisting essentially of two tailored dichroic Bragg mirrors prepared by reactive magnetron sputtering deposition. The microresonator has been filled with an ethanol solution of Nile-Blue dye. Infrared laser emission has been measured with a pump threshold as low as 0.12 MW/cm² and an external energy conversion efficiency of 41%. The application of the device as a temperature and a chemical sensor is demonstrated. Small temperature variations as well as small amount of water concentrations in the liquid laser medium are detected as a shift of the resonant laser modes.

Recent advance to 3 × 10(-5) rad near diffraction-limited beam divergence of dye laser with transverse-discharge flash-lamp pumping.

PubMed

Trusov, K K

1994-02-20

A new experimental setup of a Rhodamine 6G dye laser with a transverse-discharge flash-lamp-pumping system is presented. It differs from a previous setup [Sov. J. Quantum Electron. 16, 468-471 (1989)] in that it has a larger laser beam aperture (32 mm) and higher pumping energy (1 kJ), which made it possible to test the scalability and reach near diffraction-limited laser beam divergence of 3 × 10(-5) rad FWHM at beam energy 1.4 J. The effect of spectral dispersion in the active medium and of other optical elements on the beam divergence is also discussed.

Update on flashlamp pumped pulsed dye laser treatment for port wine stains (capillary malformation) patients

PubMed Central

Hsiao, Yen-Chang; Chang, Cheng-Jen

2011-01-01

Background and Aims: Currently, the method of choice for the treatment of port-wine stains is laser photocoagulation. Because of evolving treatment options, it is no longer enough for port-wine stains merely to be lightened through laser treatment. The best course of management consists of the most appropriate laser that will produce the most complete clearing of a lesion in the fewest treatment sessions with the least morbidity. The goal is generally accomplished with the use of yellow-light lasers. Materials (Subjects) and Methods: Absorption of laser energy by melanin causes localized heating in the epidermis, which may, if not controlled, produce permanent complications such as hypertrophic scarring or dyspigmentation. Refinements of the results can be achieved by using the flashlamp-pumped pulsed dye laser (FLPDL) in conjunction with the cryogen spray cooling (CSC) system. In our related studies, the infrared thermal image instrument is used for doctors in determining the optimum laser light dosage and preventing the side effects caused by FLPDL. Topic application of angiogenesis inhibitor (Imiquimod) in conjunction with pulsed dye laser treatment for the PWS patients has been assessed for improvement of FLPDL treatment. Results: We present the clinical effect of FLPDL, and the efficacy and safety of cooled laser treatment of PWS birthmarks. Our clinical outcome in the laser treatment of patients with PWS has been achieved to maximize thermal impact on targeted vessels, while minimizing adverse complications. Conclusions: CSC in conjunction with FLPDL can improve the treatment of PWS. The infrared image instrument is helpful for doctors in determining the optimum laser light dosage. Topic application of angiogenesis inhibitor (Imiquimod) in conjunction with laser treatment for the PWS patients is promising in the near future. PMID:24155536

Continuous-Wave Single-Frequency Operation of Fabry-Perot Laser Diodes by Self-Injection Phase Locking Using Feedback from a Fiber Bragg Grating

NASA Technical Reports Server (NTRS)

Duerksen, Gary L.; Krainak, Michael A.

1998-01-01

Single-frequency operation of uncoated Fabry-Perot laser diodes is demonstrated by phase- locking the laser oscillations through self-injection seeding with feedback from a fiber Bragg grating. By precisely tuning the laser temperature so that an axial-mode coincides with the short-wavelength band edge of the grating, the phase of the feedback is made conjugate to that of the axial mode, locking the phase of the laser oscillations to that mode.

Temperature feedback control for long-term carrier-envelope phase locking

DOEpatents

Chang, Zenghu [Manhattan, KS; Yun, Chenxia [Manhattan, KS; Chen, Shouyuan [Manhattan, KS; Wang, He [Manhattan, KS; Chini, Michael [Manhattan, KS

2012-07-24

A feedback control module for stabilizing a carrier-envelope phase of an output of a laser oscillator system comprises a first photodetector, a second photodetector, a phase stabilizer, an optical modulator, and a thermal control element. The first photodetector may generate a first feedback signal corresponding to a first portion of a laser beam from an oscillator. The second photodetector may generate a second feedback signal corresponding to a second portion of the laser beam filtered by a low-pass filter. The phase stabilizer may divide the frequency of the first feedback signal by a factor and generate an error signal corresponding to the difference between the frequency-divided first feedback signal and the second feedback signal. The optical modulator may modulate the laser beam within the oscillator corresponding to the error signal. The thermal control unit may change the temperature of the oscillator corresponding to a signal operable to control the optical modulator.

Study of nonlinear refraction of organic dye by Z-scan technique using He-Ne laser

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

Medhekar, S.; Kumar, R.; Mukherjee, S.

2013-02-05

Laser induced third-order nonlinear optical responses of Brilliant Green solution has been investigated by utilizing single beam Z-scan technique with a continuous-wave He-Ne laser radiation at 632.8 nm. It was observed that the material exhibits self-defocusing type optical nonlinearity. The measurements of nonlinear refraction were carried out at different dye concentrations and found that the increase in solution concentration leads to the linear increase of the nonlinear refractive index. The experimental results confirm great potential of the Brilliant Green for the application in nonlinear optical devices.

Laser synthesized super-hydrophobic conducting carbon with broccoli-type morphology as a counter-electrode for dye sensitized solar cells.

PubMed

Gokhale, Rohan; Agarkar, Shruti; Debgupta, Joyashish; Shinde, Deodatta; Lefez, Benoit; Banerjee, Abhik; Jog, Jyoti; More, Mahendra; Hannoyer, Beatrice; Ogale, Satishchandra

2012-11-07

A laser photochemical process is introduced to realize superhydrophobic conducting carbon coatings with broccoli-type hierarchical morphology for use as a metal-free counter electrode in a dye sensitized solar cell. The process involves pulsed excimer laser irradiation of a thin layer of liquid haloaromatic organic solvent o-dichlorobenzene (DCB). The coating reflects a carbon nanoparticle-self assembled and process-controlled morphology that yields solar to electric power conversion efficiency of 5.1% as opposed to 6.2% obtained with the conventional Pt-based electrode.

Fluorimetric studies and noncovalent labeling of protein with the near-infrared dye HITCI for analysis by CE-LIF.

PubMed

Yan, Weiying; Colyer, Christa L

2005-08-01

1,1',3,3,3',3'-Hexamethylindotricarbocyanine iodide (HITCI) is a commercially available, positively charged, indocarbocyanine dye used typically as a laser dye in the near infrared (NIR). The absorbance and fluorescence properties of HITCI in a variety of solvent systems were determined. Results indicate that the fluorescence of HITCI is not significantly affected by the pH. Titration of HITCI with human serum albumin (HSA) and trypsinogen was carried out to investigate the interactions between this dye and proteins. These studies revealed that the absorbance and fluorescence properties of the dye change upon binding to protein in a wide range of solution pH's. The potential use of HITCI as a noncovalent protein labeling probe, therefore, was explored. Determination and separation of HITCI and HITCI-protein complexes was performed by capillary electrophoresis with diode-laser induced fluorescence detection (CE-LIF). Both pre-column and on-column noncovalent labeling methods are demonstrated.

Fiber-Type Random Laser Based on a Cylindrical Waveguide with a Disordered Cladding Layer.

PubMed

Zhang, Wei Li; Zheng, Meng Ya; Ma, Rui; Gong, Chao Yang; Yang, Zhao Ji; Peng, Gang Ding; Rao, Yun Jiang

2016-05-25

This letter reports a fiber-type random laser (RL) which is made from a capillary coated with a disordered layer at its internal surface and filled with a gain (laser dye) solution in the core region. This fiber-type optical structure, with the disordered layer providing randomly scattered light into the gain region and the cylindrical waveguide providing confinement of light, assists the formation of random lasing modes and enables a flexible and efficient way of making random lasers. We found that the RL is sensitive to laser dye concentration in the core region and there exists a fine exponential relationship between the lasing intensity and particle concentration in the gain solution. The proposed structure could be a fine platform of realizing random lasing and random lasing based sensing.

Comparison study of a long-pulse pulsed dye laser and a long-pulse pulsed alexandrite laser in the treatment of port wine stains.

PubMed

Li, Li; Kono, Taro; Groff, William Frederick; Chan, Henry H; Kitazawa, Yoshihiko; Nozaki, Motohiro

2008-03-01

Port wine stains (PWSs) are commonly treated by the pulsed dye laser. Recently, a long-pulse pulsed alexandrite laser was used to treat bulky vascular malformations. In the present study, we compare the efficacy and complications of the long-pulse pulsed dye laser (LPPDL) and the long-pulse pulsed alexandrite laser (LPPAL) in the treatment of PWSs. Eleven patients with Fitzpatrick skin types III-IV were enrolled in this study. One section of each patient's PWS was treated with LPPDL and another section was treated with LPPAL. The patients' PWSs were evaluated for efficacy of elimination of erythema and for treatment-related side effects. Both LPPDL and LPPAL treatment are effective in the treatment of PWSs. Hyperpigmentation was seen in two areas treated with LPPDL and in three areas treated with LPPAL. Hypopigmentation was seen in one area treated with LPPAL, but not in any of the areas treated with LPPDL. There was no scarring. LPPAL works best with hypertrophic, purple PWSs, while LPPDL yields better clinical improvements with the flat, pink PWSs. Targeting of deoxyhemoglobin, deeper penetration, and higher fluence may explain the effectiveness of LPPAL in purple, hypertrophic PWSs. However, there is a risk of dyspigmentation when using the LPPAL.

Study of excitation transfer in laser dye mixtures by direct measurement of fluorescence lifetime

NASA Technical Reports Server (NTRS)

Lin, C.; Dienes, A.

1973-01-01

By directly measuring the donor fluorescence lifetime as a function of acceptor concentration in the laser dye mixture Rhodamine 6G-Cresyl violet, we found that the Stern-Volmer relation is obeyed, from which the rate of excitation transfer is determined. The experimental results indicate that the dominant mechanism responsible for the efficient excitation transfer is that of resonance transfer due to long range dipole-dipole interaction.

Spectral plasmonic effect in the nano-cavity of dye-doped nanosphere-based photonic crystals.

PubMed

Yadav, Ashish; Danesh, Mohammad; Zhong, Liubiao; Cheng, Gary J; Jiang, Lin; Chi, Lifeng

2016-04-22

We demonstrated three-dimensional PMMA-based photonic crystal (3D-PC) nanostructures attached to Au nanoparticles (AuNPs), which undergo self-organization into super lattice planes and enhance the fluorescence properties. This new structure exhibited interesting tunable spectral, peak broadening plasmonic behavior because of strong plasmonic interaction at high laser powers. The presented work provides an important tool to improve the efficiency of dye laser applications.

Azaquinolone dye lasers

DOEpatents

Hammond, Peter R.; Atkins, Ronald L.; Henry, Ronald A.; Fletcher, Aaron N.

1978-01-01

A dye laser comprising a laser dye solution of a compound having the general structure: ##STR1## wherein at least one of the 5, 6 and 8 ring positions is occupied by a nitrogen atom in lieu of the corresponding CR group and X is OH, alkoxy, or amino including amino substituted by at least one of the following: alkyl, aryl, acyl, aracyl, a group which taken together with the nitrogen atom of the amino group forms a heterocyclic ring, or part of one or two 5 or 6 membered aliphatic heterocyclic rings attached to ring A at positions 6 or 8 or both depending on where the N in ring A is located. R.sub.1, R.sub.3, R.sub.4, R.sub.5, R.sub.6 and R.sub.8 are hydrogen or other groups as defined below. The compounds lase in the blue to near ultraviolet region.

Azacoumarin dye lasers

DOEpatents

Hammond, Peter R.; Atkins, Ronald L.; Henry, Ronald A.; Fletcher, Aaron N.

1978-01-01

A dye laser comprising a laser dye solution of a compound having the general structure: ##STR1## wherein at least one of the 5, 6 and 8 ring positions is occupied by a nitrogen atom in lieu of the corresponding CR group and X is OH, alkoxy, or amino including amino substituted by at least one of the following: alkyl, aryl, acyl, aracyl, a group which taken together with the nitrogen atom of the amino group forms a heterocyclic ring, or part of one or two 5 or 6 membered aliphatic heterocyclic rings attached to ring A at positions 6 or 8 or both depending on where the N in ring A is located. R.sub.3, R.sub.4, R.sub.5, R.sub.6 and R.sub.8 are hydrogen or other groups as defined below. The compounds lase in the blue-green to near ultraviolet region.

Response of microchip solid-state laser to external frequency-shifted feedback and its applications

PubMed Central

Tan, Yidong; Zhang, Shulian; Zhang, Song; Zhang, Yongqing; Liu, Ning

2013-01-01

The response of the microchip solid-state Nd:YAG laser, which is subjected to external frequency-shifted feedback, is experimentally and theoretically analysed. The continuous weak response of the laser to the phase and amplitude of the feedback light is achieved by controlling the feedback power level, and this system can be used to achieve contact-free measurement of displacement, vibration, liquid evaporation and thermal expansion with nanometre accuracy in common room conditions without precise environmental control. Furthermore, a strong response, including chaotic harmonic and parametric oscillation, is observed, and the spectrum of this response, as examined by a frequency-stabilised Nd:YAG laser, indicates laser spectral linewidth broadening. PMID:24105389

Response of microchip solid-state laser to external frequency-shifted feedback and its applications.

PubMed

Tan, Yidong; Zhang, Shulian; Zhang, Song; Zhang, Yongqing; Liu, Ning

2013-10-09

The response of the microchip solid-state Nd:YAG laser, which is subjected to external frequency-shifted feedback, is experimentally and theoretically analysed. The continuous weak response of the laser to the phase and amplitude of the feedback light is achieved by controlling the feedback power level, and this system can be used to achieve contact-free measurement of displacement, vibration, liquid evaporation and thermal expansion with nanometre accuracy in common room conditions without precise environmental control. Furthermore, a strong response, including chaotic harmonic and parametric oscillation, is observed, and the spectrum of this response, as examined by a frequency-stabilised Nd:YAG laser, indicates laser spectral linewidth broadening.

Safety approaches for high power modular laser operation

NASA Astrophysics Data System (ADS)

Handren, R. T.

1993-03-01

Approximately 20 years ago, a program was initiated at the Lawrence Livermore National Laboratory (LLNL) to study the feasibility of using lasers to separate isotopes of uranium and other materials. Of particular interest was the development of a uranium enrichment method for the production of commercial nuclear power reactor fuel to replace current more expensive methods. The Uranium Atomic Vapor Laser Isotope Separation (U-AVLIS) Program progressed to the point where a plant-scale facility to demonstrate commercial feasibility was built and is being tested. The U-AVLIS Program uses copper vapor lasers which pump frequency selective dye lasers to photoionize uranium vapor produced by an electron beam. The selectively ionized isotopes are electrostatically collected. The copper lasers are arranged in oscillator/amplifier chains. The current configuration consists of 12 chains, each with a nominal output of 800 W for a system output in excess of 9 kW. The system requirements are for continuous operation (24 h a day, 7 days a week) and high availability. To meet these requirements, the lasers are designed in a modular form allowing for rapid change-out of the lasers requiring maintenance. Since beginning operation in early 1985, the copper lasers have accumulated over 2 million unit hours at a greater than 90% availability. The dye laser system provides approximately 2.5 kW average power in the visible wavelength range. This large-scale laser system has many safety considerations, including high-power laser beams, high voltage, and large quantities (approximately 3000 gal) of ethanol dye solutions. The Laboratory's safety policy requires that safety controls be designed into any process, equipment, or apparatus in the form of engineering controls. Administrative controls further reduce the risk to an acceptable level. Selected examples of engineering and administrative controls currently being used in the U-AVLIS Program are described.

DNA fragment sizing and sorting by laser-induced fluorescence

DOEpatents

Hammond, Mark L.; Jett, James H.; Keller, Richard A.; Marrone, Babetta L.; Martin, John C.

1996-01-01

A method is provided for sizing DNA fragments using high speed detection systems, such as flow cytometry to determine unique characteristics of DNA pieces from a sample. In one characterization the DNA piece is fragmented at preselected sites to produce a plurality of DNA fragments. The DNA piece or the resulting DNA fragments are treated with a dye effective to stain stoichiometrically the DNA piece or the DNA fragments. The fluorescence from the dye in the stained fragments is then examined to generate an output functionally related to the number of nucleotides in each one of the DNA fragments. In one embodiment, the intensity of the fluorescence emissions from each fragment is linearly related to the fragment length. The distribution of DNA fragment sizes forms a characterization of the DNA piece for use in forensic and research applications.

Constant peak-power single-frequency linearly-polarized all-fiber laser for coherent detection based on closed-loop feedback technology

NASA Astrophysics Data System (ADS)

Ding, Yaqian; Zhang, Xiang; Li, Dong; Wang, Dapeng; Zhang, Renzhong; Song, Chengying; Che, Haozhao; Wang, Rui; Guo, Baoling; Chen, Guanghui

2015-10-01

In this paper, a practical single-frequency high-repetition linearly-polarized eye-safe all-fiber laser with constant peak power is demonstrated. It is based on master-oscillator power amplifier (MOPA) system. A distributed feedback laser diode simulating at 1550nm with narrow linewidth of 2.3 kHz is employed as the seed source. It is modulated to a pulse laser with high repetition of 20 kHz and peak power of 10mW by an acousto-optic modulator (AOM). The pulse width is tunable between 100ns to 400ns. Two-stage cascade amplifier is established, which consists of a pre-amplifier and a power-amplifier. Amplified spontaneous emission (ASE) and stimulated billion scattering are well suppressed by special management. The output peak power of 30W is obtained, which has nearly diffraction-limited beam quality. It operates in linewidth of 1.2MHz, polarization-extinction ratio (PER) of 25dB and signal-to-noise ratio (SNR) of more than 40dB. Gain of the whole amplifier achieves nearly 35dB. Furthermore, an embedded control system (ECS) based on the WinCE operating system (OS) and the chip of S3C2440 is proposed. This control system based on closed-loop feedback technology makes the peak power keeping constant even the pulse width tunable, which is convenient for the end user of the radar. This robust portable laser is remarkable and fulfills the desire of coherent detection excellently.

Chaotic dynamics and synchronization in microchip solid-state lasers with optoelectronic feedback.

PubMed

Uchida, Atsushi; Mizumura, Keisuke; Yoshimori, Shigeru

2006-12-01

We experimentally observe the dynamics of a two-mode Nd:YVO4 microchip solid-state laser with optoelectronic feedback. The total laser output is detected and fed back to the injection current of the laser diode for pumping. Chaotic oscillations are observed in the microchip laser with optoelectronic self-feedback. We also observe the dynamics of two microchip lasers coupled mutually with optoelectronic link. The output of one laser is detected by a photodiode and the electronic signal converted from the laser output is sent to the pumping of the other laser. Chaotic fluctuation of the laser output is observed when the relaxation oscillation frequency is close to each other between the two microchip lasers. Synchronization of periodic wave form is also obtained when the microchip lasers have a single-longitudinal mode.

Modeling and experimental verification of laser self-mixing interference phenomenon with the structure of two-external-cavity feedback

NASA Astrophysics Data System (ADS)

Chen, Peng; Liu, Yuwei; Gao, Bingkun; Jiang, Chunlei

2018-03-01

A semiconductor laser employed with two-external-cavity feedback structure for laser self-mixing interference (SMI) phenomenon is investigated and analyzed. The SMI model with two directions based on F-P cavity is deduced, and numerical simulation and experimental verification were conducted. Experimental results show that the SMI with the structure of two-external-cavity feedback under weak light feedback is similar to the sum of two SMIs.

MEASUREMENTS OF AMMONIA (NH3) AND CARBON DIOXIDE (CO2) WITH DISTRIBUTED FEEDBACK (DFB) LASERS NEAR MICROMETERS IN BIOREACTOR VENT GASES. (R827123)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

SPECTROSCOPY-MEASUREMENTS OF NH3 AND CO2 WITH DISTRIBUTED FEEDBACK (DFB) LASERS NEAR 2 MM IN BIOREACTOR VENT GASES. (R827123)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

Measurements of NH 3 and CO 2 with Distributed-Feedback Diode Lasers Near 2.0 m in Bioreactor Vent Gases

NASA Astrophysics Data System (ADS)

Webber, Michael E.; Claps, Ricardo; Englich, Florian V.; Tittel, Frank K.; Jeffries, Jay B.; Hanson, Ronald K.

2001-08-01

Measurements of NH3 and CO2 were made in bioreactor vent gases with distributed-feedback diode-laser sensors operating near 2 m. Calculated spectra of NH3 and CO2 were used to determine the optimum transitions for interrogating with an absorption sensor. For ammonia, a strong and isolated absorption transition at 5016.977 cm-1 was selected for trace gas monitoring. For CO2 , an isolated transition at 5007.787 cm-1 was selected to measure widely varying concentrations [500 parts per million (ppm) to 10% ,] with sufficient signal for low mole fractions and without being optically thick for high mole fractions. Using direct absorption and a 36-m total path-length multipass flow-through cell, we achieved a minimum detectivity of 0.25 ppm for NH3 and 40 ppm for CO2 . We report on the quasi-continuous field measurements of NH3 and CO2 concentration in bioreactor vent gases that were recorded at NASA Johnson Space Center with a portable and automated sensor system over a 45-h data collection window.

Stabilized Lasers and Precision Measurements.

ERIC Educational Resources Information Center

Hall, J. L.

1978-01-01

Traces the development of stabilized lasers from the Massachusetts Institute of Technology passive-stabilization experiments of the early 1960s up through the current epoch of highly stabilized helium-neon and carbon dioxide and continuous wave dye lasers. (Author/HM)

Pulsed dye laser double-pass treatment of patients with resistant capillary malformations.

PubMed

Rajaratnam, Ratna; Laughlin, Sharyn A; Dudley, Denis

2011-07-01

The pulsed dye laser is an effective and established treatment for port-wine stains and has become the generally accepted standard of care. However, in many cases, complete clearance cannot be achieved as a significant proportion of lesions become resistant to treatment. Multiple passes or pulse-stacking techniques have been used to improve the extent and rate of fading, but concerns over increased adverse effects have limited this clinical approach. In this work, a double-pass technique with the pulsed dye laser has been described, which may allow for increased depth of vascular injury, greater efficacy, and an acceptable risk profile. Our aim was to determine the efficacy and the rate of side-effects for a double-pass protocol with a pulsed dye laser (PDL) to treat patients previously treated with PDL and/or other laser modalities. A retrospective chart review was conducted of 26 patients treated with a minimum of three double-pass treatments alone, or in combination, with single pass conventional PDL. Almost half of the patients (n = 12) showed either a moderate or significant improvement in fading compared to pre-treatment photographs with the double-pass technique. In a further 12 patients, there was a mild improvement. In two patients, there was no change. Sixteen patients developed mild side-effects: blisters (n = 5), dry scabs (n = 11) and transient hyperpigmentation (n = 4). This preliminary experience suggests that a double-pass technique at defined intervals between the first and second treatment with PDL can further lighten some port-wine stains, which are resistant to conventional single-pass treatments. This technique may be a useful addition to the laser treatment of PWS and deserves further scrutiny with randomized prospective studies and histological analysis to confirm the increased depth of vascular injury.

Measuring evaporation rates of laser-trapped droplets by use of fluorescent morphology-dependent resonances.

PubMed

Pastel, R; Struthers, A

2001-05-20

Morphology-dependent resonances (MDRs) are used to measure accurately the evaporation rates of laser-trapped 1- to 2-mum droplets of ethylene glycol. Droplets containing 3 x 10(-5) M Rhodamine-590 laser dye are optically trapped in a 20-mum hollow fiber by two counterpropagating 150-mW, 800-nm laser beams. A weaker 532-nm laser excites the dye, and fluorescence emission is observed near 560 nm as the droplet evaporates. A complete series of first-order TE and TM MDRs dominates the fluorescent output. MDR mode identification sizes the droplets and provides accurate evaporation rates. We verify the automated MDR mode identification by counting fringes in a videotape of the experiment. The longitudinal spring constant of the trap, measured by analysis of the videotaped motion of droplets perturbed from the trap center, provides independent verification of the laser's intensity within the trap.

Measuring Evaporation Rates of Laser-Trapped Droplets by Use of Fluorescent Morphology-Dependent Resonances

NASA Astrophysics Data System (ADS)

Pastel, Robert; Struthers, Allan

2001-05-01

Morphology-dependent resonances (MDRs) are used to measure accurately the evaporation rates of laser-trapped 1- to 2- m droplets of ethylene glycol. Droplets containing 3 x10-5 M Rhodamine-590 laser dye are optically trapped in a 20- m hollow fiber by two counterpropagating 150-mW, 800-nm laser beams. A weaker 532-nm laser excites the dye, and fluorescence emission is observed near 560 nm as the droplet evaporates. A complete series of first-order TE and TM MDRs dominates the fluorescent output. MDR mode identification sizes the droplets and provides accurate evaporation rates. We verify the automated MDR mode identification by counting fringes in a videotape of the experiment. The longitudinal spring constant of the trap, measured by analysis of the videotaped motion of droplets perturbed from the trap center, provides independent verification of the laser s intensity within the trap.

An overview of clinical and experimental treatment modalities for port wine stains

PubMed Central

Chen, Jennifer K.; Ghasri, Pedram; Aguilar, Guillermo; van Drooge, Anne Margreet; Wolkerstorfer, Albert; Kelly, Kristen M.; Heger, Michal

2014-01-01

Port wine stains (PWS) are the most common vascular malformation of the skin, occurring in 0.3% to 0.5% of the population. Noninvasive laser irradiation with flashlamp-pumped pulsed dye lasers (selective photothermolysis) currently comprises the gold standard treatment of PWS; however, the majority of PWS fail to clear completely after selective photothermolysis. In this review, the clinically used PWS treatment modalities (pulsed dye lasers, alexandrite lasers, neodymium:yttrium-aluminum-garnet lasers, and intense pulsed light) and techniques (combination approaches, multiple passes, and epidermal cooling) are discussed. Retrospective analysis of clinical studies published between 1990 and 2011 was performed to determine therapeutic efficacies for each clinically used modality/technique. In addition, factors that have resulted in the high degree of therapeutic recalcitrance are identified, and emerging experimental treatment strategies are addressed, including the use of photodynamic therapy, immunomodulators, angiogenesis inhibitors, hypobaric pressure, and site-specific pharmaco-laser therapy. PMID:22305042

Pump spot size dependent lasing threshold in organic semiconductor DFB lasers fabricated via nanograting transfer.

PubMed

Liu, Xin; Klinkhammer, Sönke; Wang, Ziyao; Wienhold, Tobias; Vannahme, Christoph; Jakobs, Peter-Jürgen; Bacher, Andreas; Muslija, Alban; Mappes, Timo; Lemmer, Uli

2013-11-18

Optically excited organic semiconductor distributed feedback (DFB) lasers enable efficient lasing in the visible spectrum. Here, we report on the rapid and parallel fabrication of DFB lasers via transferring a nanograting structure from a flexible mold onto an unstructured film of the organic gain material. This geometrically well-defined structure allows for a systematic investigation of the laser threshold behavior. The laser thresholds for these devices show a strong dependence on the pump spot diameter. This experimental finding is in good qualitative agreement with calculations based on coupled-wave theory. With further investigations on various DFB laser geometries prepared by different routes and based on different organic gain materials, we found that these findings are quite general. This is important for the comparison of threshold values of various devices characterized under different excitation areas.

Microwave generation in an electro-absorption modulator integrated with a DFB laser subject to optical injection.

PubMed

Zhu, Ning Hua; Zhang, Hong Guang; Man, Jiang Wei; Zhu, Hong Liang; Ke, Jian Hong; Liu, Yu; Wang, Xin; Yuan, Hai Qing; Xie, Liang; Wang, Wei

2009-11-23

This paper presents a new technique to generate microwave signal using an electro-absorption modulator (EAM) integrated with a distributed feedback (DFB) laser subject to optical injection. Experiments show that the frequency of the generated microwave can be tuned by changing the wavelength of the external laser or adjusting the bias voltage of the EAM. The frequency response of the EAM is studied and found to be unsmooth due to packaging parasitic effects and four-wave mixing effect occurring in the active layer of the DFB laser. It is also demonstrated that an EA modulator integrated in between two DFB lasers can be used instead of the EML under optical injection. This integrated chip can be used to realize a monolithically integrated tunable microwave source.

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.

UV laser interaction with a fluorescent dye solution studied using pulsed digital holography.

PubMed

Amer, Eynas; Gren, Per; Sjödahl, Mikael

2013-10-21

A frequency tripled Q-switched Nd-YAG laser (wavelength 355 nm, pulse duration 12 ns) has been used to pump Coumarin 153 dye solved in ethanol. Simultaneously, a frequency doubled pulse (532 nm) from the same laser is used to probe the solvent perpendicularly resulting in a gain through stimulated laser induced fluorescence (LIF) emission. The resulting gain of the probe beam is recorded using digital holography by blending it with a reference beam on the detector. Two digital holograms without and with the pump beam were recorded. Intensity maps were calculated from the recorded digital holograms and used to calculate the gain of the probe beam due to the stimulated LIF. In addition numerical data of the local temperature rise was calculated from the corresponding phase maps using Radon inversion. It was concluded that about 15% of the pump beam energy is transferred to the dye solution as heat while the rest is consumed in the radiative process. The results show that pulsed digital holography is a promising technique for quantitative study of fluorescent species.

Enhanced optical confinement of dye-doped dielectric nanoparticles using a picosecond-pulsed near-infrared laser

NASA Astrophysics Data System (ADS)

Kittiravechote, A.; Chiang, W.-Y.; Usman, A.; Liau, I.; Masuhara, H.

2014-07-01

We demonstrate a novel strategy to increase the capability of confining numerous dye-doped polymeric nanobeads (diameter 100 nm) with laser trapping. Unlike most classical works of optical trapping that address mainly the stiffness of the optical trap, our work concerns an increase in the number of particles confined near the laser focus. We developed an imaging system of light scattering in which a condenser lamp was employed to illuminate the focal plane of the objective lens, and the scattering of the incoherent light was specifically measured to determine the number of confined nanobeads. In contrast to preceding work that used mainly continuous-wave or femtosecond-pulsed lasers, we employed a picosecond-pulsed laser with the half-wavelength of the laser particularly falling within the absorption band of the dopant. Our results show that the number of doped nanobeads held by the laser is significantly greater than that of the bare nanobeads of the same dimension. In striking contrast, the confinement of the nanobeads of the two types was comparable when a continuous-wave laser of the same wavelength and power was employed. The number of confined dye-doped nanobeads increased nonlinearly with the power of the pulsed laser; this dependence was fitted satisfactorily with a second-order polynomial. Supported by theoretical analysis, we attribute the enhanced confinement of doped nanobeads in part to an increased effective refractive index resulting from two-photon resonance between the optical field of the laser and the dopant of the nanobead. We envisage that our findings would evoke applications that benefit from controlled confinement or aggregation of nanomaterials with the employment of near-infrared pulsed lasers.

Pulsed-Dye Laser Treatment of Port-Wine Stains in Children: Useful Tips to Avoid General Anesthesia.

PubMed

Alegre-Sánchez, Adrián; Pérez-García, Bibiana; Boixeda, Pablo

2017-09-01

Pulsed dye laser (PDL) treatment of port-wine stains (PWSs) in children is a common procedure performed in most laser units. Pain assessment in our younger patients is a major concern, especially in those with extensive PWSs. The use of general anesthesia (GA) results in pain-free treatment, but its effects on the developing brain are far from totally understood. Thus we propose some tips that avoid the use of GA in most of our young patients, including the use of topical anesthetics and cooling systems, large laser spot size and high frequencies, early and frequent treatment with parents present, and the "introduction" and "pressure" techniques, among others. © 2017 Wiley Periodicals, Inc.

Coumarin-BODIPY hybrids by heteroatom linkage: versatile, tunable and photostable dye lasers for UV irradiation.

PubMed

Esnal, I; Duran-Sampedro, G; Agarrabeitia, A R; Bañuelos, J; García-Moreno, I; Macías, M A; Peña-Cabrera, E; López-Arbeloa, I; de la Moya, S; Ortiz, M J

2015-03-28

Linking amino and hydroxycoumarins to BODIPYs through the amino or hydroxyl group lets the easy construction of unprecedented photostable coumarin-BODIPY hybrids with broadened and enhanced absorption in the UV spectral region, and outstanding wavelength-tunable laser action within the green-to-red spectral region (∼520-680 nm). These laser dyes allow the generation of a valuable tunable UV (∼260-350 nm) laser source by frequency doubling, which is essential to study accurately the photochemistry of biological molecules under solar irradiation. The tunability is achieved by selecting the substitution pattern of the hybrid. Key factors are the linking heteroatom (nitrogen vs. oxygen), the number of coumarin units joined to the BODIPY framework and the involved linking positions.

Laser tissue welding mediated with a protein solder

NASA Astrophysics Data System (ADS)

Small, Ward, IV; Heredia, Nicholas J.; Celliers, Peter M.; Da Silva, Luiz B.; Eder, David C.; Glinsky, Michael E.; London, Richard A.; Maitland, Duncan J.; Matthews, Dennis L.; Soltz, Barbara A.

1996-05-01

A study of laser tissue welding mediated with an indocyanine green dye-enhanced protein solder was performed. Freshly obtained sections of porcine artery were used for the experiments. Sample arterial wall thickness ranged from two to three millimeters. Incisions approximately four millimeters in length were treated using an 805 nanometer continuous- wave diode laser coupled to a one millimeter diameter fiber. Controlled parameters included the power delivered by the laser, the duration of the welding process, and the concentration of dye in the solder. A two-color infrared detection system was constructed to monitor the surface temperatures achieved at the weld site. Burst pressure measurements were made to quantify the strengths of the welds immediately following completion of the welding procedure.

Pulse Width Dependence Of Pigment Cell Damage At 694 nm In Guinea Pig Skin

NASA Astrophysics Data System (ADS)

Dover, Jeffrey S.; Polla, Luigi L.; Margolis, Randall J.; Whitaker, Diana; Watanabe, Schinichi; Murphy, George F.; Parrish, John A.; Anderson, R. R.

1987-03-01

351 nm, 20-nsec XeF excimer laser irradiation has previously been shown to selectively target and damage melanosomes in human skin. In the following studies selective targeting with melanosomal photodisruption has been demonstrated in pigmented guinea pig skin with a Q-switched 40-nsec ruby laser, and a 750-nsec pulsed dye laser but not with a 400-usec pulsed dye laser. The pulse width dependence of melanosomal disruption, occurring only at pulsewidths shorter than the thermal relaxation time of the melanosome (0.5 - 1.0 usec), is in accordance with the theory of selective photothermolysis. Possible mechanisms of melanosomal photodisruption include development of sudden thermal gradients leading to cavitation or shock wave production.

High power tunable mid-infrared optical parametric oscillator enabled by random fiber laser.

PubMed

Wu, Hanshuo; Wang, Peng; Song, Jiaxin; Ye, Jun; Xu, Jiangming; Li, Xiao; Zhou, Pu

2018-03-05

Random fiber laser, as a kind of novel fiber laser that utilizes random distributed feedback as well as Raman gain, has become a research focus owing to its advantages of wavelength flexibility, modeless property and output stability. Herein, a tunable optical parametric oscillator (OPO) enabled by a random fiber laser is reported for the first time. By exploiting a tunable random fiber laser to pump the OPO, the central wavelength of idler light can be continuously tuned from 3977.34 to 4059.65 nm with stable temporal average output power. The maximal output power achieved is 2.07 W. So far as we know, this is the first demonstration of a continuous-wave tunable OPO pumped by a tunable random fiber laser, which could not only provide a new approach for achieving tunable mid-infrared (MIR) emission, but also extend the application scenarios of random fiber lasers.

Development of a see-through hollow cathode discharge lamp for (Li/Ne) optogalvanic studies

NASA Astrophysics Data System (ADS)

Saini, V. K.; Kumar, P.; Sarangpani, K. K.; Dixit, S. K.; Nakhe, S. V.

2017-09-01

Development of a demountable and see-through hollow cathode (HC) discharge lamp suitable for optogalvanic (OG) spectroscopy is described. The design of the HC lamp is simple, compact, and inexpensive. Lithium, investigated rarely by the OG method, is selected for cathode material as its isotopes are important for nuclear industry. The HC lamp is characterized electrically and optically for discharge oscillations free OG effect. Strong OG signals of lithium as well as neon (as buffer gas) are produced precisely upon copper vapor laser pumped tunable dye laser irradiation. The HC lamp is capable of generating a clean OG resonance spectrum in the available dye laser wavelength scanning range (627.5-676 nm) obtained with 4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran dye. About 28 resonant OG lines are explicitly observed. Majority of them have been identified using j-l coupling scheme and assigned to the well-known neon transitions. One line that corresponds to wavelength near about 670.80 nm is assigned to lithium and resolved for its fine (2S1/2 → 2P1/2, 3/2) transitions. These OG transitions allow 0.33 cm-1 accuracy and can be used to supplement the OG transition data available from other sources to calibrate the wavelength of a scanning dye laser with precision at atomic levels.