Earth-to-Orbit Laser Launch Simulation for a Lightcraft Technology Demonstrator

NASA Astrophysics Data System (ADS)

Richard, J. C.; Morales, C.; Smith, W. L.; Myrabo, L. N.

2006-05-01

Optimized laser launch trajectories have been developed for a 1.4 m diameter, 120 kg (empty mass) Lightcraft Technology Demonstrator (LTD). The lightcraft's combined-cycle airbreathing/rocket engine is designed for single-stage-to-orbit flights with a mass ratio of 2 propelled by a 100 MW class ground-based laser built on a 3 km mountain peak. Once in orbit, the vehicle becomes an autonomous micro-satellite. Two types of trajectories were simulated with the SORT (Simulation and Optimization of Rocket Trajectories) software package: a) direct GBL boost to orbit, and b) GBL boost aided by laser relay satellite. Several new subroutines were constructed for SORT to input engine performance (as a function of Mach number and altitude), vehicle aerodynamics, guidance algorithms, and mass history. A new guidance/steering option required the lightcraft to always point at the GBL or laser relay satellite. SORT iterates on trajectory parameters to optimize vehicle performance, achieve a desired criteria, or constrain the solution to avoid some specific limit. The predicted laser-boost performance for the LTD is undoubtedly revolutionary, and SORT simulations have helped to define this new frontier.

Rb vapor-cell clock demonstration with a frequency-doubled telecom laser.

PubMed

Almat, Nil; Pellaton, Matthieu; Moreno, William; Gruet, Florian; Affolderbach, Christoph; Mileti, Gaetano

2018-06-01

We employ a recently developed laser system, based on a low-noise telecom laser emitting around 1.56 μm, to evaluate its impact on the performance of an Rb vapor-cell clock in a continuous-wave double-resonance scheme. The achieved short-term clock instability below 2.5·10 -13 ·τ -1/2 demonstrates, for the first time, the suitability of a frequency-doubled telecom laser for this specific application. We measure and study quantitatively the impact of laser amplitude and frequency noises and of the ac Stark shift, which limit the clock frequency stability on short timescales. We also report on the detailed noise budgets and demonstrate experimentally that, under certain conditions, the short-term stability of the clock operated with the low-noise telecom laser is improved by a factor of three compared to clock operation using the direct 780-nm laser.

Molecular dispersion spectroscopy based on Fabry-Perot quantum cascade lasers.

PubMed

Sterczewski, Lukasz A; Westberg, Jonas; Wysocki, Gerard

2017-01-15

Two Fabry-Perot quantum cascade lasers are used in a differential dual comb configuration to perform rapidly swept dispersion spectroscopy of low-pressure nitrous oxide with <1  ms acquisition time. Active feedback control of the laser injection current enables simultaneous wavelength modulation of both lasers at kilohertz rates. The system demonstrates similar performance in both absorption and dispersion spectroscopy modes and achieves a noise-equivalent absorption figure of merit in the low 10^-4/Hz range.

The national ignition facility: Path to ignition in the laboratory

NASA Astrophysics Data System (ADS)

Moses, E. I.; Bonanno, R. E.; Haynam, C. A.; Kauffman, R. L.; MacGowan, B. J.; Patterson, R. W., Jr.; Sawicki, R. H.; van Wonterghem, B. M.

2006-06-01

The National Ignition Facility (NIF) is a 192-beam laser facility presently under construction at LLNL. When completed, NIF will be a 1.8-MJ, 500-TW ultraviolet laser system. Its missions are to obtain fusion ignition and to perform high energy density experiments in support of the U.S. nuclear weapons stockpile. Four of the NIF beams have been commissioned to demonstrate laser performance and to commission the target area including target and beam alignment and laser timing. During this time, NIF demonstrated on a single-beam basis that it will meet its performance goals and demonstrated its precision and flexibility for pulse shaping, pointing, timing and beam conditioning. It also performed four important experiments for Inertial Confinement Fusion and High Energy Density Science. Presently, the project is installing production hardware to complete the project in 2009 with the goal to begin ignition experiments in 2010. An integrated plan has been developed including the NIF operations, user equipment such as diagnostics and cryogenic target capability, and experiments and calculations to meet this goal. This talk will provide NIF status, the plan to complete NIF, and the path to ignition.

Three-dimensional non-destructive optical evaluation of laser-processing performance using optical coherence tomography.

PubMed

Kim, Youngseop; Choi, Eun Seo; Kwak, Wooseop; Shin, Yongjin; Jung, Woonggyu; Ahn, Yeh-Chan; Chen, Zhongping

2008-06-01

We demonstrate the use of optical coherence tomography (OCT) as a non-destructive diagnostic tool for evaluating laser-processing performance by imaging the features of a pit and a rim. A pit formed on a material at different laser-processing conditions is imaged using both a conventional scanning electron microscope (SEM) and OCT. Then using corresponding images, the geometrical characteristics of the pit are analyzed and compared. From the results, we could verify the feasibility and the potential of the application of OCT to the monitoring of the laser-processing performance.

Three-dimensional non-destructive optical evaluation of laser-processing performance using optical coherence tomography

PubMed Central

Kim, Youngseop; Choi, Eun Seo; Kwak, Wooseop; Shin, Yongjin; Jung, Woonggyu; Ahn, Yeh-Chan; Chen, Zhongping

2014-01-01

We demonstrate the use of optical coherence tomography (OCT) as a non-destructive diagnostic tool for evaluating laser-processing performance by imaging the features of a pit and a rim. A pit formed on a material at different laser-processing conditions is imaged using both a conventional scanning electron microscope (SEM) and OCT. Then using corresponding images, the geometrical characteristics of the pit are analyzed and compared. From the results, we could verify the feasibility and the potential of the application of OCT to the monitoring of the laser-processing performance. PMID:24932051

Improved performance of the laser guide star adaptive optics system at Lick Observatory

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

An, J R; Avicola, K; Bauman, B J

1999-07-20

Results of experiments with the laser guide star adaptive optics system on the 3-meter Shane telescope at Lick Observatory have demonstrated a factor of 4 performance improvement over previous results. Stellar images recorded at a wavelength of 2 {micro}m were corrected to over 40% of the theoretical diffraction-limited peak intensity. For the previous two years, this sodium-layer laser guide star system has corrected stellar images at this wavelength to {approx}10% of the theoretical peak intensity limit. After a campaign to improve the beam quality of the laser system, and to improve calibration accuracy and stability of the adaptive optics systemmore » using new techniques for phase retrieval and phase-shifting diffraction interferometry, the system performance has been substantially increased. The next step will be to use the Lick system for astronomical science observations, and to demonstrate this level of performance with the new system being installed on the 10-meter Keck II telescope.« less

Demonstrator study for micro-ranging-laser device

NASA Astrophysics Data System (ADS)

Henkel, Hartmut; Bernhardt, Bodo; Pereira do Carmo, J.

2017-11-01

Within ESA's Innovation Triangle Initiative (ITI) a demonstrator breadboard for a micro-ranging-laser device "MYLRAD" has been developed. Its working principle is the measurement of the round-trip delay time of a laser beam as a phase shift. The demonstrator consists of the laser diode (30 mW, square wave AM), optics, APD detector, narrowband preamplifier, limiter, and a phase digitiser based on a novel noise-shaping synchroniser (NSS) circuit; this works without ADCs and can be built from rad-hard components for space. The system timing and the digitiser algorithm are performed by an FPGA. The demonstrator has been tested at ranges from 1 m to 30 m. With a static non-cooperative target an RMS noise of 1 mm at a result rate of 60 Hz was reached. The demonstrator needs less than 2.5 W power.

All-fiber wavelength swept ring laser based on Fabry-Perot filter for optical frequency domain imaging

PubMed Central

Jun, Changsu; Villiger, Martin; Oh, Wang-Yuhl; Bouma, Brett E.

2014-01-01

Innovations in laser engineering have yielded several novel configurations for high repetition rate, broad sweep range, and long coherence length wavelength swept lasers. Although these lasers have enabled high performance frequency-domain optical coherence tomography, they are typically complicated and costly and many require access to proprietary materials or devices. Here, we demonstrate a simplified ring resonator configuration that is straightforward to construct from readily available materials at a low total cost. It was enabled by an insight regarding the significance of isolation against bidirectional operation and by configuring the sweep range of the intracavity filter to exceed its free spectral range. The design can easily be optimized to meet a range of operating specifications while yielding robust and stable performance. As an example, we demonstrate 240 kHz operation with 125 nm sweep range and >70 mW of average output power and demonstrate high quality frequency domain OCT imaging. The complete component list and directions for assembly of the laser are posted on-line at www.octresearch.org. PMID:25401614

Quantum dot lasers: From promise to high-performance devices

NASA Astrophysics Data System (ADS)

Bhattacharya, P.; Mi, Z.; Yang, J.; Basu, D.; Saha, D.

2009-03-01

Ever since self-organized In(Ga)As/Ga(AI)As quantum dots were realized by molecular beam epitaxy, it became evident that these coherently strained nanostructures could be used as the active media in devices. While the expected advantages stemming from three-dimensional quantum confinement were clearly outlined, these were not borne out by the early experiments. It took a very detailed understanding of the unique carrier dynamics in the quantum dots to exploit their full potential. As a result, we now have lasers with emission wavelengths ranging from 0.7 to 1.54 μm, on GaAs, which demonstrate ultra-low threshold currents, near-zero chip and α-factor and large modulation bandwidth. State-of-the-art performance characteristics of these lasers are briefly reviewed. The growth, fabrication and characteristics of quantum dot lasers on silicon substrates are also described. With the incorporation of multiple quantum dot layers as a dislocation filter, we demonstrate lasers with Jth=900 A/cm 2. The monolithic integration of the lasers with guided wave modulators on silicon is also described. Finally, the properties of spin-polarized lasers with quantum dot active regions are described. Spin injection of electrons is done with a MnAs/GaAs tunnel barrier. Laser operation at 200 K is demonstrated, with the possibility of room temperature operation in the near future.

Intensity noise properties of a compact laser device based on a miniaturized MOPA system for spectroscopic applications

NASA Astrophysics Data System (ADS)

Baumgärtner, S.; Juhl, S.; Opalevs, D.; Sahm, A.; Hofmann, J.; Leisching, P.; Paschke, K.

2018-02-01

We present a novel compact laser device based on a semiconductor master-oscillator power-amplifier (MOPA) emitting at 772 nm, suitable for quantum optic and spectroscopy. The optical performance of the laser device is characterized. For miniaturized lasers the thermal management is challenging, we therefore perform thermal simulations and measurements. The first demonstrator is emitting more than 3 W optical power with a linewidth below 2lMHz. Using this MOPA design also compact devices for quantum optics (e.g. rubidium atomic clock) and seed lasers for frequency conversion can be realized [1].

Large laser projection displays utilizing all-solid-state RGB lasers

NASA Astrophysics Data System (ADS)

Xu, Zuyan; Bi, Yong

2005-01-01

RGB lasers projection displays have the advantages of producing large color triangle, high color saturation and high image resolution. In this report, with more than 4W white light synthesized by red (671nm), green (532nm) and blue (473nm) lasers, a RGB laser projection display system based on diode pumped solid-state lasers is developed and the performance of brilliant and vivid DVD dynamitic pictures on 60 inch screen is demonstrated.

Hypersonic Inlet for a Laser Powered Propulsion System

NASA Astrophysics Data System (ADS)

Harrland, Alan; Doolan, Con; Wheatley, Vincent; Froning, Dave

2011-11-01

Propulsion within the lightcraft concept is produced via laser induced detonation of an incoming hypersonic air stream. This process requires suitable engine configurations that offer good performance over all flight speeds and angles of attack to ensure the required thrust is maintained. Stream traced hypersonic inlets have demonstrated the required performance in conventional hydrocarbon fuelled scramjet engines, and has been applied to the laser powered lightcraft vehicle. This paper will outline the current methodology employed in the inlet design, with a particular focus on the performance of the lightcraft inlet at angles of attack. Fully three-dimensional turbulent computational fluid dynamics simulations have been performed on a variety of inlet configurations. The performance of the lightcraft inlets have been evaluated at differing angles of attack. An idealized laser detonation simulation has also been performed to validate that the lightcraft inlet does not unstart during the laser powered propulsion cycle.

Highly efficient dual-wavelength mid-infrared CW Laser in diode end-pumped Er:SrF2 single crystals

PubMed Central

Ma, Weiwei; Qian, Xiaobo; Wang, Jingya; Liu, Jingjing; Fan, Xiuwei; Liu, Jie; Su, Liangbi; Xu, Jun

2016-01-01

The spectral properties and laser performance of Er:SrF2 single crystals were investigated and compared with Er:CaF2. Er:SrF2 crystals have larger absorption cross-sections at the pumping wavelength, larger mid-infrared stimulated emission cross-sections and much longer fluorescence lifetimes of the upper laser level (Er3+:4I11/2 level) than those of Er:CaF2 crystals. Dual-wavelength continuous-wave (CW) lasers around 2.8 μm were demonstrated in both 4at.% and 10at.% Er:SrF2 single crystals under 972 nm laser diode (LD) end pumping. The laser wavelengths are 2789.3 nm and 2791.8 nm in the former, and 2786.4 nm and 2790.7 nm in the latter, respectively. The best laser performance has been demonstrated in lightly doped 4at.% Er:SrF2 with a low threshold of 0.100 W, a high slope efficiency of 22.0%, an maximum output power of 0.483 W. PMID:27811994

Highly efficient dual-wavelength mid-infrared CW Laser in diode end-pumped Er:SrF2 single crystals.

PubMed

Ma, Weiwei; Qian, Xiaobo; Wang, Jingya; Liu, Jingjing; Fan, Xiuwei; Liu, Jie; Su, Liangbi; Xu, Jun

2016-11-04

The spectral properties and laser performance of Er:SrF 2 single crystals were investigated and compared with Er:CaF 2 . Er:SrF 2 crystals have larger absorption cross-sections at the pumping wavelength, larger mid-infrared stimulated emission cross-sections and much longer fluorescence lifetimes of the upper laser level (Er 3+ : 4 I 11/2 level) than those of Er:CaF 2 crystals. Dual-wavelength continuous-wave (CW) lasers around 2.8 μm were demonstrated in both 4at.% and 10at.% Er:SrF 2 single crystals under 972 nm laser diode (LD) end pumping. The laser wavelengths are 2789.3 nm and 2791.8 nm in the former, and 2786.4 nm and 2790.7 nm in the latter, respectively. The best laser performance has been demonstrated in lightly doped 4at.% Er:SrF 2 with a low threshold of 0.100 W, a high slope efficiency of 22.0%, an maximum output power of 0.483 W.

Highly efficient dual-wavelength mid-infrared CW Laser in diode end-pumped Er:SrF2 single crystals

NASA Astrophysics Data System (ADS)

Ma, Weiwei; Qian, Xiaobo; Wang, Jingya; Liu, Jingjing; Fan, Xiuwei; Liu, Jie; Su, Liangbi; Xu, Jun

2016-11-01

The spectral properties and laser performance of Er:SrF2 single crystals were investigated and compared with Er:CaF2. Er:SrF2 crystals have larger absorption cross-sections at the pumping wavelength, larger mid-infrared stimulated emission cross-sections and much longer fluorescence lifetimes of the upper laser level (Er3+:4I11/2 level) than those of Er:CaF2 crystals. Dual-wavelength continuous-wave (CW) lasers around 2.8 μm were demonstrated in both 4at.% and 10at.% Er:SrF2 single crystals under 972 nm laser diode (LD) end pumping. The laser wavelengths are 2789.3 nm and 2791.8 nm in the former, and 2786.4 nm and 2790.7 nm in the latter, respectively. The best laser performance has been demonstrated in lightly doped 4at.% Er:SrF2 with a low threshold of 0.100 W, a high slope efficiency of 22.0%, an maximum output power of 0.483 W.

Experimental demonstration of low laser-plasma instabilities in gas-filled spherical hohlraums at laser injection angle designed for ignition target

NASA Astrophysics Data System (ADS)

Lan, Ke; Li, Zhichao; Xie, Xufei; Chen, Yao-Hua; Zheng, Chunyang; Zhai, Chuanlei; Hao, Liang; Yang, Dong; Huo, Wen Yi; Ren, Guoli; Peng, Xiaoshi; Xu, Tao; Li, Yulong; Li, Sanwei; Yang, Zhiwen; Guo, Liang; Hou, Lifei; Liu, Yonggang; Wei, Huiyue; Liu, Xiangming; Cha, Weiyi; Jiang, Xiaohua; Mei, Yu; Li, Yukun; Deng, Keli; Yuan, Zheng; Zhan, Xiayu; Zhang, Haijun; Jiang, Baibin; Zhang, Wei; Deng, Xuewei; Liu, Jie; Du, Kai; Ding, Yongkun; Wei, Xiaofeng; Zheng, Wanguo; Chen, Xiaodong; Campbell, E. M.; He, Xian-Tu

2017-03-01

Octahedral spherical hohlraums with a single laser ring at an injection angle of 55∘ are attractive concepts for laser indirect drive due to the potential for achieving the x-ray drive symmetry required for high convergence implosions. Laser-plasma instabilities, however, are a concern given the long laser propagation path in such hohlraums. Significant stimulated Raman scattering has been observed in cylindrical hohlraums with similar laser propagation paths during the ignition campaign on the National Ignition Facility (NIF). In this Rapid Communication, experiments demonstrating low levels of laser-driven plasma instability (LPI) in spherical hohlraums with a laser injection angle of 55∘ are reported and compared to that observed with cylindrical hohlraums with injection angles of 28 .5∘ and 55∘, similar to that of the NIF. Significant LPI is observed with the laser injection of 28 .5∘ in the cylindrical hohlraum where the propagation path is similar to the 55∘ injection angle for the spherical hohlraum. The experiments are performed on the SGIII laser facility with a total 0.35 -μ m incident energy of 93 kJ in a 3 nsec pulse. These experiments demonstrate the role of hohlraum geometry in LPI and demonstrate the need for systematic experiments for choosing the optimal configuration for ignition studies with indirect drive inertial confinement fusion.

Experimental demonstration of low laser-plasma instabilities in gas-filled spherical hohlraums at laser injection angle designed for ignition target.

PubMed

Lan, Ke; Li, Zhichao; Xie, Xufei; Chen, Yao-Hua; Zheng, Chunyang; Zhai, Chuanlei; Hao, Liang; Yang, Dong; Huo, Wen Yi; Ren, Guoli; Peng, Xiaoshi; Xu, Tao; Li, Yulong; Li, Sanwei; Yang, Zhiwen; Guo, Liang; Hou, Lifei; Liu, Yonggang; Wei, Huiyue; Liu, Xiangming; Cha, Weiyi; Jiang, Xiaohua; Mei, Yu; Li, Yukun; Deng, Keli; Yuan, Zheng; Zhan, Xiayu; Zhang, Haijun; Jiang, Baibin; Zhang, Wei; Deng, Xuewei; Liu, Jie; Du, Kai; Ding, Yongkun; Wei, Xiaofeng; Zheng, Wanguo; Chen, Xiaodong; Campbell, E M; He, Xian-Tu

2017-03-01

Octahedral spherical hohlraums with a single laser ring at an injection angle of 55^{∘} are attractive concepts for laser indirect drive due to the potential for achieving the x-ray drive symmetry required for high convergence implosions. Laser-plasma instabilities, however, are a concern given the long laser propagation path in such hohlraums. Significant stimulated Raman scattering has been observed in cylindrical hohlraums with similar laser propagation paths during the ignition campaign on the National Ignition Facility (NIF). In this Rapid Communication, experiments demonstrating low levels of laser-driven plasma instability (LPI) in spherical hohlraums with a laser injection angle of 55^{∘} are reported and compared to that observed with cylindrical hohlraums with injection angles of 28.5^{∘} and 55^{∘}, similar to that of the NIF. Significant LPI is observed with the laser injection of 28.5^{∘} in the cylindrical hohlraum where the propagation path is similar to the 55^{∘} injection angle for the spherical hohlraum. The experiments are performed on the SGIII laser facility with a total 0.35-μm incident energy of 93 kJ in a 3 nsec pulse. These experiments demonstrate the role of hohlraum geometry in LPI and demonstrate the need for systematic experiments for choosing the optimal configuration for ignition studies with indirect drive inertial confinement fusion.

Theoretical and experimental aspects of laser cutting with a direct diode laser

NASA Astrophysics Data System (ADS)

Costa Rodrigues, G.; Pencinovsky, J.; Cuypers, M.; Duflou, J. R.

2014-10-01

Recent developments in beam coupling techniques have made it possible to scale up the power of diode lasers with a laser beam quality suitable for laser cutting of metal sheets. In this paper a prototype of a Direct Diode Laser (DDL) source (BPP of 22 mm-mrad) is analyzed in terms of efficiency and cut performance and compared with two established technologies, CO2 and fiber lasers. An analytical model based on absorption calculations is used to predict the performance of the studied laser source with a good agreement with experimental results. Furthermore results of fusion cutting of stainless steel and aluminium alloys as well as oxygen cutting of structural steel are presented, demonstrating that industrial relevant cutting speeds with high cutting quality can now be achieved with DDL.

Reconfigurable Computing As an Enabling Technology for Single-Photon-Counting Laser Altimetry

NASA Technical Reports Server (NTRS)

Powell, Wesley; Hicks, Edward; Pinchinat, Maxime; Dabney, Philip; McGarry, Jan; Murray, Paul

2003-01-01

Single-photon-counting laser altimetry is a new measurement technique offering significant advantages in vertical resolution, reducing instrument size, mass, and power, and reducing laser complexity as compared to analog or threshold detection laser altimetry techniques. However, these improvements come at the cost of a dramatically increased requirement for onboard real-time data processing. Reconfigurable computing has been shown to offer considerable performance advantages in performing this processing. These advantages have been demonstrated on the Multi-KiloHertz Micro-Laser Altimeter (MMLA), an aircraft based single-photon-counting laser altimeter developed by NASA Goddard Space Flight Center with several potential spaceflight applications. This paper describes how reconfigurable computing technology was employed to perform MMLA data processing in real-time under realistic operating constraints, along with the results observed. This paper also expands on these prior results to identify concepts for using reconfigurable computing to enable spaceflight single-photon-counting laser altimeter instruments.

Laser induced extraplanar propulsion for three-dimensional microfabrication

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

Birnbaum, A. J.; Pique, A.

The laser induced extraplanar propulsion process is presented for the creation of controllable three-dimensional deformation of on-substrate components. It is demonstrated that the process is compatible with transparent substrates and ductile materials and is highly controllable in terms of the desired deformation via the adjustment of incident laser energy density. Copper films with thicknesses varying from 0.1-1 {mu}m are deformed over bending angles ranging from 0 deg. - 180 deg. A 355 nm laser at fluences ranging from 10-40 mJ/cm{sup 2} is used in conjunction with an indium-tin-oxide propulsion layer to demonstrate the process. Characterization is performed via electron andmore » laser confocal microscopy.« less

Use of 1070 nm fiber lasers in oral surgery: preliminary ex vivo study with FBG temperature monitoring.

PubMed

Fornaini, Carlo; Merigo, Elisabetta; Poli, Federica; Cavatorta, Chiara; Rocca, Jean-Paul; Selleri, Stefano; Cucinotta, Annamaria

2017-12-31

The aim of this ex vivo study was to demonstrate the performances of 1070 nm fiber lasers for the ablation of oral tissues through the evaluation of the histological modifications made by a blind pathologist and the measurement of the thermal elevation during laser irradiation by a sensor based on a fiber Bragg grating. The source used was a pulsed fiber laser emitting at 1070 nm, with 20 W maximum average output power and 100 ns fixed pulse duration. Different tests were performed by changing the laser parameters, particularly the peak power of the pulses and the repetition rate. The tissue of the measurements demonstrated that the best properties in term of cutting capability and, at the same time, the lower thermal damages to the tissues can be obtained with a peak power of 3 kW, a repetition rate of 50 kHz and a speed of 5 mm/s. This ex vivo study showed that 1070 nm fiber lasers can be very useful in oral surgery, since they provide a reduced thermal elevation in the irradiated tissues, thus consequently respecting their biological structures. Moreover, this work demonstrates that FBG sensors, based on the optical fiber technology as the laser source considered for the tests, may be good instruments to record thermal elevation when applied to the ex vivo studies on animal models.

Kilohertz VLIF (volumetric laser induced fluorescence) measurements in a seeded free gas-phase jet in the transitionally turbulent flow regime

NASA Astrophysics Data System (ADS)

Wu, Yue; Xu, Wenjiang; Ma, Lin

2018-03-01

This paper reports the demonstration of instantaneous three-dimension (3D) measurements in turbulent flows at repetition rates up to 10 kHz using VLIF (volumetric laser induced fluorescence). The measurements were performed based on the LIF signal of iodine (I2) vapor seeded in the flow. The LIF signals of I2 vapor were generated volumetrically by a thick laser slab and then simultaneously captured by a total of seven cameras from different perspectives, based on which a 3D tomographic reconstruction was performed to obtain the 3D distribution of I2 vapor concentration. Single-shot measurements obtained in a duration of hundreds of nanoseconds (limited by the pulse duration of the excitation laser) were demonstrated in a 50 × 50 × 50 mm3 at a repetition rate up to 10 kHz. These measurements demonstrated the feasibility and potential of VLIF for resolving the 4D spatiotemporal dynamics of turbulent flows. Based on the experimental results obtained, this work also studied the VLIF signal level and its effects on the reconstruction accuracy under different the measurement conditions, illustrating the capabilities and limitations of performing high speed VLIF measurements.

Composite Yb:YAG/SiC-prism thin disk laser.

PubMed

Newburgh, G A; Michael, A; Dubinskii, M

2010-08-02

We report the first demonstration of a Yb:YAG thin disk laser wherein the gain medium is intracavity face-cooled through bonding to an optical quality SiC prism. Due to the particular design of the composite bonded Yb:YAG/SiC-prism gain element, the laser beam impinges on all refractive index interfaces inside the laser cavity at Brewster's angles. The laser beam undergoes total internal reflection (TIR) at the bottom of the Yb(10%):YAG thin disk layer in a V-bounce cavity configuration. Through the use of TIR and Brewster's angles, no optical coatings, either anti-reflective (AR) or highly reflective (HR), are required inside the laser cavity. In this first demonstration, the 936.5-nm diode pumped laser performed with approximately 38% slope efficiency at 12 W of quasi-CW (Q-CW) output power at 1030 nm with a beam quality measured at M(2) = 1.5. This demonstration opens up a viable path toward novel thin disk laser designs with efficient double-sided room-temperature heatsinking via materials with the thermal conductivity of copper on both sides of the disk.

Low threshold CW Nc laser oscillator at 1060 nm study

NASA Technical Reports Server (NTRS)

Birnbaum, M.; Deshazer, L. G.

1976-01-01

A broad range of characteristics of neodymium/yag lasers were investigated. With Nd:YVO4 crystals, CW 1.06 mu lasers were operated with thresholds a factor of 2 lower than Nd:YAG and with greater slope efficiencies. Thus, the first step in the development of new oscillators suitable for application in high data rate laser communication systems which surpass the present performance of the Nd:YAG laser has been successfully demonstrated.

High Average Power Raman Conversion in Diamond: ’Eyesafe’ Output and Fiber Laser Conversion

DTIC Science & Technology

2015-06-19

Eyesafe’ output and fiber laser conversion 5a. CONTRACT NUMBER FA2386-12-1-4055 5b. GRANT NUMBER Grant 12RSZ077_124055 5c. PROGRAM ELEMENT...generating 380 W was demonstrated using a 630 W Ybdoped fiber laser system. In each case the performance was unsaturated and limited by the available pump...converter for conventional high power laser technologies including Nd doped lasers and Yb-doped fiber lasers. Diamond’s power handling capability now

Toward robot-assisted neurosurgical lasers.

PubMed

Motkoski, Jason W; Yang, Fang Wei; Lwu, Shelly H H; Sutherland, Garnette R

2013-04-01

Despite the potential increase in precision and accuracy, laser technology is not widely used in neurological surgery. This in part relates to challenges associated with the early introduction of lasers into neurosurgery. Considerable advances in laser technology have occurred, which together with robotic technology could create an ideal platform for neurosurgical application. In this study, a 980-nm contact diode laser was integrated with neuroArm. Preclinical evaluation involved partial hepatectomy, bilateral nephrectomy, splenectomy, and bilateral submandibular gland excision in a Sprague-Dawley rat model (n = 50). Total surgical time, blood loss as weight of surgical gauze before and after the procedure, and the incidence of thermal, vascular, or lethal injury were recorded and converted to an overall performance score. Thermal damage was evaluated in the liver using tissue samples stained with hematoxylin and eosin. Clinical studies involved step-wise integration of the 980-nm laser system into four neurosurgical cases. Results demonstrate the successful integration of contact laser technology into microsurgery, with and without robotic assistance. In preclinical studies, the laser improved microsurgical performance and reduced thermal damage, while neuroArm decreased intra- and intersurgeon variability. Clinical studies demonstrate dutility in meningioma resection (n = 4). Together, laser and robotic technology offered a more consistent, expedient, and precise tool for microsurgery.

Ocular dynamics and visual tracking performance after Q-switched laser exposure

NASA Astrophysics Data System (ADS)

Zwick, Harry; Stuck, Bruce E.; Lund, David J.; Nawim, Maqsood

2001-05-01

In previous investigations of q-switched laser retinal exposure in awake task oriented non-human primates (NHPs), the threshold for retinal damage occurred well below that of the threshold for permanent visual function loss. Visual function measures used in these studies involved measures of visual acuity and contrast sensitivity. In the present study, we examine the same relationship for q-switched laser exposure using a visual performance task, where task dependency involves more parafoveal than foveal retina. NHPs were trained on a visual pursuit motor tracking performance task that required maintaining a small HeNe laser spot (0.3 degrees) centered in a slowly moving (0.5deg/sec) annulus. When NHPs reliably produced visual target tracking efficiencies > 80%, single q-switched laser exposures (7 nsec) were made coaxially with the line of sight of the moving target. An infrared camera imaged the pupil during exposure to obtain the pupillary response to the laser flash. Retinal images were obtained with a scanning laser ophthalmoscope 3 days post exposure under ketamine and nembutol anesthesia. Q-switched visible laser exposures at twice the damage threshold produced small (about 50mm) retinal lesions temporal to the fovea; deficits in NHP visual pursuit tracking were transient, demonstrating full recovery to baseline within a single tracking session. Post exposure analysis of the pupillary response demonstrated that the exposure flash entered the pupil, followed by 90 msec refractory period and than a 12 % pupillary contraction within 1.5 sec from the onset of laser exposure. At 6 times the morphological threshold damage level for 532 nm q-switched exposure, longer term losses in NHP pursuit tracking performance were observed. In summary, q-switched laser exposure appears to have a higher threshold for permanent visual performance loss than the corresponding threshold to produce retinal threshold injury. Mechanisms of neural plasticity within the retina and at higher visual brain centers may mediat

Thermal Management of Quantum Cascade Lasers in an individually Addressable Array Architecture

DTIC Science & Technology

2016-02-08

Thermal Management of Quantum Cascade Lasers in an Individually Addressable Monolithic Array Architecture Leo Missaggia, Christine Wang, Michael...power laser systems in the mid-to-long-infrared wavelength range. By virtue of their demonstrated watt-level performance and wavelength diversity...quantum cascade laser (QCL) and amplifier devices are an excellent choice of emitter for those applications. To realize the power levels of interest

Novel CO2 laser robotic controller outperforms experienced laser operators in tasks of accuracy and performance repeatability.

PubMed

Wong, Yu-Tung; Finley, Charles C; Giallo, Joseph F; Buckmire, Robert A

2011-08-01

To introduce a novel method of combining robotics and the CO(2) laser micromanipulator to provide excellent precision and performance repeatability designed for surgical applications. Pilot feasibility study. We developed a portable robotic controller that appends to a standard CO(2) laser micromanipulator. The robotic accuracy and laser beam path repeatability were compared to six experienced users of the industry standard micromanipulator performing the same simulated surgical tasks. Helium-neon laser beam video tracking techniques were employed. The robotic controller demonstrated superiority over experienced human manual micromanipulator control in accuracy (laser path within 1 mm of idealized centerline), 97.42% (standard deviation [SD] 2.65%), versus 85.11% (SD 14.51%), P = .018; and laser beam path repeatability (area of laser path divergence on successive trials), 21.42 mm(2) (SD 4.35 mm(2) ) versus 65.84 mm(2) (SD 11.93 mm(2) ), P = .006. Robotic micromanipulator control enhances accuracy and repeatability for specific laser tasks. Computerized control opens opportunity for alternative user interfaces and additional safety features. Copyright © 2011 The American Laryngological, Rhinological, and Otological Society, Inc.

Flowing Air-Water Cooled Slab Nd: Glass Laser

NASA Astrophysics Data System (ADS)

Lu, Baida; Cai, Bangwei; Liao, Y.; Xu, Shifa; Xin, Z.

1989-03-01

A zig-zag optical path slab geometry Nd: glass laser cooled through flowing air-water is developed by us. Theoretical studies on temperature distribution of slab and rod configurations in the unsteady state clarify the advantages of the slab geometry laser. The slab design and processing are also reported. In our experiments main laser output characteristics, e. g. laser efficiency, polarization, far-field divergence angle as well as resonator misalignment are investigated. The slab phosphate glass laser in combination with a crossed Porro-prism resonator demonstrates a good laser performance.

Excimer laser calibration system.

PubMed

Gottsch, J D; Rencs, E V; Cambier, J L; Hall, D; Azar, D T; Stark, W J

1996-01-01

Excimer laser photoablation for refractive and therapeutic keratectomies has been demonstrated to be feasible and practicable. However, corneal laser ablations are not without problems, including the delivery and maintenance of a homogeneous beam. We have developed an excimer laser calibration system capable of characterizing a laser ablation profile. Beam homogeneity is determined by the analysis of a polymethylmethacrylate (PMMA)-based thin-film using video capture and image processing. The ablation profile is presented as a color-coded map. Interpolation of excimer calibration system analysis provides a three-dimensional representation of elevation profiles that correlates with two-dimensional scanning profilometry. Excimer calibration analysis was performed before treating a monkey undergoing phototherapeutic keratectomy and two human subjects undergoing myopic spherocylindrical photorefractive keratectomy. Excimer calibration analysis was performed before and after laser refurbishing. Laser ablation profiles in PMMA are resolved by the excimer calibration system to .006 microns/pulse. Correlations with ablative patterns in a monkey cornea were demonstrated with preoperative and postoperative keratometry using corneal topography, and two human subjects using video-keratography. Excimer calibration analysis predicted a central-steep-island ablative pattern with the VISX Twenty/Twenty laser, which was confirmed by corneal topography immediately postoperatively and at 1 week after reepithelialization in the monkey. Predicted central steep islands in the two human subjects were confirmed by video-keratography at 1 week and at 1 month. Subsequent technical refurbishing of the laser resulted in a beam with an overall increased ablation rate measured as microns/pulse with a donut ablation profile. A patient treated after repair of the laser electrodes demonstrated no central island. This excimer laser calibration system can precisely detect laser-beam ablation profiles. The calibration system correctly predicted central islands after excimer photoablation in a treated monkey cornea and in two treated human subjects. Detection of excimer-laser-beam ablation profiles may be useful for precise calibration of excimer lasers before human photorefractive and therapeutic surgery.

Robust, frequency-stable and accurate mid-IR laser spectrometer based on frequency comb metrology of quantum cascade lasers up-converted in orientation-patterned GaAs.

PubMed

Hansen, Michael G; Ernsting, Ingo; Vasilyev, Sergey V; Grisard, Arnaud; Lallier, Eric; Gérard, Bruno; Schiller, Stephan

2013-11-04

We demonstrate a robust and simple method for measurement, stabilization and tuning of the frequency of cw mid-infrared (MIR) lasers, in particular of quantum cascade lasers. The proof of principle is performed with a quantum cascade laser at 5.4 µm, which is upconverted to 1.2 µm by sum-frequency generation in orientation-patterned GaAs with the output of a standard high-power cw 1.5 µm fiber laser. Both the 1.2 µm and the 1.5 µm waves are measured by a standard Er:fiber frequency comb. Frequency measurement at the 100 kHz-level, stabilization to sub-10 kHz level, controlled frequency tuning and long-term stability are demonstrated.

High-power single spatial mode AlGaAs channeled-substrate-planar semiconductor diode lasers for spaceborne communications

NASA Technical Reports Server (NTRS)

Connolly, J. C.; Carlin, D. B.; Ettenberg, M.

1989-01-01

A high power single spatial mode channeled substrate planar AlGaAs semiconductor diode laser was developed. The emission wavelength was optimized at 860 to 880 nm. The operating characteristics (power current, single spatial mode behavior, far field radiation patterns, and spectral behavior) and results of computer modeling studies on the performance of the laser are discussed. Reliability assessment at high output levels is included. Performance results on a new type of channeled substrate planar diode laser incorporating current blocking layers, grown by metalorganic chemical vapor deposition, to more effectively focus the operational current to the lasing region was demonstrated. The optoelectronic behavior and fabrication procedures for this new diode laser are discussed. The highlights include single spatial mode devices with up to 160 mW output at 8600 A, and quantum efficiencies of 70 percent (1 W/amp) with demonstrated operating lifetimes of 10,000 h at 50 mW.

Antenna coupled photonic wire lasers

DOE PAGES

Kao, Tsung-Kao; Cai, Xiaowei; Lee, Alan W. M.; ...

2015-06-22

Slope efficiency (SE) is an important performance metric for lasers. In conventional semiconductor lasers, SE can be optimized by careful designs of the facet (or the modulation for DFB lasers) dimension and surface. However, photonic wire lasers intrinsically suffer low SE due to their deep sub-wavelength emitting facets. Inspired by microwave engineering techniques, we show a novel method to extract power from wire lasers using monolithically integrated antennas. These integrated antennas significantly increase the effective radiation area, and consequently enhance the power extraction efficiency. When applied to wire lasers at THz frequency, we achieved the highest single-side slope efficiency (~450more » mW/A) in pulsed mode for DFB lasers at 4 THz and a ~4x increase in output power at 3 THz compared with a similar structure without antennas. This work demonstrates the versatility of incorporating microwave engineering techniques into laser designs, enabling significant performance enhancements.« less

Heterogeneous Silicon III-V Mode-Locked Lasers

NASA Astrophysics Data System (ADS)

Davenport, Michael Loehrlein

Mode-locked lasers are useful for a variety of applications, such as sensing, telecommunication, and surgical instruments. This work focuses on integrated-circuit mode-locked lasers: those that combine multiple optical and electronic functions and are manufactured together on a single chip. While this allows production at high volume and lower cost, the true potential of integration is to open applications for mode-locked laser diodes where solid state lasers cannot fit, either due to size and power consumption constraints, or where small optical or electrical paths are needed for high bandwidth. Unfortunately, most high power and highly stable mode-locked laser diode demonstrations in scientific literature are based on the Fabry-Perot resonator design, with cleaved mirrors, and are unsuitable for use in integrated circuits because of the difficulty of producing integrated Fabry-Perot cavities. We use silicon photonics and heterogeneous integration with III-V gain material to produce the most powerful and lowest noise fully integrated mode-locked laser diode in the 20 GHz frequency range. If low noise and high peak power are required, it is arguably the best performing fully integrated mode-locked laser ever demonstrated. We present the design methodology and experimental pathway to realize a fully integrated mode-locked laser diode. The construction of the device, beginning with the selection of an integration platform, and proceeding through the fabrication process to final optimization, is presented in detail. The dependence of mode-locked laser performance on a wide variety of design parameters is presented. Applications for integrated circuit mode-locked lasers are also discussed, as well as proposed methods for using integration to improve mode-locking performance to beyond the current state of the art.

Quantum dash based single section mode locked lasers for photonic integrated circuits.

PubMed

Joshi, Siddharth; Calò, Cosimo; Chimot, Nicolas; Radziunas, Mindaugas; Arkhipov, Rostislav; Barbet, Sophie; Accard, Alain; Ramdane, Abderrahim; Lelarge, Francois

2014-05-05

We present the first demonstration of an InAs/InP Quantum Dash based single-section frequency comb generator designed for use in photonic integrated circuits (PICs). The laser cavity is closed using a specifically designed Bragg reflector without compromising the mode-locking performance of the self pulsating laser. This enables the integration of single-section mode-locked laser in photonic integrated circuits as on-chip frequency comb generators. We also investigate the relations between cavity modes in such a device and demonstrate how the dispersion of the complex mode frequencies induced by the Bragg grating implies a violation of the equi-distance between the adjacent mode frequencies and, therefore, forbids the locking of the modes in a classical Bragg Device. Finally we integrate such a Bragg Mirror based laser with Semiconductor Optical Amplifier (SOA) to demonstrate the monolithic integration of QDash based low phase noise sources in PICs.

Phototherapy for Improvement of Performance and Exercise Recovery: Comparison of 3 Commercially Available Devices.

PubMed

De Marchi, Thiago; Schmitt, Vinicius Mazzochi; Danúbia da Silva Fabro, Carla; da Silva, Larissa Lopes; Sene, Juliane; Tairova, Olga; Salvador, Mirian

2017-05-01

  Recent studies suggest the prophylactic use of low-powered laser/light has ergogenic effects on athletic performance and postactivity recovery. Manufacturers of high-powered lasers/light devices claim that these can produce the same clinical benefits with increased power and decreased irradiation time; however, research with high-powered lasers is lacking.   To evaluate the magnitude of observed phototherapeutic effects with 3 commercially available devices.   Randomized double-blind placebo-controlled study.   Laboratory.   Forty healthy untrained male participants.   Participants were randomized into 4 groups: placebo, high-powered continuous laser/light, low-powered continuous laser/light, or low-powered pulsed laser/light (comprising both lasers and light-emitting diodes). A single dose of 180 J or placebo was applied to the quadriceps.   Maximum voluntary contraction, delayed-onset muscle soreness (DOMS), and creatine kinase (CK) activity from baseline to 96 hours after the eccentric exercise protocol.   Maximum voluntary contraction was maintained in the low-powered pulsed laser/light group compared with placebo and high-powered continuous laser/light groups in all time points (P < .05). Low-powered pulsed laser/light demonstrated less DOMS than all groups at all time points (P < .05). High-powered continuous laser/light did not demonstrate any positive effects on maximum voluntary contraction, CK activity, or DOMS compared with any group at any time point. Creatine kinase activity was decreased in low-powered pulsed laser/light compared with placebo (P < .05) and high-powered continuous laser/light (P < .05) at all time points. High-powered continuous laser/light resulted in increased CK activity compared with placebo from 1 to 24 hours (P < .05).   Low-powered pulsed laser/light demonstrated better results than either low-powered continuous laser/light or high-powered continuous laser/light in all outcome measures when compared with placebo. The increase in CK activity using the high-powered continuous laser/light compared with placebo warrants further research to investigate its effect on other factors related to muscle damage.

Switchable dual-wavelength single-longitudinal-mode erbium fiber laser utilizing a dual-ring scheme with a saturable absorber

NASA Astrophysics Data System (ADS)

Yang, Zi-Qing; Huang, Tzu-Jung; Chang, Yao-Jen; Yeh, Chien-Hung; Chow, Chi-Wai; Chen, Jing-Heng; Chen, Kun-Huang

2018-06-01

In this work, we propose and demonstrate a switchable dual-wavelength erbium-doped fiber (EDF) ring laser with stable single-longitudinal-mode (SLM) output. Here, a dual-ring (DR) structure with an unpumped EDF of 2 m is designed to achieve SLM oscillation. Five fiber Bragg gratings (FBGs) are applied in the laser cavity serving as the reflective element to generate different dual-wavelength outputs. In the measurement, six sets of generated dual-wavelengths with various mode-spacing (Δλ) can be achieved via the five FBGs. Additionally, the stability performance of the proposed EDF DR laser is also demonstrated.

Comb-Resolved Dual-Comb Spectroscopy Stabilized by Free-Running Continuous-Wave Lasers

NASA Astrophysics Data System (ADS)

Kuse, Naoya; Ozawa, Akira; Kobayashi, Yohei

2012-11-01

We demonstrate dual-comb spectroscopy with relatively phase-locked two frequency combs, instead of frequency combs firmly fixed to the absolute frequency references. By stabilizing two beat frequencies between two mode-locked lasers at different wavelengths observed via free-running continuous-wave (CW) lasers, two combs are tightly phase locked to each other. The frequency noise of the CW lasers barely affects the performance of dual-comb spectroscopy because of the extremely fast common-mode noise rejection. Transform-limited comb-resolved dual-comb spectroscopy with a 6 Hz radio frequency linewidth is demonstrated by the use of Yb-fiber oscillators.

Feed-forward adaptive-optic correction of a weakly-compressible high-subsonic shear layer

NASA Astrophysics Data System (ADS)

Duffin, Daniel A.

Development of airborne laser systems began in the 1970s with the Airborne Laser Laboratory, a KC135 aircraft with a CO2 laser projected from a beam director mounted atop the aircraft as a hemispherical turret encased in a fairing. It was known that the turbulent air flowing around the turret and separating over the aft portions of the turret would aberrate the laser beam's wavefront (the aero-optic problem); however, the CO2 wavelength, 10.6 mum, was long enough that the aberrating turbulent flow decreased the system's performance by only about 5%. With newer airborne laser systems using wavelengths nearer 1 mum, this same turbulent flow now reduces system performance by more than 95%. It has long been known that if a conjugate waveform is used to pre-distort the outgoing laser's wavefront, the turbulence will actually correct the beam, restoring most of the system's performance. The problem with performing this compensation is that the system for performing this function, the so-called adaptive-optic system, is bandwidth limited in its conventional architecture, by orders of magnitude lower than that required to correct for the aero-optic effects. The research described in this dissertation explored changing the adaptive-optic paradigm from feedback to feed-forward by adding flow control to make the aberration environment predictable rather than unpredictable. This research demonstrated that the turbulent high-speed separated shear layer could be robustly forced into a regularized form. It was also shown that these regularized velocity patterns in the shear layer produced periodic optical aberrations. Extensive measurement and analysis of these convecting aberrations yielded the underlying structure required to produce the conjugate wavefront correction patterns required for a range of laser propagation angles through the shear layer. Ultimately, a feed-forward adaptive-optic system was developed and used to demonstrate the highest-bandwidth correction of aero-optic aberrations ever performed; the effective bandwidth of the demonstrated adaptive-optic correction was at least two orders of magnitude greater than the capabilities of existing conventional adaptive-optic systems.

Experimental demonstration of laser imprint reduction using underdense foams

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

Delorme, B.; Casner, A.; CELIA, University of Bordeaux-CNRS-CEA, F-33400 Talence

2016-04-15

Reducing the detrimental effect of the Rayleigh-Taylor (RT) instability on the target performance is a critical challenge. In this purpose, the use of targets coated with low density foams is a promising approach to reduce the laser imprint. This article presents results of ablative RT instability growth measurements, performed on the OMEGA laser facility in direct-drive for plastic foils coated with underdense foams. The laser beam smoothing is explained by the parametric instabilities developing in the foam and reducing the laser imprint on the plastic (CH) foil. The initial perturbation pre-imposed by the means of a specific phase plate wasmore » shown to be smoothed using different foam characteristics. Numerical simulations of the laser beam smoothing in the foam and of the RT growth are performed with a suite of paraxial electromagnetic and radiation hydrodynamic codes. They confirmed the foam smoothing effect in the experimental conditions.« less

Test techniques for determining laser ranging system performance

NASA Technical Reports Server (NTRS)

Zagwodzki, T. W.

1981-01-01

Procedures and results of an on going test program intended to evaluate laser ranging system performance levels in the field as well as in the laboratory are summarized. Tests show that laser ranging system design requires consideration of time biases and RMS jitters of individual system components. All simple Q switched lasers tested were found to be inadequate for 10 centimeter ranging systems. Timing discriminators operating over a typical 100:1 dynamic signal range may introduce as much as 7 to 9 centimeters of range bias. Time interval units commercially available today are capable of half centimeter performance and are adequate for all field systems currently deployed. Photomultipliers tested show typical tube time biases of one centimeter with single photoelectron transit time jitter of approximately 10 centimeters. Test results demonstrate that NASA's Mobile Laser Ranging System (MOBLAS) receiver configuration is limiting system performance below the 100 photoelectron level.

Laser-induced contamination control for high-power lasers in space-based LIDAR missions

NASA Astrophysics Data System (ADS)

Alves, Jorge; Pettazzi, Federico; Tighe, Adrian; Wernham, Denny

2017-11-01

In the framework of the ADM-Aeolus satellite mission, successful test campaigns have been performed in ESTEC's laser laboratory, and the efficiency of several mitigation techniques against Laser-Induced Contamination (LIC) have been demonstrated for the ALADIN laser. These techniques include the standard contamination control methods of materials identification with particular tendency to cause LIC, reduction of the outgassing of organic materials by vacuum bake-out and shielding of optical surfaces from the contamination sources. Also novel mitigation methods such as in-situ cleaning via partial pressures, or the usage of molecular absorbers were demonstrated. In this context, a number of highly sensitive optical measurement techniques have been developed and tested to detect and monitor LIC deposits at nanometre level.

Synthesis of arbitrary pulse waveforms in QCL-seeded ns-pulse CO₂ laser for optimization of an LPP EUV source.

PubMed

Nowak, Krzysztof M; Kurosawa, Yoshiaki; Suganuma, Takashi; Kawasuji, Yasufumi; Nakarai, Hiroaki; Saito, Takashi; Fujimoto, Junichi; Mizoguchi, Hakaru

2016-07-01

One of the unique features of the quantum-cascade-laser-seeded, nanosecond-pulse CO₂ laser, invented for the purpose of generation of extreme UV by laser-produced-plasma, is a robust synthesis of arbitrary pulse waveforms. In the present Letter we report on experimental results that are, to our best knowledge, the first demonstration of such functionality obtainable from nanosecond-pulse CO₂ laser technology. An online pulse duration adjustment within 10-40 ns was demonstrated, and a few exemplary pulse waveforms were synthesized, such as "tophat," "tailspike," and "leadspike" shapes. Such output characteristics may be useful to optimize the performance of LPP EUV source.

Free Space Optical Communication Utilizing Mid-Infrared Interband Cascade Laser

NASA Technical Reports Server (NTRS)

Soibel, A.; Wright, M.; Farr, W.; Keo, S.; Hill, C.; Yang, R. Q.; Liu, H. C.

2010-01-01

A Free Space Optical (FSO) link utilizing mid-IR Interband Cascade lasers has been demonstrated in the 3-5 micron atmospheric transmission window with data rates up to 70 Mb/s and bit-error-rate (BER) less than 10 (exp -8). The performance of the mid-IR FSO link has been compared with the performance of a near-IR link under various fog conditions using an indoor communication testbed. These experiments demonstrated the lower attenuation and scintillation advantages of a mid-IR FSO link through fog than a 1550 nm FSO link.

Comparative study of passively Q-switched c-cut Nd:YVO4/Nd:YAG lasers based on CVD graphene and controlled operation

NASA Astrophysics Data System (ADS)

Jia, Fuqiang; Liu, Pei; Li, Kang; Chen, Hao; Cheng, Yongjie; Cai, Zhiping; Copner, Nigel

2017-07-01

In this paper, a comparative study of passively Q-switched c-cut Nd:YVO4 and Nd:YAG lasers using four different layers CVD graphene as saturable absorber are demonstrated experimentally for the first time. Moreover, it is successful to accurately control the frequency of repetition rates of the CVD graphern passively Q-switched lasers by pulsed pump. The impacts of laser materials, layers of CVD graphene and cavity length on output parameters are investigated intensively as well, the result shows that the c-cut Nd:YVO4 is a promising laser media compared with Nd:YAG for passively Q-switched lasers based on CVD graphene, as it has better performances in pulse width, pulse energy and peak power. A useful and cost-effective way to generate stable pulsed lasers by CVD graphene or other novel saturable materials are demonstrated.

Ultrashort, high power, and ultralow noise mode-locked optical pulse generation using quantum-dot semiconductor lasers

NASA Astrophysics Data System (ADS)

Choi, Myoung-Taek

This dissertation explores various aspects and potential of optical pulse generation based on active, passive, and hybrid mode-locked quantum dot semiconductor lasers with target applications such as optical interconnect and high speed signal processing. Design guidelines are developed for the single mode operation with suppressed reflection from waveguide discontinuities. The device fabrication procedure is explained, followed by characteristics of FP laser, SOA, and monolithic two-section devices. Short pulse generation from an external cavity mode-locked QD two-section diode laser is studied. High quality, sub-picosecond (960 fs), high peak power (1.2 W) pulse trains are obtained. The sign and magnitude of pulse chirp were measured for the first time. The role of the self-phase modulation and the linewidth enhancement factor in QD mode-locked lasers is addressed. The noise performance of two-section mode-locked lasers and a SOA-based ring laser was investigated. Significant reduction of the timing jitter under hybrid mode-locked operation was achieved owing to more than one order of magnitude reduction of the linewidth in QD gain media. Ultralow phase noise performance (integrated timing jitter of a few fs at a 10 GHz repetition rate) was demonstrated from an actively mode-locked unidirectional ring laser. These results show that quantum dot mode-locked lasers are strong competitors to conventional semiconductor lasers in noise performance. Finally we demonstrated an opto-electronic oscillator (OEO) and coupled opto-electronic oscillators (COEO) which have the potential for both high purity microwave and low noise optical pulse generation. The phase noise of the COEO is measured by the photonic delay line frequency discriminator method. Based on this study we discuss the prospects of the COEO as a low noise optical pulse source.

Design and implementation of a laser-based absorption spectroscopy sensor for in situ monitoring of biomass gasification

NASA Astrophysics Data System (ADS)

Viveros Salazar, David; Goldenstein, Christopher S.; Jeffries, Jay B.; Seiser, Reinhard; Cattolica, Robert J.; Hanson, Ronald K.

2017-12-01

Research to demonstrate in situ laser-absorption-based sensing of H2O, CH4, CO2, and CO mole fraction is reported for the product gas line of a biomass gasifier. Spectral simulations were used to select candidate sensor wavelengths that optimize sensitive monitoring of the target species while minimizing interference from other species in the gas stream. A prototype sensor was constructed and measurements performed in the laboratory at Stanford to validate performance. Field measurements then were demonstrated in a pilot scale biomass gasifier at West Biofuels in Woodland, CA. The performance of a prototype sensor was compared for two sensor strategies: wavelength-scanned direct absorption (DA) and wavelength-scanned wavelength modulation spectroscopy (WMS). The lasers used had markedly different wavelength tuning response to injection current, and modern distributed feedback lasers (DFB) with nearly linear tuning response to injection current were shown to be superior, leading to guidelines for laser selection for sensor fabrication. Non-absorption loss in the transmitted laser intensity from particulate scattering and window fouling encouraged the use of normalized WMS measurement schemes. The complications of using normalized WMS for relatively large values of absorbance and its mitigation are discussed. A method for reducing adverse sensor performance effects of a time-varying WMS background signal is also presented. The laser absorption sensor provided measurements with the sub-second time resolution needed for gasifier control and more importantly provided precise measurements of H2O in the gasification products, which can be problematic for the typical gas chromatography sensors used by industry.

Results of Kirari optical communication demonstration experiments with NICT optical ground station (KODEN) aiming for future classical and quantum communications in space

NASA Astrophysics Data System (ADS)

Toyoshima, Morio; Takenaka, Hideki; Shoji, Yozo; Takayama, Yoshihisa; Koyama, Yoshisada; Kunimori, Hiroo

2012-05-01

Bi-directional ground-to-satellite laser communication experiments were successfully performed between the optical ground station developed by the National Institute of Information and Communications Technology (NICT), located in Koganei City in suburban Tokyo, and a low earth orbit (LEO) satellite, the "Kirari" Optical Inter-orbit Communications Engineering Test Satellite (OICETS). The experiments were conducted in cooperation with the Japan Aerospace Exploration Agency (JAXA), and called the Kirari Optical communication Demonstration Experiments with the NICT optical ground station (or KODEN). The ground-to-OICETS laser communication experiment was the first in-orbit demonstration involving the LEO satellite. The laser communication experiment was conducted since March 2006. The polarization characteristics of an artificial laser source in space, such as Stokes parameters, and the degree of polarization were measured through space-to-ground atmospheric transmission paths, which results contribute to the link estimation for quantum key distribution via space and provide the potential for enhancements in quantum cryptography on a global scale in the future. The Phase-5 experiment, international laser communications experiments were also successfully conducted with four optical ground stations located in the United States, Spain, Germany, and Japan from April 2009 to September 2009. The purpose of the Phase-5 experiment was to establish OICETS-to-ground laser communication links from the different optical ground stations and the statistical analyses such as the normalized power, scintillation index, probability density function, auto-covariance function, and power spectral density were performed. Thus the applicability of the satellite laser communications was demonstrated, aiming not only for geostationary earth orbit-LEO links but also for ground-to-LEO optical links. This paper presents the results of the KODEN experiments and mainly introduces the common analyses among the different optical ground stations.

Receiver design, performance analysis, and evaluation for space-borne laser altimeters and space-to-space laser ranging systems

NASA Technical Reports Server (NTRS)

Davidson, Frederic M.; Sun, Xiaoli; Field, Christopher T.

1995-01-01

This Interim report consists of a manuscript, 'Receiver Design for Satellite to Satellite Laser Ranging Instrument,' and copies of two papers we co-authored, 'Demonstration of High Sensitivity Laser Ranging System' and 'Semiconductor Laser-Based Ranging Instrument for Earth Gravity Measurements. ' These two papers were presented at the conference Semiconductor Lasers, Advanced Devices and Applications, August 21 -23, 1995, Keystone Colorado. The manuscript is a draft in the preparation for publication, which summarizes the theory we developed on space-borne laser ranging instrument for gravity measurements.

Impact of the Femtosecond Laser in Line with the Femtosecond Laser-Assisted Cataract Surgery (FLACS) on the Anterior Chamber Characteristics in Comparison to the Manual Phacoemulsification.

PubMed

Pahlitzsch, Milena; Torun, Necip; Pahlitzsch, Marie Luise; Klamann, Matthias K J; Gonnermann, Johannes; Bertelmann, Eckart; Pahlitzsch, Thomas

2017-01-01

To assess the alterations of the anterior chamber conditions including laser flare photometry after femtosecond laser-assisted cataract surgery (FLACS) compared to the manual phacoemulsification. Data of n=70 FLACS (mean age 67.2 ± 8.9 years) and n=40 manual phacoemulsification (mean age 69.5 ± 9.6 years) were analyzed. The procedures were performed by LenSx Alcon, USA, and Alcon Infiniti Vision System, USA. The following parameters were recorded: laser flare photometry (Kowa FM 700, Japan), anterior chamber (AC) depth, AC volume, AC angle (Pentacam, Oculus Inc., Germany), lens density, pupil diameter, endothelial cell count and pachymetry. The analysis was performed preoperatively, immediately after femtosecond laser procedure and one day postoperatively. Between FLACS and the phaco control group, there was a significant difference in the AC depth (p=0.023, 3.77 mm vs. 4.05 mm) one day postoperatively. The AC angle (p=0.016) showed a significant difference immediately after the femto laser treatment. The central and thinnest pachymetry and endothelial cell count did not show a significant difference between the two study cohorts (p=0.165, p=0.291, p=0.979). The phaco cohort (n=40) demonstrated a non-statistically significant difference in the flare photometry of 15.80 photons/ms one postoperative day compared to the FLACS group 26.62 photons/ms (p=0.322). In this study population, no evidence for an additive damage caused by the use of the femtosecond laser was demonstrated. Furthermore, no increase in the central and thinnest corneal thickness and no increased endothelial cell loss was demonstrated by the laser energy.

Characterization of electrical noise limits in ultra-stable laser systems.

PubMed

Zhang, J; Shi, X H; Zeng, X Y; Lü, X L; Deng, K; Lu, Z H

2016-12-01

We demonstrate thermal noise limited and shot noise limited performance of ultra-stable diode laser systems. The measured heterodyne beat linewidth between such two independent diode lasers reaches 0.74 Hz. The frequency instability of one single laser approaches 1.0 × 10 -15 for averaging time between 0.3 s and 10 s, which is close to the thermal noise limit of the reference cavity. Taking advantage of these two ultra-stable laser systems, we systematically investigate the ultimate electrical noise contributions, and derive expressions for the closed-loop spectral density of laser frequency noise. The measured power spectral density of the beat frequency is compared with the theoretically calculated closed-loop spectral density of the laser frequency noise, and they agree very well. It illustrates the power and generality of the derived closed-loop spectral density formula of the laser frequency noise. Our result demonstrates that a 10 -17 level locking in a wide frequency range is feasible with careful design.

Limiting of microjoule femtosecond pulses in air-guided modes of a hollow photonic-crystal fiber

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

Konorov, S.O.; Serebryannikov, E.E.; Sidorov-Biryukov, D.A.

Self-phase-modulation-induced spectral broadening of laser pulses in air-guided modes of hollow photonic-crystal fibers (PCFs) is shown to allow the creation of fiber-optic limiters for high-intensity ultrashort laser pulses. The performance of PCF limiters is analyzed in terms of elementary theory of self-phase modulation. Experiments performed with 100 fs microjoule pulses of 800 nm Ti:sapphire laser radiation demonstrate the potential of hollow PCFs as limiters for 10 MW ultrashort laser pulses and show the possibility to switch the limiting level of output radiation energy by guiding femtosecond pulses in different PCF modes.

New developments in short-pulse eye safe lasers pay the way for future LADARs and 3D mapping performances

NASA Astrophysics Data System (ADS)

Pasmanik, Guerman; Latone, Kevin; Shilov, Alex; Shklovsky, Eugeni; Spiro, Alex; Tiour, Larissa

2005-06-01

We have demonstrated that direct excitation of 3rd Stokes Raman emission in crystal can produce short (few nanosecond) eye-safe pulses. Produced beam has very high quality and the pulse energy can be as high as tens of millijoules. For pulsed diode pumped solid state lasers the demonstrated repetition rate was 250 Hz but higher repetition rates are certainly achievable. It is important that tested schemes do not have strict requirements on laser pump parameters, namely beam divergence and frequency bandwidth. The obtained results are very relevant to the development of eye-safe lasers, such as the new generation of rangefinders, target designators, and laser tracking and pin-pointing devices, as well as remote 2D and 3D imaging systems.

The forward masking effects of low-level laser glare on target location performance in a visual search task

NASA Astrophysics Data System (ADS)

Reddix, M. D.; Dandrea, J. A.; Collyer, P. D.

1992-01-01

The present study examined the effects of low-intensity laser glue, far below a level that would cause ocular damage or flashblindness, on the visually guided performance of aviators. With a forward-masking paradigm, this study showed that the time at which laser glare is experienced, relative to initial acquisition of visual information, differentially affects the speed and accuracy of target-location performance. Brief exposure (300 ms) to laser glare, terminating with a visual scene's onset, produced significant decrements in target-location performance relative to a no-glare control whereas a 150 and 300-ms delay of display onset (DDO) had very little effect. The intensity of the light entering the eye and producing these effects was far below the Maximum Permissible Exposure (MPE) limit for safe viewing of coherent light produced by an argon laser. In addition, these effects were modulated by the distance of the target from the center of the visual display. This study demonstrated that the presence of laser glare is not sufficient, in and of itself, to diminish target-location performance. The time at which laser glare is experienced is an important factor in determining the probability and extent of visually mediated performance decrements.

Advanced chip designs and novel cooling techniques for brightness scaling of industrial, high power diode laser bars

NASA Astrophysics Data System (ADS)

Heinemann, S.; McDougall, S. D.; Ryu, G.; Zhao, L.; Liu, X.; Holy, C.; Jiang, C.-L.; Modak, P.; Xiong, Y.; Vethake, T.; Strohmaier, S. G.; Schmidt, B.; Zimer, H.

2018-02-01

The advance of high power semiconductor diode laser technology is driven by the rapidly growing industrial laser market, with such high power solid state laser systems requiring ever more reliable diode sources with higher brightness and efficiency at lower cost. In this paper we report simulation and experimental data demonstrating most recent progress in high brightness semiconductor laser bars for industrial applications. The advancements are in three principle areas: vertical laser chip epitaxy design, lateral laser chip current injection control, and chip cooling technology. With such improvements, we demonstrate disk laser pump laser bars with output power over 250W with 60% efficiency at the operating current. Ion implantation was investigated for improved current confinement. Initial lifetime tests show excellent reliability. For direct diode applications <1 um smile and >96% polarization are additional requirements. Double sided cooling deploying hard solder and optimized laser design enable single emitter performance also for high fill factor bars and allow further power scaling to more than 350W with 65% peak efficiency with less than 8 degrees slow axis divergence and high polarization.

Acoustic Events and “Optophonic” Cochlear Responses Induced by Pulsed Near-Infrared LASER

PubMed Central

Maier, Hannes; Richter, Claus-Peter; Kral, Andrej

2012-01-01

Optical stimulation of neural tissue within the cochlea was described as a possible alternative to electrical stimulation. Most optical stimulation was performed with pulsed lasers operating with near-infrared (NIR) light and in thermal confinement. Under these conditions, the coexistence of laser-induced optoacoustic stimulation of the cochlea (“optophony”) has not been analyzed yet. This study demonstrates that pulsed 1850-nm laser light used for neural stimulation also results in sound pressure levels up to 62 dB peak-to-peak equivalent sound pressure level (SPL) in air. The sound field was confined to a small volume along the laser beam. In dry nitrogen, laser-induced acoustic events disappeared. Hydrophone measurements demonstrated pressure waves for laser fibers immersed in water. In hearing rats, laser-evoked signals were recorded from the cochlea without targeting neural tissue. The signals showed a two-domain response differing in amplitude and latency functions, as well as sensitivity to white-noise masking. The first component had characteristics of a cochlear microphonic potential, and the second component was characteristic for a compound action potential. The present data demonstrate that laser-evoked acoustic events can stimulate a hearing cochlea. Whenever optical stimulation is used, care must be taken to distinguish between such “optophony” and the true optoneural response. PMID:21278011

Efficient 2.96 micron dysprosium-doped ZBLAN fibre laser pumped at 1.3 micron

NASA Astrophysics Data System (ADS)

Tsang, Yuen H.; El-Taher, Atalla E.; King, Terence A.; Chang, Kuang-Po; Jackson, Stuart D.

2006-04-01

Wavelengths around 1.15 μm, 1.3 μm and 1.7 μm can be used to pump Dy-doped ZBLAN fibre in order to generate ~3 μm with high efficiency. Previously the generation of 2.9 μm from the Dy-ZBLAN fibre was demonstrated by pumping with 1.1 μm Yb-silica fibre laser sources. The laser slope efficiency and lasing threshold demonstrated was about ~5% and ~1.78 W. In this investigation, the longer wavelength absorption band ( 6H 9/2 , 6F 11/2) centred at 1.3 μm of Dy 3+-doped ZBLAN is utilised and the lasing transition around ~3 μm takes places from 6H 13/2 --> 6H 15/2. With this pumping scheme the Stokes' efficiency is expected to be up to ~45%. A quasi-continuous wave Dy 3+-ZBLAN fibre laser pumped by a ~1.3 μm Nd:YAG laser and operating at 2.96 μm with a bandwidth (FWHM) of ~14 nm has been demonstrated. For a 60cm fibre length, a threshold of 0.5W and a slope efficiency of ~20% with respect to the absorbed pump power was observed. The overall pump absorption in the fibre was around 84%. The cavity reflectivities at 2.9 μm were 99% and 50%. The demonstrated slope efficiency was 45% of the Stokes' limit. The slope efficiency was around four times higher and the threshold around 3.6 times lower than the previous performance demonstrated by using the 1.1 μm Yb fibre laser pumping scheme. The higher performance achieved compared to the 1.1 μm pump scheme is due to the higher Stokes' limit, lower pump ESA losses and higher cavity reflectivity. About 590 cm -1 Raman Stokes shift has also detected by using 514.5 nm and 488 nm Ar ion laser as excitation pump sources.

Pulsed operation of (Al,Ga,In)N blue laser diodes

NASA Astrophysics Data System (ADS)

Abare, Amber C.; Mack, Michael P.; Hansen, Mark W.; Sink, R. K.; Kozodoy, Peter; Keller, Sarah L.; Hu, Evelyn L.; Speck, James S.; Bowers, John E.; Mishra, Umesh K.; Coldren, Larry A.; DenBaars, Steven P.

1998-04-01

Room temperature (RT) pulsed operation of blue (420 nm) nitride based multi-quantum well (MQW) laser diodes grown on a-plane and c-plane sapphire substrates has been demonstrated. A combination of atmospheric and low pressure metal organic chemical vapor deposition (MOCVD) using a modified two-flow horizontal reactor was employed. The emission is strongly TE polarized and has a sharp transition in the far field pattern above threshold. Threshold current densities as low as 12.6 kA/cm2 were observed for 10 X 1200 micrometer lasers with uncoated reactive ion etched (RIE) facets on c-plane sapphire. Cleaved facet lasers were also demonstrated with similar performance on a-plane sapphire. Differential efficiencies as high as 7% and output powers up to 77 mW were observed. Laser diodes tested under pulsed conditions operated up to 6 hours at room temperature. Performance was limited by resistive heating during the electrical pulses. Lasing was achieved up to 95 degrees Celsius and up to a 150 ns pulse length (RT). Threshold current increased with temperature with a characteristic temperature, T0, of 125 K.

Performance of a 967 nm CW diode end-pumped Er:GSGG laser at 2.79 μm

NASA Astrophysics Data System (ADS)

Wu, Z. H.; Sun, D. L.; Wang, S. Z.; Luo, J. Q.; Li, X. L.; Huang, L.; Hu, A. L.; Tang, Y. Q.; Guo, Q.

2013-05-01

We demonstrated a 967 nm diode end-pumped Er:GSGG laser operated at 2.794 μm with spectral width 3.6 nm in the continuous wave (CW) mode. A maximum output power of 440 mW is obtained at an incident pumping power of 3.4 W, which corresponds to an optical-to-optical efficiency of 13% and slope efficiency of 13.2%. The results suggest that a short cavity and efficient cooling setup for the crystal help to improve laser performance.

Thermal-noise-limited higher-order mode locking of a reference cavity

NASA Astrophysics Data System (ADS)

Zeng, X. Y.; Ye, Y. X.; Shi, X. H.; Wang, Z. Y.; Deng, K.; Zhang, J.; Lu, Z. H.

2018-04-01

Higher-order mode locking has been proposed to reduce the thermal noise limit of reference cavities. By locking a laser to the HG02 mode of a 10-cm long all ULE cavity, and measure its performance with the three-cornered-hat method among three independently stabilized lasers, we demonstrate a thermal noise limited performance of a fractional frequency instability of 4.9E-16. The results match the theoretical models with higher-order optical modes. The achieved laser instability improves the all ULE short cavity results to a new low level.

A narrow linewidth tunable single longitudinal mode Ga-EDF fiber laser

NASA Astrophysics Data System (ADS)

Mohamed Halip, N. H.; Abu Bakar, M. H.; Latif, A. A.; Muhd-Yasin, S. Z.; Zulkifli, M. I.; Mat-Sharif, K. A.; Omar, N. Y. M.; Mansoor, A.; Abdul-Rashid, H. A.; Mahdi, M. A.

2018-05-01

A tunable ring cavity single longitudinal mode (SLM) fiber laser incorporating Gallium-Erbium co-doped fiber (Ga-EDF) gain medium and several mode filtration techniques is demonstrated. With Ga-EDF, high emission power was accorded in short fiber length, allowing shorter overall cavity length and wider free spectral range. Tunable bandpass filter, sub-ring structure, and cascaded dissimilar fiber taper were utilized to filter multi-longitudinal modes. Each of the filter mechanism was tested individually within the laser cavity to assess its performance. Once the performance of each filter was obtained, all of them were deployed into the laser system. Ultimately, the 1561.47 nm SLM laser achieved a narrow linewidth laser, optical signal-to-noise ratio, and power fluctuation of 1.19 kHz, 61.52 dB and 0.16 dB, respectively. This work validates the feasibility of Ga-EDF to attain a stable SLM output in simple laser configuration.

Particle damage sources for fused silica optics and their mitigation on high energy laser systems.

PubMed

Bude, J; Carr, C W; Miller, P E; Parham, T; Whitman, P; Monticelli, M; Raman, R; Cross, D; Welday, B; Ravizza, F; Suratwala, T; Davis, J; Fischer, M; Hawley, R; Lee, H; Matthews, M; Norton, M; Nostrand, M; VanBlarcom, D; Sommer, S

2017-05-15

High energy laser systems are ultimately limited by laser-induced damage to their critical components. This is especially true of damage to critical fused silica optics, which grows rapidly upon exposure to additional laser pulses. Much progress has been made in eliminating damage precursors in as-processed fused silica optics (the advanced mitigation process, AMP3), and very high damage resistance has been demonstrated in laboratory studies. However, the full potential of these improvements has not yet been realized in actual laser systems. In this work, we explore the importance of additional damage sources-in particular, particle contamination-for fused silica optics fielded in a high-performance laser environment, the National Ignition Facility (NIF) laser system. We demonstrate that the most dangerous sources of particle contamination in a system-level environment are laser-driven particle sources. In the specific case of the NIF laser, we have identified the two important particle sources which account for nearly all the damage observed on AMP3 optics during full laser operation and present mitigations for these particle sources. Finally, with the elimination of these laser-driven particle sources, we demonstrate essentially damage free operation of AMP3 fused silica for ten large optics (a total of 12,000 cm 2 of beam area) for shots from 8.6 J/cm 2 to 9.5 J/cm 2 of 351 nm light (3 ns Gaussian pulse shapes). Potentially many other pulsed high energy laser systems have similar particle sources, and given the insight provided by this study, their identification and elimination should be possible. The mitigations demonstrated here are currently being employed for all large UV silica optics on the National Ignition Facility.

High efficiency laser-assisted H - charge exchange for microsecond duration beams

DOE PAGES

Cousineau, Sarah; Rakhman, Abdurahim; Kay, Martin; ...

2017-12-26

Laser-assisted stripping is a novel approach to H - charge exchange that overcomes long-standing limitations associated with the traditional, foil-based method of producing high-intensity, time-structured beams of protons. This paper reports on the first successful demonstration of the laser stripping technique for microsecond duration beams. The experiment represents a factor of 1000 increase in the stripped pulse duration compared with the previous proof-of-principle demonstration. The central theme of the experiment is the implementation of methods to reduce the required average laser power such that high efficiency stripping can be accomplished for microsecond duration beams using conventional laser technology. In conclusion,more » the experiment was performed on the Spallation Neutron Source 1 GeV H - beam using a 1 MW peak power UV laser and resulted in ~95% stripping efficiency.« less

High efficiency laser-assisted H - charge exchange for microsecond duration beams

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

Cousineau, Sarah; Rakhman, Abdurahim; Kay, Martin

Laser-assisted stripping is a novel approach to H - charge exchange that overcomes long-standing limitations associated with the traditional, foil-based method of producing high-intensity, time-structured beams of protons. This paper reports on the first successful demonstration of the laser stripping technique for microsecond duration beams. The experiment represents a factor of 1000 increase in the stripped pulse duration compared with the previous proof-of-principle demonstration. The central theme of the experiment is the implementation of methods to reduce the required average laser power such that high efficiency stripping can be accomplished for microsecond duration beams using conventional laser technology. In conclusion,more » the experiment was performed on the Spallation Neutron Source 1 GeV H - beam using a 1 MW peak power UV laser and resulted in ~95% stripping efficiency.« less

Fibre-coupled red diode-pumped Alexandrite TEM00 laser with single and double-pass end-pumping

NASA Astrophysics Data System (ADS)

Arbabzadah, E. A.; Damzen, M. J.

2016-06-01

We report the investigation of an Alexandrite laser end-pumped by a fibre-coupled red diode laser module. Power, efficiency, spatial, spectral, and wavelength tuning performance are studied as a function of pump and laser cavity parameters. It is the first demonstration, to our knowledge, of greater than 1 W power and also highest laser slope efficiency (44.2%) in a diode-pumped Alexandrite laser with diffraction-limited TEM00 mode operation. Spatial quality was excellent with beam propagation parameter M 2 ~ 1.05. Wavelength tuning from 737-796 nm was demonstrated using an intracavity birefringent tuning filter. Using a novel double pass end-pumping scheme to get efficient absorption of both polarisation states of the scrambled fibre-delivered diode pump, a total output coupled power of 1.66 W is produced in TEM00 mode with 40% slope efficiency.

Versatile large-mode-area femtosecond laser-written Tm:ZBLAN glass chip lasers.

PubMed

Lancaster, D G; Gross, S; Fuerbach, A; Heidepriem, H Ebendorff; Monro, T M; Withford, M J

2012-12-03

We report performance characteristics of a thulium doped ZBLAN waveguide laser that supports the largest fundamental modes reported in a rare-earth doped planar waveguide laser (to the best of our knowledge). The high mode quality of waveguides up to 45 um diameter (~1075 μm(2) mode-field area) is validated by a measured beam quality of M(2)~1.1 ± 0.1. Benefits of these large mode-areas are demonstrated by achieving 1.9 kW peak-power output Q-switched pulses. The 1.89 μm free-running cw laser produces 205 mW and achieves a 67% internal slope efficiency corresponding to a quantum efficiency of 161%. The 9 mm long planar chip developed for concept demonstration is rapidly fabricated by single-step optical processing, contains 15 depressed-cladding waveguides, and can operate in semi-monolithic or external cavity laser configurations.

Fiber Based Seed Laser for CO 2 Ultrafast Laser Systems

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

Chen, Yuchuan

A compact and effective 10-micron femtosecond laser with pulse duration <500fs and repetition rate of >100Hz or smaller is desirable by DOE for seeding CO 2 ultrafast laser systems to improve the stability, reliability and efficiency in generating 10-micron laser from GW up to 100TW peak power, which is irreplaceable in driving an accelerator for particle beam generation due to the efficiency proportional to the square of the laser wavelength. Agiltron proposes a fiber based ultrafast 10-micron seed laser that can provide the required specifications and high performance. Its success will directly benefit DOE’s compact proton and ion sources. Themore » innovative technology can be used for ultrafast laser generation over the whole mid-IR range, and speed up the development of mid-IR laser applications. Agiltron, Inc. has successfully completed all tasks and demonstrated the feasibility of a fiber based 10-micron ultrafast laser in Phase I of the Program. We built a mode-locked fiber laser that generated < 400fs ultrafast laser pulses and successfully controlled the repetition rate to be the required 100Hz. Using this mode-locked laser, we demonstrated the feasibility of parametric femtosecond laser generation based on frequency down conversion. The experimental results agree with our simulation results. The investigation results of Phase I will be used to optimize the design of the laser system and build a fully functional prototype for delivery to the DOE in the Phase II program. The prototype development in Phase II program will be in the collaboration with Professor Chandrashekhar Joshi, the leader of UCLA Laser-Plasma group. Prof. Joshi discovered a new mechanism for generation of monoenergetic proton/ion beams: Shock Wave Acceleration in a near critical density plasma and demonstrated that high-energy proton beams using CO 2 laser driven collisionless shocks in a gas jet plasma, which opened an opportunity to develop a rather compact high-repetition rate ion source for medical and other applications which could be significantly cheaper than that based on RF acceleration. We propose an output energy >1 μJ, one order of magnitude higher than the DOE original requirement. The performance of the prototype will be tested at UCLA by directly seeding the CO 2 laser system driving an accelerator.« less

Modeling and optimization of actively Q-switched Nd-doped quasi-three-level laser

NASA Astrophysics Data System (ADS)

Yan, Renpeng; Yu, Xin; Li, Xudong; Chen, Deying; Gao, Jing

2013-09-01

The energy transfer upconversion and the ground state absorption are considered in solving the rate equations for an active Q-switched quasi-three-level laser. The dependence of output pulse characters on the laser parameters is investigated by solving the rate equations. The influence of the energy transfer upconversion on the pulsed laser performance is illustrated and discussed. By this model, the optimal parameters could be achieved for arbitrary quasi-three-level Q-switched lasers. An acousto-optical Q-switched Nd:YAG 946 nm laser is constructed and the reliability of the theoretical model is demonstrated.

Improved efficiency of hybrid organic photovoltaics by pulsed laser sintering of silver nanowire network transparent electrode.

PubMed

Spechler, Joshua A; Nagamatsu, Ken A; Sturm, James C; Arnold, Craig B

2015-05-20

In this Research Article, we demonstrate pulsed laser processing of a silver nanowire network transparent conductor on top of an otherwise complete solar cell. The macroscopic pulsed laser irradiation serves to sinter nanowire-nanowire junctions on the nanoscale, leading to a much more conductive electrode. We fabricate hybrid silicon/organic heterojunction photovoltaic devices, which have ITO-free, solution processed, and laser processed transparent electrodes. Furthermore, devices which have high resistive losses show up to a 35% increase in power conversion efficiency after laser processing. We perform this study over a range of laser fluences, and a range of nanowire area coverage to investigate the sintering mechanism of nanowires inside of a device stack. The increase in device performance is modeled using a simple photovoltaic diode approach and compares favorably to the experimental data.

External amplitude and frequency modulation of a terahertz quantum cascade laser using metamaterial/graphene devices.

PubMed

Kindness, S J; Jessop, D S; Wei, B; Wallis, R; Kamboj, V S; Xiao, L; Ren, Y; Braeuninger-Weimer, P; Aria, A I; Hofmann, S; Beere, H E; Ritchie, D A; Degl'Innocenti, R

2017-08-09

Active control of the amplitude and frequency of terahertz sources is an essential prerequisite for exploiting a myriad of terahertz applications in imaging, spectroscopy, and communications. Here we present a optoelectronic, external modulation technique applied to a terahertz quantum cascade laser which holds the promise of addressing a number of important challenges in this research area. A hybrid metamaterial/graphene device is implemented into an external cavity set-up allowing for optoelectronic tuning of feedback into a quantum cascade laser. We demonstrate powerful, all-electronic, control over the amplitude and frequency of the laser output. Full laser switching is performed by electrostatic gating of the metamaterial/graphene device, demonstrating a modulation depth of 100%. External control of the emission spectrum is also achieved, highlighting the flexibility of this feedback method. By taking advantage of the frequency dispersive reflectivity of the metamaterial array, different modes of the QCL output are selectively suppressed using lithographic tuning and single mode operation of the multi-mode laser is enforced. Side mode suppression is electrically modulated from ~6 dB to ~21 dB, demonstrating active, optoelectronic modulation of the laser frequency content between multi-mode and single mode operation.

Miniaturized pulsed laser source for time-domain diffuse optics routes to wearable devices

NASA Astrophysics Data System (ADS)

Di Sieno, Laura; Nissinen, Jan; Hallman, Lauri; Martinenghi, Edoardo; Contini, Davide; Pifferi, Antonio; Kostamovaara, Juha; Mora, Alberto Dalla

2017-08-01

We validate a miniaturized pulsed laser source for use in time-domain (TD) diffuse optics, following rigorous and shared protocols for performance assessment of this class of devices. This compact source (12×6 mm2) has been previously developed for range finding applications and is able to provide short, high energy (˜100 ps, ˜0.5 nJ) optical pulses at up to 1 MHz repetition rate. Here, we start with a basic level laser characterization with an analysis of suitability of this laser for the diffuse optics application. Then, we present a TD optical system using this source and its performances in both recovering optical properties of tissue-mimicking homogeneous phantoms and in detecting localized absorption perturbations. Finally, as a proof of concept of in vivo application, we demonstrate that the system is able to detect hemodynamic changes occurring in the arm of healthy volunteers during a venous occlusion. Squeezing the laser source in a small footprint removes a key technological bottleneck that has hampered so far the realization of a miniaturized TD diffuse optics system, able to compete with already assessed continuous-wave devices in terms of size and cost, but with wider performance potentialities, as demonstrated by research over the last two decades.

Using synchrotron X-ray phase-contrast micro-computed tomography to study tissue damage by laser irradiation.

PubMed

Robinson, Alan M; Stock, Stuart R; Soriano, Carmen; Xiao, Xianghui; Richter, Claus-Peter

2016-11-01

The aim of this study was to determine if X-ray micro-computed tomography could be used to locate and characterize tissue damage caused by laser irradiation and to describe its advantages over classical histology for this application. A surgical CO 2 laser, operated in single pulse mode (100 milliseconds) at different power settings, was used to ablate different types of cadaveric animal tissues. Tissue samples were then harvested and imaged with synchrotron X-ray phase-contrast and micro-computed tomography to generate stacks of virtual sections of the tissues. Subsequently, Fiji (ImageJ) software was used to locate tissue damage, then to quantify volumes of laser ablation cones and thermal coagulation damage from 3D renderings of tissue image stacks. Visual comparisons of tissue structures in X-ray images with those visible by classic light microscopy histology were made. We demonstrated that micro-computed tomography could be used to rapidly identify areas of surgical laser ablation, vacuolization, carbonization, and thermally coagulated tissue. Quantification and comparison of the ablation crater, which represents the volume of ablated tissue, and the thermal coagulation zone volumes were performed faster than we could by classical histology. We demonstrated that these procedures can be performed on fresh hydrated and non-sectioned plastic embedded tissue. We demonstrated that the application of non-destructive micro-computed tomography to the visualization and analysis of laser induced tissue damage without tissue sectioning is possible. This will improve evaluation of new surgical lasers and their corresponding effect on tissues. Lasers Surg. Med. 48:866-877, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Evaluation of six holmium:YAG optical fibers for ureteroscopy: What's new in 2009?

NASA Astrophysics Data System (ADS)

Knudsen, Bodo E.; Teichman, Joel M. H.

2010-02-01

The holmium:yttrium aluminum garnet (YAG) laser is the gold standard laser for intracorporeal lithotripsy.1 Optical fibers are utilized to transmit laser energy to the surface of a stone for fragmentation via a predominant photothermal mechanism.2 Previous work has demonstrated that performance characteristics of holmium:YAG optical fibers used for laser lithotripsy varies. Performance may difference not only between fibers made by different manufacturers but also between individual fibers produced by the same manufacturer.3,4 Fiber failure with bending, such as during lower pole ureterorenoscopy, can lead to catastrophic endoscope damage resulting in costly repair. Manufacturers continue to develop new holmium:YAG optical fibers. In this study we evaluate a series of newly commercially available fibers using a previously designed testing protocol. This study was designed to determine the performance and threshold for failure of six newly available holmium:YAG laser fibers from Cook Medical and Fibertech Gmbh. We hypothesize that fiber performance will continue to vary amongst different holmium:YAG optical fibers.

Experimental multiplexing of quantum key distribution with classical optical communication

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

Wang, Liu-Jun; Chen, Luo-Kan; Ju, Lei

2015-02-23

We demonstrate the realization of quantum key distribution (QKD) when combined with classical optical communication, and synchronous signals within a single optical fiber. In the experiment, the classical communication sources use Fabry-Pérot (FP) lasers, which are implemented extensively in optical access networks. To perform QKD, multistage band-stop filtering techniques are developed, and a wavelength-division multiplexing scheme is designed for the multi-longitudinal-mode FP lasers. We have managed to maintain sufficient isolation among the quantum channel, the synchronous channel and the classical channels to guarantee good QKD performance. Finally, the quantum bit error rate remains below a level of 2% across themore » entire practical application range. The proposed multiplexing scheme can ensure low classical light loss, and enables QKD over fiber lengths of up to 45 km simultaneously when the fibers are populated with bidirectional FP laser communications. Our demonstration paves the way for application of QKD to current optical access networks, where FP lasers are widely used by the end users.« less

Control of operating parameters of laser ceilometers with the application of fiber optic delay line imitation

NASA Astrophysics Data System (ADS)

Kim, A. A.; Klochkov, D. V.; Konyaev, M. A.; Mihaylenko, A. S.

2017-11-01

The article considers the problem of control and verification of the laser ceilometers basic performance parameters and describes an alternative method based on the use of multi-length fiber optic delay line, simulating atmospheric track. The results of the described experiment demonstrate the great potential of this method for inspection and verification procedures of laser ceilometers.

Development of fiber lasers and devices for coherent Raman scattering microscopy

NASA Astrophysics Data System (ADS)

Lamb, Erin Stranford

As ultrafast laser technology has found expanding application in machining, spectroscopy, microscopy, surgery, and numerous other areas, the desire for inexpensive and robust laser sources has grown. Until recently, nonlinear effects in fiber systems due to the tight confinement of the light in the core have limited their performance. However, with advances in managing nonlinearity through pulse propagation physics and the use of large core fibers, the performance of fiber lasers can compete with that of their solid-state counterparts. As specific applications, such as coherent Raman scattering microscopy, emerge that stand to benefit from fiber technology, new performance challenges in areas such as laser noise are anticipated. This thesis studies nonlinear pulse propagation in fiber lasers and fiber parametric devices. Applications of dissipative solitons and self-similar pulse propagation to low-repetition rate oscillators that have the potential to simplify short-pulse amplification schemes will be examined. The rest of this thesis focuses on topics relevant to fiber laser development for coherent Raman scattering microscopy sources. Coherent pulse division and recombination inside the laser cavity will be introduced as an energy-scaling mechanism and demonstrated for a fiber soliton laser. The relative intensity noise properties of mode-locked fiber lasers, with a particular emphasis on normal dispersion lasers, will be explored in simulation and experiment. A fiber optical parametric oscillator will be studied in detail for low noise frequency conversion of picosecond pulses, and its utility for coherent Raman imaging will be demonstrated. Spectral compression of femtosecond pulses is used to generate picosecond pulses to pump this device, and this technique provides a route to future noise reduction in the system. Furthermore, this device forms a multimodal source capable of providing the picosecond pulses for coherent Raman scattering microscopy and the high energy femtosecond pulses for other multiphoton imaging techniques. Finally, ideas for future extensions of this work will be discussed.

Laser-diode pumped 40-W Yb:YAG ceramic laser.

PubMed

Hao, Qiang; Li, Wenxue; Pan, Haifeng; Zhang, Xiaoyi; Jiang, Benxue; Pan, Yubai; Zeng, Heping

2009-09-28

We demonstrated a high-power continuous-wave (CW) polycrystalline Yb:YAG ceramic laser pumped by fiber-pigtailed laser diode at 968 nm with 400 mum fiber core. The Yb:YAG ceramic laser performance was compared for different Yb(3+) ion concentrations in the ceramics by using a conventional end-pump laser cavity consisting of two flat mirrors with output couplers of different transmissions. A CW laser output of 40 W average power with M(2) factor of 5.8 was obtained with 5 mol% Yb concentration under 120 W incident pump power. This is to the best of our knowledge the highest output power in end-pumped bulk Yb:YAG ceramic laser.

Flight phasemeter on the Laser Ranging Interferometer on the GRACE Follow-On mission

NASA Astrophysics Data System (ADS)

Bachman, B.; de Vine, G.; Dickson, J.; Dubovitsky, S.; Liu, J.; Klipstein, W.; McKenzie, K.; Spero, R.; Sutton, A.; Ware, B.; Woodruff, C.

2017-05-01

As the first inter-spacecraft laser interferometer, the Laser Ranging Interferometer (LRI) on the GRACE Follow-On Mission will demonstrate interferometry technology relevant to the LISA mission. This paper focuses on the completed LRI Laser Ranging Processor (LRP), which includes heterodyne signal phase tracking at μ {{cycle/}}\\sqrt{{{Hz}}} precision, differential wavefront sensing, offset frequency phase locking and Pound-Drever-Hall laser stabilization. The LRI design has characteristics that are similar to those for LISA: 1064 nm NPRO laser source, science bandwidth in the mHz range, MHz-range intermediate frequency and Doppler shift, detected optical power of tens of picoWatts. Laser frequency stabilization has been demonstrated at a level below 30{{Hz/}}\\sqrt{{{Hz}}}, better than the LISA requirement of 300{{Hz/}}\\sqrt{{{Hz}}}. The LRP has completed all performance testing and environmental qualification and has been delivered to the GRACE Follow-On spacecraft. The LRI is poised to test the LISA techniques of tone-assisted time delay interferometry and arm-locking. GRACE Follow-On launches in 2017.

Scaling studies of solar pumped lasers

NASA Astrophysics Data System (ADS)

Christiansen, W. H.; Chang, J.

1985-08-01

A progress report of scaling studies of solar pumped lasers is presented. Conversion of blackbody radiation into laser light has been demonstrated in this study. Parametric studies of the variation of laser mixture composition and laser gas temperature were carried out for CO2 and N2O gases. Theoretical analysis and modeling of the system have been performed. Reasonable agreement between predictions in the parameter variation and the experimental results have been obtained. Almost 200 mW of laser output at 10.6 micron was achieved by placing a small sapphire laser tube inside an oven at 1500 K the tube was filled with CO2 laser gas mixture and cooled by longitudinal nitrogen gas flow.

Scaling studies of solar pumped lasers

NASA Technical Reports Server (NTRS)

Christiansen, W. H.; Chang, J.

1985-01-01

A progress report of scaling studies of solar pumped lasers is presented. Conversion of blackbody radiation into laser light has been demonstrated in this study. Parametric studies of the variation of laser mixture composition and laser gas temperature were carried out for CO2 and N2O gases. Theoretical analysis and modeling of the system have been performed. Reasonable agreement between predictions in the parameter variation and the experimental results have been obtained. Almost 200 mW of laser output at 10.6 micron was achieved by placing a small sapphire laser tube inside an oven at 1500 K the tube was filled with CO2 laser gas mixture and cooled by longitudinal nitrogen gas flow.

Imaging standoff trace detection of explosives using IR-laser based backscattering

NASA Astrophysics Data System (ADS)

Fuchs, F.; Hugger, S.; Jarvis, J.; Yang, Q. K.; Ostendorf, R.; Schilling, Ch.; Bronner, W.; Driad, R.; Aidam, R.; Wagner, J.

2016-05-01

We perform active hyperspectral imaging using tunable mid-infrared (MIR) quantum cascade lasers for contactless identification of solid and liquid contaminations on surfaces. By collecting the backscattered laser radiation with a camera, a hyperspectral data cube, containing the spatially resolved spectral information of the scene is obtained. Data is analyzed using appropriate algorithms to find the target substances even on substrates with a priori unknown spectra. Eye-save standoff detection of residues of explosives and precursors over extended distances is demonstrated and the main purpose of our system. Using a MIR EC-QCL with a tuning range from 7.5 μm to 10 μm, detection of a large variety of explosives, e.g. TNT, PETN and RDX and precursor materials such as Ammonium Nitrate could be demonstrated. In a real world scenario stand-off detection over distances of up to 20 m could be successfully performed. This includes measurements in a post blast scenario demonstrating the potential of the technique for forensic investigations.

Aerodynamic Measurement Technology

NASA Technical Reports Server (NTRS)

Burner, Alpheus W.

2002-01-01

Ohio State University developed a new spectrally filtered light-scattering apparatus based on a diode laser injected-locked titanium: sapphire laser and rubidium vapor filter at 780.2 nm. When the device was combined with a stimulated Brillouin scattering phase conjugate mirror, the realizable peak attenuation of elastic scattering interferences exceeded 105. The potential of the system was demonstrated by performing Thomson scattering measurements. Under USAF-NASA funding, West Virginia University developed a Doppler global velocimetry system using inexpensive 8-bit charged coupled device cameras and digitizers and a CW argon ion laser. It has demonstrated a precision of +/- 2.5 m/sec in a swirling jet flow. Low-noise silicon-micromachined microphones developed and incorporated in a novel two-tier, hybrid packaging scheme at the University of Florida used printed circuit board technology to realize a MEMS-based directional acoustic array. The array demonstrated excellent performance relative to conventional sensor technologies and provides scaling technologies that can reduce cost and increase speed and mobility.

An audit of the use of the CO2 laser in oral and maxillofacial surgery

NASA Astrophysics Data System (ADS)

Pinheiro, Antonio L. B.; Santos de Almeida, Darcy

2004-09-01

The use of the Carbon dioxide Laser to perform surgical procedures in the oral cavity has been described as a successful method for the treatment of several conditions affecting the maxillofacial region. Several benefits of the use of the CO2 Laser have been reported and includes reduction of postoperative pain and edema, local hemosthasis, reduction of scaring and wound contraction and infection. The aim of this work is to present our clinical experience in performing several surgical procedures using the CO2 Laser to treat soft tissue pathologies of both benign and malign origin as well as on performing pre-prosthetic surgery, apical surgery and on the treatment of pre-malignancies. Our experience demonstrate that the use of the Carbon dioxide Laser in treating oral soft-tissue pathology presents advantages over conventional techniques and local discomfort and pain are the most common complaints after Laser surgery. The Carbon dioxide Laser does not offer any enhanced cure-rate for oral pathology, but rather it is a precise means of removing soft tissue lesions with little upset afterwards.

Enhanced performance of Cr,Yb:YAG microchip laser by bonding Yb:YAG crystal.

PubMed

Cheng, Ying; Dong, Jun; Ren, Yingying

2012-10-22

Highly efficient, laser-diode pumped Yb:YAG/Cr,Yb:YAG self-Q-switched microchip lasers by bonding Yb:YAG crystal have been demonstrated for the first time to our best knowledge. The effect of transmission of output coupler (T(oc)) on the enhanced performance of Yb:YAG/Cr,Yb:YAG microchip lasers has been investigated and found that the best laser performance was achieved with T(oc) = 50%. Slope efficiency of over 38% was achieved. Average output power of 0.8 W was obtained at absorbed pump power of 2.5 W; corresponding optical-to-optical efficiency of 32% was obtained. Laser pulses with pulse width of 1.68 ns, pulse energy of 12.4 μJ, and peak power of 7.4 kW were obtained. The lasers oscillated in multi-longitudinal modes. The wide separation of longitudinal modes was attributed to the mode selection by combined etalon effect of Cr,Yb:YAG, Yb:YAG thin plates and output coupler. Stable periodical pulse trains at different pump power levels have been observed owing to the longitudinal modes coupling and competition.

Group III-arsenide-nitride long wavelength laser diodes

NASA Astrophysics Data System (ADS)

Coldren, Christopher W.

Semiconductor laser diodes transmitting data over silica optical fiber form the backbone of modern day communications systems, enabling terabit per second data transmission over hundreds to thousands of kilometers of distance. The wavelength of emission of the transmission semiconductor laser diode is a critical parameter that determines the performance of the communications system. In high performance fiber optic communications systems, lasers emitting at 1300nm and 1550nm are used because of the low loss and distortion properties of the fiber in these spectral windows. The available lasers today that operate in these fiber optic transmission windows suffer from high cost and poor performance under the typical environmental conditions and require costly and unreliable cooling systems. This dissertation presents work that demonstrates that it is possible to make lasers devices with 1300nm laser emission that are compatible with low cost and operation under extreme operating conditions. The key enabling technology developed is a novel semiconductor material based structure. A group III-Arsenide-Nitride quantum well structure was developed that can be grown expitaxially on GaAs substrates. The properties of this group III-Arsenide-Nitride structure allowed high performance edge emitting and vertical cavity surface emitting lasers to be fabricated which exhibited low threshold currents and low sensitivity to operating temperature.

NASA's Preparations for ESA's L3 Gravitational Wave Mission

NASA Technical Reports Server (NTRS)

Stebbins, Robin

2016-01-01

Telescope Subsystem - Jeff Livas (GSFC): Demonstrate pathlength stability, straylight and manufacturability. Phase Measurement System - Bill Klipstein (JPL): Key measurement functions demonstrated. Incorporate full flight functionality. Laser Subsystem - Jordan Camp (GSFC): ECL master oscillator, phase noise of fiber power amplifier, demonstrate end-to-end performance in integrated system, lifetime. Micronewton Thrusters - John Ziemer (JPL): Propellant storage and distribution, system robustness, manufacturing yield, lifetime. Arm-locking Demonstration - Kirk McKenzie (JPL): Studying a demonstration of laser frequency stabilization with GRACE Follow-On. Torsion Pendulum - John Conklin (UF): Develop U.S. capability with GRS and torsion pendulum test bed. Multi-Axis Heterodyne Interferometry - Ira Thorpe (GSFC): Investigate test mass/optical bench interface. UV LEDs - John Conklin+ (UF): Flight qualify UV LEDs to replace mercury lamps in discharging system. Optical Bench - Guido Mueller (UF): Investigate alternate designs and fabrication processes to ease manufacturability. LISA researchers at JPL are leading the Laser Ranging Interferometer instrument on the GRACE Follow-On mission.

Broadband standoff detection of large molecules by mid-infrared active coherent laser spectrometry.

PubMed

Macleod, Neil A; Molero, Francisco; Weidmann, Damien

2015-01-26

A widely tunable active coherent laser spectrometer (ACLaS) has been demonstrated for standoff detection of broadband absorbers in the 1280 to 1318 cm^-1 spectral region using an external cavity quantum cascade laser as a mid-infrared source. The broad tuning range allows detection and quantification of vapor phase molecules, such as dichloroethane, ethylene glycol dinitrate, and tetrafluoroethane. The level of confidence in molecular mixing ratios retrieved from interfering spectral measurements is assessed in a quantitative manner. A first qualitative demonstration of condensed phase chemical detection on nitroacetanilide has also been conducted. Detection performances of the broadband ACLaS have been placed in the context of explosive detection and compared to that obtained using distributed feedback quantum cascade lasers.

Next-generation laser for inertial confinement fusion

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

Marshall, C; Bibeau, C; Bayramian, A

1998-03-13

We are developing and building the ''Mercury'' laser system as the first in a series of a new generation of diode-pumped solid-state lasers (DPSSL) for advanced high energy density (HED) physics experiments at LLNL. Mercury will be the first integrated demonstration of a scalable laser architecture compatible with advanced Inertial Confinement Fusion (ICF) goals. Primary performance goals include 10% efficiencies at 10 Hz and a <10 ns pulse with l {omega} energies of 100 J and with 2 {omega}/3 {omega} frequency conversion. Achieving this performance will provide a near term capability for HED experiments and prove the potential of DPSSLsmore » for inertial fusion energy (IFE).« less

Excimer laser decoating of chromium titanium aluminium nitride to facilitate re-use of cutting tools

NASA Astrophysics Data System (ADS)

Sundar, M.; Whitehead, D.; Mativenga, P. T.; Li, L.; Cooke, K. E.

2009-11-01

This work reports on the technical feasibility and establishment of a process window for removing chromium titanium aluminium nitride (CrTiAlN) coating from steel substrates by laser irradiation. CrTiAlN coating has high hardness and oxidation resistance, with applications for use with cutting tools. The motivation for removing such coatings is to facilitate re-use of tooling by enabling regrinding or reshaping of a worn tool and hence promote sustainable material usage. In this work, laser decoating was performed using an excimer laser. The effect of laser fluence, number of pulses, frequency, scanning speed and laser beam overlap on the decoating performance was investigated in detail. The minimum threshold laser fluence for removing the CrTiAlN coating was lower than that of the steel substrate and this factor is beneficial in controlling the decoating process. Successful laser removal of CrTiAlN coating without noticeable damage to the steel substrate was demonstrated.

Continuous-wave broadly tunable Cr 2+:ZnSe laser pumped by a thulium fiber laser

NASA Astrophysics Data System (ADS)

Sennaroglu, Alphan; Demirbas, Umit; Vermeulen, Nathalie; Ottevaere, Heidi; Thienpont, Hugo

2006-12-01

We describe a compact, broadly tunable, continuous-wave (cw) Cr 2+:ZnSe laser pumped by a thulium fiber laser at 1800 nm. In the experiments, a polycrystalline ZnSe sample with a chromium concentration of 9.5 × 10 18 cm -3 was used. Free-running laser output was around 2500 nm. Output couplers with transmissions of 3%, 6%, and 15% were used to characterize the power performance of the laser. Best power performance was obtained with a 15% transmitting output coupler. In this case, as high as 640 mW of output power was obtained with 2.5 W of pump power at a wavelength of 2480 nm. The stimulated emission cross-section values determined from laser threshold data and emission measurements were in good agreement. Finally, broad, continuous tuning of the laser was demonstrated between 2240 and 2900 nm by using an intracavity Brewster cut MgF 2 prism and a single set of optics.

Optimal reconstruction for closed-loop ground-layer adaptive optics with elongated spots.

PubMed

Béchet, Clémentine; Tallon, Michel; Tallon-Bosc, Isabelle; Thiébaut, Éric; Le Louarn, Miska; Clare, Richard M

2010-11-01

The design of the laser-guide-star-based adaptive optics (AO) systems for the Extremely Large Telescopes requires careful study of the issue of elongated spots produced on Shack-Hartmann wavefront sensors. The importance of a correct modeling of the nonuniformity and correlations of the noise induced by this elongation has already been demonstrated for wavefront reconstruction. We report here on the first (to our knowledge) end-to-end simulations of closed-loop ground-layer AO with laser guide stars with such an improved noise model. The results are compared with the level of performance predicted by a classical noise model for the reconstruction. The performance is studied in terms of ensquared energy and confirms that, thanks to the improved noise model, central or side launching of the lasers does not affect the performance with respect to the laser guide stars' flux. These two launching schemes also perform similarly whatever the atmospheric turbulence strength.

Laser Demonstration and Performance Characterization of an Optically Pumped Alkali Laser System

DTIC Science & Technology

2010-09-01

long by 2.54 cm wide with Brewster angle quartz widows. The cell was housed in an aluminum oven with independent control of the temperatures of the...line. A 12.7 cm long Brewster angled glass cell 2.5 cm in diameter contained the rubidium vapor and was housed in an aluminum oven to provide...hypothesize that this increase in temperature can result in thermal lensing within the laser cavity which could change the laser configuration by

Next generation laser for Inertial Confinement Fusion

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

Marshall, C.D.; Beach, J.; Bibeau, C.

1997-07-18

We are in the process of developing and building the ``Mercury`` laser system as the first in a series of a new generation of diode-pumped solid-state Inertial Confinement Fusion (ICF) lasers at LLNL. Mercury will be the first integrated demonstration of a scalable laser architecture compatible with advanced high energy density (HED) physics applications. Primary performance goals include 10% efficiencies at 10 Hz and a 1-10 ns pulse with 1{omega} energies of 100 J and with 2{omega}/3{omega} frequency conversion.

Recent Advances in Fiber Lasers for Nonlinear Microscopy

PubMed Central

Xu, C.; Wise, F. W.

2013-01-01

Nonlinear microscopy techniques developed over the past two decades have provided dramatic new capabilities for biological imaging. The initial demonstrations of nonlinear microscopies coincided with the development of solid-state femtosecond lasers, which continue to dominate applications of nonlinear microscopy. Fiber lasers offer attractive features for biological and biomedical imaging, and recent advances are leading to high-performance sources with the potential for robust, inexpensive, integrated instruments. This article discusses recent advances, and identifies challenges and opportunities for fiber lasers in nonlinear bioimaging. PMID:24416074

A tunable erbium-doped fiber ring laser with power-equalized output

NASA Astrophysics Data System (ADS)

Yeh, Chien-Hung; Lin, Ming-Ching; Chi, Sien

2006-12-01

We propose and demonstrate a tunable erbium-based fiber ring laser with power-equalized output. When a mode-restricting intracavity fiber Fabry-Perot tunable filter (FFP-TF) is combined, the proposed resonator can guarantee a tunable laser oscillation. This proposed laser can obtain the flatter lasing wavelength in an effectively operating range of 1533.3 to 1574.6 nm without any other operating mechanism. Moreover, the performances of the output power, wavelength tuning range, and side-mode suppression ratio (SMSR) were studied.

High power diode lasers for solid-state laser pumps

NASA Technical Reports Server (NTRS)

Linden, Kurt J.; Mcdonnell, Patrick N.

1994-01-01

The development and commercial application of high power diode laser arrays for use as solid-state laser pumps is described. Such solid-state laser pumps are significantly more efficient and reliable than conventional flash-lamps. This paper describes the design and fabrication of diode lasers emitting in the 780 - 900 nm spectral region, and discusses their performance and reliability. Typical measured performance parameters include electrical-to-optical power conversion efficiencies of 50 percent, narrow-band spectral emission of 2 to 3 nm FWHM, pulsed output power levels of 50 watts/bar with reliability values of over 2 billion shots to date (tests to be terminated after 10 billion shots), and reliable operation to pulse lengths of 1 ms. Pulse lengths up to 5 ms have been demonstrated at derated power levels, and CW performance at various power levels has been evaluated in a 'bar-in-groove' laser package. These high-power 1-cm stacked-bar arrays are now being manufactured for OEM use. Individual diode laser bars, ready for package-mounting by OEM customers, are being sold as commodity items. Commercial and medical applications of these laser arrays include solid-state laser pumping for metal-working, cutting, industrial measurement and control, ranging, wind-shear/atmospheric turbulence detection, X-ray generation, materials surface cleaning, microsurgery, ophthalmology, dermatology, and dental procedures.

Optical design and performance of F-Theta lenses for high-power and high-precision applications

NASA Astrophysics Data System (ADS)

Yurevich, V. I.; Grimm, V. A.; Afonyushkin, A. A.; Yudin, K. V.; Gorny, S. G.

2015-09-01

F-Theta lenses are widely used in remote laser processing. Nowadays, a large variety of scanning systems utilizing these devices are commercially available. In this paper, we demonstrate that all practical issues lose their triviality in designing high-performance F-Theta scanning systems. Laser power scaling requires attention to thermally-induced phenomena and ghost reflections. This requirement considerably complicates optimization of the optical configuration of the system and primary aberration correction, even during preliminary design. Obtaining high positioning accuracy requires taking into consideration all probable reasons for processing field distortion. We briefly describe the key engineering relationships and invariants as well as the typical design of a scanner lens and the main field-flattening techniques. Specific emphasis is directed to consideration of the fundamental nonlinearity of two-mirror scanners. To the best of our knowledge, this issue has not been yet studied. We also demonstrate the benefits of our F-Theta lens optimization technique, which uses a plurality of entrance pupils. The problems of eliminating focused ghost reflections and the effects of thermally-induced processes in high-power F-Theta lenses are considered. A set of multi-path 3D processing and laser cutting experiments were conducted and are presented herein to demonstrate the impact of laser beam degradation on the process performance. A selection of our non-standard optical designs is presented.

Super-contrast photoacoustic resonance imaging

NASA Astrophysics Data System (ADS)

Gao, Fei; Zhang, Ruochong; Feng, Xiaohua; Liu, Siyu; Zheng, Yuanjin

2018-02-01

In this paper, a new imaging modality, named photoacoustic resonance imaging (PARI), is proposed and experimentally demonstrated. Being distinct from conventional single nanosecond laser pulse induced wideband PA signal, the proposed PARI method utilizes multi-burst modulated laser source to induce PA resonant signal with enhanced signal strength and narrower bandwidth. Moreover, imaging contrast could be clearly improved than conventional single-pulse laser based PA imaging by selecting optimum modulation frequency of the laser source, which originates from physical properties of different materials beyond the optical absorption coefficient. Specifically, the imaging steps is as follows: 1: Perform conventional PA imaging by modulating the laser source as a short pulse to identify the location of the target and the background. 2: Shine modulated laser beam on the background and target respectively to characterize their individual resonance frequency by sweeping the modulation frequency of the CW laser source. 3: Select the resonance frequency of the target as the modulation frequency of the laser source, perform imaging and get the first PARI image. Then choose the resonance frequency of the background as the modulation frequency of the laser source, perform imaging and get the second PARI image. 4: subtract the first PARI image from the second PARI image, then we get the contrast-enhanced PARI results over the conventional PA imaging in step 1. Experimental validation on phantoms have been performed to show the merits of the proposed PARI method with much improved image contrast.

Solid-state laser source of narrowband ultraviolet B light for skin disease care with advanced performance

NASA Astrophysics Data System (ADS)

Tarasov, Aleksandr A.; Chu, Hong; Buchwald, Kristian

2015-02-01

Two years ago we reported about the development of solid state laser source for medical skin treatment with wavelength 310.6 nm and average power 200 mW. Here we describe the results of investigation of the advanced version of the laser, which is a more compact device with increased output power and flat top beam profile. Ti: Sapphire laser, the main module of our source, was modified and optimized such, that UV average power of the device was increased 1.7 times. Fiber optic homogenizer was replaced by articulated arm with diffraction diffuser, providing round spot with flat profile at the skin. We investigated and compare characteristics of Ti: Sapphire lasers with volume Bragg grating and with fused silica transmission grating, which was used first time for Ti: Sapphire laser spectral selection and tuning. Promising performance of last gratings is demonstrated.

Development of improved amorphous materials for laser systems

NASA Technical Reports Server (NTRS)

Neilson, G. F.; Weinberg, M. C.

1974-01-01

Crystallization calculations were performed in order to determine the possibility of forming a particular type of laser glass with the avoidance of devitrification in an outer space laboratory. It was demonstrated that under the homogenuous nucleating conditions obtainable in a zero gravity laboratory this laser glass may be easily quenched to a virtually crystal-free product. Experimental evidence is provided that use of this material as a host in a neodymium glass laser would result in more than a 10 percent increase in efficiency when compared to laser glass rods of a similar composition currently commercially available. Differential thermal analysis, thermal gradient oven, X-ray diffraction, and liquidus determination experiments were carried out to determine the basics of the crystallization behavior of the glass, and small-angle X-ray scattering and splat-cooling experiments were performed in order to provide additional evidence for the feasibility of producing this laser glass material, crystal free, in an outer space environment.

Color-encoded distance for interactive focus positioning in laser microsurgery

NASA Astrophysics Data System (ADS)

Schoob, Andreas; Kundrat, Dennis; Lekon, Stefan; Kahrs, Lüder A.; Ortmaier, Tobias

2016-08-01

This paper presents a real-time method for interactive focus positioning in laser microsurgery. Registration of stereo vision and a surgical laser is performed in order to combine surgical scene and laser workspace information. In particular, stereo image data is processed to three-dimensionally reconstruct observed tissue surface as well as to compute and to highlight its intersection with the laser focal range. Regarding the surgical live view, three augmented reality concepts are presented providing visual feedback during manual focus positioning. A user study is performed and results are discussed with respect to accuracy and task completion time. Especially when using color-encoded distance superimposed to the live view, target positioning with sub-millimeter accuracy can be achieved in a few seconds. Finally, transfer to an intraoperative scenario with endoscopic human in vivo and cadaver images is discussed demonstrating the applicability of the image overlay in laser microsurgery.

Terahertz metasurface quantum-cascade VECSELs: theory and performance

DOE PAGES

Xu, Luyao; Curwen, Christopher; Chen, Daguan; ...

2017-04-12

A longstanding challenge for terahertz quantum-cascade (QC) lasers is achieving both a high power and high-quality beam pattern, this is due in part due to their use of sub-wavelength metallic waveguides. Recently, the vertical-external-cavity surface-emitting laser (VECSEL) concept was demonstrated for the first time in the terahertz range and for a QC-laser. This is enabled by the development of an amplifying metasurface reflector capable of coupling incident free-space THz radiation to the QC-laser material such that it is amplified and re-radiated. The THz metasurface QC-VECSEL initiates a new approach for making QC-lasers with high power and excellent beam pattern. Furthermore,more » the ability to engineer the electromagnetic phase, amplitude, and polarization response of the metasurface enables lasers with new functionality. Our article provides an overview of the fundamental theory, design considerations, and recent results for high-performance THz QC-VECSELs.« less

An integrated analog O/E/O link for multi-channel laser neurons

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

Nahmias, Mitchell A., E-mail: mnahmias@princeton.edu; Tait, Alexander N.; Tolias, Leonidas

2016-04-11

We demonstrate an analog O/E/O electronic link to allow integrated laser neurons to accept many distinguishable, high bandwidth input signals simultaneously. This device utilizes wavelength division multiplexing to achieve multi-channel fan-in, a photodetector to sum signals together, and a laser cavity to perform a nonlinear operation. Its speed outpaces accelerated-time neuromorphic electronics, and it represents a viable direction towards scalable networking approaches.

Optical isolators for 2-micron fibre lasers

NASA Astrophysics Data System (ADS)

Stevens, Gary; Legg, Thomas H.; Shardlow, Peter

2015-02-01

We report on the development and testing of optical isolators for use in 2-micron fiber laser systems. A variety of potential Faraday rotator materials were characterised to identify the most suitable materials for use in the 1700-2100nm wavelength range. Isolators based on the three best performing materials were then developed and packaged as fiber-in, fiber-out and fiber-in, beam-out devices. The isolators were then tested in CW, pulsed and ultrafast laser systems. The three different designs produced different performance characteristics, but all designs demonstrated isolation >25dB and insertion losses of <1.2 dB.

Compact high reliability fiber coupled laser diodes for avionics and related applications

NASA Astrophysics Data System (ADS)

Daniel, David R.; Richards, Gordon S.; Janssen, Adrian P.; Turley, Stephen E. H.; Stockton, Thomas E.

1993-04-01

This paper describes a newly developed compact high reliability fiber coupled laser diode which is capable of providing enhanced performance under extreme environmental conditions including a very wide operating temperature range. Careful choice of package materials to minimize thermal and mechanical stress, used with proven manufacturing methods, has resulted in highly stable coupling of the optical fiber pigtail to a high performance MOCVD-grown Multi-Quantum Well laser chip. Electro-optical characteristics over temperature are described together with a demonstration of device stability over a range of environmental conditions. Real time device lifetime data is also presented.

Thermal-noise-limited higher-order mode locking of a reference cavity.

PubMed

Zeng, X Y; Ye, Y X; Shi, X H; Wang, Z Y; Deng, K; Zhang, J; Lu, Z H

2018-04-15

Higher-order mode locking has been proposed to reduce the thermal noise limit of reference cavities. By locking a laser to the HG 02 mode of a 10-cm long all ultra-low expansion (ULE) cavity and measuring its performance with the three-cornered-hat method among three independently stabilized lasers, we demonstrate a thermal-noise-limited performance of a fractional frequency instability of 4.9×10 -16 . The results match the theoretical models with higher-order optical modes. The achieved laser instability improves the all ULE short cavity results to a new low level.

Evaluation of a laser scanner for large volume coordinate metrology: a comparison of results before and after factory calibration

NASA Astrophysics Data System (ADS)

Ferrucci, M.; Muralikrishnan, B.; Sawyer, D.; Phillips, S.; Petrov, P.; Yakovlev, Y.; Astrelin, A.; Milligan, S.; Palmateer, J.

2014-10-01

Large volume laser scanners are increasingly being used for a variety of dimensional metrology applications. Methods to evaluate the performance of these scanners are still under development and there are currently no documentary standards available. This paper describes the results of extensive ranging and volumetric performance tests conducted on a large volume laser scanner. The results demonstrated small but clear systematic errors that are explained in the context of a geometric error model for the instrument. The instrument was subsequently returned to the manufacturer for factory calibration. The ranging and volumetric tests were performed again and the results are compared against those obtained prior to the factory calibration.

Fabrication of mitigation pits for improving laser damage resistance in dielectric mirrors by femtosecond laser machining

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

Wolfe, Justin E.; Qiu, S. Roger; Stolz, Christopher J.

2011-03-20

Femtosecond laser machining is used to create mitigation pits to stabilize nanosecond laser-induced damage in multilayer dielectric mirror coatings on BK7 substrates. In this paper, we characterize features and the artifacts associated with mitigation pits and further investigate the impact of pulse energy and pulse duration on pit quality and damage resistance. Our results show that these mitigation features can double the fluence-handling capability of large-aperture optical multilayer mirror coatings and further demonstrate that femtosecond laser macromachining is a promising means for fabricating mitigation geometry in multilayer coatings to increase mirror performance under high-power laser irradiation.

Cost-effective wavelength-tunable fiber laser using self-seeding Fabry-Perot laser diode.

PubMed

Yeh, Chien-Hung; Shih, Fu Y; Wang, Chia H; Chow, Chi W; Chi, Sien

2008-01-07

We propose and experimentally demonstrate a continuous wave (CW) tunable-wavelength fiber laser using self-seeding Fabry-Perot laser diode (FP-LD) without optical amplifier inside gain cavity. By employing a tunable bandpass filter (TBF) and a fiber reflected mirror (FRM) within a gain cavity, the fiber laser can lase a single-longitudinal wavelength due to the self-seeding operation. The proposed tunable wavelength laser has a good performance of the output power (> -15 dBm) and optical side-mode suppression ratio (> 40 dB) in the wavelength tuning range of 1533.75 to 1560.95 nm. In addition, the output stabilities of the fiber laser are also investigated.

Demonstration of a plenoptic microscope based on laser optical feedback imaging.

PubMed

Glastre, Wilfried; Hugon, Olivier; Jacquin, Olivier; Guillet de Chatellus, Hugues; Lacot, Eric

2013-03-25

A new kind of plenoptic imaging system based on Laser Optical Feedback Imaging (LOFI) is presented and is compared to another previously existing device based on microlens array. Improved photometric performances, resolution and depth of field are obtained at the price of a slow point by point scanning. Main properties of plenoptic microscopes such as numerical refocusing on any curved surface or aberrations compensation are both theoretically and experimentally demonstrated with a LOFI-based device.

Mode-locking of a terahertz laser by direct phase synchronization.

PubMed

Maysonnave, J; Maussang, K; Freeman, J R; Jukam, N; Madéo, J; Cavalié, P; Rungsawang, R; Khanna, S P; Linfield, E H; Davies, A G; Beere, H E; Ritchie, D A; Dhillon, S S; Tignon, J

2012-09-10

A novel scheme to achieve mode-locking of a multimode laser is demonstrated. Traditional methods to produce ultrashort laser pulses are based on modulating the cavity gain or losses at the cavity roundtrip frequency, favoring the pulsed emission. Here, we rather directly act on the phases of the modes, resulting in constructive interference for the appropriated phase relationship. This was performed on a terahertz quantum cascade laser by multimode injection seeding with an external terahertz pulse, resulting in phase mode-locked terahertz laser pulses of 9 ps duration, characterized unambiguously in the time domain.

Exploiting nonlinear properties of pure and Sn-doped Bi2Te2Se for passive Q-switching of all-polarization maintaining ytterbium- and erbium-doped fiber lasers.

PubMed

Bogusławski, Jakub; Kowalczyk, Maciej; Iwanowski, Przemysław; Hruban, Andrzej; Diduszko, Ryszard; Piotrowski, Kazimierz; Dybko, Krzysztof; Wojciechowski, Tomasz; Aleszkiewicz, Marta; Sotor, Jarosław

2017-08-07

Due to their broadband nonlinear optical properties, low-dimensional materials are widely used for pulse generation in fiber and solid-state lasers. Here we demonstrate novel materials, Bi 2 Te 2 Se (BTS) and Sn-doped Bi 2 Te 2 Se (BSTS), which can be used as a universal saturable absorbers for distinct spectral regimes. The material was mechanically exfoliated from a bulk single-crystal and deposited onto a side-polished fiber. We have performed characterization of the fabricated devices and employed them in polarization-maintaining ytterbium- and erbium-doped fiber lasers. This enabled us to obtain self-starting passively Q-switched regime at 1 µm and 1.56 µm. The oscillators emitted stable, linearly polarized radiation with the highest single pulse energy approaching 692 nJ. Both lasers are characterized by the best performance observed in all-polarization maintaining Q-switched fiber lasers with recently investigated new saturable absorbers, which was enabled by a very high damage threshold of the devices. This demonstrates the great potential of the investigated materials for the ultrafast photonics community.

Single-shot measurement of >1010 pulse contrast for ultra-high peak-power lasers

NASA Astrophysics Data System (ADS)

Wang, Yongzhi; Ma, Jingui; Wang, Jing; Yuan, Peng; Xie, Guoqiang; Ge, Xulei; Liu, Feng; Yuan, Xiaohui; Zhu, Heyuan; Qian, Liejia

2014-01-01

Real-time pulse-contrast observation with a high dynamic range is a prerequisite to tackle the contrast challenge in ultra-high peak-power lasers. However, the commonly used delay-scanning cross-correlator (DSCC) can only provide the time-consumed measurements for repetitive lasers. Single-shot cross-correlator (SSCC) becomes essential in optimizing laser systems and exploring contrast mechanisms. Here we report our progress in developing SSCC towards its practical use. By integrating both the techniques of scattering-noise reduction and sensitive parallel detection into SSCC, we demonstrate a high dynamic range of >1010, which, to our best knowledge, is the first demonstration of an SSCC with a dynamic range comparable to that of commercial DSCCs. The comparison of high-dynamic measurement performances between SSCC and a standard DSCC (Sequoia, Amplitude Technologies) is also carried out on a 200 TW Ti:sapphire laser, and the consistency of results verifies the veracity of our SSCC.

Deep learning and model predictive control for self-tuning mode-locked lasers

NASA Astrophysics Data System (ADS)

Baumeister, Thomas; Brunton, Steven L.; Nathan Kutz, J.

2018-03-01

Self-tuning optical systems are of growing importance in technological applications such as mode-locked fiber lasers. Such self-tuning paradigms require {\\em intelligent} algorithms capable of inferring approximate models of the underlying physics and discovering appropriate control laws in order to maintain robust performance for a given objective. In this work, we demonstrate the first integration of a {\\em deep learning} (DL) architecture with {\\em model predictive control} (MPC) in order to self-tune a mode-locked fiber laser. Not only can our DL-MPC algorithmic architecture approximate the unknown fiber birefringence, it also builds a dynamical model of the laser and appropriate control law for maintaining robust, high-energy pulses despite a stochastically drifting birefringence. We demonstrate the effectiveness of this method on a fiber laser which is mode-locked by nonlinear polarization rotation. The method advocated can be broadly applied to a variety of optical systems that require robust controllers.

DAWN Coherent Wind Profiling Lidar Flights on NASA's DC-8 During GRIP

NASA Technical Reports Server (NTRS)

Kavaya, Michael J.; Beyon, Jeffrey Y.; Creary, Garfield A.; Koch, Grady J.; Petros, Mulugeta; Petzar, Paul J.; Singh, Upendra N.; Trieu, Bo C.; Yu, Jirong

2011-01-01

Almost from their invention, lasers have been used to measure the velocity of wind and objects; over distances of cm to 10s of km. Long distance (remote) sensing of wind has been accomplished with continuous-wave (CW), focused pulsed, and collimated pulsed lasers; with direct and coherent (heterodyne) optical detection; and with a multitude of laser wavelengths. Airborne measurement of wind with pulsed, coherent-detection lidar was first performed in 1971 with a CW CO2 laser1, in 1972 with a pulsed CO2 laser2, in 1993 with a pulsed 2-micron laser3, and in 1999 with a pulsed CO2 laser and nadir-centered conical scanning4. Of course there were many other firsts and many other groups doing lidar wind remote sensing with coherent and direct detection. A very large FOM coherent wind lidar has been built by LaRC and flown on a DC-8. However a burn on the telescope secondary mirror prevented the full demonstration of high FOM. Both the GRIP science product and the technology and technique demonstration from aircraft are important to NASA. The technology and technique demonstrations contribute to our readiness for the 3D Winds space mission. The data analysis is beginning and we hope to present results at the conference.

Infrared Laser Ablation with Vacuum Capture for Fingermark Sampling

NASA Astrophysics Data System (ADS)

Donnarumma, Fabrizio; Camp, Eden E.; Cao, Fan; Murray, Kermit K.

2017-09-01

Infrared laser ablation coupled to vacuum capture was employed to collect material from fingermarks deposited on surfaces of different porosity and roughness. Laser ablation at 3 μm was performed in reflection mode with subsequent capture of the ejecta with a filter connected to vacuum. Ablation and capture of standards from fingermarks was demonstrated on glass, plastic, aluminum, and cardboard surfaces. Using matrix assisted laser desorption ionization (MALDI), it was possible to detect caffeine after spiking with amounts as low as 1 ng. MALDI detection of condom lubricants and detection of antibacterial peptides from an antiseptic cream was demonstrated. Detection of explosives from fingermarks left on plastic surfaces as well as from direct deposition on the same surface using gas chromatography mass spectrometry (GC-MS) was shown. [Figure not available: see fulltext.

Infrared Laser Ablation with Vacuum Capture for Fingermark Sampling.

PubMed

Donnarumma, Fabrizio; Camp, Eden E; Cao, Fan; Murray, Kermit K

2017-09-01

Infrared laser ablation coupled to vacuum capture was employed to collect material from fingermarks deposited on surfaces of different porosity and roughness. Laser ablation at 3 μm was performed in reflection mode with subsequent capture of the ejecta with a filter connected to vacuum. Ablation and capture of standards from fingermarks was demonstrated on glass, plastic, aluminum, and cardboard surfaces. Using matrix assisted laser desorption ionization (MALDI), it was possible to detect caffeine after spiking with amounts as low as 1 ng. MALDI detection of condom lubricants and detection of antibacterial peptides from an antiseptic cream was demonstrated. Detection of explosives from fingermarks left on plastic surfaces as well as from direct deposition on the same surface using gas chromatography mass spectrometry (GC-MS) was shown. Graphical Abstract ᅟ.

Demonstration of sensitivity increase in mercury free-spin-precession magnetometers due to laser-based readout for neutron electric dipole moment searches

NASA Astrophysics Data System (ADS)

Ban, G.; Bison, G.; Bodek, K.; Daum, M.; Fertl, M.; Franke, B.; Grujić, Z. D.; Heil, W.; Horras, M.; Kasprzak, M.; Kermaidic, Y.; Kirch, K.; Koch, H.-C.; Komposch, S.; Kozela, A.; Krempel, J.; Lauss, B.; Lefort, T.; Mtchedlishvili, A.; Pignol, G.; Piegsa, F. M.; Prashanth, P.; Quéméner, G.; Rawlik, M.; Rebreyend, D.; Ries, D.; Roccia, S.; Rozpedzik, D.; Schmidt-Wellenburg, P.; Severijns, N.; Weis, A.; Wyszynski, G.; Zejma, J.; Zsigmond, G.

2018-07-01

We report on a laser based 199Hg co-magnetometer deployed in an experiment searching for a permanent electric dipole moment of the neutron. We demonstrate a more than five times increased signal to-noise-ratio in a direct comparison measurement with its 204Hg discharge bulb-based predecessor. An improved data model for the extraction of important system parameters such as the degrees of absorption and polarization is derived. Laser- and lamp-based data-sets can be consistently described by the improved model which permits to compare measurements using the two different light sources and to explain the increase in magnetometer performance. The laser-based magnetometer satisfies the magnetic field sensitivity requirements for the next generation nEDM experiments.

Miniaturized pulsed laser source for time-domain diffuse optics routes to wearable devices.

PubMed

Di Sieno, Laura; Nissinen, Jan; Hallman, Lauri; Martinenghi, Edoardo; Contini, Davide; Pifferi, Antonio; Kostamovaara, Juha; Mora, Alberto Dalla

2017-08-01

We validate a miniaturized pulsed laser source for use in time-domain (TD) diffuse optics, following rigorous and shared protocols for performance assessment of this class of devices. This compact source (12×6  mm2) has been previously developed for range finding applications and is able to provide short, high energy (∼100  ps, ∼0.5  nJ) optical pulses at up to 1 MHz repetition rate. Here, we start with a basic level laser characterization with an analysis of suitability of this laser for the diffuse optics application. Then, we present a TD optical system using this source and its performances in both recovering optical properties of tissue-mimicking homogeneous phantoms and in detecting localized absorption perturbations. Finally, as a proof of concept of in vivo application, we demonstrate that the system is able to detect hemodynamic changes occurring in the arm of healthy volunteers during a venous occlusion. Squeezing the laser source in a small footprint removes a key technological bottleneck that has hampered so far the realization of a miniaturized TD diffuse optics system, able to compete with already assessed continuous-wave devices in terms of size and cost, but with wider performance potentialities, as demonstrated by research over the last two decades. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Compact GaSb/silicon-on-insulator 2.0x μm widely tunable external cavity lasers.

PubMed

Wang, Ruijun; Malik, Aditya; Šimonytė, Ieva; Vizbaras, Augustinas; Vizbaras, Kristijonas; Roelkens, Gunther

2016-12-12

2.0x µm widely tunable external cavity lasers realized by combining a GaSb gain chip with a silicon photonics waveguide circuit for wavelength selection are demonstrated. Wavelength tuning over 58 nm from 2.01 to 2.07 µm is demonstrated. In the silicon photonic integrated circuit, laser feedback is realized by using a silicon Bragg grating and continuous tuning is realized by using two thermally tuned silicon microring resonators (MRRs) and a phase section. The uncooled laser has maximum output power of 7.5 mW and threshold current density of 0.8 kA/cm². The effect of the coupling gap of the MRRs on tunable laser performance is experimentally assessed. A side mode suppression ratio better than 52 dB over the full tuning range and in the optimum operation point of more than 60 dB is achieved for the laser with weakly coupled MRRs.

Optical resolution photoacoustic microscopy using novel high-repetition-rate passively Q-switched microchip and fiber lasers.

PubMed

Shi, Wei; Kerr, Shaun; Utkin, Ilya; Ranasinghesagara, Janaka; Pan, Lei; Godwal, Yogesh; Zemp, Roger J; Fedosejevs, Robert

2010-01-01

Optical-resolution photoacoustic microscopy (OR-PAM) is a novel imaging technology for visualizing optically absorbing superficial structures in vivo with lateral spatial resolution determined by optical focusing rather than acoustic detection. Since scanning of the illumination spot is required, OR-PAM imaging speed is limited by both scanning speed and laser pulse repetition rate. Unfortunately, lasers with high repetition rates and suitable pulse durations and energies are not widely available and can be cost-prohibitive and bulky. We are developing compact, passively Q-switched fiber and microchip laser sources for this application. The properties of these lasers are discussed, and pulse repetition rates up to 100 kHz are demonstrated. OR-PAM imaging was conducted using a previously developed photoacoustic probe, which enabled flexible scanning of the focused output of the lasers. Phantom studies demonstrate the ability to image with lateral spatial resolution of 7±2 μm with the microchip laser system and 15±5 μm with the fiber laser system. We believe that the high pulse repetition rates and the potentially compact and fiber-coupled nature of these lasers will prove important for clinical imaging applications where real-time imaging performance is essential.

Laser Sources for Generation of Ultrasound

NASA Technical Reports Server (NTRS)

Wagner, James W.

1996-01-01

Two laser systems have been built and used to demonstrate enhancements beyond current technology used for laser-based generation and detection of ultrasound. The first system consisted of ten Nd:YAG laser cavities coupled electronically and optically to permit sequential bursts of up to ten laser pulses directed either at a single point or configured into a phased array of sources. Significant enhancements in overall signal-to-noise ratio for laser ultrasound incorporating this new source system was demonstrated, using it first as a source of narrowband ultrasound and secondly as a phased array source producing large enhanced signal displacements. A second laser system was implemented using ultra fast optical pulses from a Ti:Sapphire laser to study a new method for making laser generated ultrasonic measurements of thin films with thicknesses on the order of hundreds of angstroms. Work by prior investigators showed that such measurements could be made based upon fluctuations in the reflectivity of thin films when they are stressed by an arriving elastic pulse. Research performed using equipment purchased under this program showed that a pulsed interferometric system could be used as well as a piezoreflective detection system to measure pulse arrivals even in thin films with very low piezoreflective coefficients.

Fast, precise, and widely tunable frequency control of an optical parametric oscillator referenced to a frequency comb.

PubMed

Prehn, Alexander; Glöckner, Rosa; Rempe, Gerhard; Zeppenfeld, Martin

2017-03-01

Optical frequency combs (OFCs) provide a convenient reference for the frequency stabilization of continuous-wave lasers. We demonstrate a frequency control method relying on tracking over a wide range and stabilizing the beat note between the laser and the OFC. The approach combines fast frequency ramps on a millisecond timescale in the entire mode-hop free tuning range of the laser and precise stabilization to single frequencies. We apply it to a commercially available optical parametric oscillator (OPO) and demonstrate tuning over more than 60 GHz with a ramping speed up to 3 GHz/ms. Frequency ramps spanning 15 GHz are performed in less than 10 ms, with the OPO instantly relocked to the OFC after the ramp at any desired frequency. The developed control hardware and software are able to stabilize the OPO to sub-MHz precision and to perform sequences of fast frequency ramps automatically.

Performance of a Laser Ignited Multicylinder Lean Burn Natural Gas Engine

DOE PAGES

Almansour, Bader; Vasu, Subith; Gupta, Sreenath B.; ...

2017-06-06

Market demands for lower fueling costs and higher specific powers in stationary natural gas engines has engine designs trending towards higher in-cylinder pressures and leaner combustion operation. However, Ignition remains as the main limiting factor in achieving further performance improvements in these engines. Addressing this concern, while incorporating various recent advances in optics and laser technologies, laser igniters were designed and developed through numerous iterations. Final designs incorporated water-cooled, passively Q-switched, Nd:YAG micro-lasers that were optimized for stable operation under harsh engine conditions. Subsequently, the micro-lasers were installed in the individual cylinders of a lean-burn, 350 kW, inline 6-cylinder, open-chamber,more » spark ignited engine and tests were conducted. To the best of our knowledge, this is the world’s first demonstration of a laser ignited multi-cylinder natural gas engine. The engine was operated at high-load (298 kW) and rated speed (1800 rpm) conditions. Ignition timing sweeps and excess-air ratio (λ) sweeps were performed while keeping the NOx emissions below the USEPA regulated value (BSNOx < 1.34 g/kW-hr), and while maintaining ignition stability at industry acceptable values (COV_IMEP <5 %). Through such engine tests, the relative merits of (i) standard electrical ignition system, and (ii) laser ignition system were determined. In conclusion, a rigorous combustion data analysis was performed and the main reasons leading to improved performance in the case of laser ignition were identified.« less

Performance of a Laser Ignited Multicylinder Lean Burn Natural Gas Engine

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

Almansour, Bader; Vasu, Subith; Gupta, Sreenath B.

Market demands for lower fueling costs and higher specific powers in stationary natural gas engines has engine designs trending towards higher in-cylinder pressures and leaner combustion operation. However, Ignition remains as the main limiting factor in achieving further performance improvements in these engines. Addressing this concern, while incorporating various recent advances in optics and laser technologies, laser igniters were designed and developed through numerous iterations. Final designs incorporated water-cooled, passively Q-switched, Nd:YAG micro-lasers that were optimized for stable operation under harsh engine conditions. Subsequently, the micro-lasers were installed in the individual cylinders of a lean-burn, 350 kW, inline 6-cylinder, open-chamber,more » spark ignited engine and tests were conducted. To the best of our knowledge, this is the world’s first demonstration of a laser ignited multi-cylinder natural gas engine. The engine was operated at high-load (298 kW) and rated speed (1800 rpm) conditions. Ignition timing sweeps and excess-air ratio (λ) sweeps were performed while keeping the NOx emissions below the USEPA regulated value (BSNOx < 1.34 g/kW-hr), and while maintaining ignition stability at industry acceptable values (COV_IMEP <5 %). Through such engine tests, the relative merits of (i) standard electrical ignition system, and (ii) laser ignition system were determined. In conclusion, a rigorous combustion data analysis was performed and the main reasons leading to improved performance in the case of laser ignition were identified.« less

The Influence of Geometrical Structure of AlInGaN Double Quantum Well (DQWs) UV Diode Laser on Its Performance and Operating Parameters

NASA Astrophysics Data System (ADS)

Ghazai, A. J.; Thahab, S. M.; Hassan, H. Abu; Hassan, Z.

2010-07-01

The development of efficient MQWs active regions of quaternary InAlGaN in the ultraviolet (UV) region is an engaging challenge by itself. Demonstrating lasers at such low wavelength will require resolving a number of materials, growth and device design issues. However, the quaternary AlInGaN represents a more versatile material since the bandgap and lattice constant can be independently varied. We report a quaternary AlInGaN double-quantum wells (DQWs) UV laser diode (LDs) study by using the simulation program of Integrated System Engineering-Technical Computer Aided Design (ISE TCAD). Advanced physical models of semiconductor properties were used. In this paper, the enhancement in the performance of AlInGaN laser diode can be achieved by optimizing the laser structure geometry design. The AlInGaN laser diodes operating parameters such as internal quantum efficiency ηi, internal loss αi and transparency threshold current density show effective improvements that contribute to a better performance.

A study comparing three different laser-assisted hatching techniques.

PubMed

Ma, B; Wang, Y; Zhang, H; Zhang, X

2014-01-01

Laser-assisted hatching (LAH) is recognized as a useful technology to improve clinical pregnancy rates and implantation rates. This study reports the differences between a new LAH method and two conventional LAH techniques. The authors studied 151 patients with repeated implantation failure, who were divided into three groups. In group 1, the zona pellucida (ZP) was opened using LAH (n = 52). In group 2, laser-assisted thinning was performed to dissolve the outer layer of the ZP (n = 49). In group 3, laser-assisted thinning was performed to dissolve the inner layer of the ZP (n = 50). The clinical pregnancy rates and implantation rates among the groups were compared. The results demonstrate that there are significant differences in the clinical pregnancy rates and implantation rates between group 3 and the other two groups. Performing laser-assisted thinning to dissolve the inner layer of the ZP markedly increases the pregnancy rates and implantation rates of patients with repeated implantation failure.

Phase seeding of a terahertz quantum cascade laser

PubMed Central

Oustinov, Dimitri; Jukam, Nathan; Rungsawang, Rakchanok; Madéo, Julien; Barbieri, Stefano; Filloux, Pascal; Sirtori, Carlo; Marcadet, Xavier; Tignon, Jérôme; Dhillon, Sukhdeep

2010-01-01

The amplification of spontaneous emission is used to initiate laser action. As the phase of spontaneous emission is random, the phase of the coherent laser emission (the carrier phase) will also be random each time laser action begins. This prevents phase-resolved detection of the laser field. Here, we demonstrate how the carrier phase can be fixed in a semiconductor laser: a quantum cascade laser (QCL). This is performed by injection seeding a QCL with coherent terahertz pulses, which forces laser action to start on a fixed phase. This permits the emitted laser field to be synchronously sampled with a femtosecond laser beam, and measured in the time domain. We observe the phase-resolved buildup of the laser field, which can give insights into the laser dynamics. In addition, as the electric field oscillations are directly measured in the time domain, QCLs can now be used as sources for time-domain spectroscopy. PMID:20842195

Low noise erbium fiber fs frequency comb based on a tapered-fiber carbon nanotube design.

PubMed

Wu, Tsung-Han; Kieu, K; Peyghambarian, N; Jones, R J

2011-03-14

We report on a low noise all-fiber erbium fs frequency comb based on a simple and robust tapered-fiber carbon nanotube (tf-CNT) design. We mitigate dominant noise sources to show that the free-running linewidth of the carrier-envelope offset frequency (fceo) can be comparable to the best reported performance to date for fiber-based frequency combs. A free-running fceo linewidth of ~20 kHz is demonstrated, corresponding to an improvement of ~30 times over previous work based on a CNT mode-locked fiber laser [Opt. Express 18, 1667 (2010)]. We also demonstrate the use of an acousto-optic modulator external to the laser cavity to stabilize fceo, enabling a 300 kHz feedback control bandwidth. The offset frequency is phase-locked with an in-loop integrated phase noise of ~0.8 rad from 10Hz to 400kHz. We show a resolution-limited linewidth of ~1 Hz, demonstrating over 90% of the carrier power within the coherent fceo signal. The results demonstrate that the relatively simple tf-CNT fiber laser design can provide a compact, robust and high-performance fs frequency comb.

Diatomic gasdynamic lasers.

NASA Technical Reports Server (NTRS)

Mckenzie, R. L.

1972-01-01

Predictions from a numerical model of the vibrational relaxation of anharmonic diatomic oscillators in supersonic expansions are used to show the extent to which the small anharmonicity of gases like CO can cause significant overpopulations of upper vibrational states. When mixtures of CO and N2 are considered, radiative gain on many of the vibration-rotation transitions of CO is predicted. Experiments are described that qualitatively verify the predictions by demonstrating laser oscillation in CO-N2 expansions. The resulting CO-N2 gasdynamic laser displays performance characteristics that equal or exceed those of similar CO2 lasers.

Diatomic gasdynamic lasers

NASA Technical Reports Server (NTRS)

Mckenzie, R. L.

1971-01-01

Predictions from a numerical model of the vibrational relaxation of anharmonic diatomic oscillators in supersonic expansions are used to show the extent to which the small anharmonicity of gases like CO can cause significant overpopulations of upper vibrational states. When mixtures of CO and N2 are considered, radiative gain on many of the vibration-rotation transitions of CO is predicted. Experiments are described that qualitatively verify the predictions by demonstrating laser oscillation in CO-N2 expansions. The resulting CO-N2 gasdynamic laser displays performance characteristics that equal or exceed those of similar CO2 lasers.

Next-generation laser for Inertial Confinement Fusion

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

Marshall, C.D.; Deach, R.J.; Bibeau, C.

1997-09-29

We report on the progress in developing and building the Mercury laser system as the first in a series of a new generation of diode- pumped solid-state Inertial Confinement Fusion (ICF) lasers at Lawrence Livermore National Laboratory (LLNL). Mercury will be the first integrated demonstration of a scalable laser architecture compatible with advanced high energy density (HED) physics applications. Primary performance goals include 10% efficiencies at 10 Hz and a 1-10 ns pulse with 1 omega energies of 100 J and with 2 omega/3 omega frequency conversion.

Effect of Doping on the Properties of Hydrogenated Amorphous Silicon Irradiated with Femtosecond Laser Pulses

NASA Astrophysics Data System (ADS)

Denisova, K. N.; Il'in, A. S.; Martyshov, M. N.; Vorontsov, A. S.

2018-04-01

A comparative analysis of the effect of femtosecond laser irradiation on the structure and conductivity of undoped and boron-doped hydrogenated amorphous silicon ( a-Si: H) is performed. It is demonstrated that the process of nanocrystal formation in the amorphous matrix under femtosecond laser irradiation is initiated at lower laser energy densities in undoped a-Si: H samples. The differences in conductivity between undoped and doped a-Si: H samples vanish almost completely after irradiation with an energy density of 150-160 mJ/cm2.

An Acousto-Optical Sensor with High Angular Resolution

PubMed Central

Kaloshin, Gennady; Lukin, Igor

2012-01-01

The paper introduces a new laser interferometry-based sensor for diagnosis of random media by means of high accuracy angle measurements and describes the results of its development and testing. Theoretical calculations of the dependence of the range of the laser interferometer on laser beam parameters, device geometry, and atmospheric turbulence characteristics are reported. It is demonstrated that at moderate turbulence intensities corresponding to those observed most frequently in turbulent atmosphere at moderate latitudes and with low interference contrast values, the performance range of the laser interferometer-based device exceeds 5 km. PMID:22737034

Demonstration of a widely tunable digital supermode distributed Bragg reflector laser as a versatile source for near-infrared spectroscopy

NASA Astrophysics Data System (ADS)

Ciaffoni, L.; Hancock, G.; Hurst, P. L.; Kingston, M.; Langley, C. E.; Peverall, R.; Ritchie, G. A. D.; Whittaker, K. E.

2013-02-01

In this paper we report the characterization of a novel, widely tunable, diode laser source operating over the full telecom L-band (1563-1613 nm), namely the digital supermode distributed Bragg reflector (DS-DBR) laser, and its application to multi-wavelength gas sensing via absorption strategies. The spectroscopic performance of the laser has been assessed by investigating the ro-vibrational spectrum of CO2, and wavelength modulation spectroscopy was accomplished for proof-of-principle sensitive measurements in discrete spectral regions.

Efficient 2-μm Tm:YAP Q-switched and CW lasers

NASA Astrophysics Data System (ADS)

Hays, A. D.; Cole, Brian; King, Vernon; Goldberg, Lew

2018-02-01

Highly efficient, diode pumped Tm:YAP lasers generating emission in the 1.85-1.94 μm range are demonstrated and characterized. Laser optical efficiencies of 51% and 45%, and electrical efficiencies of 31% and 25% are achieved under CW and Q-switched operation, respectively. Laser performance was characterized for maximum average powers up to 20W with various cavity configurations, all using an intra-cavity lens to compensate for thermal lensing in the Tm:YAP crystal. Q-switched lasers incorportating a Cr:ZnS saturable absorber (SA), resonant mechanical mirror scanner, or acousto-optic modulator were characterized. To enable higher average output powers, measurements of the thermal lens were conducted for the Tm:YAP crystal as a function of pump power and were compared to values predicted by a finiteelement- analysis (FEA) thermal-optical model of the Tm:YAP crystal. A resonator model is developed to incorporate this calculated thermal lens and its effect on laser performance. This paper will address approaches for improving the performance of Tm:YAP lasers, and means for achieving increased average output powers while maintaining high optical efficiency for both SA and mechanical Q-switching.

Continuous-scanning laser Doppler vibrometry: Extensions to arbitrary areas, multi-frequency and 3D capture

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

Weekes, B.; Ewins, D.; Acciavatti, F.

2014-05-27

To date, differing implementations of continuous scan laser Doppler vibrometry have been demonstrated by various academic institutions, but since the scan paths were defined using step or sine functions from function generators, the paths were typically limited to 1D line scans or 2D areas such as raster paths or Lissajous trajectories. The excitation was previously often limited to a single frequency due to the specific signal processing performed to convert the scan data into an ODS. In this paper, a configuration of continuous-scan laser Doppler vibrometry is demonstrated which permits scanning of arbitrary areas, with the benefit of allowing multi-frequency/broadbandmore » excitation. Various means of generating scan paths to inspect arbitrary areas are discussed and demonstrated. Further, full 3D vibration capture is demonstrated by the addition of a range-finding facility to the described configuration, and iteratively relocating a single scanning laser head. Here, the range-finding facility was provided by a Microsoft Kinect, an inexpensive piece of consumer electronics.« less

Passivation of black phosphorus saturable absorbers for reliable pulse formation of fiber lasers

NASA Astrophysics Data System (ADS)

Na, Dongsoo; Park, Kichul; Park, Ki-Hwan; Song, Yong-Won

2017-11-01

Black phosphorus (BP) has attracted increasing attention due to its unique electrical properties. In addition, the outstanding optical nonlinearity of BP has been demonstrated in various ways. Its functionality as a saturable absorber, in particular, has been validated in demonstrations of passive mode-locked lasers. However, normally, the performance of BP is degraded eventually by both thermal and chemical damage in ambient conditions. The passivation of BP is the critical issue to guarantee a stable performance of the optical devices. We quantitatively characterized the mode-locked lasers operated by BP saturable absorbers with diversified passivation materials such as polydimethylsiloxane (PDMS) or Al2O3, considering the atomic structure of the materials, and therefore the hydro-permeability of the passivation layers. Unlike the BP layers without passivation, we demonstrated that the Al2O3-passivated BP layer was protected from the surface oxidation reaction in the long-term, and the PDMS-passivated one had a short-term blocking effect. The quantitative analysis showed that the time-dependent characteristics of the pulsed laser without passivation were changed with respect to the pulse duration, spectral width, and time-bandwidth product displaying 550 fs, 2.8 nm, and 0.406, respectively. With passivation, the changes were limited to <43 fs, <0.3 nm, and <0.012, respectively.

Passivation of black phosphorus saturable absorbers for reliable pulse formation of fiber lasers.

PubMed

Na, Dongsoo; Park, Kichul; Park, Ki-Hwan; Song, Yong-Won

2017-11-24

Black phosphorus (BP) has attracted increasing attention due to its unique electrical properties. In addition, the outstanding optical nonlinearity of BP has been demonstrated in various ways. Its functionality as a saturable absorber, in particular, has been validated in demonstrations of passive mode-locked lasers. However, normally, the performance of BP is degraded eventually by both thermal and chemical damage in ambient conditions. The passivation of BP is the critical issue to guarantee a stable performance of the optical devices. We quantitatively characterized the mode-locked lasers operated by BP saturable absorbers with diversified passivation materials such as polydimethylsiloxane (PDMS) or Al 2 O 3 , considering the atomic structure of the materials, and therefore the hydro-permeability of the passivation layers. Unlike the BP layers without passivation, we demonstrated that the Al 2 O 3 -passivated BP layer was protected from the surface oxidation reaction in the long-term, and the PDMS-passivated one had a short-term blocking effect. The quantitative analysis showed that the time-dependent characteristics of the pulsed laser without passivation were changed with respect to the pulse duration, spectral width, and time-bandwidth product displaying 550 fs, 2.8 nm, and 0.406, respectively. With passivation, the changes were limited to <43 fs, <0.3 nm, and <0.012, respectively.

Advanced Receiver/Converter Experiments for Laser Wireless Power Transmission

NASA Technical Reports Server (NTRS)

Howell, Joe T.; ONeill, Mark; Fork, Richard

2004-01-01

For several years NASA Marshall Space Flight Center, UAH and ENTECH have been working on various aspects of space solar power systems. The current activity was just begun in January 2004 to further develop this new photovoltaic concentrator laser receiver/converter technology. During the next few months, an improved prototype will be designed, fabricated, and thoroughly tested under laser illumination. The final paper will describe the new concept, present its advantages over other laser receiver/converter approaches (including planar photovoltaic arrays), and provide the latest experiment results on prototype hardware (including the effects of laser irradiance level and cell temperature). With NASA's new human exploration plans to first return to the Moon, and then to proceed to Mars, the new photovoltaic concentrator laser receiver/converter technology could prove to be extremely useful in providing power to the landing sites and other phases of the missions. For example, to explore the scientifically interesting and likely resource-rich poles of the Moon (which may contain water) or the poles of Mars (which definitely contain water and carbon dioxide), laser power beaming could represent the simplest means of providing power to these regions, which receive little or no sunlight, making solar arrays useless there. In summary, the authors propose a paper on definition and experimental results of a novel photovoltaic concentrator approach for collecting and converting laser radiation to electrical power. The new advanced photovoltaic concentrator laser receiver/converter offers higher performance, lighter weight, and lower cost than competing concepts, and early experimental results are confirming the expected excellent Performance levels. After the small prototypes are successfully demonstrated, a larger array with even better performance is planned for the next phase experiments and demonstrations. Thereafter, a near-term flight experiment of the new technology should be developed and flown, to lay the groundwork for future space power applications in the Earth-Moon neighborhood, and ultimately encompassing Mars and its environs.

High-energy mode-locked fiber lasers using multiple transmission filters and a genetic algorithm.

PubMed

Fu, Xing; Kutz, J Nathan

2013-03-11

We theoretically demonstrate that in a laser cavity mode-locked by nonlinear polarization rotation (NPR) using sets of waveplates and passive polarizer, the energy performance can be significantly increased by incorporating multiple NPR filters. The NPR filters are engineered so as to mitigate the multi-pulsing instability in the laser cavity which is responsible for limiting the single pulse per round trip energy in a myriad of mode-locked cavities. Engineering of the NPR filters for performance is accomplished by implementing a genetic algorithm that is capable of systematically identifying viable and optimal NPR settings in a vast parameter space. Our study shows that five NPR filters can increase the cavity energy by approximately a factor of five, with additional NPRs contributing little or no enhancements beyond this. With the advent and demonstration of electronic controls for waveplates and polarizers, the analysis suggests a general design and engineering principle that can potentially close the order of magnitude energy gap between fiber based mode-locked lasers and their solid state counterparts.

Renal denervation using focused infrared fiber lasers: a potential treatment for hypertension.

PubMed

Alexander, Vinay V; Shi, Zhennan; Iftekher, Fariha; Welsh, Michael J; Gurm, Hitinder S; Rising, Gail; Yanovich, Amber; Walacavage, Kim; Islam, Mohammed N

2014-11-01

Renal denervation has recently become of great interest as a potential treatment for resistant hypertension. Denervation techniques using radio frequency (RF) or ultrasound energy sources have already been explored in literature. In this study, we investigate the use of lasers as a potential energy source for renal denervation. In vitro studies are performed in porcine/ovine renal arteries with focused laser beams at 980 nm, 1210 nm, and 1700 nm to study the ability to damage renal nerves without causing injury to non-target tissue structures like the endothelium. Then, a 980 nm laser catheter prototype is built and used to demonstrate in vivo renal denervation in ovine renal arteries. This study utilizes fiber coupled infrared lasers at 980 nm, 1210 nm, and 1700 nm. In vitro laser denervation studies at 980 nm are performed in both porcine and ovine renal arteries to study the ability of focused laser beams to damage renal nerves without injuring the endothelium. In vitro studies using lasers close to the lipid absorption lines at 1210 nm and 1700 nm are also performed in porcine renal arteries to study the possibility of selectively damaging the renal nerves by targeting the lipid myelin sheaths surrounding the nerves. Then, a laser catheter prototype is designed and built for in vivo renal denervation in ovine renal arteries using the 980 nm laser (powers ranging from 2 to 4 W, 5 seconds per exposure). Histochemical evaluations of the frozen sections are performed using methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay. Histochemical analysis of in vitro laser treatments at 980 nm in porcine and ovine renal arteries show clear evidence of laser-induced renal nerve damage without injury to the endothelium and part of the media. No evidence of selective nerve damage is observed using the 1210 nm and 1700 nm lasers with the current treatment parameters. Histochemical analysis of in vivo laser treatments in ovine renal arteries using a focused 980 nm laser show clear evidence of renal nerve damage with depths of damage extending > 1.5 mm from the artery wall. Sections with laser-induced damage to the media/adventitia at depths of > 1 mm without injury to the endothelium are also observed. We demonstrate the use of focused lasers as an attractive energy source for causing renal nerve damage without injury to the artery wall and thus, may have potential therapeutic applications for conditions such as resistant hypertension, where renal denervation has been shown to be a promising form of treatment. © 2014 Wiley Periodicals, Inc.

Semiconductor optoelectronic devices for free-space optical communications

NASA Technical Reports Server (NTRS)

Katz, J.

1983-01-01

The properties of individual injection lasers are reviewed, and devices of greater complexity are described. These either include or are relevant to monolithic integration configurations of the lasers with their electronic driving circuitry, power combining methods of semiconductor lasers, and electronic methods of steering the radiation patterns of semiconductor lasers and laser arrays. The potential of AlGaAs laser technology for free-space optical communications systems is demonstrated. These solid-state components, which can generate and modulate light, combine the power of a number of sources and perform at least part of the beam pointing functions. Methods are proposed for overcoming the main drawback of semiconductor lasers, that is, their inability to emit the needed amount of optical power in a single-mode operation.

Two-well terahertz quantum cascade lasers with suppressed carrier leakage

DOE PAGES

Albo, Asaf; Flores, Yuri V.; Hu, Qing; ...

2017-09-11

The mechanisms that limit the temperature performance of diagonal GaAs/Al 0.15GaAs 0.85-based terahertz quantum cascade lasers (THz-QCLs) have been identified as thermally activated leakage of charge carriers through excited states into the continuum. THz-QCLs with energetically higher-laying excited states supported by sufficiently high barriers aim to eliminate these leakage mechanisms and lead to improved temperature performance. Although suppression of thermally activated carrier leakage was realized in a three-well THz-QCL based on a resonant-phonon scheme, no improvement in the temperature performance was reported thus far. Here, we report a major improvement in the temperature performance of a two-quantum-well direct-phonon THz-QCL structure.more » We show that the improved laser performance is due to the suppression of the thermally activated carrier leakage into the continuum with the increase in the injection barrier height. Furthermore, we demonstrate that high-barrier two-well structures can support a clean three-level laser system at elevated temperatures, which opens the opportunity to achieve temperature performance beyond the state-of-the-art.« less

Two-well terahertz quantum cascade lasers with suppressed carrier leakage

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

Albo, Asaf; Flores, Yuri V.; Hu, Qing

The mechanisms that limit the temperature performance of diagonal GaAs/Al 0.15GaAs 0.85-based terahertz quantum cascade lasers (THz-QCLs) have been identified as thermally activated leakage of charge carriers through excited states into the continuum. THz-QCLs with energetically higher-laying excited states supported by sufficiently high barriers aim to eliminate these leakage mechanisms and lead to improved temperature performance. Although suppression of thermally activated carrier leakage was realized in a three-well THz-QCL based on a resonant-phonon scheme, no improvement in the temperature performance was reported thus far. Here, we report a major improvement in the temperature performance of a two-quantum-well direct-phonon THz-QCL structure.more » We show that the improved laser performance is due to the suppression of the thermally activated carrier leakage into the continuum with the increase in the injection barrier height. Furthermore, we demonstrate that high-barrier two-well structures can support a clean three-level laser system at elevated temperatures, which opens the opportunity to achieve temperature performance beyond the state-of-the-art.« less

Two-well terahertz quantum cascade lasers with suppressed carrier leakage

NASA Astrophysics Data System (ADS)

Albo, Asaf; Flores, Yuri V.; Hu, Qing; Reno, John L.

2017-09-01

The mechanisms that limit the temperature performance of diagonal GaAs/Al0.15GaAs0.85-based terahertz quantum cascade lasers (THz-QCLs) have been identified as thermally activated leakage of charge carriers through excited states into the continuum. THz-QCLs with energetically higher-laying excited states supported by sufficiently high barriers aim to eliminate these leakage mechanisms and lead to improved temperature performance. Although suppression of thermally activated carrier leakage was realized in a three-well THz-QCL based on a resonant-phonon scheme, no improvement in the temperature performance was reported thus far. Here, we report a major improvement in the temperature performance of a two-quantum-well direct-phonon THz-QCL structure. We show that the improved laser performance is due to the suppression of the thermally activated carrier leakage into the continuum with the increase in the injection barrier height. Moreover, we demonstrate that high-barrier two-well structures can support a clean three-level laser system at elevated temperatures, which opens the opportunity to achieve temperature performance beyond the state-of-the-art.

Crystallization to polycrystalline silicon thin film and simultaneous inactivation of electrical defects by underwater laser annealing

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

Machida, Emi; Research Fellowships of the Japan Society for the Promotion of Science, Japan Society for the Promotion of Science, 1-8 Chiyoda, Tokyo 102-8472; Horita, Masahiro

2012-12-17

We propose a low-temperature laser annealing method of a underwater laser annealing (WLA) for polycrystalline silicon (poly-Si) films. We performed crystallization to poly-Si films by laser irradiation in flowing deionized-water where KrF excimer laser was used for annealing. We demonstrated that the maximum value of maximum grain size of WLA samples was 1.5 {mu}m, and that of the average grain size was 2.8 times larger than that of conventional laser annealing in air (LA) samples. Moreover, WLA forms poly-Si films which show lower conductivity and larger carrier life time attributed to fewer electrical defects as compared to LA poly-Si films.

Optical communication for space missions

NASA Technical Reports Server (NTRS)

Firtmaurice, M.

1991-01-01

Activities performed at NASA/GSFC (Goddard Space Flight Center) related to direct detection optical communications for space applications are discussed. The following subject areas are covered: (1) requirements for optical communication systems (data rates and channel quality; spatial acquisition; fine tracking and pointing; and transmit point-ahead correction); (2) component testing and development (laser diodes performance characterization and life testing; and laser diode power combining); (3) system development and simulations (The GSFC pointing, acquisition and tracking system; hardware description; preliminary performance analysis; and high data rate transmitter/receiver systems); and (4) proposed flight demonstration of optical communications.

A novel computerized surgeon-machine interface for robot-assisted laser phonomicrosurgery.

PubMed

Mattos, Leonardo S; Deshpande, Nikhil; Barresi, Giacinto; Guastini, Luca; Peretti, Giorgio

2014-08-01

To introduce a novel computerized surgical system for improved usability, intuitiveness, accuracy, and controllability in robot-assisted laser phonomicrosurgery. Pilot technology assessment. The novel system was developed involving a newly designed motorized laser micromanipulator, a touch-screen display, and a graphics stylus. The system allows the control of a CO2 laser through interaction between the stylus and the live video of the surgical area. This empowers the stylus with the ability to have actual effect on the surgical site. Surgical enhancements afforded by this system were established through a pilot technology assessment using randomized trials comparing its performance with a state-of-the-art laser microsurgery system. Resident surgeons and medical students were chosen as subjects in performing sets of trajectory-following exercises. Image processing-based techniques were used for an objective performance assessment. A System Usability Scale-based questionnaire was used for the qualitative assessment. The computerized interface demonstrated superiority in usability, accuracy, and controllability over the state-of-the-art system. Significant ease of use and learning experienced by the subjects were demonstrated by the usability score assigned to the two compared interfaces: computerized interface = 83.96% versus state-of-the-art = 68.02%. The objective analysis showed a significant enhancement in accuracy and controllability: computerized interface = 90.02% versus state-of-the-art = 75.59%. The novel system significantly enhances the accuracy, usability, and controllability in laser phonomicrosurgery. The design provides an opportunity to improve the ergonomics and safety of current surgical setups. © 2014 The American Laryngological, Rhinological and Otological Society, Inc.

Development of optical systems. [holographic technique for monitoring crystal growth

NASA Technical Reports Server (NTRS)

Vikram, Chandra S.

1995-01-01

Several key aspects of multi-color holography and laser speckle technique to study holographic reconstructions are considered in the report. Holographic fringe contrast in two-color holography in the presence of a fluid cell in the object beam is discussed in detail. A specific example of triglycine sulfate crystal growth is also considered. A breadboard design using fiber optics and diode lasers for three-color holography for fluid experiments is presented. A possible role of multi-color holography in various new applications is summarized. Finally, the use of a a laser speckle technique is demonstrated for the study of holographic reconstructions. The demonstration is performed using a Spacelab 3 hologram.

3D hybrid integrated lasers for silicon photonics

NASA Astrophysics Data System (ADS)

Song, B.; Pinna, S.; Liu, Y.; Megalini, L.; Klamkin, J.

2018-02-01

A novel 3D hybrid integration platform combines group III-V materials and silicon photonics to yield high-performance lasers is presented. This platform is based on flip-chip bonding and vertical optical coupling integration. In this work, indium phosphide (InP) devices with monolithic vertical total internal reflection turning mirrors were bonded to active silicon photonic circuits containing vertical grating couplers. Greater than 2 mW of optical power was coupled into a silicon waveguide from an InP laser. The InP devices can also be bonded directly to the silicon substrate, providing an efficient path for heat dissipation owing to the higher thermal conductance of silicon compared to InP. Lasers realized with this technique demonstrated a thermal impedance as low as 6.2°C/W, allowing for high efficiency and operation at high temperature. InP reflective semiconductor optical amplifiers were also integrated with 3D hybrid integration to form integrated external cavity lasers. These lasers demonstrated a wavelength tuning range of 30 nm, relative intensity noise lower than -135 dB/Hz and laser linewidth of 1.5 MHz. This platform is promising for integration of InP lasers and photonic integrated circuits on silicon photonics.

High Performance Capsule Implosions on the Omega Laser Facility with Rugby Hohlraums

NASA Astrophysics Data System (ADS)

Robey, Harry F.

2009-11-01

Rugby-shaped hohlraums have been proposed as a method for x-ray drive enhancement for indirectly-driven capsule implosions [1]. This concept has recently been tested in a series of shots on the OMEGA laser facility at the Laboratory for Laser Energetics at the University of Rochester. In this talk, experimental results are presented comparing the performance of D2-filled capsules between standard cylindrical Au hohlraums and rugby-shaped hohlraums. Not only did the rugby hohlraums demonstrate 18% more x-ray drive energy as compared with the cylinders, but the high-performance design of these implosions (both cylinder and rugby) also provided 20X more DD neutrons than any previous indirectly-driven campaign on Omega (and 3X more than ever achieved on Nova implosions driven with nearly twice the laser energy). This increase in performance enables, for the first time, a measurement of the neutron burn history of an indirectly-driven implosion. Previous DD neutron yields had been too low to register this key measurement of capsule performance and the effects of dynamic mix. A wealth of additional data on the fuel areal density from the suite of charged particle diagnostics was obtained on a subset of the shots that used D^3He rather than D2 fuel. Comparisons of the experimental results with numerical simulations are shown to be in excellent agreement. The design techniques employed in this campaign, e.g., smaller NIF-like laser entrance holes and hohlraum case-to-capsule ratios, provide added confidence in the pursuit of ignition on the National Ignition Facility. [4pt] [1] P. Amendt, C. Cerjan, D. E. Hinkel, J. L. Milovich, H.-S. Park, and H. F. Robey, ``Rugby-like hohlraum experimental designs for demonstrating x-ray drive enhancement'', Phys. Plasmas 15, 012702 (2008).

Arbitrary temporal shape pulsed fiber laser based on SPGD algorithm

NASA Astrophysics Data System (ADS)

Jiang, Min; Su, Rongtao; Zhang, Pengfei; Zhou, Pu

2018-06-01

A novel adaptive pulse shaping method for a pulsed master oscillator power amplifier fiber laser to deliver an arbitrary pulse shape is demonstrated. Numerical simulation has been performed to validate the feasibility of the scheme and provide meaningful guidance for the design of the algorithm control parameters. In the proof-of-concept experiment, information on the temporal property of the laser is exchanged and evaluated through a local area network, and the laser adjusted the parameters of the seed laser according to the monitored output of the system automatically. Various pulse shapes, including a rectangular shape, ‘M’ shape, and elliptical shape are achieved through experimental iterations.

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.

High-power AlGaAs channeled substrate planar diode lasers for spaceborne communications

NASA Technical Reports Server (NTRS)

Connolly, J. C.; Goldstein, B.; Pultz, G. N.; Slavin, S. E.; Carlin, D. B.; Ettenberg, M.

1988-01-01

A high power channeled substrate planar AlGaAs diode laser with an emission wavelength of 8600 to 8800 A was developed. The optoelectronic behavior (power current, single spatial and spectral behavior, far field characteristics, modulation, and astigmatism properties) and results of computer modeling studies on the performance of the laser are discussed. Lifetest data on these devices at high output power levels is also included. In addition, a new type of channeled substrate planar laser utilizing a Bragg grating to stabilize the longitudinal mode was demonstrated. The fabrication procedures and optoelectronic properties of this new diode laser are described.

Comparison Between NIST and AF Laser Energy Standards Using High Power Lasers

PubMed Central

Li, Xiaoyu; Scott (Retired), Thomas; Cromer, Chris; Cooper, David; Comisford, Steven

2007-01-01

We report the results of a high-energy laser calorimeter comparison conducted by the National Institute of Standards and Technology (NIST), Boulder, Colorado and the U.S. Air Force Primary Standards laboratory (AFPSL), Heath, Ohio. A laser power meter, used as a transfer standard, was calibrated at each laboratory, sequentially, and the measurement results were compared. These measurements were performed at a nominal power of 800 W and a wavelength of 10.6 μm using CO2 lasers. Excellent measurement agreement (1.02 %) was demonstrated, which was well within each of the expanded uncertainties from the two laboratories involved in this comparison. PMID:27110471

Industrial laser welding evaluation study

NASA Technical Reports Server (NTRS)

Hella, R.; Locke, E.; Ream, S.

1974-01-01

High power laser welding was evaluated for fabricating space vehicle boosters. This evaluation was made for 1/4 in. and 1/2 in. aluminum (2219) and 1/4 in. and 1/2 in. D6AC steel. The Avco HPL 10 kW industrial laser was used to perform the evaluation. The objective has been achieved through the completion of the following technical tasks: (1) parameter study to optimize welding and material parameters; (2) preparation of welded panels for MSFC evaluation; and (3) demonstration of the repeatability of laser welding equipment. In addition, the design concept for a laser welding system capable of welding large space vehicle boosters has been developed.

Photonic crystal fibre enables short-wavelength two-photon laser scanning fluorescence microscopy with fura-2

NASA Astrophysics Data System (ADS)

McConnell, Gail; Riis, Erling

2004-10-01

We report on a novel and compact reliable laser source capable of short-wavelength two-photon laser scanning fluorescence microscopy based on soliton self-frequency shift effects in photonic crystal fibre. We demonstrate the function of the system by performing two-photon microscopy of smooth muscle cells and cardiac myocytes from the rat pulmonary vein and Chinese hamster ovary cells loaded with the fluorescent calcium indicator fura-2/AM.

Laser toning for melasma: A single-centre experience with 38 970 cases.

PubMed

Tian, Brian

2017-06-01

Melasma is a common pigmentation in Asian women. Lasers have been used to lighten melasma, although with variable outcomes and complications. In Asia, laser toning is a common technique used to safely lighten melasma. However, no large studies have been performed to validate efficacy. In our study, we demonstrate that in 38 970 Asian women, at least 35 890 patients (92.1%) had noticeable to excellent improvement in their melasma.

Laser damage tests on InSb photodiodes at 1.064 micron and 0.532 micron

NASA Technical Reports Server (NTRS)

Bearman, G. H.; Staller, C.; Mahoney, C.

1992-01-01

InSb photodiodes were examined for performance degradation after pulsed laser illumination at 0.532 micron and 1.064 micron. Incident laser powers ranged from 6 x 10 exp-18 micron-watts to 16 micron-watts in a 50 pm diameter spot. Dark current and spectral response were both measured before and after illumination. Dark current measurements were taken with the diode blanked off and viewing only 77 K surfaces. Long term stability tests demonstrated that the blackbody did not exhibit long term drifts. Other tests showed that room temperature variations did not affect the diode signal chain or the digitization electronics used in data acquisition. Results of the experiment show that the diodes did not exhibit changes in dark current or spectral response performance as a result of the laser illumination. A typical change in diode spectral response (before/after laser exposure) was about 0.2 percent +/- 0.2 percent.

Recent developments and near term directions for Navy laser weapons system (LaWS) testbed

NASA Astrophysics Data System (ADS)

Pawlak, Robert J.

2012-11-01

The Laser Weapons System (LaWS) testbed has been a demonstrator of many High Energy Laser (HEL)-related technologies for the Navy. LaWS employs a sharedaperture design with incoherent beam combining, and makes extensive use of Commercial Off-The-Shelf (COTS) technologies in the areas of inertial sensing, fiber lasers, sensors, and video trackers. Since the system has demonstrated the art of the possible with COTS elements, it is useful to examine where performance can be increased with the greatest possible effect, as well as which modifications are necessary to support better integration with ships' systems. A review of past test events, architectures, and further plans will be provided, while emphasizing the past and future evolution of the LaWS system. These evolutions will relate within the context of technical drivers that most affected system development.

Fabrication of three-dimensional crystalline silicon-on-carbon nanotube nanocomposite anode by sputtering and laser annealing for high-performance lithium-ion battery

NASA Astrophysics Data System (ADS)

Kim, Ilwhan; Hyun, Seungmin; Nam, Seunghoon; Lee, Hoo-Jeong; Kang, Chiwon

2018-05-01

In this study, we fabricate a three-dimensional (3D) crystalline Si (c-Si)/carbon nanotube (CNT) nanocomposite anode by sputtering Si on 3D CNTs followed by laser annealing for Si crystallization — a simple, cost-effective route — for advanced Li-ion battery (LIB) applications. We use scanning electron microscopy, X-ray diffraction spectroscopy, and Raman spectroscopy to analyze the samples annealed at different laser energy densities. As a result, we confirm that laser annealing enables Si crystallization without damaging the CNTs. We assemble half-type coin cells for the battery performance test: the 3D c-Si/CNT anode sample demonstrates a specific capacity superior to that of its control counterpart; the cyclic stability is also enhanced significantly.

Frequency stabilization of a 1083 nm fiber laser to {sup 4}He transition lines with optical heterodyne saturation spectroscopies

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

Gong, W.; Peng, X., E-mail: xiangpeng@pku.edu.cn; Li, W.

2014-07-15

Two kinds of optical heterodyne saturation spectroscopies, namely, frequency modulation spectroscopy (FMS) and modulation transfer spectroscopy (MTS), are demonstrated for locking a fiber laser to the transition lines of metastable {sup 4}He atoms around 1083 nm. The servo-loop error signals of FMS and MTS for stabilizing laser frequency are optimized by studying the dependence of the peak-to-peak amplitude and slope on the optical power of pump and probe beams. A comparison of the stabilization performances of FMS/MTS and polarization spectroscopy (PS) is presented, which shows that MTS exhibits relatively superior performance with the least laser frequency fluctuation due to itsmore » flat-background dispersive signal, originated from the four-wave mixing process. The Allan deviation of the stabilized laser frequency is 5.4 × 10{sup −12}@100 s with MTS for data acquired in 1000 s, which is sufficiently applicable for fields like laser cooling, optical pumping, and optical magnetometry.« less

100W high-brightness multi-emitter laser pump

NASA Astrophysics Data System (ADS)

Duesterberg, Richard; Xu, Lei; Skidmore, Jay A.; Guo, James; Cheng, Jane; Du, Jihua; Johnson, Brad; Vecht, David L.; Guerin, Nicolas; Huang, Benlih; Yin, Dongliang; Cheng, Peter; Raju, Reddy; Lee, Kong Weng; Cai, Jason; Rossin, Victor; Zucker, Erik P.

2011-03-01

We report results of a spatially-multiplexed broad area laser diode platform designed for efficient pumping of fiber lasers or direct-diode systems. Optical output power in excess of 100W from a 105μm core, 0.15NA fiber is demonstrated with high coupling efficiency. The compact form factor and low thermal resistance enable tight packing densities needed for kW-class fiber laser systems. Broad area laser diodes have been optimized to reduce near- and far-field performance and prevent blooming without sacrificing other electro-optic parameters. With proper lens optimization this produces ~5% increase in coupling / wall plug efficiency for our design. In addition to performance characteristics, an update on long term reliability testing of 9XX nm broad area laser diode is provided that continues to show no wear out under high acceleration. Under nominal operating conditions of 12W ex-facet power at 25C, the diode mean time to failure (MTTF) is forecast to be ~ 480 kh.

National direct-drive program on OMEGA and the National Ignition Facility

NASA Astrophysics Data System (ADS)

Goncharov, V. N.; Regan, S. P.; Campbell, E. M.; Sangster, T. C.; Radha, P. B.; Myatt, J. F.; Froula, D. H.; Betti, R.; Boehly, T. R.; Delettrez, J. A.; Edgell, D. H.; Epstein, R.; Forrest, C. J.; Glebov, V. Yu; Harding, D. R.; Hu, S. X.; Igumenshchev, I. V.; Marshall, F. J.; McCrory, R. L.; Michel, D. T.; Seka, W.; Shvydky, A.; Stoeckl, C.; Theobald, W.; Gatu-Johnson, M.

2017-01-01

A major advantage of the laser direct-drive (DD) approach to ignition is the increased fraction of laser drive energy coupled to the hot spot and relaxed hot-spot requirements for the peak pressure and convergence ratios relative to the indirect-drive approach at equivalent laser energy. With the goal of a successful ignition demonstration using DD, the recently established national strategy has several elements and involves multiple national and international institutions. These elements include the experimental demonstration on OMEGA cryogenic implosions of hot-spot conditions relevant for ignition at MJ-scale energies available at the National Ignition Facility (NIF) and developing an understanding of laser-plasma interactions and laser coupling using DD experiments on the NIF. DD designs require reaching central stagnation pressures in excess of 100 Gbar. The current experiments on OMEGA have achieved inferred peak pressures of 56 Gbar (Regan et al 2016 Phys. Rev. Lett. 117 025001). Extensive analysis of the cryogenic target experiments and two- and three-dimensional simulations suggest that power balance, target offset, and target quality are the main limiting factors in target performance. In addition, cross-beam energy transfer (CBET) has been identified as the main mechanism reducing laser coupling. Reaching the goal of demonstrating hydrodynamic equivalence on OMEGA includes improving laser power balance, target position, and target quality at shot time. CBET must also be significantly reduced and several strategies have been identified to address this issue.

Design and Follow-on from 50 kJ Fusion Yield using High-Density Carbon Capsules at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Berzak Hopkins, L.; Lepape, S.; Divol, L.; Pak, A.; Goyon, C.; Dewald, E.; Ho, D. D.; Khan, S. F.; Weber, C.; Meezan, N. B.; Biener, J.; Grim, G.; Ma, T.; Milovich, J. L.; Moore, A. S.; Nikroo, A.; Ross, J. S.; Stadermann, M.; Volegov, P.; Wild, C.; Callahan, D. A.; Hurricane, O. A.; Hsing, W. W.; Town, R. P. J.; Edwards, M. J.

2017-10-01

We have demonstrated nearly 3x alpha-heating at the National Ignition Facility by using tungsten-doped High-Density Carbon (HDC) capsules in low gasfill, unlined, uranium (DU) hohlraums. Shot N170601 achieved a primary neutron yield of 1.5 x 1016 neutrons with a Deuterium-Tritium ion temperature of 4.7 keV. Predecessor experiments demonstrated high-performing, efficient performance, as noted through high neutron yield production per laser energy input. Building on these `subscale' results, follow-on experiments utilize an 8% larger target than the predecessor campaign, to increase the capsule surface area and absorbed energy. The capsule fill tube has been reduced in size from 10 to 5 micron diameter, and the laser design implements a new, ``drooping'' technique for the end of the pulse, to reduce the time between laser shut-off and capsule peak emission while still maintaining capsule mass remaining. Design of the current platform as well as avenues to potentially improve performance based on these experiments will be discussed. Work performed under the auspices of the U.S. D.O.E. by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

Design of refractive laser beam shapers to generate complex irradiance profiles

NASA Astrophysics Data System (ADS)

Li, Meijie; Meuret, Youri; Duerr, Fabian; Vervaeke, Michael; Thienpont, Hugo

2014-05-01

A Gaussian laser beam is reshaped to have specific irradiance distributions in many applications in order to ensure optimal system performance. Refractive optics are commonly used for laser beam shaping. A refractive laser beam shaper is typically formed by either two plano-aspheric lenses or by one thick lens with two aspherical surfaces. Ray mapping is a general optical design technique to design refractive beam shapers based on geometric optics. This design technique in principle allows to generate any rotational-symmetric irradiance profile, yet in literature ray mapping is mainly developed to transform a Gaussian irradiance profile to a uniform profile. For more complex profiles especially with low intensity in the inner region, like a Dark Hollow Gaussian (DHG) irradiance profile, ray mapping technique is not directly applicable in practice. In order to these complex profiles, the numerical effort of calculating the aspherical surface points and fitting a surface with sufficient accuracy increases considerably. In this work we evaluate different sampling approaches and surface fitting methods. This allows us to propose and demonstrate a comprehensive numerical approach to efficiently design refractive laser beam shapers to generate rotational-symmetric collimated beams with a complex irradiance profile. Ray tracing analysis for several complex irradiance profiles demonstrates excellent performance of the designed lenses and the versatility of our design procedure.

Tesla coil discharges guided by femtosecond laser filaments in air

NASA Astrophysics Data System (ADS)

Brelet, Yohann; Houard, Aurélien; Arantchouk, Leonid; Forestier, Benjamin; Liu, Yi; Prade, Bernard; Carbonnel, Jérôme; André, Yves-Bernard; Mysyrowicz, André

2012-04-01

A Tesla coil generator was designed to produce high voltage pulses oscillating at 100 kHz synchronisable with a nanosecond temporal jitter. Using this compact high voltage generator, we demonstrate reproducible meter long discharges in air at a repetition rate of 1 Hz. Triggering and guiding of the discharges are performed in air by femtosecond laser filaments.

Tunable Laser Development for In-Flight Fiber Optic Based Structural Health Monitoring Systems

NASA Technical Reports Server (NTRS)

Richards, Lance; Parker, Allen; Chan, Patrick

2013-01-01

Briefing based on tunable laser development for in flight fiber optic based structural health monitoring systems. The objective of this task is to investigate, develop, and demonstrate a low-cost swept lasing light source for NASA DFRC's fiber optics sensing system (FOSS) to perform structural health monitoring on current and future aerospace vehicles.

Penetrating and Intrastromal Corneal Arcuate Incisions in Rabbit and Human Cadaver Eyes: Manual Diamond Blade and Femtosecond Laser-Created Incisions.

PubMed

Gray, Brad; Binder, Perry S; Huang, Ling C; Hill, Jim; Salvador-Silva, Mercedes; Gwon, Arlene

2016-07-01

To compare morphologic differences between freehand diamond or femtosecond laser-assisted penetrating and intrastromal arcuate incisions. Freehand diamond blade, corneal arcuate incisions (180° apart, 60° arc lengths) and 150 kHz femtosecond laser (80% scheimpflug pachymetry depth corneal thickness) arcuate incisions were performed in rabbits. Intrastromal arcuate incisions (100 μm above Descemet's membrane, 100 μm below epithelium) were performed in rabbit corneas (energy 1.2 μJ, spot line separation 3 × 3 μm, 90° side cut angle). Eyes were examined by slit lamp and light microscopy up to 47 days post-procedure. Freehand diamond blade penetrating incisions, and femtosecond laser penetrating and intrastromal arcuate incisions (energy 1.8 μJ, spot line separation 2 × 2 μm) were performed in cadaver eyes. Optical coherence tomography was performed immediately after surgery and the corneas were fixed for light scanning and transmission electron microscopy. The rabbit model showed anterior stromal inflammation with epithelial hyperplasia in penetrating blade and laser penetrating wounds. The laser intrastromal and penetrating incisions showed localized constriction of the stromal layers of the cornea near the wound. In cadaver eyes, penetrating wound morphology was similar between blade and laser whereas intrastromal wounds did not affect the cornea above or below incisions. Penetrating femtosecond laser arcuate incisions have more predictable and controlled outcomes shown by less post-operative scarring than incisions performed with a diamond blade. Intrastromal incisions do not affect uncut corneal layers as demonstrated by histopathology. The femtosecond laser has significant advantages in its ability to make intrastromal incisions which are not achievable by traditional freehand or mechanical diamond blades.

Lasing in a single nanowire with quantum dots

NASA Astrophysics Data System (ADS)

Tatebayashi, Jun; Arakawa, Yasuhiko

2017-02-01

Nanowire (NW) lasers have recently attracted increasing attention as ultra-small, highly-efficient coherent light emitters in the fields of nanophotonics, nano-optics and nanobiotechnology. Although there have been several demonstrations of single NW lasers utilizing bulk materials, it is crucial to incorporate lower-dimensional quantum nanostructures into the NW in order to achieve superior device performance with respect to threshold current, differential gain, modulation bandwidth and temperature sensitivity. The quantum dot (QD) is a useful and essential nanostructure that can meet these requirements. In this presentation, we will talk about our recent research activity regarding room temperature lasing of a single GaAs NW containing 50-stacked In0.2Ga0.8As/GaAs QDs. The NW cavities consist of multiple In0.2Ga0.8As/GaAs heterostructures acting as a QD active material, which are grown on shallow (<45 nm) GaAs core NWs and followed by GaAs/Al0.1Ga0.9As/GaAs core/shell/cap structures. Lasing oscillation is achieved at the emission wavelength of 900 nm by properly designing the NW cavity and tailoring the emission energy of each QD to enhance the optical gain. Obtained threshold pump pulse fluence is 179 μJ/cm2 at room temperature and the characteristics temperature is 133K which is higher than that of conventional bulk NW lasers. Our demonstration paves the way toward ultra-small lasers with extremely low-power consumption for integrated photonic systems. Furthermore, we will discuss our recent results on the demonstration of several types of NWQD lasers in order to improve the device performance of the NWQD lasers.

Microwave tunable laser source: A stable, precision tunable heterodyne local oscillator

NASA Technical Reports Server (NTRS)

Sachse, G. W.

1980-01-01

The development and capabilities of a tunable laser source utilizing a wideband electro-optic modulator and a CO2 laser are described. The precision tunability and high stability of the device are demonstrated with examples of laboratory spectroscopy. Heterodyne measurements are also presented to demonstrate the performance of the laser source as a heterodyne local oscillator. With the use of five CO2 isotope lasers and the 8 to 18 GHz sideband offset tunability of the modulator, calculations indicate that 50 percent spectral coverage in the 9 to 12 micron region is achievable. The wavelength accuracy and stability of this laser source is limited by the CO2 laser and is more than adequate for the measurement of narrow Doppler-broadened line profiles. The room-temperature operating capability and the programmability of the microwave tunable laser source are attractive features for its in-the-field implementation. Although heterodyne measurements indicated some S/N degradation when using the device as a local oscillator, there does not appear to be any fundamental limitation to the heterodyne efficiency of this laser source. Through the use of a lower noise-figure traveling wave tube amplifier and optical matching of the output beam with the photomixer, a substantial increase in the heterodyne S/N is expected.

Thermo-optical vacuum testing of Galileo In-Orbit Validation laser retroreflectors

NASA Astrophysics Data System (ADS)

Dell'Agnello, S.; Boni, A.; Cantone, C.; Ciocci, E.; Contessa, S.; Delle Monache, G.; Lops, C.; Martini, M.; Patrizi, G.; Porcelli, L.; Salvatori, L.; Tibuzzi, M.; Intaglietta, N.; Tuscano, P.; Mondaini, C.; Maiello, M.; Doyle, D.; García-Prieto, R.; Navarro-Reyes, D.

2016-06-01

The Galileo constellation is a space research and development program of the European Union to help navigate users all over the world. The Galileo IOV (In-Orbit Validation) are the first test satellites of the Galileo constellation and carry satellite laser retroreflectors as part of their payload systems for precision orbit determination and performance assessment. INFN-LNF SCF_Lab (Satellite/lunar/GNSS laser ranging/altimetry and Cube/microsat Characterization Facilities Laboratory) has been performing tests on a sample of the laser array segment under the Thermo-optical vacuum testing of Galileo IOV laser retro-reflectors of Galileo IOV LRA project, as defined in ESA-INFN Contract No. 4000108617/13/NL/PA. We will present the results of FFDP (Far Field Diffraction Pattern) and thermal relaxation times measurements in relevant space conditions of Galileo IOV CCRs (Cube Corner Retroreflectors) provided by ESA-ESTEC. A reference for the performance of laser ranging on Galileo satellites is the FFDP of a retroreflector in its design specifications and a Galileo retroreflector, in air and isothermal conditions, should have a minimum return intensity within the range [ 0.55 ×106m2- 2.14 ×106m2 ] (ESA-INFN, 2013). Measurements, performed in SCF_Lab facility, demonstrated that the 7 Galileo IOV laser retroreflectors under test were compliant with design performance expectations (Porcelli et al., 2015). The kind of tests carried out for this activity are the first performed on spare Galileo IOV hardware, made available after the launch of the four Galileo IOV satellites (2011 and 2012), which were the operational core of the constellation. The characterisation of the retroreflectors against their design requirements is important because LRAs (Laser Retroreflector Arrays) will be flown on all Galileo satellites.

Novel preparation of N-doped SnO 2 nanoparticles via laser-assisted pyrolysis: Demonstration of exceptional lithium storage properties

DOE PAGES

Wang, Luyuan Paul; Leconte, Yann; Feng, Zhenxing; ...

2016-12-05

Here, laser pyrolyzed SnO 2 nanoparticles with an option of nitrogen (N) doping are prepared using a cost-effective method. The electrochemical performance of N-doped samples is tested for the first time in Li-ion batteries where the sample with 3% of N-dopant exhibits optimum performance with a capacity of 522 mAh g active material –1 that can be obtained at 10 A g –1 (6.7C).

High-energy, high-average-power laser with Nd:YLF rods corrected by magnetorheological finishing.

PubMed

Bagnoud, Vincent; Guardalben, Mark J; Puth, Jason; Zuegel, Jonathan D; Mooney, Ted; Dumas, Paul

2005-01-10

A high-energy, high-average-power laser system, optimized to efficiently pump a high-performance optical parametric chirped-pulse amplifier at 527 nm, has been demonstrated. The crystal large-aperture ring amplifier employs two flash-lamp-pumped, 25.4-mm-diameter Nd:YLF rods. The transmitted wave front of these rods is corrected by magnetorheological finishing to achieve nearly diffraction-limited output performance with frequency-doubled pulse energies up to 1.8 J at 5 Hz.

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.

Soliton self-frequency shift controlled by a weak seed laser in tellurite photonic crystal fibers.

PubMed

Liu, Lai; Meng, Xiangwei; Yin, Feixiang; Liao, Meisong; Zhao, Dan; Qin, Guanshi; Ohishi, Yasutake; Qin, Weiping

2013-08-01

We report the first demonstration of soliton self-frequency shift (SSFS) controlled by a weak continuous-wave (CW) laser, from a tellurite photonic crystal fiber pumped by a 1560 nm femtosecond fiber laser. The control of SSFS is performed by the cross-gain modulation of the 1560 nm femtosecond laser. By varying the input power of the weak CW laser (1560 nm) from 0 to 1.17 mW, the soliton generated in the tellurite photonic crystal fiber blue shifts from 1935 to 1591 nm. The dependence of the soliton wavelength on the operation wavelength of the weak CW laser is also measured. The results show the CW laser with a wavelength tunable range of 1530-1592 nm can be used to control the SSFS generation.

Laser-induced breakdown ignition in a gas fed two-stroke engine

NASA Astrophysics Data System (ADS)

Loktionov, E. Y.; Pasechnikov, N. A.; Telekh, V. D.

2018-01-01

Laser-induced ignition for internal combustion engines is investigated intensively after demonstration of a compact ‘laser plug’ possibility. Laser spark benefits as compared to traditional spark plugs are higher compression rate, and possibility of almost any fuel ignition, so lean mixtures burning with lower temperatures could reduce harmful exhausts (NO x , CH, etc). No need in electrode and possibility for multi-point, linear or circular ignition can make combustion even more effective. Laser induced combustion wave appears faster and is more stable in time, than electric one, so can be used for ramjets, chemical thrusters, and gas turbines. To the best of our knowledge, we have performed laser spark ignition of a gas fed two-stroke engine for the first time. Combustion temperature and pressure, exhaust composition, ignition timing were investigated at laser and compared to a regular electric spark ignition in a two-stroke model engine. Presented results show possibility for improvement of two-stroke engines performance, in terms of rotation rate increase and NO x emission reduction. Such compact engines using locally mined fuel could be highly demanded in remote Arctic areas.

Easy performance of 6-color confocal immunofluorescence with 4-laser line microscopes.

PubMed

Eissing, Nathalie; Heger, Lukas; Baranska, Anna; Cesnjevar, Robert; Büttner-Herold, Maike; Söder, Stephan; Hartmann, Arndt; Heidkamp, Gordon F; Dudziak, Diana

2014-09-01

Confocal laser scanning microscopy is an advanced technique for imaging tissue samples in vitro and in vivo at high optical resolution. The development of new fluorochrome variants do not only make it possible to perform multicolor flow cytometry of single cells, but in combination with high resolution laser scanning systems also to investigate the distribution of cells in lymphoid tissues by confocal immunofluorescence analyses, thus allowing the distinction of various cell populations directly in the tissue. Here, we provide a protocol for the visualization of at least six differently fluorochrome-labeled antibodies at the same time using a conventional confocal laser scanning microscope with four laser lines (405 nm, 488 nm, 555 nm, and 639 nm laser wavelength) in both murine and human tissue samples. We further demonstrate that compensation correction algorithms are not necessary to reduce spillover of fluorochromes into other channels when the used fluorochromes are combined according to their specific emission bands and the varying Stokes shift for co-excited fluorochromes with the same laser line. Copyright © 2014 Elsevier B.V. All rights reserved.

Mode-locked Tm,Ho:KLu(WO(4))(2) laser at 2060 nm using InGaSb-based SESAMs.

PubMed

Aleksandrov, Veselin; Gluth, Alexander; Petrov, Valentin; Buchvarov, Ivan; Steinmeyer, Günter; Paajaste, Jonna; Suomalainen, Soile; Härkönen, Antti; Guina, Mircea; Mateos, Xavier; Díaz, Francesc; Griebner, Uwe

2015-02-23

Passive mode-locking of a Tm,Ho:KLu(WO(4))(2) laser operating at 2060 nm using different designs of InGaAsSb quantum-well based semiconductor saturable absorber mirrors (SESAMs) is demonstrated. The self-starting mode-locked laser delivers pulse durations between 4 and 8 ps at a repetition rate of 93 MHz with maximum average output power of 155 mW. Mode-locking performance of a Tm,Ho:KLu(WO(4))(2) laser is compared for usage of a SESAM to a single-walled carbon nanotube saturable absorber.

Pipe flow measurements of turbulence and ambiguity using laser-Doppler velocimetry

NASA Technical Reports Server (NTRS)

Berman, N. S.; Dunning, J. W.

1973-01-01

The laser-Doppler ambiguities predicted by George and Lumley (1973) have been verified experimentally for turbulent pipe flows. Experiments were performed at Reynolds numbers from 5000 to 15,000 at the center line and near the wall. Ambiguity levels were measured from power spectral densities of FM demodulated laser signals and were compared with calculations based on the theory. The turbulent spectra for these water flows after accounting for the ambiguity were equivalent to hot-film measurements at similar Reynolds numbers. The feasibility of laser-Doppler measurements very close to the wall in shear flows is demonstrated.

Whispering gallery effect in relativistic optics

NASA Astrophysics Data System (ADS)

Abe, Y.; Law, K. F. F.; Korneev, Ph.; Fujioka, S.; Kojima, S.; Lee, S.-H.; Sakata, S.; Matsuo, K.; Oshima, A.; Morace, A.; Arikawa, Y.; Yogo, A.; Nakai, M.; Norimatsu, T.; d'Humières, E.; Santos, J. J.; Kondo, K.; Sunahara, A.; Gus'kov, S.; Tikhonchuk, V.

2018-03-01

relativistic laser pulse, confined in a cylindrical-like target, under specific conditions may perform multiple scattering along the internal target surface. This results in the confinement of the laser light, leading to a very efficient interaction. The demonstrated propagation of the laser pulse along the curved surface is just yet another example of the "whispering gallery" effect, although nonideal due to laser-plasma coupling. In the relativistic domain its important feature is a gradual intensity decrease, leading to changes in the interaction conditions. The proccess may pronounce itself in plenty of physical phenomena, including very efficient electron acceleration and generation of relativistic magnetized plasma structures.

Bismuth-doped optical fibres: A new breakthrough in near-IR lasing media

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

Dianov, Evgenii M

Recent results demonstrate that bismuth-doped optical fibres have considerable potential as near-IR active lasing media. This paper examines bismuth-doped fibres intended for the fabrication of fibre lasers and optical amplifiers and reviews recent results on the luminescence properties of various types of bismuth-doped fibres and the performance of bismuth-doped fibre lasers and optical amplifiers for the spectral range 1150 - 1550 nm. Problems are discussed that have yet to be solved in order to improve the efficiency of the bismuth lasers and optical amplifiers. (optical fibres, lasers and amplifiers. properties and applications)

75 W 40% efficiency single-mode all-fiber erbium-doped laser cladding pumped at 976 nm.

PubMed

Kotov, L V; Likhachev, M E; Bubnov, M M; Medvedkov, O I; Yashkov, M V; Guryanov, A N; Lhermite, J; Février, S; Cormier, E

2013-07-01

Optimization of Yb-free Er-doped fiber for lasers and amplifiers cladding pumped at 976 nm was performed in this Letter. The single-mode fiber design includes an increased core diameter of 34 μm and properly chosen erbium and co-dopant concentrations. We demonstrate an all-fiber high power laser and power amplifier based on this fiber with the record slope efficiency of 40%. To the best of our knowledge, the achieved output power of 75 W is the highest power reported for such lasers.

Quasi-dynamical analysis and real-time tissue temperature monitoring during laser vaporization

NASA Astrophysics Data System (ADS)

Wang, Hui; Ray, Aditi; Jebens, Dave; Chia, Ray; Hasenberg, Tom

2014-03-01

Vaporization and coagulation are two fundamental processes that can be performed during laser-tissue ablation. We demonstrated a method allowing quasi-dynamically observing of the cross-sectional images of tissue response during ablation. The results showed that coagulation depth is relatively constant during vaporization, which supports the excellent hemostasis of green laser benign prostate hyperplasia (BPH) treatment. We also verified a new technology for real-time, in situ tissue temperature monitoring, which may be promising for in vivo tissue vaporization degree feedback during laser ablation to improve the vaporization efficiency and avoid complications.

Detection of elemental mercury by multimode diode laser correlation spectroscopy.

PubMed

Lou, Xiutao; Somesfalean, Gabriel; Svanberg, Sune; Zhang, Zhiguo; Wu, Shaohua

2012-02-27

We demonstrate a method for elemental mercury detection based on correlation spectroscopy employing UV laser radiation generated by sum-frequency mixing of two visible multimode diode lasers. Resonance matching of the multimode UV laser is achieved in a wide wavelength range and with good tolerance for various operating conditions. Large mode-hops provide an off-resonance baseline, eliminating interferences from other gas species with broadband absorption. A sensitivity of 1 μg/m3 is obtained for a 1-m path length and 30-s integration time. The performance of the system shows promise for mercury monitoring in industrial applications.

A Photonic Crystal Laser from Solution Based Organo-Lead Iodide Perovskite Thin Films.

PubMed

Chen, Songtao; Roh, Kwangdong; Lee, Joonhee; Chong, Wee Kiang; Lu, Yao; Mathews, Nripan; Sum, Tze Chien; Nurmikko, Arto

2016-04-26

Perovskite semiconductors are actively investigated for high performance solar cells. Their large optical absorption coefficient and facile solution-based, low-temperature synthesis of thin films make perovskites also a candidate for light-emitting devices across the visible and near-infrared. Specific to their potential as optical gain medium for lasers, early work has demonstrated amplified spontaneous emission and lasing at attractively low thresholds of photoexcitation. Here, we take an important step toward practically usable perovskite lasers where a solution-processed thin film is embedded within a two-dimensional photonic crystal resonator. We demonstrate high degree of temporally and spatially coherent lasing whereby well-defined directional emission is achieved near 788 nm wavelength at optical pumping energy density threshold of 68.5 ± 3.0 μJ/cm(2). The measured power conversion efficiency and differential quantum efficiency of the perovskite photonic crystal laser are 13.8 ± 0.8% and 35.8 ± 5.4%, respectively. Importantly, our approach enables scalability of the thin film lasers to a two-dimensional multielement pixelated array of microlasers which we demonstrate as a proof-of-concept for possible projection display applications.

Single-shot measurement of >1010 pulse contrast for ultra-high peak-power lasers

PubMed Central

Wang, Yongzhi; Ma, Jingui; Wang, Jing; Yuan, Peng; Xie, Guoqiang; Ge, Xulei; Liu, Feng; Yuan, Xiaohui; Zhu, Heyuan; Qian, Liejia

2014-01-01

Real-time pulse-contrast observation with a high dynamic range is a prerequisite to tackle the contrast challenge in ultra-high peak-power lasers. However, the commonly used delay-scanning cross-correlator (DSCC) can only provide the time-consumed measurements for repetitive lasers. Single-shot cross-correlator (SSCC) becomes essential in optimizing laser systems and exploring contrast mechanisms. Here we report our progress in developing SSCC towards its practical use. By integrating both the techniques of scattering-noise reduction and sensitive parallel detection into SSCC, we demonstrate a high dynamic range of >1010, which, to our best knowledge, is the first demonstration of an SSCC with a dynamic range comparable to that of commercial DSCCs. The comparison of high-dynamic measurement performances between SSCC and a standard DSCC (Sequoia, Amplitude Technologies) is also carried out on a 200 TW Ti:sapphire laser, and the consistency of results verifies the veracity of our SSCC. PMID:24448655

Copper atom based measurements of velocity and turbulence in arc jet flows

NASA Technical Reports Server (NTRS)

Marinelli, William J.; Kessler, William J.; Allen, Mark G.; Arepalli, Sivaram; Scott, Carl D.

1991-01-01

Laboratory and field measurements were combined with a modeling effort to explore the feasibility of using atomic copper laser-induced fluorescence to measure velocity, turbulence, and temperature in arcjet flows. Both CW and pulsed frequency-doubled dye lasers were used to demonstrate the ability to measure velocity with 10 percent accuracy at rates of 200,000 cm/s in a rarefied flow of Cu atoms seeded in He. The pulsed laser established a threshold energy for power-broadening of the absorption line at 3.5 x 10 to the -8th J/sq cm. Field measurements at the NASA/JSC 10-MW arcjet facility demonstrated the ability to perform these measurements under actual test conditions. The use of this technique to measure freestream temperatures in the flow was examined for the 0.08/cm linewidth laser used in the NASA/JSC effort. Finally, single-shot turbulence measurements at the USAF/AEDC 35-MW H2 arcjet facility were measured with 4 percent accuracy using the laser/absorption line-overlap technique.

Broadly tunable terahertz generation in mid-infrared quantum cascade lasers.

PubMed

Vijayraghavan, Karun; Jiang, Yifan; Jang, Min; Jiang, Aiting; Choutagunta, Karthik; Vizbaras, Augustinas; Demmerle, Frederic; Boehm, Gerhard; Amann, Markus C; Belkin, Mikhail A

2013-01-01

Room temperature, broadly tunable, electrically pumped semiconductor sources in the terahertz spectral range, similar in operation simplicity to diode lasers, are highly desired for applications. An emerging technology in this area are sources based on intracavity difference-frequency generation in dual-wavelength mid-infrared quantum cascade lasers. Here we report terahertz quantum cascade laser sources based on an optimized non-collinear Cherenkov difference-frequency generation scheme that demonstrates dramatic improvements in performance. Devices emitting at 4 THz display a mid-infrared-to-terahertz conversion efficiency in excess of 0.6 mW W(-2) and provide nearly 0.12 mW of peak power output. Devices emitting at 2 and 3 THz fabricated on the same chip display 0.09 and 0.4 mW W(-2) conversion efficiencies at room temperature, respectively. High terahertz-generation efficiency and relaxed phase-matching conditions offered by the Cherenkov scheme allowed us to demonstrate, for the first time, an external-cavity terahertz quantum cascade laser source tunable between 1.70 and 5.25 THz.

On-chip optical phase locking of single growth monolithically integrated Slotted Fabry Perot lasers.

PubMed

Morrissey, P E; Cotter, W; Goulding, D; Kelleher, B; Osborne, S; Yang, H; O'Callaghan, J; Roycroft, B; Corbett, B; Peters, F H

2013-07-15

This work investigates the optical phase locking performance of Slotted Fabry Perot (SFP) lasers and develops an integrated variable phase locked system on chip for the first time to our knowledge using these lasers. Stable phase locking is demonstrated between two SFP lasers coupled on chip via a variable gain waveguide section. The two lasers are biased differently, one just above the threshold current of the device with the other at three times this value. The coupling between the lasers can be controlled using the variable gain section which can act as a variable optical attenuator or amplifier depending on bias. Using this, the width of the stable phase locking region on chip is shown to be variable.

High slope efficiency and high refractive index change in direct-written Yb-doped waveguide lasers with depressed claddings.

PubMed

Palmer, Guido; Gross, Simon; Fuerbach, Alexander; Lancaster, David G; Withford, Michael J

2013-07-15

We report the first Yb:ZBLAN and Yb:IOG10 waveguide lasers fabricated by the fs-laser direct-writing technique. Pulses from a Titanium-Sapphire laser oscillator with 5.1 MHz repetition rate were utilized to generate negative refractive index modifications in both glasses. Multiple modifications were aligned in a depressed cladding geometry to create a waveguide. For Yb:ZBLAN we demonstrate high laser slope efficiency of 84% with a maximum output power of 170 mW. By using Yb:IOG10 a laser performance of 25% slope efficiency and 72 mW output power was achieved and we measured a remarkably high refractive index change exceeding Δn = 2.3 × 10(-2).

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.

Dispersion-based Fresh-slice Scheme for Free-Electron Lasers

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

Guetg, Marc

The Fresh-slice technique improved the performance of several Self-Amplified Spontaneous Emission Free-Electron laser schemes by granting selective control on the temporal lasing slice without spoiling the other electron bunch slices. So far, the implementation required a special insertion device to create the beam yaw, called dechirper. We demonstrate a novel scheme to enable Freshslice operation based on electron energy chirp and orbit dispersion that can be implemented at any free-electron laser facility without additional hardware.

Lightweight solar array blanket tooling, laser welding and cover process technology

NASA Technical Reports Server (NTRS)

Dillard, P. A.

1983-01-01

A two phase technology investigation was performed to demonstrate effective methods for integrating 50 micrometer thin solar cells into ultralightweight module designs. During the first phase, innovative tooling was developed which allows lightweight blankets to be fabricated in a manufacturing environment with acceptable yields. During the second phase, the tooling was improved and the feasibility of laser processing of lightweight arrays was confirmed. The development of the cell/interconnect registration tool and interconnect bonding by laser welding is described.

First results with the novel petawatt laser acceleration facility in Dresden

NASA Astrophysics Data System (ADS)

Schramm, U.; Bussmann, M.; Irman, A.; Siebold, M.; Zeil, K.; Albach, D.; Bernert, C.; Bock, S.; Brack, F.; Branco, J.; Couperus, JP; Cowan, TE; Debus, A.; Eisenmann, C.; Garten, M.; Gebhardt, R.; Grams, S.; Helbig, U.; Huebl, A.; Kluge, T.; Köhler, A.; Krämer, JM; Kraft, S.; Kroll, F.; Kuntzsch, M.; Lehnert, U.; Loeser, M.; Metzkes, J.; Michel, P.; Obst, L.; Pausch, R.; Rehwald, M.; Sauerbrey, R.; Schlenvoigt, HP; Steiniger, K.; Zarini, O.

2017-07-01

We report on first commissioning results of the DRACO Petawatt ultra-short pulse laser system implemented at the ELBE center for high power radiation sources of Helmholtz-Zentrum Dresden-Rossendorf. Key parameters of the laser system essential for efficient and reproducible performance of plasma accelerators are presented and discussed with the demonstration of 40 MeV proton acceleration under TNSA conditions as well as peaked electron spectra with unprecedented bunch charge in the 0.5 nC range.

High power, high efficiency, continuous-wave supercontinuum generation using standard telecom fibers

NASA Astrophysics Data System (ADS)

Arun, S.; Choudhury, Vishal; Balaswamy, V.; Prakash, Roopa; Supradeepa, V. R.

2018-04-01

We demonstrate a simple module for octave spanning continuous-wave supercontinuum generation using standard telecom fiber. This module can accept any high power Ytterbium-doped fiber laser as input. The input light is transferred into the anomalous dispersion region of the telecom fiber through a cascade of Raman shifts. A recently proposed Raman laser architecture with distributed feedback efficiently performs these Raman conversions. A spectrum spanning over 1000nm(>1 octave) from 880-1900nm is demonstrated. The average power from the supercontinuum is ~34W with a high conversion efficiency of 44%. Input wavelength agility is demonstrated with similar supercontinua over a wide input wavelength range.

Comparison of two picosecond lasers to a nanosecond laser for treating tattoos: a prospective randomized study on 49 patients.

PubMed

Lorgeou, A; Perrillat, Y; Gral, N; Lagrange, S; Lacour, J-P; Passeron, T

2018-02-01

Q-switched nanosecond lasers demonstrated their efficacy in treating most types of tattoos, but complete disappearance is not always achieved even after performing numerous laser sessions. Picosecond lasers are supposed to be more efficient in clearing tattoos than nanosecond lasers, but prospective comparative data remain limited. To compare on different types of tattoos the efficacy of a nanosecond laser with two types of picosecond lasers. We conducted a prospective randomized study performed from December 2014 to June 2016 on adult patients with all types of tattoos. The tattoos were divided into two halves of equal size. After randomization, half of the tattoo was treated with a picosecond laser and the other half with a nanosecond laser. The evaluation was performed on standardized pictures performed before treatment and 2 months after the last session, by two physicians, not involved in the treatment, blinded on the type of treatments received. The main end point was a clearance above 75% of the tattoos. A total of 49 patients were included. Professional tattoos represented 85.7%, permanent make-up 8.2% and non-professional tattoo 6.1%. The majority were black or blue and 10.2% were polychromatic. No patient was lost during follow-up. A reduction of 75% or more of the colour intensity was obtained for 33% of the tattoos treated with the picosecond lasers compared to 14% with the nanosecond laser (P = 0.008). An improvement superior to 75% was obtained in 34% monochromic black or blue tattoos with the picosecond lasers compared to 9% for the nanosecond laser. Only one of the five polychromic tattoos achieved more than 75% of improvement with the two types of laser. Our results show a statistically significant superiority of the picosecond lasers compared to the nanosecond laser for tattoo clearance. However, they do not show better efficacy for polychromic tattoos and the difference in terms of side-effects was also minimal with a tendency of picosecond lasers to be less painful. © 2017 European Academy of Dermatology and Venereology.

Development and Characterization of a Small Spacecraft Electro-Optic Scanner for Free-Space Laser Communications

NASA Technical Reports Server (NTRS)

Davis, Scott; Lichter, Michael; Raible, Daniel

2016-01-01

Emergent data-intensive missions coupled with dramatic reductions in spacecraft size plus an increasing number of space-based missions necessitates new high performance, compact and low cost communications technology. Free space optical communications offer advantages including orders of magnitude increase for data rate performance, increased security, immunity to jamming and lack of frequency allocation requirements when compared with conventional radio frequency (RF) means. The spatial coherence and low divergence associated with the optical frequencies of laser communications lends themselves to superior performance, but this increased directionality also creates one of the primary technical challenges in establishing a laser communications link by repeatedly and reliably pointing the beam onto the receive aperture. Several solutions have emerged from wide angle (slow) mechanical articulation systems, fine (fast) steering mirrors and rotating prisms, inertial compensation gyros and vibration isolation cancellation systems, but each requires moving components and imparts a measured amount of burden on the host platform. The complexity, cost and size of current mechanically scanned solutions limits their platform applicability, and restricts the feasibility of deploying optical communications payloads on very compact spacecraft employing critical systems. A high speed, wide angle, non-mechanical solution is therefore desirable. The purpose of this work is to share the development, testing, and demonstration of a breadboard prototype electro-optic (EO) scanned laser-communication link (see Figure 1). This demonstration is a step toward realizing ultra-low Size, Weight and Power (SWaP) SmallSat/MicroSat EO non-mechanical laser beam steering modules for high bandwidth ( greater than Gbps) free-space data links operating in the 1550 nm wavelength bands. The elimination of all moving parts will dramatically reduce SWaP and cost, increase component lifetime and reliability, and simplify the system design of laser communication modules. This paper describes the target mission architectures and requirements (few cubic centimeters of volume, 10's of grams of weight with milliwatts of power) and design of the beam steering module. Laboratory metrology is used to determine the component performance including horizontal and vertical resolution (20urad) as a function of control voltage (see Figure 2), transition time (0.1-1ms), pointing repeatability and optic insertion loss. A test bed system demonstration, including a full laser communications link, is conducted. The capabilities of this new EO beam steerer provide an opportunity to dramatically improve space communications through increased utilization of laser technology on smaller platforms than were previously attainable.

Femtosecond laser polishing of optical materials

NASA Astrophysics Data System (ADS)

Taylor, Lauren L.; Qiao, Jun; Qiao, Jie

2015-10-01

Technologies including magnetorheological finishing and CNC polishing are commonly used to finish optical elements, but these methods are often expensive, generate waste through the use of fluids or abrasives, and may not be suited for specific freeform substrates due to the size and shape of finishing tools. Pulsed laser polishing has been demonstrated as a technique capable of achieving nanoscale roughness while offering waste-free fabrication, material-specific processing through direct tuning of laser radiation, and access to freeform shapes using refined beam delivery and focusing techniques. Nanosecond and microsecond pulse duration radiation has been used to perform successful melting-based polishing of a variety of different materials, but this approach leads to extensive heat accumulation resulting in subsurface damage. We have experimentally investigated the ability of femtosecond laser radiation to ablate silicon carbide and silicon. By substituting ultrafast laser radiation, polishing can be performed by direct evaporation of unwanted surface asperities with minimal heating and melting, potentially offering damage-free finishing of materials. Under unoptimized laser processing conditions, thermal effects can occur leading to material oxidation. To investigate these thermal effects, simulation of the heat accumulation mechanism in ultrafast laser ablation was performed. Simulations have been extended to investigate the optimum scanning speed and pulse energy required for processing various substrates. Modeling methodologies and simulation results will be presented.

Evaluation of laser-driven ion energies for fusion fast-ignition research

NASA Astrophysics Data System (ADS)

Tosaki, S.; Yogo, A.; Koga, K.; Okamoto, K.; Shokita, S.; Morace, A.; Arikawa, Y.; Fujioka, S.; Nakai, M.; Shiraga, H.; Azechi, H.; Nishimura, H.

2017-10-01

We investigate laser-driven ion acceleration using kJ-class picosecond (ps) laser pulses as a fundamental study for ion-assisted fusion fast ignition, using a newly developed Thomson-parabola ion spectrometer (TPIS). The TPIS has a space- and weight-saving design, considering its use in an laser-irradiation chamber in which 12 beams of fuel implosion laser are incident, and, at the same time, demonstrates sufficient performance with its detectable range and resolution of the ion energy required for fast-ignition research. As a fundamental study on laser-ion acceleration using a ps pulse laser, we show proton acceleration up to 40 MeV at 1 × 10^{19} W cm^{-2}. The energy conversion efficiency from the incident laser into protons higher than 6 MeV is 4.6%, which encourages the realization of fusion fast ignition by laser-driven ions.

Development of a compact vertical-cavity surface-emitting laser end-pumped actively Q-switched laser for laser-induced breakdown spectroscopy

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

Li, Shuo; Chen, Rongzhang; Nelsen, Bryan

2016-03-15

This paper reports the development of a compact and portable actively Q-switched Nd:YAG laser and its applications in laser-induced breakdown spectroscopy (LIBS). The laser was end-pumped by a vertical-cavity surface-emitting laser (VCSEL). The cavity lases at a wavelength of 1064 nm and produced pulses of 16 ns with a maximum pulse energy of 12.9 mJ. The laser exhibits a reliable performance in terms of pulse-to-pulse stability and timing jitter. The LIBS experiments were carried out using this laser on NIST standard alloy samples. Shot-to-shot LIBS signal stability, crater profile, time evolution of emission spectra, plasma electron density and temperature, andmore » limits of detection were studied and reported in this paper. The test results demonstrate that the VCSEL-pumped solid-state laser is an effective and compact laser tool for laser remote sensing applications.« less

Upper Eyelid Fractional CO2 Laser Resurfacing With Incisional Blepharoplasty.

PubMed

Kotlus, Brett S; Schwarcz, Robert M; Nakra, Tanuj

2016-01-01

Laser resurfacing, performed at the same time as blepharoplasty, has most commonly been applied to the lower eyelid skin but can effectively be used on the upper eyelid to reduce rhytidosis and improve skin quality. The authors evaluate the safety and efficacy of this procedure. Fractional CO2 laser resurfacing was performed in conjunction with incisional upper blepharoplasty. The ultrapulsed laser energy was applied to the sub-brow skin, the upper medial canthal skin, and the pretarsal skin in 30 patients. Photos were obtained preoperatively and at 3 months. All patients demonstrated reduction in upper eyelid rhytidosis without any serious complications. Independent rhytidosis grading (0-4) showed a mean improvement of 42%. One patient experienced wound dehiscence that satisfactorily resolved without intervention. Upper eyelid laser resurfacing is effective and can be safely performed at the same time as upper blepharoplasty. This approach reduces or eliminates the need for medial incisions to address medial canthal skin redundancy and rhytidosis and it directly treats upper eyelid wrinkles on residual eyelid and infra-brow skin during blepharoplasty.

E-beam-pumped semiconductor lasers

NASA Astrophysics Data System (ADS)

Rice, Robert R.; Shanley, James F.; Ruggieri, Neil F.

1995-04-01

The collapse of the Soviet Union opened many areas of laser technology to the West. E-beam- pumped semiconductor lasers (EBSL) were pursued for 25 years in several Soviet Institutes. Thin single crystal screens of II-VI alloys (ZnxCd1-xSe, CdSxSe1-x) were incorporated in laser CRTs to produce scanned visible laser beams at average powers greater than 10 W. Resolutions of 2500 lines were demonstrated. MDA-W is conducting a program for ARPA/ESTO to assess EBSL technology for high brightness, high resolution RGB laser projection application. Transfer of II-VI crystal growth and screen processing technology is underway, and initial results will be reported. Various techniques (cathodoluminescence, one- and two-photon laser pumping, etc.) have been used to assess material quality and screen processing damage. High voltage (75 kV) video electronics were procured in the U.S. to operate test EBSL tubes. Laser performance was documented as a function of screen temperature, beam voltage and current. The beam divergence, spectrum, efficiency and other characteristics of the laser output are being measured. An evaluation of the effect of laser operating conditions upon the degradation rate is being carried out by a design-of-experiments method. An initial assessment of the projected image quality will be performed.

Effects of clinical infrared laser on superficial radial nerve conduction

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

Greathouse, D.G.; Currier, D.P.; Gilmore, R.L.

The purposes of this study were to demonstrate the effects of infrared laser radiation on the sensory nerve conduction of a specified peripheral nerve in man and determine temperature changes in the tissue surrounding the treated nerve. Twenty healthy adults were divided into three groups: control (n = 5); experimental (n = 10), infrared laser radiation at 20 sec/cm2; and experimental (n = 5), infrared laser radiation treatment at 120 sec/cm2. Antidromic sensory nerve conduction studies were performed on the superficial radial nerve of each subject's right forearm. The infrared laser radiation was applied at a fixed intensity for fivemore » 1-cm2 segments. Latency, amplitude, and temperature measurements were recorded pretest; posttest; and posttest intervals of 1, 3, 5, 10, and 15 minutes. An analysis of variance with repeated measures was used to examine the data. No significant change was noted in the distal sensory latency or amplitude of the evoked sensory potential in either experimental or control groups as a result of the applications of the infrared laser radiation treatment. This study demonstrates that infrared laser used at clinically applied intensities does not alter conduction of sensory nerves nor does it elevate the subcutaneous temperature.« less

Widely tunable laser frequency offset lock with 30 GHz range and 5 THz offset.

PubMed

Biesheuvel, J; Noom, D W E; Salumbides, E J; Sheridan, K T; Ubachs, W; Koelemeij, J C J

2013-06-17

We demonstrate a simple and versatile method to greatly extend the tuning range of optical frequency shifting devices, such as acousto-optic modulators (AOMs). We use this method to stabilize the frequency of a tunable narrow-band continuous-wave (CW) laser to a transmission maximum of an external Fabry-Perot interferometer (FPI) with a tunable frequency offset. This is achieved through a servo loop which contains an in-loop AOM for simple radiofrequency (RF) tuning of the optical frequency over the full 30 GHz mode-hop-free tuning range of the CW laser. By stabilizing the length of the FPI to a stabilized helium-neon (HeNe) laser (at 5 THz offset from the tunable laser) we simultaneously transfer the ~ 1 MHz absolute frequency stability of the HeNe laser to the entire 30 GHz range of the tunable laser. Thus, our method allows simple, wide-range, fast and reproducible optical frequency tuning and absolute optical frequency measurements through RF electronics, which is here demonstrated by repeatedly recording a 27-GHz-wide molecular iodine spectrum at scan rates up to 500 MHz/s. General technical aspects that determine the performance of the method are discussed in detail.

Laser-induced lipolysis on adipose cells

NASA Astrophysics Data System (ADS)

Solarte, Efrain; Gutierrez, O.; Neira, Rodrigo; Arroyave, J.; Isaza, Carolina; Ramirez, Hugo; Rebolledo, Aldo F.; Criollo, Willian; Ortiz, C.

2004-10-01

Recently, a new liposuction technique, using a low-level laser (LLL) device and Ultrawet solution prior to the procedure, demonstrated the movement of fat from the inside to the outside of the adipocyte (Neira et al., 2002). To determine the mechanisms involved, we have performed Scanning and Transmission Electron Microscopy studies; Light transmittance measurements on adipocyte dilutions; and a study of laser light propagation in adipose tissue. This studies show: 1. Cellular membrane alterations. 2. LLL is capable to reach the deep adipose tissue layer, and 3. The tumescence solution enhances the light propagation by clearing the tissue. MRI studies demonstrated the appearance of fat on laser treated abdominal tissue. Besides, adipocytes were cultivated and irradiated to observe the effects on isolated cells. These last studies show: 1. 635 nm-laser alone is capable of mobilizing cholesterol from the cell membrane; this action is enhanced by the presence of adrenaline and lidocaine. 2. Intracellular fat is released from adipocytes by co joint action of adrenaline, aminophyline and 635 nm-laser. Results are consistent with a laser induced cellular process, which causes fat release from the adipocytes into the intercellular space, besides the modification of the cellular membranes.

Continuous-wave and acousto-optically Q-switched 1066 nm laser performance of a novel Nd:GdTaO4 crystal

NASA Astrophysics Data System (ADS)

Ma, Yufei; He, Ying; Peng, Zhenfang; Sun, Haiyue; Peng, Fang; Yan, Renpeng; Li, Xudong; Yu, Xin; Zhang, Qingli; Ding, Shoujun

2018-05-01

A diode-pumped acousto-optically (AO) Q-switched 1066 nm laser with a novel Nd:GdTaO4 crystal was demonstrated for the first time to the best of our knowledge. The optimization selection of output coupler was carried out in the continuous-wave (CW) operation. After that the pulsed Nd:GdTaO4 laser performances using different modulation repetition rates of 10 kHz and 20 kHz were investigated. At an absorbed pump power of 10 W and repetition rates of 10 kHz, the obtained minimum pulse width was 28 ns and the maximum peak power was 5.4 kW.

Development of soft x-ray time-resolved photoemission spectroscopy system with a two-dimensional angle-resolved time-of-flight analyzer at SPring-8 BL07LSU

NASA Astrophysics Data System (ADS)

Ogawa, Manami; Yamamoto, Susumu; Kousa, Yuka; Nakamura, Fumitaka; Yukawa, Ryu; Fukushima, Akiko; Harasawa, Ayumi; Kondoh, Hiroshi; Tanaka, Yoshihito; Kakizaki, Akito; Matsuda, Iwao

2012-02-01

We have developed a soft x-ray time-resolved photoemission spectroscopy system using synchrotron radiation (SR) at SPring-8 BL07LSU and an ultrashort pulse laser system. Two-dimensional angle-resolved measurements were performed with a time-of-flight-type analyzer. The photoemission spectroscopy system is synchronized to light pulses of SR and laser using a time control unit. The performance of the instrument is demonstrated by mapping the band structure of a Si(111) crystal over the surface Brillouin zones and observing relaxation of the surface photo-voltage effect using the pump (laser) and probe (SR) method.

Development of soft x-ray time-resolved photoemission spectroscopy system with a two-dimensional angle-resolved time-of-flight analyzer at SPring-8 BL07LSU.

PubMed

Ogawa, Manami; Yamamoto, Susumu; Kousa, Yuka; Nakamura, Fumitaka; Yukawa, Ryu; Fukushima, Akiko; Harasawa, Ayumi; Kondoh, Hiroshi; Tanaka, Yoshihito; Kakizaki, Akito; Matsuda, Iwao

2012-02-01

We have developed a soft x-ray time-resolved photoemission spectroscopy system using synchrotron radiation (SR) at SPring-8 BL07LSU and an ultrashort pulse laser system. Two-dimensional angle-resolved measurements were performed with a time-of-flight-type analyzer. The photoemission spectroscopy system is synchronized to light pulses of SR and laser using a time control unit. The performance of the instrument is demonstrated by mapping the band structure of a Si(111) crystal over the surface Brillouin zones and observing relaxation of the surface photo-voltage effect using the pump (laser) and probe (SR) method.

Laser Ranging for Effective and Accurate Tracking of Space Debris in Low Earth Orbits

NASA Astrophysics Data System (ADS)

Blanchet, Guillaume; Haag, Herve; Hennegrave, Laurent; Assemat, Francois; Vial, Sophie; Samain, Etienne

2013-08-01

The paper presents the results of preliminary design options for an operational laser ranging system adapted to the measurement of the distance of space debris. Thorough analysis of the operational parameters is provided with identification of performance drivers and assessment of enabling design options. Results from performance simulation demonstrate how the range measurement enables improvement of the orbit determination when combined with astrometry. Besides, experimental results on rocket-stage class debris in LEO were obtained by Astrium beginning of 2012, in collaboration with the Observatoire de la Côte d'Azur (OCA), by operating an experimental laser ranging system supported by the MéO (Métrologie Optique) telescope.

A hybrid CATV/16-QAM-OFDM visible laser light communication system

NASA Astrophysics Data System (ADS)

Lin, Chun-Yu; Li, Chung-Yi; Lu, Hai-Han; Chen, Chia-Yi; Jhang, Tai-Wei; Ruan, Sheng-Siang; Wu, Kuan-Hung

2014-10-01

A visible laser light communication (VLLC) system employing a vertical cavity surface emitting laser and spatial light modulator with hybrid CATV/16-QAM-OFDM modulating signals over a 5 m free-space link is proposed and demonstrated. With the assistance of a push-pull scheme, low-noise amplifier, and equalizer, good performances of composite second-order and composite triple beat are obtained, accompanied by an acceptable carrier-to-noise ratio performance for a CATV signal, and a low bit error rate value and clear constellation map are achieved for a 16-QAM-OFDM signal. Such a hybrid CATV/16-QAM-OFDM VLLC system would be attractive for providing services including CATV, Internet and telecommunication services.

Principles and performance of tapered fiber lasers: from uniform to flared geometry.

PubMed

Kerttula, Juho; Filippov, Valery; Chamorovskii, Yuri; Ustimchik, Vasily; Golant, Konstantin; Okhotnikov, Oleg G

2012-10-10

We have studied the recently demonstrated concept of fiber lasers based on active tapered double-clad fiber (T-DCF) in copropagating and counterpropagating configurations, both theoretically and experimentally, and compared the performance to fiber lasers based on conventional cylindrical fibers in end-pumped configurations. Specific properties of T-DCFs were considered theoretically using a rate-equation model developed for tapered fibers, and a detailed comparative study was carried out experimentally. Furthermore, we have studied mode coupling effects in long adiabatic tapers due to coiling and local bending. The results allow us to conclude that, with proper fiber design, the T-DCF technology offers a high-potential alternative for bright, cost-effective fiber devices.

Characterization of the Los Alamos IPG YLR-6000 fiber laser using multiple optical paths and laser focusing optics

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

Milewski, John O; Bernal, John E

2009-01-01

Fiber laser technology has been identified as the replacement power source for the existing Los Alamos TA-55 production laser welding system. An IPG YLR-6000 fiber laser was purchased, installed at SM-66 R3, and accepted in February 2008. No characterization of the laser and no welding was performed in the Feb 2008 to May 2009 interval. T. Lienert and J. Bernal (Ref. 1, July 2009) determined the existing 200 mm Rofin collimator and focus heads used with the Rofin diode pumped lasers were inadequate for use with the IPG laser due to clipping of the IPG laser beam. Further efforts inmore » testing of the IPG laser with Optoskand fiber delivery optics and a Rofin 120 mm collimator proved problematic due to optical fiber damage. As a result, IPG design optical fibers were purchased as replacements for subsequent testing. Within the same interval, an IPG fiber-to-fiber (F2F) connector, custom built for LANL, (J. Milewski, S. Gravener, Ref.2) was demonstrated and accepted at IPG Oxford, MA in August 2009. An IPG service person was contracted to come to LANL to assist in the installation, training, troubleshooting and characterization of the multiple beam paths and help perform laser head optics characterization. The statement of work is provided below: In summary the laser system, optical fibers, F2F connector, Precitec head, and a modified Rofin type (w/120mm Optoskand collimator) IWindowIBoot system focus head (Figure 1) were shown to perform well at powers up to 6 kW CW. Power measurements, laser spot size measurements, and other characterization data and lessons learned are contained within this report. In addition, a number of issues were identified that will require future resolution.« less

Rapid fibrin plug formation within cutaneous ablative fractional CO2 laser lesions.

PubMed

Kositratna, Garuna; Evers, Michael; Sajjadi, Amir; Manstein, Dieter

2016-02-01

Ablative fractional laser procedures have been shown to facilitate topical drug delivery into the skin. Past studies have mainly used ex vivo models to demonstrate enhanced drug delivery and in vivo studies have investigated laser created channels over a time course of days and weeks rather than within the first few minutes and hours after exposures. We have noticed rapid in vivo fibrin plug formation within ablative fractional laser lesions impairing passage through the laser created channels. In vivo laser exposures were performed in a porcine model. A fractional CO2 laser (AcuPulse™ system, AcuScan 120™ handpiece, Lumenis, Inc., Yokneam, Israel) was programmed in quasi-continuous wave (QCW) mode, at 40W, 50 mJ per pulse, 5% coverage, nominal 120 µm spot size, 8 × 8 mm square pattern, 169 MTZs per scan. Six millimeters punch biopsies were procured at 0, 2, 5, 10, 15, 30, 60, 90 minutes after completion of each scan, then fixed in 10% formalin. 12 repeats were performed of each time point. Skin samples were processed for serial vertically cut paraffin sections (5 μm collected every 25 μm) then H&E and special immunohistochemistry staining for fibrin and platelet. Dimensions of Microscopic Treatment Zones (MTZs) and extent of fibrin plug were assessed and quantified histologically. Ex vivo laser exposures of the identical laser parameter were performed on porcine and human skin at different storage conditions. Histology procured at various predetermined time intervals after in vivo fractional CO2 laser exposures revealed a rapidly forming fibrin plug initiating at the bottom of the MTZ lesions. At longer time intervals, the fibrin plug was extending towards the superficial sections. Within the first 5 minutes, more than 25% length of the entire laser-ablated channel was filled with a fibrin plug. With increased time intervals, the cavity was progressively filled with a fibrin plug. At 90 minutes, more than 90% length of the entire laser-ablated channel was occluded. Ex vivo exposures failed to produce any significant fibrin plug formation. The current study has demonstrated rapid fibrin plug formation after ablative fractional laser procedures. It was shown that the passage through laser created pathways is critically time dependent for in vivo exposures. In contrast, ex vivo exposures do not exhibit such time dependent passage capacity. In particular, drug, substance, and cell delivery studies for ablative fractional laser treatments should take early fibrin plug formation into consideration and further investigate the impact on transdermal delivery. © 2015 Wiley Periodicals, Inc.

Demonstration of a diode-laser-based high spectral resolution lidar (HSRL) for quantitative profiling of clouds and aerosols.

PubMed

Hayman, Matthew; Spuler, Scott

2017-11-27

We present a demonstration of a diode-laser-based high spectral resolution lidar. It is capable of performing calibrated retrievals of aerosol and cloud optical properties at a 150 m range resolution with less than 1 minute integration time over an approximate range of 12 km during day and night. This instrument operates at 780 nm, a wavelength that is well established for reliable semiconductor lasers and detectors, and was chosen because it corresponds to the D2 rubidium absorption line. A heated vapor reference cell of isotopic rubidium 87 is used as an effective and reliable aerosol signal blocking filter in the instrument. In principle, the diode-laser-based high spectral resolution lidar can be made cost competitive with elastic backscatter lidar systems, yet delivers a significant improvement in data quality through direct retrieval of quantitative optical properties of clouds and aerosols.

Fabrication of parabolic cylindrical microlens array by shaped femtosecond laser

NASA Astrophysics Data System (ADS)

Luo, Zhi; Yin, Kai; Dong, Xinran; Duan, Ji'an

2018-04-01

A simple and efficient technique for fabricating parabolic cylindrical microlens arrays (CMLAs) on the surface of fused silica by shaped femtosecond (fs) laser direct-writing is demonstrated. By means of spatially shaping of a Gaussian fs laser beam to a Bessel distribution, an inversed cylindrical shape laser intensity profile is formed in a specific cross-sectional plane among the shaped optical field. Applying it to experiments, large area close-packed parabolic CMLAs with line-width of 37.5 μm and array size of about 5 × 5 mm are produced. The cross-sectional outline of obtained lenslets has a satisfied parabolic profile and the numerical aperture (NA) of lenslets is more than 0.35. Furthermore, the focusing performance of the fabricated CMLA is also tested in this work and it has been demonstrated that the focusing power of the CMLA with a parabolic profile is better than that with a semi-circular one.

IIIV/Si Nanoscale Lasers and Their Integration with Silicon Photonics

NASA Astrophysics Data System (ADS)

Bondarenko, Olesya

The rapidly evolving global information infrastructure requires ever faster data transfer within computer networks and stations. Integrated chip scale photonics can pave the way to accelerated signal manipulation and boost bandwidth capacity of optical interconnects in a compact and ergonomic arrangement. A key building block for integrated photonic circuits is an on-chip laser. In this dissertation we explore ways to reduce the physical footprint of semiconductor lasers and make them suitable for high density integration on silicon, a standard material platform for today's integrated circuits. We demonstrated the first room temperature metalo-dielectric nanolaser, sub-wavelength in all three dimensions. Next, we demonstrated a nanolaser on silicon, showing the feasibility of its integration with this platform. We also designed and realized an ultracompact feedback laser with edge-emitting structure, amenable for in-plane coupling with a standard silicon waveguide. Finally, we discuss the challenges and propose solutions for improvement of the device performance and practicality.

Frequency domain optical parametric amplification

PubMed Central

Schmidt, Bruno E.; Thiré, Nicolas; Boivin, Maxime; Laramée, Antoine; Poitras, François; Lebrun, Guy; Ozaki, Tsuneyuki; Ibrahim, Heide; Légaré, François

2014-01-01

Today’s ultrafast lasers operate at the physical limits of optical materials to reach extreme performances. Amplification of single-cycle laser pulses with their corresponding octave-spanning spectra still remains a formidable challenge since the universal dilemma of gain narrowing sets limits for both real level pumped amplifiers as well as parametric amplifiers. We demonstrate that employing parametric amplification in the frequency domain rather than in time domain opens up new design opportunities for ultrafast laser science, with the potential to generate single-cycle multi-terawatt pulses. Fundamental restrictions arising from phase mismatch and damage threshold of nonlinear laser crystals are not only circumvented but also exploited to produce a synergy between increased seed spectrum and increased pump energy. This concept was successfully demonstrated by generating carrier envelope phase stable, 1.43 mJ two-cycle pulses at 1.8 μm wavelength. PMID:24805968

Active hyperspectral imaging using a quantum cascade laser (QCL) array and digital-pixel focal plane array (DFPA) camera.

PubMed

Goyal, Anish; Myers, Travis; Wang, Christine A; Kelly, Michael; Tyrrell, Brian; Gokden, B; Sanchez, Antonio; Turner, George; Capasso, Federico

2014-06-16

We demonstrate active hyperspectral imaging using a quantum-cascade laser (QCL) array as the illumination source and a digital-pixel focal-plane-array (DFPA) camera as the receiver. The multi-wavelength QCL array used in this work comprises 15 individually addressable QCLs in which the beams from all lasers are spatially overlapped using wavelength beam combining (WBC). The DFPA camera was configured to integrate the laser light reflected from the sample and to perform on-chip subtraction of the passive thermal background. A 27-frame hyperspectral image was acquired of a liquid contaminant on a diffuse gold surface at a range of 5 meters. The measured spectral reflectance closely matches the calculated reflectance. Furthermore, the high-speed capabilities of the system were demonstrated by capturing differential reflectance images of sand and KClO₃ particles that were moving at speeds of up to 10 m/s.

In situ FBG inscription during fiber laser operation.

PubMed

Leich, Martin; Fiebrandt, Julia; Jetschke, Sylvia; Rothhardt, Manfred; Jäger, Matthias

2013-03-01

We demonstrate the inscription of a 266 nm UV femtosecond pulse-induced fiber Bragg grating (FBG) in an Yb-doped fiber during optical pumping at 976 nm and the initiation of lasing with increasing grating reflectivity. Output spectra show the emission of the pumped fiber changing from the broad-ranged amplified spontaneous emission in the nonlasing case to the narrow-range laser operation due to the enhancement of FBG reflectivity during inscription. The proposed technique enables the direct characterization and control of FBG performance in fiber lasers. After FBG fabrication, we investigate the spectral characteristics of the fiber laser for different laser powers and study the influence of a thermal treatment of the FBG.

Low cost, patterning of human hNT brain cells on parylene-C with UV & IR laser machining.

PubMed

Raos, Brad J; Unsworth, C P; Costa, J L; Rohde, C A; Doyle, C S; Delivopoulos, E; Murray, A F; Dickinson, M E; Simpson, M C; Graham, E S; Bunting, A S

2013-01-01

This paper describes the use of 800nm femtosecond infrared (IR) and 248nm nanosecond ultraviolet (UV) laser radiation in performing ablative micromachining of parylene-C on SiO2 substrates for the patterning of human hNT astrocytes. Results are presented that support the validity of using IR laser ablative micromachining for patterning human hNT astrocytes cells while UV laser radiation produces photo-oxidation of the parylene-C and destroys cell patterning. The findings demonstrate how IR laser ablative micromachining of parylene-C on SiO2 substrates can offer a low cost, accessible alternative for rapid prototyping, high yield cell patterning.

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

Kanesue, Takeshi; Ikeda, Shunsuke

A laser ion source is a promising candidate as an ion source for heavy ion inertial fusion (HIF), where a pulsed ultra-intense and low-charged heavy ion beam is required. It is a key development for a laser ion source to transport laser-produced plasma with a magnetic field to achieve a high current beam. The effect of a tapered magnetic field on laser produced plasma is demonstrated by comparing the results with a straight solenoid magnet. The magnetic field of interest is a wider aperture on a target side and narrower aperture on an extraction side. Furthermore, based on the experimentallymore » obtained results, the performance of a scaled laser ion source for HIF was estimated.« less

Femtosecond Lasers in Ophthalmology: Surgery and Imaging

NASA Astrophysics Data System (ADS)

Bille, J. F.

Ophthalmology has traditionally been the field with prevalent laser applications in medicine. The human eye is one of the most accessible human organs and its transparency for visible and near-infrared light allows optical techniques for diagnosis and treatment of almost any ocular structure. Laser vision correction (LVC) was introduced in the late 1980s. Today, the procedural ease, success rate, and lack of disturbing side-effects in laser assisted in-situ keratomileusis (LASIK) have made it the most frequently performed refractive surgical procedure (keratomileusis(greek): cornea-flap-cutting). Recently, it has been demonstrated that specific aspects of LVC can take advantage of unique light-matter interaction processes that occur with femtosecond laser pulses.

Laser Frequency Stabilization for Coherent Lidar Applications using Novel All-Fiber Gas Reference Cell Fabrication Technique

NASA Technical Reports Server (NTRS)

Meras, Patrick, Jr.; Poberezhskiy, Ilya Y.; Chang, Daniel H.; Levin, Jason; Spiers, Gary D.

2008-01-01

Compact hollow-core photonic crystal fiber (HC-PCF)gas frequency reference cell was constructed using a novel packaging technique that relies on torch-sealing a quartz filling tube connected to a mechanical splice between regular and hollow-core fibers. The use of this gas cell for laser frequency stabilization was demonstrated by locking a tunable diode laser to the center of the P9 line from the (nu)1+(nu)3 band of acetylene with RMS frequency error of 2.06 MHz over 2 hours. This effort was performed in support of a task to miniaturize the laser frequency stabilization subsystem of JPL/LMCT Laser Absorption Spectrometer (LAS) instrument.

Feasibility of airborne detection of laser-induced fluorescence emissions from green terrestrial plants

NASA Technical Reports Server (NTRS)

Hoge, F. E.; Swift, R. N.; Yungel, J. K.

1983-01-01

The present investigation provides a demonstration of the feasibility of the airborne detection of the laser-induced fluorescence spectral emissions from living terrestrial grasses, shrubs, and trees using existing levels of lidar technology. Airborne studies were performed to ascertain system requirements necessary to detect laser-induced fluorescence from living terrestrial plants, to assess the practical acquisition of useful single-shot laser-induced fluorescence (LIF) waveforms over vegetative canopies, and to determine the comparative suitability of laser system, airborne platform, and terrestrial environmental parameters. The field experiment was conducted on May 3, 1982, over the northern portion of Wallops Island, VA. Attention is given to airborne lidar results and the description of laboratory investigations.

Broad-gain (Δλ/λ0

PubMed

Fujita, Kazuue; Furuta, Shinichi; Dougakiuchi, Tatsuo; Sugiyama, Atsushi; Edamura, Tadataka; Yamanishi, Masamichi

2011-01-31

Broad-gain operation of λ~8.7 μm quantum cascade lasers based on dual-upper-state to multiple-lower-state transition design is reported. The devices exhibit surprisingly wide (~500 cm(-1)) electroluminescence spectra which are very insensitive to voltage and temperature changes above room temperature. With recourse to the temperature-insensitivity of electroluminescence spectra, the lasers demonstrate an extremely-weak temperature-dependence of laser performances: T0-value of 510 K, associated with a room temperature threshold current density of 2.6 kA/cm2. In addition, despite such wide gain spectra, room temperature, continuous wave operation of the laser with buried hetero structure is achieved.

Channeling of multikilojoule high-intensity laser beams in an inhomogeneous plasma

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

Ivancic, S.; Haberberger, D.; Habara, H.

Channeling experiments were performed that demonstrate the transport of high-intensity (>10¹⁸ W/cm²), multikilojoule laser light through a millimeter-sized, inhomogeneous (~300-μm density scale length) laser produced plasma up to overcritical density, which is an important step forward for the fast-ignition concept. The background plasma density and the density depression inside the channel were characterized with a novel optical probe system. The channel progression velocity was measured, which agrees well with theoretical predictions based on large scale particle-in-cell simulations, confirming scaling laws for the required channeling laser energy and laser pulse duration, which are important parameters for future integrated fast-ignition channeling experiments.

Improving the Fabrication of Semiconductor Bragg Lasers

NASA Astrophysics Data System (ADS)

Chen, Eric Ping Chun

Fabrication process developments for Bragg reflection lasers have been optimized in this thesis using resources available to the group. New e-beam lithography and oxide etch recipes have been developed to minimize sidewall roughness and residues. E-beam evaporated metal contacts for semiconductor diode laser utilizing oblique angle deposition have also been developed in-house for the first time. Furthermore, improvement in micro-loading effect of DFB laser etching has been demonstrated where the ratio of tapered portion of the sidewall to total etch depth is reduced by half, from 33% to 15%. Electrical, optical and thermal performance of the fabricated lasers are characterized. Comparing the results to previous generation lasers, average dynamic resistance is decreased drastically from 14 Ohms to 7 Ohms and threshold current density also reduced from 1705A/cm2 to 1383A/ cm2. Improvement in laser performance is result of reduced loss from optimized fabrication processes. BRL bow-tie tapered lasers is then fabricated for the first time and output power of 18mW at 200mA input is measured. Benefiting from the increased effective area and better carrier utilization, reduction in threshold current density from 1383A/cm 2 to 712A/cm2 is observed.

Room-temperature lasing in a single nanowire with quantum dots

NASA Astrophysics Data System (ADS)

Tatebayashi, Jun; Kako, Satoshi; Ho, Jinfa; Ota, Yasutomo; Iwamoto, Satoshi; Arakawa, Yasuhiko

2015-08-01

Semiconductor nanowire lasers are promising as ultrasmall, highly efficient coherent light emitters in the fields of nanophotonics, nano-optics and nanobiotechnology. Although there have been several demonstrations of nanowire lasers using homogeneous bulk gain materials or multi-quantum-wells/disks, it is crucial to incorporate lower-dimensional quantum nanostructures into the nanowire to achieve superior device performance in relation to threshold current, differential gain, modulation bandwidth and temperature sensitivity. The quantum dot is a useful and essential nanostructure that can meet these requirements. However, difficulties in forming stacks of quantum dots in a single nanowire hamper the realization of lasing operation. Here, we demonstrate room-temperature lasing of a single nanowire containing 50 quantum dots by properly designing the nanowire cavity and tailoring the emission energy of each dot to enhance the optical gain. Our demonstration paves the way toward ultrasmall lasers with extremely low power consumption for integrated photonic systems.

Experimental demonstration of deep frequency modulation interferometry.

PubMed

Isleif, Katharina-Sophie; Gerberding, Oliver; Schwarze, Thomas S; Mehmet, Moritz; Heinzel, Gerhard; Cervantes, Felipe Guzmán

2016-01-25

Experiments for space and ground-based gravitational wave detectors often require a large dynamic range interferometric position readout of test masses with 1 pm/√Hz precision over long time scales. Heterodyne interferometer schemes that achieve such precisions are available, but they require complex optical set-ups, limiting their scalability for multiple channels. This article presents the first experimental results on deep frequency modulation interferometry, a new technique that combines sinusoidal laser frequency modulation in unequal arm length interferometers with a non-linear fit algorithm. We have tested the technique in a Michelson and a Mach-Zehnder Interferometer topology, respectively, demonstrated continuous phase tracking of a moving mirror and achieved a performance equivalent to a displacement sensitivity of 250 pm/Hz at 1 mHz between the phase measurements of two photodetectors monitoring the same optical signal. By performing time series fitting of the extracted interference signals, we measured that the linearity of the laser frequency modulation is on the order of 2% for the laser source used.

High-slope-efficiency 2.06 μm Ho: YLF laser in-band pumped by a fiber-coupled broadband diode.

PubMed

Ji, Encai; Liu, Qiang; Nie, Mingming; Cao, Xuezhe; Fu, Xing; Gong, Mali

2016-03-15

We first demonstrate the laser performance of a compact 2.06 μm Ho: YLF laser resonantly pumped by a broadband fiber-coupled diode. In continuous-wave (CW) operation, maximum output power of 1.63 W, corresponding to a slope efficiency of 89.2%, was obtained with a near diffraction-limited beam quality. In actively Q-switched operation, maximum pulse energy of 1.1 mJ was achieved at the repetition frequency of 100 Hz. The minimum pulse duration was 43 ns. The performance in both the CW and Q-switched regimes indicates that the current fiber-coupled diode in-band pumped Ho: YLF laser has great potential in certain conditions that require several watts of output power or several millijoules of short pulse energy.

FULAS: Design and test results of a novel laser platform for future LIDAR missions

NASA Astrophysics Data System (ADS)

Luttmann, Jörg; Klein, Jürgen; Plum, Heinz-Dieter; Hoffmann, Hans-Dieter; Hahn, Sven; Bode, Markus

2017-03-01

Spaceborne atmospheric LIDAR instruments enable the global measurement of aerosols, wind and greenhouse gases like CO2, Methane and Water. These LIDAR instruments require a pulsed single frequency laser source with emission at a specific wavelength. Pulse energies in the 10 mJ or 100 mJ range are required at bandwidth limited pulse durations in the multi-10 ns range. Pulse repetition rate requirements are typically around 100 Hz but may range from 10 Hz to some kHz. High efficiency is mandatory. Building complex laser sources providing the performance, reliability and lifetime necessary to operate such instruments in space has been recognized to be still very challenging. To overcome this, in the frame of the FULAS technology development project - funded by ESA and supported by the German Aerospace Center DLR - a versatile platform for LIDAR sources has been developed. For demonstration the requirements of the laser source in the ATLID instrument have been chosen. The design is based on a single frequency seeded, actively Q-switched, diode pumped Nd:YAG laser oscillator and an InnoSlab power amplifier with frequency tripling. The laser architecture pays special attention on Laser Induced Contamination by avoiding critical organic and outgassing materials. Soldering technologies for mounting and alignment of optics provide high mechanical stability and superior reliability. The FULAS infrared section has been assembled and integrated into a pressurized housing. The optical performance at 1064 nm has been demonstrated and thermal vacuum tests have been carried out successfully providing relevant data for the French-German climate mission MERLIN.

Department of Defense High Power Laser Program Guidance

DTIC Science & Technology

1994-06-06

Air Force Phillips Laboratory . Through FY94, laboratory operational funding, including civilian... Laboratory Effort and Air Materiel Command Ground-Based Laser (GBL) - Space Control USSPACECOM AF Phillips Laboratory Effort Point Defense Demonstration - Anti...ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING I.GANIZATION Phi 1l i ps Laboratory /LID REPORT numP•R 3550 Aberdeen Avenue, S.E. Kirtland AFB, NM

Tunable Laser Development for In-flight Fiber Optic Based Structural Health Monitoring Systems

NASA Technical Reports Server (NTRS)

Richards, Lance; Parker, Allen; Chan, Patrick

2014-01-01

The objective of this task is to investigate, develop, and demonstrate a low-cost swept lasing light source for NASA DFRC's fiber optics sensing system (FOSS) to perform structural health monitoring on current and future aerospace vehicles. This is the regular update of the Tunable Laser Development for In-flight Fiber Optic Based Structural Health Monitoring Systems website.

A pulser-sustainer carbon monoxide electric-discharge supersonic laser

NASA Technical Reports Server (NTRS)

Monson, D. J.; Srinivasan, G.

1977-01-01

Operation of a CW CO electric-discharge supersonic laser with a pulser-sustainer discharge is described. High-power operation as well as independent control over electron energy and density are demonstrated. Maximum input power achieved to date is 100 kW. The maximum output power is 6 kW or 10% of the sustainer positive-column power. Much improved performance appears possible.

High-energy laser activities at MBDA Germany

NASA Astrophysics Data System (ADS)

Mohring, Bernd; Dietrich, Stephan; Tassini, Leonardo; Protz, Rudolf; Geidek, Franz; Zoz, Jürgen

2013-05-01

At MBDA Germany a concept for a high-energy laser weapon system is investigated, which is based on existing industrial laser sources. Due to the enormous progress in the field of high-power fiber lasers, commercial industrial fiber lasers are now available delivering a nearly-diffraction limited beam quality with power levels of up to 10 kW. By using a geometric beam coupling scheme, a number of individual high-power fiber laser beams are combined together using one common beam director telescope. A total laser beam power of more than 100 kW can be achieved, which is sufficient for an operational laser weapon system. The individual beams from the different lasers are steered by servo-loops using fast tip-tilt mirrors. This principle enables the concentration of the total laser beam power at one common focal point on a distant target, also allowing fine tracking of target movements and first-order compensation of turbulence effects on laser beam propagation. The proposed beam combination concept was demonstrated by using different experimental set-ups. A number of experiments were performed successfully to investigate laser beam target interaction and target fine tracking, also at large distances and at moving targets. Content and results of these investigations are reported, which demonstrate the complete engagement sequence for a C-RAM scenario. This includes subsequent steps of target acquisition by radar and IR optics, followed by large angle coarse tracking, active fine tracking and destruction of the target by the laser system. This successful implementation of geometric beam combining is an important step for the realization of a laser weapon system in the near future.

Random lasers for lab-on-chip applications

NASA Astrophysics Data System (ADS)

Giehl, J. M.; Butzbach, F.; Jorge, K. C.; Alvarado, M. A.; Carreño, M. N. P.; Alayo, M. I.; Wetter, N. U.

2016-04-01

Random lasers are laser sources in which the feedback is provided by scattering instead of reflection and which, for this reason, do not require surfaces with optical finish such as mirrors. The investigation of such lasing action in a large variety of disordered materials is a subject of high interest with very important applications such as threedimensional and speckle-free imaging, detection of cancer tissue and photonic coding and encryption. However, potential applications require optimization of random laser performance especially with respect to optical efficiency and directionality or brightness. This work demonstrates such an optimization procedure with the goal of achieving a random laser with sufficient efficiency and brightness in order to be used in practical applications. Two random lasers are demonstrated, one solid and on liquid, that fulfil directionality and efficiency requirements. The first one consists of a neodymium doped powder laser with a record slope efficiency of 1.6%. The second one is a liquid random laser injected into a HC-ARROW waveguide which uses a microchannel connected to a much larger reservoir in order to achieve the necessary directionality. Both devices can be produced by low cost fabricating technologies and easily integrated into next-generation, lab-on-chip devices used for in-situ determination of infectious tropical diseases, which is the main goal of this project.

The development of novel Ytterbium fiber lasers and their applications

NASA Astrophysics Data System (ADS)

Nie, Bai

The aim of my Ph.D. research is to push the fundamental limits holding back the development of novel Yb fiber lasers with high pulse energy and short pulse duration. The purpose of developing these lasers is to use them for important applications such as multiphoton microscopy and laser-induced breakdown spectroscopy. My first project was to develop a short-pulse high-energy ultrafast fiber laser for multiphoton microscopy. To achieve high multiphoton efficiency and depth resolved tissue imaging, ultrashort pulse duration and high pulse energy are required. In order to achieve this, an all-normal dispersion cavity design was adopted. Output performances of the built lasers were investigated by varying several cavity parameters, such as pump laser power, fiber length and intra-cavity spectral filter bandwidth. It was found that the length of the fiber preceding the gain fiber is critical to the laser performance. Generally, the shorter the fiber is, the broader the output spectrum is. The more interesting parameter is the intra-cavity spectral filter bandwidth. Counter intuitively, laser cavities using narrower bandwidth spectral filters generated much broader spectra. It was also found that fiber lasers with very narrow spectral filters produced laser pulses with parabolic profile, which are referred to as self-similar pulses or similaritons. This type of pulse can avoid wave-breaking and is an optimal approach to generate pulses with high pulse energy and ultrashort pulse duration. With a 3nm intra-cavity spectral filter, output pulses with about 20 nJ pulse energy were produced and compressed to about 41 fs full-width-at-half-maximum (FWHM) pulse duration. Due to the loss in the compression device, the peak power of the compressed pulses is about 250 kW. It was the highest peak power generated from a fiber oscillator when this work was published. This laser was used for multiphoton microscopy on living tissues like Drosophila larva and fruit fly wings. Several imaging methods, such as two-photon-excited fluorescence, second harmonic generation, and third harmonic generation, were performed. Not only were single layers of thin tissue imaged, but also depth resolved imaging of thick samples was tested, and three-dimensional image reconstruction was demonstrated. The other project was to develop a simple fiber oscillator for laser-induced breakdown spectroscopy (LIBS). Laser pulses with high energy, high ablation efficiency and low ablation threshold are desirable for this application. We built a fiber laser using up to 200 m long fiber and scaled the output pulse energy up to 450 nJ. This laser was operated in an unusual mode-locking regime and produced noise-like pulses, which have a picosecond long pulse envelope containing multiple irregular femtosecond sub-pulses. This type of pulse was mostly ignored by many earlier researchers. Intra-cavity spectral filters did not affect the laser performance as much as in the similariton lasers and were removed from the laser cavity. Characteristics of our noise-like laser, such as MHz repetition rate, broad spectrum, and picosecond-long pulse envelope containing multiple femtosecond sub-pulses, were found to meet the requirement of an ideal laser source for LIBS. A simple LIBS setup using our laser was demonstrated and atomic emission spectra with very good signal-to-noise ratio were obtained. Composition detection, qualitative concentration determination, and trace detection were also tested. These tests show that our noise-like fiber laser is an ideal laser source for a low-cost and portable LIBS system.

High-Brightness Lasers with Spectral Beam Combining on Silicon

NASA Astrophysics Data System (ADS)

Stanton, Eric John

Modern implementations of absorption spectroscopy and infrared-countermeasures demand advanced performance and integration of high-brightness lasers, especially in the molecular fingerprint spectral region. These applications, along with others in communication, remote-sensing, and medicine, benefit from the light source comprising a multitude of frequencies. To realize this technology, a single multi-spectral optical beam of near-diffraction-limited divergence is created by combining the outputs from an array of laser sources. Full integration of such a laser is possible with direct bonding of several epitaxially-grown chips to a single silicon (Si) substrate. In this platform, an array of lasers is defined with each gain material, creating a densely spaced set of wavelengths similar to wavelength division multiplexing used in communications. Scaling the brightness of a laser typically involves increasing the active volume to produce more output power. In the direction transverse to the light propagation, larger geometries compromise the beam quality. Lengthening the cavity provides only limited scaling of the output power due to the internal losses. Individual integrated lasers have low brightness due to combination of thermal effects and high optical intensities. With heterogeneous integration, many lasers can be spectrally combined on a single integrated chip to scale brightness in a compact platform. Recent demonstrations of 2.0-microm diode and 4.8-microm quantum cascade lasers on Si have extended this heterogeneous platform beyond the telecommunications band to the mid-infrared. In this work, low-loss beam combining elements spanning the visible to the mid-infrared are developed and a high-brightness multi-spectral laser is demonstrated in the range of 4.6-4.7-microm wavelengths. An architecture is presented where light is combined in multiple stages: first within the gain-bandwidth of each laser material and then coarsely between each spectral band to a single output waveguide. All components are demonstrated on a common material platform with a Si substrate, which lends feasibility to the complete system integration. Particular attention is focused on improving the efficiency of arrayed waveguide gratings (AWGs), used in the dense wavelength combining stage. This requires development of a refined characterization technique involving AWGs in a ring-resonator configuration to reduce measurement uncertainty. New levels of low-loss are achieved for visible, near-infrared, and mid-infrared multiplexing devices. Also, a multi-spectral laser in the mid-infrared is demonstrated by integrating an array of quantum cascade lasers and an AWG with Si waveguides. The output power and spectra are measured, demonstrating efficient beam combining and power scaling. Thus, a bright laser source in the mid-infrared has been demonstrated, along with an architecture and the components for incorporating visible and near-infrared optical bands.

Requirements and Technology Advances for Global Wind Measurement with a Coherent Lidar: A Shrinking Gap

NASA Technical Reports Server (NTRS)

Kavaya, Michael J.; Kavaya, Michael J.; Yu, Jirong; Koch, Grady J.; Amzajerdian, Farzin; Singh, Upendra N.; Emmitt, G. David

2007-01-01

Early concepts to globally measure vertical profiles of vector horizontal wind from space planned on an orbit height of 525 km, a single pulsed coherent Doppler lidar system to cover the full troposphere, and a continuously rotating telescope/scanner that mandated a vertical line of sight wind profile from each laser shot. Under these conditions system studies found that laser pulse energies of approximately 20 J at 10 Hz pulse repetition rate with a rotating telescope diameter of approximately 1.5 m was required. Further requirements to use solid state laser technology and an eyesafe wavelength led to the relatively new 2-micron solid state laser. With demonstrated pulse energies near 20 mJ at 5 Hz, and no demonstration of a rotating telescope maintaining diffraction limited performance in space, the technology gap between requirements and demonstration was formidable. Fortunately the involved scientists and engineers set out to reduce the gap, and through a combination of clever ideas and technology advances over the last 15 years, they have succeeded. This paper will detail the gap reducing factors and will present the current status.

On-sky demonstration of matched filters for wavefront measurements using ELT-scale elongated laser guide stars

NASA Astrophysics Data System (ADS)

Basden, A. G.; Bardou, L.; Bonaccini Calia, D.; Buey, T.; Centrone, M.; Chemla, F.; Gach, J. L.; Gendron, E.; Gratadour, D.; Guidolin, I.; Jenkins, D. R.; Marchetti, E.; Morris, T. J.; Myers, R. M.; Osborn, J.; Reeves, A. P.; Reyes, M.; Rousset, G.; Lombardi, G.; Townson, M. J.; Vidal, F.

2017-04-01

The performance of adaptive optics systems is partially dependent on the algorithms used within the real-time control system to compute wavefront slope measurements. We demonstrate the use of a matched filter algorithm for the processing of elongated laser guide star (LGS) Shack-Hartmann images, using the CANARY adaptive optics instrument on the 4.2 m William Herschel Telescope and the European Southern Observatory Wendelstein LGS Unit placed 40 m away. This algorithm has been selected for use with the forthcoming Thirty Meter Telescope, but until now had not been demonstrated on-sky. From the results of a first observing run, we show that the use of matched filtering improves our adaptive optics system performance, with increases in on-sky H-band Strehl measured up to about a factor of 1.1 with respect to a conventional centre of gravity approach. We describe the algorithm used, and the methods that we implemented to enable on-sky demonstration.

Laser beam coupling with capillary discharge plasma for laser wakefield acceleration applications

NASA Astrophysics Data System (ADS)

Bagdasarov, G. A.; Sasorov, P. V.; Gasilov, V. A.; Boldarev, A. S.; Olkhovskaya, O. G.; Benedetti, C.; Bulanov, S. S.; Gonsalves, A.; Mao, H.-S.; Schroeder, C. B.; van Tilborg, J.; Esarey, E.; Leemans, W. P.; Levato, T.; Margarone, D.; Korn, G.

2017-08-01

One of the most robust methods, demonstrated to date, of accelerating electron beams by laser-plasma sources is the utilization of plasma channels generated by the capillary discharges. Although the spatial structure of the installation is simple in principle, there may be some important effects caused by the open ends of the capillary, by the supplying channels etc., which require a detailed 3D modeling of the processes. In the present work, such simulations are performed using the code MARPLE. First, the process of capillary filling with cold hydrogen before the discharge is fired, through the side supply channels is simulated. Second, the simulation of the capillary discharge is performed with the goal to obtain a time-dependent spatial distribution of the electron density near the open ends of the capillary as well as inside the capillary. Finally, to evaluate the effectiveness of the beam coupling with the channeling plasma wave guide and of the electron acceleration, modeling of the laser-plasma interaction was performed with the code INF&RNO.

Effect of axial length on laser spot size during photodynamic therapy: an experimental study in monkeys.

PubMed

Kondo, Mineo; Ito, Yasuki; Miyata, Kentaro; Kondo, Nagako; Ishikawa, Kohei; Terasaki, Hiroko

2006-01-01

To investigate the effect of shorter axial length on the laser spot size and laser energy during photodynamic therapy (PDT) in monkeys. Experimental study with four rhesus monkeys. PDT was performed on the normal retina of monkeys whose ocular axial lengths are shorter (19.55 to 20.25 mm) than that of humans. After the PDT, the eyes were enucleated, and the diameter of the irradiated laser spot was measured with a microcaliper. The area of actual laser spot was only 0.56 to 0.61 times of the planned area, which indicated that the laser energy/area was 1.64 to 1.78 times more intense than planned initially. These results are the in vivo demonstration that the diameter of PDT laser spot is smaller for eyes with shorter axial lengths.

Free space broad-bandwidth tunable laser diode based on Littman configuration for 3D profile measurement

NASA Astrophysics Data System (ADS)

Shirazi, Muhammad Faizan; Kim, Pilun; Jeon, Mansik; Kim, Chang-Seok; Kim, Jeehyun

2018-05-01

We developed a tunable laser diode for an optical coherence tomography system that can perform three-dimensional profile measurement using an area scanning technique. The tunable laser diode is designed using an Eagleyard tunable laser diode with a galvano filter. The Littman free space configuration is used to demonstrate laser operation. The line- and bandwidths of this source are 0.27 nm (∼110 GHz) and 43 nm, respectively, at the center wavelength of 860 nm. The output power is 20 mW at an operating current of 150 mA. A step height target is imaged using a wide-area scanning system to show the measurement accuracy of the proposed tunable laser diode. A TEM grid is also imaged to measure the topography and thickness of the sample by proposed tunable laser diode.

Investigation of continuous wave and pulsed laser performance based on Nd3+:Gd0.6Y1.4SiO5 crystal

NASA Astrophysics Data System (ADS)

Feng, Chao; Liu, Zhaojun; Cong, Zhenhua; Shen, Hongbin; Li, Yongfu; Wang, Qingpu; Fang, Jiaxiong; Xu, Xiaodong; Xu, Jun; Zhang, Xingyu

2015-12-01

We systematically investigated a laser diode (LD) pumped Nd:GYSO (Nd3+:Gd0.6Y1.4SiO5) laser. The output power of the continuous wave laser was as high as 3.5 W with a slope efficiency of 31.8%. In the Q-switched operation; the laser exhibited dual-wavelengths output (1073.6 nm and 1074.7 nm) synchronously with a Cr4+:YAG as the saturable absorber (SA). Additionally, a passively mode-locked laser was demonstrated using a semiconductor SA mirror with a maximum average output power of 510 mW at a central wavelength of 1074 nm, while the pulse width of the laser was as short as 5 ps. Our experiment proved that the Nd:GYSO mixed crystal was a promising material for a solid-state laser.

Pedestal cleaning for high laser pulse contrast ratio with a 100 TW class laser system.

PubMed

Fourmaux, S; Payeur, S; Buffechoux, S; Lassonde, P; St-Pierre, C; Martin, F; Kieffer, J C

2011-04-25

Laser matter interaction at relativistic intensities using 100 TW class laser systems or higher is becoming more and more widespread. One of the critical issues of such laser systems is to let the laser pulse interact at high intensity with the solid target and avoid any pre-plasma. Thus, a high Laser Pulse Contrast Ratio (LPCR) parameter is of prime importance. We present the LPCR characterization of a high repetition 100 TW class laser system. We demonstrate that the generated Amplified Spontaneous Emission (ASE) degrades the overall LPCR performance. We propose a simple way to clean the pulse after the first amplification stage by introducing a solid state saturable absorber which results in a LPCR improvement to better than 10(10) with only a 30% energy loss at a 10 Hz repetition rate. We finally correlated this cleaning method with experimental results.

Excimer laser decontamination

NASA Astrophysics Data System (ADS)

Sentis, Marc L.; Delaporte, Philippe C.; Marine, Wladimir; Uteza, Olivier P.

2000-04-01

The application of excimer laser ablation process to the decontamination of radioactive surfaces is discussed. This technology is very attractive because it allows to efficiently remove the contaminated particles without secondary waste production. To demonstrate the capability of such technology to efficiently decontaminate large area, we studied and developed a prototype which include a XeCl laser, an optical fiber delivery system and an ablated particles collection cell. The main physical processes taking place during UV laser ablation will be explained. The influence of laser wavelength, pulse duration and absorption coefficient of material will be discussed. Special studies have been performed to understand the processes which limit the transmission of high average power excimer laser through optical fiber, and to determine the laser conditions to optimize the value of this transmission. An in-situ spectroscopic analysis of laser ablation plasma allows the real time control of the decontamination. The results obtained for painting or metallic oxides removal from stainless steel surfaces will be presented.

Laser-plasma interactions in magnetized environment

NASA Astrophysics Data System (ADS)

Shi, Yuan; Qin, Hong; Fisch, Nathaniel J.

2018-05-01

Propagation and scattering of lasers present new phenomena and applications when the plasma medium becomes strongly magnetized. With mega-Gauss magnetic fields, scattering of optical lasers already becomes manifestly anisotropic. Special angles exist where coherent laser scattering is either enhanced or suppressed, as we demonstrate using a cold-fluid model. Consequently, by aiming laser beams at special angles, one may be able to optimize laser-plasma coupling in magnetized implosion experiments. In addition, magnetized scattering can be exploited to improve the performance of plasma-based laser pulse amplifiers. Using the magnetic field as an extra control variable, it is possible to produce optical pulses of higher intensity, as well as compress UV and soft x-ray pulses beyond the reach of other methods. In even stronger giga-Gauss magnetic fields, laser-plasma interaction enters a relativistic-quantum regime. Using quantum electrodynamics, we compute a modified wave dispersion relation, which enables correct interpretation of Faraday rotation measurements of strong magnetic fields.

Progress Toward Measuring CO2 Isotopologue Fluxes in situ with the LLNL Miniature, Laser-based CO2 Sensor

NASA Astrophysics Data System (ADS)

Osuna, J. L.; Bora, M.; Bond, T.

2015-12-01

One method to constrain photosynthesis and respiration independently at the ecosystem scale is to measure the fluxes of CO2­ isotopologues. Instrumentation is currently available to makes these measurements but they are generally costly, large, bench-top instruments. Here, we present progress toward developing a laser-based sensor that can be deployed directly to a canopy to passively measure CO2 isotopologue fluxes. In this study, we perform initial proof-of-concept and sensor characterization tests in the laboratory and in the field to demonstrate performance of the Lawrence Livermore National Laboratory (LLNL) tunable diode laser flux sensor. The results shown herein demonstrate measurement of bulk CO2 as a first step toward achieving flux measurements of CO2 isotopologues. The sensor uses a Vertical Cavity Surface Emitting Laser (VCSEL) in the 2012 nm range. The laser is mounted in a multi-pass White Cell. In order to amplify the absorption signal of CO2 in this range we employ wave modulation spectroscopy, introducing an alternating current (AC) bias component where f is the frequency of modulation on the laser drive current in addition to the direct current (DC) emission scanning component. We observed a strong linear relationship (r2 = 0.998 and r2 = 0.978 at all and low CO2 concentrations, respectively) between the 2f signal and the CO2 concentration in the cell across the range of CO2 concentrations relevant for flux measurements. We use this calibration to interpret CO2 concentration of a gas flowing through the White cell in the laboratory and deployed over a grassy field. We will discuss sensor performance in the lab and in situ as well as address steps toward achieving canopy-deployed, passive measurements of CO2 isotopologue fluxes. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-675788

Thermal management of quantum cascade lasers in an individually addressable monolithic array architecture

NASA Astrophysics Data System (ADS)

Missaggia, Leo; Wang, Christine; Connors, Michael; Saar, Brian; Sanchez-Rubio, Antonio; Creedon, Kevin; Turner, George; Herzog, William

2016-03-01

There are a number of military and commercial applications for high-power laser systems in the mid-to-long-infrared wavelength range. By virtue of their demonstrated watt-level performance and wavelength diversity, quantum cascade laser (QCL) and amplifier devices are an excellent choice of emitter for those applications. To realize the power levels of interest, beam combining of arrays of these emitters is required and as a result, array technology must be developed. With this in mind, packaging and thermal management strategies were developed to facilitate the demonstration of a monolithic QCL array operating under CW conditions. Thermal models were constructed and simulations performed to determine the effect of parameters such as array-element ridge width and pitch on gain region temperature rise. The results of the simulations were considered in determining an appropriate QCL array configuration. State-of-the-art micro-impingement cooling along with an electrical distribution scheme comprised of AlN multi-layer technology were integrated into the design. The design of the module allows for individual electrical addressability of the array elements, a method of phase control demonstrated previously for coherent beam combining of diode arrays, along with access to both front and rear facets. Hence, both laser and single-pass amplifier arrays can be accommodated. A module was realized containing a 5 mm cavity length monolithic QCL array comprised of 7 elements on 450 m pitch. An output power of 3.16 W was demonstrated under CW conditions at an emission wavelength of 9μm.

Development of an Airborne Micropulse Water Vapor DIAL

NASA Astrophysics Data System (ADS)

Nehrir, A. R.; Ismail, S.

2012-12-01

Water vapor plays a key role in many atmospheric processes affecting both weather and climate. Airborne measurements of tropospheric water vapor profiles have been a longstanding observational need to not only the active remote sensing community but also to the meteorological, weather forecasting, and climate/radiation science communities. Microscale measurements of tropospheric water vapor are important for enhancing near term meteorological forecasting capabilities while mesoscale and synopticscale measurements can lead to an enhanced understanding of the complex coupled feedback mechanisms between water vapor, temperature, aerosols, and clouds. To realize tropospheric measurements of water vapor profiles over the microscale-synopticscale areas of meteorological interest, a compact and cost effective airborne micropulse differential absorption lidar (DIAL) is being investigated using newly emerging semiconductor based laser technology. Ground based micropulse DIAL (MPD) measurements of tropospheric water vapor and aerosol profiles up to 6 km and 15 km, respectively, have been previously demonstrated using an all semiconductor based laser transmitter. The DIAL transmitter utilizes a master oscillator power amplifier (MOPA) configuration where two semiconductor seed lasers are used to seed a single pass traveling wave tapered semiconductor optical amplifier (TSOA), producing up to 7μJ pulse energies over a 1 μs pulse duration at a 10 kHz pulse repetition frequency (PRF). Intercomparisons between the ground based instrument measurements and radiosonde profiles demonstrating the MPD performance under varying atmospheric conditions will be presented. Work is currently ongoing to expand upon the ground based MPD concept and to develop a compact and cost effective system capable of deployment on a mid-low altitude aircraft such as the NASA Langley B200 King Air. Initial lab experiments show that a two-three fold increase in the laser energy compared to the ground based instrument is achievable via overdriven current pulses to the TSOA gain medium while maintaining a 1μs and 10 kHz pulse width and PRF, respectively. The increase in the laser transmitter pulse energy will allow for nighttime and daytime water vapor profile retrievals from an airborne platform operating at an 8 km altitude with 2-5 minute integration periods. Results from a numerical model demonstrating the performance of an airborne DIAL system with the mentioned transmitter enhancements will be presented and compared against the existing ground based instrument performance. Furthermore, results from laboratory experiments demonstrating the laser transmitter performance including maximum extractable energy, energy stability, and spectral purity will also be presented.

Investigation on gas medium parameters for an ArF excimer laser through orthogonal experimental design

NASA Astrophysics Data System (ADS)

Song, Xingliang; Sha, Pengfei; Fan, Yuanyuan; Jiang, R.; Zhao, Jiangshan; Zhou, Yi; Yang, Junhong; Xiong, Guangliang; Wang, Yu

2018-02-01

Due to complex kinetics of formation and loss mechanisms, such as ion-ion recombination reaction, neutral species harpoon reaction, excited state quenching and photon absorption, as well as their interactions, the performance behavior of different laser gas medium parameters for excimer laser varies greatly. Therefore, the effects of gas composition and total gas pressure on excimer laser performance attract continual research studies. In this work, orthogonal experimental design (OED) is used to investigate quantitative and qualitative correlations between output laser energy characteristics and gas medium parameters for an ArF excimer laser with plano-plano optical resonator operation. Optimized output laser energy with good pulse to pulse stability can be obtained effectively by proper selection of the gas medium parameters, which makes the most of the ArF excimer laser device. Simple and efficient method for gas medium optimization is proposed and demonstrated experimentally, which provides a global and systematic solution. By detailed statistical analysis, the significance sequence of relevant parameter factors and the optimized composition for gas medium parameters are obtained. Compared with conventional route of varying single gas parameter factor sequentially, this paper presents a more comprehensive way of considering multivariables simultaneously, which seems promising in striking an appropriate balance among various complicated parameters for power scaling study of an excimer laser.

Effect of tapered magnetic field on expanding laser-produced plasma for heavy-ion inertial fusion

DOE PAGES

Kanesue, Takeshi; Ikeda, Shunsuke

2016-12-20

A laser ion source is a promising candidate as an ion source for heavy ion inertial fusion (HIF), where a pulsed ultra-intense and low-charged heavy ion beam is required. It is a key development for a laser ion source to transport laser-produced plasma with a magnetic field to achieve a high current beam. The effect of a tapered magnetic field on laser produced plasma is demonstrated by comparing the results with a straight solenoid magnet. The magnetic field of interest is a wider aperture on a target side and narrower aperture on an extraction side. Furthermore, based on the experimentallymore » obtained results, the performance of a scaled laser ion source for HIF was estimated.« less

Active stabilization of a diode laser injection lock.

PubMed

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

2016-06-01

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

High-performance continuous-wave room temperature 4.0-μm quantum cascade lasers with single-facet optical emission exceeding 2 W

PubMed Central

Lyakh, A.; Maulini, R.; Tsekoun, A.; Go, R.; Von der Porten, S.; Pflügl, C.; Diehl, L.; Capasso, Federico; Patel, C. Kumar N.

2010-01-01

A strain-balanced, AlInAs/InGaAs/InP quantum cascade laser structure, designed for light emission at 4.0 μm using nonresonant extraction design approach, was grown by molecular beam epitaxy. Laser devices were processed in buried heterostructure geometry. An air-cooled laser system incorporating a 10-mm × 11.5-μm laser with antireflection-coated front facet and high-reflection-coated back facet delivered over 2 W of single-ended optical power in a collimated beam. Maximum continuous-wave room temperature wall plug efficiency of 5.0% was demonstrated for a high-reflection-coated 3.65-mm × 8.7-μm laser mounted on an aluminum nitride submount.

Proton-transfer lasers based on solid copolymers of modified 2-(2'-hydroxyphenyl)benzimidazoles with methacrylate monomers

NASA Astrophysics Data System (ADS)

Costela, A.; García-Moreno, I.; Mallavia, Ricardo; Amat-Guerri, F.; Barroso, J.; Sastre, R.

1998-06-01

We report on the lasing action of two newly synthesized 2-(2'-hydroxyphenyl) benzimidazole derivatives copolymerized with methyl methacrylate. The laser samples were transversely pumped with a N 2 laser at 337 nm. The influence on the proton-transfer laser performance of the distance between the chromophore group and the polymeric main chain and of the rigidity of the polymeric host matrix, were studied. Significant increases in lasing efficiency and photostability are demonstrated for some of the new materials, as compared to those previously obtained with related proton-transfer dyes also covalently bound to methacrylic monomers.

Laser-induced damage of intrinsic and extrinsic defects by picosecond pulses on multilayer dielectric coatings for petawatt-class lasers

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

Negres, Raluca A.; Carr, Christopher W.; Laurence, Ted A.

2016-08-01

Here, we describe a damage testing system and its use in investigating laser-induced optical damage initiated by both intrinsic and extrinsic precursors on multilayer dielectric coatings suitable for use in high-energy, large-aperture petawatt-class lasers. We employ small-area damage test methodologies to evaluate the intrinsic damage resistance of various coatings as a function of deposition methods and coating materials under simulated use conditions. In addition, we demonstrate that damage initiation by raster scanning at lower fluences and growth threshold testing are required to probe the density of extrinsic defects, which will limit large-aperture optics performance.

Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes

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

Phillips, Mark C.; Brumfield, Brian E.; LaHaye, Nicole

Here, we demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from 235U and 238U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security.

Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes

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

Phillips, Mark C.; Brumfield, Brian E.; LaHaye, Nicole L.

We demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from 235U and 238U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security applications.

Thermo-elasto-plastic simulations of femtosecond laser-induced multiple-cavity in fused silica

NASA Astrophysics Data System (ADS)

Beuton, R.; Chimier, B.; Breil, J.; Hébert, D.; Mishchik, K.; Lopez, J.; Maire, P. H.; Duchateau, G.

2018-04-01

The formation and the interaction of multiple cavities, induced by tightly focused femtosecond laser pulses, are studied using a developed numerical tool, including the thermo-elasto-plastic material response. Simulations are performed in fused silica in cases of one, two, and four spots of laser energy deposition. The relaxation of the heated matter, launching shock waves in the surrounding cold material, leads to cavity formation and emergence of areas where cracks may be induced. Results show that the laser-induced structure shape depends on the energy deposition configuration and demonstrate the potential of the used numerical tool to obtain the desired designed structure or technological process.

Adaptive Tunable Laser Spectrometer for Space Applications

NASA Technical Reports Server (NTRS)

Flesch, Gregory; Keymeulen, Didier

2010-01-01

An architecture and process for the rapid prototyping and subsequent development of an adaptive tunable laser absorption spectrometer (TLS) are described. Our digital hardware/firmware/software platform is both reconfigurable at design time as well as autonomously adaptive in real-time for both post-integration and post-launch situations. The design expands the range of viable target environments and enhances tunable laser spectrometer performance in extreme and even unpredictable environments. Through rapid prototyping with a commercial RTOS/FPGA platform, we have implemented a fully operational tunable laser spectrometer (using a highly sensitive second harmonic technique). With this prototype, we have demonstrated autonomous real-time adaptivity in the lab with simulated extreme environments.

Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes

DOE PAGES

Phillips, Mark C.; Brumfield, Brian E.; LaHaye, Nicole; ...

2017-06-19

Here, we demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from 235U and 238U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security.

Ultrafast, high repetition rate, ultraviolet, fiber-laser-based source: application towards Yb⁺ fast quantum-logic.

PubMed

Hussain, Mahmood Irtiza; Petrasiunas, Matthew Joseph; Bentley, Christopher D B; Taylor, Richard L; Carvalho, André R R; Hope, Joseph J; Streed, Erik W; Lobino, Mirko; Kielpinski, David

2016-07-25

Trapped ions are one of the most promising approaches for the realization of a universal quantum computer. Faster quantum logic gates could dramatically improve the performance of trapped-ion quantum computers, and require the development of suitable high repetition rate pulsed lasers. Here we report on a robust frequency upconverted fiber laser based source, able to deliver 2.5 ps ultraviolet (UV) pulses at a stabilized repetition rate of 300.00000 MHz with an average power of 190 mW. The laser wavelength is resonant with the strong transition in Ytterbium (Yb⁺) at 369.53 nm and its repetition rate can be scaled up using high harmonic mode locking. We show that our source can produce arbitrary pulse patterns using a programmable pulse pattern generator and fast modulating components. Finally, simulations demonstrate that our laser is capable of performing resonant, temperature-insensitive, two-qubit quantum logic gates on trapped Yb⁺ ions faster than the trap period and with fidelity above 99%.

Multi-Billion Shot, High-Fluence Exposure of Cr(4+): YAG Passive Q-Switch

NASA Technical Reports Server (NTRS)

Stephen, Mark A.; Dallas, Joseph L.; Afzal, Robert S.

1997-01-01

NASA's Goddard Space Flight Center is developing the Geoscience Laser Altimeter System (GLAS) employing a diode pumped, Q-Switched, ND:YAG laser operating at 40 Hz repetition rate. To meet the five-year mission lifetime goal, a single transmitter would accumulate over 6.3 billion shots. Cr(4+):YAG is a promising candidate material for passively Q-switching the laser. Historically, the performance of saturable absorbers has degraded over long-duration usage. To measure the multi-billion shot performance of Cr(4+):YAG, a passively Q-switched GLAS-like oscillator was tested at an accelerated repetition rate of 500 Hz. The intracavity fluence was calculated to be approximately 2.5 J/cm(exp 2). The laser was monitored autonomously for 165 days. There was no evidence of change in the material optical properties during the 7.2 billion shot test.. All observed changes in laser operation could be attributed to pump laser diode aging. This is the first demonstration of multi-billion shot exposure testing of Cr(4+):YAG in this pulse energy regime

High-brightness diode pump sources for solid-state and fiber laser pumping across 8xx-9xx nm range

NASA Astrophysics Data System (ADS)

Diamant, Ronen; Berk, Yuri; Cohen, Shalom; Klumel, Genady; Levy, Moshe; Openhaim, Yaki; Peleg, Ophir; Yanson, Dan; Karni, Yoram

2011-06-01

Advanced solid state laser architectures place increasingly demanding requirements on high-brightness, low-cost QCW laser diode pump sources, with custom apertures both for side and end rod pumping configurations. To meet this need, a new series of scalable QCW pump sources at 808nm and 940nm was developed. The stacks, available in multiple output formats, allow for custom aperture filling by varying both the length and quantity of stacked laser bars. For these products, we developed next-generation laser bars based on improved epitaxial wafer designs delivering power densities of 20W/mm of emission aperture. With >200W of peak QCW power available from a full-length 1cm bar, we have demonstrated power scaling to over 2kW in 10-bar stacks with 55% wall plug efficiency. We also present the design and performance of several stack configurations using full-length and reduced-length (mini) bars that demonstrate the versatility of both the bar and packaging designs. We illustrate how the ROBUST HEAD packaging technology developed at SCD is capable of accommodating variable bar length, pitch and quantity for custom rod pumping geometries. The excellent all-around performance of the stacks is supported by reliability data in line with the previously reported 20 Gshot space-grade qualification of SCD's stacks.

Scaleable multi-format QCW pump stacks based on 200W laser diode bars and mini bars at 808nm and 940nm

NASA Astrophysics Data System (ADS)

Berk, Yuri; Karni, Yoram; Klumel, Genady; Openhaim, Yaakov; Cohen, Shalom; Yanson, Dan

2011-03-01

Advanced solid state laser architectures place increasingly demanding requirements on high-brightness, low-cost QCW laser diode pump sources, with custom apertures both for side and end rod pumping configurations. To meet this need, a new series of scaleable pump sources at 808nm and 940nm was developed. The stacks, available in multiple output formats, allow for custom aperture filling by varying both the length and quantity of stacked laser bars. For these products, we developed next-generation laser bars based on improved epitaxial wafer designs delivering power densities of 20W/mm of emission aperture. With >200W of peak QCW power available from a full-length 1cm bar, we have demonstrated power scaling to over 2kW in 10-bar stacks with 55% wall plug efficiency. We also present the design and performance of several stack configurations using full-length and reduced-length (mini) bars that demonstrate the versatility of both the bar and packaging designs. We illustrate how the ROBUST HEAD packaging technology developed at SCD is capable of accommodating variable bar length, pitch and quantity for custom rod pumping geometries. The excellent all-around performance of the stacks is supported by reliability data in line with the previously reported 20 Gshot space-grade qualification of SCD's stacks.

Ultraviolet laser transverse profile shaping for improving x-ray free electron laser performance

DOE PAGES

Li, S.; Alverson, S.; Bohler, D.; ...

2017-08-17

The photocathode rf gun is one of the most critical components in x-ray free electron lasers. The drive laser strikes the photocathode surface, which emits electrons with properties that depend on the shape of the drive laser. Most free electron lasers use photocathodes with work function in the ultraviolet, a wavelength where direct laser manipulation becomes challenging. In this paper, we present a novel application of a digital micromirror device (DMD) for the 253 nm drive laser at the Linear Coherent Light Source. Laser profile shaping is accomplished through an iterative algorithm that takes into account shaping error and efficiency.more » Next, we use laser shaping to control the X-ray laser output via an online optimizer, which shows improvement in FEL pulse energy. Lastly, as a preparation for electron beam shaping, we use the DMD to measure the photocathode quantum efficiency across cathode surface with an averaged laser rms spot size of 59 μm. In conclusion, our experiments demonstrate promising outlook of using DMD to shape ultraviolet lasers for photocathode rf guns with various applications.« less

Ultraviolet laser transverse profile shaping for improving x-ray free electron laser performance

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

Li, S.; Alverson, S.; Bohler, D.

The photocathode rf gun is one of the most critical components in x-ray free electron lasers. The drive laser strikes the photocathode surface, which emits electrons with properties that depend on the shape of the drive laser. Most free electron lasers use photocathodes with work function in the ultraviolet, a wavelength where direct laser manipulation becomes challenging. In this paper, we present a novel application of a digital micromirror device (DMD) for the 253 nm drive laser at the Linear Coherent Light Source. Laser profile shaping is accomplished through an iterative algorithm that takes into account shaping error and efficiency.more » Next, we use laser shaping to control the X-ray laser output via an online optimizer, which shows improvement in FEL pulse energy. Lastly, as a preparation for electron beam shaping, we use the DMD to measure the photocathode quantum efficiency across cathode surface with an averaged laser rms spot size of 59 μm. In conclusion, our experiments demonstrate promising outlook of using DMD to shape ultraviolet lasers for photocathode rf guns with various applications.« less

Ultraviolet laser transverse profile shaping for improving x-ray free electron laser performance

NASA Astrophysics Data System (ADS)

Li, S.; Alverson, S.; Bohler, D.; Egger, A.; Fry, A.; Gilevich, S.; Huang, Z.; Miahnahri, A.; Ratner, D.; Robinson, J.; Zhou, F.

2017-08-01

The photocathode rf gun is one of the most critical components in x-ray free electron lasers. The drive laser strikes the photocathode surface, which emits electrons with properties that depend on the shape of the drive laser. Most free electron lasers use photocathodes with work function in the ultraviolet, a wavelength where direct laser manipulation becomes challenging. In this paper, we present a novel application of a digital micromirror device (DMD) for the 253 nm drive laser at the Linear Coherent Light Source. Laser profile shaping is accomplished through an iterative algorithm that takes into account shaping error and efficiency. Next, we use laser shaping to control the X-ray laser output via an online optimizer, which shows improvement in FEL pulse energy. Lastly, as a preparation for electron beam shaping, we use the DMD to measure the photocathode quantum efficiency across cathode surface with an averaged laser rms spot size of 59 μ m . Our experiments demonstrate promising outlook of using DMD to shape ultraviolet lasers for photocathode rf guns with various applications.

High power, high efficiency, continuous-wave supercontinuum generation using standard telecom fibers.

PubMed

Arun, S; Choudhury, Vishal; Balaswamy, V; Prakash, Roopa; Supradeepa, V R

2018-04-02

We demonstrate a simple module for octave spanning continuous-wave supercontinuum generation using standard telecom fiber. This module can accept any high power ytterbium-doped fiber laser as input. The input light is transferred into the anomalous dispersion region of the telecom fiber through a cascade of Raman shifts. A recently proposed Raman laser architecture with distributed feedback efficiently performs these Raman conversions. A spectrum spanning over 1000nm (>1 octave) from 880 to 1900nm is demonstrated. The average power from the supercontinuum is ~34W with a high conversion efficiency of 44%. Input wavelength agility is demonstrated with similar supercontinua over a wide input wavelength range.

Polar-direct-drive experiments with contoured-shell targets on OMEGA

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

Marshall, F. J.; Radha, P. B.; Bonino, M. J.

Polar-driven direct-drive experiments recently performed on the OMEGA Laser System have demonstrated the efficacy of using a target with a contoured shell with varying thickness to improve the symmetry and fusion performance of the implosion. The polar-driven contoured-shell implosions have substantially reduced low mode perturbations compared to polar-driven spherical-shell implosions as diagnosed by x-ray radiographs up to shell stagnation. As a result, fusion yields were increased by more than a factor of ~2 without increasing the energy of the laser by the use of contoured shells.

Polar-direct-drive experiments with contoured-shell targets on OMEGA

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

Marshall, F. J.; Radha, P. B.; Bonino, M. J.

Polar-driven direct-drive experiments recently performed on the OMEGA Laser System have demonstrated the efficacy of using a target with a contoured shell with varying thickness to improve the symmetry and fusion performance of the implosion. The polar-driven contoured-shell implosions have substantially reduced low mode perturbations compared to polar-driven spherical-shell implosions as diagnosed by x-ray radiographs up to shell stagnation. Fusion yields were increased by more than a factor of ∼2 without increasing the energy of the laser by the use of contoured shells.

Polar-direct-drive experiments with contoured-shell targets on OMEGA

DOE PAGES

Marshall, F. J.; Radha, P. B.; Bonino, M. J.; ...

2016-01-28

Polar-driven direct-drive experiments recently performed on the OMEGA Laser System have demonstrated the efficacy of using a target with a contoured shell with varying thickness to improve the symmetry and fusion performance of the implosion. The polar-driven contoured-shell implosions have substantially reduced low mode perturbations compared to polar-driven spherical-shell implosions as diagnosed by x-ray radiographs up to shell stagnation. As a result, fusion yields were increased by more than a factor of ~2 without increasing the energy of the laser by the use of contoured shells.

Design and performance of an astigmatism-compensated self-mode-locked ring-cavity Ti:sapphire laser

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

Shen, Y.; Dai, J.; Wang, Q.

1996-12-31

Based on the nonlinear ABCD matrix and the renormalized q-parameter for Gaussian-beam propagation, self-focusing in conjunction with a spatial gain profile for self-mode locking in a ring-cavity Ti:sapphire laser is analyzed. In the experiment, an astigmatism-compensated self-mode-locked ring-cavity Ti:sapphire laser is demonstrated, and self-mode-locked operation is achieved in both bidirection and unidirection with pulse durations as short as 36 fs and 32 fs, respectively. The experimental observations are in good agreement with theoretical predictions.

Fabrication of computer-generated holograms using femtosecond laser direct writing.

PubMed

Berlich, René; Richter, Daniel; Richardson, Martin; Nolte, Stefan

2016-04-15

We demonstrate a single-step fabrication method for computer-generated holograms based on femtosecond laser direct writing. Therefore, a tightly arranged longitudinal waveguide array is directly inscribed into a transparent material. By tailoring the individual waveguide length, the phase profile of an incident laser beam can be arbitrarily adapted. The approach is verified in common borosilicate glass by inscribing a designed phase hologram, which forms the desired intensity pattern in its far field. The resulting performance is analyzed, and the potential as well as limitations of the method are discussed.

Bandgap engineering of InGaAsP/InP laser structure by photo-absorption-induced point defects

NASA Astrophysics Data System (ADS)

Kaleem, Mohammad; Nazir, Sajid; Saqib, Nazar Abbas

2016-03-01

Integration of photonic components on the same photonic wafer permits future optical communication systems to be dense and advanced performance. This enables very fast information handling between photonic active components interconnected through passive optical low loss channels. We demonstrate the UV-Laser based Quantum Well Intermixing (QWI) procedure to engineer the band-gap of compressively strained InGaAsP/InP Quantum Well (QW) laser material. We achieved around 135nm of blue-shift by simply applying excimer laser (λ= 248nm). The under observation laser processed material also exhibits higher photoluminescence (PL) intensity. Encouraging experimental results indicate that this simple technique has the potential to produce photonic integrated devices and circuits.

Evaluation of the communication quality of free-space laser communication based on the power-in-the-bucket method.

PubMed

Yin, Xianghui; Wang, Rui; Wang, Shaoxin; Wang, Yukun; Jin, Chengbin; Cao, Zhaoliang; Xuan, Li

2018-02-01

Atmospheric turbulence seriously affects the quality of free-space laser communication. The Strehl ratio (SR) is used to evaluate the effect of atmospheric turbulence on the receiving energy of free-space laser communication systems. However, the SR method does not consider the area of the laser-receiving end face. In this study, the power-in-the-bucket (PIB) method is demonstrated to accurately evaluate the effect of turbulence on the receiving energy. A theoretical equation is first obtained to calculate PIB. Simulated and experimental validations are then performed to verify the effectiveness of the theoretical equation. This work may provide effective guidance for the design and evaluation of free-space laser communication systems.

Development of highly efficient laser bars emitting at around 1060 nm for medical applications

NASA Astrophysics Data System (ADS)

Pietrzak, Agnieszka; Zorn, Martin; Meusel, Jens; Huelsewede, Ralf; Sebastian, Juergen

2018-02-01

An overview is presented on the recent progress in the development of high power laser bars at wavelengths around 1060nm. The development is focused on highly efficient and reliable laser performance under pulsed operation for medical applications. The epitaxial structure and lateral layout of the laser bars were tailored to meet the application requirements. Reliable operation peak powers of 350W and 500W are demonstrated from laser bars with fill-factor FF=75% and resonator lengths 1.5mm and 2.0mm, respectively. Moreover, 60W at current 65A with lifetime <10.000h are presented. The power scaling with fill-factor enables a cost reduction ($/W) up to 35%.

Ultralow-threshold Kerr-lens mode-locked Ti:Al(2)O(3) laser.

PubMed

Kowalevicz, A M; Schibli, T R; Kärtner, F X; Fujimoto, J G

2002-11-15

An ultralow-threshold Kerr-lens mode-locked Ti:Al(2)O(3) laser achieved by use of an extended cavity design is demonstrated. Mode-locking thresholds as low as 156 mW are achieved. Pulses with durations as short as 14 fs and bandwidths of >100 nm with output powers of ~15 mW at 50-MHz repetition rates are generated by only 200 mW of pump power. Reducing the pump power requirements to a factor of 10x less than required by most conventional Kerr-lens mode-locked lasers permits inexpensive, low-power pump lasers to be used. This will facilitate the development of low-cost, high-performance femtosecond Ti:Al(2)O(3) laser technology.

Multichannel fiber laser Doppler vibrometer studies of low momentum and hypervelocity impacts

NASA Astrophysics Data System (ADS)

Posada-Roman, Julio E.; Jackson, David A.; Cole, Mike J.; Garcia-Souto, Jose A.

2017-12-01

A multichannel optical fiber laser Doppler vibrometer was demonstrated with the capability of making simultaneous non-contact measurements of impacts at 3 different locations. Two sets of measurements were performed, firstly using small ball bearings (1 mm-5.5 mm) falling under gravity and secondly using small projectiles (1 mm) fired from an extremely high velocity light gas gun (LGG) with speeds in the range 1 km/s-8 km/s. Determination of impact damage is important for industries such as aerospace, military and rail, where the effect of an impact on the structure can result in a major structural damage. To our knowledge the research reported here demonstrates the first trials of a multichannel fiber laser Doppler vibrometer being used to detect hypervelocity impacts.

Tunable and mode-locked laser action of Cr4+ in codoped forsterite Cr, Sc:Mg2SiO4

NASA Astrophysics Data System (ADS)

Sanina, V. V.; Mitrokhin, V. P.; Subbotin, K. A.; Lis, D. A.; Lis, O. N.; Ivanov, A. A.; Zharikov, E. V.

2018-01-01

The laser oscillation of tetravalent chromium and scandium codoped forsterite Cr4+,Sc:Mg2SiO4 single crystal has been demonstrated for the first time for continuous wave, tunable and mode-locked regimes. For comparison, the laser experiments have also been performed in the same configuration with the reference forsterite single crystal solely doped by chromium. The aim of scandium codoping is to inhibit the formation of parasitic trivalent chromium in the crystal. The crystal with scandium demonstrates a wider tuning range, lower lasing threshold and wider mode-locked lasing spectrum than those of the reference crystal, although the total lasing efficiency achieved by both crystals is nearly the same. The obtained results are discussed.

Demonstration of an advanced fibre laser hydrophone array in Gulf St Vincent

NASA Astrophysics Data System (ADS)

Foster, Scott; Tikhomirov, Alexei; Harrison, Joanne; van Velzen, John

2015-09-01

We have developed an 8-element fibre laser seabed array demonstrating state-of-the art performance characteristics for a fibre laser sensing system. The system employs sea-state-zero sensitivity hydrophones with a flat acoustic response over a bandwidth exceeding 5kHz and very low inertial sensitivity. The system contains no outboard electronics and few metal components making it extremely light, compact, and low complexity. The array may be deployed up to 4 km from a land or sea based platform to a depth of up to 80m. Power delivery and telemetry for all 8 sensors is achieved via a single 2mm diameter optical fibre cable weighing less than 5kg per km. We report here results of the first field trials of this system.

Coding for stable transmission of W-band radio-over-fiber system using direct-beating of two independent lasers.

PubMed

Yang, L G; Sung, J Y; Chow, C W; Yeh, C H; Cheng, K T; Shi, J W; Pan, C L

2014-10-20

We demonstrate experimentally Manchester (MC) coding based W-band (75 - 110 GHz) radio-over-fiber (ROF) system to reduce the low-frequency-components (LFCs) signal distortion generated by two independent low-cost lasers using spectral shaping. Hence, a low-cost and higher performance W-band ROF system is achieved. In this system, direct-beating of two independent low-cost CW lasers without frequency tracking circuit (FTC) is used to generate the millimeter-wave. Approaches, such as delayed self-heterodyne interferometer and heterodyne beating are performed to characterize the optical-beating-interference sub-terahertz signal (OBIS). Furthermore, W-band ROF systems using MC coding and NRZ-OOK are compared and discussed.

Neutron Production from In-situ Heavy Ice Coated Targets at Vulcan

NASA Astrophysics Data System (ADS)

Morrison, John; Krygier, A. G.; Kar, S.; Ahmed, H.; Alejo, A.; Clarke, R.; Fuchs, J.; Green, A.; Jung, D.; Kleinschmidt, A.; Najmudin, Z.; Nakamura, H.; Norreys, P.; Notley, M.; Oliver, M.; Roth, M.; Vassura, L.; Zepf, M.; Borghesi, M.; Freeman, R. R.

2015-05-01

Laser based neutron production experiments have been performed utilizing ultra-high intensity laser accelerated ions impinging upon a secondary target. The neutron yield from such experiments may be improved if the accelerated ions were primarily deuterons taking advantage of the d-d cross section. Recent experiments have demonstrated that selective deuteron acceleration from in-situ heavy ice coating of targets can produce ion spectra where deuterons comprise > 99 % of the measured ions. Results will be presented from integrated neutron production experiments from heavy ice targets coated in-situ recently performed on the Vulcan laser at Rutherford Appleton Laboratory. We are grateful for the Staff at RAL and acknowledge funding from the US DoE. AFOSR, European Social Fund, and the Czech Republic.

Structural origin and laser performance of thulium-doped germanate glasses.

PubMed

Xu, Rongrong; Xu, Lin; Hu, Lili; Zhang, Junjie

2011-12-15

The structural origin and laser performance of thulium-doped germanate glasses have been studied. The investigation includes two main sections. The first part discusses the Raman spectroscopic and thermal stability of the host glass structure. The low value of the largest phonon energy (850 cm(-1)) reduces the probability of nonradiative relaxation. The large emission cross section of the Tm(3+) : (3)F(4) level (8.69 × 10(-21) cm(2)), the high quantum efficiency of the (3)F(4) level (71%), and the low nonradiative relaxation rate of the (3)F(4) → (3)H(6) transition (0.09 ms(-1)) illustrate good optical properties of the germanate glass. In the second part, the room-temperature laser action from the thulium-doped germanate glass is demonstrated when pumped by a 790 nm laser diode. The maximum output power of 346 mW and slope efficiency of 25.6% are achieved.

Research on the compensation of laser launch optics to improve the performance of the LGS spot.

PubMed

Liu, Jie; Wang, Jianli; Wang, Yuning; Tian, Donghe; Zheng, Quan; Lin, Xudong; Wang, Liang; Yang, Qingyun

2018-02-01

To improve the beam quality of the uplink laser, a 37 channel piezo-ceramic deformable mirror was inserted into the laser launch optics to compensate the static aberrations. An interferometer was used as the calibration light source as well as the wavefront sensor to perform closed-loop correction for the moment. About 0.38λ root mean square (rms) aberrations, including the deformable mirror's initial figure error, were compensated, and the residual error was less than 0.07λ rms. Field observations with a 2 m optical telescope demonstrated that the peak intensity value of the laser guide star (LGS) spot increased from 5650 to 7658, and the full width at half-maximum (FWHM) size reduced from 4.07 arcseconds to 3.52 arcseconds. With the compensation, an improved guide star spot can be obtained, which is crucial for the adaptive optics systems of ground-based large telescopes.

Ultrafast web inspection with hybrid dispersion laser scanner.

PubMed

Chen, Hongwei; Wang, Chao; Yazaki, Akio; Kim, Chanju; Goda, Keisuke; Jalali, Bahram

2013-06-10

We report an ultrafast web inspector that operates at a 1000 times higher scan rate than conventional methods. This system is based on a hybrid dispersion laser scanner that performs line scans at nearly 100 MHz. Specifically, we demonstrate web inspection with detectable resolution of 48.6 μm/pixel (scan direction) × 23 μm (web flow direction) within a width of view of 6 mm at a record high scan rate of 90.9 MHz. We demonstrate the identification and evaluation of particles on silicon wafers. This method holds great promise for speeding up quality control and hence reducing manufacturing costs.

Data demonstrating the effects of build orientation and heat treatment on fatigue behavior of selective laser melted 17-4 PH stainless steel.

PubMed

Yadollahi, Aref; Simsiriwong, Jutima; Thompson, Scott M; Shamsaei, Nima

2016-06-01

Axial fully-reversed strain-controlled ([Formula: see text]) fatigue experiments were performed to obtain data demonstrating the effects of building orientation (i.e. vertical versus horizontal) and heat treatment on the fatigue behavior of 17-4 PH stainless steel (SS) fabricated via Selective Laser Melting (SLM) (Yadollahi et al., submitted for publication [1]). This data article provides detailed experimental data including cyclic stress-strain responses, variations of peak stresses during cyclic deformation, and fractography of post-mortem specimens for SLM 17-4 PH SS.

Data demonstrating the effects of build orientation and heat treatment on fatigue behavior of selective laser melted 17–4 PH stainless steel

PubMed Central

Yadollahi, Aref; Simsiriwong, Jutima; Thompson, Scott M.; Shamsaei, Nima

2016-01-01

Axial fully-reversed strain-controlled (R=−1) fatigue experiments were performed to obtain data demonstrating the effects of building orientation (i.e. vertical versus horizontal) and heat treatment on the fatigue behavior of 17–4 PH stainless steel (SS) fabricated via Selective Laser Melting (SLM) (Yadollahi et al., submitted for publication [1]). This data article provides detailed experimental data including cyclic stress-strain responses, variations of peak stresses during cyclic deformation, and fractography of post-mortem specimens for SLM 17–4 PH SS. PMID:26955653

Real-time quantum cascade laser-based infrared microspectroscopy in-vivo

NASA Astrophysics Data System (ADS)

Kröger-Lui, N.; Haase, K.; Pucci, A.; Schönhals, A.; Petrich, W.

2016-03-01

Infrared microscopy can be performed to observe dynamic processes on a microscopic scale. Fourier-transform infrared spectroscopy-based microscopes are bound to limitations regarding time resolution, which hampers their potential for imaging fast moving systems. In this manuscript we present a quantum cascade laser-based infrared microscope which overcomes these limitations and readily achieves standard video frame rates. The capabilities of our setup are demonstrated by observing dynamical processes at their specific time scales: fermentation, slow moving Amoeba Proteus and fast moving Caenorhabditis elegans. Mid-infrared sampling rates between 30 min and 20 ms are demonstrated.

Inertial Confinement Fusion Quarterly Report January-March 1999, Volume 9, Number 2

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

Atherton, J.

1999-03-31

This quarterly report covers the following topics: (1) Properties of and Manufacturing Methods for NIF Laser Glasses (J. H. Campbell)--The NIF amplifiers require 3380 Nd-doped laser glass slabs; continuous glass melting methods will be used for the first time to manufacture these slabs. The properties of the laser glasses are summarized and the novel continuous melting method is described. (2) Diffractive Optics for the NIF (J. A. Britten)--We have fabricated demonstration diffractive optics according to the NIF baseline design at full scale, via wet-chemical etching of patterns into fused silica. We have examined the effects of dip-coated sol-gel antireflection coatingsmore » on the performance of these optics, and have concluded that diffractive optics should remain uncoated to minimize laser-induced damage to downstream optics and to maximize environmental stability. We have also demonstrated the feasibility of combining all diffractive structures required by NIF, which vary over orders of magnitude in lateral and vertical scales, onto a single surface. (3) Producing KDP and DKDP Crystals for the NIF Laser (A. K. Burnham)--Rapid-growth KDP has overcome most of the hurdles for production of boules for NIF switch crystals and doublers, but some improvements in process reliability at the tripler's 3{omega} damage threshold are needed. The ability to meet KDP finishing specifications has been demonstrated, and the equipment for efficient NIF production is being built. (4) Engineering High-Damage-Threshold NIF Polarizers and Mirrors (C. J. Stolz)--High-fluence polarizer and mirror coatings for the NIF can be realized by engineering the coating process and design once the laser interaction with coating defects is understood. (5) Improved Antireflection Coatings for the NIF (P. K. Whitman)--We summarize our progress in developing antireflection coatings and applications processes for the NIF laser optics. We describe new materials and coating treatments to minimize the sensitivity of these porous sol-gel coatings to environmental humidity and organic contamination. (6) Developing Optics Finishing Technologies for the National Ignition Facility (T. G. Parham)--Fabrication of the 7500 meter-class lenses and flats for the NIF required extension of finishing technologies to meet cost and schedule targets. Developments at LLNL and our industrial partners are described for improved shaping, grinding, polishing, figuring, and metrology of large optics. (7) Laser-Damage Testing and Modeling Methods for Predicting the Performance of Large-Area NIF Optics (M. R. Kozlowski)--Laser damage to high-quality laser optics is limited by localized, defect-initiated processes. The damage performance of such materials is better described by statistical distributions than by discrete damage thresholds. The prediction of the damage performance of a Beamlet focus lens, based on new statistics-based damage data measurement and analysis techniques, is demonstrated. (8) Development of the NIF Target Chamber First Wall and Beam Dumps (A. K. Burnham)--NIF target designs and target chamber ablations are listed by a 1-nm/shot contamination rate of the final optics debris shield, as determined by transmittance and damage lifetime. This constraint forces a self-cleaning louvre design for the first wall and unconverted-light beam dumps. Nickel-free stainless steel is the cheapest and most practical material.« less

Random laser illumination: an ideal source for biomedical polarization imaging?

NASA Astrophysics Data System (ADS)

Carvalho, Mariana T.; Lotay, Amrit S.; Kenny, Fiona M.; Girkin, John M.; Gomes, Anderson S. L.

2016-03-01

Imaging applications increasingly require light sources with high spectral density (power over spectral bandwidth. This has led in many cases to the replacement of conventional thermal light sources with bright light-emitting diodes (LEDs), lasers and superluminescent diodes. Although lasers and superluminescent diodes appear to be ideal light sources due to their narrow bandwidth and power, however, in the case of full-field imaging, their spatial coherence leads to coherent artefacts, such as speckle, that corrupt the image. LEDs, in contrast, have lower spatial coherence and thus seem the natural choice, but they have low spectral density. Random Lasers are an unconventional type of laser that can be engineered to provide low spatial coherence with high spectral density. These characteristics makes them potential sources for biological imaging applications where specific absorption and reflection are the characteristics required for state of the art imaging. In this work, a Random Laser (RL) is used to demonstrate speckle-free full-field imaging for polarization-dependent imaging in an epi-illumination configuration. We compare LED and RL illumination analysing the resulting images demonstrating that the RL illumination produces an imaging system with higher performance (image quality and spectral density) than that provided by LEDs.

A Technology Demonstration Experiment for Laser Cooled Atomic Clocks in Space

NASA Technical Reports Server (NTRS)

Klipstein, W. M.; Kohel, J.; Seidel, D. J.; Thompson, R. J.; Maleki, L.; Gibble, K.

2000-01-01

We have been developing a laser-cooling apparatus for flight on the International Space Station (ISS), with the intention of demonstrating linewidths on the cesium clock transition narrower than can be realized on the ground. GLACE (the Glovebox Laser- cooled Atomic Clock Experiment) is scheduled for launch on Utilization Flight 3 (UF3) in 2002, and will be mounted in one of the ISS Glovebox platforms for an anticipated 2-3 week run. Separate flight definition projects funded at NIST and Yale by the Micro- gravity Research Division of NASA as a part of its Laser Cooling and Atomic Physics (LCAP) program will follow GLACE. Core technologies for these and other LCAP missions are being developed at JPL, with the current emphasis on developing components such as the laser and optics subsystem, and non-magnetic vacuum-compatible mechanical shutters. Significant technical challenges in developing a space qualifiable laser cooling apparatus include reducing the volume, mass, and power requirements, while increasing the ruggedness and reliability in order to both withstand typical launch conditions and achieve several months of unattended operation. This work was performed at the Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration.

Continuum generation in ultra high numerical aperture fiber with application to multiphoton microscopy

NASA Astrophysics Data System (ADS)

Sayler, Nicholas

Nonlinear microscopy benefits from broadband laser sources, enabling efficient excitation of an array of fluorophores, for example. This work demonstrates broadening of a narrow band input pulse (6 nm to 40 nm) centered at 1040 nm with excellent shot-to-shot stability. In a preliminary demonstration, multiphoton imaging with pulses from the fiber is performed. In particular second harmonic imaging of corn starch is performed.

Parallel processing using an optical delay-based reservoir computer

NASA Astrophysics Data System (ADS)

Van der Sande, Guy; Nguimdo, Romain Modeste; Verschaffelt, Guy

2016-04-01

Delay systems subject to delayed optical feedback have recently shown great potential in solving computationally hard tasks. By implementing a neuro-inspired computational scheme relying on the transient response to optical data injection, high processing speeds have been demonstrated. However, reservoir computing systems based on delay dynamics discussed in the literature are designed by coupling many different stand-alone components which lead to bulky, lack of long-term stability, non-monolithic systems. Here we numerically investigate the possibility of implementing reservoir computing schemes based on semiconductor ring lasers. Semiconductor ring lasers are semiconductor lasers where the laser cavity consists of a ring-shaped waveguide. SRLs are highly integrable and scalable, making them ideal candidates for key components in photonic integrated circuits. SRLs can generate light in two counterpropagating directions between which bistability has been demonstrated. We demonstrate that two independent machine learning tasks , even with different nature of inputs with different input data signals can be simultaneously computed using a single photonic nonlinear node relying on the parallelism offered by photonics. We illustrate the performance on simultaneous chaotic time series prediction and a classification of the Nonlinear Channel Equalization. We take advantage of different directional modes to process individual tasks. Each directional mode processes one individual task to mitigate possible crosstalk between the tasks. Our results indicate that prediction/classification with errors comparable to the state-of-the-art performance can be obtained even with noise despite the two tasks being computed simultaneously. We also find that a good performance is obtained for both tasks for a broad range of the parameters. The results are discussed in detail in [Nguimdo et al., IEEE Trans. Neural Netw. Learn. Syst. 26, pp. 3301-3307, 2015

Some recent studies on laser cladding and dissimilar welding

NASA Astrophysics Data System (ADS)

Kaul, Rakesh; Ganesh, P.; Paul, C. P.; Albert, S. K.; Mudali, U. Kamachi; Nath, A. K.

2006-01-01

Indigenous development of high power CO II laser technology and industrial application of lasers represent two important mandates of the laser program, being pursued at Centre for Advanced Technology (CAT), India. The present paper describes some of the important laser material processing studies, involving cladding and dissimilar welding, performed in authors' laboratory. The first case study describes how low heat input characteristics of laser cladding process has been successfully exploited for suppressing dilution in "Colmonoy6" (a nickel-base hardfacing alloy) deposits on austenitic stainless steel components. Crack free hardfaced deposits were obtained by controlling heating and cooling rates associated with laser treatment. The results show significant advantage over Colmonoy 6 deposits made by GTAW, where a 2.5 mm thick region of dilution (with reduced hardness) develops next to substrateiclad interface. The next work involves laser-assisted deposition of graded "Stellite6" (a Co-base hardfacing alloy) with smooth transition in chemical composition and hardness for enhanced resistance against cracking, esp. under thermal cycling conditions. The following two case studies demonstrate significant improvement in corrosion properties of type 304L stainless steel by laser surface alloying, achieved through cladding route. The following case study demonstrates engineering of fusion zone microstructure of end plug dissimilar weld (between alloy D9 and type 3 16M stainless steel) by controlled preferential displacement of focused laser beam, which, in-turn, enhanced its resistance against solidification cracking. Crater appearing at the termination point of laser weld is also eliminated by ramping of laser power towards the end of laser welding. The last case study involves engineering of fusion zone microstructure of dissimilar laser weld between type 304 austenitic stainless steel and stabilized 17%Cr ferritic stainless steel by controlling welding parameters.

End-to-end information system concept for the Mars Telecommunications Orbiter

NASA Technical Reports Server (NTRS)

Bridenthal, Julian C.; Edwards, Charles D.; Greenberg, Edward; Kazz, Greg J.; Noreen, Gary K.

2006-01-01

The Mars Telecommunications Orbiter (MTO) was intended to provide high-performance deep space relay links to landers, orbiters, sample-return, missions, and approaching spacecraft in the vicinity of Mars, to demonstrate interplanetary laser communications, to demonstrate autonomous navigation, and to carry out is own science investigations.

Tunable Picosecond Laser Pulses via the Contrast of Two Reverse Saturable Absorption Phases in a Waveguide Platform

PubMed Central

Tan, Yang; Chen, Lianwei; Wang, Dong; Chen, Yanxue; Akhmadaliev, Shavkat; Zhou, Shengqiang; Hong, Minghui; Chen, Feng

2016-01-01

How to enhance the optical nonlinearity of saturable absorption materials is an important question to improve the functionality of various applications ranging from the high power laser to photonic computational devices. We demonstrate the saturable absorption (SA) of VO2 film attributed to the large difference of optical nonlinearities between the two states of the phase-transition materials (VO2). Such VO2 film demonstrated significantly improved performance with saturation intensity higher than other existing ultrathin saturable absorbers by 3 orders due to its unique nonlinear optical mechanisms in the ultrafast phase change process. Owing to this feature, a Q-switched pulsed laser was fabricated in a waveguide platform, which is the first time to achieve picosecond pulse duration and maintain high peak power. Furthermore, the emission of this VO2 waveguide laser can be flexibly switched between the continuous-wave (CW) and pulsed operation regimes by tuning the temperature of the VO2 film, which enables VO2-based miniature laser devices with unique and versatile functions. PMID:27188594

Laser-induced forward transfer for printed electronics applications

NASA Astrophysics Data System (ADS)

Fernández-Pradas, J. M.; Sopeña, P.; González-Torres, S.; Arrese, J.; Cirera, A.; Serra, P.

2018-02-01

Laser-induced forward transfer (LIFT) is a printing technique based on the action of a laser pulse that is focused on a thin film of a precursor ink for getting the transfer of a droplet onto a receiver substrate. The experiments presented in this article aim to demonstrate the ability of LIFT to produce electronic circuits on paper, a substrate that is flexible, cheap and recyclable. Tests were conducted to study the printing of conductive tracks with an Ag ink. The printing of a suspension of carbon nanofibers was also studied to demonstrate the ability of LIFT for printing inks with particles with some microns in size that provoke inkjet nozzles to clog. As a proof-of-concept of the LIFT possibilities, both inks were used to print entirely by LIFT a functional humidity sensor on a piece of paper. All the LIFT experiments were performed with a Nd:YAG laser that delivers pulses of a few hundreds of ns in an attempt to approach the technique to laser systems that are already introduced in many production lines for marking and labeling.

Application of picosecond laser-induced breakdown spectroscopy to quantitative analysis of boron in meatballs and other biological samples.

PubMed

Hedwig, Rinda; Lahna, Kurnia; Lie, Zener Sukra; Pardede, Marincan; Kurniawan, Koo Hendrik; Tjia, May On; Kagawa, Kiichiro

2016-11-10

This report presents the results of laser-induced breakdown spectroscopy (LIBS) study on biological and food samples of high water content using a picosecond (ps) laser at low output energy of 10 mJ and low-pressure helium ambient gas at 2 kPa. Evidence of excellent emission spectra of various analyte elements with very low background is demonstrated for a variety of samples without the need of sample pretreatment. Specifically, limits of detection in the range of sub-ppm are obtained for hazardous Pb and B impurities in carrots and meatballs. This study also shows the inferior performance of LIBS using a nanosecond laser and atmospheric ambient air for a soft sample of high water content and thereby explains its less successful applications in previous attempts. The present result has instead demonstrated the feasibility and favorable results of employing LIBS with a ps laser and low-pressure helium ambient gas as a less costly and more practical alternative to inductively coupled plasma for regular high sensitive inspection of harmful food preservatives and environmental pollutants.

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

NASA Astrophysics Data System (ADS)

Pu, Tao; Wang, Wei wei

2018-01-01

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

Kerr-lens mode-locked Ti:Sapphire laser pumped by a single laser diode

NASA Astrophysics Data System (ADS)

Kopylov, D. A.; Esaulkov, M. N.; Kuritsyn, I. I.; Mavritskiy, A. O.; Perminov, B. E.; Konyashchenko, A. V.; Murzina, T. V.; Maydykovskiy, A. I.

2018-04-01

The performance of a Ti:sapphire laser pumped by a single 461 nm laser diode is presented for both the continuous-wave and the mode-locked regimes of operation. We introduce a simple astigmatism correction scheme for the laser diode beam consisting of two cylindrical lenses affecting the pump beam along the fast axis of the laser diode, which provides the mode-matching between the nearly square-shaped pump beam and the cavity mode. The resulting efficiency of the suggested Ti:Sapphire oscillator pumped by such a laser diode is analyzed for the Ti:sapphire crystals of 3 mm, 5 mm and 10 mm in length. We demonstrate that such a system provides the generation of ultrashort pulses up to 15 fs in duration with the repetition rate of 87 MHz, the average power being 170 mW.

High peak power Q-switched Er:YAG laser with two polarizers and its ablation performance for hard dental tissues.

PubMed

Yang, Jingwei; Wang, Li; Wu, Xianyou; Cheng, Tingqing; Jiang, Haihe

2014-06-30

An electro-optically Q-switched high-energy Er:YAG laser with two polarizers is proposed. By using two Al(2)O(3) polarizing plates and a LiNbO(3) crystal with Brewster angle, the polarization efficiency is significantly improved. As a result, 226 mJ pulse energy with 62 ns pulse width is achieved at the repetition rate of 3 Hz, the corresponding peak power is 3.6 MW. To our knowledge, such a high peak power has not been reported in literature. With our designed laser, in-vitro teeth were irradiated under Q-switched and free-running modes. Results of a laser ablation experiment on hard dental tissue with the high-peak-power laser demonstrates that the Q-switched Er:YAG laser has higher ablation precision and less thermal damage than the free-running Er:YAG laser.

Free-space laser communication technologies III; Proceedings of the Meeting, Los Angeles, CA, Jan. 21, 22, 1991

NASA Technical Reports Server (NTRS)

Begley, David L. (Editor); Seery, Bernard D. (Editor)

1991-01-01

The present volume on free-space laser communication technologies discusses system analysis, performance, and applications, pointing, acquisition, and tracking in beam control, laboratory demonstration systems, and transmitter and critical component technologies. Attention is given to a space station laser communication transceiver, meeting intersatellite links mission requirements by an adequate optical terminal design, an optical approach to proximity-operations communications for Space Station Freedom, and optical space-to-ground link availability assessment and diversity requirements. Topics addressed include nonmechanical steering of laser beams by multiple aperture antennas, a free-space simulator for laser transmission, heterodyne acquisition and tracking in a free-space diode laser link, and laser terminal attitude determination via autonomous star tracking. Also discussed are stability considerations in relay lens design for optical communications, liquid crystals for lasercom applications, and narrowband optical interference filters.

Analysis of detection performance of multi band laser beam analyzer

NASA Astrophysics Data System (ADS)

Du, Baolin; Chen, Xiaomei; Hu, Leili

2017-10-01

Compared with microwave radar, Laser radar has high resolution, strong anti-interference ability and good hiding ability, so it becomes the focus of laser technology engineering application. A large scale Laser radar cross section (LRCS) measurement system is designed and experimentally tested. First, the boundary conditions are measured and the long range laser echo power is estimated according to the actual requirements. The estimation results show that the echo power is greater than the detector's response power. Secondly, a large scale LRCS measurement system is designed according to the demonstration and estimation. The system mainly consists of laser shaping, beam emitting device, laser echo receiving device and integrated control device. Finally, according to the designed lidar cross section measurement system, the scattering cross section of target is simulated and tested. The simulation results are basically the same as the test results, and the correctness of the system is proved.

Ultrasound Guidance and Monitoring of Laser-Based Fat Removal

PubMed Central

Shah, Jignesh; Thomsen, Sharon; Milner, Thomas E.; Emelianov, Stanislav Y.

2009-01-01

Background and Objectives We report on a study to investigate feasibility of utilizing ultrasound imaging to guide laser removal of subcutaneous fat. Ultrasound imaging can be used to identify the tissue composition and to monitor the temperature increase in response to laser irradiation. Study Design/Materials and Methods Laser heating was performed on ex vivo porcine subcutaneous fat through the overlying skin using a continuous wave laser operating at 1,210 nm optical wavelength. Ultrasound images were recorded using a 10 MHz linear array-based ultrasound imaging system. Results Ultrasound imaging was utilized to differentiate between water-based and lipid-based regions within the porcine tissue and to identify the dermis-fat junction. Temperature maps during the laser exposure in the skin and fatty tissue layers were computed. Conclusions Results of our study demonstrate the potential of using ultrasound imaging to guide laser fat removal. PMID:19065554

Everlasting Dark Printing on Alumina by Laser

NASA Astrophysics Data System (ADS)

Penide, J.; Quintero, F.; Arias-González, F.; Fernández, A.; del Val, J.; Comesaña, R.; Riveiro, A.; Lusquiños, F.; Pou, J.

Marks or prints are needed in almost every material, mainly for decorative or identification purposes. Despite alumina is widely employed in many different industries, the need of printing directly on its surface is still a complex problem. In this sense, lasers have largely demonstrated their high capacities to mark almost every material including ceramics, but performing dark permanent marks on alumina is still an open challenge. In this work we present the results of a comprehensive experimental analysis on the process of marking alumina by laser. Four different laser sources were used in this study: a fiber laser (1075 nm) and three diode pumped Nd:YVO4 lasers emitting at near-infrared (1064 nm), visible (532 nm) and ultraviolet (355 nm) wavelengths, respectively. The results obtained with the four lasers were compared and physical processes involved were explained in detail. Colorimetric analyses allowed to identify the optimal parameters and conditions to produce everlasting and high contrast marks on alumina.

Micropulsed diode laser therapy: evolution and clinical applications.

PubMed

Sivaprasad, Sobha; Elagouz, Mohammed; McHugh, Dominic; Shona, Olajumoke; Dorin, Giorgio

2010-01-01

Many clinical trials have demonstrated the clinical efficacy of laser photocoagulation in the treatment of retinal vascular diseases, including diabetic retinopathy. There is, however, collateral iatrogenic retinal damage and functional loss after conventional laser treatment. Such side effects may occur even when the treatment is appropriately performed because of morphological damage caused by the visible endpoint, typically a whitening burn. The development of the diode laser with micropulsed emission has allowed subthreshold therapy without a visible burn endpoint. This greatly reduces the risk of structural and functional retinal damage, while retaining the therapeutic efficacy of conventional laser treatment. Studies using subthreshold micropulse laser protocols have reported successful outcomes for diabetic macular edema, central serous chorioretinopathy, macular edema secondary to retinal vein occlusion, and primary open angle glaucoma. The report includes the rationale and basic principles underlying micropulse diode laser therapy, together with a review of its current clinical applications. Copyright © 2010 Elsevier Inc. All rights reserved.

Q-switched oscillation in thulium-doped fiber lasers using preloaded dynamic microbending technique

NASA Astrophysics Data System (ADS)

Sakata, H.; Takahashi, N.; Ushiro, Y.

2018-01-01

We demonstrate Q-switched pulse generation in thulium-doped fiber lasers by introducing piezoelectric-driven microbend with preloaded stress. We employed a pair of corrugated chips each attached on piezoelectric actuators (PAs) to clamp the fiber in a ring laser resonator. The thulium-doped fiber is pumped by a laser diode emitting at 1.63 μm and generates the Q-switched laser pulses at around 1.9 μm by switching off the PAs. The laser pulse performance is improved by optimizing the preload and switch-off period for the PAs. The Q-switched pulses with a peak power of 2.8 W and a pulsewidth of 900 ns are observed for a launched pump power of 161 mW. We expect that the in-fiber Q-switching technique will provide efficient laser systems for environmental sensing and medical applications.

Laser Welding in Space

NASA Technical Reports Server (NTRS)

Workman, Gary L.; Kaukler, William F.

1989-01-01

Solidification type welding process experiments in conditions of microgravity were performed. The role of convection in such phenomena was examined and convective effects in the small volumes obtained in the laser weld zone were observed. Heat transfer within the weld was affected by acceleration level as indicated by the resulting microstructure changes in low gravity. All experiments were performed such that both high and low gravity welds occurred along the same weld beam, allowing the effects of gravity alone to be examined. Results indicate that laser welding in a space environment is feasible and can be safely performed IVA or EVA. Development of the hardware to perform the experiment in a Hitchhiker-g platform is recomended as the next step. This experiment provides NASA with a capable technology for welding needs in space. The resources required to perform this experiment aboard a Shuttle Hitchhiker-pallet are assessed. Over the four year period 1991 to 1994, it is recommended that the task will require 13.6 manyears and $914,900. In addition to demonstrating the technology and ferreting out the problems encountered, it is suggested that NASA will also have a useful laser materials processing facility for working with both the scientific and the engineering aspects of materials processing in space. Several concepts are also included for long-term optimization of available solar power through solar pumping solid state lasers directly for welding power.

RGB and white-emitting organic lasers on flexible glass.

PubMed

Foucher, C; Guilhabert, B; Kanibolotsky, A L; Skabara, P J; Laurand, N; Dawson, M D

2016-02-08

Two formats of multiwavelength red, green and blue (RGB) laser on mechanically-flexible glass are demonstrated. In both cases, three all-organic, vertically-emitting distributed feedback (DFB) lasers are assembled onto a common ultra-thin glass membrane substrate and fully encapsulated by a thin polymer overlayer and an additional 50 µm-thick glass membrane in order to improve the performance. The first device format has the three DFB lasers sitting next to each other on the glass substrate. The DFB lasers are simultaneously excited by a single overlapping optical pump, emitting spatially separated red, green and blue laser output with individual thresholds of, respectively, 28 µJ/cm(2), 11 µJ/cm(2) and 32 µJ/cm(2) (for 5 ns pump pulses). The second device format has the three DFB lasers, respectively the red, green and blue laser, vertically stacked onto the flexible glass. This device format emits a white laser output for an optical pump fluence above 42 µJ/cm(2).

Experimental comparison of autodyne and heterodyne laser interferometry using an Nd:YVO₄ microchip laser.

PubMed

Jacquin, Olivier; Lacot, Eric; Glastre, Wilfried; Hugon, Olivier; Guillet de Chatellus, Hugues

2011-08-01

Using an Nd:YVO₄ microchip laser with a relaxation frequency in the megahertz range, we have experimentally compared a heterodyne interferometer based on a Michelson configuration with an autodyne interferometer based on the laser optical feedback imaging (LOFI) method regarding their signal-to-noise ratios. In the heterodyne configuration, the beating between the reference beam and the signal beam is realized outside the laser cavity, while in the autodyne configuration, the wave beating takes place inside the laser cavity, and the relaxation oscillations of the laser intensity then play an important part. For a given laser output power, object under investigation, and detection noise level, we have determined the amplification gain of the LOFI interferometer compared to the heterodyne interferometer. LOFI interferometry is demonstrated to show higher performance than heterodyne interferometry for a wide range of laser powers and detection levels of noise. The experimental results are in good agreement with the theoretical predictions.

Laser source for dimensional metrology: investigation of an iodine stabilized system based on narrow linewidth 633 nm DBR diode

NASA Astrophysics Data System (ADS)

Rerucha, Simon; Yacoot, Andrew; Pham, Tuan M.; Cizek, Martin; Hucl, Vaclav; Lazar, Josef; Cip, Ondrej

2017-04-01

We demonstrated that an iodine stabilized distributed Bragg reflector (DBR) diode based laser system lasing at a wavelength in close proximity to λ =633 nm could be used as an alternative laser source to the helium-neon lasers in both scientific and industrial metrology. This yields additional advantages besides the optical frequency stability and coherence: inherent traceability, wider optical frequency tuning range, higher output power and high frequency modulation capability. We experimentally investigated the characteristics of the laser source in two major steps: first using a wavelength meter referenced to a frequency comb controlled with a hydrogen maser and then on an interferometric optical bench testbed where we compared the performance of the laser system with that of a traditional frequency stabilized He-Ne laser. The results indicate that DBR diode laser system provides a good laser source for applications in dimensional (nano)metrology, especially in conjunction with novel interferometric detection methods exploiting high frequency modulation or multiaxis measurement systems.

A mobile system for a comprehensive online-characterization of nanoparticle aggregates based on wide-angle light scattering and laser-induced incandescence

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

Huber, Franz J. T.; Will, Stefan, E-mail: stefan.will@fau.de; Erlangen Graduate School in Advanced Optical Technologies

A mobile demonstrator for the comprehensive online-characterization of gas-borne nanoparticle aggregates is presented. Two optical measurement techniques are combined, both utilizing a pulsed Nd:YAG laser as light source. Aggregate size and fractal dimension are measured by Wide-Angle Light Scattering (WALS). An ellipsoidal mirror images elastically scattered light from scattering angles between 10° and 165° onto a CCD-camera chip resulting in an almost complete scattering diagram with high angular resolution. Primary particle size and volume fraction are measured by time-resolved Laser-Induced Incandescence (TiRe-LII). Here, particles are heated up to about 3000 K by the short laser pulse, the enhanced thermal radiationmore » signal is detected with gated photomultiplier tubes. Analysis of the signal decay time and maximum LII-signal allows for the determination of primary particle diameter and volume fraction. The performance of the system is demonstrated by combined measurements on soot nanoparticle aggregates from a soot aerosol generator. Particle and aggregate sizes are varied by using different equivalence ratios of the combustion in the generator. Soot volume fraction can be adjusted by different levels of dilution with air. Online-measurements were carried out demonstrating the favorable performance of the system and the potential for industrial applications such as process control and product development. The particle properties obtained are confirmed through transmission electron microscopy analysis on representative samples.« less

A mobile system for a comprehensive online-characterization of nanoparticle aggregates based on wide-angle light scattering and laser-induced incandescence.

PubMed

Huber, Franz J T; Altenhoff, Michael; Will, Stefan

2016-05-01

A mobile demonstrator for the comprehensive online-characterization of gas-borne nanoparticle aggregates is presented. Two optical measurement techniques are combined, both utilizing a pulsed Nd:YAG laser as light source. Aggregate size and fractal dimension are measured by Wide-Angle Light Scattering (WALS). An ellipsoidal mirror images elastically scattered light from scattering angles between 10° and 165° onto a CCD-camera chip resulting in an almost complete scattering diagram with high angular resolution. Primary particle size and volume fraction are measured by time-resolved Laser-Induced Incandescence (TiRe-LII). Here, particles are heated up to about 3000 K by the short laser pulse, the enhanced thermal radiation signal is detected with gated photomultiplier tubes. Analysis of the signal decay time and maximum LII-signal allows for the determination of primary particle diameter and volume fraction. The performance of the system is demonstrated by combined measurements on soot nanoparticle aggregates from a soot aerosol generator. Particle and aggregate sizes are varied by using different equivalence ratios of the combustion in the generator. Soot volume fraction can be adjusted by different levels of dilution with air. Online-measurements were carried out demonstrating the favorable performance of the system and the potential for industrial applications such as process control and product development. The particle properties obtained are confirmed through transmission electron microscopy analysis on representative samples.

A mobile system for a comprehensive online-characterization of nanoparticle aggregates based on wide-angle light scattering and laser-induced incandescence

NASA Astrophysics Data System (ADS)

Huber, Franz J. T.; Altenhoff, Michael; Will, Stefan

2016-05-01

A mobile demonstrator for the comprehensive online-characterization of gas-borne nanoparticle aggregates is presented. Two optical measurement techniques are combined, both utilizing a pulsed Nd:YAG laser as light source. Aggregate size and fractal dimension are measured by Wide-Angle Light Scattering (WALS). An ellipsoidal mirror images elastically scattered light from scattering angles between 10° and 165° onto a CCD-camera chip resulting in an almost complete scattering diagram with high angular resolution. Primary particle size and volume fraction are measured by time-resolved Laser-Induced Incandescence (TiRe-LII). Here, particles are heated up to about 3000 K by the short laser pulse, the enhanced thermal radiation signal is detected with gated photomultiplier tubes. Analysis of the signal decay time and maximum LII-signal allows for the determination of primary particle diameter and volume fraction. The performance of the system is demonstrated by combined measurements on soot nanoparticle aggregates from a soot aerosol generator. Particle and aggregate sizes are varied by using different equivalence ratios of the combustion in the generator. Soot volume fraction can be adjusted by different levels of dilution with air. Online-measurements were carried out demonstrating the favorable performance of the system and the potential for industrial applications such as process control and product development. The particle properties obtained are confirmed through transmission electron microscopy analysis on representative samples.

Overview and Status of the Lunar Laser Communication Demonstration

NASA Technical Reports Server (NTRS)

Boroson, D. M.; Robinson, B. S.; Burianek, D. A.; Murphy, D. V.; Biswas, A.

2012-01-01

The Lunar Laser Communication Demonstration (LLCD), a project being undertaken by MIT Lincoln Laboratory, NASA's Goddard Space Flight Center, and the Jet Propulsion Laboratory, will be NASA's first attempt to demonstrate optical communications between a lunar orbiting spacecraft and Earth-based ground receivers. The LLCD space terminal will be flown on the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft, presently scheduled to launch in 2013. LLCD will demonstrate downlink optical communications at rates up to 620 Mbps, uplink optical communications at rates up to 20 Mbps, and two-way time-of-flight measurements with the potential to perform ranging with sub-centimeter accuracy. We describe the objectives of the LLCD program, key technologies employed in the space and ground terminals, and show the status of development of the several systems.

Performance upgrades in the EUV engineering test stand

NASA Astrophysics Data System (ADS)

Tichenor, Daniel A.; Replogle, William C.; Lee, Sang Hun; Ballard, William P.; Leung, Alvin H.; Kubiak, Glenn D.; Klebanoff, Leonard E.; Graham, Samual, Jr.; Goldsmith, John E. M.; Jefferson, Karen L.; Wronosky, John B.; Smith, Tony G.; Johnson, Terry A.; Shields, Harry; Hale, Layton C.; Chapman, Henry N.; Taylor, John S.; Sweeney, Donald W.; Folta, James A.; Sommargren, Gary E.; Goldberg, Kenneth A.; Naulleau, Patrick P.; Attwood, David T., Jr.; Gullikson, Eric M.

2002-07-01

The EUV Engineering Test Stand (ETS) has demonstrated the printing of 100-nm-resolution scanned images. This milestone was first achieved while the ETS operated in an initial configuration using a low power laser and a developmental projection system, PO Box 1. The drive laser has ben upgraded to a single chain of the three-chain Nd:YAG laser developed by TRW. The result in exposure time is approximately 4 seconds for static exposures. One hundred nanometer dense features have been printed in step-and-scan operation with the same image quality obtained in static printing. These experiments are the first steps toward achieving operation using all three laser chains for a total drive laser power of 1500 watts. In a second major upgrade the developmental wafer stage platen, used to demonstrate initial full-field imaging, has been replaced with the final low-expansion platen made of Zerodur. Additional improvements in the hardware and control software have demonstrated combined x and jitter from 2 to 4 nm RMS Over most of the wafer stage travel range, while scanning at the design scan speed of 10 mm/s at the wafer. This value, less than half of the originally specified jitter, provides sufficient stability to support printing of 70 nm features as planned, when the upgraded projection system is installed. The third major upgrade will replace PO Box 1 with an improved projection system, PO Box 2, having lower figure error and lower flare. In addition to these upgrades, dose sensors at the reticle and wafer planes and an EUV- sensitive aerial image monitor have been integrated into the ETS. This paper reports on ETS system upgrades and the impact on system performance.

Data driven models of the performance and repeatability of NIF high foot implosions

NASA Astrophysics Data System (ADS)

Gaffney, Jim; Casey, Dan; Callahan, Debbie; Hartouni, Ed; Ma, Tammy; Spears, Brian

2015-11-01

Recent high foot (HF) inertial confinement fusion (ICF) experiments performed at the national ignition facility (NIF) have consisted of enough laser shots that a data-driven analysis of capsule performance is feasible. In this work we use 20-30 individual implosions of similar design, spanning laser drive energies from 1.2 to 1.8 MJ, to quantify our current understanding of the behavior of HF ICF implosions. We develop a probabilistic model for the projected performance of a given implosion and use it to quantify uncertainties in predicted performance including shot-shot variations and observation uncertainties. We investigate the statistical significance of the observed performance differences between different laser pulse shapes, ablator materials, and capsule designs. Finally, using a cross-validation technique, we demonstrate that 5-10 repeated shots of a similar design are required before real trends in the data can be distinguished from shot-shot variations. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-674957.

Femtosecond all-optical synchronization of an X-ray free-electron laser

DOE PAGES

Schulz, S.; Grguraš, I.; Behrens, C.; ...

2015-01-20

Many advanced applications of X-ray free-electron lasers require pulse durations and time resolutions of only a few femtoseconds. To generate these pulses and to apply them in time-resolved experiments, synchronization techniques that can simultaneously lock all independent components, including all accelerator modules and all external optical lasers, to better than the delivered free-electron laser pulse duration, are needed. Here we achieve all-optical synchronization at the soft X-ray free-electron laser FLASH and demonstrate facility-wide timing to better than 30 fs r.m.s. for 90 fs X-ray photon pulses. Crucially, our analysis indicates that the performance of this optical synchronization is limited primarilymore » by the free-electron laser pulse duration, and should naturally scale to the sub-10 femtosecond level with shorter X-ray pulses.« less

Femtosecond laser inscribed cladding waveguides in Nd:YAG ceramics: fabrication, fluorescence imaging and laser performance.

PubMed

Liu, Hongliang; Jia, Yuechen; Vázquez de Aldana, Javier Rodríguez; Jaque, Daniel; Chen, Feng

2012-08-13

We report on the fabrication of depressed cladding waveguide lasers in Nd:YAG (neodymium doped yttrium aluminum garnet, Nd:Y3Al5O12) ceramics microstructured by femtosecond laser pulses. Full control over the confined light spatial distribution is demonstrated by the fabrication of high contrast waveguides with hexagonal, circular and trapezoidal configurations. The confocal fluorescence measurements of the waveguides reveal that the original luminescence features of Nd3+ ions are well-preserved in the waveguide regions. Under optical pump at 808 nm, cladding waveguides showed continuous wave efficient laser oscillation. The maximum output power obtained at 1064.5 nm is ~181 mW with a slope efficiency as high as 44%, which suggests that the fabricated Nd:YAG ceramic waveguides are promising candidates for efficient integrated laser sources.

Controllable Terahertz Radiation from a Linear-Dipole Array Formed by a Two-Color Laser Filament in Air.

PubMed

Zhang, Zhelin; Chen, Yanping; Chen, Min; Zhang, Zhen; Yu, Jin; Sheng, Zhengming; Zhang, Jie

2016-12-09

We demonstrate effective control on the carrier-envelope phase and angular distribution as well as the peak intensity of a nearly single-cycle terahertz pulse emitted from a laser filament formed by two-color, the fundamental and the corresponding second harmonics, femtosecond laser pulses propagating in air. Experimentally, such control has been performed by varying the filament length and the initial phase difference between the two-color laser components. A linear-dipole-array model, including the descriptions of both the generation (via laser field ionization) and propagation of the emitted terahertz pulse, is proposed to present a quantitative interpretation of the observations. Our results contribute to the understanding of terahertz generation in a femtosecond laser filament and suggest a practical way to control the electric field of a terahertz pulse for potential applications.

Femtosecond all-optical synchronization of an X-ray free-electron laser

PubMed Central

Schulz, S.; Grguraš, I.; Behrens, C.; Bromberger, H.; Costello, J. T.; Czwalinna, M. K.; Felber, M.; Hoffmann, M. C.; Ilchen, M.; Liu, H. Y.; Mazza, T.; Meyer, M.; Pfeiffer, S.; Prędki, P.; Schefer, S.; Schmidt, C.; Wegner, U.; Schlarb, H.; Cavalieri, A. L.

2015-01-01

Many advanced applications of X-ray free-electron lasers require pulse durations and time resolutions of only a few femtoseconds. To generate these pulses and to apply them in time-resolved experiments, synchronization techniques that can simultaneously lock all independent components, including all accelerator modules and all external optical lasers, to better than the delivered free-electron laser pulse duration, are needed. Here we achieve all-optical synchronization at the soft X-ray free-electron laser FLASH and demonstrate facility-wide timing to better than 30 fs r.m.s. for 90 fs X-ray photon pulses. Crucially, our analysis indicates that the performance of this optical synchronization is limited primarily by the free-electron laser pulse duration, and should naturally scale to the sub-10 femtosecond level with shorter X-ray pulses. PMID:25600823

Design of a photonic integrated based optical interrogator

NASA Astrophysics Data System (ADS)

Ibrahim, Selwan K.; Farnan, Martin; Karabacak, Devrez M.

2017-02-01

Optical sensors based on Fiber Bragg Gratings (FBGs) are used in several applications and industries. In order for fiber optic sensors to compete with electrical sensors, several critical parameters of both the sensors and sensor interrogators need to be in place such as performance, cost, size, reliability relevant to the target application. Here we have developed a tunable laser based optical interrogator which delivers high performance (up to 8kHz sweep-rate and 120dB dynamic range) and precision (<100fm) by optimizing the laser calibration of a telecom tunable laser and incorporating optical periodic wavelength references (e.g. MZI) to correct and compensate for wavelength non-linearity and noise during operation. Scaling up optical sensing systems to deliver high level of performance over a large number of sensors is enabled by synchronizing multiple interrogators. Further improvements can be achieved by using photonic integrated circuit (PIC) technology which reduces the footprint, cost, and improves performance. There exists several PIC technology platforms (e.g. InP, Si, TriPlex) that could be used to develop different optical building blocks used in the interrogator. Such building blocks include the tunable laser, couplers, photodiodes, MZIs, etc. are available on the InP platform. Here we have demonstrated the operation of an interrogator using PIC technology to replace many of the discrete optical components. The design and chip manufacturing was carried out as part of an InP multi-project wafer (MPW) run under the EU PARADIGM project. A custom package supporting fiber arrays was designed and manufactured to demonstrate the PIC functionality in an optical interrogator.

Influence of an Interfacial Effect on the Laser Performance of a Rhodamine 6G/Cellulose Acetate Waveguide on a Vinylidene Fluoride Copolymer Layer.

PubMed

Tsutsumi, Naoto; Hirano, Yoshinori; Kinashi, Kenji; Sakai, Wataru

2018-06-12

The fluorescent properties of dyes and fluorophores in condensed matter significantly affect the laser performance of organic dye lasers and fluorescent polymer lasers. Concentration quenching of fluorescence is commonly observed in condensed matter. Several approaches have been presented to suppress such quenching, such as the use of a dendrimer and the use of effective energy transfer in a guest-host system. The enhanced fluorescence of rhodamine 6G (R6G) dye on a vinylidene fluoride polymer is an alternative method for enhancing laser performance because of the roughness of the P(VDF-TrFE) surface and the interaction between polar β-crystals of P(VDF-TrFE) and R6G dye. In this paper, a significant improvement in slope efficiency (SE) is demonstrated without a significant depression in the lasing threshold for distributed feedback (DFB) and distributed Bragg reflector (DBR) lasers fabricated using an R6G-dispersed cellulose acetate (CA) matrix spin-coated onto a copolymer of vinylidene fluoride and trifluoroethylene P(VDF-TrFE) thin film. SEs of 3.4 and 1.3% were measured for DBR and DFB laser devices with CA/R6G on a P(VDF-TrFE) thin film, respectively, whereas an SE of less than 1.0% was measured for both corresponding laser devices without a P(VDF-TrFE) thin film. From the aspect of simple fabrication procedures, repeatability in device fabrication and performance, stability of the device, time for device fabrication, the present approach is the most preferable way for industrial applications, requiring only the additional step of spin-coating of a P(VDF-TrFE) thin film.

Compact Laser-Based Sensors for Monitoring and Control of Gas Turbine Combustors

NASA Technical Reports Server (NTRS)

Hanson, Ronald K.; Jeffries, Jay B.

2003-01-01

Research is reported on the development of sensors for gas turbine combustor applications that measure real-time gas temperature using near-infrared water vapor absorption and concentration in the combustor exhaust of trace quantities of pollutant NO and CO using mid-infrared absorption. Gas temperature is extracted from the relative absorption strength of two near-infrared transitions of water vapor. From a survey of the water vapor absorption spectrum, two overtone transitions near 1800 nm were selected that can be rapidly scanned in wavelength by injection current tuning a single DFB diode laser. From the ratio of the absorbances on these selected transitions, a path-integrated gas temperature can be extracted in near-real time. Demonstration measurements with this new temperature sensor showed that combustor instabilities could be identified in the power spectrum of the temperature versus time record. These results suggest that this strategy is extremely promising for gas turbine combustor control applications. Measurements of the concentration of NO and CO in the combustor exhaust are demonstrated with mid-infrared transitions using thermo-electrically cooled, quantum cascade lasers operating near 5.26 and 4.62 microns respectively. Measurements of NO are performed in an insulated exhaust duct of a C2H4-air flame at temperatures of approximately 600 K. CO measurements are performed above a rich H2-air flame seeded with CO2 and cooled with excess N2 to 1150 K. Using a balanced ratiometric detection technique a sensitivity of 0.36 ppm-m was achieved for NO and 0.21 ppm-m for CO. Comparisons between measured and predicted water-vapor and CO2 interference are discussed. The mid-infrared laser quantum cascade laser technology is in its infancy; however, these measurements demonstrate the potential for pollutant monitoring in exhaust gases with mid-IR laser absorption.

Titanium nitride formation by a dual-stage femtosecond laser process

NASA Astrophysics Data System (ADS)

Hammouti, S.; Holybee, B.; Zhu, W.; Allain, J. P.; Jurczyk, B.; Ruzic, D. N.

2018-06-01

Formation of TiN by femtosecond laser processing in controlled gas atmosphere is reported. A dual-stage process was designed and aimed to first remove and restructure the native oxide layer of titanium surface through laser irradiation under an argon-controlled atmosphere, and then to maximize titanium nitride formation through an irradiation under a nitrogen reactive environment. An extensive XPS study was performed to identify and quantify laser-induced titanium surface chemistry modifications after a single-stage laser process (Ar and N2 individually), and a dual-stage laser process. The importance of each step that composes the dual-stage laser process was demonstrated and leads to the dual-stage laser process for the formation of TiO, Ti2O3 and TiN. In this study, the largest nitride formation occurs for the dual stage process with laser conditions at 4 W/1.3 J cm-2 under argon and 5 W/1.6 J cm-2 under nitrogen, yielding a total TiN composition of 8.9%. Characterization of both single-stage and dual-stage laser process-induced surface morphologies has been performed as well, leading to the observation of a wide range of hierarchical surface structures such as high-frequency ripples, grooves, protuberances and pillow-like patterns. Finally, water wettability was assessed by means of contact angle measurements on untreated titanium surface, and titanium surfaces resulting from either single-stage laser process or dual-stage laser process. Dual-stage laser process allows a transition of titanium surface, from phobic (93°) to philic (35°), making accessible both hydrophilic and chemically functionalized hierarchical surfaces.

Mid-Infrared Laser Absorption Diagnostics for Combustion and Propulsion Applications

DTIC Science & Technology

2010-12-01

Combustion and Propulsion Applications 5a. CONTRACT NUMBER 5b. GRANT NUMBER N00014-07-1-0844 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Matthew A...Institute Mechancial, Aerospace, and Nuclear Engineering Dept Troy NY 12180-3590 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING / MONITORING...absorption sensors based on quantum cascade laser (QCL) technology for combustion and propulsion applications. To demonstrate the potential of mid-IR QCL

Low-pressure, high-temperature thermal bonding of polymeric microfluidic devices and their applications for electrophoretic separation

NASA Astrophysics Data System (ADS)

Sun, Yi; Chian Kwok, Yien; Nguyen, Nam-Trung

2006-08-01

A new method for thermally bonding poly(methyl methacrylate) (PMMA) substrates has been demonstrated. PMMA substrates are first engraved by CO2-laser micromachining to form microchannels. Both channel width and depth can be adjusted by varying the laser power and scanning speed. Channel depths from 50 µm to 1500 µm and widths from 150 µm to 400 µm are attained. CO2 laser is also used for drilling and dicing of the PMMA parts. Considering the thermal properties of PMMA, a novel thermal bonding process with high temperature and low bonding pressure has been developed for assembling PMMA sheets. A high bonding strength of 2.15 MPa is achieved. Subsequent inspection of the cross sections of several microdevices reveals that the dimensions of the channels are well preserved during the bonding process. Electroosmotic mobility of the ablated channel is measured to be 2.47 × 10-4 cm2 V-1 s-1. The functionality of these thermally bonded microfluidic substrates is demonstrated by performing rapid and high-resolution electrophoretic separations of mixture of fluorescein and carboxyfluorescein as well as double-stranded DNA ladders (ΦX174-Hae III dsDNA digest). The performance of the CO2 laser ablated and thermally bonded PMMA devices compares favorably with those fabricated by other professional means.

Dual-wavelength passively Q-switched ytterbium-doped fiber laser using Fe3O4-nanoparticle saturable absorber and intracavity polarization

NASA Astrophysics Data System (ADS)

Al-Hayali, S. K. M.; Al-Janabi, A. H.

2018-03-01

We have experimentally demonstrated the operation of a dual-wavelength passively Q-switched ytterbium-doped fiber laser by using a saturable absorber (SA) based on Fe3O4 nanoparticles in a magnetic fluid. The SA was fabricated by depositing magnetic fluid at the end of an optical fiber ferrule. By performing adjustments to the pump power and polarization controller state in the cavity, a stable dual-wavelength lasing operation was generated without intracavity spectral filters or modulation elements. The Q-switched laser output was achieved at a pump threshold of 80 mW with a maximum output pulse energy of 38.8 nJ, a repetition rate of 73.4 kHz and a minimum pulse width of 3.4 µs. To the best of the authors’ knowledge, this is the first demonstration of a dual-wavelength passively Q-switched fiber laser using Fe3O4 nanoparticles as the SA in the 1.0 µm operation region.

Gas-cell atomic clocks for space: new results and alternative schemes

NASA Astrophysics Data System (ADS)

Affolderbach, C.; Breschi, E.; Schori, C.; Mileti, G.

2017-11-01

We present our development activities on compact Rubidium gas-cell atomic frequency standards, for use in space-borne and ground-based applications. We experimentally demonstrate a high-performance laser optically-pumped Rb clock for space applications such as telecommunications, science missions, and satellite navigation systems (e.g. GALILEO). Using a stabilised laser source and optimized gas cells, we reach clock stabilities as low as 1.5·10-12 τ-1/2 up to 103 s and 4·10-14 at 104 s. The results demonstrate the feasibility of a laser-pumped Rb clock reaching < 1·10-12 τ-1/2 in a compact device (<2 liters, 2 kg, 20 W), given optimization of the implemented techniques. A second activity concerns more radically miniaturized gas-cell clocks, aiming for low power consumption and a total volume around 1 cm3 , at the expense of relaxed frequency stability. Here miniaturized "chip-scale" vapour cells and use of coherent laser interrogation techniques are at the heart of the investigations.

NDT of fiber-reinforced composites with a new fiber-optic pump–probe laser-ultrasound system☆

PubMed Central

Pelivanov, Ivan; Buma, Takashi; Xia, Jinjun; Wei, Chen-Wei; O’Donnell, Matthew

2014-01-01

Laser-ultrasonics is an attractive and powerful tool for the non-destructive testing and evaluation (NDT&E) of composite materials. Current systems for non-contact detection of ultrasound have relatively low sensitivity compared to contact peizotransducers. They are also expensive, difficult to adjust, and strongly influenced by environmental noise. Moreover, laser-ultrasound (LU) systems typically launch only about 50 firings per second, much slower than the kHz level pulse repetition rate of conventional systems. As demonstrated here, most of these drawbacks can be eliminated by combining a new generation of compact, inexpensive, high repetition rate nanosecond fiber lasers with new developments in fiber telecommunication optics and an optimally designed balanced probe beam detector. In particular, a modified fiber-optic balanced Sagnac interferometer is presented as part of a LU pump–probe system for NDT&E of aircraft composites. The performance of the all-optical system is demonstrated for a number of composite samples with different types and locations of inclusions. PMID:25302156

Channel optimization of high-intensity laser beams in millimeter-scale plasmas.

PubMed

Ceurvorst, L; Savin, A; Ratan, N; Kasim, M F; Sadler, J; Norreys, P A; Habara, H; Tanaka, K A; Zhang, S; Wei, M S; Ivancic, S; Froula, D H; Theobald, W

2018-04-01

Channeling experiments were performed at the OMEGA EP facility using relativistic intensity (>10^{18}W/cm^{2}) kilojoule laser pulses through large density scale length (∼390-570 μm) laser-produced plasmas, demonstrating the effects of the pulse's focal location and intensity as well as the plasma's temperature on the resulting channel formation. The results show deeper channeling when focused into hot plasmas and at lower densities, as expected. However, contrary to previous large-scale particle-in-cell studies, the results also indicate deeper penetration by short (10 ps), intense pulses compared to their longer-duration equivalents. This new observation has many implications for future laser-plasma research in the relativistic regime.

kW-class diode laser bars

NASA Astrophysics Data System (ADS)

Strohmaier, S. G.; Erbert, G.; Meissner-Schenk, A. H.; Lommel, M.; Schmidt, B.; Kaul, T.; Karow, M.; Crump, P.

2017-02-01

Progress will be presented on ongoing research into the development of ultra-high power and efficiency bars achieving significantly higher output power, conversion efficiency and brightness than currently commercially available. We combine advanced InAlGaAs/GaAs-based epitaxial structures and novel lateral designs, new materials and superior cooling architectures to enable improved performance. Specifically, we present progress in kilowatt-class 10-mm diode laser bars, where recent studies have demonstrated 880 W continuous wave output power from a 10 mm x 4 mm laser diode bar at 850 A of electrical current and 15°C water temperature. This laser achieves < 60% electro-optical efficiency at 880 W CW output power.

Experimental study of a quantum random-number generator based on two independent lasers

NASA Astrophysics Data System (ADS)

Sun, Shi-Hai; Xu, Feihu

2017-12-01

A quantum random-number generator (QRNG) can produce true randomness by utilizing the inherent probabilistic nature of quantum mechanics. Recently, the spontaneous-emission quantum phase noise of the laser has been widely deployed for quantum random-number generation, due to its high rate, its low cost, and the feasibility of chip-scale integration. Here, we perform a comprehensive experimental study of a phase-noise-based QRNG with two independent lasers, each of which operates in either continuous-wave (CW) or pulsed mode. We implement the QRNG by operating the two lasers in three configurations, namely, CW + CW, CW + pulsed, and pulsed + pulsed, and demonstrate their trade-offs, strengths, and weaknesses.

Visualization of the influence of the air conditioning system to the high-power laser beam quality with the modulation coherent imaging method.

PubMed

Tao, Hua; Veetil, Suhas P; Pan, Xingchen; Liu, Cheng; Zhu, Jianqiang

2015-08-01

Air conditioning systems can lead to dynamic phase change in the laser beams of high-power laser facilities for the inertial confinement fusion, and this kind of phase change cannot be measured by most of the commonly employed Hartmann wavefront sensor or interferometry due to some uncontrollable factors, such as too large laser beam diameters and the limited space of the facility. It is demonstrated that this problem can be solved using a scheme based on modulation coherent imaging, and thus the influence of the air conditioning system on the performance of the high-power facility can be evaluated directly.

Spatio-temporally resolved spectral measurements of laser-produced plasma and semiautomated spectral measurement-control and analysis software

NASA Astrophysics Data System (ADS)

Cao, S. Q.; Su, M. G.; Min, Q.; Sun, D. X.; O'Sullivan, G.; Dong, C. Z.

2018-02-01

A spatio-temporally resolved spectral measurement system of highly charged ions from laser-produced plasmas is presented. Corresponding semiautomated computer software for measurement control and spectral analysis has been written to achieve the best synchronicity possible among the instruments. This avoids the tedious comparative processes between experimental and theoretical results. To demonstrate the capabilities of this system, a series of spatio-temporally resolved experiments of laser-produced Al plasmas have been performed and applied to benchmark the software. The system is a useful tool for studying the spectral structures of highly charged ions and for evaluating the spatio-temporal evolution of laser-produced plasmas.

Temperature-insensitive long-wavelength (λ ≈14 µm) Quantum Cascade lasers with low threshold.

PubMed

Huang, Xue; Charles, William O; Gmachl, Claire

2011-04-25

We demonstrate high-performance, long-wavelength (λ ≈14 µm) Quantum Cascade (QC) lasers based on a diagonal optical transition and a "two-phonon-continuum" depletion scheme in which the lower laser level is depopulated by resonant longitudinal optical phonon scattering followed by scattering to a lower energy level continuum. A 2.8 mm long QC laser shows a low threshold current density of 2.0 kA/cm2, a peak output power of ~336 mW, and a slope efficiency of 375 mW/A, all at 300 K, with a high characteristic temperature T0 ~310 K over a wide temperature range from 240 K to 390 K.

Effect of photon energy in collagen generation by interstitial low level laser stimulation

NASA Astrophysics Data System (ADS)

Jun, Eunkwon; Ha, Myungjin; Lee, Sangyeob; Radfar, Edalat; Park, Jihoon; Jung, Byungjo

2015-03-01

Although the mechanism of low level laser therapy (LLLT) is unclear, many studies demonstrated the positive clinical performance of LLLT for skin rejuvenation. An increase in dermal collagen plays an important role in skin rejuvenation and wound healing. This study aimed to investigate collagen generation after interstitial low level laser stimulation (ILLS). Rabbits were divided into two groups: surfacing irradiation and minimally invasive irradiation. 660nm diode laser of 20mW with 10J, 13J and 15J was applied to the backside of rabbits. Collagen formation was evaluated with ultrasound skin scanner every 12 hours. Results shows that ILLS groups have denser collagen density than surfacing groups.

CW and passively Q-switched laser performance of Nd:Lu2SiO5 crystal

NASA Astrophysics Data System (ADS)

Xu, Xiaodong; Di, Juqing; Zhang, Jian; Tang, Dingyuan; Xu, Jun

2016-01-01

We demonstrated an efficient and controllable dual-wavelength continuous-wave (CW) laser of Nd:Lu2SiO5 (Nd:LSO) crystal. The maximum output power was 3.02 W at wavelength of 1075 nm and 1079 nm, and with increasing of absorbed pump power, the ratio of 1079 nm laser rose. The slope efficiency of 65.6% and optical-to-optical conversion efficiency of 63.3% were obtained. The passively Q-switched laser properties of Nd:LSO were investigated for the first time. The shortest pulse, maximum pulse energy and peak power were 11.58 ns, 29.05 μJ and 2.34 kW, respectively.

Room-temperature Q-switched Tm:BaY2F8 laser pumped by CW diode laser

NASA Astrophysics Data System (ADS)

Coluccelli, Nicola; Galzerano, Gianluca; Laporta, Paolo; Parisi, Daniela; Toncelli, Alessandra; Tonelli, Mauro

2006-02-01

We report on the realization of CW diode-pumped Tm:BaY2F8 Q-switched laser at 1.93 µm. Active Q-switching was obtained by means of an intracavity Pockels cell. A functional characterization of the laser performance is presented with particular attention to output energy, pulse duration, pulse stability, and wavelength tunability. Pulses with time duration as short as 170 ns were demonstrated at the minimum repetition rate of 5 Hz with an energy of 3.2 mJ (corresponding to a peak power of 19 kW). A wavelength tunability range from 1905 nm to 1990 nm has been observed.

Channel optimization of high-intensity laser beams in millimeter-scale plasmas

NASA Astrophysics Data System (ADS)

Ceurvorst, L.; Savin, A.; Ratan, N.; Kasim, M. F.; Sadler, J.; Norreys, P. A.; Habara, H.; Tanaka, K. A.; Zhang, S.; Wei, M. S.; Ivancic, S.; Froula, D. H.; Theobald, W.

2018-04-01

Channeling experiments were performed at the OMEGA EP facility using relativistic intensity (>1018W/cm 2 ) kilojoule laser pulses through large density scale length (˜390 -570 μ m ) laser-produced plasmas, demonstrating the effects of the pulse's focal location and intensity as well as the plasma's temperature on the resulting channel formation. The results show deeper channeling when focused into hot plasmas and at lower densities, as expected. However, contrary to previous large-scale particle-in-cell studies, the results also indicate deeper penetration by short (10 ps), intense pulses compared to their longer-duration equivalents. This new observation has many implications for future laser-plasma research in the relativistic regime.

Oxygen measurement by multimode diode lasers employing gas correlation spectroscopy.

PubMed

Lou, Xiutao; Somesfalean, Gabriel; Chen, Bin; Zhang, Zhiguo

2009-02-10

Multimode diode laser (MDL)-based correlation spectroscopy (COSPEC) was used to measure oxygen in ambient air, thereby employing a diode laser (DL) having an emission spectrum that overlaps the oxygen absorption lines of the A band. A sensitivity of 700 ppm m was achieved with good accuracy (2%) and linearity (R(2)=0.999). For comparison, measurements of ambient oxygen were also performed by tunable DL absorption spectroscopy (TDLAS) technique employing a vertical cavity surface emitting laser. We demonstrate that, despite slightly degraded sensitivity, the MDL-based COSPEC-based oxygen sensor has the advantages of high stability, low cost, ease-of-use, and relaxed requirements in component selection and instrument buildup compared with the TDLAS-based instrument.

Chirped Laser Dispersion Spectroscopy for Remote Open-Path Trace-Gas Sensing

PubMed Central

Nikodem, Michal; Wysocki, Gerard

2012-01-01

In this paper we present a prototype instrument for remote open-path detection of nitrous oxide. The sensor is based on a 4.53 μm quantum cascade laser and uses the chirped laser dispersion spectroscopy (CLaDS) technique for molecular concentration measurements. To the best of our knowledge this is the first demonstration of open-path laser-based trace-gas detection using a molecular dispersion measurement. The prototype sensor achieves a detection limit down to the single-ppbv level and exhibits excellent stability and robustness. The instrument characterization, field deployment performance, and the advantages of applying dispersion sensing to sensitive trace-gas detection in a remote open-path configuration are presented. PMID:23443389

Chirped laser dispersion spectroscopy for remote open-path trace-gas sensing.

PubMed

Nikodem, Michal; Wysocki, Gerard

2012-11-28

In this paper we present a prototype instrument for remote open-path detection of nitrous oxide. The sensor is based on a 4.53 μm quantum cascade laser and uses the chirped laser dispersion spectroscopy (CLaDS) technique for molecular concentration measurements. To the best of our knowledge this is the first demonstration of open-path laser-based trace-gas detection using a molecular dispersion measurement. The prototype sensor achieves a detection limit down to the single-ppbv level and exhibits excellent stability and robustness. The instrument characterization, field deployment performance, and the advantages of applying dispersion sensing to sensitive trace-gas detection in a remote open-path configuration are presented.

Overview of the laser activities at Rheinmetall Waffe Munition

NASA Astrophysics Data System (ADS)

Ludewigt, Klaus; Riesbeck, Thomas; Schünemann, B.; Graf, A.; Jung, Markus; Schreiber, Th.; Eberhardt, Ramona; Tünnermann, A.

2012-11-01

The paper will give an overview over the laser weapon activities at RWM (Rheinmetall Waffe Munition) over the last years. Starting from the actual scenarios for laser weapon applications as: CRAM (Counter Rocket Artillery Mortar), Air Defence and UXO (unexploded ordnance) clearing. The basic requirements of a future laser weapon as beam diameter, beam quality, tracking capability, adaptive optics were deduced. For the UXO scenario a mobile directed energy laser demonstrator for humanitarian mine and UXO clearing based on fiber lasers is presented. Based on the parameters the system concept including the cooling system, power supply and the integration into the armoured vehicle TM 170 are explained. The contribution show first experiments of UXO and IED clearing. Different technical approaches to achieve laser power in the 100 kW regime combined with very good beam quality are discussed to fulfil the requirements of the CRAM and Air Defence scenario. Spectral coupling and the beam superimposing both are performed by Rheinmetall Waffe Munition. At the spectral coupling the basic technology parameters for the fiber laser and the dielectric grating as the latest results were put into context with the power levels reached at other groups. For the beam super imposing technology the basic experiments regarding the tracking capability and compensation of the atmosphere on the test range at Unterlüß will be explained. A generic 10 kW Laser Weapon Demonstrator based on 2 Laser Weapon Modules (LWM) from RWM each 5 kW fiber Laser with beam forming and tracking integrate by the team of RWM and RAD (Rheinmetall Air Defense) into a Ground based Air Defend system consisting of Skyguard and Millenium turret are presented. The flight path of the UAV within the valley of the life firing range at Ochsenboden Switzerland is shown. Selected results of the successful tests against UAV's are presented. It shows the capability of the generic 10 kW Laser Weapon Demonstrator to track and to destroy the target. From these results the next steps of Rheinmetall Waffe Munition for a 100 kW class laser weapon are explained.

Cost-effective, transfer-free, flexible resistive random access memory using laser-scribed reduced graphene oxide patterning technology.

PubMed

Tian, He; Chen, Hong-Yu; Ren, Tian-Ling; Li, Cheng; Xue, Qing-Tang; Mohammad, Mohammad Ali; Wu, Can; Yang, Yi; Wong, H-S Philip

2014-06-11

Laser scribing is an attractive reduced graphene oxide (rGO) growth and patterning technology because the process is low-cost, time-efficient, transfer-free, and flexible. Various laser-scribed rGO (LSG) components such as capacitors, gas sensors, and strain sensors have been demonstrated. However, obstacles remain toward practical application of the technology where all the components of a system are fabricated using laser scribing. Memory components, if developed, will substantially broaden the application space of low-cost, flexible electronic systems. For the first time, a low-cost approach to fabricate resistive random access memory (ReRAM) using laser-scribed rGO as the bottom electrode is experimentally demonstrated. The one-step laser scribing technology allows transfer-free rGO synthesis directly on flexible substrates or non-flat substrates. Using this time-efficient laser-scribing technology, the patterning of a memory-array area up to 100 cm(2) can be completed in 25 min. Without requiring the photoresist coating for lithography, the surface of patterned rGO remains as clean as its pristine state. Ag/HfOx/LSG ReRAM using laser-scribing technology is fabricated in this work. Comprehensive electrical characteristics are presented including forming-free behavior, stable switching, reasonable reliability performance and potential for 2-bit storage per memory cell. The results suggest that laser-scribing technology can potentially produce more cost-effective and time-effective rGO-based circuits and systems for practical applications.

Laser direct writing of carbon/Au composite electrodes for high-performance micro-supercapacitors

NASA Astrophysics Data System (ADS)

Cai, Jinguang; Watanabe, Akira; Lv, Chao

2017-02-01

Micro-supercapacitors with small size, light weight, flexibility while maintaining high energy and power output are required for portable miniaturized electronics. The fabrication methods and materials should be cost-effective, scalable, and easily integrated to current electronic industry. Carbon materials have required properties for high-performance flexible supercapacitors, including high specific surface areas, electrochemical stability, and high electrical conductivity, as well as the high mechanical tolerance. Laser direct writing method is a non-contact, efficient, single-step fabrication technique without requirements of masks, post-processing, and complex clean room, which is a useful patterning technique, and can be easily integrated with current electronic product lines for commercial use. Previously we have reported micro-supercapacitors fabricated by laser direct writing on polyimide films in air or Ar, which showed highcapacitive performance. However, the conductivity of the carbon materials is still low for fast charge-discharge use. Here, we demonstrated the fabrication of flexible carbon/Au composite high-performance MSCs by first laser direct writing on commercial polyimide films followed by spin-coating Au nanoparticles ink and second in-situ laser direct writing using the low-cost semiconductor laser. As-prepared micro-supercapacitors show an improved conductivity and capacitance of 1.17 mF/cm2 at a high scanning rate of 10,000 mV/s, which is comparable to the reported capacitance of carbon-based micro-supercapacitors. In addition, the micro-supercapacitors have high bend tolerance and long-cycle stability.

REAL-TIME IN SITU DETECTION OF ORGANIC CONTAMINANTS BY LASER-INDUCED FLUORESCENCE SYSTEM. Final tropical report (Task 1.3).

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

Daniel J. Stepan; James A. Sorensen; Jaroslav Solc

This report summarizes the results of the field demonstration of a laser-induced fluorescence (LIF) method for characterization of brownfields and other contaminated sites. The technology was provided and demonstrated by Dakota Technologies, Inc. (DTI), of Fargo, North Dakota. LIF generates continuous data on the distribution of polycyclic aromatic hydrocarbons (PAHs) within the soil profile. The sensor used to record real-time data is deployed into the soil using a modified truck-mounted Geoprobe percussion soil probing device. The summary of observations described in the following text represents an independent evaluation of the performance, usefulness, and economics of the demonstrated technology for characterizationmore » at PAH-contaminated sites.« less

Substrate-Mediated Laser Ablation under Ambient Conditions for Spatially-Resolved Tissue Proteomics

PubMed Central

Fatou, Benoit; Wisztorski, Maxence; Focsa, Cristian; Salzet, Michel; Ziskind, Michael; Fournier, Isabelle

2015-01-01

Numerous applications of ambient Mass Spectrometry (MS) have been demonstrated over the past decade. They promoted the emergence of various micro-sampling techniques such as Laser Ablation/Droplet Capture (LADC). LADC consists in the ablation of analytes from a surface and their subsequent capture in a solvent droplet which can then be analyzed by MS. LADC is thus generally performed in the UV or IR range, using a wavelength at which analytes or the matrix absorb. In this work, we explore the potential of visible range LADC (532 nm) as a micro-sampling technology for large-scale proteomics analyses. We demonstrate that biomolecule analyses using 532 nm LADC are possible, despite the low absorbance of biomolecules at this wavelength. This is due to the preponderance of an indirect substrate-mediated ablation mechanism at low laser energy which contrasts with the conventional direct ablation driven by sample absorption. Using our custom LADC system and taking advantage of this substrate-mediated ablation mechanism, we were able to perform large-scale proteomic analyses of micro-sampled tissue sections and demonstrated the possible identification of proteins with relevant biological functions. Consequently, the 532 nm LADC technique offers a new tool for biological and clinical applications. PMID:26674367

Review on recent research progress on laser power measurement based on light pressure

NASA Astrophysics Data System (ADS)

Lai, WenChang; Zhou, Pu

2018-03-01

Accurate measuring the laser power is one of the most important issue to evaluate the performance of high power laser. For the time being, most of the demonstrated technique could be attributed to direct measuring route. Indirect measuring laser power based on light pressure, which has been under intensive investigation, has the advantages such as fast response, real-time measuring and high accuracy, compared with direct measuring route. In this paper, we will review several non-traditional methods based on light pressure to precisely measure the laser power proposed recently. The system setup, measuring principle and scaling methods would be introduced and analyzed in detail. We also compare the benefit and the drawback of these methods and analyze the uncertainties of the measurements.

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.

FM and FSK response of tunable two-electrode DFB lasers and their performance with noncoherent detection

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

Willner, A.E.; Kuznetsov, M.; Kaminow, I.P.

1989-12-01

Two-electrode DFB lasers show promise for combining high speed and frequency tunability for FDM-FSK networks. The authors have measured the FM and FSK response of such lasers up to modulation frequencies of {approximately} GHz. Using these lasers in a noncoherent detection system in which a fiber Fabry-Perot tunable optical filter converts an FSK signal into ASK format, the authors demonstrate 10{sup {minus}9} BER up to 1 Gbit/s. Nonuniform FM response and consequent tone broadening of the optical-filtering FSK spectra can lead to system power penalties due to optical-filtering effects. Thus, for a given FM response, they can project the behaviormore » of these lasers in FSK optical systems.« less

Laser performance and modeling of RE3+:YAG double-clad crystalline fiber waveguides

NASA Astrophysics Data System (ADS)

Li, Da; Lee, Huai-Chuan; Meissner, Stephanie K.; Meissner, Helmuth E.

2018-02-01

We report on laser performance of ceramic Yb:YAG and single crystal Tm:YAG double-clad crystalline fiber waveguide (CFW) lasers towards the goal of demonstrating the design and manufacturing strategy of scaling to high output power. The laser component is a double-clad CFW, with RE3+:YAG (RE = Yb, Tm respectively) core, un-doped YAG inner cladding, and ceramic spinel or sapphire outer cladding. Laser performance of the CFW has been demonstrated with 53.6% slope efficiency and 27.5-W stable output power at 1030-nm for Yb:YAG CFW, and 31.6% slope efficiency and 46.7-W stable output power at 2019-nm for Tm:YAG CFW, respectively. Adhesive-Free Bond (AFB®) technology enables a designable refractive index difference between core and inner cladding, and designable core and inner cladding sizes, which are essential for single transverse mode CFW propagation. To guide further development of CFW designs, we present thermal modeling, power scaling and design of single transverse mode operation of double-clad CFWs and redefine the single-mode operation criterion for the double-clad structure design. The power scaling modeling of double-clad CFW shows that in order to achieve the maximum possible output power limited by the physical properties, including diode brightness, thermal lens effect, and simulated Brillion scattering, the length of waveguide is in the range of 0.5 2 meters. The length of an individual CFW is limited by single crystal growth and doping uniformity to about 100 to 200 mm lengths, and also by availability of starting crystals and manufacturing complexity. To overcome the limitation of CFW lengths, end-to-end proximity-coupling of CFWs is introduced.

Quantum trajectories for high-order-harmonic generation from multiple rescattering events in the long-wavelength regime

NASA Astrophysics Data System (ADS)

He, Lixin; Li, Yang; Wang, Zhe; Zhang, Qingbin; Lan, Pengfei; Lu, Peixiang

2014-05-01

We have performed the quantum trajectory analysis for high-order-harmonic generation (HHG) with different driving laser wavelengths. By defining the ratio of HHG yields of the Nth and first rescattering events (YN/Y1), we quantitatively evaluate the HHG contributions from multiple rescatterings. The results show that the HHG yield ratio increases gradually with the increase of the laser wavelength, which demonstrates that high-order rescatterings provide ascendent contributions to HHG at longer wavelength. By calculating the classical electron trajectories, we find significant differences exist in the electron behaviors between the first and high-order rescatterings. Further investigations have demonstrated that the increasing HHG yield ratio is mainly attributed to the relatively smaller contributions from the short path of the first electron rescattering at longer laser wavelength.

Medical free-electron laser: fact or fiction?

NASA Astrophysics Data System (ADS)

Bell, James P.; Ponikvar, Donald R.

1994-07-01

The free electron laser (FEL) has long been proposed as a flexible tool for a variety of medical applications, and yet the FEL has not seen widespread acceptance in the medical community. The issues have been the laser's size, cost, and complexity. Unfortunately, research on applications of FELs has outpaced the device development efforts. This paper describes the characteristics of the FEL, as they have been demonstrated in the U.S. Army's FEL technology development program, and identifies specific medical applications where demonstrated performance levels would suffice. This includes new photodynamic therapies for cancer and HIV treatment, orthopedic applications, tissue welding applications, and multiwavelength surgical techniques. A new tunable kilowatt class FEL device is described, which utilizes existing hardware from the U.S. Army program. An assessment of the future potential, based on realistic technology scaling is provided.

High Harmonic Radiation Generation and Attosecond pulse generation from Intense Laser-Solid Interactions

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

Thomas, Alexander Roy; Krushelnick, Karl

2016-09-08

We have studied ion motion effects in high harmonic generation, including shifts to the harmonics which result in degradation of the attosecond pulse train, and how to mitigate them. We have examined the scaling with intensity of harmonic emission. We have also switched the geometry of the interaction to measure, for the first time, harmonics from a normal incidence interaction. This was performed by using a special parabolic reflector with an on axis hole and is to allow measurements of the attosecond pulses using standard techniques. Here is a summary of the findings: First high harmonic generation in laser-solid interactionsmore » at 10 21 Wcm -2, demonstration of harmonic focusing, study of ion motion effects in high harmonic generation in laser-solid interactions, and demonstration of harmonic amplification.« less

Field demonstration of an eight-element fiber laser hydrophone array

NASA Astrophysics Data System (ADS)

Foster, Scott; Tikhomirov, Alexei; Harrison, Joanne; van Velzen, John

2014-05-01

We have developed an 8-element fibre laser seabed array demonstrating state-of-the art performance characteristics for a fibre laser sensing system and highlighting the advantage this technology provides in the underwater sensing domain. The system employs sea-state-zero sensitivity hydrophones with a flat acoustic response over a bandwidth exceeding 5kHz and very low inertial sensitivity. The system contains no outboard electronics and few metal components making it extremely light, compact, and low complexity. The array may be deployed up to 4 km from a land or sea based platform to a depth of up to 80m. Power delivery and telemetry for all 8 sensors is achieved via a single 2mm diameter optical fibre cable weighing less than 5kg per km. We report here results of the first field trials of this system.

Unconventional High-Performance Laser Protection System Based on Dichroic Dye-Doped Cholesteric Liquid Crystals

NASA Astrophysics Data System (ADS)

Zhang, Wanshu; Zhang, Lanying; Liang, Xiao; Le Zhou; Xiao, Jiumei; Yu, Li; Li, Fasheng; Cao, Hui; Li, Kexuan; Yang, Zhou; Yang, Huai

2017-02-01

High-performance and cost-effective laser protection system is of crucial importance for the rapid advance of lasers in military and civilian fields leading to severe damages of human eyes and sensitive optical devices. However, it is crucially hindered by the angle-dependent protective effect and the complex preparation process. Here we demonstrate that angle-independence, good processibility, wavelength tunability, high optical density and good visibility can be effectuated simultaneously, by embedding dichroic anthraquinone dyes in a cholesteric liquid crystal matrix. More significantly, unconventional two-dimensional parabolic protection behavior is reported for the first time that in stark contrast to the existing protection systems, the overall parabolic protection behavior enables protective effect to increase with incident angles, hence providing omnibearing high-performance protection. The protective effect is controllable by dye concentration, LC cell thickness and CLC reflection efficiency, and the system can be made flexible enabling applications in flexible and even wearable protection devices. This research creates a promising avenue for the high-performance and cost-effective laser protection, and may foster the development of optical applications such as solar concentrators, car explosion-proof membrane, smart windows and polarizers.

Influence of Ionization and Beam Quality on Interaction of TW-Peak CO2 Laser with Hydrogen Plasma

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

Samulyak, Roman

3D numerical simulations of the interaction of a powerful CO2 laser with hydrogen jets demonstrating the role of ionization and laser beam quality are presented. Simulations are performed in support of the plasma wakefield accelerator experiments being conducted at the BNL Accelerator Test Facility (ATF). The CO2 laser at BNL ATF has several potential advantages for laser wakefield acceleration compared to widely used solid-state lasers. SPACE, a parallel relativistic Particle-in-Cell code, developed at SBU and BNL, has been used in these studies. A novelty of the code is its set of efficient atomic physics algorithms that compute ionization and recombinationmore » rates on the grid and transfer them to particles. The primary goal of the initial BNL experiments was to characterize the plasma density by measuring the sidebands in the spectrum of the probe laser. Simulations, that resolve hydrogen ionization and laser spectra, help explain several trends that were observed in the experiments.« less

Laser assisted drug delivery: a review of an evolving technology.

PubMed

Sklar, Lindsay R; Burnett, Christopher T; Waibel, Jill S; Moy, Ronald L; Ozog, David M

2014-04-01

Topically applied drugs have a relatively low cutaneous bioavailability. This article reviews the existing applications of laser assisted drug delivery, a means by which the permeation of topically applied agents can be enhanced into the skin. The existing literature suggests that lasers are a safe and effective means of enhancing the delivery of topically applied agents through the skin. The types of lasers most commonly studied in regards to drug delivery are the carbon dioxide (CO2 ) and erbium:yttrium-aluminum-garnet (Er:YAG) lasers. Both conventional ablative and fractional ablative modalities have been utilized and are summarized herein. The majority of the existing studies on laser assisted drug delivery have been performed on animal models and additional human studies are needed. Laser assisted drug delivery is an evolving technology with potentially broad clinical applications. Multiple studies demonstrate that laser pretreatment of the skin can increase the permeability and depth of penetration of topically applied drug molecules for both local cutaneous and systemic applications. © 2014 Wiley Periodicals, Inc.

Widely wavelength tunable gain-switched Er³⁺-doped ZBLAN fiber laser around 2.8 μm.

PubMed

Wei, Chen; Luo, Hongyu; Shi, Hongxia; Lyu, YanJia; Zhang, Han; Liu, Yong

2017-04-17

In this paper, we demonstrate a wavelength widely tunable gain-switched Er³⁺-doped ZBLAN fiber laser around 2.8 μm. The laser can be tuned over 170 nm (2699 nm~2869.9 nm) for various pump power levels, while maintaining stable μs-level single-pulse gain-switched operation with controllable output pulse duration at a selectable repetition rate. To the best of our knowledge, this is the first wavelength tunable gain-switched fiber laser in the 3 μm spectral region with the broadest tuning range (doubling the record tuning range) of the pulsed fiber lasers around 3 μm. Influences of pump energy and power on the output gain-switched laser performances are investigated in detail. This robust, simple, and versatile mid-infrared pulsed fiber laser source is highly suitable for many applications including laser surgery, material processing, sensing, spectroscopy, as well as serving as a practical seed source in master oscillator power amplifiers.

Quasi-CW 110 kW AlGaAs Laser Diode Array Module for Inertial Fusion Energy Laser Driver

NASA Astrophysics Data System (ADS)

Kawashima, Toshiyuki; Kanzaki, Takeshi; Matsui, Ken; Kato, Yoshinori; Matsui, Hiroki; Kanabe, Tadashi; Yamanaka, Masanobu; Nakatsuka, Masahiro; Izawa, Yasukazu; Nakai, Sadao; Miyamoto, Masahiro; Kan, Hirofumi; Hiruma, Teruo

2001-12-01

We have successfully demonstrated a large aperture 803 nm AlGaAs diode laser module as a pump source for a 1053 nm, 10 J output Nd:glass slab laser amplifier for diode-pumped solid-state laser (DPSSL) fusion driver. Detailed performance results of the laser diode module are presented, including bar package and stack configuration, and their thermal design and analysis. A sufficiently low thermal impedance of the stack was realized by combining backplane liquid cooling configuration with modular bar package architecture. Total peak power of 110 kW and electrical to optical conversion efficiency of 46% were obtained from the module consisting of a total of 1000 laser diode bars. A peak intensity of 2.6 kW/cm2 was accomplished across an emitting area of 418 mm× 10 mm. Currently, this laser diode array module with a large two-dimensional aperture is, to our knowledge, the only operational pump source for the high output energy DPSSL.

Dual-lasing channel quantum cascade laser based on scattering-assisted injection design.

PubMed

Wen, Boyu; Xu, Chao; Wang, Siyi; Wang, Kaixi; Tam, Man Chun; Wasilewski, Zbig; Ban, Dayan

2018-04-02

A dual lasing channel Terahertz Quantum Cascade laser (THz QCL) based on GaAs/Al 0.17 Ga 0.83 As material system is demonstrated. The device shows the lowest reported threshold current density (550A/cm 2 at 50K) of GaAs/Al x Ga 1-x As material system based scattering-assisted (SA) structures and operates up to a maximum lasing temperature of 144K. Dual lasing channel operation is investigated theoretically and experimentally. The combination of low frequency emission, dual lasing channel operation, low lasing threshold current density and high temperature performance make such devices ideal candidates for low frequency applications, and initiates the design strategy for achieving high-temperature performance terahertz quantum cascade laser with wide frequency coverage at low frequency.

Semitransparent organic photovoltaic modules with Ag nanowire top electrodes

NASA Astrophysics Data System (ADS)

Guo, Fei; Kubis, Peter; Przybilla, Thomas; Spiecker, Erdmann; Forberich, Karen; Brabec, Christoph J.

2014-10-01

Semitransparent organic photovoltaic (OPV) cells are promising for applications in transparent architectures where their opaque counterparts are not suitable. Manufacturing of large-area modules without performance losses compared to their lab-scale devices is a key step towards practical applications of this PV technology. In this paper, we report the use of solution-processed silver nanowires as top electrodes and fabricate semitransparent OPV modules based on ultra-fast laser scribing. Through a rational choice of device architecture in combination with high-precision laser patterning, we demonstrate efficient semitransparent modules with comparable performance as compared to the reference devices.

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

Wang, Yin; Wang, Wen; Wysocki, Gerard, E-mail: gwysocki@princeton.edu

In this Letter, we present a method of performing broadband mid-infrared spectroscopy with conventional, free-running, continuous wave Fabry-Perot quantum cascade lasers (FP-QCLs). The measurement method is based on multi-heterodyne down-conversion of optical signals. The sample transmission spectrum probed by one multi-mode FP-QCL is down-converted to the radio-frequency domain through an optical multi-heterodyne process using a second FP-QCL as the local oscillator. Both a broadband multi-mode spectral measurement as well as high-resolution (∼15 MHz) spectroscopy of molecular absorption are demonstrated and show great potential for development of high performance FP-laser-based spectrometers for chemical sensing.

Development of a Fiber Laser Welding Capability for the W76, MC4702 Firing Set

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

Samayoa, Jose

2010-05-12

Development work to implement a new welding system for a Firing Set is presented. The new system is significant because it represents the first use of fiber laser welding technology at the KCP. The work used Six-Sigma tools for weld characterization and to define process performance. Determinations of workable weld parameters and comparison to existing equipment were completed. Replication of existing waveforms was done utilizing an Arbitrary Pulse Generator (APG), which was used to modulate the fiber laser’s exclusive continuous wave (CW) output. Fiber laser weld process capability for a Firing Set is demonstrated.

Wavefront Tilt And Beam Walk Correction For A Pulsed Laser System

NASA Astrophysics Data System (ADS)

Bartosewcz, Mike; Tyburski, Joe

1986-05-01

The Lockheed Beam Alignment Assembly (BAA) is designed to be a space qualifiable, long life, low bandwidth beam stabilization system. The BAA will stabilize a wandering pulsed laser beam with an input beam tilt of ±750 microradians and translation of ±2.5 mm by two orders of magnitude at the bandwidth of interest. A bandwidth of three hertz was selected to remove laser and optical train thermal drifts and launch induced strain effects. The lambda over twenty RMS wavefront will be maintained in the optics at full power under vacuum test, to demonstrate space qualifiability and optical performance.

Electrically pumped continuous wave quantum dot lasers epitaxially grown on patterned, on-axis (001) Si

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

Norman, Justin; Kennedy, M. J.; Selvidge, Jennifer

High performance III-V lasers at datacom and telecom wavelengths on on-axis (001) Si are needed for scalable datacenter interconnect technologies. We demonstrate electrically injected quantum dot lasers grown on on-axis (001) Si patterned with {111} v-grooves lying in the [110] direction. No additional Ge buffers or substrate miscut was used. The active region consists of five InAs/InGaAs dot-in-a-well layers. Here, we achieve continuous wave lasing with thresholds as low as 36 mA and operation up to 80°C.

Development of a Pulsed 2-micron Laser Transmitter for CO2 Sensing from Space

NASA Technical Reports Server (NTRS)

Singh, Upendra N.; Yu, Jirong; Bai, Yingxin; Petros, Mulugeta; Menzies, Robert T.

2011-01-01

NASA Langley Research Center (LaRC), in collaboration with NASA Jet Propulsion Laboratory (JPL), is engaged in the development and demonstration of a highly efficient, versatile, 2-micron pulsed laser that can be used in a pulsed Differential Absorption Lidar (DIAL)/Integrated Path Differential Absorption (IPDA) instrument to make precise, high-resolution CO2 measurements to investigate sources, sinks, and fluxes of CO2. This laser transmitter will feature performance characteristics needed for an ASCENDS system that will be capable of delivering the CO2 measurement precision required by the Earth Science Decadal Survey (DS).

Electrically pumped continuous wave quantum dot lasers epitaxially grown on patterned, on-axis (001) Si

DOE PAGES

Norman, Justin; Kennedy, M. J.; Selvidge, Jennifer; ...

2017-02-14

High performance III-V lasers at datacom and telecom wavelengths on on-axis (001) Si are needed for scalable datacenter interconnect technologies. We demonstrate electrically injected quantum dot lasers grown on on-axis (001) Si patterned with {111} v-grooves lying in the [110] direction. No additional Ge buffers or substrate miscut was used. The active region consists of five InAs/InGaAs dot-in-a-well layers. Here, we achieve continuous wave lasing with thresholds as low as 36 mA and operation up to 80°C.

Graphene surface emitting terahertz laser: Diffusion pumping concept

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

Davoyan, Arthur R., E-mail: davoyan@seas.upenn.edu; Morozov, Mikhail Yu.; Popov, Vyacheslav V.

2013-12-16

We suggest a concept of a tunable graphene-based terahertz (THz) surface emitting laser with diffusion pumping. We employ significant difference in the electronic energy gap of graphene and a typical wide-gap semiconductor, and demonstrate that carriers generated in the semiconductor can be efficiently captured by graphene resulting in population inversion and corresponding THz lasing from graphene. We develop design principles for such a laser and estimate its performance. We predict up to 50 W/cm{sup 2} terahertz power output for 100 kW/cm{sup 2} pump power at frequency around 10 THz at room temperature.

Precision Laser Annealing of Focal Plane Arrays

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

Bender, Daniel A.; DeRose, Christopher; Starbuck, Andrew Lea

2015-09-01

We present results from laser annealing experiments in Si using a passively Q-switched Nd:YAG microlaser. Exposure with laser at fluence values above the damage threshold of commercially available photodiodes results in electrical damage (as measured by an increase in photodiode dark current). We show that increasing the laser fluence to values in excess of the damage threshold can result in annealing of a damage site and a reduction in detector dark current by as much as 100x in some cases. A still further increase in fluence results in irreparable damage. Thus we demonstrate the presence of a laser annealing windowmore » over which performance of damaged detectors can be at least partially reconstituted. Moreover dark current reduction is observed over the entire operating range of the diode indicating that device performance has been improved for all values of reverse bias voltage. Additionally, we will present results of laser annealing in Si waveguides. By exposing a small (<10 um) length of a Si waveguide to an annealing laser pulse, the longitudinal phase of light acquired in propagating through the waveguide can be modified with high precision, <15 milliradian per laser pulse. Phase tuning by 180 degrees is exhibited with multiple exposures to one arm of a Mach-Zehnder interferometer at fluence values below the morphological damage threshold of an etched Si waveguide. No reduction in optical transmission at 1550 nm was found after 220 annealing laser shots. Modeling results for laser annealing in Si are also presented.« less

Laser Induced Damage of Potassium Dihydrogen Phosphate (KDP) Optical Crystal Machined by Water Dissolution Ultra-Precision Polishing Method

PubMed Central

Gao, Hang; Wang, Xu; Guo, Dongming; Liu, Ziyuan

2018-01-01

Laser induced damage threshold (LIDT) is an important optical indicator for nonlinear Potassium Dihydrogen Phosphate (KDP) crystal used in high power laser systems. In this study, KDP optical crystals are initially machined with single point diamond turning (SPDT), followed by water dissolution ultra-precision polishing (WDUP) and then tested with 355 nm nanosecond pulsed-lasers. Power spectral density (PSD) analysis shows that WDUP process eliminates the laser-detrimental spatial frequencies band of micro-waviness on SPDT machined surface and consequently decreases its modulation effect on the laser beams. The laser test results show that LIDT of WDUP machined crystal improves and its stability has a significant increase by 72.1% compared with that of SPDT. Moreover, a subsequent ultrasonic assisted solvent cleaning process is suggested to have a positive effect on the laser performance of machined KDP crystal. Damage crater investigation indicates that the damage morphologies exhibit highly thermal explosion features of melted cores and brittle fractures of periphery material, which can be described with the classic thermal explosion model. The comparison result demonstrates that damage mechanisms for SPDT and WDUP machined crystal are the same and WDUP process reveals the real bulk laser resistance of KDP optical crystal by removing the micro-waviness and subsurface damage on SPDT machined surface. This improvement of WDUP method makes the LIDT more accurate and will be beneficial to the laser performance of KDP crystal. PMID:29534032

The influence of laser pulse duration and energy on ICP-MS signal intensity, elemental fractionation, and particle size distribution in NIR fs-LA-ICP-MS

PubMed Central

Diwakar, Prasoon K.; Harilal, Sivanandan S.; LaHaye, Nicole L.; Hassanein, Ahmed; Kulkarni, Pramod

2015-01-01

Laser parameters, typically wavelength, pulse width, irradiance, repetition rate, and pulse energy, are critical parameters which influence the laser ablation process and thereby influence the LA-ICP-MS signal. In recent times, femtosecond laser ablation has gained popularity owing to the reduction in fractionation related issues and improved analytical performance which can provide matrix-independent sampling. The advantage offered by fs-LA is due to shorter pulse duration of the laser as compared to the phonon relaxation time and heat diffusion time. Hence the thermal effects are minimized in fs-LA. Recently, fs-LA-ICP-MS demonstrated improved analytical performance as compared to ns-LA-ICP-MS, but detailed mechanisms and processes are still not clearly understood. Improvement of fs-LA-ICP-MS over ns-LA-ICP-MS elucidates the importance of laser pulse duration and related effects on the ablation process. In this study, we have investigated the influence of laser pulse width (40 fs to 0.3 ns) and energy on LA-ICP-MS signal intensity and repeatability using a brass sample. Experiments were performed in single spot ablation mode as well as rastering ablation mode to monitor the Cu/Zn ratio. The recorded ICP-MS signal was correlated with total particle counts generated during laser ablation as well as particle size distribution. Our results show the importance of pulse width effects in the fs regime that becomes more pronounced when moving from femtosecond to picosecond and nanosecond regimes. PMID:26664120

Picosecond Pulsed Laser Ablation for the Surface Preparation of Epoxy Composites

NASA Technical Reports Server (NTRS)

Palmieri, Frank; Ledesma, Rodolfo; Fulton, Tayler; Arthur, Alexandria; Eldridge, Keishara; Thibeault, Sheila; Lin, Yi; Wohl, Chris; Connell, John

2017-01-01

As part of a technical challenge under the Advanced Composites Program, methods for improving pre-bond process control for aerospace composite surface treatments and inspections, in conjunction with Federal Aviation Administration guidelines, are under investigation. The overall goal is to demonstrate high fidelity, rapid and reproducible surface treatment and surface characterization methods to reduce uncertainty associated with the bonding process. The desired outcomes are reliable bonded airframe structure, and reduced timeline to certification. In this work, laser ablation was conducted using a q-switched Nd:YVO4 laser capable of nominal pulse durations of 8 picoseconds (ps). Aerospace structural carbon fiber reinforced composites with an epoxy resin matrix were laser treated, characterized, processed into bonded assemblies and mechanically tested. The characterization of ablated surfaces were conducted using scanning electron microscopy (SEM), water contact angle (WCA) goniometry, micro laser induced breakdown spectroscopy (uLIBS), and electron spin resonance (ESR). The bond performance was assessed using a double cantilever beam (DCB) test with an epoxy adhesive. The surface characteristics and bond performance obtained from picosecond ablated carbon fiber reinforced plastics (CFRPs) are presented herein.

Optical-fiber-to-waveguide coupling using carbon-dioxide-laser-induced long-period fiber gratings.

PubMed

Bachim, Brent L; Ogunsola, Oluwafemi O; Gaylord, Thomas K

2005-08-15

Optical fibers are expected to play a role in chip-level and board-level optical interconnects because of limitations on the bandwidth and level of integration of electrical interconnects. Therefore, methods are needed to couple optical fibers directly to waveguides on chips and on boards. We demonstrate optical-fiber-to-waveguide coupling using carbon-dioxide laser-induced long-period fiber gratings (LPFGs). Such gratings can be written in standard fiber and offer wavelength multiplexing-demultiplexing performance. The coupler fabrication process and the characterization apparatus are presented. The operation and the wavelength response of a LPFG-based optical-fiber-to-waveguide directional coupler are demonstrated.

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

Xu, Luyao; Curwen, Christopher; Chen, Daguan

A longstanding challenge for terahertz quantum-cascade (QC) lasers is achieving both a high power and high-quality beam pattern, this is due in part due to their use of sub-wavelength metallic waveguides. Recently, the vertical-external-cavity surface-emitting laser (VECSEL) concept was demonstrated for the first time in the terahertz range and for a QC-laser. This is enabled by the development of an amplifying metasurface reflector capable of coupling incident free-space THz radiation to the QC-laser material such that it is amplified and re-radiated. The THz metasurface QC-VECSEL initiates a new approach for making QC-lasers with high power and excellent beam pattern. Furthermore,more » the ability to engineer the electromagnetic phase, amplitude, and polarization response of the metasurface enables lasers with new functionality. Our article provides an overview of the fundamental theory, design considerations, and recent results for high-performance THz QC-VECSELs.« less

Research on laser-induced damage resistance of fused silica optics by the fluid jet polishing method.

PubMed

Lv, Liang; Ma, Ping; Huang, Jinyong; He, Xiang; Cai, Chao; Zhu, Heng

2016-03-20

Laser-induced damage threshold (LIDT) is one important evaluation index for optical glasses applied in large laser instruments which are exposed to high light irradiation flux. As a new kind of precise polishing technology, fluid jet polishing (FJP) has been widely used in generating planar, spherical, and aspherical optics with high-accuracy surfaces. Laser damage resistances of fused silica optics by the FJP process are studied in this paper. Fused silica samples with various FJP parameters are prepared, and laser damage experiments are performed with 351 nm wavelength and a 5.5 ns pulse width laser. Experimental results demonstrate that the LIDT of the samples treated with FJP processes did not increase, compared to their original state. The surface quality of the samples is one factor for the decrease of LIDT. For ceria solution polished samples, the cerium element remaining is another factor of the lower LIDT.

Laser Beam Filtration for High Spatial Resolution MALDI Imaging Mass Spectrometry

NASA Astrophysics Data System (ADS)

Zavalin, Andre; Yang, Junhai; Caprioli, Richard

2013-07-01

We describe an easy and inexpensive way to provide a highly defined Gaussian shaped laser spot on target of 5 μm diameter for imaging mass spectrometry using a commercial MALDI TOF instrument that is designed to produce a 20 μm diameter laser beam on target at its lowest setting. A 25 μm pinhole filter on a swivel arm was installed in the laser beam optics outside the vacuum ion source chamber so it is easily flipped into or out of the beam as desired by the operator. The resulting ion images at 5 μm spatial resolution are sharp since the satellite secondary laser beam maxima have been removed by the filter. Ion images are shown to demonstrate the performance and are compared with the method of oversampling to achieve higher spatial resolution when only a larger laser beam spot on target is available.

Modification of semiconductor materials with the use of plasma produced by low intensity repetitive laser pulses

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

Wolowski, J.; Rosinski, M.; Badziak, J.

2008-03-19

This work reports experiments concerning specific application of laser-produced plasma at IPPLM in Warsaw. A repetitive pulse laser system of parameters: energy up to 0.8 J in a 3.5 ns-pulse, wavelength of 1.06 {mu}m, repetition rate of up to 10 Hz, has been employed in these investigations. The characterisation of laser-produced plasma was performed with the use of 'time-of-flight' ion diagnostics simultaneously with other diagnostic methods. The results of laser-matter interaction were obtained in dependence on laser pulse parameters, illumination geometry and target material. The modified SiO{sub 2} layers and sample surface properties were characterised with the use of differentmore » methods at the Middle-East Technological University in Ankara and at the Warsaw University of technology. The production of the Ge nanocrystallites has been demonstrated for annealed samples prepared in different experimental conditions.« less

Experimental studies on nonpenetrating filtration surgery using the CO2 laser.

PubMed

Assia, Ehud I; Rotenstreich, Yigal; Barequet, Irina S; Apple, David J; Rosner, Mordechai; Belkin, Michael

2007-06-01

This study evaluated the use of a CO2 laser for performing deep sclerectomy in nonpenetrating filtration surgery. Three experimental models were performed: enucleated sheep and cow eyes (n=18) to determine optimal irradiation parameters, live rabbit eyes (n=20) to test feasibility, and cadaver eyes (40 procedures in 20 eyes) to study effects in human eyes tissue. After a half-thickness scleral flap was created, deep sclerectomy was performed by CO2 laser applications on the scleral bed down to the trabeculo-Descemet's membrane. Fluid percolation was repeatedly achieved without penetration in sheep and cow eyes using scanned laser energy of 5-10 W at a pulse duration of 200 micros and a working distance of 35 cm. In live rabbits, deep sclerectomy was achieved without perforation in 19/20 eyes. Intraocular pressure was significantly decreased on the first postoperative day (10.3+/-5.1 mmHg lower, on average, than in the nonoperated fellow eye; P<0.001), and this persisted for 21 days. Operations on all cadaver eyes resulted in effective fluid percolation. Penetration of the scleral wall occurred in five cases only after repeated laser applications with high energy. Histologically, a thin sclerocorneal intact wall was demonstrated at the sclerectomy bed. Collateral tissue damage did not extend beyond 100 microm, and adjacent structures remained unharmed. CO2 laser-assisted deep sclerectomy is a feasible and apparently safe procedure.

A new three-dimensional nonscanning laser imaging system based on the illumination pattern of a point-light-source array

NASA Astrophysics Data System (ADS)

Xia, Wenze; Ma, Yayun; Han, Shaokun; Wang, Yulin; Liu, Fei; Zhai, Yu

2018-06-01

One of the most important goals of research on three-dimensional nonscanning laser imaging systems is the improvement of the illumination system. In this paper, a new three-dimensional nonscanning laser imaging system based on the illumination pattern of a point-light-source array is proposed. This array is obtained using a fiber array connected to a laser array with each unit laser having independent control circuits. This system uses a point-to-point imaging process, which is realized using the exact corresponding optical relationship between the point-light-source array and a linear-mode avalanche photodiode array detector. The complete working process of this system is explained in detail, and the mathematical model of this system containing four equations is established. A simulated contrast experiment and two real contrast experiments which use the simplified setup without a laser array are performed. The final results demonstrate that unlike a conventional three-dimensional nonscanning laser imaging system, the proposed system meets all the requirements of an eligible illumination system. Finally, the imaging performance of this system is analyzed under defocusing situations, and analytical results show that the system has good defocusing robustness and can be easily adjusted in real applications.

Growth, spectroscopy, and laser performance of a 2.79 μm Cr,Er,Pr:GYSGG radiation-resistant crystal.

PubMed

Luo, Jianqiao; Sun, Dunlu; Zhang, Huili; Guo, Qiang; Fang, Zhongqing; Zhao, Xuyao; Cheng, Maojie; Zhang, Qingli; Yin, Shaotang

2015-09-15

We demonstrate the growth, spectroscopy, and laser performance of a 2.79 μm Cr,Er,Pr:GYSGG radiation-resistant crystal. The lifetimes for the upper laser level (4)I(11/2) and lower laser level (4)I(13/2) are 0.59 and 0.84 ms, respectively, which are due to the doping of the Pr(3+) ions. A maximum pulse energy of 278 mJ operated at 10 Hz and 2.79 μm is obtained when pumped with a flash lamp, which corresponds to the electrical-to-optical efficiency of 0.6% and a slope efficiency of 0.7%. A maximum average power of 2.9 W at 60 Hz is achieved, which corresponds to the electrical-to-optical efficiency of 0.4% and slope efficiency of 0.8%. Compared with a Cr,Er:YSGG crystal, the Cr,Er,Pr:GYSGG crystal can be operated at a higher pulse repetition rate. These results suggest that doping deactivator Pr(3+) ions can effectively decrease the lower laser level lifetime and improve the laser repetition rate. Therefore, the application fields and range of the Cr,Er,Pr:GYSGG laser can be extended greatly due to its properties of radiation resistance and high repetition frequency.

Using acoustic levitation in synchrotron based laser pump hard x-ray probe experiments

NASA Astrophysics Data System (ADS)

Hu, Bin; Lerch, Jason; Suthar, Kamlesh; Dichiara, Anthony

Acoustic levitation provides a platform to trap and hold a small amount of material by using standing pressure waves without a container. The technique has a potential to be used for laser pump x-ray probe experiments; x-ray scattering and laser distortion from the container can be avoided, sample consumption can be minimized, and unwanted chemistry that may occur at the container interface can be avoided. The method has been used at synchrotron sources for studying protein and pharmaceutical solutions using x-ray diffraction (XRD) and small angle x-ray scattering (SAXS). However, pump-probe experiments require homogeneously excited samples, smaller than the absorption depth of the material that must be held stably at the intersection of both the laser and x-ray beams. We discuss 1) the role of oscillations in acoustic levitation and the optimal acoustic trapping conditions for x-ray/laser experiments, 2) opportunities to automate acoustic levitation for fast sample loading and manipulation, and 3) our experimental results using SAXS to monitor laser induced thermal expansion in gold nanoparticles solution. We also performed Finite Element Analysis to optimize the trapping performance and stability of droplets ranging from 0.4 mm to 2 mm. Our early x-ray/laser demonstrated the potential of the technique for time-resolved X-ray science.

Blood flow measurement in extracorporeal circulation using self-mixing laser diode

NASA Astrophysics Data System (ADS)

Cattini, Stefano; Norgia, Michele; Pesatori, Alessandro; Rovati, Luigi

2010-02-01

To measure blood flow rate in ex-vivo circulation, we propose an optical Doppler flowmeter based on the self-mixing effect within a laser diode (SM-LD). Advantages in adopting SM-LD techniques derive from reduced costs, ease of implementation and limited size. Moreover, the provided contactless sensing allows sensor reuse, hence further cost reduction. Preliminary measurements performed on bovine blood are reported, thus demonstrating the applicability of the proposed measurement method.

Subpicosecond X rotations of atomic clock states

NASA Astrophysics Data System (ADS)

Song, Yunheung; Lee, Han-gyeol; Kim, Hyosub; Jo, Hanlae; Ahn, Jaewook

2018-05-01

We demonstrate subpicosecond-timescale population transfer between the pair of hyperfine ground states of atomic rubidium using a single laser-pulse. Our scheme utilizes the geometric and dynamic phases induced during Rabi oscillation through the fine-structure excited state to construct an X rotation gate for the hyperfine-state qubit system. The experiment performed with a femtosecond laser and cold rubidium atoms, in a magnetooptical trap, shows over 98% maximal population transfer between the clock states.

A compact and portable optofluidic device for detection of liquid properties and label-free sensing

NASA Astrophysics Data System (ADS)

Lahoz, F.; Martín, I. R.; Walo, D.; Gil-Rostra, J.; Yubero, F.; Gonzalez-Elipe, A. R.

2017-06-01

Optofluidic lasers have been widely investigated over the last few years mainly because they can be easily integrated in sensor devices. However, high power pulse lasers are required as excitation sources, which, in practice, limit the portability of the system. Trying to overcome some of these limitations, in this paper we propose the combined use of a small CW laser with a Fabry-Perot optofluidic planar microcavity showing high sensitivity and versatility for detection of liquid properties and label-free sensing. Firstly, a fluorescein solution in ethanol is used to demonstrate the high performances of the FP microcavity as a temperature sensor both in the laser (high pump power above laser threshold) and in the fluorescence (low pump power) regimes. A shift in the wavelength of the resonant cavity modes is used to detect changes in the temperature and our results show that high sensitivities could be already obtained using cheap and portable CW diode lasers. In the second part of the paper, the demonstration of this portable device for label-free sensing is illustrated under low CW pumping. The wavelength positions of the optofluidic resonant modes are used to detect glucose concentrations in water solutions using a protein labelled with a fluorescent dye as the active medium.

Laser-shocked energetic materials with metal additives: evaluation of chemistry and detonation performance.

PubMed

Gottfried, Jennifer L; Bukowski, Eric J

2017-01-20

A focused, nanosecond-pulsed laser has been used to ablate, atomize, ionize, and excite milligram quantities of metal-doped energetic materials that undergo exothermic reactions in the laser-induced plasma. The subsequent shock wave expansion in the air above the sample has been monitored using high-speed schlieren imaging in a recently developed technique, laser-induced air shock from energetic materials (LASEM). The method enables the estimation of detonation velocities based on the measured laser-induced air-shock velocities and has previously been demonstrated for organic military explosives. Here, the LASEM technique has been extended to explosive formulations with metal additives. A comparison of the measured laser-induced air-shock velocities for TNT, RDX, DNTF, and LLM-172 doped with Al or B to the detonation velocities predicted by the thermochemical code CHEETAH for inert or active metal participation demonstrates that LASEM has potential for predicting the early time (<10  μs) participation of metal additives in detonation events. The LASEM results show that while Al is mostly inert at early times in the detonation event (confirmed from large-scale detonation testing), B is active-and reducing the amount of hydrogen present during the early chemical reactions increases the resulting estimated detonation velocities.

Design of laser-driven SiO2-YAG:Ce composite thick film: Facile synthesis, robust thermal performance, and application in solid-state laser lighting

NASA Astrophysics Data System (ADS)

Xu, Jian; Liu, Bingguo; Liu, Zhiwen; Gong, Yuxuan; Hu, Baofu; Wang, Jian; Li, Hui; Wang, Xinliang; Du, Baoli

2018-01-01

In recent times, there have been rapid advances in the solid-state laser lighting technology. Due to the large amounts of heat accumulated from the high flux laser radiation, color conversion materials used in solid-state laser lighting devices should possess high durability, high thermal conductivity, and low thermal quenching. The aim of this study is to develop a thermally robust SiO2-YAG:Ce composite thick film (CTF) for high-power solid-state laser lighting applications. Commercial colloidal silica which was used as the source of SiO2, played the roles of an adhesive, a filler, and a protecting agent. Compared to the YAG:Ce powder, the CTF exhibits remarkable thermal stability (11.3% intensity drop at 200 °C) and durability (4.5% intensity drop after 1000 h, at 85 °C and 85% humidity). Furthermore, the effects of the substrate material and the thickness of the CTF on the laser lighting performance were investigated in terms of their thermal quenching and luminescence saturation behaviors, respectively. The CTF with a thickness of 50 μm on a sapphire substrate does not show luminescence saturation, despite a high-power density of incident radiation i.e. 20 W/mm2. These results demonstrate the potential applicability of the CTF in solid-state laser lighting devices.

Use of the holmium:YAG laser in urology.

PubMed

Johnson, D E; Cromeens, D M; Price, R E

1992-01-01

The tissue effects of a holmium:YAG (Ho:YAG) laser operating at a wavelength of 2.1 mu with a maximum power of 15 watts (W) and 10 different energy-pulse settings was systematically evaluated on kidney, bladder, prostate, ureteral, and vasal tissue in the dog. In addition, various urologic surgical procedures (partial nephrectomy, transurethral laser incision of the prostate, and laser-assisted vasovasostomy) were performed in the dog, and a laparoscopic pelvic lymph node dissection was carried out in a pig. Although the Ho:YAG laser has a strong affinity for water, precise tissue ablation was achieved in both the contact and non-contact mode when used endoscopically in a fluid medium to ablate prostatic and vesical tissue. Using the usual parameters for tissue destruction (blanching without charring), the depth of thermal injury in the bladder and ureter was kept superficial. In performing partial nephrectomies, a 2-fold reduction in the zone of coagulative necrosis was demonstrated compared to the use of the continuous wave Neodymium:YAG laser (Nd:YAG). When used through the laparoscope, the Ho:YAG laser provided precise cutting and, combined with electrocautery, allowed the dissection to proceed quickly and smoothly. Hemostatic control was adequate in all surgical procedures. Although the results of these investigations are preliminary, our initial experience with the Ho:YAG laser has been favorable and warrants further investigations.

Demonstrated high performance of gas-filled rugby-shaped hohlraums on Omega

NASA Astrophysics Data System (ADS)

Philippe, F.; Tassin, V.; Depierreux, S.; Gauthier, P.; Masson-Laborde, P. E.; Monteil, M. C.; Seytor, P.; Villette, B.; Lasinski, B.; Park, H. S.; Ross, J. S.; Amendt, P.; Döppner, T.; Hinkel, D. E.; Wallace, R.; Williams, E.; Michel, P.; Frenje, J.; Gatu-Johnson, M.; Li, C. K.; Petrasso, R.; Glebov, V.; Sorce, C.; Stoeckl, C.; Nikroo, A.; Giraldez, E.

2014-07-01

A direct experimental comparison of rugby-shaped and cylindrical shaped gas-filled hohlraums on the Omega laser facility demonstrates that higher coupling and minimal backscatter can be achieved in the rugby geometry, leading to significantly enhanced implosion performance. A nearly 50% increase of x-ray drive is associated with earlier bangtime and increase of neutron production. The observed drive enhancement from rugby geometry in this study is almost twice stronger than in previously published results.

Laser demonstration and performance characterization of optically pumped Alkali Laser systems

NASA Astrophysics Data System (ADS)

Sulham, Clifford V.

Diode Pumped Alkali Lasers (DPALs) offer a promising approach for high power lasers in military applications that will not suffer from the long logistical trails of chemical lasers or the thermal management issues of diode pumped solid state lasers. This research focuses on characterizing a DPAL-type system to gain a better understanding of using this type of laser as a directed energy weapon. A rubidium laser operating at 795 nm is optically pumped by a pulsed titanium sapphire laser to investigate the dynamics of DPALs at pump intensities between 1.3 and 45 kW/cm2. Linear scaling as high as 32 times threshold is observed, with no evidence of second order kinetics. Comparison of laser characteristics with a quasi-two level analytic model suggests performance near the ideal steady-state limit, disregarding the mode mis-match. Additionally, the peak power scales linearly as high as 1 kW, suggesting aperture scaling to a few cm2 is sufficient to achieve tactical level laser powers. The temporal dynamics of the 100 ns pump and rubidium laser pulses are presented, and the continually evolving laser efficiency provides insight into the bottlenecking of the rubidium atoms in the 2P3/2 state. Lastly, multiple excited states of rubidium and cesium were accessed through two photon absorption in the red, yielding a blue and an IR photon through amplified stimulated emission. Threshold is modest at 0.3 mJ/pulse, and slope efficiencies increase dramatically with alkali concentrations and peak at 0.4%, with considerable opportunity for improvement. This versatile system might find applications for IR countermeasures or underwater communications.

Ultrafast Beam Switching Using Coupled VCSELs

NASA Technical Reports Server (NTRS)

Ning, Cun-Zheng; Goorjian, Peter

2001-01-01

We propose a new approach to performing ultrafast beam switching using two coupled Vertical-Cavity Surface-Emitting Lasers (VCSELs). The strategy is demonstrated by numerical simulation, showing a beam switching of 10 deg at 42 GHz.

Tone-assisted time delay interferometry on GRACE Follow-On

NASA Astrophysics Data System (ADS)

Francis, Samuel P.; Shaddock, Daniel A.; Sutton, Andrew J.; de Vine, Glenn; Ware, Brent; Spero, Robert E.; Klipstein, William M.; McKenzie, Kirk

2015-07-01

We have demonstrated the viability of using the Laser Ranging Interferometer on the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) space mission to test key aspects of the interspacecraft interferometry proposed for detecting gravitational waves. The Laser Ranging Interferometer on GRACE-FO will be the first demonstration of interspacecraft interferometry. GRACE-FO shares many similarities with proposed space-based gravitational wave detectors based on the Laser Interferometer Space Antenna (LISA) concept. Given these similarities, GRACE-FO provides a unique opportunity to test novel interspacecraft interferometry techniques that a LISA-like mission will use. The LISA Experience from GRACE-FO Optical Payload (LEGOP) is a project developing tests of arm locking and time delay interferometry (TDI), two frequency stabilization techniques, that could be performed on GRACE-FO. In the proposed LEGOP TDI demonstration one GRACE-FO spacecraft will have a free-running laser while the laser on the other spacecraft will be locked to a cavity. It is proposed that two one-way interspacecraft phase measurements will be combined with an appropriate delay in order to produce a round-trip, dual one-way ranging (DOWR) measurement independent of the frequency noise of the free-running laser. This paper describes simulated and experimental tests of a tone-assisted TDI ranging (TDIR) technique that uses a least-squares fitting algorithm and fractional-delay interpolation to find and implement the delays needed to form the DOWR TDI combination. The simulation verifies tone-assisted TDIR works under GRACE-FO conditions. Using simulated GRACE-FO signals the tone-assisted TDIR algorithm estimates the time-varying interspacecraft range with a rms error of ±0.2 m , suppressing the free-running laser frequency noise by 8 orders of magnitude. The experimental results demonstrate the practicability of the technique, measuring the delay at the 6 ns level in the presence of a significant displacement signal.

Optimization of a novel Tm fiber laser lithotripter in terms of stone ablation efficiency and retropulsion reduction

NASA Astrophysics Data System (ADS)

Yaroslavsky, Ilya; Vinnichenko, Victoria; McNeill, Tyler; Novoseltseva, Anna; Perchuk, Igor; Vybornov, Alexander; Altshuler, Gregory; Gapontsev, Valentin

2018-02-01

Recently, a Thulium (Tm) fiber laser operating at a wavelength of 1940 nm and peak power up to 500 W has been introduced as a promising energy source for laser lithotripsy. Direct comparative studies have demonstrated considerable advantages of Tm fiber laser over the current industry-standard 2100 nm Holmium:YAG (Ho:YAG) device in terms of ablation rate and retropulsion effects. In this work, we investigated avenues of further improving stone ablation efficiency and reducing retropulsion. Specifically, the roles of temporal pulse structure and fiber tip preparation were studied in detail. Experiments were conducted on Bego stone phantoms in an aqueous environment using a computerized 2D stage for controlled scanning of the fiber over the stone surface. High-resolution 3D-enabled optical microscopy was employed to assess both fiber tip damage and stone ablation rate. Retropulsion effects were quantified using a high-speed video camera. Fiber burn back was evaluated as well. Fiber performance could be preserved during prolonged (up to 15 min) procedures when the fiber tip was adequately prepared. Furthermore, the results were compared with available literature for similar experiments performed with the Ho:YAG laser. The data obtained provide an important foundation for optimizing clinical performance of Tm fiber systems for lithotripsy.

A study of laser surface treatment in bonded repair of composite aircraft structures.

PubMed

Li, Shaolong; Sun, Ting; Liu, Chang; Yang, Wenfeng; Tang, Qingru

2018-03-01

Surface pre-treatment is one of the key processes in bonded repair of aircraft carbon fibre reinforced polymer composites. This paper investigates the surface modification of physical and chemical properties by laser ablation and conventional polish treatment techniques. Surface morphology analysed by laser scanning confocal microscopy and scanning electron microscopy showed that a laser-treated surface displayed higher roughness than that of a polish-treated specimen. The laser-treated laminate exhibited more functional groups in the form of O 1 s/C 1 s atomic ratio of 30.89% for laser-treated and 20.14% for polish-treated as evidenced by X-ray photoelectron spectroscopy observation. Contact angle goniometry demonstrated that laser treatment can provide increased surface free energy and wettability. In the light of mechanical interlocking, molecular bonding and thermodynamics theories on adhesion, laser etching process displayed enhanced bonding performance relative to the polishing surface treatment. These properties resulted in an increased single lap shear strength and a cohesive failure mode for laser etching while an adhesive failure mode occurred in polish-treated specimen.

A study of laser surface treatment in bonded repair of composite aircraft structures

NASA Astrophysics Data System (ADS)

Li, Shaolong; Sun, Ting; Liu, Chang; Yang, Wenfeng; Tang, Qingru

2018-03-01

Surface pre-treatment is one of the key processes in bonded repair of aircraft carbon fibre reinforced polymer composites. This paper investigates the surface modification of physical and chemical properties by laser ablation and conventional polish treatment techniques. Surface morphology analysed by laser scanning confocal microscopy and scanning electron microscopy showed that a laser-treated surface displayed higher roughness than that of a polish-treated specimen. The laser-treated laminate exhibited more functional groups in the form of O 1 s/C 1 s atomic ratio of 30.89% for laser-treated and 20.14% for polish-treated as evidenced by X-ray photoelectron spectroscopy observation. Contact angle goniometry demonstrated that laser treatment can provide increased surface free energy and wettability. In the light of mechanical interlocking, molecular bonding and thermodynamics theories on adhesion, laser etching process displayed enhanced bonding performance relative to the polishing surface treatment. These properties resulted in an increased single lap shear strength and a cohesive failure mode for laser etching while an adhesive failure mode occurred in polish-treated specimen.

A study of laser surface treatment in bonded repair of composite aircraft structures

PubMed Central

Sun, Ting; Liu, Chang; Yang, Wenfeng; Tang, Qingru

2018-01-01

Surface pre-treatment is one of the key processes in bonded repair of aircraft carbon fibre reinforced polymer composites. This paper investigates the surface modification of physical and chemical properties by laser ablation and conventional polish treatment techniques. Surface morphology analysed by laser scanning confocal microscopy and scanning electron microscopy showed that a laser-treated surface displayed higher roughness than that of a polish-treated specimen. The laser-treated laminate exhibited more functional groups in the form of O 1 s/C 1 s atomic ratio of 30.89% for laser-treated and 20.14% for polish-treated as evidenced by X-ray photoelectron spectroscopy observation. Contact angle goniometry demonstrated that laser treatment can provide increased surface free energy and wettability. In the light of mechanical interlocking, molecular bonding and thermodynamics theories on adhesion, laser etching process displayed enhanced bonding performance relative to the polishing surface treatment. These properties resulted in an increased single lap shear strength and a cohesive failure mode for laser etching while an adhesive failure mode occurred in polish-treated specimen. PMID:29657748

In-band-pumped Ho:KLu(WO4)2 microchip laser with 84% slope efficiency.

PubMed

Loiko, Pavel; Serres, Josep Maria; Mateos, Xavier; Yumashev, Konstantin; Kuleshov, Nikolai; Petrov, Valentin; Griebner, Uwe; Aguiló, Magdalena; Díaz, Francesc

2015-02-01

We report on a continuous-wave Ho:KLu(WO4)2 (KLuW) microchip laser with a record slope efficiency of 84%, the highest value among the holmium inband-pumped lasers, delivering 201 mW output power at 2105 nm. The Ho laser operating at room temperature on the (5)I8→(5)I7 transition is in-band-pumped by a diode-pumped Tm:KLuW microchip laser at 1946 nm. Ho:KLuW laser operation at 2061 and 2079 nm is also demonstrated with a maximum slope efficiency of 79%. The microchip laser generates an almost diffraction-limited output beam with a Gaussian profile and a M2<1.1. The laser performance of the Ng-cut Ho:KLuW crystal is very similar for pump light polarizations ‖Nm and Np. The positive thermal lens plays a key role in the laser mode stabilization and proper mode-matching. The latter, together with the low quantum defect under in-band-pumping (∼0.08), is responsible for the extraordinary high slope efficiency.

Novel Approach to Increase the Energy-related Process Efficiency and Performance of Laser Brazing

NASA Astrophysics Data System (ADS)

Mittelstädt, C.; Seefeld, T.; Radel, T.; Vollertsen, F.

Although laser brazing is well established, the energy-related efficiency of this joining method is quite low. That is because of low absorptivity of solid-state laser radiation, especially when copper base braze metals are used. Conventionally the laser beam is set close to the vertical axis and the filler wire is delivered under a flat angle. Therefore, the most of the utilized laser power is reflected and thus left unexploited. To address this situation an alternative processing concept for laser brazing, where the laser beam is leading the filler wire, has been investigated intending to make use of reflected shares of the laser radiation. Process monitoring shows, that the reflection of the laser beam can be used purposefully to preheat the substrate which is supporting the wetting and furthermore increasing the efficiency of the process. Experiments address a standard application from the automotive industry joining zinc coated steels using CuSi3Mn1 filler wire. Feasibility of the alternative processing concept is demonstrated, showing that higher processing speeds can be attained, reducing the required energy per unit length while maintaining joint properties.

Enhancement of optical Kerr effect in quantum-cascade lasers with multiple resonance levels.

PubMed

Bai, Jing; Citrin, D S

2008-08-18

In this paper, we investigated the optical Kerr lensing effect in quantum-cascade lasers with multiple resonance levels. The Kerr refractive index n2 is obtained through the third-order susceptibility at the fundamental frequency chi(3)( omega; omega, omega,-omega). Resonant two-photon processes are found to have almost equal contributions to chi(3)( omega; omega, omega,-omega) as the single-photon processes, which result in the predicted enhancement of the positive nonlinear (Kerr) refractive index, and thus may enhance mode-locking of quantum-cascade lasers. Moreover, we also demonstrate an isospectral optimization strategy for further improving n2 through the band-structure design, in order to boost the multimode performance of quantum-cascade lasers. Simulation results show that the optimized stepwise multiple-quantum-well structure has n2 approximately 10-8 cm2/W, a twofold enhancement over the original flat quantum-well structure. This leads to a refractive-index change (delta)n of about 0.01, which is at the upper bound of those reported for typical Kerr medium. This stronger Kerr refractive index may be important for quantum-cascade lasers ultimately to demonstrate self-mode-locking.

Chemical and explosive detections using photo-acoustic effect and quantum cascade lasers

NASA Astrophysics Data System (ADS)

Choa, Fow-Sen

2013-12-01

Photoacoustic (PA) effect is a sensitive spectroscopic technique for chemical sensing. In recent years, with the development of quantum cascade lasers (QCLs), significant progress has been achieved for PA sensing applications. Using high-power, tunable mid-IR QCLs as laser sources, PA chemical sensor systems have demonstrated parts-pertrillion- level detection sensitivity. Many of these high sensitivity measurements were demonstrated locally in PA cells. Recently, we have demonstrated standoff PA detection of isopropanol vapor for more than 41 feet distance using a quantum cascade laser and a microphone with acoustic reflectors. We also further demonstrated solid phase TNT detections at a standoff distance of 8 feet. To further calibrate the detection sensitivity, we use nerve gas simulants that were generated and calibrated by a commercial vapor generator. Standoff detection of gas samples with calibrated concentration of 2.3 ppm was achieved at a detection distance of more than 2 feet. An extended detection distance up to 14 feet was observed for a higher gas concentration of 13.9 ppm. For field operations, array of microphones and microphone-reflector pairs can be utilized to achieve noise rejection and signal enhancement. We have experimentally demonstrated that the signal and noise spectra of the 4 microphone/4 reflector system with a combined SNR of 12.48 dB. For the 16-microphone and one reflector case, an SNR of 17.82 was achieved. These successful chemical sensing demonstrations will likely create new demands for widely tunable QCLs with ultralow threshold (for local fire-alarm size detection systems) and high-power (for standoff detection systems) performances.

Low-cost laser speckle contrast imaging of blood flow using a webcam.

PubMed

Richards, Lisa M; Kazmi, S M Shams; Davis, Janel L; Olin, Katherine E; Dunn, Andrew K

2013-01-01

Laser speckle contrast imaging has become a widely used tool for dynamic imaging of blood flow, both in animal models and in the clinic. Typically, laser speckle contrast imaging is performed using scientific-grade instrumentation. However, due to recent advances in camera technology, these expensive components may not be necessary to produce accurate images. In this paper, we demonstrate that a consumer-grade webcam can be used to visualize changes in flow, both in a microfluidic flow phantom and in vivo in a mouse model. A two-camera setup was used to simultaneously image with a high performance monochrome CCD camera and the webcam for direct comparison. The webcam was also tested with inexpensive aspheric lenses and a laser pointer for a complete low-cost, compact setup ($90, 5.6 cm length, 25 g). The CCD and webcam showed excellent agreement with the two-camera setup, and the inexpensive setup was used to image dynamic blood flow changes before and after a targeted cerebral occlusion.

Low-cost laser speckle contrast imaging of blood flow using a webcam

PubMed Central

Richards, Lisa M.; Kazmi, S. M. Shams; Davis, Janel L.; Olin, Katherine E.; Dunn, Andrew K.

2013-01-01

Laser speckle contrast imaging has become a widely used tool for dynamic imaging of blood flow, both in animal models and in the clinic. Typically, laser speckle contrast imaging is performed using scientific-grade instrumentation. However, due to recent advances in camera technology, these expensive components may not be necessary to produce accurate images. In this paper, we demonstrate that a consumer-grade webcam can be used to visualize changes in flow, both in a microfluidic flow phantom and in vivo in a mouse model. A two-camera setup was used to simultaneously image with a high performance monochrome CCD camera and the webcam for direct comparison. The webcam was also tested with inexpensive aspheric lenses and a laser pointer for a complete low-cost, compact setup ($90, 5.6 cm length, 25 g). The CCD and webcam showed excellent agreement with the two-camera setup, and the inexpensive setup was used to image dynamic blood flow changes before and after a targeted cerebral occlusion. PMID:24156082

Laser-assisted metal spinning for an efficient and flexible processing of challenging materials

NASA Astrophysics Data System (ADS)

Brummer, C.; Eck, S.; Marsoner, S.; Arntz, K.; Klocke, F.

2016-03-01

The demand for components made from high performance materials like titanium or nickel-based alloys as well as strain-hardening stainless steel is steadily increasing. However, conventional forming operations conducted on these materials are generally very laborious and time-consuming. This is where the limitations of metal spinning also become apparent. Using a laser to apply heat localized to the forming zone during metal spinning facilitates to enhance the formability of a material. In order to analyse the potential of the new manufacturing process, experimental investigations on laser-assisted shear forming and multi-pass metal spinning have been performed with austenitic stainless steel X5CrNi18-10, nickel-based alloy Inconel 718 and titanium grade 2. It could be demonstrated that the formability of these materials can be enhanced by laser-assistance. Besides the resulting enhancement of forming limits for metal spinning of challenging materials, the forming forces were reduced and the product quality was improved significantly.

Pulse Front Tilt and Laser Plasma Acceleration

NASA Astrophysics Data System (ADS)

Mittelberger, Daniel; Thévenet, Maxence; Nakamura, Kei; Lehe, Remi; Gonsalves, Anthony; Benedetti, Carlo; Leemans, Wim

2017-10-01

Pulse front tilt (PFT) is potentially present in any CPA laser system, but its effects may be overlooked because spatiotemporal pulse characterization is considerably more involved than measuring only spatial or temporal profile. PFT is particularly important for laser plasma accelerators (LPA) because it influences electron beam injection and steering. In this work, experimental results from the BELLA Center will be presented that demonstrate the effect of optical grating misalignment and optical compression, resulting in PFT, on accelerator performance. Theoretical models of laser and electron beam steering will be introduced based on particle-in-cell simulations showing distortion of the plasma wake. Theoretical predictions will be compared with experiments and complimentary simulations, and tolerances on PFT and optical compressor alignment will be developed as a function of LPA performance requirements. This work was supported by the Office of High Energy Physics, Office of Science, US Department of Energy under Contract DE-AC02-05CH11231 and the National Science Foundation under Grant PHY-1415596.

Back-support large laser mirror unit: mounting modeling and analysis

NASA Astrophysics Data System (ADS)

Wang, Hui; Zhang, Zheng; Long, Kai; Liu, Tianye; Li, Jun; Liu, Changchun; Xiong, Zhao; Yuan, Xiaodong

2018-01-01

In high-power laser system, the surface wavefront of large optics has a close link with its structure design and mounting method. The back-support transport mirror design is presently being investigated as a means in China's high-power laser system to hold the optical component firmly while minimizing the distortion of its reflecting surface. We have proposed a comprehensive analytical framework integrated numerical modeling and precise metrology for the mirror's mounting performance evaluation while treating the surface distortion as a key decision variable. The combination of numerical simulation and field tests demonstrates that the comprehensive analytical framework provides a detailed and accurate approach to evaluate the performance of the transport mirror. It is also verified that the back-support transport mirror is effectively compatible with state-of-the-art optical quality specifications. This study will pave the way for future research to solidify the design of back-support large laser optics in China's next generation inertial confinement fusion facility.

Fixed-wavelength H2O absorption spectroscopy system enhanced by an on-board external-cavity diode laser

NASA Astrophysics Data System (ADS)

Brittelle, Mack S.; Simms, Jean M.; Sanders, Scott T.; Gord, James R.; Roy, Sukesh

2016-03-01

We describe a system designed to perform fixed-wavelength absorption spectroscopy of H2O vapor in practical combustion devices. The system includes seven wavelength-stabilized distributed feedback (WSDFB) lasers, each with a spectral accuracy of  ±1 MHz. An on-board external cavity diode laser (ECDL) that tunes 1320-1365 nm extends the capabilities of the system. Five system operation modes are described. In one mode, a sweep of the ECDL is used to monitor each WSDFB laser wavelength with an accuracy of  ±30 MHz. Demonstrations of fixed-wavelength thermometry at 10 kHz bandwidth in near-room-temperature gases are presented; one test reveals a temperature measurement error of ~0.43%.

Investigation of monolithic passively mode-locked quantum dot lasers with extremely low repetition frequency.

PubMed

Xu, Tianhong; Cao, Juncheng; Montrosset, Ivo

2015-01-01

The dynamical regimes and performance optimization of quantum dot monolithic passively mode-locked lasers with extremely low repetition rate are investigated using the numerical method. A modified multisection delayed differential equation model is proposed to accomplish simulations of both two-section and three-section passively mode-locked lasers with long cavity. According to the numerical simulations, it is shown that fundamental and harmonic mode-locking regimes can be multistable over a wide current range. These dynamic regimes are studied, and the reasons for their existence are explained. In addition, we demonstrate that fundamental pulses with higher peak power can be achieved when the laser is designed to work in a region with smaller differential gain.

Modal gain characteristics of a 2 μm InGaSb/AlGaAsSb passively mode-locked quantum well laser

NASA Astrophysics Data System (ADS)

Li, Xiang; Wang, Hong; Qiao, Zhongliang; Guo, Xin; Ng, Geok Ing; Zhang, Yu; Niu, Zhichuan; Tong, Cunzhu; Liu, Chongyang

2017-12-01

Passive mode locking with a fundamental repetition rate at ˜18.46 GHz is demonstrated in a two-section InGaSb/AlGaAsSb quantum well laser emitting at 2 μm. Modal gain characteristics of the laser are investigated by performing the Hakki-Paoli method to gain better insight into the impact of the absorber bias voltage (Va) on the light output. The lasing action moves to longer wavelengths markedly with increasing negative Va. The light output contains more longitudinal modes in the mode locking regime if the gain bandwidth is larger at a certain Va. Our findings provide guidelines for output characteristics of the mode-locked laser.

Channel optimization of high-intensity laser beams in millimeter-scale plasmas

DOE PAGES

Ceurvorst, L.; Savin, A.; Ratan, N.; ...

2018-04-20

Channeling experiments were performed at the OMEGA EP facility using relativistic intensity (> 10 18 W/cm 2) kilojoule laser pulses through large density scale length (~ 390-570 μm) laser-produced plasmas, demonstrating the effects of the pulse’s focal location and intensity as well as the plasma’s temperature on the resulting channel formation. The results show deeper channeling when focused into hot plasmas and at lower densities as expected. However, contrary to previous large scale particle-in-cell studies, the results also indicate deeper penetration by short (10 ps), intense pulses compared to their longer duration equivalents. To conclude, this new observation has manymore » implications for future laser-plasma research in the relativistic regime.« less

Magnetic-particles-composed wire structures produced by pulsed laser deposition in a magnetic field

NASA Astrophysics Data System (ADS)

Nikov, Ru; Dikovska, A.; Nedyalkov, N.; Atanasov, P.

2018-03-01

We demonstrate the possibility to fabricate wire structures composed by arranged magnetic particles using pulsed laser deposition (PLD) in the presence of a magnetic field. Ablation of Ni and Co targets was performed in air by nanosecond laser pulses delivered by a Nd:YAG laser system oscillating at 355 nm. Due to the high density of the ambient, particles and clusters were formed by condensation in the plasma plume close to the target. The strong deceleration of the ablated material under these conditions further benefited the efficiency of applying a magnetic field to the plume. We also studied the effect of the target-to-substrate distance and the ambient pressure on the morphology of the deposited structures.

Channel optimization of high-intensity laser beams in millimeter-scale plasmas

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

Ceurvorst, L.; Savin, A.; Ratan, N.

Channeling experiments were performed at the OMEGA EP facility using relativistic intensity (> 10 18 W/cm 2) kilojoule laser pulses through large density scale length (~ 390-570 μm) laser-produced plasmas, demonstrating the effects of the pulse’s focal location and intensity as well as the plasma’s temperature on the resulting channel formation. The results show deeper channeling when focused into hot plasmas and at lower densities as expected. However, contrary to previous large scale particle-in-cell studies, the results also indicate deeper penetration by short (10 ps), intense pulses compared to their longer duration equivalents. To conclude, this new observation has manymore » implications for future laser-plasma research in the relativistic regime.« less

0.26-Hz-linewidth ultrastable lasers at 1557 nm

PubMed Central

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

2016-01-01

Narrow-linewidth ultrastable lasers at 1.5 μm are essential in many applications such as coherent transfer of light through fiber and precision spectroscopy. Those applications all rely on the ultimate performance of the lasers. Here we demonstrate two ultrastable lasers at 1557 nm with a most probable linewidth of 0.26 Hz by independently frequency-stabilizing to the resonance of 10-cm-long ultrastable Fabry-Pérot cavities at room temperature. The fractional frequency instability of each laser system is nearly 8 × 10−16 at 1–30 s averaging time, approaching the thermal noise limit of the reference cavities. A remarkable frequency instability of 1 × 10−15 is achieved on the long time scale of 100–4000 s. PMID:27117356

Formation of a Polycrystalline Silicon Thin Film by Using Blue Laser Diode Annealing

NASA Astrophysics Data System (ADS)

Choi, Young-Hwan; Ryu, Han-Youl

2018-04-01

We report the crystallization of an amorphous silicon thin film deposited on a SiO2/Si wafer using an annealing process with a high-power blue laser diode (LD). The laser annealing process was performed using a continuous-wave blue LD of 450 nm in wavelength with varying laser output power in a nitrogen atmosphere. The crystallinity of the annealed poly-silicon films was investigated using ellipsometry, electron microscope observation, X-ray diffraction, and Raman spectroscopy. Polysilicon grains with > 100-nm diameter were observed to be formed after the blue LD annealing. The crystal quality was found to be improved as the laser power was increased up to 4 W. The demonstrated blue LD annealing is expected to provide a low-cost and versatile solution for lowtemperature poly-silicon processes.

Boresight alignment method for mobile laser scanning systems

NASA Astrophysics Data System (ADS)

Rieger, P.; Studnicka, N.; Pfennigbauer, M.; Zach, G.

2010-06-01

Mobile laser scanning (MLS) is the latest approach towards fast and cost-efficient acquisition of 3-dimensional spatial data. Accurately evaluating the boresight alignment in MLS systems is an obvious necessity. However, recent systems available on the market may lack of suitable and efficient practical workflows on how to perform this calibration. This paper discusses an innovative method for accurately determining the boresight alignment of MLS systems by employing 3D laser scanners. Scanning objects using a 3D laser scanner operating in a 2D line-scan mode from various different runs and scan directions provides valuable scan data for determining the angular alignment between inertial measurement unit and laser scanner. Field data is presented demonstrating the final accuracy of the calibration and the high quality of the point cloud acquired during an MLS campaign.

Compact diode-pumped continuous-wave and passively Q-switched Nd:GYSO laser at 1.07 μm

NASA Astrophysics Data System (ADS)

Lin, Zhi; Huang, Xiaoxu; Lan, Jinglong; Cui, Shengwei; Wang, Yi; Xu, Bin; Luo, Zhengqian; Xu, Huiying; Cai, Zhiping; Xu, Xiaodong; Zhang, Xiaoyan; Wang, Jun; Xu, Jun

2016-08-01

We report diode-pumped continuous-wave (CW) and Q-switched Nd:GYSO lasers using a compact two-mirror linear laser cavity. Single-wavelength laser emissions at 1074.11 nm with 4.1-W power and at 1058.27 nm with 1.47-W power have been obtained in CW mode. The slope efficiencies with respect to the absorbed pump powers are 48.5% and 22.9%, respectively. Wavelength tunability is also demonstrated with range of about 8 nm. Using a MoS2 saturable absorber, maximum average output power up to 410 mW at 1074 nm can be yielded with absorbed pump power 6.41 W and the maximum pulse energy reaches 1.20 μJ with pulse repetition rate of 342.5 kHz and shortest pulse width of 810 ns. The CW laser results represent the best laser performance and the Q-switching also present the highest output power for Q-switched Nd3+ lasers with MoS2 as saturable absorber.

Using a cover layer to improve the damage resistance of gold-coated gratings induced by a picosecond pulsed laser

NASA Astrophysics Data System (ADS)

Xia, Zhilin; Wu, Yihan; Kong, Fanyu; Jin, Yunxia

2018-04-01

The chirped pulse amplification (CPA) technology is the main approach to achieve high-intensity short-pulse laser. Diffraction gratings are good candidates for stretching and compressing laser pulses in CPA. In this paper, a kind of gold-coated grating has been prepared and its laser damage experiment has been performed. The results reflect that the gratings laser damage was dominated by thermal ablation due to gold films or inclusions absorption and involved the deformation or eruption of the gold film. Based on these damage phenomena, a method of using a cover layer to prevent gold films from deforming and erupting has been adopted to improve the gold-coated gratings laser damage threshold. Since the addition of a cover layer changes the gratings diffraction efficiency, the gratings structure has been re-optimized. Furthermore, according to the calculated thermal stress distributions in gratings with optimized structures, the cover layer was demonstrated to be helpful for improving the gratings laser damage resistance if it is thick enough.

Precision laser processing for micro electronics and fiber optic manufacturing

NASA Astrophysics Data System (ADS)

Webb, Andrew; Osborne, Mike; Foster-Turner, Gideon; Dinkel, Duane W.

2008-02-01

The application of laser based materials processing for precision micro scale manufacturing in the electronics and fiber optic industry is becoming increasingly widespread and accepted. This presentation will review latest laser technologies available and discuss the issues to be considered in choosing the most appropriate laser and processing parameters. High repetition rate, short duration pulsed lasers have improved rapidly in recent years in terms of both performance and reliability enabling flexible, cost effective processing of many material types including metal, silicon, plastic, ceramic and glass. Demonstrating the relevance of laser micromachining, application examples where laser processing is in use for production will be presented, including miniaturization of surface mount capacitors by applying a laser technique for demetalization of tracks in the capacitor manufacturing process and high quality laser machining of fiber optics including stripping, cleaving and lensing, resulting in optical quality finishes without the need for traditional polishing. Applications include telecoms, biomedical and sensing. OpTek Systems was formed in 2000 and provide fully integrated systems and sub contract services for laser processes. They are headquartered in the UK and are establishing a presence in North America through a laser processing facility in South Carolina and sales office in the North East.

An optical parametric chirped-pulse amplifier for seeding high repetition rate free-electron lasers

DOE PAGES

Höppner, H.; Hage, A.; Tanikawa, T.; ...

2015-05-15

High repetition rate free-electron lasers (FEL), producing highly intense extreme ultraviolet and x-ray pulses, require new high power tunable femtosecond lasers for FEL seeding and FEL pump-probe experiments. A tunable, 112 W (burst mode) optical parametric chirped-pulse amplifier (OPCPA) is demonstrated with center frequencies ranging from 720–900 nm, pulse energies up to 1.12 mJ and a pulse duration of 30 fs at a repetition rate of 100 kHz. Since the power scalability of this OPCPA is limited by the OPCPA-pump amplifier, we also demonstrate a 6.7–13.7 kW (burst mode) thin-disk OPCPA-pump amplifier, increasing the possible OPCPA output power to manymore » hundreds of watts. Furthermore, third and fourth harmonic generation experiments are performed and the results are used to simulate a seeded FEL with high-gain harmonic generation.« less

Heat-sink free CW operation of injection microdisk lasers grown on Si substrate with emission wavelength beyond 1.3  μm.

PubMed

Kryzhanovskaya, Natalia; Moiseev, Eduard; Polubavkina, Yulia; Maximov, Mikhail; Kulagina, Marina; Troshkov, Sergey; Zadiranov, Yury; Guseva, Yulia; Lipovskii, Andrey; Tang, Mingchu; Liao, Mengya; Wu, Jiang; Chen, Siming; Liu, Huiyun; Zhukov, Alexey

2017-09-01

High-performance injection microdisk (MD) lasers grown on Si substrate are demonstrated for the first time, to the best of our knowledge. Continuous-wave (CW) lasing in microlasers with diameters from 14 to 30 μm is achieved at room temperature. The minimal threshold current density of 600  A/cm 2 (room temperature, CW regime, heatsink-free uncooled operation) is comparable to that of high-quality MD lasers on GaAs substrates. Microlasers on silicon emit in the wavelength range of 1320-1350 nm via the ground state transition of InAs/InGaAs/GaAs quantum dots. The high stability of the lasing wavelength (dλ/dI=0.1  nm/mA) and the low specific thermal resistance of 4×10 -3 °C×cm 2 /W are demonstrated.

Development of an automated diode-laser-based multicomponent gas sensor

NASA Technical Reports Server (NTRS)

Richter, D.; Lancaster, D. G.; Tittel, F. K.

2000-01-01

The implementation and application of a portable fiber-coupled trace-gas sensor for the detection of several trace gases, including CO2, CH4, and H2CO, are reported. This particular sensor is based on a cw fiber-amplified near-infrared (distributed Bragg reflector) diode laser and an external cavity diode laser that are frequency converted in a periodically poled lithium niobate crystal to the mid-IR spectroscopic fingerprint region (3.3-4.4 micrometers). A continuous absorption spectrum of CH4 and H2CO from 3.37 to 3.10 micrometers with a spectral resolution of 40 MHz (approximately 0.0013 cm-1) demonstrated the spectral performance that can be achieved by means of automated wavelength tuning and phase matching with stepper motor control. Autonomous long-term detection of ambient CO2 and CH4 over a 3- and 7-day period was also demonstrated.

Preliminary Results of the Ground/Orbiter Lasercomm Demonstration Experiment between Table Mountain and teh ETS-V1 Satellite

NASA Technical Reports Server (NTRS)

Wilson, K. E.; Lesh, J. R.; Araki, K.; Arimoto, Y.

1996-01-01

The Ground/Orbiter Lasercomm Demonstration (GOLD) is an optical communications demonstration between the Japanese Engineering Test Satellite (ETS-V1) and an optical ground transmitting and receiving station at the Table Mountain FAcility in Wrightwood California. Laser transmissions to the satellite are performed approximately four hours every third night when the satellite is at apogee above Table Mountain.

Demonstrations of Wave Optics (Interference and Diffraction of Light) for Large Audiences Using a Laser and a Multimedia Projector

ERIC Educational Resources Information Center

Ivanov, Dragia; Nikolov, Stefan

2011-01-01

This article presents a new technique for performing most well-known demonstrations of wave optics. Demonstrations which are normally very hard to show to more than a few people can be presented easily to very large audiences with excellent visibility for everyone. The proposed setup is easy to put together and use and can be very useful for…

Characterization and Design of Digital Pointing Subsystem for Optical Communication Demonstrator

NASA Technical Reports Server (NTRS)

Racho, C.; Portillo, A.

1998-01-01

The Optical Communications Demonstrator (OCD) is a laboratory-based lasercom demonstration terminal designed to validate several key technologies, including beacon acquisition, high bandwidth tracking, precision bearn pointing, and point-ahead compensation functions. It has been under active development over the past few years. The instrument uses a CCD array detector for both spatial acquisition and high-bandwidth tracking, and a fiber coupled laser transmitter. The array detector tracking concept provides wide field-of-view acquisition and permits effective platform jitter compensation and point-ahead control using only one steering mirror. This paper describes the detailed design and characterization of the digital control loop system which includes the Fast Steering Mirror (FSM), the CCD image tracker, and the associated electronics. The objective is to improve the overall system performance using laboratory measured data. The. design of the digital control loop is based on a linear time invariant open loop model. The closed loop performance is predicted using the theoretical model. With the digital filter programmed into the OCD control software, data is collected to verify the predictions. This paper presents the results of the, system modeling and performance analysis. It has been shown that measurement data closely matches theoretical predictions. An important part of the laser communication experiment is the ability of FSM to track the laser beacon within the. required tolerances. The pointing must be maintained to an accuracy that is much smaller than the transmit signal beamwidth. For an earth orbit distance, the system must be able to track the receiving station to within a few microradians. The failure. to do so will result in a severely degraded system performance.

Performance and analysis of a three-dimensional nonorthogonal laser Doppler anemometer

NASA Technical Reports Server (NTRS)

Snyder, P. K.; Orloff, K. L.; Aoyagi, K.

1981-01-01

A three dimensional laser Doppler anemometer with a nonorthogonal third axis coupled by 14 deg was designed and tested. A highly three dimensional flow field of a jet in a crossflow was surveyed to test the three dimensional capability of the instrument. Sample data are presented demonstrating the ability of the 3D LDA to resolve three orthogonal velocity components. Modifications to the optics, signal processing electronics, and data reduction methods are suggested.

High performance mode locking characteristics of single section quantum dash lasers.

PubMed

Rosales, Ricardo; Murdoch, S G; Watts, R T; Merghem, K; Martinez, Anthony; Lelarge, Francois; Accard, Alain; Barry, L P; Ramdane, Abderrahim

2012-04-09

Mode locking features of single section quantum dash based lasers are investigated. Particular interest is given to the static spectral phase profile determining the shape of the mode locked pulses. The phase profile dependence on cavity length and injection current is experimentally evaluated, demonstrating the possibility of efficiently using the wide spectral bandwidth exhibited by these quantum dash structures for the generation of high peak power sub-picosecond pulses with low radio frequency linewidths.

Lincoln's craniofacial microsomia: three-dimensional laser scanning of 2 Lincoln life masks.

PubMed

Fishman, Ronald S; Da Silveira, Adriana

2007-08-01

Examination of 2 life masks of Abraham Lincoln's face was performed by means of 3-dimensional laser surface scanning. This technique enabled documentation and analysis of Lincoln's facial contours and demonstrated his marked facial asymmetry, particularly evident in the smaller left superior orbital rim. This may have led to retroplacement of the trochlea on the left side, leading, in turn, to the mild superior oblique paresis that was manifested intermittently during adulthood.

Demonstration of a Strategy to Perform Two-Dimensional Diode Laser Tomography

DTIC Science & Technology

2008-03-01

training set allows interpolation between beam paths resulting in temperature and density maps. Finally, the TDLAS temperature and density maps are... TDLAS and Tomography Results .................................................................. 38 Introduction...38 vii Page TDLAS Burner Setup

Detection of protein-small molecule binding using a self-referencing external cavity laser biosensor.

PubMed

Meng Zhang; Peh, Jessie; Hergenrother, Paul J; Cunningham, Brian T

2014-01-01

High throughput screening of protein-small molecule binding interactions using label-free optical biosensors is challenging, as the detected signals are often similar in magnitude to experimental noise. Here, we describe a novel self-referencing external cavity laser (ECL) biosensor approach that achieves high resolution and high sensitivity, while eliminating thermal noise with sub-picometer wavelength accuracy. Using the self-referencing ECL biosensor, we demonstrate detection of binding between small molecules and a variety of immobilized protein targets with binding affinities or inhibition constants in the sub-nanomolar to low micromolar range. The demonstrated ability to perform detection in the presence of several interfering compounds opens the potential for increasing the throughput of the approach. As an example application, we performed a "needle-in-the-haystack" screen for inhibitors against carbonic anhydrase isozyme II (CA II), in which known inhibitors are clearly differentiated from inactive molecules within a compound library.

Laser assisted zona hatching does not lead to immediate impairment in human embryo quality and metabolism.

PubMed

Uppangala, Shubhashree; D'Souza, Fiona; Pudakalakatti, Shivanand; Atreya, Hanudatta S; Raval, Keyur; Kalthur, Guruprasad; Adiga, Satish Kumar

2016-12-01

Laser assisted zona hatching (LAH) is a routinely used therapeutic intervention in assisted reproductive technology for patients with poor prognosis. However, results are not conclusive in demonstrating the benefits of zona hatching in improving the pregnancy rate. Recent observations on LAH induced genetic instability in animal embryos prompted us to look into the effects of laser assisted zona hatching on the human preimplantation embryo quality and metabolic uptake using high resolution nuclear magnetic resonance (NMR) technology. This experimental prospective study included fifty embryos from twenty-five patients undergoing intra cytoplasmic sperm injection. Embryo quality assessment followed by profiling of spent media for the non-invasive evaluation of metabolites was performed using NMR spectroscopy 24 hours after laser treatment and compared with that of non-treated sibling embryos. Both cell number and embryo quality on day 3 of development did not vary significantly between the two groups at 24 hours post laser treatment interval. Time lapse monitoring of the embryos for 24 hours did not reveal blastomere fragmentation adjacent to the point of laser treatment. Similarly, principal component analysis of metabolites did not demonstrate any variation across the groups. These results suggest that laser assisted zona hatching does not affect human preimplantation embryo morphology and metabolism at least until 24 hours post laser assisted zona hatching. However, studies are required to elucidate laser induced metabolic and developmental changes at extended time periods. AH: assisted hatching; ART: assisted reproductive technology; DNA: deoxy-ribo nucleic acid; LAH: laser assisted hatching; MHz: megahertz; NMR: nuclear magnetic resonance; PCA: principal component analysis; PGD: preimplantation genetic diagnosis; TLM: time lapse monitoring.

Preliminary experiences on diode laser welding of skin

NASA Astrophysics Data System (ADS)

Reali, Umberto M.; Borgognoni, L.; Martini, L.; Chiarugi, C.; Gori, F.; Pini, Roberto; Toncelli, F.; Vanni, U.

1994-12-01

Dye enhanced laser welding has been recently proposed for skin closures to exploit the advantages of laser procedure (possible reduction of scar formation, no inflammatory reaction). In this preliminary study we used the diode laser-assisted technique to perform welding of rats' skin. In the pilot phase of the study we investigated the effect of the interaction between diode laser radiation and 20 full thickness skin wounds, performed on the shaved backs of 10 Wistar rats, using laser power in the range of 200 - 150 mW and, as the photoenhancing chromophore, Indocyanine Cardio-green (ICG) dye saturated solution in plasma. Ten wounds were sutured with 4.0 nylon thread, to provide a comparison with the traditional procedure. Wounds' samples were explanted on day 3 and 7 after the treatment, for histological evaluation. Clinical examination on the same days showed a high percentage of wounds dehiscence and presence of scales and crusts. Histologic examination demonstrated evidence of thermal injury and a heightened inflammation, superior to that of suture closures. In the second phase of the study, a lower laser power (150 - 80 mW), ICG-plasma-non saturated solution (ICG-sol) and ICG-plasma-saturated-sodium hyaluronate gel (ICG-gel), were used. Six wounds were filled with ICG-sol and six with ICG-gel, then irradiated at 150, 120 and 80 mW. Postoperative explants were performed on day 3 and 7. Clinical and histological results from this group were satisfactory: we recorded only one case of dehiscence, well healed wounds, no epidermal necrosis and a mild inflammatory reaction, reduced respect to that of traditional closure. We characterized the optimum range of parameters of diode laser-assisted technique to achieve an effective skin welding and the corresponding clinical and histologic pattern was described.

Parametric infrared tunable laser system

NASA Technical Reports Server (NTRS)

Garbuny, M.; Henningsen, T.; Sutter, J. R.

1980-01-01

A parametric tunable infrared laser system was built to serve as transmitter for the remote detection and density measurement of pollutant, poisonous, or trace gases in the atmosphere. The system operates with a YAG:Nd laser oscillator amplifier chain which pumps a parametric tunable frequency converter. The completed system produced pulse energies of up to 30 mJ. The output is tunable from 1.5 to 3.6 micrometers at linewidths of 0.2-0.5 /cm (FWHM), although the limits of the tuning range and the narrower line crystals presently in the parametric converter by samples of the higher quality already demonstrated is expected to improve the system performance further.

Development of a wideband pulse quaternary modulation system. [for an operational 400 Mbps baseband laser communication system

NASA Technical Reports Server (NTRS)

Federhofer, J. A.

1974-01-01

Laboratory data verifying the pulse quaternary modulation (PQM) theoretical predictions is presented. The first laboratory PQM laser communication system was successfully fabricated, integrated, tested and demonstrated. System bit error rate tests were performed and, in general, indicated approximately a 2 db degradation from the theoretically predicted results. These tests indicated that no gross errors were made in the initial theoretical analysis of PQM. The relative ease with which the entire PQM laboratory system was integrated and tested indicates that PQM is a viable candidate modulation scheme for an operational 400 Mbps baseband laser communication system.

LASER BIOLOGY: Peculiarities of studying an isolated neuron by the method of laser interference microscopy

NASA Astrophysics Data System (ADS)

Yusipovich, Alexander I.; Novikov, Sergey M.; Kazakova, Tatiana A.; Erokhova, Liudmila A.; Brazhe, Nadezda A.; Lazarev, Grigory L.; Maksimov, Georgy V.

2006-09-01

Actual aspects of using a new method of laser interference microscopy (LIM) for studying nerve cells are discussed. The peculiarities of the LIM display of neurons are demonstrated by the example of isolated neurons of a pond snail Lymnaea stagnalis. A comparative analysis of the images of the cell and subcellular structures of a neuron obtained by the methods of interference microscopy, optical transmission microscopy, and confocal microscopy is performed. Various aspects of the application of LIM for studying the lateral dimensions and internal structure of the cytoplasm and organelles of a neuron in cytology and cell physiology are discussed.

First demonstration of multi-MeV proton acceleration from a cryogenic hydrogen ribbon target

NASA Astrophysics Data System (ADS)

Kraft, Stephan D.; Obst, Lieselotte; Metzkes-Ng, Josefine; Schlenvoigt, Hans-Peter; Zeil, Karl; Michaux, Sylvain; Chatain, Denis; Perin, Jean-Paul; Chen, Sophia N.; Fuchs, Julien; Gauthier, Maxence; Cowan, Thomas E.; Schramm, Ulrich

2018-04-01

We show efficient laser driven proton acceleration up to 14 MeV from a 62 μm thick cryogenic hydrogen ribbon. Pulses of the short pulse laser ELFIE at LULI with a pulse length of ≈350 fs at an energy of 8 J per pulse are directed onto the target. The results are compared to proton spectra from metal and plastic foils with different thicknesses and show a similarly good performance both in maximum energy as well as in proton number. Thus, this target type is a promising candidate for experiments with high repetition rate laser systems.

An experimental verification of laser-velocimeter sampling bias and its correction

NASA Technical Reports Server (NTRS)

Johnson, D. A.; Modarress, D.; Owen, F. K.

1982-01-01

The existence of 'sampling bias' in individual-realization laser velocimeter measurements is experimentally verified and shown to be independent of sample rate. The experiments were performed in a simple two-stream mixing shear flow with the standard for comparison being laser-velocimeter results obtained under continuous-wave conditions. It is also demonstrated that the errors resulting from sampling bias can be removed by a proper interpretation of the sampling statistics. In addition, data obtained in a shock-induced separated flow and in the near-wake of airfoils are presented, both bias-corrected and uncorrected, to illustrate the effects of sampling bias in the extreme.

First demonstration of multi-MeV proton acceleration from a cryogenic hydrogen ribbon target

DOE PAGES

Kraft, Stephan; Obst, Lieselotte; Metzkes-Ng, Josefine; ...

2018-02-09

We show efficient laser driven proton acceleration up to 14 MeV from a 50 μm thick cryogenic hydrogen ribbon. Pulses of the short pulse laser ELFIE at LULI with a pulse length of ≈ 350 fs at an energy of 8 J per pulse are directed onto the target. The results were then compared to proton spectra from metal and plastic foils with different thicknesses and show a similar good performance both in maximum energy as well as in proton number. Thus, this target type is a promising candidate for experiments with high repetition rate laser systems.

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.

Sub-femtosecond timing jitter, all-fiber, CNT-mode-locked Er-laser at telecom wavelength.

PubMed

Kim, Chur; Bae, Sangho; Kieu, Khanh; Kim, Jungwon

2013-11-04

We demonstrate a 490-attosecond timing jitter (integration bandwidth: 10 kHz - 39.4 MHz) optical pulse train from a 78.7-MHz repetition rate, all-fiber soliton Er laser mode-locked by a fiber tapered carbon nanotube saturable absorber (ft-CNT-SA). To achieve this jitter performance, we searched for a net cavity dispersion condition where the Gordon-Haus jitter is minimized while maintaining stable soliton mode-locking. Our result shows that optical pulse trains with well below a femtosecond timing jitter can be generated from a self-starting and robust all-fiber laser operating at telecom wavelength.

First demonstration of multi-MeV proton acceleration from a cryogenic hydrogen ribbon target

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

Kraft, Stephan; Obst, Lieselotte; Metzkes-Ng, Josefine

We show efficient laser driven proton acceleration up to 14 MeV from a 50 μm thick cryogenic hydrogen ribbon. Pulses of the short pulse laser ELFIE at LULI with a pulse length of ≈ 350 fs at an energy of 8 J per pulse are directed onto the target. The results were then compared to proton spectra from metal and plastic foils with different thicknesses and show a similar good performance both in maximum energy as well as in proton number. Thus, this target type is a promising candidate for experiments with high repetition rate laser systems.

Polarization effects in above-threshold ionization with a mid-infrared strong laser field

NASA Astrophysics Data System (ADS)

Kang, Hui-Peng; Xu, Song-Po; Wang, Yan-Lan; Yu, Shao-Gang; Zhao, Xiao-Yun; Hao, Xiao-Lei; Lai, Xuan-Yang; Pfeifer, Thomas; Liu, Xiao-Jun; Chen, Jing; Cheng, Ya; Xu, Zhi-Zhan

2018-05-01

Using a semiclassical approach, we theoretically study the above-threshold ionization of magnesium by intense, mid-infrared laser pulses. The formation of low-energy structures in the photoelectron spectrum is found to be enhanced by comparing with a calculation based on the single-active electron approximation. By performing electron trajectory and recollision-time distribution analysis, we demonstrate that this phenomenon is due to the laser-induced ionic core polarization effects on the recolliding electrons. We also show that the polarization effects should be experimentally detectable. Our finding provides new insight into ultrafast control of strong-field photoionization and imaging of polar molecules.

Comparing Laser Welding Technologies with Friction Stir Welding for Production of Aluminum Tailor-Welded Blanks

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

Hovanski, Yuri; Carsley, John; Carlson, Blair

2014-01-15

A comparison of welding techniques was performed to determine the most effective method for producing aluminum tailor-welded blanks for high volume automotive applications. Aluminum sheet was joined with an emphasis on post weld formability, surface quality and weld speed. Comparative results from several laser based welding techniques along with friction stir welding are presented. The results of this study demonstrate a quantitative comparison of weld methodologies in preparing tailor-welded aluminum stampings for high volume production in the automotive industry. Evaluation of nearly a dozen welding variations ultimately led to down selecting a single process based on post-weld quality and performance.

3D Laser Triangulation for Plant Phenotyping in Challenging Environments

PubMed Central

Kjaer, Katrine Heinsvig; Ottosen, Carl-Otto

2015-01-01

To increase the understanding of how the plant phenotype is formed by genotype and environmental interactions, simple and robust high-throughput plant phenotyping methods should be developed and considered. This would not only broaden the application range of phenotyping in the plant research community, but also increase the ability for researchers to study plants in their natural environments. By studying plants in their natural environment in high temporal resolution, more knowledge on how multiple stresses interact in defining the plant phenotype could lead to a better understanding of the interaction between plant responses and epigenetic regulation. In the present paper, we evaluate a commercial 3D NIR-laser scanner (PlantEye, Phenospex B.V., Herleen, The Netherlands) to track daily changes in plant growth with high precision in challenging environments. Firstly, we demonstrate that the NIR laser beam of the scanner does not affect plant photosynthetic performance. Secondly, we demonstrate that it is possible to estimate phenotypic variation amongst the growth pattern of ten genotypes of Brassica napus L. (rapeseed), using a simple linear correlation between scanned parameters and destructive growth measurements. Our results demonstrate the high potential of 3D laser triangulation for simple measurements of phenotypic variation in challenging environments and in a high temporal resolution. PMID:26066990

An optical storage cavity-based, Compton-backscatter x-ray source using the MKV free electron laser

NASA Astrophysics Data System (ADS)

Hadmack, Michael R.

A compact, high-brightness x-ray source is presently under development at the University of Hawai`i Free Electron Laser Laboratory. This source utilizes Compton backscattering of an infrared laser from a relativistic electron beam to produce a narrow beam of monochromatic x-rays. The scattering efficiency is greatly increased by tightly focusing the two beams at an interaction point within a near-concentric optical storage cavity, designed with high finesse to coherently stack the incident laser pulses and greatly enhance the number of photons available for scattering with the electron beam. This dissertation describes the effort and progress to integrate and characterize the most important and challenging aspects of the design of this system. A low-power, near-concentric, visible-light storage cavity has been constructed as a tool for the exploration of the performance, alignment procedures, and diagnostics required for the operation of a high power infrared storage cavity. The use of off-axis reflective focussing elements is essential to the design of the optical storage cavity, but requires exquisite alignment to minimize astigmatism and other optical aberrations. Experiments using a stabilized HeNe laser have revealed important performance characteristics, and allowed the development of critical alignment and calibration procedures, which can be directly applied to the high power infrared storage cavity. Integration of the optical and electron beams is similarly challenging. A scanning-wire beam profiler has been constructed and tested, which allows for high resolution measurement of the size and position of the laser and electron beams at the interaction point. This apparatus has demonstrated that the electron and laser beams can be co-aligned with a precision of less than 10 microm, as required to maximize the x-ray production rate. Equally important is the stabilization of the phase of the GHz repetition rate electron pulses arriving at the interaction point and driving the FEL. A feed-forward amplitude and phase compensation system has been built and demonstrated to substantially improve the uniformity of the electron bunch phase, thus enhancing both the laser performance and the beam stability required for efficient x-ray production. Results of all of these efforts are presented, together with a summary of future work.

Analysis and Comparison of Friction Stir Welding and Laser Assisted Friction Stir Welding of Aluminum Alloy

PubMed Central

Campanelli, Sabina Luisa; Casalino, Giuseppe; Casavola, Caterina; Moramarco, Vincenzo

2013-01-01

Friction Stir Welding (FSW) is a solid-state joining process; i.e., no melting occurs. The welding process is promoted by the rotation and translation of an axis-symmetric non-consumable tool along the weld centerline. Thus, the FSW process is performed at much lower temperatures than conventional fusion welding, nevertheless it has some disadvantages. Laser Assisted Friction Stir Welding (LAFSW) is a combination in which the FSW is the dominant welding process and the laser pre-heats the weld. In this work FSW and LAFSW tests were conducted on 6 mm thick 5754H111 aluminum alloy plates in butt joint configuration. LAFSW is studied firstly to demonstrate the weldability of aluminum alloy using that technique. Secondly, process parameters, such as laser power and temperature gradient are investigated in order to evaluate changes in microstructure, micro-hardness, residual stress, and tensile properties. Once the possibility to achieve sound weld using LAFSW is demonstrated, it will be possible to explore the benefits for tool wear, higher welding speeds, and lower clamping force. PMID:28788430

Efficient laser-driven proton acceleration from cylindrical and planar cryogenic hydrogen jets

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

Obst, Lieselotte; Gode, Sebastian; Rehwald, Martin

We report on recent experimental results deploying a continuous cryogenic hydrogen jet as a debris-free, renewable laser-driven source of pure proton beams generated at the 150 TW ultrashort pulse laser Draco. Efficient proton acceleration reaching cut-off energies of up to 20 MeV with particle numbers exceeding 109 particles per MeV per steradian is demonstrated, showing for the first time that the acceleration performance is comparable to solid foil targets with thicknesses in the micrometer range. Two different target geometries are presented and their proton beam deliverance characterized: cylindrical (Ø 5 μm) and planar (20 μm × 2 μm). In bothmore » cases typical Target Normal Sheath Acceleration emission patterns with exponential proton energy spectra are detected. Significantly higher proton numbers in laser-forward direction are observed when deploying the planar jet as compared to the cylindrical jet case. As a result, this is confirmed by two-dimensional Particle-in-Cell (2D3V PIC) simulations, which demonstrate that the planar jet proves favorable as its geometry leads to more optimized acceleration conditions.« less

Efficient laser-driven proton acceleration from cylindrical and planar cryogenic hydrogen jets

DOE PAGES

Obst, Lieselotte; Gode, Sebastian; Rehwald, Martin; ...

2017-08-31

We report on recent experimental results deploying a continuous cryogenic hydrogen jet as a debris-free, renewable laser-driven source of pure proton beams generated at the 150 TW ultrashort pulse laser Draco. Efficient proton acceleration reaching cut-off energies of up to 20 MeV with particle numbers exceeding 109 particles per MeV per steradian is demonstrated, showing for the first time that the acceleration performance is comparable to solid foil targets with thicknesses in the micrometer range. Two different target geometries are presented and their proton beam deliverance characterized: cylindrical (Ø 5 μm) and planar (20 μm × 2 μm). In bothmore » cases typical Target Normal Sheath Acceleration emission patterns with exponential proton energy spectra are detected. Significantly higher proton numbers in laser-forward direction are observed when deploying the planar jet as compared to the cylindrical jet case. As a result, this is confirmed by two-dimensional Particle-in-Cell (2D3V PIC) simulations, which demonstrate that the planar jet proves favorable as its geometry leads to more optimized acceleration conditions.« less

Vertical-cavity surface-emitting laser sources for gigahertz-bandwidth, multiwavelength frequency-domain photon migration

NASA Astrophysics Data System (ADS)

O'Sullivan, Thomas D.; No, Keunsik; Matlock, Alex; Warren, Robert V.; Hill, Brian; Cerussi, Albert E.; Tromberg, Bruce J.

2017-10-01

Frequency-domain photon migration (FDPM) uses modulated laser light to measure the bulk optical properties of turbid media and is increasingly applied for noninvasive functional medical imaging in the near-infrared. Although semiconductor edge-emitting laser diodes have been traditionally used as miniature light sources for this application, we show that vertical-cavity surface-emitting lasers (VCSELs) exhibit output power and modulation performance characteristics suitable for FDPM measurements of tissue optical properties at modulation frequencies exceeding 1 GHz. We also show that an array of multiple VCSEL devices can be coherently modulated at frequencies suitable for FDPM and can improve optical power. In addition, their small size and simple packaging make them an attractive choice as components in wearable sensors and clinical FDPM-based optical spectroscopy systems. We demonstrate the benefits of VCSEL technology by fabricating and testing a unique, compact VCSEL-based optical probe with an integrated avalanche photodiode. We demonstrate sensitivity of the VCSEL-based probe to subcutaneous tissue hemodynamics that was induced during an arterial cuff occlusion of the upper arm in a human subject.

Analysis and Comparison of Friction Stir Welding and Laser Assisted Friction Stir Welding of Aluminum Alloy.

PubMed

Campanelli, Sabina Luisa; Casalino, Giuseppe; Casavola, Caterina; Moramarco, Vincenzo

2013-12-18

Friction Stir Welding (FSW) is a solid-state joining process; i.e. , no melting occurs. The welding process is promoted by the rotation and translation of an axis-symmetric non-consumable tool along the weld centerline. Thus, the FSW process is performed at much lower temperatures than conventional fusion welding, nevertheless it has some disadvantages. Laser Assisted Friction Stir Welding (LAFSW) is a combination in which the FSW is the dominant welding process and the laser pre-heats the weld. In this work FSW and LAFSW tests were conducted on 6 mm thick 5754H111 aluminum alloy plates in butt joint configuration. LAFSW is studied firstly to demonstrate the weldability of aluminum alloy using that technique. Secondly, process parameters, such as laser power and temperature gradient are investigated in order to evaluate changes in microstructure, micro-hardness, residual stress, and tensile properties. Once the possibility to achieve sound weld using LAFSW is demonstrated, it will be possible to explore the benefits for tool wear, higher welding speeds, and lower clamping force.

The detection of He in tungsten following ion implantation by laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Shaw, G.; Bannister, M.; Biewer, T. M.; Martin, M. Z.; Meyer, F.; Wirth, B. D.

2018-01-01

Laser-induced breakdown spectroscopy (LIBS) results are presented that provide depth-resolved identification of He implanted in polycrystalline tungsten (PC-W) targets by a 200 keV He+ ion beam, with a surface temperature of approximately 900 °C and a peak fluence of 1023 m-2. He retention, and the influence of He on deuterium and tritium recycling, permeation, and retention in PC-W plasma facing components are important questions for the divertor and plasma facing components in a fusion reactor, yet are difficult to quantify. The purpose of this work is to demonstrate the ability of LIBS to identify helium in tungsten; to investigate the sensitivity of laser parameters including, laser energy and gate delay, that directly influence the sensitivity and depth resolution of LIBS; and to perform a proof-of-principle experiment using LIBS to measure relative He intensities as a function of depth. The results presented demonstrate the potential not only to identify helium but also to develop a methodology to quantify gaseous impurity concentration in PC-W as a function of depth.

IR CMOS: near infrared enhanced digital imaging (Presentation Recording)

NASA Astrophysics Data System (ADS)

Pralle, Martin U.; Carey, James E.; Joy, Thomas; Vineis, Chris J.; Palsule, Chintamani

2015-08-01

SiOnyx has demonstrated imaging at light levels below 1 mLux (moonless starlight) at video frame rates with a 720P CMOS image sensor in a compact, low latency camera. Low light imaging is enabled by the combination of enhanced quantum efficiency in the near infrared together with state of the art low noise image sensor design. The quantum efficiency enhancements are achieved by applying Black Silicon, SiOnyx's proprietary ultrafast laser semiconductor processing technology. In the near infrared, silicon's native indirect bandgap results in low absorption coefficients and long absorption lengths. The Black Silicon nanostructured layer fundamentally disrupts this paradigm by enhancing the absorption of light within a thin pixel layer making 5 microns of silicon equivalent to over 300 microns of standard silicon. This results in a demonstrate 10 fold improvements in near infrared sensitivity over incumbent imaging technology while maintaining complete compatibility with standard CMOS image sensor process flows. Applications include surveillance, nightvision, and 1064nm laser see spot. Imaging performance metrics will be discussed. Demonstrated performance characteristics: Pixel size : 5.6 and 10 um Array size: 720P/1.3Mpix Frame rate: 60 Hz Read noise: 2 ele/pixel Spectral sensitivity: 400 to 1200 nm (with 10x QE at 1064nm) Daytime imaging: color (Bayer pattern) Nighttime imaging: moonless starlight conditions 1064nm laser imaging: daytime imaging out to 2Km

On the assessment of performance and emissions characteristics of a SI engine provided with a laser ignition system

NASA Astrophysics Data System (ADS)

Birtas, A.; Boicea, N.; Draghici, F.; Chiriac, R.; Croitoru, G.; Dinca, M.; Dascalu, T.; Pavel, N.

2017-10-01

Performance and exhaust emissions of spark ignition engines are strongly dependent on the development of the combustion process. Controlling this process in order to improve the performance and to reduce emissions by ensuring rapid and robust combustion depends on how ignition stage is achieved. An ignition system that seems to be able for providing such an enhanced combustion process is that based on plasma generation using a Q-switched solid state laser that delivers pulses with high peak power (of MW-order level). The laser-spark devices used in the present investigations were realized using compact diffusion-bonded Nd:YAG/Cr4+:YAG ceramic media. The laser igniter was designed, integrated and built to resemble a classical spark plug and therefore it could be mounted directly on the cylinder head of a passenger car engine. In this study are reported the results obtained using such ignition system provided for a K7M 710 engine currently produced by Renault-Dacia, where the standard calibrations were changed towards the lean mixtures combustion zone. Results regarding the performance, the exhaust emissions and the combustion characteristics in optimized spark timing conditions, which demonstrate the potential of such an innovative ignition system, are presented.

Vertically Emitting Indium Phosphide Nanowire Lasers.

PubMed

Xu, Wei-Zong; Ren, Fang-Fang; Jevtics, Dimitars; Hurtado, Antonio; Li, Li; Gao, Qian; Ye, Jiandong; Wang, Fan; Guilhabert, Benoit; Fu, Lan; Lu, Hai; Zhang, Rong; Tan, Hark Hoe; Dawson, Martin D; Jagadish, Chennupati

2018-06-13

Semiconductor nanowire (NW) lasers have attracted considerable research effort given their excellent promise for nanoscale photonic sources. However, NW lasers currently exhibit poor directionality and high threshold gain, issues critically limiting their prospects for on-chip light sources with extremely reduced footprint and efficient power consumption. Here, we propose a new design and experimentally demonstrate a vertically emitting indium phosphide (InP) NW laser structure showing high emission directionality and reduced energy requirements for operation. The structure of the laser combines an InP NW integrated in a cat's eye (CE) antenna. Thanks to the antenna guidance with broken asymmetry, strong focusing ability, and high Q-factor, the designed InP CE-NW lasers exhibit a higher degree of polarization, narrower emission angle, enhanced internal quantum efficiency, and reduced lasing threshold. Hence, this NW laser-antenna system provides a very promising approach toward the achievement of high-performance nanoscale lasers, with excellent prospects for use as highly localized light sources in present and future integrated nanophotonics systems for applications in advanced sensing, high-resolution imaging, and quantum communications.

Optofluidic FRET Lasers Using Aqueous Quantum Dots as Donors

PubMed Central

Chen, Qiushu; Kiraz, Alper; Fan, Xudong

2015-01-01

An optofluidic FRET (fluorescence resonance energy transfer) laser is formed by putting FRET pairs inside a microcavity acting as gain medium. This integration of optofluidic laser and FRET mechanism provides novel research frontiers, including sensitive biochemical analysis and novel photonic devices, such as on-chip coherent light sources and bio-tunable lasers. Here we investigated an optofluidic FRET laser using quantum dots (QDs) as FRET donors. We achieved lasing from Cy5 as the acceptor in the QD-Cy5 pair when excited at 450 nm where Cy5 has negligible absorption by itself. The threshold was approximately 14 µJ/mm2. The demonstrated capability of QDs as the donor in a FRET laser greatly improves the versatility of optofluidic laser operation due to the broad and large absorption cross section of QDs in the blue and UV spectral region. The excitation efficiency of the acceptor molecules through FRET channel was also analyzed, showing that the energy transfer rate and the non-radiative Auger recombination rate of QDs plays a significant role in FRET laser performance. PMID:26659274

Optofluidic FRET lasers using aqueous quantum dots as donors.

PubMed

Chen, Qiushu; Kiraz, Alper; Fan, Xudong

2016-01-21

An optofluidic FRET (fluorescence resonance energy transfer) laser is formed by putting FRET pairs inside a microcavity acting as a gain medium. This integration of an optofluidic laser and the FRET mechanism provides novel research frontiers, including sensitive biochemical analysis and novel photonic devices, such as on-chip coherent light sources and bio-tunable lasers. Here, we investigated an optofluidic FRET laser using quantum dots (QDs) as FRET donors. We achieved lasing from Cy5 as the acceptor in a QD-Cy5 pair upon excitation at 450 nm, where Cy5 has negligible absorption by itself. The threshold was approximately 14 μJ mm(-2). The demonstrated capability of QDs as donors in the FRET laser greatly improves the versatility of optofluidic laser operation due to the broad and large absorption cross section of the QDs in the blue and UV spectral regions. The excitation efficiency of the acceptor molecules through a FRET channel was also analyzed, showing that the energy transfer rate and the non-radiative Auger recombination rate of QDs play a significant role in FRET laser performance.

Progress in ultrafast laser processing and future prospects

NASA Astrophysics Data System (ADS)

Sugioka, Koji

2017-03-01

The unique characteristics of ultrafast lasers have rapidly revolutionized materials processing after their first demonstration in 1987. The ultrashort pulse width of the laser suppresses heat diffusion to the surroundings of the processed region, which minimizes the formation of a heat-affected zone and thereby enables ultrahigh precision micro- and nanofabrication of various materials. In addition, the extremely high peak intensity can induce nonlinear multiphoton absorption, which extends the diversity of materials that can be processed to transparent materials such as glass. Nonlinear multiphoton absorption enables three-dimensional (3D) micro- and nanofabrication by irradiation with tightly focused femtosecond laser pulses inside transparent materials. Thus, ultrafast lasers are currently widely used for both fundamental research and practical applications. This review presents progress in ultrafast laser processing, including micromachining, surface micro- and nanostructuring, nanoablation, and 3D and volume processing. Advanced technologies that promise to enhance the performance of ultrafast laser processing, such as hybrid additive and subtractive processing, and shaped beam processing are discussed. Commercial and industrial applications of ultrafast laser processing are also introduced. Finally, future prospects of the technology are given with a summary.

Laser absorption of nitric oxide for thermometry in high-enthalpy air

NASA Astrophysics Data System (ADS)

Spearrin, R. M.; Schultz, I. A.; Jeffries, J. B.; Hanson, R. K.

2014-12-01

The design and demonstration of a laser absorption sensor for thermometry in high-enthalpy air is presented. The sensor exploits the highly temperature-sensitive and largely pressure-independent concentration of nitric oxide in air at chemical equilibrium. Temperature is thus inferred from an in situ measurement of nascent nitric oxide. The strategy is developed by utilizing a quantum cascade laser source for access to the strong fundamental absorption band in the mid-infrared spectrum of nitric oxide. Room temperature measurements in a high-pressure static cell validate the suitability of the Voigt lineshape model to the nitric oxide spectra at high gas densities. Shock-tube experiments enable calibration of a collision-broadening model for temperatures between 1200-3000 K. Finally, sensor performance is demonstrated in a high-pressure shock tube by measuring temperature behind reflected shock waves for both fixed-chemistry experiments where nitric oxide is seeded, and for experiments involving nitric oxide formation in shock-heated mixtures of N2 and O2. Results show excellent performance of the sensor across a wide range of operating conditions from 1100-2950 K and at pressures up to 140 atm.

ELIMED: a new hadron therapy concept based on laser driven ion beams

NASA Astrophysics Data System (ADS)

Cirrone, Giuseppe A. P.; Margarone, Daniele; Maggiore, Mario; Anzalone, Antonello; Borghesi, Marco; Jia, S. Bijan; Bulanov, Stepan S.; Bulanov, Sergei; Carpinelli, Massimo; Cavallaro, Salvatore; Cutroneo, Mariapompea; Cuttone, Giacomo; Favetta, Marco; Gammino, Santo; Klimo, Ondrej; Manti, Lorenzo; Korn, Georg; La Malfa, Giuseppe; Limpouch, Jiri; Musumarra, Agatino; Petrovic, Ivan; Prokupek, Jan; Psikal, Jan; Ristic-Fira, Aleksandra; Renis, Marcella; Romano, Francesco P.; Romano, Francesco; Schettino, Giuseppe; Schillaci, Francesco; Scuderi, Valentina; Stancampiano, Concetta; Tramontana, Antonella; Ter-Avetisyan, Sargis; Tomasello, Barbara; Torrisi, Lorenzo; Tudisco, Salvo; Velyhan, Andriy

2013-05-01

Laser accelerated proton beams have been proposed to be used in different research fields. A great interest has risen for the potential replacement of conventional accelerating machines with laser-based accelerators, and in particular for the development of new concepts of more compact and cheaper hadrontherapy centers. In this context the ELIMED (ELI MEDical applications) research project has been launched by INFN-LNS and ASCR-FZU researchers within the pan-European ELI-Beamlines facility framework. The ELIMED project aims to demonstrate the potential clinical applicability of optically accelerated proton beams and to realize a laser-accelerated ion transport beamline for multi-disciplinary user applications. In this framework the eye melanoma, as for instance the uveal melanoma normally treated with 62 MeV proton beams produced by standard accelerators, will be considered as a model system to demonstrate the potential clinical use of laser-driven protons in hadrontherapy, especially because of the limited constraints in terms of proton energy and irradiation geometry for this particular tumour treatment. Several challenges, starting from laser-target interaction and beam transport development up to dosimetry and radiobiology, need to be overcome in order to reach the ELIMED final goals. A crucial role will be played by the final design and realization of a transport beamline capable to provide ion beams with proper characteristics in terms of energy spectrum and angular distribution which will allow performing dosimetric tests and biological cell irradiation. A first prototype of the transport beamline has been already designed and other transport elements are under construction in order to perform a first experimental test with the TARANIS laser system by the end of 2013. A wide international collaboration among specialists of different disciplines like Physics, Biology, Chemistry, Medicine and medical doctors coming from Europe, Japan, and the US is growing up around the ELIMED project with the aim to work on the conceptual design, technical and experimental realization of this core beamline of the ELI Beamlines facility.

Plasmon mode excitation and photoluminescence enhancement on silver nanoring

NASA Astrophysics Data System (ADS)

Kuchmizhak, Aleksandr A.; Gurbatov, Stanislav O.; Kulchin, Yuri N.; Vitrik, Oleg B.

2015-12-01

We demonstrate a simple and high-performance laser-assisted technique for silver nanoring fabrication, which includes the ablation of the Ag film by focused nanosecond pulses and subsequent reactive ion polishing. The nanoring diameter and thickness can be controlled by optimizing both the pulse energy and the metal film thickness at laser ablation step, while the subsequent reactive ion polishing provides the ability to fabricate the nanoring with desirable height. Scattering patterns of s-polarized collimated laser beam obliquely illuminating the nanoring demonstrate the focal spot inside the nanoring shifted from its center at a distance of ~0.57Rring. Five-fold enhancement of the photoluminescence signal from the Rhodamine 6G organic dye near the Ag nanoring was demonstrated. This enhancement was attributed to the increase of the electromagnetic field amplitude near the nanoring surface arising from excitation of the multipole plasmon modes traveling along the nanoring. This assumption was confirmed by dark-field back-scattering spectrum of the nanoring measured under white-light illumination, as well as by supporting finite-difference time-domain simulations.

A Nanowire-Based Plasmonic Quantum Dot Laser.

PubMed

Ho, Jinfa; Tatebayashi, Jun; Sergent, Sylvain; Fong, Chee Fai; Ota, Yasutomo; Iwamoto, Satoshi; Arakawa, Yasuhiko

2016-04-13

Quantum dots enable strong carrier confinement and exhibit a delta-function like density of states, offering significant improvements to laser performance and high-temperature stability when used as a gain medium. However, quantum dot lasers have been limited to photonic cavities that are diffraction-limited and further miniaturization to meet the demands of nanophotonic-electronic integration applications is challenging based on existing designs. Here we introduce the first quantum dot-based plasmonic laser to reduce the cross-sectional area of nanowire quantum dot lasers below the cutoff limit of photonic modes while maintaining the length in the order of the lasing wavelength. Metal organic chemical vapor deposition grown GaAs-AlGaAs core-shell nanowires containing InGaAs quantum dot stacks are placed directly on a silver film, and lasing was observed from single nanowires originating from the InGaAs quantum dot emission into the low-loss higher order plasmonic mode. Lasing threshold pump fluences as low as ∼120 μJ/cm(2) was observed at 7 K, and lasing was observed up to 125 K. Temperature stability from the quantum dot gain, leading to a high characteristic temperature was demonstrated. These results indicate that high-performance, miniaturized quantum dot lasers can be realized with plasmonics.

Direct-writing lithography using laser diode beam focused with single elliptical microlens

NASA Astrophysics Data System (ADS)

Hasan, Md. Nazmul; Haque, Muttahid-Ull; Trisno, Jonathan; Lee, Yung-Chun

2015-10-01

A lithography method is proposed for arbitrary patterning using an elliptically diverging laser diode beam focused with a single planoconvex elliptical microlens. Simulations are performed to model the propagation properties of the laser beam and to design the elliptical microlens, which has two different profiles in the x- and y-axis directions. The microlens is fabricated using an excimer laser dragging method and is then attached to the laser diode using double-sided optically cleared adhesive (OCA) tape. Notably, the use of OCA tape removes the need for a complicated alignment procedure and thus significantly reduces the assembly cost. The minimum focused spot of the laser diode beam is investigated by performing single-shot exposure tests on a photoresist (PR) layer. Finally, the practical feasibility of this lithography technique to generate an arbitrary pattern is demonstrated by dotted and continuous features through thin chromium layer deposition on PR and a metal lift-off process. The results show that the minimum feature size for the dotted patterns is around 6.23 μm, while the minimum linewidths for continuous patterns is 6.44 μm. In other words, the proposed focusing technique has significant potential for writing any arbitrary high-resolution pattern for applications like printed circuit board fabrication.

Laser Ground System for Communication Experiments with ARTEMIS

NASA Astrophysics Data System (ADS)

Kuzkov, Volodymyr; Volovyk, Dmytro; Kuzkov, Sergii; Sodnik, Zoran; Pukha, Sergii; Caramia, Vincenzo

2012-10-01

The ARTEMIS satellite with the OPALE laser communication terminal on-board was launched on 12 July, 2001. 1789 laser communications sessions were performed between ARTEMIS and SPOT-4 (PASTEL) from 01 April 2003 to 09 January 2008 with total duration of 378 hours. Regular laser communication experiments between ESA's Optical Ground Station (OGS - altitude 2400 m above see level) and ARTEMIS in various atmosphere conditions were also performed. The Japanese Space Agency (JAXA) launched the KIRARI (OICETS) satellite with laser communication terminal called LUCE. Laser communication links between KIRARI and ARTEMIS were successfully realized and international laser communications experiments from the KIRARI satellite were also successfully performed with optical ground stations located in the USA (JPL), Spain (ESA OGS), Germany (DLR), and Japan (NICT). The German Space Agency (DLR) performed laser communication links between two LEO satellites (TerraSAR-X and NFIRE), demonstrating data transfer rates of 5.6Gbit/s and performed laser communication experiments between the satellites and the ESA optical ground station. To reduce the influence of weather conditions on laser communication between satellites and ground stations, a network of optical stations situated in different atmosphere regions needs to be created. In 2002, the Main Astronomical Observatory (MAO) started the development of its own laser communication system to be placed into the Cassegrain focus of its 0.7m AZT-2 telescope (Fe = 10.5m), located in Kyiv 190 meters above sea level. The work was supported by the National Space Agency of Ukraine and by ESA ARTEMIS has an orbital position of 21.4° E and an orbital inclination of more than 9.75°. As a result we developed a precise tracking system for AZT-2 telescope (weighing more than 2 tons) using micro-step motors. Software was developed for computer control of the telescope to track the satellite's orbit and a tracking accuracy of 0.6 arcsec was achieved. A compact terminal for Laser Atmosphere and Communication Experiments with Satellite (LACES) has been produced. The LACES terminal includes: A CMOS camera of the pointing subsystem, a CCD camera of the tracking subsystem, an avalanche photodiode receiver module with thermoelectric cooling, a laser transmitter module with thermoelectric temperature control, a tip/tilt atmospheric turbulence compensation subsystem with movable mirrors, a four-quadrant photo-detector, a bit error rate tester module and other optical and electronic components. The principal subsystems and optical elements are mounted on a platform (weight < 20kg), which is located in the Cassegrain focus of the telescope. All systems were tested with ARTEMIS. The telemetry and dump buffer information from OPALE received by the control center in Redu (Belgium) was analyzed. During the beacon scan, the acquisition phase of laser link between OPALE laser terminal of ARTEMIS and LACES laser terminal started and laser signals from AZT-2 were detected by acquisition and tracking CCD sensors of OPALE. Some of the tests were performed in cloudy conditions. A description of our laser ground system and the experimental results will be presented in the report.

Monitoring of catalyst performance in CO2 lasers using frequency modulation spectroscopy with diode lasers

NASA Technical Reports Server (NTRS)

Wang, Liang-Guo; Sachse, Glen

1990-01-01

Closed-cycle CO2 laser operation with removal of O2 and regeneration of CO2 can be achieved by catalytic CO-O2 recombination. Both parametric studies of the optimum catalyst formulation and long-term performance tests require on line monitoring of CO, O2 and CO2 concentrations. There are several existing methods for molecular oxygen detection. These methods are either intrusive (such as electrochemical method or mass spectrometry) or very expensive (such as CARS, UV laser absorption). Researchers demonstrated a high-sensitivity spectroscopic measurement of O2 using the two-tone frequency modulation spectroscopy (FMS) technique with a near infrared GaAlAs diode laser. Besides its inexpensive cost, fast response time, nonintrusive measurements and high sensitivity, this technique may also be used to differentiate between isotopes due to its high spectroscopic resolution. This frequency modulation spectroscopy technique could also be applied for the on-line monitoring of CO and CO2 using InGaAsP diode lasers operation in the 1.55 microns region and H2O in the 1.3 microns region. The existence of single mode optical fibers at the near infrared region makes it possible to combine FMS with optical fiber technology. Optical fiber FMS is particularly suitable for making point-measurements at one or more locations in the CO2 laser/catalyst system.

Application of acoustical thermometry to noninvasive monitoring of internal temperature during laser hyperthermia

NASA Astrophysics Data System (ADS)

Krotov, Eugene V.; Yakovlev, Ivan V.; Zhadobov, Maxim; Reyman, Alexander M.; Zharov, Vladimir P.

2002-06-01

This work present the results of experimental study of applicability of acoustical brightness thermometry (ABT) in monitoring of internal temperature during laser hyperthermia and interstitial therapy. In these experiments the radiation of pulse repetition Nd:YAG laser (1064 nm) and continuous diode laser (800 nm) were used as heating sources. Experiments were performed in vitro by insertion of optical fiber inside the objects - optically transparent gelatin with incorporated light absorbing heterogeneities and samples of biological tissues (e.g. liver). During laser heating, internal temperature in absorbing heterogeneity and at fiber end were monitored by means of multi-channel ABT. The independent temperature control was performed with tiny electronic thermometer incorporated in heated zones. The results of experiments demonstrated reasonable sensitivity and accuracy of ABT for real-time temperature control during different kind of laser thermal therapies. According to preliminary data, ABT allow to measure temperature in depth up to 3-5 cm (depends on tissue properties) with spatial resolution some mm. Obtained data show that ABT is a very promising tool to give quantitative measure for different types of energy deposition (laser, microwave, focused ultrasound etc) at the depth commonly encountered in tumors of vital organs. Besides, ABT could give information about diffusion effects in heated zones or optical absorption. This work was supported by Russian Foundation for Basic Research and 6th competition-expertise of young scientists of Russian Academy of Sciences.

THz polariton laser using an intracavity Mg:LiNbO₃ crystal with protective Teflon coating.

PubMed

Ortega, Tiago A; Pask, Helen M; Spence, David J; Lee, Andrew J

2017-02-20

An enhancement in the performance of a THz polariton laser based on an intracavity magnesium-doped lithium niobate crystal (Mg:LiNbO₃) in surface-emitted (SE) configuration is demonstrated resulting from the deposition of a protective Teflon coating on the total internal reflection surface of the crystal. In this cavity geometry the resonating fields undergo total internal reflection (TIR) inside the lithium niobate, and laser damage to that surface can be a limiting factor in performance. The protective layer prevents laser damage to the crystal surface, enabling higher pump power, yielding higher THz output power and wider frequency tuning range. With the unprotected crystal, narrow-band THz output tunable from 1.50 to 2.81 THz was produced, with maximum average output power of 20.1 µW at 1.76 THz for 4 W diode pump power (limited by laser damage to the crystal). With the Teflon coating, no laser damage to the crystal was observed, and the system produced narrow-band THz output tunable from 1.46 to 3.84 THz, with maximum average output power of 56.8 µW at 1.76 THz for 6.5 W diode pump power. This is the highest average output power and the highest diode-to-terahertz conversion efficiency ever reported for an intracavity terahertz polariton laser.

Laser modulator for LISA pathfinder

NASA Astrophysics Data System (ADS)

Voland, C.; Lund, G.; Coppoolse, W.; Crosby, P.; Stadler, M.; Kudielka, K.; Özkan, C.

2017-11-01

LISA Pathfinder is an ESA experiment to demonstrate the key technologies needed for the LISA mission to detect gravitational waves in space. The LISA Pathfinder spacecraft represents one arm of the LISA interferometer, containing an optical metrology system and two proof masses as inertial references for the drag-free control system. The LISA Pathfinder payload consists of two drag-free floating test masses located in the inertial sensors with their control electronics and an optical metrology subsystem. The optical metrology subsystem monitors the movement of both test masses relative to each other and to the spacecraft with very high sensitivity and resolution. This is achieved with a heterodyne Mach- Zehnder interferometer. This interferometer requires as input two coherent laser beams with a heterodyne frequency difference of a few kHz. To generate the two laser beams with a heterodyne frequency difference a Nd:YAG laser is used together with the Laser Modulator. The Nd:YAG laser generates a single coherent laser signal at a wavelength of 1064nm which is fibre coupled to the Laser Modulator. The Laser Modulator then generates the two optical beams with the required heterodyne frequency offset. In addition, the Laser Modulator is required to perform laser amplitude stabilization and optical path difference control for the two optical signals. The Laser Modulator consists of an optical unit - the LMU - and RF synthesiser, power amplification and control electronics. These electronics are all housed in the Laser Modulator Electronics (LME). The LMU has four primary functions: • Splitting of the input laser beam into two paths for later superposition in the interferometer. • Applying different frequency shifts to each of the beams. • Providing amplitude modulation control to each of the beams. • Providing active control of the optical path length difference between the two optical paths. The present paper describes the design and performance of the LMU together with a summary of the results of the Laser Modulator engineering model test campaign.

Narrow-line, cw orange light generation in a diode-pumped Nd:YVO4 laser using volume Bragg gratings.

PubMed

Chen, Y L; Chen, W W; Du, C E; Chang, W K; Wang, J L; Chung, T Y; Chen, Y H

2009-12-07

We report on the demonstration of a narrow-line, cw orange 593-nm laser achieved via intracavity sum-frequency generation (SFG) of a diode-pumped dual-wavelength (1064 and 1342 nm) Nd:YVO(4) laser using two volume Bragg grating (VBG) reflectors. At diode pump power of up to 3.6 W, the 593-nm intracavity SFG laser radiates at the single longitudinal mode of spectral linewidth as narrow as approximately 15 MHz. More than 23-mW single-longitudinal-mode or 40-mW, <8.5-GHz (10-pm) linewidth (at 4.2-W diode pump power) 593-nm orange lights can be obtained from this compact laser system. Spectral tuning of the orange light was performed via the temperature tuning of the two VBGs in this system, achieving an effective tuning rate of ~5 pm/degrees C.

Precise Spatially Selective Photothermolysis Using Modulated Femtosecond Lasers and Real-time Multimodal Microscopy Monitoring.

PubMed

Huang, Yimei; Lui, Harvey; Zhao, Jianhua; Wu, Zhenguo; Zeng, Haishan

2017-01-01

The successful application of lasers in the treatment of skin diseases and cosmetic surgery is largely based on the principle of conventional selective photothermolysis which relies strongly on the difference in the absorption between the therapeutic target and its surroundings. However, when the differentiation in absorption is not sufficient, collateral damage would occur due to indiscriminate and nonspecific tissue heating. To deal with such cases, we introduce a novel spatially selective photothermolysis method based on multiphoton absorption in which the radiant energy of a tightly focused near-infrared femtosecond laser beam can be directed spatially by aiming the laser focal point to the target of interest. We construct a multimodal optical microscope to perform and monitor the spatially selective photothermolysis. We demonstrate that precise alteration of the targeted tissue is achieved while leaving surrounding tissue intact by choosing appropriate femtosecond laser exposure with multimodal optical microscopy monitoring in real time.

First refraction contrast imaging via Laser-Compton Scattering X-ray at KEK

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

Sakaue, Kazuyuki; Aoki, Tatsuro; Washio, Masakazu

2012-07-31

Laser-Compton Scattering (LCS) is one of the most feasible techniques for high quality, high brightness, and compact X-ray source. High energy electron beam produced by accelerators scatters off the laser photon at a small spot. As a laser target, we have been developing a pulsedlaser storage cavity for increasing an X-ray flux. The X-ray flux was still inadequate that was 2.1 Multiplication-Sign 10{sup 5}/sec, however, we performed first refraction contrast imaging in order to evaluate the quality of LCS X-ray. Edge enhanced contrast imaging was achieved by changing the distance from sample to detector. The edge enhancement indicates that themore » LCS X-ray has small source size, i.e. high brightness. We believe that the result has demonstrated good feasibility of linac-based high brightness X-ray sources via laser-electron Compton scatterings.« less

Precise Spatially Selective Photothermolysis Using Modulated Femtosecond Lasers and Real-time Multimodal Microscopy Monitoring

PubMed Central

Huang, Yimei; Lui, Harvey; Zhao, Jianhua; Wu, Zhenguo; Zeng, Haishan

2017-01-01

The successful application of lasers in the treatment of skin diseases and cosmetic surgery is largely based on the principle of conventional selective photothermolysis which relies strongly on the difference in the absorption between the therapeutic target and its surroundings. However, when the differentiation in absorption is not sufficient, collateral damage would occur due to indiscriminate and nonspecific tissue heating. To deal with such cases, we introduce a novel spatially selective photothermolysis method based on multiphoton absorption in which the radiant energy of a tightly focused near-infrared femtosecond laser beam can be directed spatially by aiming the laser focal point to the target of interest. We construct a multimodal optical microscope to perform and monitor the spatially selective photothermolysis. We demonstrate that precise alteration of the targeted tissue is achieved while leaving surrounding tissue intact by choosing appropriate femtosecond laser exposure with multimodal optical microscopy monitoring in real time. PMID:28255346

Tunable Microcavity-Stabilized Quantum Cascade Laser for Mid-IR High-Resolution Spectroscopy and Sensing.

PubMed

Borri, Simone; Siciliani de Cumis, Mario; Insero, Giacomo; Bartalini, Saverio; Cancio Pastor, Pablo; Mazzotti, Davide; Galli, Iacopo; Giusfredi, Giovanni; Santambrogio, Gabriele; Savchenkov, Anatoliy; Eliyahu, Danny; Ilchenko, Vladimir; Akikusa, Naota; Matsko, Andrey; Maleki, Lute; De Natale, Paolo

2016-02-17

The need for highly performing and stable methods for mid-IR molecular sensing and metrology pushes towards the development of more and more compact and robust systems. Among the innovative solutions aimed at answering the need for stable mid-IR references are crystalline microresonators, which have recently shown excellent capabilities for frequency stabilization and linewidth narrowing of quantum cascade lasers with compact setups. In this work, we report on the first system for mid-IR high-resolution spectroscopy based on a quantum cascade laser locked to a CaF₂ microresonator. Electronic locking narrows the laser linewidth by one order of magnitude and guarantees good stability over long timescales, allowing, at the same time, an easy way for finely tuning the laser frequency over the molecular absorption line. Improvements in terms of resolution and frequency stability of the source are demonstrated by direct sub-Doppler recording of a molecular line.

Controlled nanostructrures formation by ultra fast laser pulses for color marking.

PubMed

Dusser, B; Sagan, Z; Soder, H; Faure, N; Colombier, J P; Jourlin, M; Audouard, E

2010-02-01

Precise nanostructuration of surface and the subsequent upgrades in material properties is a strong outcome of ultra fast laser irradiations. Material characteristics can be designed on mesoscopic scales, carrying new optical properties. We demonstrate in this work, the possibility of achieving material modifications using ultra short pulses, via polarization dependent structures generation, that can generate specific color patterns. These oriented nanostructures created on the metal surface, called ripples, are typically smaller than the laser wavelength and in the range of visible spectrum. In this way, a complex colorization process of the material, involving imprinting, calibration and reading, has been performed to associate a priori defined colors. This new method based on the control of the laser-driven nanostructure orientation allows cumulating high quantity of information in a minimal surface, proposing new applications for laser marking and new types of identifying codes.

Nine-channel wavelength tunable single mode laser array based on slots.

PubMed

Guo, Wei-Hua; Lu, Qiaoyin; Nawrocka, Marta; Abdullaev, Azat; O'Callaghan, James; Donegan, John F

2013-04-22

A 9-channel wavelength tunable single-mode laser array based on slots is presented. The fabricated laser array demonstrated a threshold current in a range of 19~21 mA with the SOA unbiased at 20°C under continuous wave condition. Stable single mode performances have been observed with side-mode suppression-ratio (SMSR) > 50 dB. The output power higher than 37 mW was obtained at the SOA injected current of 70 mA for all the 9 channels within the laser array. A wavelength quasi-continuous tuning range of about 27 nm has been achieved for the laser array with the temperature variations from 10°C to 45°C. This array platform is of a single growth and monolithically integrable. It can be easily fabricated by standard photolithography. In addition, it potentially removes the yield problem due to the uncertainty of the facet cleaving.

A tunable single-monochromator Raman system based on the supercontinuum laser and tunable filters for resonant Raman profile measurements.

PubMed

Liu, X-L; Liu, H-N; Tan, P-H

2017-08-01

Resonant Raman spectroscopy requires that the wavelength of the laser used is close to that of an electronic transition. A tunable laser source and a triple spectrometer are usually necessary for resonant Raman profile measurements. However, such a system is complex with low signal throughput, which limits its wide application by scientific community. Here, a tunable micro-Raman spectroscopy system based on the supercontinuum laser, transmission grating, tunable filters, and single-stage spectrometer is introduced to measure the resonant Raman profile. The supercontinuum laser in combination with transmission grating makes a tunable excitation source with a bandwidth of sub-nanometer. Such a system exhibits continuous excitation tunability and high signal throughput. Its good performance and flexible tunability are verified by resonant Raman profile measurement of twisted bilayer graphene, which demonstrates its potential application prospect for resonant Raman spectroscopy.

Spatial and polarization entanglement of lasing patterns and related dynamic behaviors in laser-diode-pumped solid-state lasers.

PubMed

Otsuka, K; Chu, S-C; Lin, C-C; Tokunaga, K; Ohtomo, T

2009-11-23

To provide the underlying physical mechanism for formations of spatial- and polarization-entangled lasing patterns (namely, SPEPs), we performed experiments using a c-cut Nd:GdVO(4) microchip laser with off-axis laser-diode pumping. This extends recent work on entangled lasing pattern generation from an isotropic laser, where such a pattern was explained only in terms of generalized coherent states (GCSs) formed by mathematical manipulation. Here, we show that polarization-resolved transverse patterns can be well explained by the transverse mode-locking of distinct orthogonal linearly polarized Ince-Gauss (IG) mode pairs rather than GCSs. Dynamic properties of SPEPs were experimentally examined in both free-running and modulated conditions to identify long-term correlations of IG mode pairs over time. The complete chaos synchronization among IG mode pairs subjected to external perturbation is also demonstrated.