In a high-power Pr:YLF solid-state laser, the thermal effect of gain medium is one of the prime limiting factors, and its thermal damage has become the major concern. The thermal effect of Pr:YLF crystal was analyzed theoretically, and the distribution of temperature, thermal stress, thermal focal length, and pump polarization effects of the Pr:YLF crystal were simulated. The thermal effect investigation indicates that under reasonable pumping power density, crystal length, and beam waist size and location, the temperature rise and nonuniformity of thermal distortion are not intensified under high-power operation. Additionally, the relationship between Gauss or Super-Gaussian pump mode and thermal focal length of Pr:YLF crystal was simulated. To the best of our knowledge, this analysis is the first to examine the thermal effect of Pr:YLF crystal for power scaling, and this thermal effect investigation of Pr:YLF crystal provides first-hand data for a high-power, visible, solid-state laser that could be helpful for high-power Pr:YLF solid-state laser design.
Mid-infrared spectral region (2-4 μm) is acquiring significant attention due to the presence of various enabling applications in the field of remote gas detection, environmental pollution detection applications. Tm:YAP is an important crystal materials for diode-pumped laser emission of 2μm wavelength. We report a room-temperature diode pumped Tm:YAP thin disk laser. The maximum output power was 3.5 W at wavelength of 1940 nm.
We report on successful fabrication of GaSb-based type-I quantum well distributed Bragg reflector (DBR) lasers emitting around 2.3μm. Second-order Bragg gratings of chromium were patterned by electron beam lithography. For 1.5-mm-long laser diode, single mode continuous-wave operation with output power of 10mW is obtained. The devices show a stable single mode operation with high side mode suppression ratio.
An experimental investigation for the polarization analysis of the high power GaSb-based semiconductor laser diodes emitting at 2.1μm in terms of measuring Stokes parameters has been exploited and adopted, which gives further insight into understanding, manipulating and applying the polarization properties of the laser diode. Results of output performance and polarization behavior of the laser are presented in the paper. The average linear polarization of the laser diode reaches 97.72% with output power exceeding 1W at 3.5A under CW operation at 20℃, which demonstrates the dominant position of linear polarization light of the output beam. Highly linear-polarized properties could not only enhance the performance of high power GaSb-based laser diodes in traditional applications in laser processing and beam combing, but also open new application fields such as parametric convention and coherent detection.
Quantum cascade laser (QCL) emitting in the mid-wave infrared atmospheric windows (3μm to 5 μm) will be of immediate use to several civilian applications, including airborne self-defense protection system and trace gas sensing and free space optical communications. In this work, an experimental study of laser coupling in fiber-optic waveguide with small-bore diameters of d =105 μm. The output beam quality of QCL transmission out of the fiber is analyzed. The output laser nearfield and the farfiled of a QCL with nearly 500 mW continuous wave power at room temperature is measured by a two-dimensional beam quality analyzer. Results show that the output nearfield and farfield is nearly super-Gaussian distributed after tansmition from the multimode fiber.
High-power laser plays an important role in many fields, such as directed energy weapon, optoelectronic contermeasures, inertial confinement fusion, industrial processing and scientific research. The uniform nearfield and wavefront are the important part of the beam quality for high power lasers, which is conducive to maintaining the high spatial beam quality in propagation. We demonstrate experimentally that the spatial intensity and wavefront distribution at the output is well compensated simultaneously in the complex high-power solid-state laser system by using the small-aperture spatial light modulator (SLM) and deformable mirror (DM) in the front stage. The experimental setup is a hundred-Joule-level Nd:glass laser system operating at three wavelengths at 1053 nm (1ω), 527 nm (2ω) and 351 nm (3ω) with 3 ns pulse duration with the final output beam aperture of 60 mm. While the clear arperture of the electrically addressable SLM is less than 20 mm and the effective diameter of the 52-actuators DM is about 15 mm. In the beam shaping system, the key point is that the two front-stage beam shaping devices needs to precompensate the gain nonuniform and wavefront distortion of the laser system. The details of the iterative algorithm for improving the beam quality and the strategy of achiving high beam quality on spatial intensity and wavefront simultaneously are presented. Experimental results show that the output wavefront RMS value is 0.06, and simultaneously the output near-field modulation is 1.38:1 and the fluence contrast is 10.5% at 3 ns at 1053nm with 40-Joule-level energy.
Quantum cascade laser (QCL) emitting in the mid-wave infrared atmospheric windows (3 μm to 5 μm) will be of immediate use to several civilian applications, including airborne self-defense protection system and trace gas sensing and free space optical communications. At present, the mid-infrared laser sources mainly include solid-state optical parametric oscillation lasers, fiber lasers, and QCL. In these lasers, quantum cascade laser is the only one that can realize the conversion from electricity to light. Since its invention in 1994, with the deepening of scientific research, quantum cascade laser performance has been continuously improved, and the output laser power and beam quality of single transistor has been continuously improved. In this work, the output beam quality of QCL is analyzed. the evaluating method of the laser beam quality is analized in theory based on the Gaussian beam transmittion law. The output nearfiled and farfield of the single quantum cascade laser is measured in the experiment. The output divergence angle is calculated and the output beam quality is analized by using the M2 factor.
Quantum cascade laser (QCL) emitting in the mid-wave infrared atmospheric windows (3 to 5 μm) will be of immediate use to several civilian applications, including airborne self-defense protection system and trace gas sensing and free space optical communications. When the output power of a single QCL is too low, the beams of different lasers can be combined by incoherent beam combining. For incoherent beam combining the laser beams are arranged side by side on the aperture of the laser system and combine in the farfield. Incoherent beam combining has been applied very successfully to diode lasers with high robustness and reliability due to it is neither limited to any number of lasers nor to any laser characteristics. This technique is demonstrated to be compatible with QCLs in this work. In this paper, the method of incoherent beam combination of 4 independent QCL emitters with a 0.1 W continuous wave power at room temperature each is studied. Results show that the incoherent power superposition of mid-infrared QCLs can be achieved by beam combining with an efficiency of not less than 90%. The output farfield divergence angle is about 5 mrad, which is consistent with the farfield divergence angle of the four subbeams.
High-power laser plays an important role in many fields, such as directed energy weapon, optoelectronic contermeasures, inertial confinement fusion, industrial processing and scientific research. The uniform nearfield is the important part of the beam quality for high power lasers, which is conducive to maintaining the high spatial beam quality in propagation. We demonstrate experimentally that the spatial intensity distribution at the output is well compensated in the complex high-power solid-state laser system by using the small-aperture spatial light modulator (SLM) in the front stage. The experimental setup is a hundred-Joule-level Nd:glass laser system operating at three wavelengths at 1053 nm (1ω), 527 nm (2ω) and 351 nm (3ω) with 3 ns pulse duration with the final output beam aperture of 60 mm. While the clear arperture of the electrically addressable SLM is less than 20 mm. In the beam shaping system, the key point is that the front-stage SLM needs to precompensate the gain nonuniform of the laser system. Liquid crystal SLM is an effective active beam shaping device through adjusting each pixel transmittance to improve the spatial beam quality of the output laser, which can also be used as a binary optical element (BOE) with each pixel transmittance 0 or 1 to realize spatial beam shaping for high-power lasers. We present and demonstrate an efficient shaping method of the SLM used as BOE based on diffraction principle. The method can be used to control the output nearfield actively by compensating the spatial nonuniformity of transmission and amplification in the high power laser system. Results show the output nearfield beam quality improves significantly after shaping by using this method with the fluence contrast changing from 22% to 11.3% within only 2 shots in the single-shot operation laser.
In high-power laser systems, the optics suffers from different degrees of damage due to high-power laser irradiation. Studying the laser-induced damage generation and growth law of the optics is greatly benefited by the ability to accurately predict how damage sites evolve with laser exposure. In this work, the laser-induced damage growth model in optics under high-power laser irradiation is described based on the Weibull distribution model. A parameter method for solving Weibull distribution model by using the least-square method is proposed. In addition, a Monte-Carlo analysis method is used to numerically simulate the growth law of laser-induced damage in optics based on the statistical theory. Furthermore, we have also predict the laser-induced damage growth trend for 20 shots in high-power laser systems.
The mid-infrared band of 3~5 μm wavelength is a very important atmospheric window. The mid-infrared lasers are widely applied in laser countermeasure, laser illumination and trace gas detection. At present, the mid-infrared laser sources mainly include solid-state optical parametric oscillation lasers, fiber lasers, mid-infrared supercontinuum spectrum laser and mid-infrared semiconductor lasers, i.e. quantum cascade lasers. In these lasers, quantum cascade laser is the only one that can realize the conversion from electricity to light. In this paper, the method of incoherent beam combination of mid-infrared semiconductor lasers is studied. Two lasers are combined in a common aperture by using a single polarizer based on the polarization characteristics of the output laser of quantum cascade laser. Results show that the incoherent power superposition of mid-infrared quantum cascade lasers can be achieved by polarization beam combining, and the beam combining efficiency is not less than 90%. The farfield divergence angle is about 5 mrad, which is consistent with the farfield divergence angle of the two sub-beams.
High-power laser plays an important role in many fields, such as directed energy weapon, optoelectronic contermeasures, inertial confinement fusion, industrial processing and scientific research. The uniform nearfield and wavefront are the important part of the beam quality for high power lasers, which is conducive to maintaining the high spatial beam quality in propagation. We demonstrate experimentally that the spatial intensity and wavefront distribution at the output is well compensated in the complex high-power solid-state laser system by using the small-aperture spatial light modulator (SLM) and deformable mirror (DM) in the front stage. The experimental setup is a hundred-Joule-level Nd:glass laser system operating at three wavelengths at 1053 nm (1ω), 527 nm (2ω) and 351 nm (3ω) with 3 ns pulse duration with the final output beam aperture of 60 mm. While the clear arperture of the electrically addressable SLM is less than 20 mm and the effective diameter of the 52-actuators DM is about 15 mm. In the beam shaping system, the key point is that the two front-stage beam shaping devices needs to precompensate the gain nonuniform and wavefront distortion of the laser system. The details of the iterative algorithm for improving the beam quality are presented. Experimental results show that output nearfield and wavefont are both nearly flat-topped with the nearfield modulation of 1.26:1 and wavefront peak-to-valley value of 0.29 λ at 1053nm after beam shaping.
KEYWORDS: Pulsed laser operation, Pulse shaping, High power lasers, Laser systems engineering, Modulation, Solid state lasers, Distortion, Signal to noise ratio, Laser applications, Control systems
In high-power solid-state laser, initiative pulse shaping can help improve the output laser’s performance. The evaluation
for output laser pulse is also incomplete. In this paper, we propose a method of initiative pulse shaping by using arbitrary
waveform generator (AWG), and establish a relatively complete evaluation system for the output pulses shape
simultaneously. It achieves the super-Gaussian pulse output with high SNR (signal-to-noise ratio). As a consequence, a
square laser pulse with pulse adjustable width ~5ns, rising time 197ps is obtained. The power imbalance of the output
square pulse is 3.72%. The similarity between the eight-order super-Gaussian pulse and the one we get from experiment
reached 99%.
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