The 1064 nm laser damage experimental system was established to study the spatiotemporal evolution of plasma generated by K9 window, fused silica, CaF2 and MgF2. In the experiment, the ICCD camera was used to capture the plasma morphology at a fixed delay time, while a fiber optic spectrometer was used to collect spectral information of spontaneous emission during the plasma evolution process. The evolution process of plasma generated by K9 window and fused silica was relatively similar, and the evolution process of plasma generated by CaF2 and MgF2 was relatively similar too. The transient plasma morphology of different optical windows induced by 1064 nm laser were diverse, indicating that the evolution process of laser plasma had become a unique feature of optical windows. The lifetime of plasma of K9 window, fused silica, CaF2 and MgF2 was about 2000 ns, 500 ns, 500 ns and 500 ns induced by 1064 nm laser. Due to the damage thresholds of different optical windows, the time from plasma generation to disappearance was also different. The results of spectral analysis indicated that the plasma spectrum had a direct correlation with the elemental composition of the optical window itself and comparing the spectra of the same optical window under different delay conditions, it could be seen that the delay time of the maximum spectral peak intensity was correlated with the plasma lifetime of optical windows.
As a critical optical material in inertial confinement fusion (ICF), fused silica can be damaged by ultravioletlaser, which reduces its laser load capacity. The impurities existing on the fused silica surface can significantly reduce the laser damage threshold (LIDT) of fused silica. However, most of the theoretical research focus on the point defects, and few researchers systematically study the impact of impurities on optical absorption and LIDT of fused silica. Hence, in this paper, the impact of four typical impurities (Fe, Ce, Cu, Ca) on the electronic structures and optical properties of fused silica are studied by first-principles calculations. It is found that impurities can introduce defect states into the electronic structure of fused silica and enhance optical absorption in the visible-to-UV range, leading to laser damage and lower LIDT. Moreover, we find that the Ce atom with higher valency can cause stronger absorption of fused silica at UV range. Our work can provide theoretical support for the study of ultraviolet-laser damage of fused silica.
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.
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