ABSTRACT
Developing high-power laser technology and its applications necessitates improvements in the laser-irradiation resistance of liquid-crystal modulation devices. In this study, the thermal characteristics of substrate and electrode materials, including sapphire-substrate indium tin oxide (ITO) electrodes, K9 glass-substrate ITO electrodes, sapphire-substrate gallium nitride (GaN) electrodes, and liquid-crystal optical switches, are investigated using simulation and experimental methods. Results show that the sapphire-substrate GaN electrode demonstrates the best heat dissipation and that the maximum temperature at the center of the spot under 75 W laser irradiation is 319 K, 52 K lower than that of an equally thick sapphire-substrate ITO electrode and 225 K lower than that of an equally thick K9 glass-substrate ITO electrode (steady state and test time >2min). Additionally, the experimental results show that the liquid-crystal optical switch, comprising a sapphire substrate and GaN electrode, can endure continuous laser irradiation up to 18 W with a switching ratio of approximately 20:1. The optical switch with GaN electrodes on a sapphire substrate can endure a power density of 156W/c m 2, much higher than that (21W/c m 2, steady state and test time >2min) tolerable by the liquid-crystal optical switch with ITO transparent electrodes and K9 glass substrates.
ABSTRACT
We demonstrate a laser-diode-pumped multipass Nd:glass laser amplifier with a range of advanced characteristics. The amplifier exhibits high extraction efficiency, enables arbitrary shaping of spatial beam intensity, and effectively suppresses frequency modulation to amplitude modulation conversion. Our approach achieves excellent beam quality via thermal lensing and thermal depolarization compensation. When a 1.82 mJ/5 ns laser pulse was injected into the amplifier, the output energy reached up to 3.3 J with a repetition rate of 1 Hz at a central wavelength of 1053.3 nm. The near-field modulation of the amplified output beam was below 1.2, and the far-field focusing ability of the beam was 90% at 2.9 times the diffraction limit. This laser amplifier system holds potential for integration as a preamplifier within the SG-II upgrade high power laser facility.
ABSTRACT
A high-energy, high-beam-quality, high-contrast picosecond optical parametric chirped-pulse amplification (ps-OPCPA) laser system was demonstrated. The pulse from a femtosecond oscillator was stretched to 4 ps, after which it was amplified from 140 pJ to 600 µJ by an 8 ps/6 mJ pump laser in two non-collinear OPCPA stages. The total gain was >106, and the root mean square of the energy stability of the laser system was 1.6% in 10 h. The contrasts of the solid and fiber mode-locked femtosecond oscillator-seeded ps-OPCPA systems were compared, and a signal-to-noise ratio of >1011 was achieved. Using this system, the contrast of the front end in high-power picosecond petawatt laser facility was improved by â¼40 dB to >1011, beyond â¼200 ps ahead of the main pulse with an output level of 60 mJ.
ABSTRACT
To obtain a wide range of high-precision time-delay controllable devices, a 100-µm-thick nematic liquid crystal (LC) cell was fabricated using the LC HTD028200-200. Factors influencing the delay calibration accuracy of LC variable retarders (LCVRs) were analyzed theoretically and experimentally. Subsequently, within the total voltage tuning range of 0-5 V, the LCVR had a delay of 4.977-97.404 fs, total delay range of 90 fs, tuning accuracy of ±0.216fs, and tuning resolution of 0.128 fs. This device will play an important role in spectral imaging.
ABSTRACT
High laser damage threshold optical switches and spatial light modulators are in urgent demand in high power laser fields. In this Letter, liquid crystal optical switches using Si-doped GaN and Mg-doped GaN as transparent electrodes are fabricated, and the influence of the conductive properties of GaN is analyzed. The transmission and absorption characteristics of GaN and its sapphire substrate are tested. The results show that the liquid crystal device based on gallium nitride can be expected to play an important role in the fields of visible and near-infrared laser regions with a high laser damage threshold of more than 1J/cm2.
ABSTRACT
The temporal contrast levels of laser pulses in the injection laser system of the Shenguang-II facility are accurately measured and analyzed in detail. These signal-to-noise ratio levels are determined by the extinction ratios of an acousto-optic modulator, an electro-optic intensity modulator, and a combination of a Pockels cell and thin film polarizers. In addition, a drifting direct current bias voltage of an electro-optic intensity modulator and phase modulation are also demonstrated to affect the signal-to-noise ratio of the injection laser system. With a precise control of these factors, the injection laser system can output a nanosecond laser pulse with a signal-to-noise ratio of 47.37 dB. Moreover, a nanosecond laser pulse signal-to-noise ratio measuring device with a dynamic range and accuracy of 50 and 1 dB, respectively, is developed to detect the signal-to-noise ratio of a nanosecond laser pulse, which is 47.06 dB within an accuracy range of 1 dB. The signal-to-noise ratio measuring device can detect the high contrast laser pulse for the seed source unit in the high power laser facility accurately and conveniently.
ABSTRACT
As important analysis tools, microscopes with high spatial resolution are indispensable for scientific research and clinical diagnosis. We report a proof-of-principle experimental demonstration of a two-arm microscope scheme and show that, by measuring the second-order correlation of light fields, more details of an object can be obtained through recording more information about the initial illumination field. The effects arising from the transverse coherence length and the axial correlation depth of the illumination field are also discussed.
