High laser damage threshold GaN-based liquid crystal devices for 2 μm band applications

With advancements in laser technology toward higher energy levels, greater average power, and multi-wavelength applications, optical field modulation devices are required to cover broader wavelength ranges, endure higher repetition rates, and exhibit improved laser damage thresholds. Laser sources in the 2 μm band offer significant potential for both scientific and industrial applications. Nevertheless, the development of optical field modulation devices with high laser damage thresholds in this wavelength range presents significant technical challenges. Our research group has investigated the feasibility of employing GaN-based liquid crystal devices—characterized as third-generation semiconductors—for applications in the 2 μm band. These devices demonstrate spectral transmittance spanning the range of 500 nm to 3 μm, achieving the maximum on–off ratio of 256:1, withstanding laser irradiation up to 15 W at 2 μm (spot size: 1.208 mm, on–off ratio of 20:1), and supporting a peak power density tolerance of 2534 W/cm² and a maximum repetition rate of 28 Hz.