Deep ultraviolet (DUV) picosecond lasers, operating in the 200–280 nm wavelength range, offer significant advantages, such as high photon energy and high resolution. These attributes make them highly promising for applications like semiconductor detection, ensuring the production of high-quality, defect-free semiconductor devices, as well as for advanced scientific research and industrial processing. High-power DUV picosecond lasers are typically generated via nonlinear frequency conversion of infrared lasers based on master oscillator power amplifier (MOPA) configurations. Among the various DUV laser technologies, systems based on β-BBO crystals are particularly valued for their simple design and cost efficiency. However, linear and two-photon absorption, as well as dynamic color center formation in BBO, are significant limitations for high-power, high-repetition-rate UV generation, leading to thermal effects. Hence, it is important to carefully study the performance characteristics of BBO for high-power, high-repetition-rate pulse generation in the UV at 266 nm.
This study presents a high-power, all-solid-state DUV picosecond laser developed using a 1064 nm Nd:YVO₄ MOPA amplification architecture. The experimental setup employed a 50 mW, 7.8 ps, 20 MHz all-fiber SESAM mode-locked laser as the seed source, achieving an amplified output power of 140 W with a pulse duration of 8.33 ps at 1064 nm via MOPA. In the nonlinear frequency conversion process, the amplified laser pulses were initially focused onto an LBO crystal for second harmonic generation (SHG). Precise temperature control of the LBO crystal enabled the generation of a 532 nm output with 73 W of power and a pulse duration of 6.93 ps, while achieving a conversion efficiency of 52.64%. Two-photon absorption is a key factor limiting the further enhancement of deep ultraviolet (DUV) laser power. By investigating the transmittance and temperature rise of a high-power dual-wavelength laser in a β-BBO crystal, the results indicate that strong two-photon absorption occurs under high-power DUV irradiation. This absorption induces significant thermal effects, resulting in temperature gradients within the crystal and leading to phase mismatch, which severely impacts frequency conversion efficiency and output stability.
To address this issue and further increase the DUV output power, a large-spot pumping scheme (spot size: 1.5 mm × 1 mm) is adopted in this work. Under a pump peak power density of less than 1.11 GW/cm
, the thermal gradient caused by two-photon absorption is effectively suppressed, enabling a maximum fourth-harmonic output power of 11 W. The corresponding single-pulse energy reaches 13.75 μJ. The root mean square (RMS) jitter, measured over an 8-hour period, was < 0.96%.
This all-solid-state DUV laser demonstrates excellent performance characteristics, including high average power, stability, resolution, and peak power, making it a strong candidate for applications requiring efficient and high-precision processing or detection. By further increasing the pump power and optimizing the temperature control system, the output power of the laser can be significantly enhanced, broadening its applicability and competitiveness in high-end fields such as semiconductor manufacturing, advanced research, and industrial processing.