Watt-level all-solid-state single-frequency 248 nm DUV source

Area of Science:

• Laser Physics and Photonics
• Nonlinear Optics
• Deep-Ultraviolet (DUV) Technology

Background:

• All-solid-state deep-ultraviolet (DUV) laser sources are crucial for various scientific and industrial applications.
• Previous DUV sources at 248 nm have been limited in average power, hindering their practical utility.
• Sum-frequency generation (SFG) is a key nonlinear optical process for generating shorter wavelengths.

Purpose of the Study:

• To realize an all-solid-state single-frequency 248 nm deep-ultraviolet (DUV) source with significantly improved average power.
• To enhance the conversion efficiency of the sum-frequency generation process for DUV output.
• To investigate methods for increasing pulse energy and optimizing nonlinear crystal parameters.

Main Methods:

• Employed pulsed pumping to boost the pulse energy of the 1064 nm fundamental laser driver.
• Utilized simulation-guided optimization to determine the optimal length of the Lithium Triborate (LBO) crystal for the 827 nm optical parametric oscillator (OPO).
• Implemented sum-frequency generation (SFG) between 355 nm and 827 nm lasers to produce the 248 nm output.

Main Results:

• Achieved a watt-level (~1.2 W) average power for the all-solid-state single-frequency 248 nm DUV source.
• Improved the overall conversion efficiency from 1064 nm to 248 nm from 1.41% to 3.93% at a 4 kHz repetition rate.
• Measured beam quality factors M² of 1.61 (x-direction) and 1.10 (y-direction), with a linewidth of approximately 270 MHz.

Conclusions:

• This work reports the first watt-level output for an all-solid-state single-frequency 248 nm DUV source.
• The combination of pulsed pumping and optimized OPO crystal length significantly enhances DUV generation efficiency.
• The achieved performance marks a substantial advancement in high-power, narrow-linewidth DUV laser technology.