Narrow-band 1 W source at 257 nm using frequency quadrupled passively Q-switched Yb:YAG laser

Area of Science:

• Laser Physics
• Nonlinear Optics
• Spectroscopy

Background:

• Compact passively Q-switched Ytterbium-doped Yttrium Aluminum Garnet (Yb:YAG) lasers are valuable tools.
• Ultraviolet (UV) light sources are crucial for high-resolution spectroscopic techniques like UV-Raman spectroscopy.
• Efficient generation of UV wavelengths from near-infrared lasers presents a significant challenge.

Purpose of the Study:

• To describe the generation of 257 nm UV emission via fourth harmonic generation (FHG).
• To characterize the performance of a compact passively Q-switched Yb:YAG laser for UV applications.
• To evaluate the efficiency of nonlinear crystals for UV wavelength conversion.

Main Methods:

• Utilized a compact passively Q-switched Yb:YAG laser with a volume Bragg grating for narrow linewidth (0.1 nm) at 1030 nm.
• Employed frequency quadrupling, involving second harmonic generation (SHG) in lithium triborate (LBO) and subsequent frequency doubling in beta-barium borate (BBO).
• Characterized the far-field and near-field properties of the generated 257 nm emission.

Main Results:

• Generated 1.1 W of 257 nm UV emission.
• Achieved 70% conversion efficiency for SHG in LBO and 45% for the second doubling in BBO.
• Obtained an overall nonlinear conversion efficiency of 31% for the 1030 nm to 257 nm conversion.
• The 1030 nm source produced 100 kW peak power, 250 μJ pulses, and 3.6 W average power.

Conclusions:

• Demonstrated efficient generation of UV light at 257 nm from a compact Yb:YAG laser system.
• The developed system is suitable for UV-Raman spectroscopic applications due to its narrow linewidth and UV output.
• The use of LBO and BBO crystals proved effective for high-efficiency fourth harmonic generation.