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Deep-UV laser source based on χ(2) optical frequency conversion and χ(3) stimulated Raman scattering.
Optics Letters
|February 14, 2025
Summary
Researchers developed a novel deep-UV laser generation method near 200 nm using integrated nonlinear optical processes. This technique combines optical frequency conversion and stimulated Raman scattering (SRS) in a DKDP crystal, achieving high-energy deep-UV output.
Area of Science:
- Nonlinear Optics
- Laser Physics
- Materials Science
Background:
- Traditional deep-UV laser generation methods often face limitations due to phase-matching conditions.
- Stimulated Raman scattering (SRS) and optical frequency conversion are established nonlinear optical processes.
- Potassium Dideuterium Phosphate (KD2PO4 or DKDP) crystals are known for their nonlinear optical properties.
Purpose of the Study:
- To demonstrate a new, high-energy deep-UV laser generation scheme near 200 nm.
- To integrate nonlinear optical processes of second-order (χ(2)) and third-order (χ(3)) nonlinearities.
- To overcome phase-matching limitations in conventional deep-UV generation.
Main Methods:
- Utilized a Nd:YAG laser (1064 nm) as the fundamental source.
- Employed cascaded second- and fourth-harmonic generation (SHG and FHG) in LiB3O5 and DKDP crystals to obtain 266 nm radiation.
- Integrated stimulated Raman scattering (SRS) in a KGd(WO4)2 crystal to generate Stokes light.
- Applied sum-frequency generation (SFG) of Stokes light and 266 nm radiation in a DKDP crystal to achieve deep-UV output near 200 nm.
Main Results:
- Achieved 266 nm radiation with a 24.8% energy conversion efficiency from the fundamental 1064 nm laser.
- Generated Stokes light with two polarization-dependent Raman shifts (768 cm⁻¹ and 901 cm⁻¹).
- Produced deep-UV laser sources of 3.5 mJ at 216.3 nm and 3.1 mJ at 217 nm.
- Attained a total conversion efficiency of approximately 3% from 1064 nm infrared to ~200 nm deep-UV.
- Demonstrated fifth-harmonic generation (FiHG) in DKDP, overcoming phase-matching challenges.
Conclusions:
- The integrated nonlinear optical scheme successfully generated high-energy deep-UV lasers near 200 nm.
- Combining χ(2) and χ(3) nonlinear effects provides a viable alternative to traditional deep-UV generation methods.
- This approach offers a promising pathway for developing high-energy, high-peak-power deep-UV laser sources.
