Abstract
The angular non-critical phase-matching (A-NCPM) second-harmonic-generation (SHG) properties of RE1xRE21−xCOB (RE1, RE2 = Y, Gd, La, Tm, Sm, and Nd) type mixed crystals including NCPM wavelength and conversion efficiency were detailedly investigated. Theoretical calculations manifest that the A-NCPM SHG scope of these crystals is 0.72~1.42 µm, and in experiments, the A-NCPM SHG waveband of 0.72~1.25 µm has been realized, by changing the ratio of the rare-earth elements RE1 and RE2 in RE1xRE21−xCOB crystals. Comparing to the temperature-dependent A-NCPM SHG of 0.95~1.34 µm in LiB3O5 (LBO) crystal, the composition-dependent A-NCPM SHG of 0.72~0.95 µm in RE1xRE21−xCOB type crystals is unique and has special significance for the frequency conversion of Ti:Sapphire lasers. Relationships between the birefringence and radius of rare-earth ion RE3+ in RE1xRE21−xCOB mixed crystals were discussed. Aiming for the A-NCPM SHG of 0.72~1.42 µm, we supply a clear, completed, and optimized solution on how to select the compositions of RE1xRE21−xCOB mixed crystals. Under focusing light beam conditions, high efficient A-NCPM SHG for both OPO and Ti:sapphire lasers were realized experimentally by using long Y- and Z-cut RE1xRE21−xCOB crystal samples.
Highlights
Applications of visible laser beams have been growing rapidly in recent years, which can be used in the areas of entertainment, manufacturing, medicine, information technology, optical data storage, color display, and laser spectroscopy [1,2,3]
One is semiconductor lasers which directly produce visible lights [4,5], another is Pr3+, Tb3+, Sm3+ or Dy3+ ions doped laser crystals pumped by semiconductor lasers [6,7,8], the last one is frequency doubling of near-infrared lasers by nonlinear optical (NLO)
In 2017, we discovered that RECOB (RE = Y, Gd, La, Tm, Sm, and Nd) crystals were found to possess a wide birefringence range of 0.0425~0.0279 [25], in theory, the angular non-critical phase-matching (A-NCPM) SHG wavelengths might be changed dramatically for their mixed crystals RE1x RE21−x COB (RE1, RE2 = Y, Gd, La, Tm, Sm, and Nd), which showed the possibility of a widely tunable A-NCPM waveband
Summary
Applications of visible laser beams have been growing rapidly in recent years, which can be used in the areas of entertainment, manufacturing, medicine, information technology, optical data storage, color display, and laser spectroscopy [1,2,3]. In 2017, we discovered that RECOB (RE = Y, Gd, La, Tm, Sm, and Nd) crystals were found to possess a wide birefringence range of 0.0425~0.0279 [25], in theory, the A-NCPM SHG wavelengths might be changed dramatically for their mixed crystals RE1x RE21−x COB (RE1, RE2 = Y, Gd, La, Tm, Sm, and Nd), which showed the possibility of a widely tunable A-NCPM waveband. A-NCPM SHG wavelength and the rare earth radius of RE1x RE21−x COB (RE1, RE2 = Y, Gd, La, Tm, Sm, and Nd) mixed crystals is analyzed. This paper supplies a complete A-NCPM solving scheme for the frequency doubling of 0.72~1.42 μm lasers based on the pure RECOB (RE = Y, Gd, La, Tm, Sm, and Nd) and their derivative mixed crystals, which can generate 0.36~0.71 μm visible lasers with high efficiency. Under focusing light beam conditions, efficient NCPM SHG for both OPO and Ti:sapphire lasers were realized experimentally
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