Spectral acceptance for second-harmonic generation in CD*A

Abstract

The efficiency of second‐harmonic generation (SHG) in a crystal is reduced if the laser spectral width Δλ_F is too large. This paper presents the measurement of the spectral acceptance width Δλ_A in cesium dideuterium arsenate (CD*A) at the fundamental wavelength of 1.06 μm using a narrow‐band tunable Nd : glass laser, with the result LΔλ_A=2.25 cm nm, where L is the crystal length. The theory presented here of SHG with a broad‐band fundamental shows that SHG efficiency declines as Δλ_A/Δλ_F when Δλ_F is increased beyond Δλ_A. Achievement of 90% of the narrow‐band SHG efficiency requires that a Q‐switched Nd : glass laser be spectrally narrowed to 1.5 nm for a 1.5‐cm CD*A crystal.