Spectral acceptance for second-harmonic generation in CD*A

The efficiency of second-harmonic generation (SHG) in a crystal is reduced if the laser spectral width ΔλF is too large. This paper presents the measurement of the spectral acceptance width ΔλA 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 LΔλA=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 ΔλA/ΔλF when ΔλF is increased beyond ΔλA. 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.