Abstract
We studied spectra of the amplified signal from a noncollinear optical parametric amplifier (NOPA) based on a Ti:sapphire laser and BBO crystal gain medium. The signal shows characteristic structures with periodic intensity variations in the signal during the parametric amplification processes in a BBO crystal. This phenomenon is attributed to the stimulated Raman process excited by the pump pulse affected by the phase-matching condition of four-wave mixing. The effect of this stimulated Raman process on optical parametric amplification and on final pulse compression of the signal was analyzed. The results demonstrate that caution must be taken when constructing a NOPA. Specifically, great care must be taken not to use mirrors with non-uniform spectral reflectivity for obtaining a stable pulse in terms of both temporal and spectral shapes.
Highlights
These features could be explained in terms of stimulated Raman scatIn the present study, we present observed spiky features in the output spectra from a tering, initiated by small triggering intensity variations of the seed induced by the nonNOPA system
Seed delay time measured with a multichannel lock-in amplifier (MCLA) for different conditions that depend on the configurations of the precompression optical system of the seed pulse and the stretching optics of the pump pulse
Characteristic structures were observed in the amplified signal spectra from a Noncollinear optical parametric amplification (NOPA), along with periodic intensity variations in the signal during parametric amplification in a BBO crystal
Summary
Beta barium borate (β-barium borate, β-BaB2 O4 , or BBO) is one of the most frequently used crystals for frequency mixing and other second-order nonlinear optical applications because it has a wide transmission range that extends from approximately 200 nm to beyond 3 μm It is widely used for second-harmonic generation (SHG) [1,2] and optical parametric amplification (OPA) [3,4,5,6,7,8,9,10,11,12,13,14,15,16,17]. A noncollinear geometry has been used to realize group velocity matching between the signal and the idler through achromatic phase matching with the help of the spectral angular dispersion of the idler In this way, an extremely broad gain bandwidth of 7000 cm−1 has been attained. To correct this pulse-front tilting, a pulse-front matching geometry has been introduced, resulting in the generation of 4.7-fs visible pulses using a compressor composed of a prism pair and customized chirped mirrors with a bandwidth broader than
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