Broadband noncollinear optical parametric amplification under low‐frequency picosecond pump in homogeneous KTP crystal

Abstract

The nature of cubic and cascaded quadratic nonlinear responses in the KTiOPO4 crystal under picosecond pump is studied. The main attention is paid to determination of the origin and properties of the blue radiation accompanying the red light amplification process (the central wavelength ~685 nm, bandwidth ~20 nm) in a noncollinear optical parametric amplifier (NOPA) pumped by the second‐harmonic radiation of the picosecond Nd:YAG laser (532 nm). In NOPA, the amplified seed radiation (ωs) becomes so intense that it can participate in any nonlinear three‐wave interaction and also can play the role of the Stokes wave in the in the coherent anti‐Stokes Raman scattering‐process in which powerful pump radiation (ωp) of the main parametric process serves both as the pump wave and the probe wave. Possible causes of the blue light emanating from the KTP crystal and the mechanisms for their realization are analyzed. We interpret the ring of blue light around the axis located between the directions of propagation of the green pump beam and the red beam of the amplified seed radiation, as the emission of amplified parametric fluorescence (signal wave) under low‐frequency pump. This phenomenon can be used for effective amplification in picosecond NOPA of weak anti‐Stokes radiation in the experiments with time‐resolved broadband picosecond coherent Anti‐Stokes Raman Scattering.

Recent advances in linear and nonlinear Raman spectroscopy. Part XIII

“…Vereshchagin and co‐workers described broadband noncollinear optical parametric amplification under low‐frequency picosecond pump in a homogeneous KTP crystal. This phenomenon can be used for effective amplification in picosecond noncollinear optical parametric amplification of weak anti‐Stokes radiation in experiments with time‐resolved broadband picosecond CARS …”

“…This phenomenon can be used for effective amplification in picosecond noncollinear optical parametric amplification of weak anti-Stokes radiation in experiments with time-resolved broadband picosecond CARS. [124]…”

Combined parametric down‐ and up‐conversion noncollinear processes under picosecond pumping in KTP, controlled by injection seeding

“…In Vereshchagin et al [ 11 ] we reported on the observation of a few joint parametric processes resulting in appearance of radiation in spectral ranges of (450–490 nm) and (640–700 nm) at the output of the noncollinear optical parametric amplifier (NOPA). NOPA was based on a homogeneous KTP crystal pumped by picosecond pulses (532 nm, ~63 ps) and seeded by broadband red radiation of a dye modeless laser (~684 nm, bandwidth ~20 nm, ~25 ps).…”

“…Along with the basic parametric process of amplifying of the seeding wave, other nonlinear processes of three‐ and four‐wave mixing took place. The work [ 11 ] was devoted to the study of the mechanisms of the appearance in NOPA of radiation with wavelengths shorter than the pump wavelength. The spectral and angular characteristics of radiation in the green–cyan–blue spectral ranges were studied experimentally.…”

Development and applications of nonlinear optical spectroscopy: 16th ECONOS/36th ECW meeting in Jena (Germany)

“…Vereshchagin et al studied the nature of the cubic and cascaded quadratic nonlinear responses in a KTiOPO 4 crystal, when it is pumped with picosecond pulses. They observed a variety of linear and nonlinear optical phenomena, which can be utilized in frequency conversion, for instance.…”