Simultaneous broadband Raman cascading and parametric conversion in potassium titanyl phosphate

Abstract

We generated a broad spectrum of light between 1064 and 1300 nm in the infrared by cascading stimulated Raman scattering in a potassium titanyl phosphate crystal while broadband conversion of the infrared Raman cascade was simultaneously achieved in the visible through second-harmonic generation (SHG) and sum-frequency mixing. We observed that odd- and even-order cascaded Stokes components were spatially addressed at different angles of propagation in the crystal. The efficiency of SHG and sum-frequency mixing is discussed as a function of the pump polarization. We also report on significant spatial distortions of the output Stokes beams.

Phonon-assisted nonlinear optical processes in ultrashort-pulse pumped optical parametric amplifiers

“…Previous studies of SRS and stimulated polariton scattering in KTP and its periodically-poled forms 18 19 29 30 clearly indicated spectral shifts in the scattered pump pulses which helped derive the modes that are responsible for the scatter of each given Stokes beam. The unambiguous determination of the values of Stokes shifts in the scattered beams in these studies was possible due to narrow spectral widths of the picosecond pump pulses compared to the frequencies of the phonons excited in the NLO crystals.…”

“…Previous investigations of KTP- and KTA-based parametric generators showed the possibility of SRS processes coexisting with the main parametric conversion 18 19 30 . Notably, the SRS of the parametrically amplified signal wave was shown to enhance when the idler wave was tuned into resonance with the second overtone band of the phosphate ion 18 and, moreover, when the pump pulse duration was shortened to a few-picosecond durations 19 thus approaching the dephasing times of the Raman-/IR-active phonons 31 .…”

“…Notably, the SRS of the parametrically amplified signal wave was shown to enhance when the idler wave was tuned into resonance with the second overtone band of the phosphate ion 18 and, moreover, when the pump pulse duration was shortened to a few-picosecond durations 19 thus approaching the dephasing times of the Raman-/IR-active phonons 31 . A distinct feature of these studies that utilize picosecond (relatively narrowband) pump pulses is that the Raman scattering occurs in cascading manner to the parametric processes 11 30 32 33 , i.e. the Stokes-shifted signal/pump spectra can be clearly distinguished from the major peaks corresponding to the OPO-generated signal and idler waves.…”

Cascaded Stimulated Polariton Scattering in a Single-Pass KTP Crystal under Picosecond Pumping

“…SPS was realized in KTP crystals in a single-pass geometry under quite powerful picosecond pumping: KTP crystals were pumped by 802 nm [21] and 1064 nm [22] picosecond pulses. In [21], two SPS spots were observed on each side of the pump beam: one generated by the pump beam and another by non-phasematched second harmonic.…”

“…In [21], two SPS spots were observed on each side of the pump beam: one generated by the pump beam and another by non-phasematched second harmonic. In [22], seven cascaded polariton components with a frequency difference of 5.6 THz between them and concentrated in two spots on each side of the pump beam and also in the central pump spot were generated. The pump beam in [21,22] was propagated in the XOY crystal plane and was polarized perpendicular to this plane and parallel to the crystal Z-axis.…”