Stimulated Raman scattering in disodium ditungstate crystal

Abstract

Spontaneous and stimulated Raman scattering are studied in Na 2 W 2 O 7 crystal with an orthorhombic structure. The polarized Raman scattering spectra corresponding to all the six independent Raman tensor components are measured. The frequencies of the registered vibrational modes are identified. The most intense Raman mode is observed at 956.3 cm −1 with a linewidth of 3.5 cm −1 . The first observation of stimulated Raman scattering in Na 2 W 2 O 7 under excitation by the second harmonic of a mode-locked Nd:YLF laser with a pulse duration of 25 ps is reported. Raman gains at a wavelength of 523.5 nm in Na 2 W 2 O 7 and KGd(WO 4 ) 2 crystals are measured. We believe that disodium ditungstate crystal is a promising medium for Raman laser converters.

Competition between nonlinear processes excited by picosecond laser pulses in a disodium ditungstate Raman crystal for two excitation polarizations

“…Figure 7 shows the energy dependences of transmission T and inverse transmission T −1 , which turned out to be constant. This indicates that there is no noticeable TPA in the Na 2 W 2 O 7 The results obtained explain the anisotropy of the SRS properties observed in [14] under excitation by radiation with a wavelength of 523.5 nm in a Na 2 W 2 O 7 crystal. Despite the fact that the spontaneous Raman scattering showed a more intense Ag Raman mode for the geometry Z (XX) Z, where direction Z stands for c crystallographic axis, X-for the a axis and Y-for the b axis; in the experiment, SRS at a wavelength of 523.5 nm was obtained only for the polarization parallel to b axis.…”

“…It can be seen that the threshold intensity decreases with an increase in the Raman gain. The dashed line corresponds to the Raman gain of 6.8 cm GW −1 measured in Na 2 W 2 O 7 [14]. The existence of TPA and an increase in the TPA coefficient in the medium lead to a significant increase in the threshold intensity of the SRS process.…”

“…Disodium ditungstate (Na 2 W 2 O 7 ) single crystals, with high optical quality and dimensions of about 1 cm, have been available since 2010 [14,16,19]. The crystal has the orthorhombic The investigated Na 2 W 2 O 7 single crystal was grown by the low-gradient Czochralski method from solution in melt in a Pt crucible.…”

“…A new disodium ditungstate crystal Na 2 W 2 O 7 has recently been proposed for the development of a Raman laser [14]. The Raman gain under pumping by laser pulses with a duration of 25 ps and a wavelength of 523.5 nm was measured to be 6.8 cm GW −1 .…”

“…A detailed investigation of x-ray diffraction and spontaneous Raman spectroscopy of Na 2 W 2 O 7 crystals showed that it has the orthorhombic Cmca crystal structure with significant birefringence [15,16]. According to spontaneous Raman spectroscopy data, the intensity of the SRS-active A g line for geometry Z (XX) Z was larger than that for Z (YY) Z [14]. However, the SRS of picosecond pulses at a wavelength of 523.5 nm was obtained only for pump radiation along the c axis polarized along the b axis.…”