SRS in di‐glycine nitrate (NH 2 CH 2 COOH) 2 · HNO 3 crystals: Observation of high‐gain many‐phonon nonlinear interactions

Efficient high‐gain many‐phonon steady‐state stimulated Raman scattering (SRS) was excited in the novel χ (3) ‐active organic crystal of di‐glycine nitrate (DGN), (NH 2 CH 2 COOH) 2  · HNO 3 , at room temperature under picosecond laser pumping in the visible and near‐IR regions. Besides high‐order Stokes and anti‐Stokes (comb) generation in this centrosymmetric crystal, several cascaded and cross‐cascaded χ (3)  ↔ χ (3) nonlinear photon–phonon interactions were observed. The recorded Raman‐induced lasing wavelengths were identified and attributed to the SRS‐promoting optical vibration modes ω SRS1  ≈ 1058 cm −1 , ω SRS2  ≈ 2985 cm −1 , ω SRS3  ≈ 895 cm −1 , and ω SRS4  ≈ 3000 cm −1 . The measured large Raman frequency shifts (≈3000 cm −1 ) and estimated moderately high steady‐state Raman gain coefficients ( $g_{{\rm ssR}}^{{\rm St}_{1} } $  ≥ 6.5 cm · GW −1 ) make this DGN crystal attractive for a number of new applications in modern laser physics and nonlinear optics.