SRS in di‐glycine nitrate (NH₂CH₂COOH)₂ · HNO₃ crystals: Observation of high‐gain many‐phonon nonlinear interactions

Abstract

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), (NH2CH2COOH)2 · HNO3, 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 ωSRS1 ≈ 1058 cm−1, ωSRS2 ≈ 2985 cm−1, ωSRS3 ≈ 895 cm−1, and ωSRS4 ≈ 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.

Monoclinicβ-BaY2F8—a novel crystal simultaneously active for SRS and Ln3+-ion lasing

“…In addition to the SE features of Ln-and TM-ion doped crystals, in particular Ln 3+ -doped β-BaY 2 F 8 , it is important to note that their χ (3) -nonlinear properties can manifest under high intensity excitation, as the originated processes can both expand and significantly limit Laser Physics Monoclinic β-BaY 2 F 8 -a novel crystal simultaneously active for SRS and Ln 3+ -ion lasing their laser potential. The present work continues our basic research on SRS spectroscopy of insulating crystals (see, eg [19][20][21][22]) and reports on the study of χ (3) -nonlinear interactions in the monoclinic fluoride β-BaY 2 F 8 . Analysis of the χ (3) -nonlinear emission of this crystal under picosecond pumping in the visible and near infrared spectral range provides knowledge of the occurring photonphonon, as well as on the phonon-phonon coherent processes.…”

Stimulated Raman scattering in monoclinic non-centrosymmetric guanylurea(1+) hydrogen phosphite (GUHP)

“…Refs. ) it can be concluded, that the intriguing search for new crystals that can generate broadband combs with coherent components of different origins is most promising if non‐centrosymmetric crystals offering several SRS‐promoting vibration modes and manifesting different χ (3) ‐ and χ (2) ‐interactions are included. As can be seen from Fig.…”

Tetragonal LiLuF4 - A novel crystal simultaneously active for SRS- and Ln3+ -lasing

“…The present work continues our basic research on SRS spectroscopy of insulating crystals . It reports on the study of χ (3) ‐nonlinear processes in the tetragonal tetra‐fluoride LiLuF 4 initiated by picosecond pumping in the visible and near infrared spectral region.…”

“…For the analysis of Raman induced χ (3) ‐nonlinear interactions in tetragonal LiLuF 4 single crystals we employed a home‐made Xe‐flashlamp pumped picosecond Nd 3+ :Y 3 Al 5 O 12 mode‐locked laser with a two‐pass Nd 3+ :Y 3 Al 5 O 12 amplifier as excitation source, in analogy to our earlier experiments on single‐pass SRS spectroscopy of crystalline materials . The system generates τ f1 ≈ 80 ps pulses at the fundamental wavelength λ f1 = 1.06415 µm, corresponding to the main laser inter‐Stark transition 11 507 cm −1 4 F 3/2 → 4 I 11/2 2110 cm −1 of the Nd 3+ ‐lasant ions .…”

“…This allowed us to estimate the lower limit of the steady‐state Raman gain coefficients with respect to first Stokes generation related to the most active SRS‐promoting vibrational mode ω SRS1 ≈ 323 cm −1 of the LiLuF 4 crystal under pumping at λ f1 = 1.06415 µm and λ f2 = 0.53207 µm wavelength. This was done, as in our previous works on SRS spectroscopy of crystals , using the sufficiently tested method based on the well‐known relation: ≈ 30 by comparing the “threshold” pump intensity that has to be applied for a reliable detection of the first‐Stokes component of the studied LiLuF 4 crystal (with excitation geometry c ( b , b ) c and of a reference crystal. For this purpose, we chose a ≈20 mm‐long GdVO 4 crystal, having a Raman gain coefficient of ≥ 4.5 cm GW −1 for first Stokes generation at λ St1‐1 = 1.1744 µm wavelength , while it is estimated to be ≥10.4 cm GW −1 in case of pumping at λ f2 = 0.53207 µm wavelength.…”