Stimulated Raman conversion of radiation from a YAG:Nd laser with wavelengths of 1.319, 1.338, and 1.357 µm in a barium nitrate crystal

Abstract

We have studied stimulated Raman (SRS) conversion to the first Stokes component of multimode (M 2 = 8) radiation from a YAG:Nd laser with lasing wavelengths of 1.319 µm, 1.338 µm, and 1.357 µm in a barium nitrate crystal. We have obtained pulses of converted radiation with energies up to 120 mJ. We have achieved conversion efficiencies greater than 40% for each of the three Raman laser wavelengths of 1.530 µm, 1.556 µm, and 1.582 µm with divergence of the beams of converted radiation close to the diffraction-limited value (M 2 < 1.5).Key words: stimulated Raman scattering (SRS), barium nitrate, SRS laser, eye-safe spectral range.Introduction. Many areas of application for lasers require radiation sources with laser wavelength 1.5-1.6 µm. Radiation with such a wavelength is found within the atmospheric transmission window, due to the absence of strong absorption lines for carbon dioxide and water vapor in this range of the spectrum [1]. The 1.5-1.6 µm region of the spectrum also falls within the optical telecommunications window [2] and corresponds to the eye-safe spectral range [3]. Compared with radiation from conventional laser sources, radiation in the 1.5-1.6 µm spectral region is more strongly attenuated by the vitreous body of the eye by several orders of magnitude and is practically unabsorbed by the retina [4]. As a result, the attainable pulse energy for pulses in the nanosecond range may be as high as several joules with no risk of vision damage.Among currently available methods for obtaining high-power laser radiation fluxes in the 1.5-1.6 µm region, two stand out: direct lasing based on solid-state laser media activated by erbium ions [5], and nonlinear optical conversion of radiation from YAG:Nd lasers [6-9]. Optical parametric oscillation (OPO) in KTP crystals and stimulated Raman scattering (SRS) in compressed methane [6-8] and crystals [9] are used as the nonlinear optical effects.SRS conversion in crystalline media in the 1.5 µm region has undergone development with the appearance in the 1980s of a number of synthetic crystals with high Raman cross section: nitrates and tungstates [10]. Barium nitrate deserves special attention because of its unique characteristics. This crystal has a record high steady-state SRS gain (11 GW/cm at λ = 1.06 µm) [11] and good radiation resistance [12]. The Raman shift in barium nitrate is 1047 cm -1 . For pumping by radiation from a YAG:Nd laser with λ las = 1.319, 1.338, and 1.357 µm, the wavelengths of the first Stokes components are equal to respectively 1.530, 1.556, and 1.582 µm. The presence of rather strong absorption bands in barium nitrate at wavelengths longer than 1.7 µm prevents generation of a cascade of higher Stokes components.The possibility was demonstrated earlier for converting more than 40% of the radiation energy from a YAG:Nd laser with λ las = 1.338 µm to the 1.5 µm region. A pulse energy of 250 mJ was achieved in a setup with an external SRS laser based on a barium nitrate crystal [13]. When the barium nitrate crystal was placed inside the c...

A high efficiency third order Stokes Raman laser operating at 1500 nm based on a BaTeMo2O9crystal

“…SRS, an effective frequency conversion method with many advantages such as no need for phase-matching and noncentrosymmetric crystal structure, has been proved to be a promising strategy for frequency conversion in solid-state lasers [7][8][9][10]. Laser radiation in the eye-safe regions can be obtained with a Raman crystal either in the first order Stokes line pumped by 1.3 µm lasers or in the third order Stokes line pumped by more convenient 1.06 µm lasers [11,12]. In recent years, eye-safe Raman lasers have been reported based on several Raman crystals such as KGd(WO 4 ) 2 , Nd:YVO 4 , Nd:GdVO 4 , Ba(NO 3 ) 2 and BaWO 4 [13][14][15][16][17][18].…”

Нелинейная Рефракция Диэлектрических Монокристаллов При Возбуждении Ультракотроткими Лазерными Импульсами Ближнего Инфракрасного Диапазона

“…К настоящему времени разработана технология выращивания совершенных монокристаллов, перспективных для нелинейно-оптических приложений. Особый класс нелинейно-оптических кристаллов формируется на основе диэлектрических структур, перспективных для возбуждения процессов вынужденного комбинационного рассеяния (ВКР) [1][2][3][4][5][6][7]. Среди такого типа кристаллов большой практический интерес представляют следующие: KGW, KGW, легированный ионами европия (KGW : Eu 3+ ), нитрат бария (Ba(NO 3 ) 2 ), вольфрамат бария (BaWO 4 ), вольфрамат кадмия (CdWO 4 ) и молибдат свинца (PbMoO 4 ).…”