Increased wavelength options in the visible and ultraviolet for Raman lasers operating on dual Raman modes

Abstract

We report increased wavelength options from Raman lasers for Raman media having two Raman modes of similar gain coefficient. For an external-cavity potassium gadolinium tungstate Raman laser pumped at 532 nm, we show that two sets of Stokes orders are generated simultaneously by appropriate orientation of the Raman crystal, and also wavelengths that correspond to sums of the two Raman modes. Up to 14 visible Stokes lines were observed in the wavelength range 555-675 nm. The increase in Stokes wavelengths also enables a much greater selection of wavelengths to be accessed via intracavity nonlinear sum frequency and difference frequency mixing. For example, we demonstrate 30 output wavelength options for a wavelength-selectable 271-321 nm Raman laser with intracavity sum frequency mixing in BBO. We also present a theoretical analysis that enables prediction of wavelength options for dual Raman mode systems.

Measurement of Multi-Stokes Ultrashort Pulse Shapes of Synchronously Pumped Stimulated Raman Scattering on Combined Vibrational Modes in a BaWO4 Crystal

“…It was in BaWO 4 that stimulated Raman scattering (SRS) with a combined frequency shift of ν 1 + ν 2 was previously observed for the first time [4]. After that, similar effects were studied for many other crystals having a lower Raman gain, including KGd(WO 4 ) 2 , GdVO 4 , YVO 4 , SrWO 4 , SrMoO 4 , Ca 3 (VO 4 ) 2 , PbMoO 4 , and Pb(MoO 4 ) 0.2 (WO 4 ) 0.8 [5][6][7][8][9][10][11]. These effects were experimentally realized in schemes of Raman lasers with a high-Q optical cavity compensating a lower Raman gain at the secondary Raman mode rather than at the primary Raman mode.…”

Wavelength-versatile visible and UV sources based on crystalline Raman lasers

“…In the second and more recent study [100], the wavelength options were investigated for a KGW crystal oriented so that the gain is similar for both 768 cm À1 and 901 cm À1 Raman modes. It was shown that it was possible to operate simultaneously on two Raman modes (m 1 and m 2 ) and the Stokes wavelengths oscillating in the resonator consisted of not only the multiple orders of both Stokes lines but also combinations of the two Raman modes.…”

“…The selection of target wavelengths is also significantly boosted for materials that have more than one active Raman mode [92,100]. Recently, it has been shown that the number of output wavelength choices increases many-fold for Raman materials like KGW, which can be oriented to provide high gain on two Raman modes simultaneously [100].…”

“…As discussed below, the number of output wavelength options expands considerably when using Raman materials that provide high gain on two Raman modes simultaneously. Table 8 summarises the results of two studies based on a KGW Raman crystal and BBO nonlinear sum-frequency-mixing crystal pumped at 532 nm [100,104]. In the first study, the KGW Raman crystal was oriented to provide maximum gain at the 901 cm À1 Raman mode, whereupon up to eight wavelengths were observed in the range 270-320 nm.…”