Enhancement of stimulated Raman scattering in terrace-microspheres

Abstract

Terrace-microspheres of high-index glass (BaO-SiO2-TiO2 glass, nD=1.93) containing 0.3 ppm of Nd3+ were used to investigate the interaction between Raman scattering due to a glass matrix and fluorescence due to Nd3+. The terrace-microspheres were pumped with a tunable CW Ti:sapphire laser (790 nm–830 nm wavelength) for changing pumping wavelengths. With pumping in the 800–830 nm wavelength region, there was a spectral overlap between Raman scattering and Nd3+ fluorescence. Under such conditions, Nd3+ fluorescence works as a seeding and an amplifier of stimulated Raman scattering (SRS), resulting in SRS enhancement. With pumping of 20 mW power at around 830 nm wavelength, the terrace-microspheres showed the strongest SRS gain, 5–6 times of that of 790 nm wavelength pumping. SRS thresholds of the terrace-microspheres were improved from 3 mW(790 nm wavelength pumping) to 0.3 mW (830 nm pumping) due to the enhancement effect. The potential application for a multiwavelength Raman laser with a low threshold was demonstrated in the near-IR region (λ=840–940 nm).