High Efficiency Raman Lasers Based on Zr-Doped Silica Hybrid Microcavities

作者：Choi Hyungwoo; Armani Andrea M^*

来源：ACS Photonics, 2016, 3(12): 2383-2388.

DOI：10.1021/acsphotonics.6b00608

• whispering gallery mode resonator
• silica sol-gel
• Zr dopants
• Raman laser
• ultrahigh-Q silica toroid
• microcavity laser

Raman lasers form a particularly unique and I versatile class of optically pumped laser. Because they rely on stimulated Raman scattering (SRS), which is governed by the vibrational frequency of the gain material and not electronic transitions, the emission wavelength is determined by the pump wavelength, enabling broad tunability. Ultrahigh quality factor (Q) silica optical resonators are an ideal platform for Raman lasers because the long photon lifetime results in large circulating optical intensities. Previous work has demonstrated extremely low thresholds using these devices. However, only moderate Raman lasing efficiencies have been achieved in silica devices. In the present work, we demonstrate that a zirconium (Zr)-doped silica sol-gel coating can improve the performance of a silica microcavity Raman laser. Several concentrations of Zr-doped sol-gel are synthesized. The intrinsic Raman gain of the Zr-doped silica is measured using Raman spectroscopy, and the values show a clear dependence on Zr dopant concentration. Subsequently, ultrahigh-Q silica toroidal microcavities are coated with the different Zrdoped sol gels. The Raman lasing performance is characterized using a 765 nm optical pump, and the first order and cascaded Raman emissions for the coated devices are detected starting at 790 nm. The Raman lasing emission and characteristic threshold curves are quantified using both an optical spectrum analyzer and an optical spectrograph. The unidirectional pump-to-Raman conversion efficiency exhibits a marked enhancement from 3.37 to 47.43% as the Zr concentration increases.

• 出版日期2016-12