Titanium-enhanced Raman microcavity laser

Whispering gallery mode microcavities are ideally suited to form microlaser devices because the high circulating intensity within the cavity results in ultralow lasing thresholds. However, to achieve low-threshold Raman lasing in silica devices, it is necessary to have quality factors above 100 million. One approach to circumvent this restriction is to intercalate a sensitizer into the silica, which increases the Raman gain. In the present work, we demonstrate a Raman laser based on a titanium sensitized silica solgel coated toroidal microcavity. By tuning the concentration of the Ti, the Raman efficiency improves over 3× while maintaining sub-mW thresholds.