Efficient third-harmonic generation in partly periodically poled KTiOPO(4) crystal

Efficient generation of coherent blue light at 440 nm by intracavity-frequency-tripling 1319-nm emission from a Nd:YAG laser

A new route for efficiently generating coherent blue light has been explored based on intracavity effective third-harmonic generation in one partly periodically poled KTiOPO4 crystal placed inside the cavity of a diode-pumped Nd:YAG laser. To achieve efficient conversion, we use a dual-temperature oven to separately control the phase-matching conditions for the two second-order nonlinear processes. In addition, a Fabry-Perot cavity at 660 nm is incorporated into the crystal to increase the blue power significantly. When the laser is Q switched to produce long pulses, an average power of 118 mW is generated at 440 nm at a pump power of 10 W.

Experimental demonstration of waveguide-coupled round-cornered octagonal microresonators in silicon nitride

We report laterally waveguide-coupled octagonal microresonators with designed round resonator corners in silicon nitride. We demonstrate nearly single-mode add-drop filter characteristics, when 50-microm-size round-cornered octagonal microresonators are used, with an optimum coupling efficiency exceeding 96%, a finesse of approximately 30, and a Q of approximately 6400. Our experiments also reveal two unforeseen phenomena in certain microresonator shapes: a pronounced drop in coupling efficiency and resonance notches in the drop spectrum. These device characteristics hint at the recently postulated multiple orbit interference in waveguide-coupled polygonal microresonators.