Systematic design and fabrication of high-Q single-mode pulley-coupled planar silicon nitride microdisk resonators at visible wavelengths

Abstract

High quality (Q approximately 6 x 10(5)) microdisk resonators are demonstrated in a Si(3)N(4) on SiO(2) platform at 652-660 nm with integrated in-plane wrap-around coupling waveguides to enable critical coupling to specific microdisk radial modes. Selective coupling to the first three radial modes with >20dB suppression of the other radial modes is achieved by controlling the wrap-around waveguide width. Advantages of such pulley-coupled microdisk resonators include single mode operation, ease of fabrication due to larger waveguide-resonator gaps, the possibility of resist reflow during the lithography phase to improve microdisk etched surface quality, and the ability to realize highly over-coupled microdisks suitable for low-loss delay lines and add-drop filters.

Integrated GaN photonic circuits on silicon (100) for second harmonic generation

“…As pointed out in reference [21], critical coupling at visible wavelengths requires significantly reduced coupling gaps below 100 nm because the waveguide mode at 780 nm extends less beyond the waveguide boundary. Introducing a drop port to the ring resonator at such short distance will lead to severe overcoupling at 1560 nm and thus compromise the optical quality factor.…”

Integrated GaN photonic circuits on silicon (100) for second harmonic generation

“…Introducing a drop port to the ring resonator at such short distance will lead to severe overcoupling at 1560 nm and thus compromise the optical quality factor. Therefore we employ the "pulley" waveguide structure [21] shown enlarged in the inset of Fig. 3(a) to enhance the interaction length with the ring resonator and selectively couple the generated SHG out of the microring.…”

High-Q silicon optomechanical microdisk resonators at gigahertz frequencies

“…The disk's motion is optically transduced with help of a specially designed wrap-around coupling waveguide, which not only facilitates coupling to the disk's optical whispering gallery modes but also helps to excite and sense the disk's in-plane mechanical modes due to the symmetry. 12,14 As a result, disk's in-plane modes at both the fundamental and higher orders with frequency up to 1.75 GHz are observed.…”