A silicon nitride microdisk resonator with a40-nm-thin horizontal air slot

We design and fabricate pedestal-type, 15 microm diameter silicon nitride microdisk resonators on Si chip with horizontal air-slot using selective wet etching between Si, SiO2, and SiNx. As the slot structure is determined by deposition process, air slots that are as thin as 40 nm and as deep as 5 microm with ultra-smooth slot surfaces can easily be fabricated with photolithography only. Fundamental TM-like slot mode in which the E-field is greatly enhanced within slot was observed with an intrinsic Q factor of approximately 34,000 (lambdares=1523.7 nm) and energy overlap in slot region of 21.6%.