Presentation Information
[9p-A13-11]Single-peak grating ring reflector based on a quasi-BIC dark mode
〇Takahiro Serikawa1, Hisashi Ogawa1 (1.Nichia Corporation)
Keywords:
ring resonator,spectrum filter,distributed Bragg reflector
A compact, narrow-linewidth diode laser benefits from a low-loss external reflector that selects a single lasing wavelength. A ring resonator gives narrowband reflection in a small footprint, but its periodic spectrum forces one to pick a single peak.
Here we propose and verify a single-peak narrowband reflector formed by a second-order grating on an external ring resonator. Among modes whose standing wave matches the grating period, only a dark mode, in which the vertical radiation cancels, keeps a high Q. The grating does not build reflection as in a DBR but adds loss to non-selected modes, so a weak grating on a low-loss waveguide still gives high reflectivity, yet non-selected modes passes through the ring. Because the standing wave is locked to the grating, linewidth and reflectivity stay insensitive to index changes from environment or drive .
We fabricated a reflector using a buried-core waveguide operating on 780nm light. The ring radius is 100 um, the grating sits on the inner ring wall, and it operates in TM polarization. We measured 65% reflectivity, 6 dB side-peak suppression, and a 2.1 GHz half-width at half-maximum.
Here we propose and verify a single-peak narrowband reflector formed by a second-order grating on an external ring resonator. Among modes whose standing wave matches the grating period, only a dark mode, in which the vertical radiation cancels, keeps a high Q. The grating does not build reflection as in a DBR but adds loss to non-selected modes, so a weak grating on a low-loss waveguide still gives high reflectivity, yet non-selected modes passes through the ring. Because the standing wave is locked to the grating, linewidth and reflectivity stay insensitive to index changes from environment or drive .
We fabricated a reflector using a buried-core waveguide operating on 780nm light. The ring radius is 100 um, the grating sits on the inner ring wall, and it operates in TM polarization. We measured 65% reflectivity, 6 dB side-peak suppression, and a 2.1 GHz half-width at half-maximum.