We present a small footprint narrowband on-chip mirror made by integration of a distributed Bragg reflector (DBR) inside a microring resonator. The DBR covers half of the ring’s circumference and is only reflective at one of the ring resonances. Design, fabrication, and characterization of the proposed device are presented. A single reflection peak with maximum power reflectivity of 92.3% and full width at half maximum of 0.4 nm is demonstrated. The device has potential application as an in-line mirror for low-threshold, narrow linewidth single mode laser diodes.
We present analysis and design of microring resonators integrated with reflective elements to obtain custom wavelength-selective devices. We introduce a graphical method that transforms the complicated design problem of the integrated structure into a simple task of designing a reflective element possessing an appropriate reflection profile. Configurations for obtaining a comb mirror, a single peak mirror, an ultranarrow band transmission filter, and a sharp transition mirror are presented as examples.
A broadband antireflective coating for silicon was fabricated by tailoring the compositions of SiNx and SiOxNy during conventional plasma enhanced chemical vapor deposition. The coating’s refractive index was quasicontinuously graded, e.g., from 3.22 to 1.44 at 1550 nm. Over the 280–3300 nm wavelength range, the reflectance was below 8% peak and 4.3% average. The deposited stack was composed of dense dielectric materials. This enables patterning and processing into robust devices after coating deposition. Using single layer ellipsometry data, the transfer matrix method was applied to predict the multilayer coating’s reflectance spectra. The results showed good agreement with experimental data.
We present analysis of the distributed Bragg reflector in a microring resonator (DBR-MRR) structure. With appropriate design parameters, the device can closely reproduce the reflectance spectrum of a sampled grating distributed Bragg reflector (SGDBR). By inserting the grating inside a microring resonator, the structure is much more compact than an SGDBR, suppresses side mode ripples near each peak, and offers better control over its full width half maximum (FWHM). The device is expected to have applications in compact tunable lasers and other planar photonic devices.
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