Extending chip-based Kerr-comb to visible spectrum by dispersive wave engineering.

Anomalous group velocity dispersion is a key parameter for generating bright solitons, and thus wideband Kerr frequency combs. Extension of the frequency combs spectrum to visible wavelengths has been a major challenge because of the strong normal dispersion of conventional photonic materials at these wavelengths. In this paper, we numerically demonstrate a wideband frequency comb extending from near-infrared to visible wavelengths (∼1200 nm to 650 nm). The proposed frequency comb micro-resonator takes advantage of a wideband blue-shifted anomalous dispersion, achieved in an optimized over-etched silicon nitride waveguide and strong power transfer to shorter wavelengths through radiative dispersive waves, achieved by modulating the dispersion in a coupled resonator architecture. We show the possibility of obtaining a close to visible dispersive Cherenkov radiation peak that is only 10 dB below the overall comb peak and can be tuned by adjusting the coupling structure in the coupled resonator architecture.

Thermally reconfigurable device for adaptive reflection suppression on a silicon-on-insulator platform.

We demonstrate a compact, thermally reconfigurable reflection suppressor on a silicon-on-insulator (SOI) platform, without reliance on nonreciprocal mechanisms. A reflection suppression ratio of 40 dB is achieved with a footprint of 105 µm in length. The insertion loss of the device is below 0.15 dB, and its total power consumption stays below 20 mW. The operation bandwidth depends on the frequency dependence of the back reflection going into the suppressor, which is predominantly determined by the distance between the device and the source of reflection. In this work, a 20 dB reflection suppression bandwidth of 20.7 GHz was achieved.

High resolution on-chip spectroscopy based on miniaturized microdonut resonators.

We experimentally demonstrate a high resolution integrated spectrometer on silicon on insulator (SOI) substrate using a large-scale array of microdonut resonators. Through top-view imaging and processing, the measured spectral response of the spectrometer shows a linewidth of ~0.6 nm with an operating bandwidth of ~50 nm. This high resolution and bandwidth is achieved in a compact size using miniaturized microdonut resonators (radius ~2 µm) with a high quality factor, single-mode operation, and a large free spectral range. The microspectrometer is realized using silicon process compatible fabrication and has a great potential as a high-resolution, large dynamic range, light-weight, compact, high-speed, and versatile microspectrometer.

Fully reconfigurable compact RF photonic filters using high-Q silicon microdisk resonators.

We present a fully reconfigurable fourth-order RF photonic filter on SOI platform with a tunable 3-dB bandwidth of 0.9-5 GHz, more than 38 dB optical out-of-band rejection, FSR up to 650 GHz, and compact size (total area 0.25 mm(2)). The center wavelength of the filter can be tuned over a wide range with a power consumption of 10 mW/nm. The filter architecture uses a unit-cell based approach to realize the desired filter specifications. The use of high-Q resonator-based components enables a dramatic reduction in size, weight and power (SWaP) of each unit cell, with the possibility of cascading a large number of these unit cells on a single chip. Thermal reconfiguration allows for low insertion loss and therefore results in the scalability of these filters. The demonstrated filter can be used in many different applications including RF photonic front-ends and high speed optical A/D conversion.

Athermal performance in high-Q polymer-clad silicon microdisk resonators.

We present a method for eliminating the temperature dependence of the resonance wavelength in high-Q silicon-based microdisk resonators by using a polymer cladding with a negative thermo-optic coefficient. Design requirements for athermal performance are derived based on theory and simulation, and their validity is experimentally verified.

Effective impedance model for analysis of reflection at the interfaces of photonic crystals.

We present an alternative definition of impedance to describe the reflection at the interfaces of photonic crystals. We show that this effective impedance can be defined only by the properties of the photonic crystal modes and is independent of the properties of the incident region. This approximate model successfully explains the main features in the reflection spectrum and of various interface terminations of photonic crystals. In particular, we show an impedance matching condition at which reflectionless transmission of power to a low-group-velocity photonic crystal mode is possible, a property that is attractive for various dispersion-based applications of photonic crystals.