Abstract-A novel class of circular resonators, based on a radial defect surrounded by Bragg reflectors, is studied in detail. Simple rules for the design and analysis of such structures are derived using a transfer matrix formalism. Unlike conventional ring resonators, annular Bragg resonators (ABR) are not limited by the total internal reflection condition and can exhibit both large free spectral ranges and low bend losses. The Bragg reflection mechanism enables the confinement of light within a defect consisting of a low refractive index medium (such as air). Strong atom-photon interaction can be achieved in such a structure, making it a promising candidate for sensing and cavity quantum electrodynamics applications. For sensing applications, we show that the ABR structure can possess significantly higher sensitivity when compared to a conventional ring resonator sensor. Lasing action and low threshold levels are demonstrated in ABR lasers at telecommunication wavelengths under pulsed optical pumping at room temperatures. The impact of the intensity and dimensions of the pump spot on the emitted spectrum is studied in detail.

Photonic integrated circuits employing microcavities coupled to optical waveguides have been studied extensively in recent years, for their ability to provide functionality important to optical telecommunications, within a compact form. Making use of the amplitude response imparted by the resonator upon the transmission spectrum of the coupled waveguide, passive channel add-drop filters [I] and polymer optical modulators based on electrooptic tuning of the ring resonator spechum [2], have been demonstrated. For practical applications, it is desirable to engineer the drop channeVmodulator OFF state extinction to be as large as possible. Recently, it was noted [3] that the waveguide-resonator coupling and the internal loss of the resonator are significantly related in the extinction performance of such devices. An optical modulator based on the principle of controlled waveguide-resonator coupling [4] has been designed to have large OFF state extinction. Furthermore, when compared to a conventional MachZehnder interferometer (MZI) modulator, the device presented here demonstrates significant reductions in the ON-OFF switching voltage, owing to the cavity enhanced phase response of the resonator.The novel optical modulator geomehy, depicted schematically in Figure 1, consists of a 2 x 2 MZI in which a feedback path is introduced by connecting an output waveguide to an input waveguide.The MZI functions as a voltage-controllable coupler to the ring resonator formed by the feedback path. Also shown in Figure 1 is an optical microscope image of the composite modulator fabricated in active

We demonstrate low-threshold lasing at telecommunications wavelengths from high quality circular semiconductor nanoresonators employing radial Bragg reflector. Single-mode emission and mode switching are observed at room temperature under optical pumping. 02005 Optical Society ofAmerica

We fabricate different bandpass filters based on polymeric waveguide gratings by introducing phase shift defects and integrating with a 3 dB MMI coupler. We also use thermo-optic effects to dynamically tune the designed filter.