Active Microring Resonator Devices in Silicon-on-Insulator

Abstract

Abstract:Recent results from several laboratories are surveyed. The topics include SOIbased ultrafast electrooptical modulators, N x N routing switches, tunable filters-andadd/drops, Raman lasers and amplifiers, electrically pumped group IV lasers, optically pumped Er:SiO 2 -overclad slotted rings, and a variety of nonlinear optical devices. IntroductionMicrophotonic and nanophotonic components in SOI (or in SGOI or GOI) are key "enablers" for the next generation of Si-based waveguided photonic networks and opto-electronic integrated circuits (OEICs). Microring and microdisk resonators are advantageous microphotonic components because they can be interconnected densely on a chip and use minimal "real estate," allowing high functionality at low cost. Active rings offer versatility in applications, efficiency and low-power onchip actuation. The term "active" includes thermooptic (TO) electrooptic (EO) and opto-optical devices (those using nonlinear optical interactions). This talk will survey the recent results obtained at several laboratories on active microring resonator devices. Generally, the SiO 2 lower cladding in SOI, SGOI and GOI maintains the high Q of the resonators; whereas, without SiO 2 , the resulting suspended Si membrane is best for 2D photonic-crystal resonators analogous to the disks. In addition to 2D rings and disks, 3D silicon microsphere resonators have achieved visibility lately [1]. 2. Trimmable Optical Filters. Empirically, the resonators rarely "work as fabricated." Electromagnetic modeling software is not (yet) good enough to predict the resonances of a 3D device having very specific dimensions. So, in practice, the microring spectral filtering characteristic, as fabricated, does not match the design specifications. That is why trimming or tuning of the resonator(s) has become essential. Polymeric loading on the Si waveguide-controlled photo-oxidation of polysilane [2]--is a good way to trim the resonator permanently and stably. Trimming is an essential part of Luxtera's WDM [3]. Today, localized heating of the silicon waveguide (a TO index change) is the most explored and effective means of tuning the resonator, although electrooptical tuning of the ring (steady carrier injection or depletion) will be online soon. 3. Tunable Filters and Add/Drop Multiplexers. TO trimming-and-tuning has facilitated the worldrecord 1 GHz bandpass of a multi ring/MZI filter that has 5 GHz tunability [4]. The TO-activated polymeric two-ring reconfigurable add/drop multiplexer of Yamagata [5] could be realized easily in vertically stacked double-SOI containing two Si buses and two TO-tunable Si microrings, allowing significant WDM tuning. 4. 2 x 2 and N x N Optical Routing Switches. Stephen Emelett and I wrote several papers [6,7,8] on dual-microring switches (fixed-ring devices and floating-ring devices) that are readily cascaded into N x N crossbar-matrix crossconnects [9] or permutation-matrix network-routing switches. The preferred embodiments use carrier injection-or-depletion in both rings, obtained v...