Compact Thermally Tunable Silicon Wavelength Switch: Modeling and Characterization

A wavelength-selective photonic switch is developed based on a Si microring resonator using thermooptic effect. The 10-mum-diameter microring resonator uses single-mode strip Si waveguides of dimension 0.25 mum times 0.45 mum operating at 1.5 mum. Full-width at half-maximum are in the range 0.1-0.2 nm. The ultrawide tunable range (>6.4 nm) and wide free spectral range (~18 nm) of the switch element enables wavelength reconflgurable multichannel matrix switch by wavelength multiplexing/demultiplexing. Average rise delay time of 14 mus with low switching power of 3.15 mW has been achieved with 0.2-nm wavelength tuning and 78 mus, 104 mW for 6.4-nm tuning. Fall delay times are usually less than 10 mus. Thermal simulations show 10%-20% agreement with the measurements up to 3.2-nm tuning. The compact size of the switch shows its potential as an active element in photonic integrated circuits.

I. Introduction

Microring resonators are multifunctional photonic elements with many device applications such as filters [1], multiplexers [2], and modulators [3], making use of their high wavelength selectivity. As microring resonators integrated with silicon-on-insulator (SOI) technology, they are very promising for photonic integrated circuits. Because of the large refractive index difference between Si and , the SOI technology allows submicrometer single-mode waveguides. This ensures ultrahigh light confinement leading to compact photonic devices with sharp bends, making possible large-scale photonic integration [4]. While thermooptic tuning has moderate speed compared with electrooptic [3] and all-optic tuning [5], with silicon's high thermooptic coefficient, a much wider wavelength tunable range can be realized. The large tunable range and large free spectral range (FSR) of the silicon microring resonator has enabled a wavelength reconfigurable multichannel matrix switch [6].