Ultralow Power Silicon Photonics Thermo-Optic Switch With Suspended Phase Arms

In this letter, a 2 × 2 thermo-optic waveguide-based switch with ultralow power consumption is demonstrated and fabricated using a standard complementary metal-oxide-semi conductor (CMOS) process. The phase arms are suspended by removing adjacent SiO₂ and 120 μm of the underlying Si, while leaving a few SiO₂ beams to support the suspended phase arms for the purpose of structural strength. As compared to the switch without isolation layer, a significant reduction of >;98% in power consumption is achieved. It is realized by preventing the heat from leaking out of the phase arms due to the presence of the air isolation layer. Our device shows an extinction ratio of over 23 dB at 1550 nm for TE mode with an ultralow power consumption of 0.49 mW. The response time is 266 μs, including the raise time of 144 μs and the fall time of 122 μs.

I. Introduction

By enabling multiple channel data transmission, wavelength division multiplexing (WDM) technology dramatically increase the aggregate data rate in a single fiber-optic link. Recently, WDM technology has been rapidly developed and widely deployed to meet the transmission demand in optical communication system. 2 × 2 optical switch is a vital component in WDM systems, especially in the reconfiguration structures. As well known, optical network has a huge transmission capability, but the high packaging cost of optical devices has hindered the development. It is a necessary to integrate as many components as possible into one circuit to reduce the cost. In an optoelectronic circuit with high integration density, it is desired that the power consumption of individual optical component must be very low to reduce the total energy cost of the circuit. High power consumption not only decreases the final performances of integrated circuit but also reduce its lifetime. Moreover, it also increases the cost of the integrated circuit because a cooler is needed to control the temperature for stable operation. Therefore, it is very important to develop a 2 × 2 optical switch with ultralow power consumption. During the past decades, there are many thermo-optic switches demonstrated using Si process and technology. Compared to the electrooptic switch, thermo-optic switch has many advantages, including higher optical crosstalk, lower optical loss, simpler fabricating process, and lower cost. A typical thermo-optic device needs a power of more than tens of mW for a phase shift [1]–[8]. Recently, some approaches have been developed to fabricate low power thermo-optic switches. One is based on direct transmitting heat to Si waveguide through Si slab using NiSi heater, and this method achieves a power consumption of 20 mW for a phase shift [9]. Another is based on suspended structure, and the switch power of a few tens of mW was also demonstrated [10], [11]. Recently, this suspended structure was used in a 1 × 2 Si switch and achieved a low power consumption of 540 [12].