Low-loss and broadband 2 × 2 silicon thermo-optic Mach–Zehnder switch with bent directional couplers

Abstract

A low-loss and broadband silicon thermo-optic switch is proposed and demonstrated experimentally by using a Mach-Zehnder Interferometer with 2×2 3 dB power splitters based on bent directional couplers (DCs). The bent DCs are introduced here to replace the traditional 2×2 3 dB power splitters based on multimode interferometers or straight DCs, so that one achieves a coupling ratio of ∼50%∶ 50%, as well as low excess loss over a broadband. The demonstrated Mach-Zehnder switch (MZS) has a ∼140 nm bandwidth for an excess loss of <1 dB and an extinction ratio of >20 dB. The present MZS also shows excellent reproducibility and good fabrication tolerance, which makes it promising for realizing N×N optical switches.

Mode-evolution-based silicon-on-insulator 3 dB coupler using fast quasiadiabatic dynamics

“…Optical couplers are essential devices in photonics integrated circuits. 3 dB couplers split the light evenly and are widely used in multiplexing circuits [1], optical switches [2,3], and modulators [4]. The silicon-on-insulator (SOI) is a promising platform for realizing high-density photonic integrated circuits due to its compatibility with commercial complementary metal-oxide-semiconductor (CMOS) processes.…”

Programmable optical processor chips: toward photonic RF filters with DSP-level flexibility and MHz-band selectivity

“…A variety of designs have been demonstrated to date in these regards. Recently, for example, Wang et al [89] demonstrated an RF arbitrary waveform generator using a silicon circuit with tunable couplers in the order of tens of micrometers; Dai et al [90] demonstrated such couplers with a bandwidth of 140 nm and an excess loss <1 dB; Suzuki et al [91] and Miller [92] showed designs based on lattice cascades of multiple Mach-Zehnder couplers with higher fabrication tolerances. The consideration of all this could be of use for the further development of programmable optical chips which, as one important application, serve as the engine for microwave photonic implementations of reconfigurable RF filters.…”

Self-equalizing photodiodes, a hybrid electro-optical approach to tackle bandwidth limitation in high-speed signaling

“…It should be noted that carrier wavelength sensitivity of the equalizer is not completely removed as the coupling factor of the directional coupler, κ , which sets the equalization strength, is still wavelength dependent; however, this dependency is significantly lower than what is achievable with purely optical equalizers. Also there exist approaches that increase the bandwidth of the coupler and reduce the wavelength sensitivity [7,8].…”