Heterogeneously-Integrated Optical Phase Shifters for Next-Generation Modulators and Switches on a Silicon Photonics Platform: A Review

Abstract

The realization of a silicon optical phase shifter marked a cornerstone for the development of silicon photonics, and it is expected that optical interconnects based on the technology relax the explosive datacom growth in data centers. High-performance silicon optical modulators and switches, integrated into a chip, play a very important role in optical transceivers, encoding electrical signals onto the light at high speed and routing the optical signals, respectively. The development of the devices is continuously required to meet the ever-increasing data traffic at higher performance and lower cost. Therefore, heterogeneous integration is one of the highly promising approaches, expected to enable high modulation efficiency, low loss, low power consumption, small device footprint, etc. Therefore, we review heterogeneously integrated optical modulators and switches for the next-generation silicon photonic platform.

Wavelength-Tunable Vortex Beam Emitter Based on Silicon Micro-Ring with PN Depletion Diode

“…There are two main methods to modify the effective index: to use thermo-optical effect and electro-optical effect (mainly plasma dispersion effect). In the context of optical switches and modulators, the first effect is usually used in cases when GHz response frequencies are not required [ 36 ]. The main disadvantages of the thermo-optical effect for modulation and switching are milli- to microsecond response and mW order power consumption [ 38 ].…”

“…The main disadvantages of the thermo-optical effect for modulation and switching are milli- to microsecond response and mW order power consumption [ 38 ]. In contrast, the electro-optical effect is characterized by nanosecond to sub-nanosecond response and in most cases much lower, or at least comparable to the thermo-optical case, power consumption [ 36 ]. On the other hand, realizations of electro-optical effects impose higher losses and crosstalk [ 36 ], however, the advantage of quick response usually overrides these problems.…”

“…In this scheme, heaters are used to change the refractive index of the waveguide, and as a result, the effective WGM index changes, which causes the restructuring of the emitted OAM mode. In our case, an inversely-biased pn-junction offers more energy-efficient and faster switching [ 36 ] compared to the existing schemes. Therefore, we believe, that this scheme can be used also as a fast (GHz-scale) electro-optical OAM modulator.…”

Broadband Polarization-Insensitive Thermo-Optic Switches on a 220-nm Silicon-on-Insulator Platform

“…Therefore, to achieve the same phase shift, the 220-nm-width waveguide consumes more power than the 500-nm-width waveguide. The power consumption needs to be reduced, because the high energy cost and heat dissipation prohibit the application of switches in highly integrated systems [50]- [52]. Hence, we optimize the design of the metal heater by investigating the relationship between the power consumption for a π phase shift, P π , and the width of the metal, W .…”

Ultra-Compact and Efficient Microheaters on a Submicron-Thick InP Membrane

“…Energyefficient and fast phase modulators based on the Pockels effect, quantum-confined Stark effect (QCSE), or carrier-based effects can be widely found in the InP material system [3]- [5], and some can reach modulation speeds beyond 100 GHz [6], [7]. However, for emerging applications that require dense integration rather than telecom modulation speeds, such as optical computing [8]- [11], optical circuit switching [12]- [14], or optical beam forming and steering [15]- [20], these phase shifters fall short because of their millimeter-scale size [4], [5].…”