Limitation Factor Analysis for Silicon-on-Insulator Waveguide Mach–Zehnder Interference-Based Electro-Optic Switch

A proposal for digital electro-optic switches with free-carrier dispersion effect and Goos-Hanchen shift in silicon-on-insulator waveguide corner mirror

“…Namely, if the concentration of free-carriers in silicon waveguide has a variation for the guided-mode, at wavelength of 1550 nm the RIM of silicon is defined by the refined Drude-Lorenz model as 6,7 Dn ¼ À½8:8  10 À22 DN e þ 8:5  10 À18 ðDN h Þ 0:8 ; (12) where Dn is the refractive index change resulting from the variation in free carrier concentrations; DN e and DN h are the concentration variations of free electrons and free holes, respectively. Note from Eq.…”

“…(12) that the concentration variation of holes plays dominant role to Dn value, so we only consider the second term in this equation. 7,20 For the reflection of the guided-mode having effective index of N ef f at the waveguide/CTM interface, the incident and reflected optical fields should be expressed as 15 E i ¼ exp½iðxt À k i zÞ and E r ¼ R Á exp½iðxt À k r zÞ; (13) where the components of reflection coefficient R at x-and y-polarizations should be expressed as…”

“…[2][3][4] As an essential branch of high-speed PIC optical switches, the multimode interference (MMI) was also investigated besides the MZI and MRR constructions based devices. [5][6][7] However, due to the intrinsic drawbacks of all these switching schemes, there have not been any real accomplishments of product development reported so far. For instance, both the MMI type and MZI type devices are based on the interference of light waves, so they support an analog switching process.…”

“…The former has the more complex structure of EO modulation part and the latter has a relatively longer footprint length in device design. As a consequence, their switching operations are wavelength sensitive, so that they could not achieve the same high-contrast switching function for all the involved wavelengths in the modern dense wavelength division multiplexing (DWDM) optical communications systems, 6,7 leading to some intrinsic drawbacks in the performance specifications of devices and their applications. These intrinsic drawbacks include: (i) the decline of on/off contrast at some wavelength channels, weakening the isolation between two wavelength channels; (ii) the direct limitation to reducing the device footprint size; and (iii) the optical interference-determined energy dissipation per operation.…”

Low cross-talk 2 × 2 silicon electro-optic switch matrix with a double-gate configuration

“…The CT of the low-speed thermal-optic switches fabricated on silica-on-silicon and silicon-on-insulator (SOI) has been reduced to less than −30 dB [1,3]. Because of the loss penalty on phase modulation caused by free carrier absorption (FCA) [6,7], it is difficult to reduce the measured CT of a silicon electro-optic switch for a single-arm modulation scheme to less than −20 dB [8][9][10][11]. Theoretically, a low CT of −30 dB cannot be obtained for a single-MZI configuration when the modulation arms are shorter than 1 mm, even by using the double-arm modulation scheme with a prebiased π∕2 phase shift [7], which will hinder practical application.…”