Strong Coupling in Microcavity Structures: Principle, Design, and Practical Application

All-optical multi-channel switching at telecommunication wavelengths based on tunable plasmon-induced transparency

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A review of silicon subwavelength gratings: building break-through devices with anisotropic metamaterials

We demonstrate a compact high-performance adiabatic 3-dB coupler for the silicon-on-insulator platform. The refractive index of the gap region between two coupling waveguides is effectively increased using subwavelength grating, which leads to high-performance operation and a compact design footprint, with a mode-evolution length of only 25 µm and an entire device length of 65 µm. The designed adiabatic 3-dB coupler has been fabricated using electron beam lithography and the feature size used in our design is CMOS compatible. The fabricated device is characterized in the wavelength range from 1500 nm to 1600 nm, with a measured power splitting ratio better than 3 ± 0.27 dB and an average insertion loss of 0.20 dB.

Compact high-performance adiabatic 3-dB coupler enabled by subwavelength grating slot in the silicon-on-insulator platform

We propose and analyze via simulation a novel approach to implement a complementary metal-oxide-semiconductor compatible and high extinction ratio transverse magnetic pass polarizer on the silicon-on-insulator platform with a 340 nm thick silicon core. The TM-pass polarizer utilizes a highly doped p-silicon waveguide as the transverse hybrid plasmonic waveguide. We observed an extinction ratio of 30.11 dB and an insertion loss of 3.08 dB for a device length of 15 µm. The fabrication process of the proposed TM-pass polarizer is simpler compared to the state-of-the-art since it only uses silicon waveguides and does not require any special material or feature size.

CMOS compatible all-silicon TM pass polarizer based on highly doped silicon waveguide

We experimentally demonstrate a compact broadband polarization beam splitter (PBS) based on a multimode interference (MMI) coupler with internal photonic crystal (PC) for the silicon-on-insulator platform. The internal PC structure is optimized to be reflective to the transverse electric polarization and transparent to the transverse magnetic polarization over a broad wavelength range. A detailed study of the device operation, including the photonic band gap and the influence of the internal PC structure on each mode of the MMI coupler, is presented. The designed PBS has been fabricated using electron beam lithography and the feature size used in our design is CMOS compatible. The fabricated device achieves measured extinction ratios higher than 20 dB and insertion losses lower than 2 dB for both polarizations over a 77 nm wavelength range from 1522 to 1599 nm that covers the entire C -band, with a device length of only 71.5 $\mu$ m.

Compact Broadband Polarization Beam Splitter Based on Multimode Interference Coupler With Internal Photonic Crystal for the SOI Platform

We experimentally and via simulations demonstrate ultracompact single-stage and cascaded optical add-drop multiplexers using misaligned sidewall Bragg grating in a Mach–Zehnder interferometer for the silicon-on-insulator platform. The single-stage configuration has a device footprint of 400  ${\mu }\text{m}\,\times$  90  ${\mu }\text{m}$ , and the cascaded configuration has a footprint of 400  ${\mu }\text{m}\,\times$  125  ${\mu }\text{m}$ . The proposed designs have 3-dB bandwidths of 6 nm and extinction ratios of 25 dB and 51 dB, respectively, and have been fabricated for the transverse electric mode. A minimum lithographic feature size of 80 nm is used in our design, which is within the limitation of 193 nm deep ultraviolet lithography.

A CMOS Compatible Ultracompact Silicon Photonic Optical Add-Drop Multiplexer with Misaligned Sidewall Bragg Gratings

We design and experimentally demonstrate an ultra-broadband and compact two-mode multiplexer based on subwavelength-grating-slot-assisted adiabatic coupler for the silicon-on-insulator platform. The introduction of subwavelength-grating slot effectively increases the refractive index of the gap region between two strip waveguides and enhances the coupling between them, leading to high modal transmission over a short mode-evolution region, particularly at the short-wavelength regime. As a result, our two-mode multiplexer has a compact design footprint, with a mode-evolution region length of only 25  $\mu$ m and an entire device length of only 55  $\mu$ m. Simulation shows that the mode-division multiplexing (MDM) link formed by the designed two-mode multiplexers has a record bandwidth of 740 nm spanning from 1260 nm to 2000 nm, where the crosstalk is lower than −18.5 dB and the insertion loss (IL) is lower than 0.32 dB. The MDM link has been fabricated using electron beam lithography and achieves measured crosstalk lower than −18.8 dB and IL lower than 2.6 dB, over a 100 nm bandwidth from 1260 nm to 1360 nm that covers the O-band and a 130 nm bandwidth from 1500 nm to 1630 nm that covers the C-band and the L-band.

Ultra-Broadband and Compact Two-Mode Multiplexer Based on Subwavelength-Grating-Slot-Assisted Adiabatic Coupler for the Silicon-on-Insulator Platform

We design and experimentally demonstrate a broadband 1310/1550 nm wavelength demultiplexer based on a multimode interference coupler with a tapered internal photonic crystal (PC) structure for the silicon-on-insulator platform. The tapered internal PC structure is engineered to reflect the C-band light while transmitting the O-band light. Novel PC nanotapers are introduced for the internal PC structure that effectively suppress the sidelobe of the photonic bandgap and enable our device to be operable over the O-band. The device was fabricated using electron beam lithography, and its performance has been experimentally characterized. The measured extinction ratios are higher than 15 dB over a 74 nm bandwidth from 1286 to 1360 nm at the O-band, and over a 103 nm bandwidth from 1527 to 1630 nm that covers the C-band and the L-band.

Broadband 1310/1550 nm wavelength demultiplexer based on a multimode interference coupler with tapered internal photonic crystal for the silicon-on-insulator platform.

We design and demonstrate Fabry–Perot resonators with transverse coupling using Bragg gratings as reflectors on the silicon-on-insulator (SOI) platform. The effects of tailoring the cavity length and the coupling coefficient of the directional coupler on the spectral characteristics of the device are studied. The fabricated resonators achieved an extinction ratio (ER) of 37.28 dB and a Q-factor of 3356 with an effective cavity length of 110 μm, and an ER of 8.69 dB and a Q-factor of 23642 with a 943 μm effective cavity length. The resonator structure presented here has the highest reported ER on SOI and provides additional degrees of freedom compared to an all-pass ring resonator to tune the spectral characteristics.

Ghulam Saber

Papers

Compact Broadband Polarization Beam Splitter Based on Multimode Interference Coupler With Internal Photonic Crystal for the SOI Platform

A CMOS Compatible Ultracompact Silicon Photonic Optical Add-Drop Multiplexer with Misaligned Sidewall Bragg Gratings

Ultra-Broadband and Compact Two-Mode Multiplexer Based on Subwavelength-Grating-Slot-Assisted Adiabatic Coupler for the Silicon-on-Insulator Platform

Broadband 1310/1550 nm wavelength demultiplexer based on a multimode interference coupler with tapered internal photonic crystal for the silicon-on-insulator platform.

Transversely coupled Fabry–Perot resonators with Bragg grating reflectors