We have designed and fabricated Mach-Zehnder interferometer thermooptic switches using a wafer-bonded thin-silicon-on-insulator materials system. The thermally switched devices use single-mode strip waveguides with dimensions 0.26/spl times/0.6 /spl mu/m/sup 2/, operating at a wavelength of /spl lambda/=1.55 /spl mu/m. Useful device characteristics include a low switching power, 50 mW, and a fast rise time of <3.5 /spl mu/s. These results demonstrate the potential of this high-index-contrast materials system for the design of fast and low-power thermooptic switches and as an active element in photonic integrated circuits.

Fast and low-power thermooptic switch on thin silicon-on-insulator

We demonstrated a 8×8 broadband optical switch on silicon for transverse-electrical polarization using a switch-and-selector architecture. The switch has a footprint of only 8 mm × 8 mm, minimum on-chip loss of about 4 dB, and a port-to-port insertion loss variation of only 0.8 dB near some spectral regions. The port-to-port isolation is above 30 dB over the entire 80-nm-wide spectral range or above 45 dB near the central 30 nm. We also demonstrated a switching power of less than 1.5 mW per element and a speed of 2 kHz, and estimated the upper bound of total power consumption to be less than 70 mW even without optimization of the default state of the individual switch elements.

Compact, low-loss and low-power 8×8 broadband silicon optical switch

Optical switching technologies are very crucial to future mobile broadband all-optical IP networks. Many different optical switching technologies are currently available or under development. The main purpose of the article is to conduct performance comparisons on optical switching technologies in terms of basic performance, network requirements, and system requirements based on a literature survey. The technologies include switching based on optical microelectromechanical systems (MEMS), thermal optical switching, electro-optic switching, and acousto-optic switching technologies. Each optical switching technology has unique performance characteristics specific to the utilized optical phenomena. It might be crucial to integrate some technologies together to achieve a better solution for optical switching. Optical switching is a very hot topic attracting much research effort. Optical MEMS-based switching technology might be one of the most promising approaches at present. Many new optical switching technologies might be created in the near future. Through the impact of nanotechnology, some innovative approaches to optical switching might emerge.

Optical switching technology comparison: optical MEMS vs. other technologies

A tunable photonic crystal microcavity with in-filling holes has been experimentally realized by using the thermooptic effect in silicon-on-insulator waveguide at /spl lambda/=1530 nm. The device was fabricated by reactive ion etching through the silicon core layer for high vertical confinement. A thin film heater has been integrated onto the microcavity. A small change in temperature (and consequent change in refractive index) was sufficient to cause an observable resonance shift. A resonance shift of 5 nm was achieved when the heater was switched on to a current of 1.2 mA (with switching power of about 9 mW).

Tuning of photonic crystal waveguide microcavity by thermooptic effect

Silica-based planar lightwave circuit (PLC) hybrid integration is a promising way to provide highly functional photonic components. This paper is an overview of recent progress in PLC hybrid integration technology including optoelectronic semiconductor devices for the hybrid integration, various devices for wavelength-division multiplexing, and all-optical time-division multiplexing.

PLC hybrid integration technology and its application to photonic components

We propose a novel structure that reduces the switching power of a silica-based thermooptic switch (TOSW). The structure consists of silicon trenches and heat insulating grooves, which are formed beneath and beside the arms of a Mach-Zehnder interferometer, respectively. We optimize the structure using the differential-element method (DEM) and fabricate a 2 /spl times/ 2 TOSW with a switching power of only 90 mW, namely, 75% less than that of a conventional TOSW. We also obtain an insertion loss of about 1 dB and an extinction ratio of over 30 dB with a response time from 0% to 90% of 4.9 ms. We then use the structure to fabricate an 8 /spl times/ 8 matrix switch and confirm a total power consumption of 1.4 W with an average insertion loss of 7.4 dB and an extinction ratio of 50.4 dB for 64 possible optical paths.

New structure of silica-based planar lightwave circuits for low-power thermooptic switch and its application to 8 /spl times/ 8 optical matrix switch

We report a hybrid integrated multiwavelength light source in which eight DFB-LDs and an MMI coupler are integrated with a silica PLC platform. We also report 2.5 Gb/s operation using LD drivers assembled module. We have demonstrated a hybrid integrated multiwavelength light source (MLS) that operates simultaneously on 8 channels and shows low thermal interference. We also demonstrated 2.5 Gb/s operation after packaging the MLS in LD driver assembled module. We believe that this PLC hybrid integrated MLS is very practical and will be employed in future dense WDM systems.

A. Sugita

Papers

New structure of silica-based planar lightwave circuits for low-power thermooptic switch and its application to 8 /spl times/ 8 optical matrix switch

A 2.5 Gb/s hybrid integrated multiwavelength light source composed of eight DFB-LDs and an MMI coupler on a silica PLC platform