We give an overview of recent progress in passive spectral filters and demultiplexers based on silicon-on-insulator photonic wire waveguides: ring resonators, interferometers, arrayed waveguide gratings, and echelle diffraction gratings, all benefit from the high-index contrast possible with silicon photonics. We show how the current generation of devices has improved crosstalk levels, insertion loss, and uniformity due to an improved fabrication process based on 193 nm lithography.

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Silicon-on-Insulator Spectral Filters Fabricated With CMOS Technology

Athermal silicon ring resonators are experimentally demonstrated by overlaying a polymer cladding on narrowed silicon wires. The ideal width to achieve athermal condition for the TE mode of 220 nm-height SOI waveguides is found to be around 350 nm. After overlaying a polymer layer, the wavelength temperature dependence of the silicon ring resonator is reduced to less than 5 pm/degrees C, almost eleven times less than that of normal silicon waveguides. The optical loss of a 350-nm bent waveguide (with a radius of 15 microm) is extracted from the ring transmission spectrum. The scattering loss is reduced to an acceptable level of about 50 dB/cm after overlaying a polymer cladding.

/pdf/athermal-silicon-on-insulator-ring-resonators-by-overlaying-1ogg1bds7k.pdf

Athermal Silicon-on-insulator ring resonators by overlaying a polymer cladding on narrowed waveguides

Abstract An effective solution to enhance the capacity of an optical-interconnect link is utilizing advanced multiplexing technologies, like wavelength-division-multiplexing (WDM), polarization-division multiplexing (PDM), spatial-division multiplexing (SDM), bi-directional multiplexing, etc. On-chip (de)multiplexers are necessary as key components for realizing these multiplexing systems and they are desired to have small footprints due to the limited physical space for on-chip optical interconnects. As silicon photonics has provided a very attractive platform to build ultrasmall photonic integrated devices with CMOS-compatible processes, in this paper we focus on the discussion of silicon-based (de)multiplexers, including WDM filters, PDM devices, and SDM devices. The demand of devices to realize a hybrid multiplexing technology (combining WDM, PDM and SDM) as well as a bidirectional multiplexing technologies are also discussed to achieve Peta-bit optical interconnects.

Silicon-based on-chip multiplexing technologies and devices for Peta-bit optical interconnects

Silicon microring resonators have been hailed for their potential use in next-generation optical inter- connects. However, the functionality of silicon microring based devices suffer from susceptibility to thermal fluc- tuations that is often overlooked in their demonstrated results, but must be resolved for their future implemen- tation in microelectronic applications. We survey the emerging efforts that have been put forth to resolve these thermal susceptibilities and provide a comprehensive discussion of their advantages and disadvantages.

https://www.degruyter.com/downloadpdf/j/nanoph.2014.3.issue-4-5/nanoph-2013-0013/nanoph-2013-0013.xml

Resolving the thermal challenges for silicon microring resonator devices

We report the design criteria and performance of Si ring resonators for passive athermal applications in wavelength division multiplexing (WDM). The waveguide design rules address i) positive- negative thermo-optic (TO) composite structures, ii) resonant wavelength dependent geometry to achieve constant confinement factor (Γ ), and iii) observation of small residual second order effects. We develop exact design requirements for a temperature dependent resonant wavelength shift (TDWS) of 0 pm/K and present prototype TDWS performance of 0.5pm/K. We evaluate the materials selection tradeoffs between high-index contrast (HIC) and low-index contrast (LIC) systems and show, remarkably, that FSR and footprint become comparable under the constraint of athermal design.

/pdf/athermal-operation-of-silicon-waveguides-spectral-second-7vn9usmrrv.pdf

Athermal operation of Silicon waveguides: spectral, second order and footprint dependencies

In this paper, we investigate the temperature dependence of a silicon-on-insulator-based silicon nanophotonic ring resonator covered with a polymeric overlayer. Temperature-dependent wavelength shift is measured to be as low as 5 pm/degC for the TM mode in a silicon ring resonator composed of a 500 times 220 nm2 channel waveguide. We also show through simulations and experiments that the temperature dependence can be reduced for the TE mode or for both the TE and TM modes by adjusting the mode volume of a silicon nanophotonic waveguide.

Temperature Dependence of Silicon Nanophotonic Ring Resonator With a Polymeric Overlayer

We present a silicon nano-wire ring resonator with a temperature-dependent wavelength shift as low as 0.006 nm/degC by adjusting the mode volume of a SOl-based silicon waveguide covered with a polymeric material.

Ho-Kyun Ahn

Papers

Temperature Dependence of Silicon Nanophotonic Ring Resonator With a Polymeric Overlayer

Temperature-Insensitive Silicon Nano-Wire Ring Resonator