Athermal silicon subwavelength grating waveguides

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Proceedings titleProceedings of SPIE - The International Society for Optical Engineering
ConferencePhotonics North 2011, 16 May 2011 through 18 May 2011, Ottawa, ON
Article number80071L
Subjectathermal; Duty ratios; grating; Silicon photonics; Sub-wavelength; Thermo-optic coefficients; Computer simulation; Light polarization; Photonics; Waveguides
AbstractIn this paper, athermal subwavelength grating (SWG) waveguides are investigated. Both numerical simulations and experimental results show that a temperature independent behaviour can be achieved by combining two materials with opposite thermo-optic coefficients within the waveguide. SU-8 polymer with a negative thermo-optic coefficient (dn/dT = -1.1×10-4 K -1) is used in our silicon SWG waveguides to compensate for silicon's positive thermo-optic coefficient of 1.9×10-4 K-1. The grating duty ratio required to achieve an athermal behavior is reported to vary as a function of the operating wavelength and the waveguide dimensions. For example, for athermal waveguides of 260 nm in height, duty ratios of 61.3% and 83.3% were calculated for TE and TM polarized light respectively for a 450 nm wide waveguide, compared to ratios of 79% and 90% for a 350 nm wide waveguide. It is also reported that with increasing width, and increasing height, a smaller grating duty ratio is necessary to achieve an athermal behaviour. A smaller fraction of silicon would hence be needed to compensate for the polymer's negative thermo-optic effect in the waveguide core. Subwavelength sidewall grating (SWSG) waveguides are also proposed here as alternatives to high duty ratio SWG waveguides that are required for guiding TM polarized light. Assuming a duty ratio of 50%, the width of the narrow segments for temperature- independent behavior is found by numerical simulations to be 125 nm and 143 nm for TE and TM polarized light, respectively. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).
Publication date
AffiliationNational Research Council Canada (NRC-CNRC); NRC Institute for Microstructural Sciences
Peer reviewedYes
NPARC number21271272
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Record identifierd64397de-3a13-4fef-828b-acece885ea3b
Record created2014-03-24
Record modified2016-05-09
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