Athermal silicon microring resonators with titanium oxide cladding

Abstract

We describe a novel approach for CMOS-compatible passively temperature insensitive silicon based optical devices using titanium oxide cladding which has a negative thermo-optic (TO) effect. We engineer the mode confinement in Si and TiO2 such that positive TO of Si is exactly cancelled out by negative TO of TiO2. We demonstrate robust operation of the resulting device over 35 degrees.

Thermo-optic tuning of a packaged whispering gallery mode resonator filled with nematic liquid crystal

“…The exceptional sensitivity of the WGM resonators' optical properties to the changes in their geometry and refractive index may lead to significant temperature dependence due to thermos-optic and thermal expansion properties of the resonator's material. Several authors reported different approaches to eliminate the temperature crosssensitivity of sensors based on WGM resonators, such as liquid core optical ring resonators (LCORR) [3,4], microspheres [5][6][7][8][9][10][11][12], micro ring [13], microtoroid [14][15][16] Silica glass is one of the most popular materials used for fabrication of optical WGM microresonators (MRs) due to its low loss and the simplicity of fabrication of high quality resonators by melting the material into circular shapes. However, silica has relatively low thermo-optic and thermal expansion coefficients, so if a silica resonator device is used for sensing of environmental parameters or utilizes thermo-optic tuning, a means to enhance its temperature sensitivity is required.…”

Optical temperature sensor with enhanced sensitivity by employing hybrid waveguides in a silicon Mach-Zehnder interferometer

“…While a silicon nanowire itself having silica or air cladding transmits a mode with a positive temperature-dependent phase change, a negative temperature-dependent phase change can be realized in a waveguide with negative-TOC material as the core. Materials with a negative TOC like polymers [24] and titanium dioxide (TiO 2 ) [25] have already been utilized as the cladding for a narrowed silicon waveguide to reduce the temperature dependence of the silicon photonic devices, but few reports have been published on utilizing these materials in temperature sensors. Recently, an MZI-based silicon temperature sensor with TiO 2 overlaying both arms have achieved a large temperature sensitivity of −340 pm/°C, since the TiO 2 used in the work has an unexplainably ultrahigh TOC of −5 to −7 × 10 −4 /°C [26].…”

Ultrahigh Temperature-Sensitive Silicon MZI with Titania Cladding

“…There have been many efforts to adjust temperature-dependent wavelength shift (TDWS) of a photonic waveguide device using a cladding material with a negative thermo-optic coefficient (TOC) differently from a core material with a positive TOC (Kokubun et al, 1998;Lee et al, 2007Lee et al, , 2008Alipour et al, 2010;Guha et al, 2013;Bovington et al, 2014;Lee, 2014). Polymers have been popularly used as the cladding material with a negative TOC (Kokubun et al, 1998;Lee et al, 2007Lee et al, , 2008, and titania (TiO 2 ) is recently attracting attention with a highly negative TOC (Alipour et al, 2010;Guha et al, 2013;Bovington et al, 2014;Lee, 2014) and its merit of complementary-metal-oxide-semiconductor (CMOS) compatibility in fabrication when it is used for a silicon photonic waveguide device.…”

“…Polymers have been popularly used as the cladding material with a negative TOC (Kokubun et al, 1998;Lee et al, 2007Lee et al, , 2008, and titania (TiO 2 ) is recently attracting attention with a highly negative TOC (Alipour et al, 2010;Guha et al, 2013;Bovington et al, 2014;Lee, 2014) and its merit of complementary-metal-oxide-semiconductor (CMOS) compatibility in fabrication when it is used for a silicon photonic waveguide device. Silicon has a very high TOC of 1.8 × 10 −4 /°C and there have been many efforts to reduce the high TDWS of silicon photonic devices such as a ring resonator by using polymer (Kokubun et al, 1998;Lee et al, 2007Lee et al, , 2008 or titania cladding (Alipour et al, 2010;Guha et al, 2013;Lee, 2014) with a highly negative TOC.…”