Athermal silicon optical add-drop multiplexers based on thermo-optic coefficient tuning of sol-gel material

Abstract

Silicon photonics has gained interest for its potential to provide higher efficiency, bandwidth and reduced power consumption compared to electrical interconnects in datacenters and high performance computing environments. However, it is well known that silicon photonic devices suffer from temperature fluctuations due to silicon's high thermo-optic coefficient and therefore, temperature control in many applications is required. Here we present an athermal optical add-drop multiplexer fabricated from ring resonators. We used a sol-gel inorganic-organic hybrid material as an alternative to previously used materials such as polymers and titanium dioxide. In this work we studied the thermal curing parameters of the sol-gel and their effect on thermal wavelength shift of the rings. With this method, we were able to demonstrate a thermal shift down to -6.8 pm/℃ for transverse electric (TE) polarization in ring resonators with waveguide widths of 325 nm when the sol-gel was cured at 130℃ for 10.5 hours. We also achieved thermal shifts below 1 pm/℃ for transverse magnetic (TM) polarization in the C band under different curing conditions. Curing time compared to curing temperature shows to be the most important factor to control sol-gel's thermo-optic value in order to obtain an athermal device in a wide temperature range.

Design and Analysis of Ultralow Voltage Graphene on the Silicon Rich Nitride Tunable Ring Resonator-Based Add-Drop Filter for DWDM Systems

“…Te complex centered frequency around the resonant frequency ω i is written as s � j(ω − ω i ) − δω NL (U) + c i + c NL (U), and C 3 (s) is the expression of the denominator in the through-port transfer function. In the following paragraph, we assume that all ring resonators have the same Table 1: Classic materials used in ring resonator-based tunable devices compared with innovative materials on the basis of optical properties to address thermal, polarization, and low tuning efciency while keeping CMOS-compatibility [27,37].…”

“…To address the thermal dependence, athermal core materials such as Ta 2 O 5 materials [24] or top cladding materials with negative thermo-optic coefcients such as titanium dioxide [25,26], sol-gel materials [27], chalcogenides [14], and polymethyl-methacrylate (PMMA) [28] have previously been used to ofset the positive coefcient of the core and substrate materials (Table 1).…”

Study of an Integration Platform Based on an Adiabatic Active-Layer Waveguide Connection for InP Photonic Device Integration Mirroring That of Heterogeneous Integration on Silicon

“…More importantly, the polymer material, when used for covering the InGaAsP grating teeth, can help to lower the temperature dependence of the grating coupling wavelength, making it athermal. As the coefficient of thermal expansion (CTE) of the InGaAsP guiding layer is positive while the thermo-optic coefficient of the fluorinated polymer covering layer is negative, the fluorinated polymer can be used to reduce the wavelength shift of the grating (∆λ) with temperature T (see [16,19]). In fact, the thermal dependence of the refractive index of the fluorinated polymer can be tuned by incorporating different percentages of the FSU-8 content into the polymers.…”

Athermal third harmonic generation in micro-ring resonators

“…The critical criteria for effective THG of visible emission in wavelength selective MRRs lies is the phase matching between the resonances of the pump mode and the third harmonic (TH) modes. Similar to that of the Kerr frequency comb generation [17][18][19][20][21][22][23][24][25][26] , understanding and controlling the thermal behaviors of these modes remain a challenge in maximizing their THG efficiency 27 , as both the linear and nonlinear thermo-optial (TO) effects impart refractive index variations of the waveguide [19][20][21][22][23][24][25][26][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] . For platforms with a positive linear TO coefficients, the linear TO effect gives rise of tens of pm/°C temperature dependent wavelength shifts (TDWS) to the cold-cavity resonances of MRRs [17][18][19] .…”

“…For platforms with a positive linear TO coefficients, the linear TO effect gives rise of tens of pm/°C temperature dependent wavelength shifts (TDWS) to the cold-cavity resonances of MRRs [17][18][19] . It is possible to compensate the intrinsic linear TDWS by adding a cladding having a negative TO coefficient, such as polymer [31][32][33][34][35][36] or TiO 2 [37][38] and liquid crystal 39 to offset the thermal dependency 30 . These types of structures can achieve nearly athermal operation over temperature ranges of tens of degrees.…”