Characterization of 4H-Silicon Carbide addressed to thermo-optic effect at fiber-optic communication wavelengths
Francesco Giuseppe Della Corte1, Giuliana Faggio1, Andrea Gnisci1, Angela Malara2, Giacomo Messina1*, Sandro Rao1
1* DIIES Dept., University “Mediterranea” of Reggio Calabria, 89122 Reggio Calabria, Italy,
2 University “Mediterranea” of Reggio Calabria, 89122 Reggio Calabria, Italy,
The knowledge of material physical properties is essential for a proper design of micro-electronic or micro-photonic devices. Temperature is known to induce deviations of the refractive index from the value measured at room temperature. This effect, known as thermo-optic effect (TOE), may cause incorrect functioning of passive and active devices, where the wavelength dependence scales with the refractive index, such as waveguides, lasers, switches and modulators . The parameter measuring the strength of this effect is the thermo-optic coefficient (TOC), dn/dT.
Silicon carbide, considered among the most suitable materials for the design of advanced electronic systems, is known for its low TOC and large thermal conductivity , but just few polytypes have been exploited so far.
In this work, the thermo-optic coefficient was determined for 4H silicon carbide (4H-SiC)at the wavelength of interest for fiber-optic communication systems, l=1.55 mm, by using a simple direct technique based on the multiple beam interference in a Fabry-Perot cavity [1, 3]. The calculated index of refraction values showed a very good linearity in the considered temperature range leading to a TOC for 4H-SiC, dn/dT = 5.11×10-5 K-1.
Moreover, a detailed optical and structural characterization of 4H-SiC by means of micro-Raman and ellipsometric spectroscopy is presented too. Raman spectroscopy provided information on crystalline quality and spatial uniformity of samples, while refractive index, extinction and absorption coefficients were obtained in a wide wavelength range through ellipsometry.
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