Rao Sandro, Mallemace Elisa D, Cocorullo Giuseppe, Faggio Giuliana, Messina Giacomo, Della Corte Francesco G
Department DIIES, Mediterranea University, 89124, Reggio Calabria, Italy.
Department DIMES, University of Calabria, 87036, Cosenza, Italy.
Sci Rep. 2022 Mar 21;12(1):4809. doi: 10.1038/s41598-022-08232-x.
The refractive index and its variation with temperature, i.e. the thermo-optic coefficient, are basic optical parameters for all those semiconductors that are used in the fabrication of linear and non-linear opto-electronic devices and systems. Recently, 4H single-crystal silicon carbide (4H-SiC) and gallium nitride (GaN) have emerged as excellent building materials for high power and high-temperature electronics, and wide parallel applications in photonics can be consequently forecasted in the near future, in particular in the infrared telecommunication band of λ = 1500-1600 nm. In this paper, the thermo-optic coefficient (dn/dT) is experimentally measured in 4H-SiC and GaN substrates, from room temperature to 480 K, at the wavelength of 1550 nm. Specifically, the substrates, forming natural Fabry-Perot etalons, are exploited within a simple hybrid fiber free-space optical interferometric system to take accurate measurements of the transmitted optical power in the said temperature range. It is found that, for both semiconductors, dn/dT is itself remarkably temperature-dependent, in particular quadratically for GaN and almost linearly for 4H-SiC.
折射率及其随温度的变化，即热光系数，是所有用于制造线性和非线性光电器件及系统的半导体的基本光学参数。近来，4H 单晶碳化硅（4H-SiC）和氮化镓（GaN）已成为用于高功率和高温电子学的优良建筑材料，因此可以预测在不久的将来它们在光子学领域会有广泛的平行应用，特别是在波长λ = 1500 - 1600 nm 的红外通信波段。在本文中，在 4H-SiC 和 GaN 衬底中，于室温至 480 K 的温度范围内，在 1550 nm 波长下对热光系数（dn/dT）进行了实验测量。具体而言，利用形成天然法布里 - 珀罗标准具的衬底，在一个简单的混合光纤 - 自由空间光学干涉系统中，对上述温度范围内的透射光功率进行精确测量。结果发现，对于这两种半导体，dn/dT 本身显著依赖于温度，特别是对于 GaN 呈二次方关系，而对于 4H-SiC 几乎呈线性关系。
