High-Temperature Nonreciprocal Thermal Radiative Properties of Semiconductors

Objects around us constantly emit and absorb thermal radiation. The basic properties that characterize these two processes are emissivity and absorptivity, respectively. For reciprocal systems, the emissivity and absorptivity for a given direction, polarization, and frequency are tightly restricted to be equal by Kirchhoff's law of thermal radiation (1-3). Recent research has shown that materials with magneto-optical effects such as doped InAs in the presence of an external magnetic field can break Kirchhoff's law, yielding nonreciprocal thermal radiation (4-5). Despite early experimental efforts (6-7) for nonreciprocal thermal radiation, it remains a challenge to measure nonreciprocal thermal emission, especially for samples with large areas on the order of several cm² and high temperatures where band structure parameters and lattice structure alter. A theoretical model is also lacking to simulate the behavior of magneto-optical materials at elevated temperatures. Here we propose an emissometry setup that incorporates a magnetic assembly for nonreciprocal thermal emission measurement not only for large scale samples but also for temperatures as high as 1000 °C. A modified temperature-dependent Drude model is proposed to predict the radiative properties of semiconductors at high temperatures. Since the optical properties of these materials are highly temperature sensitive, our efforts provide effective experimental and theoretical platforms for high-temperature nonreciprocal thermal radiation study.


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