Development of a polarization-insensitive thermophotovoltaic emitter with a binary grating

A wavelength-selective but polarization-insensitive thermophotovoltaic emitter was numerically developed with a binary tungsten grating and its appealing emittance spectra were demonstrated with analysis. Ranges of emitter dimensions were preliminarily confined with the excitation of the surface plasmon polariton, cavity resonance, and Wood's anomaly at specified wavelengths. Then, a hybrid scheme (the rigorous coupled wave analysis together with a genetic algorithm) was able to finely tailor the grating profile such that emittance could be significantly enhanced in the near infrared region. The peak emittance at the transverse electric and transverse magnetic polarizations was 0.997 and 0.935, respectively. The emittance was actually almost twice that from a plain tungsten plate at short wavelengths but significantly reduced at long wavelengths. Moreover, such spectral emittance is insensitive to the polarization and 5% dimension modification, making the emitter ideal for thermophotovoltaic applications. Patterns of electromagnetic fields and Poynting vectors were able to confirm the excitation of physical mechanisms.