We have designed a high Q-factor polarization-dependent photodetector that combines the electronically tunable capabilities of graphene to achieve efficient dual-band polarization wave detection.

Nonreciprocal thermal radiation is valuable to the energy transmission and collection. Issues of single polarization in near-infrared band with large incident angle cast limitations on the development of nonreciprocal thermal radiation. A dual-polarization narrow-band nonreciprocal thermal radiator in near-infrared band with extremely small incident angle is proposed to address these issues. The radiator consists of periodic annular arrays, magneto-optical medium and metal reflective layer. The simulation results show that the nonreciprocity of two polarizations is greater than 85 % with ultra-high Q factor at the angle of 0.8. The finite element method and coupled mode theory that are adopted in the study offer high consistent results, which prove the accuracy of calculation results. The physical mechanism of near-infrared narrow-band nonreciprocal radiation is attributed to the excitation of cavity resonance and guided mode resonance. The proposed two-dimensional near-infrared nonreciprocal radiator that allows the dual-polarization operation at small incident angle offers it good potentials in thermal photovoltaic system and energy conversion.

Chirality and asymmetric transmission have wide-ranging applications in fields such as optics, chemical synthesis, pharmaceutical research, biological analysis, materials science and communication technology. In this work, we have demonstrated a terahertz (THz) device with strong chirality and asymmetric transmission effect based on a twisted bilayer alpha-MoO3. The unique optical response can be realized by adjusting structural parameters such as the thicknesses of the layers as well as the angle of relative rotation. It is found that the proposed structure achieves a giant circular dichroism (CD) value of 0.81 at 9.8 THz, which originates from the symmetry breaking of the structure. The phenomenon has been approved by the polarization conversion and the distributions of the electric field. In addition, the device exhibits the asymmetric transmission effect for circularly polarized wave incidence. The results show that the forward and backward transmissivity of circularly polarized waves with different handedness exhibit a significant difference of up to 0.55 at 9.2 THz. This work simultaneously achieves chirality and asymmetric transmission effect in the terahertz band, which paves the way for developing terahertz devices capable of chirality manipulation and optical isolation.