Terahertz Nonreciprocal Photonic Spin Manipulation with Light-Magneto-Joint Modulation

Nonreciprocal materials and devices play an irreplaceable role in isolating, routing, and multiplexing. However, in the terahertz (THz) band, their active control mechanisms are still limited. Herein, a THz nonreciprocal photonic spin transmission is demonstrated in the undoped InSb actively manipulated by a light-magneto-joint modulation method, in which THz cyclotron resonance of the photoinduced carriers is conjunctively excited by both pump laser and external magnetic field. Moreover, a diffusion model of photoinduced non-equilibrium carriers and its nonreciprocal dispersion model of magnetized plasma are established to interpret the experimental observation. The results indicate that the light-magneto-joint modulation achieves a broadband amplitude-phase modulation with a higher modulation depth (>2 & pi; rad phase shift), as well as an active nonreciprocal spin transmission with magnetic circular dichroism (>20dB) and the Faraday rotation effect (>90 & DEG;) in InSb, which is more efficient and faster than the traditional thermal excitation. Furthermore, the demonstration in a single-frequency THz transmission system shows that this light-magneto-joint modulation mechanism in InSb can be multifunctionally applied in active control, isolation, and polarization conversion.