Microcavity Terahertz spin-flip laser proposal

We present a novel design for a single-mode, truly sub-wavelength THz disk laser based on a nano-composite gain medium comprising an array of metal or ferromagnetic point contacts embedded in a thin dielectric layer. Stimulated emission of light occurs due to spin-flip relaxation of spin-polarized electrons injected from the ferromagnetic side of the contacts. Ultra-high electrical current densities in the contacts and a dielectric material with a large refractive index, neither condition being achievable in conventional semiconductor media, allows the thresholds of lasing to be overcome for the lowest-order modes of the disk, hence making single-mode operation possible.