Proposal for an inversionless tunable THz laser driven by room-temperature mid-infrared quantum cascade lasers

An inversionless room temperature scheme for a far-infrared and THz laser with the possibility of the wide tuning of its working frequency is suggested. The scheme is based on usual room-temperature quantum cascade lasers operating in the mid-infrared range and the use of their output as a driving field for a supplementary semiconductor heterostructure where the inversionless lasing of the far-infrared or THz radiation takes place. This structure consists of a superlattice formed by quantum wells of a special design and is incorporated into a dielectric waveguide. The optimal parameters of this structure are calculated and its operation is simulated. As a result it is shown that the working frequency of such a device can be varied by more than two times via the simple change of the mid-infrared driving field intensity. Due to the high values of the latter the suggested inversionless laser is expected to operate in the pulsed mode. It can be used as a compact and convenient widely tunable source of the far-infrared and THz radiation for fundamental studies and various applications