US Patent- Terahertz quantum cascade laser implementing a {hacek over (C)}erenkov difference-frequency generation scheme

United States Patent 9711948
Inventors

Belkin, Mikhail (Austin, TX, US) 
Adams, Robert (Austin, TX, US)
Amann, Markus Christian (Garching, DE)
Vizbaras, Augustinas (Garching, DE)

http://www.freepatentsonline.com/9711948.html

A terahertz source implementing a {hacek over (C)}erenkov difference-frequency generation scheme in a quantum cascade laser. The laser includes an undoped or semi-insulating InP substrate with an exit facet that is polished at an angle between 10° to 40°. The laser further includes a first waveguide cladding layer(s) in contact with an active layer (arranged as a multiple quantum well structure) and a current extraction layer on top of the substrate. Furthermore, the laser includes a second waveguide cladding layer(s) on top of the active layer, where the first and second waveguide cladding layers are disposed to form a waveguide structure by which terahertz radiation generated in the active layer is guided inside the laser. The terahertz radiation is emitted into the substrate at a {hacek over (C)}erenkov angle relative to a direction of the nonlinear polarization wave in the active layer, and once in the substrate, propagates towards the exit facet.