Acquisition of spectrally resolved multimode far-fields from terahertz quantum cascade lasers

Quantum cascade lasers (QCLs) are small and powerful sources covering a wide spectral range from infrared to terahertz (THz) radiation. When fabricated in metal-metal ridge waveguides, the output aperture is typically very small compared to the long wavelength of THz radiation, therefore it is challenging to obtain collimated, directional emission from such devices.