The quantum cascade laser (QCL) is based on inter-subband electron transitions inside a quantum well structure, which can be tailored to emit different wavelengths simply by changing the thickness of the constituent layers. In other words, we are no longer limited by inherent band gaps, and can demonstrate a very versatile source using one material system. Northwestern University researchers have gotten 120 watts from a room temperature quantum cascade laser. Last year the highest power level was 34 watts for a quantum cascade laser.
Broad area quantum cascade lasers (QCLs) are studied with ridge widths up to 400 µm, in room temperature pulsed mode operation at an emission wavelength around 4.45 µm. The peak output power scales linearly with the ridge width. A maximum total peak output power of 120 W is obtained from a single 400-µm-wide device with a cavity length of 3 mm. A stable far field emission characteristic is observed with dual lobes at ±38° for all tested devices, which suggests that these broad area QCLs are highly resistant to filamentation