The QF3850HHLH from Thorlabs Inc is a Fabry-Perot Quantum Cascade Laser that operates from 3.775 to 3.925 µm. This single spatial mode laser provides an optical output power of 320 mW. It has a beam divergence (FWHM) of 6 mrad and a beam diameter of 1.5 mm. This multi longitudinal mode laser has a forward voltage of 13 V and a threshold current of up to 0.2 A. It has a collimated output and operates in continuous wave (CW) mode at room temperature. The laser is available in a high heat load (HHL) package.