The QF3850T1 from Thorlabs is a Fabry-Perot Quantum Cascade Laser Diode that operates from 3.75 to 3.95 µm. This single spatial mode laser provides an optical output power of 200 mW. It has a parallel beam divergence angle (FWHM) of 30 degrees, and a perpendicular beam divergence angle (FWHM) of 40 degrees. This laser diode has a forward voltage of 13.5 V and a threshold current of up to 250 mA. It has a divergent output beam and operates in continuous wave (CW) mode at room temperature. The emitting surface of this semiconductor laser diode is protected by a ZnSe window and the diode is available in a TO-9 package.