Thorlabs offers a number of tunable, single-frequency lasers (SFL) with very narrow linewidths. Low-Noise, Frequency-Locked, and Turnkey systems are available. Component laser diodes are made in-house at Thorlabs' semiconductor manufacturing facility. Several types are available, including Volume-Holographic-Grating Stabilized (VHG), Distributed Feedback (DFB), Distributed Bragg Reflector (DBR), and External Cavity Lasers (ECL). We also offer an Ultra-Low-Noise (ULN) Laser, which is a hybrid design that uses a single angled facet gain chip coupled to an exceptionally long fiber Bragg grating.