Long-external-cavity distributed Bragg reflector laser with subkilohertz intrinsic linewidth

We report on a simple, compact, and robust 780 nm distributed Bragg reflector laser with subkilohertz intrinsic linewidth. An external cavity with optical path length of 3.6 m, implemented with an optical fiber, reduces the laser frequency noise by several orders of magnitude. At frequencies above 100 kHz the frequency noise spectral density is reduced by over 33 dB, resulting in an intrinsic Lorentzian linewidth of 300 Hz. The remaining low-frequency noise is easily removed by stabilization to an external reference cavity. We further characterize the in-fluence of feedback power and current variation on the intrinsic linewidth. The system is suitable for experiments requiring a tunable laser with narrow linewidth and low high-frequency noise, such as coherent optical commu-nication, optical clocks, and cavity QED experiments. © 2012 Optical Society of America OCIS codes: 140.3425, 140.2020, 140.4780. Highly stabilized and ultranarrow-linewidth lasers are important for applications in atomic physics, quantum measurement, and quantum information science. The traditional extended-cavity diode lasers (ECDLs) [1] and distributed Bragg reflector (DBR) lasers have typical linewidths of a few hundred kilohertz to a few ten mega