A 1.5-μm absolutely stabilized extended-cavity semiconductor laser

Summary form only given. A compact source (2-L volume) with a stable extended-cavity laser set at 1514 nm but electrically tunable over 0.3 nm using a PZT has been designed and operated as an optical reference frequency. The package also includes an NH/sub 3/ absorption cell providing several strong absorption lines, which are used to frequency-lock the laser on the side of the lines using a static loop in order to avoid residual laser frequency modulation. The frequency stability has been tested using an heterodyne beat between two identical sources. and a 10/sup -10/ relative frequency stability has been measured on a 100-s observation time. For longer observation times, some drifts unavoidable with such a stabilization method are observed: however, it has been shown that the laser frequency could stay in a +or-2-MHz range for several days, which is enough for system requirements. >