Dither-free absolute frequency locking of a 1.3 μm DFB laser on87Rb

A technique for frequency locking a semiconductor laser in the 1.3 μm region by observing the absorption in a ⁸⁷Rb vapor optically pumped by another frequency-modulated semiconductor laser is presented. This technique offers well-defined strong atomic resonances and does not require frequency dithering of the 1.3 μm laser to observe the discrimination pattern required for frequency locking. Dither-free absolute frequency locking of a DFB (distributed feedback) laser at 1324 nm was achieved using a pump laser diode operating at 795 nm (D₁-line). Applications include master oscillator of multiwavelength and coherent communication systems and reference source for an optical frequency synthesizer. Resonances in the 1.55 μm region are also available through this approach