For the practical implementation of densely packed optical wavelength division multiplexed (WDM) networks, a master oscillator which will serve as an optical frequency standard is needed. Recently, these master oscillators have been developed in 1.3- and 1.5-μm spectral regions by frequency-locking semiconductor lasers to atomic and molecular absorption lines.1-4 In most of these techniques, the laser frequencies were slightly dithered to locate the peaks of the absorption lines.1-3 However, the frequency dither not only imposes a limit on the achievable frequency stability but also is undesirable for the above application. To avoid this problem, an external frequency modulator has been used to dither only the portion of the laser beam used in the frequency-locking servo loop.4 We report the frequency locking of a 1.5-μm DFB laser to the absorption peak of an atomic Kr line without dithering the laser frequency. Instead the atomic Kr line was dithered with an ac magnetic field using the Zeeman effect.
© 1990 Optical Society of AmericaPDF Article