Laser Coherence Modulation and Its Applications

Christoph Amtmann, Roland Lammegger, Alexander Betzler +7 more

Abstract This paper discusses various frequency modulation and intensity modulation capabilities within a sample of direct laser current modulated identical vertical cavity surface emitting laser diodes. The presented analysis is based on measurements of the spectral amplitudes as a function of the applied modulation power at a constant modulation frequency of 3.517 GHz. Their evaluation by Bessel function fits produces the three modulation parameters: frequency modulation index, intensity modulation index (via the α parameter) and the side band asymmetry of the first order side bands. The variation of the laser diode’s modulation capability is discussed. It is found that the individual laser diodes show a large variation in their modulation capabilities. This requires the selection of suitable laser diodes as a laser source for atomic vapour applications with the special emphasis on a coherent population trapping based scalar magnetometers

Olga Korotkova, Greg Gbur

GORDON J. TROUP, John M. R. Stone

Yongqing Li, Min Xiao

Semiconductor diode lasers have been widely used in atomic physics and quantum optics. Advanced semiconductor lasers have the capability of modulation in intensity or optical frequency at the rate greater than a few GHz by modulating the driving current. This characteristics makes semiconductor laser diodes ideal light sources in the study of optical coherent transient phenomena with the time scale ranging from few milliseconds to sub-nanoseconds. In this paper, we discuss the applications of semiconductor lasers in coherent transient measurements and report our experimental results.

Yuan‐Yu Jau, W. Happer

A vapor of alkali-metal atoms in the external cavity of a semiconductor laser, pumped with a time-independent injection current, can cause the laser to self-modulate at the "field-independent 0-0 frequency" of the atoms. Push-pull optical pumping by the modulated light drives most of the atoms into a coherent superposition of the two atomic sublevels with an azimuthal quantum number m=0. The atoms modulate the optical loss of the cavity at the sharply defined 0-0 hyperfine frequency. As in a maser, the system is not driven by an external source of microwaves, but a very stable microwave signal can be recovered from the modulated light or from the modulated voltage drop across the laser diode. Potential applications for this new phenomenon include atomic clocks, the production of long-lived coherent atomic states, and the generation of coherent optical combs.

Hermann Haken