Microspherical cavity resonances reduce diode-laser linewidth

High Q microspheres fiber-coupled to a distributed-feedback (DFB) diode laser may be used as feedback devices and offer the potential of laser linewidth reduction and frequency control. Researchers at the Polytechnic University (Brooklyn, NY), led by Giora Griffel and Steve Arnold, collaborated with a group from the David Sarnoff Research Center (Princeton, NJ) to couple the 750-nm DFB laser output to a microsphere through a side-polished single-mode fiber. The laser output passes from fiber to

Nov 1st, 1995

Microspherical cavity resonances reduce diode-laser linewidth

High Q microspheres fiber-coupled to a distributed-feedback (DFB) diode laser may be used as feedback devices and offer the potential of laser linewidth reduction and frequency control. Researchers at the Polytechnic University (Brooklyn, NY), led by Giora Griffel and Steve Arnold, collaborated with a group from the David Sarnoff Research Center (Princeton, NJ) to couple the 750-nm DFB laser output to a microsphere through a side-polished single-mode fiber. The laser output passes from fiber to microsphere, exciting morphologically dependent resonances, so-called "whispering gallery modes," on the surface and interior of the sphere. The phenomenon has been demonstrated with single and multiple microspheres. Peaks in the scattering spectra from the microspheres correlate with dips in the laser output, an essential quality if the spheres are to operate as feedback devices. Previous feedback experiments with DFB lasers using a high-finesse Fabry-Perot etalon have demonstrated megahertz to kilohertz linewidth reductions. These optics are bulky, relegating the systems to laboratory environments. Hybrid DFB-microsphere systems may give this degree of performance enhancement in a compact package for field applications.

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