Spectral Mode Selection Research Articles

954 nm Raman fiber laser with multimode laser diode pumping

CW Raman fiber laser emitting at 954 nm under direct pumping by a high-power multimode laser diode at 915 nm is demonstrated. A cavity of the laser is formed with 2.5 km-long multimode graded-index fiber and two mirrors: highly reflective fiber Bragg grating (FBG) at one side and normally cleaved fiber end at the other side. The laser generates low-index transverse modes at the Stokes wavelength with output power above 4 W at a slope efficiency above 40%. It is shown that utilization of a narrowband FBG mirror with low reflectivity instead of the cleaved fiber end with Fresnel reflection leads to stronger spectral mode selection, but the generated power is reduced in this case.

Enhanced Spectral Mode Selection in an Aspheric Extended-Cavity Resonator

Strong spectral-mode-selection behavior has been observed in a three-mirror solid-state resonator that was constructed by colinearly aligning an aspheric feedback mirror with a standing-wave two-mirror resonator. This spectral mode selection is measured to be much stronger than that predicted by the frequency selection theory of simple Fabry-Perot cavities. Our study shows that the spatial modes and their associated eigenvalues vary at different oscillation wavelengths in a complex extended-cavity resonator. It is the interplay between spatial modes and spectral modes that induces the strong spectral-mode selection

Spatial and spectral mode selection of heralded single photons from pulsed parametric down-conversion

We describe an experiment in which photon pairs from a pulsed parametric down-conversion (PDC) source were coupled into single-mode fibers with heralding efficiencies as high as 70%. Heralding efficiency or mode preparation efficiency is defined as the probability of finding a photon in a fiber in a definite state, given the detection of its twin. Heralding efficiencies were obtained for a range of down-conversion beam-size configurations. Analysis of spatial and spectral mode selection, and their mutual correlation, provides a practical guide for engineering PDC-produced single photons in a definite mode and spectral emission band. The spectrum of the heralded photons were measured for each beam configuration, to determine the interplay between transverse momentum and spectral entanglement on the preparation efficiency.