Abstract

We investigate the spatial properties of the parametric suferfluorescence generated via single-pass, single-crystal amplification of the incoherent quantum noise, both in linear (i.e. in undepleted pump) and in nonlinear (i.e. in cascading) regimes. Examples of the near-field profiles of the signal superfluorescence in linear regime are given in Fig. 1. Fig. 1a is obtained in case of large pump-beam diameter, Φ_p, and in conditions for which the signal angular spectrum is sharply peaked along a cone surface¹ (ring spectrum). In spite of the broad-bandwidth nature of the radiation (several tens of nm) a pattern-like structure is evident in the near field. A more contrasted pattern is presented in Fig. 1b, where the radiation was detected trough a 10nm wide interferential filter. Reducing the pump-beam diameter, the beam-induced tranverse gain modulation is expected to lock the amplitudes and phases of the signal spectral components, leading to the so called spatial mode locking recently described by some of present authors in the case of gaussian-like angular spectrum². The effect of spatial mode-locking in case of ring angular spectrum is shown in Figs. 1c, with a bessel-like transverse modulation. Note that this result is obtained in condition non-critical phase-matching, i.e. in the absence of transverse walkoff. In case of walkoff the angular spectrum is limited to two plane waves, leading to the roll-like structure shown in Fig. 1d.

© 1998 IEEE