Spectral filtering and evolution of adaptive gain holographic laser oscillators

Summary form only given. We present results of the spectral filtering properties of a volume gain grating and the spectral evolution of loop schemes where grating formation and subsequent lasing action start entirely from spontaneous noise. We show the diffraction of a broadband input from a reflection grating written by the interference of two monochromatic pulses inside the gain medium. We model this interaction for a 10 GHz input bandwidth with increasing length of the amplifier. We find that the gain grating acts as a spectral filter and that the reduction in the bandwidth of the diffracted output is approximately inversely proportional to the medium length. The diffraction efficiency is reduced as a result of this filtering effect as compared to 150% for the case of a Bragg-matched monochromatic probe beam. We show that the spectral filtering of the gain grating as well as the coherence length requirement for grating formation have an important role in the spectral evolution of holographic resonators.