Laser diode made single-mode by a self-adaptive photorefractive filter

Abstract : A photorefractive crystal inserted inside an extended cavity laser diode is an adaptive frequency filter. Without any other selective element, the mutual adaptation between the modes and the dynamic photorefractive hologram leads to a single-longitudinal-mode oscillation. We demonstrated this adaptive process with a 810-nm diffraction limited laser diode and a BaTiO3 photorefractive crystal. We analyzed the transient spectra from the initially multimode oscillation until the single-mode steady state.