Abstract
Previous works on photorefractive self-organizing laser cavities were about lasers that oscillate, prior the self-organization process occurs, on a set of axial modes sharing the same transverse structure. In a well-designed broad-area laser diode extended cavity, we theoretically and experimentally demonstrate that the insertion of a photorefractive crystal can also affect the transverse modal structure to force the laser, initially oscillating on several transverse modes, to oscillate on a single transverse and axial mode. This spatial self-organization process leads to an enhancement of the single mode operating range of the laser.
Highlights
Self-organizing laser cavities contain a dynamic holographic medium that plays the role of a modal filter
We study the modal feature of a broad-area laser (BAL) diode mounted in an extended cavity that contains no spatial filter except an intracavity photorefractive crystal
In order to understand the modal behavior of the extended imaging cavity without any photorefractive crystal and close to the threshold, the output facet of the BAL diode is imaged onto the input slit of the spectrometer
Summary
Self-organizing laser cavities contain a dynamic holographic medium that plays the role of a modal filter. The oscillating modes record a common dynamic hologram, hologram that, in turn, acts as a filter for these modes This filter, being self-adapted, does not require any adjustment and it adapts to any cavity change resulting, for instance, from a modification of the thermal loading and the cavity ageing. Such cavities have been built with various dynamic holographic media: thermal holograms recorded in a non-saturable absorbing medium [1], gain gratings recorded in solid-state amplifiers [2], absorption gratings recorded in a saturable absorber cell [3]. A self-organization, based on the mutual adaptation of this dynamic spectral filter to the oscillating modes, forces the steady-state oscillation on one axial mode
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