Proceedings PaperLaser diode edge sensors for adaptive optics segmented arrays: Part 1--external cavity coupling and detector current
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An analytical study of laser diode (LD) operation coupled to external cavity scattering elements, which function as variably coupling reflectors (VCRs), is carried out with the purpose of determining the interrelationship between cavity coupling and intracavity optical intensity which determine the current generated at the rear facet PIN detector. If the external cavity coupling is position sensitive it can allow the relative position between the LD and the external cavity to be determined from the PIN or other detector mounted with the LD. If the LD and external cavity element are placed on opposite edges of two adjacent adaptive optics segments they can provide the basis for a self aligning position sensor; the amount of current detected at the PIN or other detector will depend on the relative displacement between the LD and external coupling element. Schematics of the edge sensors, the basic electronic configuration, and the optics of the external cavity are given. The ratio of the internal cavity intensity, Ic, to the saturation intensity, Is, is plotted as a function of the external cavity coupling. When this ratio approaches one, large-signal output is not a linear function of large-signal output. For operation well below saturation, the PIN detector current is directly related to Ic and may serve as a reliable detector.