Broadband optical phased-array beam steering

An array of phase retarders can be used as an optical phased array (OPA) to steer light [McManamon et al., Proc. IEEE 84(2), 268–298 (1996)]. The introduction of resets enables steering to larger angles without requiring an optical path difference (OPD) greater than one wavelength. These resets, however, are correct only at the design wavelength. The beam steerer is therefore very dispersive. It has been shown theoretically that resets of an integer multiple of the wavelength will make the beam steerer less dispersive [McManamon and Watson, Proc. SPIE 4369, 140–148 (2001)]. We offer the first experimental proof that resets of n are less dispersive than resets of a single . We also show experimentally that the dispersion associated with fixed period resets does vary, but only within a fixed limit. Last, we show the equivalent of power shifting from one order to the next as larger resets move from being divisible by one integer times the nondesign wavelength toward being divisible by the next integer times the nondesign wavelength.