Patent ID: 8994920
Filing Date: 2015-03-31
Classification: G02B,G03F

Abstract:
1. A dual-wavelength, stepped, spiral-phase lens, which is configured to receive radiation at first and second wavelengths and direct the radiation onto a photochromic layer, wherein: the lens has an optical axis, wherein the axis intercepts the photochromic layer and the first-wavelength and second-wavelength incident radiation is directed along the axis, the lens comprises a dephasing surface having phase steps, which partition the surface into at least three zones; the zones are all configured to focus at least a substantial portion of the incident first-wavelength radiation toward a common first focal point proximate the photochromic layer; the zones are all further configured to focus at least a substantial portion of the incident second-wavelength radiation toward a common second focal point coinciding with or proximate the first focal point; the phase steps are configured so that the dephasing surface's azimuthally-averaged complex amplitude transmittance around the axis is zero for the second-wavelength radiation, whereby the dephasing surface induces a second-wavelength optical null along the optical axis and at the axial intercept on the photochromic layer; the phase steps are further configured to preserve phase coherence between portions of the first-wavelength radiation transmitting through the zones, whereby the lens achieves high radiant intensity of the first-wavelength radiation at a focused-radiation spot on the photochromic layer, at the optical null; and the second-wavelength radiation induces first-wavelength optical absorbance in the photochromic layer, thereby creating a sub-wavelength optical transmittance window in the photochromic layer at the optical null through which the first-wavelength radiation transmits.