Polarization selective diffractive optical elements and applications

Computer-generated holograms (CGH) fabricated as phase-only optical elements have proven to be useful for various photonic systems applications. Such elements are normally capable of implementing fixed functionality. However, the performances of packaged photonic systems will be further enhanced with availability of CGH elements with multifunctionality in polarization or color, and programmability. We have constructed polarization selective CGH which apply an independent phase profile during readout by horizontal and vertical light polarizations1–3. These elements are composed of two surface relief etched birefringent substrates joined face to face. We describe the design methodology for arbitrary birefringent substrate and gap materials. We show how these holograms are fabricated with standard microelectronics technology, and discuss the effects of etching and alignment errors on performance. We have demonstrated high diffraction efficiency with a polarization contrast ratio of over 100:1, using a multilevel phase hologram made from two birefringent lithium niobate substrates2.