Incoupling waveguide hologram with reduced polarization sensitivity

An incoupling waveguide hologram (IWGH) with significantly reduced polariza tion sensitivity was designed and fabricated in InP for 1550-nm wavelength. The IWGH couples the light from an optical fiber, irrespectively of the st ate of polarization, into the InP waveguide and simultaneously focuses it t o a desired position in the waveguide. Conventional IWGH's are strongly pol arization sensitive with a measured 19-dB difference in the incoupling effi ciency between the TE and TM mode. In contrast, although some design parame ters turned out to be slightly in error, the fabricated IWGH's designed for reduced polarization sensitivity exhibited a 3.1-dB difference in the inco upling efficiency between the TE and TM modes.