Design, fabrication, and evaluation of a multichannel diffractive optic rotary joint

A multichannel diffractive optic rotary joint was designed, fabricated by e lectron-beam Lithography, and evaluated with regard to cross talk and to ou tput signal power variations. High cross-talk margin (>25 dB) and low outpu t signal power variations (<2 dB) were achieved. The sensitivity to input-l ight-beam wavelength uncertainty was investigated. Two design examples are presented. The first design eliminates cross talk due to unwanted diffracti on orders and shows that for a ten-channel joint the wavelength uncertainty of an 850-nm emitting laser must be less than 8 nm. In the second design c ross talk due to the second diffraction order is permitted, which results i n a tolerance level that is three times better for wavelength uncertainty. (C) 1999 Optical Society of America. OCIS codes: 050.1970, 220.0220, 220.37 40, 230.0230.