Holographic optical switching: The "ROSES" demonstrator

The design, assembly, and performance of a prototype 1 x 8 free-space switch demonstrater using reconfigurable holograms are reported. Central to the switch fabric is a ferroelectric liquid crystal (FLC) on silicon spatial light modulator (SLM) deposited with a 540 X 1 array of highly reflective and planar mirror strips. The input and output ports of the switch are fabricated as a linear array of silica planar waveguides connected to single-mode fibers, and the holographic beam-steerer operates without the need for adjustment or dynamic alignment. The waveguide array and the single Fourier transform lens for the 2f holographic replay system are housed in an opto-mechanical mount to provide stability, The switch operates at 1.55 mum wavelength and has a designed optical bandwidth of >60 nm, The first measured insertion loss and crosstalk figures are 16.9 dB and -19.1 dB, respectively. Improvements in SLM performance, the use of new addressing schemes and the introduction of better alignment techniques are expected to improve these figures considerably. The preliminary performance of a 3 x 3 optical crossconnect is also presented to show that this technology is scalable to N x N switching fabrics.