Acousto-optic switch with a near rectangular passbandfor WDM systems

The authors describe the most rectangular passband yet reported for an acousto-optic wavelength-routing switch. The device is a multicycle SAW directional-coupler-weighted AOTF, fabricated on XY lithium niobate, with a –3 dB width of 2.52 nm and a –20 dB width of 0.89 nm. For comparison, an ideal apodised AOTF with the same 3 dB width would have a –20 dB width of only 0.33 nm.