Focused ion beam lithography of multiperiod gratings for a wavelength-division-multiplexed transmitter laser array

Wavelength-division multiplexing with closely spaced multiple wavelengths is of great interest for high-capacity data transmission. One major acid very critical requirement of such a system is the fabrication of a laser array with very small wavelength separations (similar to 2 nm). In this paper, the design, fabrication, and performance of an integrated eight-channel system is described. Focused ion beam lithography, with the beam deflection sensitivity modified from its calibrated value, is used to write the critical stepped-period distributed-Bragg-reflector gratings required to provide the tightly controlled multiple laser frequencies. The outputs of the lasers are combined via curved waveguides into a single optical output.