Abstract
We present a technique to realize arbitrary optical transfer functions
based on the use of delay lines and optical waveguide couplers. In particular,
this technique is a modification of an optical transversal filter. Following
this technique, the transfer function is expressed as a truncated Fourier
series with the tap coefficients that are either purely real or purely imaginary.
The output ports of an optical waveguide coupler, conveniently and precisely,
provide a transmission function that is either purely real or purely imaginary
and thus, fit perfectly for the experimental realization of such transfer
functions. The use of simple components, such as couplers and delay lines,
alleviates the need for bulky electro-optic phase shifters and reduces the
complexity of the integration process. To exemplify this approach, an optical
field differentiator is implemented. Moreover, the effect of the practical
aspects such as frequency dependence of the refractive index and variations
of the coupling ratios of optical waveguide couplers, on the resulting transfer
function are analytically investigated.
© 2012 IEEE
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