A Phased, Optical, Coupler-Pair Switch

A number of methods 1-4 have been suggested for realizing optical switches in integrated optical format; in many cases, the schemes are extensions of the microwave art. 5,6 Recently, Papuchon et al.7 and Campbell et al.8 obtained switching by perturbing the phase synchronism in indiffused strip-guide directional couplers of about one coupling period in length. Kogelnik et al.9 have proposed a switch consisting of tandem couplers with adjustable phase mismatch between guides in each coupler. This approach results in relaxed dimensional tolerances over previously described coupler switches. However, the adjustment of phase mismatch in both couplers is required to switch between states. In this paper, we propose and analyze an optical switch consisting of directional coupler pairs with an intermediate phase-compensating network. We show that the switching between states can be achieved by a x change in the intermediate phase shift providing that each 767 coupler has been initially adjusted for hybrid performance, i.e., for 3-dB coupling. Prior to adjustment, the coupling strengths are required to be 3 dB or stronger, implying coupler lengths of £ to basic coupling periods.