Interaction-free all-optical switching in chi(2) microdisks for quantum applications.

We propose a quantum switch for telecom-band applications that is composed of a chi((2)) microdisk coupled to two fibers (or waveguides). The idea is to apply a pump pulse to shift the microdisk out of resonance, thereby switching the device between the cross and bar states in an interaction-free manner. As an example, a 2.5-microm-thick, 10 microm radius GaAs microdisk with an intrinsic Q of approximately 10(8) and a fiber-cavity-coupling Q of approximately 10(4) can achieve low-loss (< or approximately equal to 1%) switching for gigahertz-rate O-band quantum signals with milliwatt-peak-power pumps in the C band.