Integration all-optical switching in χ⁽²⁾ microdisks for quantum applications

We propose a quantum switch for telecom-band applications that is composed of a χ⁽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-μm-thick, 10 μm radius GaAs microdisk with an intrinsic Q of ∼10⁸ and a fiber-cavity-coupling Q of ∼10⁴ can achieve low-loss (≲1%) switching for gigahertz-rate O-band quantum signals with milliwatt-peak-power pumps in the C band.