A chopped quantum-well polarization-independent interferometric switch at 1.53 mu m

We have theoretically designed and realized a phase shifter for a low-loss Mach-Zehnder interferometric switch. The phase shifter is based on 0.85% te nsile strained InGaAs-InP chopped quantum-well material. We realized a Mach -Zehnder interferometric snitch with polarization-independent switching vol tages as low as 3.3 +/- 0.05 V at 1525 nm for a switch with a 4-mm-long pha se-shifting section. The wavelength sensitivity of the switch is 0.036 V/nm for TE and 0.053 V/nm for TM polarization. Calculations of the electro-ref raction in the -0.85% strained chopped quantum-wed (QW) material based on t he 4 x 4 Luttinger-Kohn Hamiltonian show that the electro-refraction due to the quantum-confined Stark effect (QCSE) for TM polarization is equal to t he sum of the mutually comparable QCSE electro-refraction and the Pockels e ffect for TE polarization in waveguides along the [1(1) over bar 0] axis. O ur first-principle model for calculating the electro-refraction is an accur ate design tool for predicting device performance in complicated layer stru ctures. The shortest possible phase shifter with a <-25 dB crosstalk penalt y due to electro-absorption unbalance can be as short as 2.2 mm. This compa ct switch is predicted to have a 6-V switching voltage and a 15-nm window f or polarization-independent switching with a <-25-dB crosstalk penalty. Wit h a slight increase of the strain, this chopped QW material can be used for polarization independent switching around 1550 nm.