An optical triode switch using phase change material (PCM) operating as a Mach-Zehnder interferometer (MZI) or as a directional coupler (DC) is proposed. The characteristics of optical triode switches are calculated by using finite-difference time-domain (FDTD) method. Ge2Sb2Te5 (GST) and Ge2Sb2Se4Te1 (GSST) are used as the PCM. In our calculation models, the signal light has a wavelength of 1550 nm, and the phase of the PCM is controlled by light with a wavelength of 1300 nm input into additional waveguides. In the MZI-type triode switch, PCM patches are laid on several crossings between the signal waveguides and the control waveguides. The DC-type triode switch consists of three parallel waveguides, and the control light is input to the center waveguide which has the PCM layer on it. The structures are optimized to have low loss and low crosstalk. In addition, the energy and pulse power required to change the phase are estimated for both types of switches.
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