Design of high extinction ratio, low loss, and compact optical modulators and switches based on GST phase change material

Abstract

In this paper, an electrically driven optical modulator and switch based on micro-ring resonators using the phase change material (PCM) of G e 2 S b 2 T e 5 (GST) is designed and their optical properties are investigated. The change in refractive index between two states in PCMs is orders of magnitude larger than conventional electro-optic and free-carrier dispersion effects. These extraordinary variations make PCMs excellent candidates for optical active devices such as modulators and switches. In our design, GST is used as the active material because it is far more stable and results in lower insertion loss compared to other PCMs such as vanadium dioxide ( V O 2 ) (at λ = 1.55 µ m , the imaginary part of the refractive index is 1.49 for GST and 2.53 for V O 2 is their metallic phases). By optimizing the GST dimensions, the device figure of merit is maximized. Three-dimensional finite-difference time-domain simulations show a very high extinction ratio of 37.3 dB with a low insertion loss of 0.427 dB for the proposed modulator and high extinction ratios of 19 dB and 10 dB in off and on states and insertion losses of 1.52 dB and 2.02 dB in off and on states, respectively, of the proposed 1 × 2 switch.

The microstructure and electrical and optical properties of Ge–Cu–Te phase-change thin films

“…As reported by Mahmoodi et al , the device figure of merit is maximized by high extinction ratio resulting from optimizing the thin film dimensions. 64…”

A Review of Silicon‐Based Integrated Optical Switches

“…Compared with previous studies reviewed above, [90,91] both the extinction ratio and insertion loss performances have been improved. In 2021, a 1 × 2 silicon integrated optical switch with GST was further proposed by Mahmoodi et al [96] The structure is shown in Figure 15. In this design, instead of depositing PCM on top of the silicon waveguide [90,91] or adding an additional PCM-loaded waveguide, [94] a sector of the silicon microring is replaced with a GST-filled slot waveguide.…”

“…The SiN layer is used to planarize and protect the silicon surface. A microheater is further added on top of the VO 2 layer laterally, and [96] ).…”

TiN-GST-TiN all-optical reflection modulator for the 2 µm wave band reaching 85% efficiency

“…Moreover, GST demonstrates a decent endurance: about 10 6 cycles (10 11 in phase change memories [36]), which can be improved by doping (N, C, Zn) [37]. However, for the desired spectral region, GSTbased optical modulator is less-explored although rigorously studied for 1.5 µm communication band [38][39][40].…”