Abstract
This paper reports on the design optimization of compact optical ON-OFF switches based on a GST-clad silicon rib waveguide and compares it to a GST-clad silicon nanowire at the telecommunication wavelength 1.55 µm. Effective index and modal loss of the quasi-TE modes are calculated by a full-vectorial H-field finite element method. It shows that the electro-refraction effect-based switch may not be viable because of the higher modal loss in the GST crystalline state. On the other hand, the larger modal loss difference between GST amorphous and crystalline states would be more suitable for an electro-absorption type switch design. The effect of silicon slab thickness, silicon core width, and GST layer thickness for both the waveguides are presented. As the presence of the GST layer modifies the mode field profiles, so the incurring coupling loss at the butt-coupled junctions between the input/output silicon waveguide and Si-GST waveguide are also calculated by using the least squares boundary residual method. These results show that the GST-clad silicon rib waveguide with a 500-nm-wide silicon core, 60-90 nm thick silicon slab, and 15-25 nm thick GST layer is the optimal self-sustained switch design. In this case, a very compact, 2-5 µm long device is expected to show an extinction ratio of more than 20 dB with the total insertion loss of only 0.36 dB.
Highlights
Miniaturization of photonic devices can have a significant contribution towards achieving the large-scale photonic integrated circuit (PIC)
Carrier depletion, which modulates carrier density by reverse biasing the junction, is relatively fast and consumes less power as little current flows through the junction. It requires a higher overlap between the PN junction and the optical field, which leads to a larger insertion loss due to the initial doping of PN junction and lower modulation efficiency due to the small change in depletion width
We focus on the design optimization of a compact electro-optic ON-OFF switch based on a GST-clad silicon rib waveguide and a GST-clad silicon nanowire waveguide at the telecommunication wavelength 1.55 μm is presented
Summary
Miniaturization of photonic devices can have a significant contribution towards achieving the large-scale photonic integrated circuit (PIC). Carrier depletion, which modulates carrier density by reverse biasing the junction, is relatively fast and consumes less power as little current flows through the junction It requires a higher overlap between the PN junction and the optical field, which leads to a larger insertion loss due to the initial doping of PN junction and lower modulation efficiency due to the small change in depletion width. The phase change material (PCM), which provides a large difference in real and imaginary parts of refractive index between two stable and reversible states, can be used to mitigate some of. These problems encountered by the free-carrier based modulators [1]. The least squares boundary residual (LSBR) method, a rigorous junction analysis approach, is used to calculate the coupling loss at the butt-coupled junctions to determine the optimal waveguide parameters in order to achieve a lower insertion loss and a higher extinction ratio of a self-sustained switch
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