Fig. 1. Schematic of the stack structure of the SNSPD with a Si slot and Ag reflector. The region surrounded by the dashed line indicates the unit cell for the numerical simulation. The pitch of the unit cell, the length of the cavity, and the width of the nanowire are denoted by P, L, and W, respectively. The direction of the incident light is shown by the black arrow, and the polarization directions of TM and TE waves are marked.

Fig. 2. Distributions of the electric field intensity in the Si-HSQ-Si slot (picture above) and that in the Ag-HSQ-Ag slot (picture below). The incident light is TM polarized, the pitch is 486 nm, and the width of the nanowire is 80 nm.

Fig. 3. Distributions of the electric field intensity in the Si-HSQ-Si slot (picture above) and that in the Ag-HSQ-Ag slot (picture below). The incident light is TE polarized, the pitch is 682 nm, and the width of the nanowire is 80 nm.

Fig. 4. Simulated pitch dependence of the optical absorptance in the nanowire. The dashed blue, solid blue, dashed red, and solid red lines represent the Ag-HSQ-Ag slot with TM incident waves, Ag-HSQ-Ag slot with TE incident waves, Si-HSQ-Si slot with TM incident waves, and Si-HSQ-Si slot with TE incident waves.

Fig. 5. Simulated cavity length dependence of the optical absorptance in the nanowire. The dashed blue, solid blue, dashed red, and solid red lines represent the Ag-HSQ-Ag slot with TM incident waves, Ag-HSQ-Ag slot with TE incident waves, Si-HSQ-Si slot with TM incident waves, and Si-HSQ-Si slot with TE incident waves.

Fig. 6. Simulated pitch dependence of the optical absorptance in the nanowire when the cavity lengths are different, and the nanowire width is fixed to 80 nm. (a) The incident light is TM polarized. (b) The incident light is TE polarized.

Fig. 7. Simulated nanowire width dependence of the optical absorptance in the nanowire. The cavity length is fixed to 200 nm. For TM waves, the pitch is 486 nm. For TE waves, the pitch is 682 nm.

Fig. 8. Simulated polarization dependence of the absorption efficiency in the polar coordinate system. The angle is defined as the angle between the polarization direction and the direction perpendicular to the nanowire. The cavity length is 200 nm, and the nanowire width is 80 nm. (a) The pitch is 682 nm. (b) The pitch is 486 nm.

Fig. 9. Simulated PER dependence on the pitch when the nanowire widths are different, and the cavity length is fixed to 200 nm. (a) The incident light is TM polarized. (b) The incident light is TE polarized.