1.6:1 bandwidth two-layer antireflection structure for silicon matched to the 190–310  GHz atmospheric window

Antireflection Structure Design Parameters^a

^a We fabricated three AR treatments for silicon ($n_{\mathrm{Si}}=3.42$): a single layer of posts, a single layer of holes, and a layer of rotated posts above a layer of holes. All features are squares of size $s$ in a square grid with $\mathrm{\Lambda }=125\mathrm{\mu m}$ spacing. All layer thicknesses, $t$, are one quarter wavelength at the target bandpass’ center frequency of ${\nu }_0=250\mathrm{GHz}$.

Dimensions of One-Layer AR Structures^a

^a We compare the design and measured (by SEM) dimensions for the two one-layer single-sided wafers. The top and base dimensions of the posts and holes are the width at the top of the structures (toward vacuum) and at the base (toward bulk silicon), respectively. All layers use a 125 μm cell size (grid spacing).

Dimensions of Two-Layer AR Structure^a

^a We compare the design and measured (by SEM) dimensions on each face of the cleaved wafer. The top and base dimensions of the posts and holes are the width at the top of the structures (toward vacuum) and at the base (toward bulk silicon). The letters (B, C, T1, T2) refer to the dimensions in Fig. 4. All layers use a 125 μm cell size (grid spacing; dimension A). The thickness of the wafer is 996 μm, which is within the range provided by the manufacturer Waferpro ($1000\pm 10\mathrm{\mu m}$).

Table 1.

Antireflection Structure Design Parameters^a

^a We fabricated three AR treatments for silicon ($n_{\mathrm{Si}}=3.42$): a single layer of posts, a single layer of holes, and a layer of rotated posts above a layer of holes. All features are squares of size $s$ in a square grid with $\mathrm{\Lambda }=125\mathrm{\mu m}$ spacing. All layer thicknesses, $t$, are one quarter wavelength at the target bandpass’ center frequency of ${\nu }_0=250\mathrm{GHz}$.

Table 2.

Dimensions of One-Layer AR Structures^a

^a We compare the design and measured (by SEM) dimensions for the two one-layer single-sided wafers. The top and base dimensions of the posts and holes are the width at the top of the structures (toward vacuum) and at the base (toward bulk silicon), respectively. All layers use a 125 μm cell size (grid spacing).

Table 3.

Dimensions of Two-Layer AR Structure^a

^a We compare the design and measured (by SEM) dimensions on each face of the cleaved wafer. The top and base dimensions of the posts and holes are the width at the top of the structures (toward vacuum) and at the base (toward bulk silicon). The letters (B, C, T1, T2) refer to the dimensions in Fig. 4. All layers use a 125 μm cell size (grid spacing; dimension A). The thickness of the wafer is 996 μm, which is within the range provided by the manufacturer Waferpro ($1000\pm 10\mathrm{\mu m}$).