Fig. 1. Optical layout of the exposure system. ${\mathrm{L}}_{1–2}$, collimating lens; Sub, photoresist-covered substrate.

Fig. 2. Phase locking loop.

Fig. 3. SEM photographs of the gratings made when (a) $s=0$, (b) $s=0.01\mathrm{mm}$, (c) $s=0.1\mathrm{mm}$, and (d) $s=1\mathrm{mm}$.

Fig. 4. Surface appearances of the gratings made when (a) $s=0$, (b) $s=0.01\mathrm{mm}$, (c) $s=0.1\mathrm{mm}$, (d) $s=1\mathrm{mm}$, and (e) the bare substrate. The arrowheads show the direction of the grating grooves.

Fig. 5. SEM photographs of the gratings made when (a) $s=0$, (b) $s=0.01\mathrm{mm}$, (c) $s=0.1\mathrm{mm}$, and (d) $s=1\mathrm{mm}$.

Fig. 6. Surface appearances of the gratings made when (a) $s=0$, (b) $s=0.01\mathrm{mm}$, (c) $s=0.1\mathrm{mm}$, (d) $s=1\mathrm{mm}$, and (e) the bare substrate. The arrowheads show the direction of the grating grooves.

Fig. 7. SEM photographs of the gratings made when (a) $s=0$, (b) $s=0.1\mathrm{mm}$, (c) $s=0.4\mathrm{mm}$, and (d) $s=1\mathrm{mm}$.

Fig. 8. Surface appearances of the gratings made when (a) $s=0$, (b) $s=0.1\mathrm{mm}$, (c) $s=0.4\mathrm{mm}$, (d) $s=1\mathrm{mm}$, and (e) the bare substrate. The arrowheads show the direction of the grating grooves.

Fig. 9. Optical path to observe the stray light of gratings.

Fig. 10. Stray light of gratings. (a) $s=0$, and the photoresist thickness was 250 nm. (b) $s=0.1\mathrm{mm}$, the photoresist thickness was 140 nm, and shifting was along the grating vector. (c) $s=0.1\mathrm{mm}$, the photoresist thickness was 250 nm, and shifting was along the grating vector. (d) $s=0.4\mathrm{mm}$, the photoresist thickness was 250 nm, and shifting was along the grating grooves. The light spots were recorded by the CCD camera with the same exposure time and gain.

Table 1. Stray Light Levels