Fig. 1. (a) BP I with body-center cubic lattice structure; (b) BP II with simple cubic lattice structure; (c) morphology of BP I(110) plane; (d) morphology of BP II(100) plane; (e) reduced morphology of BP I(110) plane; (f) reduced morphology of BP II(100) plane; (g) simplified grating of BP I(110) plane; (h) simplified grating of BP II(100) plane.

Fig. 2. Fabrication process of patterned substrate with periodic OTE grating for large-scale single-crystal BP generation. (a) Two-beam holography lithography based on the substrate with OTE and photoresist; (b) developing; (c) O2 plasma etching; (d) stripping; (e) periodic orientation of liquid crystal molecules induced by grating patterned substrate.

Fig. 3. POM images of S1, S2, and S3 at different alignment conditions. S1 in BP I (a) at homeotropic alignment with polydomain, (b) at parallel alignment with monodomain, and (c) at grating alignment (d=230nm) with single crystal. S2 in BP I (d) at homeotropic alignment with polydomain, (e) at parallel alignment with monodomain, and (f) at grating alignment (d=190nm) with single crystal. S3 in BP II (g) at homeotropic alignment with polydomain, (h) at parallel alignment with monodomain, and (i) at grating alignment (d=170nm) with single crystal. Scale bar: 100μm.

Fig. 4. Surface morphology of gratings, Kossel diagram, and reflection spectra of single crystals. SEM images of gratings were used to align of BP samples (a) S1, (b) S2, and (c) S3. The scale bar is 500 nm. (d) POM image of single crystalline BP I formed by S1. Inset: Kossel diagram of BP I(110); (e) POM image of single crystalline BP I formed by S2. Inset: Kossel diagram of BP I(110); (f) POM image of single crystalline BP II formed by S3. Inset: Kossel diagram of BP II(100). The reflection spectra of (g) S1, (h) S2, and (i) S3.

Fig. 5. Photo images of (a) S1 in BP I, (b) S2 in BP I, and (c) S3 in BP II. Scale bar: 2 mm.