Fig. 1. Working principle of BOCs and polarization-independent reflector structure. (a)(b) Schematic and top view of on-chip integrated BOCs based on the TFLN photonic platforms, the solid and dashed lines indicate wavelengths of 1560 nm and 780 nm, respectively; (c) structural schematic diagram of TFLN polarization-independent reflector

Fig. 2. Simulation analysis of characteristics of TE₀ and TM₀ modes and optical power reflection spectra of TFLN ridge waveguide based on modulation width ΔW. (a) Simulated effective refractive indices of TE₀ and TM₀ of the TFLN ridge waveguide, insets show electric field profiles of TE₀ (upper) and TM₀ (lower) modes; (b)(c) simulated optical power reflection spectra when the inputs are TE₀ and TM₀ modes, respectively; (d) calculated 3 dB bandwidth and peak reflection versus the modulation width (ΔW)

Fig. 3. Impact of variations in waveguide and grating structure parameters on the optical power reflection spectra. (a) Waveguide width; (b) unetched thickness; (c) sidewall angle; (d)(e) duty cycle and grating period; (f) impact of the number of grating periods on the peak reflectivition

Fig. 4. Device fabrication. (a) Device layout for exposure with positive photoresist, with the dashed-line box highlighting the asymmetric Bragg grating region; (b)(c) optical microscope images of the fabricated 2×2 directional coupler and asymmetric Bragg grating, respectively

Fig. 5. Characterization of device performance. (a) Schematic diagram of the transmission curve measurement system; (b)(c) simulation results of transmission spectra for input TE₀ and TM₀ modes; (d)(e) total transmission curves for TE₀ and TM₀ modes