Two-dimensional beam-steering device using a doubly periodic Si photonic-crystal waveguide

Abstract

We demonstrate a nonmechanical, on-chip optical beam-steering device using a photonic-crystal waveguide with a doubly periodic structure that repeats the increase and decrease of the hole diameter. We fabricated the device using a complementary metal-oxide-semiconductor process. We obtained a beam-deflection angle of 24° in the longitudinal direction, while maintaining a divergence angle of 0.3°. Four such waveguides were integrated, and one was selected by a Mach-Zehnder optical switch. We obtained lateral beam steering by placing a cylindrical lens above these waveguides. By combining the lateral and longitudinal beam steering, we were able to scan the collimated beam in two dimensions, with 80 × 4 resolution points.

Wavelength-division multiplexing Si photonic crystal beam steering device for high-throughput parallel sensing

“…Compared with a shallow-etched diffraction grating, the BPCW does not require precise etch depth control, so high fabrication tolerance is expected. Furthermore, due to light radiation into the air, the hole diameter was modulated as 2r 1 = 2r 0 + Δr and 2r 2 = 2r 0 − Δr with a double period of twice the lattice constant a of the photonic crystal along the light propagation direction, similar to that in [14]. The light radiation coefficient can be controlled by the hole radius difference, Δr = r 1 − r 2 , and an appropriate radiating aperture length was obtained.…”

“…The radiation coefficient α rad in Fig. 2(e) was optimized for a BPCW length of 1.4 mm by using the method described in [14]. The coefficient varies significantly with a small change in Δr and can be adjusted within the range 20-200 dB/cm.…”

“…The coefficient varies significantly with a small change in Δr and can be adjusted within the range 20-200 dB/cm. From the calculation result given in [14], if we set α rad = 100 dB/cm, the loss due to light scattering inside the fabricated BPCW with some disordering (α scat = 35 dB/cm is assumed), and light passing through without radiation from the BPCW, can be reduced to 1 dB or less; furthermore, it is possible to suppress the longitudinal divergence angle δθ (full width at half maximum) to <0.09°. If the waveguide length L is set to extend to 3 mm, it is possible to suppress δθ to <0.04°.…”

“…4(a). The fan-shaped beam spread in the φ-direction can be collimated to a spot beam by aligning a cylindrical lens above the chip in the direction along the waveguide [14]. Figure 4(f) shows the spot beam collimated with a rod lens with a diameter of 5 mm and a focal length f = 3.8 mm for various wavelengths.…”

High-efficiency end-fire 3D optical phased array based on a multi-layer Si3N4/SiO2 platform

“…The traditional way in on-chip integrated photonic research usually utilizes the single waveguide layer structure, which is also the case of most studies on OPA. For example, in [1][2][3][4][5][6][7][8], the device structure could be sophisticated due to various requirements, while all containing only one waveguide layer, and because of this, the OPA formed by a single layer can only have the exit beam upward. This actually is the reason of the relatively low emitting efficiency.…”