Demonstration of beam steering using a passive silica optical phased array with wavelength tuning

Abstract

We demonstrate beam steering using a passive silica optical phased array (OPA) with wavelength tuning. In this OPA, a constant path difference is built up to assign sequential phase delays with a wavelength variation in arrayed waveguide channels for the beam steering. From as-fabricated 1 × 101 passive silica OPA chips, we successfully achieved beam forming with a transversal divergence angle of 0.57° at a 1548.3-nm wavelength and also beam steering of 15.4° by wavelength tuning of 30.7 nm. Combining a cylindrical lens in front of the end-fire radiators, the longitudinal divergence angle could be reduced from 13.0° to 0.42°. The side-mode suppression ratio of the beam was 10.3 dB at the center position. Through simulation, we analyzed the effects of the phase errors on the beam quality, due to the effective index fluctuation of the waveguide channels, and provided an allowable error range to attain beam forming from the passive OPA.

Demonstration of wireless data transmission using passive silica optical phased array

“…This was the case when the cylindrical lens was combined with the OPA. When we characterized the beam divergence angle for the case without the lens, the trend was similar to our previous results [9], showing 0.58 in the transversal direction and 13.3 in the longitudinal direction.…”

“…For the optical power received at a distance of 5 m, the maximum value was -12.5 dBm at a wavelength of 1548.51 nm, and the minimum value was -15.4 dBm at 1563.05 nm. The difference in the received power following the phase difference was because there was a degradation of beam intensity as the beam moves from center to maximum beam steering angle like our previous study [9]. .…”

“…Such a large-scale Si-OPA, however, has fundamental issues like the complexity of active phase control and high insertion loss [6], which limits further improvements in data transmission performances. For this reason, OPA based on other photonic platforms such as silicon nitride [7], polymer [8], and silica [9] has also been actively studied in recent years. Among them, silica-based OPA is capable of passive beam steering with wavelength tuning even in hundreds of channels [9], making it a suitable solution for long-distance high-speed wireless data transmission with low insertion loss and simple phase control.…”

“…For this reason, OPA based on other photonic platforms such as silicon nitride [7], polymer [8], and silica [9] has also been actively studied in recent years. Among them, silica-based OPA is capable of passive beam steering with wavelength tuning even in hundreds of channels [9], making it a suitable solution for long-distance high-speed wireless data transmission with low insertion loss and simple phase control. In this paper, we demonstrate an optical wireless transmission using a passive silica OPA capable of beam-steering with wavelength tuning.…”

Photonic Integrated Circuits for an Optical Phased Array

“…However, due to that active phase shifters no longer exist, this approach is much more susceptible to phase errors resulting from fabrication imperfections. To improve fabrication tolerance and mitigate the impact of phase errors, low-index materials, like silicon nitride and silica, are commonly employed as waveguide materials in passive OPAs [10,103].…”