Abstract

A scalable and reconfigurable on-chip optical true time delay line consisting of Mach–Zehnder interferometer (MZI) switches and delay waveguides is proposed and demonstrated with the ultra-low-loss silica waveguide platform. The MZI switches provide the reconfiguration of the light traveling paths and hence different delays. Our proposed structure can be easily scaled to an $M$ bit delay line with a slight increase in dimensions. The footprint of our fabricated 1 bit delay line is $33\mathrm{mm}\times 13\mathrm{mm}$ ($\text{length}\times \text{width}$) and can provide a delay of 6.0 ps with an insertion loss of 1.2 dB at the operating wavelength of 1550 nm, while the footprint of the 4 bit delay line is $43\mathrm{mm}\times 14\mathrm{mm}$ and can provide a discrete delay tuning from 6.0 to 90.2 ps with a delay deviation lower than 0.2 ps and a tuning response time of 0.84 ms. The insertion losses are lower than $\sim 2.34\mathrm{dB}$, and the extinction ratios are greater than 20.42 dB. The average switching power is $\sim 132.6\mathrm{mW}$. Our proposed optical true time delay lines could find applications for optical beamforming in phased array antennas.

© 2018 Optical Society of America

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