Photonic routing is a key building block of many optical applications challenging its development. We report a 2×2 photonic coupler with splitting ratio switchable by a low-voltage electronic signal with 10~GHz bandwidth and tens of nanoseconds latency. The coupler can operate at any splitting ratio ranging from 0:100 to 100:0 with the extinction ratio of 26 dB in optical bandwidth of 1.3 THz. We show sub-nanosecond switching between arbitrary coupling regimes including balanced 50:50 beam splitter, 0:100 switch, and a photonic tap. The core of the device is based on Mach-Zehnder interferometer in a dual-wavelength configuration allowing real-time phase lock with long-term sub-degree stability at single-photon level. Using the reported coupler, we demonstrate for the first time the perfectly balanced time-multiplexed device for photon-number-resolving detectors and also the active preparation of a photonic temporal qudit state up to four time bins. Verified long-term stable operation of the coupler at the single photon level makes it suitable for wide application range in quantum information processing and quantum optics in general.
@article{arxiv.1905.08431,
title = {Fully tunable and switchable coupler for photonic routing in quantum detection and modulation},
author = {Vojtěch Švarc and Martina Nováková and Glib Mazin and Miroslav Ježek},
journal= {arXiv preprint arXiv:1905.08431},
year = {2019}
}