Physical systems with discrete energy levels are ubiquitous in nature and are fundamental building blocks of quantum technology. Realizing controllable artificial atom-and molecule-like systems for light would allow for coherent and dynamic control of the frequency, amplitude and phase of photons. In this work, we demonstrate a photonic molecule with two distinct energy-levels and control it by external microwave excitation. We show signature two-level dynamics including microwave induced photonic Autler-Townes splitting, Stark shift, Rabi oscillation and Ramsey interference. Leveraging the coherent control of optical energy, we show on-demand photon storage and retrieval in optical microresonators by reconfiguring the photonic molecule into a bright-dark mode pair. These results of dynamic control of light in a programmable and scalable electro-optic platform open doors to applications in microwave photonic signal processing, quantum photonics in the frequency domain, optical computing concepts and simulations of complex physical systems.

Electro-optic phase modulators are critical components in modern communication, microwave photonic, and quantum photonic systems. Important for these applications is to achieve modulators with low half-wave voltage at high frequencies.Here we demonstrate an integrated phase modulator, based on a thin-film lithium niobate platform, that simultaneously features small on-chip loss (∼ 1 dB) and low half-wave voltage over a large spectral range (3.5 -4.5 V at 5 -40 GHz). By driving the modulator with a strong 30-GHz microwave signal corresponding to around four half-wave voltages, we generate an optical frequency comb consisting of over 40 sidebands spanning 10 nm in the telecom L-band. The high electro-optic performance combined with the high RF power-handling ability (3.1 W) of our integrated phase modulator are crucial for future photonics and microwave systems.

This article introduces the design process of a 220 GHz subharmonic mixer with low conversion loss, which is comprised of a pair of anti-parallel Schottky diodes (SBD). For terahertz circuits, the wavelength of the electromagnetic (EM) wave is very close to the size of devices, which results in complicated parasitic effects. This will leads to a very limited optimization space for circuits design when matching the impedance. To solve this problem, we developed the precise 3D EM planar SBD model and the field-circuit co-simulation method to design this terahertz mixer. The diodes are mounted on the quartz-based suspended microstrip line.The measured results show that the single side band conversion loss is less than 12 dB during radio frequency (RF) range from 211 to 226 GHz and the minimum loss is about 5.9 dB. With the intermediate frequency fixed at 1 GHz, the conversion loss varies from 8 dB to 11.2 dB over the RF bandwidth of 211 to 221 GHz. The mixer can be applied in heterodyne receivers of terahertz systems.

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