Microwave signals are ubiquitous in wireless communications but interact too weakly with photons. A technique was developed to fabricate high-performance optical microstructures using lithium niobate, a material with powerful electro-optic properties. The new integrated photonics platform can store light and electrically control its frequency (or color) in an integrated circuit. The platform draws inspiration from atomic systems and could have a wide range of applications including photonic quantum information processing, optical signal processing, and microwave photonics.
Many quantum photonic and classical optics applications require shifting of optical frequencies, which has been difficult. Not only can the frequency be changed in a controllable manner, but this new ability can be used to store and retrieve light on demand, which has not been possible before.
The researchers previously demonstrated the ability to propagate light through lithium niobate nano-wave-guides with very little loss and control light intensity with on-chip lithium niobate modulators. In the latest research, they combined and further developed these technologies to build a molecule-like system and used this new platform to precisely control the frequency and phase of light on a chip.
The unique properties of lithium niobate, with its low optical loss and strong electro-optic nonlinearity, provide dynamic control of light in a programmable electro-optic system. This could lead to the development of programmable filters for optical and microwave signal processing and will find applications in radio astronomy, radar technology, and more.
Next, the researchers aim to develop even lower-loss optical waveguides and microwave circuits using the same architecture to enable even higher efficiencies and, ultimately, achieve a quantum link between microwave and optical photons. The energies of microwave and optical photons differ by five orders of magnitude, but the new system could possibly bridge this gap with almost 100 percent efficiency, one photon at a time. This would enable the realization of a quantum cloud — a distributed network of quantum computers connected via secure optical communication channels.