Explore and demonstrate strong acousto-optic interactions at multi-GHZ frequencies for a wide variety of applications

As the spectacular success of Laser Interferometer Gravitational-Wave Observatory (LIGO) has shown, optical cavity interferometry provides unparalleled sensitivity and is usually the method of choice for detecting weak signals. By designing efficient transducer platforms, a given perturbation can be mapped onto an optical cavity and measured close to fundamental detection limits. This project aims to develop novel receivers for very weak Radio Frequency (RF) signals (such as those encountered in, quantum computers, MRI, radio astronomy, radar, and even cell phone reception in indoor environments) based on integrated piezoelectric platforms.
As has been mentioned, weak RF signal detection is needed in quantum computers. Quantum computing platforms continue to be developed. Every physical system has fundamental limitations and a hybrid systems approach. For implementing large-scale error-corrected quantum computers and highly functional repeater-based quantum networks we need to combine the desirable properties of multiple physical systems. Such hybrid platforms require quantum transducers that can provide efficient quantum interfaces between the different physical platforms, which may operate at very different frequencies and in different physical environments. Piezoelectric optomechanical platforms represent one of the most promising routes toward achieving quantum transduction of photons between the microwave and optical frequency domains. The piezoelectric effect allows us to efficiently excite a localized mechanical mode of an opto-mechanical cavity. By engineering the cavity to support an optical mode that is strongly coupled to the mechanics, we can use the optical mode to pick up the displacement induced perturbation and thus the RF signal. This task captures the interface problems which have transition frequencies in the 1 GHz to 10 GHz frequency range, and telecom optical frequencies (near 194 THz). In recent years, some efficient quantum frequency converter, using nonlinear guided wave interactions, has been demonstrated between photons in the optical frequency domain, but these ideas cannot be directly applied to the microwave-to-optical problem because of the disparity in the frequencies (and corresponding wavelengths). To give some perspective, the free space wavelength of a 3 GHz microwave photon is 10 cm, but for the telecom-band, optical photon is 1.55 um. This size disparity makes it challenging to achieve strong Kerr-type nonlinearities for photon conversion. Piezoelectric optomechanical approaches partially have solved this size mismatch problem by converting the microwave signal into a mechanical mode that can now have the same wavelength as the optical signal.
Our goal is to understand the fundamental limits of conversion efficiency in RF to optical signal transducers (optical modulators) and detection efficiency in these RF-optical receivers. To be efficient and cost-effective we need to propose appropriate geometries and materials via strong confinement and high-quality factor. In this work, in addition to fabrication and measurement developments, we require both fundamental knowledge and detailed simulation capabilities that address the multiple physical processes involved
This project falls within the EPSRC Quantum Technologies research areas.
Any companies or collaborators involved: None