Optical-microwave mixing schemes revealing QED vacuum nonlinearity

This paper presents several new wave-mixing schemes revealing QED vacuum nonlinearity, including third harmonic generation in high-Q microwave cavities and quasi-optical resonators, and combinative frequency generation due to coupling of microwave and optical fields when laser beams are passing though a microwave cavity. Results are compared to noise floor levels. This work shows that the present powerful laser and microwave electronics facilities are not far from those needed for the vacuum nonlinearity observation based on the proposed combined schemes.