Optical anti-parity-time symmetry
Phys. Rev. Lett. 123, 193604 (2019)
Mirrorless optical parametric oscillation
Phys. Rev. Lett. 119, 150406 (2017)
Based on the EIT-enhanced backward four-wave mixing process in cold atoms, we demonstrate narrow-band Mirrorless optical parametric oscillation (MLOPO) with a tunable threshold. The pump threshold can be tuned by varying the operating parameters: the pump detuning, the coupling laser power, and the atomic density. We achieved a pump threshold as low as 15 μW, which approaches the lowest record of OPO. Our theoretical analysis reveals that with larger OD and smaller dephasing rate, the pump threshold can be further suppressed. Compared with other schemes, our method greatly reduces system complexity without degrading the performance. We also study the normalized two-photon correlation between Stokes and anti-Stokes photons and confirm its transition from non-classical biphoton regime to the classical coherent state regime.
Quantum heat engine
Phys. Rev. Lett. 119, 050602 (2017)
We construct a nontraditional quantum heat engine using electromagnetically induced transparency effect. By making use of quantum interference, we are able to break the symmetry of photon absorptive and emissive cross-section, thus enabling the system to absorb photons from a “thermal” reservoir, with wide spectrum and random wave vector, and convert them into “work”, which has a certain direction of radiation and with an ultra-narrow spectrum. There are some unique properties of this quantum heat engine. One is that the emissivity at central frequency is 9 times greater than that of a blackbody at the same ambient temperature, indicating the violation of Kirchhoff’s law. In addition, the temperature of cold reservoirs can be even higher than hot reservoirs, which is not allowed in classical heat engines.