THz wave generation from cesium vapor

Applications of THz photonics rely critically on efficient THz wave generation and detection. Here we report THz radiation from cesium and rubidium vapor plasma. By taking advantage of the very low ionization potential of cesium (3.89 eV) and rubidium (4.18 eV), we are able to produce a THz wave with an amplitude more than 8 times higher than nitrogen gas at the same pressure, showing the promise of using cesium/rubidium vapor for potential THz photonic applications. Our demonstration now opens the door towards THz air photonics based upon metallic vapors.