High-Q THz Fano Metamaterial Interacting With Vacuum Electron

By manipulating Fano resonance in metallic metamaterial, trapping and releasing of electromagnetic wave can be controlled. Simply, by varying the size of structural asymmetry to the proposed metallic slit structure, Q factor of trapped mode in metallic metamaterial can be tailored. We show that optimizing the electromagnetic property of Fano metamaterial can maximizes the interaction between convection electron and trapped mode, which gives significantly high efficiency of Cerenkov radiation larger than one from the ordinary Cerenkov and Smith-Purcell effects by order of two. We also observed inversion of the spectral asymmetry and the phase shift of high-Q trapped modes in subwavelength slits by manipulating the direction of the structural asymmetry of unit cell paving the way for full control of Fano resonances This finding is thought to be useful for many other potential applications other than Cerenkov lasing such as sensing and optical switching.