Fig. 1. Sketch of plasma waveguide and corresponding radiated field. (a) Sketch of plasma waveguide; (b) electric field component at t0=60T0 after interaction of driven laser and plasma waveguide; (c) kx×ky Fourier spectrum of radiated harmonics

Fig. 2. Corresponding 1D Fourier spectra of the radiated electric fields

Fig. 3. Polarization states of generated high-order harmonics. (a) Ellipticity kx×ky distribution of radiated harmonics; (b) variation of electric field intensity of 6^th harmonic along direction of x; (c) variation of electric field intensity of 9^th harmonic along direction of x

Fig. 4. Electron dynamic behaviors after interaction of driving laser and plasma waveguide. (a) Two-dimensional distribution of plasma electron density at t0=36T0; (b) electron spectrum at t0=36T0; (c) spatial distributions of electron longitudinal momentum (px) and transverse momenta (py and pz) at t0=36T0

Fig. 5. Parameter scanning results of key features of high-order harmonics. (a) Conversion efficiency factor p of HHG; (b) ellpticity of 9^th harmonic as a function of similarity parameterS