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Showing posts with label backward wave radiation. Show all posts
Showing posts with label backward wave radiation. Show all posts
Backward terahertz radiation can be produced by a high-intensity laser normally incident upon an underdense plasma. It is found that terahertz radiation is generated by electrons refluxing along the bubble shell. These shell electrons have similar dynamic trajectories and emit backward radiations to vacuum. This scheme has been proved through electron dynamic calculations as well as by using an ionic sphere model. In addition, the bubble shape is found to influence the radiation frequency, and this scheme can be implemented in both uniform and up-ramp density gradient plasma targets. The terahertz radiation may be used for diagnosing the electron bubble shape in the interaction between an intense laser and plasma. All results are presented via 2.5 dimensional particle-in-cell simulations.
Terahertz (THz) radiation obtained from the interaction between multiple sheet electron beams and a high-order mode (HOM) provides an effective method to extend the operating frequency and power capacity. Two ridges were introduced in the double staggered grating waveguide slow wave structure (SWS) to achieve a suitable band-gap between the HOM and low-order mode (LOM) for the HOM operation of a backward wave oscillator (BWO). The dispersion and transmission simulations of this improved SWS showed that a good frequency selective property was achieved and the LOM competition was effectively suppressed. Particle-in-cell analysis predicted that the HOM BWO could radiate >0.46 W output power in the range of 1.19-1.24 THz. It is indicated that the HOM BWO is a promising compact radiation source for generating high power THz-wave.
