Prototypes using metal, carbon fiber and composite field emission sources modulated by a laser beam

Field emission of electrons from a variety of metallic, carbon fiber and composite metal–insulator micropoint cathodes was employed in this study. Tungsten, carbon fiber and ZrC tips, were studied using a field emission microscope. These cathodes were characterized and the current–voltage (I–V) characteristics were determined. A variety of surface treatment procedures were carried out to increase the stability of emission. These electron sources were mounted in sealed prototype field emission tubes, while others were tested under medium, high and UHV conditions. The emission current switch-on phenomenon was found with all non-metallic cathodes. The emitters were then subjected to a square wave-modulated, maximally focused laser diode beam (λ=658 nm, 30 mW). The beam impedance (∼1 GΩ) and the anode capacitance (∼10 pF) act as a low-pass filter.