Comments on "Orotron—An electronic oscillator with an open resonator and reflecting grating"

In the above letter,’ Rusin and Bogomolov presented results on a new type of electron tube of the millimeter and submillimeter wave bands. We would like to call attention to our work, in which essentially the same electron tube was proposed,’ although different factors were considered3 in the theoretical analysis. Rusin and Bogomolov do not consider the groove width of the grating (grooved mirror) in the expression for the starting current. However, at the interaction between periodically distributed electric fields in the region just in front of the grooves and electron beam, the width has an effect on a beam coupling coefficient. We have obtained the electronic conductance G, in the linear kinematic theory as follows: