Design of Photonic Crystal Klystrons

2D Pho­ton­ic crys­tals (PC) with de­fects can act as stand­ing-wave res­onators, which offer ben­e­fit of high mode se­lec­tiv­i­ty for build­ing novel RF sources. We in­tro­duce our work on de­sign­ing two-cav­i­ty sin­gle-beam and mul­ti-beam klystrons using tri­an­gu­lar lat­tice metal­lic PCs. We pre­sent the cold test re­sults of the stub-cou­pled sin­gle-beam struc­ture, which show that at res­o­nance a very low re­flec­tion can be ob­tained, and the waves are well con­fined. We also pre­sent bead-pull mea­sure­ment re­sults of field strengths in the de­fect, using mod­i­fied per­tur­ba­tion equa­tion for small unit di­elec­tric cylin­der, which are in very good agree­ment to nu­mer­i­cal re­sults. A 6-beam klystron cav­i­ty is de­signed as a 6-cou­pled-de­fect struc­ture with a cen­tral stub, which only cou­ples to the in-phase mode at the low­est fre­quen­cy. Fi­nal­ly, we pre­sent a fea­si­bil­i­ty dis­cus­sion of using this mul­ti-de­fect PC struc­ture to con­struct an in­te­grat­ed klystron-ac­cel­er­a­tor cav­i­ty, along with nu­mer­i­cal re­sults show­ing a peak ac­cel­er­a­tion field of 22MV/m can be achieved.