Crystal oscillators are loosely divided via the frequency they function at and whether or not they are elementary oscillators—function in the frequency marked on the can or at even multiples of that (overtone oscillators). Substantial-repetition-rate and large-ability picosecond regenerative amplifier depending on a single bulk Nd:GdVO4 crystal 的很多特性，如温度稳定性，老化稳定性，等... https://www.hxcrystals.com/seokeywords/bulk-crystal-oscillator.html