The laser was based on a Nd:YVO4crystal a-cut slab with 1.1at.% neodymium doping operating at a wavelength of 1064nm and pumped by a semiconductor diode laser bar with the emitting line centered at a mavelength of 808nm.请问其中的1.1at.% 是什么意思?应该表示掺杂浓度,那表示多少呢?