Shaanxi;
Key;
Laboratory;
of;
Optical;
Information;
Technology,;
School;
of;
Science,;
Northwestern;
Polytechnical;
University,;
Xi'an;
710072,;
China;
The;
Key;
Laboratory;
of;
Space;
Applied;
Physics;
and;
Chemistry,;
Ministry;
of;
Education,;
Xi'an;
710072,;
China;