1 School of Information Science and Engineering, Shandong University, Jinan 250100, China
2 Department of Photonics, Taiwan Sun Yat-sen University, 70 Lienhei Road, Kaohsiung 80424, China
3 State Key Laboratory of Crystal Materials, Institute of Crystal Materials, Shandong University, Jinan 250100, China
4 Research Center for Applied Sciences, Academia Sinica, 128 Sec. 2, Academic Road, Taipei 11529, China
5 e-mail: shengzhi_zhao@sdu.edu.cn
6 e-mail: chuckcklee@yahoo.com