1. School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
2. State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Shanghai 200050, China
3. Department of Biomedical Engineering and NIH Transducer Resource Center, University of Southern California, Los Angeles, California 90089-1111, USA
4. Department of Physics and Key Laboratory of Acoustic and Photonic Materials and Devices of Ministry of Education, Wuhan University, Wuhan 430072, China
5. Medical Engineering Course, Graduate School of Engineering, Toin University of Yokohama, Yokohama 225-8501, Japan