[18p-P10-1~4] 3.16 Optics and Photonics English Session

▲ [18p-P10-3] Investigation on Third-Order Nonlinear Optical Properties of Germanium Thin Films by Z-Scan Technique

〇(M1)MENG YUAN CHUANG¹, Gong-Ru Lin², Chao-Kuei Lee^1,3 (1.Department of Photonics, National Sun Yat-sen University, Kaohsiung, Taiwan, 2.Graduate Institute of Photonics and Optoelectronics National Taiwan University, Taipei, Taiwan, 3.Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan)

Keywords:Z-scan measurement, Germanium Composites

To realize nonlinear optical applications, including wavelength generation, ultrafast optical processing, and saturable absorber for ultrafast laser, the information of optical nonlinearity property for given material is very important. Z-scan measurement is a simple, reliable technique to determine the optical nonlinearity of optical thin film. Without complex semiconductor processing to fabricate devices, only planer thin film is required for Z-scan measurement. Based on Z-scan measurement with open/close aperture configurations, the nonlinear refractive index as well as nonlinear absorption coefficient of given material can be determined. In the present work, the nonlinear optical property of Ge thin film deposited by plasma-enhanced chemical vapor deposition (PECVD) is characterized. The central wavelength of pump pulse laser is 1056nm with pulsewidth of ~100fs. In the open aperture result, the strong two-photon absorption (TPA) in Ge film is observed with the pump intensity of 10⁷ (W/cm² ), and the TPA coefficient is estimated to be ~3*10^-5 (cm/W) . For the result of close aperture, the nonlinear refractive index of Ge film is estimated to be ~1.25*10^-9 (W/cm²). In addition, the power-dependent optical nonlinearity of Ge film are investigated as well.