Germanium Nanosheets with Dirac Characteristics as a Saturable Absorber for Ultrafast Pulse Generation

Haoran Mu; Yani Liu; Sudhakara Reddy Bongu; Xiaozhi Bao; Lei Li; Si Xiao; Jincheng Zhuang; Chen Liu; Yamin Huang; Yemin Dong; Kristian Helmerson; Jiaou Wang; Guanyu Liu; Yi Du; Qiaoliang Bao

doi:10.1002/adma.202101042

Germanium Nanosheets with Dirac Characteristics as a Saturable Absorber for Ultrafast Pulse Generation

Adv Mater. 2021 Aug;33(32):e2101042. doi: 10.1002/adma.202101042. Epub 2021 Jun 21.

Authors

Haoran Mu^{1

2}, Yani Liu^{3

4}, Sudhakara Reddy Bongu⁵, Xiaozhi Bao⁶, Lei Li⁷, Si Xiao⁸, Jincheng Zhuang⁴, Chen Liu⁹, Yamin Huang¹⁰, Yemin Dong¹⁰, Kristian Helmerson², Jiaou Wang⁹, Guanyu Liu¹¹, Yi Du^{3

4}, Qiaoliang Bao¹

Affiliations

¹ Department of Materials Science and Engineering and ARC Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET), Monash University, Clayton, Victoria, 3800, Australia.
² School of Physics, Monash University, Clayton, Victoria, 3800, Australia.
³ Institute for Superconducting and Electronic Materials (ISEM), Australian Institute for Innovative Materials (AIIM), University of Wollongong, Innovation Campus, North Wollongong, New South Wales, 2500, Australia.
⁴ BUAA-UOW Joint Research Centre and School of Physics, Beihang University, Beijing, 100191, China.
⁵ Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Institute of Microscale Optoelectronics, Shenzhen University, Shenzhen, 518060, P. R. China.
⁶ Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Macau SAR, 999078, China.
⁷ Jiangsu Key Laboratory of Advanced Laser Materials and Devices, Jiangsu Collaborative Innovation Center of Advanced Laser Technology and Emerging Industry, School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou, Jiangsu, 221116, China.
⁸ Institute of Super-Microstructure and Ultrafast Process in Advanced Materials, School of Physics and Electronics, Hunan Key Laboratory for Super-Microstructure and Ultrafast Process, Central South University, Changsha, 410083, China.
⁹ Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, 100049, China.
¹⁰ State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, 865 Changning Road, Shanghai, 200050, China.
¹¹ Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications, Institute of Photonics Technology, Jinan University, Guangzhou, 510632, China.

PMID: 34151464
DOI: 10.1002/adma.202101042

Abstract

Bulk germanium as a group-IV photonic material has been widely studied due to its relatively large refractive index and broadband and low propagation loss from near-infrared to mid-infrared. Inspired by the research of graphene, the 2D counterpart of bulk germanium, germanene, has been discovered and the characteristics of Dirac electrons have been observed. However, the optical properties of germanene still remain elusive. In this work, several layers of germanene are prepared with Dirac electronic characteristics and its morphology, band structure, carrier dynamics, and nonlinear optical properties are systematically investigated. It is surprisingly found that germanene has a fast carrier-relaxation time comparable to that of graphene and a relatively large nonlinear absorption coefficient, which is an order of magnitude higher than that of graphene in the near-infrared wavelength range. Based on these findings, germanene is applied as a new saturable absorber to construct an ultrafast mode-locked laser, and sub-picosecond pulse generation in the telecommunication band is realized. The results suggest that germanene can be used as a new type of group-IV material for various nonlinear optics and photonic applications.

Keywords: germanium nanosheets; mode-locking; nonlinear optics; ultrafast carrier dynamics.

Abstract

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