Cheng Ping Kwong, Tang Chun Yin, Ahmed Safayet, Qiao Junpeng, Zeng Long-Hui, Tsang Yuen Hong
Shenzhen Research Institute, The Hong Kong Polytechnic University, 518057 Shenzhen, Guangdong, People's Republic of China.
Department of Applied Physics and Materials Research Center, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, People's Republic of China.
Nanotechnology. 2021 Jan 29;32(5):055201. doi: 10.1088/1361-6528/abc1a2.
In-plane anisotropic two-dimensional (2D) materials have gained considerable interest in the field of research, due to having the potential of being used in different device applications. Recently, among these 2D materials, group 10 transition metal dichalcogenides (TMDs) pentagonal Palladium diselenide (PdSe) is utilized in various sections of researches like nanoelectronics, thermoelectric, spintronics, optoelectronics, and ultrafast photonics, owing to its high air stability and broad absorption spectrum properties. In this paper, it is demonstrated that by utilizing this novel 2D layered PdSe material as a saturable absorber (SA) in an EDF laser system, it is possible to obtain switchable laser pulse generation modes. At first, the Q-switching operation mode is attained at a threshold pump power of 56.8 mW at 1564 nm, where the modulation range of pulse duration and repetition rate is 18.5 μs-2.0 μs and 16.4 kHz-57.0 kHz, respectively. Afterward, the laser pulse generation mode is switched to the mode-locked state at a pump power of 63.1 mW (threshold value) by changing the polarization condition inside the laser cavity, and this phenomenon persists until the maximum pump power of 230.4 mW. For this mode-locking operation, the achieved pulse duration is 766 fs, corresponding to the central wavelength and 3 dB bandwidth of 1566 nm and 4.16 nm, respectively. Finally, it is illustrated that PdSe exhibits a modulation depth of 7.01%, which substantiates the high nonlinearity of the material. To the best of the authors' knowledge, this is the first time of switchable modes for laser pulse generation are achieved by using this PdSe SA. Therefore, this work will encourage the research community to carry out further studies with this PdSe material in the future.
面内各向异性二维（2D）材料因其具有应用于不同器件的潜力而在研究领域引起了广泛关注。最近，在这些二维材料中，第10族过渡金属二硫属化物（TMDs）五角形硒化钯（PdSe）因其高空气稳定性和宽吸收光谱特性，被用于纳米电子学、热电学、自旋电子学、光电子学和超快光子学等各个研究领域。本文表明，通过在掺铒光纤（EDF）激光系统中使用这种新型二维层状PdSe材料作为可饱和吸收体（SA），可以获得可切换的激光脉冲产生模式。首先，在1564 nm处的阈值泵浦功率为56.8 mW时实现了调Q操作模式，此时脉冲持续时间和重复率的调制范围分别为18.5 μs - 2.0 μs和16.4 kHz - 57.0 kHz。之后，通过改变激光腔内的偏振条件，在泵浦功率为63.1 mW（阈值）时，激光脉冲产生模式切换到锁模状态，并且这种现象一直持续到最大泵浦功率230.4 mW。对于这种锁模操作，实现的脉冲持续时间为766 fs，对应中心波长为1566 nm，3 dB带宽为4.16 nm。最后，结果表明PdSe的调制深度为7.01%，这证实了该材料的高非线性。据作者所知，这是首次使用这种PdSe可饱和吸收体实现激光脉冲产生的可切换模式。因此，这项工作将鼓励研究界在未来对这种PdSe材料进行进一步研究。
