Tianli Feng

Shandong University

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Shengzhi Zhao

Shandong University

Kejian Yang

Shandong University

Jia Zhao

Shandong University

Tao Li

Shandong University

Yizhou Liu

Shandong University

Wenchao Qiao

Qingdao University of Science and Technology

Dechun Li

Ministry of Education of the People's Republic of China

Hongwei Chu

Ministry of Education of the People's Republic of China

Guiqiu Li

ShenZhen People’s Hospital

Jingcheng Shang

Shandong University

Cooperative Institutions

Shandong University

114

Chinese Academy of Sciences

University of Chinese Academy of Sciences

Max-Born-Institute for Nonlinear Optics and Short Pulse Spectroscopy

State Key Laboratory of Crystal Materials

Ministry of Education of the People's Republic of China

Shanghai Jiao Tong University

Shandong Normal University

Peking University

Qingdao Binhai University

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Theoretical and Experimental Investigations on Sub-Nanosecond Ktp-Opo Pumped by a Hybrid Q-Switched Laser with Aom and Mote2 Saturable Absorber

Chao Han Hongwei Chu Tianli Feng Shengzhi Zhao Dechun Li

In this paper, few-layered molybdenum ditelluride (MoTe2) nanosheets are synthesized with a liquid-phase exfoliation method. Its appearance, the spectra and the saturated absorption characteristics are measured. By using MoTe2 as saturable absorber (SA), a passively Q-switched YVO4/Nd:YVO4 laser is realized. At an incident pump power of 6.64 W, a maximum output power of 1.14 W with a minimum pulse duration of 66.2 ns is obtained. To our knowledge, this is the shortest pulse width ever achieved from a passively Q-switched laser with a MoTe2-SA at 1.06 μm. Based on this, a sub-nanosecond KTiOPO4 (KTP) based intracavity optical parametric oscillation (IOPO) pumped by a hybrid Q-switched laser with a MoTe2-SA and an acousto-optic modulator (AOM) is realized. At an incident pump power of 10.4 W and an AOM repetition rate of 10 kHz, a maximum output power of 195 mW with a minimum pulse duration of 835 ps for signal wave is obtained. To solve the IOPO rate equations, the ground-state and excited-state absorption cross sections of MoTe2 are rationally calculated to be 1.32×10−18 cm2 and 9.15×10−19 cm2 according to the observed transmittance curve, respectively, and the excited-state lifetime is 376.2 µs. The numerical solution of the equations matches well with the experimental data.

Saturable absorption

Nanosecond

Q-switching

Pulse duration

10.2139/ssrn.4454306

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Chemical vapor deposition synthesized monolayer MoS₂ for Q-switching pulse generation in the 2 µm spectral region

Optical Materials Express (2020)

Jingcheng Shang Tianli Feng Shengzhi Zhao Tao Li Jie Ma

We demonstrate a monolayer MoS 2 -based saturable absorber (SA) synthesized by chemical vapor deposition (CVD). The as-grown SA has high spatial homogeneity and shows excellent saturable absorption properties in the 2 µm wavelength region. A higher modulation depth of 21.3% and lower saturation intensity of 0.47 MW/cm 2 are achieved compared with those of other documented MoS 2 SAs to date. When applying the MoS 2 SA to a Tm:YAG ceramic laser, we observe a Q-switched pulse train with a shortest pulse duration of 388.0 ns under a pulse repetition rate of 82 kHz, which corresponds to a single pulse energy of 5.4 uJ and a peak power of 14 W. We believe that CVD constitutes an effective method towards high-quality MoS 2 saturable absorbers that possess remarkable application potential in the 2 µm wavelength region.

Saturable absorption

Pulse duration

Pulsed Laser Deposition

Saturation (graph theory)

10.1364/ome.402930

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Terahertz dielectric spectroscopy based thermal‐oxidative aging analysis of polyvinyl chloride

Microwave and Optical Technology Letters (2024)

Zhang Xian-sheng Tianli Feng Yizhang Li Jingcheng Shang

Abstract Polyvinyl chloride (PVC) is a polymer widely used in the world whereas safety problems owing to PVC aging are often reported. Thermal‐oxidative aging is known the main cause of its performance deterioration and lifetime decreasing. The existing PVC aging detection methods are complicated, making it difficult to achieve rapid on‐site diagnosis. The purpose of this paper is to evaluate the degree of PVC aging by means of terahertz technology. Samples were subject to thermal‐oxidative aging, and the corresponding dielectric spectra were measured by a terahertz time‐domain spectrometer. It turns out that the aging dependent dielectric spectra conforms to the physicochemical theory. Moreover, numerical correlation between the change in permittivity and the degree of aging, underlying a new solution for the aging forecast aimed at plastics.

Accelerated aging

10.1002/mop.33995

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Experimental and theoretical study of a passively Q-switched Nd:LuAG laser at 13 μm with a V^3+:YAG saturable absorber

Journal of the Optical Society of America B (2015)

Cheng Liu Shengzhi Zhao Guiqiu Li Kejian Yang Dechun Li

We report the characteristics of a diode-pumped continuous-wave (CW) and passively Q-switched Nd:LuAG laser emitting 1.3 μm wavelength. A maximum average output power of 954 mW was obtained under CW operation, giving a slope efficiency of 14.7%. With an V3+:YAG crystal wafer employed as saturable absorber, the passively Q-switched Nd:LuAG laser produced a minimum pulse duration of 17 ns under a repetition rate of 8 kHz, and a maximum single pulse energy of 18.9 μJ. A rate equation model is introduced to theoretically analyze the results obtained in the experiment, in which the Gaussian spatial distribution of the intracavity photon density and the longitudinal distribution of the photon density along the cavity axis are taken into account. The results of numerical calculations of the rate equations are consistent with the experimental results. The results indicated the Nd:LuAG crystal as a promising gain medium for achieving short pulses with high energy at 1.3 μm.

Saturable absorption

Rate equation

Pulse duration

Crystal (programming language)

Q-switching

Continuous wave

10.1364/josab.32.001001

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Citations (14)

Spectral and laser performance of a Tm 3+ :ScYSiO 5 crystal

Journal of Alloys and Compounds (2017)

Kejian Yang Tianli Feng Shengzhi Zhao Cheng Liu Tao Li

Crystal (programming language)

10.1016/j.jallcom.2017.04.099

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Citations (11)

Study on characteristics of diode-pumped continuous-wave tunable and passively Q-switched Tm:SSO laser

Applied Physics B (2014)

Tianli Feng Shengzhi Zhao Kejian Yang G. Q. Li D. C. Li

Continuous wave

Q-switching

Saturable absorption

Pulse repetition frequency

Pulse duration

10.1007/s00340-014-5816-z

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Citations (5)

Normal Dispersion Fiber-based Nonlinear Pulse Compressor for Generating 2-μm Watt-scale, ~100-MHz, Few-cycle Laser Pulse

2017 Asia Communications and Photonics Conference (ACP) (2022)

Tianli Feng Jingcheng Shang Shengzhi Zhao Yizhou Liu Kejian Yang

We firstly perform the nonlinear pulse compression for a 2-μm, 101.4-MHz driving laser pulse by splicing normal dispersion fiber (NDF). With the assistance of dispersion compensation of chirped mirror pair, a 28.3-fs (4.2-cycle) compressed pulse, which is 16 times narrower than the 450-fs driving pulse, is realized. The output average power of >1 W creates a new record for the fiber-based nonlinear pulse compressors with such high pulse repetition in the short-mid infrared wavelength region.

Prism compressor

Pulse compression

Chirped pulse amplification

10.1109/acp55869.2022.10088930

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Excess carrier-envelope phase noise generation in saturable absorbers

Optics Letters (2017)

Nils Raabe Tianli Feng Mark Mero Haochen Tian Youjian Song

Attosecond spectroscopy and precision frequency metrology depend on the stabilization of the carrier-envelope phase (CEP) of mode-locked lasers. Unfortunately, the phase of only a few types of lasers can be stabilized to jitters in the few-hundred millirad range. In a comparative experimental study, we analyze a femtosecond Ti:sapphire laser and three mode-locked fiber lasers. We numerically demodulate recorded time series of the free-running carrier-envelope beat note. Our analysis indicates a correlation between amplitude and frequency fluctuations at low Fourier frequencies for essentially all lasers investigated. While this correlation typically rolls off at frequencies beyond 100 kHz, we see clear indications for a broadband coupling mechanism in one of the fiber lasers. We suspect that the observed coupling mechanism acts to transfer intracavity power fluctuations into excess phase noise. This coupling mechanism is related to the mode-locking mechanism employed and not to the gain medium itself. We further verify this hypothesis by numerical simulations, which identify resonances of the saturable absorber mirror as a possible explanation for the coupling mechanism. Finally, we discuss how to avoid a detrimental influence of such resonances.

Carrier-envelope phase

Saturable absorption

Attosecond

10.1364/ol.42.001068

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Citations (20)

Gain-switched 2 µm fiber laser pumped by a Q-switching and mode-locking self-pulsing Er-doped fiber laser

Optical Fiber Technology (2024)

Xiaoran Ma Weiwei Huang Shengzhi Zhao Yizhou Liu Chun Wang

10.1016/j.yofte.2024.103681

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Citations (2)