Dual-Wavelength Fiber Laser Based on Er3+-Doped Superimposed Fiber Gratings
Feng Wang, Weihong Bi, Xinghu Fu, Peng Jiang, and Yang Wu
Based on gain homogeneity technology, a new type of dual-wavelength fiber laser is proposed and demonstrated. Linear cavity structure is used in the fiber laser, two Er3+-doped superimposed fiber gratings with reflectivity above 99% are used for wavelength selection, and Er3+-doped fiber is used as the gain medium. The experimental results show that precise adjustment of the mechanical stress at two ends of the superimposed fiber gratings can regulate the reflectivity (or transmissivity) of cavity lenses at the output end at wavelengths of λ1 and λ2, i.e. regulate the laser loss, which makes the gain and loss at two wavelengths in the resonance cavity match well, inhibits mode competition in the resonance cavity, and achieves stable simultaneous dual-wavelength laser emission with wavelength interval of 0.932 nm. The threshold power of the proposed laser is 4 mW, the 3 dB band width is 0.02 nm, the 30 dB band width is less than 0.2 nm, and the side mode suppression ratio is 51.96 dB. This laser have such advantages as simple structure, stable output at room temperature, narrow band width and low threshold.
  • Jun. 24, 2016
  • Chinese Journal of Lasers
  • Vol.43 Issue, 4 402002 (2016)
  • DOI:10.3788/cjl201643.0402002
Gain-Switched Semiconductor Pulsed Laser for Quantum Secure Communication
Qiang Zhou, Jinlu Liu, Yuanhui Gu, Fan Fan, Yunxiang Wang, and Bingjie Xu
In the last three decades, quantum information science and technology is one of the most exciting research fields. Among all the achievements, quantum secure communication technology is gradually started from experimental research to engineering application and expected to take the lead in achieving the commercial development. Towards the comprehensive popularization of the quantum secure communication system, a picosecond pulsed laser module has been designed and fabricated based on the gain-switching effect of the semiconductor laser and commercial electronic chips. The realized laser module has the following properties: operating wavelength at the low transmission loss window of fiber quantum channel, i.e., 1.5 μm; with a frequency fluctuation of less than 20 MHz; pulse time domain width of tens of picoseconds; no fixed phase correlation between any two pulses. Moreover, these properties are verified and discussed based on the requirement of weak coherent single photon source for quantum secure communication application.
  • May. 04, 2016
  • Chinese Journal of Lasers
  • Vol.43 Issue, 5 502005 (2016)
  • DOI:10.3788/cjl201643.0502005
Effects of Linewidth of Seed-Laser on Output Features of End-Pumped Alkali Vapor Amplifier
Zhigang Jiang, You Wang, Juhong Han, He Cai, Ming Gao, Guofei An, Liangping Xue, Wei Zhang, Hongyuan Wang, and Jie Zhou
In recent years, the diode pumped alkali laser (DPAL) has been rapidly developed as a new laser source. The master oscillator power-amplifier (MOPA) system is one of the most feasible engineering methods to achieve the high power scaling of DPAL. Comparing with traditional lasers, DPAL′s linewidths of both absorption and emission are extremely narrow. Therefore, the linewidth of a seed laser is one of the most important factors that effects the output characteristics of DPAL-MOPA. A theoretical microcosmic kinetic mode is established for an end-pumped DPAL-MOPA system. The linewidth of seed laser and the spectral distribution of emission cross-section are taken into account in the calculation process. The influences of linewidth of seed laser on the features, including the output power, output linewidth, extraction efficiency, gain factor, and pump absorption, are calculated and analyzed in detail. The research is helpful in construction of a power-scaled DPAL-MOPA system.
  • May. 04, 2016
  • Chinese Journal of Lasers
  • Vol.43 Issue, 5 502004 (2016)
  • DOI:10.3788/cjl201643.0502004
Study on a Non-Chain Discharge-Pumped Pulse Deuterium Fluoride Lasers
Libing You, Guangyue Yin, Qinsheng Wang, and Xiaodong Fang
The compact non-chain discharge-pumped pulse deuterium fluoride (DF) laser is studied, the discharge trigger circuit is introduced based on one-stage thyratron magnetic pulse with fast rise time. Discharging voltage of 39.5 kV and pulse rise time of 100 ns are achieved. With the condition of 190 J/L energy depositions, a uniform glow discharge is formed using compact Chang-electrode combined with ultraviolet (UV) spark pre-ionization, and the distance between the cathode and anode is 30 mm. With flat-flat cavity laser resonators, mixture gas of SF6and D2is investigated. By optimizing the gas ratio to 10:3, the laser pulse energy is up to 877 mJ. The electro-optic conversion efficiency is about 1.9% and the pulse width is 200 ns with the beam dimensions of 30 mm×9 mm.
  • May. 04, 2016
  • Chinese Journal of Lasers
  • Vol.43 Issue, 5 502003 (2016)
  • DOI:10.3788/cjl201643.0502003
Laser Diode Pumped 4.1 kW All-Fiber Laser with Master Oscillator Power Amplification Configuration
Xiaolin Wang, Hanwei Zhang, Rumao Tao, Rongtao Su, Pu Zhou, and Xiaojun Xu
A laser diode (LD) pumped all-fiber laser with master oscillator power amplification configuration is demonstrated, of which output power is more than 4 kW. The stimulated Raman scattering (SRS) and transverse mode instability (TMI) charateristics of lasers are experimentally studied under different core-diameter gain fibers and different pump wavelengths. In order to mitigate SRS, a large mode area Yb3+ doped fiber with core diameter of 30 μm is selected as gain media. In order to suppress TMI, LD with center wavelength of 915 nm is used as pump source, so the absorption coefficient of the gain fiber is lower at 915 nm, and the bending radius of the gain fiber is reduced to 10 cm to increase the loss of the higher modes. When the seed power is 100 W, the highest pump power is 5.3 kW, the laser power of 4.1 kW is achieved, and the beam quality M2 is 2.2. There are no SRS and TMI effects observed in the output laser.
  • May. 04, 2016
  • Chinese Journal of Lasers
  • Vol.43 Issue, 5 502002 (2016)
  • DOI:10.3788/cjl201643.0502002
Study of High Power Semiconductor Laser with Low Threshold Current
Menghan Liu, Bifeng Cui, Xin He, Zhenzhen Kong, Sha Li, and Xinzhu Huang
In order to solve the contradiction between large optical cavity (LOC) and low threshold current, a new semiconductor laser which has three quantum wells with higher barrier and asymmetric broad waveguide structure is designed. The laser can sustain low threshold current with large optical cavity. GaAs/AlGaAs three quantum wells and 3.6 μm super large optical cavity waveguide are grown by metal organic chemical vapor deposition (MOCVD). The 980 nm semiconductor laser is fabricated. As a result, the threshold current of 4 mm LOC semiconductor laser is 1105.5 mA and the vertical divergence angle is 15.6°. An output power of 15.9 W is reached with injection current of 25 A. The results show that the designed structure is effective for light field expanding, which can realize large optical cavity and guarantee low threshold current.
  • May. 04, 2016
  • Chinese Journal of Lasers
  • Vol.43 Issue, 5 502001 (2016)
  • DOI:10.3788/cjl201643.0502001
Investigation on Gain Properties of N31 Neodymium Glass Slab Amplifiers
Lei Wen, Lin Chen, Jianguo Liu, Yuanbin Chen, Xudong Xie, Yong Liu, Kuixing Zheng, Wei Chen, Lili Hu, and Yiqun Wu
As one of the most important element in the inertial confinement fusion (ICF) laser device, slab amplifier provides over 99% energy. The integration-test-bed (ITB) is established for the research of ICF in China with the single- beam output energy up to 19.6 kJ (pulse width 5 ns, center wavelength 1053 nm). This paper studies characteristics of N31 neodymium glass in 400 mm aperture, single-segment amplifying system of ITB. The N31 glasses with size of 810 mm×460 mm×40 mm and Nd3+ ion concentration of 3.5×1020 cm-3 are used. Results show that combined with the optimized parameters of discharge circuit for slab amplifier and structure of pump cavity, the small signal gain coefficient reaches 5.28% cm-1, the gain ratio is 15:1 , and the gain uniformity is 1.063∶1 (maximum/ average) within 360 mm beam diameter.
  • Apr. 29, 2016
  • Chinese Journal of Lasers
  • Vol.43 Issue, 4 402008 (2016)
  • DOI:10.3788/cjl201643.0402008
Backward Raman Scattering and Amplification Based on Dual Raman Cells
Dongjian Zhou, Jingwei Guo, Canhua Zhou, Weili Zhao, Jinbo Liu, Dong Liu, and Yuqi Jin
The characteristics of backward Raman scattering and amplification based on two hydrogen Raman cells are investigated. Both cells are filled with high-pressure hydrogen. The first cell is used to generate the Stokes seed light, and the second cell is used to amplify the seed light. The Stokes energy is measured at different pump energies, and different pump distributions between the two cells. When the pulsed pump energy of first and second cell separately is 100 mJ, 175 mJ, a pulsed Stokes energy of 44.0 mJ can be generated, and the corresponding photon conversion efficiency is 28.6% . The rate equations are employed to simulate the amplification process, and the theoretical results are agree with the experimental results on the whole. When the pulsed energy of Stokes seed light is as much as or greater than the pump laser, the Stokes can still keep a constant increment according to the numerical simulation. Based on the simulation results, the Raman amplification method is proposed to realize multiple laser series synthetic output.
  • Apr. 05, 2016
  • Chinese Journal of Lasers
  • Vol.43 Issue, 4 402006 (2016)
  • DOI:10.3788/cjl201643.0402006
Research on Stability of Fabry-Perot Cavity Based on PDH
Yong Guo, Qi Qiu, Yunxiang Wang, Zhiyong Wang, Jun Su, Shuangjin Shi, and Zhenfang Yu
A scheme for stabilizing the Fabry-Perot (FP) cavity based on the Pound-Drever-Hall (PDH) technique is proposed for the need of more stable FP cavity. According to the theoretical calculation model, the static and dynamic response characteristics of the FP cavity resonant optical system are analyzed in details. The error signal obtained by the static analysis can be used to lock the FP cavity, and the frequency response obtained by the dynamic response analysis helps to design a control loop to maintain the FP cavity at the chosen operating point. The numerical simulation results show that when the optical gain is 0.785 W/(°) and the error signal stays at the milliwatt level, the length stability precision of the FP cavity achieves 4 pm. The validity and feasibility of the scheme are verified by comparing the beam spot size and shape of the reflected light before and after the FP cavity locking.
  • Apr. 05, 2016
  • Chinese Journal of Lasers
  • Vol.43 Issue, 4 402003 (2016)
  • DOI:10.3788/cjl201643.0402003