面向2μm波段大功率光纤激光系统的高质量多波长及脉冲激光种子源研究

发布时间：2017-12-26 17:44

本文关键词：面向2μm波段大功率光纤激光系统的高质量多波长及脉冲激光种子源研究　出处：《北京交通大学》2017年博士论文　论文类型：学位论文

【摘要】：2 μm波段存在着性能优良的大气窗口,因而2μm波段空间光通信系统具有广阔的应用前景,在空间光通信网络中,波分复用(wavelength division multiplexing,WDM)技术依然是未来发展的趋势。在WDM系统中需要用到灵活选择激光输出波长和个数、波长间隔可调谐、高光束质量和高稳定性的多波长光纤激光器。同时,2 μm波段存在着OH-强烈的吸收窗口,高功率脉冲激光的热效应可使人体组织产生凝固或汽化效应,因此可作为激光手术刀应用于人体组织的切除或止血。空间光通信网络和激光手术刀对2μm波段激光的功率和光束质量要求越来越高,而主控振荡器功率放大器(master oscillator power amplifier,MOPA)技术可以在高功率激光输出的情况下保证优良的激光光束质量。本论文的研究工作主要集中MOPA系统用到的高质量种子源方面,针对WDM系统需要的激光器,设计了波长可调谐、波长间隔可调和单偏振(single polarization,SP)输出的双波长掺铥光纤激光器(thulium-doped fiber laser,TDFL),设计了波长可选择的多波长TDFL;针对激光手术刀需要的激光器,设计了类噪声(noise like,NL)脉冲和SP脉冲TDFL,分别对多波长和脉冲TDFL的实现方式和输出特性进行了详细的研究和分析,主要研究内容与创新点如下:(1)对 2 μm 波段均匀光纤光栅(uniform fiber Bragg grating,UFBG)、保偏光纤光栅(polarization maintaining fiber Bragg grating,PM-FBG)和保偏法布里—珀罗(polarizationmaintaining Fabry-Perot,PM-F-P)滤波器的滤波特性进行理论仿真,首次理论分析了在外力作用下,UFBG和PM-FBG中心波长漂移的特性,2 μm波段UFBG的谐振波长与轴向应力成正比,正比系数为0.15 pm/με,当施加的轴向应变为2500με时,PM-FBG的谐振波长可以漂移3.83 nm。(2)提出一种基于级联UFBG的波长间隔可调的双波长TDFL结构,利用非线性放大环形镜(nonlinear amplifying loop mirror,NALM)抑制激光腔内的模式竞争,获得工作波长分别为1941.33 nm和1941.72 nm的双波长激光输出,两个波长的光信噪比(optical signal-to-noise ratio,OSNR)均优于56 dB。通过应力调节,可实现0～5.14 nm的双波长激光间隔的调谐量;提出一种基于PM-FBG的可调谐双波长TDFL结构,获得工作波长分别为1941.40 nm和1942.21 nm的双波长激光输出,两个波长的OSNR均大于48 dB。通过应力调节,可以实现最大6.93 nm的双波长调谐量;提出一种基于PM-F-P滤波器的可切换双波长TDFL结构,获得工作波长分别为1941.82 nm和1942.21 nm的双波长激光输出,两个波长的OSNR均大于51 dB。可以实现两个偏振方向上的SP单波长激光输出,激光输出的偏振消光比(polarization extinction ratio,PER)均高于 33 dB。(3)提出一种基于非线性偏振旋转(nonlinear polarization rotation,NPR)效应和利奥(Lyot)滤波器的多波长TDFL结构,在10 dB带宽范围内(1982 nm～1998 nm)该激光器可形成17个波长稳定激射,且激射波长的OSNR达到35 dB。利用长度分别为5 m、4.22 m和2.06 m的保偏光纤制作Lyot滤波器,实现波长间隔分别为0.975 nm、1.16nm和2.38nm的多波长TDFL;提出一种基于NPR效应和保偏萨格纳克(polarization maintaining Sagnac,PM-Sagnac)环形镜的多波长 TDFL结构,利用长度为150 m的高非线性光纤增强激光腔内的NPR效应,在10 dB光谱带宽范围内(1990nm～2007.5 nm),实现了 15个波长的稳定激射,激射波长的OSNR可达到30 dB;提出一种基于全光纤型相位调制器和PM-Sagnac环形镜的多波长TDFL结构,通过优化相位调制器加载正弦信号频率,在15 dB带宽范围内(1982nm～1998nm)可实现10个波长同时激射,激光输出的OSNR可达37dB。(4)提出一种基于NALM的被动锁模TDFL结构,当泵浦光功率为2.98 W时,NL脉冲的中心波长为1990.56 nm、自相关信号尖峰宽度为518 fs、脉冲能量为26.63 nJ;提出一种基于NPR的被动锁模TDFL结构,通过调整激光腔内单模光纤的长度,从而优化锁模TDFL的色散,可实现NL锁模脉冲激光输出,其中心波长为2003.20nm、自相关信号尖峰宽度为406fs、脉冲能量为12.342nJ;提出一种混合锁模脉冲TDFL结构,当泵浦光功率为3.52 W时,SPNL脉冲激光输出的中心波长为2007.00 nm、自相关信号尖峰宽度为258 fs、脉冲能量为42.11 nJ。(5)提出一种基于PM-FBG和半导体可饱和吸收镜的可切换SP双波长脉冲TDFL结构。双波长脉冲激光的工作波长为1940.97 nm和1941.73 nm,脉冲激光输出的OSNR为57.36 dB。SP单波长激光脉冲宽度分别为3.75 ps和3.73 ps。
[Abstract]:There are excellent atmospheric windows in 2 M band, so the 2 - M band space optical communication system has broad application prospects. In the space optical communication network, wavelength division multiplexing (WDM) technology is still the trend of future development. In WDM system, multi wavelength fiber laser with flexible wavelength selection, wavelength interval tunable, high beam quality and high stability is needed. At the same time, there is a strong absorption window of OH- in the 2? M band. The thermal effect of high power pulsed laser can cause coagulation or vaporization effect of human tissue, so it can be used as a laser scalpel in human tissue resection or hemostasis. Space optical communication network and laser scalpel to require 2 m wavelength laser power and beam quality is more and more high, and the master oscillator power amplifier (master oscillator power amplifier, MOPA) technology can ensure the excellent quality of laser beam in high power laser output case. The main work of this paper focus on high quality seed source MOPA system used for WDM, laser systems, tunable wavelength and wavelength spacing adjustable single polarization design (single polarization SP) output dual wavelength thulium doped fiber laser (thulium-doped fiber laser, TDFL), the design of multi wavelength TDFL wavelength can choose the laser scalpel; according to the need, the design of noise (noise like, NL) TDFL and SP pulses, respectively for multi wavelength and pulse TDFL implementation and output characteristics were studied and analyzed in detail. The main research contents and innovations are as follows: (1) to 2 M band of uniform fiber grating (uniform fiber Bragg grating, UFBG), polarization maintaining fiber grating (polarization maintaining fiber Bragg grating, PM-FBG) and Fabri Perot (polarizationmaintaining polarizationmaintaining - Fabry-Perot, PM-F- P) the filter characteristics of the filters is simulated for the first time, the theoretical analysis under the action of external force, UFBG and PM-FBG central wavelength drift characteristics of resonant wavelength and 2 m wavelength UFBG axial stress is proportional to the proportional coefficient of 0.15 pm/ Mu epsilon, when applied axial strain is 2500 Mu epsilon, resonant wavelength PM-FBG can drift 3.83 nm. (2) we propose a cascaded UFBG wavelength interval based on tunable dual wavelength TDFL structure, using the nonlinear amplifying loop mirror (nonlinear amplifying loop mirror, NALM) model of competitive inhibition in the laser cavity to obtain working wavelength dual wavelength laser output of 1941.33 nm and 1941.72 nm, the optical signal-to-noise ratio of two wavelengths (optical signal-to-noise ratio, OSNR) were less than 56 dB. By adjusting the stress, the tunable quantity of dual wavelength laser interval can be achieved from 0 to 5.14 nm. A tunable dual wavelength TDFL structure based on PM-FBG is proposed, and the dual wavelength laser output with 1941.40 nm and 1942.21 nm wavelength is obtained. The two wavelengths of OSNR are all larger than 48 dB. Through stress adjustment, the maximum 6.93 nm dual wavelength tuning can be achieved. A dual wavelength TDFL structure based on PM-F-P filter is proposed, and the dual wavelength laser output with 1941.82 nm and 1942.21 nm wavelength is obtained, and the OSNR of two wavelengths is greater than 51 dB. The SP single wavelength laser output in two polarization directions can be realized, and the polarization extinction ratio (polarization extinction ratio, PER) of the laser output is higher than 33 dB. (3) based on nonlinear polarization rotation (nonlinear polarization, rotation, NPR) and Leo (Lyot) multi wavelength filter in the TDFL structure, in the bandwidth of 10 dB (1982 nm ~ 1998 nm) of the laser can form 17 wavelength lasing, and the lasing wavelength of OSNR reached 35 dB. The length were 5 m, 4.22 m and 2.06 m polarization maintaining fiber production of Lyot filter, wavelength interval were multi wavelength TDFL 0.975 nm, 1.16nm and 2.38nm; put forward a NPR effect and polarization Sagner (polarization maintaining Sagnac, based on the G PM-Sagnac) multi wavelength TDFL loop mirror structure, the length of for the high nonlinear fiber enhancement of NPR laser cavity 150 m, at 10 dB spectral bandwidth range (1990nm ~ 2007.5 nm), to achieve a stable 15 wavelength lasing, the lasing wavelength of OSNR can reach 30 dB; this paper proposes a multi wavelength TDFL structure optical fiber phase modulator and PM-Sagnac loop mirror based on the optimization of phase modulator by loading sinusoidal signal frequency, 15 dB bandwidth range (1982nm ~ 1998nm) can achieve 10 wavelength lasing at the same time, the laser output of OSNR can reach 37dB. (4) proposed a passive mode-locked TDFL structure based on NALM, when the pump power is 2.98 W, the central wavelength of NL pulse is 1990.56 nm, the autocorrelation signal peak width is 518 FS, pulse energy of 26.63 nJ; proposed a passive mode-locked TDFL structure based on NPR, by adjusting the laser cavity a length of single-mode fiber, so as to optimize the dispersion mode locked TDFL, can achieve NL mode-locked laser output, the center wavelength is 2003.20nm, autocorrelation signal peak width of 406fs, pulse energy of 12.342nJ; this paper proposes a hybrid mode-locked TDFL structure, when the pump power is 3.52 W, the central wavelength of SPNL pulse the laser output is 2007 nm, the autocorrelation signal peak width is 258 FS, pulse energy of 42.11 nJ. (5) a switched SP dual wavelength pulse TDFL structure based on PM-FBG and semiconductor saturable absorbable mirror is proposed. The operating wavelengths of the dual wavelength pulse laser are 1940.97 nm and 1941.73 nm, and the output OSNR of the pulse laser is 57.36 dB. The width of SP single wavelength laser pulses is 3.75 PS and 3.73 PS, respectively.
【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN248

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