基于激光器激射特性的新型应变传感系统

报道了一种基于掺铒光纤激光器瞬态特性的新型应变传感系统.用光纤环反射镜和光纤Bragg光栅(FBG)构成Fabry-Perot线型腔.腔内插入一个长周期光纤光栅(LPG)，其透射谱的中心波长为1574.4nm.FBG的带宽为0.23nm，不受力时其反射波长为1557.98nm，位于LPG的透射谱左沿；当FBG受力时激射波长向长波方向移动，激光通过LPG时透射损耗增大，腔损耗的增加将使激光激射延迟时间增加.因此，应变的大小可以通过激光产生的延迟时间来测量.这种新型应变传感器的分辨率和灵敏度由抽运光脉冲的高、 关键词： 应变传感 光纤激光器 时域测量 光纤Bragg光栅     

同带抽运高效率光纤放大器

以光纤光栅为谐振腔搭建了波长为1020 nm的光纤激光器,并通过两级级联放大获得了590 mW的最大输出功率. 利用获得的波长为1020 nm的激光进行了波长为1064 nm种子光同带抽运放大,实验研究了不同增益光纤长度时放大器的输出功率和转换效率. 当增益光纤长度为8.5 m时,放大器最大输出功率为385 mW,斜率效率为81%. 进行了波长为976 nm的半导体激光器直接抽运波长为1064 nm种子光的实验. 在增益光纤长度最优时,其斜率效率为56.4%. 实验结果表明,同带抽运方式比传统抽运方式具有更高的转换效率. 研究结果可为波长为1020 nm的激光高功率放大和波长为1064 nm的光纤激光高功率同带抽运放大提供一定的参考. 关键词： 同带抽运 光纤放大器 斜率效率     

掺镱全光纤激光器研究

依据速率方程和边界条件,对高功率多点抽运全光纤激光器进行了研究.通过自制的级联侧面泵浦耦合器搭建全光纤激光器,级联耦合器的单点泵浦效率为96%,泵浦传输损耗为10%,信号光损耗分别是0.18dB和0.87dB;线性谐振腔结构中:前向抽运的光-光转换效率为69%,低于后向抽运中70%的光-光转换效率,与理论分析一致;双向泵浦方式中,在单臂输入975nm泵浦功率为110 W的条件下,激光功率输出为311 W,中心波长为1 080nm,光谱宽度为1.6nm,光-光转换效率为70%,光束质量约为1.3.激光器性能稳定,若增加单臂泵浦功率或级联泵浦耦合器个数,可获得更高功率的激光输出.     

基于光纤激光器时域特性的液体浓度传感器

报道了一种基于掺铒光纤激光器时域特性的新型液体浓度传感系统.用光纤环反射镜和光纤Bragg光栅（FBG）构成F-P线形腔.谐振腔内插入长周期光纤光栅（LPG）,FBG的反射波长落在LPG的透射峰左侧.把LPG浸泡在待测液体中,利用LPG对环境折射率的敏感特性,即环境液体浓度的改变引起折射率改变,这将引起LPG透射谱平移,从而使腔内损耗发生变化,影响了激光器的瞬态时域特性.通过测量激光激射的延迟时间可以获得被测液体的浓度.在最佳工作条件下,系统的浓度分辨率为0.015％.     

高效率1018nm全光纤激光器实验研究

采用内包层直径为125μm的双包层掺镱光纤,搭建了谐振腔结构全光纤激光器系统,获得了1018 nm的高功率激光输出。通过优化光纤长度和控制抽运源波长,单模激光输出功率为254 W,光光转换效率达到81%,光谱中无自发辐射光和剩余抽运光,信噪比大于35 d B。由于抽运半导体激光器的输出波长随着输出功率变化,光纤激光器的转换效率也将改变,为了提高转换效率,抽运半导体激光器的输出波长需要精确控制;光纤激光器长期稳定性测试结果表明,4 h连续工作的不稳定度小于0.5%。本光纤激光器系统是同带抽运高功率光纤激光器的理想抽运源。     

自调Q、自锁模铒/镱共掺光纤激光器

研究了结构新颖的环形腔铒/镱（Er/Yb）共掺双包层光纤激光器.为了获得高功率激光输出，使用6个激光二极管（LD）同时抽运Er/Yb共掺光纤，采用光纤光栅（FBG）Sagnac环作为波长选择器，得到了中心波长为1548.11 nm、谱线宽度为0.06 nm的窄线宽激光输出；并利用增益光纤作为可饱和吸收体，实现了自调Q、自锁模脉冲输出.当抽运功率为719 mW时，激光器输出自调Q脉冲，脉冲周期为20μs，脉冲宽度为2.8μs，脉冲的平均功率为38.4mW，峰值功率为274.3mW；当抽运功率为3.6 W时，激光器输出自锁模脉冲，脉冲宽度为4ns，平均功率为319 mW，脉冲峰值功率大于10 W，重复频率为7.937 MHz.     

高功率全光纤保偏主振荡功率放大型光纤激光器的实验研究

进行了全光纤保偏主振荡功率放大型光纤激光器的实验研究. 采用两级级联放大的方式, 利用纤芯为5 μupm 的小芯径双包层保偏光纤, 在最大抽运功率为88 W 时实现了67 W的1083 nm保偏激光输出, 纤芯内的激光功率密度约为3.4 W/μupm², 光-光转换效率为76%．分析结果表明, 进一步提高抽运功率有望获得更高功率的激光输出．     

宽带可调谐单频窄线宽光纤激光器

设计出一种集可调谐带通滤波器、高精度环形滤波器和光纤环形镜于一体的全光纤复合腔结构可调谐单频窄线宽光纤激光器。采用980 nm半导体激光器作为抽运源,掺镱光纤在谐振腔内分别作为增益介质和可饱和吸收体,成功实现波长为1030～1090 nm稳定的宽谱可调谐单频窄线宽激光输出。当抽运光的抽运功率为300 mW时,在波长为1070 nm处得到的输出功率最大,为18.5 mW,斜率效率达到7.95%,持续1 h内没有出现跳模现象,功率不稳定性小于1%;当抽运功率为200 mW时,利用延迟自外差法测量线宽,得到波长调谐范围内的平均线宽为8.7 kHz,弛豫振荡频率为64 kHz。     

780W全光纤窄线宽光纤激光器

高功率窄线宽光纤激光器在相干探测、功率光谱合成等方面具有广泛的应用前景.分析了高功率窄线宽光纤激光器中受激布里渊散射效应的抑制方法,以及正弦相位调制光谱展宽理论.采用正弦相位调制技术将单频激光器的线宽展宽至2.9 GHz,通过三级放大结构对输出功率为50 mW的窄线宽种子源进行放大,实现了中心波长1064.34 nm、线宽2.9 GHz、最大功率780 W的激光输出,光—光转换效率79%,光束质量M2x=1.44,M2y=1.43.分析了相位调制前后输出功率提高的原因,认为正弦相位调制增加的纵模降低了光纤中的功率谱密度,提高了输出激光的受激布里渊散射阈值,促使相位调制后的输出功率大幅提高.该激光器的输出功率仅受限于抽运功率,进一步提高抽运功率,有望实现更高功率的窄线宽光纤激光输出.     

包层泵浦的L波段Er3+/Yb3+共掺光纤激光器

报道了一种工作波长在L波段的包层泵浦Er³⁺/Yb³⁺共掺光纤环形激光器. 环形腔内的激光工作介质为一段9 m长的Er³⁺/Yb³⁺共掺高掺杂光纤. 利用6个976 nm LD同时抽运前段Er³⁺/Yb³⁺共掺双包层光纤产生的放大自发辐射谱作二次抽运源, 使腔内增义谱由C波段移到L波段, 实现了L波段光纤激光器的稳定输出; 采用包层泵浦技术, 在抽运功率为3594.5 mW时, 测得泵浦入纤功率为2731.8 mW, 实现了输出连续功率最大518.4 mW,斜率效率达到19% 的激光输出; 所形成激光的工作波长为1613.94 nm, 激光光谱的3 dB带宽为1.5 nm, 边模抑制比接近于50 dB.     

Simultaneous detection of ammonia, methane and ethylene at 1.63 μm with diode laser photoacoustic spectroscopy

Spectral investigation around 6115 cm^-1 for simultaneous detection of ammonia, methane and ethylene in gas samples is presented. Experimental data on the ν₂+ν₃+ν₄ combination band of ammonia are reported with a resolution of 1.5 GHz. A trace gas analyzer based on a resonant photoacoustic cell and an external cavity diode laser has been used for detection. A data fitting procedure has been developed in order to improve the system sensitivity and to limit the need of a reference cell. The selected spectral region allows a sensitivity of about 60 ppm for ammonia, 6 ppm for methane and 30 ppm for ethylene with 0.3 mW laser power. An application of simultaneous detection of such molecules in a mixture reproducing their typical abundances in real gas samples from biomass gasification is discussed. PACS 42.62.Fi; 42.55.Px; 82.80.Ch     

Torsion sensing with a fiber ring laser incorporating a pair of rotary long-period fiber gratings

We experimentally demonstrate a fiber ring laser for high-resolution torsion measurement, where the laser cavity consists of a Mach-Zehnder interferometer formed with a pair of long-period fiber gratings written in a twisted single-mode fiber by a CO₂ laser. The emitting wavelength of the laser provides a measure of the rate of the torsion applied to the grating pair, while the direction of the wavelength shift indicates the sense of the applied torsion. The narrow linewidth and the large side-mode suppression ratio of the laser can provide a much more precise measurement of torsion, compared with passive fiber-optic torsion sensors. The torsion sensitivity achieved is 0.084 nm/(rad/m) in the torsion range ± 100 rad/m, which corresponds to a torsion resolution of 0.12 rad/m, assuming a wavelength resolution of 10 pm for a typical optical spectrum analyzer. The ultimate resolution of the sensor is limited by the linewidth of the laser and could be an order of magnitude higher.     

Photoacoustic system for on-line process monitoring of hydrogen sulfide (H2S) concentration in natural gas streams

A dual-channel hydrogen sulfide (H₂S) concentration measuring system based on photoacoustic spectroscopy is described. The system uses a single-mode, fiber-coupled, room-temperature-operated, telecommunication-type diode laser with a wavelength of 1574.5 nm and an output optical power of 40 mW and two identical resonant photoacoustic cells to achieve minimum detectable H₂S concentration at 0.5 ppm (3σ) in both measured natural gas streams. The instrument features excellent long-term stability and unattended automatic on-line monitoring even when operated in harsh industrial environments. The potentially deteriorating effect of temporal variation in the natural gas composition was successfully suppressed by applying a spectral baseline correction method and by introducing an additional measurement phase with measurement of a reference gas from which the H₂S has been removed. Various tests of the instrument demonstrate its reliable performance and suitability for process-control application. PACS 82.80.Kq; 42.62.Fi; 07.07.Df     

Resonant photoacoustic simultaneous detection of methane and ethylene by means. of a 1.63-μm diode laser

A compact multi-component trace-gas detector based on the resonant photoacoustic technique and a NIR external cavity diode laser has been developed. It has been characterized using a mixture of ethylene and methane diluted in ambient air. A spectroscopic investigation of combination bands and overtones between 5900 and 6250 cm^-1, obtained with an IR pulsed laser photoacoustic spectrometer, allowed us to find a wavelength region where the 2ν₃ overtone of CH₄ and the ν₅+ν₉ combination band of C₂H₄ show uncongested rotational lines. Using a single-mode scan of the diode laser in this region, around 6150 cm^-1, the sensitivity for the simultaneous detection of ethylene and methane is 8 ppm/mW and 40 ppm/mW respectively. Factors affecting the sensitivity and selectivity of the detection system and possible improvements suitable to reach the sub-ppm detection limit are discussed. Received: 1 August 2001 / Revised version: 28 November 2001 / Published online: 7 February 2002 An erratum to this article is available at .     

TDLAS–WMS based near-infrared methane sensor system using hollow-core photonic crystal fiber as gas-chamber

A near-infrared methane (CH₄) sensor system was implemented using a hollow-core photonic crystal fiber (HC-PCF) as gas-chamber. Coupling joints including ceramic ferrules and ceramic mating sleeve were used to realize butt coupling between hollow-core fiber and single-mode fiber. A near-infrared distribute feedback laser was used for CH₄ detection based on wavelength modulation spectroscopy technique. CH₄ measurements were conducted to derive the sensor-system performances. Using a 5.3 mW laser power and a 0.8 m-long HC-PCF, a minimum detection limit of ~8.7 ppm at 0.1 s averaging time was obtained and it can be further improved to 1.4 ppm at an averaging time of 10 s. A good linear calibration curve between the amplitude ratio (2f/1f) and the CH₄ concentration was obtained within the concentration range of 0–1000 ppm. This sensor system shows potential applications in distributed field measurements on CH₄ in industrial process control, environmental monitoring, etc.     

超低频率全正色散半导体可饱和吸收镜被动锁模光纤激光器

 通过延长激光器环形腔腔长,利用高浓度掺杂的单模掺镱光纤,搭建了超低重复频率、全正色散结构的半导体可饱和吸收镜被动锁模光纤激光器。激光器的中心波长、重复频率、平均功率及单脉冲能量分别为1 064 nm,281.5 kHz,11 mW和39 nJ。为了稳定中心波长,实现自启动,激光器腔体内接入了一个带通滤波器。该激光器运行稳定,无调Q不稳定现象,极大减小了半导体可饱和吸收镜被损坏的机会。     

Wavelength tunable linear cavity cladding pump Er<Superscript>3+</Superscript>/Yb<Superscript>3+</Superscript>co-doped fiber laser operating in L-band

We have demonstrated a novel tunable linear cavity Er³⁺/Yb³⁺ co-doped fiber laser, which utilizes amplified spontaneous emission as a secondary pump source so that it can operate in L-band. The tuning wavelength range can be up to 34 nm, from 1588.6 to 1622.6 nm, and the output power excursion of the laser at different wavelengths can be less than 0.4 dB by using a two sections of high-birefringence fiber loop mirror as the wavelength filter. The high output power of 200 mW is realized by using the cladding-pump.     

基于扫描光纤激光器的光纤传感解调仪研究

介绍了一种基于扫描光纤激光器的光纤传感解调系统.采用氰化氢（HCN）气体吸收池作为波长参考基准,采用三次多项式拟合的方法来确定光纤F- P可调谐滤波器的波长与驱动电压的对应关系,可调谐滤波器扫描过程中对扫描电压、多路光谱信号进行同步采样,实时标定.实验结果表明,该解调系统在1 510 nm到1 590 nm波长范围内对FBG反射峰值波长的分辨率为1.4 pm,长期波长重复性达到3.2 pm.利用该系统实现了对FBG反射峰值波长和光纤EFPI传感器腔长的高准确度解调.     

利用光谱滤波器实现自启动的全光纤超短脉冲掺Yb3+光纤激光器

讨论了利用光谱滤波器实现自启动的被动锁模掺Yb³⁺光纤环形激光器的锁模机理,并研制出全光纤结构超短脉冲掺Yb³⁺光纤环形激光器.使用980 nm二极管激光器作为抽运源,高掺杂浓度掺Yb³⁺光纤作为增益介质.在净群速度色散为正的环形腔中加入光谱滤波器,抑制Yb³⁺离子在1030 nm强发射峰的同时,通过对啁啾脉冲的光谱滤波实现脉冲压缩.光谱滤波器与光纤非线性偏振旋转效应相结合,实现了激光器在1053 nm可自启动、十分稳定的锁模运转.激光器锁模阈值功率300 mW,平均斜率效率18.3%,最大输出功率53.07 mW,对应最大输出脉冲能量3.2 nJ.锁模光脉冲中心波长1053.6 nm,3 dB带宽10.84 nm,重复频率16.45 MHz.锁模脉冲宽度为皮秒量级,经腔外光栅对压缩至188 fs. 关键词： 3+光纤激光器')" href="#">掺Yb³⁺光纤激光器 自启动锁模 全光纤