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1.
A photoacoustic gas sensor using a near-infrared tunable fiber laser and based on wavelength modulation spectroscopy technique is developed. This sensor is capable of quasi-simultaneous quantification of water vapour, acetylene, carbon dioxide, and carbon monoxide (H2O, C2H2, CO and CO2) concentrations in the fire emulator. The feasibility of using this sensor as an early fire detector was demonstrated. The fire warning gases from smoldering paper were measured. The peak concentrations of gases from smoldering paper were 20,300 ppm H2O, 2.1 ppm C2H2, 756 ppm CO, and 1612 ppm CO2 after 400 s. 相似文献
2.
A new detection method for ammonia in high concentration of CO2 and H2O is reported, which uses a wavelength modulated photoacoustic spectrometer based on a near-infrared tunable erbium-doped
fiber laser in combination with an optical fiber amplifier. The multi-wavelength (1522.44 nm, 1522.94 nm and 1545.05 nm) photoacoustic
signal measurement is established to detect multi-spectrum signal in samples. The problem of ammonia detection in high concentration
of CO2 and H2O is resolved at atmospheric pressure. The minimum detection limit of 16 ppb (signal-to-noise ratio = 1) in simulated breath
samples (5.3% CO2 and 6.2% H2O (100% relative humidity at 37°C)) is achieved. 相似文献
3.
Dumitras D. C. Dutu D. C. Matei C. Cernat R. Banita S. Patachia M. Bratu A. M. Petrus M. Popa C. 《Laser Physics》2011,21(4):796-800
Photoacoustic spectroscopy represents a powerful technique for measuring extremely low absorptions independent of the path
length and offers a degree of parameter control that cannot be attained by other methods. We report precise measurements of
the ammonia absorption coefficients at the CO2 laser wavelengths by using a photoacoustic (PA) cell in an extracavity configuration and we compare our results with other
values reported in the literature. Ammonia presents a clear fingerprint spectrum and high absorption strengths in the CO2 wavelengths region. Because more than 250 molecular gases of environmental concern for atmospheric, industrial, medical,
military, and scientific spheres exhibit strong absorption bands in the region 9.2–10.8 μm, we have chosen a frequency tunable
CO2 laser. In the present work, ammonia absorption coefficients were measured at both branches of the CO2 laser lines by using a calibrated mixture of 10 ppm NH3 in N2. We found the maximum absorption in the 9 μm region, at 9R(30) line of the CO2 laser. One of the applications based on the ammonia absorption coefficients is used to measure the ammonia levels in exhaled
human breath. This can be used to determine the exact time necessary at every session for an optimal degree of dialysis at
patients with end-stage renal disease. 相似文献
4.
A novel tunable multi-wavelength fiber ring laser based on semiconductor optical amplifier(SOA)is proposed by using a high-birefringence(Hi-Bi)fiber loop mirror(FLM)as wavelength filter.With this configuration,the wavelength spacing of this laser can be varied by using the different lengths of Hi-Bi fiber.8 wavelengths spacing on 450 GHz are experimentally obtained with more than 25-dB signal-to-noise ratio(SNR)for each channel using 1.28-m Hi-Bi fiber in Hi-Bi FLM.The output power variation between different channels is measured to be less than 5.9 dB.The linewidth of each channel is compressed from 0.347 to 0.186 nm by 1.5-m unpumped erbium-doped fiber(EDF).Meanwhile,17 wavelengths spacing on ITU-gird(100 GHz)are also obtained with 5.9-m Hi-Bi fiber in Hi-Bi FLM.All these channels can be tuned together over 0.4 nm. 相似文献
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M. B. Filho M. G. da Silva J. C. Polidoro F. J. Luna M. B.M. Monte A. Miklós F. Souza-Barros H. Vargas 《The European physical journal. Special topics》2008,153(1):547-550
We report the first results obtained with a Brazilian
sedimentary zeolite (hereafter called the zeolite concentrate, ZC) to reduce
ammonia volatilization – loss of the nitrogen nutrient – in tropical
farms. Preliminary laboratory tests were made with both ammonium sulfate and
urea into ZC. The reported field tests – obtained in rose cultivations –
show a significant effect of the use of urea mixed with ZC on the stem
growth of the rose buds. In the laboratory tests, the observations of the
retention of ammonia by ZC were done using the photoacoustic set-up
described in this work. The report data were obtained at temperatures of 25
and 60°C, simulating typical tropical weather temperatures. 相似文献
8.
Yichang MengShumin Zhang Xinzhan WangJuan Du Hongfei LiYanping Hao Xingliang Li 《Optics and Lasers in Engineering》2012,50(3):303-307
We have demonstrated an adjustable double-clad Yb3+-doped fiber laser using a double-pass Mach-Zehnder interferometer. The laser is adjustable over a range of 40 nm from 1064 nm to 1104 nm. By adjusting the state of the polarization controller, which is placed in the double-pass Mach-Zehnder interferometer, we obtained central lasing wavelengths that can be accurately tuned with controllable spacing between different tunable wavelengths. The laser has a side mode suppression ratio of 42 dB, the 3 dB spectral width is less than 0.2 nm, and the slope efficiencies at 1068 nm, 1082 nm and 1098 nm are 23%, 32% and 26%, respectively. In addition, we have experimentally observed tunable multi-wavelengths lasing output. 相似文献
9.
J. Wojtas Z. Bielecki T. Stacewicz J. Mikołajczyk M. Nowakowski 《Opto-Electronics Review》2012,20(1):26-39
At present there are many reasons for seeking new methods and technologies that aim to develop new and more perfect sensors
for different chemical compounds. However, the main reasons are safety ensuring and health care. In the paper, recent advances
in the human breath analysis by the use of different techniques are presented. We have selected non-invasive ones ensuring
detection of pathogenic changes at a molecular level. The presence of certain molecules in the human breath is used as an
indicator of a specific disease. Thus, the analysis of the human breath is very useful for health monitoring. We have shown
some examples of diseases’ biomarkers and various methods capable of detecting them. Described methods have been divided into
non-optical and optical methods. The former ones are the following: gas chromatography, flame ionization detection, mass spectrometry,
ion mobility spectrometry, proton transfer reaction mass spectrometry, selected ion flow tube mass spectrometry. In recent
twenty years, the optical methods have become more popular, especially the laser techniques. They have a great potential for
detection and monitoring of the components in the gas phase. These methods are characterized by high sensitivity and good
selectivity. The spectroscopic sensors provide the opportunity to detect specific gases and to measure their concentration
either in a sampling place or a remote one. Multipass spectroscopy, cavity ring-down spectroscopy, and photo-acoustic spectroscopy
were characterised in the paper as well. 相似文献
10.
We propose the use of an actively mode-locked fiber laser as a multitap optical source for a microwave photonic filter. The fiber laser provides multiple optical taps with an optical frequency separation equal to the external driving radio-frequency signal of the laser that governs its repetition rate. All the optical taps show equal polarization and an overall Gaussian apodization, which reduces the sidelobes. We demonstrate continuous tunability of the filter by changing the external driving radio-frequency signal of the laser, which shows good fine tunability in the operating range of the laser from 5 to 10 GHz. 相似文献
11.
Chenfang Zhang Lisong Liu Zhiming Liu Siwen Zheng Ruifeng Zhao Shuisheng Jian 《Optics Communications》2011,284(10-11):2550-2553
A stable and tunable multi-wavelength fiber laser with a polarization-maintaining erbium-doped fiber (PM-EDF) and a polarization controller (PC) is proposed and demonstrated. A homemade PM-EDF incorporated in the ring cavity is used as the gain medium. Simultaneous multi-wavelength oscillation is achieved at room temperature. The theory of the PM-EDF and PC to suppress the wavelength competition is described in detail. The 3 dB bandwidth is less than 0.01 nm. The power fluctuation and wavelength shift are measured to be less than 0.5 dB and 0.05 nm over 32 min. The wavelength tuning between single-, double-, triple-, and four-wavelength is realized. 相似文献
12.
利用光声光谱技术进行痕量气体的检测具有独特的优势,光声池是系统装置中最为重要的核心部件,它决定着整机性能的优劣.以一圆柱形共振型光声池为研究对象,基于声学与吸收光谱学的基本理论,建立了光声池声场激发的数学模型;利用数值模拟方法对光声池空腔结构进行了声学模态仿真,获得了前8阶声学模态值以及声压可视化振型;在考虑热黏性声学损耗的作用下,对光声池进行了热-声耦合多物理场仿真计算;将仿真结果与解析计算和实验结果进行对比,明确了利用数值模拟方法来计算光声池有关指标的可靠性与可行性;针对光声池的优化问题,提出了一种将响应面代理模型与遗传算法相结合的优化算法,在将原光声池中的谐振腔两端形貌更改为喇叭口形的情况下,通过优化算法获得了以光声池品质因数Q及池常数C_(cell)为最大值寻优的Pareto最优解集;选取一组解进行考察,结果表明,代理模型预测值与数值模拟值指标最大误差仅为1.3%,优化后的新型光声池Q较之前增长了48.9%, C_(cell)增长了34.4%.研究方法可为光声光谱中光声池的优化设计提供参考借鉴. 相似文献
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《中国光学快报(英文版)》2017,(10)
A tunable single-longitudinal-mode(SLM) semiconductor optical amplifier(SOA)-based fiber laser based on a dispersion-shifted fiber(DSF) is proposed and successfully demonstrated. SLM operation is obtained due to the spectral narrowing effect resulting from inverse four-wave mixing in a DSF. A tunable optical filter performs wavelength selection function. By inserting a length of DSF in the laser cavity, SLM lasing can possibly be obtained when laser oscillation is stably established after traveling through the DSF many roundtrips. Stable tunable SLM oscillation with a signal-to-noise ratio as high as 65 dB over a wavelength range of about 35 nm is achieved experimentally, and each spectral linewidth is less than 6.5 kHz. 相似文献
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Tunable dual-wavelength fiber laser based on a polarization-maintaining fiber Bragg grating and a Hi-Bi fiber optical loop mirror 总被引:1,自引:0,他引:1
R. I. Álvarez-Tamayo M. Durán-Sánchez O. Pottiez E. A. Kuzin B. Ibarra-Escamilla 《Laser Physics》2011,21(11):1932-1935
We demonstrate experimentally the operation of a linear cavity dual-wavelength fiber laser using a polarization maintaining
fiber Bragg grating (PM-FBG) as an end mirror that defines two closely spaced laser emission lines. The PM-FBG is also used
to tune the laser wavelengths. The total tuning range is ∼8 nm. The laser operates in a stable dual-wavelength mode for an
appropriate adjustment of the cavity losses for the generated wavelengths. The high birefringence (Hi-Bi) fiber optical loop
mirror (FOLM) is used as a tunable spectral filter to adjust the losses. The FOLM adjustment was performed by the temperature
control of the Hi-Bi fiber. 相似文献
17.
We propose a simple dual-wavelength Er-doped fiber laser configuration based on a dual-wavelength fiber Bragg grating written on the splice joint between two different fibers for wavelength-selective filter in the Sagnac loop interferometer. The wavelength separation between the adjacent lasing wavelengths is 1.12 nm and the side-mode suppression ratio (SMSR) is over 55 dB. The output power variation is less than 0.8 dB over a two-minute period. Moreover, the lasing wavelength can be effectively tuned using the thermal heating method. 相似文献
18.
Xinhuan Feng Linghao Cheng Jie Li Zhaohui Li Bai-ou Guan 《Optics & Laser Technology》2011,43(7):1355-1357
A simple approach for photonic generation of a tunable microwave signal is proposed and successfully demonstrated. By mixing the output from a single-longitudinal-mode Brillouin fiber ring laser with the reflected laser pump at photodetector, a microwave signal at the Brillouin shift can be obtained. Since the Brillouin shift can be changed by tuning the pump wavelength, tunable microwave can be generated. As a result a microwave signal tunable from 10.39 to 10.67 GHz has been achieved, with linewidth less than 600 KHz. 相似文献
19.
Jiajun Tian Yong Yao Jun Jun Xiao Xuelian Yu Deying Chen 《Optics Communications》2012,285(9):2426-2429
A tunable multiwavelength erbium-doped fiber laser is proposed and experimentally studied. The intensity-dependent loss (IDL) in a nonlinear optical loop mirror is utilized for stable multiwavelength lasing output. The accurate switch operation, i.e., the lasing lines emerge/disappear one by one at the longer wavelength side of the initial one, is achieved by adjusting the intra-cavity loss using a variable attenuator. The effect of the intra-cavity loss on the lasing characteristics is theoretically analyzed. Numerical results confirm the experiment measurements and suggest that both the IDL and the gain spectrum, which vary with the intra-cavity loss, lead to the observed tunable lasing behavior. 相似文献
20.
A multi-wavelength Brillouin-erbium ring-cavity fiber laser utilizing 2-m erbium doped fiber (EDF) and 70-m high nonlinear
photonic crystal fiber (PCF) is proposed and demonstrated. The output characteristics and also the impacts of pump and Brillouin
pump (BP) on the output spectra are investigated in detail. The output number and wavelength location of Brillouin lines are
tunable by adjusting the power of 1465 nm pump and BP, and a 5-channel output within 11 nm (1551–1562 nm) tuning range is
achieved by choosing appropriate pump power. 相似文献