共查询到20条相似文献,搜索用时 15 毫秒
1.
The Raman spectrum of any molecule consists of two mirror-image signals, th e Stokes and anti-Stokes Raman spectra. In most cases, unless highly specific sampling conditions are used, the anti-Stokes signal is much weaker than that of the Stokes. The recent application of intensified diode array detectors to Raman spectroscopy has produced a marked increase in the sensitivity of the technique which makes a study of the anti-Stokes spectrum potentially more rewarding than it has been to date. The present study has shown that, although of limited use for general purposes, there are some specific instances where the anti-Stokes spectrum can be of considerable practical use. Such applications are to extend the operating range of the Raman spectrometer, to study photodegradable samples and for the analysis of samples which exhibit strong fluorescence. 相似文献
2.
The two continuous wave lasers normally used for Raman spectroscopy are the argon and krypton ion lasers. These routinely provide step tuning between 459.9 and 676.4 nm. However, it is possible, using suitably coated mirrors, to obtain far red lines from the Kr+ laser at 752.5 and 799.3 nm.This additional capability offers advantages for Raman spectroscopy in the areas of fluorescence rejection, sample decomposition and resonance Raman spectroscopy. 相似文献
3.
讨论了一种新的高灵敏度甲烷遥测方法,利用可调谐激光二极管的调制光谱技术扫描甲烷的吸收峰,通过在测量光路中插入参考气池,增强低浓度情况下的吸收峰辨识能力,以提高甲烷浓度遥测信号的信噪比.此外,可以将激光器的中心波长锁定至气体吸收峰的峰值位置从而使仪器工作于吸收峰锁定模式,进行甲烷浓度的连续监测.实验结果表明,在测量距离分别为10 m和20 m时,周围环境中的甲烷积分浓度探测极限可以分别达到5 ppm·m和16 ppm·m.在吸收峰锁定工作模式下,系统在37 m距离处具有22 ppm·m的检出限,并可以监测甲烷浓度的快速变化. 相似文献
4.
In this paper, the rate equations of coupled-cavity diode lasers are studied and their improvements in the case of strong coupling are presented, and therefore, the mechanism of single-mode oscillation of the devices is discussed. 相似文献
5.
In this paper, the rate equations of coupled-cavity diode lasers are studied and their improvements in the case of strong coupling are presented, and therefore, the mechanism of single-mode oscillation of the devices is discussed. 相似文献
6.
Room-temperature (RT) continuous-wave (CW) operation of the 405-nm ridge-waveguide (RW) InGaN/GaN quantum-well diode lasers
equipped with the n-type GaN substrate and two contacts on both sides of the structure has been investigated with the aid
of the comprehensive self-consistent simulation model. As expected, the mounting configuration (p-side up or down) has been
found to have a crucial impact on the diode laser performance. For the RT CW threshold operation of the otherwise identical
diode laser, the p-side up RW laser exhibits as high as nearly 68°C maximal active-region temperature increase whereas an
analogous increase for the p-side down laser was equal to only 24°C. Our simulation reveals that the lowest room-temperature
lasing threshold may be expected for relatively narrow and deep ridges. For the structure under consideration, the lowest
threshold current density of 5.75 kA/cm2 has been determined for the 2.2-μm ridge width and the 400-nm etching depth. Then, the active-region temperature increase
was as low as only 24 K over RT. For wider 5-μm ridge, this increase is twice higher. An impact of etching depth is more essential
for narrower ridges. Quite high values (between 120 and 140 K) of the characteristic parameter T0 convince very good thermal properties of the above laser. 相似文献
7.
采用高电流注入条件下的载流子扩散方程和复折射率波导模型情况下的亥姆霍兹方程,对980 nm高功率激光二极管外延材料的非对称和对称波导结构的光吸收损耗进行了理论计算。采用低压金属有机化学气相外延技术制备了两种波导结构的外延材料,并制作了激光器件,进行了光电特性测试和对比分析。理论计算和实验结果表明:与对称波导结构相比,非对称波导结构外延材料并未减小光吸收损耗,而是减小了串联电阻,因而降低了器件的焦耳热损耗,从而提高器件的电光效率。 相似文献
8.
Room-temperature, near-infrared, semiconductor diode lasers continue to gain importance for gas monitoring applications owing to their compactness, ease of use, reasonable cost and compatibility with telecommunications-grade optical fiber components. They may probe overtone or combination vibrational bands for a large variety of atmospheric relevant molecular species. These spectral bands exhibit line strengths orders of magnitude lower than those of fundamental vibrations, occurring in the mid-infrared. As a consequence, they are often used in conjunction with long-path techniques, enabling one to perform high sensitivity local measurements through long absorption path-lengths. At this purpose, resonant optical cavities can be fruitfully employed. This paper is devoted to a discussion of the main features of cavity-enhanced absorption spectrometers, operating with near-infrared diode lasers. We report on the operating principle as well as the achievable performance of these devices, also compared to more traditional apparatus, based on the multiple reflection cells. Experimental results on water vapour and oxygen detection are reported. 相似文献
9.
10.
就高功率激光二极管阵列端面抽运大口径放大器提出一种新的耦合方式:激光二极管阵列拟球面排布,其后紧接一个导管进行耦合传输. 用三维光线追迹法对这种耦合方式的特性进行模拟分析. 结果表明,该耦合方式能实现高的抽运耦合效率和高的能量沉积效率,在面积缩束比为30的条件下,该耦合方式的耦合效率和能量沉积效率最高可分别达96.7%,93.7%;当激光二极管面阵单元发光区域不小于导管输出端口径时,该耦合方式能实现抽运场均匀平顶分布;另外,采用该耦合方式,激光二极管阵列排列方式灵活,非对称排布时也可实现两维对称性好、均匀平顶分布的抽运耦合场输出. 建立了激光二极管阵列端面耦合实验系统,实现了85.4%的耦合效率和均匀的抽运耦合场输出.
关键词:
激光二极管阵列抽运固体激光器
端面抽运
均匀抽运 相似文献
11.
Robert J. Williams Johannes Nold Maximilian Strecker Ondrej Kitzler Aaron McKay Thomas Schreiber Richard P. Mildren 《Laser \u0026amp; Photonics Reviews》2015,9(4):405-411
We report high‐power frequency conversion of a Yb‐doped fiber laser using a double‐pass pumped external‐cavity diamond Raman oscillator. Pumping with circular polarization is shown to be efficient while facilitating high‐power optical isolation between the pump and Raman laser. We achieved continuous‐wave average power of 154 W with a conversion efficiency of 50.5% limited by backward‐amplified light in the fiber laser. In order to prove further scalability, we achieved a maximum steady‐state Raman‐shifted output of 381 W with 61% conversion efficiency and excellent beam quality using 10 ms pump pulses, approximately a thousand times longer than the transient thermal time‐constant. No power saturation or degradation in beam quality is observed. The results challenge the present understanding of heat deposition in Raman crystals and foreshadow prospects for reduced thermal effects in diamond than originally anticipated. We also report the first experimental evidence for stimulated Brillouin scattering in diamond.
12.
13.
The use of a diode laser in an ESPI system is reported. These lasers have considerable potential advantages over gas lasers in terms of convenience, cost and lifetimes, and may eventually replace the latter in this type of instrument. 相似文献
14.
15.
16.
17.
18.
19.
20.
ABSTRACTWe demonstrate a silicon cone array substrate coated with gold nanoparticles and which was highly sensitive, homogeneous, and provided a large area for surface-enhanced Raman spectroscopy (SERS). A deep reactive ion-etching process was used to fabricate the high-density silicon cone array, and gold nanoparticles were formed on the silicon cone surface by magnetron sputtering. The substrate was tested with 10?6 M rhodamine 6 G solution. Enhancement of the substrate was about 60-fold greater than that of flat substrate. Moreover, SERS signals obtained from 24 random areas on the substrate showed good homogeneity with an average standard deviation of 3.9%. 相似文献