1 532 nm全光纤Er/Yb共掺杂激光器

近年来,相干探测激光雷达是测量远距离低空风切变的有效手段,1.6 μm波段固体激光器以其人眼安全、探测器件成熟等优势成为相干雷达主要光源。其增益介质Er:YAG晶体在1532 nm波段有较强的吸收峰,但吸收谱较窄,因此通过使用1 532 nm光纤激光器进行谐振泵浦可以有效提高晶体输出效率。为此,文中以Er/Yb双包层光纤为增益介质,1532 nm光纤光栅为反射腔镜,976 nm半导体激光器为泵浦源,实现了全光纤化1532 nm激光输出。输出激光最大功率73.44 W,波长可调谐范围为1531.35~1532.14 nm,波长谱宽为0.06 nm,x和y方向的光束质量M2分别为1.38和1.26,是1.6 μm固体激光器的理想泵浦源。并采用此激光器泵浦Er:YAG非平面环形腔获得1.3 W单频激光输出,斜率效率为31.76%。     

火灾烟颗粒群多分散与单分散光散射模型的比较研究

基于T矩阵法,取入射激光的波长分别为300、633、800nm,对正庚烷火烟颗粒群分形结构的多分散模型、单分散模型以及等体积的球形模型的光散射Muller矩阵元素随散射角的分布特性进行了详细的比较分析。结果表明,当λ=300nm时,散射光能很好地反映正庚烷火烟颗粒凝团的分形结构及凝团中基本颗粒的分布特性;当λ=633nm时,正庚烷火烟颗粒群分形结构的多分散模型和单分散模型的光散射特性基本一致;当λ=800nm时,正庚烷火烟颗粒群3种模型的光散射特性趋于一致。     

紫外激光无损检测潜在指印技术研究

潜在指印的显现是物证检验技术中的关键问题之一,而紫外(UV)照相技术是显现潜在指印等隐性痕迹物证的重要技术手段。采用266 nm紫外固体激光器为激发光源,利用人体指印固有物质成分对紫外光具有特殊的吸收、反射、散射及荧光特性,减弱或消除指印背景上的图案和其他细节干扰,增加指印纹线与背景的亮度反差,显出或增强潜在指印。通过紫外反射照相及紫外固有荧光照相技术,分别实现了对彩色杂志纸张、玻璃、电话背面、木纹桌面油漆面4种非渗透性物证检材及牛皮纸信封、便签纸2种渗透性物证检材表面遗留的新鲜及陈旧潜在指印的无损检测显现,并具有鉴定价值。     

蓝紫光的腔增强空气喇曼光谱

喇曼光谱是一种无损、快速检测物质成分的方法。为了提高监测灵敏度, 对408nm波段半导体激光器的腔增强自发喇曼散射进行了研究。利用输出功率500mW、线宽0.9nm的408nm半导体激光器作激发光, 把激光耦合入共焦球面镜腔, 两面共焦球面镜的反射率分别为96.5%和99.5%, 部分激光返回半导体激光器形成光反馈, 半导体激光器与共焦腔形成共振。对装置的光反馈过程进行了探讨, 并对外腔的模式匹配和频率匹配分别进行了分析。结果表明, 共焦腔内功率达到15W, 功率增强了30倍; 用90°探测构型收集喇曼信号, 完成了空气喇曼信号检测; 1s积分时间, 获得N₂信号900个计数。此共振增强腔大大增强了喇曼散射信号, 有潜力应用于多种气体的在线检测或高灵敏度检测。     

谐振腔衰荡法检测激光高反射薄膜损耗

光学薄膜的损耗类型主要涉及吸收和散射,精确测定其数值是制备具有高品质和灵敏度指标激光薄膜的前提。本文以薄膜光学和激光技术为背景,介绍了谐振腔衰荡检测高反射薄膜的原理、特性以及测试方法。以1064 nm和1311 nm的高反射膜层为例,利用Losspro激光测试装置,对于二氧化锆(ZrO2)、五氧化二钽(Ta2O5)材料获得百万分(ppm)量级精度的损耗数据后,针对不同薄膜材料和工艺方法进行了对比检测,分析认为速率控制和离子束能量对于相同材料的激光高反射薄膜具有明显的影响,进而为薄膜样品的制备奠定了技术基础。     

脉冲光入射时法布里-珀罗腔的透射特性

本文从理论与实验两方面讨论脉冲激光入射时法布里-珀罗（FP）腔的透射特性。结果表明：FP腔的输出波形分三个明显阶段：建立阶段、稳定阶段及衰荡阶段。建立阶段表示激光注入、稳定阶段表示腔内信号达到最大值、衰荡阶段则表示外部激光注入停止。衰荡阶段的衰荡时间与腔的振幅衰减系数有关。     

Quantifying spatial localization of optical mapping using Monte Carlo simulations

Optical mapping techniques used to study spatial distributions of cardiac activity can be divided into two categories. 1) Broad-field excitation method, in which hearts stained with voltage or calcium sensitive dyes are illuminated with broad-field excitation light and fluorescence is collected by image or photodiode arrays. 2) Laser scanning method, in which illumination uses a scanning laser and fluorescence is collected with a photomultiplier tube. The spatial localization of the fluorescence signal for these two methods is unknown and may depend upon light absorption and scattering at both excitation and emission wavelengths. We measured the absorption coefficients (micro a), scattering coefficients (micro s), and scattering anisotropy coefficients (g) at representative excitation and emission wavelengths in rabbit heart tissue stained with di-4-ANEPPS or co-stained with both Rh237 and Oregon Green 488 BAPTA 1. Monte Carlo models were then used to simulate absorption and scattering of excitation light and fluorescence emission light for both broad-field and laser methods in three-dimensional tissue. Contributions of local emissions throughout the tissue to fluorescence collected from the tissue surface were determined for both methods. Our results show that spatial localization depends on the light absorption and scattering in tissue and on the optical mapping method that is used. A tissue region larger than the laser beam or collecting area of the array element contributes to the optical recordings.     

应用于吸收型甲烷传感器的1650nm DFB激光器的研制

光学吸收法是一种工程上有效可行的检测痕量甲烷气体的方法,具有广泛地应用于构建煤矿坑道等场合的安全防护和报警系统的潜力.为实现针对甲烷气体1653nm吸收峰特性的单色光源,采用金属有机化合物化学气相沉积外延和纳米压印等技术手段,从多量子阱外延材料设计和金属有机化合物化学气相沉生长到器件封装,研制了1653nm分布反馈激光...     

基于激光偏振技术的海洋牧场水下成像技术研究

良好的水下视觉环境是推动海洋经济发展的前提,海洋牧场的建设对水下成像技术提 出 新的要求,但是受水体环境吸收及散射影响,光信息丢失严重,用常规光学成像方式进行水 下 图像获取会有可视距离短,图像模糊不清,对比度低等缺点。为解决海洋牧场水下成像清晰 度 低的问题,提出一种通过532 nm激光光源与偏振技术相结合的方法并 集成了一款水下相机。 532 nm波段的绿色激光光源在水体环境中受到水体影响较小,传播效 果更佳,偏振成像技术在去 背景光散射中应用广泛,采用532 nm激光光源与偏振成像技术相结合 的方法进行水下图像的获 取,并在模拟海水环境的水池中进行了海参图像获取的实验,实验结果证明在某一偏振角度 下, 532 nm激光光源与偏振成像技术相结合的方式获取的海参图像相比于 自然光下获取的原图像对比 度、清晰度更高,含有的图像信息更加丰富,验证了此方法在水下成像的可行性。     

Development and application of three-dimensional light distribution model for laser irradiated tissue

A three-dimensional model for estimating light distribution in laser irradiated tissue is presented. Multiple scattering and absorption of the laser beam are modeled using seven fluxes. One-, two-, and three-dimensional solutions are discussed and light distributions computed from the seven flux model are compared to those computed with the diffusion approximation. Methods for obtaining the phase function, absorption coefficient, and scattering coefficient for tissue are discussed and illustrated with measurements for human aortic vessel wall at the wavelength of 632.8 nm. Measured values are used in the seven flux model to estimate the rate of heat generation in the vessel wall.     

水中颗粒物大角度范围体散射函数测量方法

针对现有体散射测量系统中激光器与探测器相互遮挡导致探测角度减小的问题,设计了一款新型的水中颗粒物的体散射函数测量系统。首先,通过双潜望式光路结构,将激光发生平面与散射探测平面分离,减小了激光器对探测角度的遮挡;同时,通过潜望式出射棱镜将透射光导出水体,避免了容器的杯壁散射,提高背散射测量的准确性。根据实际工艺,改进出射棱镜,设计系统样机,实现了3°~178°大角度范围体散射函数的测量。结合系统结构与水下光传输原理,根据数据矫正算法,矫正由于测量光程及水体衰减造成的偏差。对比矫正后结果与米散射仿真结果,证明方法的可靠性。     

Stimulated Brillouin Scattering in a Single-Mode Tellurite Fiber for Amplification, Lasing, and Slow Light Generation

In this paper, Brillouin gain performances of tellurite fiber are investigated for photonics applications. We demonstrate stimulated Brillouin amplification and lasing and the simulated performance of slow light generation in a single-mode tellurite fiber. A Brillouin gain of 29 dB is achieved in a 100-m tellurite fiber with a pump power of 10 mW at 1550 nm. A peak value of Brillouin gain coefficients of 1.6989 X 10^-10 m/W is measured on the base of gain characteristics. An all-fiber Brillouin laser with the maximum unsaturated power of 54.6 mW at 1550 nm and a slope efficiency of 38.2% is achieved from a 200-m tellurite fiber by employing a ring cavity. Furthermore, widely tunable (~27 nm) Brillouin comb laser with 26 lines spaced at 7.97 GHz is obtained from the ring laser cavity including an erbium-doped fiber amplifier (EDFA). A simple theoretical model based on laser threshold theory successfully explains the properties of Brillouin comb lasers. Stimulated Brillouin scattering (SBS)-induced time delay per unit power and per unit length is also calculated using the measured data of Brillouin gain coefficients. A peak value of 0.09246 ns/mW/m and a time delay slope efficiency of 1.75 ns/dB are obtained for this tellurite fiber. Potential performance of a tellurite fiber for slow light generation is clarified on the base of Brillouin gain characteristic. Our results show that tellurite fiber is a promising gain medium for Brillouin fiber amplifiers, lasers, and slow light generation due to its low background loss and large Brillouin gain coefficient.     

Numerical Modeling of Pulsed Raman Fiber Converters at 2 $mu{hbox {m}}$

Theoretical modeling of stimulated Raman scattering (SRS) in fibers is presented for the near-infrared band around 2 mum, where pump and Stokes wave have different absorption. This model takes into account amplified spontaneous emission (ASE), SRS towards Stokes and anti-Stokes waves, absorption of the Raman medium and Rayleigh backscattering in fibers. Depending on the fiber configuration, this model includes the cavity parameters of either external or internal mirrors at the fiber ends. Input parameters are, among others, temporal profiles of the pump radiation, absorption, and gain curve of the Raman medium. The model agrees well with experimental results obtained with a GeO₂ doped core fiber pumped by a pulsed and tunable Tm:silica fiber laser emitting around 2 mum.     

基于环腔内光学缓存装置的高速扫频激光光源

傅里叶域锁模(FDML)技术可在保持扫频光源各项指标性能优越的前提下,将扫频速度提高至调谐滤波器的设计极限。为进一步提升FDML扫频激光光源的扫频速度,在激光谐振腔内引入光学缓存装置来实现对扫频光的备份。实验中基于环腔内光学缓存装置的扫频光源中心波长为1310nm,扫频范围为95nm,瞬时线宽为0.1nm,扫频速度翻倍提升至202kHz,平均输出光功率为7.5mW。利用光学缓存装置可将传统FDML高速扫频光源的扫频速度翻倍提升,对提升扫频光学相干层析成像(SS-OCT)系统的综合成像性能具有重要意义。     

光纤甲烷气体传感器的研究

基于甲烷气体近红外吸收的机理,研究了一种高灵敏度易于实现的光纤甲烷气体传感器。分析了半导体激光器的调制特性和谐波检测的基本原理,建立了传感器的数学模型。系统采用分布反馈式半导体激光器做光源,气室采用小型渐变折射率透镜构成的气室,加入参考光路和参考气室,使光源输出的中心波长锁定在气体的吸收峰上,通过光源调制实现气体浓度的谐波检测,给出了甲烷气体测量的实验结果。     

NH3的腔增强吸收光谱检测技术

为了研究腔增强吸收光谱技术是否能用于NH₃气体浓度的检测,采用扫描腔长的方法,以分布反馈式可调谐半导体激光器作光源,用两块高反射率平凹透镜（反射率约为99.9%,曲率半径约为1m）组成的光学谐振腔作吸收池,搭建腔增强吸收光谱装置。在34cm长的吸收池内测量NH₃气体分子在1.5μm附近的弱吸收谱线;通过不断增加NH₃气体浓度来改变腔内压强,每充入一次NH₃都测量并保存一次吸收光谱。通过数据处理,分析谱线宽度随气体浓度变化的关系以及吸收度随腔内压强增加的变化情况,发现都能呈现出良好的线性关系,并对残差噪声进行统计分析,得到了3.3×10-8cm-1的最小探测灵敏度。结果表明,高探测灵敏度的腔增强吸收光谱技术,可以实现NH₃气体浓度的测量,并能得到较好的探测精度。     

表面散射特性光学检测的多波长光纤传感器

论述了一种表面散射特性实时光学检测的光纤传感器。采用650 nm、1 310 nm和1 550 nm激光作为光源,对不同表面粗糙度的样品进行了测试和分析。实验结果表明,采用多波长的复合光源激光光纤传感器能有效地减小测量的非系统误差,从而极大地提高了其测量精度;此外,波长越短,粗糙度越大,散射越复杂。     

一种新颖的自反馈光注入单频窄线宽光纤激光器

报道一种基于自反馈光注入的单频窄线宽光纤激光器。激光器采用线形腔结构,用高掺杂Er3+光纤作为增益介质,利用输出信号光分束反馈与腔内振荡激光干涉,形成折射率光栅与增益光栅共同作用选择纵模,获得稳定的1 549.85 nm单频窄线宽激光输出。在975 nm单模激光二极管(LD)抽运下,激光器的抽运阈值光功率为13 mW。当抽运光功率为112 mW时,最大输出信号光功率为30.6 mW,对应的光-光转换效率为27.3%,斜率效率为30.2%,信噪比大于50 dB。采用延时自外差方法测量线宽,当使用30 km单模光纤延迟线时,测量得到激光器的3 dB线宽为4.0 kHz。     

Skin optics

Quantitative dosimetry in the treatment of skin disorders with (laser) light requires information on propagation of light in the skin related to the optical properties of the individual skin layers. This involves the solution of the integro-differential equation of radiative transfer in a model representing skin geometry, as well as experimental methods to determine the optical properties of each skin layer. These activities are unified under the name skin optics. This paper first reviews the current status of tissue optics, distinguishing between the cases of: dominant absorption, dominant scattering, and scattering about equal to absorption. Then, previously published data as well as some current unpublished data on (human) stratum corneum, epidermis and dermis, have been collected and/or (re)analyzed in terms of absorption coefficient, scattering coefficient, and anisotropy factor of scattering. The results are that the individual skin layers show strongly forward scattering (anisotropy factors between 0.7 and 0.9). The absorption and scattering data show that for all wavelengths considered scattering is much more important than absorption. Under such circumstances, solutions to the transport equation for a multilayer skin model and finite beam laser irradiation are currently not yet available. Hence, any quantitative dosimetry for skin treated with (laser) light is currently lacking.     

高非线性光纤中受激布里渊散射的抑制和光参量放大

受激布里渊散射 (SBS)的抑制是实现光纤参量放大的重要技术要求 ,已有文献报道多采用对抽运光进行相位调制的方法 ,将光功率分散到多个频率分量上来达到这一目的。提出一种二次调相的方法 ,在已有 2GHz相位调制的商品光源上施加 36 5MHz的二次相位调制 ,将高非线性光纤 (HNLF)的受激布里渊散射阈值由未加任何调制时的 10dBm至少提高到 2 3 5dBm ,达到了参量放大的要求。在此基础上 ,进行了连续波 (CW )抽运的光纤参量放大实验。实验中采用长度为 14 5 0m ,非线性系数γ =11 9W-1km-1,色散斜率S =0 0 15 5ps/(nm2 ·km)的高非线性光纤 ,使用外腔可调谐激光器 (ECL)作为信号光源 ,小信号增益带宽达到 2 6nm(增益 >10dB) ,峰值增益达到2 4dB。同时还观察到了由于非线性拉曼放大作用造成的长波长信号光增益大于短波长信号光增益的不对称性。