双折射调谐器设计的等色图原理

提出双折射调谐器设计的等色图方法，给出原理。分析表明当晶片光轴处在以折射光线为轴线、顶角为４５°的圆锥面上时，双折射调谐器具有最快的波长调谐速率；当光轴位于过折射光线并与入射面成４５°或１３５°的平面内时，调谐器抑制非所需波长的能力最强。由此给出光轴相对晶片表面的两个优化取向，对石英晶片它们分别为１８．７１２°和５９．９２２°。文中还给出了三块晶片组合的调谐器的设计例子，对其调谐特性进行了简要的讨论。     

Optical activity of a cadmium diphosphide crystal

We have experimentally studied the characteristic features of a laser beam, polarized at angles of ± 45° to the horizontal (vertical), passing through plates of varying thickness cut from a CdP₂ crystal and placed between crossed polarizers, as a function of their angle of rotation relative to the vertical axis. We show that a periodic variation in the intensity is connected with the variation in polarization of the laser beam. We have established that the laser beam remains linearly polarized not only when it passes through the sample along the optic axis, but also when it travels at up to a 17.5° angle to the optic axis. In this case, the specific rotation of the plane of polarization along the optic axis is 68.2 degrees/mm for a thicker plate and 83.3 degrees/mm for a thin plate. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 5, pp. 690–693, September–October, 2006.     

双折射滤波片的优化参量

研究了双折射滤波片的滤波和调谐性质。利用矩阵方法和反射、透射系数,给出了波片两个界面的菲涅耳系数。利用相移公式和光线轨迹公式,由入射角和光轴方位角可计算波片精确的相移公式。将上述系数和这一波片的相移公式用于琼斯矩阵,得到透射率的本征矩阵。该矩阵的本征值即为波片的透射系数。由此,给出了波片的主要性质(特别是透射宽度),讨论了波片参量(入射角、方位角和厚度)对波片性质的影响。利用相移公式,讨论了波片的调谐性质,并给出了选择参量的最佳范围。对石英波片,最佳参量为:厚度约在1500~2000μm,方位角大于45°,循环系数r尽可能大。在激光器增益较大时,选择较小的入射角。     

双折射双频激光器输出光偏振特性的实验研究

报道了双折射双频激光器输出光偏振特性的实验研究，实验发现双折射双频激光器两端输出的线偏振光的偏振方向并不一致，而相互有一定的旋转角度，实验也再次证明了激光器输出的是正交线偏振光，而不是晶体本征模的椭圆化了的偏振光。     

A sensitive method of determining optic axis azimuth based on laser feedback

A sensitive method to determine the optic axis azimuth of the birefringence element is presented, which is based on laser feedback. The phase difference between the two intensities in birefringence feedback changes with the angle between the optic axis of the birefringence element and laser original polarization. The phase difference is highly sensitive to the relative position of the optic axis and the laser original polarization. This method is used to highly precisely determine the optic axis azimuth, and is able to distinguish between the fast axis and the slow axis of the birefringence element. Theoretical analysis and experimental results are both demonstrated.     

K5Nd(MoO4)4: a self-tunable laser crystal

We report for the first time to our knowledge an experimental demonstration of wavelength self-tuning in a K5Nd(MoO4)4 broadband-emitting laser crystal (KNM), as well as a theoretical treatment of the system based on its birefringence properties. The self-frequency-tuning of the laser along the full spectral range of the KNM crystal was obtained by rotating a birefringent gain plate in its own plane. The gain plate was placed inside a resonator at Brewster's angle. The tuning characteristics of the spectral filter were obtained by use of the Jones vector formalism. The calculated wavelength-selective tuning precisely matches the experimental observations.     

Characteristics and efficiency of a compact HF laser initiated by an electron beam

A compact hydrogen fluoride laser is described and its efficiency is evaluated. The HF laser is initiated by injecting a 150 kV electron beam into a mixture of SF₆ and H₂ transversely to the laser cell axis. The optimum laser energy characteristics are determined as a function of the beam energy and gas pressure.     

Intracavity configuration for tuning and obtaining simultaneous dual-wavelength operation from CW Nd:YAG laser

In this letter, a thin slab of glass is used as Fabry–Perot etalon inside a cavity of a continuous wave (CW) Nd:YAG laser to change the behavior of its output longitudinal modes. The slab etalon is used as tuning element when it turns around the laser cavity axis. Two simultaneous longitudinal modes with a relatively wide tuning range from 5.83 MHz to 0.02 THz are obtained when the Nd:YAG laser is operated at moderate output power of about 120 mW. The mode structure of this configuration is modeled and simulated. Computer-generated diagrams are also presented schematically and compared with the experimental results.     

环形腔被动锁模掺饵光纤激光器

通过在非线性偏振旋转环形腔内引入一种可旋转的在线起偏器,在保证装置的全光纤化结构的前提下,简化了被动锁模光纤激光器的结构.通过联合调节可旋转的在线起偏器、1/2波片和1/4波片的角度实现了掺饵光纤锁模脉冲20 nm间隔的双波长调谐输出,调谐过程中观察到了锁模脉冲双波长状态.另外,从装置中去掉1/2波片后,仅调谐可旋转的在线起偏器和1/4波片也能够实现锁模脉冲的单波长稳定输出.     

环形腔被动锁模掺饵光纤激光器

通过在非线性偏振旋转环形腔内引入一种可旋转的在线起偏器,在保证装置的全光纤化结构的前提下,简化了被动锁模光纤激光器的结构.通过联合调节可旋转的在线起偏器、1/2波片和1/4波片的角度实现了掺饵光纤锁模脉冲20nm间隔的双波长调谐输出,调谐过程中观察到了锁模脉冲双波长状态.另外,从装置中去掉1/2波片后,仅调谐可旋转的在线起偏器和1/4波片也能够实现锁模脉冲的单波长稳定输出.     

压制观瞄系统多光谱光轴平行性调校技术研究

鉴于压制观瞄系统光轴平行性是实现精确压制的一项指标,其特殊性在于保证回转机械轴、可见光轴、激光光轴的平行性,提出一种采用双光楔对压制观瞄系统光轴进行调校的方法, 通过转动双光楔,使光轴发生偏转,从而完成各光轴的平行。通过分析压制观瞄系统的结构,重点介绍了双光楔调校的原理与方法,并建立数学模型。采用Matlab对数学模型进行仿真,基于该调校原理搭建实验装置进行试验,试验结果表明,采用双光楔进行光轴调校方法可使三轴调校后的平行度误差不超过0.1 mrad。     

Wide tuning characteristics of double-ring coupled lasers

The wide tuning characteristics of double-ring coupled lasers with/without an extended waveguide are analyzed and optimized using the scattering matrix formalism. To obtain the optimum design schemes of the tunable laser diodes, the cross coupling ratios of two rings, the tuning enhancement factor, the propagation loss of passive waveguides, the optical gain of an active region, and the back and front-facet reflectivity of the waveguide are taken into account. When the coupling ratio of the ring and input/output waveguides is fixed, the extinction ratio and the linewidth are decreased as the tuning enhancement factor is increased, while the tuning range is increased.     

Effect of the orientation of the optic axis on simulated scattering matrix elements of small birefringent particles

We study how the orientation of the optic axis affects single-scattering properties for small, birefringent calcite particles simulated using DDSCAT 7.1.1. We consider two irregular model particles, a flake and a rhomboid, in either a (i)?fixed or (ii)?random orientation. Simulations are performed for three volume-equivalent radii of 0.1, 0.45, and 1.0?μm. For each target, we repeat the computations for three sets of orientations of the optic axis. When a fixed spatial orientation of the target is considered, the simulations are significantly affected by the orientation of the optic axis. However, the effect is considerably weaker when assuming the same targets in random spatial orientation.     

TDLAS氧气测量系统中激光器调谐性能测试与优化

TDLAS(可调谐半导体激光吸收光谱)技术以其分子光谱高选择性、速度快、灵敏度高、非接触测量等难以取代的优势,成为燃烧过程诊断等应用的首选,可以有效用于氧气测量。DFB(分布反馈)半导体激光器以其体积小、功耗低、寿命长、线宽窄、波长可调谐等优点成为TDLAS系统的主要选择,而其调谐特性是制约系统测量性能的关键因素。根据TDLAS氧气测量系统工作要求,采用一种简单易行的实验方法对系统中用到的764 nm DFB激光器的电流波长、温度波长和电流功率等重要调谐特性进行了测试和分析,发现出射光谱窄线宽、高边模抑制比和宽波长可调谐范围等特点明显,电流波长调谐曲线近似但并非严格线性、调谐速率约0.023 nm·mA-1,温度越高阈值电流越大、PI曲线也并非严格线性,温度调谐特性曲线线性较好、波长温度调谐速率基本保持恒定约为0.056 nm·℃-1。可见各种调谐曲线的非线性失真比较明显,影响氧气测量精度。温度调谐非线性可以通过温控精度的提高来消除,电流功率调谐非线性可以通过设置参考光强来消除。为了进一步解决电流波长调谐非线性问题,根据DFB半导体激光器的调谐机理和电流波长测试结果的多项式拟合,考虑通过DA控制注入电流的方式对电流波长调谐非线性进行补偿。这种方法针对不同激光器只需在系统初次工作之前进行一次多项式拟合,方案合理、实现简单且不影响测量过程。实验证明,补偿之后的λI曲线线性拟合残差小于1 pm,远小于补偿前的22 pm,效果明显,为氧气各种参数TDLAS精确测量和反演提供了依据。     

光泵NH3分子远红外激光研究

运用量子系统的密度矩阵理论，采用迭代法计算了光泵ＮＨ３分子远红外超辐射和腔式激光的频谱特性和相应的最佳工作气压。理论计算表明相对于超辐射方式，光泵腔式ＮＨ３分子远红外激光具有宽带辐射以及纵向调谐特性，且总的输出光强在一定条件下得到提高，最佳工作气压也较低。在实验上对ＴＥＡＣＯ２－１０Ｒ（８）和９Ｒ（１６）泵浦的Ｎ 红外超辐射和腔式激光器产生的远红外辐射进行了测量。结果表明理论计算与实验结果相符。     

Experimentelle Untersuchung der Čerenkov-Strahlung in optisch einachsigen Kristallen

The relative yields of ?erenkov radiation produced by theβ-rays of P³² by passing through a thin uniaxial crystal plate have been investigated experimentally with the aid of a fast coincidence and a linear gate circuit. Measurements were performed with electrons moving (a) parallel to the optic axis of the uniaxial crystal plate and (b) perpendicular to the optic axis. The experiment showed that the yield of ?erenkov radiation when the electrons moved parallel to the optic axis of the crystal was about 15% higher than in the case of the electrons moving perpendicular to it. This is in good accordance with theory.     

Tunable multi-wavelength combined linear-cavity fiber laser source with equally changed wavelength spacing

A tunable multi-wavelength combined linear-cavity fiber laser source with equally changed wavelength spacing is proposed for the first time. The wavelength tuning is realized by stretching or compressing the fiber Bragg gratings incorporated in the laser cavity. To ensure a wavelength tuning with equally increased or decreased wavelength spacing, the gratings are mounted onto a plastic plate with angles between adjacent gratings such that the forces applied to the gratings has an equal force increment. A four-wavelength lasing with equal increased or decreased wavelength spacing is achieved experimentally.     

Subnanosecond pulse measurements of 10.6 μm radiation with tellurium

Subnanosecond infrared pulses have been measured by noncollinear secondharmonic generation in tellurium. The method is very practical because due to the high refractive index the fine tuning of the phase matching is easily obtained by rotating the crystal around the optic axis.     

Tunable Fabry-Pérot filter based on one-dimensional photonic crystals with liquid crystal components

A theoretical study of a tunable Fabry-Pérot multilayer structure composed of alternating layers of silicon and liquid crystal is presented and analyzed. The structure possesses two resonant frequencies within the stop band with tunable wavelengths and transmission properties. Tuning is achieved by allowing different orientations of the liquid crystal optical axes within the cavity and within the mirrors, while keeping the optical axes parallel to the layers. Applying the transfer matrix method for thin layers of anisotropic materials we demonstrate that the resonant wavelengths depend on the difference between the liquid crystal optical axis orientations. Besides, we are able to obtain a complete characterization of the structure in the form of its Jones matrix. From this, we propose an optical two-channel equalizer for applications around 1.55 μm that allows tuning the two resonant wavelengths and their relative amplitude levels.     

Oscillations in Total Photodetachment Cross Sections of a Triatomic Anion

The total photodetachment cross section of a linear triatomic anion is derived for arbitrary laser polarization direction. The cross section is ,shown to be strongly oscillatory when the laser polarization direction is parallel to the axis of the system; the oscillation amplitude decreases and vanishes as the angle between the laser polarization and the anion axis increases and becomes perpendicular to the axis. The average cross section over the orientations of the triatomie system is also obtained. The cross section of the triatomic anion is compared with the cross section of a two-center system. We find there are two oscillation frequencies in the triatomie anion in contrast to only one oscillation frequency in the two-center case. Closed-orbit theory is used to explain the oscillations.