Laser frequency stabilization based on Sagnac interferometric spectroscopy

A simple method based on Sagnac interferometric spectroscopy (SIS) is applied for frequency stabilization of diode lasers. Sagnac interferometric spectra of rubidium vapor are investigated both theoretically and experimentally. The interference signal at the output of the Sagnac interferometer displays a sharp dispersion feature near the atomic resonance. This dispersion curve is used as the feedback error signal to stabilize the laser frequency. Linewidth of a diode laser is stabilized down to 1 MHz by this modulation-free method.     

Joint Remote State Preparation Schemes for Two Different Quantum States Selectively

The scheme for joint remote state preparation of two different one-qubit states according to requirement is proposed by using one four-dimensional spatial-mode-entangled KLM state as quantum channel. The scheme for joint remote state preparation of two different two-qubit states according to requirement is also proposed by using one four-dimensional spatial-mode-entangled KLM state and one three-dimensional spatial-mode-entangled GHZ state as quantum channels. Quantum non-demolition measurement, Hadamard gate operation, projective measurement and unitary transformation are included in the schemes.     

Comparison of <Emphasis Type="Italic">c</Emphasis>-Nd:YVO<Subscript>4</Subscript>/YVO<Subscript>4</Subscript> raman lasers and <Emphasis Type="Italic">c</Emphasis>-Nd:YVO<Superscript>4</Superscript> self-Raman lasers

Raman lasers based on c-Nd:YVO₄ crystals can generate 1178 nm Stokes line, which can be frequency-doubled to realize 589 nm sodium lasers. We make comparative experimental studies of c-Nd:YVO₄/YVO₄ Raman lasers and c-Nd:YVO₄ self-Raman lasers. About these two kinds of lasers, the output characteristics of power, center wavelength and beam quality are measured and compared.     

Beam Recombination Characteristics in Array Laser Amplification Using Stimulated Brillouin Scattering Phase Conjugation

Beam recombination characteristics were numerically investigated in array laser amplification using stimulated Brillouin scattering phase conjugation. To clarify the effect of piston errors due to imperfect phase locking, spatial intensity profiles of the beam recombination output were calculated in both the near and the far field on the basis of Rayleigh-Sommerfeld diffraction theory. The analyses indicate that piston errors are seriously detrimental to the quality of a beam recombination output and should be eliminated by a proper phase locking. It is also found that the gap between the beam splitting-combining wedges has a negligible effect.Presented at 1996 International Workshop on Interferometry (IWI ‘96), August 27-29, Saitama, Japan.     

用多面体测试分度误差研究

采用多面体和光电平行光管测试圆刻机分度误差，比较了１２、３６、７２面体的测试特点，从数据分析中可找到一些造成误差的因素     

Temperature measurement of nonsteady arcs

The temporal change of the radial temperature profile of a free burning argon arc at power frequency and a flashover arc near the surface of a polluted plate is experimentally determined with the help of a spectroscopic system, the detail of which is described in this paper. The image of the arc is scanned by a rotating 30-facet mirror drum over the entrance slit of a grating spectrometer. The intensity of up to four spectral lines can be simultaneously measured. The temperature results for the argon arc are derived by employing the absolute intensity method and the relative intensity method. This preliminary experimental investigation shows that the system is capable of measuring and monitoring the temperature development of nonsteady arcs which may be randomly moving in a known space     

Design of interdigital transducers for crack detection in plates

Interdigital transducers (IDT) for non-destructive evaluation (NDE) of cracks in plates are designed based on an analytical model established previously. Key considerations include mode selectivity, excitation strength, collimation of wave and cost. The advantage of mode selectivity of IDT over PZT patch is presented both analytically and experimentally. Effects of parameters, namely finger spacing, width, length, number of fingers, and the size of IDT, on the excitation strength and mode selectivity are considered. This led to the design of a mobile double-sided IDT as an efficient device where excitation strength is strong and focused. The device was fabricated in-house using commercially available piezoelectric ceramics and used to develop a procedure for accurate identification of the direction and extent of cracks in plates. Three aluminum plates, one with a linear deep crack, another with a piecewise linear shallower crack and the third with a curved crack, were used to illustrate the accuracy and efficiency of both the proposed device and procedure for effective NDE.     

Theoretical analysis and experimental verification of a cost-effective chromatic dispersion monitoring method in a 40-Gb/s optical fiber communication system

A cost-effective technique for in-service chromatic dispersion monitoring in a 40-Gb/s optical communication system is proposed. Microwave devices are adopted to detect the electrical power of a specific frequency band. A simplified theoretical model is proposed and discussed focusing on the relationship between electrical power and chromatic dispersion at different frequency bands. The dynamic monitoring of chromatic dispersion is achieved using devices such as PIN detector, microwave amplifier, narrow-band microwave filter, and electrical power detector. The maximum detectable chromatic dispersion is 130 ps/nm and a resolution of 5.2 ps/nm/dB has been achieved in the frequency band centered at 12 GHz.     

基于正交小波包的茶叶近红外光谱特性分析

针对茶叶近红外光谱数据中存在着高度的共线性和高维数,根据小波包变换具有的去相关能力。通过引入保留能量和置零系数来定量描述茶叶近红外光谱小波包变换后的特性;分析与实验表明,正交小波包对近红外光谱具有较强的压缩能力,压缩后保留的能量为99．98％,而置零系数百分比高达95．87％;这一结果对近红外光谱图的存储、检索及快速处理都有着十分重要的意义。     

不同剂量重离子辐照玉米自交系的生物学效应比较

用12C6+和 36Ar18+离子束分别辐照玉米自交系干种子和浸泡种子, 研究了M1—M3代重离子束辐照的生物学效应。 结果表明: 种子发芽势和发芽率随辐照剂量的增加而下降, 不同生理状态的种子对重离子辐照的敏感性也不同。 一般12C6+ 离子辐照干种子的适宜剂量为20—25 Gy; M1代叶型发生明显的变化, M2代植株在株高、穗位、单株穗数、雄穗花药颜色、粒质、穗行数、粒重和抗性等方面均发生了变化, 并产生了许多有益的变异,包括株高和穗位降低、同位多穗、穗行数和粒重增加、粒质由粉质变为硬粒以及抗锈病和红叶病的植株等, 有益突变的频率达7.0％—17.9％;在M3代出现能够稳定遗传的,并且光合效率增加的有益突变株。由此可见,重离子束辐照是玉米种质改良的一种高效手段。 In order to study biological effects of heavy ion irradiation on maize inbred lines, the agronomic traits and photosynthetic rates were investigated from M1 to M3 of maize seeds irradiated with 12C6+ and 36Ar18+ ions．The results showed that the germination rate and planting percent of maize seeds irradiated were decrease as dosage increasing of heavy ion irradiation. Different physiological status of seeds had disparate sensibility to heavy-ion irradiation and the suitable dosage of 12C6+ ion irradiation was 20—25 Gy for dry maize seeds. The leaf type of the plant happened visible changes in M1 generation. The plant height, spike position, spike number per plant, anther color of staminate,grain texture,spike row,grain weight and resistance had changes in M2 generation. Among them occurred some beneficial mutations that include degrading of plant height and spike position height, multi spike at same position in the plant, increasing of pike row and grain change of grain texture from powder seed to hard seed,resistance to rust disease and red leaf disease and so on. The frequency of beneficial mutation was 7.0％—17.9％. Those beneficial mutations could be stably inherited and mutant plants with high photosynthetic efficiency emerged in M3 generation. The study above showed that heavy ion irradiation is a high performance means for improvement germplasm of maize.