一种新的高速多目标快速参数化检测算法

针对线性调频脉冲压缩雷达参数化检测高速多目标时受到距离徙动、多普勒扩散和速度模糊的影响,该文首先采用联合频域变标脉冲压缩处理与吕方法(2011)实现目标信号的相参积累,然后在其基础上采用基于多普勒频率模糊数搜索的方法完成高速多目标的参数化检测。算法所提出的频域变标脉冲压缩处理可同步完成距离维的徙动补偿与多普勒维的模糊数补偿,降低了实现目标参数化检测的计算复杂度,且由于算法采用相参积累方式,在低信噪比下可以进行精确的目标检测和运动参数估计。相参积累算法运算量分析、计算机仿真以及实测数据处理结果验证了该文所提算法的有效性。     

5cm超小型脉冲相参收发系统

介绍了一种超小型的５ｃｍ脉冲相参接收发射机的设计方案和实验结果,以及在５ｃｍ箭载电子设备中的应用。     

基于远场的拼接光栅压缩池的设计

 利用傅里叶光学方法得到了失调拼接光栅压缩池输出光束的远场振幅表达式,建立了分析拼接光栅的各种误差的理论模型,得到了拼接误差对脉冲的影响是附加相位延迟和角度偏转。在要求远场的一倍衍射极限区域的积分能量分布达到理想情况下的90％的条件下,对于含有口径为40 cm、脉宽为0.1~10 ps脉冲的系统进行分析并分别得到了各种误差的容限。     

Femtosecond laser pulse train effect on Doppler profile of cesium resonance lines

We present direct observation of the velocity-selective optical pumping of the Cs ground state hyperfine levels induced by the femtosecond (fs) laser oscillator centered at either D2 (6 ²S_1/2↦6 ²P_3/2, 852 nm) or D1 (6 P_1/2, 894 nm) cesium line. We utilized previously developed modified direct frequency comb spectroscopy (DFCS) which uses a fixed frequency comb for the excitation and a weak cw scanning probe laser centered at the ¹³³Cs 6 ²S_1/2↦6 ²P_3/2 transition (D2 line) for ground levels population monitoring. The frequency comb excitation changes the usual Doppler absorption profile into a specific periodic, comblike structure. The mechanism of the velocity selective population transfer between the Cs ground state hyperfine levels induced by fs pulse train excitation is verified in a theoretical treatment of the multilevel atomic system subjected to a pulse train resonant field interaction.     

激光微多普勒探测系统中降低相位噪音影响的方法研究

相干微多普勒激光雷达具有探测灵敏度高、探测信息量大等特点,特别适合于动目标探测、目标特征识别等应用.本文从线宽和探测距离两个方面讨论了模场相位随机起伏（相位噪音）对于测速准确度的影响,实验证实了相位噪音对激光微多普勒探测的影响,并探索出解决上述问题的方法——光纤补偿法.实验中,以输出波长为1.064 μm单块非平面环形腔激光器为光源,利用光纤补偿方法,并结合时频变换的算法,用外差探测的方式成功观测到了微多普勒频移,在传输距离为11 km时,系统最低探测速度达到了0.5 mm/s,速度分辨率达到了mm/s量级,频率分辨率达到了kHz量级,为微多普勒激光雷达的实际应用奠定了良好的实验基础.     

Dynamic control of photonic bandgap mediated by vacuum-induced coherence

We theoretically examine the storage and retrieval of a light pulse in a medium comprised of four-level atoms of the V − Λ-type. The two intermediate levels are probed by a weak field and vacuum-induced coherence effects lead the system to transparency. The temporal variation of the intermediate levels' splitting is used as an external parameter which allows the transfer of the impinging field to a combination of spin coherences. An auxiliary and far-detuned control field in a standing-wave configuration is used to induce a variable photonic bandgap by cross-phase modulation. It is shown that dynamic control of such a bandgap can be used to coherently manipulate the previously stored probe pulse. We use a general scheme to take into account multiwave mixing effects and solve the combined Maxwell-Bloch equations for the relevant coherences. It is shown that the system acts as an all-optical router.     

A new approach to obtain the non-Condon factors in closed form for two one-dimensional harmonic oscillators

A simple algebraic approach to calculate general Franck-Condon overlaps is extended to evaluate non-Condon factors for two one-dimensional harmonic oscillators. The method is based on the use of eigenstates of the harmonic oscillator annihilation operator which allows to obtain in terms of a multi-dimensional Hermite polynomial the overlap of harmonic oscillator functions associated with different Born-Oppenheimer potentials. The presented approach is self-contained, only basic concepts of quantum mechanics associated with the harmonic oscillator system are needed. The obtained expression for the Franck-Condon overlaps is similar to the Ansbacher’s formula and equivalent to the one calculated by Malkin and Man’ko. However our final expression has the advantages that only real numbers are involved and it is straightforward to get the limit case of equal frequencies. Concerning the non-Condon factors two approaches leading to different formulas are considered, both of which reduce to triple sums of products of three Hermite polynomials.     

干涉型复合腔激光束相干合成中分束器的相移特性研究

分析了采用分束器构建干涉型复合腔进行激光束相干合成的过程与原理.利用分束器的特征矩阵研究了分束时产生的反射与透射相移,得到了两束相干光经过分束器分束后进行相干叠加时相移满足的普适关系,从相移的角度解释了分束器一侧发生相长干涉时另一侧必然发生相消干涉这一现象.比较了分束器与光纤耦合器在激光束相干合成应用中的一些特性,并验证了所得相移关系式的正确性.     

LAXS investigation of finger phantoms

Osteoporosis is a bone condition that is caused mainly by the degradation of trabecular and cortical bone resulting in the decrease of bone strength and eventually leads to bone fracture. A low angle X-ray scattering (LAXS) system that uses mainly the coherent scattering process for the characterisation of materials was constructed to study such bone conditions. Several finger phantoms were fabricated to simulate bone of varying densities. The LAXS method was able to identify the changes in bone density quite well by comparing energy dispersive X-ray diffraction patterns as well as the angular patterns. Quantitative information can be extracted from such patterns that relate to bone loss. Signature patterns at low exposure times were produced in order to reduce the dose received with reasonable identification power but at slightly higher statistical errors compared with long exposure patterns. Use of other parameters to increase the sensitivity was attempted.     

Observation of THz coherent transition radiation from single-bunch beam at KURRI-LINAC as an intense pulsed light source

A single-bunch beam has been generated using a developed high-speed avalanche-type pulser in KURRI-LINAC in order to lift restrictions of the spectral resolution in the spectroscopic study and the delay time in the time-resolved measurement. Both of the rise and fall times of the developed pulser are 110 ps. The observation of CTR has confirmed the single-bunch beam. The degree of impurity of single bunch has been estimated to be 1.5% by the analysis of the interferogram.