共查询到20条相似文献,搜索用时 113 毫秒
1.
We present experimental results of frequency modulation transfer spectroscopy in a vapor of neutral atomic calcium. The observed
line shapes agree well with the theoretical model. We use numerical calculations in order to improve the signal shape such
that its magnitude and its slope at the zero-crossing is maximized. When optimized this way, the frequency modulation transfer
signal can be used for the sensitive optical detection of rare species or isotopes, Doppler-free frequency measurements or
as a sensitive error signal for laser frequency stabilization.
PACS 42.62.Fi; 32.70.Jz; 39.30.+w 相似文献
2.
Steinwolf A White RG Wolfe HF 《The Journal of the Acoustical Society of America》2001,109(3):1043-1052
Acoustic excitation produced by jet-engine effluxes was simulated in a progressive wave tube (APWT) facility with a computer-based control system. The APWT siren is driven by a signal generated numerically in a PC and then converted into analog form. Characteristics of the acoustic pressure measured by a microphone are analyzed in digital form and compared with those prescribed for simulation. Divergence is compensated by immediate modification of the driving signal and this action is repeated in the form of iterative process until the test specification is attained. Typical power spectral density (PSD) shapes with maxima at low and high frequencies were simulated. A "tailoring" approach has been also achieved when a test specification was determined directly from field measurements for the particular aircraft under consideration. Since acoustic pressure signals of high level differ from the Gaussian random process model, particularly in terms of asymmetric probability density function, a method has been developed to make the driving signal also non-Gaussian by simulating skewness and kurtosis parameters of the APWT acoustic excitation simultaneously with PSD control. Experimental results with Gaussian and non-Gaussian characteristics obtained for various PSD specifications including sharp and narrow peaks are presented in the paper. 相似文献
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Xue Zhang Shuangqi Zhu Peijin Li Yao Li Junjie Li Xiaowei Li Yongtian Wang Lingling Huang 《Laser \u0026amp; Photonics Reviews》2024,18(5):2301070
Structured beams are analytical solutions to wave equations that possess specific spatial profiles and rigorous transmission properties. Holography enables wavefront reconstruction by recording objective wavefront information. In this study, comprehensive wavefront control by transforming a structured beam in real space is proposed and experimentally verified, and optical holography is reconstructed in Fourier space. To obtain an arbitrary profile of the structured beam, alias transformation is performed to rebuild the coordinate system to form arbitrary user-defined shapes. Subsequently, the complex amplitude control of the metasurface to encode the alias-transformed structured beam accordingly is applied. This allows the conventional standard Hermite–Gaussian and Laguerre–Gaussian modes to be transformed into their corresponding shapes while maintaining their distinct features. Holography is realized based on pure phase modulation by interleaving the information with a structured beam, which fully utilizes the space-bandwidth product of the metasurface. These distinctive optical phenomena in both spaces expand the definition of conventional structured beams and enable further developments in laser fabrication, optical manipulation, and optical displays. 相似文献
5.
This study provides two non-contact optical techniques to investigate the transverse vibration characteristics of piezoceramic rectangular plates in resonance. These methods, including the amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and laser Doppler vibrometer (LDV), are full-field measurement for AF-ESPI and point-wise displacement measurement for LDV, respectively. The edges of these piezoceramic rectangular plates may either be fixed or free. Both resonant frequencies and mode shapes of vibrating piezoceramic plates can be obtained simultaneously by AF-ESPI. Excellent quality of the interferometric fringe patterns for the mode shapes is obtained. In the LDV system, a built-in dynamic signal analyzer (DSA) composed of DSA software and a plug-in waveform generator board can provide the piezoceramic plates with the swept-sine excitation signal, whose gain at corresponding frequencies is analyzed by the DSA software. The peaks appeared in the frequency response curve are resonant frequencies. In addition to these optical methods, the numerical computation based on the finite element analysis is used to verify the experimental results. Good agreements of the mode shapes and resonant frequencies are obtained for experimental and numerical results. 相似文献
6.
S. Knappe M. Stähler C. Affolderbach A.V. Taichenachev V.I. Yudin R. Wynands 《Applied physics. B, Lasers and optics》2003,76(1):57-63
We have studied the dispersion and absorption line shapes of coherent population trapping resonances (dark resonances) in
thermal cesium vapor. Outside the time-of-flight regime the line shapes can be described by a simple phenomenological model:
a sum of a dispersive and an absorptive Lorentzian of identical width and position, whose relative weights depend on the detuning
of the laser frequencies from the optical resonance. This functional form can be derived from a theoretical model for the
full multilevel structure of an alkali atom. The analytical expressions for the parameters of the line shape model show the
same behavior as the experimental data.
Received: 4 October 2002 / Revised version: 30 October 2002 / Published online: 8 January 2003
RID="*"
ID="*"Corresponding author. Fax: +41-26/300-9631, E-mail: robert.wynands@unifr.ch 相似文献
7.
This paper introduces a new modulation and direct detection scheme of optical phase shift keying (PSK)which is simple and practical in fiber optical communication. A phase modulator is used to modulate a continuous wave (CW) laser source and return-to-zero (RZ) signal that is changed from the initial transmitting information is used to control a phase modulator to form a optical PSK signal. In the receiver terminal, just add a signal delayed a half of one bit to itself so that the initial information can be restored. 相似文献
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With the technique of phase modulation optical heterodyne(PMOH), we detected the beat-frequency signal of the reflected wave from a F-P cavity. The frequency of the beat signal was three times of that of the modulation electric field, when the 3rd harmonic of the modulation electric field was used as the phase reference signal. The line shapes of the signal match those of the theoretical calculations, and the dispersion signal has good frequency-discrimination characteristic. 相似文献
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L. Spinelli M. Brambilla 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,6(4):523-532
Cavity solitons were recently predicted in semiconductor microresonators grown with a vertical geometry. By exploiting a previously
introduced model valid for both passive and active configurations of a multiple-quantum-well device, we studied the response
in the time domain offered by such self-organized structures in the device, when a small modulated optical signal is applied.
Using appropriate symmetry considerations, the (2+1)-dimensional problem is reduced to a tractable form, by means of a semianalytical
method. We demonstrated that large differential-gain factors, competitive with those of other all-optical and some opto-electronic
devices, are attainable, when the output signal is collected at the peak of the cavity soliton. This fact, in connection with
the reconfigurability properties already established for cavity soliton arrays, allows to conceive different schemes for optical
information handling: feasible arrangements for parallel amplification and for signal commutation are proposed.
Received: 11 December 1998 / Received in final form: 25 February
1999 相似文献
12.
An improved building boundary extraction algorithm based on fusion of optical imagery and LIDAR data
This article presents a new method of automatic boundary extraction using LIDAR-optical fusion suited to handle diverse building shapes. This method makes full use of the complementary advantages of LIDAR data and optical imagery. Different building features are extracted from the two data sources and fused to form the final complete building boundaries. First, the points of each roof patch are detected from LIDAR point cloud. This process consists of four steps: filtering, building detection, wall point removal and roof patch detection. Second, initial building edges are extracted from optical imagery using an improved Canny detector constrained by edge location information derived from the LIDAR point cloud as edge buffer areas. Finally, the roof patch and initial edges are integrated by mathematical morphology to form the final complete building boundaries. All processes have no constraints or rules on building shapes. This method is fully data-driven and suitable for any building shape. LIDAR data and aerial images of complex geographical environments are used to test the method. These experimental results demonstrate that our method can automatically extract accurate boundaries for buildings with complex shapes, and also is highly robust in complex environments. 相似文献
13.
H. H. B. Rocha J. L. S. Lima C. S. Sobrinho A. C. Ferreira J. C. Sales A. S. B. Sombra 《Optical and Quantum Electronics》2009,41(6):441-452
The dynamics characteristics of picosecond soliton-like pulses propagating through add–drop optical filters, based on lossless
uniform and Gaussian nonlinear fiber grating couplers, are numerically investigated under different power levels. To obtain
the temporal profiles, the nonlinear coupled-mode equations, that model these devices, are solved numerically. These devices
can perform the extraction (drop) of an optical signal, since there is the reflection of a pulse previously switched between
adjacent waveguides. The extraction efficiency, recurrently better at low power levels, is subordinated to the matching between
the associated spectra of the input pulses and the hybrid devices analyzed. The switching effects, as well the gratings responsiveness,
impact on the outputs profiles, since diverse temporal shapes can be obtained. The results reinforce the importance and the
potential of properly engineered structures for all-optical processing requirements. 相似文献
14.
Aberration invariant optical/digital incoherent systems 总被引:1,自引:0,他引:1
We have developed a fundamental technique for control of important known and unknown lens aberrations. Control of lens aberrations through traditional means is very difficult in high-performance optical systems. Minimizing aberrations caused by deterministic design errors as well as statistical fabrication errors has often led to costly systems and fabrication techniques. By employing a special-purpose optical phase mask and digital signal processing we can form imaging systems that are invariant, or substantially insensitive, to a number of important lens aberrations. 相似文献
15.
将结构奇异值μ综合鲁棒控制技术应用于主动抗振控制系统中,并用于解决光学移相干涉仪抗振系统的不确定性问题.采用小波分析方法将随机振动信号进行时频分析后得到低频全局信息,随后运用μ综合D-K迭代法设计鲁棒μ控制器对低频振动进行抑制.该方法克服了由模型自身和外部干扰所引起的不确定性,使得控制系统能够有效地抑制抗振模型的不确定性和外部振动的干扰,同时也具有很高的控制准确度和灵敏度.仿真结果表明,该方法使光学移相干涉仪在外部振动的干扰下具有较好的鲁棒稳定性和控制准确度,同时也能较好地抑制低频振动. 相似文献
16.
We present modeling and experimental results from the use of a 1310-nm-wavelength through-wafer optical microprobe in conjunction with a microstructure grating to monitor the motion of a lateral comb resonator stage. The optical signal that results from shuttle interaction with the microprobe beam exhibits a peak-to-valley dynamic range that corresponds to 2-microm microstructure displacement, facilitating submicrometer positional resolution on digitization. This signal was used to achieve microstructure positional feedback and effective microsystem model parameter extraction, which are essential for structure control and model-based fault detection. 相似文献
17.
When the two-photon absorption of a high intensity pump beam takes place in a semiconductor optical amplifier there is an associated fast phase change of a weak probe signal. A scheme to realize fast all-optical XOR logic function using two-photon absorption induced phase change has been analyzed. Rate equations for semiconductor optical amplifiers, for input data signals with high intensity, configured in the form of a Mach–Zehnder interferometer has been solved. The input intensities are high enough so that the two-photon induced phase change is larger than the regular gain induced phase change. The model shows that both XOR operation and pseudo-random binary sequence generation at 250 Gb/s with good signal to noise ratio is feasible. 相似文献
18.
Broad Gaussian line shapes are observed in scanning tunneling spectroscopy of single, localized electronic states induced by Cl vacancies in ultrathin NaCl films on Cu surfaces. Using a simple inelastic resonance tunneling model, we show that the observed broad line shapes are caused by a strong coupling between the localized state and the optical phonons in the film. The parameters for the model are obtained from density functional calculations, in which the occupation of the vacancy state temporarily taking place in the experiment has also been accounted for. 相似文献
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