共查询到20条相似文献,搜索用时 515 毫秒
1.
A novel optical phase-shifting method based on a well-known acousto-optic interaction is proposed. By using a pair of acousto-optic modulators (AOMs) and properly aligning them, we construct an optical phase shifter that can directly control the phase of a collimated beam. The proposed phase shifter is insensitive to the polarization of the incident beam when polarization-insensitive AOMs are used, and no calibration is necessary. The proposed approach is confirmed with experimental results. 相似文献
2.
Nonresonant cascaded acousto-optic mode coupling under an overall phase-matching condition is presented, where phase matching is not satisfied for each of the coupling stages but the sum of the two acoustic momenta matches the optical phase detuning between the source mode and the destination mode. As a special nonresonant cascaded case, conversion from LP(01) to LP(21) and LP(02) driven by a single acoustic frequency is predicted theoretically and demonstrated experimentally. 相似文献
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Isolation of a new structured acousto-optic switch based on an integrated optical polarization-independent quasi- collinear acousto-optic tunable filter is studied in detail. The factors that influence the isolation of the optical switch are analysed, the expressions of the isolation are educed, and the isolation of the device is measured in experiment. It is found that the isolation mainly depends on the TE/TM mode intensity ratio, the mode-splitter extinction rate, and the conversion efficiency. 相似文献
6.
A versatile method for self-homodyne laser linewidth measurements is presented. The acousto-optic modulator used in the standard self-heterodyne technique is replaced by electronic upconversion. This results in reduced optical loss and a simpler setup. The dependence of the detected homodyne signal on the mean phase difference between the mixed beams was averaged out with a phase modulator on the delay fiber. A delay fiber shorter than the coherence length of the laser can then be used. 相似文献
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Broadband monolithic acousto-optic tunable filter 总被引:1,自引:0,他引:1
Broadband monolithic acousto-optic tunable filters that combine a piezoelectric transducer array and an acousto-optic interaction medium in a single crystal have been investigated. A linearly chirped acoustic superlattice with an optical tuning range of lambda = 1.3-1.6 mum was formed by domain inversion in LiNbO(3) . X-propagating longitudinal acoustic waves are excited in a crossed-field scheme by a rf E(y) field applied to the superlattice and couple collinearly propagating e- and o-polarized optical modes. At mu = 1.319 mum and mu = 1.55 mum the spectral bandwidths (FWHM) were 1.54 and 2.3 nm, respectively. A relative conversion efficiency of 43%/W and a maximum conversion efficiency of 51% were measured at 1.319 mum. 相似文献
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There is a high demand for a computational model that calculates effectively the phase and amplitude distribution of the beams emerging from an acousto-optic cell. We present a model based on a new algorithm that is capable to solve the vectorial optical wave equation on consecutive planes in an optically anisotropic medium with an arbitrary refractive index distribution with limited refractive index amplitude. Strength of the presented method is that it does not require the paraxial approximation. We used the model successfully to calculate the amplitude and phase distribution of the diffracted and undiffracted beams generated in optically anisotropic and isotropic acousto-optic interaction. 相似文献
9.
Gefeson Mendes Pacheco Eugenio Scalise Nori Beraldo 《International Journal of Infrared and Millimeter Waves》1993,14(8):1619-1625
The two main constrains on the characteristics of the acousto-optic deflector are the acoustic sound attenuation and velocity. These two parameters will determine the resolution and the radio frequency bandwidth.Due to a double degenerated phase matching condition on a specific acousto-optic deflector configuration, the possibility of an improvement on the resolution of the acousto optic deflector becomes evident. This degenerescence is the result of the action of a D.C. electric field by the electro-optic effect. This configuration presents several advantages upon the early related works based on optical activity of selected materials and enables a wideband interaction in such a way that the number of resolvable channels is kept high. This has implications on the acousto-optic spectrometers for wideband radio astronomy research. 相似文献
10.
为使现代电子侦察技术能适应信号密集、宽频谱、大动态的电磁环境, 提出了一种基于声光偏转器实现相关光信号处理的方法, 分析了射频信号频率变化与布拉格衍射角的关系, 讨论了声光偏转效应对信号频率的空间滤波特性; 在理论分析的基础上, 构建了在可见光范围内实现声光偏转的相干光信号探测的实验系统, 并通过计算机仿真对比, 验证了这种方法的可行性。实验表明, 采用波长为630 nm的单频激光, 带宽为200 MHz的声光偏转器, 其频率分辨率优于1 MHz, 频率信号的空间分离效果明显, 接收灵敏度和信噪比得到改善。 相似文献
11.
We report a bandwidth variation technique in an acousto-optic filter. Utilizing the adiabatic conversion in both optical and acoustic modes, we obtain a novel hybrid waveguide composed of serial concatenation of single-mode fiber (SMF) and two-mode hollow optical fiber (HOF). On the basis of dissimilarity in the phase-matching conditions and beat-length dispersion in SMF and HOF, the FWHM of the resonant bands is varied from 3.8 to 190 nm near the 1.5-microm region in a single device. Furthermore, we theoretically analyze the acousto-optic coupling among the guided modes in HOF, which shows good agreement with experimental observations. 相似文献
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We introduce and experimentally demonstrate acousto-optic-assisted diffuse optical tomography (DOT) using a holography-based acousto-optic setup. The method is based on probing a scattering medium with a localized acoustical modulation of the phase of the scattered light. The optical properties of the scattering medium are recovered with ultrasound-limited resolution by applying DOT reconstruction methods on a set of the measured intensities of light, modulated at different locations throughout the medium. 相似文献
13.
A novel modeling technique is introduced for modeling light propagation in slightly inhomogeneous, anisotropic and optically active materials. With the aid of the model the phenomenon of acousto-optic interaction can be efficiently and accurately simulated in a completely general approach. The applied inhomogeneity caused by the sound waves can be arbitrary, similarly the incident and propagating light beams can be also arbitrary, nonparaxial. The basis of the model is described in our previous paper, in addition present work introduces further improvements. The calculation speed is significantly enhanced by increasing the speed of convergence in the case of large spatial frequency ranges and arbitrary angles between the acoustic and optical waves. We also extend our model to handle optical activity, which considerably influences the acousto-optic effect in widely used materials, like TeO2.Mathematical confirmation of the calculated field convergence to the exact solution of the Maxwell's equations is included. The simulation precisely describes the acousto-optic interaction, as a physical verification, simulation results satisfy accurately principal theoretical expectations i.e. diffracted light intensity, phase and polarization distribution. 相似文献
14.
Optical phase locking in the microradian domain: potential applications to NASA spaceborne optical measurements 总被引:1,自引:0,他引:1
We have constructed and demonstrated a high-performance optical phase-locked loop between two cw Nd:YAG lasers. The feedback system is relatively simple, employing only the laser's internal piezoelectric transducer and an external acousto-optic modulator. A residual phase noise of the order of 1microrad between two optical fields is achieved in the locked condition, as is verified by time- and frequency-domain analyses by the two-oscillator approach that is conventionally used in rf measurement. Potential applications to NASA space-based optical measurements are discussed. 相似文献
15.
It is pointed out theoretically that fiber acousto-optic mode coupling can occur between the higher-order modes with adjacent azimuthal numbers. Selective fiber mode conversion from LP01 to LP11, and then to LP21 or LP02 is demonstrated experimentally in a few-mode fiber by using a method of cascaded acousto-optic mode coupling. 相似文献
16.
《Comptes Rendus de l''Academie des Sciences Series IV Physics》2001,2(8):1213-1225
A parallel, 64K-channel implementation of the acousto-optic method of imaging optical contrasts buried in organs is presented. This implementation also associates this method with echography in a single apparatus. This allows us to prove that sensitivity to purely optical contrast is achieved. Moreover, this enables any potential user to distinguish easily optical contrast, acoustic contrast, and mixtures of both. We plan to improve this prototype with a view to future use by physicians in a hospital environment. 相似文献
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高效率LD端面抽运准连续355 nm激光器 总被引:1,自引:1,他引:0
报道了一台激光二极管(LD)端面抽运Nd:YVO4晶体腔内倍频和腔外和频相结合的声光调Q准连续355 nm 紫外激光器。采用LD端面抽运双侧翼键合YVO4基质的Nd:YVO4晶体,在腔内置入Ⅰ类相位匹配的LiB3O5(LBO)晶体进行倍频实现1 064 nm和532 nm双波长准连续激光输出,通过消色差透镜将双波长激光聚焦耦合到Ⅱ类相位匹配的LBO 晶体中进行和频,并采用双向和频光路,获得了高效率、高光束质量、高重复频率的准连续355 nm 紫外激光输出。在抽运功率为28.6 W、重复频率为20 kHz时,355 nm激光最大输出功率4.2 W,脉宽为20.6 ns,光-光转换效率为14.7%,激光器光束质量因子Mx2和My2分别为1.29和1.23。 相似文献
18.
In this paper we introduce spatial phase coding of incoherent optical signals for representing signed numbers in optical processors and present an experimental demonstration of this coding technique. If a diffraction grating, such as an acousto-optic cell, modulates a stream of light, the image of the grating can be recovered from the diffracted beam. The position of the grating image, or more precisely its phase, can be used to denote the sign of the number represented by the diffracted light. The intensity of the light represents the magnitude of the number. This technique is more economical than current methods in terms of the number of information channels required to represent a number and the amount of post processing required. 相似文献
19.
Jacquin O Glastre W Lacot E Hugon O Guillet de Chatellus H Ramaz F 《Optics letters》2012,37(13):2514-2516
We present a photon noise and diffraction-limited imaging method combining an imaging laser and ultrasonic waves. The laser optical feedback imaging (LOFI) technique is an ultrasensitive imaging method for imaging objects through or embedded within a scattering medium. However, LOFI performances are dramatically limited by parasitic optical feedback occurring in the experimental setup. In this Letter, we have tagged the ballistic photons by an acousto-optic effect in order to filter the parasitic feedback effect and to reach the theoretical and ultimate sensitivity of the LOFI technique. We present the principle and the experimental setup of the acousto-optic laser optical feedback imaging technique, and we demonstrate the suppression of the parasitic feedback. 相似文献