The Experts below are selected from a list of 4212 Experts worldwide ranked by ideXlab platform

Kun Qiu - One of the best experts on this subject based on the ideXlab platform.

  • an effective method for improving diffraction performance of magnetostatic backward volume wave based magneto optic Bragg Cells by using an appropriately tilted bias magnetic field in yig film plane
    Journal of Magnetism and Magnetic Materials, 2006
    Co-Authors: Kun Qiu
    Abstract:

    Abstract The universal magneto-optic (MO) coupled-mode equations for magnetostatic waves (MSWs) and guided optical waves (GOWs) under arbitrarily tilted bias magnetic fields are presented for the first time and, as an example, applied to the noncollinear Stokes interaction between the incident TE 0 -mode light and magnetostatic backward volume wave (MSBVW) excited by single-element microstrip line transducer in yttrium–iron–garnet (YIG) film. Our calculation indicates that, for the case of magnetization parallel to the MSBVW propagation direction, the diffraction efficiency (DE) is equal to the mode-conversion efficiency of the diffracted lights (MCDE) and the calculated curve of relative DE for the MSBVW-based MO Bragg Cell in pure YIG waveguide is in good agreement with the experimental data. In contrast, the diffraction performance can be greatly improved by optimizing the bias magnetic field and the DE gain can be increased by 6.3 dB in the tangentially magnetized film. The angular dependences of the DE and the corresponding Bragg angle upon the magnetization direction are also discussed in the paper.

M G Gazalet - One of the best experts on this subject based on the ideXlab platform.

C S Tsai - One of the best experts on this subject based on the ideXlab platform.

  • Permanent magnet-based guided-wave magnetooptic Bragg Cell modules
    Journal of Lightwave Technology, 1992
    Co-Authors: C.l. Wang, Y. Pu, C S Tsai
    Abstract:

    Compact magnetostatic forward volume wave-based guided-wave magnetooptic (MO) Bragg Cell modules have been realized by utilizing a pair of small samarium-cobalt permanent magnets together with a pair of current-carrying coils. A highly uniform DC magnetic field, has been obtained in the air gap where yttrium iron garnet-gadolinium gallium garnet (YIG-GdGG) waveguide samples are inserted. A tunable DC magnetic field as large as 2446 Oe corresponding to a tunable carrier frequency band of 6.85 GHz has been achieved. The resulting MO Bragg Cell modules, at the optical wavelength of 1.303 mu m, with carrier frequencies ranging from 2.0 to 12.0 GHz have provided performance characteristics comparable to those obtained by using a bulk electromagnet. Compact MO Bragg Cell modules have potential applications, such as scanning, switching of light beams, and real-time processing of wide-band microwave signals without requiring frequency down-conversion.

Monish Ranjan Chatterjee - One of the best experts on this subject based on the ideXlab platform.

  • secure free space communication turbulence mitigation and other applications using acousto optic chaos
    Applied Optics, 2018
    Co-Authors: Monish Ranjan Chatterjee, Ali Mohamed, Fares S Almehmadi
    Abstract:

    Use of acousto-optic (A-O) chaos via the feedback loop in a Bragg Cell for signal encryption began as a conceptual demonstration around 2008. Radio frequency (RF) chaos from a hybrid A-O feedback device may be used for secure communications of analog and digital signals. In this paper, modulation of RF chaos via first-order feedback is discussed with results corroborated by nonlinear dynamics, bifurcation maps, and Lyapunov analyses. Applications based on encryption with profiled optical beams, and extended to medical and embedded steganographic data, and video signals are discussed. It is shown that the resulting encryption is significantly robust with key tolerances potentially less than 0.1%. Results are also presented for the use of chaotic encryption for image restoration during propagation through atmospheric turbulence.

  • spectral analysis of encrypted chaotic signals using fast fourier transforms and laboratory spectral analyzers
    Proceedings of SPIE, 2012
    Co-Authors: Monish Ranjan Chatterjee, Abhinay Kundur
    Abstract:

    The use of acousto-optic chaos, as manifested via first-order feedback in an acousto-optic Bragg Cell, in encrypting a message wave and subsequently recovering the message in the receiver using a chaotic heterodyne strategy, has been reported recently [1-3]. In examining the dynamical system analytically using computer simulation, (expected) modulated chaos waveforms are obtained within specified observation windows. Because of the relatively random nature inherent in chaos waveforms, it is essentially impossible to ascertain from the visual display of the chaotic wave whether a given message signal has in fact modulated the chaotic "carrier". In fact, it has been observed from earlier work that by appropriately controlling the chaos parameters, one may "hide" the silhouette of the message from the envelope of the modulated chaos [1]. This was found to be especially true for low-frequency chaos (in the KHz range). For chaos in the mid-RF (up to 10s of MHz) range, it is seen that the silhouette is more difficult to suppress (even though this does not affect the robustness of the encryption). To adequately determine whether modulation has in fact occurred by passing the AC signal through the sound Cell bias input, one needs to examine the spectral content of the chaos wave. In this paper, we discuss the results of such spectral analyses using two different approaches, (i) fast Fourier transforms applied to the displayed waveform; and (ii) transferring the intensity-vs-time data to an Excel spreadsheet, and then applying this information to a laboratory spectrum analyzer with adequate bandwidth. The results are mutually compared and interpreted in terms of encryption and decryption properties.

  • examination of the nonlinear dynamics of a chaotic acousto optic Bragg modulator with feedback under signal encryption and decryption
    Optical Engineering, 2012
    Co-Authors: Mohammed A Alsaedi, Monish Ranjan Chatterjee
    Abstract:

    An acousto-optic Bragg Cell with first-order feedback, which exhibits chaotic behavior past the threshold for bistability, was recently examined for possible chaotic encryption and recovery of simple messages (such as low-amplitude periodic signals) applied via the bias input of the sound Cell driver. We carry out a thorough examination of the nonlinear dynamics of the Bragg Cell under intensity feedback for (i) dc variations of the feedback gain () and the phase shift parameter (0) and (ii) ac variations of 0,total under signal encryption, investigating both from two different perspectives: (i) examining chaos in view of the so-called Lyapunov exponent derived recently by Ghosh and Verma and (ii) examining chaos in terms of the familiar bifurcation maps of intensity plotted against the feedback gain and the effective bias. It is shown that overall, the nonlinear dynamical results using the two approaches broadly agree, both for dc (fixed-parameter) analyses and, more importantly, when applied to the case of ac signal encryption cases. This affirms the effectiveness of the nonlinear dynamical theory in predicting and tracking the actual physical behavior of this system for message signal transmission and recovery under complex chaotic encryption.

  • examination of chaotic signal encryption and recovery for secure communication using hybrid acousto optic feedback
    Optical Engineering, 2011
    Co-Authors: Monish Ranjan Chatterjee, Mohammed A Alsaedi
    Abstract:

    Generation of chaos from acousto-optic (A-O)Bragg Cell mod- ulators with an electronic feedback has been studied for over 3 decades. Since an acousto-optic Bragg Cell with zeroth- and first-order feedback exhibits chaotic behavior past the threshold for bistability, such a system was recently examined for possible chaotic encryption of simple mes- sages (such as a low-amplitude sinusoidal signal) applied via the bias input of the sound Cell driver. Subsequent recovery of the message signal was carried out via a heterodyne-type strategy employing a locally gener- atedchaoticcarrier,withthresholdparametersmatchedtothetransmitting Bragg Cell. In this paper, we present numerical results and detailed inter- pretations for signal encryption and recovery under hybrid A-O electronic feedback using a heterodyne strategy. Important features of this setup, such as the system robustness in terms of parameter matching (feedback gain, dc bias, and time delay) are also examined in some detail. C 2011

Riza, Nabeel A. - One of the best experts on this subject based on the ideXlab platform.

  • Photonic signal processing for inverse synthetic aperture radar imaging.
    'SPIE-Intl Soc Optical Eng', 2020
    Co-Authors: Riza, Nabeel A., Pape, Dennis R.
    Abstract:

    A robust signal processor, capable of handling a multitude of signal processing functions over a wide instantaneous signal bandwidth is needed for future military systems where shared sensor and signal processing resources will be employed. We investigated a novel 2D acousto-optic (AO) processor capable of real-time multifunction signal processing. We developed the specifications for an optoelectronic ISAR image formation processor for ship imaging based upon the AN/APS-137(H) Airborne Radar. The baseline processor is designed for high resolution imaging- slant range resolution of 0.3 m and cross range resolution of 1.2 m over 30 m X 30 m window. The optical design of the processor is based on an optically efficient, in-line, high stability, 2D interferometer using four acousto-optic devices invested by Riza. We developed specifications for the processor components, including light source, lenses, photodetector array, and Bragg Cells including a multichannel Bragg Cell to improve processor bandwidth and reduce its size. We showed that all of these components are commercially available. We breadboarded a narrow bandwidth version of the processor and demonstrated its main operation features. We showed experimentally that the processor has simultaneous spatial carrier generation capability that is controllable with high phase stability and exCellent fringe visibility

  • Ultrafast optical tomography systems using coherence agility.
    'SPIE-Intl Soc Optical Eng', 2020
    Co-Authors: Riza, Nabeel A., Arain, Muzammil A., Yaqoob Zahid
    Abstract:

    Described are three types of optical imaging systems based on source coherence agility. On axis ultrafast microsecond sub-surface imaging is achieved by use of a broadband low coherence optical source to implement fast Doppler time domain optical coherence tomography (OCT). Ibis system is formed as a combination of a fast scan acousto-optically implemented variable optical delay line with a single acousto-optic (AO) Bragg Cell optical heterodyne interferometer. A second imaging system is introduced with a no-moving parts probe design and fast microsecond speed optical spatial scanning along one dimension implemented using a fixed wavelength high coherence source with a single Bragg Cell AO interferometer. The third design involves realization of a spectral domain OCT system implemented via the use of a tunable laser in the proposed single AO Cell heterodyne interferometer.Described are three types of optical imaging systems based on source coherence agility. On axis ultrafast microsecond sub-surface imaging is achieved by use of a broadband low coherence optical source to implement fast Doppler time domain optical coherence tomography (OCT). Ibis system is formed as a combination of a fast scan acousto-optically implemented variable optical delay line with a single acousto-optic (AO) Bragg Cell optical heterodyne interferometer. A second imaging system is introduced with a no-moving parts probe design and fast microsecond speed optical spatial scanning along one dimension implemented using a fixed wavelength high coherence source with a single Bragg Cell AO interferometer. The third design involves realization of a spectral domain OCT system implemented via the use of a tunable laser in the proposed single AO Cell heterodyne interferometer

  • In-line acousto-optic interferometer as a correlator and spectrum analyzer
    'SPIE-Intl Soc Optical Eng', 2020
    Co-Authors: Riza, Nabeel A.
    Abstract:

    A novel, efficient, stable, in-line, two Bragg Cell, acousto-optic architecture is introduced for signal correlation and spectrum analysis, and experimental results are described. The processor employs an image inversion technique to produce a correlation output that does not have to be generated on a spatial carrier. The system is particularly suited for wide instantaneous bandwidth signal processing

  • High-speed programmable optical attenuator.
    'SPIE-Intl Soc Optical Eng', 2020
    Co-Authors: Riza, Nabeel A., Yaqoob Zahid
    Abstract:

    A high-speed programmable optical attenuator (POA) is introduced that can provide high dynamic range and high resolution attenuation control. An acousto-optic Bragg Cell has been used to realize the desired attenuator. Various practical architectures have been proposed to prove the concept. A typical acousta-optic deflector (AOD) based design offers a dynamic range of 46.11 dB. The average resolution is 3.08 dB/volt whereas the best resolution achieved is 0.39 dB/volt. The response time of the AO attenuator is in the sub CLS regime, and was observed as low as 0.175 mu s. The polarization dependent loss (PDL) was about 0.7 dB, whereas the excess losses were about 1.5 dB.A high-speed programmable optical attenuator (POA) is introduced that can provide high dynamic range and high resolution attenuation control. An acousto-optic Bragg Cell has been used to realize the desired attenuator. Various practical architectures have been proposed to prove the concept. A typical acousta-optic deflector (AOD) based design offers a dynamic range of 46.11 dB. The average resolution is 3.08 dB/volt whereas the best resolution achieved is 0.39 dB/volt. The response time of the AO attenuator is in the sub CLS regime, and was observed as low as 0.175 mu s. The polarization dependent loss (PDL) was about 0.7 dB, whereas the excess losses were about 1.5 dB

  • Multi-function acousto-optic signal processor
    'SPIE-Intl Soc Optical Eng', 2020
    Co-Authors: Riza, Nabeel A.
    Abstract:

    A novel two dimensional acousto-optic processor is introduced for a variety of two dimensional signal processing tasks that include ambiguity function and range-doppler processing, two dimensional raster format high resolution signal spectrum analysis, and triple correlation function generation. The optical design is based on an optically efficient, in-line, high stability, two dimensional interferometer using four acousto-optic devices. Via the simple technique of Bragg Cell carrier offset adjustments, the processor can generate the desired interferometric output on a chosen spatial carrier that is required for bias removal and electronic post-processing. The processor has bandwidth limitations based on the type of Bragg Cells used in the system.A novel two dimensional acousto-optic processor is introduced for a variety of two dimensional signal processing tasks that include ambiguity function and range-doppler processing, two dimensional raster format high resolution signal spectrum analysis, and triple correlation function generation. The optical design is based on an optically efficient, in-line, high stability, two dimensional interferometer using four acousto-optic devices. Via the simple technique of Bragg Cell carrier offset adjustments, the processor can generate the desired interferometric output on a chosen spatial carrier that is required for bias removal and electronic post-processing. The processor has bandwidth limitations based on the type of Bragg Cells used in the system