Performance of a hybrid bistable device using an acoustooptic modulator

Poon, Ting‐Chung; Cheung, S. K.

doi:10.1364/ao.28.004787

Cited by 32 publications

(8 citation statements)

References 8 publications

(2 reference statements)

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“…3 Several research groups have also investigated aspects and applications of acousto-optic bistability in the past 10 years or more. [5][6][7] Recently, Ghosh and Verma have conducted an analytical examination of the conditions for the onset of chaos in the A-O feedback system using the Lyapunov exponent. 8 The feasibility of operating the hybrid A-O devices in the chaotic regime, and treating the chaos as an equivalent information carrier which is then encrypted (modulated) by an information signal applied through the RF bias input, and thereafter recovering the message signal in a receiver using (as a first approach) a heterodyne detection method, has recently been explored with some success.…”

Section: Nonlinear Feedback System and Chaosmentioning

confidence: 99%

Examination of chaotic signal encryption and recovery for secure communication using hybrid acousto-optic feedback

Chatterjee

Alsaedi

2011

Opt. Eng

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Generation of chaos from acousto-optic (A-O)Bragg cell modulators 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 messages (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 generated chaotic carrier, with threshold parameters matched to the transmitting Bragg cell. In this paper, we present numerical results and detailed interpretations 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 Society of Photo-Optical Instrumentation Engineers (SPIE). IntroductionIn an acousto-optic (A-O) modulator, an RF signal applied to a piezo-electric transducer, bonded to a suitable crystal, will generate an acoustic wave. It is well known that the acoustic wave acts like a "phase grating" that diffracts any incident laser beam into a number of diffracted orders. The Raman-Nath regime is characterized by multiple scattered orders while in the Bragg regime there are typically only two scattered orders (zeroth-and first-orders). 1 Around 1978, it was reported that A-O devices with positive feedback gain exhibit bistability characteristics. 2 In an A-O device, the amplitude of the diffracted fields that operate in the Bragg regime, i.e., the zeroth-and first-orders, which appear at the output of the Bragg cell, are related through a set of coupled differential equations. In Refs. 3 and 4, Chrostowski and co-workers present experimental results for A-O bistability and chaos using an equivalent circuit model of the Bragg cell with feedback. In a standard setup, a Bragg cell is driven by an ultrasonic sound wave from an RF generator at 40 MHz, and the resulting sound grating diffracts an incident He-Ne laser beam into the first Bragg order under Bragg condition. The first-order is then picked up by a linear photodetector, fed to an amplifier, and then returned to the bias input of the RF generator. The arrangement is shown in Fig. 1. Nominally, the scattered light beam is intrinsically frequency or phase modulated (with the acoustic frequency). In typical waveform sources, the external bias input amplitude modulates the RF waveform. A plot of the first order intensity (I 1 ) versus the bias inputα 0 yields the well known bistable and hysteretic behavior. 3,4 The bistability and hysteresis characteristics depend strongly on the feedback gain (β), the feedback time delay (TD), and the amplitude (I inc ) of the incident

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Section: Nonlinear Feedback System and Chaosmentioning

confidence: 99%

Examination of chaotic signal encryption and recovery for secure communication using hybrid acousto-optic feedback

Chatterjee

Alsaedi

2011

Opt. Eng

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“…13 We recommend that students be required to read Ref. 13 for the details cited in that reference. The schematic diagram of the feedback system includes an acousto-optic modulator ͑AOM͒, a photodetector ͑PD͒, an electronic summer, and a feedback amplifier with gain ␤ as shown in Fig.…”

Section: Hysteresis and Optical Switchingmentioning

confidence: 99%

Modern optical signal processing experiments demonstrating intensity and pulse-width modulation using an acousto-optic modulator

Poon

McNeill

Moore

1997

American Journal of Physics

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Two experiments are presented to introduce undergraduate students in electrical engineering or physics to modern optical signal processing. Both experiments use an acousto-optic (AO) Bragg cell together with additional electronics to modify the intensity of a laser beam. Specifically, we show how an AO feedback system operating in the Bragg regime can be configured to produce amplitude modulated (AM) and pulse-width modulated optical signals. The basic components of the AO feedback system include a laser, an AO Bragg cell, an electronic AM modulator, a photodetector, an amplifier, and an electronic adder. Except for the laser, the AM modulator, and the Bragg cell, each of these components can be constructed with low cost electronics. A tutorial outlining the principles of acousto-optics is included to provide sufficient understanding of the Bragg cell. The project described in the paper has been used as a demonstration for junior- and senior-level undergraduate students in electrical engineering communications and optics classes.

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“…͑13͒ also ensures that the bistable effects are not manifest in the nonlinear system 11 and stability can be maintained easily through external control. However, it is difficult to ensure the inequality in Eq.…”

Section: Stability Analysismentioning

confidence: 99%

“…͑17͒, we find that an AO IIR filter design with feedback and nonlinearity in the feedback loop is stable. 11 The bounded nonlinearity of the form sin 2 ␣(kT) indicated in Eqs. ͑6͒ and ͑9͒ suppresses instability in the system.…”

Section: Stability Analysismentioning

confidence: 99%

Acousto-optic infinite-impulse-response digital filters for line enhancement or notch filtering

Ghosh

Paparao

1997

Opt. Eng

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A compact design of an acousto-optic high-speed infiniteimpulse-response filter for line enhancement or notch filtering is introduced. Such filters can find applications in communication systems for signal-processing tasks such as carrier and bit recovery, signal prefiltering for noise reduction, interference or jammer cancellation, and channel equalization. Stability of such filters is an important concern because of the feedback and the nonlinearity in the acousto-optic cell response. Stability conditions are derived. Theoretical analysis and numerical experiments show that an acousto-optic-cell-based infinite-impulseresponse filter can enhance the signal-to-noise ratio at the filter output by 15 to 30 dB or more, depending on the design. © 1997 Society of PhotoOptical Instrumentation Engineers. [S0091-3286(97)01009-X] Subject terms: acousto-optic high-speed infinite-impulse-response filter; line enhancement; notch filtering; signal processing.

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Performance of a hybrid bistable device using an acoustooptic modulator

Cited by 32 publications

References 8 publications

Examination of chaotic signal encryption and recovery for secure communication using hybrid acousto-optic feedback

Examination of chaotic signal encryption and recovery for secure communication using hybrid acousto-optic feedback

Modern optical signal processing experiments demonstrating intensity and pulse-width modulation using an acousto-optic modulator

Acousto-optic infinite-impulse-response digital filters for line enhancement or notch filtering

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