Effects of high space-charge fields on the response of microwave photodetectors

Williams, K.J.; Esman, R.D.; Dagenais, M.

doi:10.1109/68.285565

Cited by 122 publications

(51 citation statements)

References 8 publications

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“…Nonlinear behavior of real photodetectors leads to a saturation of microwave power when the energy per pulse is high [31,39,40]. Although our photocurrent model does not account for photodetector nonlinearity, a phenomenological inclusion to describe the SNR for a photodiode in saturation may be incorporated by considering saturation simply as a powerdependent change in [39][40][41]. Under this assumption, since the shot noise also scales with , Eq.…”

Section: Shot Noise Power and Signal-to-noisementioning

confidence: 99%

Exploiting shot noise correlations in the photodetection of ultrashort optical pulse trains

et al. 2013

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We present a frequency domain model of shot noise in the photodetection of ultrashort optical pulse trains using a time-varying analysis. Shot noise-limited photocurrent power spectral densities, signal-tonoise expressions, and shot noise spectral correlations are derived that explicitly include the finite response of the photodetector. It is shown that the strength of the spectral correlations in the shot noise depends on the optical pulse width, and that these correlations can create orders-of-magnitude imbalance between the shot noise-limited amplitude and phase noise of photonically generated microwave carriers. It is also shown that only by accounting for spectral correlations can shot noise be equated with the fundamental quantum limit in the detection of optical pulse-to-pulse timing jitter.

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Section: Shot Noise Power and Signal-to-noisementioning

confidence: 99%

Exploiting shot noise correlations in the photodetection of ultrashort optical pulse trains

et al. 2013

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“…A two-laser heterodyne system [20] has been used to characterize PD nonlinearities [3], [20], [21] as well as the large-signal saturation behavior [22], and pulsed systems [17], [18], [23] are helpful in studying the transient behavior. Small-signal measurement systems have also been used to measure certain characteristics [6], [7], [11], [14], [22]- [24] of high-current PD's. A particular implementation of a small-signal measurement system is shown in Fig.…”

Section: General Considerationsmentioning

confidence: 99%

“…This point is particularly important in optically steered phased array antennas since any increase in photodetector output signal level reduces the necessary phase-and amplitude-matched electronic gain at each antenna element. In an effort to increase the output photocurrent, a number of groups have been studying surface-illuminated [6]- [11], metal-semiconductor-metal [12], [13], waveguide [14], [15], traveling-wave [16], [17], and photodetector arrays [18], [19]. The ability to increase photocurrent depends on two primary factors: 1) space-charge limitations which are influenced by physical dimensions, structure type, illumination conditions, maximum electric field, etc.…”

Section: Introductionmentioning

confidence: 99%

Design considerations for high-current photodetectors

Williams

Esman

1999

J. Lightwave Technol.

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179

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Abstract-This paper outlines the design considerations for gigahertz-bandwidth, high-current p-i-n photodiodes utilizing InGaAs absorbers. The factors being investigated are photodetector intrinsic region length, intrinsic region doping density, temperature effects, illumination spot size, illumination wavelength, frequency, and illumination direction. Space-charge calculations are used to determine optimal device geometry and conditions which maximize saturation photocurrent. A thermal model is developed to study the effects of temperature on high-current photodetector performance. The thermal and space-charge model results are combined to emphasize the importance of thin intrinsic region lengths to obtain high current. Finally, a comparison between surface-illuminated p-i-n structures and waveguide structures is made to differentiate between the problems associated with achieving high current in each structure and to outline techniques to achieve maximum performance.

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“…For lasers of low repetition rate, such high average power levels at GHz frequencies cannot be obtained, as fast photodiodes are limited by saturation effects when illuminated with intense laser pulses. 5,11 In addition, the power is usually nearly equally distributed over a very large number of narrow harmonics. 7,8 Therefore, only a small fraction of the total output power is available at the desired microwave mode.…”

mentioning

confidence: 99%

“…This advantage, however, diminishes with lasers of lower repetition rate (unless modefiltered), because not the average power but rather the peak power leads to saturation of the photodiode in that regime. 5,11 Let us have an outlook. Laser spectroscopy has now entered the attosecond domain, [24][25][26] but spatial information on the atomic scale is still hidden from such experiments.…”

mentioning

confidence: 99%

Passive optical enhancement of laser-microwave synchronization

Gliserin

Walbran

Baum

2013

Applied Physics Letters

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Thermal noise is a fundamental limitation for synchronizing microwaves to high-power lasers of low repetition rate. Here, we describe an optical enhancement scheme that concentrates the output power of a fast photodiode into a narrow range of harmonics around a microwave frequency. The scheme is entirely passive and requires no feedback or lock. Using a 5-MHz laser and a microwave at 6.2 GHz, we demonstrate an enhancement of optical-to-microwave conversion by a factor of 4000. The uncorrelated noise on time scales up to 8 min amounts to less than 4 fs, with laser pulses intense enough for pump-probe experiments of structural dynamics.

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Effects of high space-charge fields on the response of microwave photodetectors

Cited by 122 publications

References 8 publications

Exploiting shot noise correlations in the photodetection of ultrashort optical pulse trains

Exploiting shot noise correlations in the photodetection of ultrashort optical pulse trains

Design considerations for high-current photodetectors

Passive optical enhancement of laser-microwave synchronization

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