Papers by Thomas Carruthers
2022 IEEE Photonics Conference (IPC)
It has been difficult to use the measured dispersion data to determine which transverse mode is t... more It has been difficult to use the measured dispersion data to determine which transverse mode is the best to use for producing optical frequency combs in microresonators. We propose a simulation method to do so.
Conference on Lasers and Electro-Optics, May 21, 1990
Optical Society of America Annual Meeting, 1991
The emitter photocurrent transient of a doubleheterojunction InP/Ga0.47In0.53As/InP bipolar tran... more The emitter photocurrent transient of a doubleheterojunction InP/Ga0.47In0.53As/InP bipolar transistor has been found to be much faster than its ~15-GHz microwave bandwidth would suggest, since optical injection bypasses the base resistance. Slower components, due to holes residing in the base, can be eliminated with appropriate base biasing; this feature may be useful in optical receiver circuits. At a base bias of +0.5 V, the photocurrent transient has a 12-ps duration in response to both 620- and 1530-nm ultrafast optical pulses. At higher biases a slower transient component appears, as does a transient of opposite sign but with the same ~100-ps time constant at lower base biases. One slow component, a charge-neutrality-preserving collector current, has a base-bias-controlled gain; the other components can therefore be made to cancel. The device does not possess gain when operated in this manner, but the data suggest a design for an ultrafast photodetector with gain. The device studied is as fast a photodetector at visible wavelengths as at infrared, and the additional absorption provided by the InP emitter layer increases its short-wavelength sensitivity.
Proceedings of SPIE, Jan 22, 1997
Optics Letters, Jun 14, 2017
2022 IEEE Photonics Conference (IPC), Nov 1, 2022
arXiv (Cornell University), Jun 24, 2023
We computationally investigate the transmission efficiency through moth-eye nanostructures that a... more We computationally investigate the transmission efficiency through moth-eye nanostructures that are fabricated on SiO 2 windows in the wavelength range from 0.4 to 2 μm. We investigated both truncated cones and truncated pyramids, and we varied the height, bottom width, and top width of these shapes in order to maximize the transmission efficiency. We found that there is no substantial difference in transmission between truncated cone and pyramid structures. Using the constraints from the current achievable experimental limits, a relatively uniform transmission coefficient of larger than 98.8% can be obtained from 0.4 μm to 2 μm. These transmission results are only 0.4% in absolute value lower than the transmission of a structure that is not constrained by current experimental limits.
Annual Meeting Optical Society of America, 1989
Continuum radiation from 650 to at least 1800 nm has been generated in silica optical fibers pump... more Continuum radiation from 650 to at least 1800 nm has been generated in silica optical fibers pumped by 100-ps pulses at 1064 nm from a mode-locked Q-switched Nd:YAG laser. The peak spectral power density of the ~100-ps pulses exiting the fiber, as high as 8 W/nm near 1250 nm, is easily sufficient to serve as a broadband source for characterizing fast photodetectors. The 5-m length of continuum generating singlemode silica fiber has a numerical aperture of 0.13. It contains 1.8% P2O5 in the cladding and 1.2% in its core; the 6.2-µm core also contains 10% GeO2. We have tested a number of fibers drawn from the same preform but with differing draw tensions and diameters. Efficient near infrared continuum generation and efficient second harmonic generation seem to be mutually exclusive characteristics of these fibers.
Journal of the Chemical Society, 1977
Springer eBooks, 1977
To a degree unmatched among other intrinsic conductors, the electronic properties of organic char... more To a degree unmatched among other intrinsic conductors, the electronic properties of organic charge-transfer salts1 are subject to chemical control. Among the derivatives and analogs of TTF-TCNQ,2-7 for example, even minor differences in molecular structure often manifest thanselves as sharp contrasts in electrical behavior. Indeed, despite their general chemical and crystallographic similarities, such compounds span the full range from insulators to the best organic conductors known.
Journal of Lightwave Technology, Nov 1, 2000
We study theoretically and experimentally actively modelocked fiber lasers that are used in high ... more We study theoretically and experimentally actively modelocked fiber lasers that are used in high repetition rate optical communication systems. Using an innovative numerical technique and a reduced model, we have found that the laser can operate in four different operating regimes when the laser intensity was changed; three of the regimes were experimentally observed in a laser with a sigma configuration. An excellent quantitative agreement between the theoretical and the experimental results was obtained. The use of dispersion management in the sigma laser was found to significantly improve the laser performance.
We report a simple means of measuring device response times which is similar to cross-correlation... more We report a simple means of measuring device response times which is similar to cross-correlation techniques on linked pairs of photodetectors but which avoids the bandwidth limitations imposed by interconnecting transmission lines and largely eliminates the need for elaborate device mounting procedures [1,2]. Measurements are therefore possible on devices, such as those which must be mounted singly or those which are embedded in an integrated circuit without direct electrical access, whose intrinsic response speeds were previously not observable.
Optica Advanced Photonics Congress 2022, 2022
Modern optimization techniques are used to design high-performance photodetectors. All the design... more Modern optimization techniques are used to design high-performance photodetectors. All the designs created during these optimization studies are then used to train a physics-inspired, two-stage neural network to obtain even better-performing devices.
Applied optics, 1998
Gallium arsenide ͑GaAs͒ metal-semiconductor-metal ͑MSM͒ photodetectors have unique properties inc... more Gallium arsenide ͑GaAs͒ metal-semiconductor-metal ͑MSM͒ photodetectors have unique properties including high-bandwidth, linearity, and biphase response that make them suitable as mixers and programmable weights for microwave and communications applications. An optical technique for microwave single-sideband modulation that uses GaAs MSM photodiodes as mixers is reported. It uses MSM Schottky photodiodes formed in a GaAs͞Al 0.3 Ga 0.7 As materials system to detect microwave inphase and quadrature signals on optical carriers. Modulation of the photodetector bias voltages results in a single-sideband modulation of the microwave signal. Radio frequency and undesired-sideband suppression of 36 and 27 dB, respectively, were achieved. The optical wavelength was 850 nm, and the bandwidth of the photodetectors was Ն29 GHz.
Springer eBooks, 1977
Most crystalline organic compounds are insulators or semi-conductors with roan temperature conduc... more Most crystalline organic compounds are insulators or semi-conductors with roan temperature conductivities in the range of 10-9 to 10-14Ω-1 cm-1 and exhibit exponentially decreasing conductivity profiles as the temperature is decreased.10 However in the 1960’s Melby and the duPont group made the startling discovery that a few of the many TCNQ (fig. 2) radical ion salts they prepared and studied11–17 had conductivities as high as 102Ω-1 cm-1. While this is low compared with metals like copper (σRT=5xl06 Ω-1 cm-1), it is remarkably high for an organic compound. Why do some of the TCNQ salts exhibit this high conductivity and can the conductivity of organic compounds be increased above 102Ω-1cm-1?
Optics Express, May 1, 2006
We calculate the pulse compression in a tapered microstructure optical fiber with four layers of ... more We calculate the pulse compression in a tapered microstructure optical fiber with four layers of holes. We show that the primary limitation on pulse compression is the loss due to mode leakage. As a fiber's diameter decreases due to the tapering, so does the air-hole diameter, and at a sufficiently small diameter the guided mode loss becomes unacceptably high. For the four-layer geometry we considered, a compression factor of 10 can be achieved by a pulse with an initial FWHM duration of 3 ps in a tapered fiber that is 28 m long. We find that there is little difference in the pulse compression between a linear taper profile and a Gaussian taper profile. More layers of air-holes allows the pitch to decrease considerably before losses become unacceptable, but only a moderate increase in the degree of pulse compression is obtained.
IEEE Transactions on Electron Devices, Jul 1, 2023
2023 International Applied Computational Electromagnetics Society Symposium (ACES)
Optica Advanced Photonics Congress 2022
In a theoretical study of dissipative heating in Kerr microresonators we show that thermal effect... more In a theoretical study of dissipative heating in Kerr microresonators we show that thermal effects shift the coexistence wedge and modulational instability curve of continuous waves, so as to block access to frequency combs, and exhibit a path circumventing the obstruction. Thermal oscillations occur beyond a Hopf bifurcation curve.
Conference on Lasers and Electro-Optics, 2020
We have fabricated GaAs motheye structures using contact photolithography printing. We have achie... more We have fabricated GaAs motheye structures using contact photolithography printing. We have achieved an average transmission improvement of 123% from 2000 cm -1 to 700 cm-1 (5 ¿urn-14 ¿urn) relative to an uncoated wafer.
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Papers by Thomas Carruthers