Analysis of Optically Controlled Microwave/Millimeter-Wave Device Structures (original) (raw)
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Intermixing optical and microwave signals in GaAs microstrip circuits and its applications
Microwave and Optical Technology Letters, 1993
response is small, associated with the gate junction and resembles a photodiode. These facts explain the small locking range achieved by optical injection locking. For switching applications the large photovoltaic effects can b e utilized; however, the rise and fall times are typically in the microsecond range, which means that the device is limited to switching rates of several megahertz. 6. CONCLUSIONS In this article we have reviewed the phenomenon of light interaction with MESFET. T h e importance and applications of this photodetection have been explained, and the physical mechanisms were described. It was shown that the response to modulated light is quite different from the response to constant illumination. In general, the MESFET is a relatively "slow" photodetector, and its response decreases strongly with frequency. A t low frequencies and dc the response is very large, and exhibits gain, but at microwave frequencies the response is small and similar t o a photodiode. Despite the above, the MESFET is useful a t high frequencies for applications such as injection locking and optical mixing, which cannot be obtained by photodiodes.
DC and pulse-light illuminated optical responses of microwave GaAs-MESFET oscillators
IEE Proceedings I Solid State and Electron Devices
Experimental results of two kinds of optical effects, optical tuning and optical switching, of GaAs MESFET oscillators are presented. For optical tuning, the oscillation frequency decreases with optical illumination and the maximum tuning range depends principally on oscillator mode (common-source, common-drain or common-gate), with 3.8% and 1.9% being achieved at S band and X band, respectively, with an optical power density of 0.5 mW/mm 2. The oscillator power output generally increases with optical illumination, the increase being around 1 to 2 dB at 0.5 mW/mm 2 light intensity. For optical switching, power output switching from no oscillation to 7.5 mW was obtained at X band with illumination from a 2 mW laser diode. The optical response of microwave GaAs MESFET oscillators is attributed to the capture of holes by two kinds of hole traps in the Schottky-gate depletion region. The oscillation frequency and power output changes with optical illumination become appreciably reduced with increase of optical modulation rate, becoming 10% of the constant-illumination induced change at an optical modulation rate of 1 MHz and negligibly small at 10 MHz. The drain current bias still responds above 10 MHz, with a response amount about 0.5 mA attributed to the photoconductivity effect in the channel.
Photo-devices for optical controlling of microwave circuits
Journal of telecommunications and information technology, 2001
The most important optical devices which can be used for controlling microwave circuits will be presented in the paper. The performance and the parameters of the devices such as semiconductor microwave optoelectronic switches, photodiodes and phototransistors were described. The influence of the optical illumination on their microwave parameters will be described in details, including the our own investigations and simulations results. Several applications of such devices and their potential possibilities will be presented.
Journal of Catalysis, 2005
A state of the art modeling of microwave photoswitching devices is exposed. A new 3 D electromagnetic modeling allows the design of an optically-controlled microwave phase shifter microwave starting from the traditional circuit of a microwave photoswitch. Measurements of the parameters S of this optically-controlled microwave phase shifter attests the function of this circuit by optical way and highlights the interest of the integration of this new type of microwave phase shifters in systems of antennas arrays. A new optically-controlled microwave phase shifter with a patented structure is under development.
Photoresponse of microwave transistors to high-frequency modulated lightwave carrier signal
IEEE Transactions on Microwave Theory and Techniques, 1997
Described in this paper are the photoresponse characteristics of microwave transistors, both unipolar [metal-semiconductor FET's (MESFET's) and modulationdoped FET's (MODFET's)] and bipolar [heterojunction bipolar transistors (HBT's)]. Investigation includes time-and frequencydomain measurements. For unipolar devices FET's, the two dominant photodetection mechanisms, photoconductive and photovoltaic, are clearly identified within the same device for the first time. It is shown that even high-speed FET's are limited to a photonic bandwidth of a few megahertz, if photodetection and amplification are to be achieved simultaneously. In contrast, bipolars HBT's can provide optical gain up to the millimeterwave range.
A complete microwave characterization of GaAs HEMTs under optical illumination
The present paper is devoted at presenting the main results of an extensive experimental investigation of the microwave transistor behaviour under optical illumination. The tested devices are on-wafer HEMTs based on AlGaAs/GaAs heterostructure. The light sensitivity of these transistors is investigated in terms of DC, scattering and noise parameters. The analysis is carried out by observing how the device behaviour changes under CW infrared and visible laser illumination. It is found that the light exposure affects significantly the device behaviour. In particular, the main changes consist of an increase of the drain current, the transconductance, the forward transmission coefficient, and the minimum noise figure. The optical effects have shown to be more pronounced at shorter wavelength. The observed effects of the laser illumination can be ascribed to the threshold voltage shift arising from the internal photovoltaic effect.
Optically induced measurement anomalies with voltage-tunable analog-control MMIC's
IEEE Transactions on Microwave Theory and Techniques, 1998
Monolithic microwave integrated circuits (MMIC's) may be measured under relatively high-intensity lighting conditions. Later, when they are packaged, any anomalies found in subsequent measurements could be attributed to unwanted parasitics or box modes associated with the packaging. However, optical effects may not always be considered by radiofrequency (RF) and microwave engineers. For the first time, a qualitative assessment is given for the effects of photonic absorption on three broad-band voltage-tunable analog-control circuits. Each circuit has a different function, with each fieldeffect transistor (FET) operating in a different mode: a hot FET in a variable-gain amplifier, a cold FET in an analog attenuator, and an FET varactor in an analog phase shifter. All three circuit functions have been implemented using two different FETbased technologies. The first with ion-implanted 0.5-m GaAs metal-semiconductor FET's (MESFET's) in circuits operating at either 3 or 10 GHz. The second employs epitaxially grown 0.25-m AlGaAs/InGaAs pseudomorphic high electron-mobility transistors (HEMT's) in circuits operating at 38 GHz. All the MMIC's were fabricated using commercial foundry processes and illuminated under conventional optical microscope lighting conditions. Prominent error peaks have been found at bias points unique to the three different circuit topologies. Large error peaks are found with the MESFET-based circuits, while much smaller error peaks are achieved with the corresponding pseudomorphic HEMT (pHEMT) based circuits.
Microwave On/Off Ratio Enhancement of GaAs Photoconductive Switches at Nanometer Scale
Journal of Lightwave Technology, 2000
1Abstract -This paper reports on performances enhancement of photoconductive switches in term of On/Off ratio and insertion losses. The optimization parameters on which the research has been focused are gap dimensions reduction to nanometer scale. The device characterization results up to a microwave frequency of 40 GHz and under CW illumination at a wavelength of 800 nm are presented. On/Off ratio reveals a value of 13 dB at 20 GHz under 100 mW optical power.