Array Of Active Devices Research Articles

Focused acoustic vortex by an artificial structure with two sets of discrete Archimedean spiral slits

Focused acoustic vortex (FAV) beams can steadily trap particles in three-dimensions. Previous FAV emitters are mainly based on the active device arrays. Here, we design a passive artificial structure engraved with two sets of discrete Archimedean spiral slits to generate the FAV in water. The acoustic intensity and phase distributions of FAVs are investigated theoretically and demonstrated using the finite element method. The constructive interference between two transmitted acoustic vortices through the inner and outer spiral parts achieves the FAV. It is found that the focal length and depth of the FAV can be modulated by simply changing the initial radius of the Archimedean spiral. Furthermore, we implement the Schlieren imaging experiment to verify the generation of the FAV by the artificial structure. Our design may offer potential applications in particle trapping, biomedical therapy, and medical imaging.

Dynamic characterization of piezoelectric micro-blowers for separation flow control

A micro-blower device, made by Murata™ Manufacturing Co. and originally designed for cooling electronic microprocessors, is used in the present study as an actuator for separation flow control. The dynamical performance of the device, working in pulsed mode, is experimentally investigated to deduce its abilities and limitations regarding active flow control. Both the device design and its dynamical characterization are addressed in the paper, paying particular attention to its ability to control flow. Both hot-wire anemometry and particle image velocimetry have been employed to investigate the dynamical evolution of the pulsed jet and allow the identification of the jet organized flow structures. The phase-averaging technique is applied to distinguish the large scale structure dynamics induced during the ejection phase. An array of active devices is also used to evaluate the flow control efficiency by forcing frequency strategy in order to reduce the separation area of a back facing step flow. Results show good performance in open loop flow control and applicability of such actuator for further closed loop flow control research.

Bistability and hysteresis in the emergence of pulses in microstrip Gunn-diode circuits

We develop time-domain simulations of microwave and THz radiation sources built as arrays of active devices when the radiation wavelength is small as compared to spacing between electronic components. We pursue an approach when the system is represented by equations with time-delay feedback that could generate chaos and other forms of complicated dynamics. The approach simplifies simulations of ultra-wideband effects and exceeds capabilities of frequency-domain methods. As a model case, we simulated a microstrip circuit with Gunn diode and a remote resonator emitting the radiation towards infinity. We observed the emergence of either the continuous waves or the trains of high-frequency pulses depending on the bias conditions. We found bistability and hysteresis in the onset of different oscillation modes that depends on the way of driving the bias voltage into the domain of instability of the given system. The results would allow one to improve the design of THz radiation sources with time-delay coupling between components.

Topographic substrates as strain relief features in stretchable organic thin film transistors

The fabrication of large-area active devices that can operate under large tensile strains is essential for advancing the technological applications of flexible and stretchable electronics. Here we describe a strain relief mechanism to preserve the performance of organic thin film transistors that operate under strains up to 12%. The scalable fabrication strategy utilizes sinusoidal topographic structures that are directly integrated into elastomeric substrates through controlled buckling. Organic thin film transistors are then prepared onto the prefabricated topographic substrates by conformal coating methods. The stretchability of devices fabricated on substrates with strain relief features is demonstrated by characterizing the strain-dependent performance of transistors in multiple deformation configurations. Devices fabricated on topographic substrates exhibit stabilized operation as measured by maintaining high mobilities and on–off ratios compared to the devices fabricated on flat substrates without strain relief features. The overall utility of topographic substrates is derived from the ability to embed intrinsic stretchability into arrays of active devices in large-area formats in a highly scalable manner.

A straightforward method for the FDTD analysis of quasi-optical arrays of active devices

A method for the finite-difference time-domain (FDTD) analysis of quasi-optical circuit arrays of active devices is presented in this paper. To analyze active devices such as varactor diodes and MESFETs, this method creates a set of field-state central finite-difference equations, and all the field and state variables are solved simultaneously at the same FDTD time step. It will be shown in this paper that this formulation is simple and straightforward. The analyses of quasi-optical back-to-back varactor tripler and MESFET oscillator arrays have been performed to show different applications of this method. Excellent agreements have been obtained among the results from this simulation method, analytical solutions and commercial software, and experimental measurements to show the validity of this method.

Demonstration of optically controlled data routing with the use of multiple-quantum-well bistable and electro-optical devices

We present experimental results on a 1-to-64-channel free-space photonic switching demonstration system based on GaAs/GaAlAs multiple-quantum-well active device arrays. Two control schemes are demonstrated: data transparent optical self-routing usable in a packet-switching environment and direct optical control with potential signal amplification for circuit switching. The self-routing operation relies on the optical recognition of the binary destination address coded in each packet header. Address decoding is implemented with elementary optical bistable devices and modulator pixels as all-optical latches and electro-optical and gates, respectively. All 60 defect-free channels of the system could be operated one by one, but the simultaneous operation of only three channels could be achieved mainly because of the spatial nonhomogeneities of the devices. Direct-control operation is based on directly setting the bistable device reflectivity with a variable-control beam power. This working mode turned out to be much more tolerant of spatial noises: 37 channels of the system could be operated simultaneously. Further development of the system to a crossbar of N inputs and M outputs and system miniaturization are also considered.

A hybrid cryotron technology: I--Circuits and devices

The hybrid cryotron technology is explained as an effective technique for batch fabrication of large numbers of interconnected devices. Fabrication of large arrays of active devices is made practical by the fault tolerant properties of the cryotron device and the advantages of combined stencil masking and photoetching techniques. Several assemblies have been given extensive operational and temperature cycling. These assemblies included five substrate cryotron computers and four substrate content addressed memories. Details of circuit and logic design, device characteristics, and fabrication yield are described. Present work on arrays of 10 000 interconnected devices on a single substrate is reported. Fabrication yields of 99.98 percent and time constants of 10 ns are expected in the near future in arrays of this size through improvements in fabrication process control and device utilization.