Power Of Several Watts Research Articles

Delivering wireless ultrasound energy to remote systems: Design implications for powering medical implants requiring milliwatt versus several watts of power

Current medical device technological advances either involve, miniaturization or wireless operation or both. Miniaturization enables implant placement closer to target organs, e.g., blood vessels, viscera, or neurological structures, while wireless powering of larger left-ventricular assist devices (LVAD) is desired to mitigate infection risk due to wires. Ultrasound is a viable energy modality, wirelessly propagating through material media (tissue) and either directly powers systems, or charges an integrated battery. Whether powering implantables, or non-implantable systems, such as digital devices, ultrasound power transfer approaches have to be application-specific. This talk will present data and development strategies for four distinct use-cases requiring respectively, <5 mW (miniaturized systems), ∼500 mW (implantable pulse generators, IPG), ∼2 W (non-implanted digital systems), and ∼8 W (LVADs). Choice of low-MHz frequency, planar single-element or coarse array transmit sources, as well as application-dependent receivers a few wavelengths in size (low-mW), to 45 mm diameter (∼8 W), will be described. Benchtop experiments demonstrate successful ultrasound charging of a miniaturized solid-state (250 mAh) battery within 20 minutes. Results from live porcine model studies show a 200 mAh Li-ion battery within a Ti-shelled IPG, being successfully charged without thermal-effect-related tissue changes in the propagation path. [Work partially supported by NIH/NIBIB R43EB019225.]

Pressure of Electromagnetic Radiation on a Thin Linear Vibrator in a Waveguide

The problem of electromagnetic wave pressure on a thin conductive vibrator located in a rectangular waveguide is solved. Wave H10 falls on the vibrator. The vibrator is located perpendicular to the wide wall of the waveguide. The current in the vibrator arising under the action of the electric field of the wave is calculated. The current distribution along the vibrator is almost uniform. The current in the microwave range depends little on the vibrator conductivity. Two components of the magnetic field - longitudinal and transverse exist in the H10 wave. When these components interact with the current in the vibrator, forces arise, acting on the vibrator across the waveguide and along it. The magnitude of the longitudinal force is greatest when the vibrator is located in the middle of a wide wall. It is almost 2 times greater than the force acting on the vibrator in free space at the same average radiation intensity, When the vibrator length is close to half the radiation wavelength, the force is maximum. The transverse force is determined by the interaction of the current in the vibrator with the longitudinal component of the magnetic field in the waveguide. It is maximum when the vibrator is located at the distance of ¼ of the length of the wide wall from its middle. If the length of the vibrator is less than half the wavelength of the radiation, the force is directed towards the axis of the waveguide, otherwise - in the opposite direction. The possibility of using microwave radiation pressure to create micromachines and to control the position of the vibrator in space has been evaluated. This requires a radiation power of several watts.

태양광 발전량 증대를 위한 에너지 하베스팅 연구

In energy harvesting technology, the United States and Europe are leading the technology development, but since the technology is in the stage of introduction around the world, it is a national investment to secure excellent harvesting-related technology through concentration of capabilities of domestic companies and to preoccupy the global market. The power level that can be used through energy harvesting technology is limited to low power of several watts or less, but in terms of energy cost that can be provided per unit time and unit area provided by energy harvested over a long period of several years or more even compared to the batteries currently in use, it can have a significant alternative meaning. Therefore, in this paper, a voltage coupling method near the lowest voltage of inverter operation was developed and converted as a study to increase the amount of solar power generation in the low sunlight section at sunrise and sunset through voltage tightening amplification adjustment and energy storage technology. In addition, through the solar module voltage series/parallel variable connection conversion technology, the power generation time is extended even under the lowest inverter operating voltage to increase the amount of power generation.

Frequency Multiplication in Planar Gyrotrons as a Method for Production of High-Power Multi-THz Radiation

We propose a novel source of high-power 1–3-THz radiation based on frequency multiplication in a planar gyrotron, with transverse energy extraction. In such a scheme, it is possible to increase significantly the transverse size both of the cavity and of the electron beam, and, correspondingly, the output power at the fundamental harmonic. At the same time, equidistant mode spectrum of a cavity of planar gyrotrons is favorable for generation at high-order cyclotron harmonics in the frequency multiplication regime, providing a much higher efficiency of nonlinear conversion when compared with conventional cylindrical gyrotron schemes. In simulations of a 1-THz planar gyrotron, within the multimode time-domain model, we demonstrate a possibility of kilowatt-level radiation at the second cyclotron harmonic and power of several watts at the third one. The obtained results are partially confirmed based on direct 3-D particle-in-cell (PIC) simulations.

Terahertz laser diode using field emitter arrays

High-power and broad-tunable terahertz wave generating source on chip, which has broad application prospects, remains an unachieved goal of researchers after decades of pursuing. Here, we propose a concept of terahertz laser diode, which is a dc-biased self-excited microelectronic laser oscillator using collectively modulated free electrons emitted by field-emitter-arrays as the active medium and using an inherent Fabry-P\'erot interferometer formed by port reflections as the frequency selector. It is sub-millimeter to centimeter in size and can generate continuous-wave coherent terahertz radiation with several watts of power per square millimeter. Its frequency can be tuned to cover a wide terahertz band by changing the cathode-to-anode distance and the bias voltage. It has the potential to outperform the conventional free-electron or solid-state terahertz devices in terms of portability, tunability, and output power, signifying a promising class of tunable and high-power terahertz source on chip.

Gold implanted germanium photoswitch for cavity dumping of a free-electron laser

We present a plasma switch based on gold-implanted germanium (Ge:Au) as a potential candidate for efficient cavity dumping of a free-electron laser (FEL). Ge:Au has a sub-nanosecond carrier lifetime—much shorter than the FEL pulsing period of 77 ns—and demonstrates a high photoinduced reflectivity in a broad range of infrared wavelengths from 6 to 90 μm. The Ge:Au plasma switch exhibits negligible absorption of the FEL radiation in the “off ” state and requires only moderate thermoelectric cooling for incident FEL power of several Watts. A reflectivity level of more than 50% in the “on” state is achieved over the entire spectral range of this study. The corresponding optical pump fluence exhibits a linear relationship with the FEL frequency. This scaling is corroborated by our simulations highlighting the role of a finite sub-μm thickness of the photoinduced reflecting plasma layer. The demonstrated device is promising for the realization of the FEL cavity dumping for experiments that simultaneously require higher pulse energy and lower average power.

On an improvement of low bass characteristics on the OLED flat panel speaker

Recently, researches using OLED flat panel displays as speakers have attracted attention. However, due to the local characteristics of the flat panel speaker, the bass characteristic below 500 Hz is insufficient. The flat panel loudspeaker drives several watts of power into the exciter attached to the back of the flat panel. The exciter of the flat plate has a characteristic that the sound is driven forward from the local region, so the characteristics of the bass region are deteriorated. Therefore, in this paper, the research was conducted to widen the sound by attaching the exciter to the rigid bar. It is a principle to compensate the bass region of the flat panel speaker using an array type exciter. In order to improve the bass sound, the rigidity bar is used instead of the array exciters to improve the manufacturing process and cost. Compared to the conventional flat panel speaker, when the rigid bar is attached, the bass bandwidth is improved to 200 Hz. In the future, it is necessary to minimize the effect of the rigid bar on the high-pitched area compared to using exciter array.

Three-channel Laser Diode Driver for Multimedia Laser Projectors

The paper describes the design, implementation andtest results of a three-channel laser diode driver intended for use inmultimedia laser projectors. Our development goals were to create acompact and power-efficient driver, which achieves good colormixing and supports high modulation frequencies. It is compatiblewith most laser diode configurations used in multimedia laserprojectors with a total optical output power of several watts. Thedriver is equipped with three protected signal modulation inputs. Itneeds a single regulated power supply between 9V and 18V andcontrols up to three cooling fans intended for the thermalmanagement of the laser diodes. Our initial tests show that the driverworks very well and is suitable for the long-term operation inprojector systems. In the future, we plan to perform more tests on thesignal feedback for various input signal combinations, which shouldresult in optimizations of the feedback configuration andimprovements of the modulation response of the driver.

Development of Third-Harmonic 1.2-THz Gyrotron With Intentionally Increased Velocity Spread of Electrons

We develop the concept of a continuous wave (CW) 1.185 THz (wavelength about 250- $\mu \text{m}$ ) gyrotron with an output power of several watts, intended for dynamic nuclear polarization (DNP)/nuclear magnetic resonance (NMR) spectroscopy applications. For a 15-T magnetic field provided by a commercially available cryomagnet, the required frequency can be achieved by operating at the third cyclotron harmonic. Under conditions of extreme density of the mode spectrum, we propose using interaction with an electron beam intentionally formed with a high (up to 40%) velocity spread as a selection mechanism. This ensures suppression of the most dangerous parasitic traveling modes at the first and the second cyclotron harmonics, which are very sensitive to the spread. The main parameters of the gyrotron are determined both using the start currents analysis and within the framework of a nonstationary self-consistent model. Experimental feasibility of the single-mode third-harmonic generation under conditions of mode competition is verified based on 3-D particle-in-cell (PIC) simulations.

An RF-gated wireless power transfer system for wireless MRI receive arrays.

In MRI systems, cable-free receive arrays would simplify setup while reducing the bulk and weight of coil arrays and improve patient comfort and throughput. Since battery power would limit scan time, wireless power transfer (WPT) is a viable option to continuously supply several watts of power to on-coil electronics. To minimize added noise and decouple the wireless power system from MRI coils, restrictions are placed on the coil geometry of the wireless power system, which are shown to limit its efficiency. Continuous power harvesting can also cause a large increase in the background noise of the image due to diode rectifier up-conversion of noise around the frequency of the transmitted power. However, by RF gating the transmitted power off during the MRI receive time while continuing to supply power from a storage capacitor, WPT is demonstrated to have minimal impact on image quality at received power levels up to 11 W. The integration of WPT with a 1.5T scanner is demonstrated.

Wearable Biomechanical Energy Harvesting Technologies

Energy harvesting has been attracting attention as a technology that is capable of replacing or supplementing a battery with the development of various mobile electronics. In environments where stable electrical supply is not possible, energy harvesting technology can guarantee an increased leisure and safety for human beings. Harvesting with several watts of power is essential for directly driving or efficiently charging mobile electronic devices such as laptops or cell phones. In this study, we reviewed energy harvesting technologies that harvest biomechanical energy from human motion such as foot strike, joint motion, and upper limb motion. They are classified based on the typical principle of kinetic energy harvesting: piezoelectric, triboelectric, and electromagnetic energy harvesting. We focused on the wearing position of high-power wearable biomechanical energy harvesters (WBEHs) generating watt-level power. In addition, the features and future trends of the watt-level WBEHs are discussed.

Theoretical analysis of two coupling modes of a 300-Hz three-stage thermoacoustically driven cryocooler system at liquid nitrogen temperature range

Highly reliable, compact, and efficient cryocoolers with a cooling power of several watts to several hundred watts at liquid nitrogen temperatures around 77K are indispensable for cooling superconducting devices and infrared detectors, especially in aerospace applications. This paper introduces three-stage traveling-wave thermoacoustically driven cryocooler systems operating around 300Hz that meet the demand. In addition to the potential reliability due to the lack of moving components in a thermoacoustically driven cryocooler, this configuration has the potential for both compact size and high efficiency owing to the slim resonance tube and acoustic power recovery. Numerical simulations are performed to investigate two coupling modes: coupling the cooler at the branch of the engine (BR-coupling) or coupling the cooler parallel to the engine (PA-coupling). First, the two topologies are carefully designed to obtain high total exergy efficiency and the optimal dimensions are presented. Then, the axial distributions of the phase difference and the acoustic power are further provided to better illustrate the coupling characteristics. Furthermore, a theoretical analysis is performed on the influence of the two acoustic tubes in the PA-coupling mode and the result shows the importance of the tube dimensions. With a heating temperature of 850K, total exergy efficiencies of 11.4% and 14.8% have been achieved in the BR-coupling and PA-coupling modes, respectively. The PA-coupling mode’s higher efficiency is due to recycling the acoustic power entering the pulse tube cryocooler, whereas BR-coupling fails to recycle any acoustic power. However, the energy feedback in PA-coupling may cause structural complexity. Generally speaking, both coupling mode systems show encouraging prospects for aerospace applications.

A Low-Power and Low-Voltage Power Management Strategy for On-Chip Micro Solar Cells

Fundamental characteristics of on-chip micro solar cell (MSC) structures were investigated in this study. Several MSC structures using different layers in three different CMOS processes were designed and fabricated. Effects of PN junction structure and process technology on solar cell performance were measured. Parameters for low-power and low-voltage implementation of power management strategy and boost converter based circuits utilizing fractional voltage maximum power point tracking (FVMPPT) algorithm were determined. The FVMPPT algorithm works based on the fraction between the maximum power point operation voltage and the open circuit voltage of the solar cell structure. This ratio is typically between 0.72 and 0.78 for commercially available poly crystalline silicon solar cells that produce several watts of power under typical daylight illumination. Measurements showed that the fractional voltage ratio is much higher and fairly constant between 0.82 and 0.85 for on-chip mono crystalline silicon micro solar cell structures that produce micro watts of power. Mono crystalline silicon solar cell structures were observed to result in better power fill factor (PFF) that is higher than 74% indicating a higher energy harvesting efficiency.

Tin laser-produced plasma as the light source for extreme ultraviolet lithography high-volume manufacturing: history, ideal plasma, present status, and prospects

Today intermediate-focus equivalent extreme ultraviolet (EUV) power of several watts is now available, and EUV lithography scanners are being considered as potential scanners for high-volume manufacturing (HVM) tools. However, for high-volume manufacturing with throughput of over 100 wafers per hour, EUV power of 350 W may be required. We review the history of EUV sources for lithography with tin as fuel. We discuss the ideal plasma for tin sources for extreme ultraviolet lithography (EUVL), conditions for a high conversion efficiency of 4% to 5% in 2πsr, and the existence of a repetition rate limit at around 40 kHz. We review the present status reported by EUV source suppliers and the prospects of tin laser-produced plasma as an EUV source for HVM EUVL.

Improving the stability of distributed-feedback tapered master-oscillator power-amplifiers

We report theoretical results on the wavelength stabilization in distributed-feedback master-oscillator power-amplifiers which are compact semiconductor laser devices capable of emitting a high brilliance beam at an optical power of several Watts. Based on a travelling wave equation model, we calculate emitted optical power and spectral maps in dependence on the pump of the power amplifier. We show that a proper choice of the Bragg grating type and coupling coefficient allows optimization of the laser operation, such that the laser emits a high intensity continuous wave beam for a wide range of injection currents.

3.4 THz heterodyne receiver using a hot electron bolometer and a distributed feedback quantum cascade laser

We report a heterodyne receiver using a superconducting NbN hot electron bolometer (HEB) integrated with a tight winding spiral antenna as mixer and a distributed feedback (DFB) terahertz quantum cascade laser (QCL) operating at 3.42 THz as local oscillator. The aim is to demonstrate the readiness of both devices for the detection of OH lines at 3.5 THz in a real instrument. We show that the improved single-spot beam of the terahertz QCL can easily pump the HEB mixer. We measured a double sideband receiver noise temperature of 2100 K at the optimum local oscillator power of 290 nW. This noise temperature can be further reduced to 1100 K if we correct the loss due to the use of an uncoated lens, and the losses of the window and the air. Therefore, the combination of a HEB and such a DFB QCL can in principle be used to detect an OH line at 3.5 THz. However, a high input power of several watts, which is needed to operate the QCL in a liquid-helium cryostat, poses a big challenge to the receiver stability.

PPLN 비선형 결정과 이중통과법을 이용한 DOFA 시스템에서 증폭된 연속발진형 파장가변 적외선 레이저광의 제 2고조파 발생

주기적으로 분극 반전된 비선형 결정 중에 하나인 PPLN(Periodically Poled MgO(5%) doped Lithium Niobate)과 수 W급의 고출력 연속발진형 파장가변 적외선 레이저 시스템인 DOFA(Diode Laser Oscillator & Fiber Amplifier) 시스템을 이용하여, 이 결정에서 펌핑광을 한번 통과시키는 단일통과와 두 번 통과시키는 이중통과에서의 효율적인 제2고조파 발생 조건을 실험적으로 구하였다. 단일통과에서는 최적의 위상정합온도 <TEX>$108.9^{\circ}C$</TEX>에서 최대 출력 2.45 W의 적외선(파장 = 1070 nm) 펌핑광을 사용하여 최대 245 mW의 녹색광원(파장 = 535 nm)인 제 2고조파를 만들었고, 이때의 주파수 변환 효율은 10%였다. 또한 제 2고조파 발생의 효율을 증가시키기 위해서 되 반사용 오목거울과 위상보정을 위한 쐐기유리판을 이용하여 이중통과의 제2고조파 발생장치를 구성하였다. 이때 최적의 위상정합온도 <TEX>$108.5^{\circ}C$</TEX>에서 최대 출력 2.45 W의 적외선(파장 = 1070 nm) 펌핑광을 사용하여 최대 383 mW의 녹색광원(파장 = 535 nm)인 제 2고조파를 만들었다. 이때의 변환 효율은 15.6%로써 단일통과에서의 제 2고조파 발생 효율보다 크게 증가함을 확인하였다. The optimum conditions of second harmonic generation (SHG) can be successfully achieved experimentally using single pass and double pass methods of a pumping beam. The beam has a power of several Watts radiated by a DOFA (Diode Laser Oscillator & Fiber Amplifier) system, which is a high power CW wavelength tunable infrared laser system, in a PPLN (Periodically Poled MgO doped Lithium Niobate) nonlinear crystal. In the case of a single pass method, the parameters are the wavelength of 535 nm for SHG and the output power of 245 mW generated from the pumping input beam with wavelength of 1070 nm and the power of 2.45 W at phase matching temperature of <TEX>$108.9^{\circ}C$</TEX>. The conversion efficiency of SHG was 10%. In order to enhance the output of SHG, the double pass method of the SHG system of a PPLN using a concave mirror for the retroreflection and a pair of wedged flat windows for phase compensation was also presented. In this double pass system, we obtained the SHG output beam with the wavelength of 535 nm and the maximum power of 383 mW at optimum phase matching temperature of <TEX>$108.5^{\circ}C$</TEX> by using an incident pumping beam with wavelength of 1070 nm and the power of 2.45 W. The maximum conversion efficiency is 15.6%, which is more than that of the single pass method.

Low-threshold supercontinuum generation in highly nonlinear chalcogenide nanowires

We demonstrate low-threshold supercontinuum generated in a highly nonlinear arsenic selenide chalcogenide nanowire with tailored dispersion. The tapered submicrometer chalcogenide fiber exhibits an ultrahigh nonlinearity, n(2) approximately 1.1x10(-17) m(2)/W and an effective mode area of 0.48 mum(2), yielding an effective nonlinearity of gamma approximately 93.4 W/m, which is over 80,000 times larger than standard silica single-mode fiber at a wavelength of approximately 1550 nm. This high nonlinearity, in conjunction with the engineered anomalous dispersion, enables low-threshold soliton fission leading to large spectral broadening at a dramatically reduced peak power of several watts, corresponding to picojoule energy.

Homogeneous Raman gain saturation at high pump and Stokes powers

A Raman gain spectral profile has been measured in a phosphosilicate fiber at high pump and Stokes (signal) wave powers by a coherent anti-Stokes Raman scattering (CARS) technique. It has been shown that the profile saturates homogeneously. The main saturation mechanism is proved to be the pump depletion; i.e., the Raman gain coefficient gR does not depend on the pump and signal wave power of several watts. The possible influence of stimulated Brillouin scattering and four-wave mixing is discussed. In addition, a transient regime of the CARS signal has been experimentally observed and theoretically explained.

Second Harmonic Operation at 460 GHz and Broadband Continuous Frequency Tuning of a Gyrotron Oscillator

We report the short-pulse operation of a 460 GHz gyrotron oscillator both at the fundamental (near 230 GHz) and second harmonic (near 460 GHz) of electron cyclotron resonance. During operation in a microsecond pulse length regime with 13-kV beam voltage and 110-mA beam current, the instrument generates several watts of power in two second harmonic modes, the TE/sub 2,6,1/ at 456.15 GHz and the TE/sub 0,6,1/ at 458.56 GHz. Operation in the fundamental modes, including the TE/sub 0,3,1/ mode at 237.91 GHz and the TE/sub 2,3,1/ at 233.15 GHz, is observed at output powers up to 70 W. Further, we demonstrate broadband continuous frequency tuning of the fundamental modes of the oscillator over a range of more than 2 GHz through variation of the magnetic field alone. We interpret these results in terms of smooth transitions between higher order axial modes of the resonator. The 460 GHz gyrotron is currently being processed for continuous duty operation, where it will serve as a microwave source for sensitivity-enhanced nuclear magnetic resonance (dynamic nuclear polarization) studies at 16 T (700 MHz /sup 1/H), a field strength which is two-fold higher than has been accessible with previous technology.