mW Peak Output Power Research Articles

Design and analysis of magnetostrictive two-dimensional kinetic energy harvester

Conventional energy harvesters often require high ambient vibration frequencies and can only capture vibration energy in a single direction. To address these issues, this paper designs a magnetostrictive two-dimensional kinetic energy harvester placed under the floor and capable of capturing energy in both vertical and horizontal directions. In order to achieve higher electrical power output at low-frequency input forces, a two-stage force amplification mechanism is designed to amplify the walking kinetic energy of pedestrians and the main parameters of this structure are analyzed and optimized. On the other hand, by constructing different forms of bias magnetic field, the influence of bias magnetic field on the deflection and motion of the internal magnetic domain of Terfenol-D is systematically studied, and the best bias form that can make the material shows the strongest magnetization characteristics is determined. Next, a prototype harvester was built, and an experimental vibration system was set up to test and analyze the output characteristics of the harvester comprehensively. The experimental results show that the harvester produces 21.2 mW of peak output power under sinusoidal excitation at an operating frequency of 4 Hz. Under random excitation, a peak output voltage of 2.64 V and 170 mW peak power was obtained. Under actual pedestrian walking tests, 17.62 mW peak output power is obtained to power low-power devices. The study’s results provide preliminary evidence that the designed magnetostrictive energy harvester can stably harvest kinetic energy from pedestrian walking.

A high efficiency and high power 165–180 GHz balanced doubler based on Schottky diode

In this paper, a high efficiency and high power 165–180 GHz balanced doubler based on the planar Schottky diode is presented. To maximize the efficiency of the doubler in the target frequency band, an in-band embedded impedance optimization method (IEIOM) is adopted. The method aims to extract the conjugate value of embedded impedances of the three-dimensional electromagnetic (3D-EM) model of the diode. Compared to the method of impedance optimization at a single frequency point using Load-Pull, the proposed method not only takes account for both conversion efficiency and bandwidth but also simplifies operation process. To verify the proposed concept, the doubler was fabricated and measured, which exhibits a conversion efficiency of 13%–46% at the 165–180 GHz band under 160–200 mW input power and a 90.88 mW peak output power with a 46% efficiency was measured at 178 GHz when the input power is 198 mW.

A High-Power 170 GHz in-Phase Power-Combing Frequency Doubler Based on Schottky Diodes.

In this paper, a high-power 170 GHz frequency doubler based on a Schottky diode is proposed using an in-phase power-combining structure. Unlike a conventional power-combining frequency doubler, the proposed frequency doubler utilizes the combination of a T-junction power divider and two bend waveguides to eliminate the phase difference between the two output ports of the T-junction power divider, so as to achieve in-phase power combining with a concise structure. The frequency doubler was fabricated on a 50 μm thick AlN high-thermal-conductivity substrate to reduce the impact of the thermal effect on the performance. The measured results show that the doubler exhibits a conversion efficiency of 11-31.3% in the 165-180 GHz band under 350-400 mW of input power, and a 118 mW peak output power with a 31.3% efficiency was measured at 174 GHz `when the input power was 376 mW. A good agreement was achieved between the simulation results and the measured performance of the doubler, which proves the effectiveness of the proposed in-phase power-combining structure.

Broadly tunable lens-coupled nonlinear quantum cascade lasers in the sub-THz to THz frequency range

Room-temperature terahertz (THz) quantum cascade laser sources with intracavity difference-frequency nonlinear mixing are electrically pumped monolithic semiconductor laser sources operating in the 0.6–6 THz spectral range. We report widely tunable, low-frequency THz quantum cascade laser sources using a lens-coupled Cherenkov waveguide scheme. Based on a watt-class high-power, λ ∼ 13.7 μm quantum cascade laser, the monolithic THz source is strongly coupled with a high-resistivity silicon lens, which causes a major increase in the THz coupling efficiency and demonstrates significant performance improvements. A room-temperature 1.5 THz device produces a 0.2 mW peak output power with a high-quality beam pattern. Improved THz outcoupling efficiency using the lens-coupled scheme enabled the demonstration of a high-performance external-cavity semiconductor THz source that is tunable from 420 GHz to 2 THz. The external-cavity, lens-coupled device configuration can technically be assembled into a butterfly-style package for a thumb-sized, widely frequency tunable THz semiconductor source.

Estimation of the chemical materials volumes required for the post-growth technology manufacturing InGaP/GaAs/Ge with a concentrator and planar α–Si:H/Si solar cells for 1 MW solar power plants

The direct conversion of solar energy into electricity using the photovoltaic method does not harm the environment, unlike the traditional method. Different types of solar cells require complex technological operations using non-harmless chemicals. In this work estimation of the amount of chemical material required for the post-growth technology of creating the multijunction InGaP/GaAs/Ge solar cells for modules with a Fresnel concentrator and heterojunction α -Si:H/Si solar cells for planar modules has been performed. The analysis of solar power plants based on the concentrate modules and the planar modules with 1 MW peak output power is carried out.

Defect-mediated ionic hopping and green electricity generation in Al2−xMgxO3-based hydroelectric cell

A direct evidence of enhanced water molecule splitting by increasing defect concentration in Al2−xMgxO3 hydroelectric cells (HECs) has been elaborated for green electricity generation. Existence of F, F+ and [Mg]0 defect centers in nanoporous Al2−xMgxO3 (x = 0–0.5) cell pellets has been confirmed by optical spectroscopy. Increased defect density from ~ 1.45 × 1015 cm−3 to 5.4 × 1016 cm−3 induced by increasing Mg doping concentration is found to be a key factor to control water molecule dissociation/splitting at alumina surface. Small polaron hopping-assisted ionic conduction for enhanced current density is analyzed by impedance spectroscopy. The maximum, 15 mA, current is obtained in Al2−xMgxO3 HEC for x = 0.5 concentration resulting in 13.5 mW off-load peak output power as compared to 4.95 mW peak output power in pure alumina HEC. A theoretical modeling of Nyquist spectra analyzes ion–solid interaction for real charge transfer process in HEC. Deliberate defect creation in alumina devised for water molecule dissociation at room temperature paves the way to fabricate a facile green electricity generation source in the form of HEC. Al2−xMgxO3-based hydroelectric cell is a very low-cost device to generate green electricity besides providing eco-friendly by-products without use of photocatalytic activity, acid/alkali or electrolyte. Moreover, presented innovative alumina-based HEC would be a big step for mitigating industrial waste consisting of alumina. Polaron assisted hopping of OH− ions in the lattice of Al2-xMgxO3 HEC and green electricity generation in the form of V-I plot.

A 135-190 GHz Broadband Self-Biased Frequency Doubler using Four-Anode Schottky Diodes.

This paper describes the design and demonstration of a 135–190 GHz self-biased broadband frequency doubler based on planar Schottky diodes. Unlike traditional bias schemes, the diodes are biased in resistive mode by a self-bias resistor; thus, no additional bias voltage is needed for the doubler. The Schottky diodes in this verification are micron-scaled devices with an anode area of 6.6 μm2 and an epitaxial layer thickness of 0.26 μm. For accurate design of the doubler, the 3D-EM model of the Schottky diode is built up to extract the parasitic parameters induced by the diode package when frequency rises up to the terahertz band. In order to implement broadband working, input waveguide steps, output suspended microstrip steps, and output probe with bias filter are all used as matching elements for impedance matching. Measured results show that the doubler exhibits a 3 dB bandwidth of 34% from 135 GHz to 190 GHz, with a conversion efficiency of above 4% when supplied with 100 mW of input power. A 17.8 mW peak output power with a 10.2% efficiency was measured at 166 GHz when the input power was 174 mW. The measured results agree well with the simulated results, which indicates that the self-bias scheme for Schottky diode-based frequency multipliers is feasible and effective.

An 80.4% Peak Power Efficiency Adaptive Supply Class H Power Amplifier for Audio Applications

This paper presents a novel class H power amplifier aiming for audio applications on battery-powered electronic devices. The power supply of the amplifier is adaptively adjusted to track the instantaneous input signal amplitude for higher power efficiency. By embedding audio input signal amplitude information into the class AB amplifier’s output common-mode voltage level, the amplifier is able to operate with only single-rail power supply and demonstrates more smooth transitions between the light load and heavy load mode, hence achieves lower total harmonic distortion (THD) for a wide load range. Fabricated in the AMS 0.18- $\mu \text{m}$ CMOS process, the chip consumes 3.52 mW quiescent power and is able to deliver 526 mW peak output power to a $16~\Omega $ load. The measurement results indicate that the amplifier incurs no deterioration on THD when entering the supplytracking mode and achieves a lowest THD+N ratio of −80 dB. The peak power efficiency of the system is 80.4%; moreover, it demonstrates significant higher efficiency for medium load range compared to other linear mode amplifiers.

THz quantum cascade lasers operating on the radiative modes of a 2D photonic crystal.

Photonic-crystal lasers operating on Γ-point band-edge states of a photonic structure naturally exploit the so-called "nonradiative" modes. As the surface output coupling efficiency of these modes is low, they have relatively high Q factors, which favor lasing. We propose a new 2D photonic-crystal design that is capable of reversing this mode competition and achieving lasing on the radiative modes instead. Previously, this has only been shown in 1D structures, where the central idea is to introduce anisotropy into the system, both at unit-cell and resonator scales. By applying this concept to 2D photonic-crystal patterned terahertz frequency quantum cascade lasers, surface-emitting devices with diffraction-limited beams are demonstrated, with 17 mW peak output power.

High power terahertz quantum cascade lasers with symmetric wafer bonded active regions

We increased the active region/waveguide thickness of terahertz quantum cascade lasers with semi-insulating surface plasmon waveguides by stacking two symmetric active regions on top of each other, via a direct wafer bonding technique. In this way, we enhance the generated optical power in the cavity and the mode confinement. We achieved 470 mW peak output power in pulsed mode from a single facet at a heat sink temperature of 5 K and a maximum operation temperature of 122 K. Furthermore, the devices show a broad band emission spectrum over a range of 420 GHz, centered around 3.9 THz.

Miniature swept source for point of care Optical Frequency Domain Imaging

Point of care (POC) medical technologies require portable, small, robust instrumentation for practical implementation. In their current embodiment, optical frequency domain imaging (OFDI) systems employ large form-factor wavelength-swept lasers, making them impractical in the POC environment. Here, we describe a first step toward a POC OFDI system by demonstrating a miniaturized swept-wavelength source. The laser is based on a tunable optical filter using a reflection grating and a miniature resonant scanning mirror. The laser achieves 75 nm of bandwidth centered at 1340 nm, a 0.24 nm instantaneous line width, a 15.3 kHz repetition rate with 12 mW peak output power, and a 30.4 kHz A-line rate when utilizing forward and backward sweeps. The entire laser system is approximately the size of a deck of cards and can operate on battery power for at least one hour.

Room-temperature continuous-wave 1.55 [micro sign]m GaInNAsSb laser on GaAs

The first low-threshold 1.55 µm lasers grown on GaAs are reported. Lasing at 1.55 µm was observed from a 20×2400 µm as-cleaved device with a room-temperature continuous-wave threshold current density of 579 A/cm2, external efficiency of 41%, and 130 mW peak output power. The pulsed threshold current density was 550 A/cm2 with >600 mW peak output power.

High-performance 1.5 [micro sign]m GaInNAsSb lasers grown on GaAs

Substantially reduced threshold current density and improved efficiency in long-wavelength (>1.4 µm) GaAs-based lasers are reported. A 20×1220 µm as-cleaved device showed a room temperature continuous-wave threshold current density of 580 A/cm2, external efficiency of 53%, and 200 mW peak output power at 1.5 µm. The pulsed threshold current density was 450 A/cm2 with 1145 mW peak output power.

Optically pumped lead–chalcogenide midinfrared lasers on Si substrates

Double heterostructure (DH) and quantum well (QW) EuSe/PbSe/Pb1−xEuxSe edge-emitting laser structures on Si substrates are grown by molecular-beam epitaxy. They operate up to 250 K when pumped with 870 nm low-cost laser diodes with peak powers of ∼7 W, and emit up to 200 mW peak output power at ∼5 μm wavelength. Differential quantum efficiencies are up to 20%. The threshold powers are limited by Shockley–Read recombination due to the high dislocation densities (108 cm−2) in the active layers. Nearly similar maximum operation temperatures were observed when employing (111)—instead of (100)—oriented layers, as well when using QW rather than DH structures. Reduction of dislocation densities to 107 cm−2 is feasible and will lead to nearly an order of magnitude lower threshold powers.

Optical performance of the Los Alamos free-electron laser

During a year of oscillator experiments, the Los Alamos free-electron laser has demonstrated high-power and diffraction-limited output capabilities with a factor-of-4 wavelength tunability in the infrared. A conventional, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</tex> -band RF linear accelerator produced a 100 μs long, 2000 pulse train of 35 ps wide electron-beam pulses with peak currents to 50 A and nominal energy of 20 MeV. Small-signal gain in excess of 40 percent was generated in a 1 m, plane-polarized, uniform-period undulator for wavelengths between 9 and 11 μm. Best performance included an electron-energy extraction efficiency of 1 percent, 10 MW peak output power, and a corresponding average power of 6 kW over a 90 μs pulse train. A Strehl ratio of 0.9 characterized the output spatial beam quality. By reducing the electron energy by a factor of 2, the wavelength was tuned continuously from 9 to 35 μm.