Ultra-low Power Levels Research Articles

Large regenerative parametric amplification on chip at ultra-low pump powers

Chip-based optical amplifiers can significantly expand the functionalities of photonic devices. In particular, optical-parametric amplifiers (OPAs), with engineerable gain spectra, are well suited for nonlinear-photonic applications. Chip-based OPAs typically require long waveguides that occupy a large footprint, and high pump powers that cannot be easily produced with chip-scale lasers. We theoretically and experimentally demonstrate a microresonator-assisted regenerative OPA that benefits from the large nonlinearity enhancement of microresonators and yields a high gain in a small footprint. We achieve 30-dB parametric gain with only 9 mW of cw pump power and show that the gain spectrum can be engineered to cover telecom channels inaccessible with Er-based amplifiers. We further demonstrate the amplification of Kerr-soliton comb lines and the preservation of their phase properties. Additionally, we demonstrate amplification by injection locking of optical parametric oscillators (OPOs), which corresponds to a regenerative amplifier pumped above the oscillation threshold. Dispersion engineering techniques such as coupled cavities and higher-order-dispersion phase matching can further extend the tunability and spectral coverage of our amplification schemes. The combination of high gain, small footprint, low pump power, and flexible gain-spectrum engineering of our regenerative OPA is ideal for amplifying signals from the nanowatt to microwatt regimes for portable or space-based devices where ultralow electrical power levels are required and can lead to important applications in on-chip optical-, and microwave-frequency synthesis and precise timekeeping.

TreNch: Ultra-Low Power Wireless Communication Protocol for IoT and Energy Harvesting.

Although the number of Internet of Things devices increases every year, efforts to decrease hardware energy demands and to improve efficiencies of the energy-harvesting stages have reached an ultra-low power level. However, no current standard of wireless communication protocol (WCP) can fully address those scenarios. Our focus in this paper is to introduce treNch, a novel WCP implementing the cross-layer principle to use the power input for adapting its operation in a dynamic manner that goes from pure best-effort to nearly real time. Together with the energy-management algorithm, it operates with asynchronous transmissions, synchronous and optional receptions, short frame sizes and a light architecture that gives control to the nodes. These features make treNch an optimal option for wireless sensor networks with ultra-low power demands and severe energy fluctuations. We demonstrate through a comparison with different modes of Bluetooth Low Energy (BLE) a decrease of the power consumption in 1 to 2 orders of magnitude for different scenarios at equal quality of service. Moreover, we propose some security optimizations, such as shorter over-the-air counters, to reduce the packet overhead without decreasing the security level. Finally, we discuss other features aside of the energy needs, such as latency, reliability or topology, brought again against BLE.

Electromagnetically induced transparency at optical nanofiber–cesium vapor interface**Project supported by the National Key Research and Development Program of China (Grant No. 2017YFA0304203), the National Natural Science Foundation of China (Grant Nos. 61675120, 11434007, and 61875110), Project of the National Natural Science Foundation of China for Excellent Research Team (Grant No. 61121064), the Shanxi “1331 Project” Key Subjects Construction, PCSIRT, China

Optical nanofiber (ONF) is a special tool for effectively controlling coupling of light and atoms. In this paper, we study the ladder-type electromagnetically induced transparent (EIT) under ultralow power level in a warm cesium vapor by observing the transmission of ONF that couples the 6S → 6P Cs atoms in the presence of a 6P → 8S control beam through the same fiber. The linewidth and transmission of the EIT signal are investigated at different intensities of the control laser. In addition, we theoretically study the nonlinear interaction at the ONF interface using the multi-level density matrix equations, and obtain good agreements between theory and experiments. The results may have great significance for further study of optical nonlinear effect at low power level.

Evaluation of Undesired Radio Waves Below −170 dBm/Hz From Semiconductor Switching Devices for Impact on Wireless Communications

The spread of undesired radio waves and the development of semiconductor switching devices causes serious noise interference in wireless communication systems. We introduce a system to evaluate the noise interference caused by such switching devices with high resolution. Our evaluation system consists of two parts: a high-resolution noise measurement system and an evaluation of wireless communication performance by system level simulations. The integrated power of undesired radio waves is measured within a 5-MHz bandwidth and can be detected even at an ultra-low power level of -177 dBm/Hz. The lower detection limit of the undesired radio waves is enough to evaluate the impact on wireless communication performance. We evaluated undesired radio waves from a wireless power transfer (WPT) system for charging electric vehicles. In our simulation, at the 840-MHz band, we observed an undesired radio waves level of -143 dBm/Hz near the WPT system that degraded the long-term evolution (LTE) sensitivity to -74 dBm/5 MHz.

Fabrication of package embedded spiral inductors with two magnetic layers for flexible SIP point of load converters in Internet of Everything devices

Inductive DC-DC converters are key elements in power delivery units for the development of Internet of Everything (IoE) architectures made of interconnected networks of smart devices, self-powered from different energy sources. The ultra-low power levels involved in IoE devices in addition to cost reduction of final products requires the development of new technologies for the miniaturization of all the active and passive components. In this paper, a low temperature, cheap and simple two-steps fabrication process of embedded planar inductors with two magnetic layers on a very thin, flexible and lightweight FR4 organic substrate is demonstrated for flexible System in package (SIP) based point of load DC-DC converters in IoE devices. The process uses standard printed wiring board (PWB) copper etching to define the square geometry of the planar inductors and trenches underneath the inductor copper traces. Very thick top and bottom magnetic layers are deposited using stencil printing of an FR4 compatible epoxy-NiZn ferrite composite magnetic material on top of the copper traces and into the trenches. At 30MHz, the permittivity is 3.4 and 6.23 while the dielectric loss tangent is 0.014 and 0.009 for the epoxy and composite magnetic material respectively. The composite material has a permeability of 8.46, a loss tangent value of 0.1 at a frequency of 30MHz and saturates around 0.13 Tesla. The DC resistance varies from 136mΩ to 386mΩ while at 30MHz the AC resistance varies from 1.9Ω to 10.1Ω for an inductance value from 180nH to 715nH, corresponding to an inductance density between 5.69nH/mm2 and 12.47nH/mm2 and a quality factor between 13 and 17. Flexibility and its effect on the electrical parameters of the fabricated inductors is demonstrated through bending tests. A variation of <3% for the DC resistance is obtained for 5mm bend radius. At 30MHz and for a bend radius (both upward and downward) from 3.7mm to 5mm, the flat state (unbent) AC resistance and inductance values (1.9Ω to 10.1Ω for 180nH to 715nH) decrease by 6.5% to 18% and by 2% to 4.4% respectively which increase the self-resonant frequency by 3% to 3.4% and the quality factor by 2.2% to 20%. The characterized inductors are modeled in ANSYS HFSS electromagnetic simulator and simulation results show a good correspondence with the measured inductances and quality factors, which allows a reliable prediction of the inductors behavior for DC-DC converter design and implementation for IoE devices.

Colloidal nanocrystals: Virtues of defects.

Defects in mercury telluride quantum dots can be exploited to achieve amplified spontaneous emission under continuous-wave optical pumping at ultralow power levels.

A Long-Distance RF-Powered Sensor Node with Adaptive Power Management for IoT Applications

We present a self-sustained battery-less multi-sensor platform with RF harvesting capability down to −17 dBm and implementing a standard DASH7 wireless communication interface. The node operates at distances up to 17 m from a 2 W UHF carrier. RF power transfer allows operation when common energy scavenging sources (e.g., sun, heat, etc.) are not available, while the DASH7 communication protocol makes it fully compatible with a standard IoT infrastructure. An optimized energy-harvesting module has been designed, including a rectifying antenna (rectenna) and an integrated nano-power DC/DC converter performing maximum-power-point-tracking (MPPT). A nonlinear/electromagnetic co-design procedure is adopted to design the rectenna, which is optimized to operate at ultra-low power levels. An ultra-low power microcontroller controls on-board sensors and wireless protocol, to adapt the power consumption to the available detected power by changing wake-up policies. As a result, adaptive behavior can be observed in the designed platform, to the extent that the transmission data rate is dynamically determined by RF power. Among the novel features of the system, we highlight the use of nano-power energy harvesting, the implementation of specific hardware/software wake-up policies, optimized algorithms for best sampling rate implementation, and adaptive behavior by the node based on the power received.

Ultra low-voltage ultra low-power memristor based band-pass filter design and its application to EEG signal processing

Memristor has been claimed as the passive fourth fundamental circuit element in 1971. About four decades later, a physical realization which presents memristor behavior has resulted in significant interest on memristor and it is continuing to increase at a growing rate. Memristor can provide new possibilities in analog circuit design thanks to its properties which cannot be mimicked by older passive circuit elements. Since no practically available memristor exist on the market yet, obtaining of a practical implementation which behaves like a memristor is important from the point of view real-world circuit design. In this paper, an ultra low-voltage ultra low-power DTMOS-based memristor design is presented. Ultra low-voltage, ultra low-power operational amplifier and ultra low-voltage, ultra low-power multiplier are also designed to use in the implementation. Memristor design is composed of these two type active blocks using CMOS 0.18 µm process technology with symmetric ?0.25 V supply voltages. Our memristor is used in a second order Sallen---Key band-pass filter topology. Designed memristor-based Sallen---Key band-pass filter is then used for real electroencephalogram data processing. The simulation results show that the design of adjustable memristor memristance/memductance provides tunable filter parameters and without any significant distortion with appropriate parameter set even at ultra-low power levels and at very-low frequencies.

Optically controlled polarizer using a ladder transition for high speed Stokesmetric Imaging and Quantum Zeno Effect based optical logic

We demonstrate an optically controlled polarizer at ~1323 nm using a ladder transition in a Rb vapor cell. The lower leg of the 5S(1/2),F = 1->5P(1/2),F = 1,2->6S(1/2),F = 1,2 transitions is excited by a Ti:Sapphire laser locked to a saturated absorption signal, representing the control beam. A tunable fiber laser at ~1323 nm is used to excite the upper leg of the transitions, representing the signal beam. When the control beam is linearly polarized, it produces an excitation of the intermediate level with a particular orientation of the angular momentum. Under ideal conditions, this orientation is transparent to the signal beam if it has the same polarization as the control beam and is absorbed when it is polarized orthogonally. We also present numerical simulations of the system using a comprehensive model which incorporates all the relevant Zeeman sub-levels in the system, and identify means to improve the performance of the polarizer. A novel algorithm to compute the evolution of large scale quantum system enabled us to perform this computation, which may have been considered too cumbersome to carry out previously. We describe how such a polarizer may serve as a key component for high-speed Stokesmetric imaging. We also show how such a polarizer, combined with an optically controlled waveplate, recently demonstrated by us, can be used to realize a high speed optical logic gate by making use of the Quantum Zeno Effect. Finally, we describe how such a logic gate can be realized at an ultra-low power level using a tapered nanofiber embedded in a vapor cell.

Ultralow Power, Fully Autonomous Boost Rectifier for Electromagnetic Energy Harvesters

In this paper, a complete power conditioning system for a vibration energy harvester is presented that operates at ultralow power levels. The power conditioning system, implemented with discrete components, is self-starting and fully autonomous, and based upon a full-wave boost rectifier topology. The design utilizes the stray inductance of the harvester's coil, eliminating the need for separate inductors, and employs open-loop control that reduces the quiescent power overhead to just 21 μW, while still extracting 84% of the maximum available power from the harvester. The design of the subsystems, including self-start circuitry, is described in detail, and it is shown that careful active device selection is required to minimize losses. It is experimentally demonstrated that the power converter achieves conversion efficiencies of up to 76% at submilliwatt power levels, including quiescent losses. The overall system efficiency peaks at 65% at 0.9 mW, while still achieving 51% at 200 μW. The ability of this system to operate efficiently at ultralow average power levels opens up new possibilities to further miniaturize vibration harvesters and deploy them into environments with lower vibration levels than is currently possible.

Power management of autonomous wireless sensor node for structure health monitoring

This paper presents the design concepts of wireless sensor network system constructed with autonomous sensing nodes, which operates at extremely low power levels. At first, conventional, wired civil structure health-monitoring system is reviewed. Then, the monitoring methodology is discussed focusing quantitative measurement accuracy. Issues of node synchronized sampling, multi-layer cluster, node distance and integrated sensor node module are discussed. Also, radio transceiver protocol candidates are reviewed from the point of connection to the Internet gateway. Sensor node consists of microprocessor, sensing analog front end, and radio transceiver. Last two factors are critical for power consumption. Therefore, low duty cycle measurement is essential, in order to accomplish the ultra low power level, which is equivalent to energy harvesting source, such as piezoelectric and solar cells, sensor node power management device circuit design is demonstrated for the high-spec measurement.

Ultra-low power, Zeno effect based optical modulation in a degenerate V-system with a tapered nano fiber in atomic vapor

We demonstrate an ultra-low light level optical modulator using a tapered nano fiber embedded in a hot rubidium vapor. The control and signal beams are co-propagating but orthogonally polarized, leading to a degenerate V-system involving coherent superpositions of Zeeman sublevels. The modulation is due primarily to the quantum Zeno effect for the signal beam induced by the control beam. For a control power of 40 nW and a signal power of 100 pW, we observe near 100% modulation. The ultra-low power level needed for the modulation is due to a combination of the Zeno effect and the extreme field localization in the evanescent field around the taper.

Integrated quantum optical networks based on quantum dots and photonic crystals

Single solid-state optical emitters have quantum mechanical properties that make them suitable for applications in information processing and sensing. Most of these quantum technologies rely on the capability to integrate the emitters in reliable solid-state optical networks. In this paper, we present integrated devices based on GaAs photonic crystals and InAs self-assembled quantum dots. These quantum networks are well suited to future optoelectronic devices operating at ultralow power levels, single-photon logic devices and quantum information processing.

Slow light on a chip via atomic quantum state control

Researchers exploit atomic quantum state control in a fully integrated photonic atomic spectroscopy chip to reduce the group velocity of light by a factor of 1,200 — the lowest group velocity ever reported for a solid-state material. The findings will enable the creation of on-chip nonlinear optical devices with enhanced quantum coherence operating at ultralow power levels.

Ultra-low Power Frequency Conversion in Two-photon-absorption Free Micro Ring Resonator

All-optical integrated circuits bring the promise to vastly increase the bandwidth, improve the flexibility as well as reduce the cost of future communication networks. All optical integrated components, like switches and wavelength converters, must meet fundamental requirements such as low optical losses, strong nonlinear response and ease of fabrication. To date, however, research on these devices has been based either on semiconductors, such as silicon and GaAs, or highly nonlinear glasses, such as chalcogenides which, although exhibit a Kerr nonlinearity (n2) of 100x-400x silica glass, also present limitations such as remarkable linear and nonlinear losses and, for certain applications, a not developed fabrication techniques. Specifically, the possibility to rely upon a mature technology recently has proved itself to be a powerful solution to fabricate micrometric resonant structures which are able to locally enhance the desired nonlinearities. In this work we present the first example of nonlinear optics in silica glass waveguides using continuous wave (CW) light. We achieve wavelength conversion via four wave mixing (FWM) at ultra-low (approximate to 5 mW CW) power levels in C-MOS compatible micro-ring resonator.

RF energy scavenging system utilising switched capacitor DC-DC converter

An RF energy scavenging circuit implementing a power matched Villard voltage doubler followed by a switched capacitor DC-DC converter for scavenging ultra-low RF power levels (&lt;−20 dBm) is presented. Measurement results for the circuit, fabricated in a 130 nm CMOS process, show that 1V can be generated across a 5 MΩ load from as little as −25.5 dBm of input RF energy at 2.2 GHz. This represents a 9.5 dB improvement, over the measured sensitivity of our RF energy scavenging circuit without the use of a switched capacitor DC-DC converter stage.

Ultra-low power parametric frequency conversion in a silicon microring resonator

We demonstrate parametric wavelength conversion via four-wave mixing using ultra-low peak pump powers of a few milliwatts in a micrometer-scale silicon device. The response time of our device is 100 ps allowing for implementation in high-bandwidth optical communications. At these ultra-low power levels and microscale sizes, it should be possible to realize hundreds of these devices operating simultaneously on a single chip.