Threshold Power Consumption Research Articles

Intensity noise and modulation dynamics of an epitaxial mid-infrared interband cascade laser on silicon

Interband cascade lasers typically have significantly lower threshold current and power consumption than quantum cascade lasers. They can also have advantages regarding costs and compactness with the photonic integration onto silicon substrates by epitaxial growth. This research introduces a novel examination of the relative intensity noise and the modulation dynamics of a silicon-based Fabry–Perot interband cascade laser emitting at 3.5 μm. The investigation delves into crucial parameters, such as relaxation oscillation frequency, differential gain, gain compression, and K-factor. The resonance patterns identified in relative intensity noise curves can provide essential insights for the thorough characterization of high-defect mid-infrared semiconductor structures intended for high-speed applications. Moreover, this study demonstrates the feasibility of reaching 10 Gbit/s free-space transmission using a silicon-based interband cascade laser in conjunction with an interband cascade infrared photodetector.

Thermal design engineering for improving the variation of memristor threshold

Memristor-based neural components and circuits are the key to building efficient brain-like computing systems, but their development is restricted by their unstable electrical properties of memristive artificial neurons. In this work, three thermal design schemes to regulate the electrical characteristics of threshold switching memristor were proposed, such as the thermal conductivity of the device electrode, the different substrate and local electrode. First, it was found that the lower the thermal conductivity of electrode, the lower the threshold variation of the device. Secondly, the smaller the thermal conductivity of the memristor substrate, the more stable the threshold. Thirdly, decreasing the electrode radius of the memristor from the original 50 nm to 10 nm will decrease the variation of threshold voltage by 27%. Additionally, due to the reduction of thermal dissipation, the proposed thermal design engineering also can lower the threshold voltage and power consumption. Those results on improving the threshold variation of memristor provide a stepping stone for the development of artificial neurons and neuromorphic computing systems.

Scaling Laws for Perovskite Nanolasers With Photonic and Hybrid Plasmonic Modes

AbstractSurface plasmons exhibit an extraordinary capability to reduce the structural size and improve light−matter interaction. However, for small‐sized plasmonic cavities, the optical diffraction limit makes the near‐field difficult to observe, complicating the analysis of exact lasing characteristics. In this study, a 4f measurement system is used to extract the mode parity from the interference pattern and reconstruct the near‐field of the hybrid plasmonic perovskite nanolasers. In conjunction with other measurements, a series of rigorous methods for determining the exact resonance mode and obtaining the precise lasing characteristics of perovskite nanolasers are described. By applying these methods, the scaling laws for wire‐type hybrid plasmonic perovskite lasers are successfully determined and an appropriate size is selected for achieving outstanding lasing performance with low threshold power consumption and a high group index. These methods can be applied to nanowire plasmon‐based lasers to advance the development of plasmonic devices.

Ultralow power consumption of a quantum cascade laser operating in continuous-wave mode at room temperature.

We report an ultralow power consumption of a quantum cascade laser (QCL) emitting at λ ∼ 4.6 µm operating in continuous-wave mode at room temperature. The ultralow power consumption is achieved by using a high gain active region and shortening the device size. For the device with a 0.5-mm-long cavity and 3.2-µm-wide ridge, the threshold power consumption is as low as 0.26 W with an optical output power of 12.6 mW at 10 °C in continuous-wave mode, which represents the world's most advanced level. Furthermore, the threshold power consumption varies linearly with the operating temperature, where the linear change rate of 2.3 mW/K from 10 to 40 °C is low. As a result, the devices also show low threshold power consumption values of 0.33 W even at 40 °C in continuous-wave mode with an optical output power of 6.1 mW. In addition, the lasers can maintain a single-mode operation due to the short cavity length even if no distributed feedback grating is applied.

Low power‐consumption mid‐infrared distributed feedback quantum cascade laser for gas‐sensing application

A low power-consumption distributed feedback quantum cascade laser (DFB-QCL) is developed for gas-sensing in 7 μm wavelength region. The threshold power-consumption was as low as 0.93 W with the sufficient output power of 20 mW at 20°C under continuous-wave condition. In addition, it maintained a single-mode operation between −40 and 50°C without a mode-hopping, leading to a total wavelength shift of 66 nm. This DFB-QCL would be suitable for gas-sensing application.

Interview

Dr Jun-ichi Hashimoto is a researcher at the Transmission Devices Laboratory, Sumitomo Electric Industries Ltd., Japan. Here he tells us about his research and new Electronics Letters paper, ‘Low power-consumption mid-infrared distributed feedback quantum cascade laser for gas-sensing application’ page 549. Dr Jun-ichi Hashimoto Since the late 1980s, our laboratory has been engaged in developing semiconductor devices in the optical communication field of the near infrared region (1.3–1.55 µm). We have manufactured various kinds of commercial products including laser diodes, detectors, and modulators. Recently we started developing optical devices in the mid-infrared (MIR) region. We consider a quantum cascade laser (QCL) to be a future key light source in the MIR region, and we are now focusing our attention on its development. Our developing technologies cover all fields including device design, epitaxial growth, fabrication process, and evaluation system. A QCL is a new semiconductor laser enabling an oscillation in the MIR region. It has a structure similar to a conventional pn-junction laser diode, but the core region (emission region) structure is totally different. The core region of QCL consists of several tens of unit structures stacked together, and each unit structure has an active region serving as a light-emitting region, and an injector region to transport carriers (electrons) into the next active region. Both are made of super-lattice structures. In the core region, the radiative transition occurs between the sub-bands of the conduction band of the active region, which makes it possible to oscillate in the MIR wavelength region. We developed a low power consumption distributed feedback quantum cascade laser (DFB-QCL) applicable to a light source of a portable gas sensor. To reduce its power consumption significantly, we introduced our original high-gain vertical-transition core structure, a buried-hetero waveguiding structure with a high thermal conductivity and a low optical loss, a buried-type grating favourable for a large coupling-coefficient, and a high-reflective Au-coating on the rear facet. As a result, we succeeded in realising a DFB-QCL with a low threshold power-consumption (0.93W) at 20°C. In addition, this QCL demonstrated a sufficient continuous wave (CW) output power (≈20mW), a good singlemode property (single mode suppression ratio>25 dB), and a single-lobed far-field patterns (FFPs) at 20°C. We think this DFB-QCL can be used as a light source of a portable gas sensor. The QCL we developed in this study has low power consumption (∼1W) as mentioned earlier, so it is especially promising as a light source for portable QCL gas sensors. These QCL gas sensors have compact, fast (<1s) and high-sensitive (ppb∼ppt) characteristics which could not be satisfied simultaneously with the conventional MIR gas sensors. We expect these to open up new markets in various fields in the future, such as process and/or emission gas control in factories, environmental gas sensing, breath analysis for medical diagnosis and military applications. Developing our original high-gain vertical-transition core structure proved most challenging. In order to achieve high net optical gain in the core structure design, it is important to increase the carrier transition probability between the sub-bands, as well as reducing the optical loss due to the non-radiative recombination caused predominantly by longitudinal optical phonon (LO phonon) scattering. To address this issue, our structure has a high optical gain due to the vertical-transition of carriers between the sub-bands in the conduction band of the active region. At the same time, the LO-phonon scattering is supressed effectively by optimising the coupled quantum well structure of the active region. We predict that a further power consumption reduction of QCL, such as below 0.5 W, is needed to realise cheaper and smaller mass-marketable gas sensors for consumer use. Therefore, finding a way to reduce the power consumption more drastically seems a first priority. Expanding the wavelength tuning range of QCL is another important issue to improve the detection accuracy of the gas sensor and to increase the kinds of target gas which can be detected simultaneously with one gas sensor. We would like to study the integration of QCL and the related devices striving towards better performance and a novel function such as a wider wavelength tuning range, a higher output power, a narrower beam shape, a light emission in vertical direction, and so on. We are also interested in other wavelength regions having promising markets like MIR region, and Terahertz region is one of the candidates.

Low Power Consumption Distributed-Feedback Quantum Cascade Lasers Operating in Continuous-Wave Mode above 90°C at λ ∼ 7.2 μm**Supported by the National Basic Research Program of China under Grant No 2013CB632801, the National Key Research and Development Program under Grant No 2016YFB0402303, the National Natural Science Foundation of China under Grant Nos 61435014, 61627822, 61574136 and 61306058, the Key Projects of

We report on the design and fabrication of λ ∼ 7.2 μm distributed feedback quantum cascade lasers for very high temperature cw operation and low electrical power consumption. The cw operation is reported above 90°C. For a 2-mm-long and 10-μm-wide laser coated with high-reflectivity on the rear facet, more than 170 mW of output power is obtained at 20°C with a threshold power consumption of 2.4 W, corresponding to 30mW with a threshold power consumption of 3.9 W at 90°C. Robust single-mode emission with a side-mode suppression ratio above 25 dB is continuously tunable by the heat sink temperature or injection current.

Low-dissipation 7.4-µm single-mode quantum cascade lasers without epitaxial regrowth.

We report continuous-wave operation of single-mode quantum cascade (QC) lasers emitting near 7.4 µm with threshold power consumption below 1 W at temperatures up to 40 °C. The lasers were fabricated with narrow, plasma-etched waveguides and distributed-feedback sidewall gratings clad with sputtered aluminum nitride. In contrast to conventional buried-heterostructure (BH) devices with epitaxial sidewall cladding and in-plane gratings, the devices described here were fabricated without any epitaxial regrowth processes, yet they exhibit power consumption comparable to the lowest-dissipation BH QC lasers reported to date. These low-dissipation devices are designed primarily as light sources for infrared spectroscopy instruments with limited volume, mass, and power budgets.

Conventional and sub-threshold operation regimes of CMOS digital circuits

In this paper a comparison of static and dynamic parameters of CMOS logic circuits operated in standard and sub-threshold regimes is presented. Analytic models of logic threshold voltage, logic delay and power consumption are derived for the sub-threshold operation regime. Certain analytic models analogies between these two regimes are shown. Threshold voltages of inverter, NAND and NOR logic circuits depend on the same parameters in both regimes. These circuits functional differences appear as a consequence of the drain current analytic model differences in the strong and weak inversion regimes. In both of these regimes, the inverter and transmission gate temperature characteristics are analyzed. Analytic models are verified by PSPICE simulation using the BSIM3 transistor models of the 0.18 μm CMOS technology process.

Development of Low Power Consumption DFB Quantum Cascade Lasers

We report on the development of $\lambda \sim 4.97~\mu \text{m}$ continuous-wave operation of substrate emitting distributed feedback quantum cascade lasers. A low threshold power consumption of 1.27 W is obtained at 20 °C, along with an ultralow threshold current density of 0.81 kA/cm2 by depositing the high reflection coatings on both facets. Single-lobed far-field radiation pattern with a low divergence angle of about 0.24° $\times $ 20.34° is obtained. Reliable single-mode emission with a side-mode suppression ratio about 25 dB is observed among the working temperature range of 10 °C–30 °C.

Regrowth-free single-mode quantum cascade lasers with power consumption below 1 W

We report on single-mode distributed-feedback quantum cascade lasers emitting at 4.8 μm with continuous-wave threshold power consumption as low as 0.76 W at 20 °C and 0.98 W at 50 °C. Following growth of the laser active region and semiconductor cladding layers by a single molecular beam epitaxy process, devices with 4-μm-wide ridges and vertical sidewall gratings were fabricated using plasma etching and standard dielectric and metal deposition processes. In terms of mode stability, output power, and efficiency, we show that lasers with 1-mm cavity length and high-reflectivity back-facet coatings can match the performance of buried heterostructure devices, but with the advantage of requiring only a single epitaxial growth step.

A low power and high linearity UWB low noise amplifier (LNA) for 3.1–10.6 GHz wireless applications in 0.13 μm CMOS process

In this paper, a low power ultra-wideband (UWB) CMOS LNA was designed exploiting source inductive degeneration technique operating in the frequency range of 3.1–10.6GHz. In order to achieve low noise figure and high linearity simultaneously, a modified three-stage UWB LNA with inter-stage inductors was proposed. Forward Body-Biased (FBB) technique was used to reduce threshold voltage and power consumption at the first and third stages. The second stage is a push–pull topology exploiting the complementary characteristics of NMOS and PMOS transistors to enhance the linearity performance. The proposed LNA was simulated in standard 0.13μm CMOS process. A gain of 19.5±1.5dB within the entire band was exhibited. The simulated noise figure (NF) was 1–3.9dB within the bandwidth. A maximum simulated third-order input intercept point (IIP3) of 4.56dBm while consuming 4.1mW from a 0.6 power supply was achieved. The simulated input return loss (S11) was less than −5dB from 4.9 to 12.1GHz. The output return loss (S22) was below −10.6dB and S12 was better than −70.6dB.

Room Temperature CW Operation of Mid-IR Distributed Feedback Quantum Cascade Lasers for $\hbox{CO}_{2}, \hbox{N}_{2}$O, and NO Gas Sensing

We present the design and the performance of midinfrared distributed feedback (DFB) quantum cascade lasers (QCLs) made of strain balanced Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> As/Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-y</sub> As material on InP substrates for sensing CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O, and NO in the middle wavelength range of mid-IR from 4 to 6 μm. We present the performances of our DFB QCLs at three different aspects: high power, low threshold power consumption, and wide wavelength coverage. We demonstrated a continuous wave (CW) DFB QCL with an output power of 220mW at 20°C, a CW DFB QCL with low threshold voltage of 8V and low-divergent far-field angles of 27.5° × 32.9° by reducing the number of quantum cascaded stages, a CW DFB QCL with a low threshold power consumption of 0.7W by reducing doping density in the active core, and DFB QCLs wide wavelength coverage of 325 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , 16.9% of center wavelength at 5.2 μm, within one wafer by changing the grating period. 12 DFB QCL chips have being aged for 3000 h under 25°C and a constant quasi-CW current of 0.37 A. No decrease in power was observed.

Optimizing facet coating of quantum cascade lasers for low power consumption

Typical high power consumption (∼10 W) of mid-infrared quantum cascade lasers (QCLs) has been a serious limitation for applications in battery powered systems. A partial high-reflection (PHR) coating technique is introduced for power downscaling with shorter cavity lengths. The PHR coating consists of a double layer dielectric of SiO2 and Ge. With this technique, a 4.6 μm QCL with an ultra low threshold power consumption of less than a watt (0.83 W) is demonstrated in room temperature continuous wave operation. At 25°C, the maximum output power and wall plug efficiency are 192 mW and 8.6%, respectively.

A Study of the Liquid Crystal Alignment Mechanism of Bond-Breaking Via Ion-Beam Irradiation of an Amorphous Aluminum-Oxide Surface

In this paper, we study the Ion-beam (IB) irradiated amorphous (a)-aluminum oxide () inorganic layer deposited by RF magnetron sputtering as an liquid crystal (LC) alignment layer. Uniformly vertical-aligned (VA)-LC on a- surface resulted from IB irradiation energy above 1800 eV. We assumed that LC molecular orientation depends on the intensity of Al 2p, O 1s peaks, which were confirmed through X-ray photoelectron spectroscopy (XPS) measurements. XPS showed that IB irradiation changed the chemical structure, breaking Al-O bonds by altering Al-O and O-Al bonding intensity. Also, electro-optical characteristics of vertical-aligned-LC displays (VA-LCDs) on the alignment layers were measured, which showed reduced threshold voltage and power consumption, as compared with IB irradiated and rubbed polyimide (PI) layers.

Low-threshold short-cavity diode laser for a miniature atomic clock

Short-cavity diode lasers (SCDLs) emitting at the 894-nm D1 line of caesium are developed. Low threshold currents and power consumption will make it possible to use these lasers in chip-size atomic clocks (CSACs) and magnetometers. The SCDL parameters are comparable with the parameters of surface-emitting lasers.

Design Methodology of Body-Biasing Scheme for Low Power System LSI With Multi- $V_{\rm th}$ Transistors

We proposed a multi-Vth transistor design for a body-biasing scheme to control threshold voltage Vth variation and power consumption for the 65-nm node and beyond. One of the biggest barriers in applying the body biasing to multi-Vth transistors that have a different body-biasing sensitivity was solved by using a Hf-based gate dielectric work-function modulation combined with a careful channel design. The body-biasing sensitivities for multi-Vth transistors were successfully equalized, and the sensitivity is independent of the original Vth. By using the body biasing with the optimal transistor design, die-to-die Vth variation has been efficiently suppressed even for dies with multi-Vth transistors. As a result, both 50% total Vth variation reduction and 1/50 static random access memory standby current have been achieved. This design scheme can guarantee excellent performance for future low power applications because of its simplicity and its bulk-design compatibility.

Low-threshold current low-voltage vertical-cavity surface-emitting lasers with low-Al-content p-type mirrors grown by MOCVD

InGaAs quantum-well vertical-cavity surface-emitting lasers with low-Al-content p-type mirrors grown by metalorganic chemical vapor deposition (MOCVD) have have been characterized. Series resistance in p-type Al/sub x/Ga/sub 1-x/As/GaAs mirrors decreases drastically as the Al content in Al/sub x/Ga/sub 1-x/As decreases from AlAs. Air-post devices with a p-type Al/sub 0.06/Ga/sub 0.4/As/GaAs top mirror exhibit a room temperature CW threshold current of 1.8 mA at an operating voltage of 2.0 V (with a threshold power consumption at 3.6 mW). >

Effects of some different pulse parameters on bladder inhibition and urethral closure during intravaginal electrical stimulation: an experimental study in the cat.

Intravaginal electrical stimulation (IVS) was used in the cat to induce bladder inhibition and urethral closure. The purpose of the study was to compare the efficacy of alternating constant-voltage pulses of different durations (0·1, 0·2, 0·5 and 5 ms) with that of chopped alternating pulses, each consisting of a train of five 0·5 ms pulses with 0·5 ms pauses between. The voltage requirement for an equal biological effect was lowest for the 5 ms alternating pulse, whereas the pulse power dissipation was lowest for the 0·1 ms pulse, about 10 per cent of that for the 5 ms pulse. If both voltage requirement and power dissipation are taken into account, the 0·5 ms pulse was considered the most appropriate compromise. The chopped pulse was the least efficient stimulus, since the threshold voltage was comparable to that of the 0·5 ms duration alternating pulse, implying a five times higher power dissipation. For bladder inhibition, the optimal stimulation frequency for alternating pulses was 10 Hz, both in terms of threshold voltage and power consumption. For urethral closure the voltage requirement was lowest at 50 Hz but 20 Hz was preferable in terms of power dissipation for an equal, although submaximal, effect.