Showing papers by "Yuan Gao published in 2014"

Stimulated emission and lasing from CdSe/CdS/ZnS core-multi-shell quantum dots by simultaneous three-photon absorption.

Abstract: Three-photon pumped stimulated emission and coherent random lasing from colloidal CdSe/CdS/ZnS core-multishell quantum dots are achieved for the first time. These results can offer new possibilities in biology and photonics, as well as at their intersection of biophotonics.

Highly Flexible, Electrically Driven, Top-Emitting, Quantum Dot Light-Emitting Stickers

Abstract: Flexible information displays are key elements in future optoelectronic devices. Quantum dot light-emitting diodes (QLEDs) with advantages in color quality, stability, and cost-effectiveness are emerging as a candidate for single-material, full color light sources. Despite the recent advances in QLED technology, making high-performance flexible QLEDs still remains a big challenge due to limited choices of proper materials and device architectures as well as poor mechanical stability. Here, we show highly efficient, large-area QLED tapes emitting in red, green, and blue (RGB) colors with top-emitting design and polyimide tapes as flexible substrates. The brightness and quantum efficiency are 20 000 cd/m2 and 4.03%, respectively, the highest values reported for flexible QLEDs. Besides the excellent electroluminescence performance, these QLED films are highly flexible and mechanically robust to use as electrically driven light-emitting stickers by placing on or removing from any curved surface, facilitating ...

Solution processed tungsten oxide interfacial layer for efficient hole-injection in quantum dot light-emitting diodes

Abstract: A highly efficient and stable QLED using an inorganic WO3 nanoparticle film as a hole injection layer is demonstrated.The resulting WO3 nanoparticle-based QLEDs also exhibit superior performance compared to that of the present PEDOT:PSS-based QLEDs. The results indicate that WO3 nanoparticles are promising solution-processed buffer layer materials and serve as a strong candidate for QLED technology towards the practical applications in the next-generation lighting and displays.

Quantum dots on vertically aligned gold nanorod monolayer: plasmon enhanced fluorescence

Abstract: CTAB-coated Au nanorods were directly self-assembled into a vertically aligned monolayer with highly uniform hot spots through a simple but robust approach. By coupling with CdSe/ZnS quantum dots, a maximum enhancement of 10.4 is achieved due to: increased excitation transition rate, radiative rate, and coupling efficiency of emission to the far field.

30.7 A 60Mb/s wideband BCC transceiver with 150pJ/b RX and 31pJ/b TX for emerging wearable applications

Abstract: Wearable technology is opening the door to future wellness and mobile experience Following the first generation wearable devices in the form of headsets, shoes and fitness monitors, second generation devices such as smart glasses and watches are making an entrance to the market with a great potential to eventually replace the current mobile device platform eventually (Fig 3071) Wearable devices can be carried by users in a most natural way and provide all-round connectivity 24-7 without the hassle of stopping all other activities, which enables a totally different mobile experience For wearable devices, body channel communication (BCC) is an excellent alternative of conventional wireless communication through the air, to obviate the need of high-power transceivers and bulky antennas However, present BCC transceivers [1]-[5] that mainly target biomedical and sensing applications offer rather limited data rates up to 10Mb/s, which is insufficient in transferring multimedia data for emerging wearable smart devices and content-rich information for high-end medical devices (eg multi-channel neural recording microsystems) In this paper, a highly energy-efficient and robust wideband BCC transceiver is presented, which achieves a maximum data rate of 60Mb/s by employing 1) a high input impedance and an equalizer at the RX front-end, 2) transient-detection RX architecture using differentiator-integrator combination coupled with injection-locking-based clock recovery, and 3) 3-level direct digital Walsh-coded signaling at the TX

Colloidal Quantum Dot Light-Emitting Diodes Employing Phosphorescent Small Organic Molecules as Efficient Exciton Harvesters

Abstract: Nonradiative energy transfer (NRET) is an alternative excitation mechanism in colloidal quantum dot (QD) based electroluminescent devices (QLEDs). Here, we develop hybrid highly spectrally pure QLEDs that facilitate energy transfer pumping via NRET from a phosphorescent small organic molecule-codoped charge transport layer to the adjacent QDs. A partially codoped exciton funnelling electron transport layer is proposed and optimized for enhanced QLED performance while exhibiting very high color purity of 99%. These energy transfer pumped hybrid QLEDs demonstrate a 6-fold enhancement factor in the external quantum efficiency over the conventional QLED structure, in which energy transfer pumping is intrinsically weak.

Nanosecond colloidal quantum dot lasers for sensing

Abstract: Low-threshold, gain switched colloidal quantum dot (CQD) distributed-feedback lasers operating in the nanosecond regime are reported and proposed for sensing applications for the first time to the authors’ knowledge. The lasers are based on a mechanically-flexible polymeric, second order grating structure overcoated with a thin-film of CQD/PMMA composite. The threshold fluence of the resulting lasers is as low as 0.5 mJ/cm2 for a 610 nm emission and the typical linewidth is below 0.3 nm. The emission wavelength of the lasers can be set at the design stage and laser operation between 605 nm and 616 nm, while using the exact same CQD gain material, is shown. In addition, the potential of such CQD lasers for refractive index sensing in solution is demonstrated by immersion in water.

A Monolithically Integrated Pressure/Oxygen/Temperature Sensing SoC for Multimodality Intracranial Neuromonitoring

Abstract: A fully integrated SoC for multimodality intracranial neuromonitoring is presented in this paper Three sensors including a capacitive MEMS pressure sensor, an electrochemical oxygen sensor and a solid-state temperature sensor are integrated together in a single chip with their respective interface circuits Chopper stabilization and dynamic element matching techniques are applied in sensor interface circuits to reduce circuit noise and offset On-chip calibration is implemented for each sensor to compensate process variations Measured sensitivity of the pressure, oxygen, and temperature sensors are 186 aF/mmHg, 194 pA/mmHg, and 2 mV/°C, respectively Implemented in 018 m CMOS, the SoC occupies an area of 14 mm × 4 mm and consumes 166 μW DC power A prototype catheter for intracranial pressure (ICP) monitoring has been implemented and the performance has been verified with ex vivo experiment

Efficient Energy Transfer under Two‐Photon Excitation in a 3D, Supramolecular, Zn(II)‐Coordinated, Self‐Assembled Organic Network

Abstract: Multiphoton excited fl uorescence of organic molecules is promising in the applications of effi cient nonlinear optical devices and bioimaging. However, they usually have disadvantages of poor photostability and serious fl uorescence quenching in aqueous media or solid state, which seriously limit their related applications. In this work, for the fi rst time, the two-photon excited Forster resonance energy transfer (FRET) process is used to enhance the solid-state fl uorescence of the supramolecular centre (acceptor) in an artifi cial 3D metal‐organic complex (MLC), in which a 3D Zn (II)-coordinated tetrahedral core is utilized as the donor. More interestingly, the two-photon light harvesting system, which can be pumped with an optical intensity as low as 1 MW/cm 2 , exhibits an ultrafast energy transfer rate ( ∼ 6.9 ◊ 10 8 s 1 ) and ultrahigh photostability. The underlying physical mechanisms are revealed through comprehensive steady-state and time-resolved spectroscopic analysis. This work demonstrates that the 3D MLC can be directly used in two-photon bioimaging and also sheds light on developing other multiphoton harvesting systems, such as metal‐organic frameworks.

A 3.54 nJ/bit-RX, 0.671 nJ/bit-TX Burst Mode Super-Regenerative UWB Transceiver in 0.18- $\mu{\rm m}$ CMOS

Abstract: Non-coherent ultra-wideband (UWB) transceiver employing energy detector suffers from degradation in output SNR due to the squarer. A burst mode super-regenerative UWB transceiver which can recover the received signal to rail-to-rail with relatively fewer post-amplification stages is proposed. Unlike other super-regenerative receiver architectures that use oscillator, the proposed architecture employs a positive feedback loop to achieve the super-regeneration of received signal and thus eliminates the need for external resonator or quench signal. The transceiver is suitable for low data rate sensor networks application covering spectrum of 3-5 GHz. Manufactured in CMOS 0.18-μm technology, the transceiver occupies an area of 2.2 mm × 2 mm. By exploiting the duty cycle and the transceiver on-time through the burst mode operation for a given data rate of 1 Mbps, it can achieve transmitter energy efficiency of 0.671 nJ/bit and receiver energy efficiency of 3.54 nJ/bit.

A 0.5-V sub-μW/channel neural recording IC with delta-modulation-based spike detection

Abstract: A neural recording IC with a new spike detection scheme is proposed to minimize power dissipation while preserving the waveform information of the detected spikes. A delta modulator is employed in the recording IC to reduce signal dynamic range and enable low-voltage operation. A series of output values from the delta modulator are stored in a small amount of analog memory to extract two key features of the neural signal — amplitude and frequency, which are used for accurate spike detection. Using the stored delta values, the precise spike waveform information can be conserved. A prototype recording IC with 16 channels has been fabricated using 0.18-μm CMOS technology. Measurement results demonstrate the spike detection capability successfully. The fabricated IC consumes only 0.88 μW/channel at 0.5-V supply.

A high-impedance dual-mode SAW resonator for ultra low power and high data rate FSK modulator

Abstract: This paper reports on the design and experimental realization of a dual-mode surface acoustic wave (SAW) resonator with two high-impedance resonant peaks for ultra low power binary frequency-shift-keying (FSK) modulator applications. The single-device structure of the dual-mode resonator is believe to be a promising solution to eliminate the loading effect and noise as a result of multiple switches and other parallel connected resonators, and has the potential to reduce the size and complexity of packaging, compared with the multi-resonator multi-frequency approaches. The dual-mode SAW resonator concept is realized by an in-house, two-mask process that delivered symmetric-mode resonators at 404.9 MHz with trans-impedance values of 1,100 Ω and quality factor of 3134, and anti-symmetric mode resonators at 407.6 MHz, with 900 Ω trans-impedance and 4014 quality factors. Based on the experimental results, we propose a FSK modulator that integrates this high-transimpedance dual-mode resonator and reaches data rates up to 1.5 Mbps. The FSK modulator can be used for low power transmitters in body area network (BAN) and wireless sensor networks (WSN).

A 103 pJ/bit multi-channel reconfigurable GMSK/PSK/16-QAM transmitter with band-shaping

Abstract: A 401∼406MHz GMSK/PSK/16-QAM TX with band-shaping is realized in 65nm CMOS occupying area of 0.4mm2. Coupled DLL based phase interpolated synthesizer with injection-locked ring oscillator, we achieve frequency tuning and multi-phase output without any need of phase calibration. Through direct quadrature modulation at digital PA, the TX achieves less than 6% EVM for data rate up to 12.5Mb/s. The band-shaping maximizes spectral efficiency with ACPR of −33dB. Consuming 2.57mW, the TX achieves energy efficiency of 103pJ/bit.

Integrated multimodal sensor device for intracranial neuromonitoring

Abstract: There is provided a monolithically integrated multimodal sensor device for intracranial neuromonitoring, the sensor device including: a single substrate; a temperature sensor formed on a first portion of the single substrate for detecting temperature; a pressure sensor formed on a second portion of the single substrate for detecting intracranial pressure; and an oxygen sensor formed on a third portion of the single substrate for detecting oxygen concentration. In particular, sensing portions of the temperature sensor, the oxygen sensor and the pressure sensor, respectively, are formed at different layers of the sensor device. There is also provided an integrated multimodal sensor system incorporating the sensor device and the associated methods of fabrication.

Advances in colloidal quantum dot distributed feedback lasers hybridized on glass membranes

Abstract: Mechanically-flexible lasers made of thin-films of colloidal quantum dots on glass membranes are reported. These ns-pulsed lasers have 0.5mJ/cm2 (100 kW/cm2) thresholds and are wavelength-tunable across 18 nm. Improvements of CQD-laser materials are also studied.

Anisotropic stimulated emission from aligned CdSe/CdS dot-in-rods

Abstract: Anisotropic optical properties of CdSe/CdS dot-in-rods loaded in a capillary tube are demonstrated, suggesting nanorods' alignment with a microfluidic approach. Polarized emissions from photoluminescence and whispering gallery mode lasing show promising applications for lighting and displays.

On electron-trap transformation and its unexpected frequency dependence under dynamic positive-bias temperature stressing

Abstract: In the course of our study on the frequency dependence of dynamic positive-bias temperature instability (PBTI) in the HfO2/TiN gate n-MOSFET, an unexpected result was obtained. In accordance with our recent study, electron trapping is observed to gradually evolve into a more permanent form, suggesting that some shallow electron traps are converted into deeper ones as the PBTI stress progresses. Interestingly, however, this evolution is found to exhibit a positive dependence on the gate frequency, i.e. the fraction of electron trapping that is rendered more permanent is increased with the gate frequency over the range of frequency studied (1 mHz - 1 MHz).

Dispositif à capteurs multimodaux intégrés pour neuro-surveillance intracrânienne

Abstract: La presente invention concerne un dispositif a a capteurs multimodaux integres de maniere monolithique pour la neuro-surveillance intracrânienne, le dispositif a capteurs comprenant : un substrat unique ; un capteur de temperature forme sur une premiere partie du substrat unique pour detecter la temperature ; un capteur de pression forme sur une seconde partie du substrat unique pour detecter la pression intracrânienne ; et un capteur d'oxygene forme sur une troisieme partie du substrat unique pour detecter la concentration en oxygene. En particulier, les parties de detection du capteur de temperature, du capteur d'oxygene et du capteur de pression, respectivement, sont formees au niveau de differentes couches du dispositif de detection. La presente invention concerne en outre un systeme a capteurs multimodaux integres incorporant le dispositif a capteurs et les procedes de fabrication associes.

Multi-photon Excited Amplified Spontaneous Emission and Lasing from CdSe/CdS/ZnS quantum dots

Abstract: Multi-photon pumped emission/lasing offers unique merits compared to traditional one-photon counterpart. By engineering superior CdSe/CdS/ZnS core-multi-shell quantum dots (QDs), we demonstrated the feasibility of three-photon excited amplified spontaneous emission and lasing from colloidal semiconductor QDs.