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1.
Opt Express ; 27(26): 38229-38235, 2019 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-31878593

RESUMO

An LED chip containing monolithically integrated red, green, and blue channels was fabricated and characterized. Using local strain engineering in gallium nitride p-i-n nanopillar structures, each color channel emits a distinct color with emission wavelength determined entirely by the diameter of the nanopillar. The crosstalk between color channels is negligible. As a result, individually addressable color channels can be integrated on the same substrate which will be suitable for color-tunable lighting applications. Optical and electrical properties were measured and discussed. Fabrication challenges which degraded power efficiency of the shorter-wavelength channel were analyzed. Potential strategies for improvements were proposed.

2.
Nanotechnology ; 29(16): 165201, 2018 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-29388922

RESUMO

A parabolic nanolens array coupled to the emission of a nanopillar micro-light emitting diode (LED) color pixel is shown to reduce the far field divergence. For a blue wavelength LED, the total emission is 95% collimated within a 0.5 numerical aperture zone, a 3.5x improvement over the same LED without a lens structure. This corresponds to a half-width at half-maximum (HWHM) line width reduction of 2.85 times. Using a resist reflow and etchback procedure, the nanolens array dimensions and parabolic shape are formed. Experimental measurement of the far field emission shows a HWHM linewidth reduction by a factor of 2x, reducing the divergence over the original LED.

3.
IEEE Photonics J ; 9(3)2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28751938

RESUMO

A new form of light-emitting diode (LED) light suitable for general illumination is proposed to enhance subconscious, nonimage-forming visual responses, which are essential to our well-being. Pulsing light has been shown to reduce photoreceptor adaptation and elicit stronger subconscious visual responses at an indoor illumination level. Using the silent substitution technique, a melanopsin-selective flicker can be added into white light. A linear optimization algorithm was developed to suppress any perceivable fluctuation of light intensity and colors of illuminated objects. Two examples of lights are given to illustrate the potential applications of the proposed multi-LED light for general illumination and therapeutic purposes.

4.
Sci Rep ; 7: 42962, 2017 03 03.
Artigo em Inglês | MEDLINE | ID: mdl-28256529

RESUMO

In this research, nano-ring light-emitting diodes (NRLEDs) with different wall width (120 nm, 80 nm and 40 nm) were fabricated by specialized nano-sphere lithography technology. Through the thinned wall, the effective bandgaps of nano-ring LEDs can be precisely tuned by reducing the strain inside the active region. Photoluminescence (PL) and time-resolved PL measurements indicated the lattice-mismatch induced strain inside the active region was relaxed when the wall width is reduced. Through the simulation, we can understand the strain distribution of active region inside NRLEDs. The simulation results not only revealed the exact distribution of strain but also predicted the trend of wavelength-shifted behavior of NRLEDs. Finally, the NRLEDs devices with four-color emission on the same wafer were demonstrated.

5.
Neuron ; 88(6): 1136-1148, 2015 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-26627311

RESUMO

We report a scalable method to monolithically integrate microscopic light emitting diodes (µLEDs) and recording sites onto silicon neural probes for optogenetic applications in neuroscience. Each µLED and recording site has dimensions similar to a pyramidal neuron soma, providing confined emission and electrophysiological recording of action potentials and local field activity. We fabricated and implanted the four-shank probes, each integrated with 12 µLEDs and 32 recording sites, into the CA1 pyramidal layer of anesthetized and freely moving mice. Spikes were robustly induced by 60 nW light power, and fast population oscillations were induced at the microwatt range. To demonstrate the spatiotemporal precision of parallel stimulation and recording, we achieved independent control of distinct cells ∼ 50 µm apart and of differential somato-dendritic compartments of single neurons. The scalability and spatiotemporal resolution of this monolithic optogenetic tool provides versatility and precision for cellular-level circuit analysis in deep structures of intact, freely moving animals.


Assuntos
Comportamento Animal/fisiologia , Neurônios/fisiologia , Optogenética/métodos , Estimulação Luminosa/métodos , Silício , Animais , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Optogenética/instrumentação
6.
Materials (Basel) ; 8(3): 1204-1212, 2015 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-28787997

RESUMO

This work describes a novel architecture to realize high-performance gallium nitride (GaN) bulk acoustic wave (BAW) resonators. The method is based on the growth of a thick GaN layer on a metal electrode grid. The fabrication process starts with the growth of a thin GaN buffer layer on a Si (111) substrate. The GaN buffer layer is patterned and trenches are made and refilled with sputtered tungsten (W)/silicon dioxide (SiO2) forming passivated metal electrode grids. GaN is then regrown, nucleating from the exposed GaN seed layer and coalescing to form a thick GaN device layer. A metal electrode can be deposited and patterned on top of the GaN layer. This method enables vertical piezoelectric actuation of the GaN layer using its largest piezoelectric coefficient (d33) for thickness-mode resonance. Having a bottom electrode also results in a higher coupling coefficient, useful for the implementation of acoustic filters. Growth of GaN on Si enables releasing the device from the frontside using isotropic xenon difluoride (XeF2) etch and therefore eliminating the need for backside lithography and etching.

7.
Nanotechnology ; 23(45): 455301, 2012 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-23085680

RESUMO

We present a novel approach to the fabrication of zero-mode waveguides (ZMWs) using inexpensive processing techniques. Our method is capable of rapid fabrication of circular nanoapertures with diameters ranging from 70 nm to 2 µm, allowing us to perform a detailed characterization of the dependence of the fluorescence emission on the waveguide diameter. We also validated the use of the fabricated ZMWs by detecting single molecule binding events with a signal-to-noise ratio of ten.

8.
Opt Express ; 19(4): 3218-25, 2011 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-21369144

RESUMO

We proposed a metal-clad semiconductor nanoring laser structure that exhibited a superior scaling properties for D/λ(0) > 0.5 where D is the device diameter. We theoretically analyzed the metal-cald nanoring laser and compared its scaling properties with two other similar nanolaser structures. We found that the two design parameters, namely the ring width and the ring diameter, enable independent emission wavelength control from device dimension. This property in combination with other desirable features including in-plane out-coupling and monolithic integration make the metal-clad nanoring laser highly attractive for photonic integration.

9.
Opt Lett ; 29(19): 2291-3, 2004 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-15524384

RESUMO

We demonstrate slow light via population oscillation in semiconductor quantum-well structures for the first time. A group velocity as low as 9600 m/s is inferred from the experimentally measured dispersive characteristics. The transparency window exhibits a bandwidth as large as 2 GHz.

10.
Opt Express ; 10(19): 1003-8, 2002 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-19451957

RESUMO

We demonstrate a novel buried oxide grating structure formed by selectively-oxidized AlxGa1-xAs grown on nonplanar substrates using lowpressure MOCVD for the first time. Localized aluminum content variation in AlGaAs is obtained with MOCVD growth on nonplanar substrate. Buried aluminum oxide/semiconductor distributed feedback structure is achieved with selective oxidation of these AlGaAs layers. We fabricated a resonant-cavity-enhanced photodetector with the imbedded buried-oxide structure and measured the photodetector responsivity spectrum.

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