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1.
Opt Express ; 25(17): 20466-20476, 2017 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-29041727

RESUMO

This study presents the low cost fabrication of flexible white-light-emitting diodes (w-LEDs) with nano-honeycomb-structured phosphor films. Extending the dimensions of the nano-honeycomb structures improved the color uniformity of the flexible samples, and the 950-nm pattern sample demonstrated optimal color uniformity because this nano-pattern exhibited an excellent diffusion ability owing to its pitch size. In addition to color uniformity, the use of this nano-pattern improved the luminous efficiency. The 750-nm pattern exhibited the highest luminous efficiency (235.8 lm/W), which was approximately 7% higher than that exhibited by a non-patterned phosphor film sample. Thus, flexible w-LEDs with nano-honeycomb structure optimization have great potential to be used as next-generation lighting sources.

2.
Nanomaterials (Basel) ; 7(4)2017 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-28383488

RESUMO

Most thin-film techniques require a multiple vacuum process, and cannot produce high-coverage continuous thin films with the thickness of a few nanometers on rough surfaces. We present a new "paradigm shift" non-vacuum process to deposit high-quality, ultra-thin, single-crystal layers of coalesced sulfide nanoparticles (NPs) with controllable thickness down to a few nanometers, based on thermal decomposition. This provides high-coverage, homogeneous thickness, and large-area deposition over a rough surface, with little material loss or liquid chemical waste, and deposition rates of 10 nm/min. This technique can potentially replace conventional thin-film deposition methods, such as atomic layer deposition (ALD) and chemical bath deposition (CBD) as used by the Cu(In,Ga)Se2 (CIGS) thin-film solar cell industry for decades. We demonstrate 32% improvement of CIGS thin-film solar cell efficiency in comparison to reference devices prepared by conventional CBD deposition method by depositing the ZnS NPs buffer layer using the new process. The new ZnS NPs layer allows reduction of an intrinsic ZnO layer, which can lead to severe shunt leakage in case of a CBD buffer layer. This leads to a 65% relative efficiency increase.

3.
Sci Rep ; 7: 46223, 2017 04 07.
Artigo em Inglês | MEDLINE | ID: mdl-28387382

RESUMO

We present a novel, inexpensive and non-interferometric technique to retrieve phase images by using a liquid crystal phase shifter without including any physically moving parts. First, we derive a new equation of the intensity-phase relation with respect to the change of refractive index, which is similar to the transport of the intensity equation. The equation indicates that this technique is unneeded to consider the variation of magnifications between optical images. For proof of the concept, we use a liquid crystal mixture MLC 2144 to manufacture a phase shifter and to capture the optical images in a rapid succession by electrically tuning the applied voltage of the phase shifter. Experimental results demonstrate that this technique is capable of reconstructing high-resolution phase images and to realize the thickness profile of a microlens array quantitatively.

4.
Sci Rep ; 6: 38444, 2016 12 05.
Artigo em Inglês | MEDLINE | ID: mdl-27917938

RESUMO

A novel high-quality, large-size, reflection-type topological insulator Bi2Te3-Gold (BG) film-based nonlinear optical modulator has been successfully fabricated as a two-dimensional saturable absorber mirror (SAM) by pulsed laser deposition (PLD). This BG-SAM possesses saturation fluence of 108.3 µJ/cm2, modulation depth (ΔR) of 6.5%, non-saturable loss of 38.4%, high damage threshold above 1.354 mJ/cm2 and excellent uniformity providing for the generation of passive mode-locked (ML) pulses for erbium-doped fiber lasers (EDFLs) on a large sample area. Under 124 mW 976 nm pumping, We obtained 452-fs continuous-wave ML pulses with pulse energy of 91 pJ and full width at half-maximum (FWHM) of 6.72-nm from this EDFL. The results clearly evidence that the PLD is an efficient method for fabricating BG-SAM that is suitable for a compact ultrafast ML fiber laser system.

5.
Opt Lett ; 41(7): 1616-9, 2016 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-27192301

RESUMO

Phase recovery by solving the transport-of-intensity equation (TIE) is a non-iterative and non-interferometric phase retrieval technique. From solving the TIE with conventional, one partial derivative and Hilbert transform methods for both the periodic and aperiodic samples, we demonstrate that the Hilbert transform method can provide the smoother phase images with edge enhancement and fine structures. Furthermore, compared with the images measured by optical and atomic force microscopy, the Hilbert transform method has the ability to quantitatively map out the phase images for both the periodic and aperiodic structures.

6.
J Med Biol Eng ; 35(3): 305-314, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26167141

RESUMO

Si-based antiresonant reflecting optical waveguide type B (ARROW-B) surface plasmon resonance (SPR) biosensors allow label-free high-sensitivity detection of biomolecular interactions in real time. The ARROW-B waveguide, which has a thick guiding layer, provides efficient coupling with a single-mode fiber. The Si-based ARROW-B SPR biosensors were fabricated by using the standard semiconductor fabrication processes with a single-step lithography. A fluid flow system was designed to transport samples or analytes. The waveguide consists of propagation and SPR sensing regions. The propagation regions in the front and rear of the SPR sensing region have a symmetric cladding structure to isolate them from environmental changes. A high-index O-ring is used to seal the liquid flow channel. The intensity interrogation method was used to characterize the sensors. The sensitivity of the biosensors was 3.0 × 103 µW/RIU (refractive index unit) with a resolution of 6.2 × 10-5 RIU. An in situ regeneration process was designed to make the sensors reusable and eliminate re-alignment of the optical measurement system. The regeneration was realized using ammonia-hydrogen peroxide mixture solutions to remove molecules bound on the sensor surface, such as self-assembled 11-mercapto-1undecanoic acid and bovine serum albumin. SPR was used to monitor the regeneration processes. The experimental results show that the sensing response did not significantly change after the sensor was reused more than 10 times. In situ regenerations of the sensors were achieved.

7.
Appl Opt ; 54(4): 828-33, 2015 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-25967793

RESUMO

A compact waveguide crossing constructed by a cascaded multimode tapered structure is numerically presented. By using an eigenmode expansion method, we observe that the phase difference between the two lowest guided modes can be changed after a multimode waveguide junction because of the coupling between these two guided modes. Accordingly, we propose a fourfold symmetric waveguide crossing composed of three cascaded tapered structures with Gaussian profiles on each branch. Analyzed by the finite difference time domain method, this waveguide crossing has the size of 4160 nm×4160 nm, insertion loss of 0.13 dB, cross talk of -43.5 dB, and backreflection of -33.6 dB at the wavelength of 1550 nm and broad transmission spectrum at the wavelength range of 1500-1600 nm.


Assuntos
Fenômenos Ópticos , Refratometria/instrumentação , Algoritmos , Técnicas Biossensoriais , Simulação por Computador , Campos Eletromagnéticos , Desenho de Equipamento , Análise de Elementos Finitos , Luz , Distribuição Normal , Óptica e Fotônica , Espalhamento de Radiação , Semicondutores , Silício/química
8.
Nanoscale Res Lett ; 9(1): 280, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24959108

RESUMO

In this work, CuIn1 - x Ga x Se2 (CIGS) thin films were prepared by nanosecond (ns)- and femtosecond (fs)-pulsed laser deposition (PLD) processes. Different film growth mechanisms were discussed in perspective of the laser-produced plasmas and crystal structures. The fs-PLD has successfully improved the inherent flaws, Cu2 - x Se, and air voids ubiquitously observed in ns-PLD-derived CIGS thin films. Moreover, the prominent antireflection and excellent crystalline structures were obtained in the fs-PLD-derived CIGS thin films. The absorption spectra suggest the divergence in energy levels of radiative defects brought by the inhomogeneous distribution of elements in the fs-PLD CIGS, which has also been supported by comparing photoluminescence (PL) spectra of ns- and fs-PLD CIGS thin films at 15 K. Finally, the superior carrier transport properties in fs-PLD CIGS were confirmed by fs pump-probe spectroscopy and four-probe measurements. The present results indicate a promising way for preparing high-quality CIGS thin films via fs-PLD.

9.
Opt Lett ; 39(11): 3227-30, 2014 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-24876019

RESUMO

We theoretically present the analysis and design of a nanoplasmonic bandpass filter with flat-top spectral characteristics by cascading a series of directly connected rectangular ring resonators based on metal-insulator-metal waveguides. Analyzed by the equivalent lumped circuit model of the transmission line to plasmonic waveguides, the transmission properties of a symmetric rectangular ring resonator with the directly connected input and output waveguides are approximately the same as that of a Fabry-Perot resonator. Then the thin-film design methodology is applied to realize a plasmonic bandpass filter with the squared passband. An example of cascaded two-rectangular ring resonator structure is numerically demonstrated by using the transmission line model and 2D finite difference time domain method.

10.
Opt Express ; 21(4): 4036-43, 2013 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-23481938

RESUMO

Novel plasmonic power splitters constructed from a rectangular ring resonator with direct-connected input and output waveguides are presented and numerically investigated. An analytical model and systematic approach for obtaining the appropriate design parameters are developed by designing an equivalent lumped circuit model for the transmission lines and applying it to plasmonic waveguides. This approach can dramatically reduce simulation times required for determining the desired locations of the output waveguides. Three examples are shown, the 1 × 3, 1 × 4, and 1 × 5 equal-power splitters, with the design method being easily extended to any number of output ports.


Assuntos
Metais/química , Modelos Teóricos , Refratometria/instrumentação , Ressonância de Plasmônio de Superfície/instrumentação , Simulação por Computador , Desenho Assistido por Computador , Condutividade Elétrica , Desenho de Equipamento , Análise de Falha de Equipamento
11.
Appl Opt ; 51(25): 5952-9, 2012 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-22945138

RESUMO

We present an efficient approach to design a high-channel-count multichannel fiber Bragg grating by assigning optimal sets of delay coefficients and constant phases to the corresponding channel responses. Based on approximate Fourier transform, the delay coefficients are chosen to separate all the single-channel gratings into several groups spatially in the grating structure, and the constant phases in each group are optimized to minimize the maximum index modulation to be approximately the square root of the maximum of the number of the channels in all groups times larger than that of the one-channel grating. Design examples demonstrate that the proposed method has advantages of low index modulation, low algorithmic complexity, and suitability for multichannel fiber Bragg grating designs with either identical or nonidentical spectral responses.

12.
Appl Opt ; 44(29): 6131-40, 2005 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-16237927

RESUMO

A resonant-cavity-enhanced photodiode with broad filter transmittance and high quantum efficiency was numerically designed and analyzed, fabricated, and validated experimentally. We show theoretically that the quantum-efficiency spectrum broadens because of anomalous dispersion of the reflection phase of a mirror in the device and describe conditions that allow maximal flatness of the transmitted spectrum to be achieved. To demonstrate the concepts we design, fabricate, and characterize a backilluminated In0.47Ga0.53As-based p-i-n photodiode upon a InP substrate. Experimental measurements of the fabricated devices demonstrate a peak quantum efficiency of 0.80 at 1550 nm and a FWHM of transmittance of 35.96 nm.

13.
Appl Opt ; 44(8): 1503-11, 2005 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-15796252

RESUMO

The design, fabrication, and characterization of a one-dimensional photonic crystal optical filter that has a relatively narrow, flat-topped passband within a wide stop band and small angular sensitivity is presented. The filter is based on a one-dimensional photonic crystal structure that has multiple defects, facilitating simultaneous minimization of the angular sensitivity and optimization of the passband's characteristics. We use epitaxially grown and selectively oxidized GaAs/AlxOy multilayers to achieve a high-index-contrast material system and incorporate the experimentally determined optical and material properties into the design of the device. A flat-topped bandpass filter with a bandwidth of 65 nm and a wide field of view of 50 degrees is experimentally characterized and compared with the design predictions.

14.
Opt Express ; 13(14): 5347-52, 2005 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-19498528

RESUMO

A novel integrated TM-pass waveguide polarizer with a subwavelength-wide slot is introduced and theoretically analyzed. With a proper design of the slot, the waveguide can be used as a single polarization waveguide to guide only TM polarization modes of the light signal. With 26 microm length of this TM-pass polarizer, our computer simulations predict the insertion loss of 0.54 dB for the TM polarization mode with the extinction ratio of 20.3 dB at the wavelength of 1.55 microm.

15.
Opt Express ; 13(23): 9388-97, 2005 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-19503140

RESUMO

Dispersive mirrors can be designed to create cavities that resonate at set multiple frequencies while simultaneously meeting the conditions for efficient nonlinear wave mixing. We analyze the conditions that such a cavity design must meet and the free parameters that can be used for optimization. Using numerical methods, we show the benefit in conversion efficiency attained with multiple resonances, and draw conclusions concerning the design parameters. As a specific example, we consider parametric downconversion in a triply-resonant cavity.

16.
Opt Lett ; 27(3): 191-3, 2002 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-18007752

RESUMO

We describe a novel approach to implementing wide-field-of-view narrow-band spectral filters, using an array of resonant nanocavities consisting of periodic defects in a two-dimensional three-material photonic-crystal nanostructure. We analyze the transmissivity of this type of filter for a range of wavelengths and in-plane incidence angles as a function of the defect's refractive index, the number of layers in the photonic-crystal reflectors, and the period of the defects and find that this structure diminishes the angular sensitivity of the resonance condition relative to that of a standard multilayer filter.

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