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1.
Rev Sci Instrum ; 90(9): 095102, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31575248

RESUMO

In this paper, we demonstrate the use of a surface condensation sensor board for characterizing interior space in a damp heat chamber. The sensor board is approximately 18 in. × 12 in. in dimension. A total of 324 sense electrodes are designed on the board. The uniform gap between the sense electrodes is 250 µm throughout the surface area of the board. First, the surface leakage current of the sensor board is characterized with other commercially available humidity sensors. The relationship of leakage current to humidity is determined. Surface leakage current is spatially measured inside the chamber, and localized condensation spots are identified at 85 °C/85%RH stress condition. The main goal of this article is to characterize interior space and identify less-risky locations prior to qualification of semiconductor components, optical subassemblies, and optical modules.

2.
Opt Express ; 26(10): 12499-12505, 2018 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-29801287

RESUMO

We demonstrate a novel InGaAsP/InP segmented waveguide photodetector based on directional couplers. By matching the imaginary parts of the propagation constants of the even and odd modes, we designed a photodetector with 6 elements, each with an absorber volume of only 19 µm3 and a bandwidth of 15 GHz, that has an internal quantum efficiency (QE) of 90% at 1550 nm wavelength corresponding to 1.13 A/W.

3.
Sci Rep ; 6: 25236, 2016 04 28.
Artigo em Inglês | MEDLINE | ID: mdl-27121894

RESUMO

A highly sensitive catheter probe is critical to catheter-based intravascular photoacoustic imaging. Here, we present a photoacoustic catheter probe design on the basis of collinear alignment of the incident optical wave and the photoacoustically generated sound wave within a miniature catheter housing for the first time. Such collinear catheter design with an outer diameter of 1.6 mm provided highly efficient overlap between optical and acoustic waves over an imaging depth of >6 mm in D2O medium. Intravascular photoacoustic imaging of lipid-laden atherosclerotic plaque and perivascular fat was demonstrated, where a lab-built 500 Hz optical parametric oscillator outputting nanosecond optical pulses at a wavelength of 1.7 µm was used for overtone excitation of C-H bonds. In addition to intravascular imaging, the presented catheter design will benefit other photoacoustic applications such as needle-based intramuscular imaging.


Assuntos
Estenose das Carótidas/diagnóstico por imagem , Técnicas Fotoacústicas/métodos , Dispositivos de Acesso Vascular , Humanos
4.
Biomed Opt Express ; 6(11): 4557-66, 2015 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-26601018

RESUMO

Lipid deposition inside the arterial wall is a hallmark of plaque vulnerability. Based on overtone absorption of C-H bonds, intravascular photoacoustic (IVPA) catheter is a promising technology for quantifying the amount of lipid and its spatial distribution inside the arterial wall. Thus far, the clinical translation of IVPA technology is limited by its slow imaging speed due to lack of a high-pulse-energy high-repetition-rate laser source for lipid-specific first overtone excitation at 1.7 µm. Here, we demonstrate a potassium titanyl phosphate (KTP)-based optical parametric oscillator with output pulse energy up to 2 mJ at a wavelength of 1724 nm and with a repetition rate of 500 Hz. Using this laser and a ring-shape transducer, IVPA imaging at speed of 1 frame per sec was demonstrated. Performance of the IVPA imaging system's resolution, sensitivity, and specificity were characterized by carbon fiber and a lipid-mimicking phantom. The clinical utility of this technology was further evaluated ex vivo in an excised atherosclerotic human femoral artery with comparison to histology.

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