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Arturo Chavez-Pirson

Bio: Arturo Chavez-Pirson is an academic researcher from University of Arizona. The author has contributed to research in topics: Fiber laser & Laser linewidth. The author has an hindex of 18, co-authored 37 publications receiving 1485 citations.

Papers
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Journal ArticleDOI
TL;DR: Retinal OCT at longer wavelengths significantly improves the visualization of the retinal pigment epithelium/choriocapillaris/choroids interface and superficial choroidal layers as well as reduces the scattering through turbid media and therefore might provide a better diagnosis tool for early stages of retinal pathologies such as age related macular degeneration.
Abstract: For the first time in vivo retinal imaging has been performed with a new compact, low noise Yb-based ASE source operating in the 1 microm range (NP Photonics, lambdac = 1040 nm, Deltalambda = 50 nm, Pout = 30 mW) at the dispersion minimum of water with ~7 microm axial resolution. OCT tomograms acquired at 800 nm are compared to those achieved at 1040 nm showing about 200 microm deeper penetration into the choroid below the retinal pigment epithelium. Retinal OCT at longer wavelengths significantly improves the visualization of the retinal pigment epithelium/choriocapillaris/choroids interface and superficial choroidal layers as well as reduces the scattering through turbid media and therefore might provide a better diagnosis tool for early stages of retinal pathologies such as age related macular degeneration which is accompanied by choroidal neovascularization, i.e., extensive growth of new blood vessels in the choroid and retina.

343 citations

Journal ArticleDOI
TL;DR: In this paper, the frequency dependence of optical nonlinearities of bulk GaAs at room temperature was studied and band filling and plasma screening of Coulomb enhancement of continuum states were found to be the dominant contributions to the dispersive optical non-linearities under quasi steady-state excitations.
Abstract: We report the first systematic study of the frequency dependence of optical nonlinearities of bulk GaAs at room temperature. In contrast to the previous understanding, band filling and plasma screening of Coulomb enhancement of continuum states are found to be the dominant contributions to the dispersive optical nonlinearities under quasi steady-state excitations. The partly phenomenological semiconductor plasma theory is in good agreement with the experimental data.

222 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present a systematic study of the dependence of the optical nonlinearities on quantum well thickness for GaAs/AlGaAs multiple quantum wells (MQW) at room temperature and compare them with bulk GaAs.
Abstract: We present a systematic study of the dependence of the optical nonlinearities on quantum well thickness for GaAs/AlGaAs multiple quantum wells (MQW’s) at room temperature and compare them with bulk GaAs. The maximum change in the refractive index is greatest for the MQW’s with the smallest well size and decreases with increasing well size, reaching a minimum for bulk GaAs. The maximum index change per photoexcited carrier increases by a factor of 3 as the well size decreases from bulk to 76 A MQW.

100 citations

Journal ArticleDOI
TL;DR: In this article, the spin relaxation of excitons in zero-dimensional semiconductor nanostructures was measured by using a polarization dependent time-resolved photoluminescence method.
Abstract: We report the observation of spin relaxation of excitons in zero-dimensional semiconductor nanostructures. The spin relaxation is measured in InGaAs quantum disks by using a polarization dependent time-resolved photoluminescence method. The spin relaxation time in a zero-dimensional quantum disk is as long as 0.9 ns at 4 K, which is almost twice as long as the radiative recombination lifetime and is considerably longer than that in quantum wells. The temperature dependence of the spin relaxation time suggests the importance of exciton–acoustic phonon interaction.

93 citations

Proceedings ArticleDOI
15 Oct 2013
TL;DR: In this article, the authors used a tellurite-based dispersion managed nonlinear fiber and an all-fiber based short pulse (20 ps) single mode pump source to generate a high power, single mode beam with extremely wide (1μm-5μm) and simultaneous wavelength coverage.
Abstract: Mid-infrared sources are a key enabling technology for various applications such as remote chemical sensing, defense communications and countermeasures, and bio-photonic diagnostics and therapeutics. Conventional mid-IR sources include optical parametric amplifiers, quantum cascade lasers, synchrotron and free electron lasers. An all-fiber approach to generate a high power, single mode beam with extremely wide (1μm-5μm) and simultaneous wavelength coverage has significant advantages in terms of reliability (no moving parts or alignment), room temperature operation, size, weight, and power efficiency. Here, we report single mode, high power extended wavelength coverage (1μm to 5μm) supercontinuum generation using a tellurite-based dispersion managed nonlinear fiber and an all-fiber based short pulse (20 ps), single mode pump source. We have developed this mid IR supercontinuum source based on highly purified solid-core tellurite glass fibers that are waveguide engineered for dispersion-zero matching with Tm-doped pulsed fiber laser pumps. The conversion efficiency from 1922nm pump to mid IR (2μm-5μm) supercontinuum is greater than 30%, and approaching 60% for the full spectrum. We have achieved > 1.2W covering from 1μm to 5μm with 2W of pump. In particular, the wavelength region above 4μm has been difficult to cover with supercontinuum sources based on ZBLAN or chalcogenide fibers. In contrast to that, our nonlinear tellurite fibers have a wider transparency window free of unwanted absorption, and are highly suited for extending the long wavelength emission above 4μm. We achieve spectral power density at 4.1μm already exceeding 0.2mW/nm and with potential for higher by scaling of pump power.

75 citations


Cited by
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Journal ArticleDOI
TL;DR: The theoretical concepts, experimental tools, and applications of surface photovoltage (SPV) techniques are reviewed in detail in detail as discussed by the authors, where the theoretical discussion is divided into two sections: electrical properties of semiconductor surfaces and the second discusses SPV phenomena.

1,499 citations

Journal ArticleDOI
TL;DR: Kelvin probe force microscopy (KPFM) is a tool that enables nanometer-scale imaging of the surface potential on a broad range of materials as discussed by the authors, including metallic nanostructures, semiconductor materials, and electrical devices.

1,242 citations

Journal ArticleDOI
TL;DR: The integration of OCTA in multimodal imaging in the evaluation of retinal vascular occlusive diseases, diabetic retinopathy, uveitis, inherited diseases, age-related macular degeneration, and disorders of the optic nerve is presented.

988 citations

Journal ArticleDOI
TL;DR: Extensions of OCT have been developed to enhance image contrast and to enable non-invasive depth-resolved functional imaging of the retina, thus providing blood flow, spectroscopic, polarization-sensitive and physiological information.

793 citations

Journal ArticleDOI
TL;DR: In this paper, the experimental and theoretical investigations of the linear and nonlinear optical properties of semiconductor quantum well structures, including the effects of electrostatic fields, extrinsic carriers and real or virtual photocarriers, are reviewed.
Abstract: In this article we review the experimental and theoretical investigations of the linear and nonlinear optical properties of semiconductor quantum well structures, including the effects of electrostatic fields, extrinsic carriers and real or virtual photocarriers.

791 citations