32,696 results match your criteria Optics Letters [Journal]


Active f-to-2f interferometer for record-low jitter carrier-envelope phase locking.

Opt Lett 2019 Feb;44(4):1060-1063

The f-to-2f interferometer plays a key role for carrier-envelope phase (CEP) measurement and subsequent stabilization. The CEP measurement typically relies on the application of two optical nonlinearities, namely supercontinuum generation and second-harmonic generation. Then the cascadation of these nonlinearities often leads to signal levels on the order of a few photons per pulse. Read More

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http://dx.doi.org/10.1364/OL.44.001060DOI Listing
February 2019
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3D-printed chiral metasurface as a dichroic dual-band polarization converter.

Opt Lett 2019 Feb;44(4):1056-1059

We propose a novel design of a 3D chiral metasurface behaving as a spatial polarization converter with asymmetric transmission. The metasurface is made of a lattice of metallic one-and-a-half-pitch helical particles. The proposed metasurface exhibits a dual-band asymmetric transmission accompanied by the effect of complete polarization conversion. Read More

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http://dx.doi.org/10.1364/OL.44.001056DOI Listing
February 2019

Experimental display of the extended polarization coherence theorem.

Opt Lett 2019 Feb;44(4):1052-1055

We report experimental results that show the interplay between visibility, distinguishability, and the degree of polarization, as ruled by a recent extension of the polarization coherence theorem (PCT). Theorems of this kind address duality in both quantum and classical scenarios. We particularly focus on the inherent vector nature of the polarization degree of freedom and display various effects that lie beyond the scope of the original PCT. Read More

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http://dx.doi.org/10.1364/OL.44.001052DOI Listing
February 2019

Phase transition through the splitting of self-dual spectral singularity in optical potentials: erratum.

Opt Lett 2019 Feb;44(4):1051

Some errors and particular conclusions drawn in our Letter [Opt. Lett.42, 5206 (2017)OPLEDP0146-959210. Read More

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http://dx.doi.org/10.1364/OL.44.001051DOI Listing
February 2019

Self-imaging of tailored vortex pulse arrays and spectral Gouy rotation echoes.

Opt Lett 2019 Feb;44(4):1047-1050

Self-imaging of femtosecond pulses with orbital angular momentum is studied in spectral domain by illuminating the orthogonal arrays of spiral gratings. Spectral Gouy rotation, i.e. Read More

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http://dx.doi.org/10.1364/OL.44.001047DOI Listing
February 2019

Bragg filter bandwidth engineering in subwavelength grating metamaterial waveguides.

Opt Lett 2019 Feb;44(4):1043-1046

Bragg gratings are fundamental building blocks for integrated photonic circuits. In the high-index contrast silicon-on-insulator material platform, it is challenging to accurately control the grating strength and achieve narrow spectral bandwidths. Here we demonstrate a novel Bragg grating geometry utilizing a silicon subwavelength grating (SWG) waveguide with evanescently coupled periodic Bragg loading segments placed outside the SWG core. Read More

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http://dx.doi.org/10.1364/OL.44.001043DOI Listing
February 2019

Investigation of structural mechanisms of laser-written waveguide formation through third-harmonic microscopy.

Opt Lett 2019 Feb;44(4):1039-1042

The mechanisms of laser-induced modification of transparent materials are complex combinations of different processes that depend on the material itself and a range of processing parameters. As such, the mechanisms are still subject to ongoing study. We use a custom-built adaptive third-harmonic generation (THG) microscope to study those mechanisms. Read More

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http://dx.doi.org/10.1364/OL.44.001039DOI Listing
February 2019
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Far-field super-focusing by a feedback-based wavefront shaping method.

Opt Lett 2019 Feb;44(4):1035-1038

Abbe diffraction limit has always been an important subject in conventional far-field focusing and imaging systems, where the resolution of an image is usually limited to 0.5λ/NA. Recently, the studies of the optical super-oscillation lens (SOL) enable us to break the limitation in both theory and practice successfully. Read More

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http://dx.doi.org/10.1364/OL.44.001035DOI Listing
February 2019

Fast and large-area fabrication of plasmonic reflection color filters by achromatic Talbot lithography.

Opt Lett 2019 Feb;44(4):1031-1034

To overcome the limits of traditional technologies, which cannot achieve high resolution and high throughput simultaneously, here we propose, to the best of our knowledge, a novel method, i.e., achromatic Talbot lithography, to fabricate large-area nanopatterns fast and precisely. Read More

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http://dx.doi.org/10.1364/OL.44.001031DOI Listing
February 2019

Integration of crescent laser beams into dark-field microscopes for enhancing the Raman characterization of micro/nano particles.

Opt Lett 2019 Feb;44(4):1027-1030

Dark-field microscopy is widely used to image micro/nano particles or characterize their optical response (scattering spectrum). If laser excitation is incorporated into the microscope, the microscope can further probe chemical (molecular) properties of these objects through Raman scattering. However, when the size of the particles is comparable to or smaller than the characteristic sizes of the laser beam, the conventional setup using on-axis excitation usually suffers from undesired background signals produced by illuminated substrates below the target particles. Read More

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http://dx.doi.org/10.1364/OL.44.001027DOI Listing
February 2019

Demonstration of a tilted-pulse-front pumped plane-parallel slab terahertz source.

Opt Lett 2019 Feb;44(4):1023-1026

A new type of tilted-pulse-front pumped terahertz (THz) source has been demonstrated, which is based on a LiNbOplane-parallel slab with an echelon structure on its input surface. Single-cycle pulses of 1 μJ energy and 0.30 THz central frequency have been generated with 5×10 efficiency from such a source. Read More

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http://dx.doi.org/10.1364/OL.44.001023DOI Listing
February 2019

Orbital angular momentum generation in two-mode fiber, based on the modal interference principle.

Opt Lett 2019 Feb;44(4):999-1002

In this Letter, we demonstrate, to the best of our knowledge, a novel method to generate an orbital angular momentum (OAM) based on the principle of the modal interference in a two-mode fiber. At the interference dips, the left- or right-handed circular polarized HE modes can be ideally converted into the ±1-order OAM beam. To verify this concept, we employed the femtosecond laser micro-processing technology to write micro-waveguides in the two-mode fiber and hence realized the in-line modal interferometer. Read More

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http://dx.doi.org/10.1364/OL.44.000999DOI Listing
February 2019

Holographic multi-parameter imaging of dynamic phenomena with visual and audio features.

Opt Lett 2019 Feb;44(4):995-998

In this Letter, a concept of new multi-parameter imaging that can acquire visual and audio data of dynamic object phenomena simultaneously by a holographic technique is proposed. Temporal intensity distributions give us visual information of the dynamic events. The temporal profile of the phase distribution can give different information of the dynamic events, such as audio data. Read More

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http://dx.doi.org/10.1364/OL.44.000995DOI Listing
February 2019

Analog of giant magnetoimpedance in magnetized ε-near-zero plasma.

Opt Lett 2019 Feb;44(4):991-994

In this Letter, we show that magnetized plasma with properly designed parameters at plasma frequency suffers a large magnetoimpedance change under a moderate external magnetic field. Such an interesting feature can be described as the analog of giant magnetoimpedance (GMI), which is confirmed by detailed calculation. GMI devices based on magnetized ε-near-zero plasma do not require microfabrication, and they are capable of working at tunable frequency, even in terahertz frequency range; more importantly, they can be dynamically controlled by environmental parameters such as temperature and pressure. Read More

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https://www.osapublishing.org/abstract.cfm?URI=ol-44-4-991
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http://dx.doi.org/10.1364/OL.44.000991DOI Listing
February 2019
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High-resolution femtosecond laser beam shaping via digital holography.

Opt Lett 2019 Feb;44(4):987-990

We propose a method to achieve high-resolution femtosecond laser beam shaping (HR-FLBS) via digital holography based on a digital mirror device (DMD) and optimized optical design. By programming the hologram on the DMD, we captured several patterns such as light spots, decorated letters of "HUST" (Huazhong University of Science and Technology), and a series of concentric annuli whose fine structure approaches the optical diffraction limit. The experimental results confirm that the proposed method can shape the amplitude and phase of a femtosecond laser arbitrarily with high resolution. Read More

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http://dx.doi.org/10.1364/OL.44.000987DOI Listing
February 2019

High-performance solution-processed white organic light-emitting diodes based on silica-coated silver nanocubes.

Opt Lett 2019 Feb;44(4):983-986

Solution-processed white organic light-emitting diodes (WOLEDs) with silica-coated silver nanocubes (Ag@SiO NCs) incorporated at the interface of a hole transporting layer and emission layer are studied. The concentration of Ag@SiO NCs is varied to investigate the effect of Ag@SiO NCs on the performances of WOLEDs. Owing to the sharp edges and corners, Ag NCs greatly improve the radiative rate and emission intensity of nearby blue excitons. Read More

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http://dx.doi.org/10.1364/OL.44.000983DOI Listing
February 2019

Rapid phase retrieval of ultrashort pulses from dispersion scan traces using deep neural networks.

Opt Lett 2019 Feb;44(4):979-982

The knowledge of the temporal shape of femtosecond pulses is of major interest for all their applications. The reconstruction of the temporal shape of these pulses is an inverse problem for characterization techniques, which benefit from an inherent redundancy in the measurement. Conventionally, time-consuming optimization algorithms are used to solve the inverse problems. Read More

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http://dx.doi.org/10.1364/OL.44.000979DOI Listing
February 2019

Wideband chaos from a laser diode with phase-conjugate feedback.

Opt Lett 2019 Feb;44(4):975-978

We analyze experimentally and theoretically the chaotic dynamics generated by a laser diode subjected to phase-conjugate feedback. Phase conjugation is obtained from four-wave mixing in a BaTiO photorefractive crystal. We demonstrate that the chaos bandwidth first increases linearly with feedback ratio but then saturates to relatively high values. Read More

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http://dx.doi.org/10.1364/OL.44.000975DOI Listing
February 2019

Fabry-Pérot cavity-coupled microbolometer terahertz detector with a continuously tunable air spacer gap.

Opt Lett 2019 Feb;44(4):1019-1022

This Letter demonstrates tunable NbN microbolometers operating in the terahertz frequency range. An asymmetric-coupled Fabry-Pérot cavity is constituted by simply placing a movable metallic planar mirror in the back of the silicon substrate. The incident THz radiation onto the NbN microbolometer is effectively manipulated by changing the air spacer gap to modulate the phase relation between the reflected wave and incident wave. Read More

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http://dx.doi.org/10.1364/OL.44.001019DOI Listing
February 2019

Simultaneous measurement of two ultrashort near-ultraviolet pulses produced by a multiplate continuum using dual self-diffraction dispersion-scan.

Opt Lett 2019 Feb;44(4):1015-1018

We present a new method based on self-diffraction dispersion-scan (SD d-scan) that enables the simultaneous measurement of two distinct ultrashort laser pulses in a region where they spatially and temporally overlap. This situation can arise when sampling and focusing two different spatial portions of a single inhomogeneous beam onto a medium. We demonstrate this new dual SD d-scan method by simultaneously characterizing two intense broadband ultraviolet pulses at 400 nm, with durations in the 10 fs range, originating from two different spatial portions of a beam produced by a multiplate continuum (MPC). Read More

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http://dx.doi.org/10.1364/OL.44.001015DOI Listing
February 2019

Diagnosing plasmas with wideband terahertz pulses.

Authors:
A Curcio M Petrarca

Opt Lett 2019 Feb;44(4):1011-1014

A diagnostic method for the electron plasma density and temperature based on the exploitation of wideband THz pulses is presented. The model accompanying the diagnostic method is described, and it is shown useful to characterize the plasma density and temperature profile along a symmetry axis. This diagnostic is particularly interesting for plasma-acceleration schemes or laser-produced plasma channels. Read More

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http://dx.doi.org/10.1364/OL.44.001011DOI Listing
February 2019

Bessel-like beams generated via fiber-based polymer microtips.

Opt Lett 2019 Feb;44(4):1007-1010

We present a novel and efficient approach to generating Bessel-like beams through fabricating self-growing polymer microtips at the facet of single-mode fibers. To produce these beams, the length and shape of microtips were precisely optimized. Specifically, the convex droplet height and its photopolymerization parameters feature prominently in Bessel-like beams via microtips. Read More

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http://dx.doi.org/10.1364/OL.44.001007DOI Listing
February 2019

Multimicrojoule GaSe-based midinfrared optical parametric amplifier with an ultrabroad idler spectrum covering 4.2-16  μm.

Opt Lett 2019 Feb;44(4):1003-1006

We report a multimicrojoule, ultrabroadband midinfrared optical parametric amplifier based on a GaSe nonlinear crystal pumped at ∼2  μm. The generated idler pulse has a flat spectrum spanning from 4.5 to 13. Read More

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http://dx.doi.org/10.1364/OL.44.001003DOI Listing
February 2019
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Generation of coherent mid-IR light by parametric four-wave mixing in alkali vapor.

Opt Lett 2019 Feb;44(4):971-974

The parametric four-wave mixing (4WM) process responsible for the generation of coherent blue light in alkali vapors is a self-seeded process which starts by population inversion and amplified spontaneous emission (ASE). Lately, attention has been turned toward frequency up- and down-conversion in alkali vapors, using relatively low pump powers with CW diode lasers. In this Letter, we investigate the interplay between ASE and 4WM in rubidium (Rb) vapors by studying the mid-infrared (mid-IR) radiation emitted in the forward direction at 5. Read More

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http://dx.doi.org/10.1364/OL.44.000971DOI Listing
February 2019

Synthetic subaperture-based angle-independent Doppler flow measurements using single-beam line field optical coherence tomography in vivo.

Opt Lett 2019 Feb;44(4):967-970

We demonstrate a synthetic subaperture-based angle-independent Doppler flow calculation, using a line field spectral domain optical coherence tomography system. The high speed of the system features a high phase stability over the volume, which is necessary to apply synthetic subapertures in the aperture plane. Thus, the flow component for each subaperture can be reconstructed in postprocessing. Read More

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http://dx.doi.org/10.1364/OL.44.000967DOI Listing
February 2019

Polarization-independent and high-efficiency broadband optical absorber in visible light based on nanostructured germanium arrays.

Opt Lett 2019 Feb;44(4):963-966

A broadband optical absorber based on the nanostructured germanium (Ge) film composed of single-sized circular nanodisk-nanohole arrays is proposed, which demonstrates high efficiency, strong polarization independence, and large viewing angle. Due to the electric and magnetic resonance absorption modes excited by the nanostructure arrays in highly lossy Ge film, the absorber obtains a high absorptivity, reaching above 90% over the full visible wavelength, and it can be maintained well at a large viewing angle over ±50°. Based on the geometrical symmetry, the absorber is proved to be polarization independent. Read More

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http://dx.doi.org/10.1364/OL.44.000963DOI Listing
February 2019

Exploring elliptical vortex beams with the spatial damping effect.

Opt Lett 2019 Feb;44(4):959-962

A general integral formula is analytically derived to represent the wave function of elliptical vortex modes. The derived formula can be straightforwardly employed to take account of spatial damping to explore vortex structure. Spatial damping is found to cause the central degenerate singularity of the circular vortex mode to be split into several singularities with different topological charges. Read More

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http://dx.doi.org/10.1364/OL.44.000959DOI Listing
February 2019

Abruptly autofocused and rotated circular chirp Pearcey Gaussian vortex beams.

Opt Lett 2019 Feb;44(4):955-958

In this Letter, we introduce a new class of abruptly autofocued and rotated circular chirp Pearcey Gaussian vortex beams (AARCCPGVBs) which tend to abruptly autofocused circular chirp Pearcey vortex beams or chirp Gaussian vortex beams by adjusting the spatial distribution factors. Different from other rotated beams [Opt. Lett. Read More

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http://dx.doi.org/10.1364/OL.44.000955DOI Listing
February 2019

Performance-enhanced silicon thermo-optic Mach-Zehnder switch using laterally supported suspended phase arms and efficient electrodes.

Opt Lett 2019 Feb;44(4):951-954

We report a silicon thermo-optic Mach-Zehnder switch with a broadband, low switching power, and fast response. A broadband 3 dB directional coupler is used to act as a power splitter. Laterally supported suspended phase arms are employed to substantially reduce the switching power without sacrificing too much on the temporal response. Read More

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http://dx.doi.org/10.1364/OL.44.000951DOI Listing
February 2019

Accumulation-layer hybridized surface plasmon polaritions at an ITO/LiNbO interface.

Opt Lett 2019 Feb;44(4):947-950

To circumvent the hindrance to broad practical applications associated with uses of highly lossy metals in plasmonics, electrostatic modification-based low-loss structures are conceived and demonstrated in supporting surface plasmon polaritions (SPPs). Pairing a highly polar LiNbO (LN) slab with a nonpolar indium-tin-oxide (ITO) thin film, a subnanometer ITO layer was modified into visible SPPs supportive owing to electrostatic screening; yet a theoretical treatment of a sandwiched structure with a sub-nanometer interlayer and an anisotropic substrate is still missing. In this Letter, a hybridized SPP supporting picture was drawn in the ITO/LN system, which agrees well with the 2D diffraction patterns observed out of phase gratings written with two coherent laser beams either of pure-extraordinary, pure-ordinary, or mixed polarizations. Read More

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http://dx.doi.org/10.1364/OL.44.000947DOI Listing
February 2019

Stable interferometric platform for phase modulation of seeded free-electron lasers.

Opt Lett 2019 Feb;44(4):943-946

We present a compact phase modulation setup designed for high laser intensities sufficient to drive highly nonlinear processes, such as high-gain harmonic generation in seeded free-electron lasers. This paves the way for all-extreme-ultravioloet coherent nonlinear spectroscopy. The high linearity, phase stability, and sensitivity of the setup are demonstrated by probing the quantum interference of electronic wave packets in the deep ultraviolet region (268 nm) combined with photoion time-of-flight mass spectrometry. Read More

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http://dx.doi.org/10.1364/OL.44.000943DOI Listing
February 2019
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Low-index second-order metagratings for large-angle anomalous reflection.

Opt Lett 2019 Feb;44(4):939-942

A large-angle anomalous reflector based on a low-index polylactic acid metagrating is designed around 140 GHz. By breaking the limit of fixed bar-to-bar distance and directing the beam into the second diffraction order through the optimization of the 4π phase supercell, the efficiencies for 70° and 80° reflection under normal excitation both reach 0.82 with a wide bandwidth. Read More

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http://dx.doi.org/10.1364/OL.44.000939DOI Listing
February 2019

Tailoring focused optical vortices by using spiral forked plates.

Opt Lett 2019 Feb;44(4):935-938

We propose and experimentally demonstrate a single optical element, termed as spiral forked plates (SFPs), to simultaneously generate two tightly focused optical vortices (OVs). The key idea is to combine a spiral zone plate (SZP) and a forked grating (FG) through a logic XOR operation. Both theoretical and experimental results demonstrate that SFPs not only can completely suppress the undesirable zeroth (central) order diffraction, but also can further manipulate the topological charges (TCs) of the two resultant focused OVs by varying the TCs of the SZP and FG, following the so-called TC transformation rule. Read More

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http://dx.doi.org/10.1364/OL.44.000935DOI Listing
February 2019

Improving the color-rendering index of a tandem warm white organic light-emitting device by employing a simple fabrication process.

Opt Lett 2019 Feb;44(4):931-934

We realized an efficient spectra-stable tandem white organic light-emitting device (WOLED) with pleasurable warm white emission and an extremely high color-rendering index (CRI) simultaneously by connecting a fluorescent blue unit and a phosphorescent dual-color unit via an easy-fabrication charge generation unit (CGU). Over a wide range of driving current density, the tandem warm white OLED exhibited general CRI (R) value exceeding 85 and special CRI (R) value close to 57. In addition, Duvs are within the tolerance for CRI measurements, ensuring validity and logicality of the calculated results concerning R and R. Read More

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http://dx.doi.org/10.1364/OL.44.000931DOI Listing
February 2019

Three-dimensional metacrystals with a broadband isotropic diamagnetic response and an all-angle negative index of refraction.

Opt Lett 2019 Feb;44(4):927-930

Metamaterials (MMs) and photonic crystals (PhCs) exhibiting artificially engineered physical properties have been widely studied in the past decade. However, abnormal properties could only be proposed under a limited range of polarization and directions in most of the previous studies. It is still a challenge to realize an isotropic artificial material with multiple exotic electromagnetic properties. Read More

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http://dx.doi.org/10.1364/OL.44.000927DOI Listing
February 2019
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Chromatic-dispersion-induced power-fading suppression technique for bandwidth-quadrupling dual-chirp microwave signals over fiber transmission.

Opt Lett 2019 Feb;44(4):923-926

We report a technique to overcome chromatic-dispersion-induced power fading (CDIP) for bandwidth-quadrupling dual-chirp microwave signals over fiber transmission. Normally, dual-chirp microwave signals are generated using double-sideband (DSB) modulation. However, DSB modulation suffers from CDIP significantly. Read More

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http://dx.doi.org/10.1364/OL.44.000923DOI Listing
February 2019
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Combined photoacoustic imaging to delineate the internal structure of paintings.

Opt Lett 2019 Feb;44(4):919-922

In this Letter, we present a combined photoacoustic imaging method, based on consecutive excitation using either the fundamental or the second-harmonic wavelength of a pulsed Nd:YAG laser for the stratigraphy of painted artworks. Near-infrared excitation was employed for the imaging of hidden underdrawings in mock-up samples, whereas visible light was used for the thickness mapping of the overlying paint through the detection of photoacoustic signal attenuation. The proposed methodology was proven effective in measuring thick and strongly absorbing layers, which would not be possible by means of other pure optical techniques, while also enabling the visualization of features underneath the painted surface. Read More

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https://www.osapublishing.org/abstract.cfm?URI=ol-44-4-919
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http://dx.doi.org/10.1364/OL.44.000919DOI Listing
February 2019
6 Reads

Silicon-on-insulator free-carrier injection modulators for the mid-infrared.

Opt Lett 2019 Feb;44(4):915-918

Experimental demonstrations of silicon-on-insulator waveguide-based free-carrier effect modulators operating at 3.8 μm are presented. PIN diodes are used to inject carriers into the waveguides, and are configured to (a) use free-carrier electroabsorption to create a variable optical attenuator with 34 dB modulation depth and (b) use free-carrier electrorefraction with the PIN diodes acting as phase shifters in a Mach-Zehnder interferometer, achieving a VL of 0. Read More

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http://dx.doi.org/10.1364/OL.44.000915DOI Listing
February 2019

Undersampling for fiber distributed acoustic sensing based on coherent phase-OTDR.

Opt Lett 2019 Feb;44(4):911-914

Phase-sensitive optical time-domain reflectometry (ϕ-OTDR) based on coherent detection is one of the most widely used schemes to achieve fiber distributed acoustic sensing. In previous studies, a fairly high data acquisition speed is essential for the phase-measuring coherent ϕ-OTDR, thus leading to a severe computational burden. In this Letter, we first analyze the power spectrum of the beat signal and then propose the use of undersampling theory to reduce the need for high sampling frequency. Read More

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http://dx.doi.org/10.1364/OL.44.000911DOI Listing
February 2019

Broadband optical switch for multiple spatial modes based on a silicon densely packed waveguide array.

Opt Lett 2019 Feb;44(4):907-910

A broadband thermo-optic 2×2 Mach-Zehnder switch that can control two spatial modes simultaneously on a silicon chip is demonstrated in this Letter. A broadband multimode 3 dB coupler is first realized based on symmetrically coupled waveguides with a sub-wavelength structure. The length of the coupler is only 24. Read More

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http://dx.doi.org/10.1364/OL.44.000907DOI Listing
February 2019

Nanometric sensing with laser feedback interferometry.

Opt Lett 2019 Feb;44(4):903-906

We demonstrate a nanometric sensor based on feedback interferometry in a distributed feedback (DFB) laser by using a measurement of either the optical frequency or laser voltage. We find that in an optimal range of optical feedback, the sensor operates reliably down to an extrapolated 12 nm; for the sensor demonstrated here at ∼1550  nm, this provides a minimum detectible displacement of λ/130. Read More

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http://dx.doi.org/10.1364/OL.44.000903DOI Listing
February 2019

Influence of optics vibration on synchrotron beam coherence.

Opt Lett 2019 Feb;44(4):899-902

Vibration of optics is one of the major limiting factors of the performance of state-of-the-art beamlines at low-emittance synchrotron facilities. We present a theoretical model with experimental data describing vibration-induced effects on x-ray beam coherence. Owing to the incoherent nature of vibration, the decrease in the beam spatial coherence perturbed by optics vibrations can be characterized by modeling the effective source profile of the vibrating beam. Read More

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http://dx.doi.org/10.1364/OL.44.000899DOI Listing
February 2019

Robust full Stokes imaging polarimeter with dynamic calibration.

Opt Lett 2019 Feb;44(4):891-894

We present a full Stokes imaging polarimeter using a rotating retarder in combination with a polarization camera-a detector array on which a pixelated polarizer array is attached. By itself, a polarization camera cannot capture the full Stokes parameters, but we add a rotating retarder in front and show how it can be used to provide full Stokes images. In addition, we demonstrate the advantage that it can be recalibrated dynamically while taking measurements, allowing accurate measurements even in environments where the retardance in changing. Read More

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http://dx.doi.org/10.1364/OL.44.000891DOI Listing
February 2019

Two-photon PSF-engineered image scanning microscopy.

Opt Lett 2019 Feb;44(4):895-898

We present two-photon fluorescence image scanning microscopy (ISM) with engineered excitation and detection point-spread-functions enabling 3D imaging in a single 2D scan. This demonstration combines excitation using a holographic multispot array of focused femtosecond pulses with a high-efficiency single-helix PSF phase mask detection. Camera detection along with a multiview reconstruction algorithm allows volumetric imaging of biological samples over a depth of field spanning more than 1500 nm with an axial resolution of better than 400 nm. Read More

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http://dx.doi.org/10.1364/OL.44.000895DOI Listing
February 2019

Generation of terahertz vortex pulses without any need of manipulation in the terahertz region.

Opt Lett 2019 Feb;44(4):887-890

Converting a Gaussian mode to a vortex beam is much more inconvenient in the terahertz (THz) region than in the near-infrared (NIR) region due to underdevelopment of THz components and strong THz diffraction. This Letter reports the direct generation of THz vortex pulses by optical difference-frequency between two NIR chirped pulses with different topological charges (TCs). By designing a passive and transmissive device for a collinear NIR pulse pair with conjugated TCs, we have experimentally obtained stable THz vortex pulses with a TC value of 2 or -2. Read More

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http://dx.doi.org/10.1364/OL.44.000887DOI Listing
February 2019

Subtraction imaging by the combination of higher-order vector beams for enhanced spatial resolution.

Opt Lett 2019 Feb;44(4):883-886

We demonstrate that the spatial resolution in confocal laser scanning microscopy is remarkably improved by simple image subtraction between images acquired by higher-order transverse modes of a cylindrical vector beam, referred to as radially and azimuthally polarized Laguerre-Gaussian mode beams. Two types of combinations of vector mode beams suitable for subtraction imaging are derived by a systematical study based on numerical calculations. The spatial resolution of about 100 nm is experimentally achieved without the degradation of image quality. Read More

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http://dx.doi.org/10.1364/OL.44.000883DOI Listing
February 2019

Resonant response and mode conversion of the microsphere coupled with a microfiber coupler.

Opt Lett 2019 Feb;44(4):879-882

We experimentally investigate the resonant response in a microsphere coupled with a biconical microfiber coupler (MFC) composed of single- and/or few-mode fibers. The evolution between Lorentz and Fano resonances dependent on the phase difference of the supermodes is demonstrated along the coupling region of the MFC. A flexible narrow-linewidth add-drop filter can be simultaneously achieved with the advantage of easy alignment and efficiently evanescent coupling. Read More

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http://dx.doi.org/10.1364/OL.44.000879DOI Listing
February 2019

Fluorescence characterization of heavily Eu-doped lanthanum gallate glass spheres with high quenching concentration.

Opt Lett 2019 Feb;44(4):875-878

Highly EuO-doped (up to 30 mol%) LaO-GaO glasses were synthesized by an aerodynamic levitation technique. The red emission associated with D5 level of Euwas most intense at 20 mol% EuO, indicating a small effect of concentration quenching even at high Eu concentration. The fluorescence decay curves indicated that the dominant transition mechanism at high Eu concentration was fast energy migration among the Eu ions, which averaged the environment of the Eu, yielding a nearly single-exponential decay of D5→F7 emission. Read More

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http://dx.doi.org/10.1364/OL.44.000875DOI Listing
February 2019

Plasmonic metamaterial-based filtering structures with dynamic tunability.

Opt Lett 2019 Feb;44(4):871-874

In this Letter, we report the design, analysis, and characterization of first- and second-order plasmonic metamaterial-based multi-mode filtering structures. Further, electronic adaptivity in filter transfer functions is introduced and characterized. First, the basic operating principle of the engineered multi-mode resonator-based bandpass filter is presented. Read More

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http://dx.doi.org/10.1364/OL.44.000871DOI Listing
February 2019

Modal approach to optical forces between waveguides as derived by transformation optics formalism.

Opt Lett 2019 Feb;44(4):867-870

Optical force between two lossless waveguides has been described by two approaches. One approach is the explicit description of the force by the Maxwell stress tensor. Another approach is to describe the modal force in terms of the derivative of the eigenmode frequency with respect to the distance variation. Read More

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http://dx.doi.org/10.1364/OL.44.000867DOI Listing
February 2019