58 results match your criteria Applied Physics B-Lasers And Optics[Journal]

Laser-induced incandescence for non-soot nanoparticles: recent trends and current challenges.

Appl Phys B 2022 14;128(4):72. Epub 2022 Mar 14.

Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, N2L 3G1 Canada.

Laser-induced incandescence (LII) is a widely used combustion diagnostic for in situ measurements of soot primary particle sizes and volume fractions in flames, exhaust gases, and the atmosphere. Increasingly, however, it is applied to characterize engineered nanomaterials, driven by the increasing industrial relevance of these materials and the fundamental scientific insights that may be obtained from these measurements. This review describes the state of the art as well as open research challenges and new opportunities that arise from LII measurements on non-soot nanoparticles. Read More

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Cross-calibration of a combined electrostatic and time-of-flight analyzer for energy- and charge-state-resolved spectrometry of tin laser-produced plasma.

Appl Phys B 2022 5;128(3):39. Epub 2022 Feb 5.

Advanced Research Center for Nanolithography (ARCNL), Science Park 106, 1098 XG Amsterdam, The Netherlands.

We present the results of the calibration of a channeltron-based electrostatic analyzer operating in time-of-flight mode (ESA-ToF) using tin ions resulting from laser-produced plasma, over a wide range of charge states and energies. Specifically, the channeltron electron multiplier detection efficiency and the spectrometer resolution are calibrated, and count rate effects are characterized. With the obtained overall response function, the ESA-ToF is shown to accurately reproduce charge-integrated measurements separately and simultaneously obtained from a Faraday cup (FC), up to a constant factor the finding of which enables absolute cross-calibration of the ESA-ToF using the FC as an absolute benchmark. Read More

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February 2022

Absolute SESAM characterization via polarization-resolved non-collinear equivalent time sampling.

Appl Phys B 2022 19;128(2):24. Epub 2022 Jan 19.

Department of Physics, Institute for Quantum Electronics, ETH Zürich, Auguste-Piccard-Hof 1, 8093 Zurich, Switzerland.

Semiconductor saturable absorber mirrors (SESAMs) have enabled a wide variety of modelocked laser systems, which makes measuring their nonlinear properties an important step in laser design. Here, we demonstrate complete characterization of SESAMs using an equivalent time sampling apparatus. The light source is a free-running dual-comb laser, which produces a pair of sub-150-fs modelocked laser outputs at 1051 nm from a single cavity. Read More

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January 2022

Investigation of the opto-thermo-mechanical properties of antimicrobial PET/TiO fiber using the transport of intensity equation technique.

Appl Phys B 2022 6;128(1):15. Epub 2022 Jan 6.

Physics Department, Faculty of Science, Mansoura University, Mansoura, Egypt.

The transport of intensity equation (TIE) technique is used to investigate the effect of stretching and annealing conditions on the optical features and antimicrobial activity of polyethylene terephthalate (PET) fibers treated with TiO nanoparticles. The main core of this paper gets the most preferable optical and mechanical properties for PET/TiO fiber which maintains its antibacterial activity. The variation of the refractive index of untreated PET/TiO fiber along its axis is studied. Read More

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January 2022

Mass-selective removal of ions from Paul traps using parametric excitation.

Appl Phys B 2020 9;126(11):176. Epub 2020 Oct 9.

Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Straße 3, 79104 Freiburg, Germany.

We study a method for mass-selective removal of ions from a Paul trap by parametric excitation. This can be achieved by applying an oscillating electric quadrupole field at twice the secular frequency using pairs of opposing electrodes. While excitation near the resonance with the secular frequency only leads to a linear increase of the amplitude with excitation duration, parametric excitation near results in an exponential increase of the amplitude. Read More

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October 2020

Mid-infrared sensing of CO at saturated absorption conditions using intracavity quartz-enhanced photoacoustic spectroscopy.

Appl Phys B 2019 5;125(9):159. Epub 2019 Aug 5.

Institute of Chemical Technologies and Analytics, Technische Universität Wien, Getreidemarkt 9/164, 1060 Vienna, Austria.

The sensitivity of quartz-enhanced photoacoustic spectroscopy (QEPAS) can be drastically increased using the power enhancement in high-finesse cavities. Here, low noise resonant power enhancement to 6.3 W was achieved in a linear Brewster window cavity by exploiting optical feedback locking of a quantum cascade laser. Read More

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A portable miniaturized laser heterodyne radiometer (mini‑LHR) for remote measurements of column CH and CO.

Appl Phys B 2019 Oct;125(211)

Department of Information and Computer Sciences, University of Hawai'i at Mānoa, POST Building Suite 303D, 1680 East - West Road, Honolulu, HI 96822, USA.

We present the design of a portable version of our miniaturized laser heterodyne radiometer (mini-LHR) that simultaneously measures methane (CH) and carbon dioxide (CO) in the atmospheric column. The mini-LHR fits on a backpack frame, operates autonomously, and requires no infrastructure because it is powered by batteries charged by a folding 30 W solar panel. Similar to our earlier instruments, the mini-LHR is a passive laser heterodyne radiometer that operates by collecting sunlight that has undergone absorption by CH and CO. Read More

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October 2019

Fiber laser-driven gas plasma-based generation of THz radiation with 50-mW average power.

Appl Phys B 2020 26;126(1). Epub 2019 Nov 26.

1Institute of Applied Physics, Abbe Center of Photonics, Friedrich-Schiller-University Jena, Albert-Einstein-Str. 6, 07745 Jena, Germany.

We present on THz generation in the two-color gas plasma scheme driven by a high-power, ultrafast fiber laser system. The applied scheme is a promising approach for scaling the THz average power but it has been limited so far by the driving lasers to repetition rates up to 1 kHz. Here, we demonstrate recent results of THz generation operating at a two orders of magnitude higher repetition rate. Read More

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November 2019

Are absorption and spontaneous or stimulated emission inverse processes? The answer is subtle!

Markus Pollnau

Appl Phys B 2019 21;125(2):25. Epub 2019 Jan 21.

Department of Electrical and Electronic Engineering, Advanced Technology Institute, University of Surrey, Guildford, GU2 7XH UK.

It is generally believed that absorption and stimulated emission are inverse processes, as both are driven by an external field, their strength is quantified by the same Einstein coefficient, and they occur with a defined phase, opposite to each other, namely in phase and in anti-phase with the driving field, whereas spontaneous emission is a different process that occurs with an arbitrary phase with respect to a potential incident field. Recently, the phase relation in absorption and emission was shown to differ from this believe. Here it is verified via the amplitude-phase diagram and via the interference of sine waves that, precisely speaking, only the absorption process, in which a number  + 1 of incident photons is decreased by one photon, and the emission process, in which a number of incident photons is increased by one photon, are truly inverse processes also in their phase. Read More

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January 2019

Optical remote sensing for monitoring flying mosquitoes, gender identification and discussion on species identification.

Appl Phys B 2018 Mar 17;124(3). Epub 2018 Feb 17.

Department of Physics, New Jersey Institute of Technology, 323 Martin Luther King Jr Blvd, Newark, NJ, USA.

Mosquito-borne diseases are a major challenge for Human health as they affect nearly 700 million people every year and result in over 1 million deaths. Reliable information on the evolution of population and spatial distribution of key insects species is of major importance in the development of eco-epidemiologic models. This paper reports on the remote characterization of flying mosquitoes using a continuous-wave infrared optical remote sensing system. Read More

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High-repetition-rate interferometric Rayleigh scattering for flow-velocity measurements.

Appl Phys B 2018 10;124(3). Epub 2018 Feb 10.

Spectral Energies, LLC, 5100 Springfield St., Suite 301, Dayton, OH 45431, USA.

High-repetition-rate interferometric-Rayleigh-scattering (IRS) velocimetry is implemented and demonstrated for non-intrusive, high-speed flow-velocity measurements. High temporal resolution is obtained with a quasi-continuous burst-mode laser that is capable of providing bursts of 10-msec duration with pulse widths of 10-100 nsec, pulse energy > 100 mJ at 532 nm, and repetition rates of 10-100 kHz. Coupled with a high-speed camera system, the IRS method is based on imaging the flow field though an etalon with 8-GHz free spectral range and capturing the Doppler shift of the Rayleigh-scattered light from the flow at multiple points having constructive interference. Read More

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February 2018

Flame thermometry using laser-induced-grating spectroscopy of nitric oxide.

Appl Phys B 2018 13;124(3):43. Epub 2018 Feb 13.

1Department of Physics, Clarendon Laboratory, Oxford University, Parks Road, Oxford, OX1 3PU UK.

A systematic study of laser-induced thermal-grating scattering (LITGS) using nitric oxide as an absorbing species is presented as a means of thermometry in air-fed combustion. The relative contributions to the scattered signal from degenerate four-wave mixing, DFWM, and from laser-induced thermal-grating scattering, LITGS, are studied in the time domain for NO in N buffer gas up to 4 bar, using a pulsed laser system to excite the (0,0) γ-bands of NO at 226.21 nm. Read More

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February 2018

Dispersive white light continuum single Z-scan for rapid determination of degenerate two-photon absorption spectra.

Appl Phys B 2018 22;124(7):142. Epub 2018 Jun 22.

4Institute of Applied Synthetic Chemistry, TU Wien (Technische Universitat Wien), Getreidemarkt 9, 1060 Vienna, Austria.

We present an experimental technique to determine the degenerate two-photon absorption (2PA) spectra by performing a single Z-scan using a high-spectral-irradiance white light continuum (WLC) generated by a hollow core fiber. The hollow fiber was filled with Argon (Ar) gas at a pressure of 0.6 bar and was pumped with 500 mJ, 30 fs, and 800 nm pulses. Read More

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Phase-stabilized 100 mW frequency comb near 10 μm.

Appl Phys B 2018 6;124(7):128. Epub 2018 Jun 6.

1Department of Physics, JILA, National Institute of Standards and Technology and University of Colorado, University of Colorado, Boulder, CO 80309 USA.

Long-wavelength mid-infrared (MIR) frequency combs with high power and flexible tunability are highly desired for molecular spectroscopy, including investigation of large molecules such as C. We present a high power, phase-stabilized frequency comb near 10 μm, generated by a synchronously pumped, singly resonant optical parametric oscillator (OPO) based on AgGaSe. The OPO can be continuously tuned from 8. Read More

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Highly efficient frequency doubling and quadrupling of a short-pulsed thulium fiber laser.

Appl Phys B 2018 22;124(4):59. Epub 2018 Mar 22.

Optoelectronics Research Centre, University of Southampton, Southampton, SO17 1BJ UK.

We report the second harmonic generation and fourth harmonic generation of the output from a short-pulsed (~ 80 ps) thulium-doped fiber laser, generating 976 and 488 nm wavelengths with high efficiency. With a narrow-linewidth (0.5 nm) pump at a power of 3. Read More

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Laser spectroscopy for breath analysis: towards clinical implementation.

Appl Phys B 2018 28;124(8):161. Epub 2018 Jul 28.

1Trace Gas Research Group, Molecular and Laser Physics, IMM, Radboud University, 6525 AJ Nijmegen, The Netherlands.

Detection and analysis of volatile compounds in exhaled breath represents an attractive tool for monitoring the metabolic status of a patient and disease diagnosis, since it is non-invasive and fast. Numerous studies have already demonstrated the benefit of breath analysis in clinical settings/applications and encouraged multidisciplinary research to reveal new insights regarding the origins, pathways, and pathophysiological roles of breath components. Many breath analysis methods are currently available to help explore these directions, ranging from mass spectrometry to laser-based spectroscopy and sensor arrays. Read More

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Efficient high-harmonic generation from a stable and compact ultrafast Yb-fiber laser producing 100 μJ, 350 fs pulses based on bendable photonic crystal fiber.

Appl Phys B 2017 11;123(1):43. Epub 2017 Jan 11.

1Optoelectronics Research Centre, University of Southampton, Hampshire, SO17 1BJ UK.

The development of an Yb-fiber-based chirped-pulse amplification system and the performance in the generation of extreme ultraviolet (EUV) radiation by high-harmonic generation is reported. The fiber laser produced 100 μJ, 350 fs output pulses with diffraction-limited beam quality at a repetition rate of 16.7 kHz. Read More

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January 2017

Shifting the phase of a coherent beam with a ion: influence of the scattering cross section.

Appl Phys B 2017 16;123(1):48. Epub 2017 Jan 16.

1Max-Planck-Institute for the Science of Light, Staudtstr. 2, 91058 Erlangen, Germany.

We discuss and measure the phase shift imposed onto a radially polarized light beam when focusing it onto an ion. In the derivation of the expected phase shifts, we include the properties of the involved atomic levels. Furthermore, we emphasize the importance of the scattering cross section and its relation to the efficiency for coupling the focused light to an atom. Read More

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January 2017

Ultrafast optomechanical pulse picking.

Appl Phys B 2017 16;123(1):47. Epub 2017 Jan 16.

1Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching, Germany.

State-of-the-art optical switches for coupling pulses into and/or out of resonators are based on either the electro-optic or the acousto-optic effect in transmissive elements. In high-power applications, the damage threshold and other nonlinear and thermal effects in these elements impede further improvements in pulse energy, duration, and average power. We propose a new optomechanical switching concept which is based solely on reflective elements and is suitable for switching times down to the ten-nanosecond range. Read More

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January 2017

Phase-stable, multi-µJ femtosecond pulses from a repetition-rate tunable Ti:Sa-oscillator-seeded Yb-fiber amplifier.

Appl Phys B 2017 20;123(1):17. Epub 2016 Dec 20.

1Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany.

We present a high-power, MHz-repetition-rate, phase-stable femtosecond laser system based on a phase-stabilized Ti:Sa oscillator and a multi-stage Yb-fiber chirped-pulse power amplifier. A 10-nm band around 1030 nm is split from the 7-fs oscillator output and serves as the seed for subsequent amplification by 54 dB to 80 W of average power. The µJ-level output is spectrally broadened in a solid-core fiber and compressed to ~30 fs with chirped mirrors. Read More

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December 2016

Atomic "bomb testing": the Elitzur-Vaidman experiment violates the Leggett-Garg inequality.

Appl Phys B 2017 19;123(1):12. Epub 2016 Dec 19.

1Institut Für Angewandte Physik, Universität Bonn, Wegelerstr. 8, 53115 Bonn, Germany.

Elitzur and Vaidman have proposed a measurement scheme that, based on the quantum superposition principle, allows one to detect the presence of an object-in a dramatic scenario, a bomb-without interacting with it. It was pointed out by Ghirardi that this interaction-free measurement scheme can be put in direct relation with falsification tests of the macro-realistic worldview. Here we have implemented the "bomb test" with a single atom trapped in a spin-dependent optical lattice to show explicitly a violation of the Leggett-Garg inequality-a quantitative criterion fulfilled by macro-realistic physical theories. Read More

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December 2016

Measuring and imaging nanomechanical motion with laser light.

Appl Phys B 2017 15;123(1). Epub 2016 Dec 15.

Niels Bohr Institute, Blegdamsvej 17, 2100 Copenhagen, Denmark.

We discuss several techniques based on laser-driven interferometers and cavities to measure nanomechanical motion. With increasing complexity, they achieve sensitivities reaching from thermal displacement amplitudes, typically at the picometer scale, all the way to the quantum regime, in which radiation pressure induces motion correlated with the quantum fluctuations of the probing light. We show that an imaging modality is readily provided by scanning laser interferometry, reaching a sensitivity on the order of , and a transverse resolution down to . Read More

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December 2016

Amplification of a radially polarised beam in an Yb:YAG thin-slab.

Appl Phys B 2017 5;123(8):225. Epub 2017 Aug 5.

Optoelectronics Research Centre, University of Southampton, Southampton, SO17 1BJ UK.

The use of an Yb:YAG thin-slab architecture for amplification of a radially polarised beam at 1030 nm is investigated and shown to be a promising route for power scaling. The detrimental impact of the Gouy phase shift on radial polarisation purity is considered and a simple scheme for effective phase shift management to restore polarisation purity is presented. Preliminary experiments based on a double-pass amplifier configuration yielded an output beam with a high radial polarisation extinction ratio of 15 dB and no degradation in polarisation purity despite the non- axial symmetry of amplifier gain medium. Read More

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Polarisation-preserving photon frequency conversion from a trapped-ion-compatible wavelength to the telecom C-band.

Appl Phys B 2017 18;123(9):228. Epub 2017 Aug 18.

1Institut für Quantenoptik und Quanteninformation, Technikerstrasse 21a, 6020 Innsbruck, Austria.

We demonstrate polarisation-preserving frequency conversion of single-photon-level light at 854 nm, resonant with a trapped-ion transition and qubit, to the 1550-nm telecom C band. A total photon in / fiber-coupled photon out efficiency of 30% is achieved, for a free-running photon noise rate of 60 Hz. This performance would enable telecom conversion of 854 nm polarisation qubits, produced in existing trapped-ion systems, with a signal-to-noise ratio greater than 1. Read More

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Diode laser-based thermometry using two-line atomic fluorescence of indium and gallium.

Appl Phys B 2017 7;123(12):278. Epub 2017 Nov 7.

Lund University, Lund, Sweden.

A robust and relatively compact calibration-free thermometric technique using diode lasers two-line atomic fluorescence (TLAF) for reactive flows at atmospheric pressures is investigated. TLAF temperature measurements were conducted using indium and, for the first time, gallium atoms as temperature markers. The temperature was measured in a multi-jet burner running methane/air flames providing variable temperatures ranging from 1600 to 2000 K. Read More

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November 2017

Analytical thermal model for end-pumped solid-state lasers.

Appl Phys B 2017 4;123(12):273. Epub 2017 Nov 4.

2Optoelectronics Research Centre, University of Southampton, Highfield Southampton SO17 1BJ, Southampton, United Kingdom.

Fundamentally power-limited by thermal effects, the design challenge for end-pumped "bulk" solid-state lasers depends upon knowledge of the temperature gradients within the gain medium. We have developed analytical expressions that can be used to model the temperature distribution and thermal-lens power in end-pumped solid-state lasers. Enabled by the inclusion of a temperature-dependent thermal conductivity, applicable from cryogenic to elevated temperatures, typical pumping distributions are explored and the results compared with accepted models. Read More

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November 2017

New avenues for matter-wave-enhanced spectroscopy.

Appl Phys B 2017 9;123(1). Epub 2016 Dec 9.

Faculty of Physics, VCQ, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria.

We present matter-wave interferometry as a tool to advance spectroscopy for a wide class of nanoparticles, clusters and molecules. The high sensitivity of de Broglie interference fringes to external perturbations enables measurements in the limit of an individual particle absorbing only a single photon on average, or even no photon at all. The method allows one to extract structural and electronic information from the loss of the interference contrast. Read More

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December 2016

Pulsed Rydberg four-wave mixing with motion-induced dephasing in a thermal vapor.

Appl Phys B 2016;122:18. Epub 2016 Jan 22.

5. Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany.

We report on time-resolved pulsed four-wave mixing (FWM) signals in a thermal Rubidium vapor involving a Rydberg state. We observe FWM signals with dephasing times up to 7 ns, strongly dependent on the excitation bandwidth to the Rydberg state. The excitation to the Rydberg state is driven by a pulsed two-photon transition on ns timescales. Read More

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January 2016

Multi-mode absorption spectroscopy using a quantum cascade laser for simultaneous detection of NO and HO.

Appl Phys B 2016 4;122(8):226. Epub 2016 Aug 4.

2Department of Chemistry, Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford, OX1 3QZ UK.

Detection of multiple transitions in NO and HO using multi-mode absorption spectroscopy, MUMAS, with a quantum cascade laser, QCL, operating at 5.3 μm at scan rates up to 10 kHz is reported. The linewidth of longitudinal modes of the QCL is derived from pressure-dependent fits to experimental MUMAS data. Read More

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Multi-species sensing using multi-mode absorption spectroscopy with mid-infrared interband cascade lasers.

Appl Phys B 2016 2;122(6):173. Epub 2016 Jun 2.

3Code 5604, Naval Research Laboratory, Washington, DC 20375 USA.

The application of an interband cascade laser, ICL, to multi-mode absorption spectroscopy, MUMAS, in the mid-infrared region is reported. Measurements of individual mode linewidths of the ICL, derived from the pressure dependence of lineshapes in MUMAS signatures of single, isolated, lines in the spectrum of HCl, were found to be in the range 10-80 MHz. Multi-line spectra of methane were recorded using spectrally limited bandwidths, of approximate width 27 cm, defined by an interference filter, and consist of approximately 80 modes at spectral locations spanning the 100 cm bandwidth of the ICL output. Read More

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