52 results match your criteria Applied physics. B Lasers and optics[Journal]


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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http://dx.doi.org/10.1007/s00340-019-7260-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6944260PMC

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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http://dx.doi.org/10.1007/s00340-019-7315-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6951259PMC
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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http://dx.doi.org/10.1007/s00340-019-7353-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6879434PMC
November 2019

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

Authors:
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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http://dx.doi.org/10.1007/s00340-019-7133-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6383760PMC
January 2019
1 Read

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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http://dx.doi.org/10.1007/s00340-018-6917-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6269144PMC
March 2018
1 Read

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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http://dx.doi.org/10.1007/s00340-018-6912-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6560930PMC
February 2018
1 Read

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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http://link.springer.com/10.1007/s00340-018-7011-0
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http://dx.doi.org/10.1007/s00340-018-7011-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6435023PMC
June 2018
9 Reads

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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http://dx.doi.org/10.1007/s00340-018-6996-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6435022PMC
June 2018
5 Reads

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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http://link.springer.com/10.1007/s00340-018-6925-x
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http://dx.doi.org/10.1007/s00340-018-6925-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6438644PMC
March 2018
21 Reads

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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http://dx.doi.org/10.1007/s00340-018-7030-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6428385PMC
July 2018
2 Reads

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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http://dx.doi.org/10.1007/s00340-016-6620-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7089690PMC
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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http://dx.doi.org/10.1007/s00340-016-6609-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7064021PMC
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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http://dx.doi.org/10.1007/s00340-016-6608-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7062653PMC
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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http://dx.doi.org/10.1007/s00340-016-6611-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7062651PMC
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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http://dx.doi.org/10.1007/s00340-016-6581-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7064022PMC
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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http://dx.doi.org/10.1007/s00340-016-6585-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7045900PMC
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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http://dx.doi.org/10.1007/s00340-017-6802-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6979498PMC

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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http://dx.doi.org/10.1007/s00340-017-6806-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6961519PMC

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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http://dx.doi.org/10.1007/s00340-017-6855-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6956933PMC
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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http://dx.doi.org/10.1007/s00340-017-6848-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6956956PMC
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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http://dx.doi.org/10.1007/s00340-016-6573-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5148790PMC
December 2016
7 Reads

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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http://dx.doi.org/10.1007/s00340-015-6277-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4750283PMC
January 2016
3 Reads

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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http://dx.doi.org/10.1007/s00340-016-6499-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7175658PMC

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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http://dx.doi.org/10.1007/s00340-016-6377-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7175733PMC

Design and fabrication of diffractive atom chips for laser cooling and trapping.

Appl Phys B 2016 1;122(6):172. Epub 2016 Jun 1.

1The Centre for Cold Matter, Blackett Laboratory, Imperial College London, London, SW7 2AZ UK.

It has recently been shown that optical reflection gratings fabricated directly into an atom chip provide a simple and effective way to trap and cool substantial clouds of atoms (Nshii et al. in Nat Nanotechnol 8:321-324, 2013; McGilligan et al. in Opt Express 23(7):8948-8959, 2015). Read More

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http://dx.doi.org/10.1007/s00340-016-6415-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7175734PMC

Competition of single and double rescattering in the strong-field photoemission from dielectric nanospheres.

Appl Phys B 2016 12;122(4):101. Epub 2016 Apr 12.

1Institut für Physik, Universität Rostock, 18051 Rostock, Germany.

Nanostructures exposed to ultrashort waveform-controlled laser pulses enable the generation of enhanced and highly localized near fields with adjustable local electric field evolution. Here, we study dielectric SiO nanospheres ( = 100-700 nm) under strong carrier-envelope phase-controlled few-cycle laser pulses and perform a systematic theoretical analysis of the resulting near-field driven photoemission. In particular, we analyze the impacts of charge interaction and local field ellipticity on the near-field driven electron acceleration. Read More

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http://dx.doi.org/10.1007/s00340-016-6369-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7175736PMC

Extraction of enhanced, ultrashort laser pulses from a passive 10-MHz stack-and-dump cavity.

Appl Phys B 2016 2;122(12):297. Epub 2016 Dec 2.

1Institute of Applied Physics, Abbe Center of Photonics, Friedrich-Schiller-Universität Jena, Albert-Einstein-Str. 15, 07745 Jena, Germany.

Periodic dumping of ultrashort laser pulses from a passive multi-MHz repetition-rate enhancement cavity is a promising route towards multi-kHz repetition-rate pulses with Joule-level energies at an unparalleled average power. Here, we demonstrate this so-called stack-and-dump scheme with a 30-m-long cavity. Using an acousto-optic modulator, we extract pulses of 0. Read More

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http://dx.doi.org/10.1007/s00340-016-6574-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7154790PMC
December 2016

Precision measurements and test of molecular theory in highly excited vibrational states of H ( = 11).

Appl Phys B 2016 1;122(12):294. Epub 2016 Dec 1.

1Department of Physics and Astronomy, LaserLaB, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands.

Accurate transition energies in molecular hydrogen were determined for transitions originating from levels with highly excited vibrational quantum number,  = 11, in the ground electronic state. Doppler-free two-photon spectroscopy was applied on vibrationally excited , produced via the photodissociation of HS, yielding transition frequencies with accuracies of 45 MHz or 0.0015 cm. Read More

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http://dx.doi.org/10.1007/s00340-016-6570-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7154793PMC
December 2016

Autonomous field measurements of CO in the atmospheric column with the miniaturized laser heterodyne radiometer (Mini-LHR).

Appl Phys B 2015;120(4):609-615. Epub 2015 Jul 28.

Microwave Instrument and Technology Branch, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 USA.

We present column CO measurements taken by the passive miniaturized laser heterodyne radiometer (Mini-LHR) at 1611.51 nm at the Mauna Loa Observatory in Hawaii. The Mini-LHR was operated autonomously, during the month of May 2013 at this site, working in tandem with an AERONET sun photometer that measures aerosol optical depth at 15-min intervals during daylight hours. Read More

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http://dx.doi.org/10.1007/s00340-015-6172-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4551134PMC
July 2015
22 Reads

Time-resolved digital holographic microscopy of laser-induced forward transfer process.

Authors:
H Ma V Venugopalan

Appl Phys B 2014 Mar;114(3):361-366

Department of Chemical Engineering and Materials Science, University of California, 916 Engineering Tower, Irvine, CA 92697-2575, USA ; Laser Microbeam and Medical Program, Beckman Laser Institute and Medical Clinic, University of California, Irvine, CA 92697-1475, USA ; Department of Biomedical Engineering, University of California, Irvine, CA 92697-2715, USA.

We develop a method for time-resolved digital holographic microscopy to obtain time-resolved 3-D deformation measurements of laser induced forward transfer (LIFT) processes. We demonstrate nanometer axial resolution and nanosecond temporal resolution of our method which is suitable for measuring dynamic morphological changes in LIFT target materials. Such measurements provide insight into the early dynamics of the LIFT process and a means to examine the effect of laser and material parameters on LIFT process dynamics. Read More

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http://dx.doi.org/10.1007/s00340-013-5524-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3990434PMC
March 2014
1 Read

Continuous-wave broadly tunable high-power Cr:CdS laser.

Appl Phys B 2014;117(4):1009-1014. Epub 2014 Sep 14.

Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim, Norway.

We report spectroscopic characteristics and laser properties of the mid-infrared active laser medium Cr:CdS. Temperature-dependent absorption, luminescence and lifetime measurements of the E exited state allow determination of peak emission cross section value of 1.35 × 10 cm in -polarization at room temperature. Read More

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http://dx.doi.org/10.1007/s00340-014-5921-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4372838PMC
September 2014
3 Reads

Continuous-Wave Stimulated Raman Scattering (cwSRS) Microscopy.

Appl Phys B 2013 Aug;112(1):99-103

Department of Biomedical Engineering, Texas A&M University, College Station, Texas 77843,USA.

Stimulated Raman scattering (SRS) microscopy is a powerful tool for chemically-sensitive non-invasive optical imaging. However, ultrafast laser sources, which are currently employed, are still expensive and require substantial maintenance to provide temporal overlap and spectral tuning. SRS imaging, which utilizes continuous-wave laser sources, has a major advantage, as it eliminates the cell damage due to exposure to the high-intensity light radiation, while substantially reducing the cost and complexity of the set-up. Read More

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http://dx.doi.org/10.1007/s00340-013-5405-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3775370PMC
August 2013
5 Reads

Multifocal multiphoton microscopy based on a spatial light modulator.

Appl Phys B 2013 Jun;107(3):653-657

College of Optoelectronic Engineering, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Shenzhen University, Shenzhen 518060, China.

We present a new multifocal multiphoton microscope that employs a programmable spatial light modulator to generate dynamic multifocus arrays which can be rapidly scanned by changing the incident angle of the laser beam using a pair of galvo scanners. Using this microscope, we can rapidly select the number and the spatial density of focal points in a multifocus array, as well as the locations and shapes of arrays according to the features of the areas of interest in the field of view without any change to the hardware. Read More

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http://dx.doi.org/10.1007/s00340-012-5027-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3722068PMC
June 2013
2 Reads

Active Wavelength Control of an External Cavity Quantum Cascade Laser.

Appl Phys B 2012 May 1;109(3):415-421. Epub 2012 Nov 1.

Electrical Engineering Dept., Princeton University, Princeton, NJ 08544 USA.

We present an active wavelength control system for grating-based external cavity lasers that increases the accuracy of predicting the lasing wavelength based on the grating equation and significantly improves scan-to-scan wavelength/frequency repeatability. The ultimate 3σ precision of a frequency scan is determined by the scan-to-scan repeatability of 0.042 cm. Read More

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http://dx.doi.org/10.1007/s00340-012-5075-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3592968PMC
May 2012
7 Reads

Cross-validation of theoretically quantified fiber continuum generation and absolute pulse measurement by MIIPS for a broadband coherently controlled optical source.

Appl Phys B 2012 Feb 11;106(2):379-384. Epub 2011 Oct 11.

Biophotonics Imaging Laboratory, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.

The predicted spectral phase of a fiber continuum pulsed source rigorously quantified by the scalar generalized nonlinear Schrödinger equation is found to be in excellent agreement with that measured by multiphoton intra-pulse interference phase scan (MIIPS) with background subtraction. This cross-validation confirms the absolute pulse measurement by MIIPS and the transform-limited compression of the fiber continuum pulses by the pulse shaper performing the MIIPS measurement, and permits the subsequent coherent control on the fiber continuum pulses by this pulse shaper. The combination of the fiber continuum source with the MIIPS-integrated pulse shaper produces compressed transform-limited 9. Read More

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http://dx.doi.org/10.1007/s00340-011-4746-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3491074PMC
February 2012
1 Read

Addressable, large-field second harmonic generation microscopy based on 2D acousto-optical deflector and spatial light modulator.

Appl Phys B 2012 Sep;108(4)

College of Optoelectronics Engineering, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Shenzhen University, Shenzhen 518060, China.

We present an addressable, large-field second harmonic generation microscope by combining a 2D acousto-optical deflector with a spatial light modulator. The SLM shapes an incoming mode-locked, near-infrared Ti:Sapphire laser beam into a multifocus array, which can be rapidly scanned by changing the incident angle of the laser beam using a 2D acousto-optical deflector. Compared to the single-beam-scan technique, the multifocus array scan can increase the scanning rate and the field-of-view size with the multi-region imaging ability. Read More

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http://dx.doi.org/10.1007/s00340-012-5164-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3846096PMC
September 2012
32 Reads

Effect of multimodal coupling in imaging micro-endoscopic fiber bundle on optical coherence tomography.

Appl Phys B 2012 Jan;106(3):635-643

Department of Brain and Cognitive Engineering, Korea University, 145, Anam-Ro, Sungbuk-Ku, Seoul, 136-701, South Korea.

The effect of higher order modes in fiber bundle imager-based optical coherence tomography (OCT) has been theoretically modeled using coupled fiber mode analysis ignoring the polarization and core size variation in order to visualize the pure effect of multimodal coupling of the imaging bundle. In this model, the optical imaging fiber couples several higher order modes in addition to the fundamental one due to its high numerical aperture for achieving light confinement to the single core pixel. Those modes become evident in a distance domain using A-mode (depth) OCT based on a mirror sample experiment where multiple peaks are generated by the spatial convolution and coherence function of the light source. Read More

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http://dx.doi.org/10.1007/s00340-011-4847-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3286611PMC
January 2012
2 Reads

Temperature and current coefficients of lasing wavelength in tunable diode laser spectroscopy.

Appl Phys B 2010 Aug;100(2):377-382

Toyohashi University of Technology, 1-1, Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580, Japan.

The factors determining temperature and current coefficients of lasing wavelength are investigated and discussed under monitoring CO(2)-gas absorption spectra. The diffusion rate of Joule heating at the active layer to the surrounding region is observed by monitoring the change in the junction voltage, which is a function of temperature and the wavelength (frequency) deviation under sinusoidal current modulation. Based on the experimental results, the time interval of monitoring the wavelength after changing the ambient temperature or injected current (scanning rate) has to be constant at least to eliminate the monitoring error induced by the deviation of lasing wavelength, though the temperature and current coefficients of lasing wavelength differ with the rate. Read More

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http://dx.doi.org/10.1007/s00340-009-3878-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2929129PMC
August 2010
1 Read

Investigation of gold-coated bare fiber probe for in situ intra-vitreous coherence domain optical imaging and sensing.

Appl Phys B 2010 Jun;99(4):741-746

Department of Electrical and Computer Engineering, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA, .

We have investigated the usage of gold-plated bare fiber probes for in situ imaging of retinal layers and surrounding ocular tissues using time-domain common-path optical coherence tomography. The fabricated intra-vitreous gold-plated micro-fiber probe can be fully integrated with surgical tools working in close proximity to the tissue to provide subsurface images having a self-contained reference plane independent to the Fresnel reflection between the distal end of the probe and the following medium for achieving reference in typical common-path optical coherence tomography. We have fully characterized the probe in an aqueous medium equivalent to the vitreous humor in the eye and were able to differentiate various functional retinal tissue layers whose thickness is larger than the system's resolution. Read More

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http://dx.doi.org/10.1007/s00340-010-3910-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2887671PMC
June 2010
1 Read

Optimal strategy for trapping single fluorescent molecules in solution using the ABEL trap.

Authors:
Q Wang W E Moerner

Appl Phys B 2010 Apr;99(1-2):23-30

Departments of Electrical Engineering and Chemistry, Stanford University, Stanford, CA 94305, USA.

Trapping of 10-nm-sized single fluorescent bio-molecules in solution has been achieved using high-speed position sensing and electrokinetic feedback forces in the Anti-Brownian ELectrokinetic (ABEL) trap. The high diffusion coefficient of small objects in solution requires very fast, real-time sensing of position, and this has been previously achieved using a simple rotating beam, but improved strategies are needed for the smallest objects, such as single nanometer-sized fluorescent molecules. At the same time, single molecules are limited in photon emission rate and total number of photons, so each emitted photon must be used as efficiently as possible. Read More

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http://dx.doi.org/10.1007/s00340-009-3843-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2850131PMC
April 2010
1 Read

K(alpha) x-ray emission characterization of 100 Hz, 15 mJ femtosecond laser system with high contrast ratio.

Appl Phys B 2008 Dec;94(4):569-575

INRS-EMT, Université du Québec, Varennes, J3X 1S2, Canada,

We report K(alpha) x-ray production with a high energy (110 mJ per pulse at 800 nm before compression/15 mJ at 400 nm after compression), high repetition rate (100 Hz), and high pulse contrast (better than 10(-9) at 400 nm) laser system. To develop laser-based x-ray sources for biomedical imaging requires to use high-energy and high-power ultra-fast laser system where compression is achieved under vacuum. Using this type of laser system, we demonstrate long-term stability of the x-ray yield, conversion efficiency higher than 1. Read More

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http://dx.doi.org/10.1007/s00340-008-3342-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2801139PMC
December 2008
3 Reads

Raman effects in the infrared supercontinuum generation in soft-glass PCFs.

Appl Phys B 2007 Mar;87(1):37-44

Institut für Photonik, TU Wien, Gusshausstr. 27/387, A-1040 Vienna, Austria.

Measurements of the Raman gain spectra in the SF6 and SF57 highly-nonlinear-glasses demonstrated twice as high Raman shift in comparison with the fused silica. Numerical simulation predicted that a large Raman shift in combination with high nonlinearity can significantly reduce the required input pulse intensity for supercontinuum in these glasses, retaining the necessary degree of coherence. We found, that the degradation of the SC coherence due to Raman soliton jitter can be effectively controlled by a correct choice of input intensity and fiber length. Read More

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http://dx.doi.org/10.1007/s00340-006-2545-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2958656PMC
March 2007
1 Read

13CO2/12CO2 isotopic ratio measurements using a difference frequency-based sensor operating at 4.35 micrometers.

Appl Phys B 2002 ;75(2-3):289-95

Rice Quantum Institute, Rice University, Houston, TX 77005, USA.

A portable modular gas sensor for measuring the 13C/12C isotopic ratio in CO2 with a precision of 0.8%(+/-1 sigma) was developed for volcanic gas emission studies. This sensor employed a difference frequency generation (DFG)-based spectroscopic source operating at 4. Read More

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http://dx.doi.org/10.1007/s00340-002-0960-2DOI Listing
April 2003
1 Read

Chemical sensing with pulsed QC-DFB lasers operating at 15.6 micrometers.

Appl Phys B 2002 ;75(2-3):351-7

Rice Quantum Institute, Rice University, Houston, TX 77251-1892, USA.

Pulsed thermoelectrically cooled QC-DFB lasers operating at 15.6 micrometers were characterized for spectroscopic gas sensing applications. A new method for wavelength scanning based on repetition rate modulation was developed. Read More

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http://dx.doi.org/10.1007/s00340-002-0963-zDOI Listing
April 2003
7 Reads

Development of a tunable mid-IR difference frequency laser source for highly sensitive airborne trace gas detection.

Appl Phys B 2002 ;75(2-3):281-8

National Center for Atmospheric Research, Boulder, CO 80305, USA.

The development of a compact tunable mid-IR laser system at 3.5 micrometers for quantitative airborne spectroscopic trace gas absorption measurements is reported. The mid-IR laser system is based on difference frequency generation (DFG) in periodically poled LiNbO3 and utilizes optical fiber amplified near-IR diode and fiber lasers as pump sources operating at 1083 nm and 1562 nm, respectively. Read More

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http://lasersci.blogs.rice.edu/files/2014/05/ApplPhysB-Richt
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http://dx.doi.org/10.1007/s00340-002-0948-yDOI Listing
April 2003
7 Reads

Development of a cw-laser-based cavity-ringdown sensor aboard a spacecraft for trace air constituents.

Appl Phys B 2002 ;75(2-3):255-60

The George Washington University, Washington, DC 20052, USA.

The progress in the development of a sensor for the detection of trace air constituents to monitor spacecraft air quality is reported. A continuous-wave (cw), external-cavity tunable diode laser centered at 1.55 micrometers is used to pump an optical cavity absorption cell in cw-cavity ringdown spectroscopy (cw-CRDS). Read More

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http://link.springer.com/content/pdf/10.1007/s00340-002-0969
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http://dx.doi.org/10.1007/s00340-002-0969-6DOI Listing
April 2003
1 Read

Ambient formaldehyde detection with a laser spectrometer based on difference-frequency generation in PPLN.

Appl Phys B 2001 ;72(8):947-52

Rice University, Department of Electrical and Computer Engineering, Houston, TX 77251-1892, USA.

A laser spectrometer based on difference-frequency generation in periodically poled LiNbO3 (PPLN) has been used to quantify atmospheric formaldehyde with a detection limit of 0.32 parts per billion in a given volume (ppbV) using specifically developed data-processing techniques. With state-of-the-art fiber-coupled diode-laser pump sources at 1083 nm and 1561 nm, difference-frequency radiation has been generated in the 3. Read More

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http://dx.doi.org/10.1007/s003400100549DOI Listing
January 2003
1 Read

Applications of Kalman filtering to real-time trace gas concentration measurements.

Appl Phys B 2002 Jan;74(1):85-93

Rice Quantum Institute, Rice University, Houston, TX 77251-1892, USA.

A Kalman filtering technique is applied to the simultaneous detection of NH3 and CO2 with a diode-laser-based sensor operating at 1.53 micrometers. This technique is developed for improving the sensitivity and precision of trace gas concentration levels based on direct overtone laser absorption spectroscopy in the presence of various sensor noise sources. Read More

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http://dx.doi.org/10.1007/s003400100751DOI Listing
January 2002
1 Read

Detection of biogenic CO production above vascular cell cultures using a near-room-temperature QC-DFB laser.

Appl Phys B 2002 Jan;74(1):95-9

Rice Quantum Institute, Rice University, Houston, TX 77251-1892, USA.

We report the first application of pulsed, near-room-temperature quantum cascade laser technology to the continuous detection of biogenic CO production rates above viable cultures of vascular smooth muscle cells. A computer-controlled sequence of measurements over a 9-h period was obtained, resulting in a minimum detectable CO production of 20 ppb in a 1-m optical path above a standard cell-culture flask. Data-processing procedures for real-time monitoring of both biogenic and ambient atmospheric CO concentrations are described. Read More

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http://dx.doi.org/10.1007/s003400100766DOI Listing
January 2002
1 Read

Spectroscopic detection of biological NO with a quantum cascade laser.

Appl Phys B 2001 May;72(7):859-63

Rice Quantum Institute, Rice University, Houston, TX 77251-1892, USA.

Two configurations of a continuous wave quantum cascade distributed feedback laser-based gas sensor for the detection of NO at a parts per billion (ppb) concentration level, typical of biomedical applications, have been investigated. The laser was operated at liquid nitrogen temperature near lambda = 5.2 microns. Read More

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http://dx.doi.org/10.1007/s003400100562DOI Listing
May 2001
1 Read