Applied Sciences

1010 KiB

Open AccessArticle

Multicolored Femtosecond Pulse Synthesis Using Coherent Raman Sidebands in a Reflection Scheme

by Kai Wang, Alexandra A. Zhdanova, Miaochan Zhi, Xia Hua and Alexei V. Sokolov

Appl. Sci. 2015, 5(2), 145-156; https://doi.org/10.3390/app5020145 - 11 Jun 2015

Cited by 6 | Viewed by 6446

Broadband coherent Raman generation emerges as a successful method to produce multicolored femtosecond pulses and time-shaped laser fields. In our study, coherent Raman sidebands are generated in a Raman-active crystal, driven by two-color femtosecond laser pulses. An interferogram of the sidebands based on [...] Read more.

Broadband coherent Raman generation emerges as a successful method to produce multicolored femtosecond pulses and time-shaped laser fields. In our study, coherent Raman sidebands are generated in a Raman-active crystal, driven by two-color femtosecond laser pulses. An interferogram of the sidebands based on coherent Raman scattering is produced in a novel reflection scheme. The relative spectral phases of the sidebands are obtained from the interferogram using a numerical simulation. This enables us to retrieve the ultrafast waveform using coherent Raman sidebands. Full article

(This article belongs to the Special Issue Multi-Color Laser Emission for the Generation of Ultrashort Optical Pulse)

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3352 KiB

Open AccessArticle

Autocorrelation and Frequency-Resolved Optical Gating Measurements Based on the Third Harmonic Generation in a Gaseous Medium

by Yoshinari Takao, Tomoko Imasaka, Yuichiro Kida and Totaro Imasaka

Appl. Sci. 2015, 5(2), 136-144; https://doi.org/10.3390/app5020136 - 9 Jun 2015

Cited by 2 | Viewed by 6723

Abstract

A gas was utilized in producing the third harmonic emission as a nonlinear optical medium for autocorrelation and frequency-resolved optical gating measurements to evaluate the pulse width and chirp of a Ti:sapphire laser. Due to a wide frequency domain available for a gas, [...] Read more.

A gas was utilized in producing the third harmonic emission as a nonlinear optical medium for autocorrelation and frequency-resolved optical gating measurements to evaluate the pulse width and chirp of a Ti:sapphire laser. Due to a wide frequency domain available for a gas, this approach has potential for use in measuring the pulse width in the optical (ultraviolet/visible) region beyond one octave and thus for measuring an optical pulse width less than 1 fs. Full article

(This article belongs to the Special Issue Multi-Color Laser Emission for the Generation of Ultrashort Optical Pulse)

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6685 KiB

Open AccessArticle

Adaptive Filtering Queueing for Improving Fairness

by Jui-Pin Yang

Appl. Sci. 2015, 5(2), 122-135; https://doi.org/10.3390/app5020122 - 5 Jun 2015

Cited by 3 | Viewed by 5143

Abstract

In this paper, we propose a scalable and efficient Active Queue Management (AQM) scheme to provide fair bandwidth sharing when traffic is congested dubbed Adaptive Filtering Queueing (AFQ). First, AFQ identifies the filtering level of an arriving packet by comparing it with a [...] Read more.

In this paper, we propose a scalable and efficient Active Queue Management (AQM) scheme to provide fair bandwidth sharing when traffic is congested dubbed Adaptive Filtering Queueing (AFQ). First, AFQ identifies the filtering level of an arriving packet by comparing it with a flow label selected at random from the first level to an estimated level in the filtering level table. Based on the accepted traffic estimation and the previous fair filtering level, AFQ updates the fair filtering level. Next, AFQ uses a simple packet-dropping algorithm to determine whether arriving packets are accepted or discarded. To enhance AFQ’s feasibility in high-speed networks, we propose a two-layer mapping mechanism to effectively simplify the packet comparison operations. Simulation results demonstrate that AFQ achieves optimal fairness when compared with Rotating Preference Queues (RPQ), Core-Stateless Fair Queueing (CSFQ), CHOose and Keep for responsive flows, CHOose and Kill for unresponsive flows (CHOKe) and First-In First-Out (FIFO) schemes under a variety of traffic conditions. Full article

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663 KiB

Open AccessArticle

SnCl₄·5H₂O: A Highly Efficient Catalyst for Hydration of Alkyne

by Dongxue Chen, Dantong Wang, Wei Wu and Linfei Xiao

Appl. Sci. 2015, 5(2), 114-121; https://doi.org/10.3390/app5020114 - 21 May 2015

Cited by 13 | Viewed by 9397

Abstract

SnCl₄·5H₂O is a highly efficient catalyst in the hydration of terminal alkynes that affords carbonyl compounds in high to good yields. Under the optimized reaction conditions, the moderate to excellent yields of corresponding ketones were obtained when the aromatic [...] Read more.

SnCl₄·5H₂O is a highly efficient catalyst in the hydration of terminal alkynes that affords carbonyl compounds in high to good yields. Under the optimized reaction conditions, the moderate to excellent yields of corresponding ketones were obtained when the aromatic and aliphatic terminal alkynes were used as substrates. With using diphenylacetylene as an internal alkyne, the corresponding ketone was not detected in the reaction mixture. Full article

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2636 KiB

Open AccessReview

by Jordi Naqui, Lijuan Su, Javier Mata and Ferran Martín

Appl. Sci. 2015, 5(2), 88-113; https://doi.org/10.3390/app5020088 - 18 May 2015

Cited by 2 | Viewed by 7586

Abstract

This paper reviews the recent progress in the analysis and applications of the symmetry-related electromagnetic properties of transmission lines loaded with symmetric configurations of resonant elements. It will be shown that the transmission characteristics of these reactively loaded lines can be controlled by [...] Read more.

This paper reviews the recent progress in the analysis and applications of the symmetry-related electromagnetic properties of transmission lines loaded with symmetric configurations of resonant elements. It will be shown that the transmission characteristics of these reactively loaded lines can be controlled by the relative orientation between the line and the resonant elements. Two main types of loaded lines are considered: (i) resonance-based structures; and (ii) frequency-splitting structures. In resonance-based transmission lines, a line is loaded with a single resonant (and symmetric) element. For a perfectly symmetric structure, the line is transparent if the line and resonator exhibit symmetry planes of different electromagnetic nature (electric or magnetic wall), whereas the line exhibits a notch (resonance) in the transmission coefficient if the symmetry planes behave as either electric or magnetic walls (symmetric configuration), or if symmetry is broken. In frequency-splitting lines, paired resonators are typically loaded to the transmission line; the structure exhibits a single notch for the symmetric configuration, whereas generally two split notches appear when symmetry is disrupted. Applications of these structures include microwave sensors (e.g., contactless sensors of spatial variables), selective mode suppressors (of application in common-mode suppressed differential lines, for instance) and spectral signature barcodes, among others. Full article

(This article belongs to the Special Issue Feature Papers)

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1067 KiB

Open AccessArticle

Excess Phase Noise Characterization in Multifrequency Remote Clock Distribution Based on Femtosecond Frequency Combs

by Changjun Hu, Ravi P. Gollapalli, Lin Yang and Lingze Duan

Appl. Sci. 2015, 5(2), 77-87; https://doi.org/10.3390/app5020077 - 7 May 2015

Cited by 5 | Viewed by 5987

Abstract

Remote distribution of optical frequency references, based on multifrequency sources such as femtosecond frequency combs, holds many advantages over its single-frequency counterpart. However, characterizing the excess noise caused by the transmission links or external perturbations in a multifrequency scheme posts new challenges. We [...] Read more.

Remote distribution of optical frequency references, based on multifrequency sources such as femtosecond frequency combs, holds many advantages over its single-frequency counterpart. However, characterizing the excess noise caused by the transmission links or external perturbations in a multifrequency scheme posts new challenges. We have experimentally demonstrated direct measurement of excess phase noise spectrum in both free-space and fiber-optic transfer of a frequency comb using a multiheterodyne technique. In fiber-optic distribution, we focused on the excess phase noise under a single-tone acoustic perturbation. Increased overall noise power and a change of phase noise spectrum have been observed. In free-space distribution, a fractional instability of 3 × 10⁻¹⁴ at 1 s was observed for a 60 m outdoor atmospheric transmission, and large phase modulation due to air fluctuations causes a sizable line broadening. Full article

(This article belongs to the Special Issue Feature Papers)

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1650 KiB

Open AccessArticle

Numerical Models for Exact Description of in-situ Digital In-Line Holography Experiments with Irregularly-Shaped Arbitrarily-Located Particles

by Marc Brunel, Wisuttida Wichitwong, Sébastien Coetmellec, Adrien Masselot, Denis Lebrun, Gérard Gréhan and Guillaume Edouard

Appl. Sci. 2015, 5(2), 62-76; https://doi.org/10.3390/app5020062 - 22 Apr 2015

Cited by 6 | Viewed by 5192

Abstract

We present the development of a numerical simulator for digital in-line holography applications. In-line holograms of arbitrarily shaped and arbitrarily located objects are calculated using generalized Huygens-Fresnel integrals. The objects are 2D opaque or phase objects. The optical set-up is described by its [...] Read more.

We present the development of a numerical simulator for digital in-line holography applications. In-line holograms of arbitrarily shaped and arbitrarily located objects are calculated using generalized Huygens-Fresnel integrals. The objects are 2D opaque or phase objects. The optical set-up is described by its optical transfer matrix. A wide variety of optical systems, involving windows, spherical or cylindrical lenses, can thus be taken into account. It makes the simulator applicable for design and description of in situ experiments. We discuss future applications of this simulator for detection of nanoparticles in droplets, or calibration of airborne instruments that detect and measure ice crystals in the atmosphere. Full article

(This article belongs to the Special Issue Feature Papers)

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3368 KiB

Open AccessArticle

Sum-Frequency-Generation-Based Laser Sidebands for Tunable Femtosecond Raman Spectroscopy in the Ultraviolet

by Liangdong Zhu, Weimin Liu, Yanli Wang and Chong Fang

Appl. Sci. 2015, 5(2), 48-61; https://doi.org/10.3390/app5020048 - 16 Apr 2015

Cited by 19 | Viewed by 9307

Abstract

Femtosecond stimulated Raman spectroscopy (FSRS) is an emerging molecular structural dynamics technique for functional materials characterization typically in the visible to near-IR range. To expand its applications we have developed a versatile FSRS setup in the ultraviolet region. We use the combination of [...] Read more.

Femtosecond stimulated Raman spectroscopy (FSRS) is an emerging molecular structural dynamics technique for functional materials characterization typically in the visible to near-IR range. To expand its applications we have developed a versatile FSRS setup in the ultraviolet region. We use the combination of a narrowband, ~400 nm Raman pump from a home-built second harmonic bandwidth compressor and a tunable broadband probe pulse from sum-frequency-generation-based cascaded four-wave mixing (SFG-CFWM) laser sidebands in a thin BBO crystal. The ground state Raman spectrum of a laser dye Quinolon 390 in methanol that strongly absorbs at ~355 nm is systematically studied as a standard sample to provide previously unavailable spectroscopic characterization in the vibrational domain. Both the Stokes and anti-Stokes Raman spectra can be collected by selecting different orders of SFG-CFWM sidebands as the probe pulse. The stimulated Raman gain with the 402 nm Raman pump is >21 times larger than that with the 550 nm Raman pump when measured at the 1317 cm⁻¹ peak for the aromatic ring deformation and ring-H rocking mode of the dye molecule, demonstrating that pre-resonance enhancement is effectively achieved in the unique UV-FSRS setup. This added tunability in the versatile and compact optical setup enables FSRS to better capture transient conformational snapshots of photosensitive molecules that absorb in the UV range. Full article

(This article belongs to the Special Issue Multi-Color Laser Emission for the Generation of Ultrashort Optical Pulse)

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Appl. Sci., Volume 5, Issue 2 (June 2015) – 8 articles , Pages 48-156

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