Search results for "Grating"
showing 10 items of 366 documents
High-harmonic km-long self-pulsed Raman fiber laser
2011
Raman all-fiber lasers have attracted considerable interest during the past two decades due to their convenient use and extended wavelength coverage when compared to rare-earth-doped fiber lasers. Still, little is known about their potential as pulsed laser sources. Mode locked Raman fiber lasers have been demonstrated quite recently [1,2], as well as harmonic mode-locking with a record of 500,000 intra-cavity pulses in a dissipative four-wave mixing configuration using a fiber Bragg grating [3].
Synthesis of optical pulses by use of similaritons.
2009
We propose and demonstrate experimentally a novel method for synthesizing chirp-free pulses of any desired temporal shape by means of chirp compensation and spectral filtering of optical Raman similaritons. The synthesized pulse shape is independent of the waveform, wavelength and energy of the initial pulses that are used for the similariton generation. Pulses are fully characterized by means of different techniques including cross-correlation and spectrum measurements, and the PICASO technique.
Actively mode-locked fiber laser with an acousto-optic in-fiber superlattice modulator
2009
All-fiber lasers permit the development of efficient, robust and compact coherent light sources. However, all-fiber active mode-locking is a challenging objective and very few all-fiber techniques have been published [1–3]. The development of a low-insertion-loss acoustically-induced superlattice modulator that works in the MHz range has demonstrated its suitability to perform active mode-locking of an all-fiber laser. While travelling extensional acoustic waves launched along a fiber Bragg grating (FBG) produce stationary side bands and a frequency shift [4,5], we found that the excitation of a standing extensional acoustic wave should produce no frequency shift, but the amplitude modulati…
Actively mode-locked fibre ring laser based on in-fibre acousto-optic amplitude modulation
2011
Recent advances in the development of all-fibre amplitude modulators have led to the implementation of a series of different actively mode-locked fibre lasers [1–4]. In-fibre acousto-optic modulation based on intermodal coupling induced my a standing flexural acoustic wave permits the implementation of broad bandwidth (1.5 nm), high modulation depth (0.72), low-insertion-loss (0.75 dB) all-fibre amplitude modulators that operate in the MHz frequency range. The experimental characterization of a laser with the configuration depicted in Fig. 1 (a) as a function of the radio frequency voltage that controls the modulator (see Fig. 1 (b)), the length of the Erbium doped fibre (EDF), and the opti…
Thermally induced emission of light from a metallic diffraction grating, mediated by surface plasmons
1999
The angular emission of light of wavelength 710 and 810 nm from a gold diffraction grating was studied at about 700°C. A peak in the emission was found for defined angles. This contribution is purely TM-polarised and is attributed to thermally excited surface plasmons, coupled to light waves by the diffraction grating.
Differential method for modeling dielectric-loaded surface plasmon polariton waveguides
2008
This paper demonstrates the efficiency of the differential method, a conventional grating theory, to investigate dielectric loaded surface plasmon polariton waveguides (DLSPPWs), known to be a potential solution for optical interconnects. The method is used to obtain the mode effective indices (both real and imaginary parts) and the mode profiles. The results obtained with the differential method are found to be in good agreement with those provided by the effective index method or finite elements. The versatility of the differential method is demonstrated by considering complex configurations such as trapezoidal waveguides or DLSPPWs lying on a finite width metal stripe.
Broadband asymmetric transmission of THz radiation through double metallic gratings
2013
We analyse numerically and experimentally the asymmetric transmission through sub-wavelength double metallic gratings. The possibility of achieving a broadband unidirectional transmission of THz waves through the grating is confirmed. The proposed gratings allow for efficient one-way transmission in the wavelength range from 2.5 to 3.5 mm.
Functionalized planar Bragg grating sensor for the detection of BTX in solvent vapor
2012
We report on an optical planar Bragg grating evanescent wave refractive index sensor functionalized by a simple method against aromatic hydrocarbons such as benzene, toluene and xylene (BTX) in solvent vapor. To functionalize the sensor against BTX, substituted cyclodextrins are applied to the sensor surface using dip coating. Cyclodextrins have a hydrophobic cavity, which favors the accommodation of an organic molecule of appropriate dimensions leading to a non-covalent inclusion complex. The temporal sensor response reveals a multi-exponential rise towards an equilibrium state, whose level is found to be linearly related to the exposed analyte concentration. Taking into account the spectr…
Wavelength multiplexed hydrogen sensor based on palladium-coated fibre-taper and Bragg grating
2004
A novel configuration of a wavelength multiplexed hydrogen sensor based on a palladium-coated tapered fibre and a fibre Bragg grating is presented. This scheme allows cascading several sensors along a single fibre, which increases the capability of implementing multipoint sensor networks for volumetric detection. Moreover, in this configuration the light interacts twice with the palladium layer, thus enhancing the sensitivity of the sensor.
Holographic recording in amorphous chalcogenide thin films
2007
Abstract Holographic recording by He–Ne laser (line 632.8 nm) light in amorphous As 0.55 Se 0.45 thin films for different film thickness and grating period was studied. A strong dependence of the diffraction efficiency of the gratings on the readout light wavelength (650 nm, 805 nm and 1150 nm) was observed. A decrease in diffraction efficiency for longer wavelengths is explained by a decrease in the photoinduced changes of refractive index. It is shown that high efficiency gratings can be recorded in As 0.55 Se 0.45 films with a thickness of ∼1 μm.