Search results for "WAVELENGTH"
showing 10 items of 741 documents
Modulation of coaxial modal interferometers based on long period gratings in double cladding fibers
2009
This paper reports on the dynamic modulation of coaxial interferometers based on two cascaded long period gratings written in double cladding fibers. The interferometer is modulated by a piezoelectric ceramic which stretches one the gratings at tens of kHz, the output light is intensity modulated with an efficiency of 97 %. The device operates at 1530nm, has more than 50nm bandwidth, insertion loss of 0.4 dB and a temperature drift of 0.11 nm/ degrees C.
Continuous-wave spontaneous lasing in mercury pumped by resonant two-photon absorption
2010
The first continuous-wave two-photon absorption laser-induced stimulated emission (CTALISE) is demonstrated. The 7^1S-6^1P transition in mercury at 1014nm wavelength is used and selective lasing of different isotopes is observed.
Photo-acoustic excitation and detection of guided ultrasonic waves in bone samples covered by a soft coating layer
2012
Photo-acoustic (PA) excitation was combined with skeletal quantitative ultrasound (QUS) for multi-mode ultrasonic assessment of human long bones. This approach permits tailoring of the ultrasonic excitation and detection so as to efficiently detect the fundamental flexural guided wave (FFGW) through a coating of soft tissue. FFGW is a clinically relevant indicator of cortical thickness. An OPO laser with tunable optical wavelength, was used to excite a photo-acoustic source in the shaft of a porcine femur. Ultrasonic signals were detected by a piezoelectric transducer, scanning along the long axis of the bone, 20-50 mm away from the source. Five femurs were measured without and with a soft …
Azodyed gelatin films for holographic recording
2013
Abstract In this work we present a preparation method of azo-dyed gelatin thin films for holographic recording and their photoinduced changes of optical properties. The non-toxic, commercially available and cheap ingredients were used for film preparation. The films were prepared by mixing azo-dyes with gelatin solution. The photoinduced properties of prepared films were investigated. The photoinduced dichroism and birefringence at 532 nm laser radiation were observed. The holographic recording of surface and volume gratings by 532 nm wavelength laser radiation were performed and surface relief gratings were studied with AFM. The mass transport direction in azodyed gelatin was studied.
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.
Surface relief grating recording in azo polymer films
2013
In this work holographic recording of surface relief grating in organic Poly(Disperse Red 1 – methacrylate) thin films was studied. In this compound azo dye is chemically bonded to monomers making mass transport very efficient in the presence of optical field gradient. Sample preparation was performed using different solvents and coating methods. In the obtained samples holographic recording was performed by solid-state diode pump laser with 532 nm wavelength. Polarization grating and surface relief grating formation was studied by diode laser with 660 nm wavelength. Diffraction efficiency's dependence on read-out laser beam polarization state was investigated. The depth of surface relief g…
Microwave phase shifter based on fibre Bragg grating
1998
A variable delay line is presented for phased array antennas based on a fibre Bragg grating which has a uniform period and operates at constant optical wavelength. The Bragg wavelength of a localised part of the fibre grating is modified by straining the fibre, the optical carrier is reflected by the strained part of the grating and the time delay of the microwave modulating signal is determined by the position where the strain has been applied. In this initial experiment time delay variations up to 330 ps in the frequency range 1 – 14 GHz have been achieved.
Ultraviolet radiation at Mediterranean latitudes and protection efficacy of intraocular lenses.
2011
Summary Purpose After determining the mean intensity of ultraviolet radiation to which the human eye is exposed at Mediterranean latitudes, this data is used to evaluate the efficacy of the ultraviolet filters incorporated into various intraocular lenses. Methods Ultraviolet radiation measured at Mediterranean latitudes was used as a reference for the theoretical calculation of the amount of radiation to which the human eye is exposed. The spectral transmission curve from 290 to 380 nm was measured for 10 IOLs using a UV/VIS Perkins-Elmer Lambda 800 spectrometer. Results At Mediterranean latitudes, at sea level, with a mean annual solar irradiation of 50 j/cm 2 , the human eye receives a qu…
Optical-field induced volume- and surface-relief formation phenomenon in thin films of vitreous chalcogenide semiconductors
2013
In this report the study of direct recording of the surface relief gratings on amorphous chalcogenide thin (2.5-5μm) films is presented by three different recording setups. Recording was performed on As2S3 by 532nm wavelength laser light. Additionally the evolution of surface relief in dependence from the recording time and polarization has been investigated in detail. The mechanism of the direct recording of surface relief on amorphous chalcogenide films based on the photo-induced plasticity has been discussed.
Quantitative Optical Trapping of Single Gold Nanorods
2008
We report a quantitative analysis of the forces acting on optically trapped single gold nanorods. Individual nanorods with diameters between 8 and 44 nm and aspect ratios between 1.7 and 5.6 were stably trapped in three dimensions using a laser wavelength exceeding their plasmon resonance wavelengths. The interaction between the electromagnetic field of an optical trap and a single gold nanorod correlated with particle polarizability, which is a function of both particle volume and aspect ratio.