Refractive and geometric lens characterization through multi-wavelength digital speckle pattern interferometry

Physical parameters of different types of lenses were measured through digital speckle pattern interferometry (DSPI) using a multimode diode laser as light source. When such lasers emit two or more longitudinal modes simultaneously the speckle image of an object appears covered of contour fringes. By performing the quantitative fringe evaluation the radii of curvature as well as the refractive indexes of the lenses were determined. The fringe quantitative evaluation was carried out through the four- and the eight-stepping techniques and the branch-cut method was employed for phase unwrapping. With all these parameters the focal length was calculated. This whole-field multi-wavelength method does enable the characterization of spherical and aspherical lenses and of positive and negative ones as well. (C) 2007 Elsevier B.V. All rights reserved.

Measurement of low-derivative surface lenses by two-laser holography with Bi12TiO20 crystals

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Design, construction, and performance of a real-time holographic refractometry prototype for liquid analysis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Generation of copper nanoparticles induced by fs-laser irradiation in borosilicate glass

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Simple and versatile heterodyne whole-field interferometer for phase optics characterization

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Optical emission and electron capture of rare-earth trivalent ions located at distinct sites in SnO(2) thin films

We present photoluminescence and decay of photo excited conductivity data for sol-gel SnO(2) thin films doped with rare earth ions Eu(3+) and Er(3+), a material with nanoscopic crystallites. Photoluminescence spectra are obtained under excitation with several monochromatic light sources, such as Kr(+) and Ar(+) lasers, Xe lamp plus a selective monochromator with UV grating, and the fourth harmonic of a Nd: YAG laser (4.65eV), which assures band-to-band transition and energy transfer to the ion located at matrix sites, substitutional to Sn(4+). The luminescence structure is rather different depending on the location of the rare-earth doping, at lattice symmetric sites or segregated at grain boundary layer, where it is placed in asymmetric sites. The decay of photo-excited conductivity also shows different trapping rate depending on the rare-earth concentration. For Er-doped films, above the saturation limit, the evaluated capture energy is higher than for films with concentration below the limit, in good agreement with the different behaviour obtained from luminescence data. For Eu-doped films, the difference between capture energy and grain boundary barrier is not so evident, even though the luminescence spectra are rather distinct.

Analytical expressions for the FM and AM responses of an integrated laser-modulator

The need for low-chirp and compact transmitters for high-bit-rate optical links has led to the development of integrated laser electroabsorption modulators (ILM). We have investigated feedback effects inducing frequency chirp by developing a model treating the ILM as a whole and obtained analytical expressions of the FM and AM responses. The variation of the frequency chirp with the residual facet reflectivity of the modulator section is calculated. The model predicts the unusual peak in the measured frequency responses and has been used to define design rules.

High resolution spectroscopy of 13CH3OH around the 10R(20) CO2 laser emission: New FIR laser lines, frequency measurement and assignments

We investigated the IR absorption spectrum of 13CH3OH around the frequency of the 10R(20) CO2 laser line. We found two absorption lines which can be excited by 10R(20) and studied the FIR laser emissions excited by this pump line using a waveguide CO2 laser of 300 MHz tunability. We report two new FIR laser lines of large offset, not previously observed due to their weakness and closeness to other stronger lines. We measured the frequencies of five FIR laser lines for the first time by an accurate heterodyne technique and present the complete assignments of the IR-FIR laser systems relative to this pump line. Furthermore we present new frequency values for two FIR laser lines whose frequencies had been previously wrongly measured. Copyright © 1997 Elsevier Science Ltd.

Frequency upconversion in Nd3+-doped fluoroindate glass

We report the observation of frequency upconversion in fluoroindate glasses with the following compositions: (mol%) (39 - x)InF3-20ZnF2-20SrF2-16BaF 2-2GdF3-2NaF-1GaF3-xNdF3 (x = 0.05, 0.1, 0.5, 1, 2, 3). The excitation source was a dye laser in resonance with the 4I9/2→(2G5/2, 2G7/2) transition of the Nd3+ ions. The upconverted fluorescence spectra show emissions from ∼ 350 to ∼ 450 nm, corresponding to transitions 4D3/2→4I9/2 ;4D3/2→4I11/2; 2P3/2→ 4I9/2; 4D3/2→4I13/2; 2P3/2→4I11/2; 4D3/2→4I15/2; and 2P3/2 → 4I13/2. The dependence of the fluorescence signals on the laser intensity indicates that two laser photons participate in the process. The temporal behavior of the signal indicates that energy transfer among the Nd3+ ions is the main mechanism which contributes to upconversion at 354 and 382 nm.

Time-resolved Z-scan and thermal lens measurements in Er+3 and Nd+3 doped fluoroindate glasses

In rare earth ion doped solids, a resonant non-linear refractive index, n2, appears when the laser pumps one of the ion excited states and the refractive index change is proportional to the excited state population. In these solids there are usually thermal and non-thermal lensing effects, where the non-thermal one is due to the polarizability difference, Δα, between excited and ground states of the ions. We have used the time resolved Z-scan and a mode-mismatched thermal lens technique with an Ar+ ion laser in Er+3 (20ZnF2-20SrF2-2NaF-16BaF2-6GaF3-(36 - x)InF3-xErF3, with x= 1, 2, 3 and 4 mol%) and Nd+3 (20SrF2-16BaF2-20ZnF2-2GdF3-2NaF-(40 - x)InF3-xNdF3, with x = 0.1, 0.25, 0.5-1 mol%) doped fluoroindate glasses. In both samples we found that the non-linear refraction is due to the thermal effect, while the non-thermal effect is negligible. This result indicates that in fluoride glasses Δα is very small (less than 10-26 cm3). We also measured the imaginary part of the non-linear refractive index (n″2) due to absorption saturation.

Violet-blue emissions due to frequency up-conversion in Nd3+-doped fluoroindate glasses

We report the observation of intense frequency up-conversion in Nd3+-doped fluoroindate glasses pumped by the second harmonic of a cw mode-locked Nd: YAG laser. Mechanisms for generating the observed emissions are discussed.

Intrapulpar temperature during continuous CO2 laser irradiation in human molars: An in vitro study

To establish safety parameters, we in vitro studied the increase in intrapulpal temperature caused by the use of a cw CO2 laser. A thermistor was implanted in the inner part of the pulpal chamber of 25 human lower third molars to measure the intrapulpal temperature produced by laser powers between 2-10 W and exposure times of 0.5-25.0 s. The Pearson linear correlation factor applied to the measured values showed there is a direct relationship between the independent variable and the applied power. A variance analysis produced the linear regression equation: T=1.10+(0.127)E where T is the temperature and E the energy. The results showed that, with a power of 4 W and maximum exposure time of 2.5 s (10 J) and a power density of 12738.85 W cm-2, there will be no damaging reactions affecting the pulpal tissues.