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排序方式: 共有73条查询结果,搜索用时 62 毫秒
1.
G Padmaja A V Ravi Kumar V Vidyalal P Radhakrishnan V P N Nampoori C P G Vallabhan 《Pramana》1989,32(5):L693-L698
Laser induced plasma emission spectra from highT
c superconducting samples of YBa2Cu3O7 and GdBa2Cu3O7 obtained with 1.06μm radiation from a Q switched Nd:YAG laser beam has been analysed. The results clearly show the presence of diatomic oxides
in addition to ionized species of the constituent metals in the plasma thus produced. 相似文献
2.
Litty Irimpan A. Deepthy Bindu Krishnan V.P.N. Nampoori P. Radhakrishnan 《Applied physics. B, Lasers and optics》2008,90(3-4):547-556
In the present work, we have investigated the nonlinear optical properties of self-assembled films formed from ZnO colloidal
spheres by z-scan technique. The sign of the nonlinear component of refractive index of the material remains the same; however,
a switching from reverse saturable absorption to saturable absorption has been observed as the material changes from colloid
to self-assembled film. These different nonlinear characteristics can be mainly attributed to ZnO defect states and electronic
effects when the colloidal solution is transformed into self-assembled monolayers. We investigated the intensity, wavelength
and size dependence of saturable and reverse saturable absorption of ZnO self-assembled films and colloids. Values of the
imaginary part of third-order susceptibility are calculated for particles of size in the range 20–300 nm at different intensity
levels ranging from 40 to 325 MW/cm2 within the wavelength range of 450–650 nm.
PACS 81.16.Dn; 42.65.-k; 42.65.An; 42.70.-a; 42.70.Nq; 78.20.Ci 相似文献
3.
Experimental method for measuring photoacoustic(PA) signals generated by a pulsed laser beam in liquids is described. The
pulsed PA technique is found to be a convenient and accurate method for determination of quantum yield in fluorescent dye
solutions. Concentration dependence of quantum yield of rhodamine 6G in water is studied using the above method. The results
indicate that the quantum yield decreases with increase in concentration in the quenching region in agreement with the existing
reports based on radiometric measurements. 相似文献
4.
Achamma Kurian C V Bindhu S S Harilal Riju C Issac V P N Nampoori C P G Vallabhan 《Pramana》1994,43(5):401-406
A simple method based on laser beam deflection to study the variation of diffusion coefficient with concentration in a solution
is presented. When a properly fanned out laser beam is passed through a rectangular cell filled with solution having concentration
gradient, the emergent beam traces out a curved pattern on a screen. By taking measurements on the pattern at different concentrations,
the variation of diffusion coefficient with concentration can be determined. 相似文献
5.
C V Bindhu S S Harilal Riju C Issac Geetha K Varier V P N Nampoori C P G Vallabhan 《Pramana》1995,44(3):231-235
Pulsed photoacoustic measurements have been carried out in toluene at 532 nm wavelength using a Q-switched frequency doubled
Nd:YAG laser. The variation of photoacoustic signal amplitude with incident laser power indicates that at lower laser powers
one photon absorption takes place at this wavelength while a clear two photon absorption occurs in this liquid at higher laser
powers. The studies made here demonstrate that pulsed photoacoustic technique is simple and effective for the investigation
of multiphoton processes in liquids. 相似文献
6.
The online version of the original article can be found at 相似文献
7.
Ritty J. Nedumpara P.J. Manu C.P.G. Vallabhan V.P.N. Nampoori P. Radhakrishnan 《Optics & Laser Technology》2008,40(7):953-957
The energy transfer mechanism in C 540–rhodamine 6G and C 540–rhodamine B donor–acceptor (D–A) pairs is investigated. The good spectral overlap and the proximity of D–A pair molecules, which is around 60 Å, denote the possibility of resonance energy transfer between the D–A pairs. Energy transfer is studied in two solvent environments. C 540–Rh 6G and C 540–RhB D–A pairs behave in quite different manner in different solvent environments. 相似文献
8.
Joseph LK Dayas KR Damodar S Krishnan B Krishnankutty K Nampoori VP Radhakrishnan P 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(4):1281-1285
The laser-induced luminescence studies of the rare earth titanates (R2Ti2O7) (R=La, Nd and Gd) using 355 nm radiation from an Nd:YAG laser are presented. These samples with submicron or nanometer size are prepared by the self-propagating high temperature synthesis (SHS) method and there is no known fluorescence shown by these rare earths in the visible region. Hence, the luminescence transitions shown by the La2Ti2O7 near 610 nm and Gd2Ti2O7 near 767 nm are quite interesting. Though La3+ ions with no 4f electrons have no electronic energy levels that can induce excitation and luminescence processes in the visible region, the presence of the Ti3+ ions leads to luminescence in this region. 相似文献
9.
We report the preparation and investigation of nano colloidal solutions of Ge28Sb12Se60 chalcogenide glass based on nonlinear optical transmission by the open-aperture Z-scan technique, using nanosecond laser pulses, at the excitation wavelengths of 532 nm. The Z scan spectra reveal a strong non linear absorption (reverse saturable absorption) for the nano colloid Ge28Se60Sb12 solutions. Observation of optical limiting at excitation wavelength suggests the potential of these materials to be used as optical limiters. 相似文献
10.
C. Pradeep S. Mathew B. Nithyaja P. Radhakrishnan V. P. N. Nampoori 《Applied Physics A: Materials Science & Processing》2014,115(1):291-295
In this paper we study the nonlinear optical properties of PicoGreen dye. The investigations involve the single-beam Z-scan technique and measurements were carried out at different incident intensities. Both open and closed aperture Z-scan techniques were performed at 532 nm and it was found that the dye exhibited a reverse saturable absorption with significant nonlinear absorption coefficient and intensity-dependent negative nonlinear refraction coefficient, indicating self-defocusing phenomena. The third-order nonlinear susceptibility and optical limiting threshold were also measured. 相似文献