Wavelength-frequency conversions

See A. G. Pachoiczyk, Radio A.strophysics, Freeman, New York 1970. Figure A3, p. 236 an excellent chart of frequency-wavelength conversions. 

A number of other up-conversion processes are known. The blue emission from a Yb3+/Tm3+ couple in which the active emitters are defect Tm3+ centers is mainly due to the efficient excitation ET process from Yb3+ centers. Two-frequency up-conversion has been investigated using Pr3+ defects in a fluoride glass matrix. Illumination with one pump wavelength results in GSA, while simultaneous irradiation with a second pump wavelength further excites the GSA centers via ESA. The doubly excited defects emit red light. Up-conversion and visible output only takes place at the intersection of the two beams. 

A prominent example of the latter is harmonic generation or frequency up-conversion. Here, a high-quality long wavelength laser beam is converted to the soft X-ray region through the nonlinear response of certain transmitting... 

M.H. Chou, J. Hauden, M.A. Arhore, M.M. Feger 1.5 xm band wavelength conversion based on difference frequency generation in LiNbOa waveguide with integrated coupling structure. Opt. Lett. 23, 1004 (1998)... 

This behavior is consistent with experimental data. For high-frequency excitation, no fluorescence rise-time and a biexponential decay is seen. The lack of rise-time corresponds to a very fast internal conversion, which is seen in the trajectory calculation. The biexponential decay indicates two mechanisms, a fast component due to direct crossing (not seen in the trajectory calculation but would be the result for other starting conditions) and a slow component that samples the excited-state minima (as seen in the tiajectory). Long wavelength excitation, in contrast, leads to an observable rise time and monoexponential decay. This corresponds to the dominance of the slow component, and more time spent on the upper surface. 

Commercially, the irradiation of the 5,7-diene provitamin to make vitamin D must be performed under conditions that optimize the production of the previtamin while avoiding the development of the unwated isomers. The optimization is achieved by controlling the extent of irradiation, as well as the wavelength of the light source. The best frequency for the irradiation to form previtamin is 295 nm (64—66). The unwanted conversion of previtamin to tachysterol is favored when 254 nm light is used. Sensitized irradiation, eg, with fluorenone, has been used to favor the reverse, triplet-state conversion of tachysterol to previtamin D (73,74). 

This is a simple conversion problem. The link between wavelength (A) and frequency (v) is given by Equation. ... 

This conversion problem requires two steps. Equations and relate the energy of a photon to its frequency and wavelength. 

For, SHG it is desirable to fabricate fibres which allow single mode operation at the fundamental wavelength so that all the launched power is available for conversion. The frequencies for which single mode operation is possible in a step-index uniaxial crystal cored fibre with crystal axis along the fibre axis are given by (30.)... 

Energy conversion table. Values of photon (vacuum) wavelength (nm), wavenumber (1 cm-1), frequency (THz) and energy (eV, J), as well as the energy per mole (J mol-1) of a chemical reaction can be easily converted if a ruler is placed horizontally over the chart. The bandgaps of different semiconductors are also indicated, as well as the wavelength of the intensity peak of a blackbody radiation for different temperatures. 

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