The units of the optical intensity (or light intensity) are W/m 2 or (more commonly) W/cm 2.
Assuming that you know the repetition rate of your laser (it can be measured using a fast oscilloscope) you just need to divide the measured average power by the rep rate to obtain the pulse energy E and to calculate the photon number through n=E/(h.v) subsequently, where v may be approximated by the central frequency of the pulsed laser noting to the fact that pulsed lasers are not monochromatic.
As an example, for a typical femtosecond laser with the central wavelength in the near-IR range the spectral width can be above 10 nm. For an aperture radius of 1.5 w or 2 w, this fraction is increased to 98.9% and 99.97%, respectively. or if any other way to calculate then please let me know. but you seem to have only a number of photons.- the surface of the spot, to obtain an intensity in xxx/m²- to convert photon into W, you need to know the amount of photon which arrive per unit of time. The shape of a Gaussian beam of a given wavelength λ is governed solely by one parameter, the beam waist w0. 12 for vertical path the intensity of CBC beam is close to single wavelet beam (dashed black and red curves) whereas the intensity of full aperture Gaussian beam falls much faster.
These beams can be dealt with using the above two evolution equations, but with distinct values of each parameter for An elliptical beam will invert its ellipticity ratio as it propagates from the far field to the waist. The dimension which was the larger far from the waist, will be the smaller near the waist.
The equations below assume a beam with a circular cross-section at all values of Since this solution relies on the paraxial approximation, it is not accurate for very strongly diverging beams. The word "intensity" as used here is not synonymous with "If one integrates over a surface of uniform intensity If the medium is damped, then the intensity drops off more quickly than the above equation suggests. How can I calculate the spot size of a focused laser beam?I want to calculate the spot size of a laser beam focused through microscope objective. In physics, intensity of radiant energy is the power transferred per unit area, where the area is measured on the plane perpendicular to the direction of propagation of the energy. It also varies along direction of travel due to focusing and attenuation.
Gaussian beam : PowerGaussian beam : Power The result is independent of z, as expected.
Optics & Laser Tec...Join ResearchGate to find the people and research you need to help your work.© 2008-2020 ResearchGate GmbH. For a monochromatic propagating electromagnetic wave, such as a and the local intensity is obtained by multiplying this expression by the wave velocity, c/For non-monochromatic waves, the intensity contributions of different spectral components can simply be added.
For mode-locked lasers, the shorter the pulse duration the wider the spectral width is in general. 136 0 obj <>
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Intensity Formula Intensity is the quantity of energy the wave conveys per unit time across a surface of unit area and it is also equivalent to the energy density multiplied by the wave speed. How can I calculate the Absorption coefficient from Absorbance?I prepare thin film of ZnO by pld and measured its Absorbance Uv-Vis ,then i need to Calculate Absorption coefficient from Uv.Vis.
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Cheers..National Centre for Physics, Quaid-i-Azam University, Islamabad, PakistanRegarding the second part of your answer which takes the pulsed lasers into account, it is important to note that (pulse energy)/(pulse duration) is in fact the "peak power" and not the "average power" which one can directly measure in the lab using a detector head.
hc=12400 ev*A, A is a length unit=0.1nm. This also shows the usefulness of the concept of fluence as in that case, E can be easily calculated as I explained above and one only needs to measure the spot size on the (solid) sample to obtain the fluence.Really Dr. Muhammad Aslam Baig gave good elaboration of how to obtain the the laser intensity. One should also note that in general, the average and the peak powers differ by several orders of magnitude.
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