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| − | *Taking the X and Y projections of the focused beam and fitting them with a Gaussian distribution, | + | *Taking the X and Y projections of the focused beam and fitting them with a Gaussian distribution,we are able to attain <math>\sigma_{X} = 0.63mm\,</math> and <math>\sigma_{Y} = 0.23mm \,</math>. |
| | {| cellpadding="3" style="text-align:center; margin: 1em auto 1em auto" | | {| cellpadding="3" style="text-align:center; margin: 1em auto 1em auto" |
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| − | we are able to attain <math>\sigma_{X} = 0.63mm\,</math> and <math>\sigma_{Y} = 0.23mm \,</math>.
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| | *Assuming a Gaussian distribution at the waist of the beam, we now find the FWHM (full width at half maximum) by the following relation, | | *Assuming a Gaussian distribution at the waist of the beam, we now find the FWHM (full width at half maximum) by the following relation, |
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| | :<math>\mathrm{FWHM} = 2 \sqrt{2 \ln 2}\ \sigma. </math> | | :<math>\mathrm{FWHM} = 2 \sqrt{2 \ln 2}\ \sigma. </math> |
| − | *The smallest value of <math>\mathrm{FWHM_{X}}</math> and <math>\mathrm{FWHM_{Y}}</math> were 1.49mm and 0.552mm respectively. | + | *The smallest values of <math>\mathrm{FWHM_{X}}</math> and <math>\mathrm{FWHM_{Y}}</math> were 1.49mm and 0.552mm respectively. |
| − | *The Rayleigh Length, <math>\mathrm{Z_{R}}</math> is defined as the distance from the beam waist along the axis of propagation to the point where its cross section is doubled, <math>\mathrm\omega_{R}</math>. Taking <math>\mathrm\omega_{0}</math> as the beam waist, and using the <math>\mathrm{FWHM}</math> as its value we are looking for the point where | + | *The Rayleigh Length, <math>\mathrm{Z_{R}}</math> is defined as the distance from the beam waist along the axis of propagation to the point where its cross section is doubled (<math>\mathrm\omega_{R}</math>). This value represents the "play" we will have when trying to focus the beam onto the diamond target for ablation. Taking <math>\mathrm\omega_{0}</math> as the beam waist, and using the <math>\mathrm{FWHM}</math> as its value we are looking for the point where, |
| | :<math>\omega_{R} = \sqrt{2}\ \omega_{0}. </math> | | :<math>\omega_{R} = \sqrt{2}\ \omega_{0}. </math> |
| | [[Image:rayleigh.png|center|thumb|400px|Describes the Rayleigh Length of a beam waist <math>\omega_{0}</math>.]] | | [[Image:rayleigh.png|center|thumb|400px|Describes the Rayleigh Length of a beam waist <math>\omega_{0}</math>.]] |
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| | + | *Knowing <math>\mathrm\omega_{0}</math> also allows us to calculate the theoretical fluence of the beam. Assuming maximum power of 220mJ over a 1.49mm x 0.552mm area yields <math>26J/cm^2.</math> Which is above the <math>14J/cm^2.</math> threshold value cited by Brookhaven National Laboratories who were conducting diamond ablation experiments with a 213nm Nd:YAG laser (213nm with the use of a 4 + 1 frequency mixing crystal). Our ArF excimer laser produces 193nm light that will be more readily absorbed by the surface of the diamond as diamond is opaque to wavelengths above the band gap. These calculations provide a level of confidence that we theoretically be able to ablate. |