Usually, objective lenses used for laser machining have chromatic aberration, i.e. different colors of light are focused at different positions inside transparent materials. Additionally, transparent materials like glasses have chromatic dispersion. However, the wavelength band used for laser machining is very narrow (in the nano meter range or lower) and precise. Do such wavelengths suffer from the chromatic aberration effect present in the objective lenses?
More specifically, do chromatic aberration effect of the objective lenses or chromatic dispersion of materials have any impact on the size of the micro/nano-metric structures (especially holes), fabricated inside transparent materials?
Your laser has large energy. I would guess you will be operating above critical power densities in most of your applications (or throwing away many photons if you aren't processing with multiple beams) meaning that non-linear effects will kick in before you reach physical focusing limits (you can often see white light generation and filaments instead of voids in the glass). 200 fs isn't so short that I would expect spectral content to be the main limitation in your system's optical aberrations.
Dear Shamim, I suggest that you contact RG member Prof Dr Mihai Pascu for a precise answer given that he is one of the world's expert in this area.
Dear Leonard Amaral: Thanks for your information. Definitely, I'll contact with him.
Hi Shamim: We do a lot of generation of defects with ultrashort pulsed lasers in glass and the main issues you will have are spherical aberration because it is generated when focusing through glass. This can be compensated for with optical design of you focusing objective. We are also concerned with chromic aberration as well because our lasers have multiple nm of bandwidth. We need more information about your laser to help you properly.
We are using a femtosecond laser from Cyber Laser IFRIT (Japan), operating at the central wavelength of 786.5 nm with M^2 value of less than 1.5 (indicating single mode operation). The pulse repetition rate is 1 KHz and the pulse width is 183 fs.
Your laser has large energy. I would guess you will be operating above critical power densities in most of your applications (or throwing away many photons if you aren't processing with multiple beams) meaning that non-linear effects will kick in before you reach physical focusing limits (you can often see white light generation and filaments instead of voids in the glass). 200 fs isn't so short that I would expect spectral content to be the main limitation in your system's optical aberrations.
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