Dynamical detection of optical phase changes during micro-welding of glass with ultra-short laser radiation

A. Horn, I. Mingareev, J. Gottmann, A. Werth, U. Brenk
Meas. Sci. Technol. Vol. 19, p. 015302
2008

FCPA µJewel D-400

Accelerating developments in micro- and nanotechnology require faster, more precise tools for application and diagnostics. A new ultra-fast diagnostics is presented as an advancement of a conventional phase microscopy method (Iatia QPmTM). In contrast to the conventional method using one CCD to detect three object planes, three CCDs detect these planes separately and simultaneously. The measurement technique named TQPm was analyzed and validated by measuring the optical phase of a commercial fiber. This novel visualization technique affords reliable quantitative time-resolved measurements of the optical phase, the transient refractive index or the dynamical geometry changes. The structural and optical modifications of welded glass were observed coaxially in situ during melting and welding by TQPm. Technical glass plates (Schott D263) were welded using femtosecond laser radiation (tp = 350 fs, frep = 1 MHz) focused by a microscope objective (2ω0 ≈ 4 µm) at the interface. Multi-photon absorption is the dominant phenomenon, causing heat accumulation and thereby glass melting and welding.

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