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

The accelerating developments in micro- and nanotechnology require faster and more precise tools for application and diagnostics. A new ultra-fast diagnostics is presented as an advancement of a conventional phase microscopy method (Iatia QPm (TM)). 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 has been 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 have been observed coaxially in situ during melting and welding by TQPm. Technical glass plates (Schott D263) have been welded using an ultra-short pulsed laser. By the use of femtosecond laser radiation (t(p) = 350 fs, f(rep) = 1 MHz) focused by a microscope objective (2 omega(0) approximate to 4 mu m) at the interface, multi-photon absorption is the dominant phenomenon. This causes heat accumulation and thereby glass melting and welding.