New UV optic for submicron laser processing with a frequency quadrupled Nd:YAG laser

Peter B. Heekenjann; Holger Schmidt

doi:10.1117/12.193107

4 November 1994 New UV optic for submicron laser processing with a frequency quadrupled Nd:YAG laser

Peter B. Heekenjann, Holger Schmidt

Proceedings Volume 2246, Laser Materials Processing and Machining; (1994) https://doi.org/10.1117/12.193107
Event: Optics for Productivity in Manufacturing, 1994, Frankfurt, Germany

Abstract

A new UV-optic with an integrated autofocus sensor has been developed for submicron laser processing. In general, a distinction can be made between reflective and refractive objectives. Both have different advantages and disadvantages and, therefore, must be adapted to the application. For refractive objectives designed for UV-purposes, only a limited number of materials are available. With a small spectral bandwidth, such as that for some laser sources, an all quartz lens can be used. The frequency quadrupled Nd:YAG laser already has in its basic set-up a spectral bandwidth of less than 100 GHz. In the seeded mode, only one longitudinal mode will be excited. In order to achieve focus diameters below 0.5 micrometers , at least an N.A. of 0.65 is necessary. Such an objective has been designed and built at the Laser Zentrum Hannover (LZH). For this objective, automatic focussing aids are necessary. They have to ensure that the focal plane is within the depth-of-focus (DOF), which is below +/- 0.4 micrometers for the designed objective. Currently, all available sensors in this area show major drawbacks concerning the desired flexibility in being used for different laser processes. Therefore, a sensor, based on the autofocus principle, has been modified and built at the LZH. The results have proven that the resolution and the mean deviation are within the desired range (DOF).

Citation Download Citation

Peter B. Heekenjann and Holger Schmidt "New UV optic for submicron laser processing with a frequency quadrupled Nd:YAG laser", Proc. SPIE 2246, Laser Materials Processing and Machining, (4 November 1994); https://doi.org/10.1117/12.193107

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