Fabrication of IR microlens using a fiber laser

Abstract

In two subsequent stages, various types of silicon microlenses were fabricated. A fiber laser of 1.06 µm was employed to ablate micro dips at the silicon surface and then a mixed acid solution was used to etch the wafer ultrasonically. The experimental data demonstrate spherical, cylindrical IR microlenses and IR microlens array formation with an optimum numerical aperture of 2.39 minimum microlens height of 21 μm, diameter of 32 μm and focal length of 6.7 μm with maximum resolution of 0.395 μm and magnification of (44X) was achieved. The minimum experimentally achieved microlens’ roughness was 45 nm. Theoretical calculations were conducted to estimate the temperature at the silicon surface during the ablation stage. A temperature of approximately 3590 K is established at the center of the laser-silicon in the ablation stage. Due to the controllable laser micromachining process, optoelectronics and biological imaging are viable applications for IR microlens arrays.

KEYWORDS:

• IR microlens array
• laser ablation of silicon
• chemical etching
• silicon micro machining

Acknowledgments

This work was done at the Laser and Optoelectronics Engineering department, College of Engineering, Al-Nahrain University, Iraq, as a partial requirement of a Ph.D. degree in laser and optoelectronics engineering. Author contributions: Conceptualization, B.R.; methodology, B.R.; software/numerical models, M.M.; experimental setup, M.M. and B.R.; experiments and formal analysis, M.M. and B.R.; validation, B.R..; investigation, B.R.; data curation, M.M.; writing, M.M. and B.R.; supervision, project administration, resources and funding acquisition, B.R. All authors have read and agreed to the published version of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

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Additional information

Notes on contributors

Muaath J. Mahmoud

Muaath J. Mahmoud Ph.D. in laser and optoelectronic engineering department in al Nahrain University.

Bassam G. Rasheed

Bassam G. Rasheed Ph.D. in nanotechnology, Prf. Dr. in laser and optoelectronic engineering department in al Nahrain University.