UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

Guest
2024-11-24 23:06
 HOME     CONFERENCES     SEARCH            LOGIN     NEW USER     IMAGES   


Conference: Bucharest University Faculty of Physics 2003 Meeting


Section: Optics, Spectroscopy, Plasma and Lasers


Title:
DIFFRACTIVE OPTICAL ELEMENT MADE BY WET ETCHING OF GLASS


Authors:
Mihai Kusko1, Dan Cojoc2, Raluca Muller1, Elena Manea1, Cecilia Podaru1


Affiliation:
1 National Institute for Research and Development in Microtechnologies IMT-Bucharest

2University Politechnica of Bucharest, CCO-Optoelectronics Research Center

Str. Erou Iancu Nicolae 32B, P.O. Box 38-160, Bucharest, 72225, Romania


E-mail


Keywords:


Abstract:
In this work is described the fabrication of a binary phase-contrast diffractive optical element (DOE) working in transmission obtained by wet etching of glass substrate. The contrast based Does are more efficient than the amplitude based DOEs. The diffractive optical element structure is a square of 4-mm2 area. Each DOE consists of 40000 pixels, the dimensions of each pixel is 10 ƒÝm „e10 ƒÝm. The working wavelength is 675 nm. This DOE was projected for focussing the radiation in three collinear points. We used a chrome mask to reproduce the DOE¡¦s pattern. The DOEs were obtained using Corning glass. In order to obtain a ƒà phase difference the glass substrate must be selectively etched. This was made by wet etching of glass in KOH solution through Cr/Au mask. The Cr/Au mask was obtained by photolithography. The use of KOH solution provides a reasonably roughness of etched surface and a low rate etching rate. The depth control was performed using a profilometer. The thickness of Cr/Au mask was measured before starting the etching process. The knowledge of metal mask thickness was necessary in order to estimate the etching depth only. After the mask removal, the diffractive optical element is finished. We use a 670 nm wavelength laser diode for DOE characterization. At a certain distance between glass plate with DOEs and video camera detector, the intensity pattern is close to the intensity distribution obtained by simulation.