Micro-optoelectromechanical Systems (MOEMS)

Planar microlens with front-face angle: design, fabrication, and characterization

[+] Author Affiliations
Md. Abdullah Al Hafiz

King Abdullah University of Science and Technology, Physical Sciences and Engineering Division, Thuwal 23955-6900, Kingdom of Saudi Arabia

Aron Michael, Chee-Yee Kwok

The University of New South Wales, School of Electrical Engineering and Telecommunication, Anzac Parade, Kensington, New South Wales 2052, Australia

J. Micro/Nanolith. MEMS MOEMS. 15(3), 035501 (Jul 08, 2016). doi:10.1117/1.JMM.15.3.035501
History: Received March 18, 2016; Accepted June 15, 2016
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Abstract.  This paper studies the effect of microlens front-face angle on the performance of an optical system consisting of a planar-graded refractive index (GRIN) lens pair facing each other separated by a free-space region. The planar silica microlens pairs are designed to facilitate low-loss optical signal propagation in the free-space region between the opposing optical waveguides. The planar lens is fabricated from a 38-μm-thick fluorine-doped silica layer on a silicon substrate. It has a parabolic refractive index profile in the vertical direction, which is achieved by controlled fluorine incorporation in the silica film to collimate the optical beam in the vertical direction. Horizontal beam collimation is achieved by incorporating a horizontal curvature at the front face of the lens defined by deep oxide etch. A generalized 3×3ABCDGH transformation matrix method has been derived to compute the coupling efficiency of such microlens pairs to take front-face angles that may be present due to fabrication variations or limitations and possible input/output optical fiber offset/tilt into considerations. Pairs of such planar GRIN lens with various free-space propagation distances between them ranging from 75 to 2500  μm and with front-face angles of 1.5 deg, 2 deg, and 4 deg have been fabricated and characterized. Beam propagation method simulations have been carried out to substantiate the theoretical and experimental results. The results indicate that the optical loss is reasonably low up to 1.5 deg of front-face angles and increases significantly with further increase in the front-face angle. Analysis shows that for a given system with specific microlens front-face angle, the optical loss can be significantly reduced by properly compensating the vertical position of the input and output fibers.

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© 2016 Society of Photo-Optical Instrumentation Engineers

Citation

Md. Abdullah Al Hafiz ; Aron Michael and Chee-Yee Kwok
"Planar microlens with front-face angle: design, fabrication, and characterization", J. Micro/Nanolith. MEMS MOEMS. 15(3), 035501 (Jul 08, 2016). ; http://dx.doi.org/10.1117/1.JMM.15.3.035501


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