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Theoretical analysis of free-space optical coupling loss in a multilevel optical system
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Paper Abstract

An approximate analytical solution involving the evaluation of the overlap integral method has been developed to estimate the coupled optical power in a multilevel optical system. The transmitter and receiver optics are located on different planes, vertically separated by a distance Z. 45º micro-mirror pairs are used to facilitate out-of-plane reflection of the optical beam in order for the transmitter and receiver components to be optically linked. The optical components consist of planar waveguide focusing elements, involving a combination of graded-index effect and lens front curvature. Optical signal in many active and passive optical devices can be well approximated by a Gaussian beam. The coupling loss formulas have been derived to support elliptical and circular Gaussian beam analysis. Spot size mismatch, non-ideal propagation distance, axial offset, mirror angular deviation and relative tilt between the two planes are major contributors toward optical power loss in a multilevel optical system. The derived coupling loss formulas has been applied to find the optimal coupling condition like micro-mirror positions, Z, relative distances of optical elements from the micro-mirror, beam spot size, etc. for a prototype system. BPM simulation results are in good agreement with the numerical results obtained by the approximate analytical solutions. The derived coupling loss formulas can be used to estimate optimal optical power loss in a single level or multilevel optical system in MOEMS based optical circuits as well as in a conventional optical system where paraxial approximation is assumed.

Paper Details

Date Published: 30 December 2008
PDF: 12 pages
Proc. SPIE 7268, Smart Structures, Devices, and Systems IV, 72680V (30 December 2008); doi: 10.1117/12.810212
Show Author Affiliations
Md Abdullah Al Hafiz, Univ. of New South Wales (Australia)
Mark R. Mackenzie, Univ. of New South Wales (Australia)
Chee Yee Kwok, Univ. of New South Wales (Australia)

Published in SPIE Proceedings Vol. 7268:
Smart Structures, Devices, and Systems IV
Said Fares Al-Sarawi; Vijay K. Varadan; Neil Weste; Kourosh Kalantar-Zadeh, Editor(s)

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