Title

Foundations For Low-Loss Fiber Gradient-Index Lens Pair Coupling With The Self-Imaging Mechanism

Abstract

A fiber-optic collimator that emits a Gaussian beam with its beam waist at a certain distance after the exit face of the lens is labeled a self-imaging collimator. For such a collimator, the waist of the emitted Gaussian beam and its location are partly dependent on the properties of the gradient-index (GRIN) lens. Parameters for the self-imaging collimator are formulated in terms of the parameters of a GRIN lens (e.g., pitch, core refractive index, gradient index, length) and the optical wavelength. Next, by use of the Gaussian beam approximation, a general expression for the coupling power loss between two selfimaging- type single-mode fiber (SMF) collimators is, for the first time to our knowledge, derived as a function of three types of misalignment, namely, separation, lateral offset, and angular tilt misalignment. A coupling experiment between two self-imaging collimators with changing separation distance is successfully performed and matches the proposed self-imaging mechanism coupling loss theory. In addition, using a prism, lateral offset, as well as angular tilt, misalignments are experimentally simulated for a two self-imaging collimator coupling condition by a single collimator reflective test geometry. Experimental results agree well with the proposed loss formulas for self-imaging GRIN lenses. Hence, for the first time to our knowledge, the mathematical foundations are laid for employing self-imaging-type fiber collimators in SMF-based free-space systems allowing optimal design for ultra-low-loss coupling. © 2003 Optical Society of America.

Publication Date

1-20-2003

Publication Title

Applied Optics

Volume

42

Issue

3

Number of Pages

550-565

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1364/AO.42.000550

Socpus ID

0037455453 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/0037455453

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