Measurement of the Internal Structure of an Optical Waveguide Embedded in a Flexible Optical Circuit Board by Enhancing the Signal Contrast of a Confocal Microscope

Abstract

In this study, the internal structure of an optical waveguide embedded in a flexible optical circuit board is observed with a confocal microscope. In order to increase the light reflection from an internal material interface with a very small index difference, and thus enhance the signal contrast, a theta microscopy scheme has been integrated into a conventional confocal microscope, and a high NA oil-immersion lens has been used. The interface reflectivity is increased from roughly 0.0015% to 0.025% by the proposed method, and the internal structure can thus be successfully measured.

Divided-aperture differential confocal fast-imaging microscopy

“…In 2004, Weiqian Zhao et al proposed the differential confocal microscopy (DCM) and achieved an axial resolution to 2 nm by using a high NA objective, which caused the decrease of working distance [18]. In 2011, Won-Jun Lee et al applied confocal theta technology to the measurement of the internal structure of optical waveguides [19], successfully solving the imaging problem of the inner surface slice of the optical waveguides. However, the halfheight width of their axial curve only reached 790 nm.…”

Thermo-optic Characteristics of Micro-structured Optical Fiber Infiltrated with Mixture Liquids

“…The micrometer-sized air holes running along the length of the fiber provide great freedom in optical waveguide design during the fabrication procedure [5][6]. Additionally, the infiltration of functional materials into claddings provides further responses under different external physical fields, leading to tunable propagation properties of MOFs for promising all-in-fiber optical components [7][8].…”