Fabrication and Investigation of Drawn Fiber Tapers with Spherical Microlenses

Abstract

Fabrication steps for reproducible manufacturing of drawn single mode fiber tapers with quartz glass and high-index lenses and their performance are described in detail. High coupling efficiencies on the order of 50 % with good reproducibility are obtainable. The best value so far obtained has been 62 %. Drawing conditions influencing the taper and lens geometry were evaluated experimentally. Finally, the measurements of the overall optical properties, i.e. coupling efficiency and optical feedback as a function of relevant taper and lens parameters are presented and discussed.

A novel scheme of hyperbolic-end microlens using the arc technology

“…The high coupling performance of microlenses with a hyperbolic profile was due to the improved mode matching between the laser and the fiber when compared with the currently available hemispherical microlenses, which showed a maximum coupling efficiency of 65% [9,10]. Hyperbolically shaped microlenses fabricated through the optimization of etching and fusion processes have demonstrated up to 86% coupling efficiency for a laser with an aspect ratio of 1:1.5.…”

“…The fiber core diameter, the beam spot size, and the refractive index difference were 8 mm, 5 mm, and 0.3%, respectively, at a wavelength of 1.55 mm. To obtain efficient coupling between the diode laser and fiber in a previous study, hemispherical fiber lenses with a short taper length and a large taper angle with a small radius of curvature were required [9,[11][12]. One of the convenient methods of producing short taper lengths and large taper angles in hemispherical fiber lenses has been reported [11,12].…”

“…Microlenses are generally fabricated by using either drawn-tapered fiber [9,10] or hydrofluoride (HF) chemical etching techniques [11,12], and then by melting the end of the fiber to form a tapered hemispherical-end fiber. These hemispherical microlenses with taper asymmetry and larger Fresnel's reflection loss have demonstrated imperfect coupling with a typical coupling efficiency of 50% [9,10]. A coreless fiber tip with an endface of axially symmetric hyperbola is attached to the oval-core GIO fiber followed by the SMF [13], which has a maximum coupling efficiency of 74% for a wavelength of 980 nm with a field profile aspect ratio of 5.9.…”

“…The high-coupling performance of the tapered hyperbolic-end fiber (THEF) represents a major advance in the microlens technology compared with the currently available hemispherical microlenses, which show a maximum coupling efficiency of 65% [9,10]. The hyperbolic microlens exactly transforms the incident spherical wave into a plane wave according to geometric optics.…”

Fabrication of Integrated Optical Mode Field Adapters at the End of Single/Multimode Fibers Using Fiber Splicing Machine

“…3). Other approaches to form such lenses are by photolithography, etching, micromachining or dipping into molten glass and fusing [7][8][9]. For the realization of the fiber tapers a specially adapted fiber splicing machine of Fujikura was used.…”