Abstract
An etch method based on surface tension driven flows of hydrofluoric acid microdroplets for the fabrication of low-loss, subwavelength-diameter biconical fiber tapers is presented. Tapers with losses less than 0.1 dB/mm are demonstrated, corresponding to an order of magnitude increase in the optical transmission over previous acid-etch techniques. The etch method produces adiabatic taper transitions with minimal surface corrugations. A biconical fiber taper fabricated using this method is used to demonstrate an erbium doped silica microsphere laser.
Highlights
Subwavelength-diameter biconical fiber tapers (SBFTs) have diverse applications ranging from evanescent coupling [1,2,3,4] to optical sensing [5,6,7] and nonlinear optics [8,9]
An etch method based on surface tension driven flows of hydrofluoric acid microdroplets for the fabrication of low-loss, subwavelength-diameter biconical fiber tapers is presented
By controlling the post-etch surface charge density, our SBFTs can either be passivated or further functionalized with select particles or molecules
Summary
Subwavelength-diameter biconical fiber tapers (SBFTs) have diverse applications ranging from evanescent coupling [1,2,3,4] to optical sensing [5,6,7] and nonlinear optics [8,9]. Controlled heating and pulling of a SMF is the most widespread method of fabricating low-loss SBFTs, with optical losses of about 0.1 dB/mm for waist diameters around 500 nm [10,11,12]. We present a new acid-etch method to produce SBFTs with losses comparable to heat-pulled tapers. At a wavelength of 1550 nm, the losses through our SBFTs are generally below 0.1 dB/mm for waist diameters between 500 nm to 1 μm, and losses below 0.05 dB/mm are achievable for waist diameters above 1 μm The production of these low-loss tapers requires a combination of smooth fiber surfaces to minimize scattering losses, as well as adiabatic taper transition regions to reduce power coupling between core and cladding modes [14]
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