Abstract
CO2 laser annealing of SiGe core, glass-clad optical fibers is a powerful technique for the production of single-crystal cores with spatially varying Ge concentrations. Laser power, laser scan speed and cooling air flow alter the Ge distribution during annealing. In this work, near-single crystal fibers exhibiting a central axial feature with peak Ge concentration ∼15 at% higher than the exterior of the semiconductor core have been prepared. Preferential transmission of near infrared radiation through the Ge-rich region, and spectral data confirm its role as a waveguide within the semiconductor core. This proof-of-concept step toward crystalline double-clad structures is an important advancement in semiconductor core optical fibers made using the scalable molten core method.
Highlights
Semiconductor-core optical fibers have numerous potential applications that arise from the fiber’s infrared transparency, optoelectronic and nonlinear optical properties [1,2,3,4,5]
We demonstrate, for the first time to our knowledge, radial compositional structuring of crystalline SiGe fibers and the resultant optical effects, using a commercial 80 W CO2 laser engraver to form the structures
Optical characterization Characterization of the optical transmission in the near infrared was made using a 20 mW, 1.55 μm diode laser from QPhotonics that was coupled into the sample using a lensed single mode fiber (SMF) from Oz Optics
Summary
Semiconductor-core optical fibers have numerous potential applications that arise from the fiber’s infrared transparency, optoelectronic and nonlinear optical properties [1,2,3,4,5]. A Ge-rich region in the center of a graded SiGe rib waveguide has been observed to have lower losses in the near infrared (NIR) [27], making comparable fibers of interest This is true for applications at wavelengths greater than ∼4μm, where the absorption of silica increases rapidly and the cladding could degrade performance of the fiber. We demonstrate, for the first time to our knowledge, radial compositional structuring of crystalline SiGe fibers and the resultant optical effects, using a commercial 80 W CO2 laser engraver to form the structures This is a first step towards scalable fabrication of all-semiconductor, gradient-index cores for long wavelength applications. Optimal processing has not yet been achieved, these preliminary results demonstrate the potential of laser treatment to create radial gradient structures in alloy fiber with the potential for in-fiber junction and double-clad configurations
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