Glass-clad, GaSb-core fibers were drawn and subsequently laser annealed. The asdrawn fibers were found to be polycrystalline, possess Sb inclusions, and have oxide contamination concentrations of less than 3 at%. Melting and resolidifying regions in the cores using 10.6 µm CO 2 laser radiation yielded single crystalline zones with enhanced photoluminescence (PL), including the first observation of strong room temperature PL from a crystalline core fiber. Annealed fibers show low values of tensile strain and a bandgap close to that of bulk GaSb.

Ge-on-Si structures in-situ doped with phosphorus or arsenic via metal organic chemical vapor deposition (MOCVD) were investigated. Surface roughness, strain, threading dislocation desnity, Si-Ge interdiffusion, dopant diffusion, and photoluminescence were characterized to study the impacts of defect annealing and Si substrate offcut effects on the Ge film quality and most importantly, the light emission properties. All samples have a smooth surface (roughness < 1.5 nm), and the Ge films have a small tensile strain of 0.2%. As-grown P and As-doped Ge films have threading dislocaiton densities from 2.8 × 10 8 to 1.1× 10 9 cm −2 without defect annealing.With thermal cycling, these values reduced to 1-1.5× 10 8 cm −2 . The six degree offcut of the Si substrate was shown to have little impact. In contrast to delta doping, the out-diffusion of dopants has been successfully suppressed to retain the doping concentration upon defect annealing.However, the photoluminescence intensity decreases mostly due to Si-Ge interdiffusion, which also causes a blue-shift in the emission wavelength. Compared to a benckmarking sample from the first Ge laser work doped by delta doping method in 2012, the as-grown P or As-doped Ge films have similar photoluminescence intensity at a 25% doping concentration and smoother surface, which are promising for Ge lasers with better light emission efficiencies.

We present a nanodot-induced compositionenhancement (NICE) approach for achieving high Sn composition GeSn. The approach involves the deposition of Sn dots (20-60nm in diameter) using physical vapor deposition (PVD) with a subsequent deposition of a Ge capping layer and crystallization annealing. Photoluminescence at λ=3-4 μm is demonstrated towards mid infrared photonic applications.

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