Electroluminescence of GeSn/Ge MQW LEDs on Si substrate.

Multi-quantum well light-emitting diodes, consisting of ten alternating GeSn/Ge-layers, were grown by molecular beam epitaxy on Si. The Ge barriers were 10 nm thick, and the GeSn wells were grown with 7% Sn and thicknesses between 6 and 12 nm. The electroluminescence spectra measured at 300 and 80 K yield a broad and intensive luminescence band. Deconvolution revealed three major lines produced by the GeSn wells that can be interpreted in terms of quantum confinement. We interpret that the three lines represent two direct lines, formed by transitions with the light and heavy hole band, respectively, and an indirect line. Biaxial compressive strain causes a splitting of light and heavy holes in the GeSn wells. This interpretation is supported by an effective mass band structure calculation.

Electrically pumped lasing from Ge Fabry-Perot resonators on Si.

Room temperature lasing from electrically pumped n-type doped Ge edge emitting devices has been observed. The edge emitter is formed by cleaving Si-Ge waveguide heterodiodes, providing optical feedback through a Fabry-Perot resonator. The electroluminescence spectra of the devices showed optical bleaching and intensity gain for wavelengths between 1660 nm and 1700 nm. This fits the theoretically predicted behavior for the n-type Ge material system. With further pulsed electrical injection of 500 kA/cm2 it was possible to reach the lasing threshold for such edge emitters. Different lengths and widths of devices have been investigated in order to maintain best gain-absorption ratios.

Glycosylation of human recombinant gonadotrophins: characterization and batch-to-batch consistency.

The glycan moiety of human recombinant gonadotrophins (r-hFSH, r-hLH, and r-hCG) produced in CHO cell lines has been characterized by a combination of chromatographic and mass spectrometric techniques, including both matrix-assisted laser desorption ionization and electrospray. Two glycan mapping methods have been developed for the three gonadotrophins that allow separation of the glycans according to either their charge or sialylation level or their antennarity. A method was also developed for r-hCG that permits the complete resolution of the N-glycan from the O-glycan species. Whereas the structure found for the N-glycans of the gonadotrophins was in agreement with the complex type model, the structure for an O-glycan of r-hCG, not yet described, has been unambiguously determined using nanoelectrospray ion trap mass spectrometry. Using these two glycan mapping methods, the high level of batch-to-batch consistency achieved for the glycosylation of the three recombinant gonadotrophins in commercial production has been shown. These data demonstrate the tight control that can be achieved in the manufacturing of complex recombinant therapeutic glycoproteins, which is a prerequisite to the delivering of a guaranteed dose of drug from vial to vial, and in turn to ensuring the clinical efficacy of the product.