One-pot three-component domino protocol for the synthesis of novel pyrano[2,3-d]pyrimidines as antimicrobial and anti-biofilm agents.

A simple and facile synthesis of a series of novel pyrano[2,3-d]pyrimidines has been achieved successfully via the one-pot three-component reaction of 2-amino-7-methyl-5-oxo-4-phenyl-4,5-dihydropyrano[4,3-b]pyran-3-carbonitriles, DMF-DMA and arylamines in the presence of 1-butyl-3-methylhydrogensulphate [Bmim]HSO4 ionic liquid. This method has several advantages such as high yields, clean reaction, simple methodology and short reaction times. The synthesized compounds were evaluated for their antimicrobial activity against Gram-positive, Gram-negative and different Candida strains. Among the derivatives screened, compounds 4c, 4d, 4h and 4l were found to be active against both bacterial and Candida strains with MIC values ranging from 3.9 to 31.2 µg mL(-1). In addition, compound 4l showed a good minimum bactericidal concentration, minimum fungicidal concentration and anti-biofilm activities. Furthermore, the mode of the antifungal action for the promising compound 4l was evaluated in C. albicans MTCC 1637 through an ergosterol biosynthesis inhibition process.

Enhanced electro-optic phase shifts in suspended waveguides.

We demonstrate enhanced electro-optic phase shifts in suspended InGaAs/InGaAsP quantum well waveguides compared to attached waveguides. The enhancement stems from an improved overlap between the optical mode and the multiple quantum well layers in thin waveguides when the semiconductor material beneath the waveguide is selectively etched. The measured voltage length product is 0.41 V-cm and the measured propagation loss is 2.3 +/- 0.7 dB/cm for the TE mode in the optical L-band.

Demonstration of balanced coherent detection using polymer optical waveguide integrated distributed traveling-wave photodetectors.

We have demonstrated balanced coherent detection using distributed balanced traveling-wave photodetectors integrated with single mode polymer optical waveguides. Balanced distributed traveling-wave photodetectors having 3 dB bandwidth of 20 GHz exhibited 20 dB signal to noise ratio improvement measured at 15 GHz modulation frequency in a balanced coherent detection demonstration.

A microelectromechanically tunable asymmetric Fabry-Perot quantum well modulator at 1.55 microm.

Placing a quantum well modulator in an asymmetric Fabry- Perot cavity enables significantly higher contrast ratios than are possible in a conventional surface-normal quantum well modulator. However, fixed-cavity asymmetric Fabry-Perot quantum well modulators require extremely precise and uniform crystal growth and are sensitive to small fluctuations in temperature or angle of incidence. Here, we experimentally demonstrate an InP-based microelectromechanically tunable asymmetric Fabry-Perot quantum well modulator that operates in the optical C-band. By actuating a suspended InGaAlAs reflector, the cavity mode can be perfectly matched to the appropriate quantum well absorption wavelength. The devices exhibit contrast ratios over 30 (15 dB) at 8 volts quantum well bias and modulation speeds of 1 MHz.

Low-loss suspended quantum well waveguides.

We have used surface micromachining to fabricate suspended InGaAs/InGaAsP quantum well waveguides that are supported by lateral tethers. The average measured TE propagation loss in our samples is 4.1 dB/cm, and the average measured TE loss per tether pair is 0.21 dB. These measurements are performed at wavelengths in the optical L-band, just 125 nm below the quantum well band gap.

X-ray reflectivity study of semiconductor interfaces.

The results of an X-ray reflectivity study of thick AlAs-AlGaAs and thin Ge-Si-Ge multilayers grown using metal-organic vapour-phase epitaxy and ion-beam sputtering deposition techniques, respectively, are presented. Asymmetry in interfaces is observed in both of these semiconductor multilayers. It is also observed that although the Si-on-Ge interface is sharp, an Si(0.4)Ge(0.6) alloy is formed at the Ge-on-Si interface. In the case of the III-V semiconductor, the AlAs-on-AlGaAs interface shows much greater roughness than that observed in the AlGaAs-on-AlAs interface. For thin multilayers it is demonstrated that the compositional profile as a function of depth can be obtained directly from the X-ray reflectivity data.