We present the luminescence properties of CdS nanoparticles conjugated with active DNA molecules. Having the action
of activators, CdS nanoparticles combine with DNA molecules easily and tightly. The fluorescence from CdS
nanoparticles is characteristics of bright spots under dark optical microscopy, indicating that CdS nanopaticles can be
used labeling DNA molecules. Strong photoluminescence emission of A-DNA-CdS keeps relatively steady at room
temperature in terms of the time behavior of optical bleaching, showing that CdS nanoparticles are suitable to long time
biological analysis and detection.
A tapered spot-size converter with adjustable step length in two-dimensional photonic crystals has been proposed by removing several rows of dielectric rods from the photonic crystal structure. Its functionality and performance have been numerically investigated and simulated by the finite-difference time-domain method. The device has a conversion ratio of 10:1 and more than 80% power transmission efficiency for an optical communication wavelength of 1.55 µm. The converter has high compactness and potential applications as a connector in the optical signal connection between photonic-crystal-based waveguide devices and conventional micro-optical waveguide devices or single-mode optical fibers.