Three-dimensional (3D) photonic crystals containing artificial point defects have been fabricated to emit light at optical communications wavelengths. They were constructed by stacking 0.7-micrometer-period gallium arsenide striped layers, resulting in a 3D "woodpile" photonic crystal. Indium-gallium arsenide-phosphide quantum-well layers emitting at a wavelength of 1.55 micrometers were incorporated in the center of the crystal. Samples having up to nine stacked layers were constructed, and artificial point-defect cavities of different sizes were formed in the light-emitting layer. Light emission was suppressed in the photonic crystal regions, whereas cavity modes were successfully observed at the point defects and were size dependent.

Three-dimensional (3D) photonic crystals can block photons in any direction and are expected to make possible their ultimate control. However, creating 3D crystals without any unintentional defects over large areas at optical wavelengths has been challenging. For example, opal-based crystals inevitably contain unintentional defects, it is difficult to increase the sizes of micro-manipulated crystals over approximately 6 microm and producing stacked 3D crystals with thin 2D layers requires complicated and time-consuming processes. So far, these difficulties have hindered 3D photonic-crystal research. Here, we demonstrate a novel top-down approach to creating 3D crystals that overcomes these difficulties and significantly simplifies the process. We have developed a double-angled deep-etching method, which enables the direct creation of 3D woodpile crystals in single-crystalline silicon. A strong photonic bandgap effect with >20 dB attenuation in all directions has been achieved. Furthermore, bonding a light emitter onto or between 3D crystals created in this way has been shown to enhance or suppress spontaneous emission.

We demonstrate the use of a defect to improve the transmission property of waveguide bends in two-dimensional photonic crystal slabs. We show that high reflection in the two-dimensional photonic crystal slab previously reported is due to the fact that the waveguide is multimoded at the bend while it is single moded along the straight waveguide. By making the waveguide single moded at the bend, the transmission property can be significantly improved. An extension of more than twice of high-transmission bandwidth is achieved.

Zn[2]-Cys[6] binuclear transcription factors Upc2p and Ecm22p regulate the expression of genes involved in ergosterol biosynthesis and exogenous sterol uptake in Saccharomyces cerevisiae. We identified two UPC2 ⁄ ECM22 homologues in the pathogenic fungus Candida glabrata which we designated CgUPC2A and CgUPC2B. The contribution of these two genes to sterol homeostasis was investigated. Cells that lack CgUPC2A (upc2AD) exhibited enhanced susceptibility to the sterol biosynthesis inhibitors, fluconazole and lovastatin, whereas upc2BD-mutant cells were as susceptible to the drugs as wild-type cells. The growth of upc2AD cells was also severely attenuated under anaerobic conditions. Lovastatin treatment enhanced the expression of ergosterol biosynthetic genes, ERG2 and ERG3 in wild-type and upc2BD but not in upc2AD cells. Similarly, serum-induced expression of ERG2 and ERG3 was completely impaired in upc2AD cells but was unaffected in upc2BD cells, whereas serum-induced expression of the sterol transporter gene CgAUS1 was impaired in both upc2AD and upc2BD cells. These results suggest that in C. glabrata CgUPC2A but not in CgUPC2B is the main transcriptional regulator of the genes responsible for maintaining sterol homeostasis as well as susceptibility to sterol inhibitors.