DNA microarrays are used to profile changes in gene expression between samples in a high-throughput manner, but measurements of genes with low expression levels can be problematic with standard microarray substrates. In this work, we expand the detection capabilities of a standard microarray experiment using a photonic crystal (PC) surface that enhances fluorescence observed from microarray spots. This PC is inexpensively and uniformly fabricated using a nanoreplica molding technique, with very little variation in its optical properties within- and between-devices. By using standard protocols to process glass microarray substrates in parallel with PCs, we evaluated the impact of this substrate on a one-color microarray experiment comparing gene expression in two developmental stages of Glycine max. The PCs enhanced the signal-to-noise ratio observed from microarray spots by 1 order of magnitude, significantly increasing the number of genes detected above substrate fluorescence noise. PC substrates more than double the number of genes classified as differentially expressed, detecting changes in expression even for low expression genes. This approach increases the dynamic range of a surface-bound fluorescence-based assay to reliably quantify small quantities of DNA that would be impossible with standard substrates.

We describe the design, fabrication, and characterization of a narrow band tunable guided mode resonance (GMR) reflectance filter that is actuated by optically induced trans-cis isomerization of an azobenzene liquid crystal. Constructing a plastic replica-molded containment cell with a rubbed polyimide film to initially direct the liquid crystal molecular orientation parallel to the grating lines of the GMR filter, isomerization caused by exposure to a λ=532nm laser results in a −25nm shift of the resonant reflected wavelength.

Asymmetric 2D photonic crystals were fabricated using polymer embedded PbS quantum dots on plastic substrates for enhancing optical down conversion efficiency from blue to near infrared wavelengths through enhanced extraction and excitation effects. We demonstrate 8x improvement of QD emission at normal incidence extraction from enhanced extraction and 2.5x improvement in power conversion efficiency from enhanced excitation.

A guided-mode resonant filter incorporating an electro-optically tunable liquid crystal refractive index is demonstrated at a wavelength of 655nm and a tuning range of 4nm. Rigorous coupled wave analysis and finite difference time domain analysis are used to simulate the characteristics of the filter during liquid crystal reorientation. Tuning performance is demonstrated that is consistent with the device simulations. Tunable filters in the visible wavelength range that are inexpensively fabricated over large surface areas are expected to find applications in optical limiting and video display.

The ability to selectively reflect specific wavelength bands, and to easily tune the reflected wavelength is of interest to a broad range of optical systems, including wavelength division multiplexing, spectroscopy, fluorescence microscopy, optical limiting for protection of sensors/eyes, and video display. Reflectance filters based upon anomalous optical resonances 1 that occur within certain periodic surface structures represent a class of devices that can provide 100% reflection efficiency at the resonant wavelength. Such devices, called guided-mode resonance filters (GMRF) or surface photonic crystals (PC), are especially attractive as filters because they require the deposition of only one dielectric thin film, and can be designed for wavelengths ranging from ultraviolet 2 to infrared. Recently, plastic-based replica molding approaches have been applied to produce surface PC filters 3 that enable production upon flexible sheets of plastic film in continuous rolls for application as optical biosensors. 4 For many years, the ability to tune the resonant wavelength of such devices by variation of the refractive index of one of the device components has been recognized, although dynamic tuning has only been demonstrated in a few cases. 5 We present the design, fabrication and testing of a tunable narrowband PC reflectance filter for visible wavelengths that is inexpensively fabricated both on glass and flexible plastic substrates. The device cross section is shown in Figure 1. Using a nanoreplica molding process, the periodic surface structure is produced within a UV-cured polymer material (UVCP) upon a glass or plastic (PET) substrate with a transparent indium tin oxide (ITO) thin film on its surface. A high refractive index thin film of titanium dioxide (TiO 2 ) is deposited over the surface structure and a thin layer of liquid crystal (LC) is distributed between the grating structure and an upper ITO-coated substrate. A 25 µm thick double sided adhesive is used to bond the two PET substrates together and create a spacer for the LC cell. An electric field is applied across the LC film between the lower and upper ITO electrodes.The reflectance filter has two different reflectance peaks; the TE/TM peak is observed when the polarization of incident light is parallel/perpendicular to the grating lines. An applied electric field will reorient the LC molecules and modify the refractive index of the layer above the PC. Due to the birefringence of the LC, the TE peak will experience a decrease in refractive index and thus shift to shorter wavelengths while the opposite is true for the TM case. The transmission spectrum of the device was observed using the following setup. A tungsten-halogen lamp connected to one end of a fiber optic cable was used as the incident light source. The light travels through a linear polarizer before it illuminates the mounted device through the bottom substrate. After passing through the device, the transmitted light propagates into another optical fiber connected to a spectrometer.