Integration of a multimode interference coupler with a corrugated sidewall Bragg grating in planar polymer waveguides

We demonstrate the integration of a 3-dB multimode interference coupler with a corrugated sidewall Bragg grating in planar polymer waveguides by direct electron beam writing. Both transmission and reflection spectra of the Bragg grating are measured through this integrated device directly. We use the thermooptic effect to tune the integrated waveguide grating, achieving a tuning range of 6.2 nm and a bandwidth variation of 0.3 nm within a temperature change of 62°C

Integrated microfluidic variable optical attenuator

We fabricate and measure a microfluidic variable optical attenuator, which consists of an optical waveguide integrated with a microfluidic channel. An opening is introduced in the upper cladding of the waveguide in order to facilitate the alignment and bonding of the microfluidic channel. By using fluids with different refractive indices, the optical output power is gradually attenuated. We obtain a maximum attenuation of 28 dB when the fluid refractive index changes from 1.557 to 1.584

Fabrication of functional microstructured optical fibers through a selective-filling technique

We develop a method for the fabrication of functional microstructured optical fibers (MOFs) by selectively filling the air holes with liquid phase materials, where we utilize the dependence of filling speed on the size of the air holes. As a demonstration, we construct a hybrid MOF by filling the center hollow core of a triangular lattice photonic crystal fiber with dye-doped curable polymer, and experimentally observe the two-photon fluorescence from the hybrid MOF

Soft lithography replication of polymeric microring optical resonators

We have developed a soft lithography method to replicate polymeric integrated optical devices. In this method, the master device and the molded replica are made of the same materials, allowing direct comparison. To evaluate the quality of the replication, microring optical resonators are chosen as test devices because of their sensitivity to small fabrication errors. The master devices are precisely fabricated using direct electron beam lithography. The replicas are produced by the molding technique and subsequent ultraviolet curing. Compared with the master devices, the molded devices show minimal change in both physical shape and optical performance. This correspondence indicates the merits of soft lithographic methods for fabrication of precision integrated optical devices

Soft lithography molding of polymer integrated optical devices: Reduction of the background residue

Soft lithography molding is a promising technique for patterning polymer integrated optical devices, however the presence of a background residue has the potential to limit the usefulness of this technique. We present the soft lithography technique for fabricating polymer waveguides. Several effects of the background residue are investigated numerically, including the modal properties of an individual waveguide, the coupling ratio of a directional coupler, and the radiation loss in a waveguide bend. Experimentally, the residue is found to be reduced through dilution of the core polymer solution. We find that the force with which the soft mold is depressed on the substrate does not appreciably affect the waveguide thickness or the residue thickness. Optical microscope images show that the residue is thinnest next to the waveguide

Microfluidics for biological measurements with single-molecule resolution

Single-molecule approaches in biology have been critical in studies ranging from the examination of physical properties of biological macromolecules to the extraction of genetic information from DNA. The variation intrinsic to many biological processes necessitates measurements with single-molecule resolution in order to accurately recapitulate population distributions. Microfluidic technology has proven to be useful in the facilitation and even enhancement of single-molecule studies because of the precise liquid handling, small volume manipulation, and high throughput capabilities of microfluidic devices. In this review we survey the microfluidic “toolbox” available to the single-molecule specialist and summarize some recent biological applications of single-molecule detection on chip

Highly sensitive fiber Bragg grating refractive index sensors

We combine fiber Bragg grating (FBG) technology with a wet chemical etch-erosion procedure and demonstrate two types of refractive index sensors using single-mode optical fibers. The first index sensor device is an etch-eroded single FBG with a radius of 3 μm, which is used to measure the indices of four different liquids. The second index sensor device is an etch-eroded fiber Fabry-Perot interferometer (FFPI) with a radius of ~1.5 μm and is used to measure the refractive indices of isopropyl alcohol solutions of different concentrations. Due to its narrower resonance spectral feature, the FFPI sensor has a higher sensitivity than the FBG sensor and can detect an index variation of 1.4 X 10(-5). Since we can measure the reflection signal, these two types of sensors can be fabricated at the end of a fiber and used as point sensors

Soft lithography replica molding of critically coupled polymer microring resonators

We use soft lithography replica molding to fabricate unclad polystyrene (PS) and clad SU-8 microring resonator filters. The PS resonator has an intrinsic quality factor of 1.0/spl times/10/sup 4/ at /spl lambda/=1.55 /spl mu/m, while that of the SU-8 resonator is 7100. The extinction ratios of the PS and SU-8 microring filters are -12 and -20 dB, respectively, with net insertion losses of 6.7 and 9.9 dB. The good quality factors and high extinction ratios of the microring resonator filters show the practicality of soft-lithography replica molding for the fabrication of integrated optical devices