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The waveguides and light sources are essential building blocks in optofluidics. Here, we have developed the new approach to fabricate efficient waveguides and light sources by using two-phase stratified flow of dye containing liquid and air. The liquid-core/air-cladding (LA) waveguide can overcome some of major drawbacks of the liquid-core/liquid-cladding (L 2 ) waveguide without losing its unique advantages. Specifically, stronger optical confinement, originated from the large refractive index contrast between core and cladding, enable us to achieve lower propagation losses and larger captured fractions (the amount of light to be coupled into the liquid core). In addition, the LA waveguides are free from diffusional mixing of the core and cladding fluids. The fluorescent LA waveguides can be fabricated by conventional poly(dimethylsiloxane) (PDMS) based soft lithography, which is compatible with the other parts of optofluidic devices. Therefore, the fluorescent LA waveguide can be easily integrated with precise alignment as an internal light source of optofluidic devices.

An etch-less ultraviolet nanoimprint lithography (UV-NIL) process is proposed for patterning a photonic crystal (PC) structure onto an organic light-emitting diode (OLED) substrate. In a conventional UV-NIL, anisotropic etching is used to remove the residual layers and to transfer the patterns onto the substrate. The proposed process does not require an etching process. In the process, a stamp with nano-scale PC patterns is pressed on the dispensed resin and UV light is then exposed to cure the resin. After tens of seconds, the stamp is separated from the patterned polymer layer on the substrate. Finally, high-refractive index material is coated onto the layer. The refractive index of the polymer should be very similar to that of glass. The enhancement of the light extraction was assessed by the three-dimensional (3D) finite difference time domain (FDTD) method. The OLED was integrated on a nanoimprinted substrate and the electro-luminance intensity was found to have increased by as much as 50% compared to a conventional device.

We propose and demonstrate a new type of a photonic crystal nanolaser integrated into a microfluidic chip, which is fabricated by multilayer soft lithography. Experimentally, continuous-wave operation of the lasing action has been observed owing to efficient water-cooling. Characteristics of wavelength tuning by the fluid are investigated using both theory and experiment. In addition, we propose that dynamic modulation of far-field radiation pattern can be achieved by introducing a bottom reflector and by flowing the fluid on it. Especially, by choosing effective one-wavelength distance between the reflector and the cavity, efficient unidirectional emission can be obtained.

We propose efficient unidirectional light emitters, which are enabled by the use of large Purcell effect, defect engineering, and the bottom Bragg reflector. Enhanced spontaneous emission rate enables us to achieve very efficient light sources, in which most of the emitted photons can be funneled into a specific resonant mode of interest. The far-field radiation properties of a photonic crystal resonant mode are modified by tuning the cavity geometry and by placing a reflector below the cavity. As a result, > 80% of the photons generated inside a photonic crystal resonator can be collected from the top, within a small divergence angle of ±30°.

Recent progress toward wavelength-scale photonic crystal lasers is summarized. To realize the ultimate laser, one needs to have a wavelength-scale photonic crystal cavity that is lossless. As a candidate for this ultimate laser, the two-dimensional unit-cell photonic crystal laser compatible with current injection is proposed. Experimental demonstration of the low-threshold two-dimensional photonic crystal lasers in the triangular lattice and the square lattice will be discussed. The very high quality factor in excess of 1,000,000 is theoretically predicted from the wavelength-scale resonator supporting the whispering-gallery-like photonic crystal mode.

Novel square lattice photonic band gap lasers are realized at room temperature from single cell photonic crystal slab micro-cavities fabricated in InGaAsP materials emitting at 1.5 micrometers . This single cell photonic band gap laser operates in the new class of two-dimensional mode to be classified as the smallest possible whispering gallery mode with genuine energy null at the center. The low-loss nondegenerate mode with modal volume of 0.1 ((lambda) /2)3 demonstrates a spectrometer-limited below-threshold quality factor > 2000 and a theoretical quality factor of > 10,000. Threshold incident peak pump power of 0.8 mW is achieved from this whispering-gallery-type laser mode. The other class of photonic crystal lasers is also observed outside the photonic band gap of the square lattice, operating in the mode characteristically one-dimensional.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Recent deployments of digital cameras and fast PCs have led real-time interactive systems to adopt vision-based interfaces. However, 2D vision-based interfaces, due to the lack of 3D information, have inherent weakness in tracking 3D objects in real world. In this paper, we propose a vision-based 3D interface for interactive systems that allows an object tracking on the fly in 3D by exploiting multi-view images. Due to the characteristics of interactive systems, requiring real time processing, the main challenge is a simple and robust estimation of 3D information from the images captured by asynchronous digital cameras. The proposed vision-based 3D tracking consists of three steps: (i) dynamic stereo calibration (ii) simple object segmentation (iii) robust 3D movement tracking. To show its effectiveness of the proposed framework, we applied the proposed 3D interface to an interactive 3D Gumdo simulation. Due to the simplicity and robustness of the proposed framework, it can be applied to various real-time interactive applications.