Generation Of Arbitrary Patterns Research Articles

Optical phased array with on-chip phase calibration.

Optical phased arrays (OPAs) with phase-monitoring and phase-control capabilities are necessary for robust and accurate beamforming applications. This paper demonstrates an on-chip integrated phase calibration system where compact phase interrogator structures and readout photodiodes are implemented within the OPA architecture. This enables phase-error correction for high-fidelity beam-steering with linear complexity calibration. A 32-channel OPA with 2.5-µm pitch is fabricated in an Si-SiN photonic stack. The readout is done with silicon photon-assisted tunneling detectors (PATDs) for sub-bandgap light detection with no-process change. After the model-based calibration procedure, the beam emitted by the OPA exhibits a sidelobe suppression ratio (SLSR) of -11 dB and a beam divergence of 0.97° × 0.58° at 1.55-µm input wavelength. Wavelength-dependent calibration and tuning are also performed, allowing full 2D beam steering and arbitrary pattern generation with a low complexity algorithm.

Micropatterning Co-cultures of Epithelial Cells on Filter Insert Substrates

A key feature of mature epithelium is the presence of an apical-basal polarization. In vitro this is achieved by culturing either pure populations of epithelial cells or unorganized mixtures of primary cell populations harvested from epithelial tissues in a filter insert culture system. In addition to epithelial cells however, multiple other cell types are also present in normal epithelium in a specific organization. Generally the organization of component cells within a tissue is critical for normal function. The importance of the organization of different cell populations within normal and diseased epithelium in vitro has received little attention, in part due to the lack of available methods for spatially controlling multiple cell populations while maintaining the culture conditions necessary to generate polarized and mature epithelium. We have developed a set of micropatterning techniques to spatially control the organization of co-cultures of epithelial cells on filter insert membranes under the culture conditions necessary to induce epithelial cell polarization. We describe a fibronectin microprinting method that allows arbitrary pattern generation and a parafilm insert method that allows only simple stripe geometry patterning but does not require the photolithographic equipment that the fibronectin microprinting method requires, and can be adopted by any epithelial biology lab. We also demonstrate that our micropatterning methods do not alter the formation of cilia, a marker of epithelium maturation. Our methods provide a novel tool for studying epithelial biology in polarized epithelial sheets containing multiple cell populations with controlled organization.

Quantum lithography with classical light: Generation of arbitrary patterns

Based on our previous scheme [Hemmer et al., Phys. Rev. Lett. 96, 163603 (2006)] we show the procedures to obtain any one- or two-dimensional pattern by multiple exposures. A key modification to the resonance condition is made to achieve subwavelength pattern resolution. The level separation of the substrate does not pose an upper limit to the frequency summation. So the fundamental frequency can be high and the number of Fourier terms can be large, making our scheme very suitable for subwavelength arbitrary patterns.