Self-reference extended depth-of-field quantitative phase microscopy

Author(s): Jaeduck Jang, Chae Yun Bae, Je-Kyun Park, and Jong Chul Ye

Abstract:

“This paper describes a novel quantitative phase microscopy based on a simple self-referencing scheme using Michelson interferometry. In order to achieve the homogeneous reference field for accurate phase measurement, the imaging field-of-view (FOV) is split onto the sample and homogenous background areas. The reference field can be generated by rotating the relative position of the sample and homogenous background in the object arm. Furthermore, our system is realized using an extended depth-of-field (eDOF) optics, which allows quantitative phase measurement for an increase of the depth-of-field without moving objective lens or specimen. The proposed method is confirmed by experimental results using various samples such as polystyrene beads and red blood cells (RBCs).”

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Publication: SPIE Proceedings
Issue/Year: Proc. SPIE 7570, 757018 (2010)
DOI: 10.1117/12.843082

Individually controlled multi-focus laser processing for two-photon polymerization

Author(s): Kotaro Obata, Jürgen Koch, and Boris N. Chichkov

Abstract:

“A parallel processing of two-photon polymerization structuring is demonstrated with spatial light modulator. Spatial light modulator generates multi-focus spots on the sample surface via phase modulation technique controlled by computer generated hologram pattern. Each focus spot can be individually controlled in position and laser intensity with computer generated hologram pattern displayed on spatial light modulator. The multi-focus spots two-photon polymerization achieves the fabrication of asymmetric structure. Moreover, smooth sine curved polymerized line with amplitude of 5 μm and a period of 200 μm was obtained by fast switching of CGH pattern.”

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Publication: SPIE Proceedings / Volume 7584 / Nonlinear Processing
Issue/Year: Proc. SPIE 7584, 75840L (2010)
DOI: 10.1117/12.842117

Reconfigurable Optically Induced Quasicrystallographic Three-Dimensional Complex Nonlinear Photonic Lattice Structures

Author(s): Jolly Xavier, Martin Boguslawski, Patrick Rose, Joby Joseph, Cornelia Denz

Abstract:

“Complex reconfigurable 3D photonic quasicrystals (PQCs) are fabricated in nonlinear photorefractive strontium barium niobate by an optical phase engineering-based single-step optical induction approach (see image). The approach demonstrates the embedded potential to use these structures as a reconfigurable platform for the investigation of advanced nonlinear light-matter interaction, or as templates fabricated in various photosensitive materials for photonic bandgap structures. ”

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Publication: Advanced Materials
Issue/Year: Advanced Materials, Volume 22, Issue 3, pages 356–360, January 19, 2010
DOI: 10.1002/adma.200901792

Plasmid copy number noise in monoclonal populations of bacteria

Author(s): Jérôme Wong Ng, Didier Chatenay, Jérôme Robert, Michael Guy Poirier

Abstract:

“Plasmids are extra chromosomal DNA that can confer to their hosts’ supplementary characteristics such as antibiotic resistance. Plasmids code for their copy number through their own replication frequency. Even though the biochemical networks underlying the plasmid copy number (PCN) regulation processes have been studied and modeled, no measurement of the heterogeneity in PCN within a whole population has been done. We have developed a fluorescent-based measurement system, which enables determination of the mean and noise in PCN within a monoclonal population of bacteria. Two different fluorescent protein reporters were inserted: one on the chromosome and the other on the plasmid. The fluorescence of these bacteria was measured with a microfluidic flow cytometry device. We show that our measurements are consistent with known plasmid characteristics. We find that the partitioning system lowers the PCN mean and standard deviation. Finally, bacterial populations were allowed to grow without selective pressure. In this case, we were able to determine the plasmid loss rate and growth inhibition effect.”

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Publication: Physical Review E
Issue/Year: Phys. Rev. E, Volume 81, Issue 1, 011909 (2010)
DOI: 10.1103/PhysRevE.81.011909

Nonspherical laser-induced cavitation bubbles

Author(s): Kang Yuan Lim, Pedro A. Quinto-Su, Evert Klaseboer, Boo Cheong Khoo, Vasan Venugopalan, Claus-Dieter Ohl

Abstract:

“The generation of arbitrarily shaped nonspherical laser-induced cavitation bubbles is demonstrated with a optical technique. The nonspherical bubbles are formed using laser intensity patterns shaped by a spatial light modulator using linear absorption inside a liquid gap with a thickness of 40 μm. In particular we demonstrate the dynamics of elliptic, toroidal, square, and V-shaped bubbles. The bubble dynamics is recorded with a high-speed camera at framing rates of up to 300 000 frames per second. The observed bubble evolution is compared to predictions from an axisymmetric boundary element simulation which provides good qualitative agreement. Interesting dynamic features that are observed in both the experiment and simulation include the inversion of the major and minor axis for elliptical bubbles, the rotation of the shape for square bubbles, and the formation of a unidirectional jet for V-shaped bubbles. Further we demonstrate that specific bubble shapes can either be formed directly through the intensity distribution of a single laser focus, or indirectly using secondary bubbles that either confine the central bubble or coalesce with the main bubble. The former approach provides the ability to generate in principle any complex bubble geometry.”

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Publication: Physical Review E
Issue/Year: Phys. Rev. E, Volume 81, Issue 1, 016308 (2010)
DOI: 10.1103/PhysRevE.81.016308