43 research outputs found
Engineered wavefronts for imaging applications: From conventional to metasurface optics.
No full textWavefront modulation has found use in many applications including optical manipulation in the micro-regime, optical communications, photolithography and imaging, among others. Traditionally, wavefront engineering is implemented by conventional optical components that are based on refraction or diffraction, as light propagates through these components. With the advent of computing, and micro and nanofabrication technologies, a new class of optical components has started to emerge. Metasurface optics rely on nanoscale light-matter interactions to control the wavefront of an incident light, promising new capabilities that could only be achieved previously with a combination of bulky conventional optics. This thesis explores imaging applications of engineered wavefronts, modulated using both conventional and metasurface optics. For the first application, a refractive element is employed to construct a common-path interferometer for use in determining the topological charge of beams with orbital angular momentum. Secondly, a commercial optical vortex produced using birefringent liquid crystals is utilized for high-contrast non-linear imaging. Finally, a multifunctional metasurface device is exploited to facilitate single-shot quantitative phase imaging and is applied for wavefront sensing.<br/
Nonlinear optical vortex coronagraph
No full textA nonlinear optical vortex coronagraph (n-OVC) based on sum-frequency generation (SFG) in a periodically poled lithium niobate (PPLN) crystal is presented. We demonstrate an n-OVC by mixing the image of an on-axis point source (λs = 1.6 µm) inside the PPLN crystal with a pump beam (λp = 1064 nm) imprinted with a helical phase profile from a vector vortex mask (topological charge l = 2). Due to quasi-phase matching and orbital angular momentum conservation, a coronagraphic image is produced at the SFG wavelength (λup∼ 630 nm). We validate that the n-OVC is tunable to signal wavelength but only requires a vortex mask operating at the pump wavelength. The acceptance bandwidth of the SFG process provides the n-OVC a degree of achromaticity even with a monochromatic vortex mask. The n-OVC exhibits an inner working angle of ∼λs/D and an experimental contrast of 10−4 at 3λs/D
Microswimmers for biomedical applications: Focus on light
No full textMicroswimmers are microscopic objects that can move and perform tasks in liquid environments. [...
BioBots: 3D-printed microrobots manipulated by light as potential biomedical “surgeons”
No full textMicrorobots with spherical handles for optical trapping and additional features for biological applications are fabricated by direct laser writing. Surface functionalization, combined with wavefront correction algorithms, shows promise for improved microrobot manipulation in biological fluids
Light-driven transport of microparticles with phase-gradient metasurfaces
No full textOptical tweezers have opened numerous possibilities for precise control of microscopic particles for applications in life science and soft matter research and technology. However, traditional optical tweezers employ bulky conventional optics that prevents construction of compact optical manipulation systems. As an alternative, we present an ultra -thin silicon-based metasurface that enables simultaneous confinement and propulsion of microparticles based on a combination of intensity and phase-gradient optical forces. The metasurface is constructed as a water-immersion line -focusing element that enables trapping and transport of 2 mu m particles over a wide area within a thin liquid cell. We envisage that the type of multifunctional metasurfaces reported herein will play a central role in miniaturized optical sensing, driving, and sorting of microscopic objects, such as cells or other biological entities. (C) 2022 Optica Publishing Grou
