Photon Sieve Bandwidth Broadening by Reduction of Chromatic Aberration Effects Using Second-Stage Diffractive Optics

A photon sieve is a lightweight diffractive optic which can be useful for space-based imaging applications. It is limited by chromatic aberration and a narrow bandwidth. A Fresnel zone plate is used to counteract this effect in a manner similar to that accomplished with a traditional holographic corrector. First, a radiometric analysis established a target for bandwidth improvement. Next, a sieve was designed, fabricated, and characterized. Third, the bandwidth-broadening correction scheme was developed to correct primary chromatic aberration. Finally, a zone plate was designed, fabricated, and tested. Performance of the corrected system was measured over the target bandwidth. The corrected system resolved the 3-1 group of a resolution target at the primary wavelength and across an 8-nm bandwidth. The uncorrected system resolved the smaller 6-5 group at the primary wavelength but resolved the 3-1 group over only a 2-nm range. The lower resolution of the corrected system at the primary wavelength is suspected to be a result of corrector design flaws which allowed only the central 2-4 mm to be used. When accounting for this reduced diameter, resolving the 3-1 group does indicate nearly diffraction-limited performance over a bandwidth four times greater than the uncorrected system at the same resolution. This result suggests correction is occurring. A redesign of the corrector may increase performance

The Fresnel Zone Light Field Spectral Imager

This thesis provides a computational model and the first experimental demonstration of a Fresnel zone light field spectral imaging (FZLFSI) system. This type of system couples an axial dispersion binary diffractive optic with light field (plenoptic) camera designs providing a snapshot spectral imaging capability. A computational model of the system was developed based on wave optics methods using Fresnel propagation. It was validated experimentally and provides excellent demonstration of system capabilities. The experimentally demonstrated system was able to synthetically refocus monochromatic images across greater than a 100nm bandwidth. Furthermore, the demonstrated system was modeled to have a full range of approximately 400 to 800nm with close to a 15nm spectral sampling interval. While images of multiple diffraction orders were observed in the measured light fields, they did not degrade the system\u27s performance. Experimental demonstration also showed the capability to resolve between and process two different spectral signatures from a single snapshot. For future FZLFSI designs, the study noted there is a fundamental design trade-off, where improved spectral and spatial resolution reduces the spectral range of the system

BIGRE: a low cross-talk integral field unit tailored for extrasolar planets imaging spectroscopy

Integral field spectroscopy (IFS) represents a powerful technique for the detection and characterization of extrasolar planets through high contrast imaging, since it allows to obtain simultaneously a large number of monochromatic images. These can be used to calibrate and then to reduce the impact of speckles, once their chromatic dependence is taken into account. The main concern in designing integral field spectrographs for high contrast imaging is the impact of the diffraction effects and the non-common path aberrations together with an efficient use of the detector pixels. We focus our attention on integral field spectrographs based on lenslet-arrays, discussing the main features of these designs: the conditions of appropriate spatial and spectral sampling of the resulting spectrograph's slit functions and their related cross-talk terms when the system works at the diffraction limit. We present a new scheme for the integral field unit (IFU) based on a dual-lenslet device (BIGRE), that solves some of the problems related to the classical TIGER design when used for such applications. We show that BIGRE provides much lower cross-talk signals than TIGER, allowing a more efficient use of the detector pixels and a considerable saving of the overall cost of a lenslet-based integral field spectrograph.Comment: 17 pages, 18 figures, accepted for publication in Ap

Programmable optics for ultrashort pulse management: devices and applications

The contribution of the present report to the field of ultrashort optics has several aspects: from the development of new optical devices for ultrashort pulse management, to the application of those devices for triggering laser-matter interaction processes. In this sense, the key point of this Thesis is the use of reconfigurable phase-only SLMs based on LCOS technology for spatial and temporal shaping of femtosecond pulses. The management of femtosecond pulses demands specific strategies to obtain the desired output response while preventing undesirable distortions. Our results show that programmable diffractive optics encoded in SLMs is a powerful tool for ultrashort (~30 fs) beam management. The reconfigurable nature of SLMs allows wavefront control of an input pulsed beam at a micro scale level. In this way, we have developed devices for transferring amplitude and/or phase maps onto the spatial and temporal profile of an ultrashort pulse. Moreover, our proposals result in very compact optical devices, allowing easy-to-align setups especially suitable for non-expert users. We believe that this fact may promote the use of ultrafast technology in many different scientific fields that demands user-friendly devices for ultrashort pulse control

Large diffractive/refractive apertures for space and airborne telescopes

Recent work, specifically the Lawrence Livermore National Laboratory (LLNL) Eyeglass and the DARPA MOIRE programs, have evaluated lightweight, easily packaged and deployed, diffractive/refractive membrane transmissive lenses as entrance apertures for large space and airborne telescopes. This presentation describes a new, innovative approach to the theory of diffractive and refractive effects in lenses used as telescope entrance apertures and the fabrication of the necessary large membrane optics. Analyses are presented to indicate how a broadband, highly transmissive diffractive / refractive membrane lens can be developed and fabricated, and potential applications in defense and astronomy are briefly discussed

Near-IR wide field-of-view Huygens metalens for outdoor imaging applications

The ongoing effort to implement compact and cheap optical systems is the main driving force for the recent flourishing research in the field of optical metalenses. Metalenses are a type of metasurface, used for focusing and imaging applications, and are implemented based on the nanopatterning of an optical surface. The challenge faced by metalens research is to reach high levels of performance, using simple fabrication methods suitable for mass-production. In this paper we present a Huygens nanoantenna based metalens, designed for outdoor photographic/surveillance applications in the near-infra-red. We show that good imaging quality can be obtained over a field-of-view (FOV) as large as +/-15 degrees. This first successful implementation of metalenses for outdoor imaging applications is expected to provide insight and inspiration for future metalens imaging applications

Development and implementation of quadratically distorted (QD) grating and grisms system for 4D multi-colour microscopy imaging (MCMI)

The recent emergence of super-resolution microscopy imaging techniques has surpassed the diffraction limit to improve image resolution. Contrary to the breakthroughs of spatial resolution, high temporal resolution remains a challenge. This dissertation demonstrates a simple, on axis, 4D (3D + time) multi-colour microscopy imaging (MCMI) technology that delivers simultaneous 3D broadband imaging over cellular volumes, which is especially applicable to the real-time imaging of fast moving biospecimens. Quadratically distorted (QD) grating, in the form of an off axis-Fresnel zone plate, images multiple object planes simultaneously on a single image plane. A delicate mathematical model of 2D QD grating has been established and implemented in the design and optimization of QD grating. Grism, a blazed grating and prism combination, achieves chromatic control in the 4D multi-plane imaging. A pair of grisms, whose separation can be varied, provide a collimated beam with a tuneable chromatic shear from a collimated polychromatic input. The optical system based on QD grating and grisms has been simply appended to the camera port of a commercial microscope, and a few bioimaging tests have been performed, i.e. the 4D chromatically corrected imaging of fluorescence microspheres, MCF-7 and HeLa cells. Further investigation of bioimaging problems is still in progress

Doctor of Philosophy

dissertationOptics is an old topic in physical science and engineering. Historically, bulky materials and components were dominantly used to manipulate light. A new hope arrived when Maxwell unveiled the essence of electromagnetic waves in a micro perspective. On the other side, our world recently embraced a revolutionary technology, metasurface, which modifies the properties of matter-interfaces in subwavelength scale. To complete this story, diffractive optic fills right in the gap. It enables ultrathin flat devices without invoking the concept of nanostructured metasurfaces when only scalar diffraction comes into play. This dissertation contributes to developing a new type of digital diffractive optic, called a polychromat. It consists of uniform pixels and multilevel profile in micrometer scale. Essentially, it modulates the phase of a wavefront to generate certain spatial and spectral responses. Firstly, a complete numerical model based on scalar diffraction theory was developed. In order to functionalize the optic, a nonlinear algorithm was then successfully implemented to optimize its topography. The optic can be patterned in transparent dielectric thin film by single-step grayscale lithography and it is replicable for mass production. The microstructures are 3?m wide and no more than 3?m thick, thus do not require slow and expensive nanopatterning techniques, as opposed to metasurfaces. Polychromat is also less demanding in terms of fabrication and scalability. The next theme is focused on demonstrating unprecedented performances of the diffractive optic when applied to address critical issues in modern society. Photovoltaic efficiency can be significantly enhanced using this optic to split and concentrate the solar spectrum. Focusing through a lens is no news, but we transformed our optic into a flat lens that corrects broadband chromatic aberrations. It can also serve as a phase mask for microlithography on oblique and multiplane surfaces. By introducing the powerful tool of computation, we devised two imaging prototypes, replacing the conventional Bayer filter with the diffractive optic. One system increases light sensitivity by 3 times compared to commercial color sensors. The other one renders the monochrome sensor a new function of high-resolution multispectral video-imaging