Jose A. Dominguez-Caballero

Quantitative measurement of size and three-dimensional position of fast-moving bubbles in air-water mixture flows using digital holography

We present a digital in-line holographic imaging system for measuring the size and three-dimensional position of fast-moving bubbles in air-water mixture flows. The captured holograms are numerically processed by performing a two-dimensional projection followed by local depth estimation to quickly and efficiently obtain the size and position information of multiple bubbles simultaneously. Statistical analysis on measured bubble size distributions shows that they follow lognormal or gamma distributions.

Design and analysis of multi-wavelength diffractive optics.

We present an extension of the direct-binary-search algorithm for designing high-efficiency multi-wavelength diffractive optics that reconstruct in the Fresnel domain. A fast computation method for solving the optimization problem is proposed. Examples of three-wavelength diffractive optics with over 90% diffraction efficiency are presented. These diffractive optical elements reconstruct three distinct image patterns when probed using the design wavelengths. Detailed parametric and sensitivity studies are conducted, which provide insight into the diffractive optics performance when subject to different design conditions as well as common systematic and fabrication errors.

Nanostructured gradient-index antireflection diffractive optics

We describe the fabrication and characterization of a nanostructured diffractive element with near-zero reflection losses. In this element, subwavelength nanostructures emulating adiabatic index matching are integrated on the surface of a diffractive microstructure to suppress reflected diffraction orders. The fabricated silicon grating exhibits reflected efficiencies that are suppressed by 2 orders of magnitude over broad wavelength bands and wide incident angles. Theoretical models of the fabricated structure based on rigorous coupled-wave analysis and effective medium theory are in agreement with the experimental data. The proposed principles can be applied to improve the performance of any diffractive structures, potentially leading to more efficient Fresnel lenses, holographic elements, and integrated optical systems.

Design and sensitivity analysis of Fresnel domain computer generated holograms

An iterative algorithm used for the design and optimisation of a binary phase computer generated hologram for high-resolution lithography in on-axis and off-axis geometries is presented. A sensitivity analysis is performed to estimate the effect of CGH manufacture errors using electron-beam writing.

Advances in Plankton Imaging Using Digital Holography

An in situ plankton imaging system using a high space-bandwidth product camera and fiber coupled diode laser for digital holography was developed. High quality imaging results and solutions for associated computational challenges are discussed.

Techniques based on digital multiplexing holography for three-dimensional object tracking

Three techniques based on digital multiplexing holography for tracking objects in threedimensional space are presented. Multiple holograms were combined into a single camera frame with high spatio-temporal resolution. Practical limitations and experiments are shown.

Design and Fabrication of Computer Generated Holograms for Fresnel Domain Lithography

An optimization algorithm for the design of Fresnel domain computer-generated holograms for lithographic applications is presented. The holograms are fabricated experimentally and their performance characterized. A sensitivity analysis is performed to estimate potential fabrication errors.

Stability of the Digital Holographic Inverse Problem as a Function of Particle Density

The stability of the inverse problem associated with a digital holographic system for particle imaging is discussed. The defined stability metric is computed for a given configuration to find the optimum particle density. Article not available.

Gradient-index adiabatic impedance matching (GRIN-AIM) antireflective diffractive optics

We have experimentally demonstrated suppression of reflection diffracted orders by at least 100× in a silicon grating by tapered nanostructures emulating adiabatic index matching. Novel fabrication using self-assembled nanospheres as lithographic mask was employed.