Abstract: A digital correlation processor can only process a long duration signal by sampling and digitizing the signal thousands of times and correlate them in digital domain. We have developed a new type of analog RF-Photonic fiber-optic-recirculation-loop based correlation processor that can perform a correlation processing for a single ultra-short high-frequency signal. Using this technique, we built a RF-Photonic spectrum analyzer to perform analog-autocorrelation and Fourier transform and demonstrated a high-resolution spectrum obtained from a single 30ns-short two-tone ~30GHz signal pulse. This method revolutionizes the signal detection and processing technique by providing new capability of analyzing ultra-short signal or transient event.

In this work we showcase an effective approach to substantially broaden the tuning range of microlaser-based parametric devices into the visible and UV-A spectral domains. We demonstrate the first subnanosecond pulse duration OPA continuously tunable throughout the VIS and UV-A spectral ranges. Our BBO crystal-based OPA was pumped by third harmonic (355 nm) 500 ps pulses from passively Q-switched Nd:YAG microlaser while the seed source was formed from multigrating MgO-doped periodically poled lithium niobate (MgO:PPLN) OPG-based seeder pumped by the second harmonic (532 nm) of the same microlaser. The OPA signal wave was continuously tunable from 419 nm to 728 nm via birefringent phase matching and maintained high beam quality. Unlike conventional supercontinuum seeders, the MgO:PPLN OPG seeder achieved much higher spectral power density which was crucial in achieving up to 19% OPA signal to pump conversion efficiencies. The introduction of the upconversion stage extended the tuning range of the system to 345 nm. A comprehensive characterization of both the seed source and the OPA was conducted, including energy, spatial, spectral, and temporal properties.

The soiling level of heliostat mirrors in Concentrated Solar Power (CSP) fields is one of the key factors that significantly influences optical efficiency. While several methods of monitoring heliostats soiling levels have been developed, it remains challenging to determine heliostats soiling levels quickly and non-intrusively with large area scanning. We have developed a method based on polarimetric imaging to accomplish this goal, using the natural light’s polarization information and ray tracing calculations. With the flexibility to be integrated into a UAV-based imaging system or portable imaging setup, this method holds the potential of deployment to any CSP field for mirror soiling detection high efficiency and accuracy.

We investigate correlations between the configuration statistics of random metasurfaces and their spectral response. Our metasurfaces consist of a two-dimensional array of silicon nanopillars with widths sampled from a normal distribution placed on a silica substrate. We explore the effect of tuning the parameters characterizing the distribution of nanopillar widths on the wavelength-dependent transmissivity of the random metasurface in the 400 – 800 nm wavelength range. This analysis helps us create a direct mapping between the parameters of the nanopillar width distribution and the spectral responses of the random metasurfaces. We exploit this mapping to design a photonic device encoding spectrally encrypted image data in the visible wavelength range. Our findings offer new insight into the optical properties of random media and provide avenues for developing such systems for a broad range of applications.

The number of mirror segments, the geometry of the mirror, and its orientation are crucial factors in evaluating the beam-shaping abilities of deformable mirrors. In this study, we employ a Liquid Crystal on Silicon Spatial Light Modulator (LCoS-SLM) to replicate the mechanical configuration of a deformable mirror. We quantitatively analyze how the number of mirror segments and their geometric arrangement influence the resulting structured modes. Our methodology can serve as a preliminary assessment tool before developing a deformable mirror for high-power beam shaping.

Ultrafast pulse-beams are four-dimensional, space–time phenomena that can exhibit complicated spatiotemporal coupling. Tailoring the spatiotemporal profile of an ultrafast pulse beam is necessary for a variety of applications ranging from basic science involving high-intensity light matter interactions to applied microscopy and advanced manufacturing and micromachining.

In this talk I will discuss the development of a novel single-pulse, reference-free spatiotemporal characterization technique based on two colocated synchronized measurements: (1) broadband single-shot ptychography and (2) single-shot frequency resolved optical gating. We apply the technique to measure the nonlinear propagation of an ultrafast pulse beam through a fused silica window. Our spatiotemporal characterization method represents a major contribution to the growing field of spatiotemporally engineered ultrafast laser pulse beams.

Ellipsometry is a well-known, non-destructive optical method to measure a thin film's thickness and optical properties. It has been widely used to characterize the complex permittivity of a material or to control the quality of a film's thickness in manufacturing processes. Demands on microscopic characterizations of optical properties have been greatly increased for new materials and structures such as 2D materials, photonic devices, to name a few. Conventional ellipsometry, however, has been restricted to a spatial resolution of several tens of microns due to the spot size limitation. Here, we introduce imaging spectroscopic ellipsometry (ISE), which enables 1-micron lateral resolution, and its application to novel materials and structures. The ISE technique can be extensively used for new materials research and quality control of industrial applications.

This study introduces Microsphere-Assisted Hyperspectral Imaging (MAHSI), the world’s first metrology system combining microsphere super-resolution and hyperspectral imaging. The system achieves an ultra-small measurement spot size of 14.4 nm and an optical resolution of 66 nm, overcoming the diffraction limit and enabling precise non-destructive measurements of complex 3D semiconductor structures. A high-speed novel autofocus method has been developed specifically for the ultra-close working distances required by microsphere super-resolution optics for the first time. This innovative technique only requires two spectra acquisition, as a result, it can achieve fast and precise approach of the objective lens, ensuring accurate measurements without damaging the sample. The system has successfully monitored the uniformity of cell blocks in DRAM, and demonstrates its feasibility for semiconductor metrology. As semiconductor processes become increasingly refined, the proposed MAHSI system can be innovative and effective solution for encountered metrology and inspection challenges in semiconductor device analysis.

Recent research has shown that the arrangement and density of extracellular fibers within the tumor microenvironment can signify breast cancer stage. However, most biological fibers possess inherently weak birefringence. This means visualizing these structures requires expensive and complex nonlinear optics or stains that necessitate laborious preparation and risk false diagnosis due to potential artifacts. Access to both options can be especially challenging in underserved settings, where marginalized groups are more susceptible to aggressive variants of breast cancer. We leverage the polarization-sensitive structural color in Morpho butterfly wings for stain-free imaging of extracellular fibers in breast cancer tissue biopsies. We quantitatively assessed the anisotropic colorimetric response of histological tissue sections interfaced with these nanophotonic materials. The promising diagnostic properties of this stain-free imaging platform introduces a new method of diagnostic imaging for rapid, precise, and low-cost tissue diagnostics.

Light can be much more complex than a wave that travels in a straight line. Here we explore the challenge of shaping the trajectory of light, weaving a dynamic spectrum of vortex beams through space and time. This is achieved by introducing non-separable correlations between the beam’s frequency (its temporal signature) and its orbital angular momentum (its spatial properties). We use a Fourier space-time shaper based on an axicon grating to disperse the frequencies of a pulsed beam into colinear rings which are then individually tailored with an azimuthal phase via a digital modulator. The ability to coherently control both the spatial and temporal characteristics of laser beams paves the way for innovations in ultrafast light-matter interactions, microscopy and innovative multiplexing techniques.

Laser-Induced Breakdown (LIB) plasmas have been widely investigated from both an experimental and numerical point-of-view for their potential use in aerospace applications such as turbulent mixing control, supersonic steering, shockwave control, etc. However, many of these works only take into consideration the effects of pulse energy, focusing optics, and wavelength on the plasma spark morphology. Furthermore, in many numerical studies, a Gaussian temperature distribution is assumed and either the single or two-fluid equations for plasma development are solved directly, which can be computationally expensive. We propose a model utilizing the Fourier implementation of wave-optics, coupled with a Drude-like model for the electron number density which will encapsulate electromagnetic wave dispersion caused by the plasma generation as well as electron generation via Multiphoton Ionization (MPI), electron-neutral impact ionization, electron diffusion, and recombination.

The exploration of chirality linked to the pseudoscalar topological charge ℓ in scalar vortex beams has garnered significant attention. Recently, focus has shifted to cylindrical vector vortex beams, characterized by the pseudoscalar Pancharatnam topological charge, ℓ, representing higher-order Poincarè modes. Our experimental investigation, utilizing vectorial modes with Laguerre Gaussian (LG) spatial profiles, unveils controllable optical chirality and spin densities within higher-order chiral structured beams by manipulating the Pancharatnam topological charge ℓp. The presented theoretical analysis reaffirms that the distinctive topological properties inherent in these higher-order vector modes dictate the dynamical characteristics of the fields. Anticipating practical applications in optical manipulation and information, these novel structural properties offer promising avenues for exploration.