This PDF file contains the front matter associated with SPIE Proceedings Volume 13132, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

In illumination optics, the goal is to modify a light source’s spatial distribution to achieve a specific irradiance target. By using freeform surfaces, the emitted light can be transformed into arbitrary irradiance patterns. Despite significant advances in freeform optics design, mostly for ideal light sources, current methods offer limited control over the surface shape, generally resulting in globally convex or concave surfaces. In an illumination context, smooth and oscillating freeform surfaces are possibly more interesting, but calculation methods are currently non-existent. This presentation introduces a deep learning approach for predicting such complex freeform topologies, capable of rapidly generating optics that transform a prescribed light source into arbitrary irradiance patterns. This allows for the creation of surfaces with convex, concave, and saddle regions, showcasing the potential of deep learning in accelerating illumination design.

Uniformity is a critical performance issue in illumination design. When Etendue is considered, the two main options to achieve uniformity are mixing rods and lens arrays. Mixing rods are quite effective, but they often require a large package size and usually only provide spatial mixing. A Turn-Mixer concept based on a turn prism with embedded partial mirrors has been explored as a means to provide both spatial and angular mixing. We show how this concept can be applied to mixing rod geometries.

Description and implementation case study of low étendue, ultra-bright, and non-coherent laser-based light source (1150 lm, 8000 cd) built on a 5W blue LD and YAG based single crystal phosphor for high-efficiency technical applications. The recent development of a new laser-based light source offers enhanced performance and efficiency across various domains, notably in light microscopy, medical procedures, advanced industrial applications, and far-field illumination. This innovative source, with a directional and narrow angle beam, is characterized by its high luminous flux, an impressive luminous intensity exceeding 6000 cd and ability to localize its optical power outperforming any existing LED technology by an order of magnitude. Constructed around a 5 W blue laser diode, laser based light source boasts a compact design and is highly amenable to seamless system integration. Designed explicitly for scientific, biotech, and machine vision applications, it showcases a remarkably low étendue, with 50% of its power concentrated within G ⪅ 0.4 mm2.sr, promising unparalleled system efficiency and the potential to revolutionize optical setups.

Quantum dots technology enhances light emitters and becomes increasingly important in display applications for providing higher luminance and larger color gamut. When light passes through a film with quantum dots, the light is scattered or absorbed, and a portion of the absorbed light is re-emitted at a different wavelength. The photon events within quantum dots, on the macroscopic level, can be described probabilistically using rays with unconverted or converted wavelengths. When the rays exit the material, metrics can then be evaluated from the ray data to assess display performance. Therefore, by varying the parameters of the quantum dots, the performance of quantum dot displays can be optimized. In this paper, we discuss how scattering events are modeled using quantum dots and describe examples of quantum dot device simulation and quantum dot display design.

This research investigates silicon-based absorbers to efficiently convert solar energy into heat in order to initiate chemical or physical reactions. We designed structures that utilize colloidal lithography to nano-pattern silicon-based solar absorbers as a way to enhance light trapping in the visible to near-infrared range. Colloidal lithography is a scalable and cost-effective patterning technique that uses self-assembled colloidal arrays, which removed to the costly masks in conventional lithography procedure. The silicon-based surface absorber achieved excellent absorption in the wavelength range from 380 nm to 1500 nm. The versatility and simplicity of the absorbers make them potentially applicable to a wide range of research projects and industrial products.

Micro concentrator photovoltaics (micro-CPV or μ-CPV) involves reducing the size of components in conventional CPV systems to lower costs while maintaining high conversion efficiencies of over 30%. This miniaturization of optics leads to significant material savings, which in turn enables novel optical approaches that were previously not feasible. Additionally, it allows for parallel manufacturing processes, such as roll-to-plate, to further reduce costs. In this proceeding, we present a collection of these optical technologies and their associated manufacturing processes.

Non-imaging freeform lenses are a convenient tool for intensity and beam shaping processes due to their highly customizable designs and high efficiency. The surface curvature of these lenses are designed to ensure optimal transport of energy from the light source to a target plane, and require increasingly precise fabrication to attain the desired efficiency in complicated beam shaping cases. Metasurfaces have the ability to impart any phase profile, thus mimicking any surface curvature, without additional fabrication challenges. Here we present a theoretical framework based on the optimal transport formulation from non-imaging optics, for calculating the two dimensional phase profile of a metasurface for applications with normally incident light and cylindrical symmetry.

Fresnel lenses are often designed by optimizing a virtual aspheric or freeform sag function, similar to the approach for traditional thick lenses. This method limits the degrees of freedom by constraining the vector field of surface gradient to be integrable. We introduce a method that removes the integrability constraint, while still ensuring continuous long facets. The presented method initializes a facet at a seed point and follows it along the curve of zero gradient. New seed points and facets are then added repeatedly until the whole lens surface is covered. Finally, we show how this approach can be used to realize an ´etendue squeezing line-focus solar concentrator that could not have been achieved using conventional thick lenses.

A technique for calculating étendue from flowlines is proposed for both Lambertian and non-Lambertian light fields. Hyperbolic curve fitting from flowline measurements is proposed as a means of extrapolating flowlines to the far-field for improved calculation of étendue. The technique is applicable to rotationally symmetric light fields, and to specific asymmetric light fields where analytic viewfactor calculations exist.

Non-imaging glass optical concentrators have many applications including high-speed optical wireless communication systems, optical free-space power transfer, and as a secondary concentrator for solar concentrators. Ray trace simulations are used to evaluate the maximum concentration, acceptance angle and efficiency tradeoffs for linear tapers, dielectric CPCs, and more general Dielectric Total Internal Reflection Concentrators (DTIRCs) compared to an ideal CPC. Femtosecond Laser Irradiation followed by selective Chemical Etching (FLICE) offers a fast and flexible prototyping pathway to fabricate single and multiport optical concentrators from fused silica glass plates. The fabrication of a single input to multiple output optical concentrator is presented, suitable for coupling into a multimode fiber or high-speed photodetector array. Thus, the multiport concentrator provides an advantageous form factor for concentrating or collimating applications, such as LED arrays, and is easily scalable to larger areas and number of outputs.

This presentation describes and discusses the various parts and components of a prototype that can handle 1 kW of solar power, in view of using the concentrated solar radiation and the solar-generated heat, for the processing of materials (i.e. solid substances). It is an advanced optical system - that collects, concentrates, controls and directs the solar radiation to the site of solar power utilization - to efficiently apply the output solar beam to the specific target. The principle of “double paraboloid reflection” recently proposed in our recent publications is used for the first time in this prototype. The motivation for the construction of the prototype is the validation of the work of Takashi Nakamura et al. presented at SPIE Optical Engineering + Applications events and proceedings in 2009 and 2011, in which silica optical fibers were used for passing high-flux solar energy.

Heliostat fields constitute one of the large-scale Concentrating Solar Power (CSP) options for electricity production and/or thermal storage. In a typical field, several thousand heliostats, each consisting of one or more mirrors, are precisely oriented to track and reflect the sunlight onto a receiver atop a central tower. Any misorientation of the heliostats during operation - due to structural changes, wear, tracking errors, etc. - must be detected and corrected to ensure maximum light collection essential for the economic viability of the plant. A number of metrology techniques for accurate determination of heliostats orientation during operation have been proposed and implemented. These are briefly reviewed in this paper followed by a detailed description of a novel ultrafast technique for the precise measurement and correction of the heliostats pointing errors and/or mirrors canting errors in a field.

This paper describes a heliostat metrology system which is developed based on deflectometry, utilizing a static perforated panel instead of conventional dynamic monitor displays to provide incident rays. The developed method is named Static Screen Deflectometry (SSD). This robust and scalable method is especially valuable for outdoor tests of large reflectors used in Concentrating Solar-thermal Power (CSP) systems. The developed method has been successfully demonstrated on a 2.4 𝑚 × 3.3 𝑚 float glass deformable reflector bent to focus sunlight at 113 𝑚 distance throughout a day. From images obtained from a camera at 50𝑚 distance, the reflector surface was measured to an accuracy of less than 1 𝑚𝑟𝑎𝑑 rms slope error in the full test scope.

The first automatic twisting heliostat, with 8 m² reflector, was completed and tested on-sun in January 2024. It was set up on a target-oriented dual-axis mount, with the target-axis aimed at a target 113 m to the west. The shape-twisting is purely automatic, made by a mechanical cam coupling to the cross-axis, which turns as the angle of incidence of the sun’s rays on the reflector. Three unsaturated images taken at different times of day were recorded of the sun on the target, reflected at angles of incidence of 5°, 49° and 68°. The measured FWHM of three images is very similar, about 1.09 m or 9.5 mrad, only slightly larger than an ideal solar disc, indicating that the different twisted reflector shapes are close to the ideal biconics needed to image the sun. The encircled energy measured for all three images was similar, 87% within approximately 1.30 m diameter. We report here also on a novel, tracking camera that employs a semitransparent beamsplitter fixed perpendicular to the mirror surface and to the plane of incidence. Over 2.5 hours of measurement of closed loop tracking, errors were ≤ 0.36 mrad rms, in both tracking axes.

The idea is to combine the solar energy reflected from a field of many heliostats to obtain a single focus of high concentration and high power. We exploit a new type of “twisting” heliostat” in which as the mount is moved to track the sun through the day, the reflector shape is twisted to maintain a focused image of the sun’s disc on the target, through the day over a wide range of angles of incidence. By combining the light reflected by many twisting heliostats into a single focus, we are not only able to accomplish but also maintain very high concentration and temperature through the day, with higher efficiency than has previously been possible with conventional heliostats having a fixed shape. A circular field of twisting heliostats is used to power a single intense focus atop a central tower. The light from all the heliostats is relayed to an upward facing receiver at the focus via a central Cassegrain secondary reflector located above the receiver. In a specific design targeting 1 MW of power, a 100 m diameter field arrays 431 twisting heliostats, each with a 7 m² reflector. The secondary reflector ,7.2 m in diameter, is located 24 m above the heliostat field, bringing sunlight with annual average power of 1 MW to a circular focus 0.8 m in diameter, at a concentration averaging 3,000 suns.

This research evaluates the efficiency of working fluids in direct adsorption solar collectors by incorporating magnetite (Fe₃O⁴) nanoparticles. Samples with Fe₃O₄ concentrations ranging from 0% to 1% were evaluated under direct solar exposure conditions. It was determined that the nanofluids exhibit higher thermal efficiency than pure ethylene glycol, indicating that magnetite enhances solar radiation absorption. However, higher nanoparticle concentration was observed to decrease the Specific Absorption Rate (SAR), likely due to lower radiation penetration. These results suggest that SAR could be a useful selection criterion for formulating nanofluids in DASC collector applications.

Solar energy is an abundant and renewable resource on Earth, but its potential is significantly enhanced when harnessed in space. Space-based solar energy systems present a compelling alternative to terrestrial solar power by capturing sunlight beyond Earth's atmosphere, where it is more intense and uninterrupted. In recent years, solar-powered lasers have shown a tremendous evolution in providing additional value for solar energy utilization. The solar-powered lasers are used to transform broadband solar radiation directly into a collimated, coherent, and monochromatic laser beam. However, the power density of radiations received from the sun is inadequate for irradiating the active medium of lasers. Hence, the concentrating optics is essential to enhance the power density of natural sunlight. In this study, an optical design of hybrid heliostat-parabolic mirror is presented as the primary concentrator of solar-powered lasers to enhance the concentration at the focal spot. The present study also considers different shapes (circular, rectangular) of mirrors in the rectangular packing arrangement and compares the achieved power. The simulation results evaluated that concentrated power from the circular-shaped mirror array (4 × 5) is 767.07W, and from the rectangular-shaped mirror array (4 × 4) is 942.73W. The rectangular mirrors attain a fill factor of 99.32%, significantly higher than the 77.89% fill factor of circular mirrors. This improvement is primarily due to a substantial reduction in the void area, decreasing from 22.10% for circular mirrors to only 0.67% for rectangular mirrors.