arXiv subjects

Samuel D. Crossley

Publications and source records attributed to Samuel D. Crossley.

4 recordsLinked to original sources

arXiv2025

High resolution 3D imaging of diamonds with multiphoton microscopy

Diamonds offer unique benefits for optical technology development due to their optical, chemical, electrical, mechanical, and thermal properties. These attributes also contribute to their aesthetic appeal, high commercial value, and utility in geological studies. Thus, there is high demand for nondestructive techniques that enable rapid analysis of natural and synthetic diamonds as well as diamond-like simulants. Here, we demonstrate sub-micrometer, nondestructive, three-dimensional imaging and spectral analysis of diamonds using multiphoton microscopy (MPM). This approach stimulates nonlinear optical emissions to provide unique insights into the interior structure, fluorescent defects, and formational conditions of diamonds. As a result, MPM can be used to investigate gemstone quality, vacancy centers used in quantum technologies, and the various inclusions and fluorescent emitters that may trace gemstone provenance and treatment history.

physics.optics↗

arXiv2025

Fifth Harmonic and Five-Photon Excitation Fluorescence Multiphoton Microscopy

We report the application of fifth order nonlinear optical processes for multiphoton microscopy, including fifth harmonic and 5-photon excitation fluorescence. This novel imaging modality has been characterized with spectral and power dependence measurements. The advantages of fifth harmonic and 5-photon excitation fluorescence imaging are higher resolution and use of longer wavelength excitation sources, which may allow deeper penetration depth, while still exciting near-UV to blue fluorophores. This imaging modality may find interesting applications in biological research, materials characterization, geologic studies, and semiconductor manufacturing.

physics.optics↗

arXiv2024

Fluorescent emission and nondestructive 3D textural imaging in geologic materials by multiphoton microscopy

We greatly expand the application of multiphoton microscopy to geological investigations by using a tightly focused femtosecond laser beam to excite fluorescent emissions among minimally prepared rock and mineral samples. This new finding provides a tool for spatially resolving UV-visible fluorescent sources in minerals. Using a unique combination of harmonic generation and fluorescence, we explore applications to mineralogical investigations of terrestrial rocks and astromaterials. We report first-order demonstrations for 3D imaging of fluid inclusions in minerals and radiation-induced luminescence in meteorites. Nonlinear optical mineralogy, enabled by multiphoton microscopy, provides unique insights in mineralogic samples and holds the potential to revolutionize the analysis of geologic and astromaterials samples in the coming years.

physics.geo-ph↗

arXiv2024

Neglected Silicon Dioxide Polymorphs as Clouds in Substellar Atmospheres

Direct mid-infrared signatures of silicate clouds in substellar atmospheres were first detected in Spitzer observations of brown dwarfs, although their existence was previously inferred from near-infrared spectra. With JWST's Mid-Infrared Instrument (MIRI) instrument, we can now more deeply probe silicate features from 8 to 10 microns, exploring specific particle composition, size, and structure. Recent characterization efforts have led to the identification in particular of silica (silicon dioxide, SiO$_2$) cloud features in brown dwarfs and giant exoplanets. Previous modeling, motivated by chemical equilibrium, has primarily focused on magnesium silicates (forsterite, enstatite), crystalline quartz, and amorphous silica to match observations. Here, we explore the previously neglected possibility that other crystalline structures of silica, i.e. polymorphs, may be more likely to form at the pressure and temperature conditions of substellar upper atmospheres. We evaluate JWST's diagnostic potential for these polymorphs and find that existing published transmission data are only able to conclusively distinguish tridymite, but future higher signal-to-noise transmission observations, directly imaged planet observations, and brown dwarf observations may be able to disentangle all four of the silica polymorphs. We ultimately propose that accounting for the distinct opacities arising from the possible crystalline structure of cloud materials may act as a powerful, observable diagnostic tracer of atmospheric conditions, where particle crystallinity records the history of the atmospheric regions through which clouds formed and evolved. Finally, we highlight that high fidelity, accurate laboratory measurements of silica polymorphs are critically needed to draw meaningful conclusions about the identities and structures of clouds in substellar atmospheres.

astro-ph.EP↗