Mr. Sam Jeppson Profile

Sam Jeppson

at Lawrence Livermore National Lab.

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Author

Publications (2)

Proceedings Article | 13 March 2024 Presentation + Paper

Ghost imaging using two SPAD array detectors: a parameter study towards the realization of a 3D quantum microscope

Dominique Davenport, Audrey Eshun, Brandon Demory, Paul Mos, Lin Yang, Sam Jeppson, Ashleigh Wilson, Shervin Kiannejad, Tiziana Bond, Mike Rushford, Chuck Boley, Edoardo Charbon, Claudio Bruschini, Ted Laurence

Proceedings Volume 12863, 1286307 (2024) https://doi.org/10.1117/12.3002965

KEYWORDS: Crystals, Quantum entanglement, Sensors, Quantum ghost imaging, Microscopes, Image filtering, Single photon avalanche diodes

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Proceedings Article | 13 March 2024 Presentation + Paper

Investigating fluorescent amino acids with entangled two-photon excited fluorescence

Audrey Eshun, Ashleigh Wilson, Megan Shelby, Dominique Davenport, Sam Jeppson, Brandon Demory, Shervin Kiannejad, Charles Boley, Mike Rushford, Tiziana Bond, Ted Laurence

Proceedings Volume 12863, 1286306 (2024) https://doi.org/10.1117/12.3003307

KEYWORDS: Fluorescence, Quantum entanglement, Light absorption, Ultraviolet radiation, Proteins, Photon counting, Fluorescence imaging

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Fluorescence microscopy has become integral to biological studies for the technique’s ability to elucidate structures of biomolecules for in-situ studies with high selectivity and specificity. Imaging of intrinsic indicators, such as fluorescent amino acids in proteins, provides important information, but can be challenging to accomplish. Current microscopy techniques that measure native fluorescence without the use of exogenous labels involve either direct UV excitation which is commonly non-localized and can be detrimental to the system, or multiphoton absorption which must be conducted at high intensities, therefore posing high risks of photodamage. As such, we seek to investigate an efficient way to gently excite native fluorescence in biological systems in a way that overcomes these limitations. Quantum entangled photon pairs generated via spontaneous parametric downconversion (SPDC), may be an alternative to conducting two-photon absorption (TPA) to excite fluorescence in amino acids without the high fluences currently used. These photon pairs are highly correlated in time. Thus, the arrival of one photon is simultaneously followed by the arrival of its sister photon. As a result, a molecule interacting with the photon pair should simultaneously absorb both photons, leading to a linear two-photon absorption rate, and the linearity of the two-photon process should dramatically reduce the light intensity necessary for TPA. Therefore, quantum entangled photon pairs offer the possibility of performing low intensity UV excitation using photons in the visible wavelength range. With this work, we generated and characterized entangled photons generated via SPDC, and investigated whether fluorescent amino acids can be excited, and the subsequent fluorescence induced with entangled two-photon absorption. Results show that much higher entangled two-photon rates than what are currently available are needed to measure significant signals with entangled two-photon excitation.

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