https://joewiedemann.info/publications/Recent content in Publications on Joe WiedemannHugoen-usFri, 18 Apr 2025 00:00:00 +0000https://joewiedemann.info/publications/pxs-graphite/Fri, 18 Apr 2025 00:00:00 +0000https://joewiedemann.info/publications/pxs-graphite/<h2 id="motivation">Motivation</h2> <p>Cryogenic systems have the contradictory requirement of needing high thermal conductivity during the bulk cooldown period, and maximized thermal isolation at the base temperature operation. Heat switches provide a mechanism to change the thermal conductivity between two stages. A typical design is to use a gas-gap heat switch which uses a heater to expel Helium gas as a conduction mechanism between the two sides of the switch. These active switches can be costly and require additional DC wiring instrumentation in the cryostat. For large thermal masses in bulk cooldown, this can be an excessive effort to accelerate the cooldown process. However, pyrolytic graphite sheet demonstrates passive heat switch capabilities as the phonons freeze out and create minimal loading at base temperature. By analyzing the cryogenic performance of a custom-designed graphite heat switch, we were able to implement heat switches that sped up our bulk cooldown from ~4 days to ~2 days for less than 10% the cost of a gas-gap heat switch and without additional wiring instrumentation.</p>https://joewiedemann.info/publications/rydberg-rades/Mon, 10 Jun 2024 00:00:00 +0000https://joewiedemann.info/publications/rydberg-rades/<h2 id="motivation">Motivation</h2> <p>Quantum metrology demonstrates that atomic references for precision measurements have exceptional sensitivity and self-calibrating behavior. Microwave sensing in particular is reliant on antenna calibration and requires sophisticated signal processing to attempt to distinguish between incoherent thermal radiation and coherent fields. Prior to this work, state-of-the-art microwave sensitivity measurements using atomic vapors relied on experimental techniques to reduce the laser linewidth, as the optical linewidths dominate the atomic linewidths by many orders of magnitude. This work applied techniques from NMR to decouple the sensitivity from the optics: which is enabled by the long lifetime of the Rydberg state.</p>https://joewiedemann.info/publications/oam-scintillation/Sun, 01 Mar 2020 00:00:00 +0000https://joewiedemann.info/publications/oam-scintillation/<h2 id="summary">Summary</h2> <p>This work found preliminary evidence that imparting orbital angular momentum onto Gaussian-mode laser beams can weakly improve their intensity stability in atmospheric turbulence. The experiment required building an 890-meter optical link across the Severn River and co-aligning it with a scintillometer to characterize the atmosphere during each measurement.</p> <p>This work was published in <em>Optics Communications</em> and presented at the <em>Directed Energy Professional Society</em> conference.</p> <h2 id="key-contributions">Key Contributions</h2> <ul> <li>Compared a Gaussian beam with OAM beams carrying topological charges of 1, 6, and 8</li> <li>Measured beam scintillation across a real near-maritime link under varied atmospheric conditions</li> <li>Observed a weak reduction in scintillation index as topological charge increased</li> <li>Identified the additional measurement scale needed to improve statistical significance</li> </ul> <h2 id="link-to-work">Link to Work</h2> <ul> <li><a href="https://doi.org/10.1016/j.optcom.2019.124836">DOI</a></li> </ul> <h2 id="related-work">Related Work</h2> <p>This publication is from the <a href="https://joewiedemann.info/research/oam-scintillation/">Scintillation of Laser Beams Carrying Orbital Angular Momentum</a> project.</p>