Mitigation Planning and Policies Informed by COVID-19 Modeling: A Framework and Case Study of the State of Hawaii.

In the face of great uncertainty and a global crisis from COVID-19, mathematical and epidemiologic COVID-19 models proliferated during the pandemic. Yet, many models were not created with the explicit audience of policymakers, the intention of informing specific scenarios, or explicit communication of assumptions, limitations, and complexities. This study presents a case study of the roles, uses, and approaches to COVID-19 modeling and forecasting in one state jurisdiction in the United States. Based on an account of the historical real-world events through lived experiences, we first examine the specific modeling considerations used to inform policy decisions. Then, we review the real-world policy use cases and key decisions that were informed by modeling during the pandemic including the role of modeling in informing planning for hospital capacity, isolation and quarantine facilities, and broad public communication. Key lessons are examined through the real-world application of modeling, noting the importance of locally tailored models, the role of a scientific and technical advisory group, and the challenges of communicating technical considerations to a public audience.

High-power, frequency-doubled Nd:GdVO4 laser for use in lithium cold atom experiments.

We report on an 888 nm-pumped Nd:GdVO4 ring laser operational over a wavelength range from 1340.3 nm to 1342.1 nm with a maximum output power of 7.4 W at 1341.2 nm and a beam quality parameter M2<1.1. To our knowledge this is the highest single-longitudinal-mode power obtained with a Nd:GdVO4 crystal laser. We use a commercial frequency-doubling cavity to achieve 1.2 W at 671.0 nm and 4.0 W at 670.6 nm for use in lithium cold atom experiments. Respectively, these wavelengths are approximately resonant with and 250 GHz blue-detuned from the lithium D-lines. Thus, this source provides ample power for laser cooling of lithium atoms while also offering substantial power for experiments requiring light 10's to 100's of GHz blue-detuned from the primary lithium transitions.

A self-injected, diode-pumped, solid-state ring laser for laser cooling of Li atoms.

We have constructed a solid-state light source for experiments with laser cooled lithium atoms based on a Nd:YVO4 ring laser with second-harmonic generation. Unidirectional lasing, an improved mode selection, and a high output power of the ring laser were achieved by weak coupling to an external cavity which contained the lossy elements required for single frequency operation. Continuous frequency tuning is accomplished by controlling two piezoelectric transducers (PZTs) in the internal and the external cavities simultaneously. The light source has been utilized to trap and cool fermionic lithium atoms into the quantum degenerate regime.

s-Wave collisional frequency shift of a fermion clock.

We report an s-wave collisional frequency shift of an atomic clock based on fermions. In contrast to bosons, the fermion clock shift is insensitive to the population difference of the clock states, set by the first pulse area in Ramsey spectroscopy, θ(1). The fermion shift instead depends strongly on the second pulse area θ(2). It allows the shift to be canceled, nominally at θ(2)=π/2, but correlations perturb the null to slightly larger θ(2). The frequency shift is relevant for optical lattice clocks and increases with the spatial inhomogeneity of the clock excitation field, naturally larger at optical frequencies.