Women from racial and ethnic minority groups face a disproportionate burden of cervical and breast cancers in the United States. The Coronavirus Disease 2019 (COVID-19) pandemic might exacerbate ...these disparities as supply and demand for screening services are reduced. The National Breast and Cervical Cancer Early Detection Program (NBCCEDP) provides cancer screening services to women with low income and inadequate health insurance. We examined COVID-19's impact on NBCCEDP screening services during January-June 2020. We found the total number of NBCCEDP-funded breast and cervical cancer screening tests declined by 87% and 84%, respectively, during April 2020 compared with the previous 5-year averages for that month. The extent of declines varied by geography, race/ethnicity, and rurality. In April 2020, screening test volume declined most severely in Health and Human Services Region 2 - New York (96% for breast, 95% for cervical cancer screening) compared to the previous 5-year averages. The greatest declines were among American Indian/Alaskan Native women for breast cancer screening (98%) and Asian Pacific Islander women for cervical cancer screening (92%). Test volume began to recover in May and, by June 2020, NBCCEDP breast and cervical cancer screening test volume was 39% and 40% below the 5-year average for that month, respectively. However, breast cancer screening remained over 50% below the 5-year average among women in rural areas. NBCCEDP programs reported assisting health care providers resume screening.
•Women of color face a disproportionate burden of cervical and breast cancers in the United States.•The COVID-19 pandemic reduced breast and cervical cancer screening among low-income women.•Prolonged delays in screening due to COVID-19 threaten to increase disparities in cancer outcomes.
Deep-UV (DUV) supercontinuum (SC) sources based on gas-filled hollow-core fibers constitute perhaps the most viable solution towards ultrafast, compact, and tunable lasers in the UV spectral region, ...which can even also extend into the mid-infrared (IR). Noise and spectral stability of such broadband sources are key parameters that define their true potential and suitability towards real-world applications. In order to investigate the spectral stability and noise levels in these fiber-based DUV sources, we generate an SC spectrum that extends from 180 nm (through phase-matched dispersive waves - DWs) to 4 μm by pumping an argon-filled hollow-core anti-resonant fiber at a mid-IR wavelength of 2.45 μm. We characterize the long-term stability of the source over several days and the pulse-to-pulse relative intensity noise (RIN) of the DW at 275 nm. The results indicate no sign of spectral degradation over 110 hours, but the RIN of the DW pulses at 275 nm is found to be as high as 33.3%. Numerical simulations were carried out to investigate the spectral distribution of the RIN and the results confirm the experimental measurements and that the poor noise performance is due to the high RIN of the mid-IR pump laser, which was hitherto not considered in numerical modelling of these sources. The results presented herein provide an important step towards an understanding of the noise mechanism underlying such complex light-gas nonlinear interactions and demonstrate the need for pump laser stabilization.
Ab-initio density functional perturbation theory is used for precise prediction of terahertz-frequency vibrational signatures in solid-state materials.
We use a combination of experimental THz ...time-domain spectroscopy and
ab-initio density functional perturbative theory to accurately predict the terahertz vibrational spectrum of molecules in the crystalline phase. Our calculations show that distinct vibrational modes found in solid-state materials are best described as phonon modes with strong coupling to the intramolecular degrees of freedom. Hence a computational method taking the periodicity of the crystal lattice as well as intramolecular motion into account is a prerequisite for the correct prediction of vibrational modes in such materials.
We demonstrate the first megahertz (MHz) repetition-rate, broadband terahertz (THz) source based on optical rectification in the organic crystal HMQ-TMS driven by a femtosecond Yb:fibre laser. ...Pumping at 1035 nm with 30 fs pulses, we achieve few-cycle THz emission with a smooth multi-octave spectrum that extends up to 6 THz at -30 dB, with conversion efficiencies reaching 10
and an average output power of up to 0.38 mW. We assess the thermal damage limit of the crystal and conclude a maximum fluence of ∼1.8 mJ·cm
at 10 MHz with a 1/e
pump beam diameter of 0.10 mm. We compare the performance of HMQ-TMS with the prototypical inorganic crystal gallium phosphide (GaP), yielding a tenfold electric field increase with a peak on-axis field strength of 7 kV·cm
and almost double the THz bandwidth. Our results further demonstrate the suitability of organic crystals in combination with fibre lasers for repetition-rate scaling of broadband, high-power THz sources for time-domain spectroscopic applications.
We use mono-crystalline gold platelets with ultra-smooth surfaces and superior plasmonic properties to investigate the formation of interference patterns caused by surface plasmon polaritons (SPPs) ...with scattering-type scanning near-field microscopy at 521 and 633 nm. By applying a Fourier analysis approach, we can identify and separate several signal channels related to SPPs launched and scattered by the atomic force microscopy tip and the edges of the platelet. Especially at the excitation wavelength of 633 nm, we can isolate a region in the center of the platelets where we find only contributions of SPPs which are launched by the tip and reflected at the edges. These signatures are used to determine the SPP wavelength of
= 606 nm in good agreement with theoretical predictions. Furthermore, we were still able to measure SPP signals after 20 µm propagation, which demonstrates impressively the superior plasmonic quality of these mono-crystalline gold platelets.
Attenuation of THz Beams: A “How to” Tutorial Kaltenecker, Korbinian J.; Kelleher, Edmund J. R.; Zhou, Binbin ...
Journal of infrared, millimeter and terahertz waves,
08/2019, Letnik:
40, Številka:
8
Journal Article
Recenzirano
Odprti dostop
Attenuation of ultrashort THz pulses poses a significant technological challenge due to the broadband nature of such light pulses. Several methods exist for this purpose, including crossed wire grid ...polarizers, high refractive index, high resistivity silicon wafers, and ultrathin metal films. In this review, we discuss the operational principles of these methods, and highlight some of the advantages and potential pitfalls of the methods. We describe the limits of high-frequency operation of wire grid polarizers, relevant for contemporary ultra-broadband THz sources in air photonics. We discuss the effects of multiple reflections and interference in sequences of silicon wafers for attenuation, and finally discuss the potential of using ultrathin metallic films for broadband attenuation.
This feature issue presents recent progress in long-wavelength photonics, focusing on wavelengths that span the mid-infrared (3-50 µm), the long-wavelength infrared (30-60 µm), and the terahertz ...(60-300 µm) portions of the electromagnetic spectrum. The papers in this feature issue report recent progress in the generation, manipulation, detection, and use of light across this long-wave region of the "photonics spectrum," including novel sources and cutting edge advances in detectors, long-wavelength non-linear processes, optical metamaterials and metasurfaces, and molecular spectroscopy. The range of topics covered in this feature issue provide an excellent insight into the expanding interest in long-wavelength photonics, which could open new possibilities for basic research and applications in industries that span health, environmental, and security.
We report on a new class of polymer photonic crystal fibers for low-loss guidance of THz radiation. The use of the cyclic olefin copolymer Topas, in combination with advanced fabrication technology, ...results in bendable THz fibers with unprecedented low loss and low material dispersion in the THz regime.We demonstrate experimentally how the dispersion may be engineered by fabricating both high- and low-dispersion fibers with zero-dispersion frequency in the regime 0.5-0.6 THz. Near-field, frequency-resolved characterization with high spatial resolution of the amplitude and phase of the modal structure proves that the fiber is single-moded over a wide frequency range, and we see the onset of higher-order modes at high frequencies as well as indication of microporous guiding at low frequencies and high porosity of the fiber. Transmission spectroscopy demonstrates low-loss propagation (< 0.1 dB/cm loss at 0.6 THz) over a wide frequency range.
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