Versatile multimodality imaging system based on detectorless and scanless optical feedback interferometry—a retrospective overview for a prospective vision

In this retrospective compendium, we attempt to draw a “fil rouge” along fifteen years of our research in the field of optical feedback interferometry aimed at guiding the readers to the verge of new developments in the field. The general reader will be moved at appreciating the versatility and the still largely uncovered potential of the optical feedback interferometry, for both sensing and imaging applications. By discovering the broad range of available wavelengths (0.4–120 μm), the different types of suitable semiconductor lasers (Fabry–Perot, distributed feedback, vertical-cavity, quantum-cascade), and a number of unconventional tenders in multi-axis displacement, ablation front progression, self-referenced measurements, multispectral, structured light feedback imaging and compressive sensing, the specialist also could find inspirational suggestions to expand his field of research

Nozaki-Bekki optical solitons

Recent years witnessed rapid progress of chip-scale integrated optical frequency comb sources. Among them, two classes are particularly significant -- semiconductor Fabry-Per\'{o}t lasers and passive ring Kerr microresonators. Here, we merge the two technologies in a ring semiconductor laser and demonstrate a new paradigm for free-running soliton formation, called Nozaki-Bekki soliton. These dissipative waveforms emerge in a family of traveling localized dark pulses, known within the famed complex Ginzburg-Landau equation. We show that Nozaki-Bekki solitons are structurally-stable in a ring laser and form spontaneously with tuning of the laser bias -- eliminating the need for an external optical pump. By combining conclusive experimental findings and a complementary elaborate theoretical model, we reveal the salient characteristics of these solitons and provide a guideline for their generation. Beyond the fundamental soliton circulating inside the ring laser, we demonstrate multisoliton states as well, verifying their localized nature and offering an insight into formation of soliton crystals. Our results consolidate a monolithic electrically-driven platform for direct soliton generation and open a door for a new research field at the junction of laser multimode dynamics and Kerr parametric processes

Excess mortality in US Veterans during the COVID-19 pandemic: an individual-level cohort study.

BACKGROUND: Most analyses of excess mortality during the COVID-19 pandemic have employed aggregate data. Individual-level data from the largest integrated healthcare system in the US may enhance understanding of excess mortality. METHODS: We performed an observational cohort study following patients receiving care from the Department of Veterans Affairs (VA) between 1 March 2018 and 28 February 2022. We estimated excess mortality on an absolute scale (i.e. excess mortality rates, number of excess deaths) and a relative scale by measuring the hazard ratio (HR) for mortality comparing pandemic and pre-pandemic periods, overall and within demographic and clinical subgroups. Comorbidity burden and frailty were measured using the Charlson Comorbidity Index and Veterans Aging Cohort Study Index, respectively. RESULTS: Of 5 905 747 patients, the median age was 65.8 years and 91% were men. Overall, the excess mortality rate was 10.0 deaths/1000 person-years (PY), with a total of 103 164 excess deaths and pandemic HR of 1.25 (95% CI 1.25-1.26). Excess mortality rates were highest among the most frail patients (52.0/1000 PY) and those with the highest comorbidity burden (16.3/1000 PY). However, the largest relative mortality increases were observed among the least frail (HR 1.31, 95% CI 1.30-1.32) and those with the lowest comorbidity burden (HR 1.44, 95% CI 1.43-1.46). CONCLUSIONS: Individual-level data offered crucial clinical and operational insights into US excess mortality patterns during the COVID-19 pandemic. Notable differences emerged among clinical risk groups, emphasizing the need for reporting excess mortality in both absolute and relative terms to inform resource allocation in future outbreaks

Coherent master equation for laser modelocking

Modelocked lasers constitute the fundamental source of optically-coherent ultrashort-pulsed radiation, with huge impact in science and technology. Their modeling largely rests on the master equation (ME) approach introduced in 1975 by Hermann A. Haus. However, that description fails when the medium dynamics is fast and, ultimately, when light-matter quantum coherence is relevant. Here we set a rigorous and general ME framework, the coherent ME (CME), that overcomes both limitations. The CME predicts strong deviations from Haus ME, which we substantiate through an amplitude-modulated semiconductor laser experiment. Accounting for coherent effects, like the Risken-Nummedal-Graham-Haken multimode instability, we envisage the usefulness of the CME for describing self-modelocking and spontaneous frequency comb formation in quantum-cascade and quantum-dot lasers. Furthermore, the CME paves the way for exploiting the rich phenomenology of coherent effects in laser design, which has been hampered so far by the lack of a coherent ME formalism

The Queen and I: Neural Correlates of Altered Self-Related Cognitions in Major Depressive Episode

BACKGROUND: Pervasive negative thoughts about the self are central to the experience of depression. Brain imaging studies in the general population have localised self-related cognitive processing to areas of the medial pre-frontal cortex. AIMS: To use fMRI to compare the neural correlates of self-referential processing in depressed and non-depressed participants. METHOD: Cross-sectional comparison of regional activation using Blood Oxygen Level Dependent (BOLD) fMRI in 13 non-medicated participants with major depressive episode and 14 comparison participants, whilst carrying out a self-referential cognitive task. RESULTS: Both groups showed significant activation of the dorsomedial pre-frontal cortex and posterior cingulate cortex in the 'self-referent' condition. The depressed group showed significantly greater activation in the medial superior frontal cortex during the self-referent task. No difference was observed between groups in the 'other-referent' condition. CONCLUSIONS: Major depressive episode is associated with specific neurofunctional changes related to self-referential processing

Analysis of an 80 Gallon Radioactive Waste Package retrieved from the Atlantic Ocean

This progress report summarizes studies performed at Brookhaven National Laboratory (BNL) on the properties of a radioactive waste package recovered from the floor of the Atlantic Ocean 2800 meter radioactive waste disposal site. The recovery was made during DEEPSE SURVEY OPERATION NO.5, as part of a comprehensive study of disused deepsea radioactive disposal sites by the Office of Radiation Programs of the Environmental Protection Agency. A major objective of this study is to assess the effectiveness of past packaging techniques relevant to the isolation of radionuclides from the ocean environment over the period of time they remain potentially hazardous. For this purpose, a typical radioactive waste package which had previously been located and identified through the use of the deep sea submersible ALVIN was recovered aboard the R.V. CAPE HENLOPEN, 31 July 1976. The package was recovered from the NW quadrant of the 28 meter Atlantic site and consists of an 80 gallon mild steel drum filled with a solidified mixture of concrete and radioactive materials

Theoretical description of the transverse localised structures in a face to face VCSEL configuration

A theoretical framework is derived for the description of the localised structures which have recently been observed in a system of two coupled broad-area VCSEL in a long cavity self imaging configuration. The model succeeds in reproducing, at least qualitatively, the experimental observations: the numerous types of monochromatic cavity solitons, the left or right handed vortices as well as their striking spectral characteristics