Parametric Waveform Synthesis: a scalable approach to generate sub-cycle optical transients

The availability of electromagnetic pulses with controllable field waveform and extremely short duration, even below a single optical cycle, is imperative to fully harness strong-field processes and to gain insight into ultrafast light-driven mechanisms occurring in the attosecond time-domain. The recently demonstrated parametric waveform synthesis (PWS) introduces an energy-, power- and spectrum-scalable method to generate non-sinusoidal sub-cycle optical waveforms by coherently combining different phase-stable pulses attained via optical parametric amplifiers. Significant technological developments have been addressed to overcome the stability issues related to PWS and to obtain an effective and reliable waveform control system. Here we present the main ingredients enabling PWS technology. The design choices concerning the optical, mechanical and electronic setups are justified by analytical/numerical modeling and benchmarked by experimental observations. In its present incarnation, the PWS technology enables the generation of field-controllable mJ-level few-femtosecond pulses spanning the visible to infrared range.Comment: 34 page

Using and Reporting the Delphi Method for Selecting Healthcare Quality Indicators: A Systematic Review

OBJECTIVE: Delphi technique is a structured process commonly used to developed healthcare quality indicators, but there is a little recommendation for researchers who wish to use it. This study aimed 1) to describe reporting of the Delphi method to develop quality indicators, 2) to discuss specific methodological skills for quality indicators selection 3) to give guidance about this practice. METHODOLOGY AND MAIN FINDING: Three electronic data bases were searched over a 30 years period (1978-2009). All articles that used the Delphi method to select quality indicators were identified. A standardized data extraction form was developed. Four domains (questionnaire preparation, expert panel, progress of the survey and Delphi results) were assessed. Of 80 included studies, quality of reporting varied significantly between items (9% for year's number of experience of the experts to 98% for the type of Delphi used). Reporting of methodological aspects needed to evaluate the reliability of the survey was insufficient: only 39% (31/80) of studies reported response rates for all rounds, 60% (48/80) that feedback was given between rounds, 77% (62/80) the method used to achieve consensus and 57% (48/80) listed quality indicators selected at the end of the survey. A modified Delphi procedure was used in 49/78 (63%) with a physical meeting of the panel members, usually between Delphi rounds. Median number of panel members was 17(Q1:11; Q3:31). In 40/70 (57%) studies, the panel included multiple stakeholders, who were healthcare professionals in 95% (38/40) of cases. Among 75 studies describing criteria to select quality indicators, 28 (37%) used validity and 17(23%) feasibility. CONCLUSION: The use and reporting of the Delphi method for quality indicators selection need to be improved. We provide some guidance to the investigators to improve the using and reporting of the method in future surveys

International Consensus Statement on Rhinology and Allergy: Rhinosinusitis

Background: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR‐RS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICAR‐RS‐2021 as well as updates to the original 140 topics. This executive summary consolidates the evidence‐based findings of the document. Methods: ICAR‐RS presents over 180 topics in the forms of evidence‐based reviews with recommendations (EBRRs), evidence‐based reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary. Results: ICAR‐RS‐2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidence‐based management algorithm is provided. Conclusion: This ICAR‐RS‐2021 executive summary provides a compilation of the evidence‐based recommendations for medical and surgical treatment of the most common forms of RS

Millijoule-level sub-cycle pulses from two channels of a parallel parametric waveform synthesizer

We report on an optical synthesis of two compressed channels from our parametric waveform synthesizer, leading to a 0.6 mJ 3.4 fs pulse (3.2 fs transform limited) with a central wavelength of 1.8 µn, corresponding to 0.6 optical cycles

Passively CEP stable sub-2-cycle source in the mid-infrared by adiabatic difference frequency generation

We report on the generation of a passive carrier-envelope phase (CEP) stable 1.7-cycle pulse in the mid-infrared by adiabatic difference frequency generation. With sole material-based compression, we achieve a sub-2-cycle 16-fs pulse at a center wavelength of 2.7 µm and measured a CEP stability of <190 mrad root mean square. The CEP stabilization performance of an adiabatic downconversion process is characterized for the first time, to the best of our knowledge

Millijoule-level sub-cycle pulses from two channels of a parallel parametric waveform synthesizer

We report on an optical synthesis of two compressed channels from our parametric waveform synthesizer, leading to a 0.6 mJ 3.4 fs pulse (3.2 fs transform limited) with a central wavelength of 1.8 /an, corresponding to 0.6 optical cycles

Millijoule-level sub-cycle pulses from two channels of a parallel parametric waveform synthesizer

We report on an optical synthesis of two compressed channels from our parametric waveform synthesizer, leading to a 0.6 mJ 3.4 fs pulse (3.2 fs transform limited) with a central wavelength of 1.8 /an, corresponding to 0.6 optical cycles

Tunable isolated attosecond pulse generation by sub-cycle synthesized waveforms

The future development of attosecond science will largely depend on the availability of better attosecond pulsesources. In particular, the current generation of laser-based attosecond sources suffers from a low photon-flux,especially in the soft X-ray region, and a limited tunability of attosecond pulse parameters, such as its centralenergy, bandwidth and consequently pulse duration, from a single source. The latter is of particular interestin order to selectively excite electronic transitions and to concentrate the photon flux in the spectral region ofinterest. Moreover, the possibility of controlling the pulse duration can elucidate its impact on the decoherencemechanisms that follow ionization[1].In our group we use tailored IR waveforms, obtained via coherent synthesis of the output pulses from differentOPA sources, to drive the generation of attosecond pulses via HHG. Due to the optical bandwidth of almost2 octaves, these IR waveforms can have FWHM durations down to a fraction of the central optical cycle,allowing to directly generate isolated attosecond pulses (IAPs) without additional gating[2]. Moreover bycontrolling two synthesis parameters, the relative phase among the two combined pulses and the overall CEP,we demonstrated the possibility to tune the central energy and the bandwidth of the IAPs as well as theirduration, in the XUV spectral region[3]. Recently we started investigating the generation of IAPs in the softX-ray region. Preliminary observations, shown in Fig.1, suggests the possibility to obtain IAPs with photonenergies up to ~450 eV. At present, measurements to explore the possibility of increasing IAP generationefficiency in the soft X-ray region by means of non-sinusoidal optical waveforms are underway.We believe that the possibility of tuning the IAP parameters over a wide range offered by waveform synthesiscould be a great stimulus for the development of increasingly sophisticated attosecond experiments