Broadly Tunable External Cavity Quantum Cascade Laser Development

FY07 final report for Laser Development task of ITAS project

Experimental test of modular noise propagation theory for quantum optics

We present and test against experiment a general technique that allows modular modeling of noise propagation in quantum optics experiments. Specifically, we consider a multielement frequency-doubling experiment that ultimately produces 1.7 dB/32% (3.0 dB/50% inferred) squeezing at 532 nm. Unlike previous theoretical treatments, we obtain completely analytical expressions for each element of the experiment. This allows intuitive analysis and straightforward experimental modeling. The exact role of driving noise is demonstrated: addition of a narrow linewidth mode cleaning cavity to reduce the driving noise improves the inferred squeezing from 0.75 to 3.0 dB. We find excellent agreement between the modular theory and experiment

Ultra-Trace Chemical Sensing with Long-Wave Infrared Cavity-Enhanced Spectroscopic Sensors

The infrared sensors task of Pacific Northwest National Laboratory's (PNNL's) Remote Spectroscopy Project (Task B of Project PL211) is focused on the science and technology of remote and in-situ spectroscopic chemical sensors for detecting proliferation and coun-tering terrorism. Missions to be addressed by remote chemical sensor development in-clude detecting proliferation of nuclear or chemical weapons, and providing warning of terrorist use of chemical weapons. Missions to be addressed by in-situ chemical sensor development include countering terrorism by screening luggage, personnel, and shipping containers for explosives, firearms, narcotics, chemical weapons, or chemical weapons residues, and mapping contaminated areas. The science and technology is also relevant to chemical weapons defense, air operations support, monitoring emissions from chemi-cal weapons destruction or industrial activities, law enforcement, medical diagnostics, and other applications. Sensors for most of these missions will require extreme chemical sensitivity and selectiv-ity because the signature chemicals of importance are expected to be present in low con-centrations or have low vapor pressures, and the ambient air is likely to contain pollutants or other chemicals with interfering spectra. Cavity-enhanced chemical sensors (CES) that draw air samples into optical cavities for laser-based interrogation of their chemical content promise real-time, in-situ chemical detection with extreme sensitivity to specified target molecules and superb immunity to spectral interference and other sources of noise. PNNL is developing CES based on quantum cascade (QC) lasers that operate in the mid-wave infrared (MWIR - 3 to 5 microns) and long-wave infrared (LWIR - 8 to 14 mi-crons), and CES based on telecommunications lasers operating in the short-wave infrared (SWIR - 1 to 2 microns). All three spectral regions are promising because smaller mo-lecular absorption cross sections in the SWIR are offset by the superior performance, ma-turity, and robustness of SWIR lasers, detectors, and other components, while the reverse is true for the MWIR and LWIR bands. PNNL's research activities include identification of signature chemicals and quantification of their spectroscopy, exploration of novel sensing techniques, and experimental sensor system construction and testing. In FY02, experimental QC laser systems developed with DARPA funding were used to explore continuous-wave (cw) CES in various forms culminating in the NICE-OHMS technique [1-3] discussed below. In FY02 PNNL also built an SWIR sensor to validate utility of the SWIR spectral region for chemical sensing, and explore the science and engineering of CES in field environments. The remainder of this report is devoted to PNNL's LWIR CES research. During FY02 PNNL explored the performance and limitations of several detection tech-niques in the LWIR including direct cavity-enhanced absorption, cavity-dithered phase-sensitive detection and resonant sideband cavity-enhanced detection. This latter tech-nique is also known as NICE-OHMS, which stands for Noise-Immune Cavity-Enhanced Optical Heterodyne Molecular Spectroscopy. This technique, pioneered in the near infra-red (NIR) by Dr J. Hall and coworkers at the University of Colorado, is one of the most sensitive spectroscopic techniques currently known. In this report, the first demonstra-tion of this technique in the LWIR is presented

Progress Report on Frequency - Modulated Differential Absorption Lidar

Modeling done at Pacific Northwest National Laboratory (PNNL) in FY2000 predicted improved sensitivity for remote chemical detection by differential absorption lidar (DIAL) if frequency-modulated (FM) lasers were used. This improved sensitivity results from faster averaging away of speckle noise and the recently developed quantum cascade (QC) lasers offer the first practical method for implementing this approach in the molecular fingerprint region of the infrared. To validate this model prediction, a simple laboratory bench FM-DIAL system was designed, assembled, tested, and laboratory-scale experiments were carried out during FY2001. Preliminary results of the FM DIAL experiments confirm the speckle averaging advantages predicted by the models. In addition, experiments were performed to explore the use of hybrid QC - CO2 lasers for achieving sufficient frequency-modulated laser power to enable field experiments at longer ranges (up to one kilometer or so). This approach will allow model validation at realistic ranges much sooner than would be possible if one had to first develop master oscillator - power amplifier systems utilizing only QC devices. Amplification of a QC laser with a CO2 laser was observed in the first hybrid laser experiments, but the low gain and narrow linewidth of the CO2 laser available for these experiments prevented production of a high-power FM laser beam

Long Wave Infrared Detection of Chemical Weapons Simulants

The purpose of Task 3.b under PL02-OP211I-PD07 (CBW simulant detection) was to demonstrate the applicability of the sensor work developed under this project for chemical and biological weapons detection. To this end, the specific goal was to demonstrate the feasibility of detection of chemical agents via that of simulants (Freons) with similar spectroscopic features. This has been achieved using Freon-125 as a simulant, a tunable external cavity quantum cascade laser (ECQCL), and a Herriott cell-based sensor developed at Pacific Northwest National Laboratory (PNNL) specifically for this task. The experimentally obtained spectrum of this simulant matches that found in the Northwest Infrared (NWIR) spectral library extremely well, demonstrating the ability of this technique to detect the exact shape of this feature, which in turn indicates the ability to recognize the simulant even in the presence of significant interference. It has also been demonstrated that the detected features of a typical interferent, namely water, are so different in shape and width to the simulant, that they are easily recognized and separated from such a measurement. Judging from the signal-to-noise ratio (SNR) of the experimental data obtained, the noise equivalent absorption sensitivity is estimated to be 0.5 x 10-7 to 1 x 10-6 cm-1. For the particular feature of the simulant examined in this work, this corresponds to a relative concentration of 50 to 25 parts-per-billion by volume (ppbv). The corresponding relative concentrations of other chemical targets would differ depending on the particular transition strengths, and would thus have to be scaled accordingly

Genes, Education, and Labor Market Outcomes: Evidence from the Health and Retirement Study

Recent advances have led to the discovery of specific genetic variants that predict educational attainment. We study how these variants, summarized as a genetic score variable, are associated with human capital accumulation and labor market outcomes in the Health and Retirement Study (HRS). We demonstrate that the same genetic score that predicts education is also associated with higher wages, but only among individuals with a college education. Moreover, the genetic gradient in wages has grown in more recent birth cohorts, consistent with interactions between technological change and labor market ability. We also show that individuals who grew up in economically disadvantaged households are less likely to go to college when compared to individuals with the same genetic score, but from higher socioeconomic status households. Our findings provide support for the idea that childhood socioeconomic status is an important moderator of the economic returns to genetic endowments. Moreover, the finding that childhood poverty limits the educational attainment of high-ability individuals suggests the existence of unrealized human potential

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

FY 2005 Laser Development Final Report

The Laser Development Task of Pacific Northwest National Laboratory's (PNNL) Remote Spectroscopy project (PL211I) is focused on the development of novel laser technology for a new generation of standoff and in-situ chemical sensors for detecting the proliferation of nuclear weapons. These lasers will improve the sensitivity, flexibility, or range of active standoff sensors, enable ultra-trace in situ sensors with enhanced selectivity, as well as greatly improve calibration of passive standoff sensors. In particular, laser transmitters with minimal size, weight, and power consumption (SWAP) are needed to meet the requirements for a variety of in situ or short-range stand-off sensors and sensors for small UAVs or other platforms. These laser transmitters need to be rugged and free of requirements for consumables such as liquid nitrogen. Many sensing techniques also require lasers that produce a single narrow wavelength (single longitudinal mode). Lasers that provide high continuous-wave (CW) output power on a single line at operating temperatures accessible with thermoelectric (TE) cooling are therefore essential for sensor applications

Rapid and Sensitive Quantification of Isotopic Mixtures Using a Rapidly-Swept External Cavity Quantum Cascade Laser

A rapidly-swept external-cavity quantum cascade laser with an open-path Herriott cell is used to quantify gas-phase chemical mixtures of D2O and HDO at a rate of 40 Hz (25-ms measurement time). The chemical mixtures were generated by evaporating D2O liquid near the open-path Herriott cell, allowing the H/D exchange reaction with ambient H2O to produce HDO. Fluctuations in the ratio of D2O and HDO on timescales of &lt;1 s due to the combined effects of plume transport and the H/D exchange chemical reaction are observed. Noise-equivalent concentrations (1σ) (NEC) of 147.0 ppbv and 151.6 ppbv in a 25-ms measurement time are determined for D2O and HDO, respectively, with a 127-m optical path. These NECs are improved to 23.0 and 24.0 ppbv with a 1-s averaging time for D2O and HDO, respectively. NECs &lt;200 ppbv are also estimated for N2O, 1,1,1,2–tetrafluoroethane (F134A), CH4, acetone and SO2 for a 25-ms measurement time. The isotopic precision for measurement of the [D2O]/[HDO] concentration ratio of 33‰ and 5‰ is calculated for the current experimental conditions for measurement times of 25 ms and 1 s, respectively