Measuring the temperature and heating rate of a single ion by imaging

We present a technique based on high resolution imaging to measure the absolute temperature and the heating rate of a single ion trapped at the focus of a deep parabolic mirror. We collect the fluorescence light scattered by the ion during laser cooling and image it onto a camera. Accounting for the size of the point-spread function and the magnification of the imaging system, we determine the spatial extent of the ion, from which we infer the mean phonon occupation number in the trap. Repeating such measurements and varying the power or the detuning of the cooling laser, we determine the anomalous heating rate. In contrast to other established schemes for measuring the heating rate, one does not have to switch off the cooling but the ion is always maintained in a state of thermal equilibrium at temperatures close to the Doppler limit

Efficient light-matter interaction based on 4pi focusing with a monolithic parabolic mirror

Licht-Materie Wechselwirkung ist eine Schlüsseltechnologie für zahlreiche wissenschaftliche Experimente und industriell genutzte Anwendungen. Fortschritte in der Kopplungseffizienz zwischen Licht und Materie könnten neue technische Anwendungen und neuartige Hochpräzisionsexperimente ermöglichen. Im Speziellen könnte die Umkehrbarkeit der spontanen Emission experimentell demonstriert werden. In dieser Arbeit wird deshalb ein optischer Aufbau realisiert, welcher einen 4pi Parabolspiegel nutzt, um hocheffiziente Licht-Materie Wechselwirkung im Freiraum zu erzielen. Ein quantitatives Modell wird erarbeitet, welches die Kopplungseffizienz mithilfe der dominierenden experimentellen Parameter simuliert. Das Modell wird verifiziert, indem die Kopplungseffizienz und die fokale Intensitätsverteilung im optischen Aufbau gemessen werden. Der dabei erzielte Wert der Freiraum-Kopplungseffizienz von 13.7±1.4% ist unter den höchsten bisher realisierten Werten einzuordnen. Basierend auf dem quantitativen Modell werden die technischen Limitationen des Aufbaus identifiziert. Danach werden im zweiten Teil dieser Arbeit die Wellenfrontaberrationen, welche durch die Formabweichungen des Parabolspiegels hervorgerufen werden, genauer untersucht. Sie stellen eine Limitation der experimentell erzielten Wechselwirkungseffizienz dar. Daher werden verschiedene Konzepte zur Wellenfrontkorrektur durch Phasenkonjugation präsentiert und realisiert. Zu den Technologien, die zur Wellenfrontkorrekur eingesetzt werden, gehören: Ein deformierbarer Spiegel mit kontinuierlicher Membran, ein räumlicher Phasenmodulator, ein binäres lithographisch gefertigtes computergeneriertes Hologramm und eine Phasenplatte, welche mittels Magnetorheologischen Polierens hergestellt ist. Alle Konzepte werden auf ihr Potential zur Korrektur der Strehl-Zahl und ihre Relevanz in 4pi Aufbauten untersucht. Um die experimentell-technologische Signifikanz des 4pi Parabolspiegels aufzuzeigen, werden zwei Anwendungen experimentell umgesetzt: Erstens wird die Phasenverschiebung eines schwachen, kohärenten Laserstrahls durch das einzelne Ion gemessen. Zweitens wird die Position des einzelnen Emitters mithilfe des 4pi Parabolspiegels entlang aller drei räumlichen Dimensionen mit einer Auflösung im Bereich weniger Nanometer bestimmt. Die letztgenannte Anwendung besitzt das Potential, die technische Komplexität mancher der heutzutage wichtigsten Techniken der hochauflösenden optischen Mikroskopie wesentlich zu reduzieren.Light-matter interaction is a key technology for many scientific experiments and industrial applications. Efficiency improvements in the free space coupling between light and matter could enable new technological applications or new high-precision experiments. One particular experiment benefiting from this progress will be the experimental demonstration of the time-reversibility of the spontaneous emission process. In this work, a highly efficient light-matter interface is demonstrated that is based on a 4pi parabolic mirror focusing light onto a single, trapped ion. A quantitative model to simulate the coupling efficiency is established that considers the primary experimental parameters. The quantitative model is verified by measuring the free space coupling efficiency and the effective focal intensity distribution in the experiment. The achieved value of the coupling efficiency to one of the ion’s linear dipole transitions amounts to G = 13.7 ± 1.4% and is thus among the highest values ever measured so far. Based on the quantitative model, technical limitations of the interface are determined. In the second part of this work, the most relevant technical limitation for G is subject of further investigations, the wavefront aberrations due to form-figure errors of the parabolic mirror. Different concepts of aberration correction based on phase conjugation are described and are experimentally reviewed. Among the technologies for aberration correction are: A continuous membrane deformable mirror, a phase-only spatial light modulator, a binary lithographic computer generated hologram, and a correction phase plate manufactured with magnetorheological finishing, respectively. The different concepts are evaluated concerning their Strehl ratio correction quality and their relevance for experiments based on 4pi focusing. To demonstrate the potential impact of the 4pi parabolic mirror on technical applications, two applications are experimentally demonstrated: Firstly, the phase-shift imprinted on a weak coherent laser beam by the single ion is measured. Secondly,single particle tracking with an accuracy in the nanometer regime for all spatial directions is realized. The latter utilization of the 4pi parabolic mirror has the potential to significantly impact some of today’s super-resolution light-microscopes

Amazonia as a carbon source linked to deforestation and climate change

Amazonia hosts the Earth's largest tropical forests and has been shown to be an important carbon sink over recent decades1-3. This carbon sink seems to be in decline, however, as a result of factors such as deforestation and climate change1-3. Here we investigate Amazonia's carbon budget and the main drivers responsible for its change into a carbon source. We performed 590 aircraft vertical profiling measurements of lower-tropospheric concentrations of carbon dioxide and carbon monoxide at four sites in Amazonia from 2010 to 20184. We find that total carbon emissions are greater in eastern Amazonia than in the western part, mostly as a result of spatial differences in carbon-monoxide-derived fire emissions. Southeastern Amazonia, in particular, acts as a net carbon source (total carbon flux minus fire emissions) to the atmosphere. Over the past 40 years, eastern Amazonia has been subjected to more deforestation, warming and moisture stress than the western part, especially during the dry season, with the southeast experiencing the strongest trends5-9. We explore the effect of climate change and deforestation trends on carbon emissions at our study sites, and find that the intensification of the dry season and an increase in deforestation seem to promote ecosystem stress, increase in fire occurrence, and higher carbon emissions in the eastern Amazon. This is in line with recent studies that indicate an increase in tree mortality and a reduction in photosynthesis as a result of climatic changes across Amazonia1,10.</p

Amazonia as a carbon source linked to deforestation and climate change

Amazonia hosts the Earth’s largest tropical forests and has been shown to be an important carbon sink over recent decades1,2,3. This carbon sink seems to be in decline, however, as a result of factors such as deforestation and climate change1,2,3. Here we investigate Amazonia’s carbon budget and the main drivers responsible for its change into a carbon source. We performed 590 aircraft vertical profiling measurements of lower-tropospheric concentrations of carbon dioxide and carbon monoxide at four sites in Amazonia from 2010 to 20184. We find that total carbon emissions are greater in eastern Amazonia than in the western part, mostly as a result of spatial differences in carbon-monoxide-derived fire emissions. Southeastern Amazonia, in particular, acts as a net carbon source (total carbon flux minus fire emissions) to the atmosphere. Over the past 40 years, eastern Amazonia has been subjected to more deforestation, warming and moisture stress than the western part, especially during the dry season, with the southeast experiencing the strongest trends5,6,7,8,9. We explore the effect of climate change and deforestation trends on carbon emissions at our study sites, and find that the intensification of the dry season and an increase in deforestation seem to promote ecosystem stress, increase in fire occurrence, and higher carbon emissions in the eastern Amazon. This is in line with recent studies that indicate an increase in tree mortality and a reduction in photosynthesis as a result of climatic changes across Amazonia1,10

CO2 emissions in the Amazon: are bottom-up estimates from land use and cover datasets consistent with top-down estimates based on atmospheric measurements?

Amazon forests are the largest forests in the tropics and play a fundamental role for regional and global ecosystem service provision. However, they are under threat primarily from deforestation. Amazonia's carbon balance trend reflects the condition of its forests. There are different approaches to estimate large-scale carbon balances, including top-down (e.g., CO2 atmospheric measurements combined with atmospheric transport information) and bottom-up (e.g., land use and cover change (LUCC) data based on remote sensing methods). It is important to understand their similarities and differences. Here we provide bottom-up LUCC estimates and determine to what extent they are consistent with recent top-down flux estimates during 2010 to 2018 for the Brazilian Amazon. We combine LUCC datasets resulting in annual LUCC maps from 2010 to 2018 with emissions and removals for each LUCC, and compare the resulting CO2 estimates with top-down estimates based on atmospheric measurements. We take into account forest carbon stock maps for estimating loss processes, and carbon uptake of regenerating and mature forests. In the bottom-up approach total CO2 emissions (2010 to 2018), deforestation and degradation are the largest contributing processes accounting for 58% (4.3 PgCO2) and 37% (2.7 PgCO2) respectively. Looking at the total carbon uptake, primary forests play a dominant role accounting for 79% (−5.9 PgCO2) and secondary forest growth for 17% (−1.2 PgCO2). Overall, according to our bottom-up estimates the Brazilian Amazon is a carbon sink until 2014 and a source from 2015 to 2018. In contrast according to the top-down approach the Brazilian Amazon is a source during the entire period. Both approaches estimate largest emissions in 2016. During the period where flux signs are the same (2015–2018) top-down estimates are approximately 3 times larger in 2015–2016 than bottom-up estimates while in 2017–2018 there is closer agreement. There is some agreement between the approaches–notably that the Brazilian Amazon has been a source during 2015–2018 however there are also disagreements. Generally, emissions estimated by the bottom-up approach tend to be lower. Understanding the differences will help improve both approaches and our understanding of the Amazon carbon cycle under human pressure and climate change

A Holography-Based Modal Wavefront Sensor for the Precise Positioning of a Light Emitter Using a High-Resolution Computer-Generated Hologram

In certain applications, modal wavefront sensors (MWFSs) can outperform zonal wavefront sensors, which are widely used due to their high flexibility. In this paper, a holography-based MWFS as described is developed for the fast position control of a light emitter in a deep parabolic mirror. The light source is located in the vicinity of the focal point. Instead of Zernike polynomials, more complex phase functions, which are related to certain dislocations of the light source are used as detector modes. The performance of the sensor is verified with a test setup, where the test wavefront is generated by a spatial light modulator instead of a real parabolic mirror. The design and fabrication of the required high-resolution holographic element is described and an easy way of multiplexing several single mode sensors is demonstrated

Focusing characteristics of a 4 πparabolic mirror light-matter interface

Abstract Background Focusing with a 4 π parabolic mirror allows for concentrating light from nearly the complete solid angle, whereas focusing with a single microscope objective limits the angle cone used for focusing to half solid angle at maximum. Increasing the solid angle by using deep parabolic mirrors comes at the cost of adding more complexity to the mirror’s fabrication process and might introduce errors that reduce the focusing quality. Methods To determine these errors, we experimentally examine the focusing properties of a 4 π parabolic mirror that was produced by single-point diamond turning. The properties are characterized with a single 174Yb + ion as a mobile point scatterer. The ion is trapped in a vacuum environment with a movable high optical access Paul trap. Results We demonstrate an effective focal spot size of 209 nm in lateral and 551 nm in axial direction. Such tight focusing allows us to build an efficient light-matter interface. Conclusion Our findings agree with numerical simulations incorporating a finite ion temperature and interferometrically measured wavefront aberrations induced by the parabolic mirror. We point at further technological improvements and discuss the general scope of applications of a 4 π parabolic mirror

Focusing characteristics of a 4

Background: Focusing with a 4 π parabolic mirror allows for concentrating light from nearly the complete solid angle, whereas focusing with a single microscope objective limits the angle cone used for focusing to half solid angle at maximum. Increasing the solid angle by using deep parabolic mirrors comes at the cost of adding more complexity to the mirror’s fabrication process and might introduce errors that reduce the focusing quality. Methods: To determine these errors, we experimentally examine the focusing properties of a 4 π parabolic mirror that was produced by single-point diamond turning. The properties are characterized with a single 174Yb + ion as a mobile point scatterer. The ion is trapped in a vacuum environment with a movable high optical access Paul trap. Results: We demonstrate an effective focal spot size of 209 nm in lateral and 551 nm in axial direction. Such tight focusing allows us to build an efficient light-matter interface. Conclusion: Our findings agree with numerical simulations incorporating a finite ion temperature and interferometrically measured wavefront aberrations induced by the parabolic mirror. We point at further technological improvements and discuss the general scope of applications of a 4 π parabolic mirror