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When combining multi-temporal airborne laser scanning (ALS) data sets, forest height growth assessments can be compromised due to variations in ALS acquisitions. Herein, we demonstrate the importance of assessing and harmonizing the vertical alignment of multi-temporal ALS data sets used for height growth calculations. Using four ALS acquisitions (2005-2018) in a temperate mixed wood forest, we developed an ALS data harmonization approach and quantified the impact of the harmonization on derived height periodic annual increment (PAI), comparing the ALS-derived PAI to PAI derived from non-harmonized ALS data sets and field measurements. We found significant differences in PAI derived from harmonized and non-harmonized data, and these differences were greater for shorter growth intervals. Data harmonization resulted in a consistent PAI series that reduced uncertainties associated with the different ALS acquisitions. Although overall there was a strong relationship between field and ALS height measures ([R.sup.2] [greater than or equal to] 0.88), we found a weak relationship between the field- and ALS-derived PAI ([R.sup.2] = 0.12). We identified systematic errors in field-based tree height measures in plots with complex crowns, tall trees, and restricted visibility. We demonstrate the need for harmonizing multi-temporal ALS data sets for the generation of PAI and, likewise, highlight the need of carefully scrutinize field-measured heights and associated increments. Key words: multi-temporal ALS, height increment, vertical alignment, data harmonization, temperate mixedwood forest Lors de la combinaison d'ensembles de donnees de balayage laser aeroporte (ALS) multitemporels, les evaluations de la croissance en hauteur des forets peuvent etre compromises en raison des variations dans les acquisitions de l'ALS. Nous demontrons ici l'importance d'evaluer et d'harmoniser l'alignement vertical des ensembles de donnees de l'ALS multitemporels utilises pour les calculs de croissance en hauteur. En utilisant quatre acquisitions de l'ALS (2005-2018) dans une foret mixte temperee, nous avons developpe une approche d'harmonisation des donnees de l'ALS et quantifie l'impact de l'harmonisation sur l'accroissement annuel periodique (PAI) derive de la hauteur, en comparant le PAI derive de l'ALS au PAI derive de jeux de donnees de L'ALS non harmonises et de mesures sur le terrain. Nous avons trouve des differences significatives dans le PAI derive des donnees harmonisees et non harmonisees, et ces differences etaient plus grandes pour les intervalles de croissance plus courts. L'harmonisation des donnees a permis d'obtenir une serie de PAI coherente qui a reduit les incertitudes associees aux differentes acquisitions de l'ALS. Dans l'ensemble, bien qu'il y ait une forte relation entre les mesures de hauteur sur le terrain et celles de l'ALS ([R.sup.2] [greater than or equal to] 0,88), nous avons trouve une faible relation entre le PAI derive du terrain et celui derive de l'ALS ([R.sup.2] = 0,12). Nous avons identifie des erreurs systematiques dans les mesures de hauteur des arbres basees sur le terrain dans les parcelles avec des couronnes complexes, des arbres de grande taille et une visibilite limitee. Nous demontrons la necessite d'harmoniser les ensembles de donnees de l'ALS multitemporels pour la generation du PAI et, de meme, nous soulignons la necessite d'examiner soigneusement les hauteurs mesurees sur le terrain et les accroissements associes. [Traduit par la Redaction] Mots-cles : ALS multitemporel, accroissement de hauteur, alignement vertical, harmonisation des donnees, foret mixte temperee, 1. Introduction Light Detection and Ranging (lidar) has revolutionized the capture of three-dimensional (3D) information pertaining to tree and forest structural attributes at varying spatial scales. Airborne laser scanning (ALS) [...]

Representing the spatial distribution of trees and competition interactions in growth models improves growth prediction and provides insights into spatially explicit forecasts for precise silvicultural interventions. However, this information is rarely taken into account over large areas because obtaining the spatial distribution of individual trees and estimating their competition is both expensive and time consuming. Airborne laser scanning enables rapid estimation of tree height and other attributes over large areas. In this study, we implemented an individual tree detection approach to first extract tree attributes of Pinus radiata D. Don plantations, and second to use this spatially explicit information on tree location and competition to forecast potential tree height, defined as a maximum projected tree height at rotation age. To do so, using a chronosequence of tree heights, we developed a tree height growth model using a Chapman-Richards function, utilizing the effect of inter-tree competition and stand-level top height (TH) on the tree height growth. The results showed that using chronosequence of heights, competition, and TH resulted in accurate predictions of potential tree height (root mean square error = 2.9 m; mean absolute percentage error = 0.154%). We concluded that individual tree height growth is significantly influenced by competition, with increased competition values associated with reductions in potential height growth by 22.2% at 30 years. Key words: forest plantations, competition index, Chapman-Richards, chronosequence, airborne laser scanning La representation de la distribution spatiale des arbres et des interactions de competition dans les modeles de croissance ameliore la prediction de la croissance et permet d'obtenir des previsions spatialement explicites pour des interventions sylvicoles precises. Cependant, ces informations sont rarement prises en compte sur de grandes surfaces car l'obtention de la distribution spatiale des arbres individuels et l'estimation de leur concurrence sont a la fois couteuses et longues. Le balayage laser aeroporte (ALS) permet d'estimer rapidement la hauteur des arbres et d'autres attributs sur de grandes superficies. Dans cette etude, nous mettons en oeuvre une approche de detection des arbres individuels pour extraire d'abord les attributs des arbres des plantations de Pinus radiata D. Don. Les plantations de don, et deuxiemement d'utiliser ces informations spatialement explicites sur l'emplacement des arbres et la concurrence pour prevoir la hauteur potentielle des arbres, definie comme une hauteur maximale projetee des arbres a l'age de la rotation. Pour ce faire, en utilisant une chronosequence de la hauteur des arbres, nous avons developpe un modele de croissance de la hauteur des arbres en utilisant une fonction de ChapmanRichards, en utilisant l'effet de la competition inter-arbres et de la hauteur du sommet (HS) au niveau du peuplement sur la croissance de la hauteur des arbres. Les resultats montrent que l'utilisation de la chronosequence des hauteurs, de la competition et de la hauteur de la cime permet de predire avec precision la hauteur potentielle des arbres (RMSE = 2,9 m et MAPE = 0,154 %). Nous concluons que la croissance en hauteur des arbres individuels est significativement influencee par la competition, avec des valeurs de competition accrues associees a des reductions de la croissance en hauteur potentielle de 22,2 % a 30 ans. [Traduit par la Redaction] Mots-cles : plantations forestieres, indice de competition, Chapman-Richards, chronosequence, balayage laser aeroporte, 1. Introduction Reliable growth and yield forecasting is critical for guiding forest management decision making (Garcia 1994), allowing for both long-term timber resource planning (Coops 2015; Tompalski et al. 2021) [...]

Most forest growth studies using airborne laser scanning (ALS) consider how the changes in forest attributes are observed in repeated ALS data acquisitions, but the prediction of future forest growth from ALS data is still a rarely discussed topic. This study examined the prediction of the periodic annual increment (PAI) of the width of tree rings over a period of 10 years. The requirement for this approach is that ALS data are acquired at the beginning of the growth period. This is followed by field measurements of growth by drilling after a given growth period. The PAI was modelled in terms of ALS metrics by using the principle of the area-based approach. The metrics related to intensity were particularly significant as predictors, whereas the effective leaf area index was not. The root-mean-square error (RMSE) of the predictions was slightly over 21%. Additional field information (soil type, management operations) improved the RMSE by 2.7 percentage units. Key words: area-based approach, diameter increment, forest growth, leaf area index, LiDAR. La plupart des etudes sur l'accroissement forestier utilisant le balayage par laser aeroporte (BLA) tiennent compte de la facon dont les changements des attributs forestiers sont observes dans les acquisitions de donnees repetees du BLA, mais la prevision d'un accroissement forestier futur a partir des donnees du BLA est un theme qui fait encore rarement l'objet de discussions. La presente etude a examine la prevision de l'augmentation annuelle periodique (AAP) de la largeur des anneaux de croissance des arbres sur une periode de 10 ans. La necessite d'adopter cette approche est que les donnees du BLA sont acquises au debut de la periode de croissance. Ceci est suivi de mesures de la croissance sur le terrain en faisant un forage apres une periode donnee de croissance. L'AAP a ete modelee en fonction des mesures du BLA en utilisant le principe de l'approche locale. Les mesures reliees a l'intensite etaient particulierement importantes comme variable explicative alors que l'indice foliaire reel ne l'etait pas. L'EMQ des previsions etait legerement au-dessus de 21%. Des renseignements additionnels sur le terrain (type de sol, operations de gestion) ont ameliore l'EMQ de 2,7 unites de pourcentage. [Traduit par la Redaction] Mots-cles : approche locale, augmentation du diametre, accroissement forestier, indice foliaire, LiDAR., Introduction Data acquired through airborne laser scanning (ALS) are widely used in forestry, with the forest inventories being one of the main applications of this ALS data. The main interest [...]

Horvitz-Thompson-like stand density estimation is a method for estimating the stand density from tree crown objects extracted from airborne laser scanning data through individual tree detection. The estimator is based on stochastic geometry and mathematical morphology of the (planar) set formed by the detected tree crowns. This set is used to approximate the detection probabilities of trees. These probabilities are then used to calculate the estimate. The method includes a tuning parameter, which needs to be known to apply the method. We present a refinement of the method to allow more general detection conditions than those of previous papers. We also present and discuss the methods for estimating the tuning parameter of the estimator using a functional k-nearest neighbors method. We test the model fitting and prediction in two spatially separate data sets and examine the plot-level accuracy of estimation. The estimator produced a 13% lower RMSE (root-mean-square error) than the benchmark method in an external validation data set. We also analyze the effects of similarity and dissimilarity of training and validation data on the results. Key words: segmentation, stochastic geometry, detectability, nearest neighbor, forest inventory. L'estimation de type Horvitz-Thompson de la densite de peuplement est une methode d'estimation de la densite de peuplement a partir d'objets qui sont des couronnes d'arbres obtenues par detection d'arbres individuels a partir de donnees de balayage laser aeroporte. L'estimateur est base sur la geometrie stochastique et la morphologie mathematique de l'ensemble (planaire) forme par les couronnes d'arbres detectees. Cet ensemble est utilise pour approximer les probabilites de detection des arbres. Ces probabilites sont ensuite utilisees pour calculer l'estimation. La methode comprend un parametre d'ajustement qui doit etre connu pour pouvoir l'appliquer. Nous presentons un raffinement de la methode afin de permettre des conditions plus generales de detection que celles des articles precedents. Nous presentons et discutons des methodes d'estimation du parametre d'ajustement de l'estimateur en utilisant la methode fonctionnelle des k plus proches voisins. Nous testons l'ajustement et la prediction du modele pour deux ensembles de donnees spatialement distincts et nous examinons la precision de l'estimation a l'echelle de la parcelle. L'estimateur a produit une REQM (racine de l'erreur quadratique moyenne) 13% inferieure a celle de la methode de reference pour un ensemble de donnees de validation externe. Nous analysons egalement les effets de la similitude et de la dissemblance des donnees d'entrainement et de validation sur les resultats. [Traduit par la Redaction] Mots-cles : segmentation, geometrie stochastique, detectabilite, plus proche voisin, inventaire forestier., 1. Introduction Volume and biomass related attributes are usually of primary interest in remote-sensing-based forest inventories. If these quantities are estimated at tree level, scaling them to area level requires [...]

This paper reports continuous wave (CW) laser-assisted synthesis of plasmonic aluminium nanoparticles (ANPs) by drastically reducing the laser power density from the existing 105 W/[cm.sup.2] to 9 W/[cm.sup.2] using a specially designed ultralow duty cycle chopper. The aluminium target is subjected to laser irradiation by keeping it in a liquid medium maintained at a specific temperature. The effect of chopping frequencies (F), temperatures (T), and surfactant-glucose (C) on the formation of ANPs are investigated through field emission scanning electron microscopic and UV-visible spectroscopic analyses. The energy required for the ejection of ANPs from the target is obtained from the optical source, thermal source, and the molecular collision due to convection current. The purity of the nanoparticle is determined from energy dispersive spectroscopic analysis. The analysis reveals that ANPs of sizes in the range 20-50 nm are formed when F = 30 Hz, T = 60 [degrees]C, and C = 18 mg/cc, exhibiting excellent ageing stability. The photoluminescence spectrum, power spectrum, and CIE analyses for the excitations at 350 nm and 390 nm indicate the emission to be blue, suggesting that it is a suitable fluorescence material for UV-plasmonics. Key words: CW laser, low power, aluminium, plasmonics, low duty cycle, nanoparticles. Nous presentons une methode de synthese utilisant un laser en continu (OC/CW), pour produire des nanoparticules d'aluminium (NPA/ANP) plasmoniques, en reduisant dramatiquement la densite de puissance du laser de 105 W/[cm.sup.2] a 9 W/[cm.sup.2] a l'aide d'un coupeur de faisceau a tres petit rapport cyclique. La cible d'aluminium est soumise a l'irradiation laser en la conservant dans un liquide maintenu a une temperature specifique (T). Les effets de la frequence de coupure (F), de la temperature (T) et du glucose surfactant (C) sont examines via microscopie electronique d'emission a balayage et par analyse spectroscopique UV-visible. L'energie requise pour l'emission des NPA par la cible est obtenue de la source optique, de la source thermique et de la collision moleculaire due au courant de convexion. La purete de la nanoparticule est determinee par analyse spectroscopique dispersive en energie. L'analyse revele que des NPA sont creees dans le domaine 20-50 nm lorsque F = 30 Hz, T = 60 [degrees]C et C = 18 mg/cc, montrant une excellente stabilite au vieillissement. Le spectre de photoluminescence, le spectre en puissance et les analyses CIE pour les excitations a 350 nm et a 390 nm indiquent que l'emission est bleue, suggerant que c'est un excellent materiau de fluorescence pour la plasmonique UV. [Traduit par la Redaction] Mots-cles : laser en continu, faible puissance, aluminium, plasmonique, faible rapport cyclique, nanoparticules., 1. Introduction Nanotechnology has emerged as the technology of this century, revolutionising all branches of science and technology. The exciting size- and shape-dependent behaviour of nanomaterials offers greater flexibility in [...]

More than 75 hours of online, on-demand presentations followed ANTEC 2022. These were presentations that didn't make the cut due to space limitations at the in-person event, but which were [...]

Shaping the light emission characteristics of laser systems is of great importance in various areas of science and technology. In a typical lasing arrangement, the transverse spatial profile of a laser mode tends to remain self-similar throughout the entire cavity. Going beyond this paradigm, we demonstrate here how to shape a spatially evolving mode such that it faithfully settles into a pair of bi-orthogonal states at the two opposing facets of a laser cavity. This was achieved by purposely designing a structure that allows the lasing mode to encircle a non-Hermitian exceptional point while deliberately avoiding non-adiabatic jumps. The resulting state transfer reflects the unique topology of the associated Riemann surfaces associated with this singularity. Our approach provides a route to developing versatile mode-selective active devices and sheds light on the interesting topological features of exceptional points.

Diameter at breast height (DBH) distributions offer valuable information for operational and strategic forest management decisions. We predicted DBH distributions using Norwegian national forest inventory and airborne laser scanning data and compared the predictive performances of linear mixed-effects (PPM), generalized linear-mixed (GLM), and k nearest- neighbor (NN) models. While GLM resulted in smaller prediction errors than PPM, both were clearly outperformed by NN. We therefore studied the ability of the NN model to improve the precision of stem frequency estimates by DBH classes in the 8.7 Mha study area using a model-assisted (MA) estimator suitable for systematic sampling. MA estimates yielded greater than or approximately equal efficiencies as direct estimates using field data only. The relative efficiencies (REs) associated with the MA estimates ranged between 0.95-1.47 and 0.96-1.67 for 2 and 6 cm DBH class widths, respectively, when dominant tree species were assumed to be known. The use of a predicted tree species map, instead of the observed information, decreased the REs by up to 10%. Key words: generalized linear models, linear mixed-effects models, most similar neighbor approach, number of stems, systematic sampling. Les distributions de diametre a hauteur de poitrine (DHP) offrent des informations precieuses pour les decisions de gestion forestiere operationnelles et strategiques. Nous avons predit les distributions de DHP a l'aide de l'inventaire forestier national norvegien et de donnees de balayage laser aeroporte et nous avons compare les performances predictives des modeles lineaires a effets mixtes (LEM), lineaires generalises mixtes (LGM) et des k plus proches voisins (PPV). Bien que le modele LGM ait entraine des erreurs de prediction plus petites que le modele LEM, les deux ont ete clairement surpasses par l'approche PPV. Nous avons donc etudie la capacite du modele PPV a ameliorer la precision des estimations de la frequence des tiges par classes de DHP, dans la zone d'etude de 8,7 Mha, a l'aide d'un estimateur assiste par modele (AM) adapte a un echantillonnage systematique. Les estimations AM ont produit des efficacites superieures ou a peu pres egales a celle d'estimations directes utilisant uniquement des donnees de terrain. Les efficacites relatives (ER) associees aux estimations AM variaient entre 0,95-1,47 et 0,96-1,67 pour des largeurs de classe de DHP de respectivement 2 et 6 cm, lorsque les especes d'arbres dominantes etaient presumees connues. L'utilisation d'une carte de prediction des especes d'arbres, au lieu des informations observees, a reduit les ER jusqu'a 10 %. [Traduit par la Redaction] Mots-cles: modeles lineaires generalises, modeles lineaires a effets mixtes, approche des plus proches voisins, nombre de tiges, echantillonnage systematique., 1. Introduction Forest inventories provide essential information for the sustainable management of forest resources at different spatial levels. A key forest attribute is diameter at breast height (DBH), which is [...]

Policy measures and management decisions aimed at enhancing the role of forests in mitigating climate change require reliable estimates of carbon (C)-stock dynamics in greenhouse gas inventories (GHGIs). The aim of this study was to assemble design-based estimators to provide estimates relevant for GHGIs using National Forest Inventory (NFI) data. We improve basic expansion (BE) estimators of living-biomass C-stock loss using only field data, by leveraging with remote sensing auxiliary data in model-assisted (MA) estimators. Our case studies from Norway, Sweden, Denmark, and Latvia covered an area of >70 Mha. Landsat-based forest cover loss (FCL) and one-time wall-to-wall airborne laser scanning (ALS) served as auxiliary data. ALS provided information on the C stock before a potential disturbance indicated by FCL. The use of FCL in MA estimators resulted in considerable efficiency gains, which in most cases were further increased by adding ALS. A doubling of efficiency was possible for national estimates and even larger efficiencies were observed at the subnational level. Average annual estimates were considerably more precise than pooled estimates of the NFI data from all years at once. The combination of remotely sensed and NFI field data yields reliable estimators, which is not necessarily the case when using remotely sensed data without reference observations. Key words: greenhouse gas inventory, national forest inventory, model-assisted estimator, climate convention, Global Forest Watch. Les mesures politiques et les decisions de gestion visant a mettre en valeur le role des forets dans l'attenuation des changements climatiques necessitent des estimations fiables de la dynamique des stocks de carbone (C) dans les inventaires de gaz a effet de serre (IGES). Le but de cette etude etait de reunir des estimateurs bases sur un plan d'experience afin de fournir des estimations appropriees pour les IGES a l'aide des donnees de l'inventaire forestier national (IFN). Nous ameliorons les estimateurs de base avec facteur d'extension de la perte de stock de C de la biomasse vivante en utilisant uniquement des donnees de terrain et en les appuyant par des donnees auxiliaires de teledetection au moyen d'estimateurs assistes par un modele (AM). Nos etudes de cas couvraient une superficie de plus de 70 Mha en Norvege, en Suede, au Danemark et en Lettonie. Nous avons utilise la perte de couvert forestier (PCF) basee sur des donnees Landsat et une seule couverture complete par balayage laser aeroporte (BLA) comme donnees auxiliaires. Le BLA a fourni des informations sur le stock de C avant une perturbation potentielle indiquee par la PCF. L'utilisation de la PCF dans les estimateurs AM a permis des gains d'efficacite considerables qui, dans la plupart des cas, ont ete encore augmentes en ajoutant le BLA. Un doublement de l'efficacite etait possible pour les estimations nationales et des gains d'efficacite encore plus importants ont ete observes a l'echelle sous-nationale. Les estimations annuelles moyennes etaient considerablement plus precises que les estimations regroupees des donnees de l'IFN de toutes les annees a la fois. La combinaison de donnees de teledetection et de donnees terrain de l'IFN produit des estimateurs fiables, ce qui n'est pas necessairement le cas lors de l'utilisation de donnees de teledetection sans observations de reference. [Traduit par la Redaction] Mots-cles: inventaire des gaz a effet de serre, inventaire forestier national, estimateur assiste par un modele, convention pour le climat, surveillance forestiere avec l'application Global Forest Watch., 1. Introduction The struggle to achieve a "well-below" 2 [degrees]C mean temperature increase by 2100 as concerted in the Paris agreement (United Nations 2015) requires policy measures to fulfill emission [...]

Airborne laser scanning (ALS) has emerged as a technology capable of generating descriptors of vegetation structure and best available terrain information. Research and operational implementations of ALS data have highlighted their value for characterizing forest structure and generating spatially explicit and objective spatial coverages and mapping products for forest management. Continued emphasis to enhance forest stewardship is promoting novel methods to integrate ALS to detail non-timber ecosystem values like habitat, soil, and water. Standardized criteria and indicator frameworks such as the Canadian Council of Forest Ministers provide a reliable starting point for where ALS has opportunities to characterize ecosystems objectively regardless of location. In this review of primarily Canadian work, we highlight how ALS is becoming an increasingly viable technology for deriving meaningful indicators to meet sustainable forest management criteria. We review and highlight the value of ALS for quantifying indicators of biological diversity, ecosystem condition and productivity, soil and water, and the role of forests in global ecological cycles. We conclude by highlighting the need for increased education, tech transfer, flexible software, and reporting frameworks alongside five key considerations for using ALS to derive meaningful indicators of sustainable forest management. Key words: remote sensing, forest structure, ecosystem goods and services, non-timber values, laser scanning. Le balayage laser aeroporte (BLA) s'est avere etre une technologie capable de generer des elements descriptifs de la structure de la vegetation et les meilleures informations territoriales disponibles. La recherche sur les donnees de BLA et leur utilisation operationnelle ont mis en evidence leur valeur pour caracteriser la structure forestiere et generer des couvertures spatiales objectives et spatialement explicites ainsi que des produits cartographiques pour la gestion forestiere. L'effort continu pour ameliorer l'intendance des forets consiste a promouvoir de nouvelles methodes pour integrer le BLA afin de detailler les valeurs non ligneuses des ecosystemes, comme l'habitat, le sol et l'eau. Les cadres normalises de criteres et indicateurs comme ceux du Conseil canadien des ministres des forets fournissent un point de depart fiable pour savoir ou le BLA peut servir a caracteriser objectivement les ecosystemes, quel que soit leur emplacement. Dans cet examen de travaux principalement canadiens, nous soulignons comment le BLA est en voie de devenir une technologie de plus en plus viable pour deriver des indicateurs significatifs et ainsi repondre aux criteres de gestion durable des forets. Nous examinons et soulignons ici la valeur du BLA pour quantifier les indicateurs de la diversite biologique, de l'etat et de la productivite des ecosystemes, du sol et de l'eau, et du role des forets dans les cycles ecologiques mondiaux. Nous concluons en soulignant la necessite d'une formation accrue, d'un transfert de technologie, de logiciels flexibles et de systemes de reddition de compte, ainsi que de cinq considerations cles pour l'utilisation du BLA en vue de deriver des indicateurs significatifs de gestion durable des forets. Mots-cles: teledetection, structure forestiere, biens et services ecosystemiques, valeurs non ligneuses, balayage laser., 1. Introduction The past decade in Canada has seen a paradigm shift in the way forest inventories are planned, implemented, and utilized. Canada's forests--like others around the world--are managed and [...]

Microlasers in near-degenerate supermodes lay the cornerstone for studies of non-Hermitian physics, novel light sources, and advanced sensors. Recent experiments of the stimulated scattering in supermode microcavities reported beating phenomena, interpreted as dual-mode lasing, which, however, contradicts their single-mode nature due to the clamped pump field. Here, we investigate the supermode Raman laser in a whispering-gallery microcavity and demonstrate experimentally its single-mode lasing behavior with a side-mode suppression ratio (SMSR) up to 37 dB, despite the emergence of near-degenerate supermodes by the backscattering between counterpropagating waves. Moreover, the beating signal is recognized as the transient interference during the switching process between the two supermode lasers. Self-injection is exploited to manipulate the lasing supermodes, where the SMSR is further improved by 15 dB and the laser linewidth is below 100 Hz. optical microcavity | stimulated Raman scattering | near-degenerate modes | microlasers

Microwave atomic clocks have traditionally served as the 'gold standard' for precision measurements of time and frequency. However, over the past decade, optical atomic clocks.sup.1-6 have surpassed the precision of their microwave counterparts by two orders of magnitude or more. Extant optical clocks occupy volumes of more than one cubic metre, and it is a substantial challenge to enable these clocks to operate in field environments, which requires the ruggedization and miniaturization of the atomic reference and clock laser along with their supporting lasers and electronics.sup.4,7,8,9. In terms of the clock laser, prior laboratory demonstrations of optical clocks have relied on the exceptional performance gained through stabilization using bulk cavities, which unfortunately necessitates the use of vacuum and also renders the laser susceptible to vibration-induced noise. Here, using a stimulated Brillouin scattering laser subsystem that has a reduced cavity volume and operates without vacuum, we demonstrate a promising component of a portable optical atomic clock architecture. We interrogate a .sup.88Sr.sup.+ ion with our stimulated Brillouin scattering laser and achieve a clock exhibiting short-term stability of 3.9 × 10.sup.-14 over one second--an improvement of an order of magnitude over state-of-the-art microwave clocks. This performance increase within a potentially portable system presents a compelling avenue for substantially improving existing technology, such as the global positioning system, and also for enabling the exploration of topics such as geodetic measurements of the Earth, searches for dark matter and investigations into possible long-term variations of fundamental physics constants.sup.10-12. By using a stimulated Brillouin scattering laser in a strontium-ion optical clock instead of the usual bulk-cavity-stabilized laser, the need for vacuum is removed and resonator volume is substantially reduced., Author(s): William Loh [sup.1] , Jules Stuart [sup.1] [sup.2] , David Reens [sup.1] , Colin D. Bruzewicz [sup.1] , Danielle Braje [sup.1] , John Chiaverini [sup.1] , Paul W. Juodawlkis [...]

Monolithic integration of control technologies for atomic systems is a promising route to the development of quantum computers and portable quantum sensors.sup.1-4. Trapped atomic ions form the basis of high-fidelity quantum information processors.sup.5,6 and high-accuracy optical clocks.sup.7. However, current implementations rely on free-space optics for ion control, which limits their portability and scalability. Here we demonstrate a surface-electrode ion-trap chip.sup.8,9 using integrated waveguides and grating couplers, which delivers all the wavelengths of light required for ionization, cooling, coherent operations and quantum state preparation and detection of Sr.sup.+ qubits. Laser light from violet to infrared is coupled onto the chip via an optical-fibre array, creating an inherently stable optical path, which we use to demonstrate qubit coherence that is resilient to platform vibrations. This demonstration of CMOS-compatible integrated photonic surface-trap fabrication, robust packaging and enhanced qubit coherence is a key advance in the development of portable trapped-ion quantum sensors and clocks, providing a way towards the complete, individual control of larger numbers of ions in quantum information processing systems. A surface-electrode ion-trap chip is demonstrated, which delivers all the wavelengths of light required for the preparation and operation of ion qubits., Author(s): R. J. Niffenegger [sup.1] , J. Stuart [sup.1] [sup.2] , C. Sorace-Agaskar [sup.1] , D. Kharas [sup.1] , S. Bramhavar [sup.1] , C. D. Bruzewicz [sup.1] , W. Loh [...]

Keywords SSpace security; Space policy; Lasers; Norms; Space governance Abstract The use of lasers in space is a technology area with plenty of promises for addressing challenges faced by humanity (space debris, space traffic management, planetary defense) and advancing human presence in space (space exploration, propulsion, space resource utilization). However, with this great potential comes an equal amount of risks of its intentional and unintentional misuse. We review both the beneficial and harmful uses of lasers in space and offer an analysis of the main policy challenges for mitigating the risks of misuse. With intent identification, attribution, and dual-use nature of the technology representing the main sources of mutual insecurity, transparency, and information sharing can address them. However, as we outline why the existing international space governance is unlikely to produce new norms on preventing misuse of lasers in space, we turn to discuss the existing practice and the prospects of new non-state actors using them to usher in new international norms for use of lasers in space. Author Affiliation: Department of Political Science, Institute of Political Studies, Faculty of Social Sciences, Charles University, Prague. Smetanovo Nabrezi 6, Prague 1 110 01, Czech Republic Article History: Received 27 November 2020; Revised 15 February 2022; Accepted 28 March 2022 (footnote)[white star] This article is intended for the special issue Astropolitics: The Ecosystem of Space and was presented at the Virtual Global Forum on 25th June. Byline: Petr Bohácek [pbohacek@email.cz]