Search results for "laser"
showing 10 items of 3161 documents
Optically pumped Cs magnetometers enabling a high-sensitivity search for the neutron electric dipole moment
2020
An array of 16 laser-pumped scalar Cs magnetometers was part of the neutron electric dipole moment (nEDM) experiment taking data at the Paul Scherrer Institute in 2015 and 2016. It was deployed to measure the gradients of the experiment's magnetic field and to monitor their temporal evolution. The originality of the array lies in its compact design, in which a single near-infrared diode laser drives all magnetometers that are located in a high-vacuum chamber, with a selection of the sensors mounted on a high-voltage electrode. We describe details of the Cs sensors' construction and modes of operation, emphasizing the accuracy and sensitivity of the magnetic-field readout. We present two app…
Non-linear interactions of femtosecond laser pulses with graphene : photo-oxidation, imaging and photodynamics
2017
This thesis presents a study focused on interactions of femtosecond laser pulses with graphene, a one atom thick carbon membrane. Graphene, which exhibits exceptional electronic and optoelectronic properties, could provide considerable advantage over current silicon-based electronics. Graphene alone, being semi-metal, is not sufficient for electronic applications, but requires modification. For this, a set of methods for modifying and measuring the properties of graphene was developed. With the perspective of making graphene a suitable component for electronics, optoelectronics or photonics, ultrashort laser pulses were used for drawing patterns on graphene. The procedure modifies graphene …
Electrical measurements of femtosecond laser treated graphene
2017
Tutkielman pääasiallinen tavoite oli valmistaa sähköisiin mittauksiin sopivia grafeenilaitteita ja tutkia femtosekuntilaserkäsittelyn vaikutusta grafeenin sähköisiin ominaisuuksiin. Tutkielmassa käsitellään grafeenin valmistamista kemiallisella kaasufaasipinnoituksella, laitegeometrian määrittelyä ja käsittelemättömän, sekä femtosekuntilaserilla käsitellyn grafeenin sähköisiä mittauksia. Grafeenin synteesin alustana käytettiin kupariohutkalvoja ja pääasiallisena lähtöaineena oli etanoli tai metaani. Metaanin käyttö grafeenin synteesissä johti paremmin toistettaviin tuloksiin. Lisäksi havaittiin, että synteesissä käytetyn uunin latausjärjestelmän teräksinen osa lisäsi kupariohutkalvon reikii…
Performance analysis of dual-pump nonlinear amplifying loop mirror mode-locked all-fibre laser
2019
We numerically characterise, in the three-dimensional space of adjustable cavity parameters, the performance of a recently reported layout of a flexible figure-8 laser having two independently pumped segments of active fibre in its bidirectional ring (Smirnov et al 2017 Opt. Lett. 42 1732–5). We show that this optimisation problem can be efficiently addressed by applying a regression model based on a neural-network algorithm.
Laser-assisted surgery in oral medicine: treatment of fibrous epulis with diode 915 nm
2013
Laser assisted particle removal from Silicon wafers
2023
We have studied the removal of submicrometer particles from silicon wafers by the steam laser cleaning (SLC) and dry laser cleaning (DLC) processes. These processes are currently being investigated as new promising cleaning technologies for complementing traditional methods in industrial applications. For SLC a thin liquid layer (e.g. a water-alcohol mixture) is condensed onto the substrate, and is subsequently evaporated by irradiating the surface with a short laser pulse. The DLC process, on the other hand, relies only on the laser pulse, without application of a vapor jet. Using well-characterized monodisperse polystyrene and silica particles as well as irregularly shaped alumina particl…
Fission yield studies with SPIG-equipped IGISOL : a novel method for nuclear data measurements
2010
This thesis work consists of two sections. In the first section, the development of a so-called Laser Ion Source Trap (LIST) device is described. The LIST device is based on a double SPIG (SextuPole Ion Guide) system, providing the possibility to improve the elemental selectivity of the IGISOL method via highly discriminative laser ionization occurring outside the ion guide. The improved selectivity enables the production of isotopically pure beams. The double SPIG can be used without laser ionization and replaces the conventional skimmer electrode. In this work, the SPIG is compared to the skimmer and is shown to remarkably improve both the efficiency and beam quality of the IGISOL facilit…
Effect of oxidoreduction potential and of gas bubbling on rheological properties and microstructure of acid skim milk gels acidified with glucono-del…
2009
Milk oxidoreduction potential was modified using gases during the production of a model dairy product and its effect on gel setting was studied. Acidification by glucono-delta-lactone was used to examine the physicochemistry of gelation and to avoid variations due to microorganisms sensitive to oxidoreduction potential. Four conditions of oxidoreduction potential were applied to milk: milk was gassed with air, nongassed, gassed with N(2), or gassed with N(2)H(2). The rheological properties and microstructure of these gels were determined using viscoelasticimetry, measurement of whey separation, and confocal laser scanning microscopy. It appeared that a reducing environment led to less-aggre…
Analisi e comparazione di modelli di superficie di reperti archeologici realizzati tramite laser scanner e fotogrammetria
2009
La ricerca svolta si è posta come obiettivo quello di verificare l’accuratezza di modelli di superficie (Digital Surface Model – DSM) di reperti archeologici realizzati attraverso procedure fotogrammetriche. La sperimentazione è stata condotta su alcuni reperti, già oggetto di studio in precedenti ricerche, conservati presso il museo Archeologico Regionale di Palermo. In questo lavoro vengono presentati i primi risultati relativi al rilievo della metopa di “Europa rapita dal Toro”. I DSM, generati con due differenti software di fotogrammetria, sono stati messi a confronto con il DSM ottenuto con un laser scanner a triangolazione ottica. Tale modello è stato considerato come riferimento per …
Koherentu procesu lāzeru spektroskopijas pētījumi sārmu metālu atomos un molekulās
2014
Promocijas darbs veltīts Zēmana koherenču atomu un molekulu elektroniskajos pamatstāvokļos veidošanas un sabrukšanas teorētiskajai un eksperimentālajai izpētei ar nelineārās spektroskopijas metodēm. Pirmkārt, tiek ziņots polarizācijas modulācijas pētījums, ierosinot D1 pārejas ar Cs tvaikiem pildītā šūnā. Otrkārt, izstrādāta spektroskopijas metode magnētiskā lauka stipruma divdimensiju sadalījuma kartēšanai, izmantojot fluorescences sadalījuma reģistrēšanu. Treškārt, veikts nelineāro magneto-optisko rezonanšu pētījums K2 molekulas pamatstāvoklī ar lielām leņķiskā momenta kvantu skaitļa J~100 vērtībām. Lai uzlabotu diožu lāzera ilgtermiņa frekvences stabilitāti, izstrādāta frekvences divmodu…