Search results for "femtosecond laser"
showing 4 items of 14 documents
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…
Changes in Pupil Area during Low-energy Femtosecond Laser-assisted Cataract Surgery
2018
Purpose: To study the potential changes in pupil area within low-energy femtosecond-laser assisted cataract surgery (FLACS). Methods: A retrospective assessment of the pupil size was performed in the eyes undergoing FLACS using the Ziemer LDV Z8. We measured the pupil diameters as part of the images taken preoperatively and at the completion of laser pretreatment (after releasing the suction). We calculated the pupil area in 40 eyes of 40 patients (14 right and 26 left eyes). The mean ± standard deviation (SD) of age of the patients was 74 ± 7.4 years (range: 51-87). Paired t-test was used for statistical analyses. Subgroups were built with reference to age and preoperative pupil area (smal…
Temperature measurement in gas mixtures by femtosecond Raman-induced polarization spectroscopy
2003
European Conference on Nonlinear Optical Spectroscopy (ECONOS) MAR 30-APR 01, 2003 BESANCON, FRANCE; The potential of femtosecond Raman-induced polarization spectroscopy (RIPS) for the simultaneous determination of temperature and concentrations was investigated. These measurements were related to the rotational time response of the molecular gas mixture, which was measured as a function of the pump-probe time delay. The change of the polarizability anisotropy with respect to the vibrational levels was taken into account. The results of temperature measurements in pure CO2 showed good agreement with the values obtained by a thermocouple. The RIPS technique was also applied to a CO2-N2 gas m…