Coherent nonlinear effects such as Electromagnetically Induced Transparency (EIT), Coherent Population Trapping (CPT), and Slow light are studied in thermal Rb vapor by both continuous and pulsed laser fields. This work primarily includes three parts: (I) mode-locked rubidium laser and its applications (II) enhanced coupling between optical and sound waves in the forward direction via ultra-slow light (III) optical steering via ultra-slow light in rubidium vapor. In part(I), I describe the construction and study of a mode-locked rubidium laser operating at the Rb D1 line using an active mode-locking technique inside the laser cavity. The mode-locked laser field is used to observe coherent effects in a dense rubidium gas. In part(II), I experimentally demonstrate enhanced acoustic-optic coupling that occurs when the velocity of sound is close to the group velocity of light. Dragging of the light by effective motion of the gas in a Rb cell is the origin of enhanced coupling. Good agreement between theory and experiment is found. In part(III), I experimentally demonstrate optical beam deflection in coherently driven rubidium vapor due to the steep refraction index profile in the region of EIT.

Mörkt läge är ett digitalt gränssnittsläge där text eller annan viktig information visas i ljusa färger mot en mörk bakgrund. Detta är i kontrast till ljust läge – mörk text på vit bakgrund – som ofta anses som standard. Läsförståelse är förmågan att få en förståelse av en text, och är viktig på grund av den stora användningen av skriftlig information i samhället samt för inhämtningen av ny kunskap. Denna förmåga är särskilt viktig för personer i högre former av utbildning, såsom universitet och högskolor. Denna studie undersöker mörkt läges effekt på läsförståelse. Effekten testades genom att låta deltagarna göra en kortare version av läsförståelsedelen av ett högskoleprov i både mörkt och ljust läge. Totalt deltog 15 personer, och alla var studenter från EECS – skolan för elektroteknik och datavetenskap – på KTH. Denna studie finner endast en obetydlig skillnad mellan läsförståelse i ljust eller mörkt läge, då till fördel för ljust läge. Det måste dock noteras att studien varit mycket liten när det gäller antalet testdeltagare, vilket innebär att resultaten inte är särskilt robusta och kan knappast generaliseras till andra grupper. / Dark mode is a display setting where text or other important information is displayed in light colors on a dark background. This is in contrast to light mode, where dark text is displayed on a white background, which is often considered to be the standard. Reading comprehension is the ability to gain a deeper understanding of a text, and is important for the utilization of written information in society as well as the acquisition of new knowledge. This ability is especially important for people in higher levels of education, such as universities and colleges. This study investigates the effect of dark mode on reading comprehension. The effect was tested by letting participants perform a shorter version of the reading comprehension part of an older Swedish Scholastic Aptitude Test in both dark and light mode. In total 15 people participated, and all were students from the School of Electrical Engineering and Computer Science at KTH. This study finds only an insignificant difference between reading comprehension in light or dark mode, with the difference being in favor of light mode. It should be noted that the study has been very small in regards to the number of participants, meaning that the results are not very robust and can hardly be generalized for other groups of people.