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Simulation And Analysis of Terahertz Laser Based on Graphene
, M.Sc. Thesis Sharif University of Technology ; Faez, Rahim (Supervisor)
Abstract
Graphene, a monolayer carbon-atomic honeycomb lattice crystal, has attracted attention due to its peculiar carrier transport properties owing to the gapless energy spectrum. Due to lack of applicable light source in terahertz (THz) band, further researches to finding materials that are suitable for semiconductor lasers in this band to be continued. In this thesis, the population inversion possibility that is the first provision of laser operation, was analyzed in graphene optical pumping situation. The analysis was done by numerical solving of carrier concentration and energy density relations.As a result of this analysis population inversion is obtained when the stimulation square pulse has...
Interferometric Laser Imaging for Droplet Sizing (ILIDS)in Sparse Sprays
, M.Sc. Thesis Sharif University of Technology ; Kebriaee, Azadeh (Supervisor)
Abstract
In the present work we first introduced ILIDS and review the theory of interferometry and light scattering from droplets. Bases on ILIDS method, droplets are irradiated by monochrome sheet laser, where the superposition of reflected and first-order refracted beams form a parallel fringe pattern at out of focus plane on the imaging sensor in the forward-scatter region. This pattern can be related to the droplet size by using simple geometrical optics. For the present work, an image processing algorithm is utilized to capture weak and noisy images of droplets to reduce the lost data in the sizing procedure. Since ILIDS method is applied for small and dilute spray, it is suitable for...
Design and Construction of Highly Stable pulsed Electrro-opticaly Q-Switched Nd:YAG Laser
, M.Sc. Thesis Sharif University of Technology ; Sadighi Bonabi, Rasoul (Supervisor)
Abstract
Nd:YAG laser is one of the most applicable lasers on laser researches where it’s basic wavelength and higher harmonics are used on different laser projects. It should be realized that it’s basic output has a wide pulse duration and lower peak power. Therefore, in order to increase the peak power the pulse duration is reduced by Q-switching.
In this project, in the first step, based on flash-lamp pump Nd:YAG laser a 600 mj energy per 60 µs pulse is constructed. Then a pulse duration is shorten by order of more than 3000 via electro-optics Q-switching system where we could reach up to 19 ns pulses and laser peak power is increased up to several megawatts
In this project, in the first step, based on flash-lamp pump Nd:YAG laser a 600 mj energy per 60 µs pulse is constructed. Then a pulse duration is shorten by order of more than 3000 via electro-optics Q-switching system where we could reach up to 19 ns pulses and laser peak power is increased up to several megawatts