Novel Devices for Fiber Laser Application

Abstract

In this thesis, several novel devices for fiber laser are proposed and demonstrated. The first type of device is based on modal interference in non-adiabatic fiber tapers. Using such tapers, we demonstrate a simple technique to tune the wavelength of an all-fiber erbium-doped laser. Next, we systematically investigate the use of non-adiabatic fiber tapers for sensing purposes. As a result of this investigation, we have built and characterized several simple and sensitive sensors for highly accurate measurements of strain, temperature, and refractive index.Another class of devices investigated in this dissertation is based on micro-cavities. We propose and demonstrate, for the first time, the use of high-Q micro-spherical resonators as feedback mirrors for fiber lasers. The advantages of these new "mirrors" include compactness, low cost, tunability of the reflection coefficient, and an extremely narrow reflection bandwidth.We demonstrate single-frequency and Q-switched fiber lasers based on micro-spherical mirrors. The next natural step in the development of fiber-lasers involves the phenomenon of mode-locking. For this purpose, we developed a novel type of saturable absorber based on a fiber-taper embedded in a carbon nanotube/polymer composite material (FTECntPC). Subsequently, mode-locking was successfully demonstrated in an erbium-doped fiber laser using the aforementioned FTECntPC saturable absorber. We have thoroughly investigated the dynamics of passively mode-locked fiber lasers that incorporate the FTECntPC saturable absorber. With this new saturable absorber we have been able to obtain the highest pulse energies that have been generated to date directly from a soliton all-fiber laser. In addition, with the help of the novel saturable absorber, we have been able to build and analyze the first bi-directional passively mode-locked fiber laser.