Erbium Fiber Laser Development for Applications in Sensing

The focus of this dissertation is the development of Erbium doped fiber laser sources for applications in dual pulse LIBS and hydrocarbon sensing in the oil industries. A single channel laser source suitable for the dual pulse LIBS is built and characterized which required both a higher energy ablation pulse and a second narrow linewidth resonant excitation pulse in the near UV wavelength range. For this source a two stage double pass erbium doped fiber amplifier is used to amplify the narrow linewidth laser pulse input from a DFB laser diode. The input pulse with the energy of 0.4 nJ is amplified to 4 µJ in the first stage amplifier and then is further amplified up to an energy of 50 µJ in a second stage amplification. The second stage amplification is carried out with the help of large mode area Er/Yb codoped fiber. The first and second stages of the amplification were thoroughly characterized by studying various parameters under different pump conditions. The frequency upconversion of the amplified laser pulse is carried out with the help of PPLN (frequency doubled) and BBO crystal (frequency quadrupled). The pulse energies of about 50 µJ for the fundamental pulse (1543 nm), 15 µJ frequency doubled (771.5 nm) and 1 µJ frequency quadrupled (385.7 nm) are achieved. The nonlinear effect of stimulated Brillouin Scattering (SBS) was observed and a suitable operating regime was established to avoid deleterious effects of SBS.;A fiber sensor based on the on the principle of Optical Low Coherence Reflectometry (OLCR) was developed based on a low coherence ASE Erbium fiber source. The system was characterized in detail and was tested in the determination of the refractive index and physical thickness of a few liquid hydrocarbon samples e.g. hexane and chloroform, at the bottom of an industrial high pressure test cell.