Development and Characterization of Infrared Pulsed Fiber Lasers

Abstract

Infrared pulsed lasers have become indispensable scientific instruments. To extend the range of applications for these instruments, significant work is being done to develop and characterize infrared pulsed laser sources in a compact and robust all-fiber format. This dissertation covers the development of two all-fiber pulsed laser systems operating in the short-wave infrared and a technique for characterizing the timing noise of mode-locked lasers. The first part of this dissertation will discuss the development of high-energy and eye-safe all-fiber amplifiers for direct detection LiDAR systems. Achieving high energy from singly erbium-doped fiber amplifiers is challenging due to concentration quenching effects in standard silica gain fibers. Compared to silica, phosphate glasses exhibit a more open and disordered glass matrix which allows for doping at high concentrations. The development of an all-fiber, millijoule-level, amplifier using a novel phosphate glass gain fiber will be discussed. The second part of this dissertation will focus on the development of single-cavity sources for dual-comb spectroscopy. The dual-comb technique allows for fast and precise detection of atmospheric absorption spectra. However, the complicated process of stabilizing and locking two laser cavities together presents a significant obstacle when moving these laser sources out of the laboratory. By generating two coherent dual-combs from a single cavity, free-running and single-shot dual-comb spectroscopy becomes possible. This dissertation will discuss the development of a bidirectionally mode-locked thulium-doped fiber laser for dual-comb spectroscopy. The all-fiber ring laser produces two coherently linked frequency combs in the 1.9 µm spectral region. Finally, a real-time method of measuring timing error in mode-locked lasers will be discussed. This method produces a digital record of pulse-to-pulse laser timing noise which opens new possibilities for applications that rely on mode-locked lasers such as photonic analog-to-digital converters (PADC). Strong signal degradation from laser timing noise can occur in optically sampled PADCs. Real-time correction of timing noise in a high-frequency PADC using this measurement method will be discussed.