Relaxation oscillation theory for the nd3+:yab self-frequency-doubling laser

The operation of the frequency‐doubled Nd : YAG laser may be affected by the thermo‐optical distortion in intracavity elements. A theoretical model of the laser has been developed which couples the thermo‐optical effects in the frequency‐doubling crystal and the laser parameters. Oscillatory behavior and bistable power level operation are predicted. The model is supported by experimental data.

Thermo-optical instabilities and bistable behavior with the frequency-doubled Nd : YAG laser

In this paper, a novel approach to modelling intracavity second harmonic generation (SHG) in periodically poled MgO-doped lithium niobate (PPLN) is presented and verified against experimental results. This approach involves combining the coupled nonlinear wave equations with a rate equation model for a diode-pumped solid-state Nd:YVO4 laser, taking into account both the depletion of the fundamental wave due to the energy conversion from the fundamental wave to the SHG wave and the reduction of the fundamental wave within a laser cavity due to the loss as a result of the SHG nonlinear process. It was shown that the theoretical simulation matched the experimental results well, while also providing physical insight into the importance of the fundamental wave depletion in the intracavity SHG nonlinear processes. The resulting model is computationally simple and has the potential to generalize to the other nonlinear processes such as three-wave mixing and optical parametric oscillation.

Study of fundamental wave depletion in intracavity second harmonic generation.

This thesis investigates novel dispersion compensation methods for mode-locked fiber lasers and the dynamical properties of ytterbium and thulium-holmium gain materials. The emphasis is on dielectric thin film structures and their integration into fiber cavities to control laser performance. A Gires–Tournois interferometer (GTI) made with electron beam evaporation was used for the first time to compensate for the dispersion of a fiber cavity and thus achieve ultrashort mode-locked pulses. Another thin film dispersion compensator, a Fabry-Pérot etalon, demonstrated in a mode-locked fiber laser, allowed for continuously tunable short pulse operation of an ytterbium fiber laser over a broad wavelength range. In addition to dispersive thin film structures, the thesis also presents a new type of dichroic coating deposited directly onto an optical fiber end. The dichroic coating acts as an output coupler and pump combiner, simultaneously. This enables laser cavities which are substantially shorter than would be possible with conventional fiber components. The compact all-fiber ytterbium fiber laser presented had a record high fundamental repetition rate of 571 MHz with ultrashort, 572 fs, pulses. The energy level scheme of ytterbium and thulium-holmium gain materials was studied for the first time in this thesis by analyzing the laser relaxation oscillations. Both materials exhibited a change in transition mechanism from three-level to four-level laser operation in the long-wavelength tail of the gain bandwidth.

Optical Thin Film Technology for Ultrafast Fiber Lasers

Space laser communications with the frequency doubled Nd-YAG laser offers the most efficient means for transferring wideband data from one satellite to another. A space test in 1981 of the Nd-YAG laser system operating at a rate of 1 000 Mbit s-1 will establish the basis for future systems. The system offers growth capability beyond conventional systems and is a major step forward in the application of a low power laser. The Nd-YAG laser design as well as its principles of operation are constrained by the space application. The laser is now conductively cooled, mode-locked, and frequency-doubled, and will be so operated in space. The space system will use both solar and lamp pumped lasers to allow alternate modes of operation.

Space communications: Practical application of a visible Nd: YAG laser

The behavior of relaxation oscillations in the presence of a nonlinear loss was used to determine the relevant parameters of an intracavity frequency‐doubled and mode‐locked Nd : YAG laser The acousto‐optic mode locker was used in a controlled manner to excite the relaxation oscillations which allowed the measurement of the damping time and frequency Laser output power at 053 μm and damping time is consistent with recent theory

C. J. Kennedy

Papers

Measurement of parameters in a mode‐locked and frequency‐doubled Nd : YAG laser using relaxation oscillations