ABSTRACT
Following the introduction of techniques for the mode-locking (see, for example chapter C2) of solidstate lasers in the mid 1960s, pulses of the order of a few picoseconds were readily available. The nonlinear problems caused by the relatively high intracavity flux of such pulses were soon recognized [1] and techniques were developed [2] to counteract the frequency chirping associated with this nonlinearity, primarily self-phase modulation (see chapter A4). Despite this, throughout the first two decades of technological short-pulse laser development, little effort was directed towards the production of transform-limited pulse operation. In 1973, Hasegawa and Tappert [3], first proposed the generation of solitons in single mode optical fibre, through a subtle mechanism that balanced the intensity-dependent spectral broadening and anomalous dispersion, that was a property of silica-based fibres in the spectral region above about 1.27 µm. It was not until 1980, however, when a suitable laser source was developed, that Mollenauer [4] reported the first demonstration of optical solitons. By the mid 1980s, with pulse durations from bulk lasers approaching the 100 fs regime, techniques for controlling both nonlinearity and intracavity dispersion were necessarily introduced (see chapter C2.2) and the first ‘soliton laser’ was reported [5]. With the introduction of the Kerr lens mode-locking technique [6] for reliable ultrashort pulse generation, methods of dispersion control have become vital for the production of pulses of a few tens of femtoseconds and below. The term soliton laser is now very widely applied to the generic dispersion-compensated ultrashort pulse laser although the pulses generated are generally not solitons in the strict mathematical definition, even in fibre-based systems.
