We show results obtained from a semiconductor saturable-absorber mirror mode-locked Ti:sapphire soliton laser that was operated in the multiple-pulse regime. Double, triple, and quadruple pulses were observed when the dispersion was decreased below a critical value. The pulse pairs and triplets were either widely separated or closely coupled, and spectra that resembled those of constant as well as rotating phase differences between pulses were observed. We explain our observations in the framework of the generalized complex GinzburgLandau equation as the master equation of the laser.

We have measured the nonlinear optical absorption of arsenic and oxygen implanted epitaxial GaAs for a range of ion doses and annealing temperatures. The response time, A , and a parameter, M max , which characterizes the performance of the structures as modulators, are both reduced by implantation, and correspondingly the nonbleachable losses are increased. We show that similar combinations of (A , M max) can be achieved using either ion species and various combinations of dose and annealing temperatures. Furthermore, the data were all located on a well-defined curve in the (A , M max) plane, provided amorphization, which occurs at high implant doses, was avoided. We deduce that there exists a limit to the modulation if a specific response time is required.

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We demonstrate that ion implantation can be used for response time tailoring to create high-performance indium gallium arsenide (InGaAs) quantum well semiconductor saturable absorber mirrors (SESAMs). The design and manufacture of the SESAMs are described, and their nonlinear optical and temporal responses, relevant to the mode-locking of picosecond type pulses, are given. The implanted devices shown here have response times as short as 11 ps, compared with several hundred picoseconds without implantation. They have small non-bleachable losses and low saturation fluence ({<}20µJcm-2), allowing for operation far below the damage threshold. An implantation- and annealing-induced quantum well intermixing effect is shown to be present in the SESAMs, resulting in an energy shift in the excitonic feature. This effect can be taken into account in the SESAM design or minimized, if necessary. Using the SESAMs to mode-lock a low-power Nd:YVO4 laser at 1064 nm, we have generated pulsewidths between 9 and 23 ps, depending on the cavity configuration and the SESAM used.

We present a new exact solution for ultrashort pulses generated by passively mode-locked lasers, taking into account the slow and the fast parts of the semiconductor saturable-absorber response in the nonsaturated limit.