Abstract-Mode-locked semiconductor lasers which incorporate multiple contacting segments are found to give improved performance over single-segment designs. The functions of gain, saturable absorption, gain modulation, repetition rate tuning, wavelength tuning, and electrical pulse generation can be integrated on a single semiconductor chip. The optimization of the performance of multisegment mode-locked lasers in terms of material parameters, waveguiding parameters, electrical parasitics, and segment length is discussed experimentally and theoretically.

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RF drive frequency from an actively modelocked fibre ring laser without controlling the modulator bias. In general, whenever the RF drive frequency is detuned by an amount equal to fwl2, from the frequency where stable pulses are found, the laser would produce pulses at repetition rate two times the RF drive frequency.Similarly, when detuning is -:fc 4 vf3, then the repetition rate of output pulses can be tripled.

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The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) has been extended to well over 10 million pulses by reducing the density of carriers at the semiconductp to metal interface. This was achieved by reducing the density in the vertical and lateral directions. The first was achieved by varying the spatial distribution of the trigger light thereby widening the current filaments that are characteristic of the high gain switches. We reduced the carrier density in the vertical direction by using ion implantation. These results were obtained for currents of about 10 A, current duration of 3.5 ns, and switched voltage of -2 kV. At currents of -70 A, the switches last for 0.6 million pulses. In order to improve the performance at high currents new processes such as deep diffusion and epitaxial growth of contacts are being pursued. To guide this effort we measured a carrier density of 6 x 10 l8 electrons (or holes)/ cm in filaments that carry a current of 5 A.

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