"Picosecond Regime Optical Sampler Using Semiconductor Lasers"

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[OBJECTIVE] The purpose of the present study is to construct a bread board level electro-optic sampling system in order to evaluate the capability of the ultrashort pulse technology for very fast electronics of 10-100 Gbit/s. The use of pulsed semiconductor lasers is the essential part of the presert implementation toward the realization of truly useful testing systems.[Ultrashort Pulse Generation from Semiconductor Lasers] Following the achievements of generating vey short optical pulses with FWHM less than 10 ps last year either by improving gain switching or by employing fibers for pulse compression, the focus this year is concentrated on the use of diode laser amplifier for increasing the pulse energy together with the shaping. The long er tail part usually associated with the gain switched laser pulses may be suppressed by utilizing the nonlinear gain dynamics. Namely if the incident pulse power level is properly high, the population inversion in the active medium is consumed mainly through the amplification of the main lobe, while the tail part is amplified only by the medium with almost depleted of the electron hole pairs. This idea was examined both by the computer simulation and the experiment. Specifically it was found that the configuration of reflected wave amplifier (RWA) is more efficient in shaping the pulses, because the population inversion will be more thoroughly depleted by the double path propagation.[Application of Diode Laser Ampoifier to Electro-Optic Sampling System] The use of diode laser amplifier helps the increase of signal power, meanwhile the excess noise poer from diode laser amplifier partially compensate the gain. It was examined theoretically and experimentally that the proper choice of the static retardation has an optimum point for maximizing the signal to noise ratio. Experimentally 6 dB net gain was confirmed.