Subpicosecond optical sampling spectrometer using asynchronous tunable mode-locked lasers

We have developed a subpicosecond nondegenerate pump-probe spectrometer based on the optical sampling technique using a combination of asynchronous tunable femtosecond lasers. Owing to its simple instrumentation, time evolution of subpicosecond to nanosecond excited molecular processes in solution and of exciton relaxation processes in semiconductor multiple quantum wells has been detected on an oscilloscope by an effective time base magnification of 760 000 times. Fast acquisition of the temporal profiles and ease of wavelength scanning allowed compilation of time-resolved absorption and excitation spectra. A possible extention of the spectrometer with one of the light sources being a synchrotron radiation instead of the femtosecond laser is discussed.