Mode-controlled spectral transformation of femtosecond laser pulses in microstructure fibers

Mode-controlled spectral transformation of femtosecond laser pulses in microstructure fibers is experimentally demonstrated. Coupling Ti: sapphire laser pump pulses with an initial duration of about 30 fs into different waveguide modes of a microstructure fiber is shown to switch the regime of broadband emission generation to the regime where isolated spectral components are efficiently generated. This method of control is also used in our experiments to tune the frequencies dominating the spectrum of radiation at the output of a microstructure fiber.