Ultrafast Optics with a Mode-locked Erbium Fiber Laser

We describe an ultrafast optics advanced laboratory comprising a mode-locked erbium fiber laser, auto-correlation measurements, and a free-space parallel grating dispersion compensation apparatus. The simple design of the stretched pulse laser used nonlinear polarization rotation mode-locking to produce pulses as narrow as 108 fs, full-width at half-maximum, at a repetition rate of 55 MHz and average power of 5.5 mW from the laser oscillator. A pre-amplifier following the oscillator increased average power to 21 mW. Interferometric and intensity auto-correlation measurements were made using a Michelson interferometer that takes advantage of the two-photon nonlinear response of a common silicon photodiode for the second order correlation between 1550 nm pulses. A parallel grating dispersion compensation apparatus decreased chirp and increased peak intensity, narrowing the pulse width by a factor of 13. A detailed parts list includes previously owned and common parts used by the telecommunications industry, which may decrease the cost of the lab to within reach of many undergraduate departments.