Generation of Kerr combs centered at 4.5 μm in crystalline microresonators pumped with quantum-cascade lasers.

We report on the generation of mid-infrared Kerr frequency combs in high-finesse CaF2 and MgF2 whispering-gallery-mode resonators pumped with continuous-wave room-temperature quantum cascade lasers. The combs were centered at 4.5 μm, the longest wavelength to date.

Observation of spectral broadening caused by self-phase modulation in highly multimode optical fiber.

We observed spectral broadening caused by self-phase modulation in 400- and 600-microm core diameter fibers using amplified, Q-switched, Nd:YAG laser pulses with peak powers to 150 kW. The degree of spectral broadening was not dependent linearly on the fiber length as in single-mode fibers because of the more complicated modal evolution in highly multimode fiber. Furthermore, even slight stress near the input end of the fiber reduced the observed broadening.

Synchronously pumped, femtosecond dye laser insensitive to cavity-length variations of up to 15 microm.

A synchronously pumped, hybridly mode-locked, antiresonant-ring dye laser that is insensitive to cavity-length variations of up to 15 microm is described. At a cavity length that is 70-80 microm shorter than the synchronous cavity length this laser generates stable pulses as short as 55 fsec, with a pulse width of 65 fsec being typical (assuming a sech(2) pulse shape). No evidence for colliding-pulse mode-locking effects is observed.