Abstract

We present a modified monolithic passive colliding pulse mode-locked (CPM) laser configuration, which can generate 2, 3, or 4 pulses in the cavity, giving the second, third, or fourth harmonic of the repetition rate. The laser has a contiguously electrically connected gain section and 3 separated sections placed at every quarter of the cavity length. Its operation can be switched between 2, 3, or 4 pulses depending on the bias (forward or reverse) applied to each of its 3 independent sections, changing the position and number of saturable absorbers in the cavity. The laser is a stripe loaded waveguide fabricated on a 4 quantum well GaAs/ AlGaAs material. Its structure and the fabrication procedure are similar to the CPM laser described in Ref. ¹. The total length of the laser is 600 µm and each one of its 3 independent sections is 30 pm long. It generates 120, 180, or 240-GHz repetition rate. Figure 1 shows the cross-correlation interferogram² for 4 pulse operation, where we measure 1.2-ps pulse width at 240-GHz repetition rate. Figure 2 shows the optical spectra for the same configuration. The time bandwidth product is 0.35. This is the first observation of multiple CPM laser operation.

© 1994 IEEE