Mode-Locking Based on Nonresonant Nonlinearity 351
fundamental through SHG reduced the intensity to 30% of its initial value. Only
10% of that fundamental is reflected back through the second harmonic generating
crystal. However, because the full SH signal that was generated in the first
passage is reflected back, and because it has reversed phase with respect to the
fundamental, 30% of the initial fundamental is recovered. At the first passage, the
conversion to second harmonic should be sufficient to have a sizeable depletion
of the fundamental. Therefore, this method works best for high-power lasers. The
theoretical framework for the SHG has been set in Chapter 3 (Section 3.4.1) and
can be applied for a theoretical analysis of this type of mode-locking. ...