Passive mode locking of optical parametric oscillators: an efficient technique for generating sub-picosecond pulses

Area of Science:

• Nonlinear optics
• Quantum optics
• Laser physics

Background:

• Optical parametric generation (OPO) is a key technique for frequency conversion.
• Large group velocity mismatch in nonlinear crystals presents challenges for pulse generation.
• Laser amplification principles offer insights into OPO dynamics.

Purpose of the Study:

• To establish an analogy between OPO with large group velocity mismatch and laser amplification.
• To propose a novel method for generating high peak power sub-picosecond pulses.
• To investigate the feasibility of passive mode locking in OPOs.

Main Methods:

• Analytical modeling of OPO dynamics considering group velocity mismatch.
• Incorporation of nonlinear saturable absorbers or Kerr lenses.
• Numerical simulations to confirm theoretical predictions.

Main Results:

• Demonstrated analogy between OPO and laser amplification with comparable gain recovery and walk-off times.
• Predicted photon conversion efficiency exceeding 80%.
• Predicted output pulse lengths of a few hundred femtoseconds.

Conclusions:

• OPOs with significant group velocity mismatch can be effectively modeled using laser amplification concepts.
• The proposed OPO configuration enables direct generation of high peak power sub-picosecond pulses.
• Repetitive passive mode locking is achievable with quasi-Continuous Wave (CW) pumping.