Source: USPTO .report

The Importance of Self-Starting Mode Locking in Lasers

Understanding Self-Starting Mode Locking

Some lasers face challenges in initiating the mode-locking process, requiring external interventions to transition from continuous-wave mode to generating ultrashort pulses. Self-starting mode-locked lasers can automatically initiate mode locking without external assistance, making them more practical for various applications.

Factors Affecting Self-Starting in Bulk Lasers

In bulk lasers, self-starting mode locking is typically achieved using saturable absorbers like semiconductor saturable absorber mirrors (SESAMs). The recovery time of these absorbers plays a crucial role in self-starting mode locking by reducing the saturation power for long pulses during the startup phase. Additionally, parasitic intracavity reflections and uneven spacing of resonator mode frequencies can hinder self-starting.

Challenges in Long Laser Resonators

Long laser resonators pose challenges for self-starting mode locking due to the high peak power to average power ratio, requiring precise adjustment of saturable absorber parameters. Kerr-lens mode-locked lasers face difficulties in achieving self-starting mode locking compared to bulk lasers with slow saturable absorbers.

Self-Starting in Fiber Lasers

Fiber lasers encounter difficulties in eliminating parasitic reflections, especially when incorporating bulk-optical elements. Rayleigh scattering within fibers and the use of fast saturable absorbers contribute to non-self-starting mode locking in fiber lasers. Despite the large modulation depth of absorbers, achieving self-starting mode locking in ultrafast fiber lasers remains a challenge.

Conclusion

Self-starting mode locking is a critical feature in lasers for seamless operation without external interventions. Understanding the factors influencing self-starting behavior in both bulk and fiber lasers is essential for optimizing laser performance in various applications.

Source: Chin. Phys. B
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