InP-based, strain-free SESAMs with iron-doped InGaAs bulk absorber for ultrafast solid-state glass lasers at 1.55 µm

Area of Science:

• Optics and Photonics
• Materials Science
• Semiconductor Devices

Background:

• Semiconductor Saturable Absorber Mirrors (SESAMs) are crucial for mode-locking ultrafast solid-state lasers.
• Current GaAs-based SESAMs for 1.55 µm operation require strained absorbers, leading to defects and limited performance.
• High lattice-mismatch in GaAs-based SESAMs restricts design flexibility and reduces damage thresholds.

Purpose of the Study:

• To introduce the first fully strain-free SESAMs for 1.55 µm solid-state glass lasers.
• To overcome the limitations associated with strained absorbers in traditional SESAMs.
• To enable enhanced design freedom and improved performance in ultrafast laser systems.

Main Methods:

• Fabrication of SESAMs on an InP substrate with minimal lattice-mismatch (<0.1%).
• Incorporation of an iron-doped InGaAs bulk absorber for tunable modulation depth and recovery time.
• Utilized an anti-resonant design with InAlAs/InGaAlAs and TiO2/SiO2 distributed Bragg reflectors (DBRs).

Main Results:

• Achieved record-low non-saturable losses (0.6%) for InP-based SESAMs.
• Demonstrated the first stable continuous-wave mode-locked operation of an Er,Yb:glass laser using an InP-based SESAM.
• Generated 224 fs pulses with 102.5 mW output power, 79.1 MHz repetition rate, low noise, and minimal timing jitter.

Conclusions:

• The developed strain-free InP-based SESAMs provide unprecedented design freedom and performance.
• These SESAMs enable stable and high-performance mode-locked operation in solid-state lasers.
• This breakthrough paves the way for advanced ultrafast laser applications at 1.55 µm.