Continuously tunable coherent pulse generation in a semiconductor laser.

Area of Science:

• Photonics
• Laser Physics
• Semiconductor Devices

Background:

• Laser spectral emission is typically limited by optical resonator dimensions, resulting in discrete cavity modes and fixed repetition rates.
• This lack of tunability restricts laser usability in experiments requiring spectral or temporal flexibility.

Purpose of the Study:

• To overcome the fundamental limitations of fixed spectral emission and repetition rates in lasers.
• To demonstrate a monolithic semiconductor laser with continuously tunable characteristics.

Main Methods:

• Utilized a microwave driving signal to induce spatiotemporal gain modulation along the laser cavity.
• Generated intracavity mode-locked pulses with continuously tunable group velocity.
• Achieved a continuously tunable repetition rate from 4 GHz to 16 GHz.

Main Results:

• Demonstrated a monolithic semiconductor laser with a continuously tunable repetition rate (4-16 GHz).
• Generated frequency combs with tunable mode spacings and coherent pulse trains with tunable repetition rates.
• Successfully overcame spectral gaps and fixed repetition rates inherent in traditional lasers.

Conclusions:

• The developed laser technology offers fully tunable chip-scale lasers and frequency combs.
• This innovation has significant potential for diverse fields, including high-resolution and dual-comb spectroscopy.
• Paves the way for advanced laser applications requiring high spectral and temporal flexibility.