Terahertz-rate optical pulse generation from a passively mode-locked semiconductor laser diode.

Area of Science:

• Photonics and Laser Technology
• Optoelectronics
• Ultrafast Optics

Background:

• Passive mode locking is crucial for generating ultrashort optical pulses.
• Distributed-Bragg-reflector (DBR) laser diodes are key components in photonic integrated circuits.
• Achieving terahertz repetition rates is a significant challenge in optical pulse generation.

Purpose of the Study:

• To demonstrate terahertz-rate optical pulse generation using harmonic passive mode locking in a DBR laser diode.
• To investigate the influence of bias conditions on pulse generation rates.
• To confirm the transform-limited nature of the generated pulses.

Main Methods:

• Utilizing a distributed-Bragg-reflector (DBR) laser diode.
• Implementing harmonic passive mode locking.
• Varying the bias conditions of the gain section.
• Analyzing the optical spectrum and pulse envelope characteristics.

Main Results:

• First demonstration of terahertz-rate optical pulse generation in a DBR laser diode via harmonic passive mode locking.
• Observed fundamental repetition rate of 38.8 GHz, with harmonics at 400 GHz, 800 GHz, and 1.54 THz.
• Generated 1.54 THz pulses confirmed to be transform limited, matching Fourier transform calculations of the optical spectrum.

Conclusions:

• Harmonic passive mode locking in DBR laser diodes is a viable method for achieving terahertz repetition rates.
• Bias condition control allows tuning of the generated pulse repetition rate.
• The demonstrated technique produces high-quality, transform-limited optical pulses suitable for advanced applications.