Theoretical analysis of passively mode-locked semiconductor ring lasers

Area of Science:

• Optics and Photonics
• Semiconductor Lasers
• Nonlinear Optics

Background:

• Passive mode-locked semiconductor ring lasers (PML-SRLs) are crucial for generating ultrashort optical pulses.
• Understanding the theoretical underpinnings of PML-SRLs is essential for optimizing their design and performance.
• Previous models have not fully elucidated the interplay of various parameters governing PML-SRL operation.

Purpose of the Study:

• To theoretically investigate the operation regimes and performance of passive mode-locked semiconductor ring lasers (PML-SRLs).
• To analyze the influence of optical confinement factor and injection current on PML-SRL characteristics.
• To explore the relationship between gain-loss balance, SOA stimulated rate, SA carrier lifetime, and resonator roundtrip time.

Main Methods:

• Theoretical analysis using a traveling wave model.
• Investigating the transient gain-loss balance governing all operation regimes.
• Examining the impact of waveguide properties (loss, length) and material bandwidth on mode-locking.

Main Results:

• Optical confinement factor and injection current significantly influence PML-SRL operation and performance.
• All operation regimes are dictated by transient gain-loss balance, linked to SOA stimulated rate, SA carrier lifetime, and roundtrip time.
• Mode-locking is independent of the passive waveguide, but performance degrades with increased loss or shorter length (given sufficient material bandwidth).

Conclusions:

• PML-SRL design and high performance can be advanced through a deeper understanding of theoretical parameters.
• Achieving high-energy pulses is feasible by shortening passive length and narrowing the gain spectrum.
• The transient gain-loss balance is a fundamental principle governing PML-SRL dynamics.