Temporal coherence characteristics of InGaAsP laser diode with single-longitudinal-mode oscillation

Area of Science:

• Optics and Photonics
• Semiconductor Lasers

Background:

• InGaAsP laser diodes are crucial for optical communications.
• Understanding their temporal coherence is essential for system performance.

Purpose of the Study:

• To investigate the temporal coherence characteristics of single longitudinal mode InGaAsP laser diodes.
• To correlate coherence properties with spectral fine structure.

Main Methods:

• Utilized an unbalanced Michelson interferometer for temporal coherence measurements.
• Analyzed the spectral fine structure of the laser output.

Main Results:

• Coherence characteristics are described by the Fourier transform of the spectral fine structure.
• The spectral structure comprises a main mode and two adjacent submodes.
• Observed submodes lead to a shorter coherence length than predicted by line-width measurements alone.

Conclusions:

• Spectral submodes significantly impact the temporal coherence of InGaAsP lasers.
• Direct line-width measurements may underestimate the effective coherence length in these devices.