Analytical characterization of grating-tuned external-cavity semiconductor lasers

Area of Science:

• Optics and Photonics
• Semiconductor Lasers

Background:

• External-cavity semiconductor lasers (ECLDs) are crucial for tunable laser applications.
• Accurate modeling of ECLD output power and spectral characteristics is essential for device design and optimization.

Purpose of the Study:

• To derive analytical expressions for the output spectrum of an ECLD using the ray-trace method.
• To determine explicit analytical expressions for threshold carrier density and extended cavity length for grating-selected wavelengths.
• To develop a method for predicting tunable output power by solving the carrier density deficit without using photon rate equations.

Main Methods:

• Application of the ray-trace method to model the ECLD.
• Derivation of analytical expressions for spectral output, threshold carrier density, and cavity length.
• Integration of spectral patterns with carrier rate equations to solve for carrier density deficit.

Main Results:

• An analytical expression for the output spectrum from the end facet of an ECLD was derived.
• Explicit analytical expressions for nominal threshold carrier density and required extended cavity length were obtained.
• A self-consistent solution for carrier density deficit was achieved, enabling prediction of tunable output power.

Conclusions:

• The developed analytical framework accurately describes ECLD spectral behavior and output power.
• This method provides a simplified approach to predicting tunable output power, avoiding complex photon rate equations.
• The findings contribute to a better understanding and design of tunable external-cavity semiconductor lasers.