Dual-mode DFB laser diodes with apodized surface gratings

Area of Science:

• Photonics and Laser Technology
• Semiconductor Device Fabrication

Background:

• Distributed feedback (DFB) lasers are crucial for various optical applications.
• Controlling laser performance parameters like threshold current, output power, and linewidth is essential.
• Facet reflections can negatively impact laser stability and performance.

Purpose of the Study:

• To investigate the impact of grating apodization on dual longitudinal mode DFB lasers.
• To develop design guidelines for apodized DFB lasers using analytic formulas and simulations.
• To enhance laser performance metrics including threshold current density, output power, and frequency tunability.

Main Methods:

• Fabrication of DFB lasers with and without surface grating apodization.
• Development of analytic formulas and computational simulations for design guidance.
• Characterization of fabricated devices to validate simulation results.

Main Results:

• Apodization significantly reduces threshold current density and increases output power.
• Grating apodization broadens the difference frequency tunability range (measured 15-55 GHz).
• Apodization and complex grating coupling mitigate phase effects from facet reflections, allowing higher reflectivity and narrower linewidths.

Conclusions:

• Grating apodization is an effective technique for enhancing the performance of dual longitudinal mode DFB lasers.
• The developed design guidelines and simulations accurately predict device characteristics.
• Apodized DFB lasers offer improved tunability and narrower linewidths, beneficial for advanced optical systems.