Mode stabilization of a laterally structured broad area diode laser using an external volume Bragg grating

Area of Science:

• Optics and Photonics
• Laser Physics
• Semiconductor Devices

Background:

• Broad area diode lasers (BALs) often suffer from poor beam quality and spectral instability.
• On-chip transverse Bragg resonance (TBR) gratings offer a method for mode selection within BALs.
• External feedback mechanisms are typically required to enhance mode selectivity and output characteristics.

Purpose of the Study:

• To investigate the use of an external volume Bragg grating (VBG) for stabilizing transverse and longitudinal modes of a BAL.
• To compare the performance of VBG feedback with traditional mirror feedback for TBR mode selection.
• To assess the impact of VBG feedback on output power, spectral narrowness, and alignment sensitivity.

Main Methods:

• An external VBG was integrated into a resonator assembly with a TBR BAL.
• The angular geometry of the resonator was adjusted to select the TBR mode.
• Output power, spectral characteristics, and far-field distribution were analyzed with VBG feedback.
• Performance was compared to a setup using a conventional feedback mirror.

Main Results:

• The VBG enabled effective transverse and longitudinal mode stabilization of the TBR BAL.
• VBG feedback required less critical alignment compared to a mirror.
• Higher output powers were achieved using the VBG feedback.
• Additional modulation in the far-field distribution was observed, aiding TBR concept studies.

Conclusions:

• External VBG feedback is a robust and efficient method for mode stabilization in TBR BALs.
• The VBG approach simplifies alignment and enhances output power.
• The observed far-field modulations provide new insights into the TBR phenomenon.