High average output power from a backside-cooled 2-µm InGaSb VECSEL with full gain characterization

Area of Science:

• Optics and Photonics
• Semiconductor Lasers
• Materials Science

Background:

• Intracavity heatspreaders are typically required for high-power Vertical External Cavity Surface Emitting Lasers (VECSELs), but present trade-offs, particularly for passive modelocking.
• Optimizing heat management is crucial for enhancing the performance and efficiency of VECSEL devices.

Purpose of the Study:

• To compare the lasing properties of two Indium Gallium Antimonide (InGaSb)-based VECSELs with different heat management strategies.
• To demonstrate a novel backside-cooled VECSEL design optimized for modelocking, achieving high average output power without an intracavity heatspreader.
• To introduce and validate an optical characterization method for precise measurement of wavelength-dependent gain saturation and spectral gain.

Main Methods:

• Fabrication and characterization of two InGaSb-based VECSEL chips with distinct heat management approaches.
• Utilizing a backside-cooled, non-resonant VECSEL chip design optimized for modelocking.
• Development and application of an optical characterization technique for gain measurements across a 1.9 to 3 µm wavelength range.

Main Results:

• Demonstrated a record average output power of 810 mW from a VECSEL without an intracavity heatspreader.
• Achieved similar average output power compared to a commercial VECSEL with an intracavity heatspreader, despite the optimized chip being designed for antiresonance.
• Measured small signal gain exceeding 5%, small saturation fluences, and broad gain bandwidths over 90 nm.

Conclusions:

• The backside-cooled, non-resonant VECSEL design eliminates the need for intracavity heatspreaders, enabling record output power and improved modelocking performance.
• The developed optical characterization method provides precise gain measurements, crucial for optimizing VECSEL performance.
• This work advances the development of high-power, efficient VECSELs for various optical applications.