Coherent coupling of vertical-cavity surface-emitting laser arrays and efficient beam combining by diffractive...

Area of Science:

• Optics and Photonics
• Semiconductor Lasers
• Laser Array Technology

Background:

• Injection locking is a key technique for synchronizing laser arrays.
• Vertical-cavity surface-emitting lasers (VCSELs) offer advantages in compactness and scalability.
• Maintaining phase coherence in large laser arrays is challenging.

Purpose of the Study:

• To demonstrate a phase-locked VCSEL array system using master-slave injection locking.
• To investigate the coherence and power scalability of the developed system.
• To evaluate the efficiency improvements offered by beam-transformation optics.

Main Methods:

• Master-slave injection locking of 2D VCSEL arrays.
• Frequency and phase tuning using laser-trimmed microresistors.
• Beam shaping with diffractive optical elements (DOEs) and a Fourier lens.
• Monolithic integration of VCSEL and microlens arrays.

Main Results:

• Achieved 95% system coherence for several hours and 90% for months with a 21-slave-laser array without active control.
• Demonstrated scalability by locking a 77-slave-laser array with 78% coherence.
• Reported optical system efficiency of 20-23%, improvable to 44% with beam-transformation optics.

Conclusions:

• The presented master-slave injection locking method effectively achieves high phase coherence in VCSEL arrays.
• The system exhibits excellent scalability in terms of output power and array size.
• Integrated beam-transformation optics significantly enhance overall system efficiency.