Phase-locked high-brightness interband cascade laser array with multimode interferometer couplers.

Area of Science:

• Optics and Photonics
• Semiconductor Lasers
• Mid-Infrared Technology

Background:

• Mid-infrared lasers face challenges in heat dissipation and achieving in-phase operation.
• Interband cascade lasers (ICLs) offer potential for mid-infrared applications but require improved beam control.

Purpose of the Study:

• To design and fabricate a phase-locked interband cascade laser (ICL) array.
• To utilize multimode interference (MMI) couplers for coherent operation of multiple emitters.
• To address heat dissipation and in-phase operation challenges in mid-infrared lasers.

Main Methods:

• Fabrication of a 7.5-µm-wide ridge ICL array.
• Incorporation of multimode interference (MMI) couplers for phase-locking.
• Characterization of far-field patterns and beam quality (M²).

Main Results:

• Achieved coherent operation with periodic and symmetrical interference fringes.
• Demonstrated effective phase-locking using MMI couplers.
• Obtained a nearly diffraction-limited beam quality (M² ≈ 1.31) with suppressed higher-order modes.
• Delivered high output power (390 mW from a 1×4 array).

Conclusions:

• The MMI-coupled ICL array effectively achieves phase-locking and in-phase operation.
• The design shows robust performance and scalability for high-power mid-infrared applications.
• The ICL array shows potential as an optical phased array for advanced photonic systems.