Kicking the habit/semiconductor lasers without isolators.

Area of Science:

• Photonics
• Materials Science
• Electrical Engineering

Background:

• Semiconductor lasers (SCLs) are crucial for integrated photonics but are susceptible to coherence degradation from optical back reflections.
• External Faraday-effect isolators are commonly used to mitigate back reflections but increase cost and size, hindering CMOS-compatible photonic integration.
• Developing isolator-free SCLs is a significant technological and economic challenge.

Purpose of the Study:

• To propose and demonstrate a practical and economic solution to coherence collapse in SCLs caused by optical back reflections.
• To reduce the reliance of SCLs on external Faraday-effect isolators.
• To advance CMOS-compatible photonic integrated circuit technology.

Main Methods:

• Designed and fabricated SCLs on a heterogeneous Si/III-V platform.
• Investigated the relationship between internal Q-factors and tolerance to optical reflections.
• Quantified the reflection tolerance of the novel laser design compared to commercial distributed feedback (DFB) lasers.

Main Results:

• Demonstrated an SCL design capable of withstanding 25 dB higher reflected power than commercial DFB lasers.
• Showcased a laser design that tolerates significant back reflections without coherence collapse.
• Validated the potential for high internal Q-factors to improve reflection isolation.

Conclusions:

• The developed SCL design offers a promising pathway to eliminate the need for external isolators.
• Further improvements in resonator quality (Q-factor) and optical design can enhance reflection isolation margins.
• This breakthrough is vital for the advancement of cost-effective and compact photonic integrated circuits.