Note: a high transmission Faraday optical isolator in the 9.2 μm range

Area of Science:

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

Background:

• Faraday isolators are crucial components for preventing back-reflection in optical systems.
• Indium antimonide (InSb) is a promising material for mid-infrared applications due to its unique electronic properties.
• Developing efficient isolators for the mid-infrared (mid-IR) spectrum is essential for various sensing and communication technologies.

Purpose of the Study:

• To fabricate and characterize an n-doped InSb-based Faraday isolator operating in the mid-IR wavelength range.
• To evaluate the performance of the InSb isolator in terms of isolation ratio and insertion loss.
• To investigate the temperature dependence of the isolator's performance and explore potential improvements.

Main Methods:

• Fabrication of an n-doped InSb material.
• Characterization of the Faraday isolator at a wavelength of 9.2 μm.
• Measurement of isolation ratio and insertion loss.
• Analysis of temperature-dependent performance.

Main Results:

• Achieved a high isolation ratio of 31(2) dB.
• Obtained a low insertion loss of 1.9(3) dB at 9.2 μm.
• Demonstrated the feasibility of using n-doped InSb for mid-IR Faraday isolators.

Conclusions:

• The fabricated n-doped InSb Faraday isolator exhibits excellent performance for mid-IR applications.
• The device's design is adaptable for a broad wavelength range (7.5–30 μm).
• Further enhancements, such as a two-stage isolator, could further improve performance.