Experimental Characterization of a Silicon Nitride Asymmetric Loop-Terminated Mach-Zehnder Interferometer with a...

Area of Science:

• Photonics and Materials Science
• Integrated Optics
• Nanophotonics

Background:

• Mach-Zehnder interferometers (MZIs) are widely used for sensing applications.
• Enhancing MZI sensitivity and stability is crucial for advanced lab-on-chip devices.
• Silicon nitride (SiN) offers excellent optical properties and CMOS compatibility for integrated photonics.

Purpose of the Study:

• To design, fabricate, and characterize an asymmetric loop-terminated Mach-Zehnder interferometer (a-LT-MZI) on a SiN platform.
• To enhance light-matter interaction and sensor performance using subwavelength grating (SWG) waveguides.
• To evaluate the sensor's sensitivity and stability for refractive index (RI) sensing.

Main Methods:

• Fabrication of a-LT-MZI devices on a silicon nitride platform.
• Integration of subwavelength grating (SWG) waveguides in the sensing arm.
• Experimental characterization of interference fringes and wavelength shifts in response to RI changes.
• Comparative analysis with existing MZI-based sensors.

Main Results:

• Fabricated a-LT-MZI devices demonstrated stable interference fringes and linear responses to RI variations.
• Standard a-LT-MZI structures achieved sensitivities of 288.75–301.25 nm/RIU.
• SWG-enhanced devices exhibited significantly higher sensitivities, ranging from 496–518 nm/RIU.
• The proposed sensor design showed competitive performance compared to previous MZI-based sensors.

Conclusions:

• The a-LT-MZI architecture on SiN, enhanced with SWG waveguides, provides a highly sensitive and stable platform for RI sensing.
• The device leverages SiN's scalability and CMOS compatibility for next-generation lab-on-chip photonic sensors.
• This technology holds significant potential for biochemical diagnostics, medical testing, and environmental monitoring.