Polarization insensitive silicon immersion grating based on total internal reflection

Area of Science:

• Photonics and Optical Engineering
• Materials Science for Optics

Background:

• Polarization-dependent loss (PDL) and diffraction efficiency are critical parameters for optical components.
• Immersion gratings (IGs) are widely used in spectroscopy and other optical systems.
• Achieving low PDL and high diffraction efficiency simultaneously in IGs presents a significant engineering challenge.

Purpose of the Study:

• To design and analyze a novel immersion grating (IG) with minimized polarization-dependent loss (PDL) and maximized diffraction efficiency.
• To investigate the impact of dielectric film properties on IG performance.
• To optimize the IG design for high dispersion power.

Main Methods:

• Fabrication of an IG using a silicon (Si) prism and a Si grating coated with a dielectric film.
• Analysis of the effect of the dielectric film's refractive index on diffraction efficiency for both TM and TE polarizations.
• Simulation of IG performance, focusing on PDL and diffraction efficiency.
• Experimental validation using a prototype IG.

Main Results:

• Simulated optimized IG achieved a PDL of 0.2 dB and diffraction efficiency of -0.4 dB.
• The developed dielectric film allowed for tuning TM polarization diffraction efficiency without affecting TE polarization efficiency.
• A prototype IG demonstrated a low PDL of 0.6 dB and maintained a high diffraction efficiency of -0.4 dB.
• The prototype exhibited high dispersion power.

Conclusions:

• The proposed dielectric-coated silicon immersion grating effectively achieves low PDL and high diffraction efficiency.
• The design approach allows for independent control of diffraction efficiency for different polarizations.
• This technology holds promise for advanced optical systems demanding high performance and precision.