Fabrication and evaluation of an etched infrared diffraction grating

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Infrared (IR) echelle gratings are crucial optical components.
• Traditional fabrication methods can be complex and costly.
• Silicon offers desirable material properties for grating fabrication.

Purpose of the Study:

• To evaluate the optical performance of IR echelle gratings fabricated on silicon wafers.
• To assess the diffraction efficiency and potential of etched silicon gratings.
• To explore methods for enhancing grating resolving power.

Main Methods:

• Anisotropic etching techniques were used to produce gratings on silicon wafers.
• Diffraction efficiency was measured for a 55° blaze angle, 25-µm groove spacing sample.
• Efficiency was calculated for triangular and trapezoidal groove profiles.

Main Results:

• Etched silicon gratings exhibit high diffraction efficiency, comparable to right-angle groove gratings for unpolarized light.
• The fabrication process demonstrates ease, excellent surface quality, and high reproducibility.
• Integrating gratings into prisms via internal reflection significantly boosts resolving power.

Conclusions:

• Anisotropic etching of silicon is a promising method for producing high-performance IR echelle gratings.
• The developed technique offers advantages in fabrication simplicity, surface quality, and repeatability.
• Etched silicon gratings, especially when integrated into prisms, present a pathway for compact, high-resolution spectroscopic instruments.