Multilevel-grating array generators: fabrication error analysis and experiments

Area of Science:

• Optics and Photonics
• Microfabrication Technologies
• Diffractive Optics

Background:

• Multilevel-grating array illuminators are crucial optical components.
• Understanding error sources like mask alignment and etch depth is vital for performance.
• Array uniformity error (U) and diffraction efficiency (eta) are key performance metrics.

Purpose of the Study:

• To numerically evaluate the impact of mask alignment and etch-depth errors on array uniformity error (U) and diffraction efficiency (eta).
• To demonstrate the fabrication and performance of 16-level fan-out elements with specified array sizes.
• To validate the error analysis predictions against experimental results.

Main Methods:

• Numerical evaluation of error effects on grating illuminator performance.
• Fabrication of 16-level fan-out elements using electron-beam-written binary masks.
• Utilizing optical alignment, contact copying, and reactive ion etching for fabrication.
• Experimental characterization of fabricated components to measure U and eta.

Main Results:

• Quantified the effects of mask alignment and etch-depth errors on U and eta.
• Demonstrated 16-level fan-out elements with array sizes up to 32 x 16.
• Achieved array uniformity error (U) between 5%-10% and diffraction efficiency (eta) between 83%-92% in fabricated elements.
• Observed good agreement between numerical predictions and experimental performance.

Conclusions:

• Mask alignment and etch-depth errors significantly influence the performance of multilevel-grating array illuminators.
• The employed fabrication process is capable of producing high-performance fan-out elements.
• The developed error analysis provides reliable predictions for fabricated optical components.