Meta-optic commercialization and manufacturing readiness is an important topic as optics designers begin evaluating meta-surfaces into optics modules. Moxtek has established a volume production line for visible and NIR wavelength meta-optics with a manufacturing readiness level 8. This provides a unique environment to evaluate the uniformity and capabilities of meta-optic manufacturing techniques. With a statistically significant dataset, mild variations in design concept and lens characteristics can be easily highlighted. We will present baseline MTF and efficiency data related to a variety of metalens characteristics. The goal is to highlight unique meta-optic characteristics that impact performance in volume production. Moxtek has manufactured and characterized metalenses in a wide range of wavelengths, lens diameter, and focal lengths.
Moxtek has attained the required feature fidelity for visible wavelength metalenses through e-beam lithography based mastering for a Nanoimprint Lithography (NIL) and Nb2O5 etching based manufacturing process. An overcoat is also added to the metalenses, which boosts performance and protects against handling damage. Metalens and associated test structure metrology results including MTF, veiling glare, and efficiency will be presented for various designs spanning the visible wavelength range with NA’s varying from 0.02 to 0.71. Collectively, Moxtek has demonstrated volume manufacturing of metalenses for the visible regime, which was made possible by high precision NIL and Etch processes.
AR/VR headsets operating in visible wavelengths require extremely compact and lightweight optics to allow for all day wearable comfort and functionality. This means that visible metalenses would be ideal for this application. Visible metalenses have not been available for volume production until now.
With proven visible metalens production the adaptation into applications such as AR/VR are the next step. At Moxtek, we have an established baseline visible meta-optic process line that provides greater than 90% total efficiency on a lot to lot average.
Moxtek is uniquely positioned to support application development with design validation and production ready nanoimprint masters all processed on high volume tool sets.
Building visible wavelength metalenses presents significant challenges for nanofabrication due to the high aspect ratio features and tight tolerances required for good performance. The requisite phase profiles often impart dramatic changes in nanostructure fill fraction, which are challenging to pattern via optical lithography. One metasurface of interest is a spatially-varying array of nanopillars ranging in diameter from 70nm - 180nm, with gaps between pillars ranging from 180nm - 70nm. To manufacture this and other metastructured devices in volume, Nanoimprint Lithography (NIL) becomes a key enabling technology due to its demonstrated scalability and ability to reliably replicate nanostructures with extremely tight tolerances, even with variations in local spacing.
Another requirement for building metasurfaces for visible light applications, is the ability to pattern full wafers with good repeatability in high volume. Moxtek has therefore set up a 200 mm diameter manufacturing demonstration, where high aspect ratio nanopillars of varying diameter are etched from high refractive index material in order to make visible wavelength metalenses. In this work, metalenses designed for green light were fabricated with both a square grid arrangement and with a radially periodic arrangement. The metalenses were also given a protective coating and the focusing performance was characterized. The manufacturing process evaluation has three key components: 1) characterize the processing bias (from design dimensions to final nanostructure dimensions) at various stages; 2) monitor process stability and repeatability using metrology test devices distributed over the wafer; 3) characterize and verify functioning optical devices. Collectively, we have demonstrated volume manufacturing of metalenses for the visible regime, which was made possible by high precision NIL and Etch processes.
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