The oldest and most proven technique for fabricating diffraction gratings is mechanical ruling, which has been used for mass market manufacturing since the early 1960’s. In this talk I will give the latest update on Inprentus’ use of contact‐mode lithography for fabricating aperiodic grating‐coupled waveguides for AR. I will show data demonstrating 20‐picometer pitch uniformity, low stray light levels, aperiodic modulation results, and successful replication in a high‐index (n=1.9) resin using commercially available nanoimprint lithography.
AR architectures based on TIR waveguides require surface diffraction gratings to couple light in and out. Traditionally, the spectral response of a grating is tuned by blazing, i.e., creating faceted grooves with precise angles. However, blazed facets are difficult to achieve using resist-based techniques such as e-beam lithography. In this talk I will describe a new approach to making blazed AR grating masters by mechanical ruling, in which grooves are created by deforming a metallic surface with a diamond stylus.
As resolving power targets have increased with each generation of beamlines commissioned in synchrotron radiation facilities worldwide, diffraction gratings are quickly becoming crucial optical components for meeting performance targets. However, the metrology of variable-line-spacing (VLS) gratings for high resolution beamlines is not widespread; in particular, no metrology facility at any US DOE facility is currently equipped to fully characterize such gratings. To begin to address this issue, the Optics Group at the Advanced Photon Source at Argonne, in collaboration with SOLEIL and with support from Brookhaven National Laboratory (BNL), has developed an alternative beam path addition to the Long Trace Profiler (LTP) at Argonne’s Advanced Photon Source. This significantly expands the functionality of the LTP not only to measure mirrors surface slope profile at normal incidence, but also to characterize the groove density of VLS diffraction gratings in the Littrow incidence up to 79°, which covers virtually all diffraction gratings used at synchrotrons in the first order. The LTP light source is a 20mW HeNe laser, which yields enough signal for diffraction measurements to be performed on low angle blazed gratings optimized for soft X-ray wavelengths. We will present the design of the beam path, technical requirements for the optomechanics, and our data analysis procedure. Finally, we discuss challenges still to be overcome and potential limitations with use of the LTP to perform metrology on diffraction gratings.
We introduce a method for using Fizeau interferometry to measure the intrinsic resolving power of a diffraction grating. This method is more accurate than traditional techniques based on a long-trace profiler (LTP), since it is sensitive to long-distance phase errors not revealed by a d-spacing map. We demonstrate 50,400 resolving power for a mechanically ruled XUV grating from Inprentus, Inc.
Conference Committee Involvement (3)
Advances in Metrology for X-Ray and EUV Optics IX
24 August 2020 | Online Only, California, United States
Advances in Metrology for X-Ray and EUV Optics VIII
11 August 2019 | San Diego, California, United States
Advances in Metrology for X-Ray and EUV Optics VII
6 August 2017 | San Diego, California, United States
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