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Nano-Structured Optics and Optical Surface Metrology

Summary:

The project focuses on significant metrology challenges that impede the advancement of high-performance optical and photonic systems. We develop, fabricate, and characterize innovative nano-structured optics with diffractive and sub-wavelength features for advanced imaging applications and surface metrology. The project also develops new interferometric methods for shape measurements of ultra-precise optical surfaces using test wavefronts created with advanced holograms.

Technical Goals:

  • Disseminate the SI standard of length for the form metrology of precision surfaces through the development of innovative interferometric metrology methods and calibrations.
  • Enable metrology for aspheric and free-form surfaces that is traceable to the SI through test wavefronts with known uncertainty that are generated by holographic elements.
  • Research and develop innovative optics with nano-structured diffractive and sub-wavelength features for metrology and imaging applications.

Description:

The project addresses the metrology needs of U.S. Industry and Science for the manufacture and application of ultra-precision surfaces and innovative optical elements. Ultra-precision optical elements are essential to product innovations in many high-tech areas, such as scientific applications of optics ranging from microscopy to astronomy, semiconductor manufacturing, medical technology, defense, homeland security, consumer products, communication and information technology. Advanced optical elements incorporate features that yield vastly improved performance but pose significant new measurement challenges. Examples are complex surfaces that are neither flat nor spherical, diffractive optics with micro- and nano-scale surface structures, extreme accuracies, special materials and coatings, and adaptive technologies. The development and manufacture of these advanced features depend strongly on advances in traceable metrology for optical figure and wavefront. In many high-impact applications, the required form accuracies are at the (sub-) nanometer level. No general, widely-recognized, validated way exists to characterize complex and nano-structured optical surfaces, and the application range and uncertainty of existing methods are not well understood.

Major Accomplishments:

  • Created and delivered to NASA a prototype diffractive lens of a type that might be used on the Mars Organic Molecule Analyzer (MOMA), an instrument on the rover of the forthcoming ExoMars mission (2017-2022). The lens creates a laser beam with a top-hat intensity profile for uniform heating of rock and soil samples. Demonstrated to NASA that we can make diffractive optics that are not commercially available. Became the foundation for continued collaboration. (Division Highlight)
  • Developed photon sieves for applications in surface metrology. Originally invented for x-ray optics, photon sieves eliminate higher diffraction orders by dispersing the light into a wide angular range. The result is reduced measurement uncertainty for complex surface form measurements, because high diffraction orders often cause coherent stray light.
  • Demonstrated a new method for precise measurements of the radii of spherical surfaces with large radius. The new method has caught the attention of one of the leading optics companies in the US (Optimax SI, NY). We are collaborating with Optimax the new method for radius test plate certification in an industrial setting.
  • Improved the uncertainty for measurements of the sphericity of ultra-precise reference spheres by almost an order of magnitude with a new calibration method based on lateral shearing measurements. (NIST Bronze Award)
Nano-Structured Optics Laboratory
Figure 1. Nano-Structured Optics Laboratory

Lead Organizational Unit:

pml

Customers/Contributors/Collaborators:

  • NASA/Goddard
  • Advanced Photon Source
  • University of Texas at Austin
  • University of Rochester
  • Zygo Corp.
  • Optimax, Inc.
  • PTB
  • KRISS
  • CSIRO, Australia
  • Tektronix Calibration

Facilities/Tools Used:

XCALIBIR (eXtremely accurate CALibration InterferometeR) Laboratory

  • World-class multi-configuration laser interferometer for surface form measurement of ultra-precise surfaces. Combines a phase-shifting interferometer with a set of displacement-measuring laser interferometers.
  • In clean room with temperature control.
  • nm-level measurement uncertainty
  • Designed for use with holograms for measuring aspheric and free-form surfaces

Nano-Structured Optics Laboratory

  • A unique facility built around a Lumarray ZP150B parallel photo-lithography system for the fabrication of optical holograms, diffractive optics, and effective optical media.
  • Modified at NIST for the fabrication of nano-structured optics on large and dimensionally stable optical glass substrates.
  • Minimum line width down to 350 nm (ultimately 200 nm) enables sub-wavelength features.
  • Overlay capable for high-efficiency diffractive optics (projected early 2015).
  • Temperature controlled cleanroom. 

XCALIBIR Interferometer
Figure 2. XCALIBIR Interferometer.

Staff:

Ulf Griesmann, Project Leader
Johannes A. Soons

Associates:

Quandou Wang

Contact

Physical Measurement Laboratory (PML)
Semiconductor & Dimensional Metrology Division (683)

General Information:
301-975-5609 Telephone
301-869-0822 Facsimile

100 Bureau Drive, M/S 8220
Gaithersburg, Maryland 20899-8220