Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Patrick Egan (Fed)

Patrick began at NIST in 2006 as an NRC-NIST postdoc.  At the time, his focus was on the development of an optical frequency comb metrology system for the calibration of vacuum-wavelength.  In 2008 he began to investigate highly precise measurements of the refractive index of air using a Fabry-Perot cavity-based refractometer.  The work culminated in one of the most accurate measurements of the refractive index of nitrogen and argon at 633 nm, and laid the groundwork for what developed into the 2012 Innovation in Measurement Science (IMS) project entitled "Reinventing pressure, temperature, and length".  Since 2012 he has been part of the team attempting to use highly accurate measurements of gas refractivity to realize the pascal.  As of 2017 the project is ongoing.

Since 2015 Patrick has been a staff member of the Dimensional Metrology Group, and leader of the SI Length and Traceability project.


D-to-A_eff converter

Patrick Egan, Eric S. Stanfield, John R. Stoup
Recent developments in diameter metrology at NIST have enabled the dimensional characterization of piston-cylinder assemblies (PCA) with unprecedented precision

Shrinks When It's Colder

Patrick Egan
Thermal expansion can be a leading cause of uncertainty in length metrology. A cell-based refractometer has been designed at NIST which targets 10^-6} relative


Image for 10,816,325

Deformometer for Determining Deformation of an Optical Cavity Optic

NIST Inventors
Zeeshan Ahmed , Kevin O Douglass , Stephen Eckel , Patrick Egan and Jay H. Hendricks
Patent description NIST has invented a pulse quantizer that uses arrays of one or more Josephson junctions to create a pulse voltage output that is immune to differential pulse timing shifts. When the output pulse patterns are used to encode a waveform, for example, the waveform will be free from
Created October 23, 2018, Updated December 8, 2022