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Search Publications by: Joshua Hadler (Fed)

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Displaying 1 - 25 of 51

Radiation-Pressure Enabled Traceable Laser Sources at High CW Powers

January 4, 2019
Author(s)
Paul A. Williams, Alexandra B. Artusio-Glimpse, Joshua A. Hadler, Daniel King, Ivan Ryger, Tam Vo, John H. Lehman, Kyle A. Rogers
Radiation pressure has recently been shown to have practical application for multi-kilowatt CW laser power measurement. One key advantage lies in its ability to measure without absorbing the laser beam. This enables a new measurement paradigm where laser

Time-Resolved Absorptance and Melt Pool Dynamics during Intense Laser Irradiation of a Metal

October 25, 2018
Author(s)
Brian J. Simonds, Jeffrey W. Sowards, Joshua A. Hadler, Erik A. Pfeif, Boris Wilthan, Jack R. Tanner, Paul A. Williams, John H. Lehman
Laser welding is a complex, dynamic process by which focused, high-intensity laser light is used to join two metallic surfaces and is being increasing deployed in a variety of industrial applications. Determining the time-dependent absorptance of the laser

Femtosecond Laser Eyewear Protection: Measurements and Precautions for Amplified High Power Applications

September 24, 2018
Author(s)
Christopher J. Stromberg, Sarah Wirick, Maximilian Riedel-Topper, Brian Alberding, Joshua A. Hadler, Edwin J. Heilweil
Ultrafast lasers have become increasingly important as research tools in laboratories and commercial enterprises suggesting laser safety, personal protection and awareness becomes ever more important. Laser safety eyewear are typically rated by their

Dynamic and absolute measurements of laser coupling efficiency during laser spot welds

September 3, 2018
Author(s)
Brian J. Simonds, Jeffrey W. Sowards, Joshua A. Hadler, Erik A. Pfeif, Boris Wilthan, Jack R. Tanner, Chandler Harris, Paul A. Williams
Laser absorptance (coupling efficiency) changes rapidly during laser metal processing due to temperature and multiple phase changes. We find that there is limited literature data available, but this property is vital for accurate process simulations, as

Optical Measurements of Dynamic Absorptance during High-power Laser Spot Welding

May 7, 2018
Author(s)
Brian Simonds, Jeffrey W. Sowards, Joshua A. Hadler, Boris Wilthan, Erik A. Pfeif, Jack R. Tanner, Chandler Harris, Paul A. Williams, John Lehman
We present precision measurements of the time-dependent absorptance during a 10 ms fiber-laser spot weld on 316L stainless steel. From these, the precise time and energy at which a keyhole is formed can be determined.

Effectiveness of Laser Safety Eyewear under Real-World Conditions

March 18, 2018
Author(s)
Christopher J. Stromberg, Edwin J. Heilweil, Joshua A. Hadler
Ultrafast lasers have become increasingly important as research tools in chemistry, which means laser safety is becoming more important. Laser safety glasses represent the last line of defense to protect users from potentially life-altering eye injuries

Geometric contributions to chopper wheel optical attenuation uncertainty

December 9, 2017
Author(s)
Matthew T. Spidell, Joshua A. Hadler, Michelle S. Stephens, John H. Lehman, Paul A. Williams
Calibrated reflective optical choppers are used in NIST’s high power laser calibration services due to their advantages in performance and safety over wedges and semi-transparent materials for beam power reduction. While the design, operation, and

On-site multi-kilowatt laser power meter calibration using radiation pressure

December 1, 2017
Author(s)
Paul A. Williams, Joshua A. Hadler, Brian J. Simonds, John H. Lehman
We have demonstrated the calibration of a thermal power meter against a radiation-pressure power meter in the range of 20 kW in a manufacturing test environment. The results were compared to a traditional calorimeter-based laboratory calibration undertaken

Ultrafast Laser Eyewear Protection: Measurements and Precautions

September 25, 2017
Author(s)
Christopher J. Stromberg, Joshua A. Hadler, Brian Alberding, Edwin J. Heilweil
Ultrafast laser systems are becoming more widespread throughout the research and industrial communities yet eye protection for these high power, bright pulsed sources still require scrupulous characterization and testing before use. Femtosecond lasers

Dual-beam laser thermal processing of silicon photovoltaic materials

March 14, 2016
Author(s)
Brian J. Simonds, Anthony Teal, Tian Zhang, Joshua A. Hadler, Zibo Zhou, Sergey Varlamov, Ivan Perez-Wurfl
Laser processing for photovoltaics (PV) has traditionally been used for very small dimension features where focused beams are rastered to create lines for edge isolation, scribing, and selective emitter formation and for drilling holes for drilling in wrap

Portable high-accuracy non-absorbing laser power measurement at kilowatt levels by means of radiation pressure

February 16, 2016
Author(s)
Paul A. Williams, Joshua A. Hadler, Frank C. Maring, Robert Lee, Kyle A. Rogers, Brian J. Simonds, Matthew T. Spidell, Ari D. Feldman, John H. Lehman
We describe a unique optical power meter which measures the radiation pressure to accurately determine a laser’s optical power output. This approach traces its calibration of the optical Watt to the kilogram. Our power meter is designed for high-accuracy