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Search Publications by: Joshua Hadler (Fed)

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Displaying 1 - 25 of 25

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

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

Progress toward Radiation-Pressure-Based Measurement of High-Power Laser Emission - Under Policy Review

October 6, 2014
Author(s)
Paul A. Williams, Joshua A. Hadler, Daniel King, Robert Lee, Frank C. Maring, Gordon A. Shaw, Nathan A. Tomlin, John H. Lehman, Marla L. Dowell
We present an overview of our efforts toward using optical radiation pressure as a means to measure optical power from high-power lasers. Early results with measurements ranging from tens of watts to 92 kW prove the concept, but validation uncertainties

Use of radiation pressure for measurement of high-power laser emission

October 15, 2013
Author(s)
Paul A. Williams, Joshua A. Hadler, Robert Lee, Frank Maring, John H. Lehman
We demonstrate a paradigm in absolute laser radiometry where a laser beam's power can be measured from its radiation pressure. Using an off-the-shelf high-accuracy mass scale and a 500 W Yb-doped fiber laser and a 92 kW CO2 laser, we show preliminary

Random testing reveals excessive power in commercial laser pointers

May 1, 2013
Author(s)
Joshua A. Hadler, Edna L. Tobares, Marla L. Dowell
In random testing of 122 commercial laser pointers, we observed that 89.7 % of green pointers and 44.4 % of red pointers were not in compliance with the Code of Federal Regulations, producing laser power in excess of the Accessible Emission Limit at one or

Accurate, inexpensive testing of handheld lasers for safe use and operation

March 7, 2013
Author(s)
Marla L. Dowell, Joshua A. Hadler
An accurate, inexpensive test bed for measurements of optical power emitted from handheld lasers is described. Our test bed consists of a thermopile detector, bandpass optical filters, an adjustable iris, and self-centering holders for mounting of the

Uncertainty calculation for spectral-responsivity measurements

September 1, 2009
Author(s)
John H. Lehman, Chih-Ming Wang, Marla L. Dowell, Joshua A. Hadler
This paper discusses a procedure for measuring the absolute spectral responsivity of optical-fiber power meters and computation of the calibration uncertainty. The procedure reconciles measurement results associated with a monochromator-based measurement

Reflective optical chopper used in NIST high-power laser measurements

November 1, 2008
Author(s)
Xiaoyu X. Li, Thomas Scott, Christopher L. Cromer, Joshua A. Hadler
For the past ten years, NIST has used high-reflectivity, optical choppers as beamsplitters and attenuators when calibrating the absolute responsivity and response linearity of detectors used with high-power CW lasers. The chopper-based technique has

High power laser calibrations at NIST

September 1, 2008
Author(s)
Xiaoyu X. Li, Joshua A. Hadler, Christopher L. Cromer, John H. Lehman, Marla L. Dowell
This document describes the calibration service for the responsivity of laser power meters and detectors used with continuous wave high power lasers at laser wavelengths of 1.06 and 10.6 micrometers. An overview of the calibration procedures, measurement

NIST optical fiber power measurements: intramural and international comparisons

October 1, 2007
Author(s)
Igor Vayshenker, John H. Lehman, David J. Livigni, Joshua A. Hadler
We discuss the results of intramural comparisons of NIST laser and optical fiber power meter (OFPM) measurements, and the results of OFPM comparisons between NIST and three National Measurement Institutes (NMIs). We also describe transfer standards

NIST Measurement Services: cw Laser Power and Energy Calibrations at NIST

July 1, 2007
Author(s)
Joshua A. Hadler, Christopher L. Cromer, John H. Lehman
This document describes a calibration service for absolute laser power and energy measurements of laser power meters and detectors used with continuous wave lasers at laser wavelengths between 325 and 1550 nm. In addition to a summary of the calibration

Broad Spectrum Capabilities for CW Laser Power Measurements at NIST

May 1, 2005
Author(s)
Joshua A. Hadler
Recent improvements for mid-level laser power measurements (1 μW to 1 W) have increased the range of calibrations available to customers of our CW laser power measurements. In this presentation we present an overview of our capabilities as well as recent

Intramural comparison of NIST laser and optical fiber power calibrations

March 1, 2004
Author(s)
John H. Lehman, Igor Vayshenker, David J. Livigni, Joshua A. Hadler
The responsivity of two optical detectors was determined by the method of direct substitution in four different NIST measurement facilities. The measurements were intended to demonstrate the determination of absolute responsivity as provided by NIST

New and Future Capabilities for CW Laser Power Measurements at NIST

January 1, 2003
Author(s)
Joshua A. Hadler
The CW Laser Radiometry project in the Optoelectronics Division at NIST is concerned with measuring steady-state laser, detector, and component properties such as laser power and energy, laser beam profile, detector spatial and angular responsivity