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Written by Trevor Haas on . Posted in Publication.

Precision trepanning with a fiber laser

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    An analysis is developed to establish the optimal parameters for precision trepanning using a 200 watt single mode fiber laser. Initial test results are also presented to document the mean values and standard deviations in the diameters of numerous fiber laser trepanned holes through a number of Hastelloy X material thicknesses. Analytical constraints are established for each of the following: (1) maintaining sufficient laser irradiance to assure efficient material removal without inducing plasma self-absorption, (2) selecting a laser pulse repetition frequency high enough to maintain a molten metal interface and hence increased absorption at the laser wavelength, while not exceeding the kinematic velocity limit of current trepanning heads, (3) establishing an optimum trepan “overlap ratio” to minimize perimeter irregularities consistent with high speed operation, (4) selecting a focused trepan spot diameter that achieves the optimal irradiance consistent with very modest laser power, size, and cost, (5) choosing a programmable continuous motion trepanning head and a spiral trepanning path to improve precision while minimizing both cycle time and perimeter artifacts, and (6) satisfying adiabatic energy requirements in the shortest practical time. This paper also presents important new test data indicating a standard deviation in trepanned hole diameter of only 2.37 µm when generating 36 test holes… with a system that was not yet fully optimized!
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  • Authors : Paul Jacobs
  • Abstract:

    An analysis is developed to establish the optimal parameters for precision trepanning using a 200 watt single mode fiber laser. Initial test results are also presented to document the mean values and standard deviations in the diameters of numerous fiber laser trepanned holes through a number of Hastelloy X material thicknesses. Analytical constraints are established for each of the following: (1) maintaining sufficient laser irradiance to assure efficient material removal without inducing plasma self-absorption, (2) selecting a laser pulse repetition frequency high enough to maintain a molten metal interface and hence increased absorption at the laser wavelength, while not exceeding the kinematic velocity limit of current trepanning heads, (3) establishing an optimum trepan “overlap ratio” to minimize perimeter irregularities consistent with high speed operation, (4) selecting a focused trepan spot diameter that achieves the optimal irradiance consistent with very modest laser power, size, and cost, (5) choosing a programmable continuous motion trepanning head and a spiral trepanning path to improve precision while minimizing both cycle time and perimeter artifacts, and (6) satisfying adiabatic energy requirements in the shortest practical time. This paper also presents important new test data indicating a standard deviation in trepanned hole diameter of only 2.37 µm when generating 36 test holes… with a system that was not yet fully optimized!
  • Links:

    https://doi.org/10.2351/1.5061304
  • Last Updated Date: 2008-10-01
  • Hits: 23

Written by Trevor Haas on . Posted in Publication.

Evolution of a real-time laser M2 measurement system

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    In 2011, the authors introduced a multispot, real-time  measurement technology that fulfilled the missing ability of the existing  measurement systems to dynamically measure thermal lensing in high-power fiber laser systems. Over the next years, the technology has evolved making the technology of  measurement compact, easier to use, and more accurate. The traditional  measurement technology, being a time-averaged measurement, is incapable of seeing transient changes in a laser system’s , let alone thermal lensing. The multispot approach provides an  measurement in a single laser pulse or at the frame rate of the pixelated sensor being used. This paper covers the evolution of the multispot  measurement technology and how it has matured into a state-of-the-art  measurement tool.
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  • Authors : Michael Scaggs, Gilbert Haas
  • Abstract:

    In 2011, the authors introduced a multispot, real-time  measurement technology that fulfilled the missing ability of the existing  measurement systems to dynamically measure thermal lensing in high-power fiber laser systems. Over the next years, the technology has evolved making the technology of  measurement compact, easier to use, and more accurate. The traditional  measurement technology, being a time-averaged measurement, is incapable of seeing transient changes in a laser system’s , let alone thermal lensing. The multispot approach provides an  measurement in a single laser pulse or at the frame rate of the pixelated sensor being used. This paper covers the evolution of the multispot  measurement technology and how it has matured into a state-of-the-art  measurement tool.
  • Links:

    https://doi.org/10.1117/1.OE.64.1.010701
  • Last Updated Date: 2025-01-29
  • Hits: 259

Written by Trevor Haas on . Posted in Publication.

Low loss field-mapped laser beam homogenizer

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    A new type of laser beam homogenizer has been developed which “field-maps” an illumination by using spherical, cylindrical, axicon or prism optical segments, or in some applications combination of these various elements, and placing the optical segments in a configuration whereby light passing through each optical segment directs the light to overlap at a homogenized plane with the desired shape (rectangle, square, rectangular or circular ring illumination). The geometry of the homogenized field is limited only by the fabrication techniques used in segmenting and how the segments are physically arranged. This optical concept could be called a Fresnel Homogenizer as it functions like a Fresnel lens. Fabricated in its basic form from spherical or cylindrical lenses, the lenses can be either negative or positive, depending upon the type of illumination, size and numerical aperture required. Typical fly’s eye homogenizers require 5 optical elements this new homogenizer is comprised of a single element; thereby significantly reducing the losses in the system due to diffraction and reflectance.
  • Article Picture:
  • Authors : Michael Scaggs, Gilbert Haas
  • Abstract:

    A new type of laser beam homogenizer has been developed which “field-maps” an illumination by using spherical, cylindrical, axicon or prism optical segments, or in some applications combination of these various elements, and placing the optical segments in a configuration whereby light passing through each optical segment directs the light to overlap at a homogenized plane with the desired shape (rectangle, square, rectangular or circular ring illumination). The geometry of the homogenized field is limited only by the fabrication techniques used in segmenting and how the segments are physically arranged. This optical concept could be called a Fresnel Homogenizer as it functions like a Fresnel lens. Fabricated in its basic form from spherical or cylindrical lenses, the lenses can be either negative or positive, depending upon the type of illumination, size and numerical aperture required. Typical fly’s eye homogenizers require 5 optical elements this new homogenizer is comprised of a single element; thereby significantly reducing the losses in the system due to diffraction and reflectance.
  • Links:

    https://doi.org/10.2351/1.5061244
  • Last Updated Date: 2008-10-23
  • Hits: 42

Written by Trevor Haas on . Posted in Publication.

Collimated laser homogenizer

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    A new laser beam homogenizer has been developed which converts a highly spatial coherent, Gaussian laser beam into a collimated, square homogenized field. The optical device converts a laser’s Gaussian input beam through multiplexing and recombination without optical interference and yet is collimated over > 5 meters. Laser beam property variations do not adversely affect the performance of the homogenizer in contrast to phase shifting homogenizers and can be utilized from the laser’s objective lens’ entrance pupil to its focus while maintaining the relative degree of homogenization. The degree of homogenization is limited only by diffraction effects and the input diameter of the laser beam.
  • Article Picture:
  • Authors : Michael Scaggs, Gilbert Haas
  • Abstract:

    A new laser beam homogenizer has been developed which converts a highly spatial coherent, Gaussian laser beam into a collimated, square homogenized field. The optical device converts a laser’s Gaussian input beam through multiplexing and recombination without optical interference and yet is collimated over > 5 meters. Laser beam property variations do not adversely affect the performance of the homogenizer in contrast to phase shifting homogenizers and can be utilized from the laser’s objective lens’ entrance pupil to its focus while maintaining the relative degree of homogenization. The degree of homogenization is limited only by diffraction effects and the input diameter of the laser beam.
  • Links:

    https://doi.org/10.2351/1.5061546

     
  • Last Updated Date: 2009-11-02
  • Hits: 18

Written by Trevor Haas on . Posted in Publication.

Thermal lensing compensation objective for high power lasers

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    Athermalization of focusing objectives is a common technique for optimizing imaging systems in infrared where thermal effects are a major concern. The athermalization is generally done within the spectrum of interest and not generally applied to a single wavelength. By applying athermalization techniques to a laser system, a significant reduction in thermal lensing of the laser system can be realized. We describe a passive method minimizing thermal lensing of high power lasers.
  • Article Picture:
  • Authors : Michael Scaggs, Gilbert Haas
  • Abstract:

    Athermalization of focusing objectives is a common technique for optimizing imaging systems in infrared where thermal effects are a major concern. The athermalization is generally done within the spectrum of interest and not generally applied to a single wavelength. By applying athermalization techniques to a laser system, a significant reduction in thermal lensing of the laser system can be realized. We describe a passive method minimizing thermal lensing of high power lasers.
  • Links:

    https://doi.org/10.2351/1.5062011

     
  • Last Updated Date: 2010-09-26
  • Hits: 107

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