Effect of large deflection angle on the laser intensity profile produced by AOD scanners in high precision manufacturing

Abstract

Laser beam scanners have found wide applications in a variety of laser-assisted advanced microprocessing technologies, such as printing, patterning and doping. Traditional galvo-scanners affect the accuracy of beam positioning and repeatability in high precision manufacturing due to mechanical motion of the mirrors and backlash errors. An Acousto-optic Deflector (AOD), which is made of a transparent photoelastic medium bonded to a piezoelectric transducer, is a promising device to overcome these limitations. AODs are commonly used in laser direct writing systems to provide flexible and high-speed beam scanning with high precision and accuracy.We have developed an analytic model based on Bessel functions, which will be referred to as Bessel model, to calculate the strain tensor, stress tensor and stress-induced birefringence, and the change in the refraction index of the crystal. This refraction index variation produces the volume phase grating and provides a mechanism for diffraction, and consequently, deflection of the laser beam as it propagates through the AOD crystal. Various laser parameters, such as the diffraction efficiency and the laser intensity of the diffraction pattern at different deflection angles are studied in this paper.Laser beam scanners have found wide applications in a variety of laser-assisted advanced microprocessing technologies, such as printing, patterning and doping. Traditional galvo-scanners affect the accuracy of beam positioning and repeatability in high precision manufacturing due to mechanical motion of the mirrors and backlash errors. An Acousto-optic Deflector (AOD), which is made of a transparent photoelastic medium bonded to a piezoelectric transducer, is a promising device to overcome these limitations. AODs are commonly used in laser direct writing systems to provide flexible and high-speed beam scanning with high precision and accuracy.We have developed an analytic model based on Bessel functions, which will be referred to as Bessel model, to calculate the strain tensor, stress tensor and stress-induced birefringence, and the change in the refraction index of the crystal. This refraction index variation produces the volume phase grating and provides a mechanism for diffraction, and consequently, de...