Laser propagation refers to how a laser beam travels through space or a medium. The unique characteristics of laser light, such as its coherence, monochromaticity, and collimation, make it behave differently from ordinary light sources. Understanding the principles of laser propagation is crucial in fields like optics, communication, medical technologies, and scientific research.
Lasers produce a Gaussian beam, where the intensity follows a Gaussian distribution across the cross-section of the beam. This beam has a high intensity at the center and falls off towards the edges. The figures below show the distribution of input profile with various laser modes.
In Zemax, ZBF file refers to a Zemax Beam File, which is a binary file format used to describe the spatial distribution of a laser beam in terms of its amplitude and phase. These files are used to model and analyze the propagation of laser beams through optical systems, including lenses, mirrors, and other optical components.
In the laser propagation process below, light profile at key positions such as laser source, beam waist, collimation/focusing lens, apertures/obstacles, and focal point, are usually be exacted from ZBF file. These key positions define the crucial points in a laser's propagation path where major changes or effects occur, influencing the laser’s performance and the outcome of its application.
The ZBF file contains detailed information about the electric field, including the amplitude and phase distribution across the beam's cross-section. This allows for accurate modeling of how the beam evolves as it passes through an optical system. ZBF files can also represent complex, multi-mode laser beams, including higher-order spatial modes and partially coherent beams.
The ZBF files must be restored in the path Documents\Zemax\POP\BEAMFILES. They can be launched from “Beam File Viewer”.
From a selected ZBF, the beam profile at a certain position of a propagation path can be seen, as below. The distribution of laser beam illumination varied as the scale of the defined image that presents the ZBF. Users can expect varied image size ranges defined in different location as the light propagates.
From Physical Optics Propagation, phase distribution at Image plane of the system can be also extracted apart from illumination above. Distribution can be displayed as Cross X or Y, as below,
or colorful distribution as below:
ZBF file can be generated by either Zemax or Lumerical. When importing ZBF from Lumerical, the file should be copied into Zemax folder ZEMAX\POP\BEAMFILES. Then the ZBF can be found and opened from Zemax at the tab of Beam File Viewer.