CODE V Feature Close-Up: Beam Synthesis Propagation

Powerful, Efficient Diffraction Analysis

For whatever type of optical system you’re designing – laser, microlens array, free-space photonic device, CCD, or astronomical application – CODE V Beam Synthesis Propagation (BSP) will perform beam propagation analysis more accurately and efficiently than any other commercially available tool.

BSP’s beamlet-based wave propagation algorithm was designed to deliver extremely accurate modeling of diffracted wavefronts propagating through almost any optical system.  BSP works well with systems in which the more common FFT-based diffraction calculations are less accurate or fail completely. It can propagate scalar or vector fields though any object that can be ray traced, such as GRIN materials, birefringent materials, and non-sequential surface ranges.

BSP supports full-vector field propagation. This decibel-scale plot shows the Z-component of the focal plane intensity of a Ritchey-Chrétien telescope for linearly polarized light.

BSP supports full-vector field propagation. This decibel-scale plot shows the Z-component of the focal plane intensity of a Ritchey-Chrétien telescope for linearly polarized light.

Optical Research Associates originally developed BSP for NASA to solve the stringent accuracy challenges of the Terrestrial Planet Finder mission. BSP met the mission’s requirements with its ability to accurately model irradiance that distinguished a very dim, Earth-like planet outside our solar system from the surrounding stars.  Also see the BSP data sheet below.

BSP provides:

Advanced, Beamlet-Based Algorithm

BSP uses a beamlet-based diffraction propagation algorithm that models the wave nature of light through the entire optical system. The input beam can be modeled as an apodized spherical or plane wave, or a Gaussian beam. BSP includes diffraction effects caused by factors such as aperture clipping, ray-wave disconnects (i.e., slow beams), intermediate image structure, and lens aberrations. It delivers greater accuracy than using exit-pupil diffraction computations, or beam propagation based on FFT or angular spectrum methods.

llustration of a beamlet, which consists of a base ray and a field that is localized about the base ray.

Illustration of a beamlet, which consists of a base ray and a field that is localized about the base ray.

BSP approximates the optical field as a collection of individual beamlets. A beamlet consists of a base ray and a field that is initially localized about the base ray. The base ray defines the reference location and direction for each beamlet.

Based on the fact that the wave equation is linear, these beamlets are propagated independently and can be summed anywhere downstream to get the propagated optical field. This method can propagate beams through anything that can be ray traced.

BSP’s beamlet-based algorithm is unique in its ability to propagate fewer beamlets than other beamlet-based approaches, while achieving a more accurate result.

Far-field comparison for an ideal system with a circular clipping aperture

Far-field comparison for an ideal system with a circular clipping aperture. This graph shows that BSP’s approach with 2,581 beamlets achieved better accuracy out to 25 rings than did a conventional approach with 4,927 beamlets.

Unprecedented Ease of Use for Beam Propagation

One of the most significant benefits of BSP is its Pre-Analysis feature, which allows non-expert beam propagation users to get expert results. Determining appropriate inputs for any beam propagation analysis can be challenging. Pre-Analysis feature solves this problem by recommending analysis inputs that are customized for your lens system. This helps ensure accurate results and saves countless hours in setup.

Pre-Analysis first performs a fast scan of your system using a subset of test beamlets. Based on the results, it then provides recommendations for a variety of settings, including input field sampling, output grid location, resampling surfaces, and clip checking surfaces. Pre-Analysis will also estimate an execution run time for your beam propagation analysis based on these recommended settings.

BSP’s Pre-Analysis feature recommends analysis parameters that are customized for your lens system.

BSP’s Pre-Analysis feature recommends analysis parameters that are customized for your lens system.

Flexibility to Define Detailed Beam Parameters Anywhere in the System

While Pre-Analysis makes BSP easy to use with minimal input, advanced users have the flexibility to control virtually every aspect of the propagation process, thresholds, and parameters, including Pre-Analysis recommendations. Controls are provided for:

  • Polychromatic analysis
  • Transmission variation checking
  • Clip checking fidelity
  • Computational accuracy

You also have the option to run BSP from the command line or the graphical user interface.

BSP provides advanced users with complete control over any propagation parameter,

BSP provides advanced users with complete control over any propagation parameter, including Pre-Analysis recommendations.

A Variety of Output Types for Validation and Visualization of Results

BSP provides textual and graphical output that allows you to easily visualize and understand your results. The output can represent a variety of quantities associated with the field at different surfaces, including amplitude, phase, intensity, and irradiance. From beamlet footprint plots to cross-sectional slice plots and Gaussian beam tables, you have numerous options for analyzing your data.

A BSP beamlet footprint diagnostic graphic

A BSP beamlet footprint diagnostic graphic provides the designer with a simple,
visual way to assess the size and orientation of BSP beamlets on any surface in the optical system.

Applicability to a Wide Range of Systems

Systems with astigmatic beams, polarized input optical fields, low f-numbers (e.g., microlithography lenses), or non-contiguous pupils are accurately analyzed with BSP. The feature is also useful for near-field diffraction analysis and for optical systems where the amplitude or phase is modified near the focus, such as with a grating, phase plate, or spatial filter.

BSP supports multiple wavelengths and polarization, so systems with dispersive materials, metallic surfaces, and multilayer coatings, as well as beamsplitters and polarizers, are accurately analyzed.

BSP accurately models polarization effects

BSP accurately models polarization effects,
as shown for this system containing crossed linear polarizers.

Full Integration with CODE V

BSP is fully integrated with CODE V, providing the most comprehensive optical design and analysis environment available. For example, complex field output from BSP can be used to calculate fiber coupling efficiency, including polarization-dependent loss.

Modeling Effects of Mid-Spatial-Frequency Errors

CODE V supports modeling real-world effects of mid-spatial-frequency surface errors on an optical surface. Such errors are typically encountered on surfaces fabricated using diamond turning or high-end polishing methods.

You can describe component surface errors by specifying the parameters of a power spectral density (PSD), and then use BSP to predict the diffracted image degradation due to the mid-spatial-frequency surface errors, as shown in the following BSP color plots.

Point spread function (PSF)
PSF mid spatial frequency error
PSF showing average degradation

Why compromise with another beam propagation tool when you can get the right answers more easily with BSP? Contact our sales team to request a product demonstration or trial license.

More information

BSP Data Sheet
Obtain accurate analysis of diffraction-related characteristics.