Ray Optics Module

Ray Optics Module

Software for Ray Tracing Simulations in Optically Large Systems

This tutorial model shows how to trace rays of unpolarized light through a Newtonian telescope system. The incoming light is reflected off a parabolic mirror onto a flat secondary mirror, which reflects the light into the focal plane. This type of telescope was first invented by Newton in 1668 and is still made today due to its low cost of assembly.

Image made using the COMSOL Multiphysics® software and is provided courtesy of COMSOL.

Ray Optics Module

Effective and Versatile Calculation of Ray Trajectories

The Ray Optics Module can be used to model electromagnetic wave propagation in systems in which the wavelength is much smaller than the smallest geometric detail in the model. The electromagnetic waves are treated as rays that can propagate through homogeneous or graded media. Because it is not necessary to resolve the wavelength with a finite element mesh, ray trajectories can be computed over long distances at a low computational cost. Rays can also undergo reflection and refraction at boundaries between different media.

Easy Set-up of Ray Optics Models

The Ray Optics Module contains a variety of boundary conditions, including combinations of specular and diffuse reflection. Rays can be released from within domains, from boundaries, or at a uniform grid of points. Specialized release features are also available for modeling solar radiation and for releasing reflected or refracted rays from an illuminated surface. Dedicated postprocessing tools offer you many ways to analyze ray trajectories, evaluate expressions over many rays, and even visualize interference patterns.

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Product Features

  • Absorbing media
  • Accumulated variables on domains and boundaries
  • Circular wave retarders
  • Corrections for strongly absorbing media
  • Deposited ray power on domains or boundaries
  • Dielectric films
  • Diffraction gratings
  • Diffuse scattering
  • Frequency distributions
  • Ideal depolarizers
  • Intensity computation in homogeneous media
  • Linear polarizers
  • Linear wave retarders
  • Mueller matrices
  • Non-sequential ray tracing
  • Optical path length variable
  • Option to store ray status data
  • Phase calculation
  • Phase portraits
  • Poincaré maps (spot diagrams)
  • Polarized, unpolarized, and partially coherent radiation
  • Principal wavefront radii of curvature calculation
  • Ray tracing in graded or homogeneous media
  • Ray Tracing study step based on optical path lengths
  • Ray Trajectories and Ray plots
  • Reflection and refraction at material discontinuities
  • Release rays from domains, boundaries, or a grid of points
  • Specular reflection
  • Stokes parameter calculation

Application Areas

  • Building physics and science
  • Cameras
  • Coatings
  • Imaging
  • Interferometers
  • Lasers
  • Lens systems
  • Optical components
  • Monochromators
  • Ray heating
  • Solar energy harvesting
  • Spectrometers


A modern high-power industrial fiber laser system can deliver up to 3kW of single-mode laser radiation on to surfaces to be cut, drilled, welded or marked. Even using highly transmissive materials, the optical component used to focus the laser beam onto target surfaces can be affected by the large amount of power carried by the light.

As the laser beam passes through the optical components, thermal expansion as well as variation of the refractive index of the optical materials can change the system’s focus.

This model uses the Structural Mechanics Module as well as the Ray Optics Module to compute the effect of thermal lensing on a high-power fiber laser system.

Reference: O. Maerten et al., The Characterization of Focusing Systems for High-Power Lasers with High Beam Quality, Laser + Photonics, 2009

» See model.

A paraboloidal dish can concentrate solar energy onto a target (receiver), resulting in very high local heat fluxes. This can be used to generate steam, which can be used to power a generator, or hydrogen, which can be used directly as a fuel source. In this model, the heat flux arriving on the receiver as a function of radial position is computed and compared with published values. Corrections due to the finite size of the sun, limb darkening, and surface roughness on the surface of the dish are considered.

» See model.

This model uses the Wave Optics Module and the Ray Optics module to model the propagation of rays through a diffraction grating at different angles of incidence. It uses the S-parameters computed by the Electromagnetic Waves, Frequency Domain interface on a unit cell of the grating to specify the reflectivity and transmissivity of each diffraction order in the Geometrical Optics interface, allowing ray propagation through the grating to be modeled over length scales much larger than the width of the unit cell.

» See model.

This model couples the Heat Transfer in Solids, Solid Mechanics and Geometrical Optics interfaces to compute the effect of thermal expansion of optical components on the interference pattern displayed by a Michelson interferometer.

» See model.

A Czerny-Turner monochromator spatially separates polychromatic light into a series of monochromatic rays. This model simulates a crossed Czerny-Turner configuration that consists of a spherical collimating mirror, a planar diffraction grating, a spherical imaging mirror, and an array charge coupled device (CCD) detector. The model uses the Geometrical Optics interface to compute the positions of incident rays on the detector plane, from which the device’s resolution can be derived.

» See model.

A distributed Bragg reflector (DBR) is a periodic structure formed from alternating dielectric layers that can be used to achieve nearly total reflection within a range of frequencies. The main advantage of DBRs over ordinary metallic mirrors is that DBRs can be engineered to have custom reflectances at selected wavelengths.

This application allows the performance of two different kinds of DBR filters to be simulated and characterized: Band-stop filters and Notch filters.

A band-stop filter prevents wavelengths within the range of the stop-band from transmitting. This is useful for filtering out unwanted wavelength regions from a spectrum. Band-stop filters are commonly included in many kinds of optical measurement setups, where they are used to prevent stray laser light from entering the sensitive detector equipment.

A notch filter allows a narrow range of wavelengths to pass while reflecting all other wavelengths. This is useful for selecting emission from a spectrally narrow source, such as individual transitions in a gas, while rejecting optical contamination from other emission sources.

The inputs to this application configure the properties of the geometry and the layer refractive indices.Results are presented as plots of the reflectance over a range of radiation wavelengths. The width of the stop-band is presented for both filter cases, while the reflectance of the notch and the width of the notch pass-band is also calculated.

» See model.

When the Vdara hotel first opened in Las Vegas, visitors relaxing by the pool would experience intense periods of heat at certain times of the day, at certain times of the year. This intense heat was caused by the reflection of solar radiation from the curved, reflective surface on the South-facing side of the hotel. This model shows how a caustic surface is generated in the pool area around the time and date the problems were first reported.

This model also requires the CAD Import Module.

» See model.

This model demonstrates how the sun causes 1.75 arcseconds of deflection for rays grazing the sun’s surface as observed from the earth. Einstein predicted this value after refining his theory of relativity during World War I.

» See model.

A Luneburg lens has a graded refractive index which leads to special focusing properties. This example model uses the Geometrical Optics interface to compute the ray trajectories and their optical path length.

» See model.

The simplest example of an anti-reflection coating is a quarter-wavelength layer. One big disadvantage of such a single-layer coating is that there is generally no practical material with the required refractive index to achieve a low reflectance. A combination of several layers can be used to reduce the reflection coefficient over a much wider range of wavelengths than a single layer while allowing a wider variety of real materials to be used. In this model, a quarter-quarter and a quarter-half-quarter structure are modeled.

» See model.