NEWS

New on Youtube: "Getting Started" VirtualLab Fusion Tutorials

(April 04, 2017)

The channel is a common platform of the Applied Computational Optics Group of the Institute of Applied Physics (Friedrich-Schiller-University), and the companies Wyrowski Photonics and LightTrans International. Here we will provide you with short videos on the theory and concepts of an exciting new ...

VirtualLab training courses in Jena in September 2017

(March 02, 2017)

LightTrans offers its new VirtualLab training courses: "Introduction to VirtualLab Fusion", September 18-19, 2017 "Analysis and Design of Diffractive and Micro Optical Systems”, September 20-22, 2017 NEW: "Introduction to VirtualLab Programming”, September 25, 2017 Deadli...

Free optical design seminar at Photonics West 2017

(December 19, 2016)

LightTrans is going to exhibit at Photonics West 2017 taking place in San Francisco, CA, starting on January 31, 2017. Please visit us at our booth 4629-45 in the German Pavilion during the trade show (January 31 - February 2). During the week of the trade show we offer a free optical design semina...

Analysis and Design of Gratings

Rigorous analysis of gratings

VirtualLab enables the rigorous simulation of 2D and 3D gratings with the Fourier Modal Method (FMM) including

  • surface gratings
  • volume gratings
  • diffraction gratings
  • holographic gratings
  • Bragg gratings
  • zeroth-order gratings
  • moth-eye structures

The analysis includes polarization effects (TE-TM or x-y coordinate system), free positioning with tilts and general incident waves.

Pyramid type 3D surface grating and index modulation of a volume grating between two interfaces.

Results and visualization

The following data can be computed and visualized as results of an analysis:

  • Diffraction efficiencies: table and polar diagram
  • Reflectance, transmittance, absorption
  • Near field
  • Field inside grating

The numerical accuracy can be controlled by a parameter run and approximate geometrical optics methods can be used for faster computations in case of large periods.

Efficiency diagram for a 1d beam splitter (left) and a sinusoidal surface grating (right).

Systems and applications

Gratings are being used more and more extensively in optics. Applications include

Cylindrical Micro-lens array with nano-sized antireflection structure.
  • Antireflection structures
  • Polarizers
  • Spectroscopy
  • Diffractive beam splitters
  • Photovoltaic systems
  • Fiber coupling
  • Artificial media
  • Photonic crystals
  • Wafer inspection systems

Design of antireflection gratings

 2D and 3D gratings can be used to design antireflection structures. VirtualLab provides a wide rang of templates for gratings and the programming interface of VirtualLab leads to an unlimited flexibility to describe customized grating structures. Parameter run and parametric optimization can be used to optimize structures for given merit functions, e. g. for the minimization of the reflectivity.

Pillar structure of the grating and reflectance depending on the diameter: minimum at 140 nm.

As an example pillar-type sub-wavelengths gratings can be used to control the reflectance of a surface. VirtualLab provides the Fourier Modal Method for the analysis and optimization of such 3d grating structures. The dependence on further parameters, e. g. wavelength, can be investigated.

Design of Polarization gratings

Gratings can be used to control the polarization of the transmitting light. VirtualLab allows the design of such polarization gratings.

For the spectrum of visible light (left) the minimum polarization contrast for varying slit width and modulation depth of a rectangular grating can be computed (right).

Using the polarization analyzer, the polarization contrast can be computed for the complete spectral range of visible light. This allows an optimization of the grating with respect to the contrast between x- and y-component of the electric field. In case of a rectangular grating optimal values for slit width and modulation depth can be computed.

Gratings within optical systems

Gratings are also used as part of optical systems as e. g. within imaging systems or wafer inspections systems. In such cases the grating is illuminated by a general incident wave. This requires a generalization of the modeling from idealized infinite plane waves to general incident waves.

Imaging system with a grating component.

The simulation of such systems is based on the field tracing approach of VirtualLab. Different simulation techniques are combined within one simulation. The sub-wavelength grating is analyzed rigorously using the FMM. In case of an incident wave with a low divergence fast parabasal approximation methods can be applied. The programmable component allows the full flexibility to add customized propagation methods designed for the particular application.

Related Information