WDM Design

Extremely efficient automatic design technique has been developed specifically for the designing of WDM filters. The WDM option is based on the unique know-how that is inaccessible to other thin film programs.

In order to design a WDM filter, its target specifications must be specified:

  • Filter wavelength
  • Half-width of the rejection band
  • Half-width at the 50% transmittance level
  • Shape factor (the ratio of half-widths of the rejection and transmission bands).

For more detail see WDM Filters in Design Collection article.

WDM design option is available through Synthesis –> Filter design…

WDM filter
Special comprehensive mathematical procedure  optimizes the filter design with respect to the entered specifications. The procedure is based on the global integer search (see the details in our publications).
WDM filter

  • Additional Mat mirror activates attempts to consider some mirror layers consisting of an additional material. It is enabled only if at least one additional material is selected.
  • Additional Mat cavity activates attempts to consider some mirror layers consisting of an additional material. It is enabled only if at least one additional material

OptiLayer allows additional design settings:

  • Symmetrical mirrors allows restricting Global Integer Search procedure to designs with symmetrical mirrors. This restriction increases the speed of the search procedure noticeably, it can be useful for complicated filters with many cavities (more than 6-8).
  • Symmetrical cavities allows restricting Global Integer Search procedure to designs with symmetrical cavities. This restriction increases the speed of the search procedure noticeably, it can be useful for complicated filters with many cavities (more than 6-8).
  • With Adjust to Incident, the filter is optimized with respect to the actual refractive index of incident medium. Otherwise it is optimized with respect to the incidence medium refractive index equal to that of the substrate. Practical experience shows that it is usually better to optimize a filter using the second option and then to apply an appropriate AR coating on the top of the filter.
  • 3H/3L mirror layers allows using 3H/3L layers for filter mirrors. This may improve optimization capabilities of the search procedure. In many cases it allows to obtain solutions of a better quality.
  • Composite cavities allows using filter cavities of a complicated structure. This may also improve the filter optimization.
WDM filter OptiLayer allows adjusting the performance of the filter design with respect to the actual refractive index of the incident medium if the filter was designed for the embedded case. It is possible to use 1-layer AR coating or 2-layer AR coating of the “V” type.

The first layer of the “V” coating is often of the same material as the last layer of the filter. In this case such layers form a single layer and the resulting number of design layers is increased only by 1.

If Export Filter Target is marked, WDM Filter Design option will also export WDM filter target to the OptiLayer environment.

Export to VPI…  allows you to export WDM filter spectral characteristics to VPIphotonics software. Visit www.vpiphotonics.com for more information on VPIphotonics.

Using configuration window, you can customize conventions used in the WDM Filter synthesis dialog and the WDM Error Analysis command of OptiLayer.

You can specify the Transmission level and Rejection level for setting the transmission and rejection bands of a WDM filter. Both values can be entered in absolute values and in dB. Entry fields for these values are synchronized.

Also it is possible to specify whether it is necessary to use a 50% half-width requirement (half-width at the transmission level of 50%).

For more detail see WDM Filters in Design Collection article.

 WDM config
WDM filer before and after adjustment to the incident medium.
(NEW!) Starting from Version 12.12 (2017), it is possible to design WDM filters for oblique incidence (arbitrary angle of incidence) and arbitrary polarization (s, p, A).

The corresponding setting can be found at the first page of the WDM dialog:

Synthesis –> WDM Filter

WDM AOI
Learn more in our publications:

  1. A. V. Tikhonravov and M. K. Trubetskov, “Automated Design and Sensitivity Analysis of Wavelengh-Division Multiplexing Filters ,” Appl. Opt. 41, 3176-3182 (2002).
  2. A. Tikhonravov, M. K. Trubetskov, and A. V. Voronov, “Automated monitoring of WDM filters,” in Optical Interference Coatings, OSA Technical Digest Series (Optical Society of America, 2001), paper WA3.
  3. A. V. Tikhonravov and M. K. Trubetskov, “Automated design of WDM filters,” in Optical Interference Coatings, OSA Technical Digest Series (Optical Society of America, 2001), paper WD3.
  4. A. Thelen, A. Tikhonravov, M. Trubetskov, and M. Kokarev, “Phase properties of WDM filters,” in Optical Interference Coatings, OSA Technical Digest Series (Optical Society of America, 2001), paper WD5.
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WDM filter option can be used also to design conventional narrow band pass filters with quarter wave and half-wave layer thicknesses.narrow band pass filter

Narrow band pass filter consisting of quarter wave, half-wave and full wave layers.

For more detail see WDM Filters in Design Collection article.

narrow bandpass filter

Look our video examples

Look our video examples at YouTube

OptiLayer videos are available here:
Overview of Design/Analysis options of OptiLayer and overview of Characterization/Reverse Engineering options.

The videos were presented at the joint Agilent/OptiLayer webinar.