Frequently Asked Questions

What are optical thin film filters?

Optical thin film filters are designed to transmit, reflect or absorb specific wavelength ranges of light for one or more angles of incidence and for different polarizations of light. Optical filters are used in diverse applications such as in optical networks (telecom, cable); biomedical and spectroscopic instruments; anti-reflection coatings on display or eyeglasses; remote sensing (atmospheric, satellites); entertainment (projection displays, 3D); and many other areas!

To achieve the desired optical performance, optical filters are designed with one or more thin film layers where each layer consists of a specific material and thickness. Typcially, the thin film multilayer consists of alternating materials with a low and high refractive index and with individual layer thicknesses on the order of 10 to 1000 nm (depending on the spectral range of the optical filter). The materials are selected on the basis of their optical and physical properties for the operating wavelength range of the filter. For instance, sputtered oxide materials are usually the material of choice for visible (350-750 nm) and near- and mid-IR (750-9000 nm) spectral ranges; for low and higher wavelength ranges, selenides, sulfides, fluorides and semiconductors are generally employed.

Optical thin film filter software is employed by thin film engineers to design the thin film multilayer based on the chosen materials and required optical and physical specifications. In order to realize the desired optical performance, the optical constants of the deposited thin film materials need to be accurate and the layer thicknesses have to be deposited with a very good accuracy (typically within 1 nm).

What are the advantages of thin film optical filters?

Thin film optical filters have a number of distinct advantages compared to other optical technologies for reflecting, transmitting or absorbing various spectral regions.  For example, optical thin film filters:

  • Can be fabricated in small or large sizes (i.e., from 0.3×0.3×0.5 mm to 150x300x20 mm or larger)
  • Are environmentally very stable (if using an energetic deposition process such as sputtering)
  • Are easy to handle in a device or instrument
  • Can possess either a very low or high intrinsic temperature coefficient (i.e. a filter can be designed to have either a very small or a large wavelength shift with temperature)
  • Are relatively inexpensive with prototype quantities deliverable in a short time period (two to six weeks depending on the filter complexity).
  • Can be manufactured in high volumes
What are the names of the various wavelength ranges?

The most common names of the different wavelength ranges that Iridian covers are:

  • UV (250-380 nm)     [UV = Ultra-Violet]
  • VIS (380-750 nm)    [VIS = Visible]
  • NIR (750-1400 nm)   [NIR = Near Infra-Red]
  • SWIR (1.4-3.0 µm)   [SWIR = Short Wavelength Infra-Red]
  • MWIR (3.0-8.0 µm)   [MWIR = Mid Wavelength Infra-Red]
  • LWIR (8.0-15 µm)     [LWIR = Long Wavelength Infra-Red]

In addition, for Telecom applications, there is a set of bands defined that are commonly used:

Band Description Wavelength range
O band Original 1260–1360 nm
E band Extended 1360–1460 nm
S band Short 1460–1530 nm
C band Conventional 1530–1565 nm
L band Long 1565–1625 nm
U band Ultra-Long 1625–1675 nm
How should I specify custom requirements for an optical thin film filter when requesting a quote?

The optical filter specifications required will depend on the filter application and how it is to be used. In general, typical filter optical specifications will include the wavelength ranges over which to reflect, transmit or absorb light; angle of incidence tuning range; the polarization state of light for non-normal angles of incidence; light coherency (laser or white light); optical beam size and cone angle of light; desired substrate material (with dimensions); incident light medium (air or glass) and so forth.  In additional, physical specifications such as the operating temperature range and the ambient environment of the filter should also be specified.

For a specific filter product types, additional specifications are usually required. For example,

  • Gain Flattening Filters (GFF) –
    Need to specify: Target transmittance curve along with desired Peak-to-Peak Error Function (PPEF)
  • Solid Etalons
    Need to specify: Free Spectral Range (FSR), Finesse (F) and FSR temperature variation.
  • Single Cavity Etalons
    Need to specify: -3 dB bandwidth (equivalent to the Full-Width, Half-Maximum (FWHM) is specified
  • Bandpass, Edge Pass Filters –
    Need to specify: transmit and reflect band(s) and allowed insertion loss (IL), ripple and blocking levels
What information is needed for a Purchase Order (PO)?

If you decide to place a PO after receiving a quotation, please include the following information:

  • Quotation number and date,
  • Preferred courier and your account number with that courier,
  • If you are a first time buyer and request a 30 days credit, please include credit ref
Can I order online?

Yes you can order online for any single band fluorescence filter or set, see our NEW Webstore for product listings! We will be adding additonal products shortly and welcome your inquiries for any other items on our website. We can accept telephone orders using VISA cards or standard purchase order for any of our products.