Optical filters are thin sheets designed to control the spectral characteristics of light, oftentimes used for transmitting a selected portion of light while blocking the other. Optical filters can be divided into two types: absorptive filter, which relies on the absorptive dyes to select the desired wavelength or color range; interference filter, which relies on the interference effect created by alternating thin layers of dielectric films deposited on the substrate to control the optical behaviors of light over specific wavelengths. Compared with absorptive optical filters, although leveraging dielectric optical filter coatings is not as cheap, interference filters can, for the most part, withstand high intensities without being damaged, and there’s more freedom for designs.
Hangzhou Shalom EO offers a wide selection of custom optical filter dielectric coating services for interference optical filters. Our optical filter coatings are composed of alternating multiple layers of thin films of materials with different refractive indices, that are deposited in vacuum chambers using the ion-assisted deposition (IAD) e-beam coating technique. Our filter coating catalog encompasses various optical filter coating types and can accommodate broadband, narrowband, or single wavelength requirements in all spectral regions. Optical densities, blocking wavelength ranges, and bandwidths of the filter coatings can be tailored:
Bandpass Filter/Laser Line Filter Coatings:
The bandpass filter coatings are designed to allow light within a specific range of wavelengths to pass through while rejecting wavelengths outside this range. Large optical densities are available that reject the unwanted portion of the spectrum well. Both broadband filter coatings with transparencies over a wide wavelength range and narrowband filter coatings are available. A maximum optical density OD6 can be obtained.
Laser line filters and coatings are crafted to provide boosted transmission for a very narrow bandwidth center around the laser bandwidth. Shalom EO is capable of providing coating services for laser line filters with wavelengths from UV to IR.
Superior transmission within the wavelength range of interest can be obtained with our sophisticated dielectric coating techniques utilizing the numerical calculation of the thickness of the reflecting stacks.
Long Pass Filters and Short Pass Filter (Edge Filter) Coating:
Edge filters and coatings filters are typically used to isolate a particular part of the spectrum or to separate different wavelength regions. Long-pass filter coatings exhibit high transmission for wavelengths longer than the cut-on wavelength while blocking the shorter wavelengths.
And short pass filter is the opposite, transmitting wavelengths shorter than the cut-off wavelength while attenuating the longer wavelengths. Composed of carefully designed thin dielectric films, Shalom EO’s edge filter coatings ensure deep out-of-band blocking and sharp cut-on and cut-off.
Notch Filter Coating:
Notch optical filters (bandstop filters) and coatings are the converses of bandpass filter coating. Notch optical coating blocks a narrow range of wavelengths and transmits the rest of the spectrum with a high transmission rate.
Dichroic Filter Coating:
Dichroic optical filters and coatings separate light into two components based on the wavelength, where one component is transmitted and one component is reflected.
