Precision wavelength-selective coatings that transmit specific bands while reflecting others. Used in fluorescence microscopy, display systems, beam combining and color separation.
Dichroic coatings are multi-layer interference filters designed to transmit certain wavelengths while reflecting others. Unlike absorptive color filters, dichroic coatings redirect unwanted wavelengths rather than absorbing them, reducing thermal load.
The coating stack consists of a precisely designed sequence of high and low index quarter-wave layers. Bandpass dichroics transmit a specific band and block both shorter and longer wavelengths. Longpass and shortpass dichroics create a spectral edge with steep transitions.
Edge steepness is determined by the number of layers and design complexity. Standard dichroics achieve transition widths of 5-10% of center wavelength, while steep-edge designs can achieve < 2% transition widths using 50+ layer designs.
When used at 45° angle of incidence, dichroic coatings split the beam into reflected and transmitted paths with defined spectral characteristics. This is the basis for fluorescence filter cubes, RGB color separation in projectors, and multi-wavelength beam combining.
| Parameter | Typical Values | Notes |
|---|---|---|
| Transmission Band | Custom, any band | Typically 10-500nm wide |
| Reflection Band | Custom, complementary | Or independent bands |
| Edge Steepness | 5-10% of λ (standard) | < 2% for steep-edge |
| Transmission | > 90% in pass band | Up to > 95% |
| Blocking | OD 3-6 in block band | Depends on design |
| AOI | 0°, 45° most common | Custom angles available |
| Size | Up to 300mm diameter | Custom shapes available |
| LIDT | Available: 5-30 J/cm² | At relevant wavelength |
| Substrate | BK7, fused silica, CaF2 | Per application |
| Material Pair | Range | Application |
|---|---|---|
| Ta2O5/SiO2 | 350nm-2μm | VIS-NIR fluorescence, display |
| TiO2/SiO2 | 400nm-1.5μm | Visible bandpass, RGB splitting |
| HfO2/SiO2 | 250nm-2μm | UV-VIS dichroic filters |
| Nb2O5/SiO2 | 350nm-4μm | Extended VIS-NIR |
| Al2O3/SiO2 | 200nm-500nm | Deep UV dichroic |
| Ge/ZnS | 2-14μm | IR dichroic (thermal) |
Dichroic beamsplitters in filter cubes separate excitation and emission wavelengths. Critical specs: high transmission in emission band, steep edge, and deep blocking of excitation light.
RGB color separation dichroics in LCD and DLP projectors split white light into red, green and blue channels with high efficiency and color purity.
Laser systems combine multiple wavelengths using dichroic mirrors — each mirror transmits one wavelength while reflecting another.
Notch and edge dichroic filters reject intense Rayleigh scatter while transmitting Raman-shifted signals very close to the laser line.
Multi-spectral inspection systems use dichroic filters to separate wavelength channels for simultaneous surface and subsurface imaging.
PhotonEdge offers coated optical components compatible with Dichroic Filters & Mirrors. Explore related products below.
Both use the same coating technology. 'Dichroic mirror' typically refers to components used at 45° to split a beam, while 'dichroic filter' often refers to bandpass or edge filter functions. The distinction is largely application-based.
Standard designs achieve transition widths of 5-10% of center wavelength. Steep-edge designs with 50+ layers can achieve < 2%, approaching the performance of volume holographic gratings.
Yes, with appropriate material selection and deposition. IBS-deposited dichroics can achieve LIDT > 20 J/cm². However, the steep transition regions may have higher absorption than simple HR coatings.
Blocking depth depends on coating design (number of layers) and can be enhanced with absorptive glass substrates. OD 6+ is achievable for fluorescence applications.
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