The dichroic mirror is the traffic controller of the fluorescence microscope: excitation light is reflected down onto the sample, the red-shifted emission passes straight through to the detector, and two wavelengths share one axis without a moving part. Its behaviour is a filter edge used in reflection, and the manufacturer's catalogue groups dichroic mirrors with the optical filters rather than with the plain mirrors — specifying one is specifying an edge wavelength, a reflected band and a transmitted band.
In the standard fluorescence set the dichroic works with two partners: an excitation bandpass filter before it and an emission longpass or bandpass after it. The three are specified against one wavelength plan in the enquiry, so each element's edge is confirmed against the same plan rather than chosen in isolation. Dichroics also combine laser lines — reflecting one laser wavelength while passing another — in projection, sensing and laser-display systems, where the same edge logic applies in reverse.
Specifying a Dichroic Mirror
- Edge wavelength — the transition between the reflected and transmitted bands.
- Reflected band — normally the excitation or shorter-wavelength range. No working angle is recorded for the group, so state the angle of use in the enquiry.
- Transmitted band — the longer-wavelength range that must pass with low loss.
- Size and substrate — the clear aperture the folded path needs, and the plate dimensions.
Dichroic mirrors are quoted per specification: the edge position and the two bands define the coating design, and the price follows it. If your splitter requirement is by ratio or polarisation rather than by wavelength, the beam splitters page is the correct route; if it is a plain reflection with a specified coating, see optical mirrors.
Frequently Asked Questions
At what angle is a dichroic specified?
No angle is recorded for the dichroic group in this catalogue. The edge position given in a specification is stated for its angle of use and changes if the angle changes, so state the working angle in the enquiry.
Can a dichroic combine two lasers?
Yes: reflect one line, transmit the other, on the same axis. State both wavelengths in the enquiry.
Is a dichroic a filter or a mirror?
Both — a filter edge used in reflection. This catalogue groups it with the filters, and its specification follows filter logic.
Dichroics Beyond Fluorescence
Fluorescence is the dichroic's home application, but two other duties bring buyers to this page as well, and both deserve naming. Laser line combining — merging two or three laser wavelengths onto one axis for projection, alignment or multi-wavelength instruments — uses the dichroic in reverse logic: each mirror reflects its own line and passes the lines combined before it, so the specification is a chain, and the mirrors should be quoted as a set with all wavelengths stated together. Hot and cold mirror service is the second: a hot mirror transmits the visible and reflects the infrared (removing heat from the beam), while a cold mirror reflects the visible and transmits the infrared, and both are dichroic behaviour applied to lamp and LED illumination rather than to lasers. If your requirement is one of these rather than a fluorescence set, say which in the first message — the edge positions and angle that follow from it are different, and a quotation built on the wrong duty is a round of correspondence wasted.
Request a Quotation
Tell us the component, material, dimensions and coating you need. Pricing and lead time for your specification are confirmed in the written quotation.