AR coatings are designed so that the relative phase shift between the beam reflected at the upper and lower boundaries of a thin film is 180°. Destructive interference between the two reflected beams occurs, which cancels out both beams before they exit the surface (Figure 2). The optical thickness of the optical coating must be an odd integer multiple of $\tfrac{\lambda}{4}$, where $ \small{\lambda} $ is the design wavelength or wavelength being optimized for peak performance in order to achieve the desired path difference of $\tfrac{\lambda}{2}$ between the reflected beams. When achieved, this will lead to the cancellation of the beams. The index of refraction of a thin film $ \small{\left( n_f \right)} $ needed for complete cancelation of the reflected beams can be found by using the refractive indices of the incident medium $ \small{\left( n_0 \right)} $ and the substrate $ \small{\left( n_s \right)} $.

UV-AR and UV-VIS: Ultraviolet coatings are applied to our UV fused silica lenses and UV fused silica windows to increase their coating performance in the ultraviolet region.

Because of the durability of Semrock filters, you can easily populate filter cubes, filter sliders, and filter wheels yourself without fear of damaging the filters. To maximize intended transmission and blocking and to minimize autofluorescence, filters must always be oriented so that light is incident on a specific surface of the filter. This note describes the correct orientation for the different filter types.

Broadband anti-reflection (BBAR) coatings are designed to improve transmission over a much wider waveband. They are commonly used with broad-spectrum light sources and lasers with multiple-harmonic generation. BBAR coatings typically do not achieve reflectivity values quite as low as V-coats but are more versatile because of their wider transmission band. In addition to being applied to transmissive optical components including lenses and windows, AR coatings are also used on laser crystals and nonlinear crystals to minimize reflections, as Fresnel reflections occur where air and the crystal meet.1

Dichroicmirror

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Dichroic Filterthorlabs

Fiber optic light guides are less flexible than liquid light guides, but are well-suited for the transmission of light in the visible and near-infrared range.

VIS-NIR: Our visible/near-infrared broadband anti-reflection coating is specially optimized to yield maximum transmission (>99%) in the near-infrared.

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Please use the sort buttons in the left navigation to navigate between questions and answers that are specific to Optical Imaging Systems, Fluidics, Cameras, Microfluidics, our Webstore, and Engineering Partnership.

Here we have provided comprehensive lists of commonly asked questions regarding our Semrock optical filters and related applications. This information is designed to support your inquiries, but if you don’t find the answers you are looking for we encourage you to contact us for further assistance.

$\tfrac{\lambda}{4}$ MgF2: The simplest AR coating used is $ \tfrac{\lambda}{4} $ MgF2 centered at 550nm (with an index of refraction of 1.38 at 550nm). MgF2 coating is ideal for broadband use though it gives varied results depending upon the glass type involved.

Semrock exciter and emitter filters mounted in housings feature an alignment arrow on the housing; see the illustrations below.  Orient such a filter so that the arrow points in the direction of light propagation. For microscopes, the exciter filter arrow should point away from the light source and toward the dichroic beamsplitter, and the emitter filter arrow should point away from the dichroic beamsplitter and toward the eye, detector, or camera.

Dichroic filterphotography

Edmund Optics offers all TECHSPEC® lenses with an optional single-layer, dielectric anti-reflection (AR) coating to reduce surface reflections. In addition, custom single-layer, multi-layer, V, and 2V coatings are available for both our off-the-shelf and large volume custom orders. View Custom Optical Lens Coatings for information.

Dichroiclens

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Dichroic filterflow Cytometry

Nov 4, 2020 — Commonly Used Sub-Division Scheme. Division name, Abbreviation, Wavelength, Frequency, Photon Energy, Temperature. Near infrared, NIR, IR-A ...

Table 1 shows the reflectivity and guaranteed laser-induced damage threshold (LIDT) for Edmund Optics’ standard laser V-coats.

Because reflectivity increases rapidly as the wavelength of the source moves further away from the DWL, optical components with V-coats are meant for use at exactly or very close to the intended DWL of the coating. An interesting characteristic of V-coats is that the shape of their transmission curves is semi-periodic such that the reflectivity reaches a local minimum at harmonics of the DWL (e.g. $ \tfrac{\lambda_0}{2} $ or $ \tfrac{\lambda_0}{4} $) that are not as optimized for reflectivity as at the DWL. V-coats are usually comprised of only two coating layers. Simple V-coats can consist of a single layer with a thickness of a $ \tfrac{\lambda}{4} $, but more layers may be required to adjust the bandwidth or if a coating material with an appropriate index of refraction is not available. Multilayer coatings may also compensate for different angles of incidence, but are more complicated and tend to have larger bandwidths. If the thickness of the V-coat layers is incorrect, the reflectivity of the coating increases and the DWL changes. V-coats from Edmund Optics typically achieve minimum reflectivities significantly less than 0.25%, but all standard V-coats have specified reflectivities of <0.25% at the DWL. This allows for small shifts in the DWL from coating tolerances.

VIS 0° and VIS 45°: VIS 0° (for 0° angle of incidence) and VIS 45° (for 45° angle of incidence) provide optimized transmission for 425 – 675nm, reducing average reflection to 0.4% and 0.75% respectively. VIS 0° AR coating is preferred over MgF2 for visible applications.

Dichroicglass

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Orientation of Semrock FiltersBecause of the durability of Semrock filters, you can easily populate filter cubes, filter sliders, and filter wheels yourself without fear of damaging the filters. To maximize intended transmission and blocking and to minimize autofluorescence, filters must always be oriented so that light is incident on a specific surface of the filter. This note describes the correct orientation for the different filter types.Orienting Housed Excitation and Emission FiltersSemrock exciter and emitter filters mounted in housings feature an alignment arrow on the housing; see the illustrations below.  Orient such a filter so that the arrow points in the direction of light propagation. For microscopes, the exciter filter arrow should point away from the light source and toward the dichroic beamsplitter, and the emitter filter arrow should point away from the dichroic beamsplitter and toward the eye, detector, or camera.Dichroic beamsplitters are rarely mounted in housings. See below for guidance.Orienting Dichroic Beamsplitters and Other Unhoused Optical FiltersDichroic beamsplitters and other unhoused optical filters feature orientation marks that identify the coated surface upon which light must be incident. An orientation mark is placed either on the front surface of the filter, or on the edge of the filter as a caret (^) mark. The different types of orientation marks are shown in the following drawings along with the corresponding orientation guidance.Semrock logo: The logo is on the surface facing the incident light.Line: A short line is on the surface facing the incident light. The line may be easier to see if viewed at an oblique angle.Dot: A small dot is on the surface facing the incident light. The dot may be easier to see if viewed at an oblique angle.Caret: A caret on the edge of the filter points in the direction of light travel. When the viewer faces the surface that receives the incident light, the caret points away from the viewer.Caution: A number of dichroic beamsplitters have coatings on both surfaces. Always use the above instructions to identify the coated surface that should face the incident light! If you encounter any ambiguity or difficulty, please contact Semrock for assistance in identifying the surface orientation.Further ResourcesComplete how-to instructions for microscope cube assembly are available in PDF format and video.

Dichroicmirror in fluorescence microscopy

Due to Fresnel reflection, as light passes from air through an uncoated glass substrate approximately 4% of the light will be reflected at each interface. This results in a total transmission of only 92% of the incident light, which can be extremely detrimental in many applications (Figure 1). Excess reflected light reduces throughput and can lead to laser-induced damage in laser applications. Anti-reflection (AR) coatings are applied to optical surfaces to increase the throughput of a system and reduce hazards caused by reflections that travel backwards through the system and create ghost images. Back reflections also destabilize laser systems by allowing unwanted light to enter the laser cavity. AR coatings are especially important for systems containing multiple transmitting optical elements. Many low-light systems incorporate AR coated optics to allow for efficient use of light.

Anti-reflection V-coats are a type of AR coating designed to increase transmission over a very narrow waveband centered at a specified design wavelength (DWL). This coating type is called “V-coat” because the curve of the transmission versus wavelength forms a “V,” with a minimum at the DWL. V-coats are ideal for obtaining maximum transmission when using single-frequency, small linewidth lasers, or narrow full width-half max (FWHM) light sources.1 V-coats typically have a reflectivity of less than 0.25% at the DWL. However, the reflection curve for the coating locally has a nearly parabolic shape and the reflectivity is significantly higher at wavelengths besides the DWL (Figure 3).

Dichroic beamsplitters and other unhoused optical filters feature orientation marks that identify the coated surface upon which light must be incident. An orientation mark is placed either on the front surface of the filter, or on the edge of the filter as a caret (^) mark. The different types of orientation marks are shown in the following drawings along with the corresponding orientation guidance.

Telecom-NIR: Our telecom/near-infrared is a specialized broadband AR coating for popular telecommunications wavelengths from 1200 – 1600nm.

Dichroic optical filterreplacement

Caution: A number of dichroic beamsplitters have coatings on both surfaces. Always use the above instructions to identify the coated surface that should face the incident light! If you encounter any ambiguity or difficulty, please contact Semrock for assistance in identifying the surface orientation.

NIR I and NIR II: Our near-infrared I and near-infrared II broadband AR coatings offer exceptional performance in near-infrared wavelengths of common fiber optics, laser diode modules, and LED lights.

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Edmund Optics offers all TECHSPEC® transmissive optics with a variety of anti-reflection (AR) coating options that vastly improve the efficiency of the optic by increasing transmission, enhancing contrast, and eliminating ghost images. Most AR coatings are also very durable, with resistance to both physical and environmental damage. For these reasons, the vast majority of transmissive optics include some form of anti-reflection coating. When specifying an AR coating to suit your specific application, you must first be fully aware of the full spectral range of your system. While an AR coating can significantly improve the performance of an optical system, using the coating at wavelengths outside the design wavelength range could potentially decrease the performance of the system.

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In addition, the fluorites are also corrected spherically for two or three colors instead of a single color, as are achromats. The superior correction of ...

Oct 7, 2015 — At first glance you might think the Fresnel lens (area=34×44=1496..in2) is better than the parabolic mirror (area=π(402)2=1257..in2) because ...