Anti-Reflection Coatings

We offers a wide range of Anti-Reflection coatings which may be applied to any of their glass or fused silica lenses or windows to reduce reflection losses.

Through use of our Ion Assisted Deposition (IAD) process We also specializes in AR coatings on optical fiber endfaces. Low temperature IAD coatings may be applied to most fiber endface terminations. Pre and post coating inspection is performed in the factory's dedicated facility to ensure high quality.

"Super-V” Coatings represent the ultimate in low reflection coatings (R<0.1%) for narrowband applications. They also offer laser line V Coatings, Broadband Multilayer AR Coatings, Multiband AR Coatings, Telecom AR Coatings and Single Layer AR MgF2 Coatings.

Standard coatings may be ordered by simply appending a coating suffix to the product number and specifying the number of sides to be coated. For more complex requirements please contact us and we will be pleased to advise you on the best coating for your needs.

Custom Coatings

Dalatec Corporation specializes in custom optical coatings from the ultra-violet to the near infrared. Every day they provide a variety of custom coatings from simple modifications of the catalog specifications to entirely specialized designs.
High Reflection Coatings

We offers narrowband and broadband dielectric high reflecting coatings as well as a range of metal coatings. Laser Line HR Coatings are offered for all major laser wavelengths in the range of 193 to 2100nm. Broadband HR Coatings are offered for a selection of bandwidths. They provide a very high degree of spectrally neutral reflection and represent the ultimate in optical mirror coatings. Most of the coatings listed are for use at 45 degrees angle of incidence, but we does offer a selection of Broadband, Normal Incidence HR Coatings. Other normal incidence coatings can be provided on special request.

Metal coatings, such as Protected Aluminum, Protected Silver or Protected Gold provide reflectance over an extremely broad spectral range. These coatings are protected by a thin layer of dielectric material in order to make them durable. It is also possible to enhance the performance of metal coatings by adding several dielectric layers over the metal coating.

Cemented Achromatic Doublets
These are cemented achromats with a very precise range of tolerances and specifications. They are extremely convenient general purpose lenses. Being cemented they do not need a lens cell and can be treated as an individual component.

These lenses can be used as collimators, focusing lenses or light collectors. Optimized for use at three wavelengths, 486.1, 546.1 and 656.3nm, these lenses perform well throughout the visible spectrum. They have a minimum of spherical and chromatic aberration and perform well for all paraxial imaging tasks. These achromats are coated with a broadband Anti-Reflection coating to reduce surface losses in the visible region. Optional Anti-Reflection coatings for other wavelength regions are also available.

Beamsplitters
Beamsplitters are one of the most versatile and useful optical tools available. With them you can separate light into two completely independent beams. Separation can be by either amplitude (intensity) or by wavelength. In either case the two beams retain all of the attributes (such as intensity/wavelength distribution, wavefront shape, and spatial/temporal distributions) that the original beam exhibited.

There are three basic forms of optical beamsplitter: parallel plates, cubes and pellicles. The simplest, the parallel plate, consists of a carefully generated transparent substrate with a partially reflective coating on one side and an Anti-Reflection coating on the second surface. These are usually designed to be used at an angle of 45 degrees. By making the second surface at a wedged angle to the first surface any residual ghost image can be made to fall outside of field of view of the following system.

Cube beamsplitters are simply two right angle prisms cemented together with a partially reflecting surface on the internal (protected) face. The beamsplitting film is deposited on the hypotenuse face of a precision BK7 prism whose faces are λ/4 and the prism is cemented to an identical prism to form a cube which is parallel sided within 5arcmin. The four outer faces are all Anti-Reflection (AR) coated.

Pellicles are essentially single surfaced beamsplitters. In this case one face carries the partially reflecting film and the second, uncoated, surface will produce a roughly 4% ghost image. But the ghost image will be displaced only ~2 microns laterally from the primary image and may usually be ignored.

Cylindrical Lenses
We offers a selection of high precision cylindrical lenses, both positive and negative, in glass and fused silica. These lenses are well suited for applications which require magnification in one dimension only. Examples include energy collection for linear detectors or for coupling to a slit input, source generation for barcode scanners, circularization of diode laser outputs, one-dimensional image compression, and other similar applications.

Cylindrical lenses are more difficult to manufacture than spherical lenses but we take great care to ensure that the lens power is confined to a single axis and that the lenses are tightly specified so that you can use them with confidence in a complex imaging system. The lenses offered represent some of the more general requirements of our customers. But please call if you need a different shape or size. The lenses are uncoated but standard coatings may be applied by choice of the appropriate coating suffix.

Filters & Apertures
Filter sets offer the advantage of spectral or intensity modification to suit the particular circumstances. Often it is necessary to change the characteristics of a beam of light and it is useful to have a selection of calibrated filters on hand for this purpose. Our filter sets are supplied in a convenient storage binder together with their actual spectrophotometer traces. This way you are able to select filters for use singly or in combination to modify the incident light to suit your purpose.

Dalatec Corporation offer 6 different filter sets. Short-pass and long-pass filters can be combined to restrict the spectral region of interest. Their sets cover the spectrum using 13 filters at 50nm intervals from 400 to 1000nm. Two narrow band interference filter sets permit the isolation of very narrow spectral regions. We offers a 40nm halfwidth set and a 10nm halfwidth set. In each case there are 13 filters covering the spectrum from 400 to 1000nm. Attenuation filter sets are provided for the visible spectrum and for the 1064nm YAG line. The visible range set is made from neutral density glass while the YAG set is made from a range of different glasses calibrated to provide the exact required attenuation at the YAG wavelength. Nine filters cover transmittance values in 10% intervals from 10% to 90%.

Apertures list a number of slits, pinholes and iris diaphragms. All three are useful in providing a defined or reduced physical aperture to allow only a specific amount of light through a system. The slits and pinholes are small enough that they will act as quasi-diffraction sources or spatial filters for a number of applications.

The pinholes are precision etched in either stainless steel or copper foil. The copper foil version allows for higher power levels, as the copper is able to dissipate heat more effectively than the stainless steel versions.

Diaphragms are made from a series of interlocking leaves which open and close in such a way that a quasi-circular aperture is formed. Diaphragms are extremely useful in empirically determining the need for aperture stops to reduce scatter and stray light. Some of our iris diaphragms use a two-iris system to allow them to be closed completely to a zero aperture.

Mirrors
Mirrors are a critical and commonly used component in many optical systems. They are used to fold, bend and focus optical beams. They often allow a more compact and manageable system design. Optical quality mirrors are coated on their front surface with a metallic or dielectric coating to reflect the light. Three characteristics are important when choosing an optical mirror: surface figure, surface quality and the coating specification.

Surface figure refers to the geometric variation of the actual mirror surface from the ideal. By convention this is measured in fractions of a wave of light at 633nm. Note that because the light is reflected from the surface the actual wavefront degradation will be twice the deviation specified. Optical finishing techniques all suffer from a small boundary effect at the edge of a component. This results in a slight turn down of the surface in the outer 5% of the diameter. This turn down is typically less than two or three times the nominal specification. As a result, only the central 90% of a mirror should be used in demanding applications. Our best quality mirrors are the Laser Mirrors and the Broadband Mirrors; they should be selected in most situations where wavefront distortion and scattering are of concern.

Surface quality refers to residual defects in the surface of the mirror; normally slight scratches or sleeks and digs or pits. Apart from being unsightly, surface defects contribute to scattering of the reflected light. In most imaging applications these contributions are negligible and will not cause problems. In laser systems, however, scattering can cause unwanted diffraction patterns and even (in higher power applications) contribute to the failure of the coating. Dalatec's mirror specifications follow the US Military Specification Standard MIL-0-13830A for scratch and dig performance. Their Laser Mirrors and Broadband Mirrors provide the highest levels of surface quality and should be selected for critical applications.

Different coatings are available for different applications because no one coating is able to optimize all of the reflection criteria at one time. Coatings will affect the intensity and polarization state of the reflected beam and so should be chosen with care. Spectral reflectance curves for our various coatings are shown in the preceding coatings section. Note that the highest reflectivity is sometimes restricted to a narrow spectral range. While all of our mirror coatings are durable, first surface mirror coatings should be handled with care.

Polarizers
Various materials may be used in optical polarization devices. Crystals, such as calcite, quartz and mica, exhibit different indices of refraction for different polarization orientations. These materials are referred to as being birefringent. Unpolarized light entering a birefringent crystal from the correct orientation is broken into two separate plane polarized beams. These are usually referred to as the ordinary (o-ray) and extraordinary (e-ray) rays. The plane polarized o-ray behaves according to Snell’s law, whereas the orthogonally polarized e-ray does not and is refracted at an extraordinary angle. Other polarizers make use of organic materials which can be imbedded in plastic and then aligned to make them selectively absorb different polarization directions. And thin films can be stacked to act as multiple reflective polarizers. All of these techniques have their advantages in specific applications.

In light of this, Dalatec offers a wide range of components which affect the state of polarization. These include the following calcite elements: Glan laser prisms, Glan Thompson prisms, Glan Taylor prisms, Wollaston prisms and calcite beam displacers. All are made from a very high grade of optical quality natural calcite crystals which exhibits only very slight internal striae.

Other forms of polarization component included are: thin film laser polarizers, dichroic polarizers, quartz and mica waveplates and quartz depolarizers.

Prisms
Prisms have two main uses - redirecting an optical beam and dispersing the beam into its component colors. By careful control of the prism angles it is possible to perform some interesting and useful manipulations on the imaging light entering the prism.

These products include the following deviating prisms: right angle prisms, dove prisms, penta prisms, retro-reflectors and precision wedge prisms. Dalatec also offers a range of equilateral dispersing prisms.

Prisms are made from solid pieces of optical material. All faces are flat with the non-optical surfaces being left in their as-ground condition. The optically active faces are all ground and polished to the specified degree of flatness. Prisms are more difficult to manufacture than mirrors or windows because several surfaces must be held in a precise geometrical relationship to each other. Some prisms (retro-reflectors, for example) rely greatly on the precision of these geometrical relationships.

Because prisms are made from solid materials the optical path within the prism is fairly long compared to other optical components. When prisms are used in optical systems where the beam is either convergent or divergent they will introduce optical aberrations - primarily spherical aberration. Therefore, when using prisms in imaging or focusing systems, it is important to have collimated or nearly-collimated beams in this portion of the system.

Substrates & Windows
Windows are used to create a physical barrier between environments such as air to water, vacuum to air, or one gas to another. The ideal window allows an optical beam to pass from one medium to the next without making any change to the beam. It does not change the wavelength distribution of the beam, nor does it change the transmitted wavefront or scatter any of the light out of the beam.

The ideal window allows the optical beam to pass unimpeded and unchanged. In order to come close to this ideal a high quality window is required. Windows need high transmittance, low wavefront distortion and low scatter. At the same time they need to be durable and strong.

Three different materials are available - optical quality crystal sapphire, Ultra-Violet transmitting synthetic fused silica and BK7 grade A optical glass. In each case, only homogeneous and inclusion free material is used.

Surfaces are polished to 40-20 and held parallel to 5arcsec or 3arcmin. Flatness of λ/10 is recommended but some less expensive λ/4 glass windows are offered for situations where flatness is not so critical.

A range of standard circular, square and rectangular shapes are standard but a wide variety of other shapes and sizes can be supplied to order.