Compare Model Drawings, CAD & Specs Diameter Wavelength Range Antireflection Coating Material Surface Quality Availability Price
$107
In Stock
25.4 mm 440-700 nm NC.1 Grade A N-BK7 15-5 scratch-dig
In Stock
$118
In Stock
25.4 mm 660-1000 nm NC.2 Grade A N-BK7 15-5 scratch-dig
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$129
In Stock
25.4 mm 1010-1550 nm NC.3 Grade A N-BK7 15-5 scratch-dig
In Stock
$124
In Stock
25.4 mm 440-700 nm NC.1 UV Grade Fused Silica 15-5 scratch-dig
In Stock
$134
In Stock
25.4 mm 660-1000 nm NC.2 UV Grade Fused Silica 15-5 scratch-dig
In Stock
$144
In Stock
25.4 mm 1010-1550 nm NC.3 UV Grade Fused Silica 15-5 scratch-dig
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$191
In Stock
25.4 mm 255-440 nm NC.UV UV Grade Fused Silica 15-5 scratch-dig
In Stock
$278
In Stock
25.4 mm 440-700 nm NC.1 UV Grade Fused Silica 10-2 scratch-dig
In Stock
$291
In Stock
25.4 mm 660-1000 nm NC.2 UV Grade Fused Silica 10-2 scratch-dig
In Stock
$307
In Stock
25.4 mm 1010-1550 nm NC.3 UV Grade Fused Silica 10-2 scratch-dig
In Stock
$213
In Stock
50.8 mm 440-700 nm NC.1 Grade A N-BK7 15-5 scratch-dig
In Stock
$241
In Stock
50.8 mm 660-1000 nm NC.2 Grade A N-BK7 15-5 scratch-dig
In Stock
$266
In Stock
50.8 mm 1010-1550 nm NC.3 Grade A N-BK7 15-5 scratch-dig
In Stock
$266
In Stock
50.8 mm 440-700 nm NC.1 UV Grade Fused Silica 15-5 scratch-dig
In Stock
$292
In Stock
50.8 mm 660-1000 nm NC.2 UV Grade Fused Silica 15-5 scratch-dig
In Stock
$307
In Stock
50.8 mm 1010-1550 nm NC.3 UV Grade Fused Silica 15-5 scratch-dig
In Stock
$327
In Stock
50.8 mm 255-440 nm 255-440 nm UV Grade Fused Silica 15-5 scratch-dig
In Stock
$336
In Stock
50.8 mm 440-700 nm NC.1 UV Grade Fused Silica 10-2 scratch-dig
In Stock
$359
In Stock
50.8 mm 660-1000 nm NC.2 UV Grade Fused Silica 10-2 scratch-dig
In Stock
$380
In Stock
50.8 mm 1010-1550 nm NC.3 UV Grade Fused Silica 10-2 scratch-dig
In Stock
$137
In Stock
25.4 mm 350-2000 nm Uncoated Grade A N-BK7 20-10 scratch-dig
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$224
In Stock
50.8 mm 350-2000 nm Uncoated Grade A N-BK7 20-10 scratch-dig
In Stock

Specifications

  • Angle of Incidence
    45°
  • Surface Flatness
    ≤λ/10 at 632.8 nm over the clear aperture

Features

Fresnel Reflection

A material that exhibits birefringence, or different refractive indices for different input polarizations, is said to be anisotropic. This anisotropy affects the transmission and absorption properties of light and is the primary mechanism used in polarizers and waveplates. However, even isotropic materials (same index for different polarizations) can enable polarization selection via reflection. For a linearly polarized beam, both S- and P-polarizations exhibit different changes in reflectivity versus incident angle. There is an incident angle known as Brewster’s angle (θB) at which P-polarized light is transmitted without loss, or exhibits zero reflectance, while S-polarized light is partially reflected. This angle can be determined from Snell’s law to be θB = arctan(n2/n1). The accompanying figure shows this response when light is incident from air onto a dielectric material where θB ≈ 56°.

Broadband Beam Samplers

In a beam sampler, the percentage of reflected light is determined by the Fresnel reflection from a single surface. By reflecting approximately 10% of S-polarization and 1% of P-polarization at the nominal 45° AOI, the beam sampler picks off 1-10% of an incident beam, depending on its polarization upon incidence. Reflectance from a single uncoated surface for both S- and P- polarizations is shown here. The graph exhibits reflectance of the plate as a function of incident angle, showing the minimum in the P-polarization at Brewster’s angle, 55° 34’.

N-BK7 Substrates for VIS and NIR Applications

N-BK7 is an excellent lens material for general use such as most visible and near infrared applications. It is the most common borosilicate crown optical glass, and it provides great performance at a good value. Its high homogeneity, low bubble and inclusion content, and straightforward manufacturability make it a good choice for transmissive optics.

UV Fused Silica for UV & Broadband Applications

UV Grade Fused Silica is synthetic amorphous silicon dioxide of extremely high purity providing maximum transmission from 195 to 2100 nm. This non-crystalline, colorless silica glass combines a very low thermal expansion coefficient with good optical qualities, and excellent transmittance in the ultraviolet region. Transmission and homogeneity exceed those of crystalline quartz without the problems of orientation and temperature instability inherent in the crystalline form. It will not fluoresce under UV light and is resistant to radiation. For high-energy applications, the extreme purity of fused silica eliminates microscopic defect sites that could lead to laser damage.

Slight Wedge Suppresses Unwanted Fringes

Optics with perfectly parallel faces are unsuited for use as reference elements in laser setups as reflections from both surfaces would be collinear resulting in undesired large period fringes. The introduction of a slight wedge causes unwanted reflections from the second surface to be deflected from the optical path. The back surface (S2) of these beam samplers is slightly wedged. The laser beam should enter the non-wedged surface (S1) where an arrow on the side points to.

AR Coated Back Surface Eliminates Ghosting

An antireflection coating of high damage threshold (500 W/cm2 CW, 1.0 J/cm2 with 10 nsec pulses, typical) is applied on the back surface (S2) to minimize ghost reflections. Four broadband AR coatings are offered and optimized for 45° angle of incidence beams with <0.75% reflectance. NC.1 covers the 440-700 nm spectral range, NC.2 covers the 660-1000 nm spectral range, NC.3 covers the 1010-1550 nm spectral range and NC.UV covers the 255-440 nm spectral range. Uncoated version is also available, used as beam pick-off optics, to monitor the laser beam, independent of wavelength.

Laser Cavity Applications

Polarization-selective reflectivity is exploited in laser cavities to produce strongly polarized light, as well as for fine tuning of the output laser wavelength. A Brewster’s window is used in the laser cavity, providing polarized light output with minimal power loss. It follows the formula θB = arctan(n), where θB is Brewster’s angle and n is the index of refraction of the material. Often, fixed beam polarization is necessary in order that optical components can consistently perform as they were designed.

Power Measurement Applications

A common application for beam samplers is picking off a portion of a beam in order to track changes in beam power vs time using a detector. This information may be used as part of a feedback loop to regulate power, or could simply be used to log power in order to normalize experimental results at a later time. For measuring beam power, the beam sampler should be oriented such that the laser is p-polarized. This choice will maximize transmitted power and attenuate power incident on the detector.