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MICRO-CONTROLE / Spectra-Physics
Variable Attenuator/Beamsplitters

Variable Attenuator/Beamsplitters

Product catalog summary

Overview
The document describes a high-performance variable attenuator/beamsplitter designed for splitting an incident polarized beam into two beams with a variable intensity ratio. It is suitable for applications in holography, precision interferometry, and general laboratory use.

Key Features

Preserves beam characteristics with minimal angular deviation.
Offers a wide dynamic range and low insertion loss.
High damage threshold with negligible absorption loss due to all-dielectric coatings.
Maintains constant phase relationship between transmitted beams for stable interference patterns.

Functionality
The device uses a polarizing cube beamsplitter to reflect s-polarized light and transmit p-polarized light. A rotating quartz λ/2 wave plate adjusts the input beam polarization, allowing control over the intensity of the exit beams. The 930AB models do not include an exit λ/2 wave plate.

Specifications

Aperture Diameter: 6.0 mm
Beamsplitting Ratio: Maximum T=0.2–94%, R=5–99.3%
Recommended Beamsplitting Ratio: T=3–70%, R=30–97%
Transmitted Beam Deviation: <15 arc sec
Damage Threshold: 2000 W/cm² CW, 1 J/cm² with a 10 nsec pulse

Ordering Information
Models are available with or without an exit λ/2 wave plate, suitable for different wavelengths (441.6 nm, 488 & 514.5 nm, 632.8 nm).

Applications in Holography
The device is ideal for holography due to its low loss and low beam deviation, which prevent phase shifts and spurious fringes, ensuring fringe stability and clear holograms.

Catalog excerpts

O p t i c s 643 Email: [email protected] • Web: newport.com PRISMS WINDOWS BEAMSPLITTERS FILTERS AND ATTENUATORS POLARIZATION OPTICS DIFFRACTION GRATINGS ULTRAFAST LASER OPTICS ACCESSORIES Our variable attenuator/beamsplitter splits an incident polarized beam into two beams whose intensity ratio may be continuously varied without alteration of other beam parameters. This high-performance unit can be used as a beamsplitter in holography and precision interferometry applications and as an efficient attenuator for general laboratory applications. Attenuation up to 27 dB is provided with sub-arc min beam deviation variation throughout the attenuation range. In contrast to lossy metallic beamsplitters, the 930 has all-dielectric coatings with negligible absorption loss. The phase relationship between the two transmitted beams remains constant as required for a stationary interference pattern. How does it work? The 930 variable attenuator/beamsplitter incorporates a high-performance polarizing cube beamsplitter which reflects s-polarized light 90° while transmitting p-polarized light. A rotating quartz ë/2 wave plate is placed in the incident polarized laser beam. The function of the wave plate is to control the input beam polarization incident on the beamsplitter so that the intensity of either exit beam, and the intensity ratio, can be controlled over a wide dynamic range. Pure p-polarization could be selected for maximum transmission, or pure s-polarization for maximum attenuation of the transmitted beam. The attenuation adjustment knob rotates the ë/2 wave plate, which in turn rotates the polarization vector of the beam incident on the cube beamsplitter. Except in 930AB models, another ë/2 wave plate rotates the polarization vector of the transmitted beam to match that of the reflected beam. Variable Attenuator/Beamsplitters • Preserves beam characteristics • Minimum angular deviation • Wide dynamic range • Low insertion loss • High damage threshold DEFLECTED S-POL ENERGY ATTENUATED P-POL BEAM FIXED 1/2 WAVE PLATE (NOT IN 930AB) ROTATED POLARIZATION ADJUSTABLE 1/2 WAVE PLATE POLARIZED INPUT BEAM POLARIZING BEAMSPLITTER CUBE Specifications Aperture Diameter 6.0 mm Beamsplitting Ratio, Maximum T=0.2–94% (reference beam); R=5–99.3% (object beam) Beamsplitting Ratio, Recommended T=3–70%; R=30–97% for optimum polarization purity Transmitted Beam Deviation <15 arc sec Damage Threshold 2000 W/cm2 CW, 1 J/cm2 with a 10 nsec pulse, typical 38.1 8.0 50.8 17.3 31.8 36.3 27.2 95.3 78.7 101.6 50.8 10.2 27.4 8.0 2.8 TYP 54.9 60.5 25.2 TYP 38.1 2 SCREWS, THD A SUPPLIED 2 HOLES, THD A 50.8 30.2 2 HOLES, THD A CLR 25.2 TYP 12.7 TYP 25.2 TYP 76.2 ø ø Ordering Information Model (Metric) Description Wavelength (nm) 930-44 (M-930-44) with exit ë/2 wave plate 441.6 930-51 (M-930-51) with exit ë/2 wave plate 488 & 514.5 930-63 (M-930-63) with exit ë/2 wave plate 632.8 930AB-44 (M-930AB-44) without exit ë/2 wave plate 441.6 930AB-51 (M-930AB-51) without exit ë/2 wave plate 488 & 514.5 930AB-63 (M-930AB-63) without exit ë/2 wave plate 632.8 Attention Holographers Fringe stability is key to making clear bright holograms. If the beamsplitter is lossy, local heating will cause a phase shift between the two exit beams resulting in fringe motion in the film plane. Low angular beam deviation is also critical; avoiding the need for additional compensation adjustments to eliminate spurious fringes; which could appear in the process of optimizing the contrast of real-time interference fringes. Low loss and low beam deviation make these variable attenuator/beamsplitters ideal for holographic applications.

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