Sciencetech manufactures large diameter grid polarizing beam-splitters for use in the far-infrared and terahertz spectral regions. These beamsplitters divide the incoming beam according to its polarization. The beam-splitter consist of very fine parallel aluminum lines spaced 4 µm apart on a thin mylar substrate. The aluminum lines are made through a lithographic process. The polarized light with wavelengths longer than the spacing between the lines with a very high degree of polarization. This beam splitter has the largest clear aperture available on the market for this type of device. This is especially important in the far-infrared and terahertz spectral region, where energy is at a premium. It also has the widest spectral range with a higher frequency cut-off than that of other polarizers that work in the near-millimeter wavelength range. The Sciencetech GP beam splitter is less sensitive to the angle of incidence than regular polarizers. Its line width and pitch are consistent throughout the whole area, making it especially good for interferometric applications. The standard frame is made of black anodized aluminum with an outside diameter = active internal aperture + 1.5". Special stainless steel frames are also available, ground to a flatness of better then 2 µm. The masters of the Sciencetech P280 polarizers are produced by Sciencetech's special holographic process and reproduced on a film substrate coated with aluminum using photo-lithographic techniques.
 
Effective Spectral Range
The Beam splitter polarizer will polarize well up to λ/4 meaning the minimum wavelength would be 4 times the pitch. Since this beam splitter has a 4 µm pitch, it starts working well (degree of polarization over 80%) at 16 µm. For 1,200 l/mm (or pitch of 0.8 µm) of other beam splitters, it would start working at 3.2 µm and so on.
 
Application: Vibrational Circular Dichroism (VCD)
The measurement of vibrational circular dichroism (VCD) below ~600 cm^-1 is one of the experimental challenges of the current times. Polarization-division interferometry is considered to be the most efficient approach for realizing these measurements. A crucial component for successful applications of this interferometry is the beamsplitter, which divides the incoming beam according to polarization.
 
Orientation of Grid Lines
The direction of the grid polarization lines are indicated by an arrow on the ring surface. The direction of the arrow is parallel to the lines of the polarizer. Besides using this arrow indicator, there is a relatively simple way to check the direction of polarization. Using any visible-beam laser, put the polarizer in the path of the beam. Since the grid-polarizer acts like a transmission grating, the beam will be split after passing through it (into its various “orders” of light). The direction the points of light appear is perpendicular to the grid (and therefore perpendicular to the direction of polarization).
 
Technical Specifications

• Wavelength Range: 12.5 - 5000 µm (2 - 800cm^-1)
• Grid Pitch: 4 µm
• Grid Metal: Aluminum
• Conductors cross section: 2 µm wide, 0.7 µm thick
• Manufacturing Process: Photo-Lithography
• Transmitted Intensity: >85% for wavelengths > 30 µm, >70% at 16 µm
• Degree of Polarization: >95%
• Substrate: Polyethylene Terephthalate, 6 or 12 µm thick Custom thicknesses from 1.5 to 50 µm available Other substrates available

Ring Holder (Frame around filter)

• Standard Ring Holder: stainless steel
• Custom Ring Holder: stainless steel and aluminum interferometric frames for any size available on special requests
• Outside diameter of Stainless Steel Holders: active aperture + 0.8"
• Directional Arrow Marker showing orientation of grid lines