THz Circular Polarizers

Download THz Polarizers Datasheet (PDF, 791 KB)


FIR-and-THz_Polarizers

We offer polypropylene film-based polarizers for far IR and THz spectral ranges. The film is covered with sine-shaped grooves partially coated with aluminum. The result is that polarizer behaves as a transmission grating.

The transmittion spectra of the polarizers was measured by two instruments. In the short-wave range 0.9 – 670 μm (333.1 – 0.45 THz), FT spectrometer Bruker VERTEX 70 was used. In the long-wave range 150 – 3000 μm (2 – 0.1 THz) we used Menlo Systems TERA-K8 terahertz time-domain spectrometer with 600 μm dipole antenna (fc=0.5 THz).

The measurement results are given in figs. 1 and 2.

Transmittance of a polypropylene polarizer for desired polarization

Fig. 1. Transmittance of a polypropylene polarizer for desired polarization.


Transmittance of a polypropylene polarizer for unwanted polarization

Fig. 2. Transmittance of a polypropylene polarizer for unwanted polarization.

The gap between unwanted transmittance curves (fig. 2) is due to the difference between dynamic ranges (DR) of the spectrometers that affects noise level.

Bruker VERTEX 70 spectrometer has a peak DR value of 40 dB in short wavelength range, 4-5 μm. On the other hand, in 15-100 μm range its DR value is only 22-20 dB, decreasing for longer wavelengths.

Time-domain THz spectrometer Menlo TERA-K8 provides DR value of 60 dB@600 μm for electric field amplitude measurements. As a result, the unwanted polarization transmittion curves were much lower and closer to actual values for 300-3000 μm range.

The figures below depict degree of polarization and coefficient of extinction of the output radiation. Both parameters were determined from transmittance values for desired and unwanted polarization. Their values as calculated from each spectrometer data differ by several orders of magnitude due to the reasons described above.

Degree of polarization for a polypropylene polarizer

Fig. 3. Degree of polarization for a polypropylene polarizer


Coefficient of extinction for a polypropylene polarizer

Fig. 4. Coefficient of extinction for a polypropylene polarizer


Coefficient of extinction for a polypropylene polarizer

Fig. 5. Coefficient of extinction for a polypropylene polarizer, dB


The curves above clearly indicate excellent quality of our polarizers in a very wide wavelength range. Please note that actual measurement results can be different from the values given above depending on spectrometer type and measurement mode.

The table below lists guaranteed polarizer parameters.

Specifications:

Substrate material Polypropylene      
Spectral range, μm >=15
Standard aperture, mm D25
Standard rim dimensions, mm D40х8
Maximum aperture, mm 45
Grooves per mm 1200
Effective transmittance K1, %

80-95 (avg. 90)
@ 15-1500 μm

Unwanted polarization transmittance K2, %

0.2@15 μm
<0.3 @15-250 μm
<0.02 @250-3000 μm

Degree of polarization P1=(K1-K2)/(K1+K2), %

99.5@15 μm
<99.3 @15-250 μm
<99.97 @250-3000 μm

Extinction coefficient E=K1/K2 <350 @15-250 μm
<60000 @250-3000 μm

Typical applications of film polarizers include:

  •   THz microscopy;
  •   Studying molecule orientation in crystalline and polymer films;
  •   Imaging optics;
  •   Sensors and detectors;
  •   Fourier spectroscopy;
  •   THz spectroscopy studies.

Key properties:

  •   Performance in a very wide spectral range from mid-IR to THz;
  •   High transmittance in far IR and THz regions;
  •   High degree of polarization of transmitted radiation.

Polarizers are supplied in holders (protective rings marked with groove direction).

For price quotation and delivery please fill in our Request Form.