THz Measurements

THz Measurement

The unique characteristics of THz radiation make it useful in such applications as medical imaging (for example cancer detection), materials characterization, high speed communications, and homeland security surveillance.

The way it gets selectively transmitted or absorbed by different materials enables imaging through optically opaque materials in security applications. Terahertz wavelength radiation may also be used to analyze the inner structure of materials, medicine, or food due to the unique spectral signature of various compounds in the THz spectral region. This has opened many possibilities for spectroscopic analysis in industrial and scientific applications.

As in any application involving precise use of light, measurement becomes an important issue. Measurement of THz radiation, though - especially calibrated measurement -presents some technical challenges:

  • Power levels are as low as nW, up to several hundred mW.
  • The low photon energy (in the range of meV) makes detection using photodiode sensors very difficult. This means that thermal or pyro-electric sensors are needed – but they are normally not quite sensitive enough.
  • Finding a suitable absorber for the THz spectral region is not trivial.

Ophir offers power measurement solutions from the highest to the lowest power levels, depending on the needs of any given application, as well as beam profiling solutions.

At the higher powers: The 3A-P-THz is a power sensor based on thermal detector principles, and measures short pulse and CW beam powers up to 3W. The 3A-P-THz is calibrated for THz measurements by the PTB national metrology institute in Germany. (In fact, PTB itself has used a modified Ophir 3A-P sensor as a new standard, to increase the accuracy of their own THz calibrations!)

At the lowest powers: The RM9-THz is a complete sensor measurement package that includes a NIST-calibrated pyroelectric sensor with a special THz absorber, an 18Hz chopper, and a digitally synthesized lock-in amplifier, to enable measuring THz beam powers as low as 100nW.

These sensors, compatible with all standard Ophir meters and PC Interfaces, enable you to perform accurate, calibrated and fully traceable power measurements of THz beams across a wide spectral range.

Beam Profiles of THz beams can be measured and analyzed using instruments such as the Pyrocam III-HR or Pyrocam IV.

Articles

Bridging the THz Gap in Radiometry

The Renowned German standards laboratory Physikalisch-­ Technische Bundesanstalt – PTB, has now developed a highly accurate calibration standard for calibrating Terahertz radiation based on a modified Ophir 3A-­P meter.
First performed at 2.52 THz only, PTB has now extended its unique detector-­ based radiometric calibration service to the full tuning range of a Terahertz laser spanning from 1 THz to 5 THz. Read more >

THz Beam Measurement A Practical Primer

- THz Range available to the user
- Wavelengths and Frequencies
- Tools to Image THz beams
- Optics- Type and Sources
- Cameras and Other Sensors
- Results
Read more >

There’s now a standard sensor for terahertz laser measurement

When you think of electromagnetic radiation, what pops into your head? X-Rays? Radio waves? Microwaves? Or maybe just plain old light.

What most people don’t think about – or hadn’t until recently – is the small gap in between microwaves and infrared light waves. This gap is called Terahertz, as it represents waves with a frequency of about 0.3 to 10 THz. In the last few years, there has been significant advancement in THz sources and imagers, leading to a lot of talk about T-Rays replacing X-Rays.
Read more >

Relevant products