Frequently Asked Questions

What is a Pyroelectric Detector?

It's a fast (sub microsecond), spectrally flat thermal detector whose current output (it's an AC current source) is directly proportional to the rate of change of its temperature: I = P(t)dT/dt. We make our Pyroelectric detectors from the Ferroelectric crystal Lithium Tantalate (LiTaO₃). The typical output for a sensitive Pyroelectric element is 1 uA/W.

What is Pyroelectric Detector used for?

A Pyroelectric detector when combined with a current mode (CM) or voltage mode (VM) electronic circuit can be used measure optical power or pulse energy. A Pyroelectric must be used with a chopped, modulated or pulsed source. To measure power (radiant flux in W) the detector and electronics are used in the flat Bandwidth frequency range where they can be calibrated in V/W. To measure pulse energy (joules) the detector and amplifier are used with pulses whose duration is less than the RC time constant of the circuit and can be calibrated in V/J. Since they operate based on a thermal phenomena they have incredibly broad spectral response - would you believe 0.1 to 1000 µm? In other terms - hard UV, Visible, Near IR, Far IR and Extreme IR. Yes - this includes the Terahertz (THz) Gap!

What is a TRAP detector and how does it work?

Optical TRAP detectors are different from single detectors - because they TRAP nearly all of the optical radiation that falls on them regardless of wavelength, by a unique, multi-bounce, multi detector and mirror design. Single detectors, on the other hand, reflect a good portion of the radiation away and that varies dramatically with wavelength. Therefore they must be calibrated against a secondary standard.

Some Optical TRAP detectors (like our SST-TRAP) exhibit nearly 100% Quantum Efficiency (QE) and therefore an absolute current responsivity determined from physical constants (RI=g /hc). This results in very low measurement uncertainty - less than 1% over a wide spectral range - 400 to 950 nm.

Thermal Pyroelectric TRAP detectors (like our SPT-TRAP) absorb nearly 100% of the incident radiation, independent of wavelength, and therefore have the same voltage response over a very broad spectral range. TRAP detectors have been used for decades in most Optical Primary Standards Labs around the world. Some of our design concepts come directly from the NIST Calibration Labs in Boulder, Colorado. Take a look at our pre-liminary Silicon TRAP data sheet on line.