SST-TRAP-C and SST-TRAP-D: Silicon Optical Trap Detectors

Precise, High Quantum Efficiency, Calibration Transfer Standards

We have designed a series of large aperture, high quantum efficiency optical TRAP detectors based on a unique concept developed at NIST Boulder (National Institute of Standards and Technology. We offer two models; SST-TRAP-C and SST-TRAP-D. The first is best suited for collimated or low divergence sources (<+/-10°) while the second is optimized for both collimated and divergent sources (<0.24 NA or +/-16°).

Optical TRAP detectors are intended for use in optical calibration of FO power meters, laser power meters and optical detectors. The Current Responsivity of our TRAP is determined from "physical constants" and is therefore, accurate to better than 1% from 450 to 980 nm (see "Calibration Uncertainty" in the table below). Compare this to the typical calibrated single element detector at +/-3%.

These detectors are designed into an EMI immune housing with a front bezel that includes a 1.035-40 threaded opening (THORLABS(TM) SMI) and is set to take a variety of Fiber Optic connectors, optics or alignment aids. The TRAP can be easily mounted to an optical bench with the 1/4-20 inch threaded mounting hole.

Use our SST TRAP Detector with our SST Power/Current Meter to create a complete, stand-alone, precision optical power meter.

Theory of Operation

By combining several high Quantum Efficiency photodiodes and a large, concave, broadband mirror in a multi-bounce optical configuration we can TRAP 99% of the light in the spectral range of 400 to 950 nm. The current responsivity at a particular wavelength for such a device is determined from physical constants in the equation:

R_I = qνλ / hc

Where: q is the "charge of an electron"

• ν is the "quantum efficiency"
• λ is "wavelength in m"
• h is "Planck's constant"
• c is "speed of light"

It can be simplified for everyday use to:

R_I (A/W) = νλ /1239.5

Where:

• ν is Quantum Efficiency
• λ is wavelength in nm

1239.5 is determined from physicalconstants (electron charge, planks constant, speed of light)

Here’s an example of how you’d calculate the RI for our TRAP at 632.8 nm:

R_I @ 632.8nm = 0.99 x 632.8 / 1239.5

R_I = 0.505 A/W