Gentec-eo THZ-D Manuel d'utilisateur télécharger pdf (Page 16)

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4 DAMAGE TO THE OPTICAL ABSORBER MATERIALS

At any time, the beam’s incident area should not be less than 10% of the detector’s aperture.

Please check with Gentec-EO to make measurements with such small beams.

Damage is usually caused by exceeding the manufacturer is specified maximum tolerances:

- Average Power Density

- Peak Power Density

- Single Pulse Energy Density

Refer to the THZ-D Series wattmeter specifications pages. Damage can also be caused when

using a detector with a contaminated absorber or attenuator surface.

The damage thresholds specified in the specifications section refer to a visible alteration of the

absorber surface. In practice, a slight alteration will not affect the wattmeters response. Consider

the wattmeter to be damaged and/or out of calibration when large-scale damage is evident or you

can see the metal electrode beneath the coating

In the case of a TEMoo (Gaussian) beam, the maximum peak power and energy density can be

calculated using the following equation:

Density (power or energy)  2Io

W

Where Io is the total beam power or energy

W is the beam radius at 1/e

and  = 3.1416

NOTE: The beam waist for a TEMoo beam is the radius of a circle centered on the beam axis and

containing 86 % of the beam energy. Ref.: SIEGMAN, A.E., An Introduction to Lasers

and Masers, p. 313 (Mcgraw-Hill Series in the Fundamentals of Electronic Science).

Example of energy density;

Io = 1 joule (total energy)

W = 1 cm

Energy density = 2 x 1 joule = 0.64 joule/cm

 x (1 cm)

Example of power density calculation;

Io = 1 MegaWatt (total power)

W = 1 cm

Power density = 2 x 1 MegaWatt = 0.64 MW/cm

 x (1 cm)

Contact Gentec-EO for evaluation, repair, recalibration, or replacement (refer to the WARRANTY

instructions).

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Gentec-eo THZ-D Manuel d'utilisateur Page 16