Experiment 10 with IR indicators:

Detection of visible laser beams using laser safety goggles

Laser safety goggles have, according to their destination, a very high absorption for the laser radiation to be tested. Therefore the laser beam remains invisible for the person who runs the experiment. There is a solution for red lasers when using the IR indicator IRI 1400, provided the laser safety goggles are permeable to green.

Required equipment

Red laser: Laser pointer (safety class 2)
Red-green stereo glasses or appropriate laser safety goggles permeable to green
IR indicator: IRI 1400
UV-A fluorescent lamp (e.g. bill detector) or daylight source
White paper

Safety measures

Laser beams may cause irreversible eye damage! Never look directly into the beam! Always wear appropriate laser safety goggles, except perhaps for laser pointer safety class 2!
Shortwave UV radiation decreases the life span of the indicator card and may cause eye damage! Use UV absorbing sunglasses!

Preparation: Charging

Expose IRI 1400 to daylight or fluorescent light (normal or UV) prior to use (charge). The charging time depends on the intensity of the exciting light. Normally, it takes some seconds. Important is the blue and UV part of the charging light. Incandescent bulbs are inappropriate because of their high IR level. It would discharge the carte simultaneously during charging.

Realization

Wear red-green glasses, cover the red glass.
First, direct red laser beam against the sheet of white paper. Nothing should be seen through the green glass.
Now, direct laser beam onto the active area of the IRI 1400. It will immediately emit green light. As soon as the red stimulated emission decreases, direct laser onto unused part of the active area or recharge the card as described above. Without green filter the effect which proves that the IRI 1400 is not only sensitive for IR light but also for red light, cannot be seen because the laser beam is much brighter than the stimulated green light.