Single-Variable Systems Experiments on Optical Bistability

2 Single-Variable Systems Experiments on Optical Bistability 

Interference filters can be made with ZnSe and alternating layers of ThF4 in a stack. Irradiation of such filters with light from an argon laser (514 nm) produces optical bistability in certain ranges of power of the irradiating light  

On irradiation of a given region of the filter there results two possible temperature profiles [8] as given by the transmitted light, or the absorbed light, as a function of the distance z, (calculated) see Fig. 7.5. 

In Fig. 7.5a the power of the incident light onto the filter is sufficient to keep most of the irradiated region in the upper (higher T) of the two possible stationary states labelled with T3. The non-irradiated region is at (about 20°C). There is a short connecting region in the lower stationary state, 

The upper and lower stable stationary states decay differently on stopping the irradiation by the laser. In Fig. 7.6 we calculated decays from the upper (a) and the lower stationary states [9]. The upper state (a) is annihilated by fronts moving inward from the boundaries the lower state (b) by the simultaneous decay of all regions at the higher temperatures toward T. From such measurements the power of the irradiating light at equistability can be determined. The plots of the measurements of the corresponding calculated plots in Fig. 7.6 are shown in Fig. 7.7. The similarities are clear. 

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