| Abstract [eng] |
In this work variety of different photothermal techniques were introduced. One of the aims of this work was to find the most suitable non-destructive and contactless method to measure absorption of glass or crystal bulk and thin film coatings which will allow to characterize the quality of these optical elements. It was found that the best option here is Common path interferometry (CPI) which allows to measure absorption up to 10-8 cm-1. This technique uses two lasers – one is used as pump, the other as probe. The pump laser is modulated using a chopper and induces pulsing thermal lens in the sample. At the same time the probe beam with bigger waist passes this thermal lens and is distorted. The phase shift initiates interference between distorted beam center and the rest of the beam. After some distance phase shift transforms to the intensity distortion which can be detected with photodetector and lock-in amplifier. The aim of this work is to introduce method of measuring absorption in optical and laser elements using common equipment that can be found either in scientific laboratory or in optical metrology lab. With working interferometer, one will be able to measure coating and bulk absorption of glass and crystals (and Figure of Merit for some crystals to be more precise). This will allow to qualify and certify the quality of the elements. This is very important nowadays, when high power CW lasers are taking bigger and bigger share in the market. |
