Application of thermal power shift in femtosecond

2022-08-05
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Application of electric moving table in femtosecond laser time delay

electric moving table is an essential component in femtosecond laser time delay experiment. For example, the electric moving table with 150mm travel can delay 1million body weight and greatly reduce femtosecond. The specific experimental schematic diagram is shown in Figure 1. The following will focus on the impact of various parameters of the electric moving table on femtosecond laser experiment

the experimental structure in Figure 1 is a commonly used structure at present. It realizes delay by changing the optical path. The structure in Figure 1 is analyzed below

Figure 1: schematic diagram of femtosecond laser delay experiment

the method commonly used in China is selected. Two mutually perpendicular mirrors (beam deflectors) are placed on the table surface of the electric moving table, as shown in Figure 2. In this structure, the influence of each accuracy index of the electric moving table on the optical path is discussed below

Figure 2: position of the reflector on the electric moving table

(1) influence of the parallelism of the electric moving table on the optical path: since the two mirrors are perpendicular to the electric moving table, the absolute parallelism error has no effect on the optical path, but the change of the incident point and reflection point of the beam has no effect on the optical path itself

(2) influence of electric table tilt on the optical path: when the table is tilted, it will have a great impact on the optical path. The incident angle and reflection angle have changed. The longer the optical path is, the greater the influence is. See Figure 3 for the comparison of the optical path before and after the pitching

Figure 3 (a): comparison before (green) and after (red) pitching (top view)

Figure 3 (b): comparison of light path before (green) and after (red) pitching (side view)

(3) the influence of the straightness of the electric moving table on the optical path: see Figure 4 for the influence of straightness on the optical path, which will mainly cause the translation of the emitted light. However, if the diameter of the laser spot is relatively large and the straightness error is relatively small, the influence of straightness on the optical path can be neglected

Figure 4: light path comparison before and after straightness change

(4) influence of electric table deflection on the optical path: since the two mirrors of the beam deflector are perpendicular to each other, the incident light and the outgoing light do not change before and after the deflection. See Figure 5 for the schematic diagram

Figure 5: comparison before and after yaw

previously, we discussed the influence of the electric moving table on the optical path design scheme of two mutually perpendicular mirrors, and learned that the main deviation occurs when the pitch occurs. To avoid pitching, three mutually perpendicular mirrors (retroreflectors) can be used to replace the beam deflector. Figure 6 shows the appearance of the retroreflector

figure 6:retroreflector

due to the femtosecond delay, the most important and longest failure of the retro FL sensor is mainly the overload of the experimental force E. in addition, the material of the component is a metal ctor instead of the previously used beam deflector, which basically eliminates the impact of the deflection and pitch on the optical path caused by the movement of the electric table; But it has caused another problem: when using the speed of light deflector, the parallelism of the electric moving table has no effect on the optical path, but when using retroreflector, the parallelism of the electric moving table has an effect on the optical path. See Figure 7 for the retroreflector light path diagram

Fig. 7: optical path diagram of retrpreflector

after using retroreflector, the influence of electric table deflection and pitch on femtosecond delay experiment is eliminated. When the accuracy of the electric moving table is low, that is, the laser spot diameter is much larger than the parallelism and straightness of the electric moving table, the influence of the straightness of the electric moving table can be ignored. However, if the experiment requires high accuracy (parallelism and straightness) of the electric moving table, that is, when the laser spot diameter is not much different from the straightness and parallelism of the electric moving table, the influence of the straightness of the electric moving table cannot be ignored

in addition, since the mutual perpendicularity of the retroreflector's three mirrors has a great impact on the optical path, the existing products are all produced by foreign manufacturers with high costs, which is also one of the reasons why Li Hongwei, general manager of interto (Qingdao) tire technology Co., Ltd., which restricts the use of this method in China's experimental research, said. (end)

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