二次光栅在波前测量中的应用

采用一种特殊的二次光栅用于激光波前测量,它对非零级衍射光束具有不同的聚焦效应,其光栅线为圆弧型而非直线。导出了在会聚光束情况下的两平面成像在单一像平面上的距离关系,实验上实现了二次光栅用于会聚光束的波前测量,测量得到会聚光束具有较大的散焦(-2.93λ)和球差(1.34λ),与该透镜引起波前的离焦像差理论理想值(-2.695λ)基本符合。该技术可以实现波前的高空间分辨力和高精度实时测量,大大减少光学元件数量,降低装置成本。由于大功率激光束的不稳定性,其波前变化非常快,所以该方法的实时性非常适合于这种波前变化的测量。

Wavefront Measurement by Using Quadratic Grating

A laser wavefront measurement technique by using a special quadratic grating is reported. The quadratic grating has a different focusing power in nonzero orders, for the grating lines are not line but arcs of circles, and multiple planes can be imaged onto a single image plane. The spacing relation between two planes imaged on a single plane was deduced for a convergent beam. The experiments of measuring convergent beam wavefront with a quadratic grating are carried out. It is found that the defocusing aberration is as large as -2.93λ and the spherical aberration is equal to 1.34λ, which are in good agreement with theoretical ones(the defocusing aberration is -2.695λ, λ supposed to be wavelength). This technology can realize real-time wavefront measurement with high spatial resolution, high phase accuracy, low cost and simple structure. Because wavefront of high-energy laser beam usually changes rapidly, this real-time technology is a useful measurement method on this application.