Diffractive properties measurements

The first method used for characterization of prepared microoptical elements was the measurement of diffractive properties. The 632.8 nm He-Ne laser HN-40P-1 by Carl Zeiss Jena was used as the beam source. The beam quality was improved by using a Newport spatial filter (same as for the holographic setup, see figure 19) and the beam size was expanded to approximately 3-4 mm in diameter and paralleled by lens. The final component in the beam trajectory before the beam reached the sample was the iris diaphragm to control the diameter. The total incoming intensity of this beam was up to 3 mW, measured with a Newport hand-held optical power meter model 840-C, equipped with a Newport 818-SL silicon detector for the visible range. The detector itself is equipped with EEPROM calibration module compatible with power meter. The setup is depicted on figure 17. During diffractive properties measurement the beam was incident normal (i.e. perpendicular) to the sample. The intensity was checked before each measurement. To measure diffracted and reflected orders, the detector was always moved to the corresponding position. Only to measure the zeroth reflected (0R) order intensity, the angle of incidence was changed so that it was just nearly normal to the sample. The beam area on the sample was circular of about 3 mm in diameter to avoid influence of grating inhomogeneities.