METHOD AND APPARATUS FOR REFLECTING LIGHT USING ACOUSTIC OPTICAL MODULATION

摘要

PURPOSE: To improve the measurement of the characteristics of a material based on light reflectivity by directing probe beam of monochromatic light and acoustooptically modulated pump beam to a sample. CONSTITUTION: The probe light of a light source 50 passes through the monochrometer 51 driven by the stepping motor 52 to be condensed to a sample 62 to become a variable wavelengthλand the pump beam of a light source 63 becomes a variable wavelengthλp by a stepping motor 92 and a monochrometer 62 and receives the modulation of frequencyΩm by an acoustooptical modulator 54 to direct the sample 62. The beam reflected from the sample 62 is condensed to a detector 56 to become a DC signal and an AC signal and the AC signal is applied to a two-phase lock-in amplifier 55 and a DC analogue signal is subjected to A/D conversion 66 to be inputted to a computer 70. The computer 70 has function performing control, data collection, the analysis of data containing a light reflecting spectrum and the comparison of the related parameter obtained by the analysis of the data and a logical model and evaluates the characteristics of the heterostructure of a semiconductor and changes the wavelength of pump beam and modulation frequency to measure the interfacial characteristics of a component layer.