Dual-modulated and dual-light-path spectrometer for modulated reflectance measurement

A technique of dual modulation and dual light paths is introduced into modulated reflectance measurement. Dual modulation with same phase can greatly reduce the background noise and eliminate laser scattering disturbance in Photoreflectance (PR) and electromagnetic interference in Electroreflectance (ER), respectively. So it can enhance signal-to-noise ratio and spectrum resolution for line-shape analysis. The dual-path measurement carries out real-time calibration to get rid of affection of light source dithering and electronic circuit fluctuation. Two measuring examples are presented to indicate the advantage of the dual-modulated and dual-light-path spectrometer.