A new optical front-end compensation technique to suppress the unwanted, spurious signal in photoreflectance (PR) spectroscopy is developed. In this approach an optical compensation signal, which is amplitude-matched to and in antiphase to the spurious signal, is introduced and directed to the photodetector. The combination of the compensation signal and the spurious signal results in a dc output from the photodetector which is thereafter suppressed by the lock-in amplifier, leaving only the true PR signal to be recovered and amplified. A high spurious signal suppression efficiency is demonstrated and the advantages of the technique are discussed.

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