Recent progress of infrared photoreflectance and modulated photoluminescence techniques was outlined with special attention focused on the significant improvement of signal-to-noise ratio, spectral resolution and time consumption relative to the conventional techniques. Application of these techniques to molecular beam epitaxially grown HgCdTe films was given as examples, from which the potential impact of the techniques was foreseen on the optical study of narrow-gap semiconductors and inter-subband transition of wide-gap semiconductors with low-dimensional structures.