We can monitor many parameters and characteristics by measuring TEN, such as surge frequency, spectrum width, threshold current, mode jump and stability of output light power.

The filter is put on the power spectrum before applying the inverse Fourier transform to yield the correlation output. This technique can be used in pattern recognition of grey level input image.

Laser compared to other lights has the characteristics of higher power, less divergence Angle, better monochromaticity, shorter light pulse and continuously tunable spectrum output.