Improved measurement accuracy of the spot position on an InGaAs quadrant detector by introducing Boltzmann function

The InGaAs quadrant detector (QD) is mainly used for high-precision position measurement and position tracking around the 1550-nm infrared band. This paper analyzes in depth the relationship between the light spot position and the output signals of the QD where the laser spot energy displays a Gaussian profile. It's found that the curve consistently displays an "S" shape, so a new formula is obtained by introducing Boltzmann function. Simulations and experiments result show that our new formula can achieve a much better measurement of spot position accuracy.