A quadrant detector based laser alignment method with higher sensitivity

By setting the QD in an inclined position with an angle of 45°, it has been theoretically and experimentally demonstrated that around the center of QD, the sensitivity of the device to the displacement of the spot will increase by a factor of about 1.4, followed with a worth linearity of response when the displacement is expanded. To comprise this problem, a remedy based on the Laguerre–Gaussian (LG) beam is proposed so that a better linearity can be expected and the available measurement range of position is extended. Furthermore, we gave the formula to calculate the sensitivity enhancement factor and discussed its potential influence and possible compensation by making a displacement deliberately in vertical direction.