Abstract
In order to improve the precision and beam quality of a pump laser for a spin exchange relaxation free inertial measurement device, we applied one scheme to achieve the square wave modulation and power stability control of the pump laser and another one to obtain the uniform intensity distribution of the laser beam, in which the acousto-optic modulator (AOM) and proportion integration differentiation (PID) controller were used to achieve the former, and the freeform surface lens was designed and optimized to achieve the latter based on the TracePro software. In experiments, the first-order diffraction light beam coming through the AOM had a spot size of about 1.1 × 0.7 mm2, and a spherical vapor cell with a radius of 7 mm was placed behind the freeform surface lens. Results show that the uniformity of the reshaped intensity distribution is higher than 90% within the target area with a radius of 7 mm both in the simulation and the experiment, which ensure that the uniform laser beam covers the area of cell. On the other hand, the power stability of the pump laser is controlled to be less than 0.05%. Compared with traditional methods, the complicated calculation process in optical design is better solved, and a higher uniformity with slight energy loss is achieved.
Highlights
An alkali-metal-noble-gas device has found applications in the measurement of inertial rotation [1,2,3], Lorentz and CPT violation [4,5], anomalous spin forces [6,7], etc
We applied one scheme to achieve the square wave modulation and the power stability of a pump laser, and another one to get the uniform intensity distribution of a laser beam, in which the acousto-optic modulator (AOM) and proportion integration differentiation (PID) controller are used to achieve the former, and the freeform surface lens is designed and optimized to achieve the latter based on the TracePro software
The total power of the laser was adjusted by a half-wave plate (HWP) and polarization beam splitting (PBS), and the mode of square wave modulation of the laser was realized by the first-order diffraction light of the AOM controlled by a switch driving signal
Summary
An alkali-metal-noble-gas device has found applications in the measurement of inertial rotation [1,2,3], Lorentz and CPT violation [4,5], anomalous spin forces [6,7], etc. Compared with the other beam shaping methods [26,27,28,29,30], the method with a freeform surface lens [31,32] with a high degree of freedom and less energy loss is better for achieving the uniform distribution of intensity of non-ideal laser sources. We applied one scheme to achieve the square wave modulation and the power stability of a pump laser, and another one to get the uniform intensity distribution of a laser beam, in which the acousto-optic modulator (AOM) and proportion integration differentiation (PID) controller are used to achieve the former, and the freeform surface lens is designed and optimized to achieve the latter based on the TracePro software
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