Optical rotation detection method based on acousto-optic modulation in an atomic spin co-magnetometer

Abstract

Abstract A new concept for probe light intensity stability control and high-frequency modulation based on an acousto-optic modulation in a K-Rb- 21 Ne co-magnetometer is reported. The structure and optical path are ingeniously designed to avoid the interference of zero-order diffraction light. The average rotation rate sensitivity of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mtext>7</mml:mtext> </mml:mrow> <mml:mrow> <mml:mtext>.9</mml:mtext> </mml:mrow> <mml:mo>×</mml:mo> <mml:mrow> <mml:mtext>1</mml:mtext> </mml:mrow> <mml:mrow> <mml:msup> <mml:mrow> <mml:mtext>0</mml:mtext> </mml:mrow> <mml:mrow> <mml:mrow> <mml:mtext> - 7</mml:mtext> </mml:mrow> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mtext>rad</mml:mtext> </mml:math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msup> <mml:mtext>s</mml:mtext> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msup> <mml:mtext>Hz</mml:mtext> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> <mml:mrow> <mml:mo>/</mml:mo> </mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> is achieved under the light intensity closed-loop control condition and the bias instability calculated by the Allan deviation is improved from 0.13 deg h −1 to 0.06 deg h −1 comparing with open-loop scheme. A square wave modulation with a wide range of frequencies is applied to the probe light intensity and the appropriate modulation frequency for the co-magnetometer is tested to be 10 kHz to 300 kHz and megahertz scale. Finally, the closed-loop control of light intensity has been combined with the high-frequency modulation, which could suppress the low-frequency noise contained in the probe system and improve the long-term stability of the angular velocity measurement.