ABSTRACT
We design and develop a high-performance magnetic shielding system for a long baseline fountain-type atom interferometer. The shielding system is achieved by a combination of passive shielding using permalloy and active compensation with coils. An 11.4 m-long three-layer cylindrical shield is completed by the process of welding, local annealing, and entire annealing. The active compensations compress the residual magnetic field to 8.0 nT max-to-min and the corresponding gradient below 30 nT/m over 10 m along the axial direction in which external compensation, internal compensation, and constant magnetic field (C-field) compensation reduce the inhomogeneities to 25.0, 12.6, and 1.7 nT (standard deviation) sequentially. We estimate that this system could reduce the systematic error of the quadratic Zeeman shift to the 10-13 level for the weak equivalence principle test with a simultaneous 85Rb-87Rb dual-species atom interferometer.
ABSTRACT
We design and implement a laser system for 85Rb and 87Rb dual-species atom interferometers based on acousto-optic frequency shift and tapered amplifier laser technologies. We use eight-pass acousto-optic modulators to generate repumping lasers for 85Rb and 87Rb atoms. The maximum frequency shift of the laser is 2.8 GHz, and the diffraction efficiency is higher than 20%. We use high-frequency acousto-optic modulators to generate the Raman lasers. This laser system uses only two seed lasers to provide the various frequencies required by 85Rb and 87Rb dual-species atom interferometers, which greatly improves laser usage. The laser system is applied in the equivalence principle test experiment using an 85Rb and 87Rb dual-species atom interferometer. The signal of atoms launched to 12 meters is successfully observed, and the resolution of gravity differential measurement is improved from 8×10-9 g to 1×10-10g.
ABSTRACT
We present a method to characterize and optimize a tapered-amplifier laser system (TALS) by its spectral quality through a long multi-pass rubidium absorption cell. A thermal vapor cell is used to measure the non-resonant spectrum of TALS, including the broadband amplified spontaneous emission (ASE), which is its main spectral noise. This method gives a simple quantified measurement to optimize various working parameters of a TA, including current and temperature online. It can as well be used to compare various TA chips based on their usage time during our precision measurement experiments. The results of this method are compared and found in sync with traditional methods of Fabry-Perot cavity and beat measurements. Such characterization and optimization are important for noise control in atom interferometers, atomic clocks, and other atomic manipulations. It can very well be used for investigating nonlinearity and ASE inside amplifying chips and can be utilized in other applications of ASE using bioimaging.
