We reports improvements to our Sagnac effect matter-wave interferometer gyroscope. This device now has a short-term rotation-rate sensitivity of 6×10−10 rad s−1 over 1 s of integration, which is the best publicly reported value to date. Stimulated Raman transitions are used to coherently manipulate atoms from counterpropagating thermal beams, forming two interferometers with opposite rotation phase shifts, allowing rotation to be distinguished from acceleration and laser arbitrary phase. Furthermore, electronically compensating the rotation-induced Doppler shifts of the Raman lasers allows operation at an effective zero rotation rate, improving sensitivity and facilitating sensitive lock-in detection readout techniques. Long-term stability is promising but not yet fully characterized. Potential applications include inertial navigation, geophysical studies and tests of general relativity.

https://iopscience.iop.org/article/10.1088/0264-9381/17/12/311/pdf

Rotation sensing with a dual atom-interferometer Sagnac gyroscope

We propose and study photonic generation of broadly tunable microwave signals utilizing a dual-beam optically injected semiconductor laser. By injecting a slave laser with two detuned master lasers at the stable locking states, microwave signals with frequencies corresponding to the frequency spacing of the master lasers can be generated. Without the need for a microwave reference source, the dual-beam optical injection scheme has the advantages of low cost and less system complexity. Moreover, without the limitations of period-doubling bifurcation and Hopf bifurcation, by utilizing the period-one oscillation state with a single-beam injection scheme, the microwave signals generated with the proposed scheme have a much broader tuning range. In this paper, optical and power spectra of the microwave signals generated with the dual-beam optical injection scheme are compared with those generated with the optical mixing, the single-beam injection, and the unlocked dual-beam injection schemes. Generation of tunable microwave signals up to 120 GHz is demonstrated, which is currently limited by the locking range of the slave laser determined by the frequency difference between the Hopf (higher frequency) and the saddle node (lower frequency) bifurcation curves.

Photonic Generation of Broadly Tunable Microwave Signals Utilizing a Dual-Beam Optically Injected Semiconductor Laser

In atom interferometers based on two photon transitions, the delay induced by the difference of the laser beams paths makes the interferometer sensitive to the fluctuations of the frequency of the lasers. We first study, in the general case, how the laser frequency noise affects the performance of the interferometer measurement. Our calculations are compared with the measurements performed on our cold atom gravimeter based on stimulated Raman transitions. We finally extend this study to the case of cold atom gradiometers.

Influence of lasers propagation delay on the sensitivity of atom interferometers

We study the effect of a control beam on a Lambda electromagnetically induced transparency (EIT) system in 87Rb. The control beam couples one ground state to another excited state forming a four level N-system. Phase coherent beams to drive the N-system are produced using a double injection scheme. We show that the control beam can be used to Stark shift or split the EIT resonance. Finally, we show that the when the control beam is on-resonance one observes a Doppler-free and sub-natural absorptive resonance with a width of order 100 kHz. Crucially, this narrow absorptive resonance only occurs when atoms with a range of velocities are present, as is the case in a room temperature vapour.

Narrow absorptive resonances in a four-level atomic system

We study the effect of a control beam on a Λ electromagnetically induced transparency (EIT) system in 87Rb. The control beam couples one ground state to another excited state forming a four-level -system. Phase coherent laser beams to drive the -system are produced using a double injection locking scheme. We show that the control beam can be used to Stark shift or split the EIT resonance. Finally, we show that, when the control beam is on resonance, one observes a Doppler-free and sub-natural absorptive resonance with a width of order 100 kHz. Crucially, this narrow absorptive resonance only occurs when atoms with a range of velocities are present, as is the case in a room-temperature vapour.

https://iopscience.iop.org/article/10.1088/0953-4075/42/7/075503/pdf

Narrow absorptive resonances in a four-level atomic system.

Two single-mode laser diodes have been injection locked to the +1 and −1 diffracted orders of a 4.6-GHz acousto-optical modulator. The measured locking bandwidth was 3 GHz for a locking gain of 35 dB. The microwave signal at 9.2 GHz had a measured linewidth of less than a few hertz. We used this system to drive stimulated Raman transitions between the cesium ground-state hyperfine levels. We observed Ramsey fringes and used them to characterize the microwave signal phase noise.

K. G. Haritos

Papers

Microwave signal generation with optical injection locking.