We design a fiber electro-optic modulator (FEOM)-based laser frequency-offset locking system using frequency modulation spectroscopy (FMS) with the 3F modulation. The modulation signal and the frequency-offset control signal are simultaneously loaded on the FEOM by a mixer in order to suppress the frequency and power jitter caused by internal modulation on the current or piezoelectric ceramic transducer (PZT). It is expected to accomplish a fast locking, a widely tunable frequency-offset, a sensitive and rapid detection of narrow spectral features with the 3F modulation. The laser frequency fluctuation is limited to ±1MHz and its overlapping Allan deviation is around 10-12 in twenty minutes, which successfully meets the requirements of the cold atom interferometer.
In order to obtain frequency-locked laser beam with widely tunable frequency- offset used in a clod atom interferometer, a frequency stabilization method using a fiber electro-optic modulator (FEOM) is proposed. In this method, the laser passing through a FEOM can be locked with a wide-range frequency-offset, avoiding the frequency and power jitter caused by internal modulation on the current or PZT at the same time. To evaluate the outcome of this method, a beat signal between the frequency-shifted laser and the laser locked by Doppler-free Dichroic Atomic Vapor Laser Lock was measured. The analysis of the experimental results shows that the frequency-offset of the laser beam, with a full width at half maximum less than 1 MHz, can be tuned from 200 MHz to 10 GHz, which successfully meets the requirements of cold atom interferometer.
We present an experimental set-up for the production of a beam source of cold 87Rb atoms, which is formed from a
trapped cold atomic cloud in a three-dimensional (3D) magneto-optical trap (MOT). Via a radiation pressure difference
generated by a specially designed leak tunnel along one trapping laser beam, the atoms are pushed out continuously with
low velocity and high flux. The beam was measured to have a mean velocity of 12m/s and a longitudinal velocity spread
of about 3m/s under nominal experimental conditions, based on the fluorescence and the time of flight (TOF)
technologies. And its flux can be tuned by adjusting the MOT parameters from 108 to 109 atoms/s. Especially the beam
performance dependence on trapping laser detuning and power is experimentally studied.
Two longitudinally multimode Febry-Perot diode lasers have been sideband injection-locked to the +1 and -1
sidebands of a 3.4GHz electro-optical modulator (EOM). Optical heterodyne measurement showed that powers of 99.5%
of the slave laser could be injection-locked to the +1 or -1 sidebands, and the unselected master laser carrier was
suppressed down to -24dB. Generally, the long-term stability and efficiency of the injection-locking to the +1 sideband
was worse than the -1 due to the asymmetry of the injection-locking bandwidth. The microwave signal at 6.8GHz had a
measured 3dB linewidth of less than 200Hz, without considering the noise contribution by the driving signal of the
additional acousto-optical modulator. The proposed method will be used for driving the stimulated Raman transitions in a
Rubidium based atom gyroscope.
A preparation method of cold atomic beam with fine optical characteristics is presented and discussed in this paper. The method is described as followings: cold atoms in three-dimension magneto-optical trap (3MOT) are pushed out because of the imbalanceable resonance-radiation pressure and form a cold atomic beam, whose propagation is limited in a magnetic guide. And then the atomic beam is further transversely compressed by use of two-dimension magneto-optical trap (2MOT). Finally, a state preparation laser processes the atomic beam. Consequently, the continuous cold atomic beam with lower longitudinal velocity, higher flux, much less transverse velocity and homogenous state is obtained. The simulation results show that the preparation method is feasible, which can be used in the establishment of the high-property atom interferometer.
A 3D model of a piezoelectrically actuated microjet was built to characterize acoustic wave propagation in liquid produced by the vibration of a piezoelectric transducer. The model considered the coupling between the piezoelectric transducer, the liquid and the nozzle film. Modal analysis was carried out based on numerical simulation to study the field of pressure wave. The contours of amplitude of pressure wave on the liquid-solid interface at the nozzles inlet were obtained under different resonant frequency. The results demonstrated that the transducer dominated vibration mode with an axis-symmetric distribution is more efficient for the device operation than others. The results also indicated that pressure distribution in the liquid chamber is related to driven frequencies in a different way from that of displacement of structure. The impedance analyzer was used to measure the resonant frequencies of the microjet system and validate the simulation results experimentally. The experimental results agreed well with the predicted. The microjet we developed has the optimum frequency of about 36.5KHz, which corresponds to the first axis-symmetric vibration mode dominated by the transducer, as is predicted well by the simulation result. According to comparison of pressure wave field with nozzle layout of present design under different resonant frequencies, the phenomena that the microjet behaves differently under different orders of resonant vibration are explained, and a frequency design for nozzles layout are presented according to the simulation result.
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