Light shift produced by the AC Stark effect is one of the major factors limiting the accuracy and long-term stability of a cold atom interferometer. The first order light shift can be canceled by fixing the power ratio of the Raman beams at a specified value. We report here a new method to stabilize the power ratio of the two Raman lasers with ∼100 kHz locking bandwidth, suppressing the effect of the first order light shift. We first mixed the two Raman lasers (at different optical frequencies) with a reference beam and then used two Schottky diode detectors to extract the corresponding beat note signals for each beam, which are much easier to be manipulated and processed as they are in the microwave band. The stability of the power ratio is improved by three orders of magnitude from 5.84 × 10−3 to 3.51 × 10−6 at 1 s averaging time and reaches 1.59 × 10−7 at 10 000 s integrating time when the servo loop is engaged. This method can be used in other precise quantum measurement based on the stimulated Raman transition and can be applied to compact inertial sensors.
Light shift produced by the AC Stark effect is one of the major factors limiting the accuracy and long-term stability of a cold atom interferometer. The first order light shift can be canceled by fixing the power ratio of the Raman beams at a specified value. We report here a new method to stabilize the power ratio of the two Raman lasers with ∼100 kHz locking bandwidth, suppressing the effect of the first order light shift. We first mixed the two Raman lasers (at different optical frequencies) with a reference beam and then used two Schottky diode detectors to extract the corresponding beat note signals for each beam, which are much easier to be manipulated and processed as they are in the microwave band. The stability of the power ratio is improved by three orders of magnitude from 5.84 × 10−3 to 3.51 × 10−6 at 1 s averaging time and reaches 1.59 × 10−7 at 10 000 s integrating time when the servo loop is engaged. This method can be used in other precise quantum measurement based on the stimulated Raman transition and can be applied to compact inertial sensors.
Raman pulse sequences are generally used to coherently manipulate the atomic wave packet in an atom interferometer.High power Raman beams allow more atoms join in the velocity-sensitive stimulated Raman transition,and that will be helpful for obtaining high signal to noise ratio in atom interferometer fringe.Development of high power Raman laser is important for cold atom interferometer experiments.The experimental realization of high power Raman lasers are demonstrated based on injection locking technique. Master laser is modulated by a 1.5 GHz acousto-optical modulator,and the±1 order diffraction lights are used as seeding Raman lasers.The seeding lasers are injection locked to two slave lasers which are further amplified as Raman beams.The frequency difference of Raman beams is 3.0 GHz,and the detuning range is about 200 MHz.
We present a low-phase-noise microwave control system designed for spatial-domain atom interferometers, featuring the independent outputs of three microwave channels with minimal relative phase noise between them. Utilizing a nonlinear transmission line and single-sideband mixing with a digital signal source, we achieved three channels of 6835 MHz microwave frequency outputs, exhibiting absolute phase noises of −55, −100, and −124 dBc/Hz at 1 Hz, 1 kHz, and 1 MHz frequency offsets, respectively. We measured the relative phase noise between channels for a root mean square value of ∼251 μrad. A servo loop was integrated to stabilize the power ratio between Raman laser frequency components, ensuring long-term elimination of light shifts in the atom interferometer. The waveform parameters of the three microwave outputs can be adjusted independently, allowing for flexible manipulation of the atomic interference phase. These capabilities make the proposed microwave control system highly suitable for precise frequency and phase modulation in atom interferometer-based gyroscopes and accelerometers operating within continuous spatial-domain configurations.
We present the investigation on the frequency-dependent amplification (FDA) of a tapered amplifier (TA) and the corresponding influence on Raman-type atom interferometers. In our interferometer, the output of two phase-locked diode lasers is injected into a TA to generate Raman beams. The frequency of one laser is chirped during the interfering process, which induces a variance of the Raman lasers power as a result of the FDA of the TA. The corresponding power ratio variation of the Raman lasers is measured by beat note method, which shows a linear dependence with a slope of -0.087(4)/GHz when the laser frequency changes over 2 GHz at 780 nm. The corresponding error related to AC Stark effect due to this frequency-dependent variation is estimated for our atom interferometer. The investigation presented here may provide hints for other experiments involving TAs.
Monitoring and stabilizing the power ratio of laser pairs is significant for high-precision atom interferometers, especially as the compact electro-optic-modulated all-fiber laser system prevails. In this Letter, we demonstrate a novel, to the best of our knowledge, method to in situ probe the relative power of laser pairs and to stabilize the power ratio of two Raman lasers using a high-dispersion virtually imaged phased array (VIPA) etalon. Sub-microsecond resolution on probing laser power transformation during the atom interferometer sequence is achieved and the power ratio of two Raman lasers (PRTR) is tightly locked with high bandwidth despite environmental disturbances, showing an Allan deviation of 4.39 × 10−5 at 1000 s averaging time. This method provides a novel way to stabilize the PRTR and diagnose multi-frequency laser systems for atom interferometers, and it could find potential applications in broad quantum sensing scenarios.
We demonstrate a closed-loop light-pulse atom-interferometer inertial sensor that can realize continuous decoupled measurements of acceleration and rotation rate. The sensor operates with double-loop atom interferometers, which share the same Raman light pulses in a spatially separated Mach-Zehnder configuration and use continuous cold atomic beams propagating in opposite directions from two 2D+ magneto-optical trappings. Acceleration and the rotation rate are decoupled and simultaneously measured by the sum and difference of dual-atom-interferometer signals, respectively. The sensitivities of inertial measurements are also increased to be approximately 1.86 times higher than that of a single atom interferometer. The acceleration phase shift is compensated in real time by phase locking these interferometers via the Raman laser phases from the sum-interferometer signal, and the gyroscope performance is improved. We achieve long-term stabilities of $6.1\phantom{\rule{0.2em}{0ex}}\text{\ensuremath{\mu}}\text{g}$ and 840 nrad/s for the acceleration and the rotation rate, respectively, using a short interrogation time of 0.87 ms (interference area A=0.097mm2). This work provides a building block for an atomic interferometer-based inertial measurement unit for use in field applications that require a high data rate and high stability.
Using the electro-optical modulation method to generate Raman beams for cold atom interference is one of the better methods for constructing a more compact and robust laser system. But this way will generate some residual sidebands resulting in the additional interference phase shift, which can affect the measurement accuracy of cold atom interferometer. In order to weaken the effect of laser modulation sidebands on the phase shift of cold atom interference, a double-sideband suppressed-carrier modulation laser system for cold atom interference is constructed. Based on the designed laser system, the principle of double-sideband generation and suppression is analyzed in detail, and some residual sidebands are adjusted and controlled. Moreover, some important optical parameters that affect the phase shift of cold atomic interference, such as the initial distance between the Raman retro-reflection mirror and the atomic cloud, the interrogation time between two adjacent Raman pulses, the laser modulation depth and the initial velocity of the atomic cloud, are discussed and optimized. By optimizing these relevant parameters, the influence of residual modulation sidebands on the phase shift of cold atomic interference is weakened drastically. The research results indicate, making use of the method of double-sideband suppression, the phase shift of cold atomic interference can be optimized to 0.7 mrad when the initial distance between the Raman retro-reflection mirror and the atomic cloud is 105 mm, and the interrogation time between two adjacent Raman pulses is 82 ms. More importantly, this work can provide a method for weakening the influence of Raman sideband effect on the phase shift of cold atom interferometer, and the corresponding laser system can be applied to other inertial sensors such as atomic gravimeter or atomic gravity gradiometer.