Here, we demonstrate a homemade compact portable 795nm DFB laser system for atom interferometer. The whole laser system including the control unit is integrated in a module with a dimension of 345 mm×275 mm×70 mm . The laser frequency is respect to 87Rb D1 line F=2→F’=2 transition by modulation transfer spectroscopy (MTS) technique. The short-term linewidth is less than 700kHz@1.68ms, and the short-term stability of frequency is less than 157.4 kHz@1.5min (standard deviation). The output power after a single mode polarization maintaining fiber is about 30 mW, and the laser power instability is better than 0.23%@11 h (RMS) and 2.4%@11 h (peak-to-peak value). The polarization extinction ratio (PER) for output fiber is specified to be greater than 25.9 dB, and the mode-hop-free tuning range is greater than15 GHz. The compact laser system has been applied in the state selection process of our atom interferometer and achieves about 90% state preparation efficiency.
A high dynamic range MOEMS accelerometer based on multi-order diffraction method is presented in this paper. The accelerometer consists of a frequency-stabilized laser source, a diffraction grating, and a mirror attached to a mass block with symmetric cantilever beams, to achieve a few ug resolution. The traditional interferometry only uses the ±1 order diffraction, the accelerometer can obtain high measurement accuracy but the measurement range remains only several mg. This paper introduces a new interferometric method combining ±1 and ±3 order diffraction, and the model of multi-order diffraction measurement is established. The higher order diffraction intensity is proportional to the lower order diffraction intensity, so the higher order diffraction light can be used to improve the dynamic range of the system. And positive and negative order diffraction difference can suppress the common mode noise at the same time. Theoretical analysis and experimental results show that the dynamic range of accelerometer is improved by 9 times under the condition that other conditions remain unchanged.
A panoramic long-wave infrared athermal system is introduced in this paper. The proposed system includes a panoramic annular lens (PAL) block providing a stereo field of view of (30 deg – 100 deg) × 360 deg without the need to move its components. Moreover, to ensure the imaging quality at different temperatures, a refractive/diffractive hybrid lens is introduced to achieve optical passive athermalization. The system operates in a spectral band between 8 and 12 μm, with a total length of 175 mm and a focal length of 3.4 mm. To get a bright and clear image, the aperture of the system was set to f/1.15. The introduction of aspherical surface and even-order diffractive surface not only eliminates the differential thermal but also makes the structure simple and lightweight and improves the image quality. The results show that the modulation transfer function below 20 lp/mm of the system is above 0.2 at each temperature ranging from −20°C to +60°C, which is close to the diffraction limit. The system is suitable to be applied in an uncooled infrared focal plane array detector and will serve as a static alert system. It has a number of pixels of 640×480, and the pixel size is 25 μm.
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