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A theoretical model of nuclear magnetic resonance gyroscope (NMRG) has been established in this paper by the double noble gases in closed loop. The effect on the accuracy of NMRG by the external static magnetic field was analyzed. The fluctuation of the static magnetic field causes measurement error in the Earth’s rotary rate experiment. The atoms sense a constant magnetic field, when the fluctuation of the static magnetic field is compensated by the closed loop system. The results show that the Earth’s rotary rate measurement error decreases from 13.58 to 0.22°/h, which means 62 times, when the static magnetic field is compensated in closed loop. The fluctuation of the static magnetic field in the magnetic shield decreases 571 times. A higher accuracy of the NMRG is achieved when the fluctuation of the static magnetic field is effectively suppressed by the closed loop.

Experimental setup of long distance and high resolution single-pixel imaging system was set up. Images of natural target were obtained through 34 km outdoors horizontal atmosphere in daylight, about 0.8 m resolution was achieved. The multiple resolution level of Hadamard matrix was used as measurement basis, and owing to 25% compressive sampling and differential measuring by two photon-multiplier tubes, video frame rate of 2 Hz@128128 pixels was achieved with the proposed hardware and fast Walsh transform algorithm. An signal-to-noise ratio(SNR) was defined based on human-computer interaction interface to estimate the qualities of the recovered images. The relationship between image qualities and exposure times were researched. The proposed scheme has the potential application in long distance and high resolution infrared imaging with low cost setup.

Since its first experimental demonstration in 1995, ghost imaging has attracted a great deal of attention due to its potential applications. In Yanhua Shih’s paper (Meyers R E, Deacon K S, Shih Y H 2011 Appl. Phys. Lett. 98 111115; Meyers R E, Deacon K S, Shih Y H 2012 Appl. Phys. Lett. 100 131114), he pointed out that " one of the useful features is the turbulence insensitivity of thermal light ghost imaging, i.e., atmospheric turbulence would not have any influence on the ghost images of sunlight”. However, in Jeffrey H. Shapiro’s view (Shapiro J H 2012 arXiv:1201.4513 [quant-ph]), lens-less pseudo-thermal ghost imaging is not immune to spatial resolution loss from the presence of atmospheric turbulence along the propagation paths, unless the source diameter is less than the source-plane turbulence coherence length. In the present paper, we find that the second order self-correlation of sunlight intensity is the case that can be satisfied with both theories of Shih and Shapiro. In this paper, the second order self-correlation of sunlight intensity (the intensity variance of the images acquired by the CCD camera), rather than the total intensity correlation between images and bucket detector signals (the traditional ghost imaging method), is calculated to recover the high-quality images in turbulent atmosphere under a few hundred measurements. Inspired by Boyd’s paper, titled " thermal ghost imaging with averaged speckle patterns” (Zerom P, Shi Z, O’Sullivan M N, Chan K W C, Krogstad M, Shapiro J H, Boyd R W 2012 Phys. Rev. A 86 063817), turbulence insensitivity of sunlight ghost imaging is demonstrated both theoretically and experimentally in this article. It is found that thermal ghost imaging system whose coherence time need not to be controlled to match the speed of the detectors, ghost imaging with sunlight, which has always been considered intriguing and highly desirable, now is realizable. We present theoretical and experimental results showing that a sunlight self-correlation ghost imaging system can produce high-quality images even when it uses an slow detector and passes through the turbulence near ground, as long as the signal variation is predominantly caused by the fluctuation of the sunlight intensity rather than other noise sources. Our scheme can also be used to improve the image quality in other wave bands such as infrared and ultraviolet, in the case where an poor image quality results from the turbulence or other random disturbances on the wavefront.

Single-pixel imaging is a computational imaging scheme that offers novel solutions for multi-spectral imaging, feature-based imaging, polarimetric imaging, three-dimensional imaging, holographic imaging, and optical encryption. The single-pixel imaging scheme can be used for imaging in wave band such as infrared and micro wave imaging, or will be useful in the case where the array detector technique is difficult to meet the requirement such as the sensitivity or the volume. The main limitation for its application comes from a trade-off between spatial resolution and acquisition time, in other words, from relatively high measurement and reconstruction time. Although compressive sensing technique can be used to improve the acquisition time by reducing the number of samplings, the computational time to reconstruct an image is not fast enough to satisfy the real-time video. In this paper, we propose to reduce the required signal acquisition time by using a novel sampling scheme based on optimized ordering of the Hadamard basis, and improve the image reconstruction efficiency by using fast Walsh-Hadamard transform. In our method, the Hadamard basis is rearranged in the ascendant order of the values of its " sparsity” coefficients which are obtained through " Daubechies wavelets 1 (Haar wavelets)”, " Daubechies wavelets 2” wavelet transform and discrete cosine transform, and then compute each total sum of the transformed coefficients’ absolute value, respectively. The measurement order of the Hadamard basis is then rearranged directly according to Walsh order and random permutation order. The peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM) of the retrieved images are computed and compared to test all the five reordering schemes above both in our numerical simulation and outdoor experiments. We find that the reordering method based on Haar wavelet transform is the best PSNR and SSIM and it can reconstruct image under a sampling ratio of 25% which corresponds to the recovering time in which 300 frame per second @64 × 64 pixels single-pixel imaging can be achieved. The optimized measurement order of Hadamard basis greatly simplifies post processing, resulting in significantly faster image reconstruction, which steps further toward high frame rate single-pixel imaging’s applications. Moreover, we propose a novel method to optimize measurement basis in single-pixel imaging, which may be useful in other basis optimizing, such as optimized random speckles, etc.

The physical processes in the generation and the evolution of copper plasma induced by a high power nanosecond laser pulse are investigated with time-resolved spectrum. In the solid-gas-liquid phase transition, the intensity of reflected beam evolving with time markedly reveals the absorption of laser energy in the laser-copper interacting zone. So the phase transitions on the surface of copper target result in the fact that intensity of reflected beam evolving with time obviously presents a double-peak structure. Meanwhile, the appearance times of the plasma-gas-liquid phase transition on the target surface is advanced with the increase of peak-power of laser pulse. Therefore, these transient properties can be an efficient approach to diagnosing the phase transitions of copper target when the laser irradiates the target surface.

A novel optical system for detecting and controlling the time-delay value of probe light in the femtosecond pulse pump-probe measurements is presented based on the simultaneous phase-shifting interferometry scheme. The intensity distributions of interference pattern are calculated based on the Jones theory to optimize the optical system, by which the analytical expressions for phase-shifting length between the neighboring interferograms and the relevant phase-delay value are derived. To meet the requirement of practical application, possible latent errors in the process of detecting time-delay are analyzed. In particular, a minimum time-resolution with attosecond level at 800 nm wavelength was achieved. The results show that this system satisfies the requirement of femtosecond pulse pump-probe high-precision measurement.

The formation of excited atom state 5s' D 7/2 and its transition process in the copper plasma induced by nanosecond pulse laser are studied by the time-resolved spectrum technology. The experimental results indicate the recombination of electron and ion and the collisions among particles each play a dominent role in forming excited atom state 5s' D 7/2 at different tims during its evolvement. When the collisions among particles are severe, the excited atom state 5s' D 7/2 mainly transits to low energy atom state 4p' 4 F o 9/2 . 500 ns after the peak of laser pulse arriving at target surface, the excited state 5s' D 7/2 transited to 4p' 4 F o 9/2 and 4p' 4 D 7/2 with the same probabilities by emitting lines CuI465.11 nm and CuI529.25 nm respectively.