Formaldehyde (HCHO) is an important indicator of atmospheric reactivity and one of the main precursors of urban atmospheric aerosols, which controls the oxidation capacity in the troposphere. In addition, as a toxic gas, excessive HCHO will cause great harm to human health. Therefore, it is of great significance to realize the trace detection of HCHO. The research progress of trace detection of HCHO at home and abroad is reviewed, and the detection methods of HCHO, especially the spectroscopic detection methods, are introduced in detail from the detection principle, detection spectral line and the application of light source. In addition, several typical HCHO calibration devices are compared, and different trace HCHO detection technologies are analyzed and summarized from detection sensitivity, response, selectivity, cost, integration and so on. Finally, the applications of different detection technologies in field measurement are also introduced.

As coal power is the main power source of China and one of the main sources of carbon emissions, the rapid detection of coal quality is conducive to improve the safe, low-carbon and economic operation level for coal-fired power units and promoting the intelligent development of power plants. Laser-induced Breakdown Spectroscopy (LIBS) is a rising rapid measurement technology. Because of its advantages such as no or little sample pretreatment, multi-element simultaneous analysis and online analysis, LIBS has a good application prospect in the field of rapid analysis of coal quality. This paper summarizes the basic research and application development results of the author’s team in the field of LIBS coal quality detection in recent years, with focus on the main problems encountered in LIBS coal detection and their solutions, and demonstrates the application potential of LIBS in the rapid detection of coal quality.

As important driving forces for building a wide variety of architectures and assemblies in macroscopic systems, non-covalent interactions are individually weak but collectively important. For decades of on-going pursuits on the physical origins, the portfolio of non-covalent interactions has largely expanded from conventional hydrogen bonds to diverse chemical combinations with different structural and energetic boundaries. Among many experimental techniques, rotational spectroscopy can not only offer unexplored avenues for high resolution studies in gas-phase, but also unravel the nature of non-covalent interactions in condensed phases, avoiding the interference of environmental factors. In addition, rotational spectroscopy is arguably the most accurate molecular spectroscopic technique due to its high sensitivity to mass distributions of isolated molecules and molecular complexes, even subtle differences in mass distribution (arising from isotopic substitution, isomerization, tautomerization or conformerization) can lead significant changes in the pattern of rotational transitions. In this review, the basic principles and advantages of rotational spectroscopy in characterizing non-covalent interactions are briefly introduced firstly. Then, the lastest achievements of rotational investigations in σ-hole and π-hole non-covalent interactions are comprehensively reviewed, which fully shows the ability of rotational spectroscopy in structural and energetic assessment of inter molecular non-covalent interactions, and indicates its potential contribution to the transition from fundamental understandings to applications in supramolecular chemistry and crystal engineering.

Stimulated Raman scattering (SRS) technology is a powerful method to obtain coherent radiation and explore molecular structure. SRS of O-H stretcing vibration in water molecules is studied, and it is found that SRS of water molecules excited by 532 nm laser is greatly enhanced by the application of CW (continuous-wave) seeding laser with 650 nm. When 1 mW CW laser power is introduced, the normalized SRS intensity of O-H stretching vibration at 3392 cm-1 is increased by an order of magnitude, and at the same time, two new lower frequency shoulder peaks (3356 cm-1 and 3288 cm-1) are also observed. The introduction of CW seeding laser not only lowers the threshold of SRS, but also increases the intensity of SRS. The mechanism of the enhancement of SRS intensity is attributed to that the frequency difference between pump laser (532 nm) and CW seeding laser (650 nm) matches the O-H stretching vibrational frequency of water molecule, resulting in the resonance between molecular vibration frequency and the difference frequency of the two lasers. This work shows the possibility of using resonance methods to enhance weak Raman vibration modes.

To deal with the problem of large signal noise interference in traditional Fourier transform infrared spectrometer leading to the performance degradation of the instrument, a Fourier transform infrared spectroscopy processing method based on Butterworth band-pass filter is proposed. Firstly, the transfer function of the band-pass filter circuit was deduced theoretically. Then combined with the spectrometer parameters, the specific values of the circuit components were determined by simulation using circuit software Multisim, and further optimized through experiments until the design requirements were met. Finally, the designed band-pass filter was used in spectrometer, and the signal-to-noise ratio of the instrument measured before and after adding the filter board was compared and analyzed. The experimental results show that the instrument signal-to-noise ratio obtained by the infrared spectral processingmethod based on Butterworth filter in the band of 2100～2200 cm-1 and 2500～2600 cm-1 is 1.83 and 1.96 times of that obtained by the traditional processing method without filter, respectively. It is believed that the proposed method effectively improves the signal-to-noise ratio of the instrument and the performance index of the instrument.

VIPA spectrometer, based on the strong dispersion capability of the virtually imaged phased array (VIPA), is a new type of high-performance spectral measurement technology, which has the advantages of wide spectral coverage, high time resolution, and highspectral resolution. Based on a quartz VIPA in 60 GHz free spectral region (FSR), a VIPA spectrometer for spectrum measurement in the red light band is developed, and the output spectrum of a 633 nm multi-mode laser is measured. At a time resolution of 100 μs, the output spectrum with a single measurement of 3.1 nm spectral width and 2.0 pm (1.5 GHz) high spectral resolution is obtained. And the continuous operation for 4 h shows that the spectral drift is less than 0.5 pm. The performance of the spectrometer can be further improved by using diffraction grating scanning device, area CCD with shorter exposure speed, and VIPA with larger FSR.

In view of the advantages of high utilization of optical energy and easy field of view broadening, Mach-Zehnder interferometer (MZI) has a wide range of applications in optical filtering, frequency discrimination, and so on. However, in practical applications, its spectrum will be affected by various factors, resulting in performance degradation. In this work, the theoretical expressions of MZI interference spectrum are derived considering the influence of divergence angle 2θ0 and spectrum width Δν of incident light, and then their influence on MZI spectrum is analyzed quantitatively. The results show that the larger the optical path difference l of MZI is, the more significant the influence of Δν on its spectrum is, and the greater the ratio of lto incident light wavelength λ is, the more significant the influence of θ0 on its spectrum is. When λ=355 nm and l=3 cm (the first case), Δν=10 GHz and θ0=4.5 mrad will reduce the fringe contrast K to 2.8% and 16.3%, respectively. And when λ=532 nm, l=59 cm (the second case), Δν=0.5 GHz and θ0=1.25 mrad will reduce K to 3.2% and 15%, respectively. In order to reduce the influence of the beam divergence angle, the prism field broadening technique is further studied theoretically. The results show that if the thickness d and refractive index n of the compensation prism meet the conditions of d=nl/(n-1), in the first case, K is still higher than 93.1% when θ0=50 mrad, and K will drop to 33.3% even when θ0=70. In the second case, K is still higher than 94.0% when θ0=25, and K will drop to 37.6% when θ0=35 mrad. If d takes different optimal values according to different θ0, in the first case, K is still higher than 92.1% when θ0=70 mrad. And in the second case, K is still higher than 94.4% when θ0=35 mrad.

In view of the requirements of large aperture lidar system in pollutant detection, a multi-wavelength lidar optical system is designed theoretically. The system is composed of the main receiving system and the fiber splitting coupling part, and its working wavelengths are 355, 532, 1064 nm, and the detection wavelength is 632.8 nm. The main receiving system adopts Cassegrain structure, and the fiber splitting coupling part adopts transmissive form to introduce chromatic aberration. The clear aperture of the system is Φ680 mm, and the effective focal length is 1548.53 mm. Through the selection of glass material and the distribution of optical power, the achromatic equations are established by using the corrected relative partial dispersion P andAbbe number V, and the preliminary structure is solved by PW method. The optical system is optimized by Zemax software to meet the requirements, and the final optimization results are better than λ/15 (λ=632.8 nm), which indicates that the designed optical system can be used in actual production and processing.

In order to meet the needs of large angle coverage and high information acquisition, a long working distance wide-angle industrial endoscope with visible light range is designed. The basic structure of the lens is multistage imaging, where the objective lens system adopts the reverse telephoto structure, and the transformation image system adopts the lens type. The image surface of the lens is connected with a 1/3 inch CCD. Based on the comprehensive consideration of cost and image quality, the sphericaltransmissible and unglued scheme is finally adopted. The optimization design is carried out with ZEMAX software and the image quality is evaluated. Considering the cost and image quality, the spherical transmissive and unglued scheme is finally adopted. The final lens is composed of a sapphire window, spherical lenses and a thick plane used to extend the optical path. The full field angle of the lens is 102°, a focal length is 3.25 mm and the total working length is 730 mm. The diameter of the optical system’s entrance pupil is 1 mm, the radius of the imaging dispersion spot is within 6 μm, which is close to the diffraction limit. The modulation transfer function value at 50 lp/mm is greater than 0.4, and the maximum distortion value is less than 25%. The evaluation and analysis show thatthe design results meet the technical requirements and the structure is reasonable.

The dynamics of a single Bose-Einstein condensate soliton in three different kinds of double potentials, namely symmetry double-barrier structure, symmetry double-well structure and mixed structure, with different parameters, are investigated by numerical method. A method for manipulating the position of Bose-Einstein condensate soliton is proposed, and the evolution of two solitons in double-well and double-barrier is studied. The results reveal thata single soliton will exhibit different evolutional behaviors such as oscillation, tunneling and being trapped by potential wells under the double potentials with different parameters, and two solitons will be attracted by the potential well or repelled by the potential barrier when the parameters of the double potential are controlled to appropriate values.

Through the entanglement swapping between Bell states, the relationship between the resulting state and the initial state is illustrated and utilized to design an efficient quantum secure multiparty summation protocol. In the proposed protocol, a semi-trusted third party is introduced to generate Bell states and distribute them among participants. Then according to his private data, each participant performs the corresponding encoding operations on the Bell states. Finally, all participants make Bell states measurements on the particles in their hands and achieve entanglement swapping, and the third party can calculate the summation of the private inputs based on the measurement results and the initial states. The security analysis shows that the proposed protocol is secure against external and internal attacks in theory.

In order to explore the difference of different light sources response to light source intensity fluctuation in reference-frame-independent quantum key distribution (RFI-QKD) protocol, a theoretical analysis and calculation scheme of RFI protocol key rate under imperfect light source is proposed. Through simulation, the performance of RFI-QKD protocol with weak coherence sources (WCS) is compared with that with heralded pair-coherent sources (HPCS) andheralded single-photon sources (HSPS) under intensity fluctuations with the common quantum communication parameters. The results show that compared with WCS, HSPS and HPCS have better performance and resistance to fluctuations under the same conditions, and predictable coherent light sources show best at any condition. It indicates that the proposed intensity fluctuation analysis scheme is realizable under RFI-QKD, and the simulation results can provide a valuable reference for parameterselection and optimization of RFI-QKD experimental research.

Quantum-noise randomized cipher (QNRC) is an emerging physical layer encryption scheme to improve the security of optical fiber transmission. Based on the wire-tap channel model, the transmission performance and security performance of phase shift keying (PSK) QNRC system are evaluated quantitatively with legal channel capacity and information interception probability as the performance metric, and the effects of mesoscopic power, mechanism and number of quantum state masked by quantum noise on system performance are also analyzed. The simulation results show that in order to improve the transmission performance and security performance of the system, it is necessary to use optical amplifier at the transmitting end. While ensuring the transmission performance of the system, the mesoscopic power can be reduced appropriately to improve the system′s security. Higher mechanism can improve the security of PSK-QNRC system effectively without affecting its transmission performance. The security of data is mainly limited bythe number of quantum states masked by quantum noise.

Starting from the physical equivalence between the quantum Rabi model and Jaynes-Cummings (JC) model under weak-coupling condition, rotating wave approximation, eigen energy, and dynamical evolutionof the two models are compared and analyzed, and the similarities and differences between the two models under the conditions of strong coupling and even ultra-strong coupling are summarized. Based on the physical principle that electromagnetically parametric amplification can enhance the atom-photon coherent coupling, the corresponding physical image of the transition from weak-coupling JC model to strong-coupling Rabi model is discussed. The numerical simulation results show that based on its difference and inherent relation of the ground states for the two models, the preparation of steady-state Schrdinger cat states can be realized with high efficiency by utilizing the proposed adiabatic ground-state transition scheme.

In view of the serious reality that the laser guided weapons are difficult to play their combat effectiveness due to the current active laser jamming, a dual wavelength intelligent cooperative laser guidance technology with strong anti-jamming ability isproposed. Based on the current situation and development trend of laser guided weapons at home and abroad, the overall concept of dual-wavelength multimode intelligent cooperative guidance with 1.06 μm pulse laser, 0.808 μm CW laser and Beidou Satellite Navigation System (BDS) is proposed. In the scheme, dual-wavelength multi-mode laser guidance is realized by multi-mode intelligent cooperative guidance attack technology, dual-wavelength multi-mode laser detection technology and multi-mode laser guidance anti-gamming technology. In the phase of 1.06 μm pulse laser guidance, random pulse code is adopted to prevent decipherment and laser deception jamming, and in the phase of 0.808 μm CW modulation laser guidance, narrowband filtering, correlation detection and other methods are used to resist sunlight interference. It is believed that the proposed scheme can improve the guidance performance, anti-jamming ability, and intelligent detection and identification ability of the existing laser guided weapons, and has impormant military value.

Aiming at the probe of atmospheric supercooled cloud distribution, an airborne polarization coaxial micro-pulse lidar in near-infrared wavelength is developed. The system utilizes a 1550 nm wavelengthlaser as exciting light to reduce the extinction effect of small-scale aerosol particles in the cloud, hence improving greatly the detection range and the efficiency of large-scale cloudy particles. The phase state of cloud particle is discriminated by particle depolarization ratio, and the cloudy moisture content is obtained by the proposed lidar retrieval algorithm. Then, combining the airborne temperature data and the tropospheric characteristics, the spatial distribution of supercooled cloud can be retrieved. Based on the standard atmospheric model and the cloud particle spectra from the airborne insitu instruments, the detection performance of the polarization lidar with the different wavelengths in two kinds of tropospheric clouds is simulated and analyzed. The results show that the detection range is about 1.1 km for the lower cloud, whereas the range is up to 1.5 km for the upper cloud.

In the multi-user optical code division multiple access (OCDMA) transmission system, multi-user interference (MAI) seriously affects the transmission performance of the system. In view of the fact that the multi-user interference comes from the incomplete orthogonality of codewords, the received signal and the system damage can be expressed by the autocorrelation and the cross-correlation functions of codewords. A new research idea regarding the multi-user interference as the effective information that can be reconstructed is introduced to suppress the multi-user interference, and a serial feedback interference suppression algorithm based on the digital signal processing technology is proposed. A simulation platform for two users synchronous access spectrum amplitude code optical code division multiple access (SAC-OCDMA) transmission system is built to verify the effectiveness of the algorithm in suppressing the multi-user interference. The simulation results show that compared with the optical threshold device, the serial feedback interference suppression algorithm can suppress the multi-user interference better, the improvement of the system transmission performance is greater, while the power penalty introduced is only 2.3 dB.