Lesliejunker0701

High mechanical stress can affect the performance of multilayer thin film optical coatings, causing wavefront aberrations. This is particularly important if the multilayer stack is deposited onto thin substrates, such as those used in adaptive optics. Stress in thin film coatings is dependent on the deposition process, and ion beam sputtering (IBS) thin films are known to have high compressive stress. In the present work, we show that stress in IBS $ \rm SiO_2 $SiO2 thin films can be reduced from 490 MPa to 48 MPa using high-energy $ \rm O_2 $O2 assist ion bombardment during deposition while maintaining high optical quality. A comparison of the reduction of stress in $ \rm SiO_2 $SiO2 deposited from oxide and metal targets is provided.In this paper, a novel phase-sensitive optical time-domain reflectometry ($\Phi $Φ-OTDR) based on the optimized dual-pulse heterodyne detection scheme (DHDS) is proposed, which is designed to implement distributed vibration sensing with low phase noise and high sensitivity. The optimized DHDS employs an unbalanced interferometer to separate a light pulse into dual probe pulses so that they are generated by the laser at the same time. This ensures that the measurement sensitivity of a phase-interrogation-based $\Phi $Φ-OTDR can be improved simply by increasing the space interval of the dual probe pulses while the phase noise of the $\Phi $Φ-OTDR does not deteriorate. In addition, the proposed DHDS utilizes only one acousto-optic modulator (AOM) to shift the frequencies of the dual probe pulses so as to eliminate the effects of frequency shift jitters, and thus guarantees low phase noise level of a $\Phi $Φ-OTDR. The distributed vibration sensing performances of the $\Phi $Φ-OTDR with the proposed DHDS are theoretically and experimentally studied in terms of multi-event signal restoration and phase noise level. The proposed approach solves the contradiction between the measurement sensitivity and phase noise of a $\Phi $Φ-OTDR and promotes the $\Phi $Φ-OTDR to the applications of distributed weak vibration sensing.In this paper, we propose an optical single-channel asymmetric cryptosystem for multi-image in cyan-magenta-yellow-black (CMYK) color space. To the best of our knowledge, this is the first time that multiple images in CMYK color space have been directly encrypted. The proposed optical asymmetric cryptosystem is based on the quick response (QR) encoding process and the designed Fresnel-linear canonical-fractional Fourier transform (FLFT) encryption process. Each FLFT encryption process consists of phase-truncated FLFT and random amplitude phase masks. The proposed cryptosystem without color space conversion can improve the quality of the decrypted images and avoid the loss of information. In addition, by utilizing the QR codes, the cross talk and quality-loss problems can be reduced efficiently. Numerical simulation results demonstrate that the proposed cryptosystem possesses high robustness against various types of attacks, high security for encrypting multiple color images, and fast encryption efficiency. Furthermore, the proposed cryptosystem outperforms the other relevant cryptosystems and can be extended to encrypt multiple color images in a straightforward way.The 2019 Optical Interference Coatings measurement problem comprised the determination of the total backscattering, forward scattering, reflectance, and transmittance spectra of a multilayer system.The development of photonic quantum information technologies requires research on the properties of optical adhesives at cryogenic temperatures. In the process of developing microfiber (MF)-coupled superconducting nanowire single-photon detectors (SNSPDs), we invented a cryogenic-temperature refractive index (RI) measurement method based on a kind of MF device. The device was put into the cryostat to observe the variance of MF transmittance with temperature. Then an RI-temperature relationship was established through the correspondence between the confinement conditions of MFs of various diameters in an optical adhesive-$\rm MgF_2$MgF2 environment and transmittance-temperature curves. Using this method, we analyzed the thermal-optical properties of a commercial fluorinated acrylic optical adhesive and obtained the RI values of the adhesive at various temperatures. The results were successfully applied in the development of broadband and high-efficiency MF-coupled SNSPDs.In a recent publication [Opt. Lett.43, 4727 (2018)OPLEDP0146-959210.1364/OL.43.004727], a novel class of partially coherent sources with complex degrees of coherence was introduced. Selleck SW-100 In this paper, we obtain the expression of the cross-spectral density function of the self-shifting beam generated from a light source propagating in random media. Then we calculated and simulated the behaviors of the spectral density and the spectral degree of coherence in the propagation. The results show that there will be a phenomenon of self-shifting in propagation, and the coherence of the beam is Gaussian when it is far enough from the light source. The light intensity is weakened with an increase in turbulence, while the wander of the center of the spectral density remains unchanged in different media.The ultraviolet (UV) absorption peaks of NaCl, NaOH, and $\beta $β-phenylethylamine (PEA) in an aqueous solution move toward redshift. We proposed the peak area method for the quantitative analysis of PEA, NaCl, and NaOH. First, we obtained the predictable regularities of the redshift of the single component sample. Then, we obtained the regularities of the redshift of the UV spectrum for the mixture by the peak height and peak area methods. Finally, the BP-ANN algorithm was applied to determine the concentration of the mixture using the peak height and peak area method. The results of the testing set showed that correlation coefficients ($\rm R^2$R2) of 0.992, 0.993, and 0.992 were obtained by peak height method and 0.997, 0.998, and 0.998 were obtained by peak area method for NaCl, NaOH, and PEA, respectively. Meanwhile, the relative errors of the prediction of NaCl, NaOH, and PEA obtained by peak area method were less than 3%, whereas the REP of NaCl, NaOH, and PEA obtained by peak height method were more than 5%.