5% using CF SA-LIBS. In addition, the surface patterns recorded by the stylus profilometer reveal that the single-shot SA-LIBS benefits a smaller ablative mass against standard LIBS.The ghost imaging (GI) approach is an intriguing and promising image acquisition technique that can transmit high-quality image information in a scattering environment. In this paper, we focus on two concerns recently emerged in the GI modality one is the vulnerability to forgery attacks in GI-based optical encryption [Opt. Lett.45, 3917 (2020)OPLEDP0146-959210.1364/OL.392424], and the other is the potential threat of GI to personal privacy regarding non-invasive imaging [Opt. GSK-3484862 solubility dmso Express28, 17232 (2020)OPEXFF1094-408710.1364/OE.391788]. The core idea is to recommend introducing weighted multiplicative signals [Opt. Express27, 36505 (2019)OPEXFF1094-408710.1364/OE.27.036505] into the computational GI system, whether on the transmitting end or the receiving end. At the transmitting end, the random multiplicative signal can be used as an additional key that can reduce the possibility of forgery attacks, thereby increasing image transmission security. On the receiving end, the introduction of a random multiplicative signal to a spatial scattering medium makes it a "spatiotemporal" scattering medium, whose transmittance changes with time. Further, the spatiotemporal scattering medium can disable direct imaging and GI at the same time with low cost, thereby having great potential in privacy protection in daily lives.Design and numerical characterization of a high-performance VO2-based optical modulator are proposed. The modulation is achieved by the phase transition of VO2 in a Bragg grating which can be formed by the selective VO2 deposition on a silicon strip waveguide. The interplay of the Bragg reflection and the inherent loss of the metal phase VO2 is used to increase the extinction ratio (ER) while the similarity of the refractive indices of the silicon and insulator phase VO2 resulted in a low insertion loss (IL). ER and IL of the modulator are 34.5 dB and 3.4 dB, respectively, at the wavelength of 1.55 µm, and they are, respectively, above 33 dB and below 3.5 dB across the entire optical C-band. The ER can be improved to 110 dB at the expense of an increased IL of 7.3 dB. The energy consumption and the modulation speed are estimated by considering different VO2 triggering schemes, and it is shown that the energy consumption of 91.7fJ/bit and the speed of 14 THz can be achieved with the proper VO2 stimulation. Furthermore, the robustness of the device performance to fabrication errors is studied by simulating the effect of the variation in different geometrical parameters.In this study, we propose a new optical fiber interferometer based on differential structure. The phase delay exists in the two output arms of the coupler. When the interference signal passes through the phase delay twice in the transmission, it produces a phase shift of π with the original signal. This feature can be used to differentially reduce noise. The experimental results show that the signal-to-noise ratio increases by 1.29 dB, and the waveform of the reconstructed signal is reduced by 12 nm. Thus, the structure can effectively improve the quality of the measured signal.In this paper, we investigate the backscattering depolarization of linearly and circularly polarized laser sources propagating in dense water fogs. We limit our investigation to a simple case where an active LiDAR system is pointed toward a white depolarizing Lambertian solid target. The receiver captures the reflected signal in the orthogonal channel so as to remove most of the backscattering from the water fog. It is shown that in the studied cases, a circularly polarized signal is depolarized faster than a linearly polarized signal and thus produces less contrast. We show that in the cases that can be described by the small angle approximation, the Rubenson degree of polarization (DoP) of a circularly polarized beam can be predicted by the DoP of a linearly polarized beam as DoPcir=2DoPlin-1, even for low-order multiple scattering events. In these conditions, since the linear DoP is always stronger, the contrast is expected to be better in linear polarization for ideal depolarizing targets.An improved computer-generated moiré profilometry (CGMP) with flat image calibration is proposed. In CGMP, the purification of the AC component plays a decisive role. While a composite grating modulated with both the sinusoidal grating and its background light substitutes for the sinusoidal grating itself, the sinusoidal deformed pattern and flat image can be demodulated from the captured pattern. It is found that the sinusoidal deformed pattern and flat image may deviate, which is caused by ambient light. So flat image calibration is conducted to obtain a purer AC component that can effectively suppress the influence of ambient light and ensure the measurement accuracy, even if spectrum aliasing exists. Experimental results show the feasibility and validity of the proposed method.A biosensor platform based on the plasmonic resonance of graphene in the terahertz (THz) range (0.1 to 10 THz) is designed and investigated. The initial design is to create a nanofluidic channel as a sensing layer in the substrate of a biosensor grounded by metal. The sensor consists of a rectangular graphene patch over the substrate, which can be fed by either an external near-field source or an antenna. The presence of molecules in the nanosensing layer causes small changes in the channel's properties, detectable through the scattering parameters of the designed biosensor. Since biomolecules are poorly absorbed in the initial biosensor, it can be grounded by a graphene sheet that is the same size as the graphene sheet over the substrate, which results in a performance improvement of the biosensor. It is shown that, by increasing the number of graphene sheets between the ground and the patch, high absorption occurs that enhances the sensitivity of the initial surface plasmon resonance THz biosensor. With varying refractive index of the sensing layer (Ns) in the range of 1.3-1.6, the proposed biosensors are investigated and compared with the initial biosensor. It is shown that by applying a graphene sheet between the two graphene sheets in the substrate, a maximum sensitivity of 8470 nm/RIU is achieved, which is a significant improvement, and also a sensitivity improvement of 4130 nm/RIU is achieved at Ns=1.3. In the final section, it is shown that changing the substrate material from silicon (Si) to silica (SiO2) brings a significant sensitivity enhancement in the proposed biosensor with three graphene sheets, which accounts for 15410 nm/RIU in the best scenario.