Mcmillansavage2943

Moreover, we demonstrate that FB-PCS can lead to an SER reduction of ∼50%.Optical encryption has provided a new insight for securing information; however, it is always desirable that high security can be achieved to withstand the attacks. In this Letter, we propose a new method via learning complex scattering media for optical encryption. After the recordings through complex scattering media, a designed learning model is trained. The proposed method uses an optical setup with complex scattering media to experimentally record the ciphertexts and uses a learning model to generate security keys. During the decryption, the trained learning model with its parameters is applied as security keys. In addition, various parameters, e.g., virtual phase-only masks, can be flexibly applied to further enlarge key space. It is experimentally demonstrated that the proposed learning-based encryption approach possesses high security. The proposed method could open up a new research perspective for optical encryption.The demand for low-noise, continuous-wave, frequency-tunable lasers based on semiconductor integrated photonics has advanced in support of numerous applications. In particular, an important goal is to achieve a narrow spectral linewidth, commensurate with bulk-optic or fiber-optic laser platforms. Romidepsin Here we report on laser-frequency-stabilization experiments with a heterogeneously integrated III/V-Si widely tunable laser and a high-finesse, thermal-noise-limited photonic resonator. This hybrid architecture offers a chip-scale optical-frequency reference with an integrated linewidth of 60 Hz and a fractional frequency stability of 2.5×10-13 at 1 s integration time. We explore the potential for stabilization with respect to a resonator with lower thermal noise by characterizing laser-noise contributions such as residual amplitude modulation and photodetection noise. Widely tunable, compact and integrated, cost-effective, stable, and narrow-linewidth lasers are envisioned for use in various fields, including communication, spectroscopy, and metrology.Microglia act as the first and main form of active immune defense in brain. However, in animal models, research on these cells is limited to the superficial layer of the brain, due to the lack of a deep-imaging technique. Here we break this depth limit using three-photon fluorescence (3PF) microscopy excited at the 1700-nm window. Three-photon action cross-section (ησ3) measurement lays the basis for dye selection and the resultant maximization of 3PF generation. 3PF imaging suppresses the surface background, leading to a much improved signal-to-background ratio compared to the commonly used two-photon microscopy (2PM). We can image microglia 1124 µm below the brain surface in vivo, 3.7 times deeper than previous results using 2PM for microglia imaging. This technique enables us to visualize microglia in the white matter layer in vivo for the first time.This publisher's note contains a corrections to Opt. Lett.45, 4160 (2020).OPLEDP0146-959210.1364/OL.398412.We introduce an ultra-thin attosecond optical delay line based on controlled wavefront division of a femtosecond infrared pulse after transmission through a pair of micrometer-thin glass plates with negligible dispersion effects. The time delay between the two pulses is controlled by rotating one of the glass plates from absolute zero to several optical cycles, with 2.5 as to tens of attosecond resolution with 2 as stability, as determined by interferometric self-calibration. The performance of the delay line is validated by observing attosecond-resolved oscillations in the yield of high harmonics induced by time delayed infrared pulses, in agreement with a numerical simulation for a simple model atom. This approach can be extended in the future for performing XUV-IR attosecond pump-probe experiments.For future generations of gravitational wave detectors, it is proposed to use the helical Laguerre-Gaussian LG3,3 mode to reduce thermal noise, which limits the detector sensitivity. At the same time, this requires the efficient generation of squeezed vacuum states in the LG3,3 mode for quantum noise reduction. Since this technique includes the process of second harmonic generation (SHG), we experimentally compare the conversion efficiency and harmonic output field of the LG0,0 and LG3,3 modes in a cavity-enhanced SHG using the same 7% doped MgOLiNbO3 crystal. Conversion efficiencies of 96% and 45% are achieved, respectively. The influence of mode mismatches and astigmatism is analyzed to estimate the ratio of the pump mode-dependent effective nonlinearities to be d0,0/d3,3∼5. Furthermore, we show that absorption loss in the crystal is more relevant for the LG3,3 mode.The Pancharatnam-Berry (PB) phase is generally utilized to realize a single wavelength spin-dependent function or dual-wavelength functions but operating only in one spin state. A dual-wavelength multifunctional metasurface relying on both spins has been rarely designed due to the rather complicated degrees of freedom to be considered. In this Letter, both dynamic and PB phases are adopted, instead of a pure PB phase, to propose a multiplexing metasurface that can independently and simultaneously manipulate left- and right-handed circularly polarized incidences at dual wavelengths. It is demonstrated experimentally as well as numerically that such spin-dependent dual-wavelength metalenses can make circularly polarized incidences of different wavelengths split into and focus at multi-dimensional positions. Our work demonstrates a new avenue in designing spin-dependent dual-wavelength multifunctional optical devices.Compression of an intense laser pulse using backward Raman amplification (BRA) in plasma, followed by vacuum focusing to a small spot size, can produce unprecedented ultrarelativistic laser intensities. The plasma density inhomogeneity during BRA, however, causes laser phase and amplitude distortions, limiting the pulse focusability. To solve the issue of distortion, we investigate the use of optical phase conjugation as the seed pulse for BRA. We show that the phase conjugated laser pulses can retain focusability in the nonlinear pump depletion regime of BRA, but not so easily in the linear amplification regime. This somewhat counterintuitive result is because the nonlinear pump depletion regime features a shorter amplification distance, and hence less phase distortion due to wave-wave interaction, than the linear amplification regime.