Mahmoudfoss1685

A silicon-based polarizing beam splitter (PBS) working at the 2 μm wavelength band is proposed and demonstrated experimentally by using a bent directional coupler assisted with a nano-slot waveguide. The nano-slot width is chosen as 180 nm so that the present PBS can be fabricated with MPW foundries. In theory, the designed PBS has extinction ratios (ERs) of >15 dB and >30 dB for TM- and TE- polarizations in the wavelength range of 1825-2020 nm, respectively. For the fabricated PBS, the excess losses (ELs) are low (∼0.5 dB) while the measured results show the ERs are >15 dB and >20 dB for TM- and TE-polarizations in the wavelength band of 1860-1980 nm.All-optical devices used to process optical signals without electro-optical conversion plays a vital role in the next generation of optical information processing systems. We demonstrate an efficient all-optical modulator that utilizes a periodic dielectric atomic lattice produced in a gas of 85Rb vapor. Four orders of diffraction patterns are observed when a probe laser is passed through the lattice. The frequency shift of the peak of each diffraction order can be tuned by adjusting the control laser power and two-photon detuning, enabling this device to be used as a multi-channel all-optical modulator. Both theoretical simulations and experimental results demonstrate that this modulator can operate over a frequency band extending from about 0 to 60 MHz. This work may pave the way for studying quantum information processing and quantum networking proposed in atomic ensembles.A dynamically adjustable ultra-wideband metamaterial perfect absorber (MPA) is proposed which consists of three resonance rings based on vanadium dioxide (VO2) and a metal ground layer separated by a dielectric spacer. The simulation results show that the terahertz (THz) absorption bandwidth of more than 90% absorptance reaches 3.30 THz, which covers from 2.34 to 5.64 THz, under different incident polarization angles. The range is better than that of previous VO2-based reports. Moreover, when the conductivity of VO2 changes from 200 S/m to 2×105 S/m, the absorption peak intensity can be adjusted continuously from 4% to 100%. Zimlovisertib The key is to optimize the geometric structure through interference cancellation and impedance matching theory, to achieve better absorption bandwidth and efficiency. Besides, the terahertz absorber has a wide-angle absorption effect both in TE and TM waves. Thus, the designed absorber may have many potential applications in modulating, sensing and imaging technology.We report an investigation of dispersion management of an all-polarization-maintaining Er-fiber oscillator mode-locked via a nonlinear amplification loop mirror in a figure-nine cavity configuration with two output ports. The performance of the laser was investigated within the net cavity dispersion ranging from -0.034 ps2 to +0.006 ps2. We show that the spectral and temporal phase of the pulses at both figure-nine outputs have clearly different characteristics. One of the laser outputs provides pulses with significantly better quality; nonetheless, the rejection output also offers ultrashort pulses with broad spectra. Pulses as short as 79 fs with an energy of 83 pJ were generated directly from the laser in the near-zero dispersion regime.Here, we present a compact Watt-level single-frequency continuous-wave (CW) self-tuning titaniumsapphire (TiS) laser, which is implemented using a three-plate TiS crystal as both a gain medium and frequency-tuning element. The thickness ratio of the three-plate TiS crystal is 124, of which the thinnest plate measured 1 mm. The optical axes lie on their own surfaces and parallel to each other. Based on the presented self-tuning crystal, a ring resonator is designed and built. The maximum wavelength tuning range of the single-frequency self-tuning TiS laser is 108.84 nm, as demonstrated experimentally by rotating the three-plate TiS crystal, indicating good agreement with theoretical prediction. link2 To the best of our knowledge, this is the first study to report a single-frequency CW self-tuning TiS laser, which can provide a feasible approach for achieving a compact all-solid-state single-frequency CW-tunable TiS laser.Broadband multilayer dielectric gratings (MDGs) with rectangular HfO2 grating profile were realized for the first time using a novel fabrication process that combines laser interference lithography, nanoimprint, atomic layer deposition and reactive ion-beam etching. The laser-induced damage initiating at the grating ridge was mitigated for two reasons. First, the rectangular grating profile exhibits the minimum electric-field intensity (EFI) enhancement inside the grating pillar compared to other trapezoidal profiles. Second, our etching process did not create nano-absorbing defects at the edge of the HfO2 grating where the peak EFI locates, which is unavoidable in traditional fabrication process. The fabricated MDGs showed a high laser induced damage threshold of 0.59J/cm2 for a Ti-sapphire laser with pulse width of 40 fs and an excellent broadband diffraction spectrum with 95% efficiency over 150 nm in TE polarization.Programmable reflective metasurfaces that combine the features of reconfigurable phased array antennas and reflectors are an effective solution for radar and modern communication systems. However, most of the demonstrated active metasurfaces support tunable responses for a specific frequency band. Thus, we propose a programmable metasurface that combines the advantages of multi-bit phase quantization and dual-band operations. To actively control the diverse functions, two PIN diodes are integrated on the radiating element, and these diodes are controlled by the biasing voltage. The unit cell is fabricated, and experimental characterization is performed in the waveguide measurement setup. The proposed design can be applied for imaging and high-capacity wireless communications.We present a novel method utilizing the χ(2) nonlinear optical technology, which can realize high precision measurement of linear electro-optic (EO) coefficients of nonlinear materials. By applying the linear EO effect to the nonlinear optical process, the theoretical model of this measurement method was established, and the calculation formula of the linear EO coefficient was given. In the proof-of-principle experiment, by introducing an external electric field into the fourth harmonic generation (FHG) process, we comprehensively obtained the linear EO coefficients of K(H1-xDx)2PO4 crystals and revealed the relationship between deuterium content (x) and EO coefficient (γ63) γ63 = -9.789 - 16.53x. Meanwhile, the stability of FHG was greatly improved, and the angular range of efficiency stability was increased to 4.4 times in maximum. This work not only systematically demonstrates the FHG characteristics of KDP-family crystals, which provides a good reference for the deep ultraviolet laser generation, but also offers a new way to measure the basic parameters of nonlinear optical materials.Brillouin spectroscopy emerges as a promising non-invasive tool for nanoscale imaging and sensing. One-dimensional semiconductor superlattice structures are eminently used for selectively enhancing the generation or detection of phonons at few GHz. While commercially available Brillouin spectrometers provide high-resolution spectra, they consist of complex experimental techniques and are not suitable for semiconductor cavities operating at a wide range of optical wavelengths. We develop a pragmatic experimental approach for conventional Brillouin spectroscopy that can integrate a widely tunable excitation-source. Our setup combines a fibered-based angular filtering and a spectral filtering based on a rotating single etalon and a double grating spectrometer for sequential reconstruction of Brillouin spectra. This configuration allows probing confined acoustic phonon modes in the 20-300 GHz frequency range with excellent laser rejection and high spectral resolution. Remarkably, our scheme based on the excitation and collection of the enhanced Brillouin scattering signals through the optical cavity allows for better angular filtering with decreasing phonon frequency. It can be implemented for the study of cavity optomechanics and stimulated Brillouin scattering over broadband optical and acoustic frequency ranges.We have developed an extreme ultraviolet (XUV) frequency comb for performing ultra-high precision spectroscopy on the many XUV transitions found in highly charged ions (HCI). Femtosecond pulses from a 100 MHz phase-stabilized near-infrared frequency comb are amplified and then fed into a femtosecond enhancement cavity (fsEC) inside an ultra-high vacuum chamber. The low-dispersion fsEC coherently superposes several hundred incident pulses and, with a single cylindrical optical element, fully compensates astigmatism at the w0 = 15 µm waist cavity focus. With a gas jet installed there, intensities reaching ∼ 1014 W/cm2 generate coherent high harmonics with a comb spectrum at 100 MHz rate. We couple out of the fsEC harmonics from the 7th up to the 35th (42 eV; 30 nm) to be used in upcoming experiments on HCI frequency metrology.Polarization holography has attracted considerable attention in recent years, due to its capability of recording the polarization information in polarization-sensitive material. Particularly, the faithful reconstruction (FR) can retrieve the polarization information of the recorded signal. To date, studies referring to these topics mainly concentrate on the interference between the same type of polarization such as linearly, circularly, and elliptically polarized light. In addition, most of the reading wave is strictly limited to some specified polarization state to achieve the FR. Here, we apply the linearly polarized light as the reference wave to record the circularly polarized light, and then the circular polarization state would be faithfully reconstructed by the arbitrarily polarized reading wave. We theoretically analyze its polarization characteristic based on the tensor theory and experimentally verified the analytical results. This result further extending the FR in polarization holography, and provides a practicable way to generate circular polarization which is easily fabricated. Moreover, the work would lay a favorable theoretical foundation for the future preparation of circular polarization generator and discloses a new insight in polarization manipulation for tailoring the optical field.Herein, we propose a band-limited double-phase method to improve the quality of reconstructed images encoded by double-phase holograms (DPHs) derived from complex-amplitude light waves. Although the quality of images produced by DPHs was improved compared to that of conventional holographic images, it still suffered from degradation because of the spatial shifting noise generated during the conversion from complex-amplitude holograms to phase-only holograms. link3 The proposed method overcomes this shortcoming by defining a band-limiting function according to the spatial distribution of DPHs in the frequency domain to remove the specific spatial frequency components severely affected by the spatial shifting of DPHs. The sharpness of images reconstructed from band-limited DPHs with appropriate optical filtering showed an improvement of 36.84% in simulations and 51.67% in experiments evaluated by 10-90% intensity variation.