Brownsuhr6047

We experimentally demonstrate that the terahertz (THz) emission from two-color laser filaments in gases is strongly affected by the pulse repetition rate of the driving laser. We show that at repetition rates above 100 Hz, propagation of every next laser pulse in the pulse train is altered by gas density depressions produced by the preceding laser pulses. As a result, plasma channels at higher repetition rates become shorter, leading to less efficient THz generation. In particular, we observe a 50% decrease in the emitted THz energy when the repetition rate increases from 6 Hz to 6 kHz.Polarizers serve many application fields such as imaging, display technology, and telecommunications. Focusing on the visible spectral region, we provide the design and fabrication of compact high-efficiency resonant polarizers in the crystalline silicon-on-quartz material system. We experimentally verify the improved efficiency attained by a cascaded dual-module polarizer assembled with building blocks of elemental subwavelength grating structures. We obtain a measured extinction ratio (ER) of ∼3000 in a 2 mm thick stacked prototype device across a bandwidth of ∼110nm in the 570-680 nm spectral domain. The ridge width of the constituent nanograting is ∼84nm. TAK-715 price Computed results show a high ER in spite of the lossy nature of crystalline silicon in the visible region, enabling cascaded metasurfaces while preserving high transmission.Free-space quantum key distribution is gaining increasing interest as a leading platform for long range quantum communication. However, the sensitivity of quantum correlations to scattering induced by turbulent atmospheric links limits the performance of such systems. Recently, a method for compensating for the scattering of entangled photons was demonstrated, allowing for real-time optimization of their quantum correlations. In this Letter, we demonstrate the use of wavefront shaping for compensating for the scattering of non-collinear and non-degenerate entangled photons. These results demonstrate the applicability of wavefront shaping schemes for protocols utilizing the large bandwidth and emission angle of the entangled photons.Young's double-slit-like diffraction was seen on a viewing screen placed perpendicularly to a sharply cut edge of a Z-cut iron doped LiNbO3 (LN) slab coated with indium-tin-oxide (ITO) films. The high contrast fringes observed confirm two sets of visible long-ranged surface plasmon polaritons propagating along the two ITO-LN interfaces distinctly over 5 mm path length with well-kept coherency, apart from metal uses. The indices of refraction measured with polarimetry from the ±Z-faces and changing transmission spectra obtained are consistent with the physical picture, along with dynamics of the very first reflection from the -Z-face under varying polarization angles between the two incident laser beams onto the slab.Microwave generation and modulation over the V- and W-bands are investigated using a semiconductor laser subject to both comb-like optical injection and direct modulation. The former not only excites period-one (P1) nonlinear dynamics for tunable microwave generation but also improves the stability and purity of such generated microwaves. The latter upconverts data onto the generated microwaves by superimposing the data effectively only onto the lower oscillation sideband of the P1 dynamics, which prevents the data from dispersion-induced degradation over fiber distribution. As a result, microwaves that are continuously tunable from 40 to 110 GHz with a 3-dB linewidth of less than 1 Hz and with phase noise better than -95dBc/Hz at 10-kHz offset are generated. A bit-error ratio better than the forward error correction limit, 3.8×10-3, is achieved for 12-Gb/s 16-quadrature amplitude modulation data after 25-km fiber distribution.We demonstrate frequency down-conversions of femtosecond pulses through dispersive wave generation and degenerate four-wave mixing in a gas-filled anti-resonant hollow-core fiber. These are achieved by exploiting the rapid variation of the dispersion in the fiber's transmission band edge. In this approach, the wavelength of the down-shifted radiation is governed solely by the thickness of the dielectric wall at the core-cladding interface, while other system parameters are accountable only for inducing sufficient nonlinear phase shifts. With the right choice of cladding wall thickness, the concept can be applied directly for generating high-power mid-infrared femtosecond pulses.Pixel super-resolution (PSR) techniques have been developed to overcome the sampling limit in lensless digital holographic imaging. However, the inherent non-convexity of the PSR phase retrieval problem can potentially degrade reconstruction quality by causing the iterations to tend toward a false local minimum. Furthermore, the ill posedness of the up-sampling procedure renders PSR algorithms highly susceptible to noise. In this Letter, we propose a heuristic PSR algorithm with adaptive smoothing (AS-PSR) to achieve high-fidelity reconstruction. By automatically adjusting the intensity constraints on the estimated field, the algorithm can effectively locate the optimal solution and converge with high reconstruction quality, pushing the resolution toward the diffraction limit. The proposed method is verified experimentally within a coherent modulation phase retrieval framework, achieving a twofold improvement in resolution. The AS-PSR algorithm can be further applied to other phase retrieval methods based on alternating projection.A λ=515nm laser generating joule-level pulses at 1 kHz repetition rate was demonstrated by frequency doubling 1.2 J, 2 ns temporally shaped square pulses from a cryogenically cooled YbYAG laser in an LBO crystal. A doubling efficiency of 78% resulted in 0.94 J second-harmonic pulses at 1 kHz. The unconverted light interacted with a second LBO crystal to generate >100mJ second-harmonic pulses to reach a total green average power of 1.04 kW. A conversion efficiency of 89% was achieved for 0.58 J green pulses at 1 kHz. These results open the possibility to pump high energy femtosecond lasers at kilohertz repetition rates.