Zimmermannrichter5862

In this work, a variable-pulse-oscillator is developed and coupled with a burst-mode amplifier for generation of high-energy laser pulses with width of 100 ps to 1 ms and near-Gaussian temporal pulse shape. Pulse energy as high as 600 mJ is demonstrated at 1064 nm, with a super-Gaussian spatial profile and beam quality as good as 1.6 times the diffraction limit. A time-dependent pulse amplification model is developed and is in general agreement with experimentally measured values of output pulse energy and temporal pulse shape of the amplified pulses. click here Key performance parameters (pulse energy, temporal pulse shape, and spatial beam profile and quality) are analyzed as a function of pulse width across seven orders of magnitude. Additionally, the model is used to elucidate deviations between the simulated and experimental data, showing that the relationship between pulse width and output pulse energy is dominated by the variable-pulse-width oscillator performance, not the burst-mode amplifier.Swept-source optical coherence tomography (OCT) typically relies on expensive and complex swept-source lasers, the cost of which currently limits the suitability of OCT for new applications. In this work, we demonstrate spectrally sparse OCT utilizing randomly spaced low-bandwidth optical chirps, suitable for low-cost implementation with telecommunications grade devices. Micron scale distance estimation accuracy with a resolution of 40 μm at a standoff imaging distance greater than 10 cm is demonstrated using a stepped chirp approach with approximately 23% occupancy of 4 THz bandwidth. For imaging of sparse scenes, comparable performance to full bandwidth occupancy is verified for metallic targets.We present a wavelength meter with picometer-scale resolution based on etaloning effects of inexpensive glass slides and the built-in color filters of a consumer grade CMOS camera. After calibrating the device to a commercial meter, we tested the device's calibration stability using two tunable visible lasers for a period of over 16 days. The wavelength error over that entire period has a standard deviation of 5.29 parts per million (ppm) about a most probable error of 0.90 ppm. Within 24 hours of calibration, this improves to 0.04 ppm with a standard deviation of 3.94 ppm.The scattering matrix, which quantifies the optical reflection and transmission of a photonic structure, is pivotal for understanding the performance of the structure. In many photonic design tasks, it is also desired to know how the structure's optical performance changes with respect to design parameters, that is, the scattering matrix's derivatives (or gradient). Here we address this need. We present a new algorithm for computing scattering matrix derivatives accurately and robustly. In particular, we focus on the computation in semi-analytical methods (such as rigorous coupled-wave analysis). To compute the scattering matrix of a structure, these methods must solve an eigen-decomposition problem. However, when it comes to computing scattering matrix derivatives, differentiating the eigen-decomposition poses significant numerical difficulties. We show that the differentiation of the eigen-decomposition problem can be completely sidestepped, and thereby propose a robust algorithm. To demonstrate its efficacy, we use our algorithm to optimize metasurface structures and reach various optical design goals.A spectroscopic Mueller matrix polarimeter based on spectro-temporal modulation with a compact, low-cost, and birefringent crystal-based configuration has been developed. The polarization state generator and polarization state analyzer in the system consists of a polarizer in front of two high-order retarders with equal thickness and a rotating achromatic quarter wave-plate followed by a fixed analyzer, respectively. It can acquire the 16 spectroscopic elements of the Mueller matrix in broadband with a faster measurement speed than that of the conventional spectroscopic Mueller matrix polarimeter based on a dual-rotating retarder. In addition, the spectral polarization modulation provided by the polarization state generator can produce five separate channels in the Fourier domain, which leads to a larger bandwidth of each channel than that of the existing spectral modulated spectroscopic Mueller matrix polarimeters. Experiment on the measurements of an achromatic quarter-wave plate oriented at different azimuths and SiO2 thin films deposited on silicon wafers with different thicknesses are carried out to show the feasibility of the developed spectroscopic Mueller matrix polarimeter.Michelson interferometers have been routinely used in various applications ranging from testing optical components to interferometric time-resolved spectroscopy measurements. Traditionally, plate beamsplitters are employed to redistribute radiation between the two arms of an interferometer. However, such an interferometer is susceptible to relative phase fluctuations between the two arms resulting from vibrations of the beamsplitter. This drawback is circumvented in diffraction-grating-based interferometers, which are especially beneficial in applications where highly stable delays between the replica beams are required. In the vast majority of grating-based interferometers, reflective diffraction gratings are used as beamsplitters. Their diffraction efficiency, however, is strongly wavelength dependent. Therefore transmission-grating interferometers can be advantageous for spectroscopy methods, since they can provide high diffraction efficiency over a wide spectral range. Here, we present and characterize a transmission grating-based Michelson interferometer, which is practically dispersion-free, has intrinsically high symmetry and stability and moderate throughput efficiency, and is promising for a wide range of applications.The integral photography and deconvolution techniques have been applied to identify the three-dimensional (3D) positions of particles levitating in plasma. Artifacts in the light field, i.e. ghost particles, are removed by collating between results of integral photography and direct Richardson-Lucy deconvolution (RLD). Our reconstruction system is tested with known target particles and it is found that it works well in the range of our dust experiment. By applying the integral photography and RLD techniques to the obtained experimental image, we identified the 3D positions of dust particles floating in a radio-frequency plasma. Ghost particles are eliminated from the results by deconvolution and we succeeded in obtaining the 3D structure of a dusty plasma from a single-exposure image obtained from one view port.We use low-resolution optical lithography joined with solid state dewetting of crystalline, ultra-thin silicon on insulator (c-UT-SOI) to form monocrystalline, atomically smooth, silicon-based Mie resonators in well-controlled large periodic arrays. The dewetted islands have a typical size in the 100 nm range, about one order of magnitude smaller than the etching resolution. Exploiting a 2 µm thick SiO2 layer separating the islands and the underlying bulk silicon wafer, we combine the resonant modes of the antennas with the etalon effect. This approach sets the resonance spectral position and improves the structural colorization and the contrast between scattering maxima and minima of individual resonant antennas. Our results demonstrate that templated dewetting enables the formation of defect-free, faceted islands that are much smaller than the nominal etching resolution and that an appropriate engineering of the substrate improves their scattering properties. These results are relevant to applications in spectral filtering, structural color and beam steering with all-dielectric photonic devices.Strong turbulence conditions create amplitude aberrations through the effects of near-field diffraction. When integrated over long optical path lengths, amplitude aberrations (seen as scintillation) can nullify local areas in the recorded image of a coherent beam, complicating the wavefront reconstruction process. To estimate phase aberrations experienced by a telescope beam control system in the presence of strong turbulence, the wavefront sensor (WFS) of an adaptive optics must be robust to scintillation. We have designed and built a WFS, which we refer to as a "Fresnel sensor," that uses near-field diffraction to measure phase errors under moderate to strong turbulent conditions. Systematic studies of its sensitivity were performed with laboratory experiments using a point source beacon. The results were then compared to a Shack-Hartmann WFS (SHWFS). When the SHWFS experiences irradiance fade in the presence of moderate turbulence, the Fresnel WFS continues to routinely extract phase information. For a scintillation index of S = 0.55, we show that the Fresnel WFS offers a factor of 9 × gain in sensitivity over the SHWFS. We find that the Fresnel WFS is capable of operating with extremely low light levels, corresponding to a signal-to-noise ratio of only SNR≈2-3 per pixel. Such a device is well-suited for coherent beam propagation, laser communications, remote sensing, and applications involving long optical path-lengths, site-lines along the horizon, and faint signals.We present experimental results of a low-emission self-mixing interferometer that uses a coupled interferometric effect to improve the signal produced by a vibrating target. This method is intended to be useful in applications where the target is prone to be damaged by high-intensity laser sources. The beam of a Fabry-Perot laser diode is split and ∼21% of the original emission is used to measure the harmonic micro-displacements of the target using the self-mixing effect. A portion of the residual beam, which also carries the interferometric information related to the target displacement, is reinjected back into the laser cavity by means of a fixed reflector, causing a second interferometric phenomenon that improves the signal-to-noise ratio of the measurement by up to ∼13 dB. A theoretical description of the phenomena is also proposed. Further, we apply this technique to the two most common self-mixing sensing schemes internal photodiode and junction voltage. The reported results show good agreement with theory and prove the capability of the method to enhance the SNR in SMI schemes.Illumination of a colloidal suspension of dielectric nanoparticles (50 nm in radius) with counter-propagating non-interfering laser beams of sufficient power leads to spatial redistribution of particles due to associated optical forces and formation of colloidal structures composed of thousands of nanoparticles along the beams. We employ a weak probe beam propagating through the colloidal structure and demonstrate that the colloidal structure acts effectively as a non-linear optical medium, similar to a gradient index lens, with optical transformation properties externally tunable by trapping laser power. With an increasing number of nanoparticles we observe the formation of a more complex colloidal structure axially and even laterally and we explain the origin of this process.To develop an intelligent imaging detector array, a diffractive neural network with strong robustness based on the Weight-Noise-Injection training is proposed. According to layered diffractive transformation under existing several errors, an accurate and fast object classification can be achieved. The fact that the mapping between the input image and the label in Weight-Noise-Injection training mode can be learned, means that the prediction of the optical network being insensitive to disturbances so as to improve its noise resistance remarkably. By comparing the accuracy under different noise conditions, it is verified that the proposed model can exhibit a higher accuracy.