Willumsenfenger0853

Backscatter has significant influence on detection efficiency for underwater lidar, especially for coaxial photon-counting lidar using a Geiger-mode avalanche photodiode. In this paper, based on our underwater coaxial photon-counting lidar structure and volume scatter function, a detection model with consideration of backscatter and refraction indices is proposed. Using this detection model, analysis of the detection efficiency is conducted. It reveals that in an underwater environment, higher pulse energy or a closer target range is not necessarily helpful for a higher target detection probability, which is vastly different from our traditional concepts. For example, the detection probability for a 5 m target would be 0.76 using a 200 pJ pulse and 0.55 using a 1000 pJ pulse for our coaxial photon-counting lidar. Monte Carlo simulation is conducted to verify our model and analysis, and some practical methods for improving the target detection probability in an underwater environment are proposed.An optical fiber magnetic field sensor based on serial-tilted-tapered fiber (STTF) integrated with magnetic fluid is proposed. The compact STTF structure consists of two closely tilted-tapered fibers with a length of approximately 836 µm, which results in stronger mode coupling. ZD1839 cell line The transmission characteristics of the proposed sensor under different magnetic field intensities (MFIs) have been studied. The results show that the proposed structure has an outstanding response to MFI and that the highest sensitivity is 32.67 pm/Oe in wavelength and 0.0336 dB/Oe in transmission in the range of 0-75 Oe. The minimum resolution of the proposed sensor is up to 0.6734 Oe. These types of sensors have great potential application in weak magnetic field measurements due to their compact structure and good sensing performance.A method for shaping periodic intensity distributions of strongly chirped picosecond laser pulses in the infrared range by periodic phase modulation of the spectrum is proposed. The dependence of the time modulation period and depth on the parameters of periodic phase modulation of the spectrum is analyzed by analytical and numerical methods. It is demonstrated that the intensity distribution structure obtained at second- and fourth-harmonic generation can be retained by introducing an angular chirp. The electron bunch dynamics at the photoinjector test facility at DESY in Zeuthen (PITZ) was modeled numerically using ellipsoidal laser pulses with intensity modulation.Calibration of CCD arrays is commonly conducted using dark frames. Non-absolute calibration techniques only measure the relative response of the detectors. For absolute calibration to be achieved, a second calibration is sometimes utilized by looking at sources with known radiances. A process like this can be used to calibrate photodetectors if a calibration source is available and sensor time can be spared to perform the operation. link2 A previous attempt at creating a procedure for calibrating a photodetector using the underlying Poisson nature of the photodetection statistics relied on a linear model. This effort produced the statistically applied non-uniformity calibration algorithm, which demonstrated an ability to relate the measured signal with the true radiance of the source. Reliance on a completely linear model does not allow for non-linear behaviors to be described, thus potentially producing poor photocalibration over large dynamic ranges. In this paper, a photocalibration procedure is defined that requires only first and second moments of the measurements and allows the response to be modeled using a non-linear function over the dynamic range of the detector. The technique is applied to image data containing a light source measured with different integration times showing that the non-linear technique achieves significant improvement over the linear model over a large dynamic range.For the active control of large-scale structures, especially high-rise buildings and bridges, fast and accurate measurement of local deformations is required. We present a highly accurate and fast vision-based measurement technique and, to the best of our knowledge, first experimental results for the control of an adaptive-structures prototype frame, equipped with hydraulic actuators. Deformations are detected at multiple discrete points, based on a photogrammetric approach with additional holographic spot replication. The replication leads to effective averaging of most error contributions, especially discretization and photon noise. link3 Measurements over a distance of 11.4 m result in a measurement uncertainty of 0.0077 pixel (corresponding to 0.055 mm in object space).This work examined adaptive optical prisms by using a ladder-plus-Y double quantum dot system. A good dispersion angle and high spectral angular dispersion are obtained under the application of two optical fields (pump and probe) or three optical fields where an additional optical field between quantum-dot-wetting layer states is applied. These good results are obtained at a wide window of electromagnetically induced transparency with zero susceptibility.Mode converters play an essential role in mode-division multiplexing systems. A reflective mode converter (RMC), which is utilized to accomplish the mode conversion in the contra-propagation process, can fold the optical path and realize the mode exchange in an optical network. In this paper, we propose and experimentally demonstrate an RMC based on a silicon subwavelength structure. It can convert the input fundamental mode ($\textTE_0$TE0) into the first-order mode ($\textTE_1$TE1) in a $2.0\;\unicodex00B5 \textm \times 2.0\;\unicodex00B5 \textm$2.0µm×2.0µm footprint. The simulated insertion loss and cross talk are lower than 0.6 dB and $ - 20.3\;\textdB$-20.3dB in 1525-1565 nm. Experimental results verify the functionality of the device. The measured insertion loss and cross talk are lower than 2.2 dB and $ - 16.2\;\textdB$-16.2dB. To further prove the generality of the methodology, we design another two RMCs realizing the mode conversion functions of $\textTE_0$TE0 to $\textTE_2$TE2 and $\textTE_0$TE0 to $\textTE_3$TE3 modes. The simulated insertion losses are lower than 1.1 dB and 1.8 dB.A novel three-observation-window time-gated algorithm that combines overlapped windows and discrete windows together is developed for accurate fluorescence lifetime extraction. The new algorithm adopting a rapid lifetime determination strategy can offer an excellent ability to precisely detect long fluorescence lifetime for fluorescence lifetime imaging microscopy. Monte Carlo simulation indicates that an extremely small relative standard deviation below 0.4% is obtained over a wide fluorescence lifetime range from 5 ns to 30 ns. The detection error of the short fluorescence lifetime less than 5 ns is further reduced by means of an adaptive window width method. In contrast to other algorithms, such as time-correlated single-photon counting and traditional gated-window methods, not only the detection range but also the measurement accuracy is dramatically enhanced.Optical properties of low-temperature pulsed DC-sputter deposited ($ \le 70° \rm C$≤70°C) hydrogenated carbon are presented. Increasing hydrogen incorporation into the sputter deposited carbon significantly decreases infrared optical absorption due to a decrease in deep absorptive states associated with dangling bonds. Hydrogen flow is optimized (hydrogen flow 3 sccm), achieving the best compromise between increased infrared transmittance and hardness for durable coating performance. Optical, environmental, and durability performance of pulsed DC-sputtered carbon incorporated in multilayer (a-CH/Ge) infrared antireflective coatings indicates suitability as a durable infrared optical coating for commonly used infrared substrates, including temperature sensitive chalcogenide glass.We have studied polymer-free cladding power strippers for high-power fiber laser applications. A practical, rapid, and process-on-place chemical etching technique is presented to form surface roughness for efficient removal of the cladding light. The technique is methodically studied and performance contours are determined for frequently used 130, 250, and 400 µm double-clad fibers. The stripping efficiency and the thermal performance of the fabricated strippers are investigated with respect to such process parameters as etching time and etched fiber length. At least 15 dB attenuation with $ \lt 0.045(^\circ \rm C/\rm W)$ less then 0.045(∘C/W) thermal slope is demonstrated for all fiber types. To show the power scalability of the proposed technique, $\sim600\;\rm W$∼600W power is stripped with an ultra-low thermal slope of $\sim0.021(^\circ \rm C/\rm W)$∼0.021(∘C/W) over a 400 µm fiber.The precision by which an electron spin polarization measurement can be made using a noble-gas polarimeter depends directly on the accuracy of a light-polarization measurement. Since the electron-noble gas collisions occur in a vacuum chamber and the optical polarimeter is generally outside the chamber, this work examines the effect the vacuum window has on the perceived optical polarization. A model light source, lens system, and optical polarimeter are used that approximate the situation found in a typical atomic physics experiment. It was demonstrated that a pressure difference of 1 atm on a lens will alter the perceived polarization by as much as 0.05% with typical borosilicate (BK) lenses. This effect was demonstrated to scale with the thickness of the lens used and changes signs when the direction of the stress is reversed.We demonstrated a continuously wavelength-tunable bidirectional passively $ Q $Q-switched fiber laser based on a single-walled carbon nanotube saturable absorber and a bandpass filter (BPF). By tuning the commercial BPF, the $ Q $Q-switched pulse can be obtained in the same cavity at the same pump power in clockwise (CW) and counter-clockwise (CCW) directions. The central wavelength can be continuously tuned from 1520.88 to 1568.56 nm in the CW direction, and from 1520.96 to 1568.64 nm in the CCW direction. A wide tuning range of 48 nm is achieved for two directions in the passively $ Q $Q-switched fiber laser. During the tuning process of the fiber laser, the output pulses with the same central lasing wavelength can be obtained in both oscillation directions owing to the BPF. By increasing the pump power from 130 to 350 mW, the cavity delivers a $ Q $Q-switched pulse with the central wavelength of 1560 nm whose repetition rate changes from 9.64 to 59.18 kHz for the CW direction. In the CCW direction, the repetition rate of the $ Q $Q-switched pulse changes from 10.26 to 61.03 kHz. To the best of our knowledge, it is the first time that continuous wavelength-tunable passively $ Q $Q-switched pulses have been achieved in a bidirectional erbium-doped fiber laser.In this study, we quantify quantum steering, quantum entanglement, and quantum discord and their interconnection using the technique of parametric down-conversion. Initially, two single-mode Gaussian states together with a non-linear crystal in a cavity are considered. The behavior of the three kinds of quantum correlations depend on the phase of the coherent pump field, purity, and non-classicality of the input states, and the damping rates of the cavity. The amount and time evolution of the quantum correlations enhances with the difference between the non-classicality of the initial states. In presence of the damping rates, the quantum steering and quantum entanglement (quantum discord) increase (decreases) with the purity of the input cavity field. We note that the amount and survival time of the quantum correlations can be controlled by varying the relative phase associated to the coherent pump field. The boundaries of the three kinds of quantum correlations are defined and explained with respect to each other, which form a hierarchy.