We introduce an automated approach for the design of automotive AR-HUD optical systems featuring two freeform surfaces and windshields of diverse shapes. Given optical specifications, including sagittal and tangential focal lengths, and structural constraints, our design method automatically produces diverse initial structures for various car types, enabling high-quality image generation and flexible mechanical adjustments. Thanks to the extraordinary starting point, our proposed iterative optimization algorithms exhibit superior performance, resulting in the realization of the final system. age- and immunity-structured population First, we present a common two-mirror HUD design, including its longitudinal and lateral structural aspects, which is characterized by high optical performance. Additionally, a study of typical double-mirror off-axis HUD layouts was performed, evaluating aspects such as imaging performance and the occupied space. In terms of future two-mirror HUDs, the most suitable configuration of elements is picked. The proposed AR-HUD designs, all featuring an eye-box of 130 mm by 50 mm and a field of view of 13 degrees by 5 degrees, convincingly demonstrate superior optical performance, validating the efficacy and superiority of the proposed design framework. The substantial flexibility of the proposed work in producing diverse optical setups can considerably alleviate the efforts involved in designing HUDs for a variety of automotive vehicles.

The technology of multimode division multiplexing heavily depends on mode-order converters, which are responsible for the conversion of an input mode into the needed mode. Silicon-on-insulator platforms have witnessed substantial developments in mode-order conversion schemes, as evidenced by existing research. However, the majority are constrained to translating the foundational mode into only a few predefined higher-order modes, resulting in low scalability and flexibility. Cross-mode conversion between higher-order modes mandates a complete system redesign or a cascading strategy. A novel approach for universal and scalable mode-order conversion is presented, utilizing subwavelength grating metamaterials (SWGMs) with integrated tapered-down input and tapered-up output tapers. According to this design, the SWGMs region is capable of converting a TEp mode, governed by a tapered narrowing, into a TE0-like mode field (TLMF), and vice versa. Immediately afterward, a TEp-to-TEq mode conversion can be realized by a two-step procedure, involving a TEp-to-TLMF transformation and a subsequent TLMF-to-TEq transformation, with precise design of the input tapers, output tapers, and SWGMs. Experimental demonstrations and reporting of TE0-to-TE1, TE0-to-TE2, TE0-to-TE3, TE1-to-TE2, and TE1-to-TE3 converters are presented, boasting ultra-compact lengths of 3436-771 meters. Measurements show exceptionally low insertion losses, remaining below 18dB, and acceptable levels of crosstalk, under -15dB, across various working bandwidths, including 100nm, 38nm, 25nm, 45nm, and 24nm. The proposed methodology for mode-order conversion demonstrates significant universality and scalability for on-chip mode-order transformations, offering considerable potential for optical multimode-based systems.

We examined a high-speed Ge/Si electro-absorption optical modulator (EAM), evanescently coupled to a silicon waveguide with a lateral p-n junction, for high-bandwidth optical interconnects over a temperature range from 25°C to 85°C. Furthermore, we exhibited that the same apparatus functions as a high-speed and high-efficiency germanium photodetector, leveraging the Franz-Keldysh (F-K) and avalanche-multiplication phenomena. The Ge/Si stacked structure's potential for high-performance optical modulators and integrated Si photodetectors is evident in these results.

We constructed and confirmed a broadband terahertz detector, designed to meet the requirement for broadband and high-sensitivity terahertz detection, utilizing antenna-coupled AlGaN/GaN high-electron-mobility transistors (HEMTs). An array of eighteen dipole antennas, forming a bow-tie pattern, presents a spectrum of center frequencies ranging from 0.24 to 74 terahertz. The eighteen transistors, despite sharing a source and drain, exhibit various gated channels, coupled through unique antennas. Photocurrents from each controlled channel are aggregated and delivered at the drain, the designated output. A Fourier-transform spectrometer (FTS) employing incoherent terahertz radiation from a heated blackbody generates a continuous detector response spectrum spanning 0.2 to 20 THz at 298 K, and 0.2 to 40 THz at 77 K. The experimental findings are in robust agreement with the simulations which factor in the silicon lens, antenna, and blackbody radiation law. Irradiation with coherent terahertz waves determines the sensitivity, exhibiting an average noise-equivalent power (NEP) of about 188 pW/Hz at 298 K and 19 pW/Hz at 77 K from 02 to 11 THz, respectively. A remarkable optical responsivity of 0.56 Amperes per Watt, coupled with a minimal Noise Equivalent Power of 70 picowatts per hertz, is observed at 74 terahertz and a temperature of 77 Kelvin. Evaluation of detector performance above 11 THz is achieved through a performance spectrum, calibrated by coherence performance measurements between 2 and 11 THz. This spectrum is derived by dividing the blackbody response spectrum by the blackbody radiation intensity. At a temperature of 298 Kelvin, the neutron emission polarization at 20 terahertz is quantified as approximately 17 nanowatts per hertz. At 77 Kelvin, the noise equivalent power (NEP) is estimated to be roughly 3 nano-Watts per Hertz, when operating at 40 Terahertz. In order to optimize sensitivity and bandwidth performance, factors such as high-bandwidth coupling components, reduced series resistance, shorter gate lengths, and high-mobility materials must be explored.

A method for reconstructing off-axis digital holograms, incorporating fractional Fourier transform domain filtering, is proposed. The theoretical study of fractional-transform-domain filtering includes an expression and analysis of its characteristics. Filtering strategies in a fractional-order transform domain, constrained to areas of comparable size to Fourier transform filtering, have been proven to effectively extract and utilize a wider range of high-frequency components. Experimental and simulated results show that fractional Fourier transform filtering can enhance the reconstruction imaging resolution. Pictilisib In our opinion, the presented fractional Fourier transform filtering reconstruction is a novel (and, to our knowledge, unique) approach for off-axis holographic imaging.

Gas-dynamic theory, fortified by shadowgraphic measurements, is applied to understanding the shock physics of nanosecond laser ablation of cerium metal targets. endocrine autoimmune disorders Time-resolved shadowgraphic imaging is employed to quantify the propagation and attenuation of laser-induced shockwaves within air and argon atmospheres across a range of background pressures. Higher ablation laser irradiances and reduced pressures yield stronger shockwaves, distinguished by their higher propagation velocities. Estimating the parameters of the shock-heated gas, including pressure, temperature, density, and flow velocity, immediately behind the shock front, relies on the Rankine-Hugoniot relations; these relations suggest a direct relationship between the strength of laser-induced shockwaves and the predicted pressure ratios and temperatures.

A compact nonvolatile polarization switch (295 meters) based on an asymmetric silicon photonic waveguide, coated with Sb2Se3, is simulated and proposed. The crystalline-to-amorphous phase transition in nonvolatile Sb2Se3 leads to a change in the polarization state, alternating between the TM0 and TE0 modes. Amorphous Sb2Se3, when subjected to polarization-rotation, exhibits two-mode interference, resulting in efficient TE0 to TM0 conversion. Conversely, the crystalline state of the material exhibits a lack of polarization conversion. The interference between hybridized modes is substantially suppressed, ensuring the TE0 and TM0 modes pass through the device unchanged. For both TE0 and TM0 modes, the polarization switch's design yields a remarkable polarization extinction ratio greater than 20dB and a substantially low excess loss, under 0.22dB, within the 1520-1585nm wavelength range.

Applications in quantum communication have stimulated significant interest in photonic spatial quantum states. The dynamic generation of these states using solely fiber-optic components has presented a considerable challenge. We experimentally show an all-fiber system that dynamically shifts between any general transverse spatial qubit state defined by linearly polarized modes. A few-mode optical fiber system, alongside a photonic lantern and a Sagnac interferometer-based optical switch, forms the basis of our platform. We demonstrate switching times between spatial modes, on the order of 5 nanoseconds, and showcase the applicability of this method for quantum technologies, including a measurement-device-independent quantum random number generator (MDI-QRNG) built on our platform. Within a timeframe exceeding 15 hours, the continuous operation of the generator resulted in the acquisition of over 1346 Gbits of random numbers, at least 6052% of which satisfied the MDI protocol requirements for privacy. Employing photonic lanterns, our research reveals the capability of dynamically generating spatial modes using solely fiber components. Their robustness and integration affordabilities impact photonic classical and quantum information processing considerably.

Terahertz time-domain spectroscopy (THz-TDS) is a widely employed technique for non-destructive characterization of materials. Nevertheless, the process of characterizing materials using THz-TDS involves numerous intricate steps to analyze the acquired terahertz signals and glean material-specific information. We introduce a highly effective, consistent, and rapid procedure for evaluating the conductivity of nanowire-based conducting thin films, incorporating artificial intelligence (AI) and THz-TDS. This method trains neural networks using time-domain waveforms instead of frequency-domain spectra to minimize analysis steps.