For simultaneous temperature and humidity measurement, a fiber-tip microcantilever hybrid sensor combining a fiber Bragg grating (FBG) and a Fabry-Perot interferometer (FPI) was implemented. Femtosecond (fs) laser-induced two-photon polymerization was used to integrate a polymer microcantilever onto a single-mode fiber's end, creating the FPI. The resultant device demonstrates a humidity sensitivity of 0.348 nm/%RH (40% to 90% relative humidity, at 25°C), and a temperature sensitivity of -0.356 nm/°C (25°C to 70°C, at 40% relative humidity). The FBG's design was transferred onto the fiber core via fs laser micromachining, a process involving precise line-by-line inscription, with a temperature sensitivity of 0.012 nm/°C (25 to 70 °C, under 40% relative humidity). Ambient temperature is directly measurable via the FBG, given that its reflection spectra peak shift is solely dependent on temperature, and not on humidity. The output signal from FBG instruments can be employed for temperature correction in FPI-based humidity measurement systems. Hence, the measured value of relative humidity is disconnected from the complete movement of the FPI-dip, enabling concurrent quantification of both humidity and temperature. This all-fiber sensing probe, distinguished by its high sensitivity, compact dimensions, ease of packaging, and the ability for dual-parameter measurements (temperature and humidity), is anticipated to serve as a crucial component in a wide range of applications.
We propose a photonic compressive receiver for ultra-wideband signals, employing random codes shifted for image-frequency separation. By adjusting the central frequencies of two randomly selected codes across a broad frequency spectrum, the receiver's bandwidth can be dynamically increased. Two randomly generated codes have central frequencies that are subtly different from each other concurrently. The image-frequency signal, situated differently, is distinguished from the precise true RF signal by this contrast in signal characteristics. Stemming from this notion, our system overcomes the bandwidth limitation of existing photonic compressive receivers. The experiments, which incorporated two 780-MHz output channels, showcased the ability to sense frequencies between 11 and 41 GHz. Successfully recovered were both a multi-tone spectrum and a sparse radar communication spectrum, containing, respectively, a linear frequency modulated (LFM) signal, a quadrature phase-shift keying (QPSK) signal, and a single-tone signal.
A super-resolution imaging technique, structured illumination microscopy (SIM), is capable of achieving resolution improvements of at least two-fold, varying with the illumination patterns selected. In the conventional method, linear SIM reconstruction is used to rebuild images. Although this algorithm is available, its parameters are manually tuned, potentially causing artifacts, and its use with more complex illumination patterns is not possible. Deep neural networks are now part of SIM reconstruction procedures, however, suitable training datasets, obtained through experimental means, remain elusive. We present a method that integrates a deep neural network with the structured illumination forward model to reconstruct sub-diffraction images absent any training data. By optimizing on a single set of diffraction-limited sub-images, the resulting physics-informed neural network (PINN) circumvents the necessity of any training set. We demonstrate, using simulated and experimental data, that this PINN approach's ability to accommodate a wide range of SIM illumination methods hinges on adjusting the known illumination patterns employed in the loss function. The resulting resolution enhancements are in line with theoretical predictions.
Semiconductor laser networks underpin numerous applications and fundamental inquiries in nonlinear dynamics, material processing, illumination, and information handling. Still, the task of getting the typically narrowband semiconductor lasers to cooperate inside the network relies on both a high level of spectral homogeneity and a suitable coupling design. Experimental results are presented on the coupling of 55 vertical-cavity surface-emitting lasers (VCSELs) in an array, employing diffractive optics within an external cavity. Microscopes We successfully completed spectral alignment on twenty-two lasers among the twenty-five, which are now all synchronized to an external drive laser. Moreover, we demonstrate the substantial interconnections between the lasers within the array. This approach reveals the largest network of optically coupled semiconductor lasers reported to date and the initial comprehensive characterization of such a diffractively coupled system. Our VCSEL network, characterized by the high homogeneity of its lasers, the intense interaction among them, and the scalability of its coupling methodology, is a promising platform for experimental studies of intricate systems, finding direct use as a photonic neural network.
Diode-pumped passively Q-switched Nd:YVO4 lasers emitting yellow and orange light were developed by integrating pulse pumping, intracavity stimulated Raman scattering (SRS), and second harmonic generation (SHG). The SRS process leverages a Np-cut KGW to selectively produce either a 579 nm yellow laser or a 589 nm orange laser. By designing a compact resonator, which includes a coupled cavity for both intracavity stimulated Raman scattering (SRS) and second-harmonic generation (SHG), high efficiency is attained. This design also focuses the beam waist on the saturable absorber for superior passive Q-switching performance. At 589 nanometers, the orange laser's output pulses exhibit an energy of 0.008 millijoules and a peak power of 50 kilowatts. However, the energy output per pulse and the peak power of the yellow laser emitting at 579 nanometers can be as high as 0.010 millijoules and 80 kilowatts.
Satellite laser communication in low Earth orbit has emerged as a crucial communication component, distinguished by its substantial bandwidth and minimal latency. The amount of time a satellite remains operational hinges significantly on the battery's ability to withstand repeated charging and discharging cycles. Under sunlight, low Earth orbit satellites frequently recharge, only to discharge in the shadow, thus hastening their deterioration. This paper focuses on the problem of energy-efficient routing in satellite laser communication while simultaneously developing a model of satellite aging. Based on the model's findings, a genetic algorithm is utilized to develop an energy-efficient routing scheme. Relative to shortest path routing, the proposed method boosts satellite longevity by roughly 300%. Network performance shows minimal degradation, with the blocking ratio increasing by only 12% and service delay increasing by just 13 milliseconds.
Metalenses equipped with extended depth of focus (EDOF) enlarge the capturable image range, unlocking novel applications for microscopy and imaging. In EDOF metalenses designed using forward methods, disadvantages like asymmetric point spread functions (PSFs) and uneven focal spot distribution negatively impact image quality. We propose a double-process genetic algorithm (DPGA) optimization for inverse design of these metalenses to overcome these flaws. biocidal activity By strategically employing different mutation operators in two subsequent genetic algorithm (GA) runs, the DPGA algorithm exhibits superior performance in finding the optimal solution within the entire parameter space. Employing this approach, 1D and 2D EDOF metalenses, operating at 980nm, are each individually designed, showcasing a substantial enhancement of depth of focus (DOF) compared to traditional focusing methods. Additionally, reliable maintenance of a uniformly distributed focal spot guarantees stable imaging quality throughout the longitudinal dimension. The proposed EDOF metalenses possess significant application potential within biological microscopy and imaging, and the DPGA scheme can be extended to the inverse design of other nanophotonics devices.
The terahertz (THz) band, a component of multispectral stealth technology, will play a progressively vital role in both military and civilian spheres. Modularly designed, two adaptable and transparent meta-devices were created for multispectral stealth, including coverage across the visible, infrared, THz, and microwave bands. Flexible and transparent film materials are employed in the creation and construction of three fundamental functional blocks for IR, THz, and microwave stealth. Adding or removing stealth functional blocks or constituent layers, through modular assembly, readily results in two multispectral stealth metadevices. With remarkable THz-microwave dual-band broadband absorption, Metadevice 1 displays an average 85% absorptivity in the 0.3 to 12 THz range and a value exceeding 90% in the 91-251 GHz frequency band, effectively supporting THz-microwave bi-stealth. Metadevice 2 achieves bi-stealth for infrared and microwave radiations, with a measured absorptivity greater than 90% in the 97-273 GHz band and a low emissivity of roughly 0.31 in the 8-14 meter wavelength. Optically transparent, the metadevices maintain their exceptional stealth capabilities in curved and conformal environments. 5-Chloro-2′-deoxyuridine We have developed an alternative design and manufacturing procedure for flexible, transparent metadevices, enabling multispectral stealth, especially on nonplanar surfaces.
A novel surface plasmon-enhanced dark-field microsphere-assisted microscopy approach, presented here for the first time, images both low-contrast dielectric and metallic objects. In dark-field microscopy (DFM), the imaging of low-contrast dielectric objects demonstrates improved resolution and contrast using an Al patch array substrate, in contrast to metal plate and glass slide substrates. Three substrates support the resolution of hexagonally arranged 365-nm SiO nanodots, showing contrast from 0.23 to 0.96. The 300-nm diameter, hexagonally close-packed polystyrene nanoparticles are only visible on the Al patch array substrate. Dark-field microsphere-assisted microscopy improves resolution, allowing the resolution of an Al nanodot array, characterized by a 65nm nanodot diameter and 125nm center-to-center spacing. Conventional DFM fails to achieve this level of distinction.