Terahertz time-domain spectroscopy was per-formed on samples of the iron oxides alpha-hematite and magnetite. We were able to obtain the complex refractive index and dielectric constants. For alpha-hematite, an AFM resonance was observed at 0.13 THz. Although we did not find any resonance for magnetite, it was possible to observe spectral changes by decreasing the temperature. This suggests that TDS-THz may be a useful tool to detect corrosion on iron materials.
This paper demonstrates a simple piano-inspired interface to play a full C major scale based on a optical fiber specklegram quasi-distributed sensor. The user inputs musical notes via foam pads over one multimode optical fiber connected to a laser source and a webcam. Correlating the reference and immediate specklegrams retrieves the note input, subsequently played via audio output connected to the webcam. The interface is demonstrated with a precision of ~0.94 % for eight musical notes plus a neutral state and does not depend on the input order.
An optical encoding model based on the coher-ent superposition of two Laguerre-Gaussian modes carrying orbital angular momentum is presented using Machine Learning detection method. In the encoding process, the intensity profile for the encoded data is generated based on selection of $p$ and $\ell$ indices, while the decoding process is performed using support vector machine algorithm. Different encoding systems are designed and tested via simulations to verify the robustness of the proposed optical encoding model, finding a BER = 10– 9 for 10.2 dB of signal-to-noise ratio in the best of the case.
Operating optical biosensors outside laboratories presents a major challenge. This work presents a novel approach by introducing a practical coupling mechanism and using SU-8 polymer to reduce the complexity of the fabrication process. Additionally, software techniques used for detection allow for potential improvements without requiring costly hardware. The limit of detection of the proposed device is 3 × 10 − 5 RIU.
Here, we apply a 3D discriminant analysis approach to analyze FTIR hyperspectral images of normal vs malignant Melanoma (MM) samples for skin cancer diagnosis. For this porpose we used 2 samples, for Normal (49k) and for MM(90k). Our results evidence the outstanding performance with accuracy up to 81% for big data (> 100k).
In this paper, we propose and evaluate a scheme to enhance the performance of optical networks using route segmentation (RS) limited to modulation format maximum range. We have performed this study with an incremental traffic model considering the densely-connected CORONET topology taking the C-band and C+L-bands, with and without the adoption of fiber augmentation (FA). The results show that this strategy can be an interesting way to improve the network performance regarding blocking and bit rates.
The Kerr-related nonlinear signal distortion for unrepeatered optical links is evaluated for a 100-Gb/s single-channel scenario supported by first-order distributed Raman amplification. The results, comparing systems performance in terms of bit error rate for several optical fibers with dissimilar characteristics, indicate the importance to balance nonlinear and noise degradation to fully optimize the reach and capacity of this kind of system.
By exploiting alternative fabrication processes, electronic and photonic devices can be shrunken and their performance, enhanced. In this work, we study the fabrication of micro and nano structures through thermal scanning probe lithography. With no vacuum requirements, a structure with a minimum dimension of, approximately, 100nm was successfully built, in 17 minutes. Aiming at high performance electronic applications, the structure was coated with a 30nm gold film, and then electric characterized according to its foil resistivity.
Two promising methods for generation of THz radiation are presented and discussed. The hybrid bulk-surface modes excited in a cavity with bi-periodic grating have been considered. Such modes appear due to Electrodynamic interaction of the bulk modes with surface-wave resonator modes (i.e., leaky spoof surface plasmon polariton of an open grating). The potential for the effective generation of the THz radiation in a Clinotron by the excitation of the hybrid modes has been demonstrated. Theory of a new instability in reversed biased pn-junctions with impact ionization was developed and applied for investigation of THz oscillators design.
The use of plastic optical fibers has become widespread due to their mechanical advantages and low cost, despite presenting considerable dispersion. This paper models an OFDM transmission link using the signal power, the bias current and the fiber length over an Extreme Gradient Boost regressor by fitting the multicarrier signal-to-noise ratio. The results show an improvement in the coefficient of determination, and in the error metrics, when compared to traditional modeling.
In this work we study a microchip laser designed to function as an oscillator in a Master-Oscillator Power-Amplifier (MOPA) system targeted for laser tattoo removal. Different configurations of the Nd:YAG resonator were used by changing the output coupler mirror reflectivities and the initial transmission of the Q-switch. The quasi-CW resonator provided 55.4 W of output with 51.31% and 78.2% optical and slope efficiencies, respectively. For Q-switched operation, the best configuration resulted in a peak output power of 3.6 MW with 588 ps pulse width.
We report on post-processing experiments using hollow-core photonic crystal fibers. We show that, by simultaneously heating and internally pressurizing the fibers, we can taper or modify the sizes of the fiber microstructure features. Particularly, by employing a technique for selectively obstructing the microstructure elements, we could attain tailored modifications of the fiber architecture, namely the inflation of selected cladding tubes, which can be of interest for the development of new devices and sensors.
This paper reports the implementation of 5G New Radio (5G-NR) optical fronthauls based on radio-over-fiber (RoF) technology and optical carrier-suppressed double sideband (CS-DSB) technique, operating at 60 GHz. Experimental results over 20-km fiber-optics links demonstrate the successful transmission of QPSK, 16-QAM and 64-QAM modulated signals with up to 400-MHz bandwidth. The proposed 5G-NR RoF system performance meets the 3rd Generation Partnership Project (3GPP) requirements, achieving a total throughput of 800 Mbps.
The evolution of optical networks, with a focus on supporting next-generation connectivity solutions, is driving the development of technological solutions aimed at reducing capital and operational expenditures and energy consumption while increasing capacity, reach, and information security in optical transmissions. Within this context, this paper addresses recent developments and trends in coherent systems, optical amplification, integrated photonics, software-defined networking, and the use of quantum-based cryptography, which are highlighted across various scenarios, including transport, data center interconnects, access, and mobile xHaul.
In this work, we propose an optical OFDM system using phase modulation followed by optical filtering and direct detection. A fiber Bragg grating is used as an optical filter for phase to amplitude conversion. The performance of the proposed system is investigated for both 16 QAM- and 64 QAM-OFDM signals considering different numbers of training signals for frequency-domain channel estimation. With adequate choice of the training sequence length, BER results below 10 −4 are reported for the 16 QAM based signal.
We report on the correlations between the optical emission of the Erbium and the structural conditions of ZnO host thin film. The influence of the local chemical environment on the luminescence properties of the trivalent RE ions is often disregarded, and the management of host crystallinity in Spray-Pyrolysis synthesis is provided by the precursor dilution, i. e., solution molarity (M). Here we present an analysis of Erbium photoluminescence depending on the host crystallinity, which implies different Stark fields. The use of lower molarity results in transparent films well texturized in c-axis while the use of high molarity provides an opaque powderlike film.
Aminolevulinic acid (ALA) as a prodrug can be converted to protoporphyrin IX, which can be accumulated preferentially in tumor cells, presenting theranostic applications. ALA is also a precursor to chlorophyll, essential for photosynthesis. Gamma-aminobutyric acid (GABA) is a vertebrate central nervous system neurotransmitter. In plants, intracellular levels of GABA are typically low. GABA can be significantly accumulated in response to drought, salt, and low temperature and can increase the resistance of plants against these stresses. This paper describes the synthesis and characterization of metallic nanoparticles (silver, gold, and copper) and their applications in medicine and agriculture are exploited.
We report on curvature sensing measurements using a hybrid Kagomé-tubular hollow-core photonic crystal fiber. The sensing principle is based on bending-mediated resonant couplings between core and airy cladding modes achieved at specific curvature radii and wavelengths. We consider that our investigation identifies a promising use of hollow-core fibers in sensing, thus broadening the application framework of this family of fibers.
This work presents a straightforward, low-cost method for assessing the deflection of flexible elements to envisage applications in the field of soft robotics. The sensor comprises an optical fiber specklegram transducer coupled to a cantilever-type manipulator. The results yield absolute sensitivities of 0.37 N −1 and 0.05 cm −1 concerning force and deflection measurements, respectively, with a good agreement between simulation and experimental validation.
This work presents a magneto-optical (MO) meta-grating for beamforming at $f=300$ GHz. The device comprises a periodic arrangement of aluminum and indium antimonide semiconductor. Numerical results show diffraction angles of $\pm 45^{\circ}$ , with transmittance and extinction ratios of 0.54 and 0.74, respectively. Results are promising for future dynamic THz communications.
