Optical Injection Research Articles

Triple combination of fractional carbon dioxide laser, 308-nm excimer lamp, and platelet-rich plasma in refractory vitiligo: A randomized split-body comparative study

Objectives: Vitiligo significantly impacts patients’ quality of life. Current evidence indicates that combination therapy results in faster improvement, enhancing patient adherence to treatment and leading to higher satisfaction among patients. In this study, we compare the efficacy of combined fractional carbon dioxide (FCO2) laser and excimer lamp with platelet-rich plasma (PRP) or topical tacrolimus in patients with refractory vitiligo. Material and Methods: This is a prospective, single-blind, randomized split-body clinical trial involving 41 patients with resistant focal patches of vitiligo vulgaris. Each patient had two similar lesions randomly assigned to receive either a combination of FCO2 laser, excimer lamp, and intradermal PRP injections or a combination of FCO2 laser, excimer lamp, and topical 0.1% tacrolimus (applied twice daily for 12 weeks). The FCO2 laser and PRP treatments were administered in three monthly sessions, and the excimer lamp was used twice a week over 12 weeks. The efficacy of treatment was assessed based on the physician’s assessment and patient’s satisfaction Results: Despite significant improvement in both treatment groups during the course of treatment, the PRP group showed significantly superior efficacy (more than 50% improvement) compared to the tacrolimus group (56.1% and 26.8%, respectively). Furthermore, the PRP group exhibited greater improvement in resistant acral areas compared to the tacrolimus group (51.2% and 19.5%, respectively). Conclusion: The combination of FCO2, an excimer lamp, and PRP demonstrates superior efficacy, particularly in resistant acral areas. As a result, this combination can be recommended in difficult-to-treat areas in patients with vitiligo.

Ultraviolet spectral broadening by stimulated rotational Raman scattering on nitrogen pumped with signal laser injection

We present experimental results on kilojoule ultraviolet laser output with 1% spectral broadening. Through stimulated rotational Raman scattering (SRRS) with signal laser injection, we achieve effective spectral broadening in short-range propagation, with good retention of the original near-field distribution and time waveform. Theoretical calculations show that 2% bandwidth spectral broadening can be achieved by injecting 20 kW/cm2 signal light at 2.2 GW/cm2 flux of the pump laser. In addition, high-frequency modulation in the near field can be effectively avoided through replacement of the original random noise signal light by the controllable signal light. The SRRS in the atmospheric environment excited with signal laser injection can provide wide-band light output with controllable beam quality without long-distance propagation, representing an important potential route to realization of broadband laser drivers.

Treatment of Alopecia Areata using Transdermal Delivery of 5-Fluorouracil by Fractional CO2 Laser versus Intralesional Injection of 5-Fluorouracil

Treatment of Alopecia Areata using Transdermal Delivery of 5-Fluorouracil by Fractional CO2 Laser versus Intralesional Injection of 5-Fluorouracil

Hole and electron spin lifetime in lightly n-doped silicon at low temperatures

We report on photoinduced inverse spin-Hall effect (ISHE) measurements as a function of the incident photon energy in the 4–50 K temperature range for a Pt/n-doped Si junction. Optical spin injection allows generating a spin-oriented population of electrons and holes around the Δ valleys and Γ point of the Si Brillouin zone, respectively. Spin-polarized carriers cross the Pt/Si contact and then enter the Pt overlayer, where spin-to-charge conversion occurs by means of spin-dependent scattering with Pt nuclei. For temperatures T up to 20 K, most of the dopants are not ionized, so that the electric field, stemming from the contact potential between Pt and Si, extends to the whole Si substrate, which becomes insulating, and only spin-oriented holes reach the Pt layer and contribute to the ISHE spectra. For T>20 K, donors are partially ionized, and the resulting space charge close to the Pt/Si interface leads to the formation of a Schottky contact where the electric field rapidly vanishes within a few micrometers. As a consequence, also spin-polarized electrons enter Pt by means of thermionic emission, contributing to the ISHE signal. We numerically solve the one-dimensional spin drift-diffusion equations for holes and electrons and estimate the temperature dependence of the spin lifetime in Si for both populations, demonstrating that Si may serve as a versatile platform for spintronic applications, able to leverage both electrons and holes.

Full-zone optical spin injection in AlxGa1−xAs alloys

Abstract Full-zone optical spin injection in Al x Ga1−x As alloys is investigated by analyzing the degree of circular polarization (DCP) of luminescence in a quantum well architecture. Aluminium content in AlGaAs barrier layers is varied to explore both the direct- and indirect-bandgap regimes. For all the samples, experimental data are compared with a 30-band k .p model addressing the band structure of the alloy and the optical spin injection over the entire Brillouin zone. We observe circularly polarized luminescence arising from the spin generation either around Γ or the L valley. We interpret the specific shape of the DCP within a framework accounting for smaller electron spin relaxation at the higher k points of the X valley of the AlGaAs barrier layer. Moreover, it is found that the presence of strain plays a vital role in governing the magnitude and shape of the DCP spectra for near band-edge excitation while exciting spin-polarized carriers in the direct-bandgap AlGaAs. We believe that these findings are important for the realization of AlGaAs-based spin-photonic devices aiming at possible applications in quantum technology.

Effects of Gain Saturation on Orbital Instability of Chaotic Laser Diode with External Pseudorandom Signal

In a laser diode (LD) system with optical injection, the effects of gain saturation of the LD on the orbital instability of the system are analyzed numerically. For the optical injection LD system without signal application, it is shown that the effect of optical injection is suppressed in the system with gain saturation and small optical injection, and that a higher amount of optical injection is necessary to obtain similar dynamics. Next, in the optical injection LD system with a pseudo-random signal applied to the LD drive current, it is confirmed that when the dynamics are a periodic window between chaotic and chaotic regions, chaotic dynamics are actualized as the standard deviation of the applied signal becomes larger. Furthermore, it is suggested that this phenomenon can be explained by linear stability analysis, and it is shown by introducing randomly varying tentative gain coefficients that gain fluctuations that lead to an expansion of the chaotic region. Hence, the results of this study provide research on the effects of gain saturation on chaotic oscillation in LDs with pseudo-random signals applied and contribute to the generation of more complex chaotic signals, chaotic secure communication, and random number generation.

Experimental demonstration on the proactive detection of fiber tapping in optical chaos communication.

Optical chaos communication has a physical-layer security advantage but defends passively against a malicious attack. Here, we conduct a proof-of-concept experiment of detecting the attack proactively by observing performance degradation in optical chaos communication tapped with fiber bending. Influences of the curvature radius of the bent fiber on a chaos synchronization coefficient and bit error rate are investigated. Results show that the synchronization coefficient decreases from 0.958 to 0.904 and the bit error rate increases from 1.31 × 10-4 to 1.73 × 10-3 under a curvature radius of 10 mm, revealing the attack. Bending fiber to this extent leads to a power loss of 1.81%, which is difficult to detect by the optical time-domain reflectometer but causes significant interference to chaos communication due to the concurrent change in the light polarization, jointly decreasing the effective optical injection strength for yielding chaos synchronization.

The Chaotic Behavior of an Optical Artificial Neuron

ABSTRACT The operation of an optical neural network via a feed-forward (FF) configuration is experimentally simulated in the laboratory. The FF setup is tested using optical injection (OI), and the behavior of follower laser diodes (FLDs) subjected to chaotic modulation is examined. The last two laser diodes (LDs) are exposed to different weights of chaotic modulated signals through optical filtration and attenuation. Observations of the emissions from these two FLDs during FF operation are verified by frequency spectra calculated from time-series data. Signal broadening is assessed by measuring the full width at half maximum (FWHM), and chaotic signal spikes are analyzed by counting the number of peaks associated with signal amplitudes for the FLDs. Additionally, LD control parameters, including the bias voltage of the influencer laser diodes (ILD1, ILD2) and two additional FLDs, are examined. A maximum FWHM of 1.25 GHz for FLD2 is observed with a bias voltage of 3.6 V and a modulated signal attenuation of −12 dB. To determine the synchronization state, the correlation between the ILDs and FLDs is calculated. Results indicate fluctuations between negative and positive values, with the best correlation value being 0.4. These results confirm anti-synchronized ILD-FLDs, which are crucial for ensuring privacy in transmitting units within a chaotic optical communication system simulating an optical neural network.

Efficacy of Nd:YAG Laser and Intralesional Triamcinolone Injection Combination Therapy in the Postoperative Management of Keloids.

Keloids, characterized by protruding scars that extend beyond the original skin damage site, cause significant emotional stress and reduced quality of life. Their exact pathogenesis remains unclear, with various hypotheses including growth factor imbalances and extracellular matrix changes. No single treatment is universally accepted, but multiple modalities like triamcinolone acetonide injection (TAC), laser therapies, and surgery are commonly used. This retrospective study involved East Asian patients who underwent keloid scar excision between March 2019 and June 2022. Patients were divided into two groups: one receiving only TAC injections and the other a combination of TAC and Nd:YAG laser therapy. The efficacy of treatments was evaluated using the modified Vancouver Scar Scale (mVSS) and the Patient and Observer Scar Assessment Scale (POSAS), with follow-ups at six and twelve months after operation. The study involved 111 patients. Both treatment groups showed significant improvements in mVSS and POSAS scores, but the combination therapy group demonstrated a statistically significant improvement in POSAS scores and lower recurrence rates at 12months compared to the TAC-only group. However, there was no significant difference in patient satisfaction between the groups. Dual therapy involving TAC injection and Nd:YAG laser treatment was more effective than TAC injection alone for managing keloid scars after surgery. This combination therapy showed better outcomes in preventing keloid recurrence and improving scar status at 12months after operation, along with significant improvements in patient-reported outcomes. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Intravitreal Injection and Prophylactic Laser Treatment in Pediatric Vitreoretinal Pathologies

Vascular endothelial growth factor (VEGF) is an important mediator of pathological neovascularization and vascular permeability of the eye. The increasing use of intravitreal therapies targeting VEGF has revolutionized the treatment of pediatric vitreoretinal diseases. Laser photocoagulation is the standard treatment method for retinopathy of prematurity. The aim is to ablate the avascular peripheral retina, but ablation of the peripheral retina with traditional laser therapy is destructive, causes complications, and does not prevent all vision loss, especially in cases of retinopathy of prematurity affecting zone 1 of the eye. In Coats disease, retinal telangiectasias are treated early with laser photocoagulation, but with ischemia, high levels of VEGF in the ocular fluid may contribute to increased permeability of telangiectatic blood vessels, leading to lipoprotein leakage and subsequent exudative retinal detachment. Therefore, anti-VEGF has been recommended as adjuvant therapy in the treatment of Coats disease. In this review, intravitreal injection and prophylactic laser treatment applications in Retinopathy of Prematurity and Coats Disease are mentioned.

Dual‐channel, high‐frequency optoelectronic oscillators utilizing optically‐injected lasers

AbstractWe propose a novel approach to dual‐channel optoelectronic oscillators (OEOs) with enhanced frequency band by leveraging directly modulated (DM) semiconductor lasers under optical injection. In this configuration, the frequency‐tuned optical signal from a master laser is introduced into a single‐mode slave laser, facilitating multioptical‐mode operation. The resulting multiple optical frequencies emitted by the slave laser facilitates a DM‐OEO signal at a frequency exceeding the laser's intrinsic modulation bandwidth. Through the deployment of a dual‐channel OEO based on the DM multimode laser signal, stable oscillation signals have been successfully achieved simultaneously at 15 and 18 GHz with phase noise levels of 96.43 and 95.62 dBc/Hz, respectively, at a 10‐kHz offset frequency.

ADVANCES IN AESTHETIC GYNAECOLOGY IN THE MODERN WORLD

The article is devoted to the achievements of aesthetic gynecology in the modern world, including innovative technologies and methods that allow for improvement in the appearance and functionality of female genitalia. The main directions in aesthetic gynecology, such as laser therapy, radiofrequency procedures, and injection technologies, as well as genital correction with the help of labioplasty and vaginoplasty, are considered. Particular attention is paid to the psycho-emotional health of patients and the growing awareness of available methods. The article emphasizes the importance of an individualized approach in the treatment and maintenance of women's health.

Improvement of optical noise in optical-injection-locked quantum dot lasers epitaxially grown on silicon by reducing external carrier noise

Abstract This study theoretically investigates the impact of external carrier noise from pumping sources on the optical noise of epitaxial quantum dot (QD) lasers on silicon. The findings indicate that the spectral linewidth and relative intensity noise (RIN) of silicon-based QD lasers using a quiet pump are significantly reduced. At 5.5 times the threshold current, the spectral linewidth decreases from 337.2 kHz to 213.2 kHz, and the RIN decreases from −141.3 dB Hz−1 to −168.8 dB Hz−1. This reduction is attributed to the lower external carrier noise level of the quiet pump, which also suppresses the spectral linewidth rebroadening effect at a high bias current. Moreover, when external optical injection locking is applied, the spectral linewidth further decreases to 24 kHz at an injection ratio of −70 dB and to 1.8 mHz at 0 dB. The RIN also slightly decreases to −172.4 dB Hz−1 with an injection ratio of 10. These results demonstrate that using a quiet pump is an effective and manageable strategy for significantly reducing both the spectral linewidth and RIN of QD lasers, thereby facilitating their application in next-generation photonic integrated circuits, continuous-variable quantum key distribution, quantum computing and ultra-precise quantum sensing.

Efficient Light Coupling and Propagation in Fiber Optic Systems

This study explores the propagation of light in optical fibers, focusing on the fundamental principles and practical implications for fiber optic technologies. By analyzing the wave equation, the research demonstrates that light propagates as cylindrical waves within the fiber, contrasting with spherical waves in free space. The study highlights the significance of Gaussian beams, particularly from helium-neon lasers, finding a beam waist radius of approximately 12.6 μm and its position about 1.25 μm from the focus. These parameters are critical for optimizing laser beam coupling into the fiber. The research also measures the light transit time through a 100-meter fiber, revealing a light speed of approximately 2×108 m/sec, which is influenced by the fiber's refractive index. Additionally, the relationship between diode laser output power and injection current was investigated, demonstrating a linear correlation crucial for practical applications. The findings emphasize the importance of accurate measurements and configuration in improving fiber optic communication and laser performance. This comprehensive analysis provides valuable insights into the design and optimization of optical fiber systems, contributing to advancements in communication and laser technologies.

Prediction of combustion pressure with deep learning using flame images

Deep learning methods provide data-driven techniques for handling large amounts of combustion data, thus finding the hidden patterns underlying these data. This study aims to predict combustion pressure from flame images, which provide more comprehensive information about the combustion process than traditional pressure sensors. The flame images were captured from a single-cylinder 4-stroke optical gasoline direct injection (GDI) engine at 1000 rpm, 5.7 bar IMEP, and stoichiometric combustion conditions using a high-speed camera. To achieve this prediction, we employed five different models: EfficientNetB4, ResNet50, Ensemble Adversarial Inception ResNet, convolutional neural network (CNN), and CNN-XGBoost. The training dataset comprised 1350 flame images captured from a single-cylinder optical GDI engine across different combustion stages. To ensure robustness, 150 images were used for validation. The models were subjected to a testing set of 4500 flame images obtained from different cycles, to evaluate how well they could perform on new, unseen data. The results showed that EfficientNetB4 achieved an impressive R2 of 0.94 and a low RMSE of 0.70 compared to other tested models. Saliency analysis revealed that the model focuses on subtle flame characteristics and areas without intense flames, which suggests that it detects features invisible to the human eye. Additionally, the proposed deep learning approach is applied for the sake of monitoring cycle-to-cycle variations based on in-cylinder flame propagation where it is found that it produces high accuracy compared to those obtained through pressure sensors. Our findings are intended to advance the adoption of machine learning approaches for assisting in engine design and optimization.

Coupled terahertz quantum cascade wire lasers

We present mutual optical coupling in terahertz (THz) quantum cascade wire laser arrays that are flip-chip bonded to a dielectric substrate. The mounting substrate is patterned for individual electrical contacting of each wire laser of the array. The resulting sandwich-like structure supports wire laser modes with a significant part propagating outside the cavity and mediates the long range coupling. The evanescent field part of the modes couples to the adjoining ridge, which, in turn, leads to mutual optical injection-locking between them. We demonstrate this effect for both geometrically similar and dissimilar wire lasers when biased in pulsed operation with temporally overlapping bias pulses. Finite element simulations confirm our measurement results. By applying time-shifted bias pulses to individual array elements, a controllable optical injection seeding of the wire cavity is achieved. We observe intensity modification of the laser modes with changing bias pulse overlap as a result of the injection locking. By choosing both the physical spacing of the laser ridges and the intensity of the seeding laser correctly, the relative intensities of the favored lasing modes are enhanced up to 95 percent. Understanding the coupling in THz wire laser arrays is important for future device improvements in terms of higher continuous-wave operating temperatures through better thermal dissipation, and higher output power and an improved far field due to controlled coupling of their modes.

Resolving the Trap Distribution of Chalcogenide-Based Heterojunctions via Optical Injection Deep Level Transient Spectroscopy.

Chalcogenide semiconductors have emerged as promising candidates for next-generation optoelectronics, mainly benefiting from their cost-effective processability, chemical versatility, and excellent stability. However, the device performance is limited by the complex defect characteristics, necessitating a detailed understanding of the defect density, types, and distribution. This study employs optical injection deep level transient spectroscopy to characterize the trap features of antimony bismuth sulfide-based heterojunctions. Photoexcitation offers the possibility to determine the spatial distribution of traps. It reveals distinct distributions of hole and electron traps. Short-wavelength light (570 nm) detects hole traps near the hole transport layer, while long-wavelength light (830 nm) identifies electron traps near the electron transport layer. Additional intermediate-wavelength tests (670 and 755 nm) and light field distribution simulation further elucidate the trap distribution. Transient absorption and transient photocurrent also support the non-uniform trap distribution within the chalcogenide-based photodiodes.

Heterostrain-Induced Zeeman-like Splitting in h-BN-Encapsulated Bilayer WSe2.

Heterostrain is predicted to induce exceptionally rich physics in atomically thin two-dimensional structures by modifying the symmetry and optical selection rules. In this work, we introduce heterostrain into WSe2 bilayers by combining h-BN encapsulation and high-temperature vacuum annealing. Nonvolatile heterostrain gives rise to a Zeeman-like splitting associated with the elliptically polarized optical emission of interlayer K-K excitons. Further manipulation of the interlayer exciton emission in an external magnetic field reveals that the Zeeman-like splitting cannot be eliminated even in a magnetic field of up to ±6 T. We propose a microscopic picture with respect to the layer and valley pseudospin to interpret the results. Our findings imply an intriguing way to encode binary information with the layer pseudospin enabled by the heterostrain and open a venue for manipulating the layer pseudospin with heterostrain engineering, optical pseudospin injection, and an external magnetic field.

Frequency pushing and pulling in semiconductor lasers subject to optical frequency comb injection

We theoretically investigate the frequency shift of a free-running semiconductor laser when optically injected by an optical frequency comb. By numerical integration of the laser rate equations, we have identified two types of frequency shifts, frequency pulling, and frequency pushing. The free-running slave laser seems to switch between pulling and pushing in a regular manner. We have systematically determined the dependence of these shifts on comb parameters, including comb spacing and number of lines. We have found that the occurring frequency pushing seems to be almost independent of comb signals and comb spacing, while in contrast, the frequency pulling shows weak dependence on comb signals but largely affected by comb spacing. We have also shown that carrier density dynamic is the origine of these phenomena.

Full-scale evaluation of FFU configurations in an optical cleanroom injection molding for improving thermal performance and contaminant removal

Cleanrooms are critical in the semiconductor industry, particularly for optical fabrication, where even minor contamination can compromise product quality. Effective airflow and uniform airflow distribution help to prevent contaminant accumulation, mitigate temperature variations, and avoid cross-contamination, which is crucial for achieving high-quality results and compliance with industry standards. This study introduces a novel approach to optimizing Fan Filter Unit (FFU) configurations to enhance thermal performance and contaminant removal in cleanroom settings. Integrating field measurements with advanced Computational Fluid Dynamics (CFD) simulations to comprehensively evaluate four distinct FFU designs, from dispersed to centralized configurations, focused on their impact on airflow dynamics, temperature uniformity, and particle concentration. The study identifies a significant advancement in FFU configuration by demonstrating that centralized arrangements (Designs 2 and 4) substantially improve cleanroom performance. Design 4 emerged as the most effective, showcasing a marked improvement in airflow circulation, a 12 % reduction in temperature variation, and a 15 % decrease in particle concentration compared to conventional designs. This achievement underscores the novel contribution of this study in optimizing FFU configurations to enhance both thermal performance and contaminant control. These findings not only advance the theoretical understanding of FFU design but also provide practical insights for improving cleanroom environments. The study offers a significant step forward in developing efficient cleanroom designs, contributing valuable guidelines for achieving good environmental control in sensitive manufacturing processes.