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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. [ABSTRACT FROM AUTHOR]

Orthodontic patients often suffer from mucosal discomfort due to the friction stimulation of orthodontic components on the oral mucosa, and semiconductor laser can treat the oral mucosal discomfort caused by orthodontic treatment, such as redness, swelling, ulcers, etc. This study innovatively created a persistent traumatic environment in the mouth of rats to simulate the intraoral conditions of orthodontic patients, with the aim of using animal models to broaden the understanding of semiconductor laser repair mechanisms of orthodontic traumatic ulcers. 32 male Wistar rats were randomly divided into 6 groups: 1) blank control group; 2) control group; 3) chlorhexidine group; 4) laser group 1; 5) laser group 2; 6) laser group 3. The research contents included ulcer healing degree score, enzyme-linked immunosorbent assay, histological observation of stained sections of ulcer tissue, and analysis of microbial attachment on ulcer surface. The results showed that the continuous traumatic environment significantly prolonged the healing time of ulcer (P<0.05). During the ulcer duration, the proinflammatory factor level was lower, the anti-inflammatory factor level was higher and the healing score was better in the laser group (P<0.05). The antibacterial effect of semiconductor laser is less than 0.12% chlorhexidine solution; Hematoxylin-eosin tissue sections showed lower inflammatory cell infiltration and better epithelial healing in the laser group. This study shows that continuous traumatic environment can delay ulcer healing, and semiconductor laser with appropriate irradiation time is superior to traditional 0.12% chlorhexidine solution in reducing inflammation, relieving pain and promoting ulcer tissue healing. Compared with previous studies, the animal model in this study has made some progress and is closer to the real oral conditions of orthodontic patients. The results further demonstrated the potential of semiconductor laser in the treatment of oral traumatic ulcers during orthodontics. [ABSTRACT FROM AUTHOR]

In the pursuit of creating non-absorption window (NAW) structures in high-power semiconductor laser cavities, techniques like impurity-free vacancy diffusion and rapid thermal annealing induced quantum well intermixing were employed. The challenge is to induce a desired 30 nm blue shift while safeguarding the gain-emitting region from high-temperature annealing O2− bombardment effectively inhibits quantum well mixing, as demonstrated through experiments. Epitaxial wafers subjected to this treatment exhibit just a 1 nm blue shift, compared to 32 nm without O2− bombardment. These findings provide essential insights for protecting the gain-emitting region during NAW structure fabrication. [ABSTRACT FROM AUTHOR]

The semiconductor laser (SCL) is a promising light source in photodynamic therapy (PDT). Overcoming the limitation of the low-penetration depth of PDT and enhancing its therapeutic effect on cancer treatment at a deep level requires enhancing the laser power beyond 100 mW in the CW and/or pulse mode. In this paper, we presented a theoretical guide for designing and optimizing SCL parameters to achieve high CW power and high-power short-time pulses to promote laser performance in PDT. High-power CW output was achieved by optimizing the parameters that control the light–current (L–I) characteristics. Picosecond high-power pulses were predicted based on the simulation of the laser signal under sinusoidal current modulation using the optimized CW parameters along with an appropriate selection of the modulation frequency and index signal class. The characteristics of the laser signal under intensive simulations over wide ranges of modulation frequency and index were used to classify the dynamic types of the laser signal. The operating domain of each of these types was mapped over a (modulation frequency versus index), and bifurcation diagrams were constructed to illustrate the flow among these domains. We spotted the variation of both peak power and pulse width of the periodic pulses with modulation parameters. CW output with power reaching ~ 360 mW was predicted using facet reflectivities of 0.01 and 0.99, cavity length as short as 120 µm, internal loss as small as 100 m−1, and confinement factor greater than 0.2. Periodic picosecond pulses with peak power reaching ~ 440 mW were predicted when the modulation index exceeds unity and the modulation frequency is higher than one-half of the relaxation oscillation. The pulse gets narrower with the increase in the modulation index and/or frequency. The obtained results would help design SCL with high power for efficient use in PDT. [ABSTRACT FROM AUTHOR]

Copyright of Micronanoelectronic Technology is the property of Micronanoelectronic Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We present algorithms for constructing and resolving spectral problems for novel photonic crystal surface-emitting lasers with large emission areas, given by first-order PDEs with two spatial dimensions. These algorithms include methods to overcome computer-arithmetic-related challenges when dealing with huge and small numbers. We show that the finite difference schemes constructed using relatively coarse numerical meshes enable accurate estimation of several major optical modes, which are essential in practical applications. [ABSTRACT FROM AUTHOR]

The dynamics of semiconductor lasers are modelled in the time domain using a pair of differential equations known as rate equations. The analysis, based on temporal solutions of these equations, yields practical results utilised in various applications. Alternatively, an analysis employing the phase space method, a well-established analytical tool in applied mathematics, provides a more comprehensive perspective on semiconductor laser dynamics. The main purpose of this paper is to provide a detailed and intuitive introduction to phase space analysis in the context of semiconductor laser dynamics. The goal is to offer an easily comprehensible description of the mentioned method, placing emphasis on the graphical representation and physical interpretation of the results. The method effectiveness is shown through its application to selected practical problems. Furthermore, semiconductor laser dynamics can be treated as an illustrative example, showcasing the applicability of the method, which can be readily extended to other types of lasers or even more advanced dynamic systems. [ABSTRACT FROM AUTHOR]

Copyright of Micronanoelectronic Technology is the property of Micronanoelectronic Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Chronic hyperplastic candidiasis (CHC) is a chronic oral mucosal infection caused by Candida, which has potential for malignant transformation. Diagnosing CHC can be challenging due to its various manifestations. In addition, fungal treatments often prove to be ineffective, highlighting the urgent need for a new safe and efficient treatment approach. Given the potential of CHC to transform into malignancy, it is crucial to emphasize dynamic monitoring and follow-up after treatment. Objective: We attempted to investigate the effect of semiconductor laser pretreatment combined with 5-amino-levulinic acid (5-ALA) photodynamic therapy (PDT) for CHC. Methods: We presented the successful treatment of CHC with mild dysplasia in a 30-year-old man using semiconductor laser and 5-ALA PDT after antifungal therapy proved ineffective. Toluidine blue staining, autofluorescence imaging, and DNA image cytometry were combined to dynamically monitor the progress of the disease. Results: We have obtained positive outcomes with the use of laser combined with PDT treatment. The patients experienced only mild adverse reactions after the treatment, and there was no indication of recurrence or malignant transformation during the subsequent follow-up period, as observed through various auxiliary examinations. Conclusions: This case report suggests that semiconductor laser surgery combined with PDT could be a promising treatment option for patients with CHC who do not respond to antifungal therapy. In addition, the use of combined noninvasive examinations might provide a more accurate assessment of malignant transformation in patients with CHC. [ABSTRACT FROM AUTHOR]

To improve the accuracy of signal recognition in delay-based optical reservoir computing (RC) systems, this paper proposes the use of nonlinear algorithms at the output layer to replace traditional linear algorithms for training and testing datasets and apply them to the identification of frequency-modulated continuous wave (FMCW) LiDAR signals. This marks the inaugural use of the system for the identification of FMCW LiDAR signals. We elaborate on the fundamental principles of a delay-based optical RC system using an optical-injected distributed feedback laser (DFB) laser and discriminate four FMCW LiDAR signals through this setup. In the output layer, three distinct training algorithms—namely linear regression, support vector machine (SVM), and random forest—were employed to train the optical reservoir. Upon analyzing the experimental results, it was found that regardless of the size of the dataset, the recognition accuracy of the two nonlinear training algorithms was superior to that of the linear regression algorithm. Among the two nonlinear algorithms, the Random Forest algorithm had a higher recognition accuracy than SVM when the sample size was relatively small. [ABSTRACT FROM AUTHOR]

Mobile visible light communication (VLC) is key for integrating lighting and communication applications in the 6G era, yet there exists a notable gap in experimental research on mobile VLC. In this study, we introduce a mobile VLC system and investigate the impact of mobility speed on communication performance. Leveraging a laser-based light transmitter with a wide coverage, we enable a light fidelity (LiFi) system with a mobile receiving end. The system is capable of supporting distances from 1 m to 4 m without a lens and could maintain a transmission rate of 500 Mbps. The transmission is stable at distances of 1 m and 2 m, but an increase in distance and speed introduces interference to the system, leading to a rise in the Bit Error Rate (BER). The mobile VLC experimental system provides a viable solution to the issue of mobile access in the integration of lighting and communication applications, establishing a solid practical foundation for future research. [ABSTRACT FROM AUTHOR]

A method is proposed for measuring absolute distances from the low-frequency spectrum of the interference signal of a frequency-modulated laser diode. The method of modulation of the self-mixing laser signal according to the harmonic law is used, in the spectrum of which a wide range of frequency components is observed. The connection between the maximum frequency of change of the interference signal and the absolute distance to the reflector is shown. A linear dependence of the frequency corresponding to the inflection region of the decay envelope of the interference signal spectrum on the distance is shown, which can be used to implement a non-contact distance measurement method with harmonic modulation of the self-mixing laser supply current. [ABSTRACT FROM AUTHOR]

The study of extreme events (EEs) in photonics has expanded significantly due to straightforward implementation conditions. EEs have not been discussed systematically, to the best of our knowledge, in the chaotic dynamics of a Fabry–Perot laser with optical feedback, so we address this in the current contribution. Herein, we not only find EEs in all modes but also divide the EEs in total output into two categories for further discussion. The two types of EEs have similar statistical features to conventional rogue waves. The occurrence probability of EEs undergoes a saturation effect as the feedback strength increases. Additionally, we analyze the influence of feedback strength, feedback delay, and pump current on the probability of EEs defined by two criteria of EEs and find similar trends. We hope that this work contributes to a deep understanding and serves as inspiration for further research into various multimode semiconductor laser systems. [ABSTRACT FROM AUTHOR]

Chip‐based optical frequency combs address the demand for compact, bright, coherent light sources of equidistant phase‐locked lines. Traditionally, the Fourier Transform Spectroscopy (FTS) technique is considered a suboptimal choice for resolving comb lines in chip‐based sensing applications due to the requirement of long optical delays, and spectral distortion from the instrumental line shape. Here, a sub‐nominal resolution FTS technique is developed that extracts the comb's offset frequency in any spectral region directly from the measured interferogram without resorting to nonlinear f$f$‐to‐2f$2f$ interferometry. This in turn enables 10's of MHz resolution spectrometry with millimeter optical retardations currently limited by the emission linewidth and phase noise of the used lasers. Low‐pressure Doppler‐broadened absorption lines probed by widely‐tunable chip‐scale mid‐infrared optical frequen with electrical pumping are fully resolved over a span of tens of nanometers. This versatile technique paves the way for compact, electrostatically‐actuated, or even all‐on‐chip high‐fidelity FTS, and can be readily applied to boost the resolution of existing commercial instruments with compact interferometers several hundred times. [ABSTRACT FROM AUTHOR]

Due to the progress of modern technologies in covert communication, in this work a new communication system is proposed using the chaotic system resulting from optoelectronic feedback of semiconductor laser. Where the sinusoidal signal (amplitude A and frequency f were 0.0 and 0.1 a.u, respectively) was used to examine the transmission efficiency of the signal and it was found that the purity of the received signal at the receiving unit depends on the amount of synchronization between the two systems, i.e., on the coupling factor between the transmitting and receiving systems. It was found that the ideal value of the coupling factor was 270 a.u at initial condition xi1, yi1, zi1, xi2, yi2, and zi2 are 1, 1, 0.005, 1, 1, and 0.05, respectively, as the two systems showed full synchronization between them. Through the results obtained, it was found that the chaotic system resulting from the optoelectronic feedback (OEFB) presents a modern technique for encoding the signal to send it with high confidentiality, and the reason is due to the wide bandwidth of the spectrum of the chaotic system, which allows easy selection of the appropriate frequency for encoding information, and in this way it was possible to open a new field in secret communications. In fact, the percentage matches between the transmitted signal and the received signal reach 99.99%. [ABSTRACT FROM AUTHOR]

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.

Improving the output power and efficiency of broad-area diode lasers is a prerequisite for the further development of fiber lasers, solid-state laser industries, and direct semiconductor laser applications. At present, the large amount of Joule heat generated by large drive currents and limited wall-plug efficiency presents the largest challenge for improving these lasers. In this paper, a multi-junction cascade laser with low Joule heat generation is demonstrated, showing large power and conversion efficiency. We fabricated devices with different junction numbers and compared their output power. We present double-junction lasers emitting at ~915 nm with an emitter width of 500 μm, delivering 132.5 W continuous wave output power at 70 A, which is the highest power reported so far for any single-emitter laser. The power conversion efficiencies are 66.7% and 60%, at 100 W and 132 W, respectively. [ABSTRACT FROM AUTHOR]

In this study, a scheme for generating tunable microwave frequency combs (MFCs) based on optical mutual injection is proposed and experimentally investigated. The scheme is based on the optical injection of lasers to generate MFCs, and constitutes a feedback loop by using dual-laser mutual injection to obtain MFCs with a large continuous bandwidth and tunable comb spacing. The experimental setup analyzes the effects of injected optical power, modulation frequency and amplitude, and wavelength detuning on the generated MFC signals. The experimental results indicate that when the single-frequency electrical signal is set to 2 GHz, flat MFCs with amplitude variations within 10 dB can be obtained by optimizing the injected power and the frequency detuning between the two semiconductor lasers. Furthermore, the comb spacing of the MFCs can be made tunable by varying the modulation frequency and selecting the matched operating parameters to adapt to different application scenarios. [ABSTRACT FROM AUTHOR]

This study aimed to determine the effect of photobiomodulation therapy induced by semiconductor laser irradiation on human dental pulp stem cell (hDPSC) proliferation and their differentiation into odontoblast-like cells (OLCs). The effects of various semiconductor laser irradiation conditions on hDPSCs were examined. Three groups were evaluated: a single laser irradiation at 6 h post-seeding, multiple laser irradiations up to four times every 4 days after the first dose, and a control with no laser irradiation. The cells were irradiated at 10, 30, and 150 mW using a semiconductor laser. The effect of laser irradiation on hDPSC differentiation into OLCs was also determined. Four groups were evaluated, including co-culture using basic medium and dentin discs, simple culture using OLC differentiation-inducing medium, co-culture using OLC differentiation-inducing medium and dentin discs, and control culture with basic medium. The expression of the nestin, ALP, DSPP, and DMP-1 genes was measured using real-time PCR. The multiple irradiation group irradiated at 30 mW exhibited significantly more cell proliferation than the control. The expression of nestin associated with differentiation into OLCs during each culture period tended to be lower, whereas DSPP and ALP expression was higher compared with that of the control. Multiple laser irradiations at a low power of 30 mW induced significant hDPSC proliferation and might induce differentiation into OLCs. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The study investigates microstripe bars of optically isolated single-mode lasers based on heterostructures with double asymmetry, operating under sub-nanosecond current pulse pumping conditions. For microstripe bars with different filling densities of the emitting aperture, the effect of time delay dispersion of various stripes' turn-on is demonstrated, with a maximum difference up to 50 ps. The developed microstripe bar designs demonstrate stable zero mode lasing. The microstripe bar consisting of 10 stripes with a 6 μm width and a stripe period of 20 μm demonstrates pulses with a peak power of 3 W and a duration of 140 ps under 0.4 ns current pulses pumping. [ABSTRACT FROM AUTHOR]

The study examines an extensive and complete synchronization of optimal feedback with quantum dot semiconductor laser mutual coupling system. This has been achieved by resolving the transmitter and receiver equations of the quantum dot lasers. Numerous crisis areas have been observed at the time of investigating the relationship between photon density and time. The authors have selected an optimal time delay for the optical feedback so as to render an appropriate situation for intermittent dynamics. The study analyses the impact created by a long external cavity of QDSL upon the synchronization process in this mutual coupling system, in the presence of the enhancement factor of (α =3). [ABSTRACT FROM AUTHOR]

Near-field bending of a laser diode bar (i.e., the SMILE effect) degrades the laser beam brightness, adversely affecting optical coupling and beam shaping. Previous reports mainly focused on the two-dimensional near-field bending of a laser diode bar. However, the near-field bending of a laser diode bar not only occurs in the laser bar growth direction, but also in the beam propagation direction. The present article proposes the three-dimensional near-field bending of a laser diode array, which is commonly known as the three-dimensional spatial SMILE effect. Through theoretical and simulated investigations, it has been found that a laser bar array not only deforms in the fast axis direction to cause the traditional two-dimensional SMILE effect but also experiences an additional deformation of approximately 2 μm in the laser emission direction simultaneously. Due to the SMILE effect in the beam propagation direction, not all emitters are aligned in a straight line, and some emitters experience defocusing during collimation. Consequently, there is an increase in the residual divergence angle and beam width, resulting in a degradation of the laser bar array's beam quality. According to the theoretical calculations, ZEMAX simulations, and experimental results, for a FAC (fast axis collimation) with a focal length of 300 μm, the divergence angle of single emitter after collimating in the fast axis increases from 4.95 mrad to 6.46 mrad when the offsetting of the working distance between the incident beam waist and FAC lens increases from 0 μm to 2 μm. [ABSTRACT FROM AUTHOR]

It is shown that fine and rough structures can be differentiated in the radiation spectrum of a powerful laser diode. The relationship between the spectrum's characteristics and the internal parameters of the laser's structure is established and verified experimentally during degradation of the device. The effect of losses in the resonator and the coherence of laser radiation on both fine and rough structures of the radiation spectrum is shown. [ABSTRACT FROM AUTHOR]

In this research, we demonstrate a wavelength-stable continuous wave (CW) distributed feedback (DFB) quantum cascade laser (QCL) emitting at 7.2 μm using a surface metal grating approach without epitaxial regrowth. The deep metal grating provides an appropriate DFB coupling coefficient and enhanced thermal extraction, resulting in improved lasing performance and the realization of impressive wavelength stability. Quantitatively, the temperature tuning coefficient of the single-mode emission is only 0.54 nm/°C from 20 °C to 70 °C, and the current tuning coefficient of the single-mode emission is 3.2 nm/A from 1.0 A to 1.6 A. A DFB-QCL with a 2 mm cavity length exhibits a low threshold current of 0.6 A and a power of 1.1 W with a slope efficiency of 1 W/A in the CW mode at 300 K. A single-mode operation with a side mode suppression ratio of 33 dB and a single-lobed far-field without beam steering is obtained in the working temperature range of 20–70 °C The improved wavelength stability using a deep surface metal grating approach promises simplified fabrication, which is meaningful for the commercial applications of QCLs. [ABSTRACT FROM AUTHOR]

We present algorithms for constructing and resolving spectral problems for novel photonic crystal surface-emitting lasers with large emission areas, given by first-order PDEs with two spatial dimensions. These algorithms include methods to overcome computer-arithmetic-related challenges when dealing with huge and small numbers. We show that the finite difference schemes constructed using relatively coarse numerical meshes enable accurate estimation of several major optical modes, which are essential in practical applications.

Abstract Introduction The large amount of intraoperative bleeding and the high incidence of postoperative hematuria are still common factors affecting the prostate surgery treatment effect. Our research aimed to observe the effect of prostatic enucleation using 1,470 nm semiconductor laser on the amount of bleeding in patients with different sizes of prostate hyperplasia. Methods According to the size of the prostate, forty eligible patients with benign prostatic hyperplasia (BPH) were enrolled and divided into low and high volume group in this study. Hemoglobin decline, urinating condition, complications and erectile function were collected and compared before and after surgery. Results Our data showed that hemoglobin decline was (10.0 ± 6.2) g/L and (12.1 ± 7.8) g/L, respectively for two group after surgery (P = 0.363). Urination was significantly improved following surgery in both groups of patients (P

Weak interactions of temporal cavity solitons resulting from gain saturation and recovery in a delay differential model of a long cavity semiconductor laser were studied numerically and analytically using an asymptotic approach. This paper shows that in addition to the usual soliton repulsion leading to a harmonic mode-locking regime, soliton attraction is also possible in a laser with a nonzero linewidth enhancement factor. It is shown numerically that this attraction can lead either to pulse merging or to pulse bound-state formation.

With the progress of integrated optoelectronic devices over recent decades, the semiconductor research has increasingly focused on tunable semiconductor lasers featuring a compact structure and simplified fabrication. In this manuscript, we present a proposal for a V-Cavity tunable semiconductor Laser (VCL) at a center wavelength of 940 nm. The theoretical analysis encompasses the threshold conditions of the laser, considering various cavity length differences within the waveguide layer structure. Moreover, we showcase a VCL with a waveguide width of 3 μm and a channel interval of 0.6 nm. Through the optimization of polynomial parameters associated with the curved waveguide, the VCL attains a transmittance exceeding 99.4 %. Additionally, we address the determination of optimal parameter ranges and solve the optical field distribution within the half-wave coupler. The simulation results exhibit that the half-wave coupler, employing optimized parameters, achieves remarkable single-mode selectivity when operating at a central wavelength of 940 nm. Notably, a maximum side mode suppression ratio (SMSR) of 47.9 dB is attainable with a half-wave coupler length of 45 μm and a waveguide gap of 1.7 μm.

A systematic study of a series of InGaAs/GaAs lasers in the 1–1.3 μm optical range based on quantum wells (2D), quantum dots (0D), and quantum well-dots of transitional (0D/2D) dimensionality is presented. In a wide range of pump currents, the dependences of the lasing wavelength on the layer gain constant, a parameter which allows comparing lasers with different types of active region and various waveguide designs, are measured and analyzed. It is shown that the maximum optical gain of the quantum well-dots is significantly higher, and the range of lasing rawavelengths achievable in edge-emitting lasers without external resonators is wider than in lasers based on quantum wells and quantum dots. [ABSTRACT FROM AUTHOR]

We studied the influence of the focused ion beam milling of ridge waveguides on lasing parameters of edge-emitting lasers, based on a separate confinement double heterostructure. It is shown that there are three degrees of influence, according to the etching depth: modification of the waveguide properties only, a decrease in efficiency without changing the threshold current, and a simultaneous deterioration in the threshold current and efficiency with significant modification of the optical characteristics of the laser. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effect of laser irradiation to computer-aided design/computer-aided fabrication (CAD/CAM) resin blocks coated with a silane coupling agent on the bond strength between resin blocks and composite resin. The CAD/CAM resin blocks used in this study were Cerasmart 300 (GC) and Vita Enamic (Vita); they were cut into plates and then subjected to a series of treatments. After processing with a silane coupling agent, treatment with a semiconductor laser was performed at 3.0, 5.0, and 7.0 W, followed by bonding procedures. The control group included those exposed to silane and bonded without laser application. After bonding, a mold with a simulated cavity was formed on the specimen and filled with flowable composite resin, and they were stored for 24 h or stressed by thermal cycling for subsequent testing that assessed the shear bond strength (n = 10). The results revealed that the bond strength was significantly enhanced by laser irradiation after applying a silane coupling agent (p < 0.03), whereas significant increase was not detected between the materials (p > 0.05). Particularly, 7 W laser irradiation had a significant increase on the bond strength between the composite resin and Cerasmart block after thermal cycling (p = 0.009). The SBS of the composite resin to CAD/CAM resin blocks was significantly enhanced by laser irradiation after silane coupling agent application. [ABSTRACT FROM AUTHOR]

Antimicrobial photodynamic therapy (aPDT) used to sterilize carious dentin may irritate pulp tissues because of tissue-penetrating laser and singlet oxygen generation. This study aimed to assess the effects of aPDT on rat pulp tissues. A cavity formed in a rat maxillary first molar was treated with aPDT. The combined photosensitizer and laser irradiation conditions in the aPDT groups were as follows: methylene blue and 100 mW for 60 s, brilliant blue (BB) and 100 mW for 60 s, BB and 50 mW for 120 s, and BB and 200 mW for 30 s. Each cavity was treated with an all-in-one adhesive and filled with flowable resin. aPDT was not applied for the control. In each group, the rats were sacrificed on postoperative days 1 and 14, and thin sections of the treated teeth were prepared. Pulp tissue disorganization (PTD), inflammatory cell infiltration (ICI), and tertiary dentin formation (TDF) were evaluated. At 1-day evaluation, there were significant differences between the aPDT group and controls with respect to PTD and ICI (p < 0.01); 14 days later, almost all specimens showed tertiary dentin formation. The application of aPDT caused reversible damage to the rat pulp, while in the long term, healing occurred with the formation of tertiary dentin. [ABSTRACT FROM AUTHOR]

Introduction: The large amount of intraoperative bleeding and the high incidence of postoperative hematuria are still common factors affecting the prostate surgery treatment effect. Our research aimed to observe the effect of prostatic enucleation using 1,470 nm semiconductor laser on the amount of bleeding in patients with different sizes of prostate hyperplasia. Methods: According to the size of the prostate, forty eligible patients with benign prostatic hyperplasia (BPH) were enrolled and divided into low and high volume group in this study. Hemoglobin decline, urinating condition, complications and erectile function were collected and compared before and after surgery. Results: Our data showed that hemoglobin decline was (10.0 ± 6.2) g/L and (12.1 ± 7.8) g/L, respectively for two group after surgery (P = 0.363). Urination was significantly improved following surgery in both groups of patients (P < 0.05), and no permanent urinary incontinence and sexual dysfunction and so no serious complications occurred. Conclusion: The above results suggested that prostatic enucleation using 1,470 nm semiconductor laser can be safe and effective for prostatic hyperplasia, and this surgery produced no significant effect on the amount of bleeding in whatever size of the prostate. [ABSTRACT FROM AUTHOR]

The behavior of the optical pulse release was investigated during chirped pulses amplification, which consisted of two chirped fiber Bragg grating and one semiconductor optical amplifier (SOA). This occurred when the pulse width, (rp) << carrier lifetime (rc), as well as the effect of the length parameter on the shape and spectrum of the electric field, intensity, and phase of amplified pulses, were taken into consideration. The purpose of this research is to investigate the effect of release length on the temporal electric field laser amplifier while simultaneously generating optical pulses with the help of a mode-locked laser system semiconductor. In the scenario where τp and τc are taken into account, we discovered that the length of the release has a significant impact on the modes of the phase and the electric field. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The study of extreme events (EEs) in photonics has expanded significantly due to straightforward implementation conditions. EEs have not been discussed systematically, to the best of our knowledge, in the chaotic dynamics of a Fabry–Perot laser with optical feedback, so we address this in the current contribution. Herein, we not only find EEs in all modes but also divide the EEs in total output into two categories for further discussion. The two types of EEs have similar statistical features to conventional rogue waves. The occurrence probability of EEs undergoes a saturation effect as the feedback strength increases. Additionally, we analyze the influence of feedback strength, feedback delay, and pump current on the probability of EEs defined by two criteria of EEs and find similar trends. We hope that this work contributes to a deep understanding and serves as inspiration for further research into various multimode semiconductor laser systems.

Mobile visible light communication (VLC) is key for integrating lighting and communication applications in the 6G era, yet there exists a notable gap in experimental research on mobile VLC. In this study, we introduce a mobile VLC system and investigate the impact of mobility speed on communication performance. Leveraging a laser-based light transmitter with a wide coverage, we enable a light fidelity (LiFi) system with a mobile receiving end. The system is capable of supporting distances from 1 m to 4 m without a lens and could maintain a transmission rate of 500 Mbps. The transmission is stable at distances of 1 m and 2 m, but an increase in distance and speed introduces interference to the system, leading to a rise in the Bit Error Rate (BER). The mobile VLC experimental system provides a viable solution to the issue of mobile access in the integration of lighting and communication applications, establishing a solid practical foundation for future research.

Optical chaos has attracted widespread attention owing to its complex dynamic behaviors. However, the time delay signature (TDS) caused by the external cavity mode reduces the complexity of optical chaos. We propose and numerically demonstrate the critical dispersion of chirped fiber Bragg grating (CFBG) for eliminating the TDS of laser chaos in this work. The critical dispersion, as a function of relaxation frequency and bandwidth of the optical spectrum, is found through extensive dynamics simulations. It is shown that the TDS can be eliminated when the dispersion of CFBG is above this critical dispersion. In addition, the influence of dispersive feedback light and output light from a laser is investigated. These results provide important quantitative guidance for designing chaotic semiconductor lasers without TDS. [ABSTRACT FROM AUTHOR]

We analyze the characteristics of semiconductor emitters based on separate-confinement double heterostructures with quantum wells with different configurations of waveguide layers. Lasers with narrow and broad waveguides are considered as applied to the problem of increasing the output power. Semiconductor emitters with undoped and doped waveguide layers are compared. We consider lasers with ultranarrow and broad strongly asymmetric waveguides. It is shown that the reduction of series and thermal resistance reduces the self-heating of lasers and increases the output power and efficiency. The prospects of using the epitaxial integration for designing lasers with several tunnel-coupled emitting sections for increasing the output power and luminosity are considered. The possibility of constructing monolith-integrated thyristor lasers combining the emitting section and an electron switch in a single crystal is demonstrated. [ABSTRACT FROM AUTHOR]

Weak interactions of temporal cavity solitons resulting from gain saturation and recovery in a delay differential model of a long cavity semiconductor laser were studied numerically and analytically using an asymptotic approach. This paper shows that in addition to the usual soliton repulsion leading to a harmonic mode-locking regime, soliton attraction is also possible in a laser with a nonzero linewidth enhancement factor. It is shown numerically that this attraction can lead either to pulse merging or to pulse bound-state formation. [ABSTRACT FROM AUTHOR]

In order to solve the problem of Catastrophic Optical Damage (COD) caused by the rapid rise of the cavity surface temperature during the long-term high temperature operation of the laser, it is proposed that the addition of Al2O3 coating and the thermal insulation structure together at the semi-conductor laser surface, it can reduce the temperature of laser cavity surface and prevent the generation of COD. First, a simplified semi-conductor laser model is established to analyze solid heat transfer. Then, the cavity surface temperature of the laser model is simulated at 550 K when there is no coating and no insulation structure, coating and no insulation structure, no coating and insulation structure, and when the coating and insulation structure act together, the ceramic heat insulation is used in the heat insulation structure, GaAs is used in the cavity surface material, Cu is used in the heat sink and AlGaAs is used in the contact layer. The results of 4 groups of contrast experiments show that the temperature of the cavity surface can be controlled below 393.15 K when the coating and the thermal insulation structure act together. 550 K high temperature in the laser cavity surface coating and thermal insulation structure under the dual protection, can effectively prevent the generation of COD, so that the life of the laser can be improved.

Asymmetric Mach-Zehnder interferometers (AMZIs) can, in principle, enable continuous wavelength tuning of a laser when used as intra-cavity filters. Their simplicity and good compatibility with generic foundry platforms are major advantages. However, the difficulty to develop a well-defined and robust control strategy is an important drawback which restricts the use-cases of these tunable lasers. Here, we make an in-depth investigation of the tunability properties of a laser including a single-stage AMZI in its cavity. We find that due to imperfections of Electro-Optic Phase Modulators (EOPMs), the dependence of the phase variation with the applied voltage is not linear. Because integrated EOPMs cannot be individually calibrated, these nonlinearities prevent a precise and independent tuning of the phase and amplitude of the AMZI transfer function, and thus continuous tuning cannot be reliably achieved. To overcome this issue, we propose a refined control strategy which allows for semi-continuous tuning. With this approach, we demonstrate a piece-wise continuous tuning of the emission wavelength by taking advantage of the coupling between amplitude and phase in the AMZI response. With our refined control strategy, we achieve tuning of the emission wavelength over the full free spectral range (FSR) of the AMZI.

We propose and demonstrate a measurement technique of the intrinsic modulation responses of semiconductor lasers with high sensitivity in a wide modulation frequency range. The technique is based on the two-tone optical modulation and lock-in detection of an optical spectrum having modulation sidebands. The measured modulation response of a conventional 1.55-μm distributed feedback laser indicates that the lock-in detection improves the signal-to-noise ratio by 22 dB. This significant improvement allows measurement of the modulation response up to 75 GHz even though the 3-dB bandwidth of the distributed feedback laser is only 11 GHz. Our technique is suitable for evaluation of the intrinsic modulation response of wide-bandwidth semiconductor lasers free from device parasitic effects.

Semiconductor lasers play critical roles in many different systems, ranging from optical communications to absorption spectroscopy for environmental monitoring. Despite numerous applications, many semiconductor lasers have problems such as significant beam divergence and polarization instability. External optical elements like objective lenses and polarizers are usually needed to address these issues. This Review will discuss how these issues have recently been dealt with by instead integrating metasurfaces into semiconductor lasers. This necessitates the development of innovative fabrication methods; these will also be the topic of this Review. Metasurfaces can be integrated on the emitting facet of a laser. This can help select the lasing mode or can be used just to modify the output beam properties without affecting the modes. They can also be integrated monolithically with lasers through waveguides, or work in an external cavity configuration. These integrated devices provide novel optical functions, such as direct orbital angular momentum (OAM) mode generation, wavelength tuning and holographic pattern generation. We hope this Review will help extend the use of metasurface-integrated semiconductor lasers to scientific and industrial systems that employ lasers.

Two microwave photonic signal processing structures, which are capable to realise microwave frequency division with a tunable integer or non-integer division ratio, are presented. They are based on applying an RF signal into a Mach Zehnder modulator, which is biased to generate a carrier-suppressed double sideband (DSB) or single sideband (SSB) optical signal. The carrier-suppressed DSB optical signal consists of the upper and lower $1^{\rm st}$ order sidebands with a separation of two times the input RF signal frequency. The carrier of the SSB optical signal is suppressed by a fibre Bragg grating (FBG) connected to the modulator output. Hence the FBG output consists of the upper $1^{\rm st}$ order and lower $2^{\rm nd}$ order sidebands with a separation of three times the input RF signal frequency. The carrier-suppressed DSB or SSB optical signal is injected into a semiconductor laser. The semiconductor laser is oscillated in the period-one state that generates a number of equally spaced frequency components, which are frequency locked by the injection light wave. Beating of these optical frequency components at the photodetector produces an RF signal with a frequency of 2/ $N$ or 3/ $N$ times the input RF signal frequency where $N$ can be between 3 and 6. Hence the 2/ $N$ frequency divider can realise 2/3, 1/2, 2/5 and 1/3 frequency division operation, and the 3/ $N$ frequency divider can realise 3/4, 3/5 and 1/2 frequency division operation. The proposed 2/ $N$ and 3/ $N$ frequency dividers have a very simple structure compared to the reported photonics-based microwave frequency divider that can realise both integer and non-integer frequency divisions. The frequency division ratio can be tuned by simply adjusting the forward bias current of the semiconductor laser subject to optical injection. Experimental results demonstrate the two proposed structures can realise microwave frequency division with a tunable integer and non-integer division ratio for different input RF signal frequencies of 10 to 18 GHz, and over 60 dB output signal-to-noise ratio performance. More than 27 dB suppression in the unwanted frequency components around the frequency divided signal is also demonstrated.

This paper presents a detailed experimental investigation of the nonlinear dynamics of a dual-beam optically injected semiconductor laser. Unlike previous works, we focus on the situation where the power and the frequency of the injection light wave are fixed and the free running frequency of the laser subject to optical injection is in between the two injection beams that have a large frequency separation. The nonlinear dynamics of the slave laser (SL), i.e., the laser subject to optical injection, for different SL forward bias currents are examined. Results show, in addition to the regenerated injection light wave, a fundamental oscillation together with its harmonics are generated when the SL interacts with its nearby injection beam. The SL output frequency components are stabilised when one of the harmonics of the fundamental oscillation is located at the injection beam that is far away from the free running SL. More than six-fold improvement in the frequency stability of the resultant output microwave signal, compared to that generated by optical mixing, is obtained. Experimental results also show the SL nonlinear dynamics have different behaviours when the two injection beams have different frequency separations.