Laser Devices Research Articles

Effects of wearable visual cueing on gait pattern and stability in patients with Parkinson's disease.

The present study examined the effects of wearable visual cues, provided by a wearable laser device, on the gait pattern and stability in patients with Parkinson's disease (PD). In total, 18 patients with a clinical diagnosis of idiopathic PD (Hoehn and Yahr stage II-III) and 18 healthy controls were included. The main outcome measures included spatiotemporal parameters, sagittal plane kinematic parameters of joints in lower limbs, and dynamic center of pressure (COP) parameters. Significant intra-group improvement in gait parameters was observed in PD patients. Compared with that at baseline, the gait pattern improved in PD patients under the cued condition, with longer stride length and higher toe clearance, as well as shortening of double stance phase, especially the stride length, double stance phase and toe clearance were not significantly different between cued condition and healthy control groups. In kinematics, the ankle peak dorsiflexion in swing phase and the hip range of motion (ROM) in gait cycle was significantly improved in PD patients with visual cues and close to healthy controls. Decreased anteroposterior (AP) position of COP improved gait stability in patients with PD under the cued condition. Multiple linear regression analysis showed that the AP position has a negative correlation with ankle peak dorsiflexion in swing phase. Pearson's correlation coefficients showed that the minimum toe clearance (Mini TC) was positively correlated with the ankle peak dorsiflexion in swing phase. The immediate effect of wearable visual cues improved the gait pattern and stability in PD patients, suggesting that it may be effective when applied as an alternative technique in rehabilitation training for PD patients.

Interface tomography of GaInAs/AlInAs quantum cascade laser active regions

We present a high-resolution electron tomography study of buried ultra-thin layers and their interfaces from the active region of a (Ga,In)As/(Al,In)As quantum cascade laser (QCL) test structure. Using a high-angle annular dark-field scanning transmission electron microscopy image series, a three-dimensional (3D) reconstruction of the complex layer structure is obtained. From this 3D information, we determine quantitative values for the chemical width and, simultaneously and independently, the root mean square roughness (rms) and lateral correlation length of the individual interfaces of a cascade using topographic height maps. The interfacial widths are comparably small for all interfaces within a cascade and the layer thicknesses show only a small standard deviation of less than one monolayer. The rms roughness is systematically lower at the direct (Ga,In)As-on-(Al,In)As interface compared to its inverse. In addition, using the one-dimensional height–height correlation function, different lateral correlation lengths along the two perpendicular in-plane directions are detected indicating a distinct anisotropy of the interface morphology. Our accurate and comprehensive results on the QCL test structure will serve as feedback to evaluate the growth process and help to assess the performance of corresponding future laser devices in detail.

First, second and third order NLO response of alkaline earth metals doped C6O6Li6 organometallic complexes

The geometric, electronic, linear and nonlinear (NLO) properties of pure C6O6Li6 and alkaline earth metals (AEM) doped C6O6Li6 organometallics are studied through quantum chemical methods. Interaction (Eint) and vertical ionization energies illustrate the thermodynamic and electronic stabilities of considered AEM@C6O6Li6 organometallic complexes, respectively. The highest interaction energy value is noticed for Ca@C6O6Li6 complex (–22.78 kcal/mol). After doping of alkaline earth metals, HOMO-LUMO energy gap (H-L Egap) is remarkably reduced. The variation in H-L Egap indicates the conductive properties of these complexes which occur due to transfer of electrons from the alkaline earth metals to the C6O6Li6 surface or vice versa. The electronic density shifting is also supported by natural bond orbital (NBO) charge and molecular orbitals analyses. UV–VIS analysis is used to confirm the electronic excitations. These organometallics show deep ultra-violet transparency below 200 nm which justifies their application in future laser devices. A noticeable NLO response is observed for these organometallics which is confirmed from the static first order hyperpolarizability (up to 1.90 × 104 au) and second order hyperpolarizability (up to 7.11 × 106 au) along with higher refractive index (up to 1.68 × 10−12 au) at 532 nm. The hyperpolarizability values are further enhanced at dynamic frequencies and these are increased up to 5.82 × 1010 au. These results illustrate the use of these organometallics in optical technologies for achieving better dc-Kerr effect and second harmonic generation effects.

Recent advances in thulium-doped fiber lasers based on saturable absorber materials at 2000 nm

Thulium-doped fiber laser (TDFL) devices are a promising laser source technology for applications in the wavelength of 2000 nm, such as spectroscopy, sensing, medical, among many others. Several pulse regimes employing different approaches have been constantly demonstrated in the scientific literature. Particularly, the development of new saturable absorber (SA) materials with exceptional nonlinear optical properties has become an efficient methodology for generating short pulses in fiber laser cavities at 2000 nm. Looking for clarifying the current state of the art of TDFL technology at 2000 nm, we review in this paper the main achievements of TDFLs in the last five years (2022–2018) based on SA materials. Nonlinear optical properties of these materials, experimental setup arrangements, as well as new avenues are addressed in this review for the advancements in source laser technologies operating at 2000 nm.

Prospective Evaluation of the Safety and Efficacy of Thermomechanical Fractional Injury for Perioral Rhytides.

Perioral rhytides can be treated with laser and energy-based devices. More recently, a novel fractional thermomechanical skin rejuvenation system was developed to cause controlled thermal injury through direct heat transfer. A prospective clinical trial evaluated the safety and efficacy of a thermomechanical fractional injury device (Tixel 2, Novoxel, Netanya, Israel) for perioral rhytides. Subjects with moderate-to-severe perioral rhytides were enrolled and underwent 4 monthly treatments. Twenty-three subjects were enrolled and completed all study visits. Mean age was 62.5 years, and 100.0% were women. Fitzpatrick Skin Types I-IV were included. For Fitzpatrick Wrinkle Classification System (FWCS), mean baseline score was 6.9. Per investigator, there was a mean 1.9-grade improvement in FWCS at 3-month follow-up ( p < .0001). At 3-month follow-up, 8.7% (n = 2) of subjects had a 3-grade improvement, 69.6% (n = 16) had a 2-grade improvement, and 21.7% (n = 5) had a 1-grade improvement. For physician Global Aesthetics Improvement Scale at 3-month follow-up, 69.6% (n = 16) had 76% to 100% improvement, 13.0% (n = 3) had 51% to 75% improvement, and 17.4% (n = 4) had 26% to 50% improvement. There were no severe adverse events, and subjects experienced minimal pain. A novel device using thermomechanical fractional injury was demonstrated to be safe and effective in the treatment of perioral rhytides.

Clinical application of fluorescence lasers to evaluate the efficacy of arresting caries with silver diamine fluoride

Objective: This clinical trial used fluorescence lasers to assess the effectiveness of Silver Diamine Fluoride (SDF) in preventing active dentin caries in baby teeth. Subject and method: Preschool children aged 3 to 5 years old with at least one active dentin caries lesion were selected from a SOS Children's Village in Vietnam. A total of 32 children with 126 caries lesions were treated with 38% SDF, applied only once. DIAGNOdent pen 2190 - Kavo device and sharp sickle-shaped probes were used to evaluate lesions independently at certain timepoints including: Before the intervention and 5 minutes, one day, and one week after the intervention. For the evaluation of treatment results, the caries lesions were diagnosed as prevented if their surfaces were hard and difficult to probe or the measured laser index ≤ 20, while the lesions were assessed as active if they were soft and easy to probe or the measured laser index &gt; 20. Result: In general, before SDF was applied, all decayed tooth surfaces had soft dentin and laser indexes &gt; 30. The average value of laser index measured on caries lesions was significantly reduced from 88.2 (SD = 9.3) at baseline to 19.6 (SD = 13.7) at one week after intervention (p&lt;0.001, χ2 test). Based on fluorescence laser method, the caries arrest rates were 80.2%, 73.2% and 70.6% respectively for the post-intervention periods, while the assessment by probes for caries arrest rates were 82.5%, 80.2% and 77.8%, respectively (p&lt;0.05, χ2 test). The difference between the two methods was due to some caries lesions that were smooth and hard on probing but still have laser index &gt; 20. Conclusion: The fluorescence laser device can be applied clinically to assess the effectiveness of preventing caries with SDF, the evaluation results are more accurate than the lesion probe method.

Inhalation anesthesia in laser surgery of retinopathy of prematurity

Purpose: to assess the efficacy of inhalation anesthesia with laryngeal mask in extremely premature infants with low or extremely low birthweight and somatic comorbidities during the surgery of retinopathy of prematurity (ROP) in the active phase of the disease. Materials and methods. 477 infants of 25 to 32 weeks’ gestational age were treated by delimiting retinal laser photocoagulation. Inductive anesthesia with Sevoflurane (BAXTER HEALTHCARE Corp, USA) was followed by placing a laryngeal mask. The delimiting retinal laser photocoagulation was performed using laser devices with an adapter on a binocular forehead ophthalmoscope Supra (Quantel Medical, France) and LachtaMylon (Lasermedservis, Russia,). After the surgery, the recovery from sedation and return of consciousness took 7 to 10 minutes. Results. An inhalation of Sevoflurane with the adoption of a laryngeal mask airway significantly decreases complications of anesthesia in premature infants with comorbidities and reduces the length of hospital stay. The quick clearance of Sevoflurane makes it possible to begin feeding the infant one hour after the surgery. Conclusion. Inhalation anesthesia with Sevoflurane is a method ensuring that preterm infants receive adequate anesthesia in the treatment of retinopathy of prematurity in its active phase.

Ultrapulse Fractional CO2 Laser With Different Fluences and Densities in the Prevention of Periorbital Laceration Scars: A Split-Scar, Evaluator-Blinded Study.

Periorbital laceration can result in complex, permanent scars, and even lead to serious complications such as cicatricial ectropion. Early intervention with laser devices has been suggested as a novel modality to reduce scar formation. However, no consensus exists regarding the optimal treatment parameters for scar management. This study evaluated the efficacy and safety of ultrapulse fractional CO2 laser (UFCL) with different fluences and densities in preventing periorbital surgical scars. To assess the efficacy and safety of UFCL with different fluences and densities in the prevention of periorbital laceration scars. A prospective, randomized, blinded study was conducted on 90 patients with periorbital laceration scars of 2 weeks old. Four treatment sessions of UFCL were administered to each half of the scar at 4-week intervals, with halves treated with high fluences with low density versus low fluences with low-density treatment. Vancouver Scar Scale was used to assess the 2 portions of each individual scar at baseline, final treatment, and 6 months. The patient's 4-point satisfaction scale was used to evaluate the patient's satisfaction at baseline and 6 months. Safety was evaluated by registration of adverse events. Eighty-two of 90 patients completed the clinical trial and follow-up. There was no significant difference in Vancouver Scar Scale and satisfaction score between different laser settings between the two groups (P > 0.05). Adverse events were minor and no long-term side effects were noted. Early application of UFCL is a safe, strategy to significantly improve the final traumatic periorbital scar appearance. Objective evaluation of scars did not identify differences in scar appearance between high fluences with low density versus low fluences with low density of UFCL treatment. Level III.

Impact of thermal oxidation uniformity on 150 mm GaAs- and Ge-substrate VCSELs

Vertical cavity surface emitting laser (VCSEL) devices and arrays are increasingly important in meeting the demands of today’s wireless communication and sensing systems. Understanding the origin of non-uniform wet thermal oxidation across large-area VCSEL wafers is a crucial issue to ensure highly reliable, volume-manufactured oxide-confined VCSEL devices. As VCSEL wafer diameters approach 200 mm, germanium (Ge) is emerging as an alternative substrate solution. To this end, we investigate the uniformity of 940 nm-emitting VCSEL performance across 150 mm diameter GaAs- and Ge-substrates, comparing the oxidation method in each case. Nominally identical epitaxial structures are used to evaluate the strain induced wafer bow for each substrate type with Ge exhibiting a reduction of over 100 μm in the peak-to-valley distortion when compared with GaAs. This wafer bow is found to be the principal cause of centre-to-edge oxidation non-uniformity when utilising a conduction-heated chuck furnace, in comparison to a convection-heated tube furnace. Using on-wafer testing of threshold current, differential resistance, and emission wavelength, device performance is demonstrated for the first time across a 150 mm Ge wafer, and is shown to be comparable to performance on GaAs substrates, when the effects of oxidation uniformity are removed. These results provide evidence that there is a realistic path to manufacturing high yield VCSELs, over wafer diameters approaching those used in Si-photonics, via Ge substrates.

Evaluating high power laser therapy (HPLT) as treatment for chemotherapy-induced oral mucositis in paediatric patients with oncohematological diseases.

Oral mucositis (OM) is one of the most debilitating side effects of chemotherapy. Among the current methods used in OM management, the feasibility of high power laser therapy (HPLT) has been proposed but not fully evaluated. The aim of this study was to evaluate the efficacy of HPLT in the treatment of OM in paediatric patients. Fourteen oncohematological paediatric patients treated with chemotherapy and/or hematopoietic stem cell transplantation and affected by OM at different grades were enrolled in this study. All patients were treated with a class IV laser device in four sessions for four consecutive days, OM was evaluated with the WHO-OTS scale. The perception of pain was assessed by the visual analog scale. Photographs of and information about lesions and patient questionnaires were taken and collected, respectively. Descriptive analyses and the Wilcoxon signed-rank test (nonparametric test) were used, with a statistical significance of α=.05. After a week into the treatment, 57% of patients were completely healed, whereas the whole cohort experienced a drastic decrease in pain, from an average value of 5.8-1.1 (p=.0016). The average number of injuries per patient decreased from 7.4 to 3.1 (p=.008). High power laser therapy appears to be a safe and efficacious method for managing OM. It reduces pain and severity of oral cavity injuries. Further studies are needed to determine the optimal parameters useful in OM treatment and to evaluate the relative effectiveness of HPLT to other treatments like LLLT.

Unbiased Screening of Novel Infrared Nonlinear Optical Materials with High Thermal Conductivity: Long-neglected Nitrides and Popular Chalcogenides.

Traditional infrared (IR) nonlinear optical (NLO) materials such as AgGaS2 are crucial to key devices for solid-state lasers, however, low laser damage thresholds intrinsically hinder their practical application. Here, a robust strategy is proposed for unbiased high-throughput screening of more than 140 000 materials to explore novel IR NLO materials with high thermal conductivity and wide band gap which are crucial to intrinsic laser damage threshold. Via our strategy, 106 compounds with desired band gaps, NLO coefficients and thermal conductivity are screened out, including 8 nitrides, 68 chalcogenides, in which Sr2 SnS4 is synthesized to verify the reliability of our process. Remarkably, thermal conductivity of nitrides is much higher than that of chalcogenides, e.g., 5×AgGaS2 (5.13 W/m K) for ZrZnN2 , indicating that nitrides could be a long-neglected system for IR NLO materials. This strategy provides a powerful tool for searching NLO compounds with high thermal conductivity.

Ultraviolet Exciton-Polariton Light-Emitting Diode in a ZnO Microwire Homojunction.

Low-dimensional ZnO, possessing well-defined side facets and optical gain properties, has emerged as a promising material to develop ultraviolet coherent light sources. However, the realization of electrically driven ZnO homojunction luminescence and laser devices is still a challenge due to the absence of a reliable p-type ZnO. Herein, the sample of p-type ZnO microwires doped by Sb (ZnO:Sb MWs) was synthesized individually. Subsequently, the p-type conductivity was examined using a single-MW field-effect transistor. Upon optical pumping, a ZnO:Sb MW showing a regular hexagonal cross-section and smooth sidewall facets can feature as an optical microcavity, which is evidenced by the achievement of whispering-gallery-mode lasing. By combining an n-type ZnO layer, a single ZnO:Sb MW homojunction light-emitting diode (LED), which exhibited a typical ultraviolet emission at a wavelength of 379.0 nm and a line-width of approximately 23.5 nm, was constructed. We further illustrated that strong exciton-photon coupling can occur in the as-constructed p-ZnO:Sb MW/n-ZnO homojunction LED by researching spatially resolved electroluminescence spectra, contributing to the exciton-polariton effect. Particularly, varying the cross-sectional dimensions of ZnO:Sb wires can further modulate the exciton-photon coupling strengths. We anticipate that the results can provide an effective exemplification to realize reliable p-type ZnO and tremendously promote the development of low-dimensional ZnO homojunction optoelectronic devices.

A unified calibration method of 3D laser profile measurement with different of laser-line lengths

PurposeExisting calibration methods mainly focus on the camera laser-plane calibration of a single laser-line length, which is not convenient and cannot guarantee the consistency of the results when several three-dimensional (3D) scanners are involved. Thus, this study aims to provide a unified step for different laser-line length calibration requirements for laser profile measurement (LPM) systems.Design/methodology/approach3D LPM is the process of converting physical objects into 3D digital models, wherein camera laser-plane calibration is critical for ensuring system precision. However, conventional calibration methods for 3D LPM typically use a calibration target to calibrate the system for a single laser-line length, which needs multiple calibration patterns and makes the procedure complicated. In this paper, a unified calibration method was proposed to automatically calibrate the camera laser-plane parameters for the LPM systems with different laser-line lengths. The authors designed an elaborate planar calibration target with different-sized rings that mounted on a motorized linear platform to calculate the laser-plane parameters of the LPM systems. Then, the camera coordinates of the control points are obtained using the intersection line between the laser line and the planar target. With a new proposed error correction model, the errors caused by hardware assembly can be corrected. To validate the proposed method, three LPM devices with different laser-line lengths are used to verify the proposed system. Experimental results show that the proposed method can calibrate the LPM systems with different laser-line lengths conveniently with standard steps.FindingsThe repeatability and accuracy of the proposed calibration prototypes were evaluated with high-precision workpieces. The experiments have shown that the proposed method is highly adaptive and can automatically calibrate the LPM system with different laser-line lengths with high accuracy.Research limitations/implicationsIn the repeatability experiments, there were errors in the measured heights of the test workpieces, and this is because the laser emitter had the best working distance and laser-line length.Practical implicationsBy using this proposed method and device, the calibration of the 3D scanning laser device can be done in an automatic way.Social implicationsThe calibration efficiency of a laser camera device is increased.Originality/valueThe authors proposed a unified calibration method for LPM systems with different laser-line lengths that consist of a motorized linear joint and a calibration target with elaborately designed ring patterns; the authors realized the automatic parameter calibration.

Efficacy of Portable 445 nm Laser Versus Intense Pulsed Light Treatment for Dry Eye: A Prospective Randomized Pilot Study

Objective: The aim of the study is to evaluate the efficacy of intense pulsed light (IPL) compared with a portable 445 nm laser device in the treatment of dry eye. Our hypothesis was that IPL and 445 nm laser can provide equal reduction of symptoms for patients with dry eye disease. Methods: Participants provided written informed consent as per the Helsinki declaration before a baseline testing (visit 1). All participants completed four in-clinic study visits and one telephone call over the course of ∼4 months. The patients were evaluated at baseline and received the first treatment (visit 1) at the same visit. Thereafter, treatment was repeated every 2 weeks until four treatments had been administered (visits 2-4). The evaluation of dry eye included the following tests for both eyes: tear break-up time (TBUT), in seconds, taken in three measurements using a timer; corneal fluorescein staining (CFS); and lissamine green (grading 0-5 as per Oxford grading system). Other tests included visual acuity and the measurement of intraocular pressure. A full medical history and current ocular and systemic medications were obtained. All participants completed the Dry Eye Questionnaire (DEQ5), as per DEWS II, at each visit, as well as during the final telephone assessment ∼2 months after their fourth treatment. Results: Twenty-eight eyes of 14 patients were included in the study. The eyes were randomized with 14 eyes in each group receiving either 445 nm laser or IPL. The group included 10 female and 4 male participants with average age of 64.8 years (standard deviation 13.9). The primary outcome measures of TBUT, CFS, and the DEQ5 questionnaire were statistically significantly improved. TBUT IPL versus 445 nm laser p = 0.0097 versus 0.0115, CFS IPL versus 445 nm laser p = 0.0027 versus 0.0003. The questionnaire did not discriminate between the two methods but also showed highly statistically significant improvement p = 0.0001. Conclusions: The portable 445 nm laser and IPL were equally effective in the treatment of dry eye in this cohort. No significant adverse events were noted in either treatment group. K-Laser Blue® can be considered as a substitute for IPL treatment for dry eye.

NIR emissions from Nd3+-activated phosphate-based glass system for cost-effective, tunable, and miniaturised laser devices

This work represents a phosphate-based glass system of composition (40-x) P2O5 − 30 B2O3 − 30 ZnSO4 - x Nd2O3, ( × = 0.5, 1.0, 1.5, 2.0 and 2.5 mol%) to determine the optical absorption and emission spectral characteristics. Moreover, Judd-Ofelt (J-O) intensity and radiative parameters were computed. Samples were prepared using melt-quenching method and characterized using Archimedes measurement, Ultraviolet–Visible-Near Infrared Spectroscopy and Photoluminescence Spectroscopy. The density values of these samples were reduced as the Nd2O3 concentration increased. The absorption spectra revealed 11 peaks corresponded to Nd3+ transitions from the lowest electronic energy level (4I9/2) to various excited levels. The optical energy band gap was found to be reduced with Nd3+ doping. The refractive indices (n) increased as the Nd3+ increase. The improving tendency of n was clarified in terms of the enhancing trend of samples molar volume (obtained from density), indicating a structural-optical correlation in the proposed glass system. The obtained values of Urbach energy (Eu) have an increasing trend in the range of ∼ 0.318–0.711 eV. Tow significant NIR emission peaks were assigned to the 4F5/2 → 4I9/2 and 4F3/2 → 4I9/2 transitions of Nd3+. Values of J-O intensity parameters Ω2, Ω4 and Ω6 were found in the range of (1.63–2.25)× 10−19 cm2, (2.57–2.94)× 10−19 cm2 and (1.53–1.82)× 10−19 cm2, respectively. The obtained stimulated emission cross-section for the NIR transitions from Nd3+ ((23.83–26.64)× 10−20 cm2 for 4F5/2 → 4I9/2, and (10.93–17.91)× 10−20 cm2 for 4F3/2 → 4I9/2 obviously revealed the lasing effectiveness of the titled glass system.

Lower eyelid blepharoplasty combined with ultrasound-guided percutaneous diode laser lipolysis: evaluating effectiveness with long-term outcome.

Laser lipolysis may be considered for selective removal of excess orbital fat via minimally invasive lower blepharoplasty. To control the energy delivery to a precise anatomic location while avoiding complications, ultrasound guidance can be utilized. Under local anesthesia, a diode laser probe (Belody, Minslab, Korea) was introduced percutaneously to the lower eyelid. The tip of the laser device and changes in orbital fat volume were carefully controlled with ultrasound imaging. A 1470-nm wavelength was used for orbital fat reduction (maximal energy 300J), and a 1064-nm wavelength was used to tighten the lower eyelid skin (maximal energy 200J). From March 2015 to December 2019, a total of 261 patients underwent ultrasound-guided diode laser lower blepharoplasty. The procedure took 17min on average. Total energy of 49J-510J (average = 228.31J) was delivered in 1470-nm wavelengths or 45-297J (average = 127.68J) was delivered in 1064-nm wavelengths. Most patients were very satisfied with their results. Fourteen patients experienced complications, including nine cases of transient hypesthesia (3.45%), and three skin thermal burns (1.15%). However, these complications were not observed after strict control of the energy delivery below 500J for each lower lid. Improvement in lower eyelid bags can be achieved using a minimally invasive approach in selected patients with ultrasound-guided laser lipolysis. It is a fast and safe procedure that can be performed in the outpatient setting.

Current Applications and Future Directions of Lasers in Endodontics: A Narrative Review.

The utilization of lasers has been regarded as a novel technique for the purposes of clinical use in the dental field. Recently, numerous studies have been conducted on the potential applications of laser therapy in endodontics. Moreover, due to their ablation, penetrability, and disinfection capabilities, lasers have performed well with respect to endodontic treatments, including root canal treatment, vital pulp therapy (pulp capping and pulpotomy), dentinal hypersensitivity treatment, and management of dental pain related to pulp and periradicular disease. In particular, the superiorities of laser-aided pulp therapy are emphasized through condensed clinical controlled trials, and histological studies, in this review. Moreover, the ingenious use of laser applications with respect to aiding in the acceleration of root development and the extraction of foreign matters (i.e., broken files and fiber posts) in canals has quickly become the cutting-edge trend of current research. This review offers a summary and discussion of the current literature on all the aforementioned laser applications. Moreover, the characteristics of laser devices, including erbium lasers, neodymium-doped lasers, CO2 lasers, and diode lasers, are detailed and discussed here, providing useful references for laser application in endodontics. We also focus on the different wavelengths with respect to the lasers that are applied in endodontics. High-power lasers perform well as operative instruments; in addition, low-level lasers lead to the regulation of pulp inflammation, and the promotion of pulp healing. This narrative review provides a summary of the advanced applications of lasers in conjunction with various devices in the practice of endodontics, and aims to inspire innovative perspectives on lasers in the context of the treatment of dental diseases, especially pulp diseases, in the future.

Ideal acoustic quantum spin Hall phase in a multi-topology platform

Fermionic time-reversal symmetry ({T}_{f})-protected quantum spin Hall (QSH) materials feature gapless helical edge states when adjacent to arbitrary trivial cladding materials. However, due to symmetry reduction at the boundary, bosonic counterparts usually exhibit gaps and thus require additional cladding crystals to maintain robustness, limiting their applications. In this study, we demonstrate an ideal acoustic QSH with gapless behaviour by constructing a global Tf on both the bulk and the boundary based on bilayer structures. Consequently, a pair of helical edge states robustly winds several times in the first Brillouin zone when coupled to resonators, promising broadband topological slow waves. We further reveal that this ideal QSH phase behaves as a topological phase transition plane that bridges trivial and higher-order phases. Our versatile multi-topology platform sheds light on compact topological slow-wave and lasing devices.

Heterogeneous integration of III–V semiconductor lasers on thin-film lithium niobite platform by wafer bonding

Thin-film lithium niobate (TFLN) photonic integrated circuits (PICs) have emerged as a promising integrated photonics platform for the optical communication, microwave photonics, and sensing applications. In recent years, rapid progress has been made on the development of low-loss TFLN waveguides, high-speed modulators, and various passive components. However, the integration of laser sources on the TFLN photonics platform is still one of the main hurdles in the path toward fully integrated TFLN PICs. Here, we present the heterogeneous integration of InP-based semiconductor lasers on a TFLN PIC. The III–V epitaxial layer stack is adhesively bonded to a TFLN waveguide circuit. In the laser device, the light is coupled from the III–V gain section to the TFLN waveguide via a multi-section spot size converter. A waveguide-coupled output power above 1 mW is achieved for the device operating at room temperature. This heterogeneous integration approach can also be used to realize on-chip photodetectors based on the same epitaxial layer stack and the same process flow, thereby enabling large-volume, low-cost manufacturing of fully integrated III–V-on-lithium niobate systems for next-generation high-capacity communication applications.

A Collection of Formulae for the Design of Compton Back-Scattering X-ray Sources

Along with the development of FEL X-ray sources, the design and the construction of Compton Back-Scattering (CBS) devices for different applications are being pursued. These sources are designed to provide monochromatic, high peak brightness tunable light beams, with photon energies above 10 KeV. The source brightness is the most significant figure of merit, which specifies the suitability of X-ray beams for their application in a specific field of interest and also reflects the quality of the electron beam itself, which in turn depends on the charge, emittance, energy spread, etcetera. This article is intended as an introductory review to the field and we embed a few theoretical considerations and analytical formulae to develop simple tools for the design of CBS X-ray sources. The present attempt is analogous to previous efforts, put forward to model Free Electron Laser devices, using scaling relations accounting for the entanglement between the different physical quantities contributing to the output beam performances. We comment on the reliability of our analysis by a comparison with the wealth of results (either numerical and analytical) reported in the dedicated literature.