High-peak-power optically pumped passively mode-locked semiconductor laser with minimal components

A high-peak-power sub-500-fs mode-locked optically pumped semiconductor laser is innovatively developed with only three components of a semiconductor gain chip, a semiconductor saturable absorber, and a focusing lens. The developed laser near the threshold pump power of 3.9 W can be operated with stable fundamental mode locking. The laser output can be naturally turned into the stable harmonic mode locking (HML) with the order gradually changing from 2nd to 8th by increasing the pump power from 4.0 W to 5.0 W. Due to the onset of the high-order transverse modes, the order of HML is fixed at 8th for a pump power greater than 5.0 W. For the HML with order less than 8th, the overall peak power and pulse width in the HML are approximately 0.36 kW and 550 fs, respectively. In the operation of 8th-order HML, the minimum pulse width and maximum peak power can reach 480 fs and 0.95 kW, respectively.

Orbital angular momentum densities in the astigmatic transformation of Lissajous geometric laser modes

Orbital angular momentum densities in the astigmatic transformation of Lissajous geometric laser modes are originally and systematically investigated. The quantum theory of the coherent state is exploited to derive an analytical wave representation for the transformed output beams. The derived wave function is further employed to numerically analyze the propagation dependent orbital angular momentum densities. The parts of the negative and positive regions in the orbital angular momentum density are found to rapidly change in the Rayleigh range behind the transformation.

Biomechanical evaluation of a novel tri-blade titanium implantable vertebral augmentation device

BACKGROUND CONTEXT

Titanium implantable vertebral augmentation device (TIVAD) are regarded as having potential in the treatment of vertebral compression fractures (VCFs). However, improper design in current TIVADs results in the inability to effectively restore VCF height and maintain stability. There is still an unmet clinical need for improvement.

PURPOSE

The authors tested a newly developed a TIVAD (Tri-blade fixed system) that can provide enough endplate collapse support to restore the vertebral body height in a safe retraction mechanism for VCFs using minimally invasive surgery (MIS).

STUDY DESIGN

The performed biomechanical tests included blade expansion force, lifetime of cement embedded and vertebral height restoration efficiency of porcine osteoporosis VCFs for its feasibility.

METHODS

A cylinder with 3 surface cuts that form blades that can be expanded into a conical space was designed (Tri-blade fixed system). The 3 blades can be expanded outward with angles between blades as 105°/ 105°/150° for lower left/lower right/upper arms, respectively that reach 15mm in height and 14.8 mm in width. A frame was specifically designed to measure the contact force using force sensing resistors during blade expansion. The Tri-blade fixed system was embedded into a cement block to perform fatigue testing under 2000N pressure (5*10⁶ cycles) for understanding the device lifetime limitation. The Tri-blade system was then inserted into porcine osteoporosis VCFs to examine the vertebral height restoration efficiency.

RESULTS

The average maximum contact force for the top, bottom left and right blades were 299.0N, 283.5N and 279.3N, respectively with uniformly outward expansion forces. The fatigue test found that there were no obvious cracks or damage to the cement block. The porcine osteoporosis vertebral body at the anterior, middle, and posterior heights can be restored to 21.9%, 12.6% and 6.4%, respectively.

CONCLUSIONS

This study developed a novel TIVAD with conical shape that can provide a more stable structure with sufficient/uniform expansion force, passing the fatigue test with bone cement and high effective in vertebral height restoration tests for porcine osteoporosis VCFs.

CLINICAL SIGNIFICANCE

The new 3D Tri-blade TIVAD may offer a new treatment option for VCFs.

The efficacy of vancomycin-loaded biphasic calcium phosphate bone substitute in the promotion of new bone growth and the prevention of postoperative infection

Background: Due to the increasing need for suitable alternatives to bone grafts, artificial bones made of biphasic calcium phosphate (BCP) are currently being extensively researched. These porous bone substitutes have also demonstrated considerable incorporation with the host bone, and new bone is able to grow within the porous structure. They therefore offer a potential therapeutic approach for bone defects.

Methods: Vancomycin-loaded Bicera™, a BCP bone substitute, was investigated in order to prevent implant-associated osteomyelitis and postoperative infection after orthopedic surgery. The loading capacity of Bicera™ was measured to understand its potential antibiotic adsorption volume. An antibiotic susceptibility test was also carried out to analyze the effect of Bicera™ loaded with different concentrations of vancomycin on the growth inhibition of methicillin-resistant Staphylococcus aureus (MRSA). Vancomycin-loaded Bicera™ was implanted into rabbits with bone defects, and general gross, radiographic, and histological evaluation was undertaken at 4, 12, and 24 weeks after implantation.

Results: The maximum loading capacity of vancomycin-loaded Bicera™ was 0.9 ml of liquid regardless of the vancomycin concentration. Antibiotic susceptibility tests showed that vancomycin-loaded Bicera™ inhibited the growth of MRSA for 6 weeks. In addition, animal studies revealed that new bone grew into the vancomycin-loaded Bicera™. The percentage of new bone formation from 4 to 24 weeks after implantation increased from 17% to 36%.

Conclusion: Vancomycin-loaded Bicera™ could effectively inhibit the growth of MRSA in vitro. It was found to incorporate into the host bone well, and new bone was able to grow within the bone substitute. The results of this study indicate that vancomycin-loaded Bicera™ is a potential bone substitute that can prevent implant-associated osteomyelitis and postoperative infection.

A novel surgical technique in transforaminal lumbar interbody fusion by the bone graft delivery device: evaluation of therapeutic effect in patients with minimally invasive spine surgery

Background

Transforaminal Lumbar Interbody Fusion (TLIF) is commonly associated with higher complications and longer operative time. This study aims to evaluate the effectiveness, safety, and usability of a novel minimally invasive surgery (MIS) bone graft delivery device.

Methods

73 consecutive patients with lumbar spondylosis, degenerative disc disease, spondylolisthesis, scoliosis or trauma were enrolled in this randomized controlled trial. Group 1 comprised 39 patients treated with the novel MIS bone graft delivery device. Group 2 consisted of 34 patients treated with the conventional system. The primary objective of the study was the assessment of the amount of bone graft delivery using the device. The secondary objectives were the effect of the device on operative time, pain relief, disability improvement, and bone fusion grade.

Results

Bone delivery amount was significantly higher in the MIS device group (6.7 ± 2.9 mL) compared to the conventional group (2.3 ± 0.5 mL), p < 0.001. Regarding the operation time, the MIS device group was associated significantly lower duration than the conventional group (p < 0.001). After a 3-month follow-up, 39.5% of the patients in the MIS device group and 3.5% of the patients in the conventional group were observed to achieve grade I fusion (complete fusion). There was a significant difference in fusion success rates (p < 0.01).

Conclusion

The novel MIS bone graft delivery device was associated with successful bone delivery. Our MIS device provides promising modality with less operative time and higher bone fusion rates than conventional modalities.

Trial Registration This trial was retrospectively registered on ClinicalTrials.gov (Registration date: 11/19/2021; Registration number: NCT05190055).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12893-022-01773-y.

Structured transverse modes governed by maximum entropy principle

Based on the birefringent effect of the gain medium, a diode-pumped Nd-doped vanadate laser with nearly hemispherical cavity is exploited to emulate the quantum Green functions of two-dimensional commensurate harmonic oscillators. By matching the theoretical calculations to the far-field patterns of lasing modes, the resonant transverse frequencies can be accurately determined up to extremely high orders. The Shannon entropy is further employed to calculate the spatial entanglement of the quantum Green function as a function the transverse frequency. From the resonant transverse frequencies, all lasing modes are confirmed to be in excellent agreement with the maximum entropy states. This discovery implies that the formation of lasing modes is relevant to the coupling interaction between the pump source and the laser cavity.

Continuous wave dual-wavelength Nd:YVO4 laser at 1342 and 1525 nm for generating a 714-nm emission

Continuous wave dual-wavelength lasers at 1342 and 1525 nm are developed by using separate Nd:YVO₄ and YVO₄ crystals to form compactly coupled cavities for fundamental and Raman waves, respectively. The design of the coupled cavity not only reduces the thermal lensing effect in the Nd:YVO₄ crystal, but also improves the stimulated Raman scattering (SRS) efficiency in the undoped YVO₄ crystal. In addition, the Raman crystal is coated to form a highly reflective mirror to minimize cavity losses. By using a plano-concave cavity with a pump power of 40 W, the output powers of the fundamental and Raman waves are 470 mW and 310 mW, respectively. Changed to a concave cavity, the output powers of fundamental and Raman waves are 220 mW and 510 mW, respectively. Basis on the dual-wavelength operation, the maximum output power at 714 nm can reach 2.0 W via the sum frequency generation. A light source at 714 nm can be used for laser spectroscopy of atomic and ionic radium isotopes.

Characterizing propagation-dependent spatial entanglement for structured laser beams generated by an astigmatic mode converter

The propagation-dependent spatial entanglement for the structured laser beams generated by an arbitrary incident Hermite-Gaussian (HG) mode passing through an astigmatic mode converter (AMC) is theoretically explored. The structured output beams are analytically decomposed into the expansion of HG modes for any given rotation angle of the AMC. Based on the Schmidt decomposition, the propagation-dependent spatial entanglements of the structured output modes are quantified with the von Neumann entropy. To manifest the propagation-dependent entropy, the probability distribution of the expanded HG modes in the structured output beam is quantitatively analyzed.

[Hashimoto's encephalopathy presenting with isolated cerebellar ataxia in 13 children]

Objective: To analyze the clinical characteristics, treatment and prognosis of Hashimoto's encephalopathy presenting with isolated cerebellar ataxia in children. Methods: A retrospective analysis was performed on the clinical features, laboratory tests, neuroelectrophysiological examination, imaging, treatment and outcomes of 13 patients with Hashimoto's encephalopathy presenting with isolated cerebellar ataxia, who were admitted to the Department of Pediatric Neurology of Guangzhou Women and Children's Medical Center from January 2016 to May 2021. Results: Among the 13 cases, 6 were males and 7 were females. The onset age was 2.6 (2.0,3.3) years, 9 children had precursor infection or vaccination before the first course of disease. All the 13 children had gait abnormalities or unsteady sitting, 10 had intentional tremor, 6 had dysarthria, 3 had body tremor, 2 had nystagmus, 3 had fatigue, 3 had hypotonia, 2 had vomiting and 1 had irritability. Thyroglobulin antibody (TgAb) was 500.0 (298.9,587.2) kU/L and thyroid peroxidase antibody (TPOAb) was 621.9 (449.6,869.4) kU/L in 13 cases. Autoantibodies were positive in 9 cases, and cerebrospinal fluid leukocytosis was seen in 4 cases. Regarding electroencephalography result, 4 cases had background slowing and 1 case had occasional sharp waves. Among the 3 patients who had relapses, 1 had cerebellar atrophy shown on cranial magnetic resonance imaging (MRI) during the recurrence. All the patients received intravenous immunoglobulin (IVIG) and intensive methylprednisolone therapy during the first onset, followed by the disappearance of the symptoms, 1 patient had repeated episodes which was decreased after immunosuppressive treatment with Rituximab.Followed up for 25.0 (22.5,33.3) months after the last episode, 12 achieved complete remission and 1 had a wide base gait. Conclusions: Trunk ataxia is the common symptom of Hashimoto's encephalopathy presenting with isolated cerebellar ataxia in children.Children with cerebellar ataxia should be tested for TgAb and TPOAb to detect Hashimoto's encephalopathy, avoiding missed diagnosis and treatment delays; IVIG and intensive steroid therapy is effective, and immunosuppressive therapy for patients with multiple relapses could reduce the recurrence.

Quantum entanglement by a beam splitter analogous to laser mode transformation by a cylindrical lens

Quantum entanglement by a beam splitter (BS) is shown to be analogous to laser mode transformation by an astigmatic mode converter (AMC). Schmidt decomposition is used to characterize the entanglement by an AMC for generating orbital angular momentum and by a BS for creating quantum photon interference. The probability distributions of Schmidt decomposition are calculated to manifest the sameness and difference between AMC and BS in generating entanglement. Finally, the theoretical patterns of mode transformations by an AMC are confirmed with experimental results to validate the present analysis.

Characterizing the spatial entanglement from laser modes analogous to quantum wave functions

The Schmidt decomposition is exploited to study the spatial entanglement of laser transverse modes analogous to quantum Lissajous states. Based on the inverse Fourier transform, the stationary Lissajous state can be analytically derived as a coherent superposition of degenerate Hermite-Gaussian eigenmodes. With the derived stationary state, the Schmidt modes and the participation number N can be employed to evaluate the spatial localization and the quantum entanglement. The larger the participation number, the more localized is the stationary coherent state on the Lissajous figure. Moreover, the larger the participation number, the higher is the spatial entanglement.

Clinical Efficacy of Polycaprolactone β-Calcium Triphosphate Composite for Osteoconduction in Rabbit Bone Defect Model

The combination of β-tricalcium phosphate (β-TCP) with polycaprolactone (PCL) has been considered a promising strategy for designing scaffolds for bone grafting. This study incorporated PCL with commercially available β-TCP (Osteocera^TM) to fabricate an injectable bone substitute and evaluate the effect of PCL on compressive strength and setting time of the hydraulic cement. The mechanical testing was compliant with the ASTM D695 and ASTM C191-13 standards. Results showed that PCL-TCP composite presented a well-defined architecture with uniform pore distribution and a significant increase in compressive strength compared with β-TCP alone. Eighteen rabbits, each with two surgically created bone defects, were treated using the PCL-TCP composites. The composite materials were resorbed and replaced by newly formed bone tissue. Both PCL-TCP and β-TCP demonstrated equivalent clinical effects on osteoconduction property in terms of the percentage of newly formed bone area measured by histomorphometric analysis. PCL-TCP was proven to be as effective as the commercially available β-TCP scaffold (Osteocera^TM).

Powerful Q-switched Raman laser at 589 nm with a repetition rate between 200 and 500 kHz

We demonstrate a highly powerful acousto-optically Q-switched Nd:YVO₄ yellow laser at 589 nm by using a N_p-cut KGW crystal and a phase-matching lithium triborate crystal to performance the intracavity stimulated Raman scattering and second-harmonic generation, respectively. We experimentally verify that the design of the separate cavity is superior to the conventional design of the shared cavity. By using the separate cavity, the optical-to-optical efficiency can be generally higher than 32% for the repetition rate within 200-500 kHz. The maximum output power at 589 nm can be up to 15.1 W at an incident pump power of 40 W and a repetition rate of 400 kHz.

Pedagogically fast model to evaluate and optimize passively Q-switched Nd-doped solid-state lasers

The coupled rate equations with the spatial overlap effect for four-level passively Q-switched lasers are fully considered. A transcendental equation is derived for the residual fraction of the inversion density after the finish of the Q-switched pulse. Comprehensive calculations for the transcendental equation were executed to attain an analytical function for precisely fitting the residual fraction of the inversion density. With the fitting function, a pedagogical model with the correction for high output coupling is developed to straightforwardly analyze the output pulse energy and peak power. Detailed experiments are carried out to validate the model.

Highly efficient solid-state Raman yellow-orange lasers created by enhancing the cavity reflectivity

A new, to the best of our knowledge, output coupler (OC) with enhancement of the cavity reflectivity is proposed to remarkably elevate the output powers and efficiencies of diode-pumped Nd:GdVO₄/KGW Raman yellow-orange lasers. The cavity reflectivity is effectively increased by using the double-sided dichroic coating on the OC. In comparison with the conventional single-sided coating, the conversion efficiency can be boosted from 15% to 26.3% in the experiment of a yellow laser at 578.8 nm, and the maximum output power can be increased from 5.7 to 10.5 W in the quasi-continuous-wave mode with 50% duty cycle and frequency of 500 Hz. Furthermore, in the operation of an orange laser at 588 nm, the maximum output power can be improved from 5.6 to 7.0 W by replacing the conventional OC with the new one.

Propagation-dependent evolution of interfering multiple beams and kaleidoscopic vortex lattices

In this Letter, we experimentally explore the propagation-dependent evolution of generating the pseudo-nondiffracting quasi-crystalline (crystalline) beams based on the multibeam interference. We originally derived an analytical formula to exactly manifest the propagation evolution of interfering multiple beams. With the analytical formula, the formation of quasi-crystalline structures in the focal plane can be explicitly verified. Furthermore, the distance of the effective propagation-invariant region can be verified in terms of experimental parameters. More importantly, we employed the developed formula to confirm the formation of kaleidoscopic vortex lattices by means of numerically computing the propagation-dependent phase singularities.

High-power diode-pumped Nd:GdVO4/KGW Raman laser at 578 nm

A diode-pumped neodymium-doped gadolinium vanadate (Nd:GdVO₄) laser is developed as a compact efficient yellow light at 578 nm by means of intracavity stimulated Raman scattering (SRS) in a potassium gadolinium tungstate (KGW) crystal and the second-harmonic generation in a lithium triborate crystal. The SRS process with a shift of 768cm^-1 is achieved by setting the polarization of the fundamental wave along the N_g axis of the KGW crystal. The self-Raman effect arising from the Nd:GdVO₄ crystal is systematically explored by employing two kinds of coating specification for the output coupler. With a specific coating on the output coupler to suppress the self-Raman effect, the maximum output power at 578 nm can reach 3.1 W at a pump power of 32 W. Moreover, two different lengths for the Nd:GdVO₄ crystal are individually used to verify the influence of the self-Raman effect on the lasing efficiency.

Efficient solid-state Raman yellow laser at 579.5 nm

A highly efficient diode-pumped Nd:YVO₄/KGW Raman yellow laser is developed to produce a 6.8 W yellow light at 579.5 nm accompanied by a 3.2 W Stokes wave at 1159 nm under an incident pump power of 30 W. The intracavity stimulated Raman scattering with the shift of 768cm^-1 is generated by setting the polarization of the fundamental wave along the N_g direction of an N_p-cut KGW crystal. The Nd:YVO₄ gain medium is coated as a cavity mirror to reduce the cavity losses for the fundamental wave. More importantly, the KGW crystal is specially coated to prevent the Stokes wave from propagating through the gain medium to minimize the cavity losses for the Stokes wave.

High-power structured laser modes: manifestation of quantum Green's function

The distributions of resonant frequencies in an astigmatic cavity are theoretically confirmed to be analogously equivalent to the quantum energy structures of two-dimensional commensurate harmonic oscillators. In the first part [Opt. Lett.45, 4096 (2020)OPLEDP0146-959210.1364/OL.399251] of this two-part series study, the lasing modes were verified to reveal a variety of vortex array structures. Here, in the second part of this two-part series study, the lasing modes are confirmed to agree very well with the quantum Green's functions that correspond to a bundle of Lissajous figures in the high-order regime.

Exploiting a monolithic passively Q-switched Nd:YAG laser to mimic a single neuron cell under periodic stimulation

A monolithic passively Q-switched Nd:YAG laser under periodic pulse pumping is originally exploited to emulate the response of a single neuron cell stimulated by periodic pulse inputs. Experimental results reveal that the output characteristics of the monolithic passively Q-switched laser can analogously manifest not only the firing patterns but also the frequency-locked plateaus of the single neuron cell. Moreover, the sine circle map is innovatively used to generate the output pulse sequences that can exactly correspond to experimental firing patterns. The present exploration indicates that a monolithic passively Q-switched solid-state laser is highly feasible to be developed as a compact artificial neuron cell.

High-power structured laser modes: direct generation of a vortex array

The frequency degeneracy induced by the astigmatism in a nearly hemispherical cavity is originally exploited to generate vortex array laser modes with the output power up to 300 mW. The inhomogeneous Helmholtz equation is employed to derive the wave function for manifesting the characteristics of the lasing modes. The theoretical wave function explicitly reveals the role of the Gouy phase in the formation of vortex arrays. Numerical analyses are further performed to confirm that the thermal lensing effect in the laser crystal assists the lasing transverse order to increase with increasing pump power. It is believed that the high efficiency enables the present laser modes to be useful in the applications of structured vortex beams.

Timing jitter reduction of passively Q-switched solid-state lasers by coupling resonance between pumping and firing rates

The coupling resonance between pumping and firing rates is originally proposed to achieve the timing jitter reduction of a Nd:YVO₄ laser passively Q-switched with a saturable absorber. When the pumping rate is higher than the spontaneous emission rate, it is experimentally confirmed that the pulse firing rate can be fractionally locked with the pumping rate by controlling the pump power. The locking characteristics of the firing rate display a variety of complex plateaus that can be excellently manifested with the sine-circle map. From numerical analyses, the coupling strength can be verified to be effectively enhanced by reducing the duty cycle of the pumping rate.

Criterion for optimizing high-power acousto-optically Q-switched self-Raman yellow lasers with repetition rates up to 500 kHz

The criterion for optimizing the high-power acousto-optically ${Q}$Q-switched self-Raman yellow laser is originally explored for the repetition rate within 100-500 kHz. The minimum allowed value for the gate-open time is experimentally verified to be determined by the pulse buildup time. By using the minimum allowed gate-open time, the highest conversion efficiency can be achieved to raise the output power by approximately 20% in comparison with the conventional results. At a repetition rate of 200 kHz, the maximum output power at 588 nm can be up to 8.8 W at an incident pump power of 26 W. Furthermore, a practical formula is developed to accurately calculate the threshold pump power as a function of the gate-open time for a given repetition rate.

[Clinical characteristics, treatment and prognosis of myelin oligodendrocyte glycoprotein antibody-associated optic neuritis in children]

Objective: To investigate the clinical characteristics, treatment and prognosis of myelin oligodendrocyte glycoprotein antibody-associated optic neuritis (MOG-ON) in pediatric patients. Methods: Clinical data, laboratory examination, the initial best corrected visual acuity (BCVA), fundus, neuroelectrophysiological results, MRI imaging, treatment and prognosis of children diagnosed with MOG-ON from 2016 to 2019 were retrospectively analyzed. Results: A total of 29 eyes from 16 children were involved, with a male/female ratio of 1∶1, onset age of (7.0±2.9) years. Seven of 16 patients had prodromal infection, with a unilateral/bilateral ratio of 3∶13, and 2 cases had recurrent optic neuritis. Before treatment, BCVA of 19 eyes (65.5%) was ≤0.1, among them, 4 had no sense of light, 5 had light sense, 5 with sense of hands in front of eyes, and 5 with sense of fingers in front of eyes. There were 10 eyes (34.5%) with BCVA of 0.1-0.5. After treatment, there were 4 eyes (13.8%), 5 eyes (17.2%) and 20 eyes (69.0%) in groups with BCVA of 0.1-0.5, 0.5-1.0, and>1.0, respectively. Twelve of 16 patients had optic papillitis in fundus examination during acute phase. The latency was prolonged and the amplitude was decreased in P100 wave of all the children. Thirteen out of 16 children showed swelling and thickening of optic nerve in MRI T2WI. MRI images exhibited intracranial demyelinating lesions in 12 of 16 children and long segment spinal cord lesions in 3 of 16 children. Thirteen of 16 patients showed effective results after intravenous methylprednisolone (IVMP) and intravenous immunoglobulin (IVIG) treatment. There was no relapse after administration of mycophenolate mofetil in 2 recurrent children. No progression after administration of rituximab was found in 1 child with corticosteroid insensitivity. The average follow-up time was (16±9) months and no recurrence occurred. Ten of 16 patients had full recovery, 4 had significant improvement, and 2 showed no significant improvement. Conclusions: There is no significant gender difference in the incidence of pediatric MOG-ON. Bilateral involvement and severe visual impairment are common in acute phase. Most patients have good response to IVMP combined with IVIG treatment and hence have a good prognosis. Only a few of them have neurological sequelae.

Compact efficient high-power triple-color Nd:YVO4 yellow-lime-green self-Raman lasers

A novel, to the best of our knowledge, approach is developed to realize a high-power compact efficient yellow-lime-green triple-color ${\rm Nd}:{{\rm YVO}_4}$Nd:YVO₄ self-Raman laser. The 588 nm yellow laser, the 559 nm lime laser, and the 532 nm green laser are converted from the 1064 nm fundamental wave and the 1176 nm Stokes Raman field. The simultaneous three-color operation is accomplished with three stages to step-by-step generate the 588 nm, 559 nm, and 532 nm lasers by using three different lithium triborate (LBO) crystals. By tuning the temperature of each individual LBO crystal, the 588 nm, 559 nm, and 532 nm output powers can be nearly the same and concurrently up to 2.4 W at the incident pump power of 30 W, corresponding to a conversion efficiency of 24% for the total output power.

[Clinical features and prognosis of pediatric myelin oligodendrocyte glycoprotein antibody associated acute disseminated encephalomyelitis]

Objective: To analyze the clinical features, outcome and prognosis of pediatric myelin oligodendrocyte glycoprotein (MOG) antibody associated acute disseminated encephalomyelitis (ADEM), and provide evidence for improving the diagnosis and treatment of this disease. Methods: This study involved 30 MOG antibody-associated ADEM patients in the Department of Neurology, Guangzhou Women and Children's Medical Center. Patients' clinical information were analyzed. Results: The mean onset age was (5.2±3.3) years old, the ration of male to female was 16∶14. Fifty percent of these patients had a history of precede infection or vaccination before onset. Encephalopathy and seizures were the most common clinical manifestations, followed by movement disorder. In addition, some patients had other positive autoantibodies. Brain Magnetic resonance imaging (MRI) showed extensive, asymmetrical, indefinite large patchy lesions in bilateral cortical and subcortical areas and the spinal cord was characterized by long segmental myelitis. In acute attack, the patients had a good response to corticosteroid combined immunoglobulin therapy. Most of these patients had a good prognosis and recurrence rate was about 20%. Conclusions: The onset age of MOG antibody-associated ADEM is around 5 years old. Encephalopathy and seizures were the most common clinical manifestations. Most patients have a good response to corticosteroid combined immunoglobulin therapy. Some patients may have a recurrent disease course.

Origin of continuous curves and dotted spots in laser transverse modes with geometric structures

The transverse structures of geometric modes in degenerate laser resonators with large astigmatism are systematically investigated by starting from the Gaussian wave packet formulation with ray-wave connections. The overlapping degree D between Gaussian wave packets is derived as an analytic expression that manifests the critical overlapping with D=1. The transverse patterns are confirmed to display a structure of continuous curves or dotted spots, depending on D>1 or D<1, respectively. A thorough comparison between experimental results and numerical calculations is performed to validate the theoretical analysis.

Generalized wave-packet formulation with ray-wave connections for geometric modes in degenerate astigmatic laser resonators

The parametric equations for periodic rays in degenerate astigmatic laser resonators are derived in a generalized way. The derived parametric equations clearly reveal the formation of Lissajous geometric modes with phase variation along the propagation. Using the representation of a quantum coherent state, a generalized wave-packet formula is derived to connect with the periodic rays of geometric modes. The derived wave-packet formula is not only validated through comparing with various experimental patterns, but also is directly exploited to manifest the spatial asymmetries of Lissajous lasing modes due to a highly transmissive output coupler.

Bone formation following sinus grafting with an alloplastic biphasic calcium phosphate in Lanyu Taiwanese mini-pigs

BACKGROUND

To evaluate the new bone formation after grafting with a synthetic biphasic calcium phosphate in sinuses with minimal bone height, the alloplastic and xenograft materials were compared after grafting into Lanyu Taiwanese mini-pig sinuses via split-mouth design.

METHODS

In six mini-pigs, synthetic hydroxyapatite/tricalcium phosphate (HA/TCP) particles were inserted into one of the sinus cavities using the extra-oral approach, where deproteinized bovine bone mineral (DBBM) particles were placed contralaterally. Fluorescent bony labels of Alizarin and Calcein green were delivered at weeks 4 and 8, respectively. Animals were sacrificed at week 12 and the augmented tissues were evaluated by cone-beam computed tomography, microcomputed tomography, and histology.

RESULTS

By radiographic examination, the mean thicknesses of sinus cortexes for DBBM and HA/TCP groups were similar (0.35 versus 0.38 cm) and the mean volumes augmented were also indifferent (1.29 versus 1.64 cm³ ). The distributions of bones, residual particles, and non-mineralized tissues in augmented masses between groups were undistinguishable. Under microscopy, however, macroporosities of osteons were filled with HA/TCP residual particles, whereas the newly formed bones lay on top of DBBM particle surfaces. Although the mineral deposition rates between groups were indifferent, the mean labeled surface in the HA/TCP group was significantly greater than those in the DBBM group at week 4 (35.16% versus 14.00% for HA/TCP and DBBM, respectively) but less than that at week 8 (19.33% versus 39.16%, respectively).

CONCLUSION

Sinus augmentation with synthetic HA/TCP and DBBM exhibited similar effectiveness in new bone formation.

Wave representation for asymmetric elliptic vortex beams generated from the astigmatic mode converter

An analytical wave representation is derived to express the asymmetric elliptic vortex beams generated by using an astigmatic mode converter to transform the asymmetric Hermite-Gaussian modes. The effect of the spatial asymmetry on the elliptic vortex beam can be straightforwardly considered in the analytical wave representation. A detailed comparison with experimental intensity patterns and phase structures is made. The good agreement between experimental results and theoretical analyses confirms the characterization and generation of the asymmetric elliptic vortex beams.

Efficient high-power dual-wavelength lime-green Nd:YVO4 lasers

An efficient high-power dual-wavelength lime-green Nd:YVO₄ self-Raman laser is inventively developed by using two different lithium triborate (LBO) crystals. The first and second LBO crystals are employed to generate the 559 nm lime and 532 nm green lasers, respectively. The temperature of the first LBO crystal is fixed at the optimal phase matching, whereas the temperature of the second LBO crystal is tuned to flexibly control the relative strengths between the 532 and 559 nm waves. When the temperature of the second LBO crystal is set for the maximal total output power, the 532 and 559 nm output powers, respectively, are 7.1 and 2.9 W at a pump power of 31.6 W, corresponding to a conversion efficiency of 31.6%. When the temperature is controlled for the balanced output, the 532 and 559 nm powers, respectively, are 4.3 and 4.2 W at a pump power of 31.6 W, corresponding to a conversion efficiency of 26.9%.

Exploring elliptical vortex beams with the spatial damping effect

A general integral formula is analytically derived to represent the wave function of elliptical vortex modes. The derived formula can be straightforwardly employed to take account of spatial damping to explore vortex structure. Spatial damping is found to cause the central degenerate singularity of the circular vortex mode to be split into several singularities with different topological charges. For the non-circular vortex beam, the influence of spatial damping on the distribution of singularities is not significant. Theoretical analyses are confirmed to agree very well with the experimental measurements.

Efficient high-power continuous-wave lasers at green-lime-yellow wavelengths by using a Nd:YVO4 self-Raman crystal

Efficient high-power continuous-wave Nd:YVO₄ visible lasers at versatile wavelengths of 532 (green), 559 (lime), and 588 nm (yellow) are demonstrated to be achieved by using the identical cavity mirrors and gain medium. A dichroic coating is deposited on one end surface of the gain medium to gather the backward green-yellow emission. The green, lime, and yellow outputs are individually optimized by using different phase-matched lithium triborate (LBO) crystals for second harmonic generation (SHG) of the fundamental field, sum frequency generation (SFG) of the fundamental and the stimulated Raman fields, and SHG of the stimulated Raman field, respectively. At a pump power of 31.6 W, the output powers at 532, 559, and 588 nm can be up to 6.8, 5.4, and 3.1 W. The high efficient and compact Nd:YVO₄ lasers at green-lime-yellow wavelengths can be potentially beneficial to future applications in retinal photocoagulation.

Investigation of the antiphase dynamics of the orthogonally polarized passively Q-switched Nd:YLF laser

The antiphase dynamics of Q-switched orthogonally polarized emissions have been thoroughly investigated. A Nd:YLF crystal with the anisotropic thermal lensing effect is used as the gain medium for achieving dual polarized laser. By using the Cr⁴⁺:YAG saturable absorber, the passively Q-switched output shows intriguing switching dynamics, where the number of pulses for both polarized components within one switching period is directly determined by the power ratio between the orthogonally polarized emissions. Experimental results reveal that the pulse energies of every single pulse for both orthogonally polarized states are equal with the maximum value of 223 μJ. The pulse durations for π- and σ-polarization are measured to be 15 ns and 11 ns and the corresponding peak power levels are up to 15.0 kW and 20.3 kW, respectively.

Exploring the self-mode locking and vortex structures of nonplanar elliptical modes in selectively end-pumped Nd:YVO4 lasers: manifestation of large fractional orbital angular momentum

An end-pumped Nd:YVO₄ laser under selective pumping is used to excite lasing modes with transverse patterns performed to exhibit the characteristics of multiple spots arranged on elliptical features near degenerate cavities. The spatial distribution of elliptical lasing modes is clearly revealed to be localized on the nonplanar ray orbits, so-called nonplanar elliptical modes, which possess large fractional orbital angular momentum. Moreover, temporal dynamics for the output emission of nonplanar elliptical modes are verified to obtain self-mode-locked operation. We further numerically manifest not only the influence of radial-asymmetry distributions on the vortex structures of nonplanar elliptical modes, but also the vector field of transverse lasing modes altered with twisting phase structures in the propagation direction.

Diode-pumped orthogonally polarized self-mode-locked Nd:YLF lasers subject to gain competition and thermal lensing effect

The stable condition for π-polarization emission in an a-cut Nd:YLF laser is numerical analyzed to find the critical pump power for generating the orthogonally polarized emission. With the numerical analysis, an orthogonally polarized SML lasers at wavelength of 1047 nm and 1053 nm is experimentally achieved in a simple concave-plano cavity without any additional optical element. It is experimentally observed that the polarization switching and coexistence was successfully demonstrated by introducing gain competition and anisotropic thermal lens effect. In the orthogonal polarization mode-locked operation, the pulse durations are found to be 19.1 and 18.8 ps for π- and σ-polarization with pulse repetition rates of 3.85 and 3.89 GHz, respectively.

Broad expansion of optical frequency combs by self-Raman scattering in coupled-cavity self-mode-locked monolithic lasers

Broad expansion of optical frequency comb (OFC) by the self-Raman scattering is numerically analyzed and experimentally accomplished in a coupled-cavity self-mode-locked (SML) monolithic Yb:KGW laser. The gain medium is coated to achieve the monolithic SML operation and a partially reflective mirror is further exploited to form the coupled cavity and to multiply the repetition rate up to 128.9 GHz. With a coupled reflectivity of 95%, it is experimentally found that not only the first-order but also second-order stimulated Raman scattering (SRS) can be efficiently generated. The mode-locked OFC can be consequently expanded to reach approximately 8.4 THz, leading the pulse width to be as narrow as 53 fs. At the pump power of 8.7 W, the total output power for the fundamental and the first- and second-Stokes waves can be maintained at 1.6 W. The present exploration provides a promising way to generate the ultrahigh-repetition-rate broadband OFC via the simultaneous SML and SRS processes.

Characterizing classical periodic orbits from quantum Green's functions in two-dimensional integrable systems: Harmonic oscillators and quantum billiards

A general method is developed to characterize the family of classical periodic orbits from the quantum Green's function for the two-dimensional (2D) integrable systems. A decomposing formula related to the beta function is derived to link the quantum Green's function with the individual classical periodic orbits. The practicality of the developed formula is demonstrated by numerically analyzing the 2D commensurate harmonic oscillators and integrable quantum billiards. Numerical analyses reveal that the emergence of the classical features in quantum Green's functions principally comes from the superposition of the degenerate states for 2D harmonic oscillators. On the other hand, the damping factor in quantum Green's functions plays a critical role to display the classical features in mesoscopic regime for integrable quantum billiards, where the physical function of the damping factor is to lead to the coherent superposition of the nearly degenerate eigenstates.

Generation of terahertz optical beating from a simultaneously self-mode-locked Nd:YAG laser at 1064 and 1123 nm

The reflectivity of the output coupler is designed to achieve the synchronously self-mode-locked operation at 1064 and 1123 nm in a diode-end-pumped Nd:YAG laser. Numerical analyses are performed to confirm that the designed output coupler can lead the emission lines to be predominant at 1064 and 1123 nm. Moreover, the crossover of the threshold pump powers for the 1064 and 1123 nm emission lines can be exploited to obtain the single central wavelength of 1064 nm or the single central wavelength of 1123 nm or, simultaneously, dual-central-wavelength self-mode-locked operation by finely adjusting the cavity alignment. For the dual-central-wavelength mode-locked emissions, the pulse repetition rate and the pulse duration are 4.5 GHz and 50.8 ps, respectively. The maximum output power can be up to 2.47 W at a pump power of 7.5 W. The synchronization of the 1064 and 1123 nm mode-locked pulses generates the optical beating pulse trains with repetition rates up to 14.7 THz.

Exploiting concave-convex linear resonators to design end-pumped solid-state lasers with flexible cavity lengths: Application for exploring the self-mode-locked operation

The characteristics of a convex-concave linear resonator under the thermal lensing effect are theoretically analyzed to find an analytical model for designing end-pumped solid-state lasers with flexible cavity lengths. By exploiting the design model, the power scaling for continuous-wave operation under strong thermal lensing can be easily achieved in the proposed resonator with different cavity lengths. Furthermore, the proposed resonator is applied to explore the exclusive influence of cavity length on the self-mode-locked (SML) operation. It is discovered that the lasing longitudinal modes will split into multiple groups in optical spectrum to lead to a multi-pulse mode-locked temporal state when the cavity length increases. Finally, a theoretical model is derived to reconstruct the experimental results of SML operation to deduce a simple relationship between the group number of lasing modes and the cavity length.

Exploring vortex structures in orbital-angular-momentum beams generated from planar geometric modes with a mode converter

It is theoretically demonstrated that the planar geometric mode with a π/2 mode converter, so called the circularly geometric mode, can be solved from the inhomogeneous Helmholtz equation by considering the pump distribution on the lasing mode. Theoretical analysis clearly reveal that the vortex structures of circularly geometric modes are determined by the minimum order of transverse lasing modes, the total number of transverse lasing modes and the degenerate condition in the cavity. Moreover, we experimentally manifest that the circularly geometric mode can be generated from the selective pumped solid-state laser with an external π/2 mode converter. To explore the vortex structures of the generated geometric modes, the interference patterns are performed by an experimental apparatus consisting of a Mach-Zehnder interferometer. The good agreement between experimental observations and numerical calculations confirms the analysis of vortex structures is reliable.

Synchronized self-mode-locked 1061-nm and 1064-nm monolithic Nd:YAG laser at cryogenic temperatures with two orthogonally polarized emissions: generation of 670 GHz beating

A dual-wavelength self-mode-locked monolithic Nd:YAG laser at 1061 and 1064 nm is realized at cryogenic temperatures. At an incident pump power of 5.5 W, the total output power can reach 2.5 W and the mode-locked pulse width is 29 ps at a pulse repetition rate of 7.75 GHz. The synchronization of the dual-wavelength emissions leads to a beat frequency of 670 GHz in the individual mode-locked pulse. It is further discovered that the laser output consists of two orthogonally polarized components with a central frequency difference of 127 MHz. The central frequency difference between two orthogonal polarizations mainly arises from the external mechanical stress introduced by the copper holder for the laser crystal.

Observation of reflection feedback induced the formation of bright-dark pulse pairs in an optically pumped semiconductor laser

It is experimentally demonstrated that the tiny reflection feedback can lead the optically pumped semiconductor laser (OPSL) to be operated in a self-mod-locked state with a pulse train of bright-dark pulse pairs. A theoretical model based on the multiple reflections in a phase-locked multi-longitudinal-mode laser is developed to confirm the formation of bright-dark pulse pairs. The present finding can offer an important insight into the temporal dynamics in mode-locked OPSLs.

Exploring transverse pattern formation in a dual-polarization self-mode-locked monolithic Yb: KGW laser and generating a 25-GHz sub-picosecond vortex beam via gain competition

Formation of transverse modes in a dual-polarization self-mode-locked monolithic Yb: KGW laser under high-power pumping is thoroughly explored. It is experimentally observed that the polarization-resolved transverse patterns are considerably affected by the pump location in the transverse plane of the gain medium. In contrast, the longitudinal self-mode-locking is nearly undisturbed by the pump position, even under the high-power pumping. Under central pumping, a vortex beam of the Laguerre-Gaussian LGp,l mode with p = 1 and l = 1 can be efficiently generated through the process of the gain competition with a sub-picosecond pulse train at 25.3 GHz and the output power can be up to 1.45 W at a pump power of 10.0 W. Under off-center pumping, the symmetry breaking causes the transverse patterns to be dominated by the high-order Hermite-Gaussian modes. Numerical analyses are further performed to manifest the symmetry breaking induced by the off-center pumping.

Generation of orthogonally polarized self-mode-locked Nd:YAG lasers with tunable beat frequencies from the thermally induced birefringence

The simultaneous self-mode-locking of two orthogonally polarized states in a Nd:YAG laser is demonstrated by using a short linear cavity. A total output power of 3.8 W can be obtained at an incident pump power of 8.2 W. The beat frequency Δfc between two orthogonally polarized mode-locked components is observed and measured precisely. It is found that the beat frequency increases linearly with an increase in the absorbed pump power. The origin of the beat frequency can be utterly manifested by considering the thermally induced birefringence in the Nd:YAG crystal. The present result offers a promising approach to generate orthogonally polarized mode-locked lasers with tunable beat frequency.

Manifesting the evolution of eigenstates from quantum billiards to singular billiards in the strongly coupled limit with a truncated basis by using RLC networks

The coupling interaction between the driving source and the RLC network is explored and characterized as the effective impedance. The mathematical form of the derived effective impedance is verified to be identical to the meromorphic function of the singular billiards with a truncated basis. By using the derived impedance function, the resonant modes of the RLC network can be divided into the open-circuit and short-circuit states to manifest the evolution of eigenvalues and eigenstates from closed quantum billiards to the singular billiards with a truncated basis in the strongly coupled limit. The substantial differences of the wave patterns between the uncoupled and strongly coupled eigenmodes in the two-dimensional wave systems can be clearly revealed with the RLC network. Finally, the short-circuit resonant states are exploited to confirm that the experimental Chladni nodal-line patterns in the vibrating plate are the resonant modes subject to the strong coupling between the oscillation system and the driving source.

High-peak-power optically-pumped AlGaInAs eye-safe laser with a silicon wafer as an output coupler: comparison between the stack cavity and the separate cavity

An intrinsic silicon wafer is exploited as an output coupler to develop a high-peak-power optically-pumped AlGaInAs laser at 1.52 μm. The gain chip is sandwiched with the diamond heat spreader and the silicon wafer to a stack cavity. It is experimentally confirmed that not only the output stability but also the conversion efficiency are considerably enhanced in comparison with the separate cavity in which the silicon wafer is separated from other components. The average output power obtained with the stack cavity was 2.02 W under 11.5 W average pump power, corresponding to an overall optical-to-optical efficiency of 17.5%; the slope efficiency was 18.6%. The laser operated at 100 kHz repetition rate and the pulse peak power was 0.4 kW.