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Optical coherence tomography (OCT) is a novel imaging modality that provides volumetric in-vivo high-resolution (1-15μm) images in real-time. Multi-channel OCT (MOCT) imaging utilizes many imaging channels simultaneously yielding several advantages over single-channel OCT. The benefits of MOCT are at the cost of the added requirement of several imaging beams, which demands high power output from the laser source. Dual-core Ytterbium (Yb) doped fiber was used in two configurations to demonstrate its use as a MOCT light source gain medium: 1) within a ring cavity resonator and 2) in a post-amplification regime with a low powered seed-laser. The amplification wavelength range was tailored to be centered at ~1060nm, where light absorption and scattering is at a minimum in water. In the post-amplification configuration, the output power was increased from 5mW to >200mW, with the axial resolution reducing from 10μm to 12μm. We also present initial in-vivo MOCT imaging of a tadpole.

Materials with high thermo mechanical properties are required as laser media for high-powered lasers. One of such materials is lutetium-aluminum garnet (LuAG) doped with ytterbium. In the present work, we discuss for the first time a full comparative study of 5% Yb-doped LuYAG ceramics with variation Lu/Y ratio. Samples were prepared with addition of B2O3, MgO and SiO2 which were used as sintering aids. Grain sizes, shrinkage curves, lattice constants and transmission spectra were measured for all samples. Thermal conductivity was measured in a wide temperature range for all studied samples. Output power of 12 W and 60% slope efficiency were obtained on the 5% Yb:LuAG disk laser.

In this work, we establish a comprehensive spectral model to realize effective design of high-power ytterbium-Raman fiber amplifiers (YRFAs) employing different types of Raman-pump lasers, and propose an intuitive approach for the optimization of high-power YRFAs. Quantitative comparisons with the experimental results are given in two high-power YRFAs employing Raman-pump lasers with different spectral linewidth. The consistency of measured and simulated power ratios and spectral properties of different components in the two YRFAs confirms the fidelity of the spectral model. Further theoretical analysis reveals that the impact of Raman-pump lasers on YRFAs is mainly determined by the relative intensity noise (RIN) of Raman-pump lasers up to the cutoff frequency of the pump RIN transfer function of the YRFA. Notably, the RIN of Raman-pump lasers could provide a well reference for the superior design of Raman-pump lasers in high-power YRFAs.

Ultra-narrow clock transition of ytterbium atoms has enabled not only quantum metrology but also quantum simulation of various quantum phenomena. One of such examples is a new possibility of realizing dissipative open quantum systems with minimal heating by optical pumping through the clock transition. Nevertheless, the access to the clock transition and relevant optical pumping often requires a complex laser system. Here we delineate a simple design and characterization of a home-made clock laser system that is capable of driving ytterbium clock transition at 578 nm. A fundamental laser at 1156 nm based on a quantum dot gain chip in a long external cavity configuration seeds the standard bow-tie cavity and generates up to 45 mW power of frequency-doubled yellow light at 578 nm. We have stabilized the laser frequency to a high-finesse ULE (ultra-low expansion) cavity via electronic feedback to the current. We examine the atomic spectroscopy at the clock transition in fermionic $$^{173}$$ Yb atoms, which would allow us to implement controlled dissipation with minimal heating. With the clock laser system built in this work, we envision exploring non-Hermitian physics in various platforms including spin-orbit-coupled fermions and topological bands.

Extremely short, high-energy pulses are essential in modern ultrafast science. In a seminal paper in 19961, Nisoli and co-workers demonstrated the first intense pulse compression employing a gas-filled hollow-core fibre. Despite the huge body of scientific work on this technology stemming from ultrafast and attosecond research, here we identify an unexplored few-cycle visible-light generation mechanism, which relies on the nonlinear mixing of hollow-core fibre modes. Using a commercially available ytterbium laser, we generate 4.6 fs, 20 μJ pulses centred at around 600 nm (~2 cycles, ~4 GW peak power), ~40 times shorter than the input 175 fs, 1 mJ pulses at 1,035 nm. Our approach thus directly projects few-hundred-femtosecond-long infrared pulses into the single-cycle regime at visible frequencies, without the need for additional post-compression. As a powerful application of our findings, we present a compact, multicolour pump–probe set-up with a temporal resolution of a few optical cycles. Direct generation of few-cycle high-energy visible pulses is demonstrated via the nonlinear mixing of hollow-core fibre modes. Compression of near-infrared laser pulses by a factor of 40 with no additional dispersion compensation delivers 4.6 fs, 20 μJ pulses (~2 cycles, ~4 GW peak power) centred at around 600 nm.

Based on a distributed-feedback (DFB) semiconductor laser, an ytterbium fibre amplifier, an Nd : YVO4 amplifier, and a frequency converter, we designed a hybrid picosecond laser for satellite laser ranging. A gain exceeding 108 is achieved while maintaining the temporal shape and spectrum of the pulses, with a low noise level and a divergence close to the diffraction limit. The pulse energy after conversion to the second harmonic at λ = 532 nm is 2.2 mJ with a duration of 27 ps and a repetition rate of 1 kHz. It is shown that the main effects limiting the peak power are spectrum broadening due to self-phase modulation in a fibre amplifier and large-scale self-focusing in the Nd : YVO4 amplifier. Optimisation of the amplifier geometry and the use of a uniform profile of the pump radiation intensity make it possible to reduce the effect of self-focusing and increase the energy efficiency of the amplifier.

Nanopowders of the compositions BaHf1 – xYbxO3 – δ (x = 0.04, 0.08, 0.10) and BaCe0.9 – xZrxY0.1O3 – δ (x = 0, 0.5, 0.6, 0.7, 0.8) were synthesized by the combined crystallization of nitric acid salts and the citrate-nitrate method. Those nanopowders were used to produce ceramic materials with a cubic crystal structure of the perovskite type, with a grain size of ~20–70 nm. The study of electrophysical properties revealed that they have a proton type of conductivity in the temperature range of 500–700°C; σ = 10–2–10–5 S/cm. The type and mechanism of electrical conductivity of ceramics of the composition BaHf1 – xYbxO3 – δ (x = 0.04, 0.08, 0.10) were studied both experimentally and using theoretical calculations by computer modeling using the electron density functional method; the results are in good agreement. The research shows the prospects of using the obtained ceramic materials as proton-conducting electrolytes for solid oxide fuel cells.

A distributed temperature monitoring inside a cavity of ytterbium DFB and holmium fiber lasers has been demonstrated with a spatial resolution of 1 and 5 mm, respectively, for the first time to the best of our knowledge. For this, we use an optical backscatter reflectometer, which measures intracore temperature, and compare it with the data of an IR thermographic camera, which measures temperature from the surface of a fiber. In the case of holmium fiber laser pumped at a wavelength of 1125 nm with a power of 6 W, the maximum temperature variation along the ∼3-m active fiber reaches ∼60 °C. In the case of ytterbium DFB laser, we observe a strong inhomogeneity of the temperature along the DFB cavity, which leads to a significant decrease in the lasing efficiency. When pumped by a single-mode laser diode at a wavelength of 976 nm with a power of up to 526 mW, the maximum temperature difference reaches 37 °C for the 37-mm DBF cavity.

The comparison of optical oscillators is used both to determine their spectral characteristics and to perform fundamental research. To describe each individual laser system, it is necessary to compare at least three independent laser oscillators. Three ultrastable lasers with wavelengths of 1140, 1550, and 871 nm located in different laboratories at the Lebedev Physical Institute have been compared. A femtosecond frequency comb has been used to transfer stability between different spectral ranges. A fractional frequency instability has been obtained with the three-cornered hat method and phase noise of each laser has been analyzed. Using this method, it has been shown that the characteristics of the laser system at a wavelength of 871 nm are appropriate to control the quantum state of an optical qubit on a quadrupole transition in an ytterbium ion with a n-atural width of 3.1 Hz.

The article presents the results of studies of the surfaces of parts processed by the contactless method of laser polishing. The results of technological surface treatment using a laser technological complex based on an ytterbium fibre laser with a power of 5 kW are presented. The results of studies of the surface roughness of the samples after laser treatment, including the non-uniform character due to the redistribution of the liquid metal melt over the surface, are shown. Requirements for metrological support of additive technology have been developed using the example of the process of laser remelting in order to improve quality and further automation.

We demonstrate a microfiber Bragg grating as the reflective refractometer with the function of self-photoheating. The rare earth-doped fiber provides not only the photosensitivity to the UV modulation but also the effective pump laser absorption and photoheating conversion. The rare earth-doped microfiber Bragg grating, which is cladding-removed by the hydrofluoric acid, can detect the tiny refractive index change with a resolution of 10−4 RIU scale. The self-photoheating could be realized by 980 nm pump absorption and non-radiative transition process of the ytterbium and erbium ions, which are well-preserved by the core structure after etching. Monitored by the reflective grating signal, the photoheating can manipulate 30 °C increase of the device in the air, 8 °C in the ethanol, and 4 °C in the water. The second time-scale heating/cooling response allows the sensor to act as ad optical switch for engineering temperature. The work may open a new route for accelerative biosensing and pollutant determination and treatment.

In this study, a switchable ytterbium-doped fiber laser based on symmetrical long-period fiber grating (LPFG) is presented. The LPFG is used as a wavelength-selective filter (WSF). Utilizing this WSF, the laser can emit one, two, or multiple stable output beams by adjusting the temperature on the LPFG from 20 °C to 600 °C. In addition, switching is also possible by adjusting the curvature of the LPFG from 0.399 to 0.709 m−1. The symmetrical LPFG was fabricated by combining the cladding shaping with the thermal core expansion techniques by using a CO2-laser LZM-100 glass-processing system. The experimental results show a side-mode suppression ratio (SMSR) of 49 dB and a linewidth of 0.06 nm, within the range from 1038 to 1080 nm. In conclusion, the main achievement of this switchable laser is the high SMSR and stable output for high values of temperature, using a repeatable, simple, easy construction, and cost-effective laser tuning technique.

We have assessed the effect of optical lattice laser field parameters (polarisation, intensity, and wavelength) of a cold-ytterbium atomic frequency standard on the systematic uncertainty of precision clock transition frequency measurements. The spectrum and polarisation of the laser field of the lattice have been investigated in detail directly in the spatial region of interaction of cold ytterbium atoms with the laser field. The Stark shift of the clock transition in the vicinity of the magic wavelength of the laser has been estimated as a function of the experimentally measured laser field intensity in the dipole approximation. The estimates have been used to calculate the residual systematic uncertainty in the light shift of the optical lattice laser frequency.

A combination of characterization techniques has been used to provide new understanding of the complex crystallization behavior of as-sprayed amorphous Yb2Si2O7-based air-plasma-sprayed environmental barrier coatings (EBCs). During crystallization heat-treatment, initially a mixture of metastable α-Yb2Si2O7 and X1-Yb2SiO5 phases form, along with stable β-Yb2Si2O7 and X2-Yb2SiO5 phases. Eventually the metastable phases transform to the stable β-Yb2Si2O7 (major) and X2-Yb2SiO5 (minor) phases. The significant volume expansion associated with these transformations partially contributes towards the anomalous expansion measured in these EBCs after crystallization, but it does not account for all the measured expansion. In this context, in similar EBCs, it is also observed that the porosity increases upon crystallization heat-treatment, primarily in the form of thin, interconnected pores, which also contributes to the measured anomalous expansion. Based on this understanding, guidelines are provided for ‘near-net-shape’ crystallization of phase-pure, dense β-Yb2Si2O7 EBCs that are free of vertical cracks.

In this letter, a novel acousto-optical (AO) Q-switch is designed by using $\alpha $ -BaTeMo $_{\mathbf {2}}~\text{O}_{\mathbf {9}}$ crystal grown by the flux method. The acousto-optical modulator (AOM) exhibits a high polarization extinction ratio of 65 dB with a rise time of 32.8 ns and insertion loss of 3.66 dB. An actively Q-switched ytterbium doped all fiber laser at 1035 nm is successfully realized by using the prepared AOM. Under a pump power of 404.9 mW, a maximum output power of 1.66 W is obtained with pulse width of 167 ns at the modulation rate of 10 kHz. The results show that the $\alpha $ -BaTeMo $_{\mathbf {2}}~\text{O}_{\mathbf {9}}$ AOM is a potential Q-switch for all fiber lasers.

A novel terbium (Tb3+) and ytterbium (Yb3+) co-doped optical quality CsGd(MoO4)2 single crystals were grown by the low-thermal-gradient Czochralski method. Photoluminescence spectra were measured a...

Ytterbium, thulium (Yb3+ ,Tm3+ ) co-doped β-NaYF4 upconversion nanocrystals (U-NCs) were synthesized by a convenient hydrothermal method using sodium citrate as a capping agent. X-ray diffraction (XRD) analysis revealed that NCs phase structures were dependent on reaction time. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) results showed that the morphology of U-NCs could be controlled by adjusting the concentration of sodium citrate added in the hydrothermal reaction. Moreover, the emission spectra of the U-NCs were investigated to evaluate upconversion efficiency. Strong luminescence intensity of the U-NCs was observed after tuned with optimized concentration of sodium citrate. Furthermore, the U-NCs were incubated with MCF-7 cells at 37°C for 24 h. Under irradiation of a 980 nm laser, the upconversion blue emission of the NCs in MCF-7 cells can be clearly observed through a confocal microscope with an upconversion imaging system and high quality upconversion luminescence images can be acquired. Thus, prepared β-NaYF4 :Yb3+ ,Tm3+ NCs provide us with highly efficient luminescent probes which can be applied for diverse bio-applications.

A fiber-optic laser fluorimeter operating in the near-infrared spectral range (900-1100 nm) has been developed. The fluorimeter is intended for luminescent diagnostics of skin and mucous membrane neoplasms. It uses a diagnostic agent based on the ytterbium complex of 2,4-di(α-methoxyethyl)deuteroporphyrin IX dipotassium salt. The device provides high values of the index of luminescent diagnostic contrast between neoplasm and normal tissue.

A novel few-mode fiber (FMF) based saturable absorber (SA) that works on the principle of nonlinear multimode interference has been proposed. To optimize the FMF parameters for the fabrication of SA, which is a combination of FMF with two single mode fibers (SMFs), a detailed numerical simulation is performed. The developed SMF-FMF-SMF structure exhibits a modulation depth and saturation intensity of 30.6% and 11.01 MW $/$ cm2, respectively. By inserting the fabricated SA in an all-normal dispersion Ytterbium doped cavity, we have been able to generate a laser pulse duration of 300 fs with an average power/pulse energy of 2.4 mW/64.8 pJ and a repetition rate of 37 MHz as an output. Thus, the proposed SA helps in generating stable pulses from the laser with enhanced output characteristics. We envisage that the fabricated SA would play an indispensable role in the development of ultrafast fiber lasers.

Purpose of research.Testing a method for additive formation of low-melting materials through the use of a low-powersolid-state (ytterbium) laser (maximum power 50 W). A series of experiments have been carried. As a result of those experiments, the elements of shaping mode have been obtained. They ensure the shaping of products without complete meltingof the construction material while preserving the shape of a rough workpiece. Thus, the possibility of using this type ofequipment for shaping products from low-melting materials in an additive way has been confirmed, which is the basis forfurther research on other materials, as well as the additional use of a shielding atmosphere.Methods.Methods of experiment planning and empirical data processing have been used for conducting experiments.Results.The possibility of using a low-power laser for the set tasks has been confirmed. Values ranges of shapingmodes have been obtained, which ensure the formation of products made of low-melting materials by the partial melting technique through an additive method.Conclusion.The experimental studies have shown that a low-power solid-state laser can be applied for shapingproducts made of low-melting materials using an additive method. Applying the results of this study will allow furtherdevelopment of additive shaping of other metals (such as copper or aluminum), for which it is necessary to upgradethe equipment in terms of creating a shielding atmosphere in the melt zone, as well as increasing the laser power.

A key aspect of ceramic matrix composites integration is related to a reliable joining technique. An ytterbium disilicate based glass-ceramic material is processed by reactive viscous flow sintering between a barium aluminium borosilicate glass and ytterbium oxide and it is used to join SiC/SiC and C/SiC composites. The joining temperature and the in situ formation of the Yb2Si2O7 is optimised at 1200°C without pressure, on the basis of the sintering and crystallisation mechanisms. The mechanical characterization of SiC/SiC and C/SiC joined with the ytterbium disilicate-based glass-ceramic, tested by single-lap offset at RT, exhibits an apparent shear strength of 35 MPa, similar to their interlaminar shear strength. The proposed system displays self-healing behaviour at 1000 °C and 1150 °C, as demonstrated by the partial and complete sealing of induced cracks by Vickers indentation on its surface at different loads, thus suggesting that it can effectively be used as promising joining material for CMCs.

Featuring simultaneous multicolor imaging for multiple targets, a synergistic strategy has become promising for fluorescence imaging applications. Visible and first near infrared (NIR-I, 700–900 nm) fluorophores have been explored for multicolor imaging to achieve good multi-target capacity, but they are largely hampered by the narrow imaging bands available (400–900 nm, bandwidth 500 nm), the broad emission spectra of many fluorophores, shallow tissue penetration and scattering loss. With attractive characteristic emission peaks in the second NIR window (NIR-II, 1000–1700 nm), a narrow emission spectrum, and deeper tissue penetration capability, rare-earth doped nanoparticles (RENPs) have been considered by us to be outstanding candidates for multicolor bioimaging. Herein, two RENPs, NaYF4:Yb20Er2@NaYF4 and NaYF4:Nd5@NaYF4, were prepared and modified with polyethylene glycol (PEG) to explore simultaneous imaging in the NIR-IIb (1530 nm, under 980 nm laser excitation) and the NIR-II (1060 nm, under 808 nm laser excitation) windows. The PEGylated-RENPs (RENPs@PEG) were able to simultaneously visualize the circulatory system, trace the lymphatic system, and evaluate the skeletal system. Our study demonstrates that RENPs have high synergistic imaging capability in multifunctional biomedical applications using their NIR-II fluorescence. Importantly, the two RENPs@PEG are complementary to each other for higher temporal resolution in NaYF4:Nd5@NaYF4@PEG and higher spatial resolution in NaYF4:Yb20Er2@NaYF4@PEG, which may provide more comprehensive and accurate imaging diagnosis. In conclusion, RENPs are highly promising nanomaterials for multicolor imaging in the NIR-II window.

Additive manufacturing technique has since become one of the more prominent manufacturing operations over the past years. The applications of this manufacturing technique are boundless as new process parameters of the operation affects the new structure of the components and provides different applications. This manufacturing process is the production of 3D metallic components by melting the raw material to produce that component. This is attained by the application of thermal energy on the raw material layer by layer until a solid component is formed, after cooling the product. The aim of this research study is to investigate the influence of temperature distribution and thermal stresses on the laser additive manufactured Titanium alloy grade 5. This was carried out using 3000 W continuous wave Ytterbium Laser System (YLS). The temperature distribution contour was investigated in this research and the influence of the optimal process parameters on the final coating geometry. The spot diameter and the distance between the base alloy and the laser nozzle influences the peak temperature distribution in the molten pool. The peak temperature at the start was 529 K while at the end of the base alloy it increased to 534 K. The crystal structures in the melt pool are changed by the rate of solidification. The 3D numerical investigation provided clarification and had substantial effects in the prediction of the overall resulting molten pool size and geometry size.

A portable high-sensitivity device for recording weak luminescence signals in the near infrared (NIR) region (900–1100 nm) has been developed for applications in laser oncofluorometry. The device consists of a housing with optical lenses, interference filters, and a high-sensitivity NIR photodiode module with a preamplifier, protection circuit, and power supply. It is shown that the use of interference filters of the SL 930–1100 type can significantly increase the efficiency of the device. The use of a photodiode module unit with a sensitivity peak near 960 nm, which maximally coincides with the luminescence peak of ytterbium porphyrin complexes, ensures the sensitivity of detecting weak luminescence signals at the level of several fW.

Modern literature has demonstrated the use of fluorescent probes in optical microscopy. Most recently, Ytterbium (Yb3+) and Thulium (Tm3+) doped nanocrystals have been used to achieve the imaging of single upconversion nanoparticles in the Stimulated Emission Depletion (STED) microscope. However, precise control of the stimulated emission at 800 nm caused by the discharge of the metastable 3H4 energy level of the Tm3+ acceptor probe would provide enhanced imaging in modern microscopy by suppressing visible fluorescence emitted from the focal plane. In this interdisciplinary paper, Model-Free Control is combined with Sliding Control to shape 800 nm pulsed emission of the lanthanide co-doped dual-laser system. This is achieved by controlling the stimulated emission rate via automatic adjustment of the probing laser pump power. This new type of controller will not be impacted by model errors like its model-based counterparts and can be fabricated by complementary metal oxide semiconductor (CMOS) processes paving way to photonic integration. Numerical simulation of the controller is executed and shows that the error between desired pulsed emission and the system's output was below 0.0057%. Mathematical analysis of the control technique and the results obtained from numerical simulations are presented.

Spectral-luminescent characteristics of erbium ions in photo-thermo-refractive (PTR) glasses doped with different concentrations of ytterbium and erbium oxides were investigated in this work. X-ray diffraction pattern of studied glasses was carried out. Judd-Ofelt parameters of intensity Ωt were obtained and used for deriving emission cross-sections and radiative lifetimes. It was found that the peak emission cross-sections values at a wavelength of 1.53 μm obtained from F-L and McCumber methods are 0.59 × 10−20 cm2 and 0.60 × 10−20 cm2, respectively, which are very similar and compared with those of silicate glasses. A quite high value of quantum yield at the wavelength of 1.53 μm for the sample with 0.1 mol% Er2O3 co-doped with ytterbium oxide has been investigated. Energy transfer efficiency from ytterbium ions to erbium ones was found to be 80% and 86% for erbium- and 1 mol% and 2 mol% Yb2O3-co-doped PTR glass, respectively. Laser properties of 2Yb-01Er PTR glass were carried out. The gain spectrum starts to be positive when the population inversion parameter gets to 0.5. Laser action was demonstrated at room temperature. It was found that the round-trip losses of the Er/Yb-PTR element are 0.28%.

The operation of the Ytterbium (Yb)-doped silica fiber laser is investigated under high temperature gradients generated by various cryogenic materials. A continuous-wave (CW) double-clad single-mode fiber laser working at 1082.51 nm with a linewidth (FWHM) of 0.16 nm and an average power of 10 W was used to study the effect of cooling rate on its output characteristics such as signal power, efficiency, central wavelength and spectral bandwidth. The cooling process is performed along the gain fiber using a cryogenic bath, while the cryo-coolants don't touch other laser components such as fiber Bragg gratings (FBGs), combiners and optical couplers. A series of rigorous experiments are carried out at room temperature - RT (22.5 °C) and cryo-states when the gain fiber is immersed in different coolants i.e., dry-ice ethylene-glycol - DIEG slurry (-29 °C), dry-ice debris (-58 °C) and liquid nitrogen - LN2 (-189.2 °C) with various pump powers ranging 2.9 - 16.5 W. The gain fiber of 10 m long demonstrates a 36 % power efficiency at LN2 against 66.4 % at RT. The signal power as well as the laser efficiency linearly reduces with temperature drop as to the linewidth undergoes a lucid spectral narrowing accompanying blue shift, mainly owing to the notable temperature response of the absorption / emission cross-section, broadening mechanisms and thermal population as well as energy level schemes, including sublevel and hyperfine structures of the transition accordingly.

The absorption and luminescence spectra and the excited state lifetime of Yb3+ in SOCl2–GaCl3–Yb3+ solutions are measured. Information on the Stark splitting of energy levels and on the absorption and stimulated emission cross sections of Yb3+ in SOCl2–GaCl3 is obtained. The possibility of creating a diode-pumped ytterbium laser based on SOCl2–GaCl3–Yb3+ inorganic liquid is considered.

This study experimentally demonstrates a Q-switched fibre laser using a new tungsten tri-oxide (WO 3 )-based saturable absorber (SA). Using the drop and casting approach, we managed to prepare a thin film that contained WO 3 powders in polyvinyl alcohol. A small bit of the film was used to form an SA which was placed in a ytterbium-doped fibre laser cavity to generate a Q-switched laser. The laser, operating at 1063.78 nm, was realised at the threshold pump power of 85 mW with a repetition rate of 23.87 kHz and a pulse width of 5.56 μs. At the pump power of 147 mW, the laser produced the maximum pulse energy of 625 nJ, signal-to-noise ratio of 59 dB, the repetition rate of 39.79 kHz and pulse width of 2.37 μs. To the best of our knowledge, this is the first demonstration of using WO 3 SA to generate the pulse laser in the 1 μm region.

The purpose of this 2 part review is to evaluate various debonding techniques for orthodontic ceramic bracket removal and their clinical applications. In this part 2 of the literature review, in vitro and in vivo studies on electrothermal debonding and Laser debonding techniques have been reviewed. Electrothermal debonding is a physiologically acceptable alternative to mechanical debonding. It requires minimal force following thermal softening of adhesive material and produces minimal changes to enamel surfaces compared to conventional methods. Minimal effects on enamel and intrapulpal temperature changes are noted with ytterbium fiber laser, diode laser and Tm:YAP laser. Different parameters are possible with CO2 laser, Nd:YAG laser and Er:YAG laser that may need further research before considering them in clinical practice. Keywords: Debonding, Orthodontic ceramic brackets, Literature Review, Electrothermal debonding, Laser debonding.

The temporal dynamics of diode-side-pumped Yb – Er laser, with a passive Co2+ : MgAl2O4 Q switch illuminated by a light beam (total fluence of 0.15 – 0.16 J cm−2) from a semiconductor pulsed module, is investigated. It is shown that, using this external illumination, one can change the lasing onset delay and the time jitter ΔT gi. The dependence of ΔT gi on the interval between the instant of switching the illumination module on and the lasing peak position t i has a minimum at |t i| ≈ 10 μs. The decrease in ΔT gi with a change in |t i| from 90 to 10 μs indicates that instant of lasing peak occurrence for the Yb – Er laser is partially controlled by the pulse from the highly stable semiconductor module. If |t i| < 10 μs, the enhanced luminescence fluence in the cavity of Yb – Er laser exceeds 0.16 J cm−2; the light beam from the module does not affect much the lasing process in the ytterbium – erbium laser; and, as a consequence, the time jitter recovers the initial value.

We report for the first time a 1050 nm Yb:YAG thin disk laser multi-pass pumped by a 1030 nm laser with minimal thermal load and stable laser mode. The low quantum defect and anti-Stokes fluorescence cooling decrease the heat generation inside gain medium efficiently, leading to a maximum total fractional thermal load of 1.05% in consideration of the additional thermal load caused by roughness surface on the side of thin disk. And no significant temperature difference was observed in pumped area. In addition, the thin disk shaped structure with multi-pass pumping scheme can not only overcome the shortcoming of low absorption coefficient at 1030 nm but also stabilize the laser mode fundamentally, and the beam quality and efficiency are then promoted. Besides, this laser can scale the output power easily by increasing the number of pump passes and pumped spot size. As a result, a 60-pass pumping scheme delivered an average power of 6.32 W operated at fundamental mode, and the optical to optical efficiency and slope efficiency were 18.1% and 31.4%, respectively.

The surfaces of Yb–Si(111) and O–Yb–Si(111) structures (with a thickness of ytterbium nanofilms of 16 monolayers (6.08 nm)) have been investigated for the first time using scanning tunnel microscopy, which has provided data on the morphology and phase composition of these surfaces. It is found that, prior to oxygen adsorption, the nanofilms exhibit a high degree of homogeneity over their thickness, grow in accordance with a mechanism very close to the layer-by-layer growth, and have a homogeneous crystalline structure. After oxygen adsorption, an island layer of oxygen molecules is formed with a thickness of 0.112 nm. It is shown that the nanofilms morphology in the regions of the film surface coated by a monomolecular oxygen film changes significantly, while the morphology of the surface regions uncoated with the adsorbed layer remains unchanged.

An experimental set-up was constructed based on an ytterbium pulsed laser with a passive holmium fiber shutter, which provides time-domain reflectometry research the length of active fiber samples after drawing and during storage. The possibility of studying non-uniformities in the fiber and quantifying the attenuation coefficient of the optical signal at the source wavelength is discussed. The results indicate the possibility of conducting studies of this type, as well as the potential development of reflectometers for the needs of laboratories of enterprises that produce active optical fibers commercially.

In this study, nano-sized Yb2SiO5 powders were prepared by a cocurrent coprecipitation method. The influence of Si/Yb molar ratio and calcination temperature on the phase composition and structure of Yb2SiO5 were investigated, and the synthesis mechanism of Yb2SiO5 was also discussed. Results indicated that the Si/Yb molar ratio has a significant influence on the phase composition of Yb2SiO5 powders. Under nonstoichiometric conditions, trace of Yb2O3 and Yb2Si2O7 will be formed as impurities in the as-prepared Yb2SiO5 powders. In addition, the elevated calcination temperature can promote the formation of stable X2-Yb2SiO5. During the synthesis process, a -[Si-O-Yb]- network structure was formed in the Yb2SiO5 precursors, which resulted from the in-situ replacement of Si by Yb atoms. The -[Si-O-Yb]- network will transformed to a X1-Yb2SiO5 firstly during the calcination process. With the calcination temperature increased, the metastable X1-Yb2SiO5 can convert to a stable X2-Yb2SiO5 gradually through a reconstructive process. Yb2O3 and Yb2Si2O7 may also be formed during the reconstructive process of X1-Yb2SiO5.

A cladding-pumped all-fiber chirped femtosecond pulse Yb-doped mode-locked laser operating near 977 nm was demonstrated for the first time. Nonlinear polarization evolution was used as the mode-locking mechanism. The laser was self-starting and extremely stable (the stability of the repetition rate of 41.6 MHz was better than that of 15 Hz). Amplification near 977 nm was achieved using a specially designed cladding-pumped Yb-doped fiber. The main feature of the current laser design was its increased intracavity nonlinearity, which resulted in a strong self-phase modulation and significant widening of the generated pulse spectrum. This nonlinearity allowed us to generate pulses compressible down to a duration of 230 fs using an external diffraction grating compressor.

In paper laser thermal oxidation of austenitic stainless steels AISI 201, 304L of different surface mill finishes, the hot and cold rolled was investigated by the Ytterbium-doped fibre laser (λ=1070 nm) with an output power of 400W by varying scanning speed in the range 5÷20m/s in the air atmosphere. The influence of laser oxidation parameters on the surface colour was evaluated by colorimetric identification.

We present mode-selection in a laser and an amplifier from a multicore Ytterbium (Yb) doped step-index fiber with six large mode area and low numerical aperture (NA) cores, fabricated using a combination of chelate delivery system (CDS) and stack and draw technique. The six cores are placed in a ring shape with each core having a diameter of $\sim 19~\mu \text{m}$ and NA of ~0.068, or V-number of ~3.8 at $1.06~\mu \text{m}$ . The cores are placed with a 1.1 pitch-to-core ratio, which efficiently promotes supermode generation and creates a good modal separation to facilitate mode selection. Mode selection of the multicore fiber is investigated in a laser as well as an amplifier configuration. With an intracavity pinhole, we are able to select the fundamental in-phase supermode for lasing up to 33.9W output power with a 52% slope efficiency. In the amplifier configuration, a Gaussian beam from a seed source is successfully coupled to the fundamental supermode in the multicore fiber. The seed source is amplified to ~43.5W from 0.14 W input power.

Photothermal heating represents a major constraint that limits the performance of many nanoscale optoelectronic and optomechanical devices including nanolasers, quantum optomechanical resonators, and integrated photonic circuits. Here, we demonstrate the direct laser refrigeration of a semiconductor optomechanical resonator >20 K below room temperature based on the emission of upconverted, anti-Stokes photoluminescence of trivalent ytterbium ions doped within a yttrium-lithium-fluoride (YLF) host crystal. Optically-refrigerating the lattice of a dielectric resonator has the potential to impact several fields including scanning probe microscopy, the sensing of weak forces, the measurement of atomic masses, and the development of radiation-balanced solid-state lasers. In addition, optically refrigerated resonators may be used in the future as a promising starting point to perform motional cooling for exploration of quantum effects at mesoscopic length scales, temperature control within integrated photonic devices, and solid-state laser refrigeration of quantum materials. Optically refrigerated resonators may be useful in optical devices and exploring quantum effects. Here, the authors show laser refrigeration of a semiconductor mechanical oscillator Yb:YLF host crystal and lowering the thermal load temperature.

We demonstrated the self-oriented growth of ytterbium silicate films at high deposition rates using laser chemical vapor deposition (laser CVD). β-Yb2Si2O7, X1-Yb2SiO5, and X2-Yb2SiO5 phases preferred (001)β and (110)β, (100)X1 and (021)X2, and (221)X2 orientations, respectively. The self-oriented growth was associated with crystallographic features, namely the edge-sharing Yb–O polyhedral networks in each phase. Deposition rates of the β-Yb2Si2O7 and X1/X2-Yb2SiO5 films ranged 114–423 and 353–943 μm h−1, respectively. Post annealing implied that β-Yb2Si2O7 and X2-Yb2SiO5 were the stable phases at elevated temperatures and the obtained films maintained their cone-like and columnar structures after annealing at 1673 K in air.

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Accepted: 2020-04-17, 資料番号: PA2110002000

Imaging and manipulating individual atoms with submicrometer separation can be instrumental for quantum simulation of condensed matter Hamiltonians and quantum computation with neutral atoms. Quantum gas microscope experiments in most cases rely on quite costly solutions. Here we present an open-source design of a microscope objective for atomic strontium consisting solely of off-the-shelf lenses that is diffraction-limited for 461${\,}$nm light. A prototype built with a simple stacking design is measured to have a resolution of 0.63(4)${\,\mu}$m, which is in agreement with the predicted value. This performance, together with the near diffraction-limited performance for 532${\,}$nm light makes this design useful for both quantum gas microscopes and optical tweezer experiments with strontium. Our microscope can easily be adapted to experiments with other atomic species such as erbium, ytterbium, and dysprosium, as well as Rydberg experiments with rubidium.

Multifunctional lanthanide-doped upconversion nanoparticles (UCNPs) have spread their wings in the fields of flexible optoelectronics and biomedical applications. One of the ongoing challenges lies in achieving UCNP-based nanocomposites, which enable a continuous-wave (CW) laser action at ultralow thresholds. Here, gold sandwich UCNP nanocomposites [gold (Au

We demonstrate an all-fiber ultra-low numerical aperture high power fiber laser system operating in the continuous-wave regime at a central wavelength of 1080 nm. A special Ytterbium-doped fiber preform has been designed and fabricated by using modified chemical vapor deposition technique with the deposition percentages of 0.03mol% of Yb2O3, 1.8mol% of Al2O3, and 2.1mol% of P2O5. Then it has been drawn to obtain an active fiber having core/cladding diameters of 26 μm/410 μm respectively. The numerical aperture of the fiber has been first predicted as 0.034 from refractive index profile of the preform. Afterward, this number has been verified with a simple test setup by altering the bending diameter of the fiber and the excitation conditions of it. To test the high power performance, a laser system has been constructed in a master oscillator power amplifier configuration, and ~ 80 W seed signal power is amplified to 1.05 kW. The quality of the laser output beam has been measured in terms of M 2 value along both x and y coordinates as 1.11 and 1.16 respectively. This work was supported in part by The Scientific and Technological Research Council of Turkey (TUBİTAK)

A passively Q-switched ytterbium-doped fibre laser (YDFL) using a nickel oxide-based saturable absorber is proposed and demonstrated. The Q-switched YDFL is capable of generating a stable output with a minimum pulse width of 6.9 µs and maximum repetition rate of 57.01 kHz. The generated pulses are highly stable, with an observed signal-to-noise ratio of ~ 33 dB. The output of the laser can be tuned over a wavelength range of 18 nm from 1035 to 1053 nm. The Q-switched YDFL would find use in multiple applications ranging from medicine to manufacturing.

We demonstrated an Yb-doped mode-locked fiber laser system delivering both dissipative-soliton-resonance (DSR) and noise-like pulse (NLP) simultaneously. The pulse widths of DSR and NLP were 7.1 ns and 4.3 ns, respectively. Meanwhile, the spectrum widths at 1056 nm of DSR and NLP were 0.5 nm and 21.5 nm, respectively. In this dual mode-locking state operation, the intracavity laser powers (DSR, NLP) increased 24% and 41% compared to that in single mode-locking states at the pump power of 600 mW, respectively. To the best of our knowledge, it is the first time to trigger DSR and NLP simultaneously by sharing one pump in a fiber laser system.