Fast Photoluminescence Research Articles

Oxidized Graphite Nanocrystals for White Light Emission

We investigated the formation of graphite nanocrystals covered with graphite oxide for white light generation. The nanoparticles were formed using cost-efficient oxidation of a carbon-based dye pigment at different temperatures and verified using X-ray diffraction and Raman measurements. Formation of the graphite nanoparticles via thermal annealing was observed, while their light emission increased at higher oxidation temperatures. This was associated with a higher amount of oxygen defect groups. The time-resolved photoluminescence measurements showed linearly faster decays at shorter wavelengths and similar decays at different annealing temperatures. Broadband and linear vs. excitation emission spectra of the particles were found to be suitable for white-light-emitting devices and phosphor markers. The fast photoluminescence decay opens the possibility for the application of nanoparticles in optical wireless communication technology.

Optical wireless communication using a flexible and waterproof perovskite color converter.

In this Letter, the CH3NH3PbBr3 nanocrystals (NCs) are embedded into the interstices of the fluorine (polyvinyl fluoride/polyvinylidene fluoride, PVF/PVDF) matrix on polyethylene terephthalate (PET) substrate to introduce new advantages, such as being flexible and waterproof, while maintaining the high optical performance of perovskites. The sample's photoluminescence (PL) spectra under 325 nm laser is a green emission peaked at 537 nm with full width at half maximum (FWHM) of about 21.2 nm and a fast PL decay time. As a color converter, it shows high optical absorption and can transform light from solar-blind ultraviolet to a blue region into a green region in air, water, and bending conditions. While excited by a 270 nm ultraviolet light-emitting diode (LED), the system's observed -3 dB bandwidth with the color converter is near 4.4 MHz in air and water conditions with well-eye diagrams at a data rate of 30 Mbps. Finally, we demonstrate an audio transmission application with an ultraviolet light source, a color conversion layer, and a low-cost silicon-based photodetector.

Structural and spectroscopic insights into the performance of K3Tb(PO4)2 green phosphor.

A narrow-band green emitting K3Tb(PO4)2 phosphor has been synthesized by a novel single-crystal growth approach involving the application of an inert flux. Its structural and spectroscopic peculiarities have been systematically studied by means of single-crystal X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy analysis, and diffuse reflectance, infrared and photoluminescence spectroscopy. The layered framework of the title compound is organized by linking together slightly distorted phosphate tetrahedra with non-condensed TbO7 polyhedra into [Tb(PO4)2]3- sheets interconnected by potassium cations. K3Tb(PO4)2 reveals an intense slow green photoluminescence (PL) (decay time constant τ is near 2.6 ms) under excitation in the range from VUV (100 nm) up to blue light (484 nm). Intensive narrow lines of the 5D4 → 7F6-0 (4f8 → 4f8) radiative transitions in Tb3+ ions form the PL spectra. Besides, fast violet PL (time constant τ < 20 ns) occurs under PL excitations in a narrow range from 250 to 325 nm. Dependencies of the PL quantum yield, and the green and violet PL decays on the excitation wavelength have been analyzed taking into account the multi-phonons, cross-relaxation processes and exciting light absorption by the inherent defects in the K3Tb(PO4)2 crystal lattice. The dependency of the complex characteristics of PL quantum yield on the excitation wavelength and violet photoluminescence is ascribed to the formation of Tb4+ ions. The color coordinates and color purity of the emission were estimated for the cases of PL excitation in the 160-371 nm spectral range. It has been shown that these characteristics are similar to or even better than those reported for conventional commercial green phosphors. The high values of correlated color temperature (T> 4863 K) of the emission indicates the potential use of K3Tb(PO4)2 for enhancing cold-light emitting devices.

Nanocomposite scintillation perovskite-delignified wood photonic guides for X-ray imaging

Nanocrystalline scintillators with low-cost, fast response, and high light yield are widely used for X-ray imaging. However, they fail in high-energy X-ray imaging because of the fundamental limitations due to lateral radiation spreading in thicker device-compatible active layers. This issue is resolved by using the novel nanocomposite containing CsPbBr3 scintillation single-microcrystalites embedded into transparent, natural wood-derived light-guiding fibrous structures. The CsPbBr3 crystals convert X-ray to visible photons with a high photoluminescence quantum efficiency (76 %), and an average fast photoluminescence decay time of 25.9 ns. The delignified wood-derived fiber-like lumina effectively guide light, while suppressing the lateral spreading of scintillation photons. This unique porous nanocomposite material offers an excellent X-ray detection performance, and linear response in a wide parameter range. The developed scintillator screen achieves well-resolved, high-contrast X-ray imaging, featuring a very high spatial resolution of 11.9 lp/mm at a modulation transfer function of 0.2, thus exceeding the benchmark industry standards and offering a new advanced materials platform for radiation detection and dosimetry applications.

Modified luminescent properties from green afterglow to efficient orange emission in zirconium-based organometallic chloride scintillator by Sb3+ doping

Zero-dimension (0D) metal halides based on metals with the 5s2 lone pair have attracted great attentions due to their strong triplet broadband emission. However, the conversion from weak afterglow to efficient and fast photoluminescence by regulating the composition of 0D metal halides is still a tough challenge. Herein, Sb3+ ions-doped 0D (Ph4P)2ZrCl6·4CH3CN metal halides were synthesized by a simple solution crystallization method. Compared with the weak triplet green 560 nm afterglow from the organic Ph4P+ components, the emission of the Sb3+-doped material exhibits a strong orange photoluminescence at 660 nm with a high photoluminescence quantum yield of 72% by a host to dopant energy transfer process. In addition, a flexible large-sized X-ray scintillator screen with an area of 16 cm2 was prepared using polydimethylsiloxane as the host matrix, which exhibits excellent scintillation properties with light yields of 8,290 photons/MeV, low detectable limits of 0.986 μGy/s, and a near-infrared broadband emission from 600 nm to 850 nm under steady-state X-ray excitation, which is highly compatible with the response range of the long-wave sensitive silicon-based photodetectors. Therefore, this work not only provides a deep insight into the energy transfer process in the 0D metal halide materials but also opens an alternative approach to realize flexible large-size near-infrared X-ray imaging based on the 0D metal halide scintillator.

High molecular weight multifunctional fluorescent polyurea: Isocyanate-free fast synthesis, coating applications and photoluminescence studies

Isocyanate-free synthesis of high molecular weight polyurea (PUrea) is a challenging and important area of research, considering the health and safety concerns related to isocyanates and a wide range of day-to-day uses of polyurea. In this article, an isocyanate and phosgene-free synthesis of high molecular weight fluorescent polyurea (Mn > 150,000) is reported via triazolinedione (TAD)-indole click reactions. Both the bisTAD and bis-indole monomers are synthesized from diphenyl carbonate using solvent-free reactions. The synthesis of polyurea is finished within 15 min under ambient conditions, without the use of any additives and catalysts, which is a remarkable advantage in comparison to all other reported methods in the literature. The molecular weight (Mn) of the polyurea can be defined as either very high molecular weight >150,000 g/mol or low molecular weight ∼ 3500–4000 g/mol via choosing a suitable solvent for the polymerization reaction. This approach is also useful for polyurea-based hydrophobic coatings as evidenced by the water contact angle analysis. The indole-derived aromatic moieties introduced within the polymer backbone; impart photoluminescence properties and polymers show excitation-dependent emission behavior.

Ultrahigh Spatial Resolution, Fast Decay, and Stable X‐Ray Scintillation Screen through Assembling CsPbBr3 Nanocrystals Arrays in Anodized Aluminum Oxide

AbstractA scintillation screen with ultrahigh spatial resolution, fast decay time, and high stability is the key to commercial application. Herein, a pixelated‐structure scintillation screen of CsPbBr3 nanocrystal arrays based on anodized aluminum oxide (AAO) is reported, and its scintillation properties for X‐ray imaging are explored. It is of note that ultrahigh spatial resolution (2 µm), fast photoluminescence decay time (9 ns), and high stability (&gt;42 d) are successfully achieved by the pixelated CsPbBr3‐AAO arrays scintillation screen. Considering the decent scintillation properties and high stability, one has reason to assume that the pixelated CsPbBr3‐AAO arrays scintillation screen may find an application as a new X‐ray scintillation screen.

(Invited) Silicon Nanosheets as Candidates for Silicon-Based Optoelectronics

Colloidal Group IV nanomaterials (Si, Ge, Sn and their alloys) are of great interest due to their potential to offer broadly tunable optical properties. By manipulating composition, size, or surface chemistry Group IV nanomaterials have potential to serve as nontoxic, earth abundant phosphors or semiconductors that can be used for optoelectronic applications that span the ultraviolet to the mid-infrared spectral ranges. The synthesis of colloidal Group IV nanostructures is challenging due to the highly covalent character of Si and Ge, and typically require temperatures in excess of 400°C to form crystalline particles. We have recently reported new synthetic methods for Si and Ge nanomaterials derived from precursors synthesized in the solid-state, including suboxides and Zintl phases. In each of these cases, colloidal nanostructures can be accessed by selectively removing unwanted components from the solid-state precursor, liberating nanostructures that are terminated with atomic or molecular species such as hydrogen atoms or methyl groups. We also characterize the structural properties of the Group IV nanostructures that we synthesized using a combination of infrared spectroscopy, solid-state NMR, and pair distribution function analysis to confirm the structure and order. In the case of Si and Ge, single-atom thick nanosheets were synthesized, their stability and decomposition at elevated temperatures were characterized. The optical properties of Group IV nanomaterials have sparked debate over the past few decades. We found that Si nanosheets exhibit fast (nanosecond) photoluminescence lifetime, which is several orders of magnitude greater than Si nanocrystals, and offer potential explanations for the observed difference. Finally we show that Si and Ge nanocrystals and nanosheets can be used for sensing applications, including infrared photodetectors and ionophore-based sensing schemes.

Real-Time Imaging of Short-Wave Infrared Luminescence Lifetimes for Anti-counterfeiting Applications.

Rare-earth doped nanoparticles (RENPs) have been widely used for anti-counterfeiting and security applications due to their light frequency conversion features: they are excited at one wavelength, and they display spectrally narrow and distinguished luminescence peaks either at shorter wavelengths (i.e., frequency/energy upconversion) or at longer wavelengths (frequency/energy downconversion). RENPs with a downconversion (DC) photoluminescence (PL) in short-wave infrared (SWIR) spectral range (~1,000–1,700 nm) have recently been introduced to anti-counterfeiting applications, allowing for multilevel protection based on PL imaging through opaque layers, due to a lesser scattering of SWIR PL emission. However, as the number and spectral positions of the discrete PL bands exhibited by rare-earth ions are well-known, it is feasible to replicate luminescence spectra from RENPs, which results in a limited anti-counterfeiting security. Alternatively, lifetime of PL from RENPs can be used for encoding, as it can be finely tuned in broad temporal range (i.e., from microseconds to milliseconds) by varying type of dopants and their content in RENPs, along with the nanoparticle morphology and size. Nevertheless, the current approach to decoding and imaging the RENP luminescence lifetimes requires multiple steps and is highly time-consuming, precluding practical applications of PL lifetime encoding for anti-counterfeiting. Herein, we report the use of a rapid lifetime determination (RLD) technique to overcome this issue and introduce real-time imaging of SWIR PL lifetime for anti-counterfeiting applications. NaYF4:20% Yb, x% Er (x = 0, 2, 20, 80)@NaYF4 core@shell RENPs were synthesized and characterized, revealing DC PL in SWIR region, with maximum at ~1,530 nm and PL lifetimes ranging from 3.2 to 6 ms. Imaging of the nanoparticles with different lifetimes was performed by the developed time-gated imaging system engaging RLD method and the precise manipulation of the delay between the excitation pulses and camera gating windows. Moreover, it is shown that imaging and decrypting can be performed at a high rate (3–4 fps) in a cyclic manner, thus allowing for real-time temporal decoding. We believe that the demonstrated RLD-based fast PL lifetime imaging approach can be employed in other applications of photoluminescent RENPs.

Directional and Fast Photoluminescence from CsPbI3 Nanocrystals Coupled to Dielectric Circular Bragg Gratings.

Lead halide perovskite nanocrystals (NCs), especially the all-inorganic perovskite NCs, have drawn substantial attention for both fundamental research and device applications in recent years due to their unique optoelectronic properties. To build high-performance nanophotonic devices based on perovskite NCs, it is highly desirable to couple the NCs to photonic nanostructures for enhancing the radiative emission rate and improving the emission directionality of the NCs. In this work, we synthesized high-quality CsPbI3 NCs and further coupled them to dielectric circular Bragg gratings (CBGs). The efficient couplings between the perovskite NCs and the CBGs resulted in a 45.9-fold enhancement of the photoluminescence (PL) intensity and 3.2-fold acceleration of the radiative emission rate. Our work serves as an important step for building high-performance nanophotonic light emitting devices by integrating perovskite NCs with photonic nanostructures.

Time-resolved mid-infrared photoluminescence from highly strained InAs/InGaAs quantum wells grown on InP substrates

We measured time-resolved mid-infrared photoluminescence (PL) from highly strained InAs/InGaAs quantum wells (QWs) grown on InP substrates with a wavelength up-conversion technique. The InAs QWs at 4 K exhibit a narrow PL peaked at a wavelength of 2.125 μm and a PL lifetime as long as 1.1 ns, which supports high homogeneity of the QW thickness and few defects. As the pump fluence increases, a fast PL decay appears within the first 200 ps due to Auger recombination. The temperature dependence of the PL intensity and PL decay reveals interfacial nonradiative trap states in the QWs.

Monodisperse Long-Chain Sulfobetaine-Capped CsPbBr3 Nanocrystals and Their Superfluorescent Assemblies.

Ligand-capped nanocrystals (NCs) of lead halide perovskites, foremost fully inorganic CsPbX3 NCs, are the latest generation of colloidal semiconductor quantum dots. They offer a set of compelling characteristics—large absorption cross section, as well as narrow, fast, and efficient photoluminescence with long exciton coherence times—rendering them attractive for applications in light-emitting devices and quantum optics. Monodisperse and shape-uniform, broadly size-tunable, scalable, and robust NC samples are paramount for unveiling their basic photophysics, as well as for putting them into use. Thus far, no synthesis method fulfilling all these requirements has been reported. For instance, long-chain zwitterionic ligands impart the most durable surface coating, but at the expense of reduced size uniformity of the as-synthesized colloid. In this work, we demonstrate that size-selective precipitation of CsPbBr3 NCs coated with a long-chain sulfobetaine ligand, namely, 3-(N,N-dimethyloctadecylammonio)-propanesulfonate, yields monodisperse and sizable fractions (>100 mg inorganic mass) with the mean NC size adjustable in the range between 3.5 and 16 nm and emission peak wavelength between 479 and 518 nm. We find that all NCs exhibit an oblate cuboidal shape with the aspect ratio of 1.2 × 1.2 × 1. We present a theoretical model (effective mass/k·p) that accounts for the anisotropic NC shape and describes the size dependence of the first and second excitonic transition in absorption spectra and explains room-temperature exciton lifetimes. We also show that uniform zwitterion-capped NCs readily form long-range ordered superlattices upon solvent evaporation. In comparison to more conventional ligand systems (oleic acid and oleylamine), supercrystals of zwitterion-capped NCs exhibit larger domain sizes and lower mosaicity. Both kinds of supercrystals exhibit superfluorescence at cryogenic temperatures—accelerated collective emission arising from the coherent coupling of the emitting dipoles.

Dynamics of electron transfer in melanin-trinitrofluorenone system

The kinetics of photoluminescence (PL) and time-resolved emission spectra (TRES) of melanin solutions with an effective electron acceptor 2,4,7-trinitrofluorenone (TNF) have been studied. Based on the analysis of the kinetic decay curves and TRES, the fast and slow PL decay components can be distinguished, which characterize the processes of a relaxation of excited states and charge transfer in the melanin-TNF molecular system. In this paper, the observed dependences have been analyzed and the model to explain such behavior of PL dynamic characteristics has been proposed.

Biexciton Dynamics in Single Colloidal CdSe Quantum Dots.

The investigation of biexciton dynamics in single colloidal quantum dots (QDs) is critical to biexciton-based applications. Generally, a biexciton exhibits an extremely low photoluminescence (PL) quantum yield as well as very fast PL decay due to strong nonradiative Auger recombination, making it difficult to investigate the biexciton dynamics. Here, we develop a quantitative method based on intensity- and time-resolved photon statistics to investigate the biexciton dynamics in single colloidal QDs. This robust method can be used under high-excitation conditions to determine the absolute radiative and Auger recombination rates of both neutral and charged biexciton states in a single QD level, and the corresponding ratios between the two states agree with the theoretical predictions of the asymmetric band structures of CdSe-based QDs. Furthermore, the surface traps are found to provide additional nonradiative recombination pathways for the biexcitons, and their contributions are quantified by the method.

Direct Observation of Shallow Trap States in Thermal Equilibrium with Band‐Edge Excitons in Strongly Confined CsPbBr3 Perovskite Nanoplatelets

AbstractLead halide perovskites exhibit great potential for light‐emitting devices. Enhanced photoluminescence (PL) is obtained in perovskite materials of reduced dimensionalities due to the large exciton binding energy. However, as the nanocrystal size is reduced, the surface‐to‐volume ratio increases, leading to an abundance of surface defects. Here, a fast PL decay, 3–10 ps, is observed in quasi‐1D CsPbBr3 perovskite nanoplatelets using broadband fluorescence upconversion spectroscopy. This decay is attributed to reversible trapping of band‐edge excitons into dark states that lie close to the band edge. A simplified model is proposed to further confirm the presence of shallow traps and to fit the data obtained by ultrafast spectroscopy for multiple samples. Finally, the presence of deep trap states in aged nanoplatelets is revealed, likely arising from desorption of the organic capping ligands from the surface. Exciton trapping into these states is slower, 20–30 ps, but leads to a decrease in the photoluminescence quantum yield. These results may not only explain the extended luminescence lifetimes that have been reported for perovskite nanocrystals but also demonstrate the potential of combining ultrafast transient absorption and fluorescence up‐conversion to obtain a full description of the spectroscopic properties of the material.

Multistep Electron Injection Dynamics and Optical Nonlinearity Investigations of π-Extended Thioalkyl-Substituted Tetrathiafulvalene Sensitizers

A comprehensive investigation is presented on the photophysical and third-order nonlinear optical (NLO) properties of two thioalkyl-substituted tetrathiafulvalene molecules (referred here as G1 and G3) to understand their utility as photosensitizers for dye-sensitized solar cell (DSSC) and optoelectronic applications. Both steady-state and time-resolved (in the fs–ns time regime) absorption and photoluminescence (PL) spectroscopy techniques were employed to comprehend the excited-state properties of the molecules in solution as well as in thin films deposited on both quartz and mesoporous TiO2 layers. The spectroscopy measurements in solution and thin films deposited on quartz provided the excited-state properties of dye molecules. Time-resolved PL measurements at the dye–TiO2 interface provided initial evidence of electron injection by fast PL quenching decay dynamics for both the molecules. Detailed target analysis of the femtosecond transient absorption spectroscopy (TAS) data of the dye–TiO2 sample revealed a multistep ultrafast electron injection for both molecules with the fastest injection component being 374 and 314 fs for G1 and G3 molecules, respectively. The ultrafast NLO properties of G1 and G3 were studied using the Z-scan technique with 800 nm, ∼70 fs laser pulses. The open aperture measurements showed three-photon absorption with magnitudes of coefficients 4.7 × 10–5 cm3/GW2 and 5.2 × 10–5 cm3/GW2, and the closed aperture measurements provided second hyperpolarizability (γ) values of 3.5 × 10–31 esu and 4.2 × 10–31 esu for G1 and G3, respectively. Additionally, the onset of optical limiting was estimated to be 5.8 × 10–3 J/cm2 and 5.7 × 10–3 J/cm2 for G1 and G3 molecules, respectively.

Charge‐Carrier Trapping and Radiative Recombination in Metal Halide Perovskite Semiconductors

AbstractTrap‐related charge‐carrier recombination fundamentally limits the performance of perovskite solar cells and other optoelectronic devices. While improved fabrication and passivation techniques have reduced trap densities, the properties of trap states and their impact on the charge‐carrier dynamics in metal‐halide perovskites are still under debate. Here, a unified model is presented of the radiative and nonradiative recombination channels in a mixed formamidinium‐cesium lead iodide perovskite, including charge‐carrier trapping, de‐trapping and accumulation, as well as higher‐order recombination mechanisms. A fast initial photoluminescence (PL) decay component observed after pulsed photogeneration is demonstrated to result from rapid localization of free charge carriers in unoccupied trap states, which may be followed by de‐trapping, or nonradiative recombination with free carriers of opposite charge. Such initial decay components are shown to be highly sensitive to remnant charge carriers that accumulate in traps under pulsed‐laser excitation, with partial trap occupation masking the trap density actually present in the material. Finally, such modelling reveals a change in trap density at the phase transition, and disentangles the radiative and nonradiative charge recombination channels present in FA0.95Cs0.05PbI3, accurately predicting the experimentally recorded PL efficiencies between 50 and 295 K, and demonstrating that bimolecular recombination is a fully radiative process.

Planar Optical Waveguides Using Poly(styrene-ethylene-butylene-styrene) Activated with Inorganic Lead Halide Perovskite Nanoplates

Lead halide perovskite nanoplates support strongly quantum confined excitons, high photoluminescence quantum yield, fast and narrow photoluminescence spectra. Future use of these nanomaterials is s...

Fully convolutional networks for chip-wise defect detection employing photoluminescence images

Efficient quality control is inevitable in the manufacturing of light-emitting diodes (LEDs). Because defective LED chips may be traced back to different causes, a time and cost-intensive electrical and optical contact measurement is employed. Fast photoluminescence measurements, on the other hand, are commonly used to detect wafer separation damages but also hold the potential to enable an efficient detection of all kinds of defective LED chips. On a photoluminescence image, every pixel corresponds to an LED chip’s brightness after photoexcitation, revealing performance information. But due to unevenly distributed brightness values and varying defect patterns, photoluminescence images are not yet employed for a comprehensive defect detection. In this work, we show that fully convolutional networks can be used for chip-wise defect detection, trained on a small data-set of photoluminescence images. Pixel-wise labels allow us to classify each and every chip as defective or not. Being measurement-based, labels are easy to procure and our experiments show that existing discrepancies between training images and labels do not hinder network training. Using weighted loss calculation, we were able to equalize our highly unbalanced class categories. Due to the consistent use of skip connections and residual shortcuts, our network is able to predict a variety of structures, from extensive defect clusters up to single defective LED chips.

Sapphire advanced mitigation process: wet etch to expose sub-surface damage and increase laser damage resistance and mechanical strength.

A novel, to the best of our knowledge, method of wet chemical etching of sapphire workpieces (such as optics, wafers, windows, and cones), called the sapphire advanced mitigation process (or sapphire AMP), has been developed that exposes sub-surface mechanical damage created during the optical fabrication process and significantly enhances the surface laser damage resistance ($ \gt {2{\times}}$>2×) and mechanical strength (up to $\sim{2.6{\times}}$∼2.6×). Sapphire AMP involves first treating the workpiece with a mixture of sulfuric and phosphoric acid $([{\rm H_{2}{\rm SO_{4}}}]:[{\rm H_{3}{\rm PO_{4}}}]=1:3)$([H2SO4]:[H3PO4]=1:3) at 220°C, followed with phosphoric acid at 160°C, then with sodium hydroxide base (NaOH) and surfactant at 40°C, and finally with a high-pressure deionized water spray rinse. Sapphire AMP has been demonstrated on both A- and C-plane sapphire workpieces. The mechanism of this etch process involves the reaction of the sapphire $({\rm Al_{2}}{\rm O_{3}})$(Al2O3) surface with sulfuric acid $({\rm H_{2}}{\rm SO_{4}})$(H2SO4) forming aluminum sulfate $[{{\rm Al}_2}{({{\rm SO}_4})_3}]$[Al2(SO4)3], which has low solubility. The high phosphoric acid content in the first and second steps of sapphire AMP results in the efficient conversion of ${{\rm Al}_2}{({{\rm SO}_4})_3}$Al2(SO4)3 to aluminum phosphate $({\rm AlPO_{4}})$(AlPO4), which is very soluble, greatly reducing reaction product redeposition on the workpiece surface. Sapphire AMP is shown to expose sub-surface mechanical damage on the sapphire surface created during the grinding and polishing processes, whose etched morphology has either isotropic or anisotropic evolution depending on the nature of the initial surface damage. Sapphire AMP was also designed to remove the key known surface, laser absorbing precursors (namely, foreign chemical impurities, the fracture surface layer of preexisting sub-surface damage, and reaction product or foreign species redeposition or precipitation). Static and sliding indention induced surface microfractures on sapphire are shown after sapphire AMP to have a significant decrease in the fast photoluminescence intensity (a known metric for measuring the degree of laser damaging absorbing precursors). In addition, the onset of laser damage (at 351 nm 3 ns) on sapphire AMP treated workpieces was shown to increase in fluence from $\sim{4}$∼4 to $ \gt {9}.{5}\;{{\rm J/cm}^2}$>9.5J/cm2. Finally, biaxial ball-on-ring mechanical tests on sapphire disks showed an increase in the failure stress from 340 MPa (with pre-existing 28 µm flaws) to $\sim{900}\;{\rm MPa}$∼900MPa after sapphire AMP, which is attributed to the blunting of the surface microfractures.