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Phosphor is an important part of the new generation of light-emitting diodes (LEDs), which requires high luminous intensity and high-temperature resistance. In this study, a series of excellent (Ba1−x−yCax)AlSi5O2N7:yEu2+ phosphors was developed, which were synthesized by a high-temperature solid-state reaction in a reducing atmosphere. In addition, the crystallinity and luminescence intensity of the samples could be enhanced by some amount of Ca2+ substitution. The luminescence intensity was the highest when the Eu2+ concentration reached 0.06. Furthermore, the thermal stability of the luminescence was studied in detail. The results were satisfactory, showing that the luminescence intensity of the (Ba1−xCax)AlSi5O2N7:Eu2+ phosphors exhibited unique negative-thermal-quenching characteristics both at high (273–473 K) and low (4–273 K) temperatures. And the phosphor combined with UV LED chip and red phosphor Sr2Si5N8:Eu2+ can achieve a CRI of 90.4 in white LED application which indicated the (Ba1−xCax)AlSi5O2N7:Eu2+ phosphor has potential in LED applications.

A series of novel SrMg2(PO4)2:Ce3+,Tb3+(SMP:Ce3+,Tb3+) phosphors with tunable emission spectra were produced via high temperature solid phase method. XRD, fluorescence spectrum and fluorescence lifetime for SMP:Ce3+,Tb3+ were studied in detail. Under the excitation at 308 nm, SMP:Ce3+,Tb3+ samples can emit high efficiency tunable blue-green light by controlling the proportion of dopant concentration. Through the spectral overlap and the regular change of fluorescence lifetime, it is proved that there is a significant energy transfer between Ce3+ and Tb3+ in SMP matrix and the energy transfer mechanism is determined to be an electric dipole–dipole interaction with energy transmission efficiency of 55%. In additional, Commission International de L'Eclairage (CIE) color coordinates and thermal stability were studied. All above findings suggest that SMP:Ce3+,Tb3+ can be regarded as the potential bluish green phosphor for LED applications.

As is well known, a way to obtain a high color resolution and saturation of a liquid crystal display and thereby obtain a higher visual accuracy and comfort in the coming 5G era remains an urgent challenge. In the present study, a new type of phosphor composite material doped with Ln3+ ions provides a promising alternative to the color filters used in White light-emitting diodes (WLEDs), achieving a better performance regarding the realization of a wider color gamut. The advantages of this composite material are illustrated through an abundant phase and morphology analysis along with a discussion regarding the X-ray photoelectron spectroscopy of the valence bond of Ce ions, which maintain the luminescence properties of the phosphor while providing a stable and solid amorphous environment. An improved spectral performance was obtained through color filtering at 580 nm along with the regulating effects of red, green, and blue emissions according to the doped Ln3+ ions. Notably, we fabricated a high-performance WLED based on a Ln3+-doped PiG with a correlated color temperature of 5037 K, color rendering index of 72.8, and high color gamut of 91.97%, providing a new choice for the development of luminescence materials with a high color resolution and saturation.

We report a detailed spectroscopic investigation of a series of fluorotellurite glasses with different Er3+ ions concentration in system 50TeO2-27BaF2-9ZnF2-8YF3-3MgF2-3NaF-xErF3-1HoF3(x = 1,2,3 mol%). Intense 2 μm emission and 2.75 μm emission with high absorption and emission cross-section were observed under 980 nm LD pumping, and the maximum gain coefficient around 2750 nm was as high as 2.41 cm−1, suggesting the prepared glasses are a competitive candidate for mid-infrared laser materials. Besides, it was found that the trend of 2 μm and 2.75 μm emission intensity varied with Er3+ ions concentration was different. Energy transfer process was discussed subsequently to explain this phenomenon. Furthermore, we quantitatively investigate the energy transfer efficiency from Er3+: 4I13/2 level to Ho3+: 5I7 level.

White light-emitting diodes (LEDs), as a fourth-generation green lighting source, have been widely used in various fields. At present, most white LEDs have based on a mixture of silicone with poor heat resistance and phosphors as luminescent components, which prevent them from adapting to high-temperature environments and limit their applications of high-power lighting. To improve the optical properties and reliability of white LEDs, phosphor solid is proposed as a new alternative, which not only has the strong stability of glass, but also completely retains the luminescent properties of phosphor. Therefore, in this study, tellurite glass was used as the matrix of phosphor solids to improve the luminescence performance by optimizing the composition of the matrix glass. In addition, rare earth ions were introduced into the tellurium glass matrix, and the dissolution ability of the matrix to rare earth ions was explored to improve the luminous quality of white LEDs.

A series of novel Ce3+ and/or Sm3+ activated Y4SiAlO8N (YSAON) phosphors are successfully synthesized by a conventional solid-state reaction method. The formation of monophasic YSAON is confirmed by X-ray powder diffraction (XRD) analysis. The crystal structure of YSAON is solved by XRD refinement data. DFT calculations indicate that Y4SiAlO8N has an indirect band gap of 3.819 eV. Based on the analysis of crystal structure and lifetime curves, four emission sites of YSAON:0.02Ce3+ are identified, which are Y1 (413 nm, 448 nm), Y2 (428 nm, 469 nm), Y3 (619 nm, 698 nm) and Y4 (512 nm, 569 nm), respectively. The concentration quenching of Ce3+ in YSAON is investigated in detail and it is confirmed to be due to dipole–dipole interactions. Photoluminescence excitation (PLE) and photoluminescence (PL) spectral measurements showed that the Ce3+ and Sm3+ co-doped phosphor could be efficiently excited by near-UV light, and exhibited four emission bands peaked at 485 nm, 565 nm, 605 nm and 650 nm, respectively. The CIE chromaticity coordinates of the obtained white light can be tuned by adjusting the content of Ce3+ and Sm3+ ions. Therefore, we anticipate that these materials can be used in near-UV chip pumped white LEDs.

Transparent Cr 4+ doped SiO 2 -Al 2 O 3 -ZnO-Li 2 O-K 2 O glass ceramics were prepared by conventional melting method. X-ray diffraction analysis revealed that dual nanocrystals of Zn 1.7 SiO 4 and Li 1.14 Zn 1.43 SiO 4 were precipitated in the glass matrix after 700 °C heating treatment. Broad infrared luminescence centered at 1261 nm and 1304 nm with a full width at half maximum (FWHM) of more than 250 nm was observed excited by an 808 nm excitation laser diode. And the lifetime was about 145.85 μs at 1261 nm and 179.56 μs at 1304 nm. Compared with Cr 4+ doped SiO 2 -Al 2 O 3 -ZnO-Li 2 O-K 2 O glass ceramics containing single phase of Zn 1.7 SiO 4 or Li 1.14 Zn 1.43 SiO 4 , this novel glass ceramics had wider FWHM and longer lifetime.

The influence of coating thickness on laser-induced damage (LID) characteristics of anti-reflection (AR) coatings irradiated by 1064 nm nanosecond laser pulses was investigated. Two HfOsub2/sub/SiOsub2/subAR coatings with different physical thicknesses, 0.7 and 2.7 μm, were prepared and tested. To study the effect of coating thickness on a laser-induced damage threshold (LIDT) in isolation, electric field intensities (EFIs) at the substrate-coating interface were kept the same by using proper AR designs. Moreover, 2 nm artificial gold particles with a density of 10 mmsup-2/supwere implanted into the substrate-coating interface to achieve reliable experimental results. An optical microscope (OM) and a scanning electron microscope (SEM) were used for an online LIDT test and offline LID morphology observation, respectively. The typical LID morphology of thicker AR coatings was flat bottom craters with diameters of 20-50 μm, which can be easily observed by an online OM. For thinner AR coatings, hemispherical craters with diameters down to 1 μm were found as typical LID morphology by a SEM. However, these tiny craters could not be observed by an online OM. Moreover, such tiny craters did not grow with subsequent pulses, so they did not degrade the functional laser damage resistance of the thin AR coatings. When identified with an online OM, the LIDT of thinner AR coatings is found to be about two times higher than the thicker ones, and large delamination was mainly found as the LID morphology of AR coatings with high fluence. When observed with a SEM, the LIDT of thin AR coatings with tiny craters was over 60% lower than the LIDT of thick AR coatings, which agrees with the model that less energy is required to form smaller LID craters of thinner coatings.

A series of Ce 3 + /Sm 3 + doped glasses were prepared in this study and their luminescence properties were analyzed. A combination of blue and orange-red emission band was observed from these glasses, and tunable white light emission could be observed by adjusting concentration ratio of Ce 3 + to Sm 3 + under UV light excitation. Energy transfer (ET) from Ce 3 + to Sm 3 + is discovered by directly observing significant overlap of the excitation spectrum of Sm 3 + and the emission spectrum of Ce 3 + ions. The energy transfer from Ce 3 + to Sm 3 + via a dipole–dipole mechanism was confirmed by the luminescence spectra, the decay lifetime and the calculation of energy transfer efficiency of the glasses. Based on the results in this study, the Ce 3 + /Sm 3 + doped glasses could be used as a potential matrix material for ultraviolet light emitting diode (LED) chip based white LEDs.

Growth behaviors of initial damage sites are important in investigating laser-induced damage mechanisms of optical materials and in evaluating the lifetime of optical components. The characteristics of the initial damage sites initiated by different fluences were investigated to determine the effects of the initial conditions on damage growth. Two kinds of experiments, fixed and ramp-up fluences, were conducted under a 355 nm small laser beam to obtain the growth behaviors in terms of morphology, lateral size, as well as crater and crack depth. Preliminary statistical results revealed the relationship between the growth trends and initiating and subsequent laser fluences. As the main features of damage growth, visible cracks are categorized into three main types, which are associated with the laser irradiation.

A green-emitting phosphor, Eu 2+ -activated Ba 3 Si 6 O 9 N 4 phosphor, was synthesized by a conventional solid state reaction method. X-ray diffraction patterns showed that the synthesized phosphor sintered at 1300 °C for 6 h was a Ba 3 Si 6 O 9 N 4 pure phase. It could be efficiently excited by UV–blue light (280–500 nm) and showed a single intense broad emission band (470–625 nm). Suitable excitation range makes it match well with the emission of near-UV or blue LEDs. Concentration quenching of the doped-Eu 2+ ions occurred at x =0.15, and the critical distance is calculated to be about 1.807 nm by theory of energy transfer. The result indicates that Ba 3 Si 6 O 9 N 4 :Eu 2+ is a promising green-emitting phosphor for white LEDs.

Laser-induced damage of high reflection (HR) coatings, working at near ultraviolet (NUV) and near infrared (NIR) regions was investigated. For NIR HR coatings, the nodules still remain the most limiting defects. The E-field intensity (EFI) enhancement in nodules plays a central role for triggering laser-induced damage. We established a simple model for EFI enhancement in nodules using the focusing and light penetrating concept. With the help of finite-difference time domain (FDTD) simulations, we found that refractive indices and nodular geometries affected the focal length as well as the size of focal spots. Furthermore, the angular reflection bandwidth (ARB) of nodules determined the fraction of light that can penetrate to the focal region. For NUV HR coatings, we explored the increase of the laser-induced damage threshold (LIDT) by increasing the incident angle from 0 degrees to 65 degrees for S-polarization. The EFI in a 65 degree HR coating is more than 4 times lower compared to 0 degree HR coatings, which suggests that the LIDT of 65 degree HR coating is much higher compared to 0 degree HR coating. However, we found some contradictory results. For small testing laser beam size with a diameter of 20 μm, the LIDT of 65 degree HR coating is 3.5 times higher compared to a 0 degree HR coating. However, for a large sized testing laser beam with a diameter of 1000 μm, the LIDT of 65 degree HR coating is 2 times lower compared to a 0 degree HR coating. Possible reasons for the observed damage phenomena are discussed.

A novel phosphor Ba3Si6O9N4 doped with Eu and M (M=Ce3+, Mn2+ and Dy3+) has been synthesized by a solid state reaction at 1350 °C for 6 h under 90%N2/10%H2 atmosphere. It could be efficiently excited by UV–blue light (280–500 nm) and showed a single intense broadband emission (470–625 nm). Suitable excitation range make it match well with the emission of near-UV LEDs or blue LEDs. It was found that the luminescence intensity of the Ba3Si6O9N4:Eu2+ phosphors can be efficiently enhanced by codoping with M. The addition of M in Ba3Si6O9N4:Eu2+ remarkably enhances the luminescent intensity by the factor of 198%, 166% and 188% for Ce3+, Mn2+ and Dy3+, respectively. The Ba3Si6O9N4:Eu2+ phosphor has potential application as a phosphor for white light-emitting diodes.

Eu2+ doped silicate glasses were prepared of the system 52SiO2–48MO: xEu2+(in molar ratio, M=Ca, Sr, Ba; x=1, 3, 5, 7, 9) by a high temperature melt-quenching method in a reducing atmosphere. Glass ceramics containing MSiO3:Eu2+(M=Ca, Sr, Ba) nano-phosphors were obtained after the heat treatment of the glass samples. The excitation, emission spectra and lifetime decay curves of 4f65d1→4f7 of Eu2+ were measured and interpreted with respect to their crystal structures and multi-site occupations of divalent europium in the hosts. Their excitation bands mainly extend from 450 to 250 nm, which is adaptable to the main emission region of the UV LED chip. With UV light excitation, the Eu2+ emission in CaSiO3, SrSiO3 and BaSiO3 shows blue, green and yellow colors centered at 440, 505 and 555 nm, respectively. The critical Eu2+concentration was studied and determined to be x=5 for both CaSiO3 and SrSiO3 and x=7 for BaSiO3 phosphors. The results show that the Eu2+ doped glass ceramic phosphors containing MSiO3 (M=Ca, Sr, Ba) nano-crystals can be used as potential matrix materials for a high power white LED pumped by the UV LED chip.

Transparent Cr 4+ doped SiO 2 –Al 2 O 3 –ZnO–Li 2 O–K 2 O glass ceramics were prepared by conventional melting method. X-ray diffraction analysis revealed that the Zn 1.7 SiO 4 nanocrystals were precipitated in the glass matrix after heating treat between 625 °C and 700 °C for 2 h. The crystallite size is about 5 nm after the heat treatment was performed at 650 °C. The energy levels of Cr 4+ -doped glass ceramics are close to the cross of 1 E and 3 T states. Broad infrared luminescence centered at 1307 nm with a full width at half maximum (FWHM) of more than 246 nm was observed from the sample heat treated at 650 °C excited by an 808 nm excitation laser diode. And the lifetime was about 1.97 μs at 1307 nm. The results show the transparent glass ceramics containing Cr 4+ -doped Zn 1.7 SiO 4 have potential application in optical communication.

A near infrared to visible blue, green, and red upconversion luminescence in a Tb3+-doped CaO-Al2O3-SiO2 glass was studied, which was excited using 800 nm femtosecond laser irradiation. The upconversion luminescence was attributed to 5D3 → 7F5, 5D3 → 7F4, 5D3 → 7F3, 5D4 → 7F6, 5D4 → 7F5, 5D4 → 7F4, and 5D4 → 7F3 transitions of Tb3+. The relationship between upconversion luminescence intensity and the pump power indicated that a three-photon simultaneous absorption process was dominant in this upconversion luminescence. The intense red, green, and blue upconversion luminescence of Tb3+-doped CaO-Al2O3-SiO2 glass may be potentially useful in developing three-dimensional display applications.

The initial sizes and growth behavior of damage sites on the exit surface of fused silica under 355nm laser irradiation have been preliminary studied to investigate the effects of various angle and polarization.

The delaminate occurred at higher laser irradiation with proper overcoat thickness in HfO2/SiO2 polarizers. Electric-field profile is analyzed to understand the relationship between the overcoat thickness, plasma scald and delaminate.

The automated laser damage threshold test systems of different test modes are developed recently with micron-scale damage events automated detection, location and re-inspection. The system is carried out using a 10 ns pulsed Nd:YAG laser with a repetition rate of 10 Hz. In view of the requirements of weak site identification and growth test for initial damage sites, we pay more attention to the raster scan protocol. The automated test system is enabled by the pulsed stage movement method. A one pulse to one image correspondence have been set up during scans, which is available for the later confirmation of the automated damage detection results and the growth study at specified test sites. The new and grown defects are decided by comparing the pre-image and current image at the same place during different scans. Currently, the defect comparison rules and tolerance are being optimized to improve the accuracy of test systems.

The influence of the incidence angle and polarization state on the damage site characteristics of fused silica under 355 nm laser irradiation was investigated. The initial damage morphologies and growth behaviors of the damage sites on the exit surface at incidence angles of 0° and 45° as well as in P and S states were compared to investigate the effects of various angles and polarization states. The relationships between the size of the initial damage sites and the laser fluence, as well as the growth threshold, were discussed. The damage morphologies of the craters and cracks at different incidence angles and polarization states were then investigated. Finally, the growth characteristics of the lateral size, crater depth, and crack depth were compared and analyzed.

The laser-damage growth characteristics of initial damage sites play an important role in investigating the laser-induced damage mechanisms and determining the lifetime of the optics in application. We investigate the damage growth behaviors of fused silica under 1064, and 532-nm nanosecond-pulsed laser irradiation. The relationships between the sizes of initial damage sites and the laser fluence, as well as the initial damage morphology evolutions and the laser shot numbers, are discussed. Moreover, the growth characteristics of the initial damage sites generated by the same fluence but under different subsequent fluence irradiation are compared with those of initial damage sites generated by different fluence but under the same subsequent fluence irradiation. Finally, the differences between the damage morphologies and the growth features at the same conditions under different wavelengths are also provided and discussed.

Cr4+-doped transparent β-Zn2SiO4 glass-ceramics were prepared by heat treatment on the as-made glasses. It was confirmed from the absorption spectra that Cr4+-doped β-Zn2SiO4 glass-ceramics are indeed a low-field system. The broadband infrared emission centering at 1342 nm with the full width at half-maximum of more than 285 nm was observed by exciting the glass-ceramics with the excitation of an 808 nm laser diode. The observed infrared emission could be attributed to Cr4+ ions at low-field sites in β-Zn2SiO4 glass-ceramics.