Self-organization naturally provides materials that can manipulate light and light-matter interactions in a manner that allows buildind new nano-photonic devices. We show how light can naturally induce chiral structures¹, or help us design new light harvesting devices like NIR photodetector² using the rectification effect induced by dipole orientation in a thin fim.³ Our designed device structure allows the fabrication of hot electron-based photodetectors that are highly sensitive to the NIR range, that are sensitive to polarization, and that are easy and cost-effective to fabricate. The approach developed herein represents a significant milestone towards the development of energy conversion devices based on hot electrons and plasmonics, which benefit integrated optoelectronics and photocatalysis.
1. Mazaheri, L.; Lebel, O.; Nunzi, J.M. Transfer of chirality from light to a Disperse Red-1 molecular glass surface, Opt. Lett. 42 (2017) 4845.
2. Mirzaee, S.M.A.; Lebel, O.; Nunzi, J.M. A simple unbiased hot-electron polarization-sensitive near-infrared photo-detector. ACS Appl. Mater. Inter. 10 (2018) 11862.
3. Sentein, C.; Fiorini, C.; Lorin, A.; Nunzi, J.M. Molecular rectification in oriented polymer structures. Adv. Mater. 9 (1997) 809.

Jean-Michel Nunzi graduated from l'Ecole de Physique et Chime, Paris in 1982, he joined l’Ecole Polytechnique for a PhD on the nonlinear optics of surface plasma waves (plasmons). He was then hired as full-time Researcher in Organic Photonics at the Atomic Energy Commission (Saclay) in 1984.
He joined the Department of Physics at the University of Angers as Professor in 2000, where he built the Plastic Solar Cells Technology Research Team.
He moved to Queen’s University as Tier 1 Canada Research Chair in Chiral Photonics in 2006 and in Photonics for Life since 2013. He studies Organic and nano-Photonics, including the Chemistry, Instrumentation, Processing and Physics of nanomaterials and devices as well as their use for sustainable development. His Google H-factor is 53.

The ever-growing application of deep-ultraviolet (deep-UV, λ < 200 nm) nonlinear optical (NLO) materials in various fields requires searching for candidates to generate the deep-UV lasers through direct second-harmonic generation (SHG) method. Among them, fluorooxoborates, benefiting from the large optical band gap, high anisotropy and ever-greater possibility to form non-centrosymmetric structures activated by the large polarization of the functionalized [BO_xF_4-x]^(x+1)- (x =1, 2 and 3) building blocks, have been considered as the new fertile fields for searching the deep-UV NLO materials. Two series of fluorooxoborates AB₄O₆F (A = NH₄, Na, Rb, Cs, K/Cs and Rb/Cs) and MB₅O₇F₃ (M = Ca and Sr) were rationally designed and synthesized, which not only inherit the favorable structural characteristics of KBBF, but also possess superior optical properties. Property characterizations reveal that these two series possess the optical properties (deep-UV cutoff edges, large SHG responses, improved growth habit and also large birefringence to ensure the phase matching behavior in the deep-UV spectral region, etc.) required for the deep-UV NLO applications, which make them potential candidates to produce the deep-UV coherent light by the direct SHG process.

Prof. Shilie Pan has been Professor of XJIPC, CAS since 2007 as the “One-hundred talent” scholar. He received his Ph.D. degree from the University of Science & Technology of China in 2002. Before 2007, he worked as a postdoctor in Technical Institute of Physics & Chemistry, CAS, and later at Northwestern University in USA. Prof. Pan is now the director of New Opto-electronic Functional Materials Laboratory. His current research interests focus on synthesis, crystal growth, properties characterization, structure-property relationships and devices in new optical-electronic functional materials. As the first author or the corresponding author, Prof. Pan has published more than 390 papers in peer-reviewed international journals such as J. Am. Chem. Soc., Angew. Chem. Int. Edit, etc. And he has 9 authorized US patents, 68 authorized Chinese patents. He was also awarded National Ten Thousand Talents Project, National Science Fund for Distinguished Young Scholars, National Youth Science and Technology Innovation Leading Talent, China Youth Science and Technology Award, New Century National Hundred, Thousand and Ten Thousand Talent Project.

Graphene has potential photonic applications in optical modulators, photodetectors, light harvesting or emitting devices. However, its zero-bandgap electronic structure limits graphene role to transparent electrode. This is why graphene needs to be combined with a complementary photonic material to create a hybrid component with novel properties for advanced photonics.
In this context, the supramolecular self-assembly of organic building blocks on graphene is an original bottom-up approach towards novel materials displaying unusual properties. Hence, the possible fine-tuning of inter-constituents distances and orientations offered by the design of the building blocks makes the self-assembly approach very appealing for adjusting graphene photonic properties.
The experimental proof of concept shows the suitability of self-assembly techniques for the development of multi-functional hybrid dye/graphene 2D materials for nanophotonics, optoelectronics, light emitting or harvesting devices.

André-Jean Attias is a Professor of Polymer Chemistry at Sorbonne Université (Paris, France). He received his engineer degree from 'Ecole Supérieure de Physique et de Chimie de Paris' (ESPCI), Paris, France in 1982 and joined the French Space Research Agency (ONERA) in 1983 and was awarded a Ph.D. degree in Macromolecular Science from Université Pierre & Marie Curie in 1988.
In 2002 he moved to Université Pierre & Marie Curie to join the Chemistry Department as full professor and he founded a research group on organic optoelectronics.
In 2017, he was appointed the founding director of the Building Blocks for Future Electronics Laboratory (2B-FUEL), an International joint research unit between CNRS-Sorbonne Université-Yonsei University, located in Seoul (Korea). Since 1st April 2017 he is adjunct professor at Yonsei University.
His current research activity deals with surface-confined supramolecular self-assembly to generate nanostructures and function of patterned surfaces for applications in the areas of organic nano-photonics and-electronics, spintronics, and renewable energies. He is author or co-author of numerous papers in peer-reviewed high impact factor journals and gave since his academic position more than 50 invited talks, plenary and keynote lectures in international conferences and symposia.

As for imaging applications of lens materials over the visible-wavelengths range, which are either inorganic or polymeric, a multitude of compositions spreading in a wide area of the visible-range Abbe diagram are enabling design of lens assemblies with optical aberrations minimized down to (almost) any desired level. Compared with this situation, taking a look at thermal imaging applications over the long-wavelength infrared (LWIR) range, i.e., 8 ~ 12 m, only a few optical materials have been commercialized; single-crystalline Ge, poly-crystalline ZnSe and chalcogenide glass. Since these crystalline materials should not only feature fixed optical constants such as refractive index and its dispersion but also be processed via direct machining, only chalcogenide glass is able to broaden the LWIR-range Abbe diagram. Moreover, the inherent moldability bestowed to chalcogenide glass enhances its cost effectiveness in various sectors of the thermal imaging market. In this talk, a recent progress achieved in compositional optimization of chalcogenide glass for use as (molded) lenses in the LWIR domain is to be delivered with an emphasis paid to possibility of all-glass-based LWIR lens assembly.

Yong Gyu Choi received a B.S. degree from KAIST in 1991. Then, he moved to POSTECH where he earned his M.S. and Ph.D. degrees in 1994 and in 1998, respectively. During the period of 1994 to 1998, his works were focused on processing and characterizing amorphous materials doped with rare-earth elements. He became a senior research staff of ETRI in early 1998, where he was mainly involved in development of fiber amplifiers and fiber lasers for use in optical telecommunications. After 6 years of experience at ETRI, he joined Korea Aerospace University as a faculty member. During the ETRI period, he visited University of Southampton and University of Sydney as a visiting research fellow. He enjoyed his first sabbatical leave at IMI-NFG, Lehigh University in 2010-2011. For his second sabbatical leave in 2017-2018, he stayed at Zhejiang University.
His current research interests cover from optical functionalities of doped or undoped glasses to structural analysis of optical materials especially with X-ray absorption spectroscopy using synchrotron radiation.

Due to high demands in lightings, automobiles and display applications, high power and high brightness white LEDs (wLEDs) have been extensively studied spurring their commercial applications. However, weak chemical and thermal stabilities of organic resins which embed color converting phosphors in conventional white LED deteriorated their color coordination and long term stability. Various inorganic color converters have been proposed to provide reliable high power wLEDs. Among them, phosphor in glass (PiG) has been successfully commercialized recently replacing organic resins with its long term stability and high versatility. PiG can be easily fabricated by simple mixture of a transparent glass and phosphors followed by a sintering process. When a PiG mixed with Y₃Al₅O₁₂:Ce³⁺ (YAG:Ce³⁺) and silicate glass was packaged with a blue LED, a white LED could be achieved and its color coordination could be easily varied with the phosphor content and PiG thickness. The PiG showed improved thermal and long term stability and thus applied to the automobile headlamp for the first time. After its commercialization, extensive studies have been reported to further extend its application and improve color converting properties. In this talk, recent progress of PiG will be reviewed and various approaches to overcome technical issues related to PiG will be discussed.

1997.2.~2001.8. Ph.D., Dept. of Materials Sci. & Eng., Pohang Univ. of Sci. and Tech. (POSTECH)
2001.9.~2003.5. Post-doctral research staff, Dept. of Materials Sci. & Eng., Pohang Univ. of Sci. and Tech. (POSTECH)
2002.3.~2003.2. Post-doctral research staff, Institute for Materials Research, University of Leeds, U.K.
2003.6.~2006.3. Senior research staff, IT Convergence & Component Laboratory, Electronics and Communications Research Institute (ETRI)
2006.4.~Present Div. of Advanced Materials Eng., Kongju National University

Single-mode lasers at nanoscale are highly desirable for practical applications, however, most of reported semiconductor nanolasers exhibit multimode structure. In this report, we firstly realize single-mode lasers in cesium lead halide perovskite microcavities covering the whole visible region at room-temperature. All-inorganic cesium lead halide (CsPbX₃, X = Cl, Br, I) microcavities with different morphologies are fabricated by a dual-source chemical vapor deposition method. Thank to smooth surface and regular spherical structure, single-mode laser is successfully realized in a sub-micron microcavity with a very narrow linewidth, low lasing threshold and a high Q factor(>10⁴). Modulating the halide composition and sizes of the microcavities, single-mode laser can be continuously tuned from 425 to 715 nm. The work illustrates that the well-controlled synthesizing metal cesium lead halide perovskite nano/microspheres may offer an alternative route to produce a widely tunable and greatly miniaturized single-mode laser.

Dr. Hongxing Dong is a professor of Shanghai Institute of Optics and Fine Mechanics. His current research interests are centered on the fabrication of functional nano/microstructures and the development of advanced optical cavity based optoelectronic devices. He has published more than 60 papers in peer-refereeing international journals, including PRL、ACS Nano、AOM、ACS Photonics etc.. He has been awarded with the Youth Top-notch Talent Support Program in Shanghai, the Youth Innovation Promotion Association, Shanghai Rising-star Program, First Prize in Science and Technology of Shananxi Colleges and Universities, Second Prize for Science and Technology of Shannxi Province.

A graded-index plastic optical fiber (GI POF) has been a promising medium for the indoor applications because of its flexibility, safety, and high bandwidth. Recently, we have proposed a low-noise GI POF that has noise reduction effects due to its strong mode coupling closely related to microscopic heterogeneous properties of the core material [1-3]. Here, we develop a graded-index plastic optical fiber (GI POF) for radio-over-fiber (RoF) that allows for higher carrier-to-noise ratio or more carrier transmission than conventional multimode fibers (MMFs). This will pave the way to achieve RoF indoor networks, where various RF signals such as mobile (5G), wireless (WiFi), and broadcasting (4K/8K UHD) are transmitted, in the next-generation Internet-of-things (IoT) era.
[1] A. Inoue and Y. Koike, “Low-noise graded-index plastic optical fiber for significantly stable and robust data transmission,” J. Lightwave Technol. 36, 5887 (2018).
[2] A. Inoue and Y. Koike, “Intrinsically stabilized plastic optical fiber link subject to external optical feedback,” IEEE Photon. J. 11, 7201207 (2019).
[3] A. Inoue and Y. Koike, “Unconventional plastic optical fiber design for very short multimode fiber link,” Opt. Express 27, 12061 (2019).

Azusa Inoue
Project Associate Professor/Deputy Director of Keio Photonics Research Institute at Keio University.
Azusa Inoue received the B.S., M.S., and Ph.D. degrees in electrical engineering from Keio University, Yokohama, Japan, in 2002, 2004, and 2008, respectively. In 2008–2010, he was a Postdoctoral Fellow with Kyushu University, Fukuoka, Japan. From 2010, he has worked on graded-index plastic optical fibers with Keio University. Since 2018, he has been working as a Project Associate Professor with Keio University and a Deputy Director with Keio University Photonics Research Institute (KPRI).
Yasuhiro Koike
Professor/Director of Keio Photonics Research Institute at Keio University
Yasuhiro Koike is highly regarded internationally as the inventor of Graded-Index Plastic Optical fiber (GI POF). He also invented Zero Birefringent Polymer and Super Birefringent Polymer which have been used in major LCD TVs. He was a Core Researcher of the research project of Face-to-Face Communication system based on the above mentioned technologies on the FIRST Program which was initiated by the Cabinet Office of Japan in 2010. He has been the General Chair of International POF Conference since 1992. He was conferred as an Honorary Doctorate of Eindhoven University of Technology in 2007. He is a recipient of International Engineering and Technology Award of the Society of Plastics Engineers (SPE), the Fujiwara Award, and Medal with Purple Ribbon awarded by Emperor of Japan, SID Special Recognition Award, etc.

The suppression of Stimulated Brillouin scattering (SBS) in optical fibers is one of the current issues of the fiber laser technique development. Many different means are proposed for the suppression including refractive index and fiber profile modulations. However, the material modification being technically the simplest way seems to be very promising to reach the goal. Two dimensional materials like monolayer graphene, black phosphorus, transient atoms chalcogenides, etc. are newsworthy due to their nonlinear optical properties like two-photon absorption (2PA) and saturable absorption saturation providing good perspectives of their application in laser techniques, optical informatics and telecommunications. Recently we observed a strong quenching of SBS in liquids when added vanishing concentrations of the nanoparticles both absorptive (graphene) and non-absorptive (hexagonal boron nitride, hBN). It has been shown that 2PA of hBN nanoflakes is strong even for nanosecond laser radiation and enough to produce local heating centers in suspensions creating interfaces in liquids which scatter light almost as effectively as graphene nanoparticles. Since hBN has strong 2PA and has no linear absorption in the wide range it seems to be a perfect dopant into polymers and maybe glass to suppress SBS in fibers in high-power laser systems of visible and telecommunication wavelength ranges. Other absorptive nanoparticles like nanotubes providing better thermodynamic stability of the designed material can be also considered.

Dr. Ivan Kislyakov is currently a visiting professor at Shanghai Institute of Optics and Fine Mechanics of Chinese Academy of Science. After obtaining his PhD in physics and math in 2004 from Saint Petersburg State University (Russia), he worked as the head of the Laboratory of Nanostructured Materials of Vavilov State Optical Institute and an associate professor at the Laser Optics Department of ITMO University in Saint Petersburg (Russia) for several years. In 2017 and 2018 he was awarded a Visiting Scientists under the CAS President’s International Fellowship Initiative. He is engaged in two-dimensional nonlinear optical nanomaterials, effects and applications. He carries out the basic research on nonlinear optical effects of fullerenes, graphene, carbon nanotubes, boron nitride and other nanostructures and obtains original results discovering the physical properties and elaborating photonic devices and applications of materials. He is a member of OSA, and a corresponding author published in Optics Express, Applied Physics Letters, Optical Materials and other specialized journals.

The development of novel scintillators with high light yields and fast decay is of considerable interest. In my talk, I will briefly introduce some recent results of our development of novel inorganic scintillators. Conventionally, Ce³⁺ and Eu²⁺ have been extensively studied and applied as activators in various scintillators because of their fast and efficient parity-allowed 5d–4f emissions. In contrast, we have developed novel scintillators with high light yields with Yb²⁺ as a luminescence center. For example, we have developed SrCl₂:Yb²⁺ and SrBr₂:Yb²⁺ whose light yields were determined to be 54,000 and 62,000 photons/MeV, exceeding the light yield of a commercial halide scintillator, NaI:Tl+ (40,000 photons/MeV). As another approach, we have developed Tl-based self-activated scintillators whose light yields exceed 40,000 photons/MeV.
Also, basic process of excited states in inorganic scintillators will quantitatively discussed on the basis of our recent results of transient spectroscopy. Most scintillators are composed of an insulator host with dopants as the luminescence centers. In such scintillators, excited states are initially generated in the insulator host upon exposure to ionizing radiation. Subsequently, the excitation energy is transferred to the luminescence centers and, finally, scintillation occurs through the radiative transitions of the centers. Of these basic processes, little is known about the energy transfer process despite its importance. In this study, we analyzed the excited states in the host with the aim of better understanding the energy transfer process. The excited states in the host were analyzed using transient absorption spectroscopy.　

Prof. Masanori Koshimizu is currently a member of Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, Japan. He received his B.Eng. (1999), M.Eng. (2001) and Ph.D. (2007) degrees in quantum engineering and systems science from University of Tokyo. He held the position of Assistant Professor (2004) at the present Department, and was promoted to Associate Professor in 2011. He received Masao Horiba Award in 2012, and Award for Young Scientists from the Japan Society of Radiation Chemistry in 2013. His research interests include development of optical (including scintillation) materials based on nanostructures. His interests also covers the interaction of materials with ionizing radiation.

Semiconducting quantum dot nanocrystals have unique optical properties such as high quantum yields and broad emission spectral wavelengths that are tunable by the quantum confinement effect. Considerable effort directed at modifying the surface of quantum dots using capping agents have led to a simple solution-based process, the stabilization of quantum dots, and their uniform dispersion in solvent. Due to these unique properties, quantum dots are of increasing importance in the fundamental studies and in a wide range of technological applications such as optical power limiters, light emitting devices, photovoltaics, lasers, and fluorescent labels for bioimaging. Tacking the full potential of quantum dots in optoelectronic devices require efficient mechanisms for transfer of energy or electrons produced in the optically excited quantum dots. We have investigated various organic-inorganic hybrids based on quantum dot-decorated and quantum dot-coupled systems on semiconducting substrates or molecules to achieve energy or charge transfer. The hybridization of p-type π-conjugated molecules to the surface of n-type quantum dots can induce distinct luminescence and charge transport characteristics due to energy and/or charge transfer effects. These kinds of energy/charge transporting properties are also observable in the perovskite quantum dots. The novel properties of hybrids consisting of quantum dots decorated or attached to conducting materials could find applications in molecular electronics and optoelectronics, including luminescent displays and energy harvesting cells.

Kwang-Sup Lee is a Professor of the Department of Advanced Materials at the Hannam University, Korea. He also holds a position as the Research Professor at the Institute for Lasers, Photonics and Biophotonics in the University at Buffalo, State University of New York, USA. He received his Ph.D degree in polymer science from the Freiburg University, Germany in 1984. He was a postdoctoral fellow at the Max-Planck-Institute for Polymer Research, Germany from 1985 to 1986 and a visiting professor at the Naval Research Laboratory, USA in 1998. Prof. Lee’s research interests lie in the field of photofunctional materials including the synthesis of conjugated organics and polymers, quantum dots, carbon nanotubes, and organic-inorganic hybrid materials and fabrication of device involving them. He has authored and coauthored more than 250 journal articles and book chapters, and also 40 patents. He has chaired and co-chaired more than 20 conferences and symposia, and has given about 250 plenary, keynote, and invited talks. Prof. Lee is a Fellow of SPIE (USA) and EM Academy (USA) and he is currently serving as editorial board members for several international scientific journals including Advances in Polymer Science (Springer, Germany), NPG Asia Materials (Nature, UK), OSA Continuum, (OSA, USA), Nonlinear Opt. Quantum Opt. (OCP, USA).

Integrated photonics that can be both bendable and stretchable open up emerging applications ranging from flexible optical interconnects, broadband photonic tuning to conformal sensors on biological tissues. In this talk, we will discuss a new technology to realize monolithic photonic integration on plastic substrates. Our technology capitalizes on the exceptional properties of amorphous chalcogenide glass materials including broadband infrared (IR) transparency, wide accessible range of refractive indices, as well as low deposition temperature. High-index-contrast multi-layer 2.5-D photonic devices with record optical performance were fabricated using simple, low-cost contact lithography. A novel multi-neutral-axis design is implemented to render the structure highly mechanically flexible, allowing repeated bending and stretching of devices without measurable optical performance degradation. We further demonstrated hybrid integration of active optoelectronic components onto the flexible photonic platform, which potentially enables complete system-on-a-flexible-chip solutions for a wide cross-section of applications.

Dr. Lan Li received her B. S. degree from University of Science and Technology of China (2010) and Ph.D. degree from University of Delaware (2016), both in Materials Science and Engineering. Since then she has been the postdoctoral associate at the Massachusetts Institute of Technology until Feb., 2019. She is currently the assistant professor at the School of Engineering in Westlake University. Her research interest focuses on nanophotonic materials and devices, infrared optical glass materials, integrated flexible photonic device fabrication, characterization and application.

Oxide glass prepared by melt-quenching is usually consisted of network former (NWF) and network modifier (NWM) groups. Although P₂O₅ is generally classified as NWF groups from the viewpoint of glass forming ability, P₂O₅ differs from other NWF oxides because of the P=O bond. Phosphate glass has significant potential for various applications, owing to its unique physical and structural properties. Understanding the network structure of a phosphate glass system is therefore one of the most important unresolved issues facing glass science.
Several metal oxides are classified as intermediate groups that can act as either NWF or NWM groups. ZnO is classified as being part of the intermediate group. Zinc phosphate (ZP) glass is a promising material for use as lead-free sealing glass, or as good host for emitting centers. For application of optical materials, examination of glass network is important, because the role of the intermediate group depends on the glass composition.
Here, we report on the relationship between network structure of ZP glass and the luminescence properties of the activators. We use a combination of ³¹P magic angle spinning NMR, Zn K-edge extended X-ray absorption fine structure, as well as X-ray and neutron diffraction data to determine the dependence of this connectivity on the chemical composition and on the zinc coordination. Based on the network structure of several ZP glasses, we discuss the relationship between optical properties and structure of the activator-doped ZP glasses.

Dr. Hirokazu Masai received his Ph. D degree at Kyoto University (2005). He joined Tohoku University as an assistant professor in 2006 after postdoctoral researcher at Nagaoka University of Technology and Tohoku University. He was, then, employed as an assistant professor at Kyoto University for 7 years (2010 ~ 2017). From 2017, he joined National Institute of Advanced Industrial Science and Technology (AIST) as a senior researcher. His past results are organic-inorganic hybrid materials, functional glass-ceramics, oxide glass phosphors, and so on. He is currently studying the fabrication of functional amorphous materials and the relationship between the physical properties and structures of inorganic materials.

The optical properties of localized surface plasmon resonances that occur on metallic nanostructures have been the subject of intense study for the past few decades. In particular, the chirality of the optical near-field has gained substantial interest. In this study, we observed photoemission electron images of the achiral rectangular gold nanostructure under the irradiation of left and right circular polarized (LCP and RCP) light using multi-photon photoemission electron microscopy (MP-PEEM). Gold nanostructures were fabricated on the ITO-coated glass substrate using electron beam lithography. Near-field properties of Au rectangular structures with different aspect ratios, such as mapping and spectra, were investigated using MP-PEEM to explore the origin of near-field chirality generation. For example, a gold rectangular structure showed two near-field peaks derived from T- and L- modes and the near-field circular dichroism (CD) calculated by the difference of the near-field spectra in the local region of LCP and RCP excitation also showed two peaks. However, the peaks of near-field CD slightly differed from those of the near-field spectrum and matched with cross points of phase angles of two modes. We concluded that the origin of the near-field chirality can be traced to an interaction between T- and L-modes, which is maximized when their phase angles are harmonized.

Tomoya Oshikiri
Assistant Professor, Research Institute for Electronic Science, Hokkaido University
E-mail: oshikiri@es.hokudai.ac.jp
Academic background:
2005-2008 Ph.D. in Science, Osaka University, Japan
2003-2005 Master of Science, Osaka University, Japan
1999-2003 Bachelor of Science, Osaka University, Japan
Professional career:
2012-pres. Assistant Professor, Research Institute for Electronic Science, Hokkaido University
2008-2012 Researcher, Mitsubishi Rayon, Co. Ltd.
Research interests:
Plasmonics, Photochemistry, Artificial photosynthesis, Light energy conversion

In this work, highly-efficient mid-infrared 2.8 μm laser performances of Er doped CaF₂ and SrF₂ crystals and single crystal fibers (SCF) were investigated, which were codoped with the local lattice structure regulators of Y, La or Gd ions. In lightly doped Er3+:SrF2 single crystal, CW laser was obtained with a slope efficiency of 41%, significantly exceeding the Stokes efficiency of 35%. In Er³⁺:CaF₂-SrF₂ mixed single crystal, CW laser was obtained with a slope efficiency of 39.2% and output power of 1.42W, respectively. In Er³⁺:SrF₂ SCF, CW laser was obtained with a slope efficiency of 35% and output power of 0.86W, respectively. Even in 0.5 at% doped Er:SrF₂ SCF, CW laser operation was realized at 2.8μm with a slope efficiency of 20%.

Self-frequency-doubled Yb:Ca₄YO(BO₃)₃ (Yb:YCOB) crystal with large size and different doping concentration can be easily grown by the Czochralski method. The crystal has good practical potential for self-frequency-doubling due to its excellent combination of nonlinear and laser properties. The fluorescence spectra and absorption spectra exhibited a small and broad anisotropic vibronic emission peak at about 1130 nm with the emission cross section of about 5 × 10⁻²² cm². Successfully, the fundamental wavelength of the polarized vibronic Yb:YCOB radiation shifted from 1130 nm to 1140 nm by suppressing the electronic emission.
Taking advantage of its shifting vibronic emission and self-frequency-doubling behavior of Yb:YCOB crystal, a watt-level self-frequency-doubled yellow laser at the 570 nm wavelength was realized with the cut direction along the optimized orientation out of the principal planes possessed the maximum effective nonlinear coefficient. The maximum output power at 570 nm came up to 1.08 W. This work provides a way for the realization of yellow lasers and promising, attractive source with a compact structure. Meanwhile, a maximum green light output power of 710 mW at 523 nm was obtained by cavity design, and the result is the best performance ever reported about the SFD green light with Yb:YCOB crystal.

Haohai Yu was born in Shandong, China, in 1981. He received the Ph.D. degree from Shandong University, Jinan, in 2008. He is currently with the State Key Laboratory of Crystal Materials and Institute of Crystal Materials, Shandong University. He is mainly engaged in the research of artificial crystals and crystal physics, and carried out systematic exploration in optoelectronic functional crystals, crystal physics and laser devices and applications. His current research interests are electron-phonon-coupled laser and nonlinear crystal devices, and some of the results have been industrialized and practical. He has published more than 80 SCI academic papers, some of which were published in Adv. Mater., JACS, ACS Nano, Appl. Phys. Lett. Opt. Lett. The paper has cited more than 1,800 times (SCI H-index = 28).

Polycrystalline ceramics such as Y₃Al₅O₁₂, MgAl₂O₄, AlON, Y₂O₃, and etc. own high mechanical properties, broad UV-MIR transmission range, and excellent chemical and physical stability, which make them the ideal candidate for demanding optical applications including laser gain media, phosphor converters, and protective windows. During the past years, huge efforts have been focused on the processing development for high optical quality and high mechanical strength. In this work, the development progress of these materials have been reviewed. The key processing parameters for high optical quality of these ceramics were discussed. The microstructure evolution, sintering aid, and their effects on optical and mechanical properties were analyzed in detail. Some applications such as gain media for high power lasers, and protective windows were demonstrated. Finally, the future research directions of these ceramics were proposed.

Prof. Jian Zhang currently is the deputy director at the Research Centre for Transparent Ceramics, Shanghai Institute of Ceramics, Chinese Academy of Sciences (SICCAS). He got his PhD from SICCAS in 2005 and then he worked as a research assistant over there. From 2007 to 2012, he was the research fellow at Institute for Materials Research, University of Leeds (2007-2008), and Temasek Laboratories of Nanyang Technological University (2008-2012). His current research interests focused on processing science and technology for transparent ceramics (Garnet, Sesquioxide, Spinel and etc.), and exploring their optical and photonic applications such as laser gain media, optical windows, transparent armors and etc. In the above area, he and his team has published ~220 journal papers, 1 book and delivered ~50 invited/oral presentations for international and domestic conferences. He co-chaired the 7^th (Singapore, 2011) and 11^th (China, 2015) Laser Ceramics Symposium. From 2019, he served as the editorial committee member for Journal of Synthetic Crystals.