SHIMAMURA.Kiyoshi@nims.go.jp
- (Left) 2-inch diameter core-free Y3Al5O12 (YAG) single crystal. This single crystal, which is coreless and highly homogeneous, is useful for high-power lasers and lenses.
- (Upper right) 3-inch diameter Tm,Ho:LiYF4 single crystal. Useful for eye-safe lasers.
- (Lower right) Ca3TaAl3Si2O14 (CTAS) single crystal operates as a piezoelectric material at high temperatures. It exhibits a high resistivity of 1011 Ω·cm at 400°C, which is higher than LTGA.
Optical single crystals group | Research Center for Electronic and Optical Materials
Optical single crystals group
Group leader
Group members
AIM and GOAL
- Design, bulk growth, and characterization of new single crystal materials
- Development of proper growth techniques to achieve the best material properties
APPROACH
- A wide range of crystals for optical applications is covered: laser and nonlinear optical crystals, magneto-optical crystals, scintillator/dosimeter crystals, wide bandgap semiconductor, piezoelectric and ferroelectric single crystals, etc.
- Our current main research targets are: Single crystal phosphors for high-brightness lighting devices. Faraday rotators for optical isolators used for laser machinery. Piezoelectric crystals for high temperature use such as combustion pressure sensors. Gallium oxide as novel wide bandgap semiconductor. Chalcogenides for IR optical applications.
- Collaboration with universities, national institutes and industries are actively promoted, and the international cooperation is also actively pursued in order to promote new viewpoints and original ideas.
FIG 1 CZ-grown Ce:YAG single crystal phosphor. This novel phosphor exhibits superior internal quantum efficiency compared with conventional ceramic based phosphors even at high temperatures. Therefore, this is suitable for high-brightness white lighting applications.
FIG 2 Large-size TSLAG single crystal. This novel crystal shows large Faraday rotation angle and high transmittance, and therefore exhibits better performance for optical isolators which protect the light source of laser machinery.
Solid and melt
Czochralski furnace for oxide
single-crystal growth
Czochralski furnace for fluoride
single-crystal growth
Four-elliptical Xenon lamp
Floating Zone furnace for single-crystal growth
Four-elliptical halogen lamp
Floating Zone furnace for single-crystal growth
Machining and micro-fab
Large-scale Cold Isostatic Pressing (CIP)
apparatus
Inner diameter blade cutting machine
Structures
X-ray single crystal orientation measuring device
(Laue camera)
Cut surface inspection device
SHIMAMURA, Kiyoshi / Group Leader
novel functional single-crystal materials
Overview
Research is being carried out on the design and bulk single crystallization of new single-crystal materials, as well as their evaluation and device development. Optical single crystals—including laser, nonlinear optical, magneto-optical, and scintillator crystals—are the central focus, alongside bulk single crystals for next-generation applications such as wide bandgap semiconductors, piezoelectric, and ferroelectric materials. Various material systems, ranging from oxides to halides and nitrides, are being explored, and crystal growth techniques appropriate for each are being developed. Collaboration with universities, research institutes, and companies is actively pursued, together with international exchanges, with the aim of conducting wide-ranging research—from basic studies to practical applications—from new perspectives.
Characteristics
- Bulk single-crystal growth of materials with ultra-high melting points
- Bulk single-crystal growth of halides, with a focus on fluorides
- Design of functional single-crystal materials with properties surpassing conventional characteristics
- A wide range of investigations, from optical to piezoelectric and semiconductor materials
- Development of novel crystal growth techniques, such as bulk single-crystal growth by hydrothermal synthesis
Major reserch
Single-crystal phosphors for ultra-high brightness white lighting using blue LEDs. (Left) Ce:Y3Al5O12 (YAG), (Right) Ce:Lu3Al5O12 (LuAG) single-crystal phosphors. Compared to conventional ceramic powder phosphors, these exhibit higher internal quantum efficiency that is maintained even at high temperatures, and resist temperature increases even under strong blue irradiation. As a result, the luminous intensity of white LEDs is overwhelmingly higher than that of conventional products.
summary
Materials exhibiting superior properties compared to conventional ones and capable of large single-crystal growth have been devised, and their bulk single-crystal growth and properties are being demonstrated. Ongoing fundamental research, device fabrication, and testing will be conducted in parallel.
NAKAMURA, Masaru
Exploration and Crystal Growth of High-Quality Sulfide Single Crystals
Overview
A key feature of sulfides is their superior optical properties, such as transparency extending into the infrared (IR) region compared to oxides. Consequently, they are promising materials for optical devices operating in the infrared range. Beyond optical applications, they also hold great promise for thermoelectric and solar cell materials. Furthermore, they have recently regained significant attention as two-dimensional (2D) materials.
Characteristics
The superior characteristics of sulfides include:
- Excellent infrared transparency extending to wavelengths of 10 µm and beyond
- Outstanding thermoelectric properties combined with non-toxicity
- Recent resurgence of interest as 2D materials
Major reserch
To date, we have grown various single crystals using distinct techniques: SnS single crystals via the horizontal gradient freeze (HGF) method, AgBiS2 single crystals by the slow cooling method, GeS single crystals via vapor transport using a molten GeS source, and GaS and HT-GeS2 single crystals by the Bridgman method.
Optical measurements revealed that GaS and HT-GeS2 single crystals exhibit broad optical transmission windows extending up to 14 µm and 22.5 µm, respectively, demonstrating their high potential for infrared optical applications. Furthermore, SnS, GeS, GaS, and HT-GeS2 are also categorized as two-dimensional (2D) materials; in particular, 2D-SnS has been theoretically predicted to exhibit piezoelectric properties comparable to Pb(Zr,Ti)O3(PZT).
summary
To date, we have grown various sulfide single crystals using several distinct methods, successfully obtaining the following primary crystals:
- SnS single crystal (Applications: 2D materials, photovoltaics)
- AgBiS2 single crystal (Applications: thermoelectric devices, photovoltaics)
- GeS single crystal (Applications: 2D materials)
- GaS single crystal (Applications: infrared optical devices, 2D materials)
- HT-GeS2 single crystal (Applications: infrared optical devices, 2D materials)
Moving forward, we will continue to explore novel sulfides that leverage their unique, superior properties and pursue research and development on their single crystal growth techniques.
VILLORA, Garcia
novel functional optical crystals
Overview
- Optical isolators are needed for laser machinery, marking, and high-power LDs. New novel Faraday rotators are demanded for higher laser powers and shorter wavelengths.
- Environmentally friendly, high-energy X-ray and compact, high-performance neutron scintillator single crystals are needed to realize a safe and secure society.
Characteristics
- Improvement of Tb-garnets for IR Faraday rotators and development of new UV-visible Faraday rotators.
- Materials with high light yield, stable without deliquescence, and capable of large single-crystal growth. Furthermore, development of materials possessing the specific properties required for X-ray and neutron applications.
- Development of novel crystal growth techniques, such as bulk single-crystal growth by hydrothermal synthesis
Major reserch
- (Top) 2-inch diameter Tb3(Sc,Lu)2Al3O12 (TSLAG) single crystal. As a Faraday rotator for laser processing machines, it excels in quality, cost, and performance.
- (Lower left) CeF3 single crystal Faraday rotator, useful from near-ultraviolet to visible wavelengths.
- (Lower right) CeF3, PrF3, and LiREF4 (RE = Tb, Dy, Ho, Er, Yb) single crystals. Useful as Faraday rotators and laser crystals, covering deep ultraviolet to visible wavelengths.
- (Top) Tb:YTaO4 (YTO) single crystal grown by the FZ method. Useful as an X-ray scintillator. It is high density, exhibits higher light yield than CdWO4 single crystals, and is Cd-free, making it environmentally friendly.
- (Lower left) Ce:Li6Y(BO3)3 single crystal, useful as a neutron scintillator. It surpasses Li glass in Li concentration, luminescence, lifetime, and productivity.
- (Lower right) Ce:Lu1.8Y0.2SiO5 (LYSO) single crystal grown by hydrothermal synthesis. Compared to crystals grown by the Czochralski method, it features lower defect levels and exclusive Ce3+ valency, which is expected to enhance luminescence.
summary
- Tb-Sc-garnets are already incorporated into Yb-amplified fiber-lasers by Fujikura Ltd.
- CeF3 is implemented in commercial UV-VIS optical isolators.
- To realize a safe and secure society, we will accelerate the development of scintillator single crystals, aiming for larger size and higher quality.
- Advancement of single-crystal growth technology by the hydrothermal technique.
Current Members (as of 2026)
Graduate Research Assistant
MOREIRA Joel Noberto MOREIRA.JoelNoberto@nims.go.jp
Trainee
ODA, Haruyuki ODA.Haruyuki@nims.go.jp
Fields of Electronic and Photofunctional Materials Research Center
