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
Search and growth of high-performance sulfide single crystals
Overview
Sulfides have excellent optical properties, allowing a wider transparency range into the infrared range compared to oxides. Therefore, they are promising materials for infrared optical devices. In addition to optical applications, they are also expected to be used as thermoelectric and solar cell materials. In addition, they have attracted renewed attention as 2D materials in recent years. In this research, high-purity sulfur purified by distillation has been used.
SnS, AgBiS2, GeS, and GaS single crystals were successfully grown.
Characteristics
The high performance of sulfides is as follows.
- Over 10µm transmission range
- Non-toxic and excellent thermoelectric properties
- Rediscovered as a 2D material
Major reserch
We have successfully grown SnS single crystals by the slow cooling method in a horizontal temperature gradient furnace, AgBiS2 single crystals by the slow cooling method, GeS single crystals by the vapor transport method using a molten GeS source, and GaS single crystals by the Bridgman method.
GaS single crystals have been found to have a transmission range of up to 14 µm and can be used as an optical material in the infrared. SnS, GeS, and GaS are also 2D materials.
2D SnS is theoretically predicted to have piezoelectric properties comparable to Pb(Zr, Ti)O3:PZT. We are jointly investigating the piezoelectric properties of 2D SnS using SnS single crystals.
summary
We have successfully grown various sulfide single crystals using different methods. As a result, we have mainly obtained the following sulfide single crystals.
In the future, we will search for sulfides with more high-performance properties and develop methods for growing their single crystals.
- SnS single crystals (applications: 2D materials, solar cells)
- AgBiS2 single crystals (applications: thermoelectric elements, solar cells)
- GeS single crystals (applications: 2D materials)
- GaS single crystals (applications: infrared optical devices, 2D materials)
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
