The transition of cobalt ions located at tetrahedral sites will produce strong absorption in the visible and nearinfrared regions,and is expected to work in a passively Q-switched solid-state laser at the eye-safe wav...The transition of cobalt ions located at tetrahedral sites will produce strong absorption in the visible and nearinfrared regions,and is expected to work in a passively Q-switched solid-state laser at the eye-safe wavelength of 1.5μm.In this study,Co^(2+)ions were introduced into the wide bandgap semiconductor material ZnGa_(2)O_(4),and large-sized and high-quality Co^(2+)-doped ZnGa_(2)O_(4)crystals with a volume of about 20 cm^(3)were grown using the vertical gradient freeze(VGF)method.Crystal structure and optical properties were analyzed using X-ray powder diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and absorption spectroscopy.XRD results show that the Co^(2+)-doped ZnGa_(2)O_(4)crystal has a pure spinel phase without impurity phases and the rocking curve full width at half maximum(FWHM)is only 58 arcsec.The concentration of Co^(2+)in Co^(2+)-doped ZnGa_(2)O_(4)crystals was determined to be 0.2 at.%by the energy dispersive X-ray spectroscopy.The optical band gap of Co^(2+)-doped ZnGa_(2)O_(4)crystals is 4.44 eV.The optical absorption spectrum for Co^(2+)-doped ZnGa_(2)O_(4)reveals a prominent visible absorption band within 550−670 nm and a wide absorption band spanning from 1100 to 1700 nm.This suggests that the Co^(2+)ions have substituted the Zn^(2+)ions,which are typically tetrahedrally coordinated,within the lattice structure of ZnGa_(2)O_(4).The visible region's absorption peak and the near-infrared broad absorption band are ascribed to the^(4)A_(2)(4F)→^(4)T_(1)(4P)and 4A2(4F)→^(4)T_(1)(4F)transitions,respectively.The optimal ground state absorption cross section was determined to be 3.07×10^(−19)cm^(2)in ZnGa_(2)O_(4),a value that is comparatively large within the context of similar materials.This finding suggests that ZnGa_(2)O_(4)is a promising candidate for use in near-infrared passive Q-switched solid-state lasers.展开更多
The(010)-oriented substrates of β-Ga_(2)O_(3) are endowed with the maximum thermal conductivity and fastest homoepi-taxial rate,which is the preferred substrate direction for high-power devices.However,the size of(01...The(010)-oriented substrates of β-Ga_(2)O_(3) are endowed with the maximum thermal conductivity and fastest homoepi-taxial rate,which is the preferred substrate direction for high-power devices.However,the size of(010)plane wafer is critically limited by die in the commercial edge-defined film-fed growth(EFG)method.It is difficult to grow the β-Ga_(2)O_(3) crystal with(010)principal face due to the(100)and(001)are cleavage planes.Here,the 2-inch diameter(010)principal-face β-Ga_(2)O_(3) sin-gle crystal is successfully designed and grown by improved EFG method.Unlike previous reported techniques,the single crys-tals are pulled with[001]direction,and in this way the(010)wafers can be obtained from the principal face.In our experi-ments,tree-like defects(TLDs)in(010)principal-face bulk crystals are easy to generate.The relationship between stability of growth interface and origin of TLDs are thoroughly discussed.The TLDs are successfully eliminated by optimizing growth condi-tions.The high crystalline quality of(010)-oriented substrates are comprehensive demonstrated by full width at half maximum(FWHM)with 50.4 arcsec,consistent orientation arrangement of(010)plane,respectively.This work shows that the(010)-ori-ented substrates can be obtained by EFG method,predicting the commercial prospects of large-scale(010)-oriented β-Ga_(2)O_(3) substrates.展开更多
As a wide-bandgap semiconductor(WBG), β-Ga_2O_3 is expected to be applied to power electronics and solar blind UV photodetectors. In this review, defects in β-Ga_2O_3 single crystals were summarized, including dislo...As a wide-bandgap semiconductor(WBG), β-Ga_2O_3 is expected to be applied to power electronics and solar blind UV photodetectors. In this review, defects in β-Ga_2O_3 single crystals were summarized, including dislocations, voids, twin, and small defects. Their effects on device performance were discussed. Dislocations and their surrounding regions can act as paths for the leakage current of SBD in single crystals. However, not all voids lead to leakage current. There's no strong evidence yet to show small defects affect the electrical properties. Doping impurity was definitely irrelated to the leakage current. Finally, the formation mechanism of the defects was analyzed. Most small defects were induced by mechanical damages. The screw dislocation originated from a subgrain boundary. The edge dislocation lying on a plane slightly tilted towards the(102) plane, the(101) being the possible slip plane. The voids defects like hollow nanopipes, PNPs, NSGs and line-shaped grooves may be caused by the condensation of excess oxygen vacancies, penetration of tiny bubbles or local meltback. The nucleation of twin lamellae occurred at the initial stage of "shoulder part" during the crystal growth. These results are helpful in controlling the occurrence of crystal defects and improving the device performance.展开更多
High thickness uniformity and large-scale films of α-Ga_(2)O_(3) are crucial factors for the development of power devices.In this work, a high-quality 2-inch α-Ga_(2)O_(3) epitaxial film on c-plane sapphire substrat...High thickness uniformity and large-scale films of α-Ga_(2)O_(3) are crucial factors for the development of power devices.In this work, a high-quality 2-inch α-Ga_(2)O_(3) epitaxial film on c-plane sapphire substrates was prepared by the mist-CVD method.The growth rate and phase control mechanisms were systematically investigated. The growth rate of the α-Ga_(2)O_(3) films was limited by the evaporation of the microdroplets containing gallium acetylacetonate. By adjusting the substrate position(z) from 80 to 50 mm, the growth rate was increased from 307 nm/h to 1.45 μm/h when the growth temperature was fixed at 520 °C.When the growth temperature exceeded 560 °C, ε-Ga_(2)O_(3) was observed to form at the edges of 2-inch sapphire substrate.Phase control was achieved by adjusting the growth temperature. When the growth temperature was 540 °C and the substrate position was 50 mm, the full-width at half maximum(FWHM) of the rocking curves for the(0006) and(10-14) planes were 0.023° and 1.17°. The screw and edge dislocations were 2.3 × 10~6 and 3.9 × 10~(10)cm~(-2), respectively. Furthermore, the bandgaps and optical transmittance of α-Ga_(2)O_(3) films grown under different conditions were characterized utilizing UV-visible and near-IR scanning spectra.展开更多
As one of the ultra-wide bandgap {UWBG)semiconducting materials,gallium oxide has attractive properties with a wide bandgap of about 4.8 eV and a high breakdown field of about 8 MWcm,which offers an alternative platfo...As one of the ultra-wide bandgap {UWBG)semiconducting materials,gallium oxide has attractive properties with a wide bandgap of about 4.8 eV and a high breakdown field of about 8 MWcm,which offers an alternative platform for various applications such as high performance power switches,RF amplifiers,solar blind photodetectors,and harsh environment signal processing.展开更多
Defect engineering is pivotal in comprehending physical mechanisms that govern carrier transport and device performance.The defect evolution and carrier manipulation in Sn-doped Ga_(2)O_(3)bulk crystals subjected to d...Defect engineering is pivotal in comprehending physical mechanisms that govern carrier transport and device performance.The defect evolution and carrier manipulation in Sn-doped Ga_(2)O_(3)bulk crystals subjected to different thermal treatments were investigated,utilizing depth-profiled deep-level transient spectroscopy(DLTS)and frequency-dependent capacitance-voltage(C-V-f)techniques.In untreated Sn-doped Ga_(2)O_(3)with an electron concentration of 6.37×10^(17)cm^(−3),two dominant electron traps,E_(T1)(E_(C)−0.68 eV)and E_(T2)(E_(C)−0.76 eV),were identified,corresponding to gallium vacancy(V_(Ga))and the neutral complex of V_(Ga)-V_(O),respectively,and characterized as bulk traps.Fe Ga-related defects,E_(T3)(E_(C)−0.84 eV),were concentrated near surface.Nitrogen annealing significantly reduced E_(T1),increased E_(T2)density from 6.13×10^(15)to 1.1×10^(16)cm^(−3),and raised the interfacial state density(D_(it))to 3.36×10^(15)eV^(−1)cm^(−2),accompanied by an elevated electron concentration of 7.48×10^(18)cm^(−3).In contrast,air annealing enhanced E_(T1),with a density of 1.42×10^(16)cm^(−3),suppressed of E_(T2)/E_(T3)traps,resulting in a lower D_(it)of 1.74×10^(14)eV^(−1)cm^(−2),and a reduced electron concentration to 3.01×10^(16)cm^(−3).The findings reveal that a reducing environment induces V_(O)formation and converts discrete V_(Ga)acceptors into neutral V_(Ga)-V_(O)complexes,leading to downward surface band bending and electron accumulation.Conversely,V_(Ga)-V_(O)complexes are dissociated into V_(Ga)acceptors in oxidizing conditions,leading to an upward surface band bending and electron compensation.This work underscores the carrier concentration manipulation by defect engineering in Ga_(2)O_(3),offering insights essential for developing high-performance gallium oxide electronics.展开更多
Single-crystal fibers(SCFs)exhibit a significant potential for high-power laser applications owing to their superior thermal management capabilities.To enhance pump power and mitigate damage at the injection end of SC...Single-crystal fibers(SCFs)exhibit a significant potential for high-power laser applications owing to their superior thermal management capabilities.To enhance pump power and mitigate damage at the injection end of SCFs,a segmented YAG/Yb:YAG/YAG SCF with a diameter of~200μm was directly grown using a one-step laserheated pedestal growth(LHPG)method.The crystallinity and uniformity of the as-grown fiber were evaluated through a real-time back-reflection Laue camera system.Employing a low-loss segmented YAG/Yb:YAG/YAG SCF as the laser gain medium,investigations were conducted on both continuous-wave(CW)oscillators and ultrafast pulse amplifiers.The CW laser operation at 1030.9 nm achieved a maximum output power of 117.6 W with a slope efficiency of~46%,while the ultrafast amplifier system generated pulses with an average power of 101.2 W at a repetition rate of 30.8 MHz.To the best of our knowledge,this represents the highest average power achieved from a single-stage amplifier based on an Yb:YAG SCF.Preliminary pulse compression was performed at a signal power of 5o.6 W using a grating pair,resulting in a compressed pulse width of 786 fs with a compression efficiency of 58%.This study highlights the potential of crystal fiber lasers for a new generation of high-power laser systems.展开更多
Owing to the advantages of ultra-wide bandgap and rich material systems,gallium oxide(Ga_(2)O_(3))has emerged as a highly viable semiconductor material for new researches.This article mainly focuses on the growth proc...Owing to the advantages of ultra-wide bandgap and rich material systems,gallium oxide(Ga_(2)O_(3))has emerged as a highly viable semiconductor material for new researches.This article mainly focuses on the growth processes,material characteristics,and applications of Ga_(2)O_(3).Compared with single crystals and the epitaxial growth of other wide-bandgap semiconductors,large-size and high-quality𝛽-Ga_(2)O_(3) single crystals can be efficiently grown with a low cost,making them highly competitive.Thanks to the availability of high-quality single crystals,epi-taxial films,and rich material systems,high-performance semiconductor devices based on Ga_(2)O_(3) go through a booming development in recent years.The defects and interfaces of Ga_(2)O_(3) are comprehensively analyzed owing to their significant influence on practical applications.In this study,the two most common applications of Ga_(2)O_(3) materials are introduced.The high breakdown electric field,high working temperature,and excellent Baliga’s figure-of-merit of Ga_(2)O_(3) represent an inspiring prospect for power electronic devices.In addition,the excellent absorption in deep-ultraviolet band provides new ideas for optoelectronic detectors and ensures the dramatic progress.Finally,the summary,challenges,and prospects of the Ga_(2)O_(3) materials and devices are presented and discussed.展开更多
Single crystal fibers(SCF)are considered to be a combination of bulk crystals and conventional fibers,thereby possessing the stable physical and chemical properties accompanied with excellent waveguide properties.This...Single crystal fibers(SCF)are considered to be a combination of bulk crystals and conventional fibers,thereby possessing the stable physical and chemical properties accompanied with excellent waveguide properties.This paper gives a detailed introduction to the development history of single crystal fibers,including the evolution of the growth technique and the optimization of the growth process.Laser-heated pedestal growth(LHPG)and Micro-pulling-down(μ-PD)methods are considered to be the most widely used growth techniques for growing single crystal fibers,and the advantages of the two methods are also introduced in detail.The second part of this paper describes the characterization of single crystal fibers,including diameter fluctuation,crystal quality and optical losses.A series of cladding approaches for SCF,such as magnetron sputtering,sol-gel,liquid phase epitaxy,co-drawing LHPG,ion implantation and micro-structure cladding will be reviewed.In addition,the research status of single crystal fiber laser and single crystal fiber sensor are also summarized in view of the current research foundation.展开更多
A compact saturable absorber mirror（SAM） based on few-layer molybdenum disulfide（MoS2） nanoplatelets was fabricated and successfully used as an efficient saturable absorber（SA） for the passively Q-switched solid...A compact saturable absorber mirror（SAM） based on few-layer molybdenum disulfide（MoS2） nanoplatelets was fabricated and successfully used as an efficient saturable absorber（SA） for the passively Q-switched solid-state laser at 1 μm wavelength. Pulses as short as 182 ns were obtained from a ytterbium-doped（Yb:LGGG） bulk laser Q-switched by the MoS2 SAM, which we believe to be the shortest one ever achieved from the MoS2 SAs-based Q-switched bulk lasers. A maximum average output power of 0.6 W was obtained with a slope efficiency of 24%,corresponding to single pulse energy up to 1.8 μJ. In addition, the simultaneous dual-wavelength Q-switching at 1025.2 and 1028.1 nm has been successfully achieved. The results indicate the promising potential of few-layer MoS2 nanoplatelets as nonlinear optical switches for achieving efficient pulsed bulk lasers.展开更多
Ba_(0.77)Ca_(0.23)TiO_(3)(BCT)single crystal has been widely studied as a promising lead-free ferroelectric material.In this work,high-quality BCT crystal was successfully grown by the Czochralski(CZ)method.The as-gro...Ba_(0.77)Ca_(0.23)TiO_(3)(BCT)single crystal has been widely studied as a promising lead-free ferroelectric material.In this work,high-quality BCT crystal was successfully grown by the Czochralski(CZ)method.The as-grown crystal is crack-free and shows black coloration.It possesses a high dielectric stability over a wide temperature range,while the dielectric loss is rather small below 90℃.Furthermore,it possesses excellent ferroelectric properties with residual polarization strength(Pr)and coercive field(Ec)of 17.93μC/cm^(2) and 8.47 kV/cm,respectively.Besides,BCT crystal shows large electromechanical coupling factors,with kt,k31,k33 and k15 of 0.535,0.254,0.714 and 0.721,respectively.The piezoelectric coefficients d31,d33 and d15 are measured to be−36.5,130 and 246 pC/N,respectively.展开更多
基金the support by the fund of the National Key Research and Development Program of China (Grant No. 2024YFA1208800)National Natural Science Foundation of China (NSFC) (Grant No. U23A20358)+2 种基金Natural Science Foundation of Shandong Province (Grant Nos. ZR2023ZD05 and 2022TSGC2120)the Shenzhen Fundamental Research Program (Grant No. GJHZ20220913142605011)Xiaomi Foundation/Xiaomi Young Talents Program
文摘The transition of cobalt ions located at tetrahedral sites will produce strong absorption in the visible and nearinfrared regions,and is expected to work in a passively Q-switched solid-state laser at the eye-safe wavelength of 1.5μm.In this study,Co^(2+)ions were introduced into the wide bandgap semiconductor material ZnGa_(2)O_(4),and large-sized and high-quality Co^(2+)-doped ZnGa_(2)O_(4)crystals with a volume of about 20 cm^(3)were grown using the vertical gradient freeze(VGF)method.Crystal structure and optical properties were analyzed using X-ray powder diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and absorption spectroscopy.XRD results show that the Co^(2+)-doped ZnGa_(2)O_(4)crystal has a pure spinel phase without impurity phases and the rocking curve full width at half maximum(FWHM)is only 58 arcsec.The concentration of Co^(2+)in Co^(2+)-doped ZnGa_(2)O_(4)crystals was determined to be 0.2 at.%by the energy dispersive X-ray spectroscopy.The optical band gap of Co^(2+)-doped ZnGa_(2)O_(4)crystals is 4.44 eV.The optical absorption spectrum for Co^(2+)-doped ZnGa_(2)O_(4)reveals a prominent visible absorption band within 550−670 nm and a wide absorption band spanning from 1100 to 1700 nm.This suggests that the Co^(2+)ions have substituted the Zn^(2+)ions,which are typically tetrahedrally coordinated,within the lattice structure of ZnGa_(2)O_(4).The visible region's absorption peak and the near-infrared broad absorption band are ascribed to the^(4)A_(2)(4F)→^(4)T_(1)(4P)and 4A2(4F)→^(4)T_(1)(4F)transitions,respectively.The optimal ground state absorption cross section was determined to be 3.07×10^(−19)cm^(2)in ZnGa_(2)O_(4),a value that is comparatively large within the context of similar materials.This finding suggests that ZnGa_(2)O_(4)is a promising candidate for use in near-infrared passive Q-switched solid-state lasers.
基金support by the fund of the National Natural Science Foundation of China(NSFC)(Grant No.U23A20358,51932004)Key-Area Research and Development Program of Guangdong Province(Grant No.2020B010174002)+3 种基金Natural Science Foundation of Shandong Province(Grant No.ZR2023ZD05,2022TSGC2120)the Shenzhen Fundamental Research Program(Grant No.GJHZ20220913142605011)the 111 Project 2.0(Grant No.BP2018013)Laboratory Construction and Management Research Project of Shandong University(Grant No.sy20233203)。
文摘The(010)-oriented substrates of β-Ga_(2)O_(3) are endowed with the maximum thermal conductivity and fastest homoepi-taxial rate,which is the preferred substrate direction for high-power devices.However,the size of(010)plane wafer is critically limited by die in the commercial edge-defined film-fed growth(EFG)method.It is difficult to grow the β-Ga_(2)O_(3) crystal with(010)principal face due to the(100)and(001)are cleavage planes.Here,the 2-inch diameter(010)principal-face β-Ga_(2)O_(3) sin-gle crystal is successfully designed and grown by improved EFG method.Unlike previous reported techniques,the single crys-tals are pulled with[001]direction,and in this way the(010)wafers can be obtained from the principal face.In our experi-ments,tree-like defects(TLDs)in(010)principal-face bulk crystals are easy to generate.The relationship between stability of growth interface and origin of TLDs are thoroughly discussed.The TLDs are successfully eliminated by optimizing growth condi-tions.The high crystalline quality of(010)-oriented substrates are comprehensive demonstrated by full width at half maximum(FWHM)with 50.4 arcsec,consistent orientation arrangement of(010)plane,respectively.This work shows that the(010)-ori-ented substrates can be obtained by EFG method,predicting the commercial prospects of large-scale(010)-oriented β-Ga_(2)O_(3) substrates.
基金the Financial support from the National key Research and Development Program of China(Nso.2018YFB0406502,2016YFB1102201)the National Natural Science Foundation of China(Grant No.51321091)+2 种基金the key Research and Development Program of Shandong Province(No.2018CXGC0410)the Young Scholars Program of Shandong University(No.2015WLJH36)the 111 Project 2.0(No.BP2018013)
文摘As a wide-bandgap semiconductor(WBG), β-Ga_2O_3 is expected to be applied to power electronics and solar blind UV photodetectors. In this review, defects in β-Ga_2O_3 single crystals were summarized, including dislocations, voids, twin, and small defects. Their effects on device performance were discussed. Dislocations and their surrounding regions can act as paths for the leakage current of SBD in single crystals. However, not all voids lead to leakage current. There's no strong evidence yet to show small defects affect the electrical properties. Doping impurity was definitely irrelated to the leakage current. Finally, the formation mechanism of the defects was analyzed. Most small defects were induced by mechanical damages. The screw dislocation originated from a subgrain boundary. The edge dislocation lying on a plane slightly tilted towards the(102) plane, the(101) being the possible slip plane. The voids defects like hollow nanopipes, PNPs, NSGs and line-shaped grooves may be caused by the condensation of excess oxygen vacancies, penetration of tiny bubbles or local meltback. The nucleation of twin lamellae occurred at the initial stage of "shoulder part" during the crystal growth. These results are helpful in controlling the occurrence of crystal defects and improving the device performance.
基金National Natural Science Foundation of China (Grant Nos. 52002219, 51932004 and 61975098)Key-Area Research and Development Program of Guangdong Province (Grant No. 2020B010174002)+2 种基金Shenzhen Fundamental Research Program (Grant No. JCYJ20210324132014038)Natural Science Foundation of Shandong (Grant No. ZR202105230005)the 111 Project 2.0 (Grant No. BP2018013)。
文摘High thickness uniformity and large-scale films of α-Ga_(2)O_(3) are crucial factors for the development of power devices.In this work, a high-quality 2-inch α-Ga_(2)O_(3) epitaxial film on c-plane sapphire substrates was prepared by the mist-CVD method.The growth rate and phase control mechanisms were systematically investigated. The growth rate of the α-Ga_(2)O_(3) films was limited by the evaporation of the microdroplets containing gallium acetylacetonate. By adjusting the substrate position(z) from 80 to 50 mm, the growth rate was increased from 307 nm/h to 1.45 μm/h when the growth temperature was fixed at 520 °C.When the growth temperature exceeded 560 °C, ε-Ga_(2)O_(3) was observed to form at the edges of 2-inch sapphire substrate.Phase control was achieved by adjusting the growth temperature. When the growth temperature was 540 °C and the substrate position was 50 mm, the full-width at half maximum(FWHM) of the rocking curves for the(0006) and(10-14) planes were 0.023° and 1.17°. The screw and edge dislocations were 2.3 × 10~6 and 3.9 × 10~(10)cm~(-2), respectively. Furthermore, the bandgaps and optical transmittance of α-Ga_(2)O_(3) films grown under different conditions were characterized utilizing UV-visible and near-IR scanning spectra.
文摘As one of the ultra-wide bandgap {UWBG)semiconducting materials,gallium oxide has attractive properties with a wide bandgap of about 4.8 eV and a high breakdown field of about 8 MWcm,which offers an alternative platform for various applications such as high performance power switches,RF amplifiers,solar blind photodetectors,and harsh environment signal processing.
基金supported by the National Key R&D Program of China(2022YFB3605403)the Provincial Science and Technology Major Project of Jiangsu(BG2024030)the National Natural Science Foundation of China(62425403,62234007,62293521,U21A20503,U21A2071,62004183).
文摘Defect engineering is pivotal in comprehending physical mechanisms that govern carrier transport and device performance.The defect evolution and carrier manipulation in Sn-doped Ga_(2)O_(3)bulk crystals subjected to different thermal treatments were investigated,utilizing depth-profiled deep-level transient spectroscopy(DLTS)and frequency-dependent capacitance-voltage(C-V-f)techniques.In untreated Sn-doped Ga_(2)O_(3)with an electron concentration of 6.37×10^(17)cm^(−3),two dominant electron traps,E_(T1)(E_(C)−0.68 eV)and E_(T2)(E_(C)−0.76 eV),were identified,corresponding to gallium vacancy(V_(Ga))and the neutral complex of V_(Ga)-V_(O),respectively,and characterized as bulk traps.Fe Ga-related defects,E_(T3)(E_(C)−0.84 eV),were concentrated near surface.Nitrogen annealing significantly reduced E_(T1),increased E_(T2)density from 6.13×10^(15)to 1.1×10^(16)cm^(−3),and raised the interfacial state density(D_(it))to 3.36×10^(15)eV^(−1)cm^(−2),accompanied by an elevated electron concentration of 7.48×10^(18)cm^(−3).In contrast,air annealing enhanced E_(T1),with a density of 1.42×10^(16)cm^(−3),suppressed of E_(T2)/E_(T3)traps,resulting in a lower D_(it)of 1.74×10^(14)eV^(−1)cm^(−2),and a reduced electron concentration to 3.01×10^(16)cm^(−3).The findings reveal that a reducing environment induces V_(O)formation and converts discrete V_(Ga)acceptors into neutral V_(Ga)-V_(O)complexes,leading to downward surface band bending and electron accumulation.Conversely,V_(Ga)-V_(O)complexes are dissociated into V_(Ga)acceptors in oxidizing conditions,leading to an upward surface band bending and electron compensation.This work underscores the carrier concentration manipulation by defect engineering in Ga_(2)O_(3),offering insights essential for developing high-performance gallium oxide electronics.
基金National Key Research and Development Program of China(2023YFB406900)National Natural Science Foundation of China(62435012,U24A20312,52202008,62175132)+1 种基金Natural Science Foundation of Shandong Province(ZR2022QE013)Outstanding Young and Middle-aged Scholars of Shandong University(Tao Li)。
文摘Single-crystal fibers(SCFs)exhibit a significant potential for high-power laser applications owing to their superior thermal management capabilities.To enhance pump power and mitigate damage at the injection end of SCFs,a segmented YAG/Yb:YAG/YAG SCF with a diameter of~200μm was directly grown using a one-step laserheated pedestal growth(LHPG)method.The crystallinity and uniformity of the as-grown fiber were evaluated through a real-time back-reflection Laue camera system.Employing a low-loss segmented YAG/Yb:YAG/YAG SCF as the laser gain medium,investigations were conducted on both continuous-wave(CW)oscillators and ultrafast pulse amplifiers.The CW laser operation at 1030.9 nm achieved a maximum output power of 117.6 W with a slope efficiency of~46%,while the ultrafast amplifier system generated pulses with an average power of 101.2 W at a repetition rate of 30.8 MHz.To the best of our knowledge,this represents the highest average power achieved from a single-stage amplifier based on an Yb:YAG SCF.Preliminary pulse compression was performed at a signal power of 5o.6 W using a grating pair,resulting in a compressed pulse width of 786 fs with a compression efficiency of 58%.This study highlights the potential of crystal fiber lasers for a new generation of high-power laser systems.
基金supported by the National Natural Science Foun-dation of China(Grants No.61925110,U20A20207,61821091,62004184,62004186,61774081,62004147,51932004,52002219,and 51961145110)the Ministry of Science and Technology of China(Grant No.2018YFB0406500)+6 种基金the Strategic Priority Research Pro-gram of the Chinese Academy of Sciences(Grant No.XDB44000000)the Key Research Program of Frontier Sciences of the CAS(Grant No.QYZDB-SSW-JSC048)the Key-Area Research and Development Program of Guangdong Province(Grant No.2020B010174002)the Fundamental Research Funds for the Central Universities under(Grants No.WK2100000014 and WK2100000010)funding sup-port from the University of Science and Technology of China(Grant No.KY2100000109)the China Postdoctoral Science Foundation(Grants No.2020M671895 and BX20200320)the Opening Project of the Key Laboratory of Microelectronics Devices and Integration Technology at the Institute of Microelectronics of CAS,and the Key Laboratory of Nanodevices and Applications in Suzhou Institute of Nano-Tech and Nano-Bionics of CAS。
文摘Owing to the advantages of ultra-wide bandgap and rich material systems,gallium oxide(Ga_(2)O_(3))has emerged as a highly viable semiconductor material for new researches.This article mainly focuses on the growth processes,material characteristics,and applications of Ga_(2)O_(3).Compared with single crystals and the epitaxial growth of other wide-bandgap semiconductors,large-size and high-quality𝛽-Ga_(2)O_(3) single crystals can be efficiently grown with a low cost,making them highly competitive.Thanks to the availability of high-quality single crystals,epi-taxial films,and rich material systems,high-performance semiconductor devices based on Ga_(2)O_(3) go through a booming development in recent years.The defects and interfaces of Ga_(2)O_(3) are comprehensively analyzed owing to their significant influence on practical applications.In this study,the two most common applications of Ga_(2)O_(3) materials are introduced.The high breakdown electric field,high working temperature,and excellent Baliga’s figure-of-merit of Ga_(2)O_(3) represent an inspiring prospect for power electronic devices.In addition,the excellent absorption in deep-ultraviolet band provides new ideas for optoelectronic detectors and ensures the dramatic progress.Finally,the summary,challenges,and prospects of the Ga_(2)O_(3) materials and devices are presented and discussed.
基金We gratefully acknowledge the financial support from the National key Research and Development Program of China(Grant No.2016YFB1102201,2018YFB0406502)the key Research and Development Program of Shandong province(Grant No.2018CXGC0410,2017GGX20116 and 2018JMRH0207)+1 种基金the Young Scholars Program of Shandong University(Grant No.2015WLJH36)the 111 Project 2.0(Grant No.BP2018013).
文摘Single crystal fibers(SCF)are considered to be a combination of bulk crystals and conventional fibers,thereby possessing the stable physical and chemical properties accompanied with excellent waveguide properties.This paper gives a detailed introduction to the development history of single crystal fibers,including the evolution of the growth technique and the optimization of the growth process.Laser-heated pedestal growth(LHPG)and Micro-pulling-down(μ-PD)methods are considered to be the most widely used growth techniques for growing single crystal fibers,and the advantages of the two methods are also introduced in detail.The second part of this paper describes the characterization of single crystal fibers,including diameter fluctuation,crystal quality and optical losses.A series of cladding approaches for SCF,such as magnetron sputtering,sol-gel,liquid phase epitaxy,co-drawing LHPG,ion implantation and micro-structure cladding will be reviewed.In addition,the research status of single crystal fiber laser and single crystal fiber sensor are also summarized in view of the current research foundation.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51321091, 61275142, 61308042, and 91022003)China Postdoctoral Science Foundation (Grant Nos. 2013M531594, 2014T70633)
文摘A compact saturable absorber mirror（SAM） based on few-layer molybdenum disulfide（MoS2） nanoplatelets was fabricated and successfully used as an efficient saturable absorber（SA） for the passively Q-switched solid-state laser at 1 μm wavelength. Pulses as short as 182 ns were obtained from a ytterbium-doped（Yb:LGGG） bulk laser Q-switched by the MoS2 SAM, which we believe to be the shortest one ever achieved from the MoS2 SAs-based Q-switched bulk lasers. A maximum average output power of 0.6 W was obtained with a slope efficiency of 24%,corresponding to single pulse energy up to 1.8 μJ. In addition, the simultaneous dual-wavelength Q-switching at 1025.2 and 1028.1 nm has been successfully achieved. The results indicate the promising potential of few-layer MoS2 nanoplatelets as nonlinear optical switches for achieving efficient pulsed bulk lasers.
基金support from the National Natural Science Foundation of China(Grant No.52002218)the Natural Science Foundation of Shandong Province(Grant No.ZR2020QE031)+2 种基金the State Key Laboratory of Solidification Processing in NWPU(Grant No.SKLSP202209)the National Key Research and Development Program of China(Grant No.2022YFB3605704)the Qilu Young Scholars Program of Shandong University.
文摘Ba_(0.77)Ca_(0.23)TiO_(3)(BCT)single crystal has been widely studied as a promising lead-free ferroelectric material.In this work,high-quality BCT crystal was successfully grown by the Czochralski(CZ)method.The as-grown crystal is crack-free and shows black coloration.It possesses a high dielectric stability over a wide temperature range,while the dielectric loss is rather small below 90℃.Furthermore,it possesses excellent ferroelectric properties with residual polarization strength(Pr)and coercive field(Ec)of 17.93μC/cm^(2) and 8.47 kV/cm,respectively.Besides,BCT crystal shows large electromechanical coupling factors,with kt,k31,k33 and k15 of 0.535,0.254,0.714 and 0.721,respectively.The piezoelectric coefficients d31,d33 and d15 are measured to be−36.5,130 and 246 pC/N,respectively.
