Faculty Profiles

Published Papers - GU Ping

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Butylparaben induces glycolipid metabolic disorders in mice via disruption of gut microbiota and FXR signaling

Du H., Cui L., Zhao X., Yu Z., He T., Zhang B., Fan X., Zhao M., Zhu R., Zhang Z., Li M., Li J., Oh Y., Gu Ning

Journal of Hazardous Materials 474 2024.08 [Refereed]

Lambda-cyhalothrin induces lipid accumulation in mouse liver is associated with AMPK inactivation

Daqian Yang, Xiaotong Sun, Xiangjuan Wei, Boya Zhang, Xingpei Fan, Haining Du, Ruijiao Zhu, Yuri Oh, Ning Gu

Food and Chemical Toxicology ( Elsevier BV ) 172 113563 - 113563 2023.02 [Refereed]

DOI

High-fat diet and palmitate inhibits FNDC5 expression via AMPK-Zfp57 pathway in mouse muscle cells

Qian Guo, Boya Zhang, Haining Du, Ruijiao Zhu, Xiaotong Sun, Xingpei Fan, Xiangjuan Wei, DaQian Yang, Yuri Oh, Lei Fan, Changlin Wang, Ning Gu

Chemico-Biological Interactions ( Elsevier BV ) 369 110265 - 110265 2023.01 [Refereed]

DOI

Probiotics protect against hepatic steatosis in tris (2-chloroethyl) phosphate-induced metabolic disorder of mice via FXR signaling

Yang D, Wei X, Zhang B, Zhu R, Hu H, Fan X, Du H, Chen X, Zhang Z, Zhao M, Oh Y, Gu Ning

Food Chem Toxicol 169 ( 113440 ) 2022.11 [Refereed]

DOI

Malting barley carbon dots-mediated oxidative stress promotes insulin resistance in mice via NF-κB pathway and MAPK cascade.

Zhang B, Yu L, Zhu R, Wei X, Fan X, Hu H, Yang D, Du H, Zhao M, Li L, Oh Y, Feng Y, Gu Ning

J Nanobiotechnology 20 ( 331 ) 1 - 19 2022.07 [Refereed]

DOI

Thiamethoxam induces nonalcoholic fatty liver disease in mice via methionine metabolism disturb via nicotinamide N-methyltransferase overexpression

Daqian Yang, Xiaoting Zhang, Lei Yue, Hailong Hu, Xiangjuan Wei, Qian Guo, Boya Zhang, Xingpei Fan, Yuan Xin, Yuri Oh, Ning Gu

Chemosphere ( Elsevier BV ) 273 129727 - 129727 2021.06 [Refereed]

DOI

Effects of oral administration of polystyrene nanoplastics on plasma glucose metabolism in mice

Xingpei Fan, Xiangjuan Wei, Hailong Hu, Boya Zhang, Daqian Yang, Haining Du, Ruijiao Zhu, Xiaotong Sun, Yuri Oh, Ning Gu

Chemosphere ( Elsevier Ltd ) 2021

Microplastic (MP) and nanoplastic (NP) induce neurotoxicity, cytotoxicity, and reproductive system toxicity in mammals. However, the impacts of NPs on the endocrine system are obscure. Here, monodisperse polystyrene nanoplastics (PS-NPs) were prepared by emulsion polymerization and the accumulation of fluorescent PS-NPs in various organs, including the liver, kidney, spleen, and pancreas, was examined. The oral administration of PS-NPs induced visceral organ injury, and the main toxicities were damage to hepatic function and the abnormity of lipid metabolism. Global transcriptome sequencing (RNA-Seq) revealed the impact of PS-NPs on the genes involved in reactive oxygen species (ROS) generation and the PI3K/Akt signaling pathway, which is associated with glucose metabolism in mice. Chronic exposure to PS-NPs significantly increased plasma glucose levels and ROS levels, but did not affect plasma insulin secretion. The phosphorylation of insulin receptor substrate (IRS)-1 at Ser307 was raised, which decreased the phosphorylation of Akt (at Ser473) in the PI3K/Akt pathway. Collectively, these findings suggested that the oral administration of PS-NPs significantly increased ROS, hepatic triglycerides, and cholesterol accumulation. The high levels of ROS disturbed the PI3K/Akt pathway, causing insulin resistance and increased plasma glucose in the mouse liver.

DOI

Probiotics protect against hepatic steatosis in tris (2-chloroethyl) phosphate-induced metabolic disorder of mice via FXR signaling

Yang D, Wei X, Zhang B, Zhu R, Hu H, Fan X, Du H, Chen X, Zhang Z, Zhao M, Oh Y, Gu Ning

169 ( 113440 ) 2020.09 [Refereed]

DOI

The toxic effects of titanium dioxide nanoparticles on plasma glucose metabolism are more severe in developing mice than in adult mice

Hailong Hu, Boya Zhang, Li Li, Qian Guo, Daqian Yang, Xiangjuan Wei, Xingpei Fan, Jing Liu, Qiong Wu, Yuri Oh, Yujie Feng, Kun Chen, Changlin Wang, Liping Hou, Ning Gu

Environmental Toxicology ( John Wiley and Sons Inc. ) 35 ( 4 ) 443 - 456 2020.04

Titanium dioxide nanoparticles (TiO2 NPs) are authorized food additives, and children have the highest exposure. Therefore, children are likely more susceptible to the adverse effects of TiO2 NPs than adults. Previous study showed that oral administration of 50 mg/kg body weight (bw) TiO2 NPs increase plasma glucose in mice. However, few studies have directly compared the adverse effects of exposure to TiO2 NPs on plasma glucose metabolism of different age groups. In this study, the developing (age 3 weeks) and adult mice (age 10 weeks) were orally administered with 50 mg/kg bw TiO2 NPs per day. The TiO2 NPs induced hyperglycemia earlier in the developing mice than in the adult mice. Then mechanisms were analyzed after mice were oral administration of TiO2 NPs for 8 weeks and 26 weeks, respectively. Results showed that the treatment with TiO2 NPs activated xenobiotic biodegradation in livers of both developing and adult mice at the early stage. However, only in the developing mice, TiO2 NPs induced endoplasmic reticulum (ER) stress in livers and increased reactive oxygen species in livers and sera in the early stage. The ER stress and ROS activated an inflammation response and mitogen-activated protein kinase pathways, thereby inducing insulin resistance in the livers of developing mice at the early stage. The response of the adult mice was delayed, and these changes were observed in the late stage of the study. The results of this study all suggest that children are more susceptible than adults to the toxicity of orally administered TiO2 NPs.

DOI

Molecular mechanisms underlying zinc oxide nanoparticle induced insulin resistance in mice

Hu H, Guo Q, Fan X, Wei X, Yang D, Zhang B, Liu J, Wu Q, Oh Y, Feng Y, Chen K, Hou L, Gu N

Nanotoxicology. 14 ( 1 ) 59 - 76 2020.02 [Refereed]

The saturated fatty acid palmitate induces insulin resistance through Smad3-mediated down-regulation of FNDC5 in myotubes.

Qian Guo, Xiangjuan Wei, Hailong Hu, Daqian Yang, Boya Zhang, Xingpei Fan, Jing Liu, Hongjuan He, Yuli Oh, Qiong Wu, Yao Zhang, Chuanpeng Liu, Changlin Whang, Ning Gu

Biochemical and Biophysical Research Communications. Vol. 520(3):619-626, 2019. 5206 ( 3 ) 619 - 626 2019.12 [Refereed]

Mechanisms of titanium dioxide nanoparticle-induced oxidative stress and modulation of plasma glucose in mice

Hailong Hu, Xingpei Fan, Yao Yin, Qian Guo, Daqian Yang, Xiangjuan Wei, Boya Zhang, Jing Liu, Qiong Wu, Yuri Oh, Kun Chen, Yujie Feng, Liping Hou, Li Li, Ning Gu

Environmental Toxicology ( John Wiley and Sons Inc. ) 34 ( 11 ) 1221 - 1235 2019.11

Titanium dioxide nanoparticles (TiO2 NPs) are reported to increase plasma glucose levels in mice at specific doses. The production and accumulation of reactive oxygen species (ROS) is potentially the most important factor underlying the biological toxicity of TiO2 NPs but the underlying mechanisms are unclear at present. Data from genome-wide analyses showed that TiO2 NPs induce endoplasmic reticulum (ER) stress and ROS generation, leading to the inference that TiO2 NP-induced ER stress contributes to enhancement of ROS in mice. Resveratrol (Res) effectively relieved TiO2 NP-induced ER stress and ROS generation by ameliorating expression of a common set of activated genes for both processes, signifying that ER stress and ROS are closely related. TiO2 NP-induced ER stress occurred earlier than ROS generation. Upon treatment with 4-phenylbutyric acid to relieve ER stress, plasma glucose levels tended toward normal and TiO2 NP increased ROS production was inhibited. These results suggest that TiO2 NP-induced ER stress promotes the generation of ROS, in turn, triggering increased plasma glucose levels in mice. In addition, Res that displays the ability to reduce ER stress presents a dietary polyphenol antioxidant that can effectively prevent the toxicological effects of TiO2 NPs on plasma glucose metabolism.

DOI

Silicon dioxide nanoparticles induce insulin resistance through endoplasmic reticulum stress and generation of reactive oxygen species.

Hailong Hu, Xingpei Fan, Qian Guo, Xiangjuan Wei, Daqian Yang, Boya Zhang, Jing Liu, Qiong Wu, Yuri Oh, Yujie Feng, Kun Chen, Liping Hou, Ning Gu

Particle and Fibre Toxicology Vol.16 ( 41 ) 1 - 18 2019.11 [Refereed]

C/EBPβ mediates palmitate-induced musclin expression via the regulation of PERK/ATF4 pathways in myotubes.

Qian Guo, Hailong Hu, Xiaohuan Liu, DaQian Yang, Yao Yin, Boya Zhang, Hongjuan He, Yuri Oh, Qiong Wu, Chuanpeng Liu, Ning Gu

Am J Physiol Endocrinol Metab. 316 ( 6 ) E1081-E1092 - E1092 2019.06 [Refereed]

Glucosamine induces increased musclin gene expression through endoplasmic reticulum stress-induced unfolding protein response signaling pathways in mouse skeletal muscle cells.

1) Qian Guo,Hailong Hu,Ying Zhoua,Yuheng Yan,Xiangjuan Wei,Xingpei Fan,Daqian Yang,Hongjuan He,Yuri Oh,Kun Chen,Qiong Wu,Chuanpeng Liu,Ning Gu.

Food Chem Toxicol, 125 95 - 105 2019.03 [Refereed]

RNA sequencing analysis shows that titanium dioxide nanoparticles induce endoplasmic reticulum stress, which has a central role in mediating plasma glucose in mice

Hailong Hu, Li Li, Qian Guo, He Zong, Yuheng Yan, Yao Yin, Yu Wang, Yuri Oh, Yujie Feng, Qiong Wu, Ning Gu

Nanotoxicology ( Taylor and Francis Ltd ) 12 ( 4 ) 341 - 356 2018.04 [Refereed]

Titanium dioxide nanoparticles (TiO2NPs) constitute the top five NPs in use today. In this study, oral administration of 50, 100, and 200 mg/kg body weight (b.w.) TiO2NPs increases plasma glucose in mice, whereas 10 and 20 mg/kg b.w. TiO2NPs did not. RNA sequencing (RNA-seq) technology was used to investigate genome-wide effects of TiO2NPs. Clustering analysis of the RNA-seq data showed the most significantly enriched gene ontology terms and KEGG pathways related to the endoplasmic reticulum (ER) and ER stress. Molecular biology verification showed that 50 mg/kg b.w. and higher doses TiO2NPs activated a xenobiotic biodegradation response and increased expression of cytochrome P450 family genes in mouse livers, thus inducing ER stress in mice. ER stress-activated MAPK and NF-κB pathways and induced an inflammation response, resulting in phosphorylation of the insulin receptor substrate 1 and, consequently, insulin resistance. This was the main mechanism by which TiO2NPs increased plasma glucose in mice. Meanwhile, ER stress disturbed the monooxygenase system, and thus generated reactive oxygen species (ROS). Relief of ER stress with 4-phenylbutyric acid inhibited all the above effects of TiO2NPs, including the generation of ROS. Therefore, TiO2NP-induced ER stress was a decisive factor with a central role in plasma glucose disturbance in mice.

DOI

Hypoxia in 3T3-L1 adipocytes suppresses adiponectin expression via the PERK and IRE1 unfolded protein response

Qian Guo, Sanli Jin, Hailong Hu, Ying Zhou, Yuheng Yan, He Zong, Yu Wang, Hongjuan He, Yuri Oh, Chuanpeng Liu, Ning Gu

Biochemical and Biophysical Research Communications ( Elsevier B.V. ) 493 ( 1 ) 346 - 351 2017.11 [Refereed]

Adiponectin, an adipocytokine produced by adipocytes, functions as an anti-inflammatory and anti-apoptotic substance, while also enhancing insulin sensitivity. Patients or model animals with obesity or diabetes typically present attenuated expression of adiponectin. Moreover, obesity and diabetes are often accompanied with hypoxia in adipose tissue, which may result in endoplasmic reticulum (ER) stress as well as low expression of adiponectin. The purpose of this study was to investigate the specific role of the unfolded protein response (UPR) involved in the low expression of adiponectin induced by hypoxia. Subjecting 3T3-L1 adipocytes to hypoxia significantly reduced adiponectin expression and activated the PERK and IRE1 signaling pathways in a time-dependent manner. The ATF6 signaling pathway showed no obvious changes with hypoxia treatment under a similar time course. Moreover, the down-regulated expression of adiponectin induced by hypoxia was relieved once the PERK and IRE1 signaling pathways were suppressed by the inhibitors GSK2656157 and 4μ8C, respectively. Overall, these data demonstrate that hypoxia can suppress adiponectin expression and activate the PERK and IRE1 signaling pathways in differentiated adipocytes, and this two pathways are involved in the suppression of adiponectin expression induced by hypoxia.

DOI

Growth of zinc sulfide by mist chemical vapor deposition depending on mist size and thermal conditions in susceptor: Growth of zinc sulfide by mist chemical vapor

Kazuyuki Uno, Yuichiro YAMASAKI、Gu PING, Ichiro Tanaka

physica status solidi (c) 13 7 - 9 2016.04 [Refereed]

A mechanistic study to increase understanding of titanium dioxide nanoparticles-increased plasma glucose in mece

Hu Hailong, Guo Qian, Wang Changlin, Ma Xiao, He Hongjuan, Oh Yuri, Feng Yujie, Wu Qiong, Ning Gu

Food and Chemical Toxicology 95 175 - 187 2016 [Refereed]

Growth of zinc sulfide by mist chemical vapor deposition depending on mist size and thermal conditions in susceptor

Kazuyuki Uno, Yuichiro Yamasaki, Ping Gu, Ichiro Tanaka

PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 13 NO 7-9 ( WILEY-V C H VERLAG GMBH ) 13 ( 7-9 ) 448 - 451 2016 [Refereed]

Zinc sulfide (ZnS) films were successfully grown by using mist chemical vapor deposition (mist-CVD) with fine-channel susceptor made of quartz. For the investigation of growth dynamics, two types of mist generators and two types of susceptors were prepared and distribution profiles of film thickness were examined. Thermal efficiency of susceptor depends on heat-penetration efficiency and line-velocity of the mists, which are influenced by the fine-channel gap-height of the susceptors. Using larger size of mists requires higher thermal efficiency in susceptor to obtain a flat thickness distribution. This result indicates that the optimization of the mist size and the susceptor structure is important for the film uniformity of grown films by the mist-CVD. (C) 201 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

DOI

Palmitate increases musclin gene expression through activation of PERK signaling pathway in C2C12 myotubes

Ning Gu, Qian Guo, Ke Mao, Hailong Hu, Sanli Jin, Ying Zhou, Hongjuan He, Yuri Oh, Chuanpeng Liu, Qiong Wu

Biochemical and Biophysical Research Communications ( Academic Press Inc. ) 467 ( 3 ) 521 - 526 2015.11 [Refereed]

Musclin is a type of muscle-secreted cytokine and its increased gene expression induces insulin resistance in type 2 diabetes. However, the mechanism underlying increased musclin gene expression is currently unclear. Excessive saturated fatty acids (SFA) can activate the secretion of several muscle-secreted cytokines as well as endoplasmic reticulum (ER) stress pathway, thereby contributing to the development of type 2 diabetes. The purpose of this study was to investigate the mechanisms responsible for the effect of palmitate, the most abundant SFA in the plasma, on the gene expression of musclin in C2C12 myotubes. Treatment of C2C12 myotubes with palmitate or tunicamycin significantly increased the expression of musclin as well as ER stress-related genes, but treatment with oleate did not. Pre-treatment of C2C12 myotubes with 4-phenyl butyrate suppressed the expression of ER stress-related genes, simultaneously, resulting in decreased expression of the musclin gene induced by palmitate or tunicamycin. These results indicate that ER stress is related to palmitate-induced musclin gene expression. Moreover, palmitate-induced musclin gene expression was significantly inhibited in C2C12 myotubes when PERK pathway signaling was suppressed by knockdown of the PERK gene or treatment with GSK2656157, a PERK autophosphorylation inhibitor. However, there was no difference in the palmitate-induced musclin gene expression when IRE1 and ATF6 signaling pathways were suppressed by knockdown of the IRE1 and ATF6 genes. These findings suggest that palmitate increases musclin gene expression via the activation of the PERK signaling pathway in C2C12 myotubes.

DOI

Growth mechanism of zinc sulfide films by mist chemical vapor deposition

Yuichiro Yamasaki, Kazuyuki Uno, Gu Ping, Ichiro Tanaka

Zairyo/Journal of the Society of Materials Science, Japan ( Society of Materials Science Japan ) 64 ( 9 ) 707 - 710 2015.09 [Refereed]

The mist chemical vapor deposition (mist CVD) method, which uses ultrasonically atomized solutions as sources, is an environmental friendly and cost-effective technology for the growth of compound semiconductors. This growth process is realized under atmospheric pressure and allows us to use many kinds of salts, complexes, and compounds with low toxicity for sources. Using the oxidizability of water including the source, most of the previous reports of the mist-CVD method are on oxide materials. In this study, we fabricated zinc sulfide (ZnS) films by mist-CVD method using thiourea-based water solutions as sources. Investigating the growth of ZnS by mist-CVD under various growth conditions and experimental setups, we proposed zinc-chloride complexes are necessary for the growth of ZnS and vaporized mist sources act as precursors.

DOI

Titanium dioxide nanoparticles increase plasma glucose via reactive oxygen species-induced insulin resistance in mice.

Hu Hailong, Guo Qian, Wang Changlin, Ma Xiao, He Hongjuan, Oh Yuri, Feng Yujie, Wu Qiong, Gu Ning

Journal of Applied Toxicology 35 ( 10 ) 1122 - 1132 2015 [Refereed]

Effects of oral administration of titanium dioxide fine-sized particles on plasma glucose in mice

Ning Gu, Hailong Hu, Qian Guo, Sanli Jin, Changlin Wang, Yuri Oh, Yujie Feng, Qiong Wu

Food and Chemical Toxicology 86 124 - 131 2015 [Refereed]

4-Phenylbutyric Acid Increases GLUT4 Gene Expression through Suppression of HDAC5 but not Endoplasmic Reticulum Stress

Hailong Hu, Li Li, Changlin Wang, Hongjuan He, Ke Mao, Xiao Ma, Ruoyu Shi, Yuri Oh, FengWei Zhang, Ying Lu, Qiong Wu, Ning Gu

CELLULAR PHYSIOLOGY AND BIOCHEMISTRY ( KARGER ) 33 ( 6 ) 1899 - 1910 2014 [Refereed]

Background:The chemical chaperone 4-phenylbutyric acid (4-PBA) has been shown to relieve endoplasmic reticulum (ER) stress. Therefore, it improves insulin sensitivity and promotes glucose metabolism in skeletal muscle. Glucose transporter type 4 (GLUT4), as a major glucose transporter protein, plays a central role in glucose metabolism. Until now, it has been unclear whether 4-PBA affects GLUT4 gene expression and thus, contributes to glucose metabolism. Methods: C2C12 myotubes were treated with 4-PBA, tunicamycin or butyrate and subjected to Western blot and RT-PCR. Results: 4-PBA-treated C2C12 myotubes increased GLUT4 expression and promoted glucose metabolism. Most interestingly, GLUT4 gene expression induced by 4-PBA was not associated with ER stress even in the presence of tunicamycin, an ER stress inducer. Moreover, we also found that 4-PBA inhibited histonedeacetylase 5 (HDAC5) expression in C2C12 myotubes, resulting in hyperacetylation of the histone H3 at the myocyte enhancer factor 2 (MEF2) binding site. This increased the binding of MEF2A to the site on the GLUT4 promoter, resulting in increased GLUT4 expression. Conclusions: Our data indicate that 4-PBA increases GLUT4 expression by acetylating the MEF2 site to increase the MEF2A binding through a mechanism that involves suppression of the HDAC5 pathway, but without involving ER stress. Copyright (C) 2014 S Karger AG, Basel

DOI

Size dependent optical properties of quinacridonequinone nanoparticles prepared by liquid laser ablation in water

Ikuko Akimoto, Masahiro Ohata, Nobuhiko Ozaki, Ping Gu

CHEMICAL PHYSICS LETTERS 552 102 - 107 2012.11 [Refereed]

DOI

Formation of nanoparticles of organic molecules by liquid laser ablation

Ikuko Akimoto, Masahiro Ohata, Nobuhiko Ozaki, Gu Ping

Materials Research Society Symposium Proceedings 1455 55 - 60 2012 [Refereed]

We carried out laser ablation of three organic molecules, rubrene (Rb), Oralith Brilliant Pink R (BP) and quinacridonequinone (QQ) in a poor solvent, water. As a result, nanoparticles of BP and QQ were formed, but those of Rb were not formed because of photodissociation. For a rigid molecule, QQ, optical properties of colloidal solutions were investigated in relation to the size of the included nanoparticles. A linear correlation between the blue shift of the absorption peak energy and the decrease in the diameter of the nanoparticles was found, indicating that the nanoparticle diameter can be easily estimated from the absorption spectrum of a colloidal solution. From the solution, a nanoparticle film was fabricated on an electrode by the electrophoretic deposition method. © 2012 Materials Research Society.

DOI

Terahertz-photomixing efficiency of a photoconductive antenna embedded in a three-dimensional photonic crystal

M Iida, M Tani, P Gu, K Sakai, M Watanabe, H Kitahara, S Kato, M Suenaga, H Kondo, MW Takeda

JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS ( INST PURE APPLIED PHYSICS ) 42 ( 12A ) L1442 - L1445 2003.12 [Refereed]

We report on generation of coherent terahertz radiation by photomixing with a photoconductive antenna placed in a three-dimensional photonic crystal cavity. We observed efficiency peaks around the frequencies near the photonic bandedges and at the planar defect modes. The efficiency peaks observed near the photonic bandedges are associated with the increase of the optical mode density at the bandedge. The relatively low efficiency at the planar defect mode frequencies are explained by the mode diffusion in the lateral direction of the defect layer.

DOI

Highly efficient terahertz radiation from YBa2Cu3O7-delta thin film log-periodic antennas

M Tonouchi, H Saijo, M Hangyo, O Morikawa, P Gu, M Tani, K Sakai

PHYSICA C ( ELSEVIER SCIENCE BV ) 357 1600 - 1602 2001.08 [Refereed]

We report on the radiation power of the terahertz (THz) beam from YBa2Cu3O7-delta (YBCO) thin film antennas. InSb hot-electron bolometer is used to estimate the radiation power after being calibrated in the THz beam generation and detection system. The 100-nm-thick and 30-mum-wide YBCO thin film bridges are connected to a self-complimentary log-periodic toothed planar antenna or a bow-tie antenna. Femtosecond optical pulses are focused onto the center bridge of the antennas being biased with a current up to 1 A. The detected power increases in proportion with increasing bias current, and reaches over 22 muW in the average at an excitation power of 98 mW. (C) 2001 Elsevier Science BY. All rights reserved.

Generation of THz radiation by excitation of InAs with a femtosecond free-electron laser

M Tani, S Kono, P Gu, K Sakai, M Usami, M Shinn, JF Gubeli, G Neil, JZ Xu, R Kersting, XC Zhang

ULTRAFAST ELECTRONICS AND OPTOELECTRONICS, PROCEEDINGS ( OPTICAL SOC AMERICA ) 49 166 - 170 2001 [Refereed]

Ultrabroadband detection of THz radiation by LT-GaAs photoconductive antenna gated with 15-fs laser pulses

S Kono, M Tani, P Gu, K Sakai

ULTRAFAST PHENOMENA XII ( SPRINGER-VERLAG BERLIN ) 66 218 - 220 2001 [Refereed]

Coherent THz wave generation by photomixing in photonic crystal cavity

M Tani, P Gu, K Sakai, M Suenaga, H Kondo, H Kitahara, MW Takeda

CLEO(R)/PACIFIC RIM 2001, VOL I, TECHNICAL DIGEST ( IEEE ) 196 - 197 2001 [Refereed]

Coherent phonons in InSb and their properties from femtosecond pump-probe experiments

OV Misochko, P Gu, K Sakai

PHYSICA B-CONDENSED MATTER ( ELSEVIER SCIENCE BV ) 293 ( 1-2 ) 33 - 37 2000.12 [Refereed]

Detection of up to 20 THz with a low-temperature-grown GaAs photoconductive antenna gated with 15 fs light pulses

S Kono, M Tani, P Gu, K Sakai

APPLIED PHYSICS LETTERS ( AMER INST PHYSICS ) 77 ( 25 ) 4104 - 4106 2000.12 [Refereed]

Temperature dependence of terahertz radiation from n-type InSb and n-type InAs surfaces

S Kono, P Gu, M Tani, K Sakai

APPLIED PHYSICS B-LASERS AND OPTICS ( SPRINGER-VERLAG ) 71 ( 6 ) 901 - 904 2000.12 [Refereed]

The azimuthal angle dependence and the temperature dependence of terahertz (THz) radiation generated from n-type (111) InSb and n-type (111) InAs surfaces irradiated with similar to 80 fs near-infrared laser pulses are investigated. The azimuthal angle dependence shows that the contribution of the difference-frequency mixing (DFM) is not dominant for both materials at the excitation density of similar to 1 GW/cm(2). At an appropriate azimuthal angle, the radiation due to DFM is excluded from the total THz radiation and the temperature dependence of THz radiation due to the surge current is observed. The increase of THz radiation with decrease of the temperature is found to be much more pronounced for InSb than for InAs. The different temperature dependence can be attributed to the different radiation mechanisms dominant for both materials. Especially, the temperature dependence of the THz radiation from InSb is well explained by the photoDember effect.

Generation of coherent terahertz radiation by photomixing of dual-mode lasers

M Tani, P Gu, M Hyodo, K Sakai, T Hidaka

OPTICAL AND QUANTUM ELECTRONICS ( KLUWER ACADEMIC PUBL ) 32 ( 4-5 ) 503 - 520 2000.05 [Refereed]

We have reviewed and discussed the generation of continuous-wave terahertz radiation by the photomixing of dual-mode lasers, which includes a multi-mode laser diode (LD), a dual-mode microchip laser, a monolithic dual-mode DBR LD, and a widely tunable dual-mode external cavity LD. It is demonstrated by several experiments that the beat frequency of a dual-mode laser is more stable than the original laser modes because of the common-mode rejection effect. We also suggest a novel scheme by which the optical beat is stabilized to less than 1 kHz and its frequency can be precisely determined as well.

Terahertz radiation from LO phonon-plasmon coupling modes in InSb film

P Gu, M Tani, K Sakai, TR Yang

2000 25TH INTERNATIONAL CONFERENCE ON INFRARED AND MILLIMETER WAVES CONFERENCE DIGEST ( IEEE ) 67 - 68 2000 [Refereed]

Magnetic field dependence of THz radiation from InSb surface

Ping Gu, Masahiko Tani, Kiyomi Sakai

IQEC, International Quantum Electronics Conference Proceedings ( IEEE ) 171 - 172 1999

Generation of cw-terahertz radiation using a two-longitudinal-mode laser diode

P Gu, M Tani, M Hyodo, K Sakai, T Hidaka

JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS ( JAPAN J APPLIED PHYSICS ) 37 ( 8B ) L976 - L978 1998.08 [Refereed]

Coherent cw-terahertz (THz) radiation has been generated by photomixing with a photoconductive antenna fabricated on a low-temperature-grown (LTG) GaAs film using a two-longitudinal-mode distributed Bragg reflector (DBR) laser diode (LD). The frequency of the emitted radiation corresponds to the difference frequency between the two modes of the LD. The linewidth of the radiation is much narrower than that of each laser mode oscillating in the same cavity due to the common-mode rejection effect between the two modes oscillating in the same cavity. This property of the two-mode LD, as well as its compactness and ease of optical alignment, make the device promising as an excitation laser source for photomixing.

Generation of sub-THz radiation using a two-longitudinal-mode laser diode

Ping Gu, Masahiko Tani, Kiyomi Sakai, Takehiro Hidaka

Conference on Lasers and Electro-Optics Europe - Technical Digest ( IEEE ) 261 - 262 1998

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Published Papers - GU Ping