Browsing by Author "Yang, He"
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Item Broadband laser polarization control with aligned carbon nanotubes(ROYAL SOC CHEMISTRY, 2015) Yang, He; Fu, Bo; Li, Diao; Tian, Ying; Chen, Ya; Mattila, Marco; Yong, Zhenzhong; Li, Ru; Hassanien, Abdou; Yang, Changxi; Tittonen, Ilkka; Zhaoyu, Re; Bai, Jintao; Li, Qingwen; Kauppinen, Esko I.; Lipsanen, Harri; Sun, Zhipei; Department of Micro and Nanosciences; Department of Applied Physics; NanoMaterials; Ilkka Tittonen Group; Harri Lipsanen Group; Zhipei Sun Group; Tsinghua UniversityItem Enhanced terahertz emission from mushroom-shaped InAs nanowire network induced by linear and nonlinear optical effects(IOP Publishing Ltd., 2022-02-19) Xi, Fugang; Yang, He; Khayrudinov, Vladislav; He, Yuhang; Haggren, Tuomas; Zhou, Yixuan; Lipsanen, Harri; Sun, Zhipei; Xu, Xinlong; Department of Electronics and Nanoengineering; Department of Neuroscience and Biomedical Engineering; Centre of Excellence in Quantum Technology, QTF; Harri Lipsanen Group; Zhipei Sun Group; Northwest UniversityThe development of powerful terahertz (THz) emitters is the cornerstone for future THz applications, such as communication, medical biology, non-destructive inspection, and scientific research. Here, we report the THz emission properties and mechanisms of mushroom-shaped InAs nanowire (NW) network using linearly polarized laser excitation. By investigating the dependence of THz signal to the incidence pump light properties (e.g. incident angle, direction, fluence, and polarization angle), we conclude that the THz wave emission from the InAs NW network is induced by the combination of linear and nonlinear optical effects. The former is a transient photocurrent accelerated by the photo-Dember field, while the latter is related to the resonant optical rectification effect. Moreover, the p-polarized THz wave emission component is governed by the linear optical effect with a proportion of ∼85% and the nonlinear optical effect of ∼15%. In comparison, the s-polarized THz wave emission component is mainly decided by the nonlinear optical effect. The THz emission is speculated to be enhanced by the localized surface plasmon resonance absorption of the In droplets on top of the NWs. This work verifies the nonlinear optical mechanism in the THz generation of semiconductor NWs and provides an enlightening reference for the structural design of powerful and flexible THz surface and interface emitters in transmission geometry.Item Femtosecond Mode-locked Yb:KYW Laser Based on InP Nanowire Saturable Absorber(IEEE, 2022-03-01) Liu, Junting; Ye, Shuai; Wang, Feifei; Sun, Xiaohui; Khayrudinov, Vladislav; Lipsanen, Harri; Nie, Hongkun; Yang, He; Yang, Kejian; Zhang, Baitao; He, Jingliang; Shandong University; Department of Electronics and Nanoengineering; Beihang University; Department of Electronics and NanoengineeringIn this letter, indium phosphide (InP) nanowires (NWs) are fabricated by Au-nanoparticle assisted vapor-liquid-solid method and applied as a saturable absorber (SA) for continuous-wave (CW) mode-locked femtosecond Yb:KYW bulk laser. I-scan method was used to characterize the saturable absorption properties of the prepared InP NWs SA. Pulses as short as 394 fs with the repetition rate of 41.5 MHz and maximum average output power of 315 mW are achieved. To the best of our knowledge, this is the first demonstration of InP NWs working as SA for the fs-pulse generation in the solid-state bulk laser. The results indicate that InP NWs are a promising SA candidate for applications in ultrafast photonic devices.Item InAs-Nanowire-based Broadband Ultrafast Optical Switch(AMERICAN CHEMICAL SOCIETY, 2019-07-18) Liu, Junting; Khayrudinov, Vladislav; Yang, He; Sun, Yue; Matveev, Boris; Remennyi, Maxim; Yang, Kejian; Haggren, Tuomas; Lipsanen, Harri; Wang, Fengqiu; Zhang, Baitao; He, Jingliang; Department of Electronics and Nanoengineering; Harri Lipsanen Group; Shandong University; Nanjing University; Ioffe InstituteDue to their tunable optical properties with various shapes, sizes and compositions, nanowires (NWs) have been regarded as a class of semiconductor nanostructures with great potential for photodetectors, light-emitting diodes, gas sensors, microcavity lasers, optical modulators and converters. Indium arsenide (InAs), an attractive III-V semiconductor NW with the advantages of narrow bandgap and large electron mobility, has attracted considerable interest in infrared optoelectronic and photonic devices. Here, we studied the ultrafast carrier dynamics and nonlinear optical responses of InAs NWs ranging from 1.0 to 2.8 µm, and demonstrated the InAs-NW-based ultrafast broadband optical switch for passively Q-switching in all-solid-state laser systems. Furthermore, we achieved ultrafast optical modulation for laser mode-locking at 1.0 μm, paving the way for their applications in the field of ultrafast optics. These exotic optical properties indicate that InAs NWs have significant potential for various optoelectronic and photonic devices, especially in the mid-infrared wavelength range.Item Low‐Power Continuous‐Wave Second Harmonic Generation in Semiconductor Nanowires(2018-10) Yuan, Qingchen; Fang, Liang; Yang, He; Gan, Xuetao; Khayrudinov, Vladislav; Lipsanen, Harri; Sun, Zhipei; Zhao, Jianlin; Northwestern Polytechnical University; Department of Electronics and Nanoengineering; Centre of Excellence in Quantum Technology, QTFSemiconductor nanowires (NWs) are promising for realizing various on‐chip nonlinear optical devices, due to their nanoscale lateral confinement and strong light–matter interaction. However, high‐intensity pulsed pump lasers are typically needed to exploit their optical nonlinearity because light couples poorly with nanometric‐size wires. Here, microwatts continuous‐wave light pumped second harmonic generation (SHG) in AlGaAs NWs is demonstrated by integrating them with silicon planar photonic crystal cavities. Light–NW coupling is enhanced effectively by the extremely localized cavity mode at the subwavelength scale. Strong SHG is obtained even with a continuous‐wave laser excitation with a pump power down to urn:x-wiley:18638880:media:lpor201800126:lpor201800126-math-0001W, and the cavity‐enhancement factor is estimated around 150. Additionally, in the integrated device, the NW's SHG is more than two orders of magnitude stronger than third harmonic generations in the silicon slab, though the NW only couples with less than 1% of the cavity mode. This significantly reduced power requirement of NW's nonlinear frequency conversion would promote NW‐based building blocks for nonlinear optics, especially in chip‐integrated coherent light sources, entangled photon pairs and signal processing devices.Item Monolithic Saturable Absorber with Gallium Arsenide Nanowires Integrated on the Flexible Substrate for Optical Pulse Generation(MDPI AG, 2023-09) Zhao, Yifan; Yang, He; Khayrudinov, Vladislav; Lipsanen, Harri; Su, Xinyang; Qi, Mei; Lu, Baole; Song, Ningfang; Beihang University; Department of Electronics and Nanoengineering; Beijing Jiaotong University; Northwest UniversityIn this work, we demonstrated a kind of flexibly monolithic saturable absorber (SA) with GaAs nanowires (NWs) on polyimide (PI) plastic substrate for broadband optical modulation at 1.0 and 1.5 µm, separately. The monolithic SA sample was prepared by the metalorganic vapor phase epitaxy (MOVPE) method. The crystal structure and element analysis were examined carefully by high-resolution scanning transmission electron microscopy (HRSTEM) and energy-dispersive X-ray spectroscopy (EDX). We observed a high-density distribution of NWs on the flexible substrate by scanning electron microscopy (SEM). In addition, linear and nonlinear optical properties of the sample were examined by testing the photoluminescence and absorption properties, which showed its potential application as an optical switch due to the pure semiconducting properties. After the characterizations, we experimentally demonstrated this monolithic SA for laser modulation at 1.0 and 1.5 µm, which yielded the minimum optical pulse widths of 1.531 and 6.232 µs, respectively. Our work demonstrated such a kind of monolithic flexible NW substrate-integrated device used for broadband optical modulation, which not only eased the integration process of NWs onto the fiber endface, but also proved the potential of easily integrating with more semiconducting nanomaterials (e.g., graphene, MoS2, …) to realize monolithic active flexible photonic systems, such as a microscale phase modulator, delay-line, and so on, paving an easy avenue for the development of both active and flexible photonic devices.Item Nanowire network–based multifunctional all-optical logic gates(2018-07-27) Yang, He; Khayrudinov, Vladislav; Dhaka, Veer; Jiang, Hua; Autere, Anton; Jussila, Henri; Lipsanen, Harri; Sun, Zhipei; Department of Electronics and Nanoengineering; Department of Applied Physics; Aalto Nanofab; NanoMaterials; Centre of Excellence in Quantum Technology, QTF; Harri Lipsanen Group; Zhipei Sun GroupAll-optical nanoscale logic components are highly desired for various applications because light may enable logic functions to be performed extremely quickly without the generation of heat and cross-talk. All-optical computing at nanoscale is therefore a promising alternative but requires the development of a complete toolbox capable of various logic functionalities. We demonstrate nanoscale all-optical switches by exploiting the polarization-dependent light emission property of crossbar InP and AlGaAs nanowire networks. These networks can perform various logic operations, such as AND, OR, NAND, and NOR binary logic functions. Furthermore, on the basis of these logic operations, our networks successfully enable all-optical arithmetic binary calculations, such as n-bit addition, to be conducted. Our results underscore the promise of assembled semiconductor nanowire networks as a building block of on-chip all-optical logic components for future nanophotonics.Item New Approach for Thickness Determination of Solution-Deposited Graphene Thin Films(2017-06-30) Jussila, Henri; Albrow-Owen, Tom; Yang, He; Hu, Guohua; Aksimsek, Sinan; Granqvist, Niko; Lipsanen, Harri; Howe, Richard C.T.; Sun, Zhipei; Hasan, Tawfique; Department of Electronics and Nanoengineering; Harri Lipsanen Group; Zhipei Sun Group; University of Cambridge; BioNavis LtdSolution processing-based fabrication techniques such as liquid phase exfoliation may enable economically feasible utilization of graphene and related nanomaterials in real-world devices in the near future. However, measurement of the thickness of the thin film structures fabricated by these approaches remains a significant challenge. By using surface plasmon resonance (SPR), a simple, accurate, and quick measurement of the deposited thickness for inkjet-printed graphene thin films is reported here. We show that the SPR technique is convenient and well-suited for the measurement of thin films formulated from nanomaterial inks, even at sub-10 nm thickness. We also demonstrate that the analysis required to obtain results from the SPR measurements is significantly reduced compared to that required for atomic force microscopy (AFM) or stylus profilometer, and much less open to interpretation. The gathered data implies that the film thickness increases linearly with increasing number of printing repetitions. In addition, SPR also reveals the complex refractive index of the printed thin films composed of exfoliated graphene flakes, providing a more rigorous explanation of the optical absorption than that provided by a combination of AFM/profilometer and the extinction coefficient of mechanically exfoliated graphene flakes. Our results suggest that the SPR method may provide a new pathway for the thickness measurement of thin films fabricated from any nanomaterial containing inks.Item Nonlinear optical absorption properties of InP nanowires and applications as a saturable absorber(OPTICAL SOC AMER, 2020-06-01) Liu, Junting; Nie, Hongkun; Yan, Bingzheng; Yang, Kejian; Yang, He; Khayrudinov, Vladislav; Lipsanen, Harri; Zhang, Baitao; He, Jingliang; Shandong University; Centre of Excellence in Quantum Technology, QTF; Department of Electronics and Nanoengineering; Harri Lipsanen GroupIndium phosphide (InP) nanowires (NWs) have attracted significant attention due to their exotic properties that are different from the bulk counterparts, and have been widely used for light generation, amplification, detection, modulation, and switching, etc. Here, high-quality InP NWs were directly grown on a quartz substrate by the Au-nanoparticle assisted vapor-liquid-solid method. We thoroughly studied their nonlinear optical absorption properties at 1.06 mu m by the open-aperture Z-scan method. Interestingly, a transition phenomenon from saturable absorption (SA) to reverse saturable absorption (RSA) was observed with the increase of the incident laser intensity. In the analysis, we found that the effective nonlinear absorption coefficient (beta(eff) similar to -10(2) cm/MW) under the SA process was 3 orders of magnitude larger than that during the RSA processes. Furthermore, the SA properties of InP NWs were experimentally verified by using them as a saturable absorber for a passively Q-switched Nd:YVO4solid-state laser at 1.06 mu m, where the shortest pulse width of 462 ns and largest single pulse energy of 1.32 mu J were obtained. Moreover, the ultrafast carrier relaxation dynamics were basically studied, and the intraband and inter-band ultrafast carrier relaxation times of 8.1 and 63.8 ps, respectively, were measured by a degenerate pump-probe method with the probe laser of 800 nm. These results well demonstrate the nonlinear optical absorption properties, which show the excellent light manipulating capabilities of InP NWs and pave a way for their applications in ultrafast nanophotonic devices. (C) 2020 Chinese Laser PressItem Nonlinear optical response of strain-mediated gallium arsenide microwire in the near-infrared region(De Gruyter, 2024-05-03) Cui, Xiangpeng; Huo, Wenjun; Qiu, Linlu; Zhao, Likang; Wang, Junjie; Lou, Fei; Zhang, Shuaiyi; Khayrudinov, Vladislav; Tam, Wing Yim; Lipsanen, Harri; Yang, He; Wang, Xia; Department of Electronics and Nanoengineering; Harri Lipsanen GroupItem Optical harmonic generation in monolayer group-VI transition metal dichalcogenides(2018-09-17) Autere, Anton; Jussila, Henri; Marini, Andrea; Saavedra, J. R.M.; Dai, Yunyun; Säynätjoki, Antti; Karvonen, Lasse; Yang, He; Amirsolaimani, Babak; Norwood, Robert A.; Peyghambarian, Nasser; Lipsanen, Harri; Kieu, Khanh; De Abajo, F. Javier García; Sun, Zhipei; Department of Electronics and Nanoengineering; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; Harri Lipsanen Group; Barcelona Institute of Science and Technology; University of Arizona; University of Eastern Finland; ICREAMonolayer transition metal dichalcogenides (TMDs) exhibit high nonlinear optical (NLO) susceptibilities. Experiments on MoS2 have indeed revealed very large second-order (χ(2)) and third-order (χ(3)) optical susceptibilities. However, third-harmonic generation results of other layered TMDs have not been reported. Furthermore, the reported χ(2) and χ(3) of MoS2 vary by several orders of magnitude, and a reliable quantitative comparison of optical nonlinearities across different TMDs has remained elusive. Here, we investigate second- and third-harmonic generation, and three-photon photoluminescence in TMDs. Specifically, we present an experimental study of χ(2) and χ(3) of four common TMD materials (MoS2, MoSe2, WS2, and WSe2) by placing different TMD flakes in close proximity to each other on a common substrate, allowing their NLO properties to be accurately obtained from a single measurement. χ(2) and χ(3) of the four monolayer TMDs have been compared, indicating that they exhibit distinct NLO responses. We further present theoretical simulations of these susceptibilities in qualitative agreement with the measurements. Our comparative studies of the NLO responses of different two-dimensional layered materials allow us to select the best candidates for atomic-scale nonlinear photonic applications, such as frequency conversion and all-optical signal processing.Item Optical properties and applications of anisotropic low-dimensional nanomaterials(Aalto University, 2018) Yang, He; Elektroniikan ja nanotekniikan laitos; Department of Electronics and Nanoengineering; Photonics; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Sun, Zhipei, Prof., Aalto University, Department of Electronics and Nanoengineering, FinlandThis thesis focuses on the optical properties and applications of low dimensional anisotropic nanomaterials, such as carbon nanotubes (CNTs), nanowires (NWs), black phosphorus (BP). The whole thesis can be divided by three main parts. The first part introduces the fabrication methods of various anisotropic nanomaterials. For instance, as-grown CNTs are synthesized and aligned as an array by a mechanical drawing method. As-grown NWs are aligned by a combing method, and our results show that >95% of the NWs are well aligned. Different from CNTs and NWs, BP has the intrinsic anisotropic optical response due to its anisotropic atomic structure. The mechanical exfoliation method for preparation of few-layer BP is presented, which is also applicable for other two-dimensional layered materials. The second part introduces the optical characterization methods of the nanomaterials studied in this thesis. Various polarization-dependent microscopes are introduced to characterize their anisotropic properties, such as polarized absorption/transmission spectroscopy, polarized Raman microscopy, polarization-resolved optical microscopy. These microscopes provide useful methods to verify the anisotropic optical response of these nanomaterials. The third part is the most important one in the thesis, which presents the optical applications of these anisotropic nanomaterials. Firstly, aligned CNTs are used in fiber laser systems to modulate the polarization state of the laser output, which shows excellent performance with the degree of polarization of 89.1% at 1 µm (87.5% at 1.5 µm) for linear polarization modulation. We also demonstrate four-wave mixing based photon-pair generation with CNTs. Secondly, photoluminescence of the combed nanowires is examined to be polarization dependent for multifunctional logic gates. We construct all-optical arithmetic devices with NWs, which provide new means for the realization of all-optical logic gates. Lastly, anisotropic two-dimensional nanomaterials (e.g., BP, ReS2, ReSe2) are studied to demonstrate their waveplate performance. Finally, I summarize the whole contents and give my personal outlook on the study of novel anisotropic nanomaterials to explore their applications in both photonic and optoelectronic fields.Item Passively Mode-Locked Solid-State Laser with Absorption Tunable Graphene Saturable Absorber Mirror(Institute of Electrical and Electronics Engineers, 2019-07-01) Wang, Yiran; Zhang, Baitao; Yang, He; Hou, Jia; Su, Xiancui; Sun, Zhipei; He, Jingliang; Department of Electronics and Nanoengineering; Department of Applied Physics; Centre of Excellence in Quantum Technology, QTF; Zhipei Sun Group; Shandong University; Hangzhou Dianzi University; Liaocheng UniversityTwo-dimensional layered materials have attracted huge interest in the generation of ultrafast laser for their excellent saturable absorption properties. However, it is still challenging to precisely control their saturable absorption properties. Here, by alternatively changing the electric field intensity on the surface of high-reflection mirror, we successfully control the nonlinear absorption properties (e.g., saturable fluence, modulation depth) of graphene-based saturable absorber mirrors (GSAM) at the optical telecommunication wavelength of 1.3 mu m and their applications in solid-state lasers for the first time. Modulation depth of 1.2% is obtained from a GSAM with deposition of a lambda/8 ( = 1.3 mu m) thick SiO2 layer between the monolayer graphene and a high-reflection mirror, while modulation depth is increased to 4.3% with a lambda/4 thick SiO2 layer insertion in another GSAM. Pulses with the duration of 20 ps (lambda/8 thick SiO2 insertion) and 7.4 ps (lambda/4 thick SiO2 insertion) are achieved, respectively, based on the two mirrors. Our results indicate that this method is easy and reliable to versatility modulate the saturable absorption properties of other two-dimensional layered materials beyond graphene for the generation of ultrafast solid-state lasers.Item Photon-Pair Generation with a 100 nm Thick Carbon Nanotube Film(2017-06-27) Lee, Kim Fook; Tian, Ying; Yang, He; Mustonen, Kimmo; Martinez, Amos; Dai, Qing; Kauppinen, Esko I.; Malowicki, John; Kumar, Prem; Sun, Zhipei; Department of Applied Physics; Department of Electronics and Nanoengineering; NanoMaterials; Zhipei Sun Group; Northwestern University; Aston University; National Center for Nanoscience and Technology Beijing; Air Force Research LaboratoryNonlinear optics based on bulk materials is the current technique of choice for quantum-state generation and information processing. Scaling of nonlinear optical quantum devices is of significant interest to enable quantum devices with high performance. However, it is challenging to scale the nonlinear optical devices down to the nanoscale dimension due to relatively small nonlinear optical response of traditional bulk materials. Here, correlated photon pairs are generated in the nanometer scale using a nonlinear optical device for the first time. The approach uses spontaneous four-wave mixing in a carbon nanotube film with extremely large Kerr-nonlinearity (≈100 000 times larger than that of the widely used silica), which is achieved through careful control of the tube diameter during the carbon nanotube growth. Photon pairs with a coincidence to accidental ratio of 18 at the telecom wavelength of 1.5 μm are generated at room temperature in a ≈100 nm thick carbon nanotube film device, i.e., 1000 times thinner than the smallest existing devices. These results are promising for future integrated nonlinear quantum devices (e.g., quantum emission and processing devices).Item Ultrafast carrier dynamics and nonlinear optical response of InAsP nanowires(OPTICAL SOC AMER, 2021-09-01) Liu, Junting; Yang, He; Khayrudinov, Vladislav; Lipsanen, Harri; Nie, Hongkun; Yang, Kejian; Zhang, Baitao; He, Jingliang; Department of Electronics and Nanoengineering; Harri Lipsanen Group; Shandong UniversityIndium arsenide phosphide (InAsP) nanowires (NWs), a member of the III -V semiconductor family, have been used in various photonic and optoelectronic applications thanks to their unique electrical and optical properties such as high carrier mobility and adjustable band gap. In this work, we synthesize InAsP NWs and further explore their nonlinear optical properties. The ultrafast carrier dynamics and nonlinear optical response are thoroughly studied based on the nondegenerate pump probe and Z-scan experimental measurements. Two different characteristic carrier lifetimes (similar to 2 and similar to 15 ps) from InAsP NWs are observed during the excited-carrier relaxation process. Based on the physical model analysis, the relaxation process can be ascribed to the carrier cooling process via carrier-phonon scattering and Auger recombination. In addition, based on the measured excited-carrier lifetime and Pauli-blocking principle, we discover that InAsP NWs show strong saturable absorption properties at the wavelengths of 532 and 1064 nm. Last, we demonstrate for the first time a femtosecond (similar to 426 fs) solid-state laser based on an InAsP NWs saturable absorber at 1.04 mu m. We believe that our work provides a better understanding of the InAsP NWs optical properties and will further advance their photonic applications in the near-infrared range. (C) 2021 Chinese Laser PressItem A Universal Pick-and-Place Assembly for Nanowires(WILEY-VCH VERLAG, 2022-09-22) Ali, Utku Emre; Yang, He; Khayrudinov, Vladislav; Modi, Gaurav; Cheng, Zengguang; Agarwal, Ritesh; Lipsanen, Harri; Bhaskaran, Harish; Department of Electronics and Nanoengineering; Harri Lipsanen Group; University of Oxford; Beihang University; University of PennsylvaniaWith the introduction of techniques to grow highly functional nanowires of exotic materials and demonstrations of their potential in new applications, techniques for depositing nanowires on functional platforms have been an area of active interest. However, difficulties in handling individual nanowires with high accuracy and reliability have so far been a limiting factor in large-scale integration of high-quality nanowires. Here, a technique is demonstrated to transfer single nanowires reliably on virtually any platform, under ambient conditions. Functional nanowires of InP, AlGaAs, and GeTe on various patterned structures such as electrodes, nanophotonic devices, and even ultrathin transmission electron microscopy (TEM) membranes are transferred. It is shown that the versatility of this technique further enables to perform on-chip nano-optomechanical measurements of an InP nanowire for the first time via evanescent field coupling. Thus, this technique facilitates effortless integration of single nanowires into applications that were previously seen as cumbersome or even impractical, spanning a wide range from TEM studies to in situ electrical, optical, and mechanical characterization.
