Susobhan Das

@aalto.fi

Postdoctoral Researcher
Aalto University



              

https://researchid.co/susobhan

RESEARCH INTERESTS

Nonlinear optics
2D-Materials
Nanophotonics
Plasmonics
Metamaterial
Electromagnetics
Optical Imaging

52

Scopus Publications

866

Scholar Citations

18

Scholar h-index

29

Scholar i10-index

Scopus Publications

  • Nanoscale thickness Octave-spanning coherent supercontinuum light generation
    Susobhan Das, Md Gius Uddin, Diao Li, Yadong Wang, Yunyun Dai, Juha Toivonen, Hao Hong, Kaihui Liu, and Zhipei Sun
    Springer Science and Business Media LLC
    AbstractCoherent broadband light generation has attracted massive attention due to its numerous applications ranging from metrology, sensing, and imaging to communication. In general, spectral broadening is realized via third-order and higher-order nonlinear optical processes (e.g., self-phase modulation, Raman transition, four-wave mixing, multiwave mixing), which are typically weak and thus require a long interaction length and the phase matching condition to enhance the efficient nonlinear light-matter interaction for broad-spectrum generation. Here, for the first time, we report octave-spanning coherent light generation at the nanometer scale enabled by a phase-matching-free frequency down-conversion process. Up to octave-spanning coherent light generation with a −40dB spectral width covering from ~565 to 1906 nm is demonstrated in discreate manner via difference-frequency generation, a second-order nonlinear process in gallium selenide and niobium oxide diiodide crystals at the 100-nanometer scale. Compared with conventional coherent broadband light sources based on bulk materials, our demonstration is ~5 orders of magnitude thinner and requires ~3 orders of magnitude lower excitation power. Our results open a new way to possibly create compact, versatile and integrated ultra-broadband light sources.

  • Enhanced Nonlinear Optical Responses in MoS<inf>2</inf> via Femtosecond Laser-Induced Defect-Engineering
    Suvi‐Tuuli M. Akkanen, Juan C. Arias‐Muñoz, Aleksei V. Emelianov, Kamila K. Mentel, Juhani V. Tammela, Mikko Partanen, Susobhan Das, Ahmed Faisal, Mika Pettersson, and Zhipei Sun
    Wiley
    Abstract2D materials are a promising platform for applications in many fields as they possess a plethora of useful properties that can be further optimized by careful engineering, for example, by defect introduction. While reliable high‐yield defect engineering methods are in demand, most current technologies are expensive, harsh, or non‐deterministic. Optical modification methods offer a cost‐effective and fast mechanism to engineer the properties of 2D materials at any step of the device fabrication process. In this paper, the nonlinear optical responses of mono‐, bi‐, and trilayer molybdenum disulfide (MoS2) flakes are enhanced by deterministic defect‐engineering with a femtosecond laser. A 50‐fold enhancement in the third harmonic generation (THG) and a 3.3‐fold increase in the second harmonic generation (SHG) in the optically modified areas is observed. The enhancement is attributed to resonant SHG and THG processes arising from optically introduced mid‐band gap defect states. These results demonstrate a highly controllable, sub‐micrometer resolution tool for enhancing the nonlinear optical responses in 2D materials, paving the way for prospective future applications in optoelectronics, quantum technologies, and energy solutions.

  • Light-Driven Multidirectional Bending in Artificial Muscles
    Zahra Madani, Pedro E. S. Silva, Hossein Baniasadi, Maija Vaara, Susobhan Das, Juan Camilo Arias, Jukka Seppälä, Zhipei Sun, and Jaana Vapaavuori
    Wiley
    AbstractUsing light to drive polymer actuators can enable spatially selective complex motions, offering a wealth of opportunities for wireless control of soft robotics and active textiles. Here, the integration of photothermal components is reported into shape memory polymer actuators. The fabricated twist‐coiled artificial muscles show on‐command multidirectional bending, which can be controlled by both the illumination intensity, as well as the chirality, of the prepared artificial muscles. Importantly, the direction in which these artificial muscles bend does not depend on intrinsic material characteristics. Instead, this directionality is achieved by localized untwisting of the actuator, driven by selective irradiation. The reaction times of this bending system are significantly – at least two orders of magnitude – faster than heliotropic biological systems, with a response time up to one second. The programmability of the artificial muscles is further demonstrated for selective, reversible, and sustained actuation when integrated in butterfly‐shaped textiles, along with the capacity to autonomously orient toward a light source. This functionality is maintained even on a rotating platform, with angular velocities of 6°/s, independent of the rotation direction. These attributes collectively represent a breakthrough in the field of artificial muscles, intended to adaptive shape‐changing soft systems and biomimetic technologies.

  • Interlayer Coupling Limit in Artificially Stacked MoS<inf>2</inf> Homojunctions
    Juan C. Arias‐Muñoz, Henri Kaaripuro, Yi Zhang, Susobhan Das, Henry A. Fernandez, and Zhipei Sun
    Wiley
    AbstractInterlayer interactions are one of the crucial parameters of two‐dimensional (2D) layered materials‐based junctions. Understanding the limits of interlayer coupling and defining the “maximum building block thickness” in artificially stacked 2D layered materials are key tasks that hold significant importance, not only in fundamental physics, but also in practical applications such as electronics, photonics, and optoelectronics. Here, the interlayer coupling limits are optically investigated of a model 2D layered semiconductor, MoS2, revealing the evolution of distinct interaction mechanisms between layers via artificial stacking. As the total thickness increases, a reduction in the stacking angle influence on the properties of the homojunctions is reflected in the photoluminescence and second harmonic generation responses. The results show that the effective coupling limit for vertically stacked 2D metamaterials resides in three‐layer flakes. The findings pave the way to advanced and complex devices of 2D superlattices for photonics and optoelectronics.

  • Broadband miniaturized spectrometers with a van der Waals tunnel diode
    Md Gius Uddin, Susobhan Das, Abde Mayeen Shafi, Lei Wang, Xiaoqi Cui, Fedor Nigmatulin, Faisal Ahmed, Andreas C. Liapis, Weiwei Cai, Zongyin Yang,et al.
    Springer Science and Business Media LLC
    AbstractMiniaturized spectrometers are of immense interest for various on-chip and implantable photonic and optoelectronic applications. State-of-the-art conventional spectrometer designs rely heavily on bulky dispersive components (such as gratings, photodetector arrays, and interferometric optics) to capture different input spectral components that increase their integration complexity. Here, we report a high-performance broadband spectrometer based on a simple and compact van der Waals heterostructure diode, leveraging a careful selection of active van der Waals materials- molybdenum disulfide and black phosphorus, their electrically tunable photoresponse, and advanced computational algorithms for spectral reconstruction. We achieve remarkably high peak wavelength accuracy of ~2 nanometers, and broad operation bandwidth spanning from ~500 to 1600 nanometers in a device with a ~ 30×20 μm2 footprint. This diode-based spectrometer scheme with broadband operation offers an attractive pathway for various applications, such as sensing, surveillance and spectral imaging.

  • Strain Engineering for Enhancing Carrier Mobility in MoTe<inf>2</inf> Field-Effect Transistors
    Abde Mayeen Shafi, Md Gius Uddin, Xiaoqi Cui, Fida Ali, Faisal Ahmed, Mohamed Radwan, Susobhan Das, Naveed Mehmood, Zhipei Sun, and Harri Lipsanen
    Wiley
    AbstractMolybdenum ditelluride (MoTe2) exhibits immense potential in post‐silicon electronics due to its bandgap comparable to silicon. Unlike other 2D materials, MoTe2 allows easy phase modulation and efficient carrier type control in electrical transport. However, its unstable nature and low‐carrier mobility limit practical implementation in devices. Here, a deterministic method is proposed to improve the performance of MoTe2 devices by inducing local tensile strain through substrate engineering and encapsulation processes. The approach involves creating hole arrays in the substrate and using atomic layer deposition grown Al2O3 as an additional back‐gate dielectric layer on SiO2. The MoTe2 channel is passivated with a thick layer of Al2O3 post‐fabrication. This structure significantly improves hole and electron mobilities in MoTe2 field‐effect transistors (FETs), approaching theoretical limits. Hole mobility up to 130 cm−2 V−1 s−1 and electron mobility up to 160 cm−2 V−1 s−1 are achieved. Introducing local tensile strain through the hole array enhances electron mobility by up to 6 times compared to the unstrained devices. Remarkably, the devices exhibit metal–insulator transition in MoTe2 FETs, with a well‐defined critical point. This study presents a novel technique to enhance carrier mobility in MoTe2 FETs, offering promising prospects for improving 2D material performance in electronic applications.

  • Gold Au(I)<inf>6</inf> Clusters with Ligand-Derived Atomic Steric Locking: Multifunctional Optoelectrical Properties and Quantum Coherence
    Sourov Chandra, Alice Sciortino, Susobhan Das, Faisal Ahmed, Arijit Jana, Jayoti Roy, Diao Li, Ville Liljeström, Hua Jiang, Leena‐Sisko Johansson,et al.
    Wiley

  • Coupling Effects in Transition Metal Dichalcogenide Homojunctions with Linear and Nonlinear Optical Spectroscopies
    Juan Arias Muñoz, Henri Kaaripuro, Yi Zhang, Susobhan Das, Andreas C. Liapis, and Zhipei Sun
    Optica Publishing Group
    We investigate artificially stacked few-layer MoS2 homojunctions with linear and nonlinear optical spectroscopies, observing various coupling effects in the layers.

  • Coupling Effects in Transition Metal Dichalcogenide Homojunctions with Linear and Nonlinear Optical Spectroscopies
    Juan Arias Muñoz, Henri Kaaripuro, Yi Zhang, Susobhan Das, Andreas C. Liapis, and Zhipei Sun
    Optica Publishing Group
    We investigate artificially stacked few-layer MoS2 homojunctions with linear and nonlinear optical spectroscopies, observing various coupling effects in the layers.


  • Coupling Effects in Transition M e t al Dichalcogenide Homojunctions with Linear and Nonlinear Optical Spectroscopies


  • Coherent modulation of chiral nonlinear optics with crystal symmetry
    Yi Zhang, Xueyin Bai, Juan Arias Muñoz, Yunyun Dai, Susobhan Das, Yadong Wang, and Zhipei Sun
    Springer Science and Business Media LLC
    AbstractLight modulation is of paramount importance for photonics and optoelectronics. Here we report all-optical coherent modulation of third-harmonic generation (THG) with chiral light via the symmetry enabled polarization selectivity. The concept is experimentally validated in monolayer materials (MoS2) with modulation depth approaching ~100%, ultra-fast modulation speed (&lt;~130 fs), and wavelength-independence features. Moreover, the power and polarization of the incident optical beams can be used to tune the output chirality and modulation performance. Major performance of our demonstration reaches the fundamental limits of optical modulation: near-unity modulation depth, instantaneous speed (ultra-fast coherent interaction), compact footprint (atomic thickness), and unlimited operation bandwidth, which hold an ideal optical modulation solution for emerging and future nonlinear optical applications (e.g., interconnection, imaging, computing, and quantum technologies).

  • Optical Control of High-Harmonic Generation at the Atomic Thickness
    Yadong Wang, Fadil Iyikanat, Xueyin Bai, Xuerong Hu, Susobhan Das, Yunyun Dai, Yi Zhang, Luojun Du, Shisheng Li, Harri Lipsanen,et al.
    American Chemical Society (ACS)
    High-harmonic generation (HHG), an extreme nonlinear optical phenomenon beyond the perturbation regime, is of great significance for various potential applications, such as high-energy ultrashort pulse generation with outstanding spatiotemporal coherence. However, efficient active control of HHG is still challenging due to the weak light–matter interaction displayed by currently known materials. Here, we demonstrate optically controlled HHG in monolayer semiconductors via the engineering of interband polarization. We find that HHG can be efficiently controlled in the excitonic spectral region with modulation depths up to 95% and ultrafast response speeds of several picoseconds. Quantitative time-domain theory of the nonlinear optical susceptibilities in monolayer semiconductors further corroborates these experimental observations. Our demonstration not only offers an in-depth understanding of HHG but also provides an effective approach toward active optical devices for strong-field physics and extreme nonlinear optics.

  • Direct Epitaxial Growth of InP Nanowires on MoS<inf>2</inf>with Strong Nonlinear Optical Response
    Abde Mayeen Shafi, Susobhan Das, Vladislav Khayrudinov, Er-Xiong Ding, Md Gius Uddin, Faisal Ahmed, Zhipei Sun, and Harri Lipsanen
    American Chemical Society (ACS)

  • Inducing Strong Light-Matter Coupling and Optical Anisotropy in Monolayer MoS<inf>2</inf> with High Refractive Index Nanowire
    Abde Mayeen Shafi, Faisal Ahmed, Henry A. Fernandez, Md Gius Uddin, Xiaoqi Cui, Susobhan Das, Yunyun Dai, Vladislav Khayrudinov, Hoon Hahn Yoon, Luojun Du,et al.
    American Chemical Society (ACS)
    Mixed-dimensional heterostructures combine the merits of materials of different dimensions; therefore, they represent an advantageous scenario for numerous technological advances. Such an approach can be exploited to tune the physical properties of two-dimensional (2D) layered materials to create unprecedented possibilities for anisotropic and high-performance photonic and optoelectronic devices. Here, we report a new strategy to engineer the light–matter interaction and symmetry of monolayer MoS2 by integrating it with one-dimensional (1D) AlGaAs nanowire (NW). Our results show that the photoluminescence (PL) intensity of MoS2 increases strongly in the mixed-dimensional structure because of electromagnetic field confinement in the 1D high refractive index semiconducting NW. Interestingly, the 1D NW breaks the 3-fold rotational symmetry of MoS2, which leads to a strong optical anisotropy of up to ∼60%. Our mixed-dimensional heterostructure-based phototransistors benefit from this and exhibit an improved optoelectronic device performance with marked anisotropic photoresponse behavior. Compared with bare MoS2 devices, our MoS2/NW devices show ∼5 times enhanced detectivity and ∼3 times higher photoresponsivity. Our results of engineering light–matter interaction and symmetry breaking provide a simple route to induce enhanced and anisotropic functionalities in 2D materials.

  • Engineering the Dipole Orientation and Symmetry Breaking with Mixed-Dimensional Heterostructures
    Md Gius Uddin, Susobhan Das, Abde Mayeen Shafi, Vladislav Khayrudinov, Faisal Ahmed, Henry Fernandez, Luojun Du, Harri Lipsanen, and Zhipei Sun
    Wiley
    Engineering of the dipole and the symmetry of materials plays an important role in fundamental research and technical applications. Here, a novel morphological manipulation strategy to engineer the dipole orientation and symmetry of 2D layered materials by integrating them with 1D nanowires (NWs) is reported. This 2D InSe -1D AlGaAs NW heterostructure example shows that the in-plane dipole moments in InSe can be engineered in the mixed-dimensional heterostructure to significantly enhance linear and nonlinear optical responses (e.g., photoluminescence, Raman, and second harmonic generation) with an enhancement factor of up to ≈12. Further, the 1D NW can break the threefold rotational symmetry of 2D InSe, leading to a strong optical anisotropy of up to ≈65%. These results of engineering dipole orientation and symmetry breaking with the mixed-dimensional heterostructures open a new path for photonic and optoelectronic applications.

  • On-chip photonics and optoelectronics with a van der Waals material dielectric platform
    Xiaoqi Cui, Mingde Du, Susobhan Das, Hoon Hahn Yoon, Vincent Yves Pelgrin, Diao Li, and Zhipei Sun
    Royal Society of Chemistry (RSC)
    On-chip dielectric platform using van der Waals materials is experimentally demonstrated for light propagation, emission, and detection, indicating its great potential for faster, smaller, and more efficient photonic integrated circuits.

  • Switchable Photoresponse Mechanisms Implemented in Single van der Waals Semiconductor/Metal Heterostructure
    Mingde Du, Xiaoqi Cui, Hoon Hahn Yoon, Susobhan Das, MD Gius Uddin, Luojun Du, Diao Li, and Zhipei Sun
    American Chemical Society (ACS)
    van der Waals (vdW) heterostructures based on two-dimensional (2D) semiconducting materials have been extensively studied for functional applications, and most of the reported devices work with sole mechanism. The emerging metallic 2D materials provide us new options for building functional vdW heterostructures via rational band engineering design. Here, we investigate the vdW semiconductor/metal heterostructure built with 2D semiconducting InSe and metallic 1T-phase NbTe2, whose electron affinity χInSe and work function ΦNbTe2 almost exactly align. Electrical characterization verifies exceptional diode-like rectification ratio of >103 for the InSe/NbTe2 heterostructure device. Further photocurrent mappings reveal the switchable photoresponse mechanisms of this heterostructure or, in other words, the alternative roles that metallic NbTe2 plays. Specifically, this heterostructure device works in a photovoltaic manner under reverse bias, whereas it turns to phototransistor with InSe channel and NbTe2 electrode under high forward bias. The switchable photoresponse mechanisms originate from the band alignment at the interface, where the band bending could be readily adjusted by the bias voltage. In addition, a conceptual optoelectronic logic gate is proposed based on the exclusive working mechanisms. Finally, the photodetection performance of this heterostructure is represented by an ultrahigh responsivity of ∼84 A/W to 532 nm laser. Our results demonstrate the valuable application of 2D metals in functional devices, as well as the potential of implementing photovoltaic device and phototransistor with single vdW heterostructure.

  • Probing Electronic States in Monolayer Semiconductors through Static and Transient Third-Harmonic Spectroscopies
    Yadong Wang, Fadil Iyikanat, Habib Rostami, Xueyin Bai, Xuerong Hu, Susobhan Das, Yunyun Dai, Luojun Du, Yi Zhang, Shisheng Li,et al.
    Wiley
    Electronic states and their dynamics are of critical importance for electronic and optoelectronic applications. Here, we probe various relevant electronic states in monolayer MoS2 , such as multiple excitonic Rydberg states and free-particle energy bands, with a high relative contrast of up to 200 via broadband (from ∼1.79 to 3.10 eV) static third-harmonic spectroscopy, which is further supported by theoretical calculations. Moreover, we introduce transient third-harmonic spectroscopy to demonstrate that third-harmonic generation can be all-optically modulated with a modulation depth exceeding ∼94% at ∼2.18 eV, providing direct evidence of dominant carrier relaxation processes, associated with carrier-exciton and carrier-phonon interactions. Our results indicate that static and transient third-harmonic spectroscopies are not only promising techniques for the characterization of monolayer semiconductors and their heterostructures, but also a potential platform for disruptive photonic and optoelectronic applications, including all-optical modulation and imaging. This article is protected by copyright. All rights reserved.

  • Ultrafast transient sub-bandgap absorption of monolayer MoS<inf>2</inf>
    Susobhan Das, Yadong Wang, Yunyun Dai, Shisheng Li, and Zhipei Sun
    Springer Science and Business Media LLC
    AbstractThe light–matter interaction in materials is of remarkable interest for various photonic and optoelectronic applications, which is intrinsically determined by the bandgap of the materials involved. To extend the applications beyond the bandgap limit, it is of great significance to study the light–matter interaction below the material bandgap. Here, we report the ultrafast transient absorption of monolayer molybdenum disulfide in its sub-bandgap region from ~0.86 µm to 1.4 µm. Even though this spectral range is below the bandgap, we observe a significant absorbance enhancement up to ~4.2% in the monolayer molybdenum disulfide (comparable to its absorption within the bandgap region) due to pump-induced absorption by the excited carrier states. The different rise times of the transient absorption at different wavelengths indicate the various contributions of the different carrier states (i.e., real carrier states in the short-wavelength region of ~&lt;1 µm, and exciton states in the long wavelength region of ~&gt;1 µm). Our results elucidate the fundamental understanding regarding the optical properties, excited carrier states, and carrier dynamics in the technologically important near-infrared region, which potentially leads to various photonic and optoelectronic applications (e.g., excited-state-based photodetectors and modulators) of two-dimensional materials and their heterostructures beyond their intrinsic bandgap limitations.

  • Giant All-Optical Modulation of Second-Harmonic Generation Mediated by Dark Excitons
    Yadong Wang, Susobhan Das, Fadil Iyikanat, Yunyun Dai, Shisheng Li, Xiangdong Guo, Xiaoxia Yang, Jinluo Cheng, Xuerong Hu, Masood Ghotbi,et al.
    American Chemical Society (ACS)
    All-optical control of nonlinear photonic processes in nanomaterials is of significant interest from a fundamental viewpoint and with regard to applications ranging from ultrafast data processing to spectroscopy and quantum technology. However, these applications rely on a high degree of control over the nonlinear response, which still remains elusive. Here, we demonstrate giant and broadband all-optical ultrafast modulation of second-harmonic generation (SHG) in monolayer transition-metal dichalcogenides mediated by the modified excitonic oscillation strength produced upon optical pumping. We reveal a dominant role of dark excitons to enhance SHG by up to a factor of ∼386 at room temperature, 2 orders of magnitude larger than the current state-of-the-art all-optical modulation results. The amplitude and sign of the observed SHG modulation can be adjusted over a broad spectral range spanning a few electronvolts with ultrafast response down to the sub-picosecond scale via different carrier dynamics. Our results not only introduce an efficient method to study intriguing exciton dynamics, but also reveal a new mechanism involving dark excitons to regulate all-optical nonlinear photonics.

  • Broadband Plasmon-Enhanced Four-Wave Mixing in Monolayer MoS<inf>2</inf>
    Yunyun Dai, Yadong Wang, Susobhan Das, Shisheng Li, Hui Xue, Ahmadi Mohsen, and Zhipei Sun
    American Chemical Society (ACS)
    Two-dimensional transition-metal dichalcogenide monolayers have remarkably large optical nonlinearity. However, the nonlinear optical conversion efficiency in monolayer transition-metal dichalcogenides is typically low due to small light–matter interaction length at the atomic thickness, which significantly obstructs their applications. Here, for the first time, we report broadband (up to ∼150 nm) enhancement of optical nonlinearity in monolayer MoS2 with plasmonic structures. Substantial enhancement of four-wave mixing is demonstrated with the enhancement factor up to three orders of magnitude for broadband frequency conversion, covering the major visible spectral region. The equivalent third-order nonlinearity of the hybrid MoS2-plasmonic structure is in the order of 10–17 m2/V2, far superior (∼10–100-times larger) to the widely used conventional bulk materials (e.g., LiNbO3, BBO) and nanomaterials (e.g., gold nanofilms). Such a considerable and broadband enhancement arises from the strongly confined electric field in the plasmonic structure, promising for numerous nonlinear photonic applications of two-dimensional materials.

  • Luminescent Gold Nanocluster-Methylcellulose Composite Optical Fibers with Low Attenuation Coefficient and High Photostability
    Ville Hynninen, Sourov Chandra, Susobhan Das, Mohammad Amini, Yunyun Dai, Sakari Lepikko, Pezhman Mohammadi, Sami Hietala, Robin H. A. Ras, Zhipei Sun,et al.
    Wiley
    Because of their lightweight structure, flexibility, and immunity to electromagnetic interference, polymer optical fibers (POFs) are used in numerous short-distance applications. Notably, the incorporation of luminescent nanomaterials in POFs offers optical amplification and sensing for advanced nanophotonics. However, conventional POFs suffer from nonsustainable components and processes. Furthermore, the traditionally used luminescent nanomaterials undergo photobleaching, oxidation, and they can be cytotoxic. Therefore, biopolymer-based optical fibers containing nontoxic luminescent nanomaterials are needed, with efficient and environmentally acceptable extrusion methods. Here, such an approach for fibers wet-spun from aqueous methylcellulose (MC) dispersions under ambient conditions is demonstrated. Further, the addition of either luminescent gold nanoclusters, rod-like cellulose nanocrystals or gold nanocluster-cellulose nanocrystal hybrids into the MC matrix furnishes strong and ductile composite fibers. Using cutback attenuation measurement, it is shown that the resulting fibers can act as short-distance optical fibers with a propagation loss as low as 1.47 dB cm-1 . The optical performance is on par with or even better than some of the previously reported biopolymeric optical fibers. The combination of excellent mechanical properties (Young's modulus and maximum strain values up to 8.4 GPa and 52%, respectively), low attenuation coefficient, and high photostability makes the MC-based composite fibers excellent candidates for multifunctional optical fibers and sensors.

  • Broadband Four-Wave Mixing Enhancement in 2D Transition-Metal Dichalcogenides Using Plasmonic Structures
    Yunyun Dai, Yadong Wang, Susobhan Das, Hui Xue, Mohsen Ahmadi, Shisheng Li, and Zhipei Sun
    IEEE
    Nanoscale nonlinear optics provides a host of fascinating phenomena ( e.g. , saturable absorption), remarkably useful for photonic applications. [1] - [3] Recently, two-dimensional (2D) transition-metal dichalcogenides (TMDs) have attracted tremendous interest due to their fascinating optical nonlinearity [4] - [6] , such as the gate-tunability, showing the great potential for diverse on-chip nonlinear optical devices. [7] However, the applications of TMDs are limited due to the low conversion efficiency at their atomic thickness. Plasmonics provides an excellent platform for enhancing light-matter interactions in TMDs, deserving further investigation (e.g., wave mixing).

  • Single-step chemical vapour deposition of anti-pyramid MoS<inf>2</inf>/WS<inf>2</inf>vertical heterostructures
    Xueyin Bai, Shisheng Li, Susobhan Das, Luojun Du, Yunyun Dai, Lide Yao, Ramesh Raju, Mingde Du, Harri Lipsanen, and Zhipei Sun
    Royal Society of Chemistry (RSC)
    Abnormal anti-pyramid MoS2/WS2 vertical heterostructures were synthesized by a facile single-step chemical vapour deposition.

RECENT SCHOLAR PUBLICATIONS

  • Nanoscale thickness Octave-spanning coherent supercontinuum light generation
    S Das, MG Uddin, D Li, Y Wang, Y Dai, J Toivonen, H Hong, K Liu, Z Sun
    Light: Science & Applications 14 (1), 41 2025

  • Enhanced Nonlinear Optical Responses in MoS2 via Femtosecond Laser‐Induced Defect‐Engineering
    STM Akkanen, JC Arias‐Muoz, AV Emelianov, KK Mentel, JV Tammela, ...
    Advanced Functional Materials 34 (46), 2406942 2024

  • Light‐Driven Multidirectional Bending in Artificial Muscles
    Z Madani, PES Silva, H Baniasadi, M Vaara, S Das, JC Arias, J Seppl, ...
    Advanced Materials 36 (38), 2405917 2024

  • Interlayer Coupling Limit in Artificially Stacked MoS2 Homojunctions
    JC Arias‐Muoz, H Kaaripuro, Y Zhang, S Das, HA Fernandez, Z Sun
    Advanced Functional Materials 34 (11), 2310365 2024

  • Broadband miniaturized spectrometers with a van der Waals tunnel diode
    MG Uddin, S Das, AM Shafi, L Wang, X Cui, F Nigmatulin, F Ahmed, ...
    Nature Communications 15 (1), 571 2024

  • Strain Engineering for Enhancing Carrier Mobility in MoTe2 Field‐Effect Transistors
    AM Shafi, MG Uddin, X Cui, F Ali, F Ahmed, M Radwan, S Das, ...
    Advanced Science 10 (29), 2303437 2023

  • Coupling Effects in Transition Metal Dichalcogenide Homojunctions with Linear and Nonlinear Optical Spectroscopies
    JA Muoz, H Kaaripuro, Y Zhang, S Das, AC Liapis, Z Sun
    CLEO: Applications and Technology, JW2A. 65 2023

  • Gold Au(I)6 Clusters with Ligand‐Derived Atomic Steric Locking: Multifunctional Optoelectrical Properties and Quantum Coherence
    S Chandra, A Sciortino, S Das, F Ahmed, A Jana, J Roy, D Li, V Liljestrm, ...
    Advanced Optical Materials 11 (8), 2202649 2023

  • Interlayer Coupling Limit in Artificially Stacked MoS
    JC Arias-Muoz, H Kaaripuro, Y Zhang, S Das, HA Fernandez, Z Sun
     2023

  • Polarization rotation using Molybdenum trioxide in 3 m SOI platform
    D Shahwar, S Das, MDG Uddin, M Cherchi, Z Sun, T Aalto
    EPJ Web of Conferences 287, 01010 2023

  • Sciences, Beijing Institute of Technology, Beijing 100081, China;? orcid. org/0000-0002-1186-1864 Yi Zhang-Department of Electronics and Nanoengineering, Aalto University
    Y Wang, F Iyikanat, X Bai, X Hu, S Das, Y Dai, Y Zhang, L Du, S Li, ...
    NANO LETTERS 2022

  • Optical control of high-harmonic generation at the atomic thickness
    Y Wang, F Iyikanat, X Bai, X Hu, S Das, Y Dai, Y Zhang, L Du, S Li, ...
    Nano Letters 22 (21), 8455-8462 2022

  • Direct Epitaxial Growth of InP Nanowires on MoS2 with Strong Nonlinear Optical Response
    AM Shafi, S Das, V Khayrudinov, EX Ding, MG Uddin, F Ahmed, Z Sun, ...
    Chemistry of Materials 34 (20), 9055-9061 2022

  • Coherent modulation of chiral nonlinear optics with crystal symmetry
    Y Zhang, X Bai, J Arias Muoz, Y Dai, S Das, Y Wang, Z Sun
    Light: Science & Applications 11 (1), 216 2022

  • Engineering the Dipole Orientation and Symmetry Breaking with Mixed‐Dimensional Heterostructures
    MG Uddin, S Das, AM Shafi, V Khayrudinov, F Ahmed, H Fernandez, L Du, ...
    Advanced Science 9 (20), 2200082 2022

  • Inducing Strong Light–Matter Coupling and Optical Anisotropy in Monolayer MoS2 with High Refractive Index Nanowire
    AM Shafi, F Ahmed, HA Fernandez, MG Uddin, X Cui, S Das, Y Dai, ...
    ACS applied materials & interfaces 14 (27), 31140-31147 2022

  • Switchable photoresponse mechanisms implemented in single van der Waals semiconductor/metal heterostructure
    M Du, X Cui, HH Yoon, S Das, MDG Uddin, L Du, D Li, Z Sun
    ACS nano 16 (1), 568-576 2022

  • On-chip photonics and optoelectronics with a van der Waals material dielectric platform
    X Cui, M Du, S Das, HH Yoon, VY Pelgrin, D Li, Z Sun
    Nanoscale 14 (26), 9459-9465 2022

  • Probing Electronic States in Monolayer Semiconductors through Static and Transient Third‐Harmonic Spectroscopies
    Y Wang, F Iyikanat, H Rostami, X Bai, X Hu, S Das, Y Dai, L Du, Y Zhang, ...
    Advanced Materials 34 (3), 2107104 2022

  • Broadband Plasmon-Enhanced Four-Wave Mixing in Monolayer MoS2
    Y Dai, Y Wang, S Das, S Li, H Xue, A Mohsen, Z Sun
    Nano Letters 21 (14), 6321-6327 2021

MOST CITED SCHOLAR PUBLICATIONS

  • Quantitative analysis of surface enhanced Raman spectroscopy of Rhodamine 6G using a composite graphene and plasmonic Au nanoparticle substrate
    R Goul, S Das, Q Liu, M Xin, R Lu, R Hui, JZ Wu
    Carbon 111, 386-392 2017
    Citations: 84

  • Complex refractive index tunability of graphene at 1550 nm wavelength
    F Xu, S Das, Y Gong, Q Liu, HC Chien, HY Chiu, J Wu, R Hui
    Applied Physics Letters 106 (3), 031109 2015
    Citations: 69

  • Ultrafast transient sub-bandgap absorption of monolayer MoS2
    S Das, Y Wang, Y Dai, S Li, Z Sun
    Light: Science & Applications 10 (1), 27 2021
    Citations: 53

  • Electrical Control of Interband Resonant Nonlinear Optics in Monolayer MoS2
    Y Dai, Y Wang, S Das, H Xue, X Bai, E Hulkko, G Zhang, X Yang, Q Dai, ...
    ACS nano 14 (7), 8442-8448 2020
    Citations: 51

  • Switchable photoresponse mechanisms implemented in single van der Waals semiconductor/metal heterostructure
    M Du, X Cui, HH Yoon, S Das, MDG Uddin, L Du, D Li, Z Sun
    ACS nano 16 (1), 568-576 2022
    Citations: 48

  • Near-infrared electro-optic modulator based on plasmonic graphene
    S Das, A Salandrino, JZ Wu, R Hui
    Optics letters 40 (7), 1516-1519 2015
    Citations: 45

  • Broadband Plasmon-Enhanced Four-Wave Mixing in Monolayer MoS2
    Y Dai, Y Wang, S Das, S Li, H Xue, A Mohsen, Z Sun
    Nano Letters 21 (14), 6321-6327 2021
    Citations: 39

  • Luminescent gold nanocluster‐methylcellulose composite optical fibers with low attenuation coefficient and high photostability
    V Hynninen, S Chandra, S Das, M Amini, Y Dai, S Lepikko, P Mohammadi, ...
    Small 17 (27), 2005205 2021
    Citations: 39

  • Nanobomb optical coherence elastography
    CH Liu, D Nevozhay, A Schill, M Singh, S Das, A Nair, Z Han, S Aglyamov, ...
    Optics letters 43 (9), 2006-2009 2018
    Citations: 34

  • Coherent modulation of chiral nonlinear optics with crystal symmetry
    Y Zhang, X Bai, J Arias Muoz, Y Dai, S Das, Y Wang, Z Sun
    Light: Science & Applications 11 (1), 216 2022
    Citations: 32

  • Broadband miniaturized spectrometers with a van der Waals tunnel diode
    MG Uddin, S Das, AM Shafi, L Wang, X Cui, F Nigmatulin, F Ahmed, ...
    Nature Communications 15 (1), 571 2024
    Citations: 24

  • Difference frequency generation in monolayer MoS 2
    Y Wang, M Ghotbi, S Das, Y Dai, S Li, X Hu, X Gan, J Zhao, Z Sun
    Nanoscale 12 (38), 19638-19643 2020
    Citations: 24

  • Nonappa
    S Chandra, A Sciortino, S Das, F Ahmed, A Jana, J Roy, D Li, V Liljestrm, ...
    Beaune, G, 1900620-1900629
    Citations: 24

  • Giant all-optical modulation of second-harmonic generation mediated by dark excitons
    Y Wang, S Das, F Iyikanat, Y Dai, S Li, X Guo, X Yang, J Cheng, X Hu, ...
    ACS photonics 8 (8), 2320-2328 2021
    Citations: 23

  • Longitudinal elastic wave imaging using nanobomb optical coherence elastography
    CH Liu, D Nevozhay, H Zhang, S Das, A Schill, M Singh, S Aglyamov, ...
    Optics letters 44 (12), 3162-3165 2019
    Citations: 21

  • Single-step chemical vapour deposition of anti-pyramid MoS 2/WS 2 vertical heterostructures
    X Bai, S Li, S Das, L Du, Y Dai, L Yao, R Raju, M Du, H Lipsanen, Z Sun
    Nanoscale 13 (8), 4537-4542 2021
    Citations: 19

  • Nanophotonic modal dichroism: mode-multiplexed modulators
    S Das, S Fardad, I Kim, J Rho, R Hui, A Salandrino
    Optics letters 41 (18), 4394-4397 2016
    Citations: 19

  • Theory and design of off-axis microring resonators for high-density on-chip photonic applications
    R Haldar, S Das, SK Varshney
    Journal of Lightwave Technology 31 (24), 3976-3986 2013
    Citations: 19

  • Optical control of high-harmonic generation at the atomic thickness
    Y Wang, F Iyikanat, X Bai, X Hu, S Das, Y Dai, Y Zhang, L Du, S Li, ...
    Nano Letters 22 (21), 8455-8462 2022
    Citations: 18

  • Engineering the Dipole Orientation and Symmetry Breaking with Mixed‐Dimensional Heterostructures
    MG Uddin, S Das, AM Shafi, V Khayrudinov, F Ahmed, H Fernandez, L Du, ...
    Advanced Science 9 (20), 2200082 2022
    Citations: 18