Nanoscale thickness Octave-spanning coherent supercontinuum light generation Susobhan Das, Md Gius Uddin, Diao Li, Yadong Wang, Yunyun Dai, et al. Light Science and Applications, 2025 Coherent 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.
Giant Multiphoton Luminescence and Band Renormalization with Hot Electron–Hole Plasma in Multilayer GaSe Yunyun Dai, Jorg Hader, Yi Zhang, Luojun Du, Henry Fernandez, et al. Advanced Optical Materials, 2025 Efficient photoluminescence (PL) of layered semiconductors is crucial for advancing next‐generation photonic devices. However, thermal effect‐induced destruction typically hinders the practical applications, such as biosensing and imaging. Here, the upconversion PL of multilayer GaSe is reported, which circumvents thermal damage. A high‐order multiphoton (up to 8‐photon) PL is first reported in multilayer GaSe. Both experimental and theoretical results reveal a power‐dependent redshift of the PL peak (≈40 meV, equivalent to 2% of the bandgap) and PL spectral broadening (full width at half maximum increased by ≈2 times), attributed to the hot electron–hole plasma. Time‐resolved PL resolves the multistage of carrier relaxation, revealing an ultrafast transition (≈58 ps) from electron–hole plasma to excitonic states, which establishes hot electron–hole plasma engineering as a critical mechanism for manipulating PL processes in Group‐III–VI chalcogenides. Furthermore, wavelength‐dependent two‐ and three‐photon PL spectra are explored. These results establish a microscopic framework connecting hot electron–hole plasma dynamics with macroscopic optoelectronic phenomena, providing critical insights for designing ultrafast photonic modulators and nonlinear optical devices based on 2D layered semiconductors.
Broadband miniaturized spectrometers with van der Waals junctions Md Gius Uddin, Susobhan Das, Abde Mayeen Shafi, Lei Wang, Xiaoqi Cui, et al. 9th IEEE Electron Devices Technology and Manufacturing Conference Shaping the Future with Innovations in Devices and Manufacturing Edtm 2025, 2025 Miniaturized spectrometers are crucial for applications in onchip and implantable devices, requiring high spectral resolution in limited spaces. Here, we present our van der Waals heterojunction-based spectrometers that achieve tunable spectral responses through band structure engineering, offering sub-nanometer wavelength resolution and a broad operational bandwidth of $\\sim 500$ to 1600 nanometers.
Enhanced Nonlinear Optical Responses in MoS2 via Femtosecond Laser-Induced Defect-Engineering Suvi‐Tuuli M. Akkanen, Juan C. Arias‐Muñoz, Aleksei V. Emelianov, Kamila K. Mentel, Juhani V. Tammela, et al. Advanced Functional Materials, 2024 2D 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, et al. Advanced Materials, 2024 Using 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 MoS2 Homojunctions Juan C. Arias‐Muñoz, Henri Kaaripuro, Yi Zhang, Susobhan Das, Henry A. Fernandez, et al. Advanced Functional Materials, 2024 Interlayer 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, et al. Nature Communications, 2024 Miniaturized 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 MoTe2 Field-Effect Transistors Abde Mayeen Shafi, Md Gius Uddin, Xiaoqi Cui, Fida Ali, Faisal Ahmed, et al. Advanced Science, 2023 Molybdenum 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.
Coupling Effects in Transition M e t al Dichalcogenide Homojunctions with Linear and Nonlinear Optical Spectroscopies 2023 Conference on Lasers and Electro Optics CLEO 2023, 2023
Giant Multiphoton Luminescence and Band Renormalization with Hot Electron–Hole Plasma in Multilayer GaSe Y Dai, J Hader, Y Zhang, L Du, H Fernandez, Y Wang, X Bai, Y Wang, ... Advanced Optical Materials, e01603 , 2025 2025 Citations: 1
Broadband Miniaturized Spectrometers with van der Waals Junctions MG Uddin, S Das, AM Shafi, L Wang, X Cui, F Nigmatulin, F Ahmed, ... 2025 9th IEEE Electron Devices Technology & Manufacturing Conference (EDTM), 1-3 , 2025 2025
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 2025 Citations: 14
Enhanced Nonlinear Optical Responses in MoS 2 via Femtosecond Laser‐Induced Defect‐Engineering STM Akkanen, JC Arias‐Muñoz, AV Emelianov, KK Mentel, JV Tammela, ... Advanced Functional Materials 34 (46), 2406942 , 2024 2024 Citations: 20
Light‐Driven Multidirectional Bending in Artificial Muscles Z Madani, PES Silva, H Baniasadi, M Vaara, S Das, JC Arias, J Seppälä, ... Advanced Materials 36 (38), 2405917 , 2024 2024 Citations: 33
Interlayer Coupling Limit in Artificially Stacked MoS 2 Homojunctions JC Arias‐Muñoz, H Kaaripuro, Y Zhang, S Das, HA Fernandez, Z Sun Advanced Functional Materials 34 (11), 2310365 , 2024 2024 Citations: 4
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 2024 Citations: 78
Strain Engineering for Enhancing Carrier Mobility in MoTe 2 Field‐Effect Transistors AM Shafi, MG Uddin, X Cui, F Ali, F Ahmed, M Radwan, S Das, ... Advanced Science 10 (29), 2303437 , 2023 2023 Citations: 33
Coupling Effects in Transition Metal Dichalcogenide Homojunctions with Linear and Nonlinear Optical Spectroscopies JA Muñoz, H Kaaripuro, Y Zhang, S Das, AC Liapis, Z Sun CLEO: Applications and Technology, JW2A. 65 , 2023 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 Liljeström, ... Advanced Optical Materials 11 (8), 2202649 , 2023 2023 Citations: 6
Polarization rotation using Molybdenum trioxide in 3 µm SOI platform D Shahwar, S Das, MDG Uddin, M Cherchi, Z Sun, T Aalto EPJ Web of Conferences 287, 01010 , 2023 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 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 2022 Citations: 31
Direct Epitaxial Growth of InP Nanowires on MoS 2 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 2022 Citations: 14
Coherent modulation of chiral nonlinear optics with crystal symmetry Y Zhang, X Bai, J Arias Muñoz, Y Dai, S Das, Y Wang, Z Sun Light: Science & Applications 11 (1), 216 , 2022 2022 Citations: 37
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 2022 Citations: 24
Inducing Strong Light–Matter Coupling and Optical Anisotropy in Monolayer MoS 2 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 2022 Citations: 22
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 2022 Citations: 61
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 2022 Citations: 17
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 2022 Citations: 20
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 2017.0 Citations: 93
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 2024.0 Citations: 78
Ultrafast transient sub-bandgap absorption of monolayer MoS 2 S Das, Y Wang, Y Dai, S Li, Z Sun Light: Science & Applications 10 (1), 27 , 2021 2021.0 Citations: 78
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 2015.0 Citations: 76
Electrical Control of Interband Resonant Nonlinear Optics in Monolayer MoS 2 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 2020.0 Citations: 63
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 2022.0 Citations: 61
Broadband Plasmon-Enhanced Four-Wave Mixing in Monolayer MoS 2 Y Dai, Y Wang, S Das, S Li, H Xue, A Mohsen, Z Sun Nano Letters 21 (14), 6321-6327 , 2021 2021.0 Citations: 54
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 2021.0 Citations: 53
Near-infrared electro-optic modulator based on plasmonic graphene S Das, A Salandrino, JZ Wu, R Hui Optics letters 40 (7), 1516-1519 , 2015 2015.0 Citations: 48
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 2018.0 Citations: 38
Coherent modulation of chiral nonlinear optics with crystal symmetry Y Zhang, X Bai, J Arias Muñoz, Y Dai, S Das, Y Wang, Z Sun Light: Science & Applications 11 (1), 216 , 2022 2022.0 Citations: 37
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 2021.0 Citations: 34
Light‐Driven Multidirectional Bending in Artificial Muscles Z Madani, PES Silva, H Baniasadi, M Vaara, S Das, JC Arias, J Seppälä, ... Advanced Materials 36 (38), 2405917 , 2024 2024.0 Citations: 33
Strain Engineering for Enhancing Carrier Mobility in MoTe 2 Field‐Effect Transistors AM Shafi, MG Uddin, X Cui, F Ali, F Ahmed, M Radwan, S Das, ... Advanced Science 10 (29), 2303437 , 2023 2023.0 Citations: 33
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 2022.0 Citations: 31
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 2020.0 Citations: 31
Nonappa S Chandra, A Sciortino, S Das, F Ahmed, A Jana, J Roy, D Li, V Liljeström, ... Beaune, G, 1900620-1900629 , 0 Citations: 28
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 2022.0 Citations: 24
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 2019.0 Citations: 24
Inducing Strong Light–Matter Coupling and Optical Anisotropy in Monolayer MoS 2 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 2022.0 Citations: 22
