Browsing by Author "Li, Diao"

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  • Active synchronization and modulation of fiber lasers with a graphene electro-optic modulator
    (2018-08-01) Li, Diao; Xue, Hui; Wang, Yadong; Qi, Mei; Kim, Wonjae; Li, Changfeng; Riikonen, Juha; Ren, Zhaoyu; Bai, Jintao; Lipsanen, Harri; Sun, Zhipei
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We report the synchronization of two actively Q-switched fiber lasers operating at 1.5 μm and 2 μm with a shared broadband graphene electro-optic modulator. Two graphene monolayer sheets separated with a high-k HfO2 dielectric layer are configured to enable broadband light modulation. The graphene electro-optic modulator is shared by two optical fiber laser cavities (i.e., an erbium-doped fiber laser cavity and a thulium/holmium-codoped fiber laser cavity) to actively Q-switch the two lasers, resulting in stable synchronized pulses at 1.5 μm and 2 μm with a repetition rate ranging from 46 kHz to 56 kHz.
  • All-optical intensity modulator by polarization dependent graphene-microfiber waveguide
    (2017-09-29) Wang, Ruiduo; Li, Diao; Wu, Hao; Jiang, Man; Sun, Zhipei; Tian, Yonghui; Bai, Jintao; Ren, Zhaoyu
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We demonstrated all-optical intensity modulator based on polarization-dependent graphene-covered microfiber (GMF) waveguide. By controlling the polarization mode of incident light, a greatly adjustable enhanced interaction between the propagating light and the graphene can be obtained via the evanescent field of the microfiber. By employing 980-nm pump light and 1550-nm signal light in continuous wave, the strong light–graphene interaction enables a maximum modulation depth of ∼20.86 dB, and by pumping 980 nm wave pulses, we obtained the temporal response characteristics of signal light with modulation rate of 5.13 kHz. This all-optical intensity modulator is compatible with optical fiber systems, and features with ease of fabrication, and steerable high modulation depth, which show potential in graphene's applications such as all-optical switching and all-optical communications.
  • Broadband laser polarization control with aligned carbon nanotubes
    (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
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
  • Broadband synchronization of ultrafast pulse generation with double-walled carbon nanotubes
    (2023-08-02) Zheng, Jiancheng; Li, Diao; Liu, Peng; Cui, Xiaoqi; Zhang, Bin; Geng, Wei; Zhang, Qiang; Xu, Zhenyu; Kauppinen, Esko I.; Sun, Zhipei
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Double-walled carbon nanotubes have shown competitive properties in broadband optical pulse generation owning to the intrinsic electronic properties. Synchronization of ultrafast optical pulses in multiple wavelengths is a key technique for numerous applications, such as nonlinear frequency conversion, ultrafast pump-probe, coherent Raman scattering spectroscopy, coherent optical synthesis, etc. In this work, we demonstrate the mode-locking and synchronization of 1.55 μm pulses with 1 μm and 1.9 μm pulses via a single saturable absorber based on double-walled carbon nanotubes. The large optical nonlinearity and broadband optical absorption in the double-walled carbon nanotubes enable independent and synchronized mode-locking in >900 nm bandwidth. In addition, we present a creative concept to realize multi-wavelength synchronization from a single laser system. Our results demonstrate a straightforward and feasible approach towards pulse synchronization over ultra-broad bandwidth with flexible wavelength selection in the near-infrared region.
  • Chirality logic gates
    (2022-12-07) Zhang, Yi; Wang, Yadong; Dai, Yunyun; Bai, Xueyin; Hu, Xuerong; Du, Luojun; Hu, Hai; Yang, Xiaoxia; Li, Diao; Dai, Qing; Hasan, Tawfique; Sun, Zhipei
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The ever-growing demand for faster and more efficient data transfer and processing has brought optical computation strategies to the forefront of research in next-generation computing. Here, we report a universal computing approach with the chirality degree of freedom. By exploiting the crystal symmetry–enabled well-known chiral selection rules, we demonstrate the viability of the concept in bulk silica crystals and atomically thin semiconductors and create ultrafast (<100-fs) all-optical chirality logic gates (XNOR, NOR, AND, XOR, OR, and NAND) and a half adder. We also validate the unique advantages of chirality gates by realizing multiple gates with simultaneous operation in a single device and electrical control. Our first demonstrations of logic gates using chiral selection rules suggest that optical chirality could provide a powerful degree of freedom for future optical computing.
  • Direct Synthesis of Semiconducting Single-Walled Carbon Nanotubes Toward High-Performance Electronics
    (2023-07) Liu, Peng; Khan, Abu Taher; Ding, Er Xiong; Zhang, Qiang; Xu, Zhenyu; Bai, Xueyin; Wei, Nan; Tian, Ying; Li, Diao; Jiang, Hua; Lipsanen, Harri; Sun, Zhipei; Kauppinen, Esko I.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The large-scale synthesis of high-purity semiconducting single-walled carbon nanotubes (s-SWCNTs) plays a crucial role in fabricating high-performance and multiapplication-scenario electronics. This work develops a straightforward, continuous, and scalable method to synthesize high-purity and individual s-SWCNTs with small-diameters distribution (≈1 nm). It is believed that the water and carbon dioxide resulting from the decomposition of isopropanol act as oxidizing agents and selectively etch metallic SWCNTs, hence enhancing the production of s-SWCNTs. The performance of individual-SWCNTs field effect transistors confirms the high abundance of s-SWCNTs, presenting a mean mobility of 376 cm2 V−1 s−1 and a high mobility of 2725 cm2 V−1 s−1 with an on-current to off-current (Ion/Ioff) ratio as high as 2.51 × 107. Moreover, thin-film transistors based on the as-synthesized SWCNTs exhibit excellent performance with a mean mobility of 9.3 cm2 V−1 s−1 and Ion/Ioff ratio of 1.3× 105, respectively, verifying the enrichment of s-SWCNTs. This work presents a simple and feasible route for the sustainable synthesis of high-quality s-SWCNTs for electronic devices.
  • Gold Au(I)6 Clusters with Ligand-Derived Atomic Steric Locking: Multifunctional Optoelectrical Properties and Quantum Coherence
    (2023-04-18) Chandra, Sourov; Sciortino, Alice; Das, Susobhan; Ahmed, Faisal; Jana, Arijit; Roy, Jayoti; Li, Diao; Liljeström, Ville; Jiang, Hua; Johansson, Leena Sisko; Chen, Xi; Nonappa; Cannas, Marco; Pradeep, Thalappil; Peng, Bo; Ras, Robin H.A.; Sun, Zhipei; Ikkala, Olli; Messina, Fabrizio
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    An atomically precise ultrasmall Au(I)6 nanocluster where the six gold atoms are complexed by three sterically interlocking stabilizing ligands is reported, allowing a unique combination of efficient third harmonic generation (THG), intense photoluminescence quantum yield (35%), ultrafast quantum coherence, and electron accepting properties. The reaction of 6-(dibutylamino)-1,3,5-triazine-2,4-dithiol (TRZ) with HAuCl4 leads to complexation by thiolation. However, intriguingly, another reduction step is needed to form the centrosymmetric Au(I)6TRZ3 clusters with the multifunctional properties. Here, ascorbic acid is employed as a mild reducing agent, in contrast to the classic reducing agents, like NaBH4 and NaBH3CN, which often produce mixtures of clusters or gold nanoparticles. Such Au(I)6 nanocluster films produce very strong THG response, never observed for nanoclusters. The clusters also produce brilliant single and multiphoton luminescence with exceptional stability. Density functional theory calculations and femtosecond transient absorption studies suggest ultrafast ligand-to-metal charge transfer, quantum coherence with long decoherence time 200–300 fs, and fast propagation of excitation from the core to the surrounding solvent. Finally, novel electron-accepting ground state properties allow p-doping of 2D field-effect transistor devices. Summarizing, the potential of ultrasmall sterically interlocked Au(I) clusters, i.e., complexes allowed by the new sequential reduction protocol, towards multifunctional devices, fast photoswitches, and quantum colloidal devices is shown.
  • Hybrid Photodetection Mechanisms Tuned with Tunneling
    (2022) Yoon, Hoon Hahn; Fernandez, Henry A.; Nigmatulin, Fedor; Dai, Yunyun; Ahmed, Faisal; Cui, Xiaoqi; Bai, Xueyin; Li, Diao; Du, Mingde; Lipsanen, Harri; Sun, Zhipei
     A4 Artikkeli konferenssijulkaisussa
    In this paper, we report two strategies for realizing the hybrid photodetection mechanisms for high-performance broadband photodetectors built with tunable van der Waals (vdW) heterojunction interfaces. All electrically-controlled photoresponse tuned by the atomically-thin tunneling barrier and bandgap contrast across the vdW heterojunction interfaces can be used to adjust the tunneling resistance and suppress the dark current. Adjusting the hybrid photodetection through the switching operation can lead to an optimized optical switching ratio covering from the ultra-violet to the mid-infrared ranges. The representative device structures suitable for each strategy (1) naturally formed oxidation layer (2) energy band alignment, and their characterization exhibit how the hybrid gauge of the photodetection mechanisms can be tuned by quantum tunneling and charge trapping at the vdW heterointerfaces.
  • Nanoscale thickness Octave-spanning coherent supercontinuum light generation
    (2025) Das, Susobhan; Uddin, Md Gius; Li, Diao; Wang, Yadong; Dai, Yunyun; Toivonen, Juha; Hong, Hao; Liu, Kaihui; Sun, Zhipei
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    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.
  • On-chip photonics and optoelectronics with a van der Waals material dielectric platform
    (2022-07-07) Cui, Xiaoqi; Du, Mingde; Das, Susobhan; Yoon, Hoon Hahn; Pelgrin, Vincent Yves; Li, Diao; Sun, Zhipei
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    During the last few decades, photonic integrated circuits have increased dramatically, facilitating many high-performance applications, such as on-chip sensing, data processing, and inter-chip communications. The currently dominating material platforms (i.e., silicon, silicon nitride, lithium niobate, and indium phosphide), which have exhibited great application successes, however, suffer from their own disadvantages, such as the indirect bandgap of silicon for efficient light emission, and the compatibility challenges of indium phosphide with the silicon industry. Here, we report a new dielectric platform using nanostructured bulk van der Waals materials. On-chip light propagation, emission, and detection are demonstrated by taking advantage of different van der Waals materials. Low-loss passive waveguides with MoS2 and on-chip light sources and photodetectors with InSe have been realised. Our proof-of-concept demonstration of passive and active on-chip photonic components endorses van der Waals materials for offering a new dielectric platform with a large material-selection degree of freedom and unique properties toward close-to-atomic scale manufacture of on-chip photonic and optoelectronic devices.
  • Polarization and thickness dependent absorption properties of black phosphorus: New saturable absorber for ultrafast pulse generation
    (2015-10-30) Li, Diao; Jussila, Henri; Karvonen, Lasse; Ye, Guojun; Lipsanen, Harri; Chen, Xianhui; Sun, Zhipei
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Black phosphorus (BP) has recently been rediscovered as a new and interesting two-dimensional material due to its unique electronic and optical properties. Here, we study the linear and nonlinear optical properties of BP flakes. We observe that both the linear and nonlinear optical properties are anisotropic and can be tuned by the film thickness in BP, completely different from other typical two-dimensional layered materials (e.g., graphene and the most studied transition metal dichalcogenides). We then use the nonlinear optical properties of BP for ultrafast (pulse duration down to ∼786 fs in mode-locking) and large-energy (pulse energy up to >18 nJ in Q-switching) pulse generation in fiber lasers at the near-infrared telecommunication band ∼1.5 μ. We observe that the output of our BP based pulsed lasers is linearly polarized (with a degree-of-polarization ∼98% in mode-locking, >99% in Q-switching, respectively) due to the anisotropic optical property of BP. Our results underscore the relatively large optical nonlinearity of BP with unique polarization and thickness dependence, and its potential for polarized optical pulse generation, paving the way to BP based nonlinear and ultrafast photonic applications (e.g., ultrafast all-optical polarization switches/modulators, frequency converters etc.).
  • Polarization management in silicon photonics
    (2024) Shahwar, Dura; Yoon, Hoon Hahn; Akkanen, Suvi-Tuuli; Li, Diao; Muntaha, Sidra tul; Cherchi, Matteo; Aalto, Timo; Sun, Zhipei
     A2 Katsausartikkeli tieteellisessä aikakauslehdessä
    Polarization management plays a key role in various applications, such as optical communications, imaging, and sensing. It not only mitigates detrimental effects (e.g., polarization mode dispersion in optical communication) but also enables advanced functionalities, such as polarization multiplexing and optical isolation. Herein, we review the state-of-the-art approaches for on-chip polarization management. Additionally, we discuss strategies for developing non-reciprocal photonic devices and the challenges associated with monolithic integration in photonics circuits.
  • Scalable graphene electro-optical modulators for all-fibre pulsed lasers
    (2021-06-07) Lau, Kuen Yao; Pyymaki Perros, Alexander; Li, Diao; Kim, Maria; Sun, Zhipei
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Recently, graphene electro-optical modulators have emerged as a viable alternative to the conventional modulators due to their broadband operation, ultrafast responsivity, small footprint, and low energy consumption. Here, we report scalable graphene electro-optical modulators for all-fibre pulsed laser applications. An actively Q-switched all-fibre laser is demonstrated with a scalable graphene electro-optical modulator for the first time, which is different from the previously reported work that typically implemented graphene electro-optical modulators in a free-space optical system. Our electrically modulated actively Q-switched fibre laser outputs at the centre wavelength of ~1961.9 nm, the tunable repetition rate of 56.5 to 62.5 kHz, the maximum pulse energy of ~80 nJ, and the signal-to-noise ratio of ~46.6 dB. This work demonstrates that the scalable all-fibre integrated graphene electro-optical modulator approach is promising for producing pulsed fibre lasers at 2 µm with high performance and easy integration which are useful in various applications such as medical treatment, material processing, and spectroscopy. This journal is
  • Switchable Photoresponse Mechanisms Implemented in Single van der Waals Semiconductor/Metal Heterostructure
    (2022-01-25) Du, Mingde; Cui, Xiaoqi; Yoon, Hoon Hahn; Das, Susobhan; Uddin, Md; Du, Luojun; Li, Diao; Sun, Zhipei
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    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.
  • Synchronized triple-wavelength fiber lasers at 1, 1.55, and 1.9 µm
    (2023-05-15) Zheng, Jiancheng; Li, Diao; Liu, Peng; Cui, Xiaoqi; Geng, Wei; Zhang, Qiang; Xu, Zhenyu; Kauppinen, Esko I.; Sun, Zhipei
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Synchronized lasers working at different wavelengths are of great significance for numerous applications, such as high-energy femtosecond pulse emission, Raman microscopy, and precise timing distribution. Here, we report synchronized triple-wavelength fiber lasers working at 1, 1.55, and 1.9 µm, respectively, by combining the coupling and injection configurations. The laser system consists of three fiber resonators gained by ytterbium-doped fiber, erbium-doped fiber, and thulium-doped fiber, respectively. Ultrafast optical pulses formed in these resonators are obtained by passive mode-locking with the use of a carbon-nanotube saturable absorber. A maximum cavity mismatch of ∼1.4 mm is reached by the synchronized triple-wavelength fiber lasers in the synchronization regime by finely tuning the variable optical delay lines incorporated in the fiber cavities. In addition, we investigate the synchronization characteristics of a non-polarization-maintaining fiber laser in an injection configuration. Our results provide a new, to the best of our knowledge, perspective on multi-color synchronized ultrafast lasers with broad spectral coverage, high compactness, and a tunable repetition rate.
  • Temporal soliton dynamics of synchronised ultrafast fibre lasers
    (2023-09-25) Zheng, Jiancheng; Li, Diao; Cui, Xiaoqi; Liu, Peng; Zhang, Qiang; Zhu, Zhiwei; Yang, Song; Zhang, Yusheng; Sun, Jiaxing; Chen, Xianfeng; Haima, Yang; Kauppinen, Esko; Sun, Zhipei
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Synchronised ultrafast soliton lasers have attracted great research interest in recent decades. However, there is a lack of comprehensive understanding regarding the buildup mechanism of synchronised pulses. Here, we report a dynamic analysis of independent and synchronised solitons buildup mechanisms in synchronised ultrafast soliton lasers. The laser comprises an erbium-doped fibre cavity and a thulium-doped fibre cavity bridged with a common arm. Pulses operating at two different wavelengths formed in the cavities are synchronised by cross-phase modulation-induced soliton correlation in the common fibre arm. We find that the whole buildup process of the thulium-doped fibre laser successively undergoes five different stages: continuous wave, relaxation oscillation, quasi-mode-locking, continuous wave mode-locking and synchronised mode-locking. It is found that the starting time of the synchronised solitons is mainly determined by the meeting time of dual-color solitons. Our results will further deepen the understanding of dual-color synchronised lasers and enrich the study of complex nonlinear system dynamics.
  • Tunable Quantum Tunneling through a Graphene/Bi2Se3 Heterointerface for the Hybrid Photodetection Mechanism
    (2021-12-15) Yoon, Hoon Hahn; Ahmed, Faisal; Dai, Yunyun; Fernandez Pizarro, Henry; Cui, Xiaoqi; Bai, Xueyin; Li, Diao; Du, Mingde; Lipsanen, Harri; Sun, Zhipei
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Graphene-based van der Waals heterostructures are promising building blocks for broadband photodetection because of the gapless nature of graphene. However, their performance is mostly limited by the inevitable trade-off between low dark current and photocurrent generation. Here, we demonstrate a hybrid photodetection mode based on the photogating effect coupled with the photovoltaic effect via tunable quantum tunneling through the unique graphene/Bi2Se3 heterointerface. The tunneling junction formed between the semimetallic graphene and the topologically insulating Bi2Se3 exhibits asymmetric rectifying and hysteretic current-voltage characteristics, which significantly suppresses the dark current and enhances the photocurrent. The photocurrent-to-dark current ratio increases by about a factor of 10 with the electrical tuning of tunneling resistance for efficient light detection covering the major photonic spectral band from the visible to the mid-infrared ranges. Our findings provide a novel concept of using tunable quantum tunneling for highly sensitive broadband photodetection in mixed-dimensional van der Waals heterostructures.
  • Ultra-Broadband and Electro-Optical Tunable Absorption in Double-Walled Carbon Nanotubes
    (2024) Li, Diao; Ahmadi, Mohsen; Zhang, Qiang; Liu, Peng; Xu, Zhenyu; Wei, Nan; Kauppinen, Esko I.; Sun, Zhipei
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Electro-optical modulators are critical elements in the rapidly developing data communication, optical interconnects, silicon-based photonic systems and terahertz technologies. The limited optoelectronic properties and complicated material growth in traditional semiconductors hinder the rapidly surging demand for modulator performance, energy efficiency, cost, etc. The emergence of two-dimensional materials and one-dimensional carbon nanotubes in recent decades has brought new opportunities with their tremendous selection degree of freedom for exceptional optoelectronic properties. In this article, we present ultra-broadband and electro-optical tunable absorption modulators by employing double-walled carbon nanotube films in a capacitor geometry, spanning the visible to terahertz spectra. The formation of supercapacitors around the ionic gel electrolyte and carbon nanotube film interfaces accounts for the large carrier transition and optical conductivity change, which behaves a thickness dependent electroabsorption dynamics. Our findings not only broaden the understanding of low-dimensional material applications in electro-optics but also pave the way for future developments in high-performance broadband modulators.
  • Wavelength and pulse duration tunable ultrafast fiber laser mode-locked with carbon nanotubes
    (2018-02-09) Li, Diao; Jussila, Henri; Wang, Yadong; Hu, Guohua; Albrow-Owen, Tom; Howe, Richard C. T.; Ren, Zhaoyu; Bai, Jintao; Hasan, Tawfique; Sun, Zhipei
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Ultrafast lasers with tunable parameters in wavelength and time domains are the choice of light source for various applications such as spectroscopy and communication. Here, we report a wavelength and pulse-duration tunable mode-locked Erbium doped fiber laser with single wall carbon nanotube-based saturable absorber. An intra-cavity tunable filter is employed to continuously tune the output wavelength for 34 nm (from 1525 nm to 1559 nm) and pulse duration from 545 fs to 6.1 ps, respectively. Our results provide a novel light source for various applications requiring variable wavelength or pulse duration.
  • Widely-tunable harmonic mode-locked fiber laser by the combination of spectral filtering and gain management
    (2023-01) Yang, Song; Zheng, Jiancheng; Qi, Yaoyao; Shi, Yiwen; Li, Diao; Nie, Xuchen; Sun, Zhipei
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Controlled flexible ultrafast pulses are of great importance in many application fields, such as metrology. Here, we report a compact pulse width tunable passively harmonic mode-locked fiber laser by exploiting the combination effect of spectral filtering and gain management. The spectral filtering is achieved by adopting a bandwidth tunable filter, resulting in pulse width tunable and changing the harmonic order (i.e., repetition rate). On the other hand, gain management can tune the harmonic order, while the emission pulse width typically remains the same. Thus, a combination of these two effects can make the pulse width tunable in a broad range at a fixed repetition rate. At the 6th-order harmonic mode-locking (76.8 MHz), the pulse width can be tuned from ∼ 0.8 ps to 4.3 ps by adjusting the bandwidth and pump strength. The development of pulse width tunable laser sources at a high-repetition rate would find potential applications in fields such as optical sensing and biomedical imaging.