Few-layer Platinum Diselenide as a New Saturable Absorber for

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Functional Nanostructured Materials (including low-D carbon)

Few-layer Platinum Diselenide as a New Saturable Absorber for Ultrafast Fiber Lasers Jian Yuan, Haoran Mu, Lei Li, Yao Chen, Wenzhi Yu, Kai Zhang, Baoquan Sun, Shenghuang Lin, Shaojuan Li, and Qiaoliang Bao ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b03045 • Publication Date (Web): 30 May 2018 Downloaded from http://pubs.acs.org on May 31, 2018

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ACS Applied Materials & Interfaces

Few-layer Platinum Diselenide as a New Saturable Absorber for Ultrafast Fiber Lasers Jian Yuan

1, ∥

∥

∥

, Haoran Mu1,2 , Lei Li3, , Yao Chen1, Wenzhi Yu1, Kai Zhang 4,

Baoquan Sun 1，Shenghuang Lin1,5,*, Shaojuan Li1,* and Qiaoliang Bao1,2,* 1

Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory

for Carbon-Based Functional Materials and Devices, and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215123, People’s Republic of China 2

Department of Materials Science and Engineering, Monash University, Clayton,

Victoria 3800, Australia. 3

Jiangsu Key Laboratory of Advanced Laser Materials and Devices, School of

Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou, Jiangsu 221116, People’s Republic of China 4

CAS Key Laboratory of Nano-Bio Interface, i-Lab Suzhou Institute of Nano-Tech

and Nano-Bionics Chinese Academy of Sciences 398 Ruoshui Road, Suzhou 215123, Jiangsu, P. R. China 5

Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong,

P.R. China. KEYWORDS: 2D TMDs, Platinum Diselenide, Nonlinear optical property, Saturable absorbers, Mode-locked fiber laser,

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Abstract: A multilayer Platinum Diselenide (PtSe2) film was experimentally demonstrated as a new type of saturable absorber with the capability to deliver robust dissipative solitons in a passively mode-locked fiber laser. The PtSe2 film synthesized by chemical vapor deposition was placed onto the ferule of a single mode optical fiber through a typical dry transfer process. The nonlinear optical measurements reveal efficient saturable absorption characteristics in terms of a large modulation depth (26%) and low saturable intensity (0.346 GW cm−2) at the wavelength of 1064 nm. An all-fiber ring cavity was built in which the PtSe2 film was sandwiched between two ferules as the saturable absorber and Ytterbium-doped fiber was used as the optical gain medium. Robust dissipative soliton pulses with a 3-dB spectral bandwidth of 2.0 nm and pulse duration of 470 ps centered at 1064.47 nm were successfully observed in the normal dispersion regime. Moreover, our mode-locked lasers also exhibit good long-term stability. Our finding suggests that multilayer PtSe2 may find potential applications in nonlinear optics and ultrafast photonics.


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1.

Introduction

Mode-locking technique based on saturable absorbers (SAs) has been proved to be one of the efficient techniques to realize ultrafast pulse generation since it has many merits such as good mechanical stability, high reliability, excellent beam quality, high power scalability, easy implementation, compactness and low cost. SAs have been extensively studied in bulk ion-doped crystals1 and semiconductors2, especially in semiconductor saturable absorption mirrors (SESAM)3 for over 20 years, but the fabrication process of SESAM is complicated and the price is expensive. More recently, two-dimensional (2D) materials, such as graphene4, 5, transition metal dichalcogenides (TMDs including MoS2, WS2, eg.)6, 7 and black phosphorus8, 9, have raised as a new family of SAs and attracted intensive research interests for developing new ultrafast photonic applications. Tremendous efforts have been implemented to fabricate the passively mode-locked pulse lasers employing 2D materials. In particular, graphene based SAs have been extensively studied and developed due to ultra-fast carrier dynamics at the picoseconds timescale10-12 and saturable absorption over a broad wavelength range from 1000 nm to 2500nm,13. However, the absorption coefficient in graphene is relatively low (e.g., 2.3% per layer) due to zero band gap, which has impressed certain limitations for photonic applications in which a strong light-matter interaction is demanded. Fortunately, TMDCs with sizable bandgap and strong resonant optical absorption in specific wavelengths are making up the shortage of graphene14. For example, H. Zhang et al. demonstrated mode-locked pulse generation centered at 1054.3 nm (bandwidth: 2.7 nm, pulse duration: 800 ps) using MoS2 as the saturable absorber.6 Reza Khazaeinezhad et al. revealed that a mode-locked fiber laser with multilayer MoS2 film as the saturable absorber can achieve a relatively large bandwidth of 12.38 nm at the center laser wavelength of 1568 nm.15. Most recently, Z. Luo et al. reported pico-second pulse generation (pulse duration: 1.45 ps, signal-to-noise ratio: 61.5 dB) at 1558 nm by using few-layer MoSe2 as the saturable absorber.16 Nevertheless, from optical physics point of view, 2D materials with a small



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bandgap (~ 0.8 eV) are more suitable for infrared photonics and optical communication. However, previously reported TMDs SAs such as MoS2 and WS2 etc. have considerably large bandgaps (for example, monolayer MoS2: 1.78 eV; monolayer WS2: 1.84 eV; monolayer MoSe2: 1.5 eV; monolayer WSe2: 1.52 eV)17, 18. Consequently, the strong resonant absorption of these materials occurs at visible wavelengths.19, 20 However, fiber lasers usually operate at infra-wavelength (1064 nm to 2000 nm, corresponding to photon energies of 0.5 to 1 eV), in which the participation of interband optical transition in the “perfect crystals” of these materials are impossible. Relying on the atomic defects and resulting intermediate states in the bandgap of these materials, the mode-locking operation was demonstrated.

6, 15

However, the introduction of defects makes optical processes in the samples complex and nonlinear optical effects unreliable. Different from most of the members of 2D TMDs, platinum diselenide (PtSe2) has a semimetal to semiconductor transition when approaching monolayer thickness.21 Previous researches suggest that monolayer PtSe2 has an indirect band gap of 1.2 eV and bilayer PtSe2 has an indirect band gaps of 0.20 eV.22 To this point, the small bandgap of PtSe2 allows all photons in fiber lasers (with photon energies of 0.5 to 1 eV) jump directly from the valence band to conduction band, which results in robust saturable absorption and inherently stable mode-locking operation. Moreover, the results obtained from photoresponse experiments clearly indicate that it can be utilized as mid-infrared photo-active material with fast response and strong light absorption from visible to mid-infrared,23 which are highly desired for high frequency optoelectronics and ultrafast photonics at infrared wavelengths. As compare to extensively studied MoS2 and WS2 SAs, the saturable absorption of the 2D PtSe2 have not been investigated yet, it is nontrivial to investigate the nonlinear absorption properties in 2D PtSe2 and develop ultrafast laser applications. In this article, the saturable absorption of few-layer PtSe2 was discovered and characterized. According to the nonlinear optical measurements, a large modulation depth and a relatively low saturable intensity were observed in a few nanometer thick PtSe2 film, which underpins the potential application for mode-locked pulse lasers. By incorporating few-layer PtSe2 film into Ytterbium-doped fiber laser, stable ACS Paragon Plus Environment

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mode-locking state was realized. And pico-second ultrafast pulses were obtained with a large SNR of over 50 dB.

2.

RESULTS AND DISCUSSION As indicated by previous studies, the PtSe2 belongs to the D33d (P3m1) space

group with the CdI2-type trigonal (1T) structure. The crystal structure of PtSe2 is shown in Figure 1a, in which one layer of Pt atoms are sandwiched between two layers of Se atoms.21 As shown in the schematic diagram of Figure 1b, few-layer PtSe2 film was successfully synthesized via chemical vapor deposition (CVD) inside a double heating zone furnace. A platinum (Pt) film was pre-deposited onto a SiO2/Si substrate (with 300 nm oxide) via electron beam evaporation. The SiO2/Si substrate with Pt film was located at the downstream of the quartz tube with high heating temperature. And 180 mg selenium (Se, 99.997%; Alfa Aesar) powder was filled in a crucible at the upstream of low-temperature heating zone in the quartz tube. After that, the carrier gas (argon) was purged into the furnace to remove the residual air before carrying out the experiment. When the temperature of the Pt film at the downstream reached 450 oC, the Se powder was immediately heated to 245 oC. Then the temperature of Pt/SiO2/Si substrate was kept at 450 oC for 2 hours to form PtSe2 film. Figure 1c shows a representative optical image of the as-produced few-layer PtSe2 film. The inset of Figure 1c depicts the morphology of PtSe2 film characterized by atomic force microscopy (AFM). The line profile of the flake reveals that the thickness is ~10 nm, corresponding to ~20 atomic layers. To investigate the crystalline property of the obtained samples, X-ray diffraction (XRD) technique was employed and the corresponding XRD patterns can be found in Figure 1d. It can be seen that the PtSe2 film possesses one pronounced peak located at 2θ =17.2° and two small diffraction peaks at around 2θ =33.5° and 2θ =52.5° corresponding to the (0 0 1), (0 0 2) and (0 0 3) crystal planes respectively, which agrees very well with the previous reports on few-layer PtSe2, 24-26 revealing the 2D nature of the PtSe2 film. Furthermore, Raman spectroscope equipped with a 633 nm



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laser was also utilized to identify and characterize the PtSe2 layer (Figure 1e). The Raman spectrum of the PtSe2 film reveals two feature peaks located at ~176 cm−1 and ~210 cm−1. The peak centered at ~176 cm-1 is attributed to the Eg in-plane vibration mode of Se atoms moving away from each other within the layer, and the peak centered at ∼210 cm−1 corresponds to the A1g out-of-plane vibration mode of Se atoms in opposing directions, similar to other 1T structure materials such as HfS2, ZrS2 and CdI2.27, 28 The distribution of the ratio of Pt and Se atoms for PtSe2 sample has also been studied by X-ray photoelectron spectroscopy (XPS). The corresponding spectra of the Pt 4f and Se 3d regions are displayed in Figure 1f, suggesting a high chemical purity. The binding energies for the Pt 4f7/2 and 4f5/2 are located at ~72.95 eV and ~76.32 eV and the binding energies for the Se 3d5/2 and Se 3d3/2 are located at 54.23 and 55.14 eV, respectively, in consistent with the reported values for PtSe2.26 The atomic ratio of Pt/Se can be calculated by using the formula of APt4f and ASe3d are the areas of Pt corresponding sensitive factors.

26, 29

4f

and Se

୬(୔୲) ୬(ୗୣ) 3d

=(

஺ು೟ర೑ ௌು೟ర೑

஺ೄ೐య೏

)/(

ௌೄ೐య೏

), where

peaks, SPt4f and SSe3d are the

Accordingly, the calculated relative atomic ratio

of Pt/Se is ~ 0.48 (~1: 2), suggesting a nearly complete transformation from Pt to the selenide. To further explore the atomic structure, crystallinity, and elemental composition of the PtSe2 films, the as-grown samples were transferred onto the copper grid using the poly (methyl methacrylate) (PMMA) assisted method and studied by a transmission electron microscopy (TEM), a bright-field scanning TEM (STEM), and energy-dispersive X-ray spectrum (EDS). Figure 2a depicts a typical TEM image for the studied continuous PtSe2 film and the inset exhibits its corresponding low-magnification TEM image. The high-resolution TEM (HRTEM) image (Figure 2b) of the studied PtSe2 nanosheet indicates that the crystal plane spacing of the sample is 0.261 nm, which corresponds to the (002) plane of PtSe2. Figure 2c shows the selected area electron diffraction (SAED) pattern of PtSe2 layer, which indicates that the obtained sample is polycrystalline. The three distinguished dash red circles ACS Paragon Plus Environment

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are assigned to (001), (101) and (002) planes with lattice spacings of 5.23, 2.79 and 2.61 Å, respectively, which is also consistent with our XRD result. Figure 2d shows the studied area for the STEM EDS (energy-dispersive X-ray spectroscopy) mapping of Pt and Se elements. The corresponding mapping images can be found in Figure 2g and f, which confirms that the studied sample really consists of Pt and Se elements, and the elemental uniformity of the as-grown PtSe2 film over the whole platelet. Notably, the STEM-EDS results as shown in Figure 2g and h also depict the film having the weight percent of Se is calculated to be 45.25%, and the relative atomic ratio of Pt/Se is about 0.49 (~1: 2), revealing a perfect match between the Pt and Se elements in the obtained sample. To study the optical properties (linear and nonlinear) of the PtSe2 film, the samples were transferred onto quartz substrates and measured by a UV-via-IR absorption spectrometer and an open aperture Z-scan system. Figure 3a shows the corresponding optical absorption spectrum. It is found that the PtSe2 film owns a strong light absorption over a wide wavelength range from 250 to 2200 nm, which fully covers the visible to near-infrared wavelengths. Figure 3b shows the open aperture Z-scan results measured at 1064 nm. The PtSe2 sample was placed on the Z-axis movement stage and when the sample was gradually approaching to the focus point (Z = 0), which means the incident light intensity was continually increased, the transmission rate of the PtSe2 sample was increasing. The dependence between transmission rate of the sample and the incident light intensity was thereby recorded, as shown by the blue dots in Figure 3b, where the typically optical saturable absorption phenomenon was observed. The nonlinear transmission curve with respect to the incident light intensity can also be directly provided by extracting the Z-scan experimental data, which was shown in Figure 3c. Through fitting by the following formula: 30, 31

α (I ) =

αS 1+ I / IS

+ α NS

(1)

where αS is the saturable component (referred to as modulation depth), αNS is the nonsaturable component, and Is is the saturation absorption intensity. The saturable ACS Paragon Plus Environment


intensity is calculated to be 0.346 GW cm-2 and the normalized modulation depth is 26%. To further confirm the saturable absorption characteristics, the balanced dual-detector measurements were also implemented. The details of the configurations can be found in previous works.32 Figure 3d shows the power-dependent nonlinear optical transmission data. While increasing the input power from low to high value (forward), the modulation depth is calculated to be 25.6% and the saturation intensity is 53.4 MW/cm2. While the input power was decreased from high to low value (backward), the modulation depth is 26.4% and the saturation intensity is 55.2 MW/cm2. The results from both forward and backward scanning of the power agree very well with each other, attesting to good stability and high optical damage threshold. Notably, the modulation depth of PtSe2 film is much higher than that of multilayered graphene (~8%) and MoS2 (~13.6%) at the same wavelength,4, 33 which indicates that the PtSe2 film can be used as a new nonlinear absorption material for pulse reshaping as that demonstrated in conventional saturable absorbers.6, 34 Then we investigated the mode-locking performance of PtSe2 SA by incorporating it into the ring cavity of a 1 µm fiber laser. The laser cavity we designed is schematically illustrated in Figure 4. The detailed setting up process is described in the experimental section. PtSe2 film was successfully transferred onto the cross-section of a single-mode fiber ferule through a standard dry transfer process with the aid of polystyrene (PS), as shown in the left inset of Figure 5a. Under the observation of the optical microscope (the right inset of Figure 5a), it can be seen that the surface topography of the PtSe2 SA is integrated and it fully covers the core area of the fiber end-facet. Before the measurement, the self-mode locking effect in the initial cavity, which could be possibly introduced by the polarization dependence of fiber components, should be excluded. The output characteristics of the laser cavity without the PtSe2 SA were checked. It is found that no mode-locking indication appeared under any polarization state while varying the pump power from low to very high value (~600 mW). However, once the PtSe2 saturable absorber was incorporated into the laser cavity, by slightly adjusting the intra-cavity polarization state, the mode-locked pulse generation was successfully obtained at a threshold pump power ACS Paragon Plus Environment

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of 115 mW. Subsequently, while increasing the pump power up to 286 mW, the mode-locked pulse generation was steadily obtained, as presented in Figure 5. The optical spectrum with steep edges in Figure 5a indicates that it is a typical dissipative soliton mode-locking state.35 The output spectrum reveals a central wavelength at 1064.47 nm with a 3-dB spectral bandwidth of 2 nm. As shown in Figure 5b, the repetition rate of the mode-locked pulse train is 4.08 MHz, in consistent with the cavity length (49.02 m). The pulse train in a large range is also displayed in the inset of Figure 5b, attesting to good stability. The single pulse envelope is depicted in Figure 5c. Through the fitting by Gaussian function35, it is calculated that the full width at half maximum (FWHM) of the single pulse, or so called pulse duration, is∼470 ps. The peak power is 4.9 W and the pulse energy is 2.31 nJ. The pulse chirping is calculated to be as large as 249.6. It has been suggested that a large pulse chirping is one of the characteristics of dissipative solitons, because the laser cavity should be all-normal dispersion and the soliton pulses are formed by the balance among the nonlinearity, optical gain, the cavity dispersion and optical loss.35 Figure 5d shows the radio-frequency (RF) spectrum of the mode-locked pulsesand a high signal-to-noise ratio (SNR) of 53 dB is observed. The corresponding wideband (0 to 300 MHz) radio frequency spectrum is depicted in the inset of Figure 5d, further confirming very stable operation regime of the laser output. The output power as a function of the input pump power is plotted in Figure 6a. As the pump power increased from 90 mW to 400 mW, the corresponding output power increases linearly from 1.04 to 12.19 mW, yielding a power conversion efficiency of around 3%. The relatively low output power under the mode-locking state is mainly due to the strong absorption of PtSe2. Nevertheless, it is noteworthy that the mode-locking state can be maintained while changing the pump power over a large range, suggesting robust mode-locking performance enabled by the PtSe2 saturable absorber. To investigate the long-term stability of our fiber lasers, the output spectra of the mode-locked dissipative soliton pulse were continuously monitored for 12-hours. The evolution of the central wavelength and the spectral bandwidth are shown in ACS Paragon Plus Environment


Figure 6b. It can be seen that the central wavelength slightly shifts from 1064.47 nm to 1064.49 nm and its 3-dB bandwidth has a relatively small variation from 1.99 to 2.06 nm. These results indicate that PtSe2 holds intriguing potential as a new type of nonlinear optical material for ultrafast and nonlinear optics.

3.

CONCLUSIONS In summary, both linear and nonlinear optical properties of few-layer PtSe2

prepared by chemical vapor deposition were studied. The saturable absorber based on PtSe2 film has a large modulation depth of 26% and a relatively low saturation intensity of 0.346 GW cm-2 at the near-infrared band. We have successfully demonstrated that PtSe2 film can be used as an efficient nonlinear absorption media to generate mode-locking pulses in an Ytterbium-doped fiber laser. The mode-locked pulse centered at 1064.47 nm has a pulse duration of 470 ps, a 3-dB spectral bandwidth of 2.0 nm, a repetition rate of 4.08 MHz and a SNR of 53 dB. Considering many attractive merits, it is anticipated that few-layer PtSe2 may find applications in ultrafast and nonlinear optics at even longer wavelength where a nonlinear absorption material is required.

EXPERIMENTAL SECTION Material Characterization The morphology and thickness of the PtSe2 was examined using optical microscopy (Leica, DM2700 M) and atomic force microscopy (AFM, Cypher S, Asylum Research). The crystal structure was investigated by X-ray diffraction (XRD, PANalytical, Empyrean) and the crystallinity was verified by transmission electron microscopy (TEM, FEI Tecnai F30, acceleration voltage: 200 kV). The chemical atomic ratio was measured by using X-ray photoelectron spectroscopy (Japan, ULTRA DLD). The Raman spectra were measured at 633 nm on a micro-Raman spectrometer (HORIBA JOBIN-YVON, LABRAM HR800). The estimated laser


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power reaching the sample is around 10 mW and a high magnification objective lens ( ×100, NA = 0.9) was used. The grating of the spectrometer has 1800 lines/mm. The linear optical absorption were measured on a UV–vis–NIR spectrometer (Lambda 750, Perkin Elmer). Z-scan Measurements. Z-scan measurements were performed to study the non-linear index and the non-linear absorption coefficient by using a femtosecond pulse laser. The few-layer PtSe2 sample under investigation was placed at Z-axis of the incident beam and moved along the light propagation direction. The transmittance of few-layer PtSe2 is defined as the ratio of the pulse energy passing the sample to the total incident pulse energy. The transmittance of few-layer PtSe2 sample changes since the irradiance is changing, while the sample is moving to or from the focus point (z=0). The details of the open-aperture Z-scan measurements were described in our previous report.30,35 Laser Performance Characterization. In the fiber laser cavity, an Ytterbium-doped fiber (THORLABS, Yb1200-4/125, 75 cm) was used as the gain medium, which was reversely pumped by a laser diode (975 LD, 975 nm) by a wavelength division multiplexer (WDM, 980/1060 nm). A polarization-independent isolator (ISO) was used to ensure the light propagation direction. A polarization controller (PC) is placed between the pump and saturable absorber to adjust the cavity polarization state as well as intracavity birefringence. A 10 dB port of a coupler was used to realize 10% output. The output time-domain profile and the frequency-domain spectra were simultaneously monitored by an optical spectrum analyzer (Yokogawa, AQ6370C) and an oscilloscope (Tektronix, MDO3104, 500 MHz), the output power was recorded by an optical power meter (EXFO, PM-1623).

ACKNOWLEDGEMENTS

We acknowledge the financial support from the National Natural Science Foundation of China (No. 61604102, 11404372, 51290273 and 91433107), National Key



Research & Development Program (No. 2016YFA0201902), Australian Research Council (FT150100450, CE170100039 and IH150100006), the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) and Collaborative Innovation Center of Suzhou Nano Science and Technology. Q. Bao acknowledges support from the MCN Tech Fellowship. H. Mu acknowledges the Monash Graduate Scholarship (MGS) and Monash International Postgraduate Research Scholarship (MIPRS) for his Ph.D. research.

AUTHOR INFORMATION

Corresponding Author Shaojuan Li, Qiaoliang Bao and Shenghuang Lin Tel: (+61)-3-99054927; Fax: (+86)-512-65882846; E-mail: [email protected], [email protected], [email protected] Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Jian Yuan, Haoran Mu and Lei Li contributed equally to this work.

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Figure 1. (a) The side view and top view of crystal structure of a monolayer PtSe2 (b) Schematic diagram of the PtSe2 film synthesis process using a vapor phase selenization method. (c) Optical micrograph of the PtSe2 film, scale bar is 20 um, AFM image is shown inset, scale bar is 5 um. (d)

XRD of PtSe2 measured at room

temperature. (e) The Raman spectra of PtSe2 under 633 nm laser. (f) The high-resolution XPS spectra of Pt 4f and Se 3d.



Figure 2. (a) TEM image of PtSe2 layer, The Low magnification TEM image of PtSe2 layer on TEM grid is shown in the inset, the scale bar is 500nm. (b) The high-resolution TEM image of PtSe2 layer. The scale bar is 2 nm. (c) The SAED image. (d) The corresponding Bright-field STEM image the rectangular region in (a). The scale bar is 20 nm. (e) and (f) are the corresponding Pt and Se elemental maps from the rectangular region in (d), respectively. The scale bar in (d) also applies to (e) and (f). (g) EDS spectrum and (h) the table of elemental ratio for PtSe2 layer.


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Figure 3. Optical characterizations of 10 nm PtSe2 layer. (a) UV-visible-NIR absorption spectrum of PtSe2 layer on quartz sheet. (b) Saturable absorption data measured by an open-aperture Z-scan at 1064 nm, (c) Nonlinear transmission curve of PtSe2

saturable absorber. (d) The power-dependent nonlinear optical transmission of

PtSe2 saturable absorber at 1064 nm obtained from dual-detector measurements.



Figure 4. Experimental setup of the Ytterbium -doped fiber laser ring cavity. WDM: Wavelength division multiplex. YDF: Ytterbium-doped fiber. PC: Polarization controller. Isolator: Polarization independent isolator.


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Figure 5. Laser mode-locking characteristics using the PtSe2 layer saturable absorber. (a) Optical spectra. Inset (right): Photograph of the fiber pigtail with a PtSe2 film coating on the fiber end facet. Inset (left): optical image of PtSe2 film covering on the core area of the fiber end facet. (b) The wide-band oscilloscope tracings. (c) Individual pulse profile. (d) RF spectral profile. Insert: the wideband RF spectrum. The pump power is 185mW.



Figure 6. (a) Output power as a function of pump power at 1064 nm. (b) Long-term stability of the mode-locked dissipative soliton.


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Table of Content graphic (TOC)

In this work, we experimentally demonstrate the use of multilayer platinum diselenide (PtSe2) film as a new type of saturable absorber. The PtSe2 film shows efficient saturable absorption characteristics with a modulation depth of 26% and saturable intensity about 0.346 GW cm−2 at the wavelength of 1064 nm. By inserting it into Ytterbium-doped fiber ring cavity, stable dissipative soliton pulses can be generated in the normal dispersion regime with a 3-dB spectral bandwidth of 2.0 nm, pulse duration of 470 ps centered at 1064.47 nm and good long-term stability. This work suggests that multilayer PtSe2 can be useful nonlinear optical material and may find important application in photonic devices.


Few-layer Platinum Diselenide as a New Saturable Absorber for

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