Germanium Nanosheets with Dirac Characteristics as a Saturable Absorber for Ultrafast Pulse Generation

Mu, Haoran; Liu, Yani; Bongu, Sudhakara Reddy; Bao, Xiaozhi; Li, Lei; Xiao, Si; Zhuang, Jincheng; Liu, Chen; Huang, Yongjun; Dong, Yong; Helmerson, Kristian; Wang, Jiaou; Liu, Guanyu; Du, Yi; Bao, Qiaoliang

doi:10.1002/adma.202101042

Cited by 46 publications

(38 citation statements)

References 74 publications

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“…Table 3 shows the nonlinear absorption and mode-locking parameters for the Ge thin-film and Ge nano-sheet SAs [ 63 ]. Although the modulation depth and nonlinear absorbance of the Ge thin-film in this work are slightly smaller than those of the Ge nano-sheet, the Ge thin-film still provides a larger SAM coefficient and smaller satu-rated intensity, demonstrating a shorter pulsewidth and wider 3 dB bandwidth.…”

Section: Resultsmentioning

confidence: 99%

Low-Temperature PECVD Growth of Germanium for Mode-Locking of Er-Doped Fiber Laser

et al. 2022

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A low-temperature plasma-enhanced chemical vapor deposition grown germanium (Ge) thin-film is employed as a nonlinear saturable absorber (SA). This Ge SA can passively mode-lock the erbium-doped fiber laser (EDFL) for soliton generation at a central wavelength of 1600 nm. The lift-off and transfer of the Ge film synthesized upon the SiO2/Si substrate are performed by buffered oxide etching and direct imprinting. The Ge film with a thickness of 200 nm exhibits its Raman peak at 297 cm−1, which both the nanocrystalline and polycrystalline Ge phases contribute to. In addition, the Ge thin-film is somewhat oxidized but still provides two primary crystal phases at the (111) and (311) orientations with corresponding diffraction ring radii of 0.317 and 0.173 nm, respectively. The nanocrystalline structure at (111) orientation with a corresponding d-spacing of 0.319 nm is also observed. The linear and nonlinear transmittances of the Ge thin-film are measured to show its self-amplitude modulation coefficient of 0.016. This is better than nano-scale charcoal and carbon-black SA particles for initiating the mode-locking at the first stage. After the Ge-based saturable absorber into the L-band EDFL system without using any polarized components, the narrowest pulsewidth and broadest linewidth of the soliton pulse are determined as 654.4 fs and 4.2 nm, respectively, with a corresponding time–bandwidth product of 0.32 under high pumping conditions.

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Section: Resultsmentioning

confidence: 99%

Low-Temperature PECVD Growth of Germanium for Mode-Locking of Er-Doped Fiber Laser

et al. 2022

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“…Furthermore, the all-optical modulation can be realized in simple configurations such as optical fibers or silicon waveguides, which have a miniature size for compact and integrated operation [165]. There are many different all-opticalmodulators till now, including saturable absorbers [166][167][168], polarization controllers [169,170], wavelength converters [171] and optical limiters [172]. The operation mechanisms of most of these devices are based on the strong optical nonlinearities of 2D materials (especially the third-order susceptibility).…”

Section: All-optical Modulatorsmentioning

confidence: 99%

Interface and surface engineering of black phosphorus: a review for optoelectronic and photonic applications

Yuan

et al. 2022

Mater. Futures

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Since being rediscovered as an emerging 2D material, BP with extraordinary energy structure and unusually strong interlayer interactions offer new opportunities for optoelectronics and photonics. However, due to the thin atomic body and the ease of degradation with water and oxides, BP is highly sensitive to the surrounding environment. Therefore, high-quality engineering of interfaces and surfaces plays an essential role in BP-based applications. In this review, begun with a review of properties of BP, different strategies of interface and surfaces engineering for high ON-OFF ratio, enhanced optical absorption, and fast optical response are reviewed and highlighted, and recent state-of-the-art advances on optoelectronic and photonic devices are demonstrated. Finally, the opportunities and challenges are outlooked for future BP-related research.

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“…First, novel metal nanomaterials such as 2D germanene, an allotrope of germanium as well as a kind of Dirac materials, have shown fast carrier relaxation time and large nonlinear absorption which can be considered as an excellent SA. [75] In 2021, Mu et al successfully employed germanene SA to achieve Q-switching, Qswitched mode-locking, and mode-locking at 1550 nm. [75] It is reasonable to infer that other metal nanomaterials with Dirac characteristics could also be applied to nonlinear optical applications.…”

Section: Challenges and Perspectivesmentioning

confidence: 99%

“…[75] In 2021, Mu et al successfully employed germanene SA to achieve Q-switching, Qswitched mode-locking, and mode-locking at 1550 nm. [75] It is reasonable to infer that other metal nanomaterials with Dirac characteristics could also be applied to nonlinear optical applications. Transparent glass matrices are promising media for MNP dispersion to achieve ultrafast operation because of their robustness and high transparency.…”

Section: Challenges and Perspectivesmentioning

confidence: 99%

“…Modulation depth and saturation intensity of MNPs can be regulated by modifying the number of layers and concentration of MNPs. [75,76] In 2012, Jiang et al first obtained Q-switched pulses with gold nanocrystal SA. [77] Recently, increasing related reports have emerged and further demonstrate the excellent properties of metal nanomaterials in ultrafast applications.…”

Section: Introductionmentioning

confidence: 99%

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Recent Advances and Challenges in Ultrafast Photonics Enabled by Metal Nanomaterials

Wang

Liu

Chao

et al. 2022

Advanced Optical Materials

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absorbers (SAs) are widely used to obtain ultrafast lasers. Mode-locking indicates a fixed phase between longitudinal modes in spectral domain, while Q-switching refers to the giant pulse formation due to the tunable Q factor of the laser cavity. Saturable absorption represents the optical modulation that absorption coefficient of SAs decreases with the increase of incident optical intensity, where SAs are often categorized into artificial and real SAs. [7][8][9] Artificial SAs mainly consist of nonlinear polarization evolution, [10,11] nonlinear optical loop mirrors, [12][13][14] and nonlinear amplification loop mirrors, [15,16] which fulfill the function of saturable absorption by means of nonlinear effects. By contrast, real SAs are characterized by the inherent nonlinear absorption property of the materials. Semiconductor saturable absorber mirror is a typical real SA and widely used in diverse lasers. However, several drawbacks such as complex fabrication and narrow operating bandwidth restrict its applications. [17][18][19][20][21] Under such circumstances, nanomaterials emerge as SAs of distinction where 2D nanomaterials have been widely investigated because of the unique optical properties induced by the energy band structures. [22][23][24][25][26][27][28] Graphene possesses zero bandgap and ultrafast carrier dynamics properties, contributing to a broad operating bandwidth and fast response time. [29][30][31][32][33][34][35][36] Nevertheless, the modulation depth of ≈2.3% per layer limits Nanomaterials with outstanding optical properties are widely used in ultrafast photonics. Especially, metal nanomaterials have attracted increasing attention in recent years owing to the surface plasmon resonance that further enhances their nonlinear optical response, making them suitable for generating ultrafast pulses in a wide range of wavebands. Herein, the fabrication and integration processes of typical metal nanomaterials such as gold, silver, and copper, as well as their applications in ultrafast lasers are reviewed. The synthesis methods of metal nanomaterials, which can be divided into dry and wet methods, are first introduced with their characteristics and advantages summarized. Moreover, the integration approaches that are used to incorporate metal nanomaterials into laser cavities are discussed, where sandwich structure based on polymer film and deposition method, as well as evanescent-wave structure based on D-shaped and tapered fiber are demonstrated. Besides, the state of the art of typical ultrafast lasers enabled by metal nanoparticles is systematically reviewed. Finally, current challenges and perspectives on the development of ultrafast photonics enabled by metal nanomaterials are proposed.

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Germanium Nanosheets with Dirac Characteristics as a Saturable Absorber for Ultrafast Pulse Generation

Cited by 46 publications

References 74 publications

Low-Temperature PECVD Growth of Germanium for Mode-Locking of Er-Doped Fiber Laser

Low-Temperature PECVD Growth of Germanium for Mode-Locking of Er-Doped Fiber Laser

Interface and surface engineering of black phosphorus: a review for optoelectronic and photonic applications

Recent Advances and Challenges in Ultrafast Photonics Enabled by Metal Nanomaterials

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