Raman Mapping Characterization of All-Fiber CVD Monolayer Graphene Saturable Absorbers for Erbium-Doped Fiber Laser Mode Locking

Rosa, Henrique G.; Steinberg, David; Zapata, Juan D.; Saito, L. A. M.; Cárdenas, Álvaro E. Márquez; Gomes, José Carlos Viana; Souza, E. A. Thoroh de

doi:10.1109/jlt.2015.2467173

Cited by 24 publications

(4 citation statements)

References 36 publications

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“…For instance, the structural defects cause higher non-saturable loss, higher saturation intensity, and lower MD [138]. The defects of the graphene can be investigated through Raman mapping characteristics, in which higher defects level is associated with increased graphene layers [139].…”

Section: Graphenementioning

confidence: 99%

Recent research and advances of material-based saturable absorber in mode-locked fiber laser

Lau

Hou

2021

Optics & Laser Technology

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Section: Graphenementioning

confidence: 99%

Recent research and advances of material-based saturable absorber in mode-locked fiber laser

Lau

Hou

2021

Optics & Laser Technology

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“…[ 101 ] Despite higher absorption, the thicker graphene layer is always accompanied by higher defects which are detectable by higher I D : I G ratio from the Raman spectrum. [ 103 ] These defects will increase the absorption and scattering losses of the graphene. Several studies investigate the optimization of graphene layers to achieve higher saturable absorption (modulation depth) to non‐saturable loss ratio.…”

Section: Cnt and Graphenementioning

confidence: 99%

A Comparison for Saturable Absorbers: Carbon Nanotube Versus Graphene

Lau

Liu

Qiu

2022

Advanced Photonics Research

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Saturable absorption is a nonlinear optical phenomenon that is characterized by the reduced optical loss at high light intensity. At low light intensity, the saturable absorber (SA) absorbs light and results in an optical loss. When the light intensity is increased, the available energy states become depleted, leading to a reduction in absorption. For semiconductors, the saturated optical absorption under strong excitation is in conjunction with the Pauli expulsion of occupying carriers at the edge of the filled conduction band thus allowing photons to penetrate through the material without further absorption. [1] When incorporated into a mode-locked laser cavity, the saturable absorption process begins from the inherent noise fluctuations of a laser cavity. A dominant noise spike with the highest intensity will saturate the absorber and decreases the absorbance loss such as the pedestal peaks. [2] Next, this noise spike is amplified in subsequent round trips until a stable pulse train is eventually formed. This favors the generation of ultrafast laser pulses over continuous-wave laser operation. During the formation of ultrafast laser pulses, the SA is operated either as slow or fast SA. The main difference between these two SA configurations is their relaxation time. The relaxation time of a slow SA is longer than its pulse duration measured from the mode-locked laser. The long time constant results in reduced saturation intensity due to slow recovery of absorption. [3] Therefore, the slow SA self-starts the modelocked laser at a lower power threshold. In contrast, the relaxation time of fast SA is shorter than its pulse duration measured from the mode-locked laser. Owing to the fast relaxation time, the electrons in the conduction band will return to the valence band at a period shorter than the pulse duration. This constitutes the higher power threshold to self-start the mode-locked laser.Despite the difficulty to self-start the mode-locking, the fast SA is responsible for the stabilization of the laser. The fast SA has ultrafast carrier relaxation time for the SA to recover from bleaching with minimal time. [4] Besides stabilization, ultrafast relaxation time is also crucial to shortening the pulse duration of the mode-locked laser. [5] Before the advent of ultrashort pulse with relaxation time ranging from a few ps to a few hundred fs, semiconductor saturable absorber mirror (SESAM) was demonstrated with a complex post-fabrication process. For instance, ion implantation is needed to reduce its relaxation time to ps time scale. This encourages the discovery of a material with sub-picosecond recovery time, such as carbon nanotube (CNT) [6] and graphene. [7] Both CNT and graphene have ultrafast and slow recovery from saturation. In a femtosecond laser, the CNT will typically act as a slow SA due to its recovery time of few ps, whereas the graphene will typically act as a fast SA due to its

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“…Furthermore, the quality and number of layers are investigated by Raman spectrum spectroscopy. The Raman spectrum obtained for SG-SAM is exhibited in Figure 2 c. The SAM shows two clear Raman peaks at 1584 and 2675 cm −1 corresponding to the G band and 2D band of graphene [ 40 , 41 ], respectively. The peak intensity of the 2D band is considerably higher than that of the G band, confirming the presence of only one graphene layer in the SAM.…”

Section: Sample Preparation and Characterizationmentioning

confidence: 99%

SiO2 Passivated Graphene Saturable Absorber Mirrors for Ultrashort Pulse Generation

et al. 2022

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Owing to its broadband absorption, ultrafast recovery time, and excellent saturable absorption feature, graphene has been recognized as one of the best candidates as a high-performance saturable absorber (SA). However, the low absorption efficiency and reduced modulation depth severely limit the application of graphene-based SA in ultrafast fiber lasers. In this paper, a single-layer graphene saturable absorber mirror (SG-SAM) was coated by a quarter-wave SiO2 passivated layer, and a significantly enhanced modulation depth and reduced saturation intensity were obtained simultaneously compared to the SG-SAM without the SiO2 coating layer. In addition, long-term operational stability was found in the device due to the excellent isolation and protection of the graphene absorption layer from the external environment by the SiO2 layer. The high performance of the SAM was further confirmed by the construction of a ring-cavity EDF laser generating mode-locked pulses with a central wavelength of 1563.7 nm, a repetition rate of 34.17 MHz, and a pulse width of 830 fs.

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Raman Mapping Characterization of All-Fiber CVD Monolayer Graphene Saturable Absorbers for Erbium-Doped Fiber Laser Mode Locking

Cited by 24 publications

References 36 publications

Recent research and advances of material-based saturable absorber in mode-locked fiber laser

Recent research and advances of material-based saturable absorber in mode-locked fiber laser

A Comparison for Saturable Absorbers: Carbon Nanotube Versus Graphene

SiO2 Passivated Graphene Saturable Absorber Mirrors for Ultrashort Pulse Generation

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