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Dissolution-and-reduction CVD synthesis of few-layer graphene on ultra-thin nickel film lifted off for mode-locking fiber lasers.

Peng KJ, Lin YH, Wu CL, Lin SF, Yang CY, Lin SM, Tsai DP, Lin GR - Sci Rep (2015)

Bottom Line: In contrast, the reflection-type SA only compresses the pulsewidth from 875 to 796 fs with corresponding spectral linewidth broadened from 2.2 to 3.3 nm.The reflection-type graphene mode-locker increases twice of its equivalent layer number to cause more insertion loss than the transmission-type one.Nevertheless, the reflection-type based saturable absorber system can generate stabilized soliton-like pulse easier than that of transmission-type system, because the nonlinearity induced self-amplitude modulation depth is simultaneously enlarged when passing through the graphene twice under the retro-reflector design.

View Article: PubMed Central - PubMed

Affiliation: Graduate Institute of Photonics and Optoelectronics, Department of Electrical Engineering, National Taiwan University (NTU), No.1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan, Republic of China.

ABSTRACT
The in-situ dissolution-and-reduction CVD synthesized few-layer graphene on ultra-thin nickel catalyst film is demonstrated at temperature as low as 550 °C, which can be employed to form transmission-type or reflection-type saturable absorber (SA) for mode-locking the erbium-doped fiber lasers (EDFLs). With transmission-type graphene SA, the EDFL shortens its pulsewidth from 483 to 441 fs and broadens its spectral linewidth from 4.2 to 6.1 nm with enlarging the pumping current from 200 to 900 mA. In contrast, the reflection-type SA only compresses the pulsewidth from 875 to 796 fs with corresponding spectral linewidth broadened from 2.2 to 3.3 nm. The reflection-type graphene mode-locker increases twice of its equivalent layer number to cause more insertion loss than the transmission-type one. Nevertheless, the reflection-type based saturable absorber system can generate stabilized soliton-like pulse easier than that of transmission-type system, because the nonlinearity induced self-amplitude modulation depth is simultaneously enlarged when passing through the graphene twice under the retro-reflector design.

No MeSH data available.


Structural and optical properties of few-layer graphene grown under hydrogen-free and low-temperature PECVD.(a) The AFM image and (b) the cross-sectional profile scanned from point A of the synthesized few-layer graphene. (c) The non-linear transmittance of the synthesized graphene. (d) The Raman spectra of commercial single-layer graphene and hydrogen-free synthesized few-layer graphene.
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f1: Structural and optical properties of few-layer graphene grown under hydrogen-free and low-temperature PECVD.(a) The AFM image and (b) the cross-sectional profile scanned from point A of the synthesized few-layer graphene. (c) The non-linear transmittance of the synthesized graphene. (d) The Raman spectra of commercial single-layer graphene and hydrogen-free synthesized few-layer graphene.

Mentions: In order to measure the thickness and calculate the layer number of the few-layer graphene, the ultra-thin nickel catalyst film was etched by FeCl3 and the lifted graphene was transferred to a smooth Si wafer afterwards. The atomic-force microscopy (AFM) top-view image and cross-sectional profile of few-layer graphene on Si wafer shown in Fig. 1a,b reveal a height difference of 2.5 nm between the Si substrate and the transferred graphene. Considering that the height of monolayer graphene is about 0.33 nm23, the layer number of few-layer graphene synthesized by in-situ dissolution-and-reduction after the hydrogen-free and low-temperature PECVD growth is roughly estimated as 6 ~ 7 layers. To characterize the saturable absorption feature of the few-layer graphene, the nonlinear transmittance obtained under the pumping with high-peak-power fiber laser (central wavelength at 1570 nm) is shown in Fig. 1c. When the pumping average power increases from 0.008 to 3.23 mW, the transmittance of few-layer graphene nonlinearly increases from 87.5% to 91% with a ΔT of 3.5%. The absorption saturates at a pumping power of more than 3.23 mW due to the Pauli blocking effect, where the photons could pass through the optically bleached graphene. The corresponding modulation depth of the few-layer graphene is about 28%, which is already comparable with those of about 30% as obtained from the seven-layer graphene synthesized under high-temperature and hydrogen-rich environment8. Such a competitive feature has corroborated the reliability of dissolution-and-reduction syhthesized few-layer graphene grown under hydrogen-free and low-temperature PECVD.


Dissolution-and-reduction CVD synthesis of few-layer graphene on ultra-thin nickel film lifted off for mode-locking fiber lasers.

Peng KJ, Lin YH, Wu CL, Lin SF, Yang CY, Lin SM, Tsai DP, Lin GR - Sci Rep (2015)

Structural and optical properties of few-layer graphene grown under hydrogen-free and low-temperature PECVD.(a) The AFM image and (b) the cross-sectional profile scanned from point A of the synthesized few-layer graphene. (c) The non-linear transmittance of the synthesized graphene. (d) The Raman spectra of commercial single-layer graphene and hydrogen-free synthesized few-layer graphene.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4556966&req=5

f1: Structural and optical properties of few-layer graphene grown under hydrogen-free and low-temperature PECVD.(a) The AFM image and (b) the cross-sectional profile scanned from point A of the synthesized few-layer graphene. (c) The non-linear transmittance of the synthesized graphene. (d) The Raman spectra of commercial single-layer graphene and hydrogen-free synthesized few-layer graphene.
Mentions: In order to measure the thickness and calculate the layer number of the few-layer graphene, the ultra-thin nickel catalyst film was etched by FeCl3 and the lifted graphene was transferred to a smooth Si wafer afterwards. The atomic-force microscopy (AFM) top-view image and cross-sectional profile of few-layer graphene on Si wafer shown in Fig. 1a,b reveal a height difference of 2.5 nm between the Si substrate and the transferred graphene. Considering that the height of monolayer graphene is about 0.33 nm23, the layer number of few-layer graphene synthesized by in-situ dissolution-and-reduction after the hydrogen-free and low-temperature PECVD growth is roughly estimated as 6 ~ 7 layers. To characterize the saturable absorption feature of the few-layer graphene, the nonlinear transmittance obtained under the pumping with high-peak-power fiber laser (central wavelength at 1570 nm) is shown in Fig. 1c. When the pumping average power increases from 0.008 to 3.23 mW, the transmittance of few-layer graphene nonlinearly increases from 87.5% to 91% with a ΔT of 3.5%. The absorption saturates at a pumping power of more than 3.23 mW due to the Pauli blocking effect, where the photons could pass through the optically bleached graphene. The corresponding modulation depth of the few-layer graphene is about 28%, which is already comparable with those of about 30% as obtained from the seven-layer graphene synthesized under high-temperature and hydrogen-rich environment8. Such a competitive feature has corroborated the reliability of dissolution-and-reduction syhthesized few-layer graphene grown under hydrogen-free and low-temperature PECVD.

Bottom Line: In contrast, the reflection-type SA only compresses the pulsewidth from 875 to 796 fs with corresponding spectral linewidth broadened from 2.2 to 3.3 nm.The reflection-type graphene mode-locker increases twice of its equivalent layer number to cause more insertion loss than the transmission-type one.Nevertheless, the reflection-type based saturable absorber system can generate stabilized soliton-like pulse easier than that of transmission-type system, because the nonlinearity induced self-amplitude modulation depth is simultaneously enlarged when passing through the graphene twice under the retro-reflector design.

View Article: PubMed Central - PubMed

Affiliation: Graduate Institute of Photonics and Optoelectronics, Department of Electrical Engineering, National Taiwan University (NTU), No.1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan, Republic of China.

ABSTRACT
The in-situ dissolution-and-reduction CVD synthesized few-layer graphene on ultra-thin nickel catalyst film is demonstrated at temperature as low as 550 °C, which can be employed to form transmission-type or reflection-type saturable absorber (SA) for mode-locking the erbium-doped fiber lasers (EDFLs). With transmission-type graphene SA, the EDFL shortens its pulsewidth from 483 to 441 fs and broadens its spectral linewidth from 4.2 to 6.1 nm with enlarging the pumping current from 200 to 900 mA. In contrast, the reflection-type SA only compresses the pulsewidth from 875 to 796 fs with corresponding spectral linewidth broadened from 2.2 to 3.3 nm. The reflection-type graphene mode-locker increases twice of its equivalent layer number to cause more insertion loss than the transmission-type one. Nevertheless, the reflection-type based saturable absorber system can generate stabilized soliton-like pulse easier than that of transmission-type system, because the nonlinearity induced self-amplitude modulation depth is simultaneously enlarged when passing through the graphene twice under the retro-reflector design.

No MeSH data available.