Graphene Saturable Absorber Research Articles

Efficient graphene saturable absorbers on D-shaped optical fiber for ultrashort pulse generation.

We demonstrated a method to construct high efficiency saturable absorbers based on the evanescent light field interaction of CVD monolayer graphene deposited on side-polished D-shaped optical fiber. A set of samples was fabricated with two different core-graphene distances (0 and 1 μm), covered with graphene ranging between 10 and 25 mm length. The mode-locking was achieved and the best pulse duration was 256 fs, the shortest pulse reported in the literature with CVD monolayer graphene in EDFL. As result, we find a criterion between the polarization relative extinction ratio in the samples and the pulse duration, which relates the better mode-locking performance with the higher polarization extinction ratio of the samples. This criterion also provides a better understanding of the graphene distributed saturable absorbers and their reproducible performance as optoelectronic devices for optical applications.

誘電体多層膜ミラーへのグラフェン可飽和吸収体転写技術改善による可視光パルスファイバレーザー発振特性の向上

誘電体多層膜ミラーへのグラフェン可飽和吸収体転写技術改善による可視光パルスファイバレーザー発振特性の向上

Graphene Mode-Locked Fiber Laser at 2.8 <inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula>

Mid-infrared erbium (Er3+)-doped ZrF4–BaF2–LaF3–AlF3–NaF fiber laser mode-locked by multilayer graphene saturable absorber was demonstrated. Mode-locked pulses at 2.8 $\mu \text{m}$ with an average output power of 18 mW at a repetition rate of 25.4 MHz, corresponding to a pulse energy of 0.7 nJ, were obtained. The pulsewidth was measured to be $\sim 42$ ps by a home-made autocorrelator. Our experiment has validated the mode-locking capability of graphene in the 3- $\mu \text{m}$ wavelength region.

A graphene saturable absorber for a Tm:YLF pumped passively Q-switched Ho:LuAG laser

Abstract A passively Q-switched Ho:LuAG solid-state laser using a graphene saturable absorber pumped by a continuous-wave diode-pumped Tm:YLF laser was first reported in this letter. Single layer graphene grown by chemical vapor deposition and transferred onto a thin quartz plate was fabricated as the SA. For the continuous-wave mode, a maximum output power of 0.87 W at 2100.7 nm was obtained under the output coupler T = 10%, corresponding to the slope efficiency of 30.8% and the optical conversion efficiency of 18.9%. For the passively Q-switched mode, a stable PQS Ho:LuAG laser under the highest incident pump power of 4.3 W was obtained, corresponding to the maximum average output power, the maximum repetition frequency and the minimum pulse width being 0.37 W, 48.8 kHz and 752.2 ns, respectively. Our results illustrate that graphene can be used well as a saturable absorber in a Ho-doped solid-state laser at 2 μm wavelength.

Monolayer graphene saturable absorber with sandwich structure for ultrafast solid-state laser

The uniform-quality, large-area, monolayer graphene saturable absorber (SA) with sandwich structure was fabricated, tested, and successfully applied for the generation of diode-pumped Yb:Y2SiO5 mode-locked laser. Without extra negative dispersion elements, the shortest pulse with duration of ∼883 fs was obtained at 1042.6 nm with an output power of ∼1 W. These promising experimental results suggested that the low-cost, high-quality graphene SA could potentially be employed in practical, high-power, ultrafast mode-locking laser systems.

Intracavity KTP OPO pumped by a doubly Q-switched laser with AOM and a monolayer graphene saturable abosorber

An intracavity KTiOPO4 (KTP) optical parametric oscillator (IOPO) pumped by a doubly Q-switched YVO4/Nd:YVO4 laser with an acousto-optic modulator (AOM) and a monolayer graphene saturable absorber has been realized for the first time. The average output power, the pulse duration, single pulse energy and the peak power of signal light versus incident pump power have been measured. At an incident pump power of 11.7W and an AOM repetition rate of 10kHz, the shortest pulse duration of 1.24ns was obtained, corresponding to a single pulse energy of 9.5μJ and a peak power of 7.9kW. In comparison, the doubly IOPO (DIOPO) pumped by doubly Q-switched laser with AOM and graphene saturable absorber can generate pulses with narrower pulse width and higher peak power than the singly IOPO (SIOPO) pumped only by AOM Q-switched laser.

Sub-90 fs a stretched-pulse mode-locked fiber laser based on a graphene saturable absorber.

In this paper a stretched-pulse, mode-locked Er-doped fiber laser based on graphene saturable absorber (SA) is presented. A 60 layer graphene/polymer composite was used as a SA. The all-fiber dispersion managed laser resonator with the repetition frequency of 21.15 MHz allows for Gaussian pulses generation with the full width at half maximum (FWHM) of 48 nm. The generated chirped pulses were compressed outside the cavity to the 88 fs using a piece of standard single mode fiber. The average output power and pulse energy were of 1.5 mW and 71 pJ, respectively.

Dual-loss-modulated Q-switched Tm:LuAG laser with AOM and monolayer graphene.

A laser-diode-pumped dual-loss-modulated Q-switching Tm:LuAG laser with an acousto-optic modulator (AOM) and monolayer graphene saturable absorber (SA) around 2μm is presented for the first time to the best of our knowledge. The average output power and the pulse widths for different repetition rates have been measured. In comparison with the singly Q-switching laser with AOM or with monolayer graphene SA, the dual-loss-modulated Q-switching laser could generate shorter pulse width and higher peak power. The maximum pulse width compression ratio was found to be 3.11, and the highest peak power was enhanced 97.4 times. The experimental results show that the dual-loss-modulated technology is an efficient method for compressing the pulse width, improving the peak power, and enhancing the pulse stability for the Q-switched lasers at 2μm.

Graphene Q-switched fiber laser with broadband, random, multimode oscillation

We have demonstrated a Q-switched erbium-doped ring fiber laser based on graphene saturable absorber (GSAs). Stable Q-switched pulses with broadband, random, and multimode oscillation have been observed. The novel spectrum is caused by the combined effect of perturbations of the cavity and the suppressed mode competition.

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

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.

Graphene mode-locked Cr:LiSAF laser at 850 nm.

We report, for the first time to our knowledge, a mode-locked femtosecond Cr:LiSAF laser initiated with a high-quality monolayer graphene saturable absorber (GSA), synthesized by chemical-vapor deposition. The tight-focusing resonator architecture made it possible to operate the Cr:LiSAF laser with only two 135 mW, 660 nm low-cost single-mode diode lasers. At a pump power of 270 mW, the laser produced nearly transform-limited 68 fs pulses with an average power of 11.5 mW at 850 nm. The repetition rate was around 132 MHz, corresponding to a pulse energy and peak power of 86 pJ and 1.26 kW, respectively. Once mode locking was initiated with the GSA, stable, uninterrupted femtosecond pulse generation could be sustained for hours. The saturation fluence and the modulation depth of the GSA were further determined to be 28 μJ/cm2 and 0.62%, respectively.

Investigation of Graphene Dispersion From Kelly Sideband in Stable Mode-Locked Erbium-Doped Fiber Laser by Few-Layer Graphene Saturable Absorbers

In this paper, stable passively mode-locked fiber lasers (MLFLs) constructed using graphene saturable absorbers (SAs) with different layer numbers of ∼1 to ∼15 have been reported. The flat linear transmission spectrum in the range from 1540 to 1580 nm without any distinct absorption peak implies that the graphene SAs exhibit low dispersion in this region. Therefore, stable soliton-like pulses are generated because of negative dispersion provided by the fiber laser cavity, which requires no additional single-mode fiber (SMF) for dispersion compensation. Power-dependent transmission measurements show that the saturation intensity ranges from 1.2 to 3.2 MW/cm2 and that the modulation depth (MD) of the graphene SAs increases with the number of graphene layers. All the samples were observed to easily mode-lock the laser with a stable mode-locking state persistently operated over hours. By analyzing the soliton Kelly sidebands, we deduced the group delay dispersion (GDD) for different layers of the graphene. The calculated results show that the variation of sample GDD is within the calculation error, indicating that the GDD of graphene is small to be negligible. This result is consistent with the experimental results reported by Chang et al . [Appl. Phys. Lett. 97, 211102 (2010)] using the phase-shift method. This study demonstrates that different layers graphene SAs have different MD contributions to the generation of laser pulses with different pulse widths.

Nanosecond pulse generation in a passively Q-switched Nd:GGG laser at 1331 nm by CVD graphene saturable absorber

We report on a nanosecond pulse generation in a diode end-pumped passively Q-switched Nd:GGG laser at the low-gain transition line of 1331 nm. A three-layer CVD graphene thin film was transferred from Cu foil to a BK7 glass substrate for the use of saturable absorber. A stable Q-switching laser operation was obtained with maximum average output power of 0.69 W and slope efficiency of about 11.0% with respect to the absorbed pump power. The shortest pulse duration and the maximum repetition rate of the pulse trains were registered to be 556 ns and 166.7 kHz with corresponding maximum pulse energy 4.14 μJ and pulse peak power 7.45 W. This is the first demonstration of CVD-graphene-based Q-switched laser operation at 1.3 μm, to the best of our knowledge.

Polarization insensitive graphene saturable absorbers using etched fiber for highly stable ultrafast fiber lasers.

In this paper, we introduce a graphene-based saturable absorber (GSA) with high damage threshold employing symmetrical evanescent wave interaction for highly stable mode-locking of ultrafast fiber lasers. To enhance the evanescent wave interaction between the graphene layer and the propagating light, graphene flakes are mixed with polydimethylsiloxane (PDMS), and the graphene/PDMS composite is coated onto a chemically etched fiber. The GSA exhibits polarization insensitivity due to its symmetric cross-section, which enables stable operation against environmental disturbance such as stress, bending, and temperature variation. Finally, we demonstrate a fiber laser generating 216 fs pulses with an 80 dB signal-to-noise ratio.

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

We present a study on the characterization and quality evaluation of all-fiber chemical vapor deposition (CVD) graphene saturable absorber samples for Erbium-doped fiber laser (EDFL) mode locking. Optical fiber end faces covered by CVD graphene were analyzed by Raman spectroscopy, and classification criteria related to graphene Raman bands properties were adopted in order to evaluate samples quality. The analysis revealed that for all samples, the fiber core was 100% covered by graphene, with 88% average monolayer graphene coverage, and 82% low defect graphene coverage. Graphene samples were used as saturable absorbers in EDFL, and soliton-like pulses as short as 599 fs were generated, with average pulse duration of 620 ± 10 fs among all samples.

Actively Q-switched ytterbium-doped fiber laser by an all-optical Q-switcher based on graphene saturable absorber.

We demonstrate an all-optical Q-switcher based on graphene saturable absorber (GSA). Due to the cross absorption modulation (XAM) effect in graphene, we can change the transmittance of signal light periodically by introducing a train of laser pulses into graphene. This allows controlling the Q-factor of the cavity. This Q-switcher has many advantages such as all-fiber structure, all-optical modulation, broadband applications. With this Q-switcher, we have successfully fabricated an actively Q-switched ytterbium-doped fiber laser. The pulse repetition rate can be tuned from 30.32 kHz to 101.29 kHz. What's more, synchronization of the Q-switched laser pulses and modulation laser pulses can be realized, which has many potential applications such as nonlinear frequency conversion, multi-color pump probe spectroscopy and Raman scattering spectroscopy.

Dual-loss-modulated passively Q-switched Tm:LuAG laser with multi-walled carbon nanotube and monolayer graphene

By simultaneously using a multi-walled carbon nanotube (MWCNT) and a monolayer graphene saturable absorber (SA) in the cavity, a laser-diode-pumped dual-loss-modulated passively Q-switched Tm:LuAG laser at 2 mu m is demonstrated for the first time. In comparison with the singly passively Q-switched laser with MWCNT or monolayer graphene SA, the doubly passively Q-switched laser with both MWCNT and monolayer graphene SA can generate shorter pulse width and higher peak power. A maximum pulse width compression ratio of 2.8 and a highest peak power enhancement factor of 4 were obtained at the incident pump power of 5.8 W, respectively. The experimental results show that the dual-loss modulation is an efficient method to compress the pulse widths and improve the peak powers of the Q-switched lasers at 2 mu m.

Efficient graphene Q-switched 946 nm Nd:YAG laser

For the first time, graphene saturable absorber (SA) is used as the Q-switcher for a 946nm Nd:YAG laser. Using a 5–7 layer graphene SA with initial transmission of 78% and an output coupler with transmission of 5%, efficient Q-switching operation is realized. When the absorbed pump power is raised to 9.5W, a maximum output power of 0.9W is obtained, corresponding to an optical conversion efficiency of 9.5%. The pulse repetition frequency and the pulse width are 225kHz, 162ns, respectively, resulting a pulse energy of 4μJ and a peak power of 24.7W. With a BiB3O6 (BIBO) crystal as the frequency doubler, 473nm blue laser is generated. The present research manifests graphene has great potential for short wavelength laser modulation.

Single-layer graphene saturable absorber for diode-pumped passively Q-switched Tm:KLu(WO4)2 laser at 2 μm

We demonstrate a diode-pumped passively Q-switched Tm-laser emitting near 2 μm using single-layer graphene as the saturable absorber. The commercially available graphene samples were characterized by Raman spectroscopy and pump–probe measurements indicating high quality layered graphene. The Q-switched Tm:KLuW laser generated maximum pulse energy of ~1 μJ with a slope efficiency of 11%. The maximum average output power was 34 mW at a repetition rate of 35 kHz.

Monolayer graphene saturable absorbers with strongly enhanced evanescent-field interaction for ultrafast fiber laser mode-locking.

We demonstrate an efficient all-fiber saturable absorber (SA) that evanescently interacts with a graphene monolayer. Strong nonlinear interaction between the graphene sheet and evanescent wave was realized in both experiments and numerical calculations by employing an over-cladding structure on high-quality monolayer graphene that uniformly covered the side-polished fiber. A passively mode-locked Er-doped fiber laser was built, including our in-line graphene SA, which stably generated ultrashort pulses with pulse duration of 377 fs at a repetition rate of 37.7 MHz. The corresponding 3-dB spectral bandwidth of the laser was measured to be 8.6 nm at the central wavelength of 1607.7 nm. We also experimentally observed that the spectral bandwidth and pulse duration of the laser output could be controlled by proper selection of the refractive index of the over-cladding material on the monolayer-graphene SA.