David Steinberg

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.

Explaining simultaneous dual-band carbon nanotube mode-locking Erbium-doped fiber laser by net gain cross section variation

In this paper we report the pulse evolution of a simultaneously mode-locked Erbium-doped fiber laser at 1556-nm-band and 1533-nm-band. We explain the dual wavelength laser operation by means of net gain cross section variations caused by the population inversion rate dependence on the pump power. At 1556-nm-band, we observed pulse duration of 370 fs with bandwidth of 8.50 nm and, for pump power higher than 150 mW, we observe the rise of a CW and mode-locked laser, sequentially, at 1533-nm-band. We show that both bands are simultaneously mode-locked and operate at different repetition rates.

200-fs mode-locked Erbium-doped fiber laser by using mechanically exfoliated MoS 2 saturable absorber onto D-shaped optical fiber

For the first time, we demonstrated the fabrication of mechanically exfoliated molybdenum disulfide (MoS2) samples deposited onto a D-shaped optical fiber. The MoS2 exfoliated flakes were deposited onto a stacked of 1.2 µm PVA (polyvinyl alcohol) and 300 nm PMMA (polymethyl methacrylate) layers and then transferred directly onto a side polished surface of D-shaped optical fiber with polishing length of 17 mm and no distance from the fiber core. The sample exhibited a high polarization performance as a polarizer with relative polarization extinction ratio of 97.5%. By incorporating the sample as a saturable absorber in the Erbium-doped fiber laser (EDFL), bandwidth of 20.5 nm and pulse duration of 200 fs were generated, which corresponded to the best mode-locking results obtained for all-fiber MoS2 saturable absorber at 1.5 µm wavelength.

Influence of Carbon Nanotubes Saturable Absorbers Diameter on Mode-Locking Erbium-Doped Fiber Laser Performance

We present a study about the influence of saturable absorbers single-wall carbon nanotubes (CNT) diameter on the passive mode-locking Erbium doped fiber laser performance. We used several samples of CNT with different mean diameters (from 0.8 to 1.4 nm) and distributions to fabricated CNT/polymer films. Films with 1.0 nm mean diameter CNT showed best results in terms of larger laser bandwidths and shorter pulse durations, compared to the other CNT samples used in our experiments. This result is due to the fact that 1.0 nm diameter CNT absorption energy gap (∼0.8 eV) is close to the photon energy of operating Erbium-doped fiber laser wavelength (∼1557 nm). Laser bandwidths up to 8.7 nm and pulse durations as short as 0.55 ps were obtained.

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.

Graphene oxide and reduced graphene oxide as saturable absorbers onto D-shaped fibers for sub 200-fs EDFL mode-locking

We present high mode-locking performances from an erbium-doped fiber laser (EDFL) by using graphene oxide (GO) and reduced graphene oxide (r-GO) as saturable absorbers (SA) deposited onto the polished surface of a D-shaped optical fiber. The samples were prepared with different concentrations and its characterization was performed by using an optical microscope, a Raman spectrometer, nonlinear saturable absorption measurements, polarization setup, and laser mode-locking analysis. As a 1550-nm polarizer, the best GO (r-GO) samples exhibited higher polarization extinction ratio (PER) of 7.94 (7.65) dB, corresponding to 84 (83) %, both showing similar graphene TE absorption behavior. In a managed-intracavity dispersion laser, broadest bandwidths of 27.2 and 24.1 nm and the corresponding shortest pulse duration of 190 fs could be generated when incorporating the SA with high modulation depth (above 20%), being so far the best mode-locking results ever reported in the literature for GO and r-GO SA onto D-shaped optical fibers in EDFL.

Sub-300fs mode-locked erbium doped fiber laser using graphene oxide and reduced graphene oxide onto D-shaped optical fibers

We present the ultrashort pulse generation of sub-300 fs from a mode-locked Erbium doped fiber laser by using spin-coated graphene oxide and reduced graphene oxide saturable absorbers deposited onto polished surface of D-shaped optical fibers.

Ultrashort pulse generation using mechanically exfoliated graphite onto D-shaped optical fiber in erbium doped fiber laser

We present the ultrashort pulse generation of 250 fs from a mode-locked Erbium doped fiber laser by using mechanically exfoliated graphite saturable absorbers deposited onto side-polished surface of a D-shaped optical fiber.

O-band passive mode-locked Raman fiber laser based on Single Wall Carbon Nanotubes as saturable absorbers

We present a passive mode-locked Raman laser incorporating SWCNT (Single-Wall Carbon Nanotubes) as saturable absorbers operating in O-band. We construct two single mode fiber lasers to generate ultrashort pulses near zero dispersion wavelength fiber. As results, pulse-trains were achieved in two different regimes and we compared the output bandwidth, rate repetition and pulse durations from both lasers. With high accumulated dispersion, nanoseconds square duration pulses were generated from laser cavity. So we study the pulse duration behavior introducing a dispersion shifted fiber (DSF) inside the cavity and verified a strong relation between pulse shortening and DSF length.