Showing papers on "Erbium published in 2014"

Large Energy, Wavelength Widely Tunable, Topological Insulator Q-Switched Erbium-Doped Fiber Laser

Abstract: We report on the generation of large energy, widely wavelength tunable pulses in an erbium-doped fiber laser passively Q-switched by a topological insulator saturable absorber (TI-SA). The TI-SA is prepared through an optical deposition method. Its saturating intensity and modulation depth are measured to be about 57 MW/cm2 and 22%, respectively. We show that the high modulation depth of TI-SA allows the generation of stable Q-switched pulses with per-pulse energy up to 1.5 μJ and its broadband saturable absorption favors the tunable Q-switching operation from 1510.9 nm to 1589.1 nm. Our study suggests that TI: Bi2Te3 could be a promising saturable absorber for both the high energy and broadband optical applications.

A femtosecond pulse erbium fiber laser incorporating a saturable absorber based on bulk-structured Bi2Te3 topological insulator.

Abstract: We experimentally demonstrate the use of a bulk-structured Bi2Te3 topological insulator (TI) as an ultrafast mode-locker to generate femtosecond pulses from an all-fiberized cavity. Using a saturable absorber based on a mechanically exfoliated layer about 15 μm thick deposited onto a side-polished fiber, we show that stable soliton pulses with a temporal width of ~600 fs can readily be produced at 1547 nm from an erbium fiber ring cavity. Unlike previous TI-based mode-locked laser demonstrations, in which high-quality nanosheet-based TIs were used for saturable absorption, we chose to use a bulk-structured Bi2Te3 layer because it is easy to fabricate. We found that the bulk-structured Bi2Te3 layer can readily provide sufficient nonlinear saturable absorption for femtosecond mode-locking even if its modulation depth of ~15.7% is much lower than previously demonstrated nanosheet-structured TI-based saturable absorbers. This experimental demonstration indicates that high-crystalline-quality atomic-layered films of TI, which demand complicated and expensive material processing facilities, are not essential for ultrafast laser mode-locking applications.

Mode-locked erbium-doped fiber laser based on evanescent field interaction with Sb2Te3 topological insulator

Abstract: In this Letter, we demonstrate a mode-locked Er-doped fiber laser incorporating antimony telluride (Sb2Te3) topological insulator (TI) as a saturable absorber (SA). The laser was capable of generating 270 fs-short soliton pulses at 1560 nm wavelength, which are the shortest solitons generated with a TI-based saturable absorber so far. In order to form a saturable absorber, a bulk piece of Sb2Te3 was deposited on a side-polished single-mode fiber with the presence of a low refractive index polymer. Such saturable absorber exhibits modulation depth at the level of 6% with less than 3 dB of non-saturable losses. Our study shows that TI-based saturable absorbers with evanescent field interaction might compete with SAs based on carbon nanomaterials, like graphene or nanotubes. Additionally, thanks to the interaction with the evanescent field, the material is not exposed to high optical power, which allows to avoid optical or thermal damage.

Organo-erbium systems for optical amplification at telecommunications wavelengths.

Abstract: Modern telecommunications rely on the transmission and manipulation of optical signals. Optical amplification plays a vital part in this technology, as all components in a real telecommunications system produce some loss. The two main issues with present amplifiers, which rely on erbium ions in a glass matrix, are the difficulty in integration onto a single substrate and the need of high pump power densities to produce gain. Here we show a potential organic optical amplifier material that demonstrates population inversion when pumped from above using low-power visible light. This system is integrated into an organic light-emitting diode demonstrating that electrical pumping can be achieved. This opens the possibility of direct electrically driven optical amplifiers and optical circuits. Our results provide an alternative approach to producing low-cost integrated optics that is compatible with existing silicon photonics and a different route to an effective integrated optics technology.

Monolithic erbium- and ytterbium-doped microring lasers on silicon chips.

Abstract: We demonstrate monolithic 160-µm-diameter rare-earth-doped microring lasers using silicon-compatible methods. Pump light injection and laser output coupling are achieved via an integrated silicon nitride waveguide. We measure internal quality factors of up to 3.8 × 105 at 980 nm and 5.7 × 105 at 1550 nm in undoped microrings. In erbium- and ytterbium-doped microrings we observe single-mode 1.5-µm and 1.0-µm laser emission with slope efficiencies of 0.3 and 8.4%, respectively. Their small footprints, tens of microwatts output powers and sub-milliwatt thresholds introduce such rare-earth-doped microlasers as scalable light sources for silicon-based microphotonic devices and systems.

Erbium-doped spiral amplifiers with 20 dB of net gain on silicon

Abstract: Spiral-waveguide amplifiers in erbium-doped aluminum oxide on a silicon wafer are fabricated and characterized. Spirals of several lengths and four different erbium concentrations are studied experimentally and theoretically. A maximum internal net gain of 20 dB in the small-signal-gain regime is measured at the peak emission wavelength of 1532 nm for two sample configurations with waveguide lengths of 12.9 cm and 24.4 cm and concentrations of 1.92 × 10^20 cm^-3 and 0.95 × 10^20 cm^-3, respectively. The noise figures of these samples are reported. Gain saturation as a result of increasing signal power and the temperature dependence of gain are studied.

Double-wall carbon nanotubes for wide-band, ultrafast pulse generation.

Abstract: We demonstrate wide-band ultrafast optical pulse generation at 1, 1.5, and 2 μm using a single-polymer composite saturable absorber based on double-wall carbon nanotubes (DWNTs). The freestanding optical quality polymer composite is prepared from nanotubes dispersed in water with poly(vinyl alcohol) as the host matrix. The composite is then integrated into ytterbium-, erbium-, and thulium-doped fiber laser cavities. Using this single DWNT–polymer composite, we achieve 4.85 ps, 532 fs, and 1.6 ps mode-locked pulses at 1066, 1559, and 1883 nm, respectively, highlighting the potential of DWNTs for wide-band ultrafast photonics.

Erbium-doped waveguide DBR and DFB laser arrays integrated within an ultra-low-loss Si3N4 platform.

Abstract: Record low optical threshold power and high slope efficiency are reported for arrays of distributed Bragg reflector lasers integrated within an ultra-low-loss Si(3)N(4) planar waveguide platform. Additionally, arrays of distributed feedback laser designs are presented that show improvements in pump-to-signal conversion efficiency of over two orders of magnitude beyond that found in previously published devices. Lithographically defined sidewall gratings provide the required lasing feedback for both cavity configurations. Lasing emission is shown over a wide wavelength range (1534 to 1570 nm), with output powers up to 2.1 mW and side mode suppression ratios in excess of 50 dB.

CMOS-compatible 75 mW erbium-doped distributed feedback laser

Abstract: On-chip, high-power, erbium-doped distributed feedback lasers are demonstrated in a CMOS-compatible fabrication flow. The laser cavities consist of silicon nitride waveguide and grating features, defined by wafer-scale immersion lithography and an erbium-doped aluminum oxide layer deposited as the final step in the fabrication process. The large mode size lasers demonstrate single-mode continuous wave operation with a maximum output power of 75 mW without any thermal damage. The laser output power does not saturate at high pump intensities and is, therefore, capable of delivering even higher on-chip signals if a stronger pump is utilized. The amplitude noise of the laser is investigated and the laser is shown to be stable and free from self-pulsing when the pump power is sufficiently above threshold.

Passive synchronization of erbium and thulium doped fiber mode-locked lasers enhanced by common graphene saturable absorber.

Abstract: In this work we present for the first time, to the best of our knowledge, a passively synchronized thulium (Tm) and erbium (Er) doped fiber laser mode-locked by a common graphene saturable absorber (GSA). The laser consists of two ring resonators combined with a 90 cm long common fiber branch incorporating the saturable absorber (SA). Such laser generates optical solitons centered at 1558.5 nm and 1938 nm with pulse durations of 915 fs and 1.57 ps, respectively. Both laser loops were passively synchronized at repetition frequency of 20.5025 MHz by nonlinear interaction (cross phase modulation, XPM) in common fiber branch between generated pulses. The maximum cavity mismatch of the Er-laser in synchronization regime was 0.78 mm. The synchronization mechanism was also investigated. We demonstrate that the third order nonlinearities of graphene enhance the synchronization range. In our case the range was increased about 85%. The integrated RMS timing jitter between the synchronized pulses was 67 fs.

Photon Upconversion in a Molecular Lanthanide Complex in Anhydrous Solution at Room Temperature

Abstract: Molecular photon upconversion luminescence was observed from an ion-associated complex of an erbium chelate of 2-thenoyltrifluoroacetone and a near-infrared-emitting cyanine dye in anhydrous solution at room temperature. In the complex erbium was sensitized by the organic antenna dye excited at 808 nm. The result was characteristic erbium emission at 510–565 nm with second-order dependence on the excitation power, suggesting a dye-sensitized energy transfer upconversion mechanism. Compared to inorganic upconverting nanoparticles, the organic molecular dye-sensitized complexes are expected to offer higher molar absorptivity, smaller well-defined size, and simpler addition of functional groups.

Stable $Q$ -Switched Erbium-Doped Fiber Laser Based on Topological Insulator Covered Microfiber

Abstract: We demonstrated a stable passively Q-switched Er-doped fiber laser around the optical communication band with a microfiber-based topological insulator (TI) Bi2Te3 saturable absorber. The saturable absorber was fabricated by the optical deposition method and its nonlinear transmission ~1568 nm was characterized. By virtue of the TI saturable absorber, stable Q-switched pulses can be formed with pulse repetition rate increasing from 2.6 to 12 kHz, and pulse duration decreasing from 50 μs to 9.5 μs through altering the pump strength. Our results evidently show the effectiveness of Bi2Te3-based saturable absorber and its potential applications for pulsed laser generation.

Passive mode locking of ytterbium- and erbium-doped all-fiber lasers using graphene oxide saturable absorbers

Abstract: Broadband graphene oxide/PVA films were used as saturable absorbers (SAs) for mode locking erbium-doped fiber laser (EDFL) and ytterbium-doped fiber laser (YDFL) at 1.06 μm and 1.55 μm. They provide modulation depths of 3.15% and 6.2% for EDFL and YDFL, respectively. Stable self-starting mode-locked pulses are obtained for both lasers, confirming that the graphene oxide is cost-effective. We have generated mode-locked pulses with spectral width, repetition rate, and pulse duration of 0.75 nm, 9.5 MHz, and 2.7 ps. This is the shortest pulse duration directly obtained from an all-normal-dispersion YDFL with graphene-oxide saturable absorber.

Fibre tip sensors for localised temperature sensing based on rare earth-doped glass coatings.

Abstract: We report the development of a point temperature sensor, based on monitoring upconversion emission from erbium:ytterbium-doped tellurite coatings on the tips of optical fibres. The dip coating technique allows multiple sensors to be fabricated simultaneously, while confining the temperature-sensitive region to a localised region on the end-face of the fibre. The strong response of the rare earth ions to changing temperature allows a resolution of 0.1–0.3 °C to be recorded over the biologically relevant range of temperatures from 23–39 °C.

Reduced erbium-doped ceria nanoparticles: one nano-host applicable for simultaneous optical down- and up-conversions.

Abstract: This paper introduces a new synthesis procedure to form erbium-doped ceria nanoparticles (EDC NPs) that can act as an optical medium for both up-conversion and down-conversion in the same time. This synthesis process results qualitatively in a high concentration of Ce3+ ions required to obtain high fluorescence efficiency in the down-conversion process. Simultaneously, the synthesized nanoparticles contain the molecular energy levels of erbium that are required for up-conversion. Therefore, the synthesized EDC NPs can emit visible light when excited with either UV or IR photons. This opens new opportunities for applications where emission of light via both up- and down-conversions from a single nanomaterial is desired such as solar cells and bio-imaging.

High-order harmonic noise-like pulsing of a passively mode-locked double-clad Er/Yb fibre ring laser

Abstract: In this paper, we study noise-like pulse generation in a km-long fibre ring laser including a double-clad erbium?ytterbium fibre and passively mode-locked through nonlinear polarization evolution. Although single noise-like pulsing is only observed at moderate pump power, pulse energies as high as 120?nJ are reached in this regime. For higher pump power, the pulse splits into several noise-like pulses, which then rearrange into a stable and periodic pulse train. Harmonic mode locking from the 2nd to the 48th orders is readily obtained. At pump powers close to the damage threshold of the setup, much denser noise-like pulse trains are demonstrated, reaching harmonic orders beyond 1200 and repetition frequencies in excess of a quarter of a GHz. The mechanisms leading to noise-like pulse breaking and stable high-order harmonic mode locking are discussed.

Green-to-red light tuning by up-conversion emission via energy transfer in Er3+-Tm3+-codoped germanium-tellurite glasses

Abstract: The luminescence properties through up-conversion emission process of Er 3 + –Tm 3 + -codoped germanium–tellurite glasses was carefully investigated by using UV–visible–near-infrared absorption spectroscopy, emission spectroscopy and lifetime measurement under near-infrared laser diode excitation at 976 nm. The glass samples were prepared by the conventional melt-casting technique. The Er 3 + and Tm 3 + ions act in this glass matrix as donor and acceptor, respectively, and can generate under 976 nm laser excitation a visible emission tunable from the green to the red color by varying the Tm 3 + ion concentration. Two mechanisms are involved to obtain this up-conversion emission and its tunability from the green to the red light: (i) the excited state absorption (ESA) of Erbium ions Er 3 + :( 4 I 11/2 → 4 F 7/2 ) and; (ii) the energy transfers (ETs) between Erbium Er 3 + and Thulium Tm 3 + ions. Such processes were studied by means of quantum efficiency and ET probability. It was verified that both of them depend on the Tm 3 + ion concentration. The relative intensity of the red emission was increased up to 2.6 times for the glasses containing 0.1 mol% and 1.0 mol% of Thulium oxide Tm 2 O 3 if compared with the Erbium Er 3 + single doped glass. The spectroscopic study presented in this work has permitted to fully describe the color rendering, ranging from green to red through yellow and orange, of the light emitted by the Er 3 + –Tm 3 + -codoped germanium–tellurite glasses under a low power laser diode excitation at 976 nm (30 mW).

10 W single-mode Er/Yb co-doped all-fiber amplifier with suppressed Yb-ASE

Abstract: In this work we demonstrate a single-frequency, single-mode all-fiber master oscillator power amplifier (MOPA) source, based on erbium?ytterbium co-doped double-clad fiber emitting 10?W of continuous wave power at 1565?nm. In the power amplifier stage, the amplified spontaneous emission from Yb3+ ions (Yb-ASE) is forced to recirculate in a loop resonator in order to provide stable lasing at 1060?nm. The generated signal acts as an additional pump source for the amplifier and is reabsorbed by the Yb3+ ions in the active fiber, allowing an increase in the efficiency and boosting the output power. The feedback loop also protects the amplifier from parasitic lasing or self-pulsing at a wavelength of 1??m. This allows one to significantly scale the output power in comparison to a conventional setup without any Yb-ASE control.

Optical switching and photoluminescence in erbium-implanted vanadium dioxide thin films

Abstract: Vanadium dioxide (VO2) is under intensive consideration for optical switching due to its reversible phase transition, which features a drastic and rapid shift in infrared reflectivity. Classified as an insulator–to–metal transition, the phase transition in VO2 can be induced thermally, electrically, and optically. When induced optically, the transition can occur on sub-picosecond time scales. It is interesting to dope VO2 with erbium ions (Er3+) and observe their combined properties. The first excited-state luminescence of Er3+ lies within the wavelength window of minimal transmission-loss in silicon and has been widely utilized for signal amplification and generation in silicon photonics. The incorporation of Er3+ into VO2 could therefore result in a novel photonic material capable of simultaneous optical switching and amplification. In this work, we investigate the optical switching and photoluminescence in Er-implanted VO2 thin films. Thermally driven optical switching is demonstrated in the Er-implanted VO2 by infrared reflectometry. Photoluminescence is observed in the thin films annealed at ∼800 °C or above. In addition, Raman spectroscopy and a statistical analysis of switching hysteresis are carried out to assess the effects of the ion implantation on the VO2 thin films. We conclude that Er-implanted VO2 can function as an optical switch and amplifier, but with reduced switching quality compared to pure VO2.

Influence of other rare earth ions on the optical refrigeration efficiency in Yb:YLF crystals

Abstract: We investigated the effect of rare earth impurities on the cooling efficiency of Yb3+:LiYF4 (Yb:YLF). The refrigeration performance of two single crystals, doped with 5%-at. Yb and with identical history but with different amount of contaminations, have been compared by measuring the cooling efficiency curves. Spectroscopic and elemental analyses of the samples have been carried out to identify the contaminants, to quantify their concentrations and to understand their effect on the cooling efficiencies. A model of energy transfer processes between Yb and other rare earth ions is suggested, identifying Erbium and Holmium as elements that produce a detrimental effect on the cooling performance.

Fluorescence characteristics and energy transfer of ytterbium-sensitized erbium-doped fluorophosphate glass for amplifier applications

Abstract: Yb3+/Er3+ codoped fluorophosphate glass has been investigated for developing broadband waveguide amplifier application. Spectroscopic properties and energy transfer microparameters of prepared glasses have been discussed. The spectral components of 1.55 μm emission are analyzed and an equivalent four-level system is proposed to estimate the stark splitting for the 4I15/2 and 4I13/2 levels in Er3+ doped fluorophosphate glass. The results indicate that highly doped Yb3+ ions could transfer energy to Er ions efficiently in fluorophosphate glass and Er3+/Yb3+ doped fluorophosphate glass is preferable for broadband Er3+-doped waveguide amplifier application.

Hybrid mode-locked erbium-doped all-fiber soliton laser with a distributed polarizer.

Abstract: A soliton-type erbium-doped all-fiber ring laser hybrid mode-locked with a co-action of arc-discharge single-walled carbon nanotubes (SWCNTs) and nonlinear polarization evolution (NPE) is demonstrated. For the first time, to the best of our knowledge, boron nitride-doped SWCNTs were used as a saturable absorber for passive mode-locking initiation. Moreover, the NPE was introduced through the implementation of the short-segment polarizing fiber. Owing to the NPE action in the laser cavity, significant pulse length shortening as well as pulse stability improvement were observed as compared with a SWCNTs-only mode-locked laser. The shortest achieved pulse width of near transform-limited solitons was 222 fs at the output average power of 9.1 mW and 45.5 MHz repetition frequency, corresponding to the 0.17 nJ pulse energy.

Optical spectroscopy and population behavior between I-4(11/2) and I-4(13/2) levels of erbium doped germanate glass

Abstract: In this paper, mid-infrared emission properties and energy transfer mechanism were investigated in Er3+ doped germanate glass pumped by 980 nm diode laser. Spontaneous radiative transition probability and emission cross section at 2.7 μm were calculated to be as high as 36.45 s−1 and 1.61 × 10−20 cm2, respectively. Corresponding upconversion emission spectra and radiative lifetimes of 4I13/2 level were determined to elucidate the mid-infrared luminescent characteristics. Moreover, population behaviors of Er3+: 4I11/2 and 4I13/2 level were analyzed numerically via Inokuti-Hirayama model, rate equations and Dexter’s theory. In addition, DSC curves of developed samples were measured and thermal stabilities were studied to evaluate the ability of resisting thermal damage and crystallization. The results indicate that erbium activated germanate glass is a promising candidate for mid-infrared applications. This work may provide beneficial guide for investigation of population behaviors of Er3+ ions at 2.7 μm emissions.

Fabrication, structural characterization, dielectric and electrical parameters of the synthesized nano-crystalline erbium oxide

Abstract: Nano crystalline erbium oxide (Er2O3) was synthesized in the laboratory through sol-gel method. The effect of different annealing temperatures on the crystal structure has been studied using x-ray diffraction (XRD). The comparison of the specific surface area (s); calculated using Brunauer, Emmett & Teller theory and (XRD) results, was made and found in agreement with an approximate error of 7%. The morphology of the samples has been studied using scanning electron microscope (SEM) and particles are found having a spherical morphology. Elemental analysis of the erbium oxide was also carried using energy dispersive spectrum (EDS) of the synthesized samples. Fourier transform infrared spectrum (FTIR) of the prepared samples showed the characteristic peaks for Er2O3. The dielectric properties of Er2O3 were also studied in the wide range of frequency (100 Hz - 5MHz). The activation energy for erbium oxide was found to be between 0.5–0.8 eV in the temperature range of 373 K–573 K. Hall effect measurements were done on the synthesized erbium oxide and it was found that erbium oxide can have useful applications in the Hall effect sensors (HES).

Broadband near infrared emission in antimony-germanate glass co-doped with erbium and thulium ions

Abstract: Antimony-germanate glasses co-doped with Er 3 + / Tm 3 + ions as a material for active waveguides application have been investigated. In result of optimizations of rare earths, concentration wide ( Δλ FWHM = 420 nm ) luminescence emission in the range of 1.4 to 1.9 μm was obtained for molar composition of 1%Er 2 O 3 : 0.25%Tm 2 O 3 . The influence of the molar ratio of active ions on the luminescence spectra has been investigated. Luminescent properties of fabricated glass indicate that elaborated glass is promising material for broad tunable integrated laser sources and broadband optical amplifiers.

Experimental evidence of Er 3+ ion reduction in the radiation-induced degradation of erbium-doped silica fibers

Abstract: The gain of erbium-doped fiber amplifiers is damaged by irradiation partly because of creation of color centers responsible of excess absorption at pump and signal wavelengths. Based on the combination of thermally stimulated luminescence and spectrophotometry, this Letter demonstrates that a part of the gain loss should be associated with the reduction of the density of Er3+ ions by irradiation.