Xiaolan Sun

A PbS quantum dots fiber amplifier excited by evanescent wave

A PbS quantum dots (QDs) fiber amplifier was fabricated and characterized by using a standard single mode fiber (SMF) coupler. The fiber amplifier was fabricated by coating PbS QDs doped sol-gel films onto the tapered SMF coupler. Through the evanescent wave, the PbS quantum dots were excited. With a 980 nm wavelength laser diode (LD) as the pump, the fiber amplifier exhibited a wide band optical gain at 1310 nm with the largest gain as high as 10 dB. The amplified spontaneous emission (ASE) noise is very low resulted from the amplifier configuration of evanescent wave exciting, which is critical to improve the signal-to-noise ratio. Therefore the proposed fiber amplifier will find great potential in the fiber-optic communication systems.

Optical fiber amplifiers based on PbS/CdS QDs modified by polymers.

Optical fiber amplifiers based on PbS/CdS semiconductor quantum dots (QDs) modified by an amphiphilic polymer were demonstrated. Well-defined QDs and an amphiphilic copolymer were first prepared and the amphiphilic copolymer was then used to disperse the QDs into silica sol to allow uniform and reproducible incorporation of QDs into the silica coating of the optical fibers. QD-doped silica sol was deposited on the fusion tapered fiber coupler via dip-coating. A 1550 nm semiconductor light emitting diode as the signal source and a 980 nm laser diode as the pump source were injected into the fiber coupler simultaneously. Through evanescent wave excitation, a signal gain as high as 8 dB was obtained within the wavelength range between 1450 and 1650 nm. In addition, the optical fiber amplifiers based on PbS/CdS QDs showed enhanced thermal stability when compared to amplifiers based on PbS QDs.

Enhanced thermal stability of oleic-acid-capped PbS quantum dot optical fiber amplifier

Poor thermal stability has remained a severe obstacle for practical applications of optical fiber amplifiers based on quantum dots (QDs). We demonstrate that thermal stability at elevated temperatures can be achieved by using oleic-acid-capped QDs. Optical fiber amplifiers using oleic-acid-capped QDs for the gain medium exhibited stable gain of more than 5 dB at 1550 nm between 25 °C and 50 °C that did not degrade upon cooling. In contrast, fiber amplifiers employing oleylamine-capped QDs exhibited reduced gain when heated and subsequently cooled.

Synthesis of poly(ionic liquid)-based nano-objects with morphological transitions via RAFT polymerization-induced self-assembly in ethanol

There have been few reports on polymerization-induced self-assembly of poly(ionic liquid)-based block copolymers, with limited access to higher order morphologies. Herein, a full range of morphologies including spheres, worms, and vesicles is readily synthesized via RAFT ethanolic dispersion polymerization of 1-butyl-3-(4-vinylbenzyl) imidazolium tetrafluoroborate to generate poly(N,N-dimethylacrylamide)-b-poly(ionic liquid) nano-objects.

Characterization and fabrication of rare-earth doped amplifying fibers based on atomic layer deposition

Nano-Rare Earth Doped Fibers (NREDFs) have shown great application for optical fiber amplifiers, fiber lasers and sensors. The rapid development of fiber communication systems has a higher requirement on the NREDFs. Atomic layer deposition (ALD) is a chemical vapor deposition technique based on the sequential use of self-terminating gas-solid reactions. As a film deposition technique, ALD is known for its effective material utilization at low temperatures, accuracy thickness control, excellent step coverage, good uniformity and adhesion, good conformability. In this paper, ALD was used to fabricate high concentration alumina-erbium co-doped amplifying fibers. Based on Modified Chemical Vapor Deposition (MCVD) and ALD, using nanomaterials as a dopant, the alumina-erbium co-doped amplifying fibers were fabricated. The main advantages of this novel method include good uniformity, high dispersibility, and high doping concentration. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) images and X-ray energy dispersive spectroscopy (EDS) showed the physical and chemical features of the deposited film upon a porous silica soot layer. Photoluminescence (PL) and absorption spectra were used to characterize the optical properties. The fibers have high gain, low noise, high power and are independent of polarization, which make them desirable for fiber devices.

Gain stability in fluorine polymer modified PbS quantum dot fiber amplifier

The gain for quantum dot fiber amplifiers (QDFA) was stabilized by capping with fluorine-containing polymers - reducing degradation after 60 days from 77% to 26% and degradation at elevated temperature from 93% to 32%.

Physical characteristics and optical properties of PbS nanoclusters: DFT simulation and experimental study

The physical characteristics and optical properties of PbS nanoclusters are investigated by using density functional theory (DFT) of first-principles. Microstructure models of (PbS)n (n=1-9) nanoclusters and bulk materials are built on Materials Studio platform, and its energy band structures, highest occupied molecular orbital-lowest unoccupied molecular orbital gap (HOMO-LUMO gap), density of state (DOS), and optical properties are calculated, respectively. Compared to PbS bulk materials, PbS nanoclusters show a discrete energy gap as well as the DOS, because of the quantum confinement effect. It is interesting that the HOMO-LUMO gap of (PbS)n (n=1-9) shows oscillates with the increasing of the n number. However, when its size is large enough, the HOMO-LUMO gap is gradually decrease with the increasing of size (>27 atoms). And, the HOMO-LUMO gap of PbS nanoclusters of different sizes is range from 2.575 to 0.58 eV, which covers the low loss communication band of optical communication. In addition, PbS nanomaterials (NMs) with small size are synthesized by using oleylamine as ligands. Sizes of PbS NMs can be accurately controlled through control of the reaction time as well as the growth temperature. The photoluminescence (PL) spectra show strong size dependence, which is large red shift with increasing size of the NMs. This trend is basically in agreement with the theoretical calculation above. Moreover, transmission electron microscopy (TEM) further reveals the morphology of PbS NMs. PbS NMs can be used in optical fiber amplifiers and fiber lasers because of its unique optical properties in optical communication bands.

High Gain Quantum Dots Fiber Amplifier over O-band Based on Tapered Fiber Coupler

An O-band Quantum Dots fiber amplifier based on tapered fiber coupler coated with PbS QDs-doped film was proposed. A maximum signal gain of 24 dB at 1310 nm with 100 nm bandwidth was obtained experimentally.

Ultra-broadband multi-sized PbS quantum dots fiber amplifier based on a symmetric fiber coupler

We proposed an ultra-broadband multi-sized PbS quantum dots(QDs) fiber amplifier based on a symmetric fused tapered coupler. The 2x2 tapered fiber coupler was coated with a mixture of PbS QDs in two different sizes. By using the multisized PbS QDs as the gain medium, a maximum bandwidth of 400 nm (1200~1600 nm) has been achieved under evanescent wave excitation. In addition, with a 70 mW of 980 nm pump, we obtained a small signal gain of greater than 14 dB in this region.

A polymer-modified PbS quantum dot fiber amplifier excited by evanescent wave

A novel polymer-modified PbS quantum dot (QD) optical fiber amplifier was proposed and demonstrated. It was fabricated by depositing a PbS QD doped film around the tapered single mode fiber (SMF) coupler. The PbS QDs were synthesized in an organic phase and then transfer into water by polymer modification. A 1550 nm semiconductor light emitting diode as the signal source and a 980 nm laser diode source as the pump were injected into the fiber coupler simultaneously. Through evanescent wave excitation, we obtained a significant gain of about 6dB within the wavelength range between 1450 and 1650 nm.