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.
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 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.
Silver nanoparticles have been found many interesting applications, such as absorption amplifiers in dye-sensitized solar
cells. However, silver nanoparticles are easily oxidized. In order to protect silver nanoparticles, atomic layers of TiO2were deposited onto silver nanoparticles coated to a glass slide. Then the glass slide was exposed to corrosive I-/I3- solutions, and the degree of silver etching was measured via scanning electron microscopy (SEM) and ultraviolet-visible
spectroscopy (UVS). It was found that 3 nm (30 cycles) of Al2O3 with 9 nm of (90 cycles) TiO2 could completely protect
silver nanoparticles from oxidization.
A polymer optical waveguide amplifier based on PbS quantum dots (QDs) is demonstrated. It is fabricated by coating
PbS quantum dots film on a SU-8 optical channel waveguide. The PbS QDs are synthesized by a combined colloidal and
sol-gel method. The SU-8 polymer optical channel waveguide is fabricated by using a direct ultraviolet (UV)
photolithography technology. With a Wavelength Division Multiplexer (WDM), the signal and pump waves can be
combined and injected into the optical channel waveguide which is covered by QDs. The optical wave interacts with the
PbS QDs through evanescent wave and is amplified. By using a 10mm length waveguide, a 3.0dB gain was observed at
1310nm wavelength with 980nm pump.
A novel PbS quantum dots (QDs) fiber amplifier based on SiO2 Sol-Gel method was proposed. The QDs doped
SiO2 films was deposited onto a fused tapered fiber coupler based on standard single mode fiber (SMF). With a 980 nm
wavelength laser diode (LD) as the pump, 1550 nm signal and 980 nm pump light waves were injected into the tapered
region simultaneously, through the evanescent wave, we obtained the gain at 1576 nm wavelength as high as 5 dB. The
proposed fiber amplififier can implement the property of a small, integrated, high output, low noise, high gain, low cost,
which meet the need of the future of optical fiber communication system.
A PbSe quantum dots (QDs) fiber amplifier has been demonstrated. The PbSe QDs were synthesized via sol-gel self-assembly
method. The size of PbSe QDs was controlled to 5.5 nm through control of the reaction time as well as the
growth temperature. Transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy were used to
characterize the PbSe QDs samples. The fiber amplifier was fabricated by coating the QDs onto a tapered optical fiber
coupler. Through evanescent wave, the QDs were excited to realize optical amplification. A 1550 nm semiconductor
light emitting diode (SLED) as the signal source and a 980 nm laser diode (LD) source as the pump were injected into
the fiber coupler simultaneously.
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.
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