216 MHz repetition rate passively mode-locked electrically-pumped VECSEL

Electrically pumped vertical external cavity surface emitting laser is passively mode-locked at record-low repetition rate of 216 MHz demonstrating potential peak power scalability. A quantum dot saturable absorber is used to achieve stable operation

Modification of structural, thermal and optical properties of PC-PET/CdSe NCP using gamma radiation

In the current study we synthesized a nanocomposite (NCP) from polycarbonate/polybutylene terephthalate (PC-PET) blend and CdSe nanoparticles (NPs) through ex-situ casting methodology. CdSe NPs were synthesized using thermolysis technique with N2 gas flow. X-ray diffraction data for CdSe NPs are reported. The Rietveld refinement indicated that the synthesized CdSe acclimatizes cubic zinc blends constitution of a lattice parameter 6.057 Å and an average grain size of 2 nm. The PC-PET/CdSe NCP samples were irradiated by gamma doses between 20 and 230 kGy. The induced variations in the structure, thermal and optical properties of the gamma irradiated PC-PET/CdSe NCP have been illustrated by means of TEM, XRD, TGA, FTIR and UV–vis spectroscopes. The irradiation with doses in the range 50–230 kGy leads to the domination of crosslinking that improves the amorphous content. This increases the degradation temperature from 417 to 432 °C indicative of an enhancement in the thermostability of the NCP samples. Also, the optical band gap is reduced from 4.28 to 3.76 eV which is ascribed to the enhancement in the amorphous content of the irradiated PC-PET/CdSe NCP. This specifies that the gamma irradiation causes a more compactness of the NCP and leads to appropriate spreading of CdSe NPs within the PC-PET matrix. Additionally, the CIE approach was used to describe the colored samples. It is found that the PC-PET/CdSe NCP acquires color due to gamma doses, as the color intensity reached a remarkable color difference larger than 5 (14.9) which is a reasonable challenge in saleable reproduction on printing press

Broadly tunable quantum-dot based ultra-short pulse laser system with different diffraction grating orders

No abstract available

Broadly tunable picosecond pulses quantum-dot mode-locked laser

No abstract available

Broadly tunable picosecond pulses quantum-dot mode-locked laser

No abstract available

Preparation, structural characterization, optical, photoluminescence, AC electrical conductivity and broadband dielectric properties of WO3 reinforced PEG/CS blend for futuristic optoelectronic and energy storage devices

Polymer nanocomposites (PNCs) composed of biopolymers and metallic oxides are important classes of materials. In addition to the environmental and economic considerations, these materials became the best candidates for various industrial fields. In the current study, solution cast procedure is used to prepare polymer nanocomposites (PNCs) based on polyethylene glycol (PEG)/chitosan (CS) blend and varying concentrations of tungsten trioxide nanoparticles (WO3 NPs), as a nanofiller. TEM micrograph shows that WO3 NPs have particle sizes of 5–32 nm their shapes are cubic and spherical. The XRD results reveal the semicrystalline of PEG/CS blend through showing three distinct diffraction peaks at 2θ = 7.42°, 19.47° and 23.62° and the degree of crystallinity is decreased after the incorporation of WO3 NPs due to the formation of polymer-nanoparticle interactions as indicated by FTIR spectra. The values of optical energy bandgap (direct and indirect) reduce while the Urbach energy increases with raising the concentration of WO3 NPs in the PEG/CS matrix. The PEG/CS-WO3 films' PL spectra show a photoemission peak at about 387 nm, where this peak loses intensity and becomes broader due to the induced defects and increase of disordering within the nanocomposite films. Additionally, the results of the dielectric investigation show an increase in the dielectric constant, dielectric loss, and AC electrical conductivity, which may be a sign of an increase of charge carriers and the content of amorphous regions that assists the movement of charge carriers. The DC electrical conductivity and conduction mechanism are also reported. Argand plot shows a half semicircle implying the Debye-type relaxation mechanism. The experimental results suggest the use of PEG/CS-WO3 nanocomposites as a possible contender for futuristic energy storage and optoelectronic applications

Women's labour supply decisions in the light of possible fiscal reforms

SIGLEAvailable from British Library Document Supply Centre-DSC:7755.0364(36/99) / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Broadly tunable quantum-dot based ultra-short pulse laser system with different diffraction grating orders

A broadly tunable quantum-dot based ultra-short pulse master oscillator power amplifier with different diffraction grating orders as an external-cavity resonance feedback is studied. A broader tuning range, narrower optical spectra as well as higher peak power spectal density (maximun of 1.37 W/nm) from the second-order diffraction beam are achieved compared to those from the first-order diffraction beam in spite of slightly broader pulse duration from the second-order diffraction

Tunable master-oscillator power-amplifier based on chirped quantum-dot structures

A broadly tunable master-oscillator power-amplifier (MOPA) picosecond optical pulse source is demonstrated, consisting of an external cavity passively mode-locked laser diode with a tapered semiconductor amplifier. By employing chirped quantum-dot structures on both the oscillator's gain chip and amplifier, a wide tunability range between 1187 and 1283 nm is achieved. Under mode-locked operation, the highest output peak power of 4.39 W is achieved from the MOPA, corresponding to a peak power spectral density of 31.4 dBm/nm. © 1989-2012 IEEE