Spectroscopic properties of Er3+ doped TeO2-BaO (Li2O, Na2O)-La2O3 glasses for 1.5-mu m optical amplifiers

This paper reports on the optical spectroscopic properties and thermal stability of Er3+-doped TeO2-BaO (Li2O,NaO)-La2O3 glasses for developing 1.5-mu m fiber amplifiers. Upon excitation at 977 nm laser diode, an intense 1.53-mu m infrared fluorescence has been observed with a broad full width at half maximum (FWHM) of about 60 nm for the Er3+-doped TeO2-BaO (Li2O, Na2O)-La2O3 glass with 10 mol% of BaO. The calculated fluorescence lifetime and the emission cross-sections of the 1.53-mu m transition are 2.91 ms and similar to 9.97 x 10(-21) cm(2), respectively. It is noted that the gain bandwidth, a, x FWHM, of the TeO2-BaO-La2O3Er2O3 glass is about 600, which is significantly higher than that in silicate and phosphate glasses. Meanwhile, it is interesting to note that the TeO2-BaO-La2O3-Er2O3 glass has shown a high glass thermal stability and good infrared transmittance. As a result, TeO2-BaO (Li2O, Na2O)-La2O3 glass with 10 mol% of BaO has been considered to be more useful as a host for broadband optical fiber amplifier. (c) 2005 Elsevier B.V. All rights reserved.

High quantum fluorescence yield of Er3+ at 1.5 mu m in an Yb3+, Ce3+-codoped CaF2 crystal

For the first time, a quaternary doping system of Er3+, Yb3+, Ce3+, Na+:CaF2 single crystal was demonstrated to have high fluorescence yield in the eye-safe 1.5 mu m region under 980 nm laser diode pumping, with relatively broad and flat gain curves. A simplified model was established to illustrate the effect of Ce3+ on the branching ratio for the Er3+4I11/2 -> I-4(13/2) transition. With 0.2-at.% Er3+ and 2.0-at.% Ce3+ in the quaternary-doped CaF2 crystal, the branching ratio was estimated to be improved more than 40 times by the deactivating effect of Ce3+ on the Er3+ 4I11/2 level. The quaternary-doped CaF2, system shows great potential to achieve high laser performance in the 1.5 mu m region. (c) 2006 Elsevier B.V. All rights reserved.

Metamorphic InGaAs Quantum Well Laser Diodes at 1.5 mu on GaAs Grown by Molecular Beam Epitaxy

We report a 1.5-mu m InGaAs/GaAs quantum well laser diode grown by molecular beam epitaxy on InGaAs metamorphic buffers. At 150 K, for a 1500 x 10 mu m(2) ridge waveguide laser, the lasing wavelength is centred at 1.508 mu m and the threshold current density is 667 A/cm(2) under pulsed operation. The pulsed lasers can operate up to 286 K.

Enhancement of the spectral width of high-power 1.5 mu m integrated superluminescent light source by quantum well intermixing process

A novel type of integrated InGaAsP superluminescent light source was fabricated based on the tilted ridge-waveguide structure with selective-area quantum well (QW) intermixing. The bandgap structure along the length of the device was modified by impurity free vacancy diffusion QW intermixing, The spectral width was broadened from the 16 nm of the normal devices to 37 nm of the QW intermixing enhanced devices at the same output power level. High superluminescent power (210 mW) was obtained under pulsed conditions with a spectral width of 37 nm.

Low threshold current density 1.5 mu m strained-MQW laser by n-type modulation-doping

1.5 mu m. n-type modulation-doping InGaAsP/InGaAsP strained multiple quantum wells grown by low pressure metalorganic chemistry vapor decomposition technology is reported for the first time in the world. N-type modulation-doped lasers exhibit much lower threshold current densities than conventional lasers with undoped barrier layers. The lowest threshold current density we obtained was 1052.5 A/cm(2) for 1000 mu m long lasers with seven quantum wells. The estimated threshold current density for an infinite cavity length was 94.72A/cm(2)/well, reduced by 23.3% compared with undoped barrier lasers. The n-type modulation doping effects on the lasing characteristics in 1.5 mu m devices have been demonstrated.

Structural and optical properties of InAs/GaAs quantum dots emitting at 1.5 mu m

We have demonstrated 1.5 mum light emission from InAs quantum dots (QDs) capped with a thin GaAs layer. The extension of the emission wavelength can be assigned to the large QD height. We also investigate the effect of growth interruption on the PL properties and the shape of InAs QDs fabricated by migration-enhanced growth (MEG). Contrary to expectation, we observed a remarkable blueshift of the emission energy with the growth interruption in MEG mode. Detailed investigations reveal that the blueshift is related to the reduced island height with the growth interruption, which is confirmed by reflection high-energy electron diffraction (RHEED) patterns and atomic force microscopy (AFM) measurement results. Accordingly, the structure changes of the islands are interpreted in terms of thermodynamic and kinetic theories. (C) 2004 Elsevier B.V. All rights reserved.

Unselective regrowth of 1.5-mu m InGaAsP multiple-quantum-well distributed-feedback buried heterostructure lasers

Unselective regrowth for fabricating 1.5-mu m InGaAsP multiple-quantum well (MQW) distributed-feedback (DFB) buried heterostructure (BH) lasers is developed. The experimental results exhibit superior characteristics, such as a low threshold of 8.5 mA, high slope efficiency of 0.55 mW/mA, circular-like far-field patterns, the narrow line-width of 2.5 MHz, etc. The high performance of the devices effectively proves the feasibility of the new method to fabricate buried heterostructure lasers. (c) 2006 Society of Photo-Optical Instrumentation Engineers.

A 1.5 mu m n-type InGaAsP/InGaAsP modulation-doped multiple quantum well DFB laser by MOCVD

1.5 mu m n-type InGaAsP/InGaAsP modulation-doped multiple quantum well (MD-MQW) DFB lasers have been fabricated successfully by low pressure metal organic chemical vapour deposition (LP-MOCVD) technology. The experimental results indicate that n-type MD-MQWs can effectively reduce the threshold Current compared with conventional multiple quantum well DFB lasers. Theoretical analysis indicates that such an effect is due to the much smaller absorption loss and lower Auger recombination, compared with that in an undoped MQW structure. Moreover, the introduction of n-type dopant of suitable levels of concentration in the barrier layers enhances the dynamic characteristics of DFB lasers, due to a coupling between the adjacent quantum well layers and tunnelling-assisted injection, which can reduce the relatively long capture time and increase the effective differential gain 1/X dG/dn .

1.5 mu m luminescence characteristic of erbium in B, P doped a-SiO : H films

Hydrogenated amorphous silicon films co-doped with oxygen (O), boron (B) and phosphorus (P) were fabricated using PECVD technique. The erbium (Er) implanted samples were annealed in a N-2 ambient by rapid thermal annealing. Strong photoluminescence (PL) spectra of these samples were observed at room temperature. The incorporation of O, B and P could not only enhance the PL intensity but also the thermal annealing temperature of the strongest PL intensity. It seems that the incorporation of B or P can decrease the grain boundary potential barriers thus leading to an easier movement of carriers and a stronger PL intensity. Temperature dependence of PL indicated the thermal quenching of Er-doped hydrogenated amorphous silicon is very weak.

PULSED ELECTRICAL OPERATION OF 1.5-MU-M VERTICAL-CAVITY SURFACE-EMITTING LASERS

Vertical cavity surface emitting lasers operating in the 1.3- and 1.5-mu m wavelength ranges are highly attractive for telecommunications applications. However, they are far less well-developed than devices operating at shorter wavelengths. Pulsed electrically-injected lasing at 1.5 mu m, at temperatures up to 240 K, is demonstrated in a vertical-cavity surface-emitting laser with one epitaxial and one dielectric reflector. This is an encouraging result in the development of practical sources for optical fiber communications systems.

1.5 mu m DFB integrated with vertical tapered spotsize converter fabricated by selective MOVPE

1.5 mu m DFB LD butt-joint integrated with vertical tapered spotsize converter was fabricated by LP-MOVPE. The vertical far field angle (FWHM) was decreased from 34degrees to 10degrees the threshold currents was as low as 19.8mA, the output power was 9.6mw at 100mA without HR coating and the SMSR was 35.8dB. The 1-dBm misalignment tolerance was 3.2 mu m, while the counterpart of the device without SSC was 2.2 mu m.

Fabrication and spectroscopic broadening properties for 1.5 mu m amplification of Er3+-doped BaF2 nanoparticles

We show the potential application of Er3+-doped BaF2 nanoparticles prepared from microemulsion technology for 1.5 mu m amplification in telecommunication. Nanoparticles with different sizes of about 8, 10, and 20.5 nm were prepared. The XRD patterns showed the excursion of diffraction peaks. When the particle size is smaller or the diffraction angle is larger, this kind of excursion will be more serious.

GaAs-based room-temperature continuous-wave 1.59 mu m GaInNAsSb single-quantum-well laser diode grown by molecular-beam epitaxy

Starting from the growth of high-quality 1.3 mu m GaInNAs/GaAs quantum well (QW), the QW emission wavelength has been extended up to 1.55 mu m by a combination of lowering growth rate, using GaNAs barriers and incorporating some amount of Sb. The photoluminescence properties of 1.5 mu m range GaInNAsSb/GaNAs QWs are quite comparable to the 1.3 mu m QWs, revealing positive effect of Sb on improving the optical quality of the QWs. A 1.59 mu m lasing of a GaInNAsSb/GaNAs single-QW laser diode is obtained under continuous current injection at room temperature. The threshold current density is 2.6 kA/cm(2) with as-cleaved facet mirrors. (c) 2005 American Institute of Physics.

Influence of growth parameters of frequency-radio plasma nitrogen source on extending emission wavelengths from 1.31 mu m to 1.55 mu m GaInNAs/GaAs quantum wells grown by molecular-beam epitaxy

High (42.5%) indium content GaInNAs/GaAs quantum wells with room temperature emission wavelength from 1.3 mu m to 1.5 mu m range were successfully grown by Radio Frequency Plasma Nitrogen source assisted Molecular Beam Epitaxy. The growth parameters of plasma power and N-2 How rate were optimized systematically to improve the material quality. Photoluminescence and transmission electron microscopy measurements showed that the optical and crystal quality of the 1.54 mu m GaInNAs/GaAs QWs was kept as comparable as that in 1.31 mu m.

1.3 mu m high indium content (42.5%) GaInNAs/GaAs quantum wells grown by molecular beam epitaxy

High structural and optical quality 1.3 mu m GaInNAs/GaAs quantum well (QW) samples with 42.5% indium content were successfully grown by molecular beam epitaxy. The growth of well layers was monitored by reflection high-energy electron diffraction (RHEED). Room temperature photoluminescence (PL) peak intensity of the GaIn0.425NAs/GaAs (6 nm / 20 nm) 3QW is higher than, and the full width at half maximum (FWHM) is comparable to, that of In0.425GaAs/GaAs 3QW, indicating improved optical quality due to strain compensation effects by introducing N to the high indium content InGaAs epilayer. The measured (004) X-ray rocking curve shows clear satellite peaks and Pendellosung fringes, suggesting high film uniformity and smooth interfaces. The cross sectional TEM measurements further reveal that there are no structural defects in such high indium content QWs. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.