Photovoltage and luminescence study of stacked InAs/GaAs self-organized quantum dots

The ground and excited state excitonic transitions of stacked InAs self-organized quantum dots (QDs) in a laser diode structure are studied. The interband absorption transitions of QDs are investigated by non-destructive PV spectra, indicating that the strongest absorption is related to the excited states with a high density and coincides with the photon energy of lasing emission. The temperature and excitation (electric injection) intensity dependences of photoluminescence and electroluminescence indicate the influence of state filling effect on the luminescence of threefold stacked QDs. The results indicate that different coupling channels exist between electronic states in both vertical and lateral directions.

Kinetic modeling of N incorporation in GaInNAs growth by plasma-assisted molecular-beam epitaxy

We have studied the growth of GaInNAs by a plasma-assisted molecular-beam epitaxy (MBE). It was found that the N-radicals were incorporated into the epitaxial layer like dopant atoms. In the range of 400-500 degrees C, the growth temperature (T-g) mainly affected the crystal quality of GaInNAs rather than the N concentration. The N concentration dropped rapidly when T-g exceeded 500 degrees C. Considering N desorption alone is insufficient to account for the strong falloff of the N concentration with T-g over 500 degrees C, the effect of thermally-activated N surface segregation must be taken into account. The N concentration was independent of the arsenic pressure and the In concentration in GaInNAs layers, but inversely proportional to the growth rate. Based on the experimental results, a kinetic model including N desorption and surface segregation was developed to analyze quantitatively the N incorporation in MBE growth. (C) 2000 American Institute of Physics. [S0003-6951(00)00928-1].

Small-signal and large-signal performance test of high-speed optoelectronics devices

This paper presents measurement methods for determining the reflection coefficients and frequency responses of semiconductor laser diodes, photodiodes, and EA modulator chips. A novel method for determining the intrinsic frequency responses of laser diodes is also proposed, and applications of the developed measurement methods are discussed. We demonstrate the compensation of bonding wire on the capacitances of both the submount and the laser diode, and present a method for estimating the potential modulation bandwidth of TO packaging technique. Initial study on removing the effects of test fixture on large-signal performances of optoelectronic devices at high data rate is also given.

Fabrication of a novel silica PLC hybrid integrated triplexer

A new-style silica planar lightwave circuit (PLC) hybrid integrated triplexer, which can demultiplex 1490-nm download data and 1550-nm download analog signals, as well as transmit 1310-nm upload data, is presented. It combines SiO2 arrayed waveguide gratings (AWGs) with integrated photodetectors (PDs) and a high performance laser diode (LD). The SiO2 AWGs realize the three-wavelength coarse wavelength-division multiplexing (CWDM). The crosstalk is less than 40 dB between the 1490- and 1550-nm channels, and less than 45 dB between 1310- and 1490- or 1550-nm channels. For the static performances of the integrated triplexer, its upload output power is 0.4 mW, and the download output photo-generated current is 76 A. In the small-signal measurement, the upstream 3-dB bandwidth of the triplexer is 4 GHz, while the downstream 3-dB bandwidths of both the analog and digital sections reach 1.9 GHz.

Spectrum broadening and reshaping via gain compensation of fiber amplifier

We report a novel technique to broaden and reshape the spectrum of picosecond laser pulse based on the seeder of gain switch laser diode and Yb(3+)-doped fiber amplifier (YDFA). From compensating the seed spectrum with the gain of YDFA, the seed pulse of 7 nm bandwidth is broadened to 20 nm, and the flat top spectral shape is obtained as well. A self-made fiber coupled tunable filter is used to realize the tunable output laser with the wavelength range from 1053 nm to 1073 nm and the line width of 1.4 nm.

Optical properties of a novel neodymium pentafluoropropionate binuclear complex

A novel neodymium pentafluoropropionate binuclear complex, Nd(C(2)F(5)COO)(3)Dipy (Dipy: 2,2'-dipyridyl), was synthesized and characterized by single-crystal X-ray diffraction. At a concentration of 0.2 M in DMSO-d(6), the Judd-Ofelt parameters (Omega(2), Omega(4), Omega(6)) were calculated from the UV-Vis spectrum. According to the small value of Omega(2) and the zero splitting energy of (4)F/(3/2) level, a symmetric ligand field of the complex was confirmed in DMSO-d(6). Strong emission of the complex in DMSO-d(6) at 1057 nm with a decay time about 1.3 mu s were detected when excited at 800 nm pumped by a laser diode. The stimulated emission cross-section of (4)F(3/2) -> (4)I(11/2) fluorescence transition was 2.36 x 10 (20) cm(2) and comparable with some laser glasses, which indicated good radiative properties of this neodymium pentafluoropropionate binuclear complex in liquid matrix. (c) 2008 Elsevier B.V. All rights reserved.

808-nm fiber coupled module with a CW output power up to 130 W

A fiber coupled module is fabricated with integrating the emitting light from four laser diode bars into multimode fiber bundle. The continuous wave (CW) output power of the module is about 130 W with a coupling efficiency of around 80%. The output power is very stable after the temperature cycling and vibration test. No apparent power decrease has been observed as the device working continuously for 500 h.

Design of side-pumped Nd : YAG lasers

Design of the typical laser diode side-pumped Nd:YAG rod system has been discussed using the conventional ray tracing method in this paper. Firstly introduce two basic matrices, refractional and translational matrix, described the transmission of nonparaxial light ray in the medium without concerning the absorption of light. And then, using those matrices, analyze the distribution of pump light in the crystal respectively under the condition of directly pumped system and indirectly pumped system with a cylindrical quartz rod as focusing lens. From the result of simulation, we compare the advantage and disadvantage of the two pumped method, and mainly consider how to select the diameter of the focus lens and cooling tube, indicate the effect of deionized water and cooling tube have on the pump light distribution in the active material. At last, make some conclusions about the side-pumped Nd:YAG laser system.

650nm AlGaInP quantum well lasers for the application of DVD

Main application of 650nm band laser diodes are for digital versatile disk (DVD). We demonstrate here the 650nm AlGaInP LD grown by LP-MOCVD with the structure of selected buried ridge waveguide. Excellent performance of LD have been achieved such as threshold current, threshold current density as low as 20mA and 350A/cm(2) respectively at room temperature, the operating temperature up to 90 for the linear power output of 5mw. RIN is about -130db/Hz, The samples of LD have been certified by PUH manufacturers.

Photovoltage and luminescence study of stacked InAs/GaAs self-organized quantum dots

The ground and excited state excitonic transitions of stacked InAs self-organized quantum dots (QDs) in a laser diode structure are studied. The interband absorption transitions of QDs are investigated by non-destructive PV spectra, indicating that the strongest absorption is related to the excited states with a high density and coincides with the photon energy of lasing emission. The temperature and excitation (electric injection) intensity dependences of photoluminescence and electroluminescence indicate the influence of state filling effect on the luminescence of threefold stacked QDs. The results indicate that different coupling channels exist between electronic states in both vertical and lateral directions.

Tb3+/Yb3+ heavily-doped tellurite glasses with efficient green light emission

Without introducing concentration quenching phenomenon, a few wt% of Tb3+ and Yb3+ ions were doped into a group of easily-fiberized tellurite glasses characterized by loose polyhedron structures and rich interstitial positions. Intense green upconversion emission from Tb3+ ions centered at 539 nm due to transition 5D4→7F5 was observed by direct excitation of Yb3+ ions with a laser diode at 976 nm. Optimizing the concentration ratio of Tb3+/Yb3+, a tellurite glass with composition of 80TeO2-10ZnO-10Na2O (mol%)+1.0wt% Tb2O3+3.0wt% Yb2O3 was found to present the highest green light intensity and therefore is especially suitable for efficient green fiber laser development.

Tunable and efficient diode-pumped Yb3+: GYSO laser

Effective diode-pumped cw tunable laser action of a new alloyed crystal Yb:Gd(2(1-)x) Y2xSiO5 (Yb:GYSO, x = 0.5) is demonstrated for the first time. The alloyed crystal retains excellent laser properties of Gd2SiO5 (GSO), as well as the favorable growth properties and the desirable physical of Y2SiO5 (YSO). With a 5-at.% Yb: GYSO sample, we achieved 2.44 W output power at 1081.5 nm and a slope efficiency of 57%. And its laser wavelength could be tuned from 1030nm to 1089 nm. (c) 2006 Optical Society of America.

Stabilization of optical Fabry-Perot sensor by active feedback control of diode laser

This paper presents the design and characterization of a fiber Fabry-Perot interferometer (FFPI) acoustic wave detector with its Q point being stabilized actively. The relationship between the reflectivity of the F-P cavity facets and cavity length was theoretically analyzed, and high visibility of 100% was realized by optimized design of the F-P cavity. To prevent the drifting of the Q point, a new stabilization method by actively feedback controlling of the diode laser is proposed and demonstrated, indicating the method is simple and easy operating. Measurement shows that good tracing of Q point was effectively realized. (c) 2008 Elsevier B.V. All rights reserved.