Three-transition cascade erbium laser at 1.7, 2.7, and 1.6 µm

We report on an upconversion cascade laser in an erbium-doped ZBLAN fiber emitting simultaneously on the three transitions 4S3/2 -> 4I9/2 at 1.7 um, 4I11/2 -> 4I13/2 at 2.7 um, and 4I13/2 -> 4I15/2 at 1.6 um. At moderate pump powers, the laser transition at 1.6 um supports 2.7-um lasing and permits a slope efficiency at 2.7 um of 15% versus launched pump power. Above the threshold of upconversion lasing at 1.7 um, the slope efficiency at 2.7 um increases to 25.4%. Taking pump excited-state absorption into account, this value represents more than 90% of the theoretical slope efficiency. A transversely single-mode output power of 99 mW is achieved at 2.7 um

Double cascade erbium fiber laser at 1.7 µm, 2.7 µm, and 1.6 µm

The output power of the erbium laser at 2.7 um (4I11/2 -> 4I13/2) is enhanced due to simultaneous laser action at 1.7 um (4S3/2 -> 4I9/2) and 1.6 um (4I13/2 -> 4I15/2) in an Er3+-doped fluorozirconate fiber. The laser cascade overwhelms the saturation effect for the transition at 2.7 um by suppressing the laser transition at 850 nm (4S3/2 -> 4I13/2) with lasing at 1.7 um [1]. The population of the level 4S3/2 occurs for pump wavelengths around 800 nm due to strong pump excited state absorption (ESA). A fluorozirconate fiber (core diameter: 6 um, N.A.: 0.4, 3000 ppm Er3+, length: 1.1 m) fabricated be Le Verre Fluoré was used for the measurements. The fiber laser set-up was of the Fabry-Perot type. The mirrors used as input and output mirror had reflectivities of 99% at 1.7 um, 98% at 1.6 um, 32% at 2.7 um and approximately 10% at 850 nm. Transmissivity at 792 nm was 84%. It was estimated that 70% of the impinging pump power was launched into the core. Using the pump wavelength at 792 nm, the laser at 2.7 um was the first initiated. The transition at 1.7 um had a higher threshold power at about 300 mW launched pump power. Figure 1 shows the laser spectra for the cascade lasers at 1.6 um and 1.7 um. The maxima are located at 1.6 um and 1.72 um. [1] M. Pollnau, Ch. Ghisler, G. Bunea, M. Bunea, W. Lüthy, H. P. Weber: Appl. Phts. Lett. 66, No. 26, (June 1995), p. 3564-3566. [2] J. Schneider, D. Hauschild, Ch. Frerichs, L. Wetenkamp: Int. J. Infrared and Millimeter Waves 15, No. 11, (November 1994), p. 1907-1922

85 °C error-free operation at 38 Gb/s of oxide-confined 980-nm vertical-cavity surface-emitting lasers

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 100, 081103 (2012) and may be found at https://doi.org/10.1063/1.3688040.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, BauelementeEC/FP7/224211/EU/VISIT - Vertically Integrated Systems for Information Transfer/VISI

Electrically driven single photon source based on a site-controlled quantum dot with self-aligned current injection

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 101, 211119 (2012) and may be found at https://doi.org/10.1063/1.4767525.Electrical operation of single photon emitting devices employing site-controlled quantum dot (QD) growth is demonstrated. An oxide aperture acting as a buried stressor structure is forcing site-controlled QD growth, leading to both QD self-alignment with respect to the current path in vertical injection pin-diodes and narrow, jitter-free emission lines. Emissions from a neutral exciton, a neutral bi-exciton, and a charged exciton are unambiguously identified. Polarization-dependent measurements yield an exciton fine-structure splitting of (84 ± 2) μeV at photon energies of 1.28–1.29 eV. Single-photon emission is proven by Hanbury Brown and Twiss experiments yielding an anti-bunching value of g(2)(0) = 0.05 under direct current injection.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, Bauelement

Parton-Hadron Duality: Resonances and Higher Twists

We explore the physics of the parton-hadron duality in the nucleon structure functions appearing in lepton-nucleon scattering. We stress that the duality allows one to extract the higher-twist matrix elements from data in the resonance region, and learn about the properties of resonances if these matrix elements are known. As an example, we construct the moments of $F_2(x, Q^2)$ for the low and medium $Q^2$ region, and from which we study the interplay between higher twists and the resonance contributions.Comment: 7 pages with 4 figures and 1 table, REVTeX, MIT-CTP-234

Lateral positioning of InGaAs quantum dots using a buried stressor

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 100, 093111 (2012) and may be found at https://doi.org/10.1063/1.3691251.We present a “bottom-up” approach for the lateral alignment of semiconductor quantum dots (QDs) based on strain-driven self-organization. A buried stressor formed by partial oxidation of (Al,Ga)As layers is employed in order to create a locally varying strain field at a GaAs(001) growth surface. During subsequent strained layer growth, local self-organization of (In,Ga)As QDs is controlled by the contour shape of the stressor. Large vertical separation of the QD growth plane from the buried stressor interface of 150 nm is achieved enabling high optical quality of QDs. Optical characterization confirms narrow QD emission lines without spectral diffusion.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, Bauelement