High-speed 1.55 μm operation of low-temperature-grown GaAs-based resonant-cavity-enhanced p-i-n photodiodes

The 1.55 μm high-speed operation of GaAs-based p-i-n photodiodes was demonstrated and their design, growth and fabrication were discussed. A resonant-cavity-detector structure was used to selectively enhance the photoresponse at 1.55 μm. The bottom mirror of the resonant cavity was formed by a highly reflecting 15-pair GaAs/AlAs Bragg mirror and molecular-beam epitaxy was used for wafer growth. It was found that the fabricated devices exhibited a resonance of around 1548 nm and an enhancement factor of 7.5 was achieved when compared to the efficiency of a single-pass detector

Excitation power dependence of the Purcell effect in photonic crystalmicrocavity lasers with quantum wires

[EN] The Purcell effect dependence on the excitation power is studied in photonic crystal microcavity lasers embedding InAs/InP quantum wires. In the case of non-lasing modes, the Purcell effect has low dependence on the optical pumping, attributable to an exciton dynamics combining free and localized excitons. In the case of lasing modes, the influence of the stimulated emission makes ambiguous the determination of the Purcell factor. We have found that this ambiguity can be avoided by measuring the dependence of the decay time on the excitation power. These results provide insights in the determination of the Purcell factor in microcavity lasers.We want to acknowledge financial support from the Spanish MICINN through grants (Nos. S-0505-TIC-0191, TEC2008-06756-C03-01/-03, TEC2011-29045-C04-03, TEC2011-29120-C05-01/04, and CAM S2009ESP-1503). J.C.-F. thanks the Spanish MCI for his FPI grant (No. BES-2006-12300).Canet-Ferrer, J.; Prieto, I.; Muñoz Matutano, G.; Martínez, L.; Muñoz-Camuniez, L.; Llorens, J.; Fuster, D.... (2013). Excitation power dependence of the Purcell effect in photonic crystalmicrocavity lasers with quantum wires. Applied Physics Letters. 102(20). https://doi.org/10.1063/1.4807439S10220Gérard, J., Sermage, B., Gayral, B., Legrand, B., Costard, E., & Thierry-Mieg, V. (1998). Enhanced Spontaneous Emission by Quantum Boxes in a Monolithic Optical Microcavity. Physical Review Letters, 81(5), 1110-1113. doi:10.1103/physrevlett.81.1110Englund, D., Fattal, D., Waks, E., Solomon, G., Zhang, B., Nakaoka, T., … Vučković, J. (2005). Controlling the Spontaneous Emission Rate of Single Quantum Dots in a Two-Dimensional Photonic Crystal. Physical Review Letters, 95(1). doi:10.1103/physrevlett.95.013904Munsch, M., Mosset, A., Auffèves, A., Seidelin, S., Poizat, J. P., Gérard, J.-M., … Senellart, P. (2009). Continuous-wave versus time-resolved measurements of Purcell factors for quantum dots in semiconductor microcavities. Physical Review B, 80(11). doi:10.1103/physrevb.80.115312Yoshie, T., Scherer, A., Hendrickson, J., Khitrova, G., Gibbs, H. M., Rupper, G., … Deppe, D. G. (2004). Vacuum Rabi splitting with a single quantum dot in a photonic crystal nanocavity. Nature, 432(7014), 200-203. doi:10.1038/nature03119Badolato, A. (2005). Deterministic Coupling of Single Quantum Dots to Single Nanocavity Modes. Science, 308(5725), 1158-1161. doi:10.1126/science.1109815Hennessy, K., Badolato, A., Winger, M., Gerace, D., Atatüre, M., Gulde, S., … Imamoğlu, A. (2007). Quantum nature of a strongly coupled single quantum dot–cavity system. Nature, 445(7130), 896-899. doi:10.1038/nature05586Strauf, S. (2010). Towards efficient quantum sources. Nature Photonics, 4(3), 132-134. doi:10.1038/nphoton.2010.11Altug, H., Englund, D., & Vučković, J. (2006). Ultrafast photonic crystal nanocavity laser. Nature Physics, 2(7), 484-488. doi:10.1038/nphys343Azzini, S., Gerace, D., Galli, M., Sagnes, I., Braive, R., Lemaître, A., … Bajoni, D. (2011). Ultra-low threshold polariton lasing in photonic crystal cavities. Applied Physics Letters, 99(11), 111106. doi:10.1063/1.3638469Nozaki, K., Kita, S., & Baba, T. (2007). Room temperature continuous wave operation and controlled spontaneous emission in ultrasmall photonic crystal nanolaser. Optics Express, 15(12), 7506. doi:10.1364/oe.15.007506Strauf, S., Hennessy, K., Rakher, M. T., Choi, Y.-S., Badolato, A., Andreani, L. C., … Bouwmeester, D. (2006). Self-Tuned Quantum Dot Gain in Photonic Crystal Lasers. Physical Review Letters, 96(12). doi:10.1103/physrevlett.96.127404Kippenberg, T. J., Spillane, S. M., & Vahala, K. J. (2004). Demonstration of ultra-high-Q small mode volume toroid microcavities on a chip. Applied Physics Letters, 85(25), 6113-6115. doi:10.1063/1.1833556Arakawa, Y., & Sakaki, H. (1982). Multidimensional quantum well laser and temperature dependence of its threshold current. Applied Physics Letters, 40(11), 939-941. doi:10.1063/1.92959Kapon, E. (1992). Quantum wire lasers. Proceedings of the IEEE, 80(3), 398-410. doi:10.1109/5.135356Canet-Ferrer, J., Munoz-Matutano, G., Fuster, D., Alen, B., Gonzalez, Y., Gonzalez, L., & Martinez-Pastor, J. P. (2011). Localization effects on recombination dynamics in InAs/InP self-assembled quantum wires emitting at 1.5 μm. Journal of Applied Physics, 110(10), 103502. doi:10.1063/1.3660260Alén, B., Martı́nez-Pastor, J., Garcı́a-Cristobal, A., González, L., & Garcı́a, J. M. (2001). Optical transitions and excitonic recombination in InAs/InP self-assembled quantum wires. Applied Physics Letters, 78(25), 4025-4027. doi:10.1063/1.1379991Cao, M., Daste, P., Miyamoto, Y., Miyake, Y., Nogiwa, S., Arai, S., … Suematsu, Y. (1988). GaInAsP/InP single-quantum-well (SQW) laser with wire-like active region towards quantum wire laser. Electronics Letters, 24(13), 824. doi:10.1049/el:19880561Atlasov, K. A., Calic, M., Karlsson, K. F., Gallo, P., Rudra, A., Dwir, B., & Kapon, E. (2009). Photonic-crystal microcavity laser with site-controlled quantum-wire active medium. Optics Express, 17(20), 18178. doi:10.1364/oe.17.018178Martinez, L. J., Alén, B., Prieto, I., Fuster, D., González, L., González, Y., … Postigo, P. A. (2009). Room temperature continuous wave operation in a photonic crystal microcavity laser with a single layer of InAs/InP self-assembled quantum wires. Optics Express, 17(17), 14993. doi:10.1364/oe.17.014993Mao, M.-H., & Chien, H.-C. (2012). Transient behaviors of current-injection quantum-dot microdisk lasers. Optics Express, 20(3), 3302. doi:10.1364/oe.20.003302Gregersen, N., Suhr, T., Lorke, M., & Mørk, J. (2012). Quantum-dot nano-cavity lasers with Purcell-enhanced stimulated emission. 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Observation of inverse Compton emission from a long γ-ray burst.

Long-duration γ-ray bursts (GRBs) originate from ultra-relativistic jets launched from the collapsing cores of dying massive stars. They are characterized by an initial phase of bright and highly variable radiation in the kiloelectronvolt-to-megaelectronvolt band, which is probably produced within the jet and lasts from milliseconds to minutes, known as the prompt emission1,2. Subsequently, the interaction of the jet with the surrounding medium generates shock waves that are responsible for the afterglow emission, which lasts from days to months and occurs over a broad energy range from the radio to the gigaelectronvolt bands1-6. The afterglow emission is generally well explained as synchrotron radiation emitted by electrons accelerated by the external shock7-9. Recently, intense long-lasting emission between 0.2 and 1 teraelectronvolts was observed from GRB 190114C10,11. Here we report multi-frequency observations of GRB 190114C, and study the evolution in time of the GRB emission across 17 orders of magnitude in energy, from 5 × 10-6 to 1012 electronvolts. We find that the broadband spectral energy distribution is double-peaked, with the teraelectronvolt emission constituting a distinct spectral component with power comparable to the synchrotron component. This component is associated with the afterglow and is satisfactorily explained by inverse Compton up-scattering of synchrotron photons by high-energy electrons. We find that the conditions required to account for the observed teraelectronvolt component are typical for GRBs, supporting the possibility that inverse Compton emission is commonly produced in GRBs

Heavy element production in a compact object merger observed by JWST

The mergers of binary compact objects such as neutron stars and black holes are of central interest to several areas of astrophysics, including as the progenitors of gamma-ray bursts (GRBs)1, sources of high-frequency gravitational waves (GW)2 and likely production sites for heavy element nucleosynthesis via rapid neutron capture (the r-process)3. Here we present observations of the exceptionally bright gamma-ray burst GRB 230307A. We show that GRB 230307A belongs to the class of long-duration gamma-ray bursts associated with compact object mergers4–6, and contains a kilonova similar to AT2017gfo, associated with the gravitational-wave merger GW1708177–12. We obtained James Webb Space Telescope mid-infrared (mid-IR) imaging and spectroscopy 29 and 61 days after the burst. The spectroscopy shows an emission line at 2.15 microns which we interpret as tellurium (atomic mass A=130), and a very red source, emitting most of its light in the mid-IR due to the production of lanthanides. These observations demonstrate that nucleosynthesis in GRBs can create r-process elements across a broad atomic mass range and play a central role in heavy element nucleosynthesis across the Universe

Enhancement of Solar Cell Efficiency for Space Applications Using Two-Dimensional Photonic Crystals

The effects of having a nanopatterned photonic crystal (PC) structure in the surface of a solar cell can be usefully employed to increase the energy conversion efficiency, which may be critical for space applications. In this work, we have measured the reflectance (R) and transmittance (T) of thin InP layers (270 nm thick) bonded to a glass substrate and nanopatterned with holes down to the glass in a triangular symmetry lattice separated by a lattice parameter a=450nm and maintaining a value of r/a=0.32. The optical spectra were measured with angular resolution in the range from 0.55 to 2.0 eV. There are noticeable changes in the spectra of the PC sample, with minima and maxima of the R and T clearly shifted with respect to the unpatterned sample, and new features that alter significantly the overall lineshape of each spectrum. Those features correspond in a first approximation to the well-known Fano-like resonances of the discrete photonic modes of the PC lattice and they have been used before to determine experimentally the position of the PC bands. The observed features can be translated to the optical absorption (A) defined as A=1-R-T provided there are low or negligible scattering effects. The generated absorption spectra show enhancements above and below the electronic band edge of the InP that can be correlated with the photonic band structure. Even using a thicker semiconductor layer, the abovementioned effects can justify to use a photonic crystal front surface with sub-wavelength motifs. In this way, we have fabricated and characterized a complete Ge/InGaP solar cell with a 2D-PC on its front surface. An increase in the photocurrent up to a 8% was achieved on a solar cell with a 40% of its surface covered with a PC pattern. Enhancements of the external quantum efficiency (EQE) of 22% for a wide range of wavelengths and up to a 46% for specific wavelengths have been measured, without use of any anti-reflection coating (ARC). A correlation with the area of photonic crystal patterning has been clearly observed. Finally, a low-cost nanofabrication procedure to obtain high quality two-dimensional photonic crystals in large areas (up to square cm) is described

InN-based optical waveguides developed by RF sputtering for all-optical applications at 1.55 μm

We report on the design, fabrication, and optical characterization of InN-based optical waveguides aiming at their application as all-optical limiters at 1.55 $\mu \text{m}$. The InN guiding layers are grown by radio frequency (RF) sputtering on sapphire substrates. Experimental cutback method and nonlinear optical transmittance measurements were performed for the developed devices. The waveguides present nonlinear behavior associated with two photon absorption process. A nonlinear absorption coefficient ranging from $\sim 43$ to 114 cm/GW is estimated from optical measurements. These results open the possibility of using RF sputtering as a low cost and thermally harmless technique for the development and overgrowth of InN-based optical waveguides in future III-nitride all-optical integrated circuits working at telecom wavelengthsMinisterio de Economía y CompetitividadComunidad de MadridUniversidad de Alcal