We present experimental studies based on all three methods by which the generation of squeezed light in semiconductors has thus far been demonstrated experimentally: Fourwave mixing, multi-photon absorption and direct generation at the source. Four-wave mixing was used to generate femtosecond-pulsed quadrature squeezed light by cross-phase modulation in single-crystal hexagonal CdSe at wavelengths between 1.42 and 1.55 μm. We measured 0.4 dB squeezing (1.1 dB is inferred at the crystal) using 100 fs pulses. The wavelength and the intensity dependence, as well as variations in the local oscillator configuration were investigated. At higher intensities squeezing was shown to deteriorate owing to competing nonlinear processes. We also characterised the nonlinear optical properties of CdSe in this wavelengths range using an interferometric autocorrelator. In addition, we studied the feasibility of extending this technique to AlGaAs waveguides. The key problems are addressed and solutions are proposed. In a different experiment we used an AlGaAs waveguide to demonstrate for the first time photon-number squeezing by multi-photon absorption. By tuning the pump energy through the half bandgap energy we could effectively select two- or three-photon absorption as the dominant mechanism. Squeezing by these two mechanisms could be clearly distinguished and was found to be in good agreement with longstanding theoretical predictions. We also established the generality of the effect, by demonstrating the same mechanism in organic semiconductors, where it led to the first ever observation of squeezed light in an organic material. Finally, we present our measurements of photon-number squeezing in high-efficiency double heterojunction AlGaAs light-emitting diodes. We measured squeezing of up to 2.0 dB. In addition, we observed quantum noise correlations when several of these devices were connected in series.

Made available in DSpace on 2014-10-09T12:33:45Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:00Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:33:45Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:04:00Z (GMT). No. of bitstreams: 0 / O presente trabalho realiza a investigação dos parâmetros hiperfinos, incluindo a sua natureza dinâmica, em compostos ligantes em solução a temperatura ambiente (295 K) e resfriada (77K) através da espectroscopia de Correlação Angular γγ Perturbada (CAP). Para a realização das medidas experimentais, utilizou-se núcleos de prova radioativos de 111In111Cd, 181Hf181Ta e 111mCd111Cd, que decaem através de cascata gama. As amostras foram preparadas diluindo-se soluções com os núcleos radioativos em água, quando se investigou a interação do núcleo de prova com o ligante água; adicionando-se soluções com os núcleos radioativos em solução tampão, quando se investigou a interação do núcleo de prova com os íons ligantes provenientes do próprio tampão (CO32- e HCO31-) e com o OH1-; e adicionando-se soluções com os núcleos radioativos em soluções do ligante ácido etilenodiaminotetracético (EDTA), este em pH entre 4,0 e 5,0, (que corresponde ao pH da própria solução saturada do EDTA) e em solução tampão de pH entre 9 e 10. Assim foi possível investigar os efeitos gerados por cada um desses métodos de preparação de amostras nas medidas CAP. Finalmente foi feita uma análise comparativa para os vários métodos de inserção dos núcleos de prova na amostra, considerando-se aspectos químicos e nucleares. A inexistência de medidas para esse tipo de amostra, justifica a importância dos resultados obtidos. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

Recently, the Parkin group has synthesized tris[(1-isopropylbenzimidazol-2-yl)dimethylsilyl]methane, [Tismᴾʳⁱᴮᵉⁿᶻ]H, a bulky tetradentate tripodal ligand, which upon deprotonation can coordinate to metal centers via three nitrogen donor atoms and a carbon bridgehead to form metal atrane compounds. The [Tismᴾʳⁱᴮᵉⁿᶻ] ligand has been previously shown to stabilize metal hydride complexes, for example [Tismᴾʳⁱᴮᵉⁿᶻ]MgH [Tismᴾʳⁱᴮᵉⁿᶻ]ZnH. However, no attempts had been previously made to employ this ligand to stabilize heavier Group 12 analogues of these complexes, namely the cadmium and mercury hydride derivatives. In addition, all [Tismᴾʳⁱᴮᵉⁿᶻ] complexes previously reported have employed metals in the first or second oxidation states. In this work, an investigation is undertaken to use the [Tismᴾʳⁱᴮᵉⁿᶻ] ligand to stabilize rare examples of cadmium and mercury hydrides, as well as survey how this ligand binds to Group 13 and transition metals in a variety of oxidation states. In Chapter 1, a series of [Tismᴾʳⁱᴮᵉⁿᶻ] cadmium complexes are reported, including the novel cadmium hydride species [Tismᴾʳᴮᵉⁿᶻ]CdH, which is only the third terminal cadmium hydride species to be structurally characterized by X-ray diffraction. The reactivity of this complex has been probed, revealing the first detailed report of reactivity for a Cd-H bond, as well as the first comparison in relative reactivity between an analogous Cd-H and Zn-H bond. This reactivity of [Tismᴾʳⁱᴮᵉⁿᶻ]CdH includes the ability to insert CO₂ and CS₂, and the resulting cadmium formate and dithioformate complexes have been characterized and discussed, with the latter being the first structurally characterized example of a cadmium dithioformate complex. In addition, [Tismᴾʳⁱᴮᵉⁿᶻ]CdH can undergo hydride extraction to yield the ion pair {[Tismᴾʳⁱᴮᵉⁿᶻ]Cd}[HB(C6F5)₃], a rare example of trigonal monopyramidal cadmium complex. Finally, [Tismᴾʳⁱᴮᵉⁿᶻ]CdMe was synthesized, revealing a different coordination mode of the [Tismᴾʳⁱᴮᵉⁿᶻ] ligand than in the analogous [Tismᴾʳⁱᴮᵉⁿᶻ]ZnMe. In Chapter 2, a series of [Tismᴾʳⁱᴮᵉⁿᶻ] mercury complexes are reported and compared with their cadmium analogues. This comparison revealed several notable differences between [Tismᴾʳⁱᴮᵉⁿᶻ] mercury and cadmium complexes, most notably that the M-O-Si bond angle in [Tismᴾʳⁱᴮᵉⁿᶻ]HgOSiPh₃ is bent, as opposed to the linear [Tismᴾʳⁱᴮᵉⁿᶻ]CdOPh₃ derivative. The synthesis and characterization of [Tismᴾʳⁱᴮᵉⁿᶻ]HgH, the first mercury hydride complex to be structurally characterized by X-ray diffraction, is also reported. This complex has been crystallized in both the κ⁴ and κ³-coordination mode of the [Tismᴾʳⁱᴮᵉⁿᶻ] ligand, representing the first example of a [Tismᴾʳⁱᴮᵉⁿᶻ] compound to be structurally characterized in two coordination modes. In Chapter 3, the synthesis of Group 13 and transition metal [Tismᴾʳⁱᴮᵉⁿᶻ] complexes are reported. These compounds include the first examples of [Tismᴾʳⁱᴮᵉⁿᶻ]M(III) complexes, which reveal that trivalent Group 13 [Tismᴾʳⁱᴮᵉⁿᶻ]M halide compounds form charged ion pairs, whereas trivalent transition metal chloride compounds form six-coordinate octahedral complexes. The investigation into Group 13 [Tismᴾʳᴮᵉⁿᶻ] complexes also led to the structural characterization of [Tismᴾʳⁱᴮᵉⁿᶻ]In→InI₃, the first example of a [Tismᴾʳⁱᴮᵉⁿᶻ] compound with a metal-metal bond. A series of [Tismᴾʳⁱᴮᵉⁿᶻ]MCl (M = Mn, Fe, Co, Cu) complexes are reported and their metrical data compared, along with an investigation into the reactivity of [Tismᴾʳⁱᴮᵉⁿᶻ]NiBr, which led to spectroscopic evidence for a [Tismᴾʳⁱᴮᵉⁿᶻ]NiH complex. Finally, the gold complex [κ1-Tismᴾʳⁱᴮᵉⁿᶻ]AuPPh₃ is reported, which adopts a novel κ1-coordination of the [Tismᴾʳⁱᴮᵉⁿᶻ] ligand.