The need for higher bandwidth and people's desire to be "always connected" have spurred a new era of silicon photonics. The traditional integrated electrical transmission lines have been an obstacle preventing ultra high speed communication. Using monolithic chips of integrated optoelectronic circuits from silicon provides an economic way to realize Tetra Byte/Second bandwidth in a variety of areas such as "fiber to the home" and the buses linking chips inside computer. The heart of such optoelectronics-silicon laser-is still in pursuit. One of the most promising approaches is the erbium doped silicon nanocrystals embedded in silica system. External photon or hot electrons injection excites the silicon nanocrystals, which then transfer their energies to nearby erbium ions to emit light at 1.55 μm wavelength range. In this thesis, we investigate the effects of cavity and electric field on energy transfer from Si nanocrystals (Si-nc's) to Er ions, and simulate material gain in such systems. Our results show that microcavity can enhance the Forster energy transfer and material gain, reducing the requirements for Si-nc pumping. The electric field will hinder the radiation decay of Si-nc, but we have to further explore the tunneling mechanism before concluding the overall effect of electric field. Some future work needs to be done, which will shine some light on the design of the silicon laser.
The need for higher bandwidth and people's desire to be "always connected" have spurred a new era of silicon photonics. The traditional integrated electrical transmission lines have been an obstacle preventing ultra high speed communication. Using monolithic chips of integrated optoelectronic circuits from silicon provides an economic way to realize Tetra Byte/Second bandwidth in a variety of areas such as "fiber to the home" and the buses linking chips inside computer. The heart of such optoelectronics-silicon laser-is still in pursuit. One of the most promising approaches is the erbium doped silicon nanocrystals embedded in silica system. External photon or hot electrons injection excites the silicon nanocrystals, which then transfer their energies to nearby erbium ions to emit light at 1.55 μm wavelength range. In this thesis, we investigate the effects of cavity and electric field on energy transfer from Si nanocrystals (Si-nc's) to Er ions, and simulate material gain in such systems. Our results show that microcavity can enhance the Forster energy transfer and material gain, reducing the requirements for Si-nc pumping. The electric field will hinder the radiation decay of Si-nc, but we have to further explore the tunneling mechanism before concluding the overall effect of electric field. Some future work needs to be done, which will shine some light on the design of the silicon laser.
Energy transfer in erbium doped optical waveguides based on silicon This thesis describes the energy transfer processes\noccurring in materials that can be used for the fabrication of silicon compatible optical integrated circuits, operating at 1.54 mm.The thesis consists of three parts: Part I discusses energy transfer in optical waveguide amplifiers on silicon. The waveguide amplifiers use an intra-4f transition of the rare earth ion erbium occurring at 1.54 mm. To achieve significant amplification, high\n Er concentrations (> 10 20 cm -3 ) are required. At these concentrations Er ions can interact, resulting in co-operative\n upconversion, in which one excited Er ion is excited into a higher energy state, while a neighboring Er ion returns to the ground\n state. In Part I this and other gain limiting effects are investigated. In particular, it is shown that the atomic-scale Er distribution\n is of crucial importance for the performance of Er doped waveguide amplifiers. Part II discusses the energy transfer processes\n occurring in Er doped silicon. It is shown that Er in silicon can be excited by electron-hole pair recombination in an\n impurity-Auger effect. This effect may be used to fabricate an electrically pumped Er doped waveguide amplifier. The reverse\n process can also occur: an excited Er ion can de-excite and generate an electron-hole pair in the silicon, due to a non-radiative\n backtransfer process. This process has an efficiency of 70% at room temperature. This observation enables the fabrication of an\n Er doped photo-detector in a Si waveguide operating at 1.54 mm. The performance of such a detector is discussed. Part III\n discusses the interaction between Er and silicon nanocrystals embedded in SiO2. Si nanocrystals efficiently absorb visible light,\n resulting in the generation of quantum confined electron-hole pairs. The electron-hole pairs efficiently transfer energy to Er.\n Due to the energy transfer, the effective Er absorption cross section is five orders of magnitude larger than for direct optical\n excitation. Silicon nanocrystals may thus be used to increase the pumping efficiency of an Er doped waveguide amplifier. It is\n shown that a single nanocrystal can excite ~1 Er ion at a time and that an optical gain of 0.6 dB/cm may be achieved in a typical\n nanocrystal sensitized waveguide amplifier. Due to the broad absorption band of Si nanocrystals, a broad band light source can\n be used as pump source in such a nanocrystal sensitized Er doped waveguide amplifier.
Erbium is a rare-earth metal that, when incorporated in a solid, can emit light at a wavelength of 1.5 μm. It plays a key role in current day telecommunication technology as the principle ingredient of optical fiber amplifiers. In this thesis the control of the Er spontaneous emission in three different types of microphotonic materials is described. Part I of this thesis focuses on the effect of a metallo-dielectric interface on the spontaneous emission of optical emitters in silica glass. It is shown that Er ions near a Ag interface can couple to surface plasmons (SPs) via a near-field interaction. By coupling SPs out into the far field, large changes in the Er photoluminescence emission distribution, spectra, and polarization can be observed. The excitation of SPs also results in an increase of the Er photoluminescence decay rate. The observed decay rates are in good agreement with calculations based on a classical dipole oscillator model. From the change in photoluminescence decay rate of Si nanocrystals near a Ag interface it is shown that Si nanocrystals can efficiently excite SPs and have an internal quantum efficiency of 77 %. Part II focuses on the effect of a microcavity on the spontaneous emission of Er and describes how ion implantation can be used to dope dielectric microresonators with optically active Er ions. The fabrication and characterization of an Er ion-implanted silica microsphere resonator is described that shows lasing at 1.5 μm when pumped above its lasing threshold. Ion implantation is also used to dope toroidal microcavities on a Si chip with Er. The microtoroids are doped by either pre-implantation into the SiO2 base material, or by post-implantation in a fully fabricated microtoroid. The optical activation of Er ions in the microtoroid is investigated and Er lasing at 1.5 μm is observed for both types of microcavities with the lowest threshold (4.5 μW) for the pre-implanted microtoroids. Part III describes the fabrication of an Er-doped Si-inverse opal photonic crystal. These photonic crystals can potentially have a photonic bandgap that can fully inhibit the spontaneous emission of on optical emitter. Fabrication criteria are derived for such a photonic crystal, based on the lattice parameter, filling fraction, and Si refractive index. In the opal photonic crystal composed of both Si and SiO2 we show that Er ions can be selectively excited in both the Si and SiO2 part of the photonic crystal by changing the excitation wavelength and/or the measurement temperature.
Abstract—In this article the details of Erbium doped Fiber Amplifier (EDFA) in presence of Silicon nanocrystal (Si-Nc) is investigated. In this analysis Si-Nc and Er ions in matrix of fiber are assumed two and five levels respectively. For this structure rate equation for transient and steady state analysis is considered. The range of Er (+3) concentration and pump intensity at 488 nm are considered [10 17 − 10 21]1/cm 3 and [10 17 − 10 23] photon/cm 2 · sec respectively in this paper. Based on numerical simulation of this problem we observed that with increasing of concentration of the Si-Nc the fiber length for given optical gain is decreased. For example in the case of 40 dB optical gain, we calculated fiber length to be 1.1 × 10 5 cm without Si-Nc and 5 × 10 2 cm for σCCa = 1 × 10 −17 cm 2 (confined carrier absorption cross-section) and 5 cm for σCCa =1 × 10 −19 cm 2 respectively. Our simulations show that for second level with increasing pump intensity the population rise and fall times are decreased. But, for third level the population rise time is decreased and fall time is depends to level of Er ion interactions. We observed that with increasing Er ions optical net gain is increased and finally has a maximum. After this special value of Er ions because of increasing in interaction between ions the net gain finally begin to decrease. In this analysis we let to Er ions have inhomogeneous distribution. Also, we observed that in this case with increasing of the distribution peak, the net gain is increased, interaction between ions is increased, the coupling coefficient to the Si-Ncs is increased and losses due to Si-Ncs are decreased. Finally effect of Kexiton (maximum number of exciton in single Si-Nc) on amplification process is considered and we observed that in the case of Kexiton = 2 the optical gain considerably and introduced losses due to Si-Nc are increased. 28 Rostami and SalmanOgli 1.
Quantum-based communication systems can potentially achieve the ultimate security from eavesdropping and greatly reduce the operating powers on chip. Light-speed transmission, noise immunity, and low noise properties make photons indispensable for quantum communication to transfer a quantum state through a transmission line. Furthermore, the field of silicon nanophotonics is fast growing field which is driven by the attractive and promising improvements it has to offer in high speed communication systems and on chip optical interconnects. Consequently, there is a high demand to develop the building blocks for photon manipulation in silicon nanophotonic circuits. The goal of the work is to enable high performance optoelectronic computing and communication systems that overcome the barriers of electronics and dramatically enhance the performance of circuits and systems. We will focus our attention on solving some of the issues with the current systems regarding photon storage, routing, isolation, switching, and energy conversion. We realize a continuously tunable optical memory which breaks the time-bandwidth limit by more than thirty times. This enabled the storage of ultra-short pulses of light for hundreds of picoseconds. Also, we investigate on-chip photon scattering when transmitted through micro-scale optical cavities. In addition, we develop novel dynamic quantum mechanical models that predict quantum-like behavior of single and multi-photon wavepackets. Furthermore, we report for the first time that efficient red shifts in silicon are achievable with free carrier injection which generally produces blue wavelength shifts. We realize adiabatic wavelength conversion and discrete photonic transitions of single photons in silicon cavities. Moreover, we demonstrate a basic quantum network on chip with an on-chip photon source. We present a novel design for CMOS compatible optical isolator on silicon chip using a system of active cavities. And finally, we analyze a novel ultra-fast broadband modulator in silicon based on free-carrier absorption effect in SOI waveguides integrated with Schottky diodes.
In recent years, silicon photonics has achieved great success in optical communication area. More and more on-chip optoelectronic devices have been realized and commercialized on silicon photonics platform, such as silicon-based modulators, filters and detectors. However, on-chip light sources are still not achieved because that silicon is an indirect bandgap material. To solve this problem, the rare earth element erbium (Er) is considered, which emits light covering 1.5 μm to 1.6 μm and has been widely used in fiber amplifiers. Compared to Er-doped fiber amplifiers (EDFA), the Er ion concentration needs to be more than two orders higher for on-chip Er-based light sources due to the compact size integration requirements. Therefore, the choice of the host material is crucially important. In this paper, we review the recent progress in on-chip Er-based light sources and the advantages and disadvantages of different host materials are compared and analyzed. Finally, the existing challenges and development directions of the on-chip Er-based light sources are discussed.
Summary form only given: Amplification in rare-earth doped solid state planar optical structures has attracted a lot of interest in recent years due to the fact that the rare earth ions show sharp absorption and emission bands and relatively long luminescence lifetimes. In particular the erbium (Er) ion is very attractive because of its intra 4f-transition from the first excited state to the ground state around 1.53 mum (4I13/2-4I15/2). The main problem of the erbium doped waveguide amplifiers (EDWAs) is that high values of the Er3+concentration are required to reach high gain figures in a compact length, but in this way the concentration quenching effects become very considerable and detrimental to the optical gain, since they reduce the population in the first excited state. A good solution to overcome this dramatic drawback is to consider erbium doped photonic crystal amplifier (EDPCA). In fact the small group velocity of electromagnetic eigenmodes brings about the enhancement of stimulated emission if the photonic crystals are doped by active media as the rare earth ions E3+r or Yt3+. This phenomenon originates from the long interaction time between radiation field and the matter caused by the small group velocity near the edge of the photonic band gap. The efficient confinement of light is achievable not only by tuning the input signal at the band edge of the gap of the photonic crystal but it is also obtainable by introducing local defects inside photonic crystals. The density of electromagnetic states inside a cavity is significantly modified and the spontaneous emission of atoms in a cavity can be either enhanced or inhibited. Erbium doped silica-titania one-dimensional photonic crystal microcavities have been analyzed by solving the erbium rate equations and the Maxwell equations by means of an auxiliary differential equation finite difference time domain technique. Since the performance of optical amplifiers depends on the populations of the energy levels participating in radiative transitions, determined principally by the distribution and concentration of the rare-earth ions and by the pumping conditions, the relations between these parameters and the transmittance of the EDPCMA have been studied