Large Photonic Band Gaps in Certain Periodic and Quasi-Periodic Networks in two and three dimensions

The photonic band structures in certain two- and three-dimensional periodic networks made of one-dimensional waveguides are studied by using the Floquet-Bloch theorem. We find that photonic band gaps exist only in those structures where the fundamental loop exhibits anti-resonant transmission. This is also true for quasi-periodic networks in two and three dimensions, where the photonic band structures are calculated from the spectra of total transmission arising from a source inside the samples. In all the cases we have studied, it is also found that the gap positions in a network are dictated by the frequencies at which the anti-resonance occurs.Comment: 7 pages, 10 figures and 1 table. Published in Phys. Rev. B, 70, 125104 (2004

Quantum Maxwell-Bloch equations for spontaneous emission in optical semiconductor devices

We present quantum Maxwell-Bloch equations (QMBE) for spatially inhomogeneous optical semiconductor devices taking into account the quantum noise effects which cause spontaneous emission and amplified spontaneous emission. Analytical expressions derived from the QMBE are presented for the spontaneous emission factor beta and the far field pattern of amplified spontaneous emission in broad area quantum well lasers

Many-body effects in a semiconductor microcavity laser: Experiment and theory

Many-body effects are observed in the threshold properties of selectively oxidized vertical-cavity surface-emitting lasers. These microcavity lasers represent the state-of-the-art in low threshold semiconductor injection lasers

Quantum Maxwell-Bloch equations for spatially inhomogeneous semiconductor lasers

We present quantum Maxwell-Bloch equations (QMBE) for spatially inhomogeneous semiconductor laser devices. The QMBE are derived from fully quantum mechanical operator dynamics describing the interaction of the light field with the quantum states of the electrons and the holes near the band gap. By taking into account field-field correlations and field-dipole correlations, the QMBE include quantum noise effects which cause spontaneous emission and amplified spontaneous emission. In particular, the source of spontaneous emission is obtained by factorizing the dipole-dipole correlations into a product of electron and hole densities. The QMBE are formulated for general devices, for edge emitting lasers and for vertical cavity surface emitting lasers, providing a starting point for the detailed analysis of spatial coherence in the near field and far field patterns of such laser diodes. Analytical expressions are given for the spectra of gain and spontaneous emission described by the QMBE. These results are applied to the case of a broad area laser, for which the frequency and carrier density dependent spontaneous emission factor beta and the evolution of the far field pattern near threshold are derived.Comment: 22 pages RevTex and 7 figures, submitted to Phys.Rev.A, revisions in abstract and in the discussion of temporal coherenc

Optical Electronics

The five years that have intervened since the appearance of the third edition of OPTICAL ELECTRONICS witnessed significant technical developments in the field and the emergence of some major trends. A few of the important developments are 1. Optical fiber communication has established itself as the key communication technology. 2. The semiconductor laser and especially the longer wavelength GaInAsP/InP version has emerged as the main light source for high-data-rate optical fiber communication systems. 3. Quantum well semiconductor lasers started replacing their conventional counterparts for high-data-rate long distance communication and most other sophisticated applications including ultra-low threshold and mode- locked lasers. 4. Optical fiber amplifiers are causing a minor revolution in fiber communication due to their impact on very long distance transmission and on large scale optical distribution systems. The accumulated weight of the new developments was such that when I last taught the course at Caltech in 1989 I found myself using a substantial fraction of course material that was not included in the text. The fourth edition brings this material into the fold. The main additions to the third edition, include major revisions and new chapters dealing with 1. Jones calculus and its extension to Faraday effect elements. 2. Radiometry and infrared detection. 3. Optical fiber amplifiers and their impact on fiber communication links. 4. Laser arrays. 5. Distributed feedback lasers, including multi-element lasers with phase shift sections. 6. Quantum well and ultra-low threshold semiconductor lasers. 7. Photorefractive crystals and two-beam coupling in dynamic holography and image processing. 8. Two-beam coupling and phase conjugation in stimulated Brillouin scattering. 9. Intensity fluctuations and coherence in semiconductor lasers and their impact on fiber communication systems. The book continues to be aimed at the student interested in learning how to generate and manipulate optical radiation and how to use it to transmit information. At Caltech the course is taken, almost in equal proportions, by electrical engineering, physics, and applied physics students. About half the students tend to be seniors and the rest graduate students. The prerequisites for taking the course at Caltech are a sound undergraduate background in electromagnetic theory—usually a one year course in this area—and an introduction to atomic physics. The hands-on and research flavor of the book owes greatly to the exciting mix of visitors, talented students, and postdocs who bombard me continually with their newest findings and thoughts

Wafer bonding for fabrication of three-dimensional photonic band gap crystals

Photonic band gap (PBG) crystals are artificially engineered periodic dielectric structures which exhibit forbidden frequency regions where electromagnetic waves cannot propagate. Since the use of three-dimensional PBG crystals was first proposed in 1987 to control optical properties, these structures have generated considerable interest due to their potential applications over a wide frequency range. However, the demonstration of practical three-dimensional PBG crystals has been limited to larger-dimensional structures operating below far-infrared frequencies because of difficulties in fabricating small complex structures;In this work, we have devised techniques for use in fabricating 3-D PBG crystals with micrometer length scales operating in the mid-infrared region. This microfabrication-based approach uses alternating steps of wafer fusion bonding, selective substrate etching, and pattern etching to sequentially build up PBG crystals in a layer-by-layer fashion. The wafer fusion technique was utilized to stack up GaAs thin films. To enhance the bonding, a thin (Ga,In)As bonding layer has been incorporated into the structure to improve the bonding strength between two PBG layers;The surfaces and interfaces of the bonded samples have been characterized mechanically and optically to further determine the optimum bonding conditions for PBG crystals. Using (Ga,In)As layers, smooth and uniform bonded surfaces and good adhesion at the interfaces have been achieved at annealing temperatures of ~650°C. By reducing the anneal times and In content in (Ga,In)As alloys, the overall transmission intensities have been improved over the entire spectrum, particularly at higher frequencies;Using wafer fusion bonding techniques, we have successfully constructed multi-layer structures with PBG dimensions at micron length scales. With improved stacking interfaces, wafer bonding and micromachining techniques provide a promising way to realize photonic crystals with stop bands around 10 [mu]m

Coupling techniques between dielectric waveguides and planar photonic crystals

El objetivo de esta tesis es la investigación de estructuras y técnicas de acoplo para minimizar las pérdidas de acoplo entre guías dieléctricas y cristales fotónicos planares. En primer lugar se ha estudiado el modelado del acoplo entre guías dieléctricas y guías en cristal fotónico así como la influencia de los principales parámetros del cristal en la eficiencia de acoplo. Se han obtenido expresiones cerradas para las matrices de reflexión y transmisión que caracterizan totalmente el scattering que ocurre en el interfaz formado entre una guía dieléctrica y una guía en cristal fotónico. A continuación y con el fin de mejorar la eficiencia de acoplo desde guías dieléctrica de anchura arbitraria, se ha propuesto como contribución original una técnica de acoplo basada en la introducción de defectos puntuales en el interior de una estructura de acoplo tipo cuña realizada en el cristal fotónico. Diferentes soluciones, incluida los algoritmos genéticos, han sido propuestas con el objetivo de conseguir el diseño óptimo de la configuración de defectos. Una vez conseguido un acoplo eficiente desde guías dieléctricas a guías en cristal fotónico, se ha investigado el acoplo en guías de cavidades acopladas. Como contribución original se ha propuesto una técnica de acoplo basada en la variación gradual del radio de los defectos situados entre cavidades adyacentes. Además, se ha realizado un riguroso análisis en el dominio del tiempo y la frecuencia de la propagación de pulsos en guías acopladas de longitud finita. Dicho estudio ha tenido como objetivo la caracterización de la influencia de la eficiencia del acoplo en los parámetros del pulso. Finalmente, se han presentado los procesos de fabricación y resultados experimentales de las estructuras de acoplo propuestas.Sanchis Kilders, P. (2005). Coupling techniques between dielectric waveguides and planar photonic crystals [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/1854Palanci

External Cavity Quantum Cascade Lasers

In this thesis we deploy mid-infrared quantum cascade lasers (QCLs) in external linear cavity (EC) and external ring cavity (ERC) configurations, with the aim to develop the platform as a source for high resolution gas spectroscopy. Initially, the temporal evolution of pulsed ERC-QCL system is compared to that of standard Fabry Perot (FP) QCLs to provide insight into the role played by the additional external feedback provided by ECs and ERCs. Time-resolved spectral measurements show that external feedback promotes single longitudinal mode operation on a shorter timescale than is the case for FP-QCLs. A room temperature wavelength tunable external ring cavity QCL is presented which shows improved performance over its linear counterpart due to its ability to support unidirectional emission regimes. Spectral comparisons between linear and ring cavities show that these regimes lead to improved performance due to the suppression of spatial hole burning (SHB), an instability common to linear laser resonators. An active modulation scheme based on a number of bespoke power amplifiers and bias-tees is developed. These systems are used to produce mode-locked pulse trains in external cavity and external ring cavity QCLs by modulating the QCL gain medium’s drive current at frequencies matching the cavity’s round trip frequency. Spectral and temporal comparisons are made between these two cases. Asymmetric pulse propagation is observed in the case of the ERC-QCL which has been suggested as promising platform for ultrashort mode-locked mid-infrared pulses