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Simulating Quantum Cascade Lasers with the Position and Energy Resolving Lindblad approach

Muñoz Basagoiti, Maitane LU (2019) FYSM60 20191
Mathematical Physics
Department of Physics
Abstract
Over the past two decades, Quantum Cascade Lasers (QCLs) have become an increasingly popular source for mid-infrared and terahertz radiation. Nowadays, their experimental development progresses fast with the aid of computer simulations. These reproduce carrier dynamics in the gain medium of the laser based on different transport models. A fast and reliable simulation package for QCLs is key for the future realization of optimized structures. In this thesis, we have tested the validity of a recently presented QCL simulation package called Lindblad-QCL. The package is based on a heuristic and phenomenological density matrix approach: the Position and Energy Resolving Lindblad approach. We have run several QCL simulations using the... (More)
Over the past two decades, Quantum Cascade Lasers (QCLs) have become an increasingly popular source for mid-infrared and terahertz radiation. Nowadays, their experimental development progresses fast with the aid of computer simulations. These reproduce carrier dynamics in the gain medium of the laser based on different transport models. A fast and reliable simulation package for QCLs is key for the future realization of optimized structures. In this thesis, we have tested the validity of a recently presented QCL simulation package called Lindblad-QCL. The package is based on a heuristic and phenomenological density matrix approach: the Position and Energy Resolving Lindblad approach. We have run several QCL simulations using the Lindblad-QCL simulation package and compared the results to experimental data. These simulations provide a good qualitative description of the QCL active medium. We have extended the simulation package implementing interface roughness scattering and analysed the impact of temperature in the simulations. The results we present in this thesis show that Lindblad-QCL is a candidate to become a strong QCL simulation package. (Less)
Popular Abstract
Lasers play a fundamental role in our everyday lives through a myriad of applications: from scanning items in the supermarket and listening to our favourite music CDs to correcting vision problems through eye surgery. In this thesis, we have simulated a special kind of laser, the Quantum Cascade Laser (QCL), through a recently published approach to quantum transport called PERLind and a Python-based simulation package, LQCL.

The word LASER is an acronym that stands for Light Amplification through the Stimulated Emission of Radiation, a physical phenomenon theoretically predicted by Albert Einstein in 1917. A century has past ever since and it is now impossible to conceive the world of today without laser technology. The concept of... (More)
Lasers play a fundamental role in our everyday lives through a myriad of applications: from scanning items in the supermarket and listening to our favourite music CDs to correcting vision problems through eye surgery. In this thesis, we have simulated a special kind of laser, the Quantum Cascade Laser (QCL), through a recently published approach to quantum transport called PERLind and a Python-based simulation package, LQCL.

The word LASER is an acronym that stands for Light Amplification through the Stimulated Emission of Radiation, a physical phenomenon theoretically predicted by Albert Einstein in 1917. A century has past ever since and it is now impossible to conceive the world of today without laser technology. The concept of stimulated emission arose at the dawn of Quantum Mechanics, when physicists were developing the idea that light comes in discrete units of energy; they called these particles of light photons. To produce a photon, the electrons in an atom jump from one energy level to another. The energy of the resulting photon is equal to the energy difference between both levels. This process can occur spontaneously or stimulated by the presence of another photon. During stimulated emission, a photon triggers the emission of a second photon; that is, light is amplified. Lasers operate by avalanching this process. A beam of laser light has typically a narrow linewidth, which means that it essentially consists of photons carrying the same energy.

In this thesis, we have simulated Quantum Cascade Lasers (QCLs). A QCL is a unique type of laser which emits photons in the mid-infrared and terahertz frequencies. It is made of semiconductor materials, which makes it cheap and compact. Mid-infrared and terahertz frequencies correspond to energies lower than visible light and they are very useful, among others, in Astronomy and Chemistry to determine the composition of gases. For instance, the radiation emitted by a QCL can be used for non-invasive medical procedures such as scanning the lungs of a patient without even undressing them. Unlike regular lasers, in QCLs we can control what the laser energy levels will look like during the fabrication of the device. The QCL is then designed to provide photons of almost any desired energy in a range of frequencies.

Simulating QCLs allows us to explore in detail each laser design and helps us understand how to engineer more efficient and powerful devices. Transport models describe how electrons jump between the laser levels and move along the device. There exits a wide variety of models for that purpose. In this thesis, we have used the Position and Energy Resolving Lindblad approach (PERLind) to describe the transport of electrons in QCLs. This method has a great advantage: it is fast and computationally light. Thus, it can be used to systematically look for optimized designs that can ultimately yield better QCLs in the future. (Less)
Popular Abstract (Spanish)
Los láseres juegan un papel fundamental en nuestro día a día a través de innumerables aplicaciones: desde escanear los artículos en el supermercado y escuchar nuestros CDs de música favoritos, hasta corregir problemas de visión mediante cirugía ocular. En esta tesis, hemos simulado Láseres de Cascada Cuántica (Quantum Cascade Laser, por sus siglas en inglés) empleando un modelo de transporte cuántico llamado PERLind y un código Python llamado LQCL.

La palabra LASER es en realidad un acrónimo para Amplificación de la Luz por Emisión Estimulada de Radiación (Light Amplification Through Stimulated Emission of Radiation por sus siglas en inglés), fenómeno predicho por Albert Einstein en 1917. Un siglo después, es imposible concebir el mundo... (More)
Los láseres juegan un papel fundamental en nuestro día a día a través de innumerables aplicaciones: desde escanear los artículos en el supermercado y escuchar nuestros CDs de música favoritos, hasta corregir problemas de visión mediante cirugía ocular. En esta tesis, hemos simulado Láseres de Cascada Cuántica (Quantum Cascade Laser, por sus siglas en inglés) empleando un modelo de transporte cuántico llamado PERLind y un código Python llamado LQCL.

La palabra LASER es en realidad un acrónimo para Amplificación de la Luz por Emisión Estimulada de Radiación (Light Amplification Through Stimulated Emission of Radiation por sus siglas en inglés), fenómeno predicho por Albert Einstein en 1917. Un siglo después, es imposible concebir el mundo de hoy sin la tecnología láser. El concepto de emisión estimulada surgió en los albores de la Mecánica Cuántica, cuando los físicos comenzaban a desarrollar la idea de que la luz está formada por unidades discretas de energía; llamaron a estas partículas de luz fotones. Para producir un fotón, los electrones en un átomo saltan de un nivel a otro. La energía del fotón resultante es igual a la diferencia de energías entre ambos niveles. Este proceso puede suceder espontáneamente o de forma estimulada por la presencia de un segundo fotón. Durante la emisión estimulada, un fotón desencadena la emisión de un segundo fotón; es decir, la luz es amplificada. Los láseres operan magnificando este proceso. El haz de un láser se caracteriza por su monocromaticidad, esto es, los fotones emitidos tienen esencialmente la misma energía.

En esta tesis, hemos simulado Láseres de Cascada Cuántica o QCLs. Un QCL es un láser que emite fotones con frecuencias en el infrarrojo medio y los terahercios. Es un láser fabricado a base de materiales semiconductores, por lo que es compacto y barato. Las frecuencias en el infrarrojo y los terahercios corresponden a energías menores que la energía de la luz visible y son muy útiles en Astronomía y Química, entre otros, para determinar la composición de un gas. Por ejemplo, la radiación emitida por un QCL puede usarse para diagnósticos médicos no invasivos como escanear los pulmones de un paciente sin que este tenga que desvestirse. A diferencia de un láser común, en un QCL podemos controlar la forma de los niveles energéticos del láser durante la fabricación del dispositivo. Por tanto, el láser puede ser diseñado para que emita fotones en prácticamente todas las frecuencias dentro de un determinado rango.

Simular láseres QCL nos permite explorar en detalle cada diseño y nos ayuda a entender cómo desarrollar dispositivos más eficientes y potentes. Un modelo de transporte describe las transiciones electrónicas que ocurren entre los niveles de energía del láser. Existe una gran variedad de modelos. En esta tesis, hemos usado un modelo Lindblad con resolución en posición y energía (Position and Energy Resolving Lindblad en inglés) para describir el transporte electrónico en un QCL. Este modelo tiene una gran ventaja: es rápido y computacionalmente ligero. Por tanto, puede ser usado para buscar de forma sistemática diseños optimizados que podrían conducir a mejores QCLs en el futuro. (Less)
Please use this url to cite or link to this publication:
author
Muñoz Basagoiti, Maitane LU
supervisor
organization
course
FYSM60 20191
year
type
H2 - Master's Degree (Two Years)
subject
keywords
quantum cascade lasers, quantum transport, simulations, electron transport
language
English
id
8987031
date added to LUP
2019-06-24 13:42:08
date last changed
2019-06-24 13:42:08
@misc{8987031,
  abstract     = {{Over the past two decades, Quantum Cascade Lasers (QCLs) have become an increasingly popular source for mid-infrared and terahertz radiation. Nowadays, their experimental development progresses fast with the aid of computer simulations. These reproduce carrier dynamics in the gain medium of the laser based on different transport models. A fast and reliable simulation package for QCLs is key for the future realization of optimized structures. In this thesis, we have tested the validity of a recently presented QCL simulation package called Lindblad-QCL. The package is based on a heuristic and phenomenological density matrix approach: the Position and Energy Resolving Lindblad approach. We have run several QCL simulations using the Lindblad-QCL simulation package and compared the results to experimental data. These simulations provide a good qualitative description of the QCL active medium. We have extended the simulation package implementing interface roughness scattering and analysed the impact of temperature in the simulations. The results we present in this thesis show that Lindblad-QCL is a candidate to become a strong QCL simulation package.}},
  author       = {{Muñoz Basagoiti, Maitane}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Simulating Quantum Cascade Lasers with the Position and Energy Resolving Lindblad approach}},
  year         = {{2019}},
}