Thesis
Simulation of radiation-driven instabilities
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2025
- Thesis identifier
- T17211
- Person Identifier (Local)
- 201671713
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- This research seeks to extend the understanding of optomechanical collective effects particularly using modelling based on coherent scattering of light by cold atoms in free space. We develop a microscopic model and use simulations where we will vary the properties of the pump field including the use of structured light and bandwidth modulation looking for distinctive behaviours in measurable outputs. Modelling is developed based on a weak classical input light field and multiple two level atomic states with minimal population of the excited states. Firstly we will seek to build and validate a model based on coupled dipole theory with stationary atoms in regimes where we would expect to see established collective effects such as superradiance. We will then look to couple equations of motion based on cooperative optomechanical forces such that we incorporate centre of mass motion into our modelling. We can proceed to investigate established cooperative effects such as Collective Atomic Recoil Lasing, (CARL) and optical binding and extend our understanding of these by adding to existing models or varying key parameters of the cold atomic cloud or pump field. An investigation of optical binding of multiple cold atoms using our model is presented. Our results show the existence of stable and metastable configurations of atoms, and the occurrence of regular ‘breathing’ in a 2D atomic lattice due to optical forces arising from cooperative scattering. As well as the familiar homogeneous plane wave fixed frequency light we will be considering orbital angular momentum in our pump field and looking to use modulated partially coherent pump fields more consistent with broadband signals found in nature. Firstly we focus on CARL where previous work has been generally focused on pattern formation due to mutual light field, atomic cloud interaction involving linear momentum transfer. We look to investigate similar pattern formation or ’bunching’ specifically resulting from orbital angular momentum (OAM) in chapter 4.We find that the light-matter coupling allows for the superradiant transfer of the atoms between the discrete OAM states. Tuning the ring parameters and the azimuthal mode number of the pump light, specific angular momentum states can be populated. Further to this we go on to investigate the effects of amplitude modulation of the light field signal with a view to extending the frequency range of the light field and extend prior work indicating enhancement of cooperative effects in the case of phase modulation in the case of CARL in chapter 5. We successfully demonstrate enhancement of measurable cooperative effects in our case corresponding to the resulting temperature increase in the atomic cloud.
- Advisor / supervisor
- Robb, Gordon
- Resource Type
- DOI
Relations
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