Mode transforming vortex laser with optical levitation
File(s)
Author(s)
Munj, Abdul-Haseeb
Type
Thesis
Abstract
The work in this thesis spans two primary fields of inquiry. The first focuses on the
development of a novel laser system capable of direct optical vortex (OV) emission, while
the second aims to demonstrate its application in the optical levitation of reflective hollow
microspheres.
We first present the non-standard use of a wedge-plate shearing interferometer (WPSI)
as a TEM00 Gaussian to LG01 OV mode conversion device. A detailed description of
its geometric configuration and interferometric process is presented. It gives an idealised
power conversion of 99.6 % in favour of the of the LG01 OV-mode. However, since the OV
is generated in its face-reflection, the incident power conversion is equal to only its Fresnel
reflectance. Power scaling potential is improved through intracavity use of the WPSI.
A unidirectional ring cavity was used with a 20:1 power imbalance in favour of clock-
wise propagation which enhanced incident power to enable watt-level OV output power
(1.15 W). The unconverted power is recycled back into the cavity. In this configuration
we demonstrate the generation of OV beams with high beam-quality (M2 = 1.94, 2.09) and
high LG01 mode-purity (97.8 %).
In the second part, we demonstrate the use of this system in optical levitation. This work
was motivated by the desire to levitate metallic (possible reflective) hollow-sphere (shells
with low internal refractive index) targets for experiments with high-intensity, high-energy
laser systems particularly in the generation of high-density plasmas, point X-ray sources,
and charged-particle acceleration. We demonstrate the optical levitation of shells 20 to
110 μm in diameter (masses of 25 ng to 230 ng) at long focal length (f = 40 mm) and
measure <5 μm spatial stability in air and low vacuum.
development of a novel laser system capable of direct optical vortex (OV) emission, while
the second aims to demonstrate its application in the optical levitation of reflective hollow
microspheres.
We first present the non-standard use of a wedge-plate shearing interferometer (WPSI)
as a TEM00 Gaussian to LG01 OV mode conversion device. A detailed description of
its geometric configuration and interferometric process is presented. It gives an idealised
power conversion of 99.6 % in favour of the of the LG01 OV-mode. However, since the OV
is generated in its face-reflection, the incident power conversion is equal to only its Fresnel
reflectance. Power scaling potential is improved through intracavity use of the WPSI.
A unidirectional ring cavity was used with a 20:1 power imbalance in favour of clock-
wise propagation which enhanced incident power to enable watt-level OV output power
(1.15 W). The unconverted power is recycled back into the cavity. In this configuration
we demonstrate the generation of OV beams with high beam-quality (M2 = 1.94, 2.09) and
high LG01 mode-purity (97.8 %).
In the second part, we demonstrate the use of this system in optical levitation. This work
was motivated by the desire to levitate metallic (possible reflective) hollow-sphere (shells
with low internal refractive index) targets for experiments with high-intensity, high-energy
laser systems particularly in the generation of high-density plasmas, point X-ray sources,
and charged-particle acceleration. We demonstrate the optical levitation of shells 20 to
110 μm in diameter (masses of 25 ng to 230 ng) at long focal length (f = 40 mm) and
measure <5 μm spatial stability in air and low vacuum.
Date Issued
2024-12-20
Date Awarded
01/06/2025
License URL
Advisor
Damzen, Mike
Kerridge-Johns, William
Sponsor
Engineering and Physical Sciences Research Council
Publisher Department
Department of Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)