Vortex Laser using a Sagnac Ring as an Output Coupler

Vortex laser beams carry orbital angular momentum (OAM), which results in a
central phase singularity. The orbital angular momentum makes them of interest
in fields like particle trapping, microscopy, resolution imaging, astronomy, highspeed
metrology, communication and quantum information. Current methods of
vortex generation are power limited, expensive and ine_cient. A design for a world-_rst vortex laser, using a Sagnac interferometer (SI) as an output coupler has been investigated in this project.
The vortex laser produces high quality vortices at multiple power outputs, notably
a left-handed vortex with a beam quality of M2 x = 2.09 and M2y
= 2.07 at 2.3W output power. An etalon was introduced into the SI, which allowed the ymisalignment to be controlled and reversed very precisely and easily. Switching the
handedness resulted in no power loss and a beam quality of M2
x = 2.07 and M2y = 2.04. Both had an optical efficiency of approximately 19%. The transmission curve showed that the SI acted most efficiency as an output coupler at roughly 16% transmission. The corresponding power curve showed a slope efficiency of 25%, only slightly below that of a conventional output coupler at 28%. Thermal lensing effects in the gain medium limit the maximum power of the output, this can be overcome with better cavity design. These results suggest that this design has potential in industries requiring high power, high quality vortices with easy handedness control.
Looking forward, optimising the cavity for significantly higher powers is a priority.
Compacting the SI and manufacturing it as a single element would allow it's uses to be further explored and open up the door for usage outside of the laser lab. The vortex laser could relatively easily be modified for pulsed operation and broad spectrum vortex generation.

The main impact of the proposed Hub will be in training quantum engineers with a skillset to understand cutting-edge quantum research and a mindset toward developing this innovation, and the entrepreneurial skills to lead the market. This will grow the UK capacity in quantum technology. Through our programme, we nurture the best possible work force who can start new business in quantum technology. Our programme will provide multi-level skills training in quantum engineering in order to enhance the UK quantum technologies landscape at several stages. Through the training we will produce quantum engineers with training in innovation and entrepreneurship who will go into industry or quantum technology research positions with an understanding of innovation in quantum technology, and will bridge the gap between the quantum physicist and the classical engineer to accelerate quantum technology research and development. Our graduates will have to be entrepreneurial to start new business in quantum technology. By providing late-stage training for current researchers and engineers in industry, we will enhance the current landscape of the quantum technology industry. After the initial training composed of advanced course works, placements and short projects, our students will act as a catalyzer for collaboration among quantum technology researchers, which will accelerate the development of quantum technology in the UK. Our model actively encourages collaboration and partnerships between Imperial and national quantum tehcnology centres and we will continue to maintain the strong ties we have developed through the Centre for Doctoral Training in order to enhance our on-going training provisions. The Hub will also have an emphasis on industrial involvement. Through our new partnerships students will be exposed to a broad spectrum of non-academic research opportunities. An important impact of the Hub is in the research performed by the young researchers, PhD students and junior fellows. They will greatly enhance the research capacity in quantum technology. Imperial College has many leading engineers and quantum scientists. One of the important outcomes we expect through this Hub programme is for these academics to work together to translate the revolutionary ideas in quantum science to engineering and the market place. We also aim to influence industry and policy makers through our outreach programme in order to improve their awareness of this disruptive technology.