But many advanced applications require several laser properties at once: high repetition rates, high pulse energy and specific wavelengths. Improving one can make it harder to achieve the others.
Backed by a Novo Nordisk Foundation NERD grant, Yazhou Wang and his team are investigating a newly discovered phenomenon called Multi-Pulse Accumulation of Coherent Molecular Oscillation (MACMO), which could offer a new way around this challenge.
MACMO occurs when ultrafast laser pulses interact with molecular gases inside hollow-core optical fibres. Instead of each pulse interacting independently, the effect can build up over multiple pulses, creating a new way to convert laser light to different frequencies.
The researchers will investigate how the phenomenon works and whether it can be developed into practical laser technology.
When pulses work together
At the heart of MACMO is an interaction between light and molecules. When an ultrafast laser pulse passes through a molecular gas, it can set the molecules into coordinated motion, which can in turn influence the frequency of the light.
What makes MACMO particularly interesting is that this effect can accumulate over many laser pulses. Instead of relying on a single intense pulse, researchers will investigate whether a train of pulses can collectively drive the molecular response and build up frequency conversion.
Hollow-core fibres provide an ideal environment for this. They guide light through a gas-filled core rather than solid glass, allowing researchers to precisely control the interaction between laser pulses and different molecular gases.
Together, this could provide a new platform for manipulating ultrafast light.
From a surprising observation to fundamental physics
Before the technology can be developed, researchers first need to understand the fundamental science behind MACMO. They will combine theoretical modelling and experiments to study how the molecular response develops and accumulates from pulse to pulse, and how it depends on the gas and laser properties.
This knowledge will lay the foundation for new ultrafast laser sources operating at high repetition rates in the near- and mid-infrared.
These wavelengths are particularly interesting for applications where conventional laser sources can struggle to provide the desired combination of performance: pulse energy and repetition rate. Applications count amongst other things, medical diagnostics, environmental monitoring, and biological imaging, which will be one of the project’s first application areas.
A technology with a wider horizon
Although biological imaging provides an important target application, the potential reach of the technology extends much further.
If MACMO can be harnessed to create compact, high-repetition-rate ultrafast laser sources across useful wavelength ranges, the technology could eventually find applications in areas such as quantum photonics, photoemission spectroscopy, high-brightness electron sources, precision micromachining and free-space optical communications.
For Wang and his team, the project therefore sits at the intersection of fundamental physics and technological development.
The researchers are starting with a newly discovered phenomenon, the underlying physics of which is not yet fully understood. Over the next six years, they will work to uncover the principles governing it and then use those principles to explore what a new generation of ultrafast laser sources could look like.
The result could be a new approach to controlling light at extreme speeds, with applications wherever precise, powerful and rapidly repeating laser pulses are needed.
