Laser ablation is used to make functional nonlinear optical nanoparticles

Types of nonlinear optical nanoparticles fabricated by laser ablation. Credit: Compuscript Ltd

Nonlinear optics is an important area of research that has many uses in fields like making lasers, making nanostructures, designing sensors, optoelectronics, biophotonics, quantum optics, and more. Nonlinear optical materials are the basic building blocks that are used in a wide range of fields, from science to industry to the military. After many years of research and development, nonlinear optics has become the foundation for many cutting-edge and widely used optical systems, such as laser fabrication, optical imaging, information processing and communications, and nanoscale lithography. Many fields could be helped by progress in this area.

Nanotechnologies have made it possible to make new materials and go beyond what was thought to be possible with nonlinear optics. Nanoparticles are one of the most important things that scientists have been studying for thousands of years. Nanoparticles have a lot of potential because they can be designed and made to have better nonlinear optical properties than their bulk counterparts. In the past ten years, optical devices and parts that use nonlinear optical nanoparticles have gotten more and more attention because they work better and can do more than one thing. Many of them are also good at getting along with living things, which gives nonlinear optical devices more uses.

So, nonlinear optical applications make use of nanoparticles a lot. How to make nonlinear optical nanoparticles on a large scale, with high repeatability, and at a low cost is still a challenge for making nanoparticles. To deal with this problem, different ways of putting things together have been looked into. Chemical methods and laser ablation are two of the most common ways to make something. Chemical methods can be used to make nanoparticles on a large scale in factories. There are also problems with chemical approaches, such as impurities and clumping. On the other hand, laser ablation is a better way to make nonlinear optical nanoparticles because it is more direct, better for the environment, and can be done anywhere. Applications based on nonlinear optical nanoparticles offer a lot of flexibility and options to meet the needs of different devices.

Prof. Hong Minghui’s research group at the National University of Singapore looks at the latest developments in nonlinear optics related to the amplitude/intensity of light. The change in the amount of light that gets through a material system can be described by two nonlinear phenomena: saturable absorption and optical limiting. The process of saturable absorption is when the light absorption goes down as the light gets brighter. In other words, a material with saturable absorption tends to become more “transparent” when hit by more light. High power lasers are often made with materials that have saturable absorption.

On the other hand, the optical limiting effect is the opposite of what we just talked about. When the light gets brighter, an optically limiting material lets less light through. So, the reverse saturable absorption is another name for the optical limiting. It is also a very important effect that is used in things like protective materials, military weapons, optical switching, and high-power laser sources.

Even though they are both important, saturable absorption and optical limiting usually require a lot of light to happen. So, they are mostly seen in devices that use a high-peak-power pulsed laser. This condition could cause permanent damage to the eyes. The high cost and complicated design of high-power lasers also make it hard for them to be used in real life. One of the main goals of research in this field is to find good materials with good nonlinear properties. The progress will not only greatly improve the performance of current optical nonlinear systems, but it will also open up new ways to design functional devices to meet the growing needs of quantum optics, advanced sensors, artificial intelligence, next-generation optical computers, and many other frontier topics.

This review, which was published in Opto-Electronic Science, sums up the recent progress in this area. It focuses on the methods and uses a number of case studies to show what has been done. It also goes into more depth on some topics to give more perspectives on their main benefits and accomplishments. Another focus is on the challenges and future directions of research, with the most recent research works showing new opportunities and potentials. The development of nonlinear optical nanoparticles made by laser ablation is summed up, showing that they can have better performance and more than one use. Laser ablation is a green, efficient, and universal way to make nanoparticles. It can make nanoparticles quickly in one step and could be used for mass production.

Further information: Lianwei Chen et al, Functional nonlinear optical nanoparticles synthesized by laser ablation, Opto-Electronic Science (2022). DOI: 10.29026/oes.2022.210007

Source: Compuscript Ltd