Why can lasers move objects?

Laser, the light of modern technology, has attracted the attention of many scientists and engineers since its inception due to its unique properties and application prospects. Among numerous applications, the technology of laser moving objects is particularly noteworthy. It is not only described in science fiction novels, but also widely used in practical scientific research and industrial manufacturing. So, why can lasers move objects? What scientific principles and technical details are behind this?

Firstly, we need to understand the basic characteristics of lasers. Laser, also known as "light amplified by stimulated radiation," has high monochromaticity, coherence, and directionality. These characteristics enable laser energy to be highly concentrated, producing extremely high energy density in a very small space. It is precisely this energy density that provides the possibility for lasers to move objects.


The principle of laser moving objects is mainly based on the momentum exchange of photons. In quantum mechanics, photons are regarded as particles with momentum. When laser is irradiated onto the surface of an object, photons interact with atoms or molecules on the surface of the object, generating momentum exchange. Although photons themselves have extremely small mass and momentum, the number of photons in a laser is enormous, so the accumulated momentum exchange is enough to generate a small thrust on an object.

However, the thrust generated solely by photon momentum exchange is extremely weak and far from sufficient to directly move macroscopic objects. Therefore, in practical applications, laser moving objects often rely on a technique called "optical tweezers" or "optical traps". This technology precisely controls the focusing and scanning of the laser, creating a stable energy field on the surface of the object. When an object enters this energy field, the photon momentum exchange it experiences is accumulated and amplified, generating sufficient thrust to move the object.
The implementation of optical tweezers technology relies on high-precision optical and control systems. Firstly, it is necessary to generate a high-power and highly stable laser beam. Then, the laser beam is focused onto the micrometer or even nanometer scale through precise optical components. Next, the focusing position, scanning speed, and scanning trajectory of the laser beam are precisely controlled by the control system, so that the object can move according to the predetermined path and speed.

The application prospects of laser moving object technology are very broad. In the field of micro nano manufacturing, laser moving object technology can be used to manufacture high-precision and high complexity micro nano devices. In the biomedical field, laser tweezers technology can be used to manipulate tiny organisms such as cells and viruses, providing new means for biological research and medical treatment. In addition, laser moving object technology can also be applied in fields such as optical capture, optical manipulation, and optical microfabrication, providing strong support for scientific research and technological innovation.



Of course, laser moving object technology also faces some challenges and limitations. Firstly, due to the extremely weak thrust generated by photon momentum exchange, the speed and accuracy of laser moving objects are limited to a certain extent. Secondly, laser moving object technology requires high-precision optical and control system support, resulting in high cost and technical difficulty. In addition, laser moving object technology may also be affected by environmental factors such as temperature, humidity, vibration, etc., which require sufficient testing and verification in practical applications.

In summary, the reason why lasers can move objects is based on the principle of photon momentum exchange and the application of optical tweezers technology. With the continuous progress and development of science and technology, laser moving object technology will be applied and developed in more fields, creating a better future for humanity.