What is the shortest light pulse?

A recent study by German scientists found a new method to achieve the shortest flash so far, which lasts only 80 attosecond (attosecond, 1 attosecond is10-18th power second, one thousandth of a femtosecond), while the previous record was 130 attosecond in 2007. New ultrashort optical pulses have been used to capture laser pulse images that are too short to be photographed. Related papers were published in the journal Science on June 20th.

optical pulse

Optical pulse is the intermittent light emission of light source within a certain time interval. E = MC 2 can be calculated, and the influencing factor is the medium in the middle.

Basic information

Theoretical overview

Optical pulse is the intermittent luminescence, light quality and energy of light source in a certain time interval. When studying photons, Einstein's mass-energy equation E = MC 2 can be used to calculate, but when the microscopic field is not studied, it is usually ignored. The influencing element is the medium in the middle, but it has little influence.

Optical pulse principle

The light pulse with short duration and high intensity can penetrate the material, and the light pulse penetrating the material is not transmitted, but dissipated in the material in the form of heat. The surface and inner layer of the material produce a temperature gradient, and heat is transferred from the surface to the inner layer in the form of conduction. Heat conduction continues until the temperature of the material reaches a constant and stable state, and the required time is determined by the heat emitted and the thermal properties of the material. The duration of light pulse is shorter than that of heat conduction, and the energy of light pulse is stored on the material surface for a very short time, during which there is almost no heat conduction. In fact, it is to instantly heat the thin layer surface to make its temperature higher than the steady-state temperature reached by continuous beam heating with the same average power.

Application of optical pulse

Light pulse can kill microorganisms on solid food and baked food such as aseptic packaging materials, liquid food, meat and fish. Light treatment of meat products can prolong the shelf life of refrigeration. Pre-made foods such as potatoes, tomatoes, bananas, apples, macaroni and rice can be treated with light pulse to extend the shelf life. Although tomatoes are easy to be infected with mold in cold storage, they can be stored for 30 days after light pulse treatment. Similarly, packaged white bread slices can be kept fresh within 2 weeks after pulse treatment, while untreated slices will soon become moldy. Light pulse not only reduced the number of Listeria monocytogenes and Salmonella inoculated in meat, but also changed little in the nutritional composition of meat.

Light pulse can increase the shelf life and safety of meat. In addition to food sterilization, light pulses are also used in the following products and fields:

(1) Ingredients and finished products for manufacturing cosmetics.

② Equipment, products, devices and areas requiring high cleanliness.

③ Medical and dental equipment before use.

④ Food processing equipment to reduce the degree and possibility of cross-contamination.

⑤ Treating or semi-treating sewage to reduce microbial load.

⑥ Air or other gases or gaseous compounds to reduce the microbial load.