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Main performance parameters of laser - wavelength

1. Definition of wavelength

Laser wavelength represents the wavelength of the electromagnetic wave carried by the laser. An important characteristic of laser light compared to other types of light is that it is monochromatic light, which means that its wavelength is very pure and has only one well-defined frequency. This is because factors such as the amplification medium and excitation method used in the laser can limit the photons to vibrate only at a certain wavelength. The specific value of the laser wavelength is related to factors such as the laser structure and the materials used. For different application scenarios and needs, lasers of different wavelengths can be selected to achieve the required functions. For example, in the fields of environmental monitoring, communications, medical treatment, and material processing, lasers with different wavelengths are selected for different media and reflection properties.

The difference between different wavelengths of laser:

The wavelength of red laser is generally between 630nm and 680nm, and the light emitted is red. It is also the most common laser (mainly used in the field of medical mammography, etc.);

The wavelength of green laser is generally around 532nm (mainly used in the field of laser ranging, etc.);

The wavelength of blue laser is generally between 400nm-500nm (mainly used in laser surgery and engraving fields, etc.);

Ultraviolet laser is between 350nm-400nm (mainly used in biomedicine and material processing fields, etc.);

Infrared laser is the most special. Depending on the wavelength range and application field, the wavelength of infrared laser is generally in the range of 700nm-1mm. The infrared band can be further divided into three sub-bands: near infrared (NIR), mid infrared (MIR) and far infrared (FIR). The near-infrared wavelength range is approximately between 750nm and 1400nm, and is widely used, such as optical fiber communications, biomedical imaging, and infrared night vision equipment. The mid-infrared wavelength range is approximately between 1,400 nm and 10,000 nm, and is commonly used in detection analysis, spectroscopy, thermal imaging and other fields. The far-infrared wavelength range is approximately between 10,000nm and 1mm, and is used in fields such as remote control, remote sensing, and semiconductor manufacturing.

It should be noted that the light emitted by the laser has a single wavelength, which means that optically, the laser is a highly focused beam with a much higher energy density than beams of other wavelengths. Because lasers can be focused to very small points, they have a wide range of applications in many fields, such as laser manufacturing, medical care, and communications. Therefore, studying and controlling laser wavelength is one of the core contents of laser technology and applications.

2. Classification of wavelengths

Laser wavelength is divided into center wavelength and peak wavelength, which are quite different in definition and properties.

The center wavelength refers to the center position of the wavelength distribution of the laser output, also called the average wavelength or central frequency. It refers to the center position of the laser wavelength distribution, which can be measured by a laser output sensor or spectrometer. The measured λ2 is the longest wavelength corresponding to 50% of the maximum relative spectral intensity and then subtracts the measured value of λ1 which is the shortest wavelength corresponding to 50% of the maximum relative spectral intensity divided by 2 to get the center wavelength.

In spectral analysis, the center wavelength is one of the indicators that describes the characteristics of laser wavelength. For a laser with a single wavelength, its center wavelength is equal to the peak wavelength of the laser. However, for a laser with a wavelength distribution, the center wavelength of the laser is the center of gravity of the wavelength distribution curve. The center wavelength is usually expressed in units such as nanometers (nm) or picoseconds (ps). The center wavelength of laser is one of the important parameters to measure the properties of laser output wavelength, and has important application value in many fields. For example, in optical communications, lasers of different wavelengths are used to implement multi-wavelength discrete multiplexing (WDM) technology, and the center wavelength is an important parameter to measure the characteristics of lasers with different wavelengths. In the fields of laser medicine and laser processing, the central wavelength of the laser also plays an important role in determining the characteristics and mode of action of the laser.

The peak wavelength refers to the wavelength position with maximum output power in the output wavelength distribution curve, also called the maximum power wavelength. In spectral analysis, the peak wavelength is an important parameter of the laser wavelength. To test the peak wavelength, you need to use a monochromator, spectrometer or wavelength meter to find out the laser peak wavelength. Then you need to perform ten or more times to calculate the total value, multiply it by the peak wavelength of the main spectral line of the laser beam, and then divide it by the measured The number of times is the peak wavelength. For monochromatic lasers, the peak wavelength is the wavelength of the laser. However, in lasers with a wide wavelength distribution, the peak wavelength may be in a wider part of the wavelength distribution curve, so it does not fully represent the wavelength properties of the laser. For this kind of laser with a wide wavelength distribution, its wavelength properties need to be described by other parameters of the wavelength distribution curve, such as center wavelength, full width at half maximum, etc.

In many applications, the peak wavelength of the laser is very important in determining at which wavelength the laser treatment is performed. For example, in laser cutting, different materials need to be cut with lasers of different wavelengths. This requires determining the appropriate laser peak wavelength based on the characteristics of the material and the characteristics of the laser.

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