Many people now like to use a hand-held green laser pointer as a toy. This device is also often used for speech and other occasions. The Food and Drug Administration issued through the system, pointing out that the laser emitted by the handheld laser pointer may be harmful to the eyes. It seems obvious, but many people still cause eye damage due to the laser emitted by the laser pointer.
The reason for this is that some irresponsible parents treat the child with a laser pointer as a toy. There is a great risk. If the child points the laser at a reflective surface, the reflected beam may be emitted more than the original one. The beam is more intense.
Although according to the standard, the visible light intensity of the hand-held laser pen is limited. Even at this intensity, the laser can still cause transient flash blindness if it is directly irradiated to the eye. If this happens repeatedly or someone does not blink or cannot quickly under the laser irradiation Looking away, there is a risk of permanent eye damage.
In addition, some hand-held laser pointer power was also found for sale. At present, such handheld laser pointers are mainly sold through the Internet. So how to distinguish the power level of a handheld laser pointer? Here is a tip for users. If a laser pointer uses a button battery, its power may be in the acceptable range. The laser pointer uses AA or AAA batteries. High-power laser pointers are usually emphasized with some words when they are sold. For example, strong, super, military, military grade, super light, high energy, lithium battery.
Therefore, we will choose a laser material that can emit on a broadband (spectral width of tens of nanometers), and construct a cavity to allow the laser effect to be generated across the entire wavelength range, and therefore on a large number of modes. All these modes must be synchronized: if all these modes are transmitted at the same time, the transmitted pulse will only be very short. But each of them is randomly synchronized, depending on the spontaneous emission that produces it. In order to solve this problem, a "saturable absorber" is added to the cavity, which is opaque at low light intensity. Therefore, people can only amplify short pulses, and it is these short pulses that are emitted: this is a mode. locking. Then they need to be amplified further to obtain high-power pulses.