There are three conditions for generating laser light: pump source, gain medium, and laser cavity. The pump source is responsible for providing energy, the gain medium is responsible for providing the conditions for population inversion, and the resonant cavity is responsible for oscillating and amplifying back and forth. Before the laser comes out, only the pump source and gain medium can emit light. This is called fluorescence. Generally speaking, the fluorescence that can be emitted by the gain medium cannot be very wide, which is the primary reason why it is difficult to produce white laser light. Ordinary white light is often the effect of superimposing multiple luminous sources. At the same time, in the design of the brightest high power laser pointer flashlight, the cavity length must be an integer multiple of half the wavelength to ensure that the waves oscillating back and forth produce interference constructively. This also results in only a few discrete wavelengths that can be amplified, that is, laser light.
Street, road and highway lights are a basic element to improve safety and prevent traffic accidents. Studies have shown that darkness causes a large number of car accidents, especially those involving pedestrians. The pedestrian accident rate at night is more than three times that of the day. Street lights can reduce the pedestrian accident rate by about 50%. Illuminated intersections and highway intersections have fewer accidents than unlit intersections. Adequate street lighting is also an effective way to prevent attacks on property and people at night. In addition, street lampposts are also a special place for hanging decorations or commemorative banners during festivals or other special events. Street lights provide a clean and convenient way to illuminate streets, roads and highways.