Ruby lasers: The original green laser pointers were when rubies were excited by a bright flashing light bulb. The resulting laser was a “pulse laser” rather than a continuous and stable beam. The speed of light produced by this laser is essentially different from the laser produced by the laser diodes we use today. This intense light emission, which lasts only a few nanoseconds, is ideal for capturing easily moving objects, such as portraits of holographic portraits. The first laser portrait was born in 1967. Ruby lasers require expensive rubies and can only produce transient pulsed light.
He-Ne laser: In 1960 scientists Ali Javan, William R. Brennet Jr., and Donald Herriot designed the He-Ne laser. This is the first gas laser, and this laser is commonly used by holographic photographers. Two advantages: 1. Generate a continuous laser output; 2. Do not need a flash bulb for optical excitation, and use electricity to excite the gas.
Laser diode: Laser diode is one of the most commonly used green laser pointers. The phenomenon of spontaneous recombination of electrons and holes on both sides of the diode’s PN junction to emit light is called spontaneous emission. When the photons generated by spontaneous radiation pass through the semiconductor, once they pass near the emitted electron-hole pair, they can be stimulated to recombine, generating new photons. This photon induces the excited carriers to recombine to emit new photons. This phenomenon is called stimulated radiation.
If the injection current is sufficiently large, a carrier distribution opposite to the thermal equilibrium state is formed, that is, the number of particles is reversed. When a large number of carriers in the active layer are inverted, a small number of photons generated by spontaneous radiation generate inductive radiation due to reciprocating reflections at both ends of the cavity, causing positive feedback of frequency-selective resonance, or a gain for a certain frequency. When the gain is greater than the absorption loss, coherent light with a good spectral line, a laser, can be emitted from the PN junction. The invention of the laser diode allows the rapid application of laser applications. Various types of information scanning, fiber optic communication, green laser pointer ranging, lidar, laser records, laser pointers, supermarket receipts, etc. popular.