It is the remote controlling distance of green laser pointer

Fourth, the coherence. In the laser cavity amplification by stimulated emission of radiation to form the chain-type, get some of the characteristics of the same photon. From the cavity output beam is almost parallel light, the radiation source inter-related, radiation characteristics are the same. Therefore, the temporal coherence and spatial coherence of the laser are very good, excellent coherent light source. Usually active substances, the excitation energy and the cavity of the three together are collectively referred to as the laser. In accordance with the activation material laser is divided into four categories; solid-state lasers, gas lasers, liquid lasers, semiconductor lasers. The following summarized the basic characteristics of various lasers. Gas lasers. The laser active material is a gas or a mixture of gases. It is the remote controlling distance of  green laser pointer .
Gas lasers were powered by the discharge excitation, the work is mostly continuous. Common gas lasers, helium-neon lasers, CO2 lasers, argon ion laser, krypton ion lasers and xenon ion lasers. Figure 4-6 shows the schematic diagram of a helium-neon laser. The gas charge in a sealed tube with Brewster window, and both ends of the tube is endowed with high voltage. When the laser tube discharge tube of the dense plasma of free electrons accelerated in strong electric field. The free-electron impact of helium atoms to release energy, incentives for activated atom of helium. He-Ne lasers in the infrared range (3.39-micron, 1.15 micron) emission, can also be used 6328; angstroms in the visible range. It is unnecessary for the customer to point the emitter of wireless presenter green laser pointer to the receiver.
Nitrogen-neon laser stability, long life, inexpensive, suitable for holographic and laser interferometry. Solid-state lasers. The solid-state laser active material is a small amount of chromium or neodymium crystal or glass. The solid-state lasers using optical excitation, mostly on the pulse. To maximize the efficiency of optical excitation, the reflection cross-section of the condenser chamber is usually designed as a single elliptical or oval, rod-like lights in the ellipse a focus of the laser crystal is located in another focus, so that most of the incentive and light reflection into the laser crystal. Common active material ruby, neodymium-doped yttrium aluminum garnet and neodymium glass. Figure 4-4 for the ruby laser schematic. If green laser pointer has been locked by the customer.
Ruby sapphire crystal mixed with 0.05% chromium ions from the shape of a diameter of 5 to 20 mm, length 50 to 200 mm cylinder, two face as much as possible parallel to the Brewster angle incentive light using the xenon lamp, xenon lamp coupled kV DC high voltage to the discharge glow, reflection condenser chamber gathering incentives chromium ions in ruby as the active material. Ruby laser wavelength of 6943 angstroms, can be pulsed or continuous two ways. The solid-state lasers of high mechanical strength, easy to use, high output power, especially suitable for materials processing and medicine. If the customer doesn’t want to use   laser pointer.