The 100mW laser pointer diode The figure is essentially a semiconductor diode, according to the PN junction is the same material, can be divided into homojunction laser diode, a single heterojunction (SH), double heterostructure (DH) and quantum well (QW) laser diode quantum well laser diodes with low threshold current, the advantages of high output power, is the mainstream market applications products compared with other types of 5mW laser pointer, laser diodes with high efficiency, small size, long life advantages, but its small output power (generally less than 2mW, but now they have power greater than 10W single tube products), linear poor, not very good color, its application in the cable television system in a very limited and can not transmit multi-channel, high-performance analog signal in the two-way optical receiver module in return, fired up the general quantum-well laser diodes are used as the light source.One of the forming factors of 200mW Laser Pointerperformance price ratio is function. Cold flute of "optoelectronics" course report about the basic structure of the semiconductor laser diode shown in the shown, perpendicular to the PN junction of a pair of parallel planar surface composition Fabry - Perot cavity, they can be semiconductor crystal cleavage plane, it can be polished plane remaining on both sides of the surface is relatively rough, for outside the other direction to eliminate the main direction of the laser role in semiconductor light emission usually results from carrier recombination, when the PN junction semiconductor has a positive voltage, it will weaken the PN junction barrier, forcing the electrons from the N region by PN junction into the P region, holes from the P region into the N region through the PN junction, PN junction into the vicinity of these non-equilibrium electron and hole complex will occur, which emits photons at wavelength λ, the formula is as follows: λ = hc / Eg (1) where: h-Planck constant; c-the speed of light; Eg-band gap semiconductor above because of the spontaneous recombination electrons and holes and the phenomenon known as spontaneous emission of light when the spontaneous emission generated by .Another forming factor of green laster pointerperformance price ratio is structure.When photons by the semiconductor, has been fired once through the electron - hole pairs near the compound can stimulate both produce new photons, the photons induce excitation of the carriers has been issued for the new complex phenomenon known as stimulated photon radiation if the injection current is large enough, it will reverse the formation and thermal equilibrium carrier distribution, ie inversion when the active layer of the carrier in the case of a large number of inversion, a small amount of spontaneous emission of photons due cavity back and forth across the surface reflection of the induced radiation, resulting in frequency-selective resonant positive feedback, or to a frequency with a gain when the gain is greater than the absorption loss, the PN junction can be issued from the coherent light has a good line - laser, which is the simple principle of laser diodes as technology and process development, the actual use of the semiconductor laser diode has a complex multi-layer structure. The third forming factor of Blue Laser Pointerperformance price ratio is color.There are two commonly used laser diode: ① PIN photodiode which received optical power photocurrent generated, it will bring the amount of sub-noise. ② avalanche photodiode which can provide internal amplification than PIN photodiode transmission distance, but the quantum noise even more.