LED and LD although only one letter of the difference, but they are not the same two types of products. See the following for specific differences.
One, what is the LED?
LED is the abbreviation for Light Emitting Diode (Light Emitting Diode). Widely seen in daily life, such as household appliances lights, car fog lights and so on. The most significant feature of LED is the long service life and high photoelectric conversion efficiency. In the PN junction of some semiconductor materials, the injected minority carriers are combined with the majority carrier to release the excess energy in the form of light, which converts the electrical energy directly into light energy. PN junction plus reverse voltage, a small number of carriers is difficult to inject, so do not light. The use of injection-type electroluminescence principle of the manufacture of the diode called light-emitting diodes, known as LED.
Second, LD is what?
LD is the abbreviation of the laser diode, the laser diode is the physical structure of the junction of the light-emitting diodes placed a layer of optical activity of the semiconductor, the end of the polished with a partial reflection function, thus forming a light resonant cavity. In the case of forward biasing, the LED junction emits light and interacts with the optical resonator to further energize the emission of a single wavelength of light from the junction, the physical properties of which are related to the material. The working principle of a semiconductor laser diode is theoretically the same as a gas laser. Laser diodes in the computer CD-ROM drive, laser printers in the print head and other small power optoelectronic devices have been widely used.
Three, two in the principle, structure, performance differences.
1. The difference in the working principle: LED is the use of injected into the active area of the carrier spontaneous emission compound luminescence, and LD is stimulated by the composite light emission.
2. The difference in the structure: LD has an optical resonant cavity, so that the resulting photon oscillation in the cavity to enlarge, LED no resonator.
3. Differences in performance: LED no critical value of the characteristics of the spectral density than LD several orders of magnitude, LED light output power, divergence angle.
In summary, compared to LD, LED has its own characteristics: there is no critical value of the character, there is no type configuration noise, stable and no temperature control, long life, high yield, cheap.