Difference in luminescence principle: LED is the use of the injection of active region of spontaneous emission of composite luminescence, while LD is the excited emission of composite luminescence. The direction of the photon emitted by the led, the phase is random, the photon emitted by the laser diode is in the same direction, in the same phase.
LED stands for Light Emitting Diode. Widely used in daily life, such as the indicator light of household appliances, car rear fog lamp and so on. The most notable feature of LED is its long service life and high photoelectric conversion efficiency. In the PN junction of some semiconductor materials, the excess energy is released in the form of light when the injected minority carrier is recombined with the majority carrier, thus converting electric energy directly into light energy. PN junction and reverse voltage, minority carrier injection is difficult, so no light. This use of injection electroluminescence principle of the diode called light emitting diode, known as LED.
LD is the abbreviation of laser diode. The physical structure of laser diode is to install a layer of photoactive semiconductor between the junctions of light-emitting diodes. Its end face is partially reflected after polishing, thus forming an optical resonator cavity.
In the case of forward bias, the LED emits light and interacts with the optical resonator, which further excites the emitting of a single wavelength of light from the junction. The physical properties of this light are material dependent. Semiconductor laser diodes work theoretically in the same way as gas lasers. Laser diode has been widely used in computer CD drive, laser printer printing and other small power photoelectric devices.
The difference between the two in principle, architecture and efficiency.
(1) Differences in working principles: LED uses spontaneous emission composite luminescence of carriers injected into active region, while LD is stimulated emission composite luminescence.
(2) Differences in architecture: LD has an optical resonator to make the generated photons oscillate and amplify in the cavity, while LED has no resonator.
(3) Performance difference: There is no critical value for LED, and the spectral density is several orders of magnitude higher than LD.