The difference between LED and LD

- Aug 21, 2018-

The difference between LED and LD

   Although LED and LD have only one letter difference, they are not the same two types of products. Correct distinction to prevent being cheated.

1.What is the LED?

    LED is an abbreviation for Light Emitting Diode. Widely seen in daily life, such as the indicator lights of household appliances, anti-fog lights after the car. The most notable feature of LEDs is their long life and high photoelectric conversion efficiency. In the PN junction of some semiconductor materials, the injected minority carriers are combined with the majority carriers to release excess energy in the form of light, thereby directly converting electrical energy into light energy. The PN junction adds a reverse voltage, and minority carriers are difficult to inject, so they do not emit light. Such a diode fabricated by the principle of injection electroluminescence is called a light-emitting diode, and is generally called an LED.

2.what is LD?

     LD is the abbreviation of laser diode. The physical structure of laser diode is to place a photoactive semiconductor between the junctions of LEDs. The end face is polished to have a partial reflection function, thus forming an optical cavity. In the case of forward biasing, the LED junction emits light and interacts with the optical cavity, thereby further exciting the emission of a single wavelength of light from the junction, the physical properties of which are material dependent. The working principle of a semiconductor laser diode is theoretically the same as that of a gas laser. Laser diodes are widely used in small-capacity optoelectronic devices such as optical disk drives on computers and print heads in laser printers. 

led and ld.jpg

So, the difference in the principle, structure and performance of the two.

1. The difference in working principle: LED is the spontaneous emission of composite radiation by the carrier injected into the active region, and LD is the combined radiation of stimulated radiation.

2. Difference in architecture: The LD has an optical cavity, so that the generated photons are oscillated and amplified in the cavity, and the LED has no resonant cavity.

3. Difference in performance: LED has no critical value characteristics, spectral density is several orders of magnitude higher than LD, LED light output power is small, divergence angle is large.

In summary, compared to LD, LED has its own characteristics: there is no critical value feature, no type configuration noise, stable operation and no temperature control, long working life, high yield and low price.