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Asked: 2020-01-19T00:20:36+00:00 In:

What is the difference between Laser diode (LD) and Light-emitting diode (LED)?

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A laser is also known as laser diodes (LD), and light-emitting diode (LED) is an optoelectronic device, both devices generated light. But the way they emit light have different characteristics.

The laser emits converging light while the output of the LED is highly divergent. Eyes protection should be used when dealing with these optoelectronic devices, especially in the case of Laser as it generates high energy beam.

Why are laser diodes preferred over LED? What are the key attributes that make them different from each other?

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    3 Answers

    1. Level 2
      This answer was edited.

      LED stands for Light-emitting Diode. LED is a semiconductor light source that emits light when it passes through the current.
      LASER stands for Light Amplification by Stimulation of Emitted Radiation. A Laser is a light-emitting system based on the stimulated emission of electromagnetic radiation by an optical amplification process.

      Differences between laser diodes and LED 

      • The key difference between LED and Laser diodes is the light beam. The emission of light by LED consists of different colours, while the light beam generated by Laser diodes is only one colour.
      • The LED and Laser diodes functioning principle created significant differences. LED essentially works on the principle of electro-luminance, which means electrons are laminated. In comparison, Laser diodes operate on the stimulated emission principle.
      • Another key difference is the junction area between LED and Laser diodes. In the case of the Laser diodes, the area of the junction is particularly narrow as light can pass from the extremely small area. On the flip side in LED, the junction area is wider. Therefore, light can pass across a broad area.
      • The concentration of the Laser is very high while it is very weak in LED. A laser is therefore used in the medical field in the surgical system because it contains enough energy even to cut down the target.
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    3. Level 6
      This answer was edited.

      LED

      • LED has a small size, longer lifetime, reliability and low power demand.
      • Spontaneous emission of the photon generation occurs in LED.
      • Divergent and incoherent light beams are created by the LED.
      • The response time of the LED is very slow.
      • There is a wide variety of wavelengths and low bandwidth.
      • In comparison to Laser diodes, the LED costs are lower.
      • The light-generating intensity is less in LEDs.
      • LED coupling with fibre is less effective.
      • Multimode fibre is used by LED.
      • Due to its simple circuit, no additional circuit is necessary for LED.
      • There are two types of LED: Surface emitter and Edge emitter.

       LASER Diode

      • Lasers diodes are larger, longer service life, less efficient and need more power than LED.
      • Generate photon in Laser diode occurs through stimulated emissions.
      • The emission of Laser diode light is monochromatic, straight, and coherent.
      • Types of Laser (a) semiconductor Laser and (b) Gas Laser.
      • Laser diodes time response is faster than LED.
      • In Laser diode, the range of wavelengths is small, whereas bandwidth is also higher compared to LED.
      • A laser diode is more costly than LED.
      • The Laser diode coupling with fibre is more effective and higher.
      • Laser diode uses both single and multi-mode fibres.
      • In the Laser diode, an additional circuit is required for the isolation of the temperature reaction.
      • Two types of Laser diode: semiconductor and gas Laser.
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    4. Level 1
      This answer was edited.

      The main difference between the LED and diode is that the LED emitting light causes the diode to flow in just one direction and opposes the flow in the other.

      Comparison table: Differences between the Laser diode and the LED

       

      SpecificationsLASER diodeLight emitting diode
      Ease of useLaser diodes are more difficult to use.LED diodes are very easy to use.
      Nature of emission of lightThe light emitted from a Laser diode is monochromatic i.e single colour light.The light emitted from a LED diode is polychromatic i.e multiple colour light.
      DirectionalityThese devices are highly directional.In contrast, the LED is not directional.
      EnergyThey are highly energetic as compared to LEDs.In LED, the energy associated is very poor.
      Drive currentThe current threshold of 5-40mA is needed here.The drive current requirement is 50 to 100mA.
      FeedbackIn Laser didoes, sufficient feedback is important for optical source treatment.Feedback in LEDs is not necessary.
      Life spanThey have a longer life.They have a long life.
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