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Laser Diode (LD) is a semiconductor device that has a similar working principle as a light-emitting diode (LED). Like LEDs, Laser Diodes use the same technological processes.
- Laser diodes are also widely known as injection laser diodes (ILD).
- Diodes are the simplest form of semiconductor capable of performing a broad range of functions.
- When voltage is applied, the recombination of an electron with a hole takes place at the p-n junction.
- Due to this recombination, an electron in a high energy level drop to a low energy level with the emission of radiation in the form of a photon.
- This is spontaneous emission and continually generating light with the same phase, coherence, and wavelength leads to stimulated emission.
- Laser diodes have a wide range of applications like barcode readers, fiber optic communications, laser pointers, laser printing, CD/DVD/Blu-ray disc reading/recording, and laser scanning.
| Table of Content |
Key Terms: Laser diode, Semiconductor Diode, LEDs, p-Type, n-Type, Wavelength, Injection Lasers, Frequency, Phase, Waves
What is Laser Diode?
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A Laser Diode is a semiconductor device that helps in the emission of coherent radiation (usually of waves that have the same frequency and phase) that is commonly either produced in the visible or infrared (IR) spectrum.
- A Laser diode is a PIN diode, the active region is the intrinsic region, and the carriers (electron and hole) are pumped there from the N and P regions.
- The laser diode needs to be installed into the laser module in order to emit laser. The module containing the diode laser is called the laser diode module.
- The technology laser diodes use is very similar to the working principles of an LED (Light emitting diode).
- Much like LEDs, a laser diode is generally referred to as a semiconductor diode that is widely used for the transmission of signals via optical fiber.
- Laser diodes are found in daily equipment we use, like laser printers and remote control devices. They also play a huge part in intrusion detection systems as well.
| LASER is abbreviated from “Light Amplification by Stimulated Emission of Radiation.” |
Laser Diode
Also Check:
| Important Concept Related Topics | ||
|---|---|---|
| Junction Transistor | Digital Electronics and Logic Gates | Extrinsic Semiconductors |
| Intrinsic Semiconductors | Bridge Rectifier | Application of Junction Diode |
Working Principle of a Laser Diode
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Laser Diodes are composed of two layers of semiconductors, p-type and n-type. Generally, the layers of semiconductors are often composed of GaAs, which are further doped with other materials, such as selenium, or silicon, depending on their nature and characteristic properties.
Laser diodes usually follow the principle of stimulated emission. Emissions, quite evidently, follow either of the three types,
- Stimulated absorption
- Stimulated emission
- Spontaneous emission
Laser Working Principle
The mechanical standpoint, in simple terms, of a laser diode is that every atom is capable of emitting photons, when in its excited state, given that the electrons belonging at higher energy levels are instigated prior by an external source of energy.
- Apparently, an electron, during its migration to the lower energy level, is evidently seen to release an amount of energy quite equivalent to the gap between them.
- These electrons usually return after absorbing energy.
- A laser diode commonly follows the principle of stimulated emission.
- The process is applicable only when we hit a photon with an electron in the conduction band for obtaining light radiation.
- However, when the photon strikes, an additional photon also reaches the valence bond. This helps to obtain two photons to emit light.
Types of Laser Diode
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There are multiple types of laser diodes,
- Double Heterostructure Laser Diode: It is also known as a double heterojunction semiconductor laser. Heterostructure is known to be a material that usually is crushed between two p-type and n-type materials. The active and potential region of this diode is used for better optical amplification; which is an added advantage of using it nonetheless.
- Quantum Well laser Diode: The quantum well is basically a thin layer located in the middle of a diode. Quantum energy, in a nutshell, is usually utilized for the conversion of electrons from higher energy to lower energy.
- Separate Confinement Heterostructure Laser Diode: In general, these layers evidently contain a lower refractive index that further improves the emission of light.
- Vertical Cavity Surface Emitting Laser Diode: This laser diode helps the emitted light to exit the device in a perpendicular direction to the chip. Evidently, the optical cavity is usually against the current flow’s axis.
- External Cavity Diode Laser: External cavity diode laser is a tunable diode laser. These lasers are wavelength-tuneable and they exhibit a small emission spectral line width.
- Fabry Perot Laser: A Fabry Perot laser diode (FP laser diode) is the most common type of laser diode, having a laser resonator which is a Fabry perot interferometer. As a result, substantial light reflections occur at both ends, but not within the gain medium.
Related MCQ Examples of Laser DiodesQues. Within a Laser diode, where is the laser beam produced in the Diode?
Ans. The answer is “c”, p-n Junction. Ques. The base voltage is 5 V, and the resistor at the base input is 10k \(\Omega\), in an amplifier, then calculate its base current.
Ans. The answer is “a”, 430 \(\mu\)A |
Characteristics of Laser Diodes
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Here are some significant characteristics of laser diodes,
- Laser diodes typically produce a narrow light containing only a singular color. Meaning, it is monochromatic.
- Lasers, for the most part, have the same frequency and wavelength.
- The radiated light is mostly directed into a narrow pathway which can simply be propelled via an optical fiber.
- Laser diodes, more often than not, are coherent and can also travel substantial distances.
- The significant property of the laser diode is the approach or threshold. It will not turn on until the power of the threshold value is applied.
Characteristics of laser diode
Applications of Laser Diode
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There are multiple applications of laser diodes that are highly noticeable in our daily lives. Some of them are,
- Laser diodes can be found in CDs, and relevant devices.
- Laser diodes are often also used for barcode readers.
- It also supports connectivity services; much like Optical Fiber Communication.
- Laser diodes also help in laser screening and printing.
- There are other equipment that involves the composition of laser diodes, such as rangefinders and spectrometers.
Advantages and Disadvantages of Laser Diode
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Laser diode typically uses a p-n junction in order to generate coherent radiation with the same frequency and phase, either in the visible or infrared spectrum. The Advantages and Disadvantages of Laser Diode are:
| Advantages of Laser Diode | Disadvantages of Laser Diodes |
|---|---|
| When compared to other light-emitting equipment, the operational power of a laser diode is relatively less. | Laser diodes are often more expensive, unlike other similar devices. |
| These diodes can be handled quite simply since they are small. | The light radiation produced by laser diodes often negatively affects the eyes. |
| It has a very high efficiency. | Laser diodes have a critical heating problem. |
Previous Year Questions
- The V-I characteristic of a diode is shown in the figure … [VITEEE 2018]
- A diode detector is used to detect an amplitude modulated wave … [JEE Mains 2013]
- The current-voltage relation of diode is given … [JEE Mains 2015]
- A zener breakdown occurs in a zener diode when … [JKCET 2019]
- A zener diode is used as … [JKCET 2014]
- Avalanche breakdown in a … [AMUEEE 2010]
- In the given circuit, the current through zener diode is … [JEE Mains 2018]
- What is the conductivity of a semiconductor sample having electron concentration … [JEE Mains 2017]
- A junction diode has a resistance of … [WBJEE 2009]
- A p−n photodiode is made of a material with a band gap of 2eV … [NEET 2008]
- A n−p−n transistor is connected to common emitter configuration … [NEET 2016]
- Consider the junction diode as ideal … [NEET 2016]
- For the given circuit of p-n junction diode … [NEET 2008]
- If the forward bias voltage in a … [JKCET 2015]
- In breakdown region, a Zener diode behaves as a … [JKCET 2007]
Things to Remember
- A Laser Diode is a device that helps produce coherent radiation that is commonly either produced in the visible or infrared (IR) spectrum.
- Laser diodes tend to have waves that are of the same frequency and phase.
- LASER is a well-known abbreviation of “Light Amplification by Stimulated Emission of Radiation.”
- There are different types of Laser Diodes, like Double Heterostructure Laser Diode, Quantum Well laser Diode, Separate Confinement Heterostructure Laser Diode, and Vertical Cavity Surface Emitting Laser Diode.
- A laser diode follows the principle of Stimulated Emission.
Also Check:
Sample Questions
Ques. Define Laser diodes. (2 marks)
Ans. A Laser Diode is known to be a device that facilitates the emission of coherent radiation, usually of waves that have the same frequency and phase. It is commonly either produced in the visible or infrared (IR) spectrum. Laser diodes, in brief, are found in daily instruments we use, like laser printers, CDs and remote control devices. They also play a huge part in intrusion detection systems as well. A Laser Diode is typically a semiconductor device that has a similar working principle like a light-emitting diode (LED).
Ques. What is the fundamental working principle of Laser Diodes? (2 marks)
Ans. Laser Diodes are composed of two layers of semiconductors, namely, p-type and n-type. Now, these layers of semiconductors are further composed of GaAs, which are additionally doped with relevant materials, much like selenium, or silicon, depending on its nature and characteristic properties. In simple words, the principle of a laser diode is that every atom is able to emit photons when in their excited state, given that the electrons belonging at higher energy levels are incited prior by an external source of energy. It usually follows the principle of Stimulated Emission.
Ques. What are the possible types of emission? (3 marks)
Ans. There are three types of emissions,
- Stimulated absorption: The electrons at the lower energy levels escalate to higher energy levels, by means of an external source of energy.
- Stimulated emission: when photons are hit by electrons, they gain energy and tend to release an extra photon, thus involving the process of stimulated emission.
- Spontaneous emission:Electrons in the higher energy level are often unstable in nature, which makes them move to lower energy levels. But, the change of level usually leads to the release of energy. The released energy comes in the form of light, thus producing photons.
Ques. List at least 5 major advantages of Laser Diodes. (5 marks)
Ans. Here are 4 major advantages of laser diodes,
- The operational power associated with a laser diode is relatively less, unlike many other light-emitting equipment.
- Laser diodes can be handled quite easily since they are small in structure, encouraging simple movement.
- It has a very high efficiency.
- Laser diodes are highly reliable as well.
- Laser diodes usually come with an inexpensive operational cost, alongside being highly operable for relatively long hours.
Ques. List 5 major applications of Laser Diodes. (5 marks)
Ans. There are innumerable applications of laser diodes, since they are often visible in our everyday life
- Laser diodes can be easily detected in CDs, DVDs and other relevant devices.
- Laser diodes can also be used for barcode readings.
- It also supports connectivity services. Optical Fiber Communication can be listed among the instances of it.
- Laser diodes also assist in laser screening and printing.
- There are other equipment that involve composition of laser diodes, much like rangefinders and spectrometers.
Ques. Name and define two types of laser diodes. (3 marks)
Ans. Two different types of laser diodes are:
-Double Heterostructure Laser Diode: Heterstructure is apparently a material that usually is found between two p-type and n-type materials. The active and potential region of this diode is further utilized for better optical amplification; that acts as an added advantage of using it nonetheless.
-Quantum Well laser Diode: The quantum well is known to be a thin layer located in the middle of a diode. Quantum energy, in short, is usually utilized for the conversion of electrons from the higher energy to lower energy.
Ques. What are two major categories of laser diodes? (3 marks)
Ans. The two major categories of laser diodes are,
- Injection Laser Diode: Light radiation, generally, passes via the waveguide. It is very similar to the structure and usage of LEDs, except LEDs utilize larger channels of semiconductors, unlike Injection Laser Diode.
- Optical Pumped Semiconductor Laser: In this equipment, the injection laser diodes usually act as an external pump. In simple words, the amplification is commonly enacted by the help of stimulating emission. There are numerous benefits, mostly like impeding stimulating emission.
Ques. What is a Diode? (1 mark)
Ans. Diode is an electronic component which is responsible to conduct electricity in one direction alone. They have two terminals and display low resistance to the flow of current.
Ques. What is Vertical Cavity Surface Emitting Laser Diode? (2 marks)
Ans. Vertical Cavity Surface Emitting Laser Diode helps the emitted light to exit the device in a perpendicular direction to the chip. Evidently, the optical cavity is usually against the current flow’s axis.
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