A laser is an electronic device that stimulates molecules or atoms to emit light beams at a specific wavelength and amplifies those light rays, usually generating a thin electromagnetic radiation beam. The emission typically covers a limited range of ultraviolet, visible, or infrared wavelengths. Various different kinds of lasers have been designed, with varied properties and applications. The full form of laser is “Light Amplification by the Stimulated Emission of Radiation”. Laser is a concept derived from the suggestion put forward by Albert Einstein (1916). He suggested that under controlled conditions, atoms could emulate excess light beams (stimulated by EM radiation or some spontaneous internal reactions). In 1928, for the first time, stimulated emission was detected by Rudolf Walther Ladenburg. At that time, this discovery had no major applications. However, with the development of better emission technology, more and more direct applications have arisen. A laser diode is a kind of semiconductor device that employs a p-n junction for generating coherent radiation which has the same phase and frequency. It is either in the infrared or visible spectrum. It is also known as an injection laser diode. This technology is similar to normal LED technology.
Lasers are differentiated from other light beam sources by their coherence. Transverse or spatial coherence is usually expressed via the output being a thin light beam, which is diffraction restricted. Laser light beams can be precisely focused to a very small spot, acquiring extreme irradiance, or the beams can possess very low divergence to focus their power into a long distance. Longitudinal or temporal coherence implies a polarised wave at one frequency whose phase is correlated along a great length (the coherence length). A laser beam generated by a thermal or other incoherent source possesses an instantaneous phase or amplitude that changes arbitrarily with respect to position and time. Therefore, it has a short coherence length.
Important Laser Diode Questions with Answers
1) What is meant by laser diodes?
A laser diode is a kind of semiconductor device that employs a p-n junction for generating coherent radiation which has the same phase and frequency. It is either in the infrared or visible spectrum. It is also known as an injection laser diode. This technology is similar to normal LED technology.
2) What is meant by double heterostructure laser diodes?
The heterostructure is a substance between two p-type and n-type materials. Due to the presence of a heterostructure substance, this kind of laser diode is known as a double heterostructure laser diode. The primary advantage of this laser diode is that the active area is utilised for greater optical amplification.
3) What is meant by a quantum well laser diode?
The quantum well is a very narrow middle section in the diode. Quantum energy is employed for transforming electrons from higher energy levels to lower energy levels (responsible for enhancing efficiency).
4) What is meant by a separate confinement heterostructure diode?
In this laser diode, there are two extra sections along with the main three sections. These layers possess a much lesser refractive index (light emission is also improved).
5) What is meant by a vertical-cavity surface-emitting diode?
In this kind of laser diode, its optical cavity is along the current flow axis.
6) What are the important applications of lasers?
Lasers are employed in semiconducting chip production, laser printers, DNA sequencing tools, barcode scanners, optical disc drives, law and military enforcement devices for setting targets and calculating speed and range, welding and cutting materials, laser skin treatments and surgery, and laser lighting display monitors. Semiconductor lasers that are in the blue to near-UV have been used instead of light-emitting diodes to activate fluorescence as a source of white light. This allows a much smaller light emitting point due to the much better radiance of a laser.
7) What are the main principles behind the working of a laser?
Lasers are differentiated from other light beam sources by their coherence. Transverse or spatial coherence is usually expressed via the output being a thin light beam, which is diffraction-restricted. Laser light beams can be precisely focused to a very small spot, acquiring extreme irradiance, or the beams can possess very low divergence to focus their power into a long distance. Longitudinal or temporal coherence implies a polarised wave at one frequency whose phase is correlated along a great length (the coherence length). A laser beam generated by a thermal or other incoherent source possesses an instantaneous phase or amplitude that changes arbitrarily with respect to position and time. Therefore, it has a short coherence length.
8) What are the main characteristics of laser diodes?
Coherent Light: A light beam with a single wavelength released by an LED with a broad wavelength.
The significant characteristic of laser diodes is their threshold or approach. These lasers do not work until a minimum power is provided to the system. If the light is under its minimum energy, then the light emission will be much weaker than the threshold relative to the full energy.
Monochromatic Beam: Laser diodes only radiate narrow light comprising only a single colour.
Well-directed Beam: Laser light beams are focused into a narrow beam which helps to concentrate light into a single point.
9) What are the main advantages of a laser diode?
When a laser diode is stacked against other light-emitting apparatuses, the working power is very low in laser diodes. The handling of laser diodes is simple and easy as they have better ergonomics (size and structure). The light produced by these diodes has high efficiency.
10) Laser is a concept derived from the suggestion put forward by ________ (1916).
Answer: Albert Einstein
Explanation: Laser is a concept derived from the suggestion put forward by Albert Einstein (1916).
11) The full form of laser is “___________”.
Answer: Light Amplification by the Stimulated Emission of Radiation
Explanation: The full form of laser is “Light Amplification by the Stimulated Emission of Radiation”.
12) In 1928, for the first time, stimulated emission was detected by __________.
Answer: Rudolf Walther Ladenburg
Explanation: In 1928, for the first time, stimulated emission was detected by Rudolf Walther Ladenburg.
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Practice Questions
1) What is meant by laser?
2) What is the full form of “laser”?
3) What is the main difference between a laser and other light devices?
4) What is meant by coherence?
5) What is the relationship between coherence and laser?
6) What are the disadvantages of lasers?
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