Construction and working of Semiconductor Laser
Posted Date: 24-Oct-2011
Dr Amita Maurya
This resource gives the construction, application and working of Gallium Arsenide (GaAs) semiconductor laser. These semiconductor lasers are widely used in optical communication. It works at threshold voltage condition resulting in laser gain at 9000 Angstrom wavelength.
PN-junction Laser: A semiconductor laser is a specially fabricated pn junction device (both the p and n regions are highly doped) which emits coherent light when it is forward biased. It is made from Gallium Arsenide (GaAs) which operated at low temperature and emits light in near IR region. Now the semiconductor lasers are also made to emit light almost in the spectrum from UV to IR using different semiconductor materials. They are of very small size (0.1 mm long), efficient, portable and operate at low power. These are widely used in Optical fibre communications, in CD players, CD-ROM Drives, optical reading, laser printing etc.
p and n regions are made from same semiconductor material (GaAs). A p type region is formed on the n type by doping zinc atoms. The diode chip is about 500 micrometer long and 100 micrometer wide and thick. the top and bottom faces has metal contacts to pass the current. the front and rare faces are polished to constitute the resonator (fig 1).
When high doped p and n regions are joined at the atomic level to form pn-junction, the equilibrium is attained only when the equalization of fermi level takes place in this case the fermi level is pushed inside the conduction band in n type and the level pushed inside the valence band in the p type (Fig 2).
When the junction is forward biased, at low voltage the electron and hole recombine and cause spontaneous emission. But when the forward voltage reaches a threshold value the carrier concentration rises to very high value. As a result the region "d" contains large number of electrons in the conduction band and at the same time large number of holes in the valence band. Thus the upper energy level has large number of electrons and the lower energy level has large number of vacancy, thus population inversion is achieved. The recombination of electron and hole leads to spontaneous emission and it stimulate the others to emit radiation. Ga As produces laser light of 9000 Å in IR region.
Energy Level Diagram of Semiconductor Laser
How Does An Oil Refinery Work?
How Automated windshield wiper system works ?
Read related articles:
Did you like this resource? Share it with your friends and show your love!
Responses to "Construction and working of Semiconductor Laser"
No responses found. Be the first to respond...
Notify me by email when others post comments to this article.
Do not include your name, "with regards" etc in the comment. Write detailed comment, relevant to the topic.
No HTML formatting and links to other web sites are allowed.
This is a strictly moderated site. Absolutely no spam allowed.
to fill automatically.
(Will not be published, but
to validate comment)
Type the numbers and letters shown on the left.
Subscribe to Email
Get Jobs by Email
Forum posts by Email
Articles by Email
Awards & Gifts
j r kumar
Last 7 Days
ISC Technologies, Kochi - India. Copyright © All Rights Reserved.