A laser diode, also known as an injection laser or diode laser, is a semiconductor device that produces coherent radiation (in which the waves are all at the same frequency and phase) in the visible or infrared (IR) spectrum when current passes through it. Laser diodes are used in optical fiber systems, compact disc (CD) players, laser printers, remote-control devices, and intrusion detection systems.

Laser diodes differ from conventional lasers, such as the helium-neon (He-Ne), ruby, and gas types, in several ways.

Small size and weight: A typical laser diode measures less than one millimeter across and weighs a fraction of a gram, making it ideal for use in portable electronic equipment.

Low current, voltage, and power requirements: Most laser diodes require only a few milliwatts of power at 3 to 12 volts DC and several milliamperes. Therefore, they can operate using small battery power supplies.

Low intensity: A laser diode cannot be used for spectacular purposes such as burning holes in metal, bringing down satellites, or blinding aircraft pilots. Nevertheless, its coherent output results in high efficiency and ease of modulation for communications and control applications.

Wide-angle beam: A laser diode produces a "cone" rather than a "pencil" of visible light or IR, although this "cone" can be collimated using convex lense

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LASER Diode – How it WorksPosted by D Mohankumar in Theory with 3 comments Tagged with: laser

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Laser is of prime importance in Optical memories, Fiber optic communications, Military applications, Surgical procedures, CD players, Printers etc. Various forms of lasers like Gallium Arsenide laser, Helium Neon laser, Carbon dioxide laser etc are used in various applications. CD players use laser technology to read the optically recorded data in the form of Bits and Pits on the CD.

Laser is a narrow beam of Photons emitted by specially made laser diodes. Laser diode is similar to an ordinary LED, but it generates a beam of high intensity light. A laser is a device in which a number of atoms vibrate to produce a beam of radiation in which all the waves have single wavelength and are in Phase with each other.

Monochromatic LaseA laser diode, or LD, is an electrically pumped semiconductor laser in which the active medium is formed by a p-n junction of a semiconductor diode similar to that found in a light-emitting diode. The

laser diode is the most common type of laser produced.r

Laser light is Monochromatic and can be focused as a pencil beam The beam of a typical laser has 4×0.6mm widening at a distance of 15 meters. Like an LED, laser diode converts electrical energy into light energy.

How it Works?The most common laser diode generates semiconductor or injection laser. In these lasers, a population of Inversion Electrons is produced by applying a voltage across its p-n junction. Laser beam is then available from the semiconductor region. The p-n junction of laser diode has

polished ends so that, the emitted photons reflect back and forth and creates more electron-hole pairs. The photons thus generated will be in phase with the previous photons. This will give a Pencil Beam and all the photons in the beam are Coherent and in phase.

Applications of Laser

Laser diodes can be switched on and off at frequencies as high as 1GHz, making them ideal in Telecommunication applications. Since laser generates heat on hitting the body tissue, it is an ideal solution to heal sensitive parts like Retina of Eye and brain. Laser can be used to pinpoint the lesions so that nearby tissues are not affected as in the case of surgery.

Laser Diode

A Word of Caution

Laser is a high intensity penetrating beam and is extremely dangerous when focused on to the Eye. Low cost Laser pointers are now available in the market and some people handle them carelessly and may even give to children to play with. A Laser pointer with output power higher than 5 mW is harmful. Take utmost care while handling laser diodes. Always take precautionary measures while trouble shooting CD players, Laser printers etc.

The author D Mohankumar is not an active member anymore. Please take into consideration that the presented information might not be correct.

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3 Responses to "LASER Diode – How it Works"

1. Syed Shiyas on January 28, 2010 at 5:44 pm

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Please add a simple laser diode application circuit too.Thank you.

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o ElectroSchematics.com on January 29, 2010 at 7:14 pm

  

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Syed Shiyas here is a laser based door alarm published by D.Mohankumar http://electroschematics.com/4929/laser-based-door-alarm/

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2. cjoann51 on May 2, 2012 at 8:11 am

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do you have any simple circuit for laser based intruder alarm?

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