The most widely used semiconductor light sources are Light Emitting Diode (LEDs) and Lasers. Among these light sources, lasers have gained more importance due its directional properties high energy density.Laser is originated from light amplification by stimulated Emission of Radiation. The Laser is a source of highly directional, monochromatic, coherent light and finds many applications in a medical field, industries, optical communication systems, Entertainment electronics etc.There are many devices used to generate laser. Among these devices, laser di¬odes are commonly used due to its iight weight, small size, and low power consumption and also due to high efficiency to produce light and cheap rate. Laser diodes are the diodes which emit laser. When a devices called LASER DIODE, this generally refers to the combination of semiconductor chip that does actual lasing along with a monitor photo diode chip housed in a package that look like a metal can transistor with a window in the top.

Laser Diode


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Review of Last Lecture
Laser light is coherent(in phase and having the
same wavelength)
Laser Process is based on Stimulated Emission
Two most common excitation techniques of
population inversion are light and electricity.
Four General Categories of Lasers includes Gas
Lasers, Solid State Laser, Semiconductor Lasers
and Dye Lasers

Laser Diode

Light emitters are a key element in any fiber
optic system.
This component converts the electrical signal
into a corresponding light signal that can be
injected into the fiber.
The light emitter is an important element
because it is often the most costly element in the
system, and its characteristics often strongly
influence the final performance limits of a given
link.

Laser diodes are complex semiconductors that convert
an electrical current into light.
The conversion process is fairly efficient in that it
generates little heat compared to incandescent lights.
Five inherent properties make lasers attractive for use in
fiber optics.
1. They are small.
2. They possess high radiance (i.e., They emit lots of
light in a small area).
3. The emitting area is small, comparable to the
dimensions of optical fibers.
4. They have a very long life, offering high reliability.

Laser Diode Performance
Characteristics

Several key characteristics lasers determine their usefulness in a
given application. These are:
Peak Wavelength: This is the wavelength at which the source
emits the most power. It should be matched to the wavelengths
that are transmitted with the least attenuation through optical
fiber. The most common peak wavelengths are 1310, 1550, and
1625 nm.
Spectral Width: Ideally, all the light emitted from a laser would
be at the peak wavelength, but in practice the light is emitted in a
range of wavelengths centered at the peak wavelength. This
range is called the spectral width of the source.