Question

1. What is the physics behind the light amplification of optical amplifiers? What are the required conditions to make the amplification happen?

2. Describe what happens below, at, and above the lasing threshold of a laser in terms of its output power, population inversion, and gain coefficient.

Answer 1

1.An optical amplifier is a device that

amplifies an optical signal directly, without the need to first convert it to an electrical

signal. An optical amplifier may be thought of as a laser without an optical cavity, or

one in which feedback from the cavity is

suppressed. Optical amplifiers are

important in optical communication and laser physics. They are used as optical

repeaters in the long distance fiberoptic

cables which carry much of the world's

telecommunication links.

2.The lasing threshold is the lowest

excitation level at which a laser's output is

dominated by stimulated emission rather

than by spontaneous emission. Below the

threshold, the laser's output power rises

slowly with increasing excitation. Above

threshold, the slope of power vs. excitation

is orders of magnitude greater. The

linewidth of the laser's emission also

becomes orders of magnitude smaller above the threshold than it is below. Above the

threshold, the laser is said to be lasing. The

term "lasing" is a back formation from

"laser," which is an acronym, not an agent

noun.

#Hope this helps.Thanks.