What is the difference between Lasers and LED's (light emitting diodes)?
Lasers are monochromatic (single color wavelength), collimated (non-divergent) and coherent (wavelengths in- phase) in contrast, LED's are neither coherent nor collimated and generate a broader band of wavelengths (multiple). In addition, a significant difference between the two is the power output. The peak power output of lasers is measured in watts, while that of LED's, is measured in milliwatts. Also, LED's usually have a 50% duty cycle, meaning that they are "on" 50% of the time and "off" 50% of the time regardless of what frequency (pulses per second) setting is used.
There are many light emitting products on the market today, claiming to be lasers that do not meet scientifically defined attributes for being a true laser. For example, products that use Light Emitting Diodes or LEDs as they are more commonly known, do in fact produce light, however the light is not intense, producing very little energy and is non-coherent, similar to light produced by common household light bulbs. Non-coherent or non-culminated light is the result of photons moving in random directions at random times, generating random frequencies. The most common use of LEDs is in electronic equipment, such as cell phones and VCRs, to inform the users that the item is ON. LEDs are cheap and easy to reproduce (Pontinen 1992). Obviously, these devices are NOT lasers. This misconception is in large part a by-product of marketing. Some sales professional use the word "laser" in order to describe a process such as in "laser pointers" which refers more to mankind's collective imagination than scientific comprehension.