Excerpt from HMP 7 Chapter 7
Laser Fundamentals
This chapter could be titled "from photons to etalons." It begins with a review of the fundamentals of electromagnetic radiation and then proceeds to a detailed explanation of how the lasers that are most commonly used in holography (CW lasers) work.
To sufficiently understand the operation of lasers, their many advantages and their necessity in the production of holograms, one must first comprehend certain properties of our physical world.The entire universe consists of only two things: matter and energy. Matter is all things that have physical substance; energy is the mover, or potential mover, of physical substance. Matter is the stuff we see, smell and feel. It has mass and occupies space.
Energy, on the other hand, is more abstract. It is most often invisible, though sometimes not. Yet, it is everywhere. It lurks in the crevices of every molecule and sweeps the skies with its magnificence. A master of transformation, energy facilely converts itself from one of its many forms to another, all without sacrifice.
Energy is the driving force behind all forms of motion: the motion of our car, the motion of planets, the motion of atoms. Nothing moves without it. Matter, without energy, is reduced to a dark, frozen lump of nothingness. In a dynamic universe, matter both possesses energy and is affected by it.
Energy not only changes form; it is also easily passed from one object to another. Interestingly enough, no matter how many times it transforms or transfers, the amount of energy involved in any given transaction never changes. The law of conservation of energy, one of the most important laws in the universe, dictates that energy is never created or destroyed; it can only be transferred to another object or converted into a different form of energy.
Because the amount of energy in the universe remains fixed, phrases such as "energy shortage" and "depleted energy" are misnomers. You can not lose energy, nor can you be in short supply. The amount of energy in our environment is so great that it is beyond our comprehension. The discomforts in past decades from "energy shortages" were created only by our inability to either convert energy to a usable form or distribute usable energy to where it was needed.
Energy is measured in joules, in honor of the British scientist James Joule. One joule is roughly the amount of energy required to lift an apple from your kneecap over your head.
A glass of apple cider has 502,092 joules (equal to 120 calories—the calorie is another unit of energy often used when referring to the content of food) of food energy. A gallon of gasoline has over 200 million joules of energy.
The process of applying energy to matter is called work (also measured in joules). Work is the mechanism that transfers energy through a system. It is produced by applying a force on an object such that motion occurs over a distance. For example, when you pick up a book, you have performed work on the book. The heavier the book, the greater the force that is necessary to raise it—therefore, the more work done. The farther you raise the book, the greater the dis...
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