Light Amplification by Stimulated Emission of Radiation LASER Light Amplification by Stimulated Emission of Radiation

What is LASER The acronym LASER, constructed from Light Amplification by Stimulated Emission of Radiation, has become so common and popular in everyday life that it is now referred to as laser. The output of a laser is a coherent electromagnetic field. In a coherent beam of electromagnetic energy, all the waves have the same frequency and phase.

Properties 1. Monochromatic The light emitted from a laser is monochromatic, that is, it is of one wavelength (color).  In contrast, ordinary white light is a combination of many different wavelengths (colors).

2. Directional Lasers emit light that is highly directional.  Laser light is emitted as a relatively narrow beam in a specific direction. Ordinary light, such as coming from the sun, a light bulb, or a candle, is emitted in many directions away from the source.

3. Coherent The light from a laser is said to be coherent, which means the wavelengths of the laser light are in phase in space and time.

Difference between Laser and Light

Spectrum The typical incandescent light bulb produces a broad spectrum of light, meaning that it puts out the entire visible spectrum of light. This is why these bulbs appear to be white. Lasers put out a specific wavelength of visible light. This wavelength is what dictates a laser's color, as seen by the eye.

2. Coverage An incandescent bulb puts out light in every direction at the same time. This is why it lights entire rooms when on. Lasers emit light in a single, narrow beam, lighting only a small area

3. Efficiency A great percentage of the energy used by a standard light bulb is wasted as heat. Lasers are much more efficient because more of the energy used to create the light is focused in the beam. This is why some lasers can burn or even cut.

Production Incandescent light is produced by simply running alternating current through an electrically resistant filament. As the filament gets hotter, it begins to glow, emitting visible light. Laser light is produced by electrically exciting atoms until they release energy in the form of a photon, which is what we see.

Dangers While there are incandescent bulbs with brightness levels capable of being painful to look at, few except the very brightest can cause permanent eye damage. The intensity of the light produced by a laser beam can permanently blind a person in seconds.

History 1900, Planck deduced the relationship between energy and the frequency of radiation, essentially saying that energy could be emitted or absorbed only in discrete chunks – which he called quanta – even if the chunks were very small.

In 1917, Einstein proposed the process that makes lasers possible, called stimulated emission. He theorized that, besides absorbing and emitting light spontaneously, electrons could be stimulated to emit light of a particular wavelength.

In 1954, Charles Townes and Arthur Schawlow invented the maser (microwave amplification by stimulated emission of radiation), using ammonia gas and microwave radiation - the maser was invented before the (optical) laser

May 16, 1960: Theodore H. Maiman, a physicist at Hughes Research Laboratories in Malibu, Calif., constructs the first laser using a cylinder of synthetic ruby measuring 1 cm in diameter and 2 cm long, with the ends silver-coated to make them reflective and able to serve as a Fabry-Perot resonator. Maiman uses photographic flashlamps as the laser’s pump source.

Structure Basic Components Laser Material The lasing material, also commonly referred to as the laser medium or the gain medium. It is situated inside the optical cavity, and a method to supply energy to the lasing material. The gain medium is basically a material that can be a solid, liquid, or gas. It can also be molecules or atoms of a crystal.

2. Pump Source Electricity and light such as flash lamp or another laser are examples of pump sources. The laser medium absorbs this pump energy, which places some of the laser medium particles into excited or high-energy quantum states.

3. Optical Cavity The optical cavity is a type of cavity resonator. Inside the optical cavity, it contains a coherent light beam between reflective surfaces.

1. Gain Medium 2. Laser pumping energy 3. High reflector 4. Output coupler 5. Laser beam

How it works How atoms give light 1.They start off in their stable "ground state" with electrons in their normal places.

2. When they absorb energy, one or more electrons are kicked out farther from the nucleus into higher energy levels. We say the atom is now "excited.“

3. However, an excited atom is unstable and quickly tries to get back to its stable, ground state. So it gives off the excess energy it originally gained as a photon of energy (wiggly line): a packet of light.

How laser works