Lasers

Question 1

What are the properties of Conventional Light Sources?

Answer 1

• Conventional light sources emit broad
  spectra, radiation out form a diffuse point.
• Intensity is spread across a wide wavelength
  range (poor efficiency), and decays with an
  inverse square law (poor utility).

Question 2

What are the Essential Components of a Solid-state Laser

Answer 2

A solid state laser must include:
• An optical (photon) energy-input source,
• A laser medium (or lasing material),
• An optical resonant cavity,
• An output port.

Question 3

What is a solid-state laser?

Answer 3

A solid-state laser is a laser that uses a lasing material distributed in a solid matrix

Question 4

What are conventional sources?

Answer 4

Conventional sources emit light in all directions. The light is then modulated in a given direction with optical systems like reflectors and lenses.

Question 5

What are the types of lasers?

Answer 5

Solid, liquid, gas and free-electron.

Question 6

What are Gas lasers?

Answer 6

Gas lasers (helium and helium-neon, HeNe, are the most common gas lasers) have a primary output of visible red light.

Question 7

What are semiconductor lasers?

Answer 7

Semiconductor lasers, sometimes called diode lasers, are not solid-state lasers. These electronic devices are generally very small and use low power.

Question 8

What are dye lasers?

Answer 8

Dye lasers use complex organic dyes, such as rhodamine 6G, in liquid solution or suspension as lasing media

Question 9

How does a solid-state laser work?

Answer 9

The crystal produces laser light after light is pumped into it by either a lamp or another laser.

Question 10

What are the steps in producing Photons?

Answer 10

1. The optical stimulus (pump) excites electrons in the lasing medium to a higher energy-level.
2. If the pumping power (wattage, i.e. photons per second) is low, then the medium
   returns to the ground state by spontaneous emission, depleting the available excited electrons. But,
3. If the pumping power is great enough, there is a continuously replenished source of
   electrons in the excited state – a population inversion.
4. Now these excited electrons decay by stimulated emission, and as a result have identical wavelength, direction and phase to the passing photon.

Question 11

When producing a photon, if the pumping power (wattage, i.e. photons per second) is low, then what happens?

Answer 11

the medium returns to the ground state by spontaneous emission, depleting the available excited electrons.

Question 12

What are the steps in producing a beam?

Answer 12

• Spontaneously emitted photons are randomly directional, we still don’t have a laser beam.
• The pair of mirrors at either end form an optical ‘resonant cavity’,
• Only photons travelling very close to the axis of the laser are internally reflected.
• And so, only these reflected photons go on to give stimulated emission.
• This cavity must be precisely parallel, and an integer multiple of the photon wavelength.
• The front mirror is typically a ~95% mirror so that some light is allowed out, but is mostly reflective to sustain the lasing.

Question 13

What do solid lasers include?

Answer 13

Solid lasers can include ruby (research), GaN (Blue-ray player), AlGaAs (laser pointers),

Question 14

What do liquid lasers include?

Answer 14

Liquid lasers (less common) use chemical dyes tunable by wavelength,

Question 15

What do gas lasers include?

Answer 15

Gas lasers, are pumped by electrical discharge (used mostly for research),

Question 16

What are free-electron lasers?

Answer 16

Free-electron lasers use a high-speed electron as the lasing medium, can produce x-rays.

Question 17

What are the risks of lasers and what does it depend on?

Answer 17

Laser exposure risk depends on the wavelength, power and design and includes Tissue burns, eye damage, endotracheal tube fire, drape fire, and explosion of gases

Question 18

How are the risks of lasers overcome?

Answer 18

• Lasers should carry a classification labelling which dictate the appropriate control processes.
• Common lab PPE are laser glasses/goggles, but these must be appropriate for the wavelength being used.

Question 19

Give applications of laser beams

Answer 19

Applications of Laser Beams
• Measurement (collimation),
• Detection (wavelength),
• Data storage,
• Spectroscopy,
• Cutting tools,
• Weapons (military research),

Question 20

How are laser beams used in measurement?

Answer 20

A collimator is a device that narrows a beam of particles or waves. To narrow can mean either to cause the directions of motion to become more aligned in a specific direction (i.e., make collimated light or parallel rays)

Question 21

What is a laser?

Answer 21

A device that generates an intense beam of coherent monochromatic light (or other electromagnetic radiation) by stimulated emission of photons from excited atoms or molecules (optical amplification)

Question 22

How is lasers used in spectroscopic techniques?

Answer 22

Ultrafast laser spectroscopy is a spectroscopic technique that uses ultrashort pulse lasers for the study of dynamics on extremely short time scales

Question 23

How are lasers used in cutting?

Answer 23

Laser cutting is a technology that uses a laser to cut materials, and is typically used for industrial manufacturing applications, but is also starting to be used by schools, small businesses, and hobbyists. …

Question 24

How can a laser be a weapon?

Answer 24

A laser produces very intense energy that can travel over very long distances. That’s why a laser can become a weapon while the light from an incandescent bulb typically can’t. To do this, a laser has to produce light in a nonconventional way. “Laser” stands for light amplification by stimulated emission of radiation.

Question 25

How is a laser created?

Answer 25

A laser is created when the electrons in atoms in special glasses, crystals, or gases absorb energy from an electrical current or another laser and become “excited’’. The excited electrons move from a lower-energy orbit to a higher-energy orbit around the atom’s nucleus. When they return to their normal or “ground” state, the electrons emit photons (particles of light).

Question 26

How is laser light different from normal light?

Answer 26

1) Its light contains only one wavelength (one specific color). The particular wavelength of light is determined by the amount of energy released when the excited electron drops to a lower orbit.
2) Laser light is directional. Whereas a laser generates a very tight beam, a flashlight produces light that is diffuse. Because laser light is coherent, it stays focused for vast distances, even to the moon and back.

Question 27

Give an application of lasers in biology

Answer 27

The laser is an effective tool for destroying cancer cells

Question 28

What is LASER an acroymn for?

Answer 28

Light 
Amplification by 
Stimulate
Emission of 
Radiation

Question 29

What are the three laser light properties?

Answer 29

Monochromic, coherent, and directional

Question 30

What is monochromatic?

Answer 30

Contains one specific wavelength of light (one specific color).

Question 31

What does the wavelength of light determined by?

Answer 31

The wavelength of light is determined by the amount of energy released when the electron drops to a lower orbit.

Question 32

How is laser light coherent?

Answer 32

It is “organized”– each photon moves into step with other. Meaning all the photons have waves fronts that lunch in unison

Question 33

What is directional in terms of laser light vs. flashlight?

Answer 33

A laser light has a very tight beam and is very strong and concentrated. A flashlight in contrast releases light in many directions,t he light is very weak and diffuses.

Question 34

Why can’t you look at a laser with your eyes?

Answer 34

The reason lasers can do so much damage is that they produce bright light which is well concentrated into a thin beam. … If you hold the laser beam steadily into someone’s eye, then there is a good chance the laser beam will burn up cells on the retina (back of the eyeball), causing a permanent blind spot in his vision.

Question 35

Where on the electromagnetic spectrum do most lasers operate

Answer 35

UV, visible, and infared