If you observe all the lasers in the market today, you’d notice that they have a variety of colors.
There’s a scientific explanation of why laser pointers can have different colors. The different colors are mainly based on their wavelength (or frequency). It can also be contributed by the materials used to produce the lasers.
Read on to find out what best explains why a laser beam might appear green and another, red. Also, you can figure out how these lasers with different colors are produced.
What is the difference between green and red laser?
What best explains why one laser beam might appear green and another appears red lies on their wavelength. As stated previously, a laser’s wavelength or frequency is responsible for its color.
If you see the chart above, red and blue lasers lay on opposite ends of the curve. Blue lasers have a wavelength ranging from 400 to 500nm with only 3% visibility to the human eyes.
Meanwhile, red lasers have a wavelength with a range of 650 to 700 with a visibility of 24%. Green lasers, on the other hand, possess the most visibility ranging from 88% to 100%. However, they don’t have the highest wavelength, placing at 532 to 555 nanometers on the wavelength scale.
On the far left and far-right side of the curve, we have ultraviolet and infrared respectively. Ultraviolet has a wavelength of 193-337nm while infrared has a wavelength of up to 10,000nm. This makes these two laser lights invisible to the naked eye as the range of visibility for the human eyes is 390-780nm.
During the stimulated emission stage, the energy of the photon produced contributes to what the laser color will be. So, the higher energy photons that are produced, the shorter the wavelength of the light will be. This means blue laser lights produce high energy photons while red laser lights produce lower energy photons.
What do different color lasers do?
These different-colored laser pointers are used for various reasons and in various places.
For instance, the red laser pointer, which is the most popular type of laser pointer, can be used for casual use.
This includes during presentations, for light photography, science experiments, to entertain your pets, and more.
This is because red laser pointers of less than 5mW can cause the least amount of potential damage.
On the other hand, since green laser pointers are generally more visible and powerful than red laser pointers, its uses are more focused and specific.
For example, green laser pointers are used for astronomy, especially stargazing. Green lasers have a light that is brighter, can also be visible during daytime, and the light can go for longer distances than red lasers.
Green lasers are also used as a laser sight for guns and rifles.
Next, yellow and orange lights are typically used in hospitals. They can help treat viral infections sclerosis, and even psychological illnesses like panic attacks, anxiety disorders, and depression.
Aside from treating major injuries and mental sicknesses, yellow lasers can also be found in skin and aesthetic clinics. It helps get rid of acne, stimulates collagen production, reduces redness and inflammation, and promotes new skin growth.
Blue lasers possess a shorter wavelength than all the other colors. This means blue laser beams can have a stronger focus or resolution.
Because of its stronger focus, blue lasers are typically used in interferometers such as laser printers, compact discs, data recording, digital photofinishing, and DVD or CD players.
Now that you have the gist of why some lasers appear blue and some appear red, you can choose a laser pointer with the color that is most suitable for you.
An Overview of the Laser
Type of lasers
First, let’s dive into all the laser types. The difference in laser type is mainly due to the lasing material used.
There are 5 main types of lasers available today and these are:
- Solid-state lasers use solid matrix-like ruby or neodymium:yttrium-aluminum-garnet (Nd: Yag)
- Gas lasers use helium and helium-neon (HeNe)
- Dye lasers use complex organic dyes like rhodamine 6G; can be tuned to any wavelength
- Semiconductor lasers use laser diodes; very small and low powered
- Excimer lasers mix reactive gases like chlorine and fluorine with inert gases like argon, xenon, and krypton
These varying lasing materials are responsible for the level of wavelength and power output emitted by the laser.
How laser pointers produce different colored lights
Second, let’s explore how light is produced. There are two ways an atom can produce light and it’s through spontaneous emission or stimulated emission.
Spontaneous emission is when the energy source within the laser emits light all by itself.
It does that when the energy source (atom, molecule, or subatomic particle) moves from a high (excited) energy state into a ground state (low energy level).
Spontaneous emission occurs at random intervals.
On the contrary, stimulated emission refers to the interaction between an incoming photon with a specific frequency and an excited atom.
Once they interact, the photon will bring the excited atom to a lower energy level. Here, the atoms are stimulated to produce radiation, hence the term stimulated emission.
What happens next is a chain reaction of photons that would produce coherent light, coining the term laser, or Light Amplification by Stimulated Emission.
Although the colors are different, all laser pointers use stimulated emission to produce light.
Red, orange, yellow, green and blue lasers
As stated above, the difference between red, orange, yellow, green and blue lasers lies mainly on their wavelength or their source type.
The following table explains the difference between several color laser pointers.
|Laser Color||Laser Type||Wavelength (nm) or frequency (Hz)|
|Red||A battery-powered laser diode, or diode-pumped solid-state laser||Up to 680nm|
|Orange||Diode-pumped solid-state laser, with complex lasing lines of ND:YVO4, 1064 nm, and 1342nm||593.5nm|
|Yellow||Diode-pumped solid-state laser||589nm|
|Green||Diode-pumped solid-state frequency-doubled laser||532 – 555nm|
|Blue||Diode-pumped solid-state frequency-doubled laser or Blu-ray||360 – 480nm|
You can also determine the color and wavelength by the type of energy source your laser pointer uses. Take a look at the following table:
|Laser Source Type||Wavelength (nm)|
|Argon fluoride (UV)||193|
|Krypton fluoride (UV)||248|
|Xenon chloride (UV)||308|
|Rhodamine 6G dye (tunable)||570-650|
|Ruby (CrAIO3) (red)||694|
|Carbon dioxide (FIR)||10,600|