Getting started with lasers

Published by Nicky Ang under Science on February 29, 2008

Wow! this is a very exciting world as I dive into laser science, a branch of modern optical physics. Let me introduce you to the world of lasers in English (I hope).

What is a laser?
Laser stands for Light Amplification by Stimulated Emission of Radiation. This means a monochromatic light source that is well collimated. In English, it means a very pure and narrow single color light.

Laser brightness (output power) is measured in watts.

Lasers that are visible to the human eye range from violet to red and are determined by the wavelength (nm or nanometers). Below is the visible spectrum chart containing measurements in terahertz (THz) and nanometers (nm). An example of a device that uses laser is your typical DVD/CD player or your laser printer.

Getting started
I started with a simple RM5 keychain laser pointer that can be purchased from any pasar malam (night/flea market). This typical pointer uses three button cells (4.5V) as power supply. The typical output power is 1mW and the laser light is deep red color (650nm red dot). Normally, you will see this type of pointer being used widely during office presentations. Also we can use this pointer to exercise our dog/cat as they will chase around trying to catch the red dot.

Advanced lasers
Soon I managed to grab hold of very much powerful lasers for optical experiments. There are some shops such as Wicked Lasers and Techlasers that sell very powerful laser pointers. I got both 5mW and 125mW pointers from Wicked Lasers (WL). Unlike the keychain pointer, these lasers emit a green beam (532nm).

These laser pointers are powered by two AAA batteries. According to manufacturer’s website, the batteries typically last about 90 mins of continuous usage.

(From top: 1mW keychain, 125mW WL Fusion, 5mW WL Core)

 

(125mW WL Fusion and 5mW WL Core)

Now comes the exciting part
This is the part you’ve been waiting for. Pictures of real laser in action. I will put three pictures together starting from the 1mW keychain, 5mW WL Core and 125mW WL Fusion.

(1mW keychain laser pointer. Only the red dot is visible)

 

(5mW WL Core. Much brighter and notice the straight beam)

 

(125mW WL Fusion. Beam is thicker and highly visible)

As you can see my entire room was lit when I fire up the 125mW Fusion laser. This is to give you a perspective how bright and powerful it is. Oh, did I mention that it’s actually brighter than the sun?

Burning experiments
My favourite experiment with powerful laser pointers is lighting matches. In fact a 125mW beam produces enough heat to melt black plastic bags, pop black balloons and light matches.

Why black? In optics, black surface absorb all light, hence you see the color as black. Whereas a white surface means all lights is reflected. A red surface means only red light is reflected, the rest is absorbed.

Hence black balloons and plastic bags absorb enough laser light to heat up the surface.

(Laser almost hitting the match tip)

 

(Match lights up instantly)

Laser safety
Lasers can be very dangerous if not handled properly. First and foremost, never point any laser pointers directly to your eyes or anyone else. This includes your pets or any other animals.

Even the 1mW pasar malam keychain pointer can cause eye damage if exposed for a few seconds.

Next article
In my upcoming post, I will discuss more about lasers and many more experiments we can do with it. Until then, for your safety, never try this at home. J