Physics Demo Number: 181

Approximate

Run Time: 10 min

Partially Open-Cavity, Single Brewster-Window Laser

Demo Description

A laser tube is mounted on an optical bench so that one of its end mirrors is mounted externally to the tube on an optical bench sliding holder. Careful alignment of the external mirror starts the lasing action, as long as the open part of the lasing cavity is not blocked.

 

Scientific Principles

  • Operation of a HeNe laser with only essential structures for the tube in place, thus allowing for a Conceptually Transparent View of the Lasing Process

Equipment

  • Dedicated Laser Tube

  • Dedicated Power Supply

  • Dedicated End Mirror and Slide

  • Dedicated Optical Bench

  • Dedicated (Science Shop Made) Aluminum Holding Base ( or micro-optical table) To Align Optical Bench

  • Dedicated Double Lucite Housing (Science Shop Made) Containing all of above Components

 

Equipment Location

  • All components in Kit [181] on [C-4-2]

Instructions

The first four components listed under Equipment above are seen in the first two pictures. This is how they look outside of the new housing.






The third picture is a drawing of the essential setup of the first four components.


The next three photos depict the newly housed components.

This arrangement is much safer for both the apparatus and the demonstrator.

It is also now vastly easier to show the effect since the alignment of the mirror is pretty well locked down rock-solid .

The fourth picture shows the "laser- tube-power supply-optical bench" from the first photo all now tied down to the custom made aluminum optical table with the laser tube now shielded by a Lucite safety housing.

Moreover all of the just mentioned components are housed inside an overall Lucite dust shield, which is seen in the background of the sixth photo, where it has been removed and lifted off (by removing the six thumbscrews seen in the foreground of the photo).

Close inspection* of the fifth photo should allow one to see the laser beam on the vertical bin post in the background.

*Note that in most of the photos  in all these writeups, if one uses Firefox  to look at a  photo, the photo can be seen much enlarged.

Writeup created by David A. Burba
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