How Lasers Actually Work

Lasers are optical amplifiers, optical oscillators, and in a way, the most sophisticated light source ever invented. Not only are lasers extremely useful, but they are also champions of magnitude: While different laser types cover the electromagnetic spectrum from radiation (<10 nm) over the visible spectrum to far infrared light (699 μm), their individual output band can be as narrow as a few µHz. Their high temporal and spatial coherence lets them cover hundreds of meters in a tight beam of lowest divergence as a perfectly sinusoidal, electromagnetic wave. Some lasers reach peak power outputs of several exawatts, while their beams can be focused down to the smallest spot sizes in the hundreds and even tens of nanometers. Laser is the acronym for Light Amplification by Stimulated Emission Of Radiation, which suggests that it makes use of a phenomenon called stimulated emission, but well, how exactly do they do that? It’s time to look the laser in the eye (Disclaimer: don’t!).

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Tens of thousands saved by building a BAM microscope out of LEGO

A Brewster Angle Microscope (BAM) can run you around $100,000. If you don’t have that lying around you could just use some LEGO pieces to build your own. Having been faced with no budget to buy the hardware, and needing the data to finish his PhD, [Matthew] figured out a way to build something passable on the cheap.

These microscopes bounce a light source off of a pool of water and into the lens of a camera. The thing is the angle of the sender and receiver must be just perfect at 53.1 degrees. [Matthew] was able to afford a used camera, and started experimenting with some lab equipment to mount the rig. But he just couldn’t get the adjustments right. Since he had to move the mounting hardware by hand it was impossible not to over or under shoot the corrections. But then he had a eureka moment. LEGO pieces have very accurate tolerances, and you can get geared and motorized parts. He leveraged the quality of the toy into a BAM whose alignment can be tweak with great precision.

It may not look like much, but you can see stearic acid floating through the microscope’s field of vision in the clip after the break. This is exactly the type of observations he needed to perform. Of course if you just need a microscope you can use a laser and a drop of water.

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