How do Mem-Gems work?

Constructive interference of laser light brings your image to life

Constructive Interference

Space is like a three-dimensional pond surface

If you have ever looked at a pond, you may have noticed little waves on the surface. Light waves are electromagnetic waves, which means that instead of moving molecules of water around on a pond surface, they actually distort the electromagnetic field of space itself. And rather than being confined to a surface of a pond, light waves can travel in three-dimensions. Light waves are amazing!

duck pond ripples



All the photons are one wavelength

The smallest measurable unit of light (a single photon) is created when an electron (the little charged guy orbiting the nucleus of an atom) hops down in energy. In a laser, a light photon can trigger an adjacent electron to release a photon in a chain reaction called stimulated emission (the SE LASER). As a result of all the complicated physics going on in a laser, all the photons of light emitted by a laser are nearly the same color. Unlike most things we see in our day-to-day lives that reflect sunlight of all colors to varying degrees, a laser emits just one wavelength of light. That's why lasers have such a futuristic appearance that's unlike anything you see in normal sunlight.

laser show

Laser safety


Lasers are spatially coherent light sources. That means that they shine in one direction, so they can be bright even if you're far away from them. Your eyes have evolved to focus light to enable you to see. However, this also means that a laser beam can actually be focused by your eye to a small spot on your retina, and permanently damage your eye. Furthermore, sudden exposure can cause temporarily surprise and blindness that can be dangerous if driving a car or operating heavy machinery. However, there are some basic physics principles that can help us stay safe:
  1. The power of a laser increases its danger level because it will take less time to cause damage to the retina. Therefore, we recommend: use a low-power laser (Class II or less).
  2. Do not stare at any direct reflections, so don't shine a laser at a mirror, shiny metal, or other optically reflective surface. Project images onto diffuse specular surfaces such as a white painted wall.
  3. Do not intentionally stare at a laser beam. If something is uncomfortable, look away.
  4. For more information about laser safety, see:


Controlling interference

A Mem-Gem™ uses a specially patterned laboratory-grown sapphire to control the optical interference of light

Since we know that light is a wave, and lasers have just a single wavelength, we can use physics to control how that light will interfere. We use software to turn your image into a special pattern called a phase-mask that controls light. By perfectly tuning the surface of your laboratory-grown sapphire Mem-Gem™ so that some areas create destructive interference and other areas create constructive interference, and repeating this process millions of times, we can build up a diffractive optical element that will project an image under laser light illumination. Each pixel in the Mem-Gem™ represents one Fourier mode of the resulting image projection, and that's why your image is hidden in sunlight. Similar to how musicians in a symphony orchestra create sound waves to celebrate music, we believe that Mem-Gems™ use light waves to celebrate the memory that you wish to treasure!


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