English: A laser output coupler measuring 1 inch in diameter and 3/8 inch thick, with a flatness of 1/20 of the wavelength of the light. The coating is centered at 550 nm, and is 75--80% reflective to wavelengths between 500 and 600 nm. The photo on the left shows its reflectivity to yellow light but its high transmissivity to red and blue light. The photo on the right shows it both reflecting and transmitting 589 nm laser light. Due to the nature of lasers, the beam appears brighter when coming toward the observer than it does when moving away.