Experimental Feedback (an ongoing project)
These photos show experimental mirrors used to form the laser oscillator, with emphasis on some of the most basic and common materials conceivable. Warning - not for the lab-at-heart :-)

I'm amazed at the level of performance that could be obtained using some of these homemade mirrors. Copper is evidently an excellent reflector at 694 nanometers. Of course, this ruby laser obviously has extraordinarily high gain. But DIY copper mirrors do appear to hold potential for future laser experiments, where high gain hosts are involved at IR and NIR wavelengths. I can't wait to try one of these on a CO2 laser.

Although the craft mirrors did work, the internal beam quickly chewed a hole through the reflective coating. Good quality broadband mirrors are of little value with this laser. But it is very convenient that a scrap piece of copper, or even a polished penny, works as well as it does.
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