Hades vs electrical tape

[Aseras]

a grin lense is just a flat piece of glass with a density gradient in it. kinda like a fresnel lense with denser materials rather than rings cut directly in the material like a fresnel lens. they only work well if you can get them right against an emission point, like the diode or the edge of a fiber optic couple.

try getting closer to the diode. a standard magnifying glass right against the aperture should reduce the dot significantly at about a foot or so away from the lense. I use a digital camera with a tv connected to see mine.

 

[BlueFusion]

you guys know that regular silica glass blocks a lot of IR (more as you get further into the IR; a close one like 780 will still pass most). For far IR, US $3k per lens is not uncommon. However, white quartz is transparent to mid range IR. If any of you have the resources to grind your own lenses try it with a piece of quartz.

 

[Aseras]

AFAIK cheap fused quartz and almost silica is NIR ( < 980 nm ) happy. The expensive stuff with less impurities allows deep uv transmission but starts blocking IR, but not really much below ~2000nm.