> As a test, I once used an IR detector circuit (Sanyo I believe) in it's
> barest form - detector, 10uF cap, power, and scope probe.
>
> I illuminated the front of the detector with a laser pointer (CW output).
> Lots of light!


Lots of light around 630nM, which is outside the passband of the IR
filter.
Sunlight is broad-spectrum, and has a fair amount in the right band to
get through the filter. Still, it's an excellent demo that the filter
does what it's designed to do.