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Ken,

Attached are some spectra from a cheap 405nm laser pointer and a 532 green. The 405nm ?lasers are direct lasers using a Gallium Nitride media and aren’t frequency doubled. The 532 nm laser pointers uses a 808 nm IR pump into a Nd:YAG crystal to get 1064nm IR output which then goes into a KTP crystal that produces the 532nm green output.

Some people can get confused when looking at raw spectra and don’t take into account second order grading effects and report other IR peaks. Note in the 405nm 2d order picture the peak at 817.51 nm which is a 2d order ?effect where the grating allows leakage from the primary signal at a twice the wavelength (408.75 *2 = 817.50nm). I am not running a 2d order blocking filter on these spectra so you see bleed through but at a much reduced intensity. The 532 spectra show the 808nm pump but not the 1064nm due to the limited range of the spectrometer. Both 1064 and 808nm IR are making it through at a reduced power but some pointers don’t have IR blocking filters on the output and have hazardous levels of IR that you can’t see.

Dud

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Thanks Geo.? Yes, Dud offered to run an analysis, so I’ll be dropping a sample in the mail to him so he can run an analysis.? He also mentioned checking the sample with a 405 nm laser pointer.? I did that last year when I first collected the samples, and did indeed see a similar response of both fluorescence and phosphorescence.? I’d be interested to see a spectrogram of a typical 405 nm laser diode to see where its UV peaks come in.? I know many laser diodes actually produce their primary output in the infrared region, and they use a frequency-doubling ‘filter’ to “boost” the response into the visible range.? Therefore, I can understand that a 405 nm laser diode is probably producing its primary emission at 810 nm, which would be in the infrared region and ?‘invisible’ to the naked eye.? I don’t know if there is frequency tripling going on to produce a 270 nm peak, or if perhaps the “blue” 405 nm laser diode is producing another longer wavelength peak that is being frequency-shifted into the UV region.

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Nope, never did venture into the “flame speaker” realm.? Sounds very interesting.? What was the ‘fuel’ for the flame? Was it something like methane or propane, spiked with an aerosol of metal salts?? Or was the flame actually a plasma of ionized air or some other inert gas?? Yeah, the old days of ham radio with big iron, kilovolts, and vacuum tubes like the 807.? The noobs don’t know what they were/are missing.

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Thanks for the comments, Geo.? Another member of the group, Charles Young, also offered to run an XRF analysis.? Perhaps when all is said and done, both will share their results with the group.

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73 Geo.

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Ken, WB0OCV

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