IPL head teardown (How does it produce light?)

[discomike]

So I found this IPL machine in the electronics recycling bin and I decided to take a few useful/interesting parts. It's supposed to produce broad spectrum pulsed light and I thought I would contain a normal xenon flash bulb to do so. It turns out that it doesn't and a quick google did not turn up an answer to how it works - so i'm asking for your help in explaining it.


Overview of parts.


Head with coolant hoses coming in.


Head removed, wires coming in are 2 thick ones going to the light source, and narrow ones to peltier cooler.


Bottom part removed (peltier cooler connects to the "nozzle" part (touching the skin) and prism to cool it.


Prism is broken, not sure if this was the reason it was discarded or it happened afterwards. I used to have a collegue who designed these machines and he mentioned they had lots of problems with the reliability of the prisms and the suppliers not meeting their specifications.


View down the light source, only two wires coming in and a resistor connected across the terminals (see first pic).


Reflective foil on the outside of the prism to keep light in


Pretty =)


The light thingy has glass rods glued to the front (are they lenses or is light produced in them?).


They are placed over the gaps between the metal bars (is that where the light is coming from?).


Metal bars are held on with conductive foam/glue.


Beneath it is some other metal and maybe ceramic substrate/isolator. Cables are connected to either side as seen, is there some high voltage that causes arcing to produce light? This is in open air? Cables are 12 AWG which suggests decent current (and low voltage? they are not marked with any voltage but have fairly thick silicone insulation).


What a coincidence.


And that's all.

Any input or comments is very welcome.

[ruffy91]

Looks like a solid-state laser.
The rods are doped laser rods.

[mikeselectricstuff]

Looks like high  power laser diodes, or possibly just LEDs - bare die sandwiched between the metal blocks.
I think the clear rods may simply be for focussing, though they could be doped for wavelength conversion.
Peltier element will be for temp stabilisation to get the right wavelength.

[discomike]

Ah thanks for the info, so this is probably a dermatological laser instead of an IPL. The machine was missing the front panel and control boards so I was just assuming it was supposed to produce a broad spectrum (uncoherent) light.

I found a patent description on google with this picture (patent for a selft-contained unit):
https://www.google.com/patents/US7118563



And this excerpt from the description:

A typical diode laser bar 500 including multiple diode emitters 510, such as that illustrated at FIG. 9 (and such as may be manufactured bySpectra-Physics, Inc., of Mountain View, Calif., or Coherent, Inc., of Santa Clara, Calif.), has a continuous optical power output of 20–40 watts, and a maximum peak power output approaching 100 watts. For this reason, a hair-regrowth-inhibition device with an output optical peak power of over 25 W can be designed with only one or two bars 500, rather than 25 or more discrete laser diodes. Each laser diode bar 500 has many individual emitters 510 preferably fabricated on a monolithic structure, and requires roughly 40 amperes of current at a voltage of slightly under 2.0 volts to produce 30 watts of optical peak power output for more than 50 milliseconds.
...
The laser light propagates through a square tube having a cross-section of 9 mm by 9 mm, through an opal-glass diffuser and sapphire window pair 626. The sapphire window, which is in contact with the skin during treatment, is held near room temperature by small thermoelectric modules mounted on either side of the diode bars.

Thanks again, and I'll have a look under the microscope if I can see anything on the bars =)