Laser epilation.

AFAIK the wavelength range is way broader than this. Ruby 694nm lasers are (were) very popular and effective. Also 1064nm YAGs are being used in epilation.

Look here:

LesioQ

and

If this could be done with relative safety, myself and my wife, and no doubt countless others would be interested in this project. I investigated electrolysis in the past, as I get infected facial hairs (for a long time just had a full beard). The woman who did (this was a free sample trial of her service) it removed quite a bit from below the corner of my mouth, but alas, it ALL returned . Did I mention the full beard? I grew it back after the trial.

Maybe this is one that Sam oughta get involved with, and put it on his Laser FAQ? My wife, like most women, struggle with unwanted hairs here and there, and again, if this was fairly safe and relatively inexpensive ($100-$150?), would be great "useful" project.

I'll keep looking here for more interest.

Hello Martin,

Like I said I'm not up with laser diodes but just a couple of thoughts: The first is they must have a transient thermal impedance which allows short term high applied power. Second, how is their output related to overdrive. Do they stop lasing or just become monumentally inefficient? How is life against overdrive.

In terms of beam size, I'm not sure how fluence is related to dispersion by the time it's penetrated say 5mm to the hair root. Pulse width required seems to be related to the thermal time constant of the follicle (cooling time). The pulse gets it hot quickly then the energy has to 'bleed' into the root cells. Too long a pulse and substantial tissue damage occurs.

I look forward to more replies.

Pauline Aston.

I don't think you can "buy" much power like that. Apparently (and this is somewhat borne out by my limited experience of killing LDs), laser diodes are far more sensitive to overcurrent than normal LEDs, though I don't know by what mechanism. I see what you're trying to do, but I still think you're onto a loser with (say) a 2W nominal laser diode where the 2W is the heatsinked CW rating. If you could make that trade-off to any significant extent, people would be doing it all the time to turn their 2W CW pump diodes into 20W pulsed diodes, and I haven't heard much here about people doing that. But I may be wrong.

I still think a laser designed to be pulsed (e.g. flashlamp-pumped) is likely to be more successful. You can (or used to be able to) get flashlamp-pumped YAG units from Meredith Instruments. These would emit at about 1064nm, but someone else did say that YAG is being used for epilation. The spot would be invisible, but the effect on the skin and hair would not, I suspect!

5mm?! I'd have thought more like 2 or 3mm. When I feel my chin, I'm sure there's not even 5mm between the outside of the skin and the bone. On the legs there may be more. But I suppose the point about the attenuation by the intervening skin (however thick) remains valid.

I'm not sure this is true. It may be. But on the other hand, you can ablate material with pico- or nanosecond pulses. I'm not sure how "thermal time constant" fits in in that scenario. But I would say that the gap _between_ pulses needs to be sufficient to allow the skin to cool.

Perhaps someone brave with a pump diode feels like trying it out on the back of their hand! (I wouldn't!) And perhaps someone with an SSY1 or equivalent would try it too! (AFTER doing some calculations to ensure that something more dangerous would not occur!) I seem to remember that those SSY1s emit pulses in the NANOsecond range, not milliseconds. So the power is MUCH higher for a given flash energy. Not sure what difference that would make. Probably more ablation and I guess the damage might be confined more to the surface of the skin, rather than penetrating deeper. I've no doubt it'd vapourise the hair above the surface of the skin, but don't know what would happen to that below it.

Martin

--
M.A.Poyser                                                  Tel.: 07967 110890
Manchester, U.K.                                http://www.fleetie.demon.co.uk

... Over the years I've spent several thousand pounds on laser hair

Not to change the subject out from under you, but what about that goop they advertise on late-night TV that seems to work like Zip-Strip? You slather a handful on where you want hair gone, and according to the ad, you wipe it off after some undisclosed amount of time, and all the hair just wipes off as if it wasn't even connected. Maybe it's camera tricks (like maybe that hair all over that arm was just lying there loose?)

Good Luck! Rich

With a healthy male androgen supply, if you dissolve the top off hairs, they're back sometimes the same day like stubble. Works with real girls for fluff removal but anything else - forget it! You should see the rash from sensitive skin areas too.

Back to lasers.......

Regards,

Pauline Aston

Out of curiosity, is this type of device effective for those with black or brown skin, or is the light pulse absorbed more by darker (more pigmented) skin? Not that it's really an issue to me, but my skin is normally a lighter brown, from a heritage consisting partly of native american indian.

I hope someone comes up with some kind of solution to this. I keep thinking of possibilities...like permanent hair removal around...ummmm...shall we say, a woman's "bikini" area? Is this process safe for use in these, errrr, "sensitive" regions?

Ummm, yes...let's get back to lasers...

Seems, though, that if this were going to be fairly inexpensive and safe, there would probably be some coompany already producing a home version, like those worthless du-it-yerself home hair removal contraptions.

Well, yes, but...

... even if it were possible to produce a laser-based product cheapish, that were powerful enough to epilate to any useful extent, the function would necessitate that the form of the device be such that the beam would emerge from the end from an aperture, which would normally be held against the skin to be treated.

What if someone held the thing up to their eye, or someone else's, and pressed the button?

Blindness, that's what.

I think that's got to be a large part (if not all) of the reason such products are (I assume) not available. Litigation. Even if the product could get legal clearance to be sold in the first place, which also seems unlikely.

You can get laser-based skin-puncturing products for diabetics to make small holes in their fingers for obtaining blood samples (I think), but with those products, the shape of the device can be such that only a finger can be inserted, and the beam does not make it into "free space" because if no finger were present, it would hit an "end stop".

Martin

--
M.A.Poyser                                                  Tel.: 07967 110890
Manchester, U.K.                                http://www.fleetie.demon.co.uk

Sadly, the darker the skin, the more melanin, so the more energy is dissipated in the skin putting a limit on who can be treated. There is some consideration related to wavelength, which is why I limited my bandwidth below the possible resonance range earlier, but even a small amount of sun tan is significant. There are several papers about on wavelength, fluence and time variation to treat different skins.

The more intimate areas are ok because they never see the sun (well usually).

Pauline Aston.

Yes, it's called "Catastrophic Optical Damage" or COD. The field strength at the mirror is sufficient to cause it to self destruct and it is vitually intantaneous.

Depends on the specific diode as well. Some have a COD threshold just above their maximum ratings. Others will tolerate more.

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