[beloch]

To those looking for more concrete info on how this razor is supposed to work, here's the patent for it:

http://www.google.com/patents/US9017322

As far as I can tell, the idea is to use evanescent coupling to transfer light into hair follicles. There's no free space laser beam, just an optical fiber that you drag across your face. They also claim that chromophores (color bearing molecules) in hair can be severed at relatively low powers with a mixture of several specific frequencies of light.

So, what this product needs in order to work is a fiber that's durable enough to survive being dragged across skin while having very little cladding so as to allow evanescent coupling. That could be very hard to do, so the heads on these laser razors may wear out after a few shaves just like a metal razor. Second, they need to pack a high power multi-wavelength laser source and the power reserve to run it into a very tiny handle. Again, this is probably going to be pretty tricky.

There's nothing here that looks outright impossible to me. Just very, very tricky.

[OopsCriticality]

Nice find on the patent.

> So, what this product needs in order to work is a fiber that's durable enough to survive being dragged across skin while having very little cladding so as to allow evanescent coupling.

Facial hairs are alleged to be of similar toughness to copper wire when dry (see [0], too lazy to find a better reference). I have a difficult time conceiving how one could drag a multimode fiber across one's face without abrading the fiber to the point of failure.

> Second, they need to pack a high power multi-wavelength laser source and the power reserve to run it into a very tiny handle.

What is even trickier is incorporating a cooling mechanism for the theoretical self-contained, handheld, high-power, battery-powered white laser.

> There's nothing here that looks outright impossible to me. Just very, very tricky.

If it were not self-contained in a handheld unit, then yes, maybe it would be possible. I'm going to say that the their device, based on the proposed renderings, is impossible even if one were to throw Apple's war chest of money at it. There are also the problems of eye safety, skin exposure, heat, and fumes that remain to be overcome.

[0] http://www.economist.com/node/2281888

[Florin_Andrei]

> chromophores (color bearing molecules) in hair can be severed at relatively low powers

What if you're blond?

[TazeTSchnitzel]

Laser hair removal doesn't work well with light hair from what I recall, they usually require you to use electrolysis instead.

I imagine that we're not doing something radically different here, so the answer to this would probably be 'it won't work'.

[GhotiFish]

wait a sec, I have blond hairs in my beard. In fact, a lot of guys i know do.

[jpatokal]

Most blond people don't have blond beards.

Source: blond hair, reddish-brown facial hair.

[darryl42]

Or grey

[homulilly]

Even if all this is workable I still don't see what's preventing the hair from being heated to the point it damages the surrounding tissue.

[monochromatic]

I'm also not sure what keeps the light from coupling into your skin, instead of just the hairs.

[OniBait]

From what I recall on their original Kickstarter info, the frequency of the laser light only reacts with something that is in hair and not skin. The "breakthrough" was finding something that worked for blond hairs.