Light has a fun property of being bent when it passes through substances that have different optical densities. With some combinations of material and process we can exploit this property to achieve total internal reflection[0]. With a cylindrical glass rod we can fire light down it in such a way that it bounces off the walls and makes it to the far end without ever exiting through the sides. This is used in fiber optic communications to achieve low levels of loss transmitting light very large distances.
However, the total internal reflection can partly break down if we apply something to the side of the glass tube, like touching it with a finger. The laser will strike through the glass cylinder and onto whatever is touching it, this is known as frustrated total internal reflection. What's supposedly happening in this product is the razor blade has a fiber with a laser being shone through it, when the fiber comes into the contact with a hair the laser exits the fiber and the thermal energy burns the hair.
The problems here are pretty severe.
• If such a fiber did exist it would give you severe burns on contact with your skin (a very close shave indeed). It would be like trying to shave with a red hot block of steel held up to your face.
• Ever burnt some hair? It smells ghastly. I burned my beard once and the nauseating smell didn't go away for hours. Trying to convince consumers to go on a date while smelling like burning keratin would near impossible.
• The amount of laser power going through the fiber would have the potential to remove your eyesight if you broke it. If you wanted to use this you would need to be wearing eye protection (sealed goggles), skin protection like welding gear, have signage and locks on your bathroom to prevent anybody unprotected from entering.
• The amount of energy required for this sort of effect would be colossal, lasers are inefficient and need a lot of cooling (high power ones are often water cooled). If this existed just the hand piece would be something like a petrol pump nozzle leading to a massive cooling system and power supply.
• Any slight impurity in the fiber would cause it to instantly melt when the laser was turned on. Unless something is perfectly optically clear there is some loss to heat as light passes through it. Glass fibers made for telecommunications are incredibly clear, but they still have enough loss that repeaters are needed on long runs due to losses.
While I'm not making any statement about the feasibility of the Skarp, I think you might be exaggerating the size of a moderately powerful modern lasers. At my company's R&D lab I have some 1W CO2 lasers that, similar to what what you describe, are about the size of loaf of bread. They run on three phase power, have inch-thick cables and required hilariously large cooling shrouds. Two facts about those types of lasers: They are cavity lasers designed to have very good beam quality, and they are OLD.
I have a cabinet full of other types of newer, moderately powerful laser modules which vary from pin diodes to modules the size of a AA battery, to things the size of cigars. Some of them are pretty darned powerful. Any laser modules that are water cooled would DEFINITELY not be something you would want to hold up to your face, but I also don't think that's the kind of power required for cutting hair. I'm not saying that any laser running on a AAA battery at a useful power could last a useful amount of time, if you could figure out some secret sauce method for very quickly coupling a high intensity pulse (hairs have a very small area, after all) onto some hairs at a wavelength that they like to soak up then it seems.... possible. In theory the laser wavelength and power could even be tuned dynamically to match the hairs, that is if they had somehow figured out a way to fit a Mach-Zender modulator, an electro-optical modulator and a frequency comb into a razor handle--ha!
Anyhow, I might be wrong in all this, but my point is mostly that it wouldn't take a water cooled laser to burn some hair. Come visit me in Vancouver and we can test it out (on your beard).
Perhaps a little exaggeration, agreed. The wavelengths you want are in the UV end of things, which I assumed would be mostly clumsy CO2 tubes. Just the concept of giving a consumer a high power laser they can't even see makes me extremely uncomfortable regardless of how plausible the rest of it is. Mistakes with that sort of thing are permanent, you don't get any second chances if you blast out your retina.
However, the total internal reflection can partly break down if we apply something to the side of the glass tube, like touching it with a finger. The laser will strike through the glass cylinder and onto whatever is touching it, this is known as frustrated total internal reflection. What's supposedly happening in this product is the razor blade has a fiber with a laser being shone through it, when the fiber comes into the contact with a hair the laser exits the fiber and the thermal energy burns the hair.
The problems here are pretty severe.
• If such a fiber did exist it would give you severe burns on contact with your skin (a very close shave indeed). It would be like trying to shave with a red hot block of steel held up to your face.
• Ever burnt some hair? It smells ghastly. I burned my beard once and the nauseating smell didn't go away for hours. Trying to convince consumers to go on a date while smelling like burning keratin would near impossible.
• The amount of laser power going through the fiber would have the potential to remove your eyesight if you broke it. If you wanted to use this you would need to be wearing eye protection (sealed goggles), skin protection like welding gear, have signage and locks on your bathroom to prevent anybody unprotected from entering.
• The amount of energy required for this sort of effect would be colossal, lasers are inefficient and need a lot of cooling (high power ones are often water cooled). If this existed just the hand piece would be something like a petrol pump nozzle leading to a massive cooling system and power supply.
• Any slight impurity in the fiber would cause it to instantly melt when the laser was turned on. Unless something is perfectly optically clear there is some loss to heat as light passes through it. Glass fibers made for telecommunications are incredibly clear, but they still have enough loss that repeaters are needed on long runs due to losses.
[0]: https://en.wikipedia.org/wiki/Total_internal_reflection