If you focus a laser with a convex lens, what is the power of the light at the focal point?

Student, you think too simple, do you know what kind of beam comes out of the laser? What is the phenomenon of a laser beam in a small area? To know, the laser out of the beam, called the Gaussian beam, due to the coherence of the laser itself, he himself will affect their own propagation in space, the formation of a Gaussian propagation beam, and this Gaussian beam, only in a characteristic position, the spot radius is relatively small, and you use a convex lens focusing, in fact, is the Fourier transform of this Gaussian beam, out of the same Gaussian beam, the beam can only ensure that the convergence at a certain distance, after the end of their own coherence and scattered, similarly, you converge multiple lasers with a point, although the coherence is not as good as a single laser, however, they will also form a non-coherent interference between them, affecting the convergence of the light, so it is really 10 100mw laser, converge to a point, definitely not just 1w, and to consider the coherence of the interference, the more you focus with a convex lens, the more you focus with a convex lens. The smaller the point you converge, the stronger the interference, the greater the energy dissipation, so I think it is simply impossible to fully converge with a point, can only be realized in a small range of light intensity to how much, of course, if you do not keep in mind the loss, the total power must be 1w, but definitely not in a point of 1w but, for example, distributed in the 1mm ^ 2 or even greater! Now coherent fiber optic focusing technology is a difficult point, and then again, the lens is a phase difference, OK, after the lens to consider the phase difference, there is no focal point, the lens edge of the light and the center of the light itself does not converge with a point, you also choose to focus on the lens, this is indeed lack of consideration, it would be better to try to focus with the left-handed material, using his perfect lens effect! (Note that as long as you don't keep track of losses, there is always so much energy, energy conservation, no need to discuss it, and what I'm trying to tell you is that with a lens, it is impossible to get the laser to converge to a point at all!) I suggest you go read two books, one is Principles of Lasers, and see what it says about what a laser beam really looks like, and how it really changes after passing through a lens! Another book is "physical optics and applied optics", this book describes in detail what is going on in the lens, lens aberration, chromatic aberration!