3 ms·
> What does "unbounded" mean in this context? The radial intensity distribution of a Bessel beam is described by Bessel functions, which are not square integra
by red_dinosaur 8y ago
> What does "unbounded" mean in this context?
The radial intensity distribution of a Bessel beam is described by Bessel functions, which are not square integrable (integral is not finite), see https://upload.wikimedia.org/wikipedia/commons/thumb/5/5d/Bessel_Functions_%281st_Kind%2C_n%3D0%2C1%2C2%29.svg/600px-Bessel_Functions_%281st_Kind%2C_n%3D0%2C1%2C2%29.svg.png https://upload.wikimedia.org/wikipedia/commons/thumb/5/5d/Be....
Realizing a true Bessel beam would thus require infinite power.
A true Bessel beam is created by interfering (in 2D) two plane waves, see https://upload.wikimedia.org/wikipedia/commons/thumb/b/b8/Bessel_beam.svg/1920px-Bessel_beam.svg.png https://upload.wikimedia.org/wikipedia/commons/thumb/b/b8/Be.... You can see in the image that the "Bessel beam" area is bounded, it is the conical shape where the beams overlap.
> What is an example of a "bounded" beam?
A "standard" Gaussian laser beam, see https://upload.wikimedia.org/wikipedia/commons/thumb/a/a9/Laser_gaussian_profile.svg/506px-Laser_gaussian_profile.svg.png https://upload.wikimedia.org/wikipedia/commons/thumb/a/a9/La...
- SideburnsOfDoom 8y ago> The radial intensity distribution So, unbounded width of the beam? As opposed to unbounded length, which is generally expected in light beams.
- SiempreViernes 8y agoWell, for truly unbounded length you need to keep the source on for infinite time of course. But light beams do get very long for very modest work, and properly focused they can propagate very long distances indeed.
- SideburnsOfDoom 8y agoSo, to be clear here - is the answer yes or no? Are we talking about beam width - i.e. unbounded in a direction at right angles to the direction of travel?