What makes photons from a laser cavity so directional?

[intervoxel]

How can a mirror reflect 99,999% of incident light? Or in other words what makes a photon exiting a laser cavity so directional?
In fact, I never found a really convincing answer. Thank you.

 

[trurle]

Laser mirrors are usually dielectric multilayer mirrors and commonly reflect up to 99.99% in target line. Also, even conventional metal mirrors have higher reflection coefficients in middle infrared range. For example, gold mirrors are 99.0% reflective at 10um wavelength.

 

[ZapperZ]

How can a mirror reflect 99,999% of incident light? Or in other words what makes a photon exiting a laser cavity so directional?
In fact, I never found a really convincing answer. Thank you.

Your question is vague. No mirror can reflect ALL wavelengths at 99.999% efficiency. The regular mirror that you and I are used to may appear to be a good reflector of visible light, but put that in a UV-VIS spectrometer, and you'd be surprised at reflectivity spectrum, even in the visible range. And forget about UV, because such a mirror is hopeless.

Mirrors in laser cavity has been specifically selected so that it has the highest reflectivity in a very narrow range of wavelengths. So it has been finely tuned to work under a very narrow parameter.

Zz.

 

[intervoxel]

Your question is vague. No mirror can reflect ALL wavelengths at 99.999% efficiency. The regular mirror that you and I are used to may appear to be a good reflector of visible light, but put that in a UV-VIS spectrometer, and you'd be surprised at reflectivity spectrum, even in the visible range. And forget about UV, because such a mirror is hopeless.

Mirrors in laser cavity has been specifically selected so that it has the highest reflectivity in a very narrow range of wavelengths. So it has been finely tuned to work under a very narrow parameter.

Zz.

Nice answer, ZapperZ. Let's suppose now one single photon with the correct wave length to get maximum reflection. What happens to the properties of the photon to have higher probability of detection in a very closed angle cone in the direction of reflection?

 

[ZapperZ]

Nice answer, ZapperZ. Let's suppose now one single photon with the correct wave length to get maximum reflection. What happens to the properties of the photon to have higher probability of detection in a very closed angle cone in the direction of reflection?

Why should I do this work for you especially when this is still quite vague?

Zz.

 

[PeterDonis]

The OP has received a warning for insulting another member. Thread closed.