[theThinker (OP)]

Hello,

Nd:YAG (neodymium-doped yttrium aluminum garnet; Nd:Y3Al5O12) is a crystal that is used as a lasing medium for solid-state lasers.

A "typical" laser has one end coated HR - highly reflective and the other end partial reflective. In the description of a company product for Nd:YAG laser rod, the ends are coated AR@1064nm/AR@1064nm. AR means anti-reflective. Can lasing occur in such a laser rod if we just shine some appropriate flashtube at it just like with a ruby laser rod.
 

[Zer0]

I'm clueless...
maybe @hamdani yusuf Knows!

[Bored chemist]

Hello,

Nd:YAG (neodymium-doped yttrium aluminum garnet; Nd:Y3Al5O12) is a crystal that is used as a lasing medium for solid-state lasers.

A "typical" laser has one end coated HR - highly reflective and the other end partial reflective. In the description of a company product for Nd:YAG laser rod, the ends are coated AR@1064nm/AR@1064nm. AR means anti-reflective. Can lasing occur in such a laser rod if we just shine some appropriate flashtube at it just like with a ruby laser rod.
 

I'm fairly sure you would need to add external mirrors- as you say
 

one end coated HR - highly reflective and the other end partial reflective

[evan_au]

The reflective coating probably depends on whether you are using it as a laser source, or as an optical amplifier.
- As a laser source, you want to pump it "eg with a Xenon flash", and any spontaneous emission needs to reflect backwards and forwards many times from (mostly) mirrored ends, to ensure that all of the atoms in a meta-stable high-energy state are triggered to drop to the low-energy state via Stimulated Emission. This produces a phase-coherent monochromatic beam with fairly low divergence.
- As an optical amplifier, you want to minimise amplification of any spontaneous emission from the lasing medium. That means anti-reflective coatings, to ensure that the Stimulated Emission is triggered primarily by the incoming signal which is to be amplified. The signal to be amplified makes only one pass through the lasing medium.

For pulse-based applications (like the US National Ignition Facility), the pump signal comes from Xenon flash lamps. All of the amplified laser light has to arrive at the Deuterium target within a few picoseconds. I have seen images of the Neodymium glass blocks which seemed to be about 2 meters long; if you relied on traditional passive partially-reflective end-coatings, the incoming narrow pulse would be broadened into a negative-exponential pulse with a half life of around 10,000 picoseconds. (In fact, NIF uses a very fast active optical switch, which quickly changes from reflective to transparent).
https://en.wikipedia.org/wiki/National_Ignition_Facility#Laser

For continuous applications (like telecommunications), the pump is a continuous Infra-Red laser fed into the doped optical fiber amplifier (early devices used Erbium, but other elements are now being used to amplify different optical bands). The incoming weak signal makes one pass through the optical amplifier, and comes out the far end with up to 5,000 times greater power.
https://en.wikipedia.org/wiki/Optical_amplifier#Basic_principle_of_EDFA

[theThinker (OP)]

Thanks,
 Rather complicated.