Is a GASER a theoretical possibility? This question (basically an analogy ) is inspired by several questions and answers that appeared on stackexchange. 
We first define GASER, for the purpose of this question. 
GASER - gravitational (wave) amplification by stimulated emission of (gravitational ) radiation. 
Many relevant questions and answers (relevant in relation to my question) can be found on stackexchange. 
Are gravitational waves transverse or longitudinal waves, or do they have unique/unknown properties?
Since there are gravitational lenses, are there gravitational mirrors?
Why do lasers require mirror at the ends?
What is Chirped Pulse Amplification, and why is it important enough to warrant a Nobel Prize?
Chirped pulse amplification, combined with fibre lasers and spectral beam combining can lead to some very powerful lasers. 
Black holes  (even microscopic ) cannot yet be created and manipulated at will. Assuming this will be possible in the future (that's a big IF , but this is a theoretical question ),  are there any suitable distributions of black holes ( and regular matter ) in space - time that would make a GASER possible?  
 A: Probably not, for the following reasons:
Roughly speaking, lasing occurs when a photon passes close by an atom that has had one of its electrons lifted into a metastable energy state, where the decay of that electron would generate a photon of exactly the same wavelength as that of the passing photon. The decay is triggered by the photon's close passage and the new photon matches the phase, wavelength, and direction of the other. Then you put reflectors (one of which is partially-mirrored) at opposite ends of the chamber containing a large number of such excited atoms so after bouncing around within the chamber, many of the resulting photons will be following parallel paths along the axis connecting the mirrors; when the resulting coherent beam becomes strong enough, it will emerge from the partially-silvered mirror as a laser beam. 
No one knows how to generate a convenient population of gravitons at will, or how to point them into and then confine them within a potential well so as to quantize their allowed energy states, or how to excite a large number of them into an energy population inversion and retain them there, or how to de-excite them with more gravitons, or how to make a half-silvered mirror for gravitons. 
