As noted in the comments, this summary of the experiment comes from several books by David Wilcock, an influential lecturer in the New Age circuit. Wilcock cites a PDF entitled "Crisis in Life Sciences. The Wave Genetics Response," but rather than talking about absorption, this file refers to Garyaev's claim that a quartz filled with DNA will creates a glow in a physical space that lasts for a month after the quartz has been taken away from the space, in other words, a ghost.
Garyaev has also published scientific papers claiming, more mundanely, to have observed DNA-created biophotons, in an actual leading science journal called Quantum Electronics. The American Institute of Physics translates every article in this journal into English, so you can read about his experiment in "Two-photon-excited luminescence of solid-state DNA", Quantum Electronics 24.6 (1994), and "Two-photon-excited luminescence of genetic structures", Quantum Electronics 26.2 (1996). Around this time, however, he broke away from the mainstream academy, claiming a conspiracy against him.
Scientifically speaking, luminescence is the opposite phenomenon of "absorbing every photon in the room". This nonsensical word soup appears to have been invented by Wilcock, as I cannot find it in the actual writings of Garyaev, although these are admittedly numerous and quite perplexing. I believe that this is not a description of what Garyaev claimed to witness in any experiment he did.
Garyaev is apparently a well-known Internet troll and hangs out on the forum molbiol.ru, which has a thread with more information on his all-encompassing theory (he claims, for example, that DNA ghosts hang around inside a woman's body after abortion, and that through the ghosts of sperm, children can bear the DNA of an ex-lover, a common fringe claim called telegony). He also has an English-language website at eng.wavegenetic.ru where he shows how he does his experiments, as well as some of the many fascinating claims he has made.