However annoying (and i have a YAP YAP chiweenie..so I know)
His barking is saying "i want to play" and since he remembers "laser pointer" as fun (play)..thats what he is going back to. (and he's a smart fur critter because he "remembers" it being on the stairs..two years later
)
Dogs will tell you "i need more attention" if you listen to thier suttle cues, and bark like mad if you dont. (as you are well finding out)
I suggest a tug toy, or something interactive for you and him to do together (besides the bike ride, which by the way the bike ride is great..most people dont even bother with that).
When YOU absolutely need a break...give him a busy bone, or a chewy, I've found penut butter inside a kong toy is and instant "shut up" and "go play by yourself" toy around here. Keeps em busy for quite awhile.
You may have to put him in a "quiet zone" (kennel, other room ect)...for some "down time". at some point..if he just insists you "play" even though you've played yourself out.
But I think if you spend some more "interactive" time (besides just the bike ride)..he will likely stop obsessing over the stairs.
Baby gate it for now would probably be good too as winston suggested already. (they make em with a door now, so you just open and close it).
And I know this may sound counter productive but if you dont have as much time with him as He'd like...maybe hire a neighborhood kid to come play and romp with him in the back yard.
Kids will do anything for a little pocket money, and doggie benifits from it greatly.