Assuming that you didn’t come in from the subway, beyond this door is actually just a regular subway, not more of the lab (unless that changed or I misunderstood your statement).
You can open that steel door in multiple ways. The easiest one would probably be to use an acetylene torch on it to cut it open.
You can also blast it open with explosives.
You can smash it open with enough strength and some tools or a Sonic Resonator CBM.
You can dig through the wall on its side with a pickaxe or a drill.
And you might be able to send an NPC to loot the place, as this opens all doors (last I checked the code), but I’m not sure if that is fully implemented yet or how to do that.