Something about your wiring or maybe your laser did not come with a constant-current circuit like mine did.. in bags of 10 for less than $5 as 4.5V (works fine on 5V) 20mA --> 5mW laser modules.
Take extreme care where the beam goes, the reflections can blind eyes too. A buddy of mine caught his beam off a curved mirror and for about two full hours he wasn't sure that that one eye wouldn't see red permanently.
I wire pin to button to ground then set the pin mode to INPUT_PULLUP that supplies the pin with 5V through at least 20K resistance which is a lot. When the button is up, the weak 5V raises the pin HIGH. When the button is down the connection to ground drains the 5V as fast as it is supplied. The current Amps = Volts / Ohms = 5 / 20000 = 0.00025A = 0.25mA at most (resistance may be 20K to 50K Ohms) which is pin-safe low power.
Note that pin HIGH is switch OPEN/OFF/UP and pin LOW is switch CLOSED/ON/DOWN.
HIGH is button UP, LOW is button DOWN, can you work with that? Then there's just the matter of bounce....
The subjects linked to below will answer a lot you have and haven't yet asked.
Knowing basic DC electricity really helps. Get down to charges in wire level as what happens with Arduino goes there.