If the detector puts-out a voltage, yes. The Arduino has a 10-bit analog-to-digital converter (it reads 0-1023) with a range of 0-5V, or optionally 0-1.1V, or you can supply your own voltage-reference.
You'd probably need a amplifier, but of course we don't know anything about your detector.
If your asking for help with your laser-detector, you may not find experts here... That's a chemistry/science question... Personally, I have no idea if this will work, and if it does work it would depend on the type of gas and the concentration.