My apologies if I belittled your knowledge.
Most of the modern IR detectors have optical and carrier filters built in, all you have to do is give them power and the demodulated signal appears on the output pin. It is almost impossible to find IR receivers without on-board filters these days.
To control an LM555 astable, the method I used in the past was to drive data into the reset pin. Be careful with some variants of 555, while some can sink/source 200mA or more, there are some versions that are only rated to very low current and they will not drive an IR LED directly.
Brian.