I tried the following circuit but its not working for me.
Can you explain what was not working. Was it the circuit or was the circuit working but the results were not good enough.
Where is the arduino in all this?
The catch is I should not use 555 timer for modulation.
This makes it sound like a school assignment?
Why do you want to modulate the IR, that circuit you posted doesn't modulate. Do you want transmitted (beam breaking) or reflective like that in the circuit you posted.