I had this problem with visual light sensors circuit. What I did was built a wheatstone bridge circuit with sensors on two opposite sides of the bridge and two resistors for the other two legs. Since it is a balanced bridge, the output is zero when light hit both sensors. When one sensor received light from my transmitter, the bridge became unbalanced and I detected it. This thing worked great! Completely insensitive to ambient light but detected the modulated light wave easily.