  Inter-Symbol Interference (ISI) is the main challenge of bio-inspired
diffusion-based molecular communication. In real biological systems, the
degradation of the remaining molecules from a previous transmission is used to
mitigate ISI. While most prior works have proposed the use of enzymes to
catalyze the molecule degradation, enzymes also degrade the molecules carrying
the information, which drastically decreases the signal strength. In this
paper, we propose the use of photolysis reactions, which use the light to
instantly transform the emitted molecules so they are no longer recognized
after their detection. The light is emitted at an optimal time, allowing the
receiver to detect as many molecules as possible, which increases both the
signal strength and ISI mitigation. A lower bound expression on the expected
number of the observed molecules at the receiver is derived. The bit error
probability expression is also formulated. Both the expected number of observed
molecules and the bit error expressions are validated with simulation results,
which show a visible enhancement when using photolysis reactions. The
performance of the proposed method is evaluated using the
Interference-to-Total-Received molecules metric (ITR) and the derived bit error
probability.
