Some quantum/nonlinear optics calculators and a QKD Monte Carlo simulation. For technical details, see:
http://books.google.com/books?hl=en&lr=&id=RogcPECSNewC
fwmbw.c - a calculator for the four-wave-mixing bandwidth of an AlGaAs waveguide, including a calculation of the Sellemeier coefficients for AlGaAs.
fractional_clock.c - a Monte Carlo simulation of BB84 QKD that incorporates detector dead times. Called fractional_clock because, unlike an earlier version, this one operates in real-time; the simulation clock tick can be a fraction of the Monte Carlo QKD clock cycle. See this paper for results: