Hello @julliet,
Basically when you decided not to go with Sigmoid or Softmax you lose ability to convert logits to probability like values. If you need probabilities try to use any continuous function maps (-inf, +inf) to [0,1] and pass this f(logits) to the call of criterion.
Examples of such mappings: f(logits) = 0.5 * (1 + tanh(logits/2)) or Sigmoid