Grate the zest of 1 orange and the lime into a large bowl. Squeeze 1 tablespoon of juice from the grated orange and 2 tablespoons of juice from the grated lime into the bowl (you may need a second lime to get the 2 tablespoons of juice). Whisk in the soy sauce and the oil. Set the dressing aside.
Use a sharp knife to slice the rind and pith from the remaining oranges. Working over a mixing bowl, cut the segments away from the membrane that holds the orange together. Place into a bowl. Add the mesclun and cucumbers to the orange segments.
Using a large sharp knife, cut the salmon into ½ cm thick slices. Add the salmon to the bowl. Drizzle with the dressing, and toss gently to coat. Allow the flavors to meld for at least 2 minutes.
Divide the salad among 4 serving plates or one large platter. Sprinkle with the toasted sesame seeds, and serve.