Coarsely cut salmon into cubes and place in the bowl of a food processor. Add dill, chives, thyme, salt, pepper, lemon zest, lemon juice and 2 teaspoons of oil. Pulse briefly 2 or 3 times to roughly chop fish and combine ingredients. The salmon will hold together like ground meat yet still have some shape. Do not overprocess.
Shape salmon mixture into 6 patties about 3/4 inch thick. Place patties on a small baking sheet covered with plastic wrap. Refrigerate, covered, for 2 hours.
To cook, place panko crumbs in a shallow bowl. Gently turn patties in crumbs to coat all over.
Heat remaining 2 tablespoons oil in a large nonstick skillet over medium-high heat. Sauté patties 3 minutes; turn, sauté 3 minutes longer or until golden and crisp.
Serve burgers on warmed buns. Top with a generous dollop of Cucumber Sauce. Pass extra sauce. Makes 6 servings.
Peel and coarsely grate cucumber. Press excess liquid from cucumber between several sheets of paper towels. Combine the cucumber, yogurt, mayonnaise, scallion, dill and salt in a small bowl. Refrigerate, covered, for 2 hours.