Coulis is a French term referring to a thick purée or sauce.
Place first 3 ingredients in a blender; process until smooth. Pour into a bowl; stir in cilantro, jalapeño, 1/8 teaspoon salt, and 1/8 teaspoon pepper. Set coulis aside.
Drizzle 1 tablespoon lime juice over chicken. Sprinkle 1/8 teaspoon salt and 1/8 teaspoon pepper over chicken and potato slices. Prepare grill. Place chicken on grill rack coated with cooking spray, and grill 10 minutes. Turn chicken, and continue to cook. Place potato slices on grill rack, and grill 5 minutes. Turn potato slices. Place radicchio and green onions on grill rack, and grill 3 minutes, turning after 1 1/2 minutes. Remove chicken, potatoes, radicchio, and green onions from grill. Serve with papaya coulis.