Line a mesh strainer with a paper coffee filter or paper towel. Spoon yogurt into filter, and place strainer over a bowl. Cover with plastic wrap, and chill 4 hours.
Spoon yogurt into a bowl, discarding strained liquid.
Stir in diced cucumber and next 7 ingredients. Cover and chill yogurt mixture until ready to serve. Garnish, if desired. Serve with pita chips and fresh vegetables.
Note: The sauce may also be served as a spread for tomato or roast beef sandwiches.