Virtual image phase array

A virtual image phase array (VIPA) includes two parallel surfaces, a first highly-reflective surface with a highly-reflective coating, and a second partially-reflective surface. The first highly-reflective surface also requires an input zone with an anti-reflection coating, which abuts the highly-reflective coating, with a transition zone therebetween. Light enters the VIPA through the input zone, and reflects back and forth between the highly and partially reflective surfaces, gradually leaking out through the partially reflective surface. To minimize the transition zone and thereby minimize the input angle of incidence and maximize the number of reflections per unit of length, the substrate coated with the highly-reflective coating is subsequently polished at an acute angle resulting in the transition zone having the same sharp angle.