Fabrication and evaluation of erosion-resistant multispectral optical windows

Abstract

Thin ZnS claddings can be bonded to ZnSe substrates to form a composite window designed to display rain-erosion resistance equivalent to ZnS alone, but with broadband transmittance and scattering levels comparable to ZnSe. Joining of the window components is achieved by means of a thin As-S-Se glass layer, using a technique we have termed optical brazing. Optical path differences in the composite window are primarily due to heterogeneities in the ZnS and ZnSe components; no degradation in optical quality due to the glass bond is evident. Rain-erosion data confirm that the composite window is as resistant to multiple drop impact damage as monolithic ZnS.