Production scale deposition of multilayer film structures for birefringent optical components

Many modern optical systems require polarization control of light in addition to spectral control. Light modulation applications include displays, optical data storage, digital imaging, metrology, instrumentation, optical communications and others. Within the information display sector, liquid crystal displays with polarization control components are prevalent. These components are often close to an image plane and thus have stringent defect requirements. Use of these components to control contrast and modulation drives the requirement of uniformity and part-to-part consistency. In a birefringent material the interaction of light with matter depends on the polarization state and orientation of the material. Bulk materials like quartz possess crystalline structures and hence exhibit molecular birefringence. Liquid crystal materials, stretched foils, and obliquely deposited columnar films are examples of engineered materials that have a microstructure or molecular orientation that creates birefringence. But even a stack of thin isotropic layers has birefringent properties when illuminated at non-normal incidence angle. We discuss two deposition technologies which JDSU has scaled into volume production. The first is based on liquid crystal polymers and the second on vacuum multilayer thin-film deposition. Production scale deposition requires high throughput, high uniformity, batch-to-batch reproducibility, and low defect capability. Both processes are standardized on 200 mm wafers, which allows for modular manufacturing within the same work cell and clean room. The two technologies are used together to create specifically tailored birefringent optics. Independent control of in-plane and out-of-plane retardance is enabled. Excellent layer thickness control, knowledge of the optical properties, and suitable metrology enable JDSU to adjust processes to address various customer needs in a rapid manner.