Hybrid assembly and bonding of miniature optical components on micromachined substrates

摘要

Compact systems such as multielement lasers and optical instruments require the precise location of miniature components such as lenses, mirrors, beamsplitters and nonlinear crystals. Anisotropic and reactive ion etching allow precision wells tobe produced that will accept optical components without the need for individual component alignment. To demonstrate this approach a miniature optical system has been designed that can include mirrors, graded index (GRIN) lenses, cube beamsplitters and apotassium niobate crystal for second harmonic generation. This has been used to investigate the translational and rotational precision with which elements may be located and attached to an anisotropically etched silicon substrate. This study investigatesthe use and effectiveness of; anodic bonding of poled ferroelectric crystals and optical glasses such as BK7; assembly strategies using video servoing and miniature component manipulators; and optomechanical design approaches which leverage thebenefits of photolithography. The anodic bonding of BK7 is performed at temperatures in the range of 200 to 500°C, whereas the bonding of potassium niobate must be performed around 200°Cin order to prevent the crystal from depoling. Two step anisotropicetch processes have been developed which allow silicon dioxide masking layers and low cost potassium hydroxide etching of deep features with smooth sidewalls.