Optical coherence tomography (OCT) systems have huge potential for applications beyond the traditional ophthalmology as a general-purpose medical instrument for optical biopsy. The widening of the range of applications is expected to significantly increase production volume and, consequently, puts pressure on unit cost. This trend calls for a flexible and miniaturized system fabricated in a batch process. In this paper, the different OCT configurations are compared for suitability in such an implementation. The required flexibility favors operation in the spectral domain, using a broadband light source in combination with a spectrometer, while the miniaturization and low unit-cost in batch fabrication can be achieved using silicon micro-system technologies. The feasibility of miniaturizing OCT components has already been demonstrated, amongst others a beam splitter using 45° saw dicing of a glass substrate and appropriate thin-film coating the integration of the essential components into a single OCT microsystem remains a challenge. In this paper, the wafer-level fabrication of a Michelson interferometer for a miniaturized OCT system is presented, using an improved 45° saw dicing process, which is suitable for wafer-level co-integration of also the other components of the OCT microsystem.

This paper reports on the development of a technology for the wafer-level fabrication of an optical Michelson interferometer, which is an essential component in a micro opto-electromechanical system (MOEMS) for a miniaturized optical coherence tomography (OCT) system. The MOEMS consists on a titanium dioxide/silicon dioxide dielectric beam splitter and chromium/gold micro-mirrors. These optical components are deposited on 45° tilted surfaces to allow the horizontal/vertical separation of the incident beam in the final micro-integrated system. The fabrication process consists of 45° saw dicing of a glass substrate and the subsequent deposition of dielectric multilayers and metal layers. The 45° saw dicing is fully characterized in this paper, which also includes an analysis of the roughness. The optimum process results in surfaces with a roughness of 19.76 nm (rms). The actual saw dicing process for a high-quality final surface results as a compromise between the dicing blade's grit size (#1200) and the cutting speed (0.3 mm s−1). The proposed wafer-level fabrication allows rapid and low-cost processing, high compactness and the possibility of wafer-level alignment/assembly with other optical micro components for OCT integrated imaging.

The wafer-level fabrication of a Michelson interferometer using optical MEMS technologies is presented. The intended application is in Optical Coherence Tomography (OCT). The micro fabrication involves two steps: the 45° saw dicing of glass substrate and the subsequent deposition of a dielectric multilayer and metallic layers to obtain a beam splitter and waveguide micro mirrors, respectively. The Michelson interferometer was designed for use in the near-infrared range of 800–900 nm. A 50/50 non-polarized beam splitter was obtained with only four layers (using titanium dioxide and silicon dioxide). The micro mirrors for the required spectral range were fabricated by sputtering of chromium and gold layers. The dicing cuts, which were performed with a custom-made 45° dicing blade, resulted in smooth slopes. The surface’s roughness is 19.76 nm at setting and can be reduced to approximately 50% with a soft additional dicing cut. The height of the 45° surfaces was approximately 400 μm, which is in accordance with the design. The micro Michelson interferometer can be easily integrated with other optical components into a complete OCT miniaturized system.