Design Study of Integrated Optical Coherence Tomography Using MEMS Technology

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Department of Applied Physics & Optoelectronics, Shri G. S. Institute of Technology & Science, Indore 452 003 MP India \affiliationDepartment of Applied Physics & Optoelectronics, Shri G. S. Institute of Technology & Science, Indore 452 003 MP India \emailjtandrews@sgsits.ac.in \affiliationSchool of Physics, Laser Bhawan, Devi Ahilya University, Indore 452 017 MP India

AbstractIntegrate chip based optical coherence tomography is an combination of passive optical waveguides optoelectronics devices such as simple optical waveguide, 3dB bidirectional coupler, active optical delay line, source and detector etc. OCT has a multi-function modality and the integrated multi-modality imaging system can readily switch between different imaging modalities, which will make it a powerful diagnostic tool in a clinical environment. In this article we explored the possibility of implementation to miniaturized integrated OCT on a chip.
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jtandrews@sgsits.ac.in

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Integrated OCT, MEMS, Optical MEMS

Introduction

Optical Coherence Tomography (OCT) is becoming a multipurpose modality in area of biomedical imaging as well as a diagnostics tool. OCT offers high resolution, non-contact, non-invasive or minimal invasive and non-destructive medical diagnosis applications at low cost with an option for portability in measurement. The measurement technique behind OCT is based on the principles of low coherence interferometry (Huang 1991). OCT has sufficient special resolution about 1 to 15 \(\mu\)m depending on the light source employed. The reported penetration depth in skin up to 3 mm is achieved depending on the numerical aperture of the focusing lenses. At this resolution, skin appendages and blood vessels can be visualized. Repeatability of measurement at point of study sample or imaging point greatly increased due to the non-destructive capabilities of OCT (Solanki 2013).

On the other hand, to take the OCT to next level of applications the device needed to be downsized without compromizing on resolution and speed of measurements. The optical components could be downsized with micro meter sized optical elements. Micro-electromechanical systems (MEMS) devices have been adopted for OCT applications and OCT utilizing a scanning MEMS device in the the sampling arm of a Michleson interferrometer have been presented (Pan 2001, McCormick 2007). Towards miniaturization of OCT as endoscopic probe based on MEMS micro-mirror technology has been significant role in the development of integrated miniature OCT. A variety of MEMS device based on electro-thermal, electrostatic, electromagnetic and pneumatic actuation mechanisms have been demonstrated in various endoscopic OCT application (Sun 2011). But, In spite of MEMS endoscopic probe, the other ideal active and passive optical components still have to be fabricate for complete OCT on a single chip.

Recent technological advancements in the optoelectronic and MEMS industry have led to a revival of interest in more applications area. Micro-opto-electro-mechanical-systems (MOEMS) devices have inclusion of integrated optoelectronics and MEMS technologies, which are includes several active and passive monolithically or heterogeneously (Hybrid) integrated or 2D/3D micro-machined optical and MEMS components. This new family of devices and systems is generally called Optical MEMS or MOEMS. Further, MOEMS devices take advantage of high integration density, high reliability, high bandwidth, and low cost fabrication for mass production. While in some cases MOEMS technology focuses on the replacement of conventional big devices. Miniaturization of MOEMS base device has been achieved with the use of integrated optics and micro fabrication techniques. Various optical micro machined devices of this type have been demonstrated over the past two decades (Madou 1997). MOEMS is a most rapidly growing area of research and market development with great potential to impact daily life. The basic concept is the miniaturization of combined optical, mechanical, and electronic functions into an integrated assembly. Micro-opto-electro-mechanical-systems (MOEMS) are very new, but, have the potential to be broadly utilized in much area such as telecommunication, military, particularly in display arenas, remote sensing, guided surgery, optical data storage and imaging. The ability to integrate micro-optical elements with movable structures and micro-actuators has opened up many new opportunities for optical and optoelectronic systems. It allows us to manipulate optical beams more effectively than conventional methods, and is scalable to large optical systems. The most active researches have been conducted in the fiber-optic communications industry while such a device is often used in wavelength-division multiplexing (WDM) technology. Another industry looking into spatial light modulator/diffraction devices is the digital display industry. These display industry aims to develop MEMS based micro-array devices capable of modulating the wavelength of projected light, such as the color pixels of a typical projector or DLP display (Kim 1999, Kessel 1998). MEMS are fabricated using the techniques and materials of microelectronics. These technology has opened up many new possibilities and optical functions on chip has been demonstrated for optical and optoelectronic systems (Wu 1997, Tuantranont 2000, Noell 2002). Recently, MEMS based system have received great attention and found numerous applications in biomedical instrumentation and allow the realization on miniature optical system exhibiting low power consumption, small size, high operation speed. A variety of scanners for imaging in OCT have been developed based on MEMS technology and these MEMS mirrors/scanning lenses have previously been employed in bio-optic applications such as confocal microscopy (Kwon 2003) cell sorting (Pei 2004) florescence (Piyawattanametha 2008) and endoscopic OCT (E-OCT) (Pan 2001,