Quentin Tanguy

A Compact Fourier Transform Spectrometer on a Silicon Optical Bench With an Electrothermal MEMS Mirror

This paper reports a compact Fourier transform spectrometer system with a large-stroke electrothermal microelectromechanical systems (MEMS) mirror and other optical components all integrated on a micromachined silicon optical bench with the footprint of 2 cm × 2 cm. The linear optical path difference (OPD) scan range generated by the MEMS mirror reaches up to 450 μm, and the tilting of the mirror plate is reduced down to <;±0.002° by using a new openloop control method. A spectral resolution of 40 cm-1, or 1.1 nm at 532 nm, has been achieved. The overall size of the system is reduced dramatically and the performance is improved significantly compared with the prior work.

Design and Fabrication of a 2-Axis Electrothermal MEMS Micro-Scanner for Optical Coherence Tomography

This paper introduces an optical 2-axis Micro Electro-Mechanical System (MEMS) micromirror actuated by a pair of electrothermal actuators and a set of passive torsion bars. The actuated element is a dual-reflective circular mirror plate of 1 mm in diameter. This inner mirror plate is connected to a rigid frame via a pair of torsion bars in two diametrically opposite ends located on the rotation axis. A pair of electrothermal bimorphs generates a force onto the perpendicular free ends of the mirror plate in the same angular direction. An array of electrothermal bimorph cantilevers deflects the rigid frame around a working angle of 45∘ for side-view scan. The performed scans reach large mechanical angles of 32∘ for the frame and 22∘ for the in-frame mirror. We denote three resonant main modes, pure flexion of the frame at 205 Hz, a pure torsion of the mirror plate at 1.286 kHz and coupled mode of combined flexion and torsion at 1.588 kHz. The micro device was fabricated through successive stacks of materials onto a silicon-on-insulator wafer and the patterned deposition on the back-side of the dual-reflective mirror is achieved through a dry film photoresist photolithography process.

Optical coherence tomography endoscopic probe based on a tilted MEMS mirror.

This paper reports a compact microendoscopic OCT probe with an outer diameter of only 2.7 mm. The small diameter is enabled by a novel 2-axis scanning MEMS mirror with a preset 45° tilted angle. The tilted MEMS mirror is directly integrated on a silicon optical bench (SiOB). The SiOB provides mechanical support and electrical wiring to the mirror plate via a set of bimorph flexure, enabling a compact probe mount design without the requirement of a 45° slope, which is capable to dramatically reduce the probe size and ease the assembly process. Additionally, the SiOB also provides trenches with properly-designed opening widths for automatic alignment of the MEMS mirror, GRIN lens and optical fiber. The 45°-tilted MEMS mirror plate is actuated by four electrothermal bimorph actuators. The packaged 2.7 mm-diameter probe offers 2-axis side-view optical scanning with a large optical scan range of 40° at a low drive voltage of 5.5 Vdc in both axes, allowing a lateral scan area of 2.2 mm × 2.2 mm at a 3 mm working distance. High-resolution 2D and 3D OCT images of the IR card, ex vivo imaging of meniscus specimens and rat brain slices, in vivo imaging of the human finger and nail have been obtained with a TDOCT system.

A 2-axis electrothermal MEMS micro-scanner with torsional beam

In this paper we introduce a 2-axis MEMS micro-scanner with large scanning range of frame (32°) and mirror (22°) using a compact and optimized electrothermal bimorph actuator and torsional beams to tip and tilt a dual-reflective mirror plate.

A Monolithic Michelson interferometer with a large piston MEMS micromirror

We demonstrated a MEMS based Monolithic Michelson interferometer with both the movable mirror and fixed mirror vertically oriented and integrated on a silicon bench for the first time. Both mirrors are single-crystal silicon based and their vertical orientation is attained by a proper thermal bimorph design and a unique stopper mechanism. This device enables miniature Fourier transform spectrometers.

MOEMS-based imaging probe with integrated Mirau micro-interferometer and MEMS microscanner for swept-source OCT endomicroscopy

The early diagnosis of cancer is essential since it can be treated more effectively when detected earlier. Visual inspection followed by histological examination is, still today, the gold standard for clinicians. However, a large number of unnecessary surgical procedures are still performed. New diagnostics aids are emerging including the recent techniques of optical coherence tomography (OCT) which permits non-invasive 3D optical biopsies of biological tissues, improving patient’s quality of life. Nevertheless, the existing bulk or fiber optics systems are expensive, only affordable at the hospital and thus, not sufficiently used by physicians or cancer’s specialists as an early diagnosis tool. We developed an endoscopic microsystems based on Mirau interferometry and applied for swept source OCT imaging applied for gastroenterology. The architecture is based on a miniature spectrally tuned a single-channel Mirau interferometer integrated with an electro-thermal MEMS microscanner scanning the sample area.

The SS-OCT endomicroscopy probe based on MOEMS Mirau micro-interferometer for early stomach cancer detection

In this paper, we present the construction and preliminary experimental results of a MOEMS fiber-based integrated probe for endoscopic optical imaging of stomach tissue using a Swept-Source Optical Coherence Tomography (SSOCT). The probe consists of a Mirau micro-interferometer, combined with a GRIN lens collimator and a micromirror scanner. We describe the building blocks of the probe, especially the monolithically integrated Mirau mirointerferometer, fabricated by wafer-level vertical stacking and anodic bonding of Si/glass components, and the electrothermal 2-axis MEMS microscanner allowing large swept angles (up to ±22°) at high frequencies (> kHz) for low driving voltages (<20 V). The results of probe characterization, performed in a designed SS-OCT system, have confirmed proper operation of the probe. The B-scan images were obtained for central wavelength of λc = 840 nm, swept range of Dλ = 60 nm and A-scan frequency of fA= 110 kHz. The axial resolution of the probe is equal to 5.2 μm (determined by applied swept source), whereas the lateral resolution, measured by use of USAF test pattern, is 9.8 μm.

A 2-axis MEMS scanning micromirror with a 45° auto-positioning mechanism for endoscopic probe

In this paper, we report a novel 2-axis electrothermal MEMS micro-scanner with an initial tilt at 45° out of its support plane. A new type of mechanical stopper is designed to hold the structure in the initial oblique bending position, which enables a cross axis decoupling. The micro-scanner is a key component of a fully integrated endoscopic imaging probe for 3D Swept Source (SS) Optical Coherence Tomography (OCT) imaging system and is developed with the objective of proposing an assembly adapted for industrial manufacturing.

Miniature multimodal endoscopic probe based on double-clad fiber

Optical coherence tomography (OCT) can obtain light scattering properties with a high resolution, while photoacoustic imaging (PAI) is ideal for mapping optical absorbers in biological tissues, and ultrasound (US) could penetrate deeply into tissues and provide elastically structural information. It is attractive and challenging to integrate these three imaging modalities into a miniature probe, through which, both optical absorption and scattering information of tissues as well as deep-tissue structure can be obtained. Here, we present a novel side-view probe integrating PAI, OCT and US imaging based on double-clad fiber which is used as a common optical path for PAI (light delivery) and OCT (light delivery/detection), and a 40 MHz unfocused ultrasound transducer for PAI (photoacoustic detection) and US (ultrasound transmission/receiving) with an overall diameter of 1.0 mm. Experiments were conducted to demonstrate the capabilities of the integrated multimodal imaging probe, which is suitable for endoscopic imaging and intravascular imaging.

A wide-angle immersed MEMS mirror and its application in optical coherence tomography

In this paper we report a wide-angle two-axis electrothermal MEMS scanning mirror and its application in optical coherence tomography (OCT). The wide-angle scanning was achieved by combining the large scan range of the MEMS mirror and the “Snells Window” effect. By immersing the electrothermal MEMS mirror into a mineral oil, the original 32° field of view (FOV) can be increased up to about 75°. The wide-angle immersed mirror was employed in an OCT system and 3D OCT images were successfully obtained.