Photonic MEMS Research Articles

Integrated Photonic MEMS Switch for Visible Light

Integrated Photonic MEMS Switch for Visible Light

Efficient Surfactant-Mediated Photovoltaic Manipulation of Fl-Scale Aqueous Microdroplets for Diverse Optofluidic Applications on LiNbO3 Platform.

The electrodeless biocompatible manipulation of femtoliter-scale aqueous microdroplets remains challenging to date. The appropriate isolation of electrostatic charges from fL-scale aqueous microdroplets is crucial for electrodeless optoelectronic manipulation based on space-charge-density modulation. Here, we propose surfactant-mediated photovoltaic manipulation, in which the surfactant layers self-assembled at the water-oil and oil-LN interfaces are employed to isolate photovoltaic charges. The reduced electrostatic attenuation, remarkable hydrophobicity, and strong electrical breakdown suppression of the surfactant layers enable the stable and swift manipulation of fL-scale aqueous microdroplets using μW-level laser in an oil medium. By virtue of the surfactant-mediated photovoltaic manipulation, we realized a controllable merging/touching/detaching switch of aqueous microdroplets by adjusting the laser illumination intensity and position and demonstrated the cascading biochemical operations and microreactions of aqueous microdroplets and microdroplet strings. To demonstrate its potential in photonic MEMS assemblies, we demonstrated the end coupling of a tightly focused-laser-beam into a ZnO microrod leveraging the refraction effect occurring at the water/oil interface. Moreover, because of the selective permeability of the droplet-interface-bilayer developed between the touching microdroplets, we achieved in situ adjustment of the size of the microdroplets and the fluorescent solute contained in the microdroplets, aiming at constructing multicomponent fluorescent microdroplets with tunable whispering-gallery-mode (WGM) characteristics. This article is protected by copyright. All rights reserved.

Vacuum-sealed silicon photonic MEMS tunable ring resonator with an independent control over coupling and phase.

Ring resonators are a vital element for filters, optical delay lines, or sensors in silicon photonics. However, reconfigurable ring resonators with low-power consumption are not available in foundries today. We demonstrate an add-drop ring resonator with the independent tuning of round-trip phase and coupling using low-power microelectromechanical (MEMS) actuation. At a wavelength of 1540 nm and for a maximum voltage of 40 V, the phase shifters provide a resonance wavelength tuning of 0.15 nm, while the tunable couplers can tune the optical resonance extinction ratio at the through port from 0 to 30 dB. The optical resonance displays a passive quality factor of 29 000, which can be increased to almost 50 000 with actuation. The MEMS rings are individually vacuum-sealed on wafer scale, enabling reliable and long-term protection from the environment. We cycled the mechanical actuators for more than 4 × 109 cycles at 100 kHz, and did not observe degradation in their response curves. On mechanical resonance, we demonstrate a modulation increase of up to 15 dB, with a voltage bias of 4 V and a peak drive amplitude as low as 20 mV.

Modeling of surface roughness in deeply etched photonic MEMS mirrors and filters

We study the impact of the surface roughness on the response of deeply etched silicon Bragg mirrors and resonators. The transfer matrix method is extended to account for the roughness in multilayered systems. The model is first verified numerically using the finite difference time domain (FDTD) method for surface roughness values up to 80 nm at a wavelength of 1550 nm. The response of the mirrors and filters having an RMS roughness of 30 nm is calculated by the developed model and compared with the numerical results of the FDTD results, and it shows a good agreement. Then the model results are compared with the experimental data of a Bragg mirror and filter, fabricated by the deep reactive ion etching Bosch process of silicon on an insulator wafer; they show a very good agreement in the insertion loss and 3-dB bandwidth due to the roughness model. Finally, the transmission, 3-dB bandwidth and quality factor of the optical filters based on single, double, and triple silicon layer mirrors are examined using the model and accounting for Gaussian beam excitation. The presented model can be used to guide the requirements on the fabrication quality of optical surfaces and the choice of the optimum number of layers.

A photonic MEMS interposer to solve electronic and optical assembly challenges

AbstractPhotonic applications often face industry‐specific assembly requirements that can be challenging to overcome. There is a need for micron‐accurate alignment, device miniaturization and integration in challenging form factors. Special materials and packaging must be developed for the best performance of the devices in exacting environmental conditions. In the medical field, these requirements are additionally complicated by the demanding ISO 13485 regulations. The article demonstrates how solutions are found in a combination of new and existing technology in microelectronics packaging and now made suitable for photonics.

Design and analysis of photonic MEMS based micro ring resonators for pressure sensing application

The proposed work consists of a ring resonator-based pressure sensor. Double and triple ring photonic crystal resonators are configured in series and in parallel combinations. The sensing layer is designed and simulated for a varying pressure of 3–9 MPa using ansys workbench to obtain the stress and deformation experienced by the sensor. The equivalent refractive index value for every stress is computed and shift in wavelength is determined by simulation of the photonic crystal ring resonator (PCRR) structures in the optical tool. Finite-difference time-domain results show that ‘three rings coupled in parallel’ PCRR structure have the best sensitivity and good quality factor than other sensing configurations. A maximum sensitivity of 49.77 nm MPa−1 and a quality factor of 3260.25 is observed for the triple-ring parallel PCRR. The proposed type of sensor has remarkable biosensing applications.

Silicon nanostructure-based photonic MEMS sensor for biosensing application

We explored the design of an optical pressure sensor. The objective is to create a photonic microelectromechanical system-based cantilever sensor design to detect prostate-specific antigen, a protein biomarker associated with prostate cancer. Sensor’s performance for the early detection of cancerous cells is dependent on sensitivity. The designed sensor consists of a hexagonal ring integrated with microcantilevers. Two types of microcantilever such as rectangular profile and V profile with integrated photonic sensing layer are investigated for sensitivity, quality factor, and resonant wavelength. The analysis shows that a geometrical modification of microcantilever has a significant effect on sensitivity enhancement. The finite difference time domain tool is used for designing photonic ring resonator patches. Numerical analysis of microcantilever is considered to investigate surface stress behavior. The cantilever deformation due to applied pressure resulted in a change in the index of refraction. Results show that the sensitivity of 55 nm / MPa for a triangular-shaped microcantilever obtained is higher compared to the rectangular-shaped microcantilever with a sensitivity of 0.19 nm / MPa. The designed structures have significantly higher sensitivities than the previously published sensitivity of 3.27 nm / MPa at wavelength 1550 nm. The maximum quality factor obtained for the rectangular shape is 2852 and 77,510 for the triangular shape. Triangular-shaped microcantilever can minimize winding inflexibility or stiffness. This capability of the triangular-shaped microcantilever enhances feasibility in making the final packaging and future fabrication.

32 × 32 silicon photonic MEMS switch with gap-adjustable directional couplers fabricated in commercial CMOS foundry

We report on a 32 × 32 silicon photonic micro-electro-mechanical-system (MEMS) switch with gap-adjustable directional couplers. The switch is fabricated on 200-mm silicon-on-insulator wafers in a commercial complementary metal-oxide-semiconductor (CMOS) foundry. The fabricated device has a maximum on-chip loss of 7.7 dB and an extinction ratio of 50.8 dB. The switching voltage is 9.45 V and the 20-dB bandwidth is 28.7 nm. Our work shows a promising path for mass production of silicon photonic MEMS switches in commercial CMOS foundries.

Silicon photonic wavelength cross-connect with integrated MEMS switching

We report on monolithically integrated wavelength cross-connects (WXCs) on an enhanced silicon photonic platform with integrated micro-electro-mechanical-system (MEMS) actuators. An 8 × 8 WXC with 8 wavelength channels comprising 16 echelle gratings and 512 silicon photonic MEMS switches is integrated on a 9.7 mm × 6.7 mm silicon chip. The WXC inherits the fundamental advantages of silicon photonic MEMS space switches, including low loss, broad optical bandwidth, large fabrication tolerance, and simple digital control. The WXC exhibits a low crosstalk of −30 dB, a submicrosecond switching time of 0.7 µs, and on-chip optical insertion losses varying from 8.8 dB to 16.4 dB. To our knowledge, it is the largest channel capacity (64 channels = 8 ports × 8 wavelengths) integrated WXC ever reported.

All‐Silicon Double‐Cavity Fourier‐Transform Infrared Spectrometer On‐Chip

AbstractIt is expected that miniaturized infrared spectrometers will enable spectral sensing anywhere. Their applications are almost infinite, including in smart devices, monitoring of air and water quality, healthcare wearables, among many others. Free‐space on‐chip, or photonic MEMS, interferometers are an attractive solution since they provide the required miniaturization while achieving the optical throughput needed for device sensitivity. A Fourier‐transform spectrometer on‐chip is presented based on cascading silicon broadband photonic MEMS cavities. The double‐cavity configuration shrinks the size of the optical engine dramatically with respect to the Michelson configuration, while overcoming the need for bringing the micromirrors in physical contact as in case of a single cavity. The all‐silicon interfaces provide low enough reflectivity such that the response of the cavity can be approximated by a single harmonic allowing Fourier transform operation of the spectrometer. The spectrometer is fabricated using deep etching of a silicon‐on‐insulator substrate allowing release of movable elements. The optical engine size is 300 µm × 400 µm. The device is tested in the wavelength range of 1.1–2.1 µm and spectroscopy measurement of different materials with 7.5 nm spectral resolution is demonstrated and compared to a reference spectrometer.

Multicast silicon photonic MEMS switches with gap-adjustable directional couplers.

We report on 4x20 silicon photonic MEMS switch that is capable of multicasting. The switch is built on passive optical crossbar network with gap-adjustable directional couplers. The switch has high on-off extinction ratio (59 dB), low insertion loss (< 4.0 dB), small footprint (1.2x4.5 mm2), and fast response (9.8 µs). The switching voltage is 9.6 V and 20 dB bandwidth is 31.5 nm. One-to-two and one-to-four multicast operations are demonstrated.

Scalable Row/Column Addressing of Silicon Photonic MEMS Switches

In this letter, we demonstrate a scalable addressing scheme for silicon photonic MEMS switches. For a crossbar architecture switch fabric of dimension N × N, the row/column addressing scales with 2 · N electrodes, much reduced from the N <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> electrodes in individual addressing. It also compares favorably with other optical switch architectures, including path-independent insertion loss, Beneš, or switch-and-select networks, in terms of electrical interface. We have designed, fabricated, and experimentally characterized the performance of a 4 × 4 silicon photonic MEMS switch.

Fabrication and characterization of suspended beam structures for SiO2 photonic MEMS

This paper proposes a microfabrication process for the reliable release of SiO2 beam structures. These structures are intended to be utilized in SiO2 photonic MEMS. A major fabrication challenge is the release of thick (>10 μm) SiO2 structures with high yield. A single mask process is developed based on temporary reinforcement of the SiO2 structure. A supporting layer of Si functions as a reinforcing layer during etching and release, thereby enabling a high fabrication yield. Furthermore, the process allows to create structures of which the final Si support thickness is configurable from tens of micrometers to zero, thereby providing additional design freedom.The fabrication process is tested on a silicon wafer with a ∼15 μm thick thermal oxide layer. The obtained suspended structures are mechanically characterized. Two deformation effects can be distinguished: a curvature of the beam and a slope at the base of the beam. These effects are caused by the compressive mean stress and the gradient stress in the thermal SiO2. The curvature of the SiO2–Si beams corresponds to a concave downward profile while the SiO2 beams without supporting Si reveal a small curvature in the opposite direction (concave upward). The slope at the base is approximately for the SiO2 beams and between and 0° for the SiO2–Si beams. The acquired bending stiffness of long SiO2 beams is in the newton per meter range (e.g. 0.8 N m−1 for a cantilever measuring 1000 μm in length and 13 μm in width).

Analysis of Novel Building Blocks for Photonic MEMS Based on Deep 1D Photonic Crystals

This papers deals with the study of novel building blocks suitable for architectures of MEMS tunable lasers integrated in SOI platforms. These building blocks are based on the use of 1D photonic crystals (1D PCs) made of silicon-air thin layers stacks. These provide high reflectivity in certain wavelength range as well as access to simple Fabry-Perot cavities. The latter was studied more in detail and simulations are presented along with preliminary experimental results. A tilted Fabry-Perot cavity was analyzed for its potential of mode selector to prevent for mode hopping and thus enable continuous mode tuning by control of separation gap. As 1D PCs exhibit dispersion characteristics, this behavior is analyzed as well for its potential use for compensation purposes of wavelength dependence of the refractive index in the III-V gain medium.

2A1-F03 パリレン保護によるSi細線MEMS変調素子の作製方法の検討(MEMSとナノテクノロジー)

2A1-F03 パリレン保護によるSi細線MEMS変調素子の作製方法の検討(MEMSとナノテクノロジー)

Advanced etching of silicon based on deep reactive ion etching for silicon high aspect ratio microstructures and three-dimensional micro- and nanostructures

Different processes involving an inductively coupled plasma reactor are presented either for deep reactive ion etching or for isotropic etching of silicon. On one hand, high aspect ratio microstructures with aspect ratio up to 107 were obtained on sub-micron trenches. Application to photonic MEMS is presented. Isotropic etching is also used either alone or in combination with anisotropic etching to realize various 3D shapes.