The next generation of silicon-based photonic processors and neural and quantum networks need to be adaptable, reconfigurable, and programmable. Phase change technology offers proven nonvolatile ...electronic programmability; however, the materials used to date have shown prohibitively high optical losses, which are incompatible with integrated photonic platforms. Here, we demonstrate the capability of the previously unexplored material Sb2Se3 for ultralow-loss programmable silicon photonics. The favorable combination of large refractive index contrast and ultralow losses seen in Sb2Se3 facilitates an unprecedented optical phase control exceeding 10π radians in a Mach-Zehnder interferometer. To demonstrate full control over the flow of light, we introduce nanophotonic digital patterning as a previously unexplored conceptual approach with a footprint orders of magnitude smaller than state-of-the-art interferometer meshes. Our approach enables a wealth of possibilities in high-density reconfiguration of optical functionalities on silicon chip.
Abstract
The antimony-based chalcogenide Sb
2
Se
3
is a rapidly emerging material for photonic phase change applications owing to its ultra-low optical losses at telecommunication wavelengths in both ...crystalline and amorphous phases. Here, we investigate the dynamical response of these materials from nanoseconds to milliseconds under optical pumping conditions. We apply bichromatic pump-probe transient reflectance spectroscopy which is a widely used method to study the optical performance of optical phase change materials during phase transitions induced by direct pulsed optical switching. Amorphous regions of several hundreds of nanometers in diameter are induced by pulsed excitation of the material using a wavelength of 488 nm above the absorption edge, while the transient reflectance is probed using a continuous wave 980 nm laser, well below the absorption edge of the material. We find vitrification dynamics in the nanosecond range and observe crystallization on millisecond time scales. These results show a large five-orders of magnitude difference in time scales between crystallization and vitrification dynamics in this material. The insights provided in this work are fundamental for the optimisation of the material family and its employment in photonic applications.
A dicing free SOI process for MEMS devices Sari, Ibrahim; Zeimpekis, Ioannis; Kraft, Michael
Microelectronic engineering,
07/2012, Letnik:
95
Journal Article, Web Resource
Recenzirano
Odprti dostop
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► We present a wafer level and dicing free MEMS-SOI fabrication process. ► Based on this work, a detailed set of design rules is also developed. ► This enables the process to be used ...for a wide range of MEMS devices. ► The process is demonstrated to fabricate high performance accelerometers. ► Using the design rules, they were fabricated with a high yield of >95%.
This paper presents a full wafer, dicing free, dry release process for MEMS silicon-on-insulator (SOI) sensors and actuators. The developed process is particularly useful for inertial sensors that benefit from a large proof mass, for example accelerometers and gyroscopes. It involves consecutive front and backside deep reactive ion etching (DRIE) of the substrate to define the device features, release holes, and trenches. This is followed by hydrofluoric acid vapor phase etching (HF VPE) to release the proof mass and the handle wafer underneath to allow vertical displacements of the proof mass. The release process also allows the devices to be detached from each other and the substrate without the need of an extra dicing step that may damage the delicate device features or create debris. In the work described here, the process is demonstrated for the full wafer release of a high performance accelerometer with a large proof mass measuring 4×7mm2. The sensor was successfully fabricated with a yield of over 95%.
The development of the next generation of optical phase change technologies for integrated photonic and free-space platforms relies on the availability of materials that can be switched repeatedly ...over large volumes and with low optical losses. In recent years, the antimony-based chalcogenide phase-change material Sb2Se3 has been identified as particularly promising for a number of applications owing to good optical transparency in the near-infrared part of the spectrum and a high refractive index close to silicon. The crystallization temperature of Sb2Se3 of around 460 K allows switching to be achieved at moderate energies using optical or electrical control signals while providing sufficient data retention time for non-volatile storage. Here, we investigate the parameter space for optical switching of films of Sb2Se3 for a range of film thicknesses relevant to optical applications. By identifying optimal switching conditions, we demonstrate endurance of up to 107 cycles at reversible switching rates of 20 kHz. Our work demonstrates that the combination of intrinsic film parameters with pumping conditions is particularly critical for achieving high endurance in optical phase change applications.
Abstract
Phase‐change materials (PCMs) are seeing tremendous interest for their use in reconfigurable photonic devices; however, the most common PCMs exhibit a large absorption loss in one or both ...states. Here, Sb
2
S
3
and Sb
2
Se
3
are demonstrated as a class of low loss, reversible alternatives to the standard commercially available chalcogenide PCMs. A contrast of refractive index of Δ
n
= 0.60 for Sb
2
S
3
and Δ
n
= 0.77 for Sb
2
Se
3
is reported, while maintaining very low losses (
k
< 10
−5
) in the telecommunications C‐band at 1550 nm. With a stronger absorption in the visible spectrum, Sb
2
Se
3
allows for reversible optical switching using conventional visible wavelength lasers. Here, a stable switching endurance of better than 4000 cycles is demonstrated. To deal with the essentially zero intrinsic absorption losses, a new figure of merit (FOM) is introduced taking into account the measured waveguide losses when integrating these materials onto a standard silicon photonics platform. The FOM of 29 rad phase shift per dB of loss for Sb
2
Se
3
outperforms Ge
2
Sb
2
Te
5
by two orders of magnitude and paves the way for on‐chip programmable phase control. These truly low‐loss switchable materials open up new directions in programmable integrated photonic circuits, switchable metasurfaces, and nanophotonic devices.
The development of the next generation of optical phase change technologies for integrated photonic and free-space platforms relies on the availability of materials that can be switched repeatedly ...over large volumes and with low optical losses. In recent years, the antimony-based chalcogenide phase-change material Sb 2 Se 3 has been identified as particularly promising for a number of applications owing to good optical transparency in the near-infrared part of the spectrum and a high refractive index close to silicon. The crystallization temperature of Sb 2 Se 3 of around 460 K allows switching to be achieved at moderate energies using optical or electrical control signals while providing sufficient data retention time for non-volatile storage. Here, we investigate the parameter space for optical switching of films of Sb 2 Se 3 for a range of film thicknesses relevant to optical applications. By identifying optimal switching conditions, we demonstrate endurance of up to 10 7 cycles at reversible switching rates of 20 kHz. Our work demonstrates that the combination of intrinsic film parameters with pumping conditions is particularly critical for achieving high endurance in optical phase change applications.
In this paper, a mechanical amplification concept for microelectromechanical systems (MEMS) physical sensors is proposed with the aim to improve their sensitivity. The scheme is implemented using a ...system of micromachined levers (microlevers) as a deflection amplifying mechanism. The effectiveness of the mechanism is demonstrated for a capacitive accelerometer. A proof-of-concept single-axis mechanically amplified accelerometer with an amplification factor of 40 has been designed, simulated, and fabricated, and results from its evaluation are presented in this paper. The sensor's amplified output has a sensitivity of 2.39 V/g using an open-loop capacitive pick-off circuit based on charge amplifiers. Experimental results show that the addition of the mechanical amplifier does not alter the noise floor of the sensor. The measured natural frequency of the first mode of the sensor is at 734 Hz, and the full-scale measurement range is up to 7 g with a maximum nonlinearity of 2%. It is shown, through comparison with a conventional design, that the mechanically amplified accelerometer provides higher deflection without sacrificing bandwidth.
In response to the growing need for efficient processing of temporal information, neuromorphic computing systems are placing increased emphasis on the switching dynamics of memristors. While the ...switching dynamics can be regulated by the properties of input signals, the ability of controlling it via electrolyte properties of a memristor is essential to further enrich the switching states and improve data processing capability. This study presents the synthesis of mesoporous silica (mSiO2) films using a sol–gel process, which enables the creation of films with controllable porosities. These films can serve as electrolyte layers in the diffusive memristors and lead to tunable neuromorphic switching dynamics. The mSiO2 memristors demonstrate short-term plasticity, which is essential for temporal signal processing. As porosity increases, discernible changes in operating currents, facilitation ratios, and relaxation times are observed. The underlying mechanism of such systematic control was investigated and attributed to the modulation of hydrogen-bonded networks within the porous structure of the silica layer, which significantly influences both anodic oxidation and ion migration processes during switching events. The result of this work presents mesoporous silica as a unique platform for precise control of neuromorphic switching dynamics in diffusive memristors.
Abstract
A new family of phase change material based on antimony has recently been explored for applications in near-IR tunable photonics due to its wide bandgap, manifested as broadband transparency ...from visible to NIR wavelengths. Here, we characterize
$$\hbox {Sb}_{2} \hbox {S}_{3}$$
Sb
2
S
3
optically and demonstrate the integration of this phase change material in a silicon nitride platform using a microring resonator that can be thermally tuned using the amorphous and crystalline states of the phase change material, achieving extinction ratios of up to 18 dB in the C-band. We extract the thermo-optic coefficient of the amorphous and crystalline states of the
$$\hbox {Sb}_{2}\hbox {S}_{3}$$
Sb
2
S
3
to be 3.4 x
$$10^{-4}\hbox {K}^{-1}$$
10
-
4
K
-
1
and 0.1 x 10
$$^{-4}\hbox {K}^{-1}$$
-
4
K
-
1
, respectively. Additionally, we detail the first observation of bi-directional shifting for permanent trimming of a non-volatile switch using continuous wave (CW) laser exposure (
$$-5.9$$
-
5.9
to 5.1 dBm) with a modulation in effective refractive index ranging from +5.23 x
$$10^{-5}$$
10
-
5
to
$$-1.20$$
-
1.20
x 10
$$^{-4}$$
-
4
. This work experimentally verifies optical phase modifications and permanent trimming of
$$\hbox {Sb}_{2}\hbox {S}_{3}$$
Sb
2
S
3
, enabling potential applications such as optically controlled memories and weights for neuromorphic architecture and high density switch matrix using a multi-layer PECVD based photonic integrated circuit.
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