Piotr Kropelnicki

Development of stress-induced curved actuators for a tunable THz filter based on double split-ring resonators

Using stress-induced curved cantilevers to form double split-ring resonator (DSRR) in three-dimensional configuration, an electrically tunable microelectromechanical system (MEMS) based out-of-plane metamaterials THz filter is experimentally demonstrated and characterized. While the achieved tunable range for the resonant frequency is 0.5 THz at 20 V bias, quality factor of the resonant frequency is improved as well. This MEMS based THz filter using released DSRR structures shows its potential in tunable metamaterials applications such as sensors, optical switches, and filters.

Electrothermally actuated microelectromechanical systems based omega-ring terahertz metamaterial with polarization dependent characteristics

We present the design, simulation, fabrication, and characterization of a continuously tunable Omega-ring terahertz metamaterial. The tunability of metamaterial is obtained by integrating microactuators into the metamaterial unit cell. Electrothermal actuation mechanism is used to provide higher tuning range, larger stroke, and enhanced repeatability. The maximum achieved tuning range for the resonant frequency is around 0.30 THz for the input power of 500 mW. This shows the potential of using electrothermally actuated microactuators based tunable metamaterial design for application such as filters, absorbers, sensors, and spectral imagers.

Micro-electro-mechanically switchable near infrared complementary metamaterial absorber

We experimentally demonstrate a micro-electro-mechanically switchable near infrared complementary metamaterial absorber by integrating the metamaterial layer to be the out of plane movable microactuator. The metamaterial layer is electrostatically actuated by applying voltage across the suspended complementary metamaterial layer and the stationary bottom metallic reflector. Thus, the effective spacing between the metamaterial layer and bottom metal reflector is varied as a function of applied voltage. With the reduction of effective spacing between the metamaterial and reflector layers, a strong spectral blue shift in the peak absorption wavelength can be achieved. With spacing change of 300 nm, the spectral shift of 0.7 μm in peak absorption wavelength was obtained for near infrared spectral region. The electro-optic switching performance of the device was characterized, and a striking switching contrast of 1500% was achieved at 2.1 μm. The reported micro-electro-mechanically tunable complementary metamaterial absorber device can potentially enable a wide range of high performance electro-optical devices, such as continuously tunable filters, modulators, and electro-optic switches that form the key components to facilitate future photonic circuit applications.

Dual band complementary metamaterial absorber in near infrared region

In this paper, we present the dual band absorption characteristics of complementary metamaterial absorber in near infrared (1.3–2.5 μm) region. The dual band absorption is caused by two distinct resonance mechanisms—electrical resonance and cavity resonance. Electrical resonance occurs in the metal layer—top complementary metamaterial and the cavity resonance occurs in the spacer cavity formed between the top complementary metamaterial and bottom metal reflector layers. In order to elucidate the resonant mechanisms and study the effects of geometrical variations on both the resonant absorption behaviours, two sets of experiment were performed. It was seen that with increasing complementary metamaterial pattern dimension, the electrical resonance absorption peak showed a blue shift, while the cavity resonance showed a slight red shift. However, on the other hand, for the increase in spacer thickness, the cavity resonance peak showed a strong red shift, while the electrical resonance peak remained uninfluen...

A nanoelectromechanical systems actuator driven and controlled by Q-factor attenuation of ring resonator

In this Letter, an optical gradient force driven Nanoelectromechanical Systems (NEMS) actuator, which is controlled by the Q-factor attenuation of micro-ring resonator, is demonstrated. The actuator consists of a tunable actuation ring resonator, a sensing ring resonator, and a mechanical actuation arc. The actuation displacement can reach up to 14 nm with a measured resolution of 0.8 nm, when the Q-factor of the ring resonator is tuned from 15 × 103 to 6 × 103. The potential applications of the NEMS actuator include single molecule manipulation, nano-manipulation, and high sensitivity sensors.

Dual mode acoustic wave sensor for precise pressure reading

In this letter, a Microelectromechanical system acoustic wave sensor, which has a dual mode (lateral field exited Lamb wave mode and surface acoustic wave (SAW) mode) behavior, is presented for precious pressure change read out. Comb-like interdigital structured electrodes on top of piezoelectric material aluminium nitride (AlN) are used to generate the wave modes. The sensor membrane consists of single crystalline silicon formed by backside-etching of the bulk material of a silicon on insulator wafer having variable device thickness layer (5 μm–50 μm). With this principle, a pressure sensor has been fabricated and mounted on a pressure test package with pressure applied to the backside of the membrane within a range of 0 psi to 300 psi. The temperature coefficient of frequency was experimentally measured in the temperature range of −50 °C to 300 °C. This idea demonstrates a piezoelectric based sensor having two modes SAW/Lamb wave for direct physical parameter—pressure readout and temperature cancellatio...

Micro-electro-mechanically tunable metamaterial with enhanced electro-optic performance

We experimentally demonstrate a micro-electro-mechanically tunable metamaterial with enhanced electro-optical performance by increasing the number of movable cantilevers in the symmetrical split ring resonator metamaterial unit cell. Simulations were carried out to understand the interaction of the incident terahertz radiation with out-of-plane deforming metamaterial resonator. In order to improve the overall device performance, the number of released cantilever in a unit cell was increased from one to two, and it was seen that the tunable range was doubled and the switching contrast improved by a factor of around five at 0.7 THz. This simple design approach can be adopted for a wide range of high performance electro-optical devices such as continuously tunable filters, modulators, and electro-optic switches to enable future photonic circuit applications.

Viscosity and density decoupling method using a higher order Lamb wave sensor

Viscosity and density are two important physical parameters of liquid. Such parameters are widely used for label-free chemical detection. Conventional technologies employ acoustic wave sensors to detect viscosity and density. In these sensors, the liquid under test directly contacts with the surface of the sensor. The produced acoustic wave in the sensor leaks to the adjacent liquid layer, causing a shift in the resonance frequency of the sensor. However, such sensors are not able to separately measure the viscosity and density because these two parameters jointly affect the shift of frequency. Although some indirect methods for decoupling these two parameters have been investigated, either dual-device or simultaneous measurement of frequency and attenuation is required. In this paper, a novel AlN based acoustic wave sensor is developed for decoupling viscosity and density. Multiple higher order modes of Lamb waves are generated in this sensor and employed to interact with the adjacent liquid under test. The frequency change of two unique modes (mode C and mode D) has been found in a linear relationship with viscosity and density, respectively. With this unique feature, viscosity and density of a liquid can be distinguished by a single device, which is promising for potential industrial applications, label-free chemical detection and clinical diagnosis.

Development of Polycrystalline Silicon Based Photonic Crystal Membrane for Mid-Infrared Applications

Free-standing polycrystalline silicon (Si) based photonic crystal (PhC) membranes with etched circular and square holes are developed to display high reflectivity in the mid-infrared (MIR) region. Greater than 90% reflection was measured in the MIR wavelengths around 3.58 μm. By using square air holes in the PhC membrane, the mechanical strength of the polycrystalline Si membrane can be enhanced as square air holes have a lower filling factor of 36% of air holes, compared to 49% in circular air holes while keeping the reflectance around 3.45 μm more than 90%. Such Si PhC membranes offer opportunities for specific applications like filters. To illustrate the feasibility of such devices, simulation works are done by configuring two Si PhC membranes to create a Fabry-Perot interferometer operating in MIR region. The filtered peak shows a full width half maximum of 0.08 nm which corresponds to a quality factor of around 43800, thus demonstrating the possibility of high-resolution applications such as gas sensing and hyperspectral imaging.

CMOS-compatible ruggedized high-temperature Lamb wave pressure sensor

This paper describes the development of a novel ruggedized high-temperature pressure sensor operating in lateral field exited (LFE) Lamb wave mode. The comb-like structure electrodes on top of aluminum nitride (AlN) were used to generate the wave. A membrane was fabricated on SOI wafer with a 10 µm thick device layer. The sensor chip was mounted on a pressure test package and pressure was applied to the backside of the membrane, with a range of 20–100 psi. The temperature coefficient of frequency (TCF) was experimentally measured in the temperature range of −50 °C to 300 °C. By using the modified Butterworth–van Dyke model, coupling coefficients and quality factor were extracted. Temperature-dependent Youngs modulus of composite structure was determined using resonance frequency and sensor interdigital transducer (IDT) wavelength which is mainly dominated by an AlN layer. Absolute sensor phase noise was measured at resonance to estimate the sensor pressure and temperature sensitivity. This paper demonstrates an AlN-based pressure sensor which can operate in harsh environment such as oil and gas exploration, automobile and aeronautic applications.