Hengky Chandrahalim

Dielectrically Transduced Single-Ended to Differential MEMS Filter

A single-ended input to balanced output 425MHz mechanically coupled electromechanical filter is presented. This technology provides 1MHz channel select filtering while eliminating the need for RF switches and baluns in front-end transceivers. The filter achieves 8dB insertion loss with -50dB stop-band rejection and -48dB common-mode suppression

Performance comparison of Pb(Zr0.52Ti0.48)O3-only and Pb(Zr0.52Ti0.48)O3-on-silicon resonators

This paper provides a quantitative comparison and explores the design space of lead zirconium titanate (PZT)–only and PZT-on-silicon length-extensional mode resonators for incorporation into radio frequency microelectromechanical system filters and oscillators. We experimentally measured the correlation of motional impedance (RX) and quality factor (Q) with the resonators’ silicon layer thickness (tSi). For identical lateral dimensions and PZT-layer thicknesses (tPZT), the PZT-on-silicon resonator has higher resonant frequency (fC), higher Q (5100 versus 140), lower RX (51 Ω versus 205 Ω), and better linearity [third-order input intercept point (IIP3) of +43.7 dBm versus +23.3 dBm]. In contrast, the PZT-only resonator demonstrated much wider frequency tuning range (5.1% versus 0.2%).

Channel-Select Micromechanical Filters Using High-K Dielectrically Transduced MEMS Resonators

This paper demonstrates electrically and mechanically coupled channel-select filters comprised of dielectrically transduced thickness shear mode resonators. The filters are fabricated on the 3.2 μm thick device layer of a heavily doped SOI wafer with a 30 nm thick hafnium dioxide film sandwiched between the polysilicon electrodes and the silicon device layer. An 809 MHz half-wave thickness shear resonator is demonstrated with a quality factor (Q) of 7,800 in air and a motional impedance (RX) of 59 Ω. An array of such resonators is coupled electrically and mechanically to form dielectrically transduced MEMS filters. Electrically coupled channel-select filters with 814 MHz center frequency, 600 kHz bandwidth, -4 dB insertion loss (IL) and < 1dB pass-band ripple are presented. In addition, a mechanically coupled 804 MHz center frequency filter is demonstrated exhibiting -34 dB stop-band rejection and a 20 dB shape factor of 1.28.

Towards biodegradable wireless implants

A new generation of partially or even fully biodegradable implants is emerging. The idea of using temporary devices is to avoid a second surgery to remove the implant after its period of use, thereby improving considerably the patients comfort and safety. This paper provides a state-of-the-art overview and an experimental section that describes the key technological challenges for making biodegradable devices. The general considerations for the design and synthesis of biodegradable components are illustrated with radiofrequency-driven resistor–inductor–capacitor (RLC) resonators made of biodegradable metals (Mg, Mg alloy, Fe, Fe alloys) and biodegradable conductive polymer composites (polycaprolactone–polypyrrole, polylactide–polypyrrole). Two concepts for partially/fully biodegradable wireless implants are discussed, the ultimate goal being to obtain a fully biodegradable sensor for in vivo sensing.

Digitally-tunable mems filter using mechanically-coupled resonator array

This paper reports on the design of a bandwidth-tunable RF MEMS filter using a series-coupled array of dielectrically-transduced square-extensional mode resonators. The proposed digital tuning scheme provides channel-agility and bandwidth granularity for analog spectral processors and RF spectrum analyzers. The resonators and filters are fabricated on the 3 mum thick device layer of a heavily doped SOI wafer with a 100 nm thick silicon nitride film sandwiched between the polysilicon electrodes and the silicon device layer. A 511 MHz overtone square-extensional mode resonator is demonstrated with a quality factor (Q) of 1,800 in air and motional impedance (RX) of 1.1 kOmega. An array of four such resonators is coupled mechanically to form a channel-select filter with 1.4 MHz bandwidth at 509 MHz center frequency. By switching the DC-biasing scheme, the filter is split into narrower high and low sub-bands, each 700 kHz wide.

Monolithically Integrated Piezomems SP2T Switch and Contour-Mode Filters

This paper provides the first experimental demonstration of monolithically integrated piezoelectric MEMS RF switches with contour mode filters. Lead zirconate titanate (PZT) thin films are utilized to enable both low-voltage switch operation and filter tunability. This research leverages previous work using PZT actuators for low-voltage, wide-band switches and PZT transduced silicon resonators. The two device technologies are combined using a hybrid fabrication process that combines the key components of each device fabrication into a single unified process using silicon-on-insulator (SOI) substrates. The voltage tunable and switchable PiezoMEMS filter array provides a drop-in solution for frequency-agile channel selectivity.

Monolithic optofluidic ring resonator lasers created by femtosecond laser nanofabrication

We designed, fabricated, and characterized a monolithically integrated optofluidic ring resonator laser that is mechanically, thermally, and chemically robust. The entire device, including the ring resonator channel and sample delivery microfluidics, was created in a block of fused-silica glass using a 3-dimensional femtosecond laser writing process. The gain medium, composed of Rhodamine 6G (R6G) dissolved in quinoline, was flowed through the ring resonator. Lasing was achieved at a pump threshold of approximately 15 μJ mm(-2). Detailed analysis shows that the Q-factor of the optofluidic ring resonator is 3.3 × 10(4), which is limited by both solvent absorption and scattering loss. In particular, a Q-factor resulting from the scattering loss can be as high as 4.2 × 10(4), suggesting the feasibility of using a femtosecond laser to create high quality optical cavities.

Fully-differential mechanically-coupled PZT-on-silicon filters

This paper reports on the design of a 2-pole differential MEMS filter using mechanically-coupled overtone width-extensional resonators. The resonators and filters are fabricated in the 10 mum thick device layer of a SOI wafer and transduced by a 0.5 mum PZT (lead zirconate titanate) thin film deposited on the top surface of the wafer. A 206.3 MHz overtone width-extensional filter is demonstrated with 653 kHz bandwidth, -25 dB insertion loss (IL) and -62 dB stop-band rejection in air. Uncompensated temperature coefficient of frequency (TCF) of -16 ppm/degC and third-order input intercept point (IIP3) of +52.5 dBm are demonstrated by the filter. The piezoelectric response of the filter is controlled by varying the electric field across the PZT transducer. A 20 dB improvement in IL and 0.22% center frequency tuning resulted by applying 20 V DC tuning voltage.

Aqueous Transduction of Poly-Sige Disk Resonators

This paper demonstrates an electrostatic transducer for lateral contour-mode resonators in which the transduction gaps are filled with a liquid dielectric (water) having much higher permittivity than air ( kappawater = 80.1). Aqueous transduction is more efficient than air-gap transduction (lower motional impedance) and has a higher frequency tuning range compared than solid-dielectric transduction. We have demonstrated a 42 MHz poly-SiGe disk resonator with de-ionized (Dl) water confined to the electrode gaps. The resonator has a measured quality factor (Q) of 3,800, motional impedance (Rx) of 3.9 kOmega and 3% series frequency tuning range.

Reconfigurable Solid-state Dye-doped Polymer Ring Resonator Lasers

This paper presents wavelength configurable on-chip solid-state ring lasers fabricated by a single-mask standard lithography. The single- and coupled-ring resonator hosts were fabricated on a fused-silica wafer and filled with 3,3′-Diethyloxacarbocyanine iodide (CY3), Rhodamine 6G (R6G), and 3,3′-Diethylthiadicarbocyanine iodide (CY5)-doped polymer as the reconfigurable gain media. The recorded lasing threshold was ~220 nJ/mm2 per pulse for the single-ring resonator laser with R6G, marking the lowest threshold shown by solid-state dye-doped polymer lasers fabricated with a standard lithography process on a chip. A single-mode lasing from a coupled-ring resonator system with the lasing threshold of ~360 nJ/mm2 per pulse was also demonstrated through the Vernier effect. The renewability of the dye-doped polymer was examined by removing and redepositing the dye-doped polymer on the same resonator hosts for multiple cycles. We recorded consistent emissions from the devices for all trials, suggesting the feasibility of employing this technology for numerous photonic and biochemical sensing applications that entail for sustainable, reconfigurable, and low lasing threshold coherent light sources on a chip.