Session N30: Microwave and Optical Physics Applications in Telecommunications

Unique Polarization Switching of Wurtzite Ferroelectrics

Wurtzite (Al,Sc)N bas been utilized as microwave resonator and filter devices in telecommunications due to its large electromechanical coupling. The recent discovery of ferroelectricity in (Al,Sc)N films provides opportunities for device applications such as tunable filters and non-volatile memories. In this talk, I will present unique polarization reorientation behaviors of the wurtzite ferroelectric material: (1) strain insensitivity to the switching energy barrier and coercive field based on Landau-Devonshire thermodynamic analysis and experimental demonstration, and (2) anomalously abrupt kinetics in ferroelectric switching. We discovered the local chemical bonding environment and non-linear nucleation/domain growth competition in the switching process are key for the unique behaviors in wurtzite ferroelectrics. A developed model incorporating the nucleation – growth competition enables rational description of the anomaly in the observed switching kinetics. Those fundamental understandings on lattice dynamics in wurtzite ferroelectric materials provide insights on improving electromechanical coupling and controlling domain structure, which lead new device applications.   

Electro-Optic Millimeter-Wave Sources and Receivers for THz Electronics

Emerging applications in the millimeter-wave (mmWave) bands for 6G and beyond require new source and receiver instruments for high-frequency circuit characterization. Synthesizing and measuring arbitrary waveforms for characterizing circuits’ time-domain, nonlinear harmonic, and intermodulation responses is especially important for optimizing energy efficiency and stability. Today’s digital-to-analog and analog-to-digital converters lack the bandwidth, precision, and programmability needed for new mmWave integrated circuits. Here, we study applications of optical frequency combs, photodiodes, and electro-optic materials to synthesis and network analysis on-wafer of mmWave arbitrary waveforms with >100 GHz instantaneous bandwidth.

To synthesize arbitrary waveforms, we generate an electro-optic frequency comb, apply fine amplitude and phase control to pairs of comb lines (beat notes), and demultiplex the beat notes to uni-traveling carrier photodiodes. We apply this to arbitrary waveform generation with 100 GHz of instantaneous bandwidth on a single photodiode. By connecting several photodiodes on-wafer to a frequency combiner covering DC to 1 THz, we will enable much greater amplitude and bandwidth.

To explore network analysis on-wafer, we demonstrate an electro-optic imaging system for measuring millimeter-wave propagation along a coplanar waveguide (CPW). A custom polarization-resolved microscope images small electro-optic effects due to millimeter-wave voltages between the signal and ground of the CPW. By sampling multiple positions along the CPW, the amplitude and phase of all tones (up to 500 GHz in the first experiment) at multiple mmWave reference planes can be measured simultaneously, revealing forward and backward traveling waves. Dual electro-optic frequency combs demonstrate time-domain waveform imaging on-wafer with >100 GHz of bandwidth. A second configuration demonstrates continuous wave electro-optic vector network analysis with 70 measurement planes on-wafer.

With electro-optic synthesis and network analysis, we will measure new electronics such as NIST’s ultrawideband comb generators and mixers, making use of instantaneous bandwidth and time-domain capabilities that cannot be achieved otherwise.   

Micromachined YIG Resonators

In this talk I will present micromachining technology for fabricating thin-film YIG resonators and filters on a chip. Specifically, I will discuss how we incorporated standard MEMS etching technology [1] and microwave back-end-of-line (BEOL) metallization techniques [2] to demonstrate high quality-factor (Q) octave-tunable YIG resonators [3]. I will showcase the capability of our YIG technology platform by demonstrating notch [4] and band-pass filters [5,6] for frequency-agile radio communication systems.

 

This work is a close collaboration between the OxideMEMS Lab at Purdue University and Dr. Renyuan (Ryan) Wang’s team at BAE Fast Labs.

[1] Renyuan Wang, Sunil A. Bhave and Kushal Bhattacharjee, "Design and fabrication of S0 Lamb wave thin-film Lithium Niobate micromechanical resonators," IEEE Journal of Microelectromechanical Systems 24(2) 300-308 (2015).

[2] Jeff Pulskamp, Daniel Judy, Roger Kaul, Ronald Polcawich, Hengky Chandrahalim and Sunil A. Bhave, "Monolithically integrated piezo-MEMS SP2T switch and contour-mode filters," 22nd IEEE International Conference on Micro Electro Mechanical Systems (MEMS 2009), Sorrento, Italy, January 25-29, 2009, pp. 900-903.

[3] Sen Dai, Sunil A. Bhave and Renyuan Wang, "Octave tunable magnetostatic YIG resonators on a chip," IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 67(11) 2454-2460 (2020).

[4] Yiyang Feng, Sudhanshu Tiwari, Sunil A. Bhave, and Renyuan Wang, "Micro-machined Tunable Magnetostatic Forward Volume Wave Bandstop Filter," IEEE Microwave and Wireless Technology Letters 33(6), 807-810 (2023).

[5] Connor Dewitt, Renyuan Wang, Sudhanshu Tiwari, and Sunil A. Bhave, "An edge-coupled magnetostatic bandpass filter," arxiv:2312.10583.

[6] Connor Dewitt, Sudhanshu Tiwari, Sunil A. Bhave and Renyuan Wang, "A distributed magnetostatic resonator," arxiv:2401.08911.   

Periodically Poled Aluminum Scandium Nitride Bulk Acoustic Wave Resonators for Communications in the 6G Era

Abstract – Bulk Acoustic Wave (BAW) filter technologies find application in radio frequency (RF) communication systems for Wi-Fi, 3G, 4G, and 5G applications. In the beyond-5G (potential 6G) era, high frequency bands (>8 GHz) are expected to require resonators with high quality factor (Q) and electromechanical coupling (), once RF spectrum use in these bands increases. However, both Q and of traditional piezoelectric film based resonators, such as aluminum nitride (AlN) and aluminum scandium nitride (AlScN), decreases when scaled to high frequency (>8 GHz) while maintaining its impedance. In this talk, we present high frequency (~18 GHz) resonators constructed from AlScN periodically poled piezoelectric films (P3F) that achieve high quality factors and electromechanical coupling to show its potential for emerging RF communications in the beyond-5G era.   

Emergent tunability in polar vortices

Superlattice films of layers of PbTiO 3 and SrTiO3 form polar vortices under the right lattice periodicity conditions. Low frequency and terahertz experiments observed both negative permittivity and interesting collective dynamics that could lead to other emergent behavior. Gigahertz complex permittivity data could provide a new insight into polar vortices dynamics and how emergent behavior develops with periodicity, but the measurements present challenges given the anisotropic nature of these complex thin films. Here, we tested a new metrology that uses coplanar waveguides designed to be sensitive to different components of the complex permittivity tensor. We tested 12 different 100 nm thick films with periodicities with and without a SrRuO 3 bottom electrode to understand how dispersion and tunability emerge with the formation of polar vortices. Taken together, these results provide new insights into the high frequency dynamics of polar vortices and how they may lead to new devices. After summarizing this work, we will discuss other ongoing research activities at the National Institute of Standards and Technology (NIST) including several new projects funded to support the CHIPS Act (Creating Helpful Incentives to Produce Semiconductors).