High efficiency radio frequency antennas for amplifier free quantum sensing applications

At a Glance

Metadata	Details
Publication Date	2023-04-01
Journal	Review of Scientific Instruments
Authors	S. S. Mahtab, Peker Milas, D. Tim Veal, Michael G. Spencer, Birol Ozturk
Institutions	Cornell University, Morgan State University
Citations	3
Analysis	Full AI Review Included

Executive Summary

Core Achievement: Developed high-efficiency single and double ring coplanar Radio Frequency (RF) antennas specifically optimized for amplifier-free quantum sensing applications.
Efficiency Metric: Achieved exceptional experimental return loss (S11) up to -37 dB at the target frequency of 2.87 GHz (the zero-field splitting frequency of Nitrogen Vacancy (NV) defects in diamond).
System Simplification: The high efficiency eliminates the need for an external RF amplifier; ODMR experiments were successfully run using only the 0 dB output of a standard RF signal generator.
Magnetic Field Generation: Antennas generate a large-area, uniform magnetic field, with simulated maximum intensities reaching 155.7 A/m for the double ring design.
Tunability Demonstrated: Resonant frequency tuning was achieved by adjusting the antenna ring size, enabling adaptation for quantum sensing platforms based on other defects (e.g., Silicon Carbide or Cubic Boron Nitride).
Fabrication: Antennas were fabricated using standard photolithography on low-loss, high-performance PCB substrates (Isola IS-680-280 and Rogers 4003).
Impact: This work is a crucial step toward the miniaturization and realization of field-portable quantum magnetometers.

Technical Specifications

Parameter	Value	Unit	Context
Maximum Experimental Return Loss (S11)	-37	dB	Single and Double Ring Antennas
Operating Frequency (NV ZFS)	2.87	GHz	Negatively charged NV defect
Required RF Input Power	0	dBm	Amplifier-free ODMR operation
ODMR Contrast Observed	~1	%	With 0 dBm input power
Applied External Magnetic Field	0.5	mT	Used for ODMR splitting measurements
Isola IS-680-280 Dielectric Constant (ε_r)	2.80	N/A	Substrate material
Rogers 4003 Dielectric Constant (ε_r)	3.38	N/A	Substrate material
Rogers 4003 Thickness	0.508	mm	Substrate thickness
Copper Cladding Thickness	0.035	mm	All substrates
Single Ring Antenna Area (L x W)	38 x 40	mm²	Isola substrate
Double Ring Antenna Area (L x W)	38 x 40	mm²	Rogers substrate
Maximum Simulated H-Field (Double Ring)	155.7	A/m	Between ring and ground plane
Frequency Shift (Single Ring, +1 mm size)	2.72	GHz	Demonstrating tunability
Frequency Shift (Single Ring, -1 mm size)	3.01	GHz	Demonstrating tunability

Key Methodologies

Design and Simulation: Coplanar single and double split ring antennas were designed and optimized using Ansys HFSS software, targeting the 2.87 GHz NV zero-field splitting frequency.
Substrate Selection: Low-loss tangent substrates were chosen: Isola IS-680-280 (ε_r=2.80) and Rogers 4003 (ε_r=3.38), both featuring 0.035 mm thick copper cladding.
Photolithography: High-resolution masks (25000 DPI) were prepared. Substrates were spin-coated with positive photoresist (Microposit S1813 G2) at 3000 RPM.
Etching and Cleaning: Patterns were transferred using a custom UV-exposure setup. Copper was etched using Ferric Chloride (FeCl₃) solution, and remaining photoresist was stripped with acetone.
RF Integration: Coaxial female SMA connectors were soldered to the fabricated PCB antennas for signal input.
RF Characterization: Return loss (S11) measurements were performed using a Vector Network Analyzer (LiteVNA) to confirm high efficiency and resonant frequency.
Quantum Sensing Setup: A bulk diamond sample (Element Six DNV-B14) was placed on the antenna in the region of maximum simulated magnetic field intensity.
ODMR Measurement: A custom confocal photoluminescence setup was used with a 532 nm DPSS laser. Microwaves were supplied by a high-pressure (HP) Agilent 8648C RF signal generator at 0 dB output power (amplifier-free operation).
Data Processing: Expectation-Maximization (E-M) based machine learning algorithms were employed to minimize instrumental noise and precisely determine ODMR spectra, enabling detection of signal changes less than 0.1%.

Commercial Applications

Field-Portable Quantum Magnetometry: The primary application is enabling the miniaturization of NV diamond magnetometers by eliminating the bulky and power-intensive RF amplifier component.
Solid-State Defect Sensing: Applicable to quantum sensing experiments utilizing other solid-state defects in wide bandgap semiconductors, including Silicon Carbide (SiC) and Cubic Boron Nitride (cBN), due to demonstrated frequency tunability.
Low-Power RF Systems: The high-efficiency, low-loss antenna design is suitable for integrated circuits requiring minimal power consumption for microwave delivery.
Integrated PCB Quantum Devices: The coplanar design facilitates seamless integration onto a single Printed Circuit Board (PCB) alongside control electronics, reducing system complexity and size.
High-Frequency Wireless Communications: The design principles (coplanar split rings on low-loss substrates) are relevant for high-efficiency antennas used in standards like WLAN (2.4/5.2/5.8 GHz) and WiMAX.

View Original Abstract

Radio frequency (RF) signals are frequently used in emerging quantum applications due to their spin state manipulation capability. Efficient coupling of RF signals into a particular quantum system requires the utilization of carefully designed and fabricated antennas. Nitrogen vacancy (NV) defects in diamond are commonly utilized platforms in quantum sensing experiments with the optically detected magnetic resonance (ODMR) method, where an RF antenna is an essential element. We report on the design and fabrication of high efficiency coplanar RF antennas for quantum sensing applications. Single and double ring coplanar RF antennas were designed with −37 dB experimental return loss at 2.87 GHz, the zero-field splitting frequency of the negatively charged NV defect in diamond. The efficiency of both antennas was demonstrated in magnetic field sensing experiments with NV color centers in diamond. An RF amplifier was not needed, and the 0 dB output of a standard RF signal generator was adequate to run the ODMR experiments due to the high efficiency of the RF antennas.

Tech Support

Original Source

DOI: https://doi.org/10.1063/5.0136233

References

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