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Digest of technical papers/Digest of technical papers - IEEE International Solid-State Circuits Conference

A unilateral three-level maser employing a ruby-loaded comb-type structure

R. W. De Grasse, E. O. Schulz-DuBois, H. E. D. Scovil

Published Jan 1, 1959• 0 citations
Publisher

Abstract

BROADBAND VERY-LOW-NOISE microwave amplification has been obtained in a propagating microwave structure by using the emissive property of a three-level solid state maser material. Previous maser amplifiers have employed standing-wave cavity-type microwave structures for coupling to the emissive material.3 Such cavity-type maser amplifiers are limited in bandwidth and gain by the microwave cavity circuit. The bandwidth is limited by regenerative effects in the cavity and the gain is limited by the stringent requirements placed upon the input match and the circulator.

DOI
10.1109/isscc.1959.1157052

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BROADBAND VERY-LOW-NOISE microwave amplification has been obtained in a propagating microwave structure by using the emissive property of a three-level solid state maser material. Previous maser amplifiers have employed standing-wave cavity-type microwave structures for coupling to the emissive material.3 Such cavity-type maser amplifiers are limited in bandwidth and gain by the microwave cavity circuit. The bandwidth is limited by regenerative effects in the cavity and the gain is limited by the stringent requirements placed upon the input match and the circulator.
Masers once represented the state of the art in low-noise microwave amplification technology but eventually became obsolete due to their need for cryogenic cooling. Masers based on solid-state spin systems perform most effectively as amplifiers, since they provide a large density of spins and can, therefore, operate at relatively high powers. While solid-state maser oscillators have been demonstrated at room temperature, continuous-wave amplification in these systems has only ever been realized at cryogenic temperatures. Here, we report on a continuous-wave solid-state maser amplifier operating at room temperature. We achieve this feat using a practical setup that includes an ensemble of nitrogen-vacancy center spins in a diamond crystal, a strong permanent magnet, and a simple laser diode. We describe important amplifier characteristics including gain, bandwidth, compression power, and noise temperature and discuss the prospects of realizing a room-temperature near-quantum-noise-limited amplifier with this system. Finally, we show that in a different mode of operation the spins can be used to reduce the microwave noise in an external circuit to cryogenic levels, all without the requirement for physical cooling. Published by the American Physical Society 2024
Advances in microwave quantum technologies increasingly demand amplifiers that are capable of boosting extremely weak signals with minimal added noise at millikelvin temperatures. To date, this requirement has been met almost exclusively by superconducting devices such as Josephson- and kinetic-inductance-based parametric amplifiers. Masers—the microwave counterparts of lasers—were predicted in the 1950s to achieve quantum-limited noise performance. However, their development later declined because their operation required low temperatures, making them difficult to deploy widely. In this thesis, I demonstrate a diamond spin maser amplifier operating at millikelvin temperatures, marking the first non-superconducting amplifier approaching the quantumnoise limit. The device employs substitutional nitrogen spins (P1 centers) in diamond, where population inversion is achieved through active microwave pumping via a four-spin crossrelaxation mechanism, assisted by fast-relaxing spins within the same crystal. The amplifier exhibits a maximum power gain exceeding 30 dB, a gain-bandwidth product of 2.8 MHz, and an output 1-dB compression point of −65 dBm (at a gain of 20 dB), measured at 6.595 GHz. The noise performance of the maser amplifier is quantitatively characterized using an impedance-matched, temperature-variable noise source integrated into a dilution refrigerator. This approach enables a direct and reliable determination of the input-referred added noise, revealing a minimum noise of approximately 3 quanta. Furthermore, a semi-classical rateequation model is developed to describe the coupled spin–photon dynamics and to provide insight into the gain behavior and population inversion process. By revisiting masers in the millikelvin regime, this work highlights their potential as a solid-state platform for low-noise microwave amplification with high compression power applicable to quantum computing, magnetic resonance spectroscopy, and fundamental physics.
This research investigates the realization of parametric amplification in superconducting circuits and structures where nonlinearity is provided by Josephson junction (JJ) elements. We aim to develop a systematic analysis over JJ-based devices toward design of novel traveling-wave Josephson parametric amplifiers (TW-JPA). Chapters of this thesis fall into three categories: lumped JPA, superconducting periodic structures and discrete Josephson transmission lines (DJTL). \nThe unbiased Josephson junction (JJ) is a nonlinear element suitable for parametric amplification through a four-photon process. Two circuit topologies are introduced to capture the unique property of the JJ in order to efficiently mix signal, pump and idler signals for the purpose of signal amplification. Closed-form expressions are derived for gain characteristics, bandwidth determination, noise properties and impedance for this kind of parametric power amplifier. The concept of negative resistance in the gain formulation is observed. A design process is also introduced to find the regimes of operation for gain achievement. Two regimes of operation, oscillation and amplification, are highlighted and distinguished in the result section. Optimization of the circuits to enhance the bandwidth is also carried out. \nMoving toward TW-JPA, the second part is devoted to modelling the linear wave propagation in a periodic superconducting structure. We derive closed-form equations for dispersion and s-parameters of infinite and finite periodic structures, respectively. Band gap formation is highlighted and its potential applications in the design of passive filters and resonators are discussed. The superconducting structures are fabricated using YBCO and measured, illustrating a good correlation with the numerical results. \nA novel superconducting Transmission Line (TL), which is periodically loaded by Josephson junctions (JJ) and assisted by open stubs, is proposed as a platform to realize a traveling-wave parametric device. Using the TL model, this structure is modeled by a system of nonlinear partial differential equations (PDE) with a driving source and mixed-boundary conditions at the input and output terminals, respectively. This model successfully emulates parametric and nonlinear microwave propagation when long-wave approximation is applicable. The influence of dispersion to sustain three non-degenerate phased-locked waves through the TL is highlighted. \nA rigorous and robust Finite Difference Time Domain (FDTD) solver based on the explicit Lax-Wendroff and implicit Crank-Nicolson schemes has been developed to investigate the device responses under various excitations. Linearization of the wave equation, under small-amplitude assumption, dispersion and impedance analysis is performed to explore more aspects of the device for the purpose of efficient design of a traveling-wave parametric amplifier. \nKnowing all microwave characteristics and identifying different regimes of operation, which include impedance properties, cut-off propagation, dispersive behaviour and shock-wave formation, we exploit perturbation theory accompanied by the method of multiple scale to derive the three nonlinear coupled amplitude equations to describe the parametric interaction. A graphical technique is suggested to find three waves on the dispersion diagram satisfying the phase-matching conditions. Both cases of perfect phase-matching and slight mismatching are addressed in this work. The incorporation of two numerical techniques, spectral method in space and multistep Adams-Bashforth in time domain, is employed to monitor the unilateral gain, superior stability and bandwidth of this structure. Two types of functionality, mixing and amplification, with their requirements are described. These properties make this structure desirable for applications ranging from superconducting optoelectronics to dispersive readout of superconducting qubits where high sensitivity and ultra-low noise operation is required.