Dr. Boon Kok Tan

Abstract:

The well-established technology of the superconducting quantum parametric amplifier (SPA) can be reconfigured to perform functions beyond amplification, such as frequency multiplication, by utilising the low-noise, low-loss superconducting nonlinear transmission line. This versatile technology holds potential for various applications, including ‘pumping’ a millimetre (mm) or sub-mm wave heterodyne mixer or driving a high-frequency SPA. Its significance lies in the ability to incorporate a high-purity signal source into the cryogenic stage alongside the primary detector, thereby eliminating noise associated with room temperature sources. Additionally, there is potential for on-chip integration with the detector circuit, leading to a more compact architecture.
This manuscript details the design of a travelling-wave parametric multiplier (TWPaM) that exploits the nonlinear wave-mixing mechanism to enhance the third harmonic growth from a strong pump tone injected into the travelling wave parametric amplifier (TWPA)-like device. While this functionality has been demonstrated previously, it exhibited narrowband performance. In this manuscript, we present our approach to designing a dispersion engineering scheme that enables the generation of broadband tunable tripler tones with high conversion efficiency. We showcase our design methodology using a niobium titanium nitride (NbTiN) high-gap thin-film transmission line as an example. Our presentation includes the theoretical model governing the physics of higher harmonics generation, emphasising phase-matching conditions that allow for broadband operation while suppressing unwanted modes. Although the ultimate aim is to develop a mm/sub-mm TWPaM, we aim to demonstrate the feasibility of their operation with a scaled microwave design in this manuscript. We will show that we can theoretically achieve close to 35% conversion efficiency across approximately 60% operational bandwidth.

Abstract:

In pursuit of advancing large array receiver capabilities and enhancing the 16-element Heterodyne Array Receiver Program (HARP) instrument on the James Clerk Maxwell Telescope (JCMT), we have successfully fabricated 230 GHz finline superconductor-insulator-superconductor (SIS) mixers. These mixers are critical for assessing the potential and prospective for the HARP instrument’s upgrade. Unlike the existing HARP’s mixer, we replace the probe antenna with an end-fire unilateral finline as the waveguide to planar circuit transition. This mixer design is expected to operate from about 160–260 GHz (approximately 47% bandwidth), and the mixer chips’ current-voltage (I-V) curves have been characterized, showing promising results with a quality factor (Rsg/Rn) exceeding 9.3. Evaluation of the double-sideband (DSB) receiver noise temperature (Trx) is currently underway. Once successfully characterised, our immediate aim is to scale the mixer to operate at HARP’s frequency range near 345 GHz to achieve similar broad RF bandwidth performance. Ongoing simulations are currently being conducted for the design of the 345 GHz finline mixer. This work marks a crucial step toward enhancing HARP receiver performance with better sensitivity and wider Intermediate Frequency (IF) bandwidth, enabling higher-frequency observations, and expanding the scientific potential of the JCMT and its collaborative partners.

Abstract:

The development of superconducting travelling-wave parametric amplifiers (TWPAs) over the past decade has highlighted their potential as low-noise amplifiers for use in fundamental physics experiments and industrial applications. However, practical challenges, including signal-idler contamination, complex pump injection and cancellation, impedance mismatch, and the reciprocal nature of the device, have made it challenging to deploy TWPAs in real-world applications. In this paper, we introduce an innovative solution to these issues through phase-controlled balanced-TWPA architectures. These architectures involve placing two TWPAs in parallel between a pair of broadband couplers. By carefully controlling the phases of the tones propagating along the TWPAs, we can effectively separate the signal and idler tones, as well as the pump(s), using a straightforward injection and cancellation mechanism. The balanced-TWPA architecture offers versatility and flexibility, as it can be reconfigured either intrinsically or externally to suit different application needs. In this manuscript, we provide a comprehensive discussion of the working principles of the balanced-TWPA, including various configurations designed to meet diverse application requirements. We also present the expected gain-bandwidth products in comparison to traditional TWPAs and conduct tolerance analysis to demonstrate the feasibility and advantages of the balanced-TWPA architecture. By addressing the practical challenges associated with TWPAs, the balanced-TWPA architecture represents a promising advancement in the field, offering a more practical and adaptable solution for a wide range of applications.

Abstract:

Traveling wave parametric amplifiers (TWPAs) offer the most promising solution for high gain, broadband, and quantum noise limited amplification at microwave frequencies. Experimental realization of TWPAs has proved challenging with often major discrepancies between the theoretically predicted and the measured gain performance of the devices. Here, we extend the conventional modeling techniques to account for spatial variation in the surface impedance of the thin film and the parametric sum-frequency conversions effect, which subsequently results in accurate reproduction of experimental device behavior. We further show that such an analysis may be critical to ensure fabricated TWPAs can operate as designed.