We present the first results from a rotating Michelson-Morley experiment that uses two orthogonally orientated cryogenic sapphire resonator oscillators operating in whispering gallery modes near 10 ...GHz. The experiment is used to test for violations of Lorentz invariance in the framework of the photon sector of the standard model extension (SME), as well as the isotropy term of the Robertson-Mansouri-Sexl (RMS) framework. In the SME we set a new bound on the previously unmeasured kappa(ZZ)(e-) component of 2.1(5.7) x 10(-14), and set more stringent bounds by up to a factor of 7 on seven other components. In the RMS a more stringent bound of -0.9(2.0) x 10(-10) on the isotropy parameter, P(MM) = delta-beta + 1 / 2 is set, which is more than a factor of 7 improvement.
A report is presented on the improvement by an optimised hexagonal metallic cavity of the electromagnetic field confinement in a hollow-core resonator based on out-of-plane two-dimensional photonic ...band-gap crystal cladding. A resonator was constructed with silica rods to prove the concept at frequencies around 30 GHz. It is shown that the technique can reduce the resonator size by 8.1 times without loss in quality.
A Fabry-Perot resonator operating at 39 GHz, with two pairs of quarter-wavelength single-crystal quartz Bragg reflectors has been realized. For the length of 98.26 mm, its Q-factor is about 560000, ...which is 4.3 times better than for the same resonator without Bragg reflectors. Rigorous finite-difference frequency-domain analysis has been applied to the problem and is compared with simplified semi-analytical solutions. Good agreement between theoretical and experimental resonant frequency arid Q-factors has been obtained. Thermal compensation of the resonant frequency of the Fabry-Perot has been proposed employing rods and cylinders made of metals with different thermal expansion coefficients.
The Bragg reflection technique improves the Q-factor of a resonator by reducing conductor and dielectric losses. This is achieved by designing a low-loss inner resonant region (usually free space) ...surrounded by an outer anti-resonant region made of distributed Bragg reflector layers. In this paper we develop a simple non-Maxwellian model and apply it to design three distinct cylindrical Bragg resonators based on the same set of single-crystal sapphire plates and rings by changing only the dimension of the cavity that supports the structure. To accomplish this, the simple model allows an arbitrary thickness for either the horizontal or the cylindrical dielectric reflectors by relaxing the condition that they must be lambda4 thick. The model also allows for higher-order field variations in both the resonant and the anti-resonant regions. The resonators were constructed and experimental results were compared with the simple model and the rigorous method of lines analysis. For the fundamental mode, an unloaded Q-factor of 234,000 at 9.7 GHz was obtained. This is larger than that for a whispering gallery mode resonator. The resonator also exhibited a greatly reduced spurious mode density when compared to an overmoded whispering gallery mode resonator.
Cryogenic sapphire oscillators (CSO) developed at the University of Western Australia (UWA) have now been in operation around the world continuously for many years. Such oscillators, due to their ...excellent spectral purity are essential for interrogating atomic frequency standards at the limit of quantum projection noise; otherwise aliasing effects will dominate the frequency stability due to the periodic sampling between successive interrogations of the atomic transition. Other applications, which have attracted attention in recent years, include tests on fundamental principles of physics, such as tests of Lorentz invariance. This paper reports on the long-term operation and performance of such oscillators. We compare the long-term drift of some different CSOs. The drift rates turn out to be linear over many years and in the same direction. However, the magnitude seems to vary by more than one order of magnitude between the oscillators, ranging from 10 14 per day to a few parts in 10 13 per day
We investigate reentrant and dielectric loaded cavities for the purpose of extending the range of axion cavity haloscopes to lower masses, below the range where the Axion Dark Matter experiment ...(ADMX) has already searched. Reentrant and dielectric loaded cavities were simulated numerically to calculate and optimize their form factors and quality factors. A prototype reentrant cavity was built and its measured properties were compared with the simulations. We estimate the sensitivity of axion dark matter searches using reentrant and dielectric loaded cavities inserted in the existing ADMX magnet at the University of Washington and a large magnet being installed at Fermilab.
Phase-noise spectral density of a 9-GHz oscillator has been reduced to -160 dBc/Hz at 1-kHz offset frequency, which is the lowest phase noise ever measured at microwave frequencies. This performance ...was achieved by frequency locking a conventional loop oscillator to a high-Q sapphire dielectric resonator operating at the elevated level of dissipated power (~0.4 W). Principles of interferometric microwave signal processing were applied to generate the error signal for the frequency control loop. No cryogenics were used. Two almost identical oscillators were constructed to perform classical two-oscillator phase-noise measurements where one oscillator was phase locked to another. The phase locking was implemented by electronically controlling the level of microwave power dissipated in the sapphire dielectric resonator
We propose and analyze a quantum electromechanical system composed of a monolithic quartz bulk acoustic wave oscillator coupled to a superconducting transmon qubit via an intermediate LC electrical ...circuit. Monolithic quartz oscillators offer unprecedentedly high effective masses and quality factors for the investigation of mechanical oscillators in the quantum regime. Ground-state cooling of such mechanical modes via resonant piezoelectric coupling to an LC circuit, which is itself sideband cooled via coupling to a transmon qubit, is shown to be feasible. The fluorescence spectrum of the qubit, containing motional sideband contributions due to the couplings to the oscillator modes, is obtained and the imprint of the electromechanical steady state on the spectrum is determined. This allows the qubit to function both as a cooling resource for, and transducer of, the mechanical oscillator. The results described are relevant to any hybrid quantum system composed of a qubit coupled to two (coupled or uncoupled) thermal oscillator modes.
A concept of interferometric measurements has been applied to the development of ultra-sensitive microwave noise measurement systems. These systems are capable of reaching a noise performance limited ...only by the thermal fluctuations in their lossy components. The noise floor of a real time microwave measurement system has been measured to be equal to -193 dBc/Hz at Fourier frequencies above 1 kHz. This performance is 40 dB better than that of conventional systems and has allowed the first experimental evidence of the intrinsic phase fluctuations in microwave isolators and circulators. Microwave frequency discriminators with interferometric signal processing have proved to be extremely effective for measuring and cancelling the phase noise in oscillators. This technique has allowed the design of X-band microwave oscillators with a phase noise spectral density of order -150 dBc/Hz at 1 kHz Fourier frequency, without the use of cryogenics. Another possible application of the interferometric noise measurements systems include "flicker noise-free" microwave amplifiers and advanced two oscillator noise measurement systems.
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