In an infrared photodetector, noise current (dark current) is generated throughout the volume of the detector. Reducing the volume will reduce dark current, but the corresponding smaller area will also reduce the received signal. By using a separate antenna to receive light, one can reduce the detector area without reducing the signal, thereby increasing its signal to noise ratio (SNR). Here, we present a dielectric resonator antenna (DRA) coupled infrared photodetector. Its performance is compared to a conventional resonant cavity enhanced slab detector. The Noise Equivalent Power (NEP) is used as a figure of merit for the comparison. Formulas for the NEP are derived for both cases. A pBp photodiode detector is assumed in the comparison. The active region of the photodiode is an InAs/GaSb Type II Superlattice (T2SL). A Genetic Algorithm is used to optimize the dimensions of the detector and the DRA to achieve the smallest NEP. The result is a photodetector that converts over 85% of the incident light into carriers with a volume reduced by 95%. This optimal geometry leads to a NEP reduced by 6.02dB over that of the conventional resonant cavity enhanced slab detector.
The authors report on observation of Bragg confined mode in a hollow cylindrical dielectric cavity. A resonance was observed at 13.4 $GHz$ with an unloaded Q-factor of order $2\times10^5$, which is more than a factor of 6 above the dielectric loss limit. Previously such modes have only been realized from pure Transverse Electric modes with no azimuthal variations and only the $E_ϕ$ component. From rigorous numeric simulations it is shown that the mode is a hybrid mode with non-zero azimuthal variations and with dominant $E_r$ and $E_ϕ$ electric field components and $H_z$ magnetic field compone…
A split post dielectric resonator in a copper enclosure and a single post dielectric resonator in a cavity with superconducting end-plates have been constructed and used for the complex permittivity measurements of single crystal substrates. (La,Sr)(Al,Ta)O3, LaAlO3, MgO and quartz substrates have been measured at temperatures from 20 K to 300 K in the split post resonator and from 15 K to 80 K in the single post resonator. The TE01delta mode resonant frequencies and unloaded Qo-factors of the empty resonators at temperature of 20 K were: 9.952 GHz and 25,000 for the split post resonator and 1…
We demonstrate that a proton irradiation with fluences of $3.6\times10^{10}$/cm$^{2}$ at low energy ($<$ 36 MeV) and $1.46 \times 10^{10}$/cm$^{2}$ at high energy (40 MeV and 90 MeV combined) on the dielectric mirrors of Fabry-Pérot cavities with a finesse of about 700 000 causes less than 5% change in the finesse. Furthermore, no influence on the coupling efficiency to the cavities was observed, the efficiency being approximately 70%. The irradiation was carried out with a spectrum approximating the proton energy spectrum of a highly elliptic Earth orbit with duration of 5 years, proposed for…
The basic theory underlying the realization of simple multiple-band non-homogeneous dielectric resonators, whose spectral response is the overlap of single-resonator frequency bands, is developed exploiting a general approach discussed in the previous companion paper. The limit frequencies of the proposed devices, given only by the dielectric properties of the involved materials, can differ in principle by several decades. Experimental confirmations have been obtained on a composite structure built up with teflon and polyethylene; as predicted by the theory, the overall band includes frequenci…
A comparative study of unloaded Q-factor measurements of a TE011 mode sapphire dielectric resonator with unloaded Q-factor value of 731,000 at a frequency of 10 GHz and temperature of 65 K using two best Q-factor measurement methods are presented. The Transmission (TMQF) and Reflection methods are based on relevant multi-frequency S-parameter measurements and circle fitting procedures to compute the unloaded Q-factor of the resonator. For accurate comparison of the methods a delay compensation procedure (introduced in the TMQF technique to remove delay due to non-calibrated cables) has been ap…
Several basic properties of homogeneous planar Whispering Gallery dielectric resonators are investigated through a general approach. In particular the values for the minimum and maximum allowed radius, defined by irradiation and dielectric losses, respectively, are obtained in terms of the complex dielectric constant of the involved media. The same approach is employed in the analysis of the limit allowed frequencies of a fixed family of mode, leading to the definition of the "ideal" frequency band. The role of the transverse mode is then discussed, and the "effective" frequency band is introd…
A Bragg resonator uses dielectric plates within a metallic cavity to confine the energy within a central free space region. The importance of the permittivity is shown with a better Q-factor possible using higher permittivity materials of larger intrinsic dielectric losses. This is because the electric energy in the reflectors decreases proportionally to the square root of permittivity and the coupling to the metallic losses decrease linearly. In a sapphire resonator with a single reflector pair a Q-factor of 2.34x10^5 is obtained, which may be improved on by up to a factor of 2 using higher p…
The loss tangent of medium, low and very low loss dielectric substrates (including the Rogers RT Duroid 5880 and 6010.2, LaAlO3, (La, Sr)(Al, Ta)O3, MgO and Quartz) was measured at varying temperatures with two TE01δ dielectric resonators to ensure verification of the tests. The accuracy of the measurements has been researched and discussed for split post dielectric resonator (SPDR) in a copper enclosure and a single post dielectric resonator (SuPDR) in a superconducting enclosure in the temperature range from 15K to 300 K.
We present frequency tuning mechanisms for dielectric resonators, which undergo "super-mode" interactions as they tune. The tunable schemes are based on dielectric materials strategically placed inside traditional cylindrical resonant cavities, necessarily operating in Transverse Magnetic modes for use in axion haloscopes. The first technique is based on multiple dielectric disks with radii smaller than that of the cavity. The second scheme relies on hollow dielectric cylinders similar to a Bragg resonator, but of different location and dimension. In particular we engineer a significant increa…
A theoretical model based on the transverse resonance method is proposed for the description of cylindrical multilayer dielectric resonator sensors. From this model, the resonant frequency and the sensitivities with respect to geometrical and physical parameters are computed by means of a combination of symbolic and numerical procedures. These are gathered together in a package in view of the computer assisted design of this range of sensors. On this occasion, a few design patterns for engineering applications are sketched.
Two nominally identical ultra-stable cryogenic microwave oscillators are compared. Each incorporates a dielectric-sapphire resonator cooled to near 6 K in an ultra-low vibration cryostat using a low-vibration pulse-tube cryocooler. The phase noise for a single oscillator is measured at -105 dBc/Hz at 1 Hz offset on the 11.2 GHz carrier. The oscillator fractional frequency stability is characterized in terms of Allan deviation by 5.3 x 10^-16 tau^-1/2 + 9 x 10^-17 for integration times 0.1 s < tau < 1000 s and is limited by a flicker frequency noise floor below 1 x 10^-16. This result is better…
We comment on a recently published paper, Phys. Rev. Applied 9, 014028 (2018), which presents frequency-tuning mechanisms for dielectric resonators and demonstrates their potential application to axion haloscopes. One of the schemes introduces a cylindrical dielectric hollow and splits it in the axial direction to tune the frequency. The authors claim that this scheme offers a 1 to 2-order-of-magnitude improvement in axion search sensitivity in exploiting a higher-order resonant mode. We find that their study is based on unrealistic cavity modeling and inappropriate choice of the figure of mer…
The frequency band 1-15 GHz provides exciting prospects for resonant axion haloscopes as indicated by cosmological and astrophysical arguments. Among the challenges currently addressed to reach the required sensitivity, the development of high quality factor cavities that tolerate multi-Tesla fields plays a central role. We report a 3D resonator based on a right circular copper cavity with hollow cylinders that confine higher order modes around the cylinder axis. Its effective volume at 10.3\,GHz is $3.4 \cdot 10^{-2}$ liters, and under an 8\,T-field we measured an internal quality factor of m…
We describe the design of a low-phase-modulated (PM) noise, 40 GHz oscillator that uses a conventional air-dielectric cavity resonator as a frequency discriminator to improve the PM noise of a commercial 10 GHz dielectric resonator oscillator (DRO) frequency multiplied by four. The main features of this design incorporate (1) unloaded cavity quality factor (Q) of 30,000, (2) high coupling coefficient, (3) large carrier suppression by use of interferometric signal processing, (4) large operating signal power of approximately 1 watt (W), and (5) relatively small size. In addition, we report the …
The realization and characterization of a high quality factor resonator composed of two hollow-dielectric cylinders with its pseudo-TM$_{030}$ mode resonating at 10.9 GHz frequency is discussed. The quality factor was measured at the temperatures 300 K and 4 K obtaining $\mbox{Q}_{300\mbox{K}}=(150,000\pm 2,000)$ and $\mbox{Q}_{4\mbox{K}}=(720,000\pm 10,000)$respectively, the latter corresponding to a gain of one order of magnitude with respect to a traditional copper cylindrical-cavity with the corresponding TM$_{010}$ mode resonating at the same frequency. The implications to dark-matter axi…
Axions are a popular dark matter candidate which are often searched for in experiments known as ``haloscopes" which exploit a putative axion-photon coupling. These experiments typically rely on Transverse Magnetic (TM) modes in resonant cavities to capture and detect photons generated via axion conversion. We present a study of a resonant cavity design for application in haloscope searches, of particular use in the push to higher mass axion searches (above $\sim$60$\,μ$eV). In particular, we take advantage of azimuthally varying TM$_{m10}$ modes which, whilst typically insensitive to axions du…
The concept of nonradiative dielectric resonator is generalized in order to include axially open configurations having rotational invariance. The resulting additional nonradiative conditions are established for the different resonance modes on the basis of their azimuthal modal index. An approximate chart of the allowed dielectric and geometrical parameters for the TE011 mode is given. A practical realization of the proposed device based on commercial fused quartz tubes is demonstrated at millimeter wavelengths, together with simple excitation and tuning mechanisms. The observed resonances are…
The nonlinear surface resistance Rs of the YBa2Cu3O7-x superconducting thin films on the MgO substrates was researched in the Hakki-Coleman dielectric resonator at the microwave signal powers from -18 dBm to +30 dBm at the ultra high frequency of 25 GHz in the range of temperatures from 12 K to 85 K. The dependences of the surface resistance on the temperature RS(T) in the YBa2Cu3O7-x superconducting thin films at the microwaves were measured. The dependence of the surface resistance on the microwave power RS(P) in the YBa2Cu3O7-x superconducting thin films at the microwaves were found at the …
