Microwave cavity light shining through a wall optimization and experiment

It has been proposed that microwave cavities can be used in a photon regeneration experiment to search for hidden sector photons. Using two isolated cavities, the presence of hidden sector photons could be inferred from a 'light shining through a wall' phenomenon. The sensitivity of the experiment has strong a dependence on the geometric construction and electromagnetic mode properties of the two cavities. In this paper we perform an in depth investigation to determine the optimal setup for such an experiment. We also describe the results of our first microwave cavity experiment to search for hidden sector photons. The experiment consisted of two cylindrical copper cavities stacked axially inside a single vacuum chamber. At a hidden sector photon mass of 37.78 micro eV we place an upper limit on the kinetic mixing parameter chi = 2.9 * 10^(-5). Whilst this result lies within already established limits our experiment validates the microwave cavity `light shining through a wall' concept. We also show that the experiment has great scope for improvement, potentially able to reduce the current upper limit on the mixing parameter chi by several orders of magnitude.Comment: To be published in PR

Microwave cavity hidden sector photon threshold crossing

Hidden sector photons are a weakly interacting slim particle arising from an additional U(1) gauge symmetry predicted by many standard model extensions. We present and demonstrate a new experimental method using a single microwave cavity to search for hidden sector photons. Only photons with a great enough energy are able to oscillate into hidden sector photons of a particular mass. If our cavity is driven on resonance and tuned over the corresponding threshold frequency, there is an observable drop in the circulating power signifying the creation of hidden sector photons. This approach avoids the problems of microwave leakage and frequency matching inherent in photon regeneration techniques

Lithographyically defined, room temperature low threshold subwavelength red-emitting hybrid plasmonic lasers

Hybrid plasmonic lasers provide deep subwavelength optical confinement, strongly enhanced light-matter interaction and together with nanoscale footprint promise new applications in optical communication, bio-sensing and photolithography. The subwavelength hybrid plasmonic lasers reported so far often use bottom up grown nanowires, nanorods and nanosquares, making it difficult to integrate these devices into industry-relevant high density plasmonic circuits. Here, we report the first experimental demonstration of AlGaInP based, red-emitting hybrid plasmonic lasers at room temperature using lithography based fabrication processes. Resonant cavities with deep subwavelength 2D and 3D mode confinement of lambda square/56 and lambda cube/199, respectively are demonstrated. A range of cavity geometries (waveguides, rings, squares and disks) show very low lasing thresholds of 0.6-1.8 mJ/cm square with wide gain bandwidth (610 nm-685 nm), which are attributed to the heterogeneous geometry of the gain material, the optimized etching technique, and the strong overlap of the gain material with the plasmonic modes. Most importantly, we establish the connection between mode confinements and enhanced absorption and stimulated emission, which play a critical role in maintaining low lasing thresholds at extremely small hybrid plasmonic cavities. Our results pave the way for the further integration of dense arrays of hybrid plasmonic lasers with optical and electronic technology platforms.Comment: 20 page

Resonant Regeneration in the Sub-Quantum Regime -- A demonstration of fractional quantum interference

Light shining through wall experiments (in the optical as well as in the microwave regime) are a powerful tool to search for light particles coupled very weakly to photons such as axions or extra hidden sector photons. Resonant regeneration, where a resonant cavity is employed to enhance the regeneration rate of photons, is one of the most promising techniques to improve the sensitivity of the next generation of experiments. However, doubts have been voiced if such methods work at very low regeneration rates where on average the cavity contains less than one photon. In this note we report on a demonstration experiment using a microwave cavity driven with extremely low power, to show that resonant amplification works also in this regime. In accordance with standard quantum mechanics this is a demonstration that interference also works at the level of less than one quantum. As an additional benefit this experiment shows that thermal photons inside the cavity cause no adverse effects.Comment: 14 pages, 5 figure

(Invited) The inversion behaviour of narrow band gap MOS systems: experimental observations, physics based simulations and applications

Impedance spectroscopy of the metal-oxide semiconductor (MOS) system has played a central role in the development of silicon-based complementary MOS (CMOS) technology over the past 50 years [1, 2]. With current research interest into alternative semiconductor channels to silicon for MOSFET and tunnel FET technologies, the measurement and interpretation of the overall impedance of the MOS structure requires detailed analysis to separate and quantify the contribution of interface states, and near interface traps (border traps), on the capacitance and conductance response, and to separate the contribution of these electrically active defect states from the ac response of minority carriers in the case of genuine inversion of the semiconductor/dielectric interface

Luminescencja jonów chromu w naturalnych krzemianach

This work presented here results of electron absorption and luminescence investigations of 14 natural silicates, which have contained chromium Cr3 + ion. The contents of it was from 0,02% and less (kunzite) to 11,2% (uvarovite). Many of minerals had also manganese, vanadium and iron admixture. Luminescence measurement as well as decay time were taken at room temperature and 77 K—4 K. The luminescence dependence on ligand crystal-field was analysed. Examples of strong and weak ligand crystal fields were demonstrated. Kammererite, pyrope, Cr-grossular, tsavorite, tanzanite, spodumene, emerald, Cr-idocrase, kotchubeite and two crystal sites in kyanite were include to the first group. Weak crystal-field was found for uwarowite, one crystal site in kyanite, fuchsite diopsyde and Cr-amphibole. The dependence of the 2E level splitting on ligand crystal field symmetry was mentioned. The smallest splitting (65 cm"1) was found for trigonal crystal field C3j in grossulars and emerald. For comparison in Cr-doped corundum the R-lines splitting is 29 cm"1. For tetragonal C4v crystal field in idocrase the splitting is 132 cm1 and the biggest are for triclinic and monoclinic symmetry in tanzanite and kyanite up to 335 cm *. The influence of the first and next-neighbour coordination on crystal field parameters was discussed for fuchsite and kotchubeite, diopside and spodumene and grossular and idocrase. The influence of other transition elements on chromium luminescence was found, too. In kyanite the chromium ions were presented in different crystal sites and among them the energy transfer was very probable. Vanadium ions were presented in tsavorite and tanzanite and the energy from chromium ions was passed on to them. It was the cause of unexpected short decay time. Because of manganese ions in spodumene the several different chromium sites were created and their decay time were short, either. For pyrope and Cr-amphibole the chromium luminescence were completely quenched for reason of iron high content. For two chromium chlorites-kammererite and kotchubeite — the clusters and Cr-Cr pairs were found. It was because of low luminescence intensity and short decay time of them. The influence of other transition ions presented in studied crystals and the high chromium content on luminescence properties was detected only qualitatively. Author had not enough examples of each kind of minerals with different contents of doped ions to discusse this problem quantitatively. The electronic and vibronic energy levels — strong and weak — were discussed. In this work for the first time the luminescence of Cr3 + ions in Cr-grossular, tsavorite, uvarovite, tanzanite, idocrase, diopside, fuchsite, kotchubeite and kammererite were presented and discussed. For the first time for chromium ions in minerals the energies of excited levels and crystal-field parameters were calculated for Cr-grossular, kyanite, tanzanite and idocrase

Factors influencing the use of public dental services: An application of the Theory of Planned Behaviour

Background There is limited evidence of the influence of psychosocial factors and health beliefs on public dental patient's patterns of service use in Australia. The research aims were to examine associations between dental attitudes and beliefs of public dental service users and dental visiting intention and behaviour using the Theory of Planned Behaviour. Methods 517 randomly selected adult public dental patients completed a questionnaire assessing dental attitudes and beliefs which was matched with electronic records for past and future dental service use. A questionnaire measured intentions, attitudes, subjective norms and perceptions of behavioural control and self-efficacy in relation to visiting public dentists. A measure of dental attendance at public dental clinics was obtained retrospectively (over 3 1/2 years) and prospectively (over a one year period following the return of the questionnaire) by accessing electronic patient clinical records. Results Participants had positive attitudes, subjective norms and self-efficacy beliefs towards dental visiting but perceived a lack of control over visiting the dentist. Attitudes, subjective norms, self-efficacy and perceived control were significant predictors of intention (P < 0.05). Intentions, self-efficacy and past dental attendance were significant predictors of actual dental attendance (P < 0.05). Conclusion Public dental patients held favourable attitudes and beliefs but perceived a lack of control towards dental visiting. Reducing structural barriers may therefore improve access to public dental services.Liana Luzzi and A John Spence