29 research outputs found
DC-powered Fe3+:sapphire Maser and its Sensitivity to Ultraviolet Light
The zero-field Fe3+:sapphire whispering-gallery-mode maser oscillator
exhibits several alluring features: Its output is many orders of magnitude
brighter than that of an active hydrogen maser and thus far less degraded by
spontaneous-emission (Schawlow-Townes) and/or receiving-amplifier noise. Its
oscillator loop is confined to a piece of mono-crystalline rock bolted into a
metal can. Its quiet amplification combined with high resonator Q provide the
ingredients for exceptionally low phase noise. We here concentrate on novelties
addressing the fundamental conundrums and technical challenges that impede
progress. (1) Roasting: The "mase-ability" of sapphire depends significantly on
the chemical conditions under which it is grown and heat-treated. We provide
some fresh details and nuances here. (2) Simplification: This paper obviates
the need for a Ka-band synthesizer: it describes how a 31.3 GHz loop
oscillator, operating on the preferred WG pump mode, incorporating Pound
locking, was built from low-cost components. (3) "Dark Matter": A Siegman-level
analysis of the experimental data determines the substitutional concentration
of Fe3+ in HEMEX to be less than a part per billion prior to roasting and up to
a few hundred ppb afterwards. Chemical assays, using different techniques
(incl. glow discharge mass spectra spectroscopy and neutron activation
analysis) consistently indicate, however, that HEMEX contains iron at
concentrations of a few parts per million. Drawing from several
forgotten-about/under-appreciated papers, this substantial discrepancy is
addressed. (4) Excitons: Towards providing a new means of controlling the
Fe3+:sapph. system, a cryogenic sapphire ring was illuminated, whilst masing,
with UV light at wavelengths corresponding to known electronic and
charge-transfer (thus valence-altering) transitions. Preliminary experiments
are reported.Comment: pdf only; submitted to the proceedings of the 24th European Frequency
and Time Forum, 13-15th April, 201
Static Envelope Patterns in Composite Resonances Generated by Level Crossing in Optical Toroidal Microcavities
We study level crossing in the optical whispering-gallery (WG) modes by using toroidal microcavities. Experimentally, we image the stationary envelope patterns of the composite optical modes that arise when WG modes of different wavelengths coincide in frequency. Numerically, we calculate crossings of levels that correspond with the observed degenerate modes, where our method takes into account the not perfectly transverse nature of their field polarizations. In addition, we analyze anticrossing with a large avoidance gap between modes of the same azimuthal number
Pulsed Electron Spin Resonance of an Organic Microcrystal by Dispersive Readout
We establish a testbed system for the development of high-sensitivity
Electron Spin Resonance (ESR) techniques for small samples at cryogenic
temperatures. Our system consists of a Niobium Nitride thin-film planar
superconducting microresonator designed to have a concentrated mode volume to
couple to a small amount of paramagnetic material, and to be resilient to
magnetic fields of up to 400 mT. At 65 mK we measure high-cooperativity
coupling () to an organic radical microcrystal containing
spins in a pico-litre volume. We detect the spin-lattice decoherence
rate via the dispersive frequency shift of the resonator. Techniques such as
these could be suitable for applications in quantum information as well as for
pulsed ESR interrogation of very few spins and could provide insights into the
surface chemistry of, for example, the material defects in superconducting
quantum processors.Comment: 8 pages 5 figure
`Maser-in-a-Shoebox': a portable plug-and-play maser device at room-temperature and zero magnetic-field
Masers, the microwave analogues of lasers, have seen a renaissance owing to
the discovery of gain media that mase at room-temperature and zero-applied
magnetic field. However, despite the ease with which the devices can be
demonstrated under ambient conditions, achieving the ubiquity and portability
which lasers enjoy has to date remained challenging. We present a maser device
with a miniaturized maser cavity, gain material and laser pump source that fits
within the size of a shoebox. The gain medium used is pentacene-doped in
para-terphenyl and it is shown to give a strong masing signal with a peak power
of -5 dBm even within a smaller form factor. The device is also shown to mase
at different frequencies within a small range of 1.5 MHz away from the resonant
frequency. The portability and simplicity of the device, which weighs under 5
kg, paves the way for demonstrators particularly in the areas of low-noise
amplifiers, quantum sensors, cavity quantum electrodynamics and long-range
communications
N-Heteroacenes as an Organic Gain Medium for Room-Temperature Masers
The development of future quantum devices such as the maser, i.e., the microwave analog of the laser, could be well-served by the exploration of chemically tunable organic materials. Current iterations of room-temperature organic solid-state masers are composed of an inert host material that is doped with a spin-active molecule. In this work, we systematically modulated the structure of three nitrogen-substituted tetracene derivatives to augment their photoexcited spin dynamics and then evaluated their potential as novel maser gain media by optical, computational, and electronic paramagnetic resonance (EPR) spectroscopy. To facilitate these investigations, we adopted an organic glass former, 1,3,5-tri(1-naphthyl)benzene to act as a universal host. These chemical modifications impacted the rates of intersystem crossing, triplet spin polarization, triplet decay, and spinâlattice relaxation, leading to significant consequences on the conditions required to surpass the maser threshold
Level Crossing in Toroidal on-Chip Microcavities
Level crossing between optical whispering-gallery modes is studied in toroidal microcavities. We photograph azimuthal and radial envelope patterns of crossed optical modes. We also investigate anti-crossing between modes and polarization evolution