Analysis of the whispering gallery mode sapphire Fe³⁺maser under magnetic field

Abstract

This article describes the influence of the magnetic field on a small amount of residual Fe 3+ ion impurities contained in a sapphire resonator excited on a whispering gallery mode and cooled down to 4 K. The energy levels and transition probabilities between pairs of levels of the system are calculated in order to determine the effect of the magnetic field on the maser output power and also on the pump power threshold.

Ultrasensitive microwave spectroscopy of paramagnetic impurities in sapphire crystals at millikelvin temperatures

“…Unlike other spectroscopic studies of doped sapphire crystals, here we use an ultra-sensitive approach to detect and analyse naturally occurring, extremely low concentration ion impurities. Some preliminary observations of interactions with Fe 3+ ions in such crystals have been made in the past [12][13][14][15][16] . Broadly speaking, the present work represents a systematic study of ion-photon interactions over the X and K u band of microwave frequencies (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20).…”

Physics of the sapphire whispering-gallery-mode solid-state MASER oscillator

“…In another form, the power P s in a resonator will be maximum when the pump has a power strong enough. Using the equation (16), the maximum power of the signal maser reads :…”

“…Since the experimental demonstration of this new type of solid-state maser [11,12,13,14], few theoretical works have been published to explain its main features [15,16,17]. Particularly, the effectiveness of the maser process, i.e.…”

Absorbance and energy levels for a Fe3+ ion in α-Al2O3. Optical pumping applied to a 31 GHz maser

“…The excited levels decay quickly to the ground state with a lifetime τ 0 1 ms. All relaxation in the ground state are governed by the spin-lattice effect with a characteristic time τ 1 ≈ 10 ms at 4 K. It is also determined that the spin-to-spin relaxation is very fast with a characteristic time τ 2 ≤ 20 ns. If we neglect coherence and we deal only with level populations, so a model with a simple rate equations is sufficient to describe the interaction [32]. There is a possibility that the excited ions may fall on intermediate levels, but since τ 0 τ 1 they relax rapidly to ground state.…”