Quieter Quantum Amplifiers

Vitaliy V. Shtykov, Sergey M. Smolskiy

Mihai Oane

The development of masers in the 1950's made possible amplifiers that were much quieter than other contemporary amplifiers. An analysis of narrow-band yields a fundamental theorem (Caves theorem) for phase-insensitive linear amplifiers; it requires that such an amplifier, will add noise as large as half-quantum of zero-point fluctuations. For phase-sensitive linear amplifiers the theorem establish a lower limit on the product of the noises added to the two phases. In the last decade it was shown theoretically that solid-state masers without inversion may be obtained in multilevel spin systems in dilute paramagnetic solids at high temperature subjected to several strong fields. In the present paper the author applies the Caves theorem to the maser without inversion in order to find out the best ways in which the proposed device can work.

A. Jann, Y. Ben-Aryeh

Mihai Oane, Florin F. Popescu, Shyh‐Lin Tsao +4 more

The development of masers in the 1950s made possible amplifiers that were much quieter than other contemporary amplifiers. An analysis of narrow-band yields a fundamental theorem (Caves theorem) for phase-insensitive linear amplifiers; it requires that such an amplifier, will add noise as large as half-quantum of zero-point fluctuations. For phase-sensitive linear amplifiers the theorem establish a lower limit on the product of the noises added to the two phases. In the last decade it was shown theoretically that solid-state masers without inversion may be obtained in multilevel spin systems in dilute paramagnetic solids at high temperature subjected to several strong microwave fields. In the present paper the authors apply the Caves theorem to the maser without inversion in order to find out the best ways in which the proposed device can work.

M. W. P. Strandberg

Shmuel Sternklar, Yaakov Glick

A comparison of the noise characteristics of χ(3) and photorefractive coherent amplifiers reveals basic differences in their dependence on operating parameters. Unlike all types of χ(3) amplifiers, which are shown to have a well-defined optimum working point in the region of the self-stimulated scattering threshold, the photorefractive amplifier can be made increasingly quieter by lowering the pump power. This is demonstrated by use of highly doped Co:BaTiO3 in a tight-focus reflection grating geometry. It is shown that scattering from inhomogeneities in the crystal is the major limiting noise source and is significantly higher than predictions resulting from fundamental considerations such as random space-charge noise. An extremely high small-signal gain of 107 was measured with this crystal and geometry. To our knowledge this is the highest photorefractive gain reported to date.