Abstract
We study theoretically the lasing properties and the cavity lifetime of super and sub-luminal lasers. We find that obtaining the necessary conditions for superluminal lasing requires care and that a laser operating under these conditions can under some conditions tend towards bi-frequency lasing. In contrast, conditions for a subluminal laser are less stringent, and in most situations its steady-state properties are well predicted by the self-consistent single-frequency laser equations. We also study the relaxation time of power perturbation in super and sub-luminal lasers using a finite-difference-time-domain tool and present the impact of the lasing power, the group velocity and the dispersion properties of the cavity on the relaxation dynamic of such perturbations. For the subluminal laser, we find that the time constant changes by a factor that is close to the group index. In contrast, for the superluminal laser, we find that the time constant does not change by the factor given by the group index, and remains close to or above the value for an empty cavity. These finding may be interpreted to imply that the quantum noise limited linewidth of the subluminal laser decreases with increasing group index, while the same for the superluminal laser does not increase with decreasing group index. The implications of these findings on the sensitivity of sensors based on these lasers are discussed in details.
Highlights
The ability to control the velocity of wave propagation has been the focus of numerous studies during the last two decades [1]
Studies in slow and fast light have initiated a variety of applications in diverse fields such as telecom, nonlinear optics, sensing and more [1,2,3,4,5,6,7,8]
The incorporation of slow/fast light media and structures in such cavities induces non-trivial impact on their fundamental properties such as cavity life-time, resonance frequencies, etc. The former becomes crucial in active cavities in which the gain medium is utilized for obtaining the desired dispersion properties. Parameters such as the roundtrip time and Q-factor, which are commonly considered as fixed properties of the “cold” cavity, become dynamic and dependent on the lasing conditions
Summary
The ability to control the velocity of wave propagation has been the focus of numerous studies during the last two decades [1]. In addition to the fundamental interest in sub/super luminal group velocity, cavities incorporating slow and fast light effects have tremendous potential for applications in many fields such as, sensing, data buffering, optical memories, true delay lines, etc. The incorporation of slow/fast light media and structures in such cavities induces non-trivial impact on their fundamental properties such as cavity life-time, resonance frequencies, etc. The former becomes crucial in active cavities (i.e. lasers) in which the gain medium is utilized for obtaining the desired dispersion properties.
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