Optical resonators are essential components of lasers and other wavelength-sensitive optical devices. A resonator is characterized by a set of modes, each with a resonant frequency omega and resonance width Delta omega=1/tau, where tau is the lifetime of a photon in the mode. In a cylindrical or spherical dielectric resonator, extremely long-lived resonances are due to `whispering gallery' modes in which light circulates around the perimeter trapped by total internal reflection. These resonators emit light isotropically. Recently, a new category of asymmetric resonant cavities (ARCs) has been proposed in which substantial shape deformation leads to partially chaotic ray dynamics. This has been predicted to give rise to a universal, frequency-independent broadening of the whispering-gallery resonances, and highly anisotropic emission. Here we present solutions of the wave equation for ARCs which confirm many aspects of the earlier ray-optics model, but also reveal interesting frequency-dependent effects characteristic of quantum chaos. For small deformations the lifetime is controlled by evanescent leakage, the optical analogue of quantum tunneling. We find that the lifetime is much shortened by a process known as `chaos-assisted tunneling'. In contrast, for large deformations (~10%) some resonances are found to have longer lifetimes than predicted by the ray chaos model due to `dynamical localization'.Comment: 4 pages RevTeX with 7 Postscript figure
High-power and highly directional semiconductor cylinder-lasers based on a new optical resonator with deformed cross-section are reported. In the favorable directions of the far-field, a power increase of up to three orders of magnitude over the conventional circularly symmetric lasers was obtained. A "bowtie"-shaped resonance is responsible for the improved performance of the lasers in the higher range of deformations, in contrast to "whispering-gallery"-type modes of circular and weakly deformed lasers. This new resonator design, although demonstrated here in mid-infrared quantum-cascade lasers, should be applicable to any laser based on semiconductors or other high-refractive index materials.Lasers consist of two basic components. First, the active material in which light of a certain wavelength range is generated from an external energy source, such as electric current; second, the laser resonator, which contains the active material, provides feedback for the stimulated emission of light. The resonator largely influences the special features of the emitted light: power, beam directionality, and spectral properties, as well as the laser's physical features such as size and shape. Semiconductor lasers are the most widely used and versatile class of lasers. Their most common resonators are FabryPerot cavities, in which two cleaved semiconductor crystal planes act as parallel mirrors, reflecting the light back and forth through the active material.There have been many attempts to improve resonator properties. In particular, an increase of the reflectivity of the resonator mirrors is highly desirable. This allows low thresholds for the onset of laser action and a smaller volume of active material with concomitant moderate energy requirements and the ability to pack the lasers in a small space. * To whom correspondence should be addressed; email:fc@lucent One excellent example is the development of microdisk semiconductor lasers (1). These lasers exploit total internal reflection of light to achieve a mirror reflectivity near unity. Micro-disk, -cylinder or -droplet lasers form a class of lasers based on circularly symmetric resonators, which lase on "whispering-gallery modes" of the electromagnetic field (2,3,4). In such a mode light circulates around the curved inner boundary of the resonator, reflecting from the walls of the resonator with an angle of incidence always greater than the critical angle for total internal reflection, thus remaining trapped inside the resonator. There are only minute losses of light caused by evanescent leakage (tunneling) and scattering from surface roughness. This principle allowed the fabrication of the world's smallest lasers (2). Besides possible future applications in optical computing and networking, micro-lasers are of strong interest for research problems of cavity quantum electrodynamics, such as resonatorenhanced spontaneous emission and threshold-less lasers (5). Small resonators may also serve as model systems for the study of wave phenomena in mesoscopic systems, parti...
Asymmetric resonant cavities with highly noncircular but convex cross sections are predicted theoretically to have high-Q whispering gallery modes with highly anisotropic emission. We develop a ray dynamics model for the emission pattern and present numerical and experimental confirmation of the theory.
A ray-optics model is developed to describe the spoiling of the high-Q (whispering gallery) modes of ring-shaped cavities as they are deformed from perfect circularity. A sharp threshold is found for the onset of Q spoiling as predicted by the Kolmogorov-Arnol'd-Moser (KAM) theorem of nonlinear dynamics. Beyond the critical deformation b(c), Q ~ (b - b(c))(-alpha), alpha asymptotically equal to 2.4-2.6. The escaping light emerges in certain specific directions, which may be predicted.
Molecular sieves, such as nanoporous AlPO4-5, can host a wide variety of laser active dyes. We embedded pyridine 2 molecules as a representative of a commercially available dye which fits into the channel pores of the host matrix. Many efficient dye molecules, such as rhodamines, do not fit into the pores. But modifying the structure of the dyes to appear like the used templates allows to increase the amount of encapsulated dyes. The properties of resulting microlasers depend on size and shape of the microresonators, and we discuss a model for microscopic hexagonal ring resonators. In terms of pump needed to reach lasing threshold molecular sieve microlasers are comparable to VCSELs. For dyes which fit into the pores we observed a partial regeneration of photo-induced damage.
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