M. Gerlach

Nanojets and directional emission in symmetric photonic molecules

Symmetric directional emission of light from multisphere photonic molecules is experimentally shown in this work. The photonic molecules are illuminated in the vertical direction with a defocused laser beam. The emission is attributed to photonic nanojets generated in the structure. Furthermore, spectral analysis exhibit whispering gallery mode resonances of coupled and uncoupled modes. A benzene molecule-like structure consisting of a 7-microspheres cyclic photonic molecule shows a field emission pattern similar to the spatial distribution of the orbitals of the benzene molecule.

Radiation-pressure-induced mode splitting in a spherical microcavity with an elastic shell

In this work, we present a novel method to reveal azimuthal whispering gallery modes (WGMs) in a spherical microcavity coated with a nano-meter thick polyelectrolyte shell and one monolayer of CdTe semiconductor quantum dots. The new approach in this experiment is based on the deformation of the spherical shape in a non-contact way using the radiation pressure from a laser beam, which causes the lifting of the degeneracy of the WGMs. The resonance peak linewidth and splitting parameters can be efficiently controlled by the strength of the radiation pressure and the elastic properties of the surface shell.

Confined optical modes in small photonic molecules with semiconductor nanocrystals

We report on the coherent coupling of whispering gallery modes (WGMs) in a photonic molecule formed from two melamine-formaldehyde spherical microcavities coated with a thin shell of light-emitting CdTe nanocrystals (NCs). Utilizing different excitation conditions, the splitting of the WGM resonances originating from bonding and antibonding branches of the photonic states is observed, and fine structure consisting of very sharp peaks resulting from lifting of the WGM degeneracy has been detected. Time-resolved measurements showed a slight increase in the spontaneous emission rate of NCs in a photonic molecule when compared to the spontaneous emission rate for NCs coating a single microsphere.

Whispering gallery modes in photoluminescence and Raman spectra of a spherical microcavity with CdTe quantum dots: anti-Stokes emission and interference effects

We have studied the photoluminescence and Raman spectra of a system consisting of a polystyrene latex microsphere coated by CdTe colloidal quantum dots. The cavity-induced enhancement of the Raman scattering allows the observation of Raman spectra from only a monolayer of CdTe quantum dots. Periodic structure with very narrow peaks in the photoluminescence spectra of a single microsphere was detected both in the Stokes and anti-Stokes spectral regions, arising from the coupling between the emission of quantum dots and spherical cavity modes.

Mode manipulation in system of coupled microcavities with whispering gallery modes

In recent years the studies of electromagnetic modes in solid spherical microcavities have been of great interest both for their potential applications and fundamental optical properties. A system of coherently coupled microcavities may be called a “photonic molecule” and can be employed in the tight-binding device in order to manipulate photons in micrometer length scale. In this work we demonstrate the possibility of mode manipulation in systems of symmetric photonic molecules formed by placing several high-Q micro-spheres in contact. We observe photonic nanojets that reflect the symmetry of the photonic molecule, with 3 jets located at 120 degrees with respect to each other for the triangular photonic molecule. A benzene molecule-like structure consisting of a 7-microspheres cyclic photonic molecule shows a field emission pattern similar to the spatial distribution of the orbitals of the benzene molecule. We also present some results showing the coexistence of whispering gallery modes and photonic nanojets in the same structure.

Coupled cavity modes in photonic molecules with semiconductor nanocrystals

We present a detailed study of the localized coupled-cavity modes in a photonic molecule formed from two dielectric spherical microcavities with CdTe nanocrystals, which show a multi-peak narrowband modal structure resulting from lifting of the mode degeneracy with respect to the azimuthal quantum number. The waveguiding through the coupled microcavities and wavelength switching effect is demonstrated. The feasibility of photonic molecules as the basis for a multi-channel, wavelength-tunable optical delay device is analysed.

Modification of photon states in photonic molecules with semiconductor nanocrystals

We report on the coherent coupling of whispering gallery modes (WGMs) in a photonic molecule formed from two melamine formaldehyde spherical microcavities coated with a thin shell of CdTe nanocrystals. Utilizing different excitation conditions, the splitting of the WGM resonances originating from bonding and antibonding branches of the photonic states is observed and a fine structure consisting of very sharp peaks resulting from lifting of the WGM degeneracy has been detected. Observation of optical wavelength switching with controllable spectral position and separation is reported.

Mode manipulation in small microsphere systems

In this work we demonstrate the possibility of mode manipulation in systems of symmetric photonic molecules formed by placing several microspheres in contact. We observe photonic nanojets that reflect the symmetry of the photonic molecule, with 3 jets located at 120 degrees with respect to each other for the triangular molecule. We also present some results showing the coexistence of whispering gallery modes and nanojets in the same structure.

Symmetric photonic molecules formed from coupled microspheres

Coherent coupling of optical resonances in spherical microcavities results in the formation of so called photonic molecules. The name originates from the analogy to chemical molecules. The coupled optical modes are similar to the atomic orbitals of a chemical molecule. In this work, we studied the resonance spectrum of the symmetric photonic molecules. Furthermore, symmetric directional emission of light from the photonic molecules is experimentally shown. The photonic molecules are illuminated in the vertical direction with a defocused laser beam. The emission is attributed to photonic nanojets generated in the structure. Spectral analysis exhibit whispering gallery mode resonances of coupled and uncoupled modes. A benzene molecule-like structure consisting of a 7-microspheres cyclic photonic molecule shows a field emission pattern similar to the spatial distribution of the orbitals of the benzene molecule.

Mode Splitting Induced by Radiation Pressure in a Spherical Microcavity

In this paper, we present a novel method to reveal the azimuthal whispering gallery modes (WGMs) in a spherical microcavity. The microcavity has a soft shell on its surface which is coated with CdTe nanocrystals. The deformation of the spherical shape using radiation pressure from a laser beam causes the lifting of the degeneracy of the WGMs. The splitting can be efficiently controlled by the strength of the radiation pressure and the elastic properties of the surface shell.