Modes In Photonic Molecules Research Articles

Fano resonances from coupled whispering-gallery modes in photonic molecules.

We present a rigorous investigation of resonant coupling between microspheres based on multipole expansions. The microspheres have diameters in the range of several micrometers and can be used to realize various photonic molecule configurations. We reveal and quantify the interactions between the whispering gallery modes inside individual microspheres and the propagation modes of the entire photonic molecule structures. We show that Fano-like resonances in photonic molecules can be engineered by tuning the coupling between the resonant and radiative modes when the structures are illuminated with simple dipole radiation.

Strong coupling of different cavity modes in photonic molecules formed by two adjacent microdisk microcavities

Strong couplings between cavity modes in photonic molecules formed by two preselected nearly identical microdisk microcavities with embedded quantum dots are investigated. By continuously tuning the refractive index of one microdisk, clear anticrossings in the resonant peak energies associated with crossings in the peak linewidths can be observed. The coupling strengths are extracted by the coupled mode theory and analyzed by the model considering the effective potential confining the electromagnetic waves in the microcavities.

Fine structure of coupled optical modes in photonic molecules

We report on the coherent coupling of whispering gallery modes (WGM) in a photonic molecule formed from two melamine-formaldehyde spherical microcavities with a thin shell of CdTe nanocrystals. Utilizing a microporous polymer structure to orient the photonic molecule, we have excited the photonic molecule both on and off axis. This controllable geometry has allowed the observation of an off-axis fine structure that consists of very sharp peaks resulting from the removal of the WGM degeneracy with respect to the azimuthal quantum number $m$. The mode splittings are in very good agreement with theory.

Photonic molecule lasing.

Lasing at resonantly coupled whispering-gallery mode frequencies is observed in photonic molecules consisting of bispheres of 4.2 and 5.1 microm in diameter placed in a silicon V-groove. We examine spatial profiles of photonic molecule modes by use of frequency-resolved imaging and reveal bonding and antibonding mode features. From the lasing threshold characteristics, we quantitatively measure the quality factor and the spontaneous-emission coupling ratio of the photonic molecule modes and confirm that strong coherent coupling leads to photonic molecule modes.

Spectral broadening of 40-fs Ti:sapphire laser pulses in photonic-molecule modes of a cobweb-microstructure fiber

Photonic-molecule modes of a cobweb-microstructure fiber allow efficient nonlinear optical spectral broadening of nanojoule femtosecond light pulses. Spectral widths of approximately 200 nm are achieved at the output of a 6-cm sample of such a fiber for 40-fs Ti:sapphire laser pulses with an energy of a few nanojoules coupled into photonic-molecule modes. Higher values of the group index and a lower group-velocity dispersion, attainable with higher-order photonic-molecule modes, allow the efficiency of spectral broadening of femtosecond laser pulses to be increased relative to the efficiency of spectral broadening in the fundamental photonic-molecule mode.

Supercontinuum generation in photonic-molecule modes of microstructure fibers

Supercontinuum generation in microstructure fibers with a core in the form of a cyclic polyatomic photonic molecule is studied. Air holes arranged in a two-dimensional holey structure in the cladding of this fiber and a larger hole at the center of the fiber form a cyclic-molecule-like structure, consisting of an array of small-diameter glass channels linked by narrow bridges, around the central hole. This photonic-molecule microstructure-integrated bundle of fibers can guide the light through total internal reflection, providing a very high light confinement degree due to the large refractive index step. The properties of supercontinuum emission produced in such fibers can be controlled by coupling the energy of femtosecond light pulses into different photonic-molecule modes of the fiber.

Optical Modes in Photonic Molecules

Photonic molecules have been fabricated by coupling pairs of micrometer-sized semiconductor cavities via a narrow channel. The optical modes in these structures have been studied spectroscopically as a function of the coupling and the mode energies are compared to detailed calculations. These results provide a rich picture of photonic modes in these molecules.