2 research outputs found
Dynamical Tuning of Nanowire Lasing Spectra
Realizing
visionary concepts of integrated photonic circuits, nanospectroscopy,
and nanosensing will tremendously benefit from dynamically tunable
coherent light sources with lateral dimensions on the subwavelength
scale. Therefore, we demonstrate an individual nanowire laser based
device which can be gradually tuned by reversible length changes of
the nanowire such that uniaxial tensile stress is applied to the respective
semiconductor gain material. By straining the device, the spontaneous
excitonic emission of the nanowire shifts to lower energies caused
by the bandgap reduction of the semiconductor. Moreover, the optical
gain spectrum of the nanolaser can be precisely strain-tuned in the
high excitation regime. The tuning of the emission does not affect
the laser threshold of the device, which is very beneficial for practical
applications. The applied length change furthermore adjusts the laser
resonances inducing a redshift of the longitudinal modes. Thus, this
concept of gradually and dynamically tunable nanolasers enables controlling
and modulating the coherent emission on the nanoscale without changing
macroscopic ambient conditions. This concept holds therefore huge
impact on nanophotonic switches and photonic circuit technology
Inhibition and Enhancement of the Spontaneous Emission of Quantum Dots in Micropillar Cavities with Radial-Distributed Bragg Reflectors
We present a micropillar cavity where nondesired radial emission is inhibited. The photonic confinement in such a structure is improved by implementation of an additional concentric radial-distributed Bragg reflector. Such a reflector increases the reflectivity in all directions perpendicular to the micropillar axis from a typical value of 15–31% to above 98%. An inhibition of the spontaneous emission of off-resonant excitonic states of quantum dots embedded in the microcavity is revealed by time-resolved experiments. It proves a decreased density of photonic states related to unwanted radial leakage of photons out of the micropillar. For on-resonance conditions, we find that the dot emission rate is increased, evidencing the Purcell enhancement of spontaneous emission. The proposed design can increase the efficiency of single-photon sources and bring to micropillar cavities the functionalities based on lengthened decay times