Abstract
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.
Highlights
N anoscale photonic devices with increasing functionality, such as photonic chips[1,2] or lab-on-a-chip devices,[2−4] are a promising driving force for the future technological progress
We fabricated dynamically strainable NW laser devices using CdS NWs in order to establish a proof of principle design for tunable nanolasers
Micro-PL measurements in the spontaneous emission regime revealed a bandgap reduction in the NW, which can be controlled by uniaxial tensile stress
Summary
N anoscale photonic devices with increasing functionality, such as photonic chips[1,2] or lab-on-a-chip devices,[2−4] are a promising driving force for the future technological progress. The huge elastic limit leads to a significant enlargement of the linear strain tuning range; NWs are suited for straining applications.[23] In this work, a controlled bandgap modification and the subsequent shift of the emission wavelength[27] is achieved by straining individual CdS NW devices by applying uniaxial stress. This enables a controlled dynamical modification of the optical emission and allows transferring the principle of strain-tuning from the spontaneous to the stimulated emission regime. The right pad is outside of the range of the line scan around ∼21−25 μm
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