Abstract
Due to their small sizes and low threshold, nanolasers play a pivotal role in the field of low-energy scalable photonic technologies. High-speed modulation of nanolasers is needed for their application in data communication, but its implementation has been hampered by the small scales involved, leading to large electrical parasitics. Here we experimentally demonstrate the proof-of-principle of a novel modulation technique, namely, mode-field switching, which unlocks the control of the laser operation via the modulation of the electromagnetic field. In particular, we show that stimulated emission can be inhibited by switching the lasing mode from bright to dark in a three-coupled cavity system. The experimental results are in good agreement with a model that combines coupled-mode theory and rate equations. Using this model, we show that time-dependent detuning schemes enable storage and release of energy under the form of short pulses, placing mode-field switching among the techniques for laser modulation and pulse generation. This scheme is general and can be implemented in every platform displaying coupled and tuneable resonances.
Highlights
The miniaturization of laser sources at the nanoscale represents a remarkable achievement that may unlock various applications in many fields,1 including optical interconnects,2 sensors,3,4 artificial optical neural networks,5,6 and data storage.7 Within this context, photonic crystals (PhC) and self-assembled quantum dots (QDs) represent an interesting platform combining low optical loss, high carrier confinement, and thereby low threshold current.8For applications in optical interconnects and data storage, a crucial requirement for nanolasers is the possibility to modulate their output at high speed
To reduce the non-radiative recombination caused by surface states, the devices underwent an additional passivation step as described in Ref. 24. This step consists of chemical passivation obtained by dipping the sample into a diluted ammonia sulfide solution, followed by a plasma-enhanced chemical vapor deposition (PECVD) step resulting in a conformal thin layer of SiO2 covering all surfaces, including the walls of the air holes
These pulses are focused onto the L7 area [red spot in Fig. 4(a), top, spot diameter ≈ 2 μm], exciting the QDs located in that region, and the emission is first collected via the same objective and measured with a spectrometer or with a superconducting single-photon photodetector
Summary
The miniaturization of laser sources at the nanoscale represents a remarkable achievement that may unlock various applications in many fields, including optical interconnects, sensors, artificial optical neural networks, and data storage. Within this context, photonic crystals (PhC) and self-assembled quantum dots (QDs) represent an interesting platform combining low optical loss, high carrier confinement, and thereby low threshold current.. When implemented electrically, all of these schemes require the injection of short current pulses into the nanolaser gain medium, which typically has submicrometer dimensions This small dimension is coupled to a large series resistance and a parallel capacitance, leading to an RC time constant limiting the achievable modulation bandwidth well below the intrinsic one. Matter interaction in the target cavity, as well as the modal losses, when the cavities are designed to have unbalanced quality (Q) factors.13 This scheme, named mode-field switching, has initially been implemented to control the spontaneous emission (SpE) rate (up to a factor ∼2) in two-cavity systems, and to dynamically vary the resonator Q factor, while recent work predicted and realized the complete inhibition of SpE of QDs in three-cavity structures.. Its general nature potentially allows its implementation in every platform displaying tuneable resonances
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