Abstract
In recent years, there has been marked increase in research aimed to introduce alkali vapours into guided-wave configurations. Owing to the significant reduction in device dimensions, the increase in density of states, the interaction with surfaces and primarily the high intensities carried along the structure, a plethora of light–vapour interactions can be studied. Moreover, such platform may exhibit new functionalities such as low-power nonlinear light–matter interactions. One immense challenge is to study the effects of quantum coherence and shifts in nanoscale waveguides, characterized by ultra-small mode areas and fast dynamics. Here, we construct a highly compact 17 mm long serpentine silicon-nitride atomic vapour cladding waveguide. Fascinating and important phenomena such as van-der-Waals shifts, dynamical stark shifts and coherent effects such as strong coupling (in the form of Autler–Townes splitting) are observed. Some of these effects may play an important role in applications such as all-optical switching, frequency referencing and magnetometry.
Highlights
In recent years, there has been marked increase in research aimed to introduce alkali vapours into guided-wave configurations
Such integration of vapour with guided systems has served for the demonstration of a myriad of effects ranging from basic linear spectroscopy[1,6,8,13], to a variety of nonlinear effects such as electromagnetic-induced transparency[14] (EIT), enhanced two-photon absorption[2,10], phase switching[4], all-optical modulation[7,15] and slow light[12]
We have demonstrated the atomic cladding waveguide (ACWG), consisting of a silicon-nitride (SiN) core surrounded by a cladding of Rb vapour, which is introduced by integrating an atomic vapour cell above the optical chip[6]
Summary
There has been marked increase in research aimed to introduce alkali vapours into guided-wave configurations. When introducing a pump-field resonant with a different excited state, we are able to observe strong coupling in the form of a high-contrast Autler–Townes splitting, which can be exploited for highly efficient all-optical switching, using microwatts of power levels. At such high intensity levels, we observe light shifts of B200 MHz. Compared with previous demonstrations, the current device achieves enhanced performance in terms of optical density and non-linearities. Such fast transit times accompanied with fast induced Rabi frequencies allow one to observe coherent effects, and fast switching speeds, which are highly advantageous in applications such as all-optical switching
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