Coherent light sources are one of the most crucial foundations in both scientific disciplines and advanced applications. As a prominent platform, ultrahigh-Q whispering-gallery mode (WGM) microcavities have witnessed significant developments of novel light sources. However, the intrinsic chiral symmetry of WGMs microcavity geometry and the resulting equivalence between the two directions of laser propagation in a cavity severely limits further applications of microlasers.
Very recently, a team of researchers led by Professor Xiao Yun-Feng and Professor Gong Qihuang at Peking University, in collaboration with Professor Qiu Cheng-Wei at National University of Singapore and Professor Stefan Rotter at Vienna University of Technology, has demonstrated a spontaneously symmetry-broken microlaser in an ultrahigh-Q WGM microcavity, exhibiting reconfigurable propagating directions of the chiral laser. This work has been published online in Nature Communications on February 28, 2019 (DOI: 10.1038/s41467-020-14861-5).
In previous studies, existing solutions for a chiral microlaser mainly resort to explicitly breaking the structure symmetry of a WGM microcavity. Unfortunately, the scalability and reconfigurability of these preceding strategies are strongly limited since the devices, once fabricated, come with a prefixed, non-tailorable laser directionality. In this work, the researchers achieve a reconfigurable chiral microlaser in a symmetric WGM microcavity by utilizing the cavity-enhanced optical Kerr nonlinearity.
"We employed microcavity Raman lasers in the experiment, which generally involve a pair of balanced clockwise (CW) and counterclockwise (CCW) waves," said Cao Qi-Tao, a Ph.D. student at Peking University and one of the co-first authors of this work. The Raman laser waves in the two directions are coupled together through linear surface Rayleigh scattering and nonlinear phase modulation by optical Kerr effect.
As the power of the microlaser with a particular phase increases and reaches a threshold, the linear coupling is completely compensated by the nonlinear coupling. Above this threshold, the chiral symmetry of the laser field breaks spontaneously, and the Raman wave evolves randomly into a chiral state with a CW or CCW dominated laser propagation. Experimentally, an unprecedented ratio of counter-propagating emission intensities is obtained exceeding 160:1.
Furthermore, the directionality of such the chiral microlaser is all-optically and dynamically controlled by the bias in the pump direction, and the symmetry breaking threshold is adjustable using a nanotip scatterer.
"Our results break the perception boundary of how to realize a reconfigurable coherent light source, to enable a powerful reconfigurability of a laser's directionality and chirality, and to extend a long-ranging impact on on-chip nanophotonics and nonlinear processes," said Professor Xiao. "Such a spontaneously chiral emitting laser also can be extended to various microstructures, and is almost free from the material limit due to the ubiquity of the Kerr nonlinearity."
More information: Qi-Tao Cao, Rui-Shan Liu, Heming Wang, Yu-Kun Lu, Cheng-Wei Qiu, Stefan Rotter, Qihuang Gong, and Yun-Feng Xiao, Reconfigurable symmetry-broken laser in a symmetric microcavity, Nature Communications (Febuary 28, 2020), DOI: 10.1038/s41467-020-14861-5
Huang Weijian | EurekAlert!
Scientists see energy gap modulations in a cuprate superconductor
02.04.2020 | DOE/Brookhaven National Laboratory
BESSY II: Ultra-fast switching of helicity of circularly polarized light pulses
02.04.2020 | Helmholtz-Zentrum Berlin für Materialien und Energie
Drops of water falling on or sliding over surfaces may leave behind traces of electrical charge, causing the drops to charge themselves. Scientists at the Max Planck Institute for Polymer Research (MPI-P) in Mainz have now begun a detailed investigation into this phenomenon that accompanies us in every-day life. They developed a method to quantify the charge generation and additionally created a theoretical model to aid understanding. According to the scientists, the observed effect could be a source of generated power and an important building block for understanding frictional electricity.
Water drops sliding over non-conducting surfaces can be found everywhere in our lives: From the dripping of a coffee machine, to a rinse in the shower, to an...
90 million-year-old forest soil provides unexpected evidence for exceptionally warm climate near the South Pole in the Cretaceous
An international team of researchers led by geoscientists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) have now...
The bacteria that cause tuberculosis need iron to survive. Researchers at the University of Zurich have now solved the first detailed structure of the transport protein responsible for the iron supply. When the iron transport into the bacteria is inhibited, the pathogen can no longer grow. This opens novel ways to develop targeted tuberculosis drugs.
One of the most devastating pathogens that lives inside human cells is Mycobacterium tuberculosis, the bacillus that causes tuberculosis. According to the...
An international team with the participation of Prof. Dr. Michael Kues from the Cluster of Excellence PhoenixD at Leibniz University Hannover has developed a new method for generating quantum-entangled photons in a spectral range of light that was previously inaccessible. The discovery can make the encryption of satellite-based communications much more secure in the future.
A 15-member research team from the UK, Germany and Japan has developed a new method for generating and detecting quantum-entangled photons at a wavelength of...
Together with their colleagues from the University of Würzburg, physicists from the group of Professor Alexander Szameit at the University of Rostock have devised a “funnel” for photons. Their discovery was recently published in the renowned journal Science and holds great promise for novel ultra-sensitive detectors as well as innovative applications in telecommunications and information processing.
The quantum-optical properties of light and its interaction with matter has fascinated the Rostock professor Alexander Szameit since College.
02.04.2020 | Event News
26.03.2020 | Event News
23.03.2020 | Event News
03.04.2020 | Materials Sciences
03.04.2020 | Life Sciences
03.04.2020 | Life Sciences