Showing papers by "Chang-Ling Zou published in 2023"
TL;DR: In this paper , a universal mechanism for fully stabilizing the mode-locked microcomb was proposed and experimentally verified, by incorporating two global tuning approaches and the autonomous thermal locking mechanism, the pump laser frequency and repetition rate of the microcomb can be controlled independently in real-time without interrupting the generated comb.
Abstract: Abstract The mode-locked microcomb offers a unique and compact solution for photonics applications, ranging from the optical communications, the optical clock, optical ranging, the precision spectroscopy, novel quantum light source, to photonic artificial intelligence. However, the photonic micro-structures are suffering from the perturbations arising from environment thermal noises and also laser-induced nonlinear effects, leading to the frequency instability of the generated comb. Here, a universal mechanism for fully stabilizing the microcomb is proposed and experimentally verified. By incorporating two global tuning approaches and the autonomous thermal locking mechanism, the pump laser frequency and repetition rate of the microcomb can be controlled independently in real-time without interrupting the microcomb generation. The high stability and controllability of the microcomb frequency enables its application in wavelength measurement with a precision of about 1 kHz. The approach for the full control of comb frequency could be applied in various microcomb platforms, and improve their performances in timing, spectroscopy, and sensing.
4 citations
TL;DR: In this paper , an organic composite material system is proposed to synthesize reconfigurable PT-symmetric microcavities with controllable complex refractive indices for realizing tunable single-mode laser outputs.
Abstract: Synthetic photonic materials exploiting the quantum concept of parity–time (PT) symmetry lead to an emerging photonic paradigm—non‐Hermitian photonics, which is revolutionizing the photonic sciences. The non‐Hermitian photonics dealing with the interplay between gain and loss in PT synthetic photonic material systems offers a versatile platform for advancing microlaser technology. However, current PT‐symmetric microcavity laser systems only manipulate imaginary parts of the refractive indices, suffering from limited laser spectral bandwidth. Here, an organic composite material system is proposed to synthesize reconfigurable PT‐symmetric microcavities with controllable complex refractive indices for realizing tunable single‐mode laser outputs. A grayscale electron‐beam direct‐writing technique is elaborately designed to process laser dye‐doped polymer films in one single step into microdisk cavities with periodic gain and loss distribution, which enables thresholdless PT‐symmetry breaking and single‐mode laser operation. Furthermore, organic photoisomerizable compounds are introduced to reconfigure the PT‐symmetric systems in real‐time by tailoring the real refractive index of the polymer microresonators, allowing for a dynamically and continuously tunable single‐mode laser output. This work fundamentally enhances the PT‐symmetric photonic systems for innovative design of synthetic photonic materials and architectures.
1 citations
TL;DR: In this paper , a machine learning algorithm is used to predict the unknown temperature by taking full advantage of multiple resonances, and the results show the average error of 3.8'×'10-3'°C within the range from 25.00°C to 40.00`C by employing a generalized regression neural network.
Abstract: Whispering gallery mode (WGM) resonators provide an important platform for fine measurement thanks to their small size, high sensitivity, and fast response time. Nevertheless, traditional methods focus on tracking single-mode changes for measurement, and a great deal of information from other resonances is ignored and wasted. Here, we demonstrate that the proposed multimode sensing contains more Fisher information than single mode tracking and has great potential to achieve better performance. Based on a microbubble resonator, a temperature detection system has been built to systematically investigate the proposed multimode sensing method. After the multimode spectral signals are collected by the automated experimental setup, a machine learning algorithm is used to predict the unknown temperature by taking full advantage of multiple resonances. The results show the average error of 3.8 × 10-3°C within the range from 25.00°C to 40.00°C by employing a generalized regression neural network (GRNN). In addition, we have also discussed the influence of the consumed data resource on its predicted performance, such as the amount of training data and the case of different temperate ranges between the training and test data. With high accuracy and large dynamic range, this work paves the way for WGM resonator-based intelligent optical sensing.
TL;DR: In this paper , an external scatterer is introduced to cancel the reflection of signal photons by an atom due to nonideal chiral interactions, which leads to unidirectional propagation even when the photon-atom interactions are not ideal.
Abstract: Coherently manipulating single photons in nanophotonic structures with unidirectional propagation is one of the central goals for integrated quantum information processing. Photonic devices constructed by a single atom coupled to a whispering-gallery-mode microresonator (WGMM) with nonideal chiral photon-atom interactions inevitably induce undesired photon scattering. Here, an external scatterer is introduced to the WGMM to cancel the reflection of signal photons by an atom due to nonideal chiral interactions. By properly tuning the positions of the scatterer, destructive and constructive interferences between reflected photons of different pathways are utilized to control the reflection properties of single incident photons. The results show that the reflection probabilities can be suppressed by applying the interplay between chirality and backscattering. Constructing perfect destructive interferences directly leads to unidirectional propagation even when the photon-atom interactions are not ideal. Because the amplitudes of the reflected photons produced by the scatterer can be enhanced to meet requirements of perfect destructive interfering processes, unidirectional propagation is preserved against dissipations.
TL;DR: In this paper , a general and systematic theoretical framework based on perturbation theory in company with mean field treatment is provided to capture the quantum effects and the form of nonlinear dissipation and parasitic Hamiltonian as well as their relationship to the nonlinear coupling rate are predicted.
Abstract: Mean‐field treatment (MFT) is frequently applied to approximately predict the dynamics of quantum optics systems. It simplifies the system Hamiltonian by neglecting the quantum statistics of certain modes that are driven strongly by lasers or couple weakly with other modes. However, the neglected quantum correlations between different modes result in unanticipated quantum effects and might lead to significantly distinct system dynamics. Here, a general and systematic theoretical framework based on perturbation theory in company with MFT is provided to capture these quantum effects. The form of nonlinear dissipation and parasitic Hamiltonian as well as their relationship to the nonlinear coupling rate are predicted. Furthermore, the indicator is also proposed as a measure of the accuracy of mean‐field treatment. As an example, this theory is applied to quantum frequency conversion, in which mean‐field treatment is commonly applied, to test its limitation under strong pump and large coupling strength. The analytical results show excellent agreement with the numerical simulations. This work clearly reveals the residual quantum effects neglected by MFT and provides a more precise theoretical framework for nonlinear optics and quantum optics.
18 May 2023
TL;DR: In this paper , a free space-to-chip pipeline is proposed to efficiently transport single atoms from a magneto-optical trap to an on-chip evanescent field trap.
Abstract: A free-space-to-chip pipeline is proposed to efficiently transport single atoms from a magneto-optical trap to an on-chip evanescent field trap. Due to the reflection of the dipole laser on the chip surface, the conventional conveyor belt approach can only transport atoms close to the chip surface but with a distance of about one wavelength, which prevents efficient interaction between the atom and the on-chip waveguide devices. Here, based on a two-layer photonic chip architecture, a diffraction beam of the integrated grating with an incident angle of the Brewster angle is utilized to realize free-space-to-chip atom pipeline. Numerical simulation verified that the reflection of the dipole laser is suppressed and that the atoms can be brought to the chip surface with a distance of only 100nm. Therefore, the pipeline allows a smooth transport of atoms from free space to the evanescent field trap of waveguides and promises a reliable atom source for a hybrid photonic-atom chip.
18 Jul 2023
TL;DR: In this article , the challenges and advances needed across those areas covering design tools, simulation capabilities, fabrication processes, the need for entirely new components, integration and hybridization and the characterization of devices are identified.
Abstract:
Photonic technologies offer numerous functionalities that can be used to realize astrophotonic instruments. The most spectacular example to date is the ESO Gravity instrument at the Very Large Telescope in Chile that combines the light-gathering power of four 8-m telescopes through a complex photonic interferometer. Fully integrated astrophotonic devices offer critical advantages for instrument development, including extreme miniaturization when operating at the diffraction-limit, plus integration, superior thermal and mechanical stabilization owing to the small footprint, and high replicability offering significant cost savings. Numerous astrophotonic technologies have been developed to address shortcomings of conventional instruments to date, including the development of photonic lanterns to convert from multimode inputs to single mode outputs, complex aperiodic fiber Bragg gratings to filter OH emission from the atmosphere, beam combiners enabling long baseline interferometry with for example, ESO Gravity, and laser frequency combs for high precision spectral calibration of spectrometers. Despite these successes, the facility implementation of photonic solutions in astronomical instrumentation is currently limited because of 1) low throughputs from coupling to fibers, coupling fibers to chips, propagation and bend losses, device losses, etc., 2) difficulties with scaling to large channel count devices needed for large bandwidths and high resolutions, and 3) efficient integration of photonics with detectors. In this roadmap, we identify 23 key areas that need further development. We outline the challenges and advances needed across those areas covering design tools, simulation capabilities, fabrication processes, the need for entirely new components, integration and hybridization and the characterization of devices. To realize these advances the astrophotonics community will have to work cooperatively with industrial partners who have more advanced manufacturing capabilities. With the advances described herein, multi-functional integrated instruments will be realized leading to novel observing capabilities for both ground and space based platforms, enabling new scientific studies and discoveries.
TL;DR: In this paper , the phase of spin precession was measured for laser-trapped atoms in a bias magnetic field of 20 mG. The phase was determined by the spin states in the excited level and in the ground level.
Abstract: Quantum nondemolition (QND) measurement enhances the detection efficiency and measurement fidelity, and is highly desired for its applications in precision measurements and quantum information processing. We propose and demonstrate a QND measurement scheme for the spin states of laser-trapped atoms. On ${}^{171}\mathrm{Yb}$ atoms held in an optical dipole trap, a transition that is simultaneously cycling, spin-selective, and spin-preserving is created by introducing a circularly polarized beam of a control laser to optically dress the spin states in the excited level, while leaving the spin states in the ground level unperturbed. We measure the phase of spin precession of $5\ifmmode\times\else\texttimes\fi{}{10}^{4}$ atoms in a bias magnetic field of 20 mG. This QND approach reduces the optical absorption detection noise by $\ensuremath{\sim}19\phantom{\rule{0.2em}{0ex}}\mathrm{dB}$, to an inferred level of 2.3 dB below the atomic quantum projection noise. In addition to providing a general approach for efficient spin-state readout, this all-optical technique allows quick switching and real-time programming for quantum sensing and quantum information processing.
04 Apr 2023
TL;DR: In this article , an atom-referenced stabilized soliton microcomb generation system based on the integrated microring resonator is presented, which can be easily implemented and generalized to various photonic platforms, thus paving the way towards the portable and ultraprecise optical sources for high precision spectroscopy.
Abstract: For the applications of the frequency comb in microresonators, it is essential to obtain a fully frequency-stabilized microcomb laser source. Here, we demonstrate an atom-referenced stabilized soliton microcomb generation system based on the integrated microring resonator. The pump light around $1560.48\,\mathrm{nm}$ locked to an ultra-low-expansion (ULE) cavity, is frequency-doubled and referenced to the atomic transition of $^{87}\mathrm{Rb}$. The repetition rate of the soliton microcomb is injection-locked to an atomic-clock-stabilized radio frequency (RF) source, leading to mHz stabilization at $1$ seconds. As a result, all comb lines have been frequency-stabilized based on the atomic reference and could be determined with very high precision reaching $\sim18\,\mathrm{Hz}$ at 1 second, corresponding to the frequency stability of $9.5\times10^{-14}$. Our approach provides an integrated and fully stabilized microcomb experiment scheme with no requirement of $f-2f$ technique, which could be easily implemented and generalized to various photonic platforms, thus paving the way towards the portable and ultraprecise optical sources for high precision spectroscopy.
13 May 2023
TL;DR: In this article , a hybrid photonic-atom chip platform based on a GaN-on-sapphire chip and the transport of an ensemble of atoms from free space towards the chip with an optical conveyor belt was demonstrated.
Abstract: Trapped atoms on photonic structures inspire many novel quantum devices for quantum information processing and quantum sensing. Here, we have demonstrated a hybrid photonic-atom chip platform based on a GaN-on-sapphire chip and the transport of an ensemble of atoms from free space towards the chip with an optical conveyor belt. The maximum transport efficiency of atoms is about 50% with a transport distance of 500 $\mathrm{\mu m}$. Our results open up a new route toward the efficiently loading of cold atoms into the evanescent-field trap formed by the photonic integrated circuits, which promises strong and controllable interactions between single atoms and single photons.
TL;DR: In this paper , the authors explore cavity-enhanced Rydberg OB with a thermal cesium vapor cell and show that the phase transition signal at the critical point is enhanced more than 10 times that without the cavity, implying an enhancement of two orders of magnitude in the sensitivity.
Abstract: Optical bistability (OB) of Rydberg atoms provides a new, to the best of our knowledge, platform for studying nonequilibrium physics and a potential resource for precision metrology. To date, the observation of Rydberg OB has been limited in free space. Here, we explore cavity-enhanced Rydberg OB with a thermal cesium vapor cell. The signal of Rydberg OB in a cavity is enhanced by more than one order of magnitude compared with that in free space. The slope of the phase transition signal at the critical point is enhanced more than 10 times that without the cavity, implying an enhancement of two orders of magnitude in the sensitivity for Rydberg-based sensing and metrology.
22 Jun 2023
TL;DR: In this article , a modified detector tomography model that reduces the number of variables that need optimization is presented. But the model is not suitable for large number of pixels, and the accuracy of the reconstructed optical coherent and thermal states remains above 99%, and the second and third order correlations agree well with the theoretical values for a mean number of photons up to 100.
Abstract: Photon-number resolving detectors with hundreds of pixels are now readily available, while the characterization of these detectors using detector tomography is computationally intensive. Here, we present a modified detector tomography model that reduces the number of variables that need optimization. To evaluate the effectiveness and accuracy of our model, we reconstruct the photon number distribution of optical coherent and thermal states using the expectation-maximization-entropy algorithm. Our results indicate that the fidelity of the reconstructed states remains above 99%, and the second and third-order correlations agree well with the theoretical values for a mean number of photons up to 100. We also investigate the computational resources required for detector tomography and find out that our approach reduces the solving time by around a half compared to the standard detector tomography approach, and the required memory resources are the main obstacle for detector tomography of a large number of pixels. Our results suggest that detector tomography is viable on a supercomputer with 1~TB RAM for detectors with up to 340 pixels.