arXiv subjects

Chang-Ling Zou

Publications and source records attributed to Chang-Ling Zou.

At least 163 records · Page 9Linked to original sources

arXiv2018

Extremely terahertz electric-field enhancement in a high-Q photonic crystal slab cavity with nanoholes

A one-dimensional photonic-crystal (PC) cavity with nanoholes is proposed for extremely enhancing the THz electric fields by utilizing the electromagnetic (EM) boundary conditions, where both slot effect (for the perpendicular component of the electric displacement field) and anti-slot effect (for the parallel component of the electric field) contribute to the considerable field enhancement. The EM energy density can be enhanced in the high refractive index material by a factor of (εh/εl)^2, where εh and εl are the permittivities of the high and low refractive index materials, respectively. Correspondingly, the mode volume can be enhanced by a factor of 288 as compared with the regular THz PC cavity and is three orders of magnitude smaller than the diffraction limitation. While the proposed THz cavity design also supports the modes with high Q > 10^4, which lead to strong Purcell enhancement of spontaneous emission by a factor exceeds 10^6. Our THz cavity design is feasible and appealing for experimental demonstrations, since the semiconductor layer where the EM is maximized can naturally be filled with a quantum engineered active materials, which is potential for developing the room-temperature coherent THz radiation sources.

physics.optics↗

arXiv2018

Doubly-resonant-cavity electromagnetically induced transparency

We present an experimental study on the cavity-atom ensemble system, and realize the doubly-resonant cavity enhanced electromagnetically induced transparency, where both the probe and control lasers are resonant with a Fabry-Perot cavity. We demonstrate the precise frequency manipulating of the hybrid optical-atomic resonances, through either temperature or cavity length tuning. In such a system, the control power can be greatly enhanced due to the cavity, and all-optical switching is achieved with a much lower control laser power compared to previous studies. A new theoretical model is developed to describe the effective three-wave mixing process between spin-wave and optical modes. Interesting non-Hermitian physics are predicted theoretically and demonstrated experimentally. Such a doubly-resonant cavity-atom ensemble system without a specially designed cavity can be used for future applications, such as optical signal storage and microwave-to-optical frequency conversion.

physics.optics↗

arXiv2018

Experimental repetitive quantum channel simulation

Universal control of quantum systems is a major goal to be achieved for quantum information processing, which demands thorough understanding of fundamental quantum mechanics and promises applications of quantum technologies. So far, most studies concentrate on ideally isolated quantum systems governed by unitary evolutions, while practical quantum systems are open and described by quantum channels due to their inevitable coupling to environment. Here, we experimentally simulate arbitrary quantum channels for an open quantum system, i.e. a single photonic qubit in a superconducting quantum circuit. The arbitrary channel simulation is achieved with minimum resource of only one ancilla qubit and measurement-based adaptive control. By repetitively implementing the quantum channel simulation, we realize an arbitrary Liouvillian for a continuous evolution of an open quantum system for the first time. Our experiment provides not only a testbed for understanding quantum noise and decoherence, but also a powerful tool for full control of practical open quantum systems.

quant-ph↗

arXiv2018

Optimal third-harmonic generation in an optical microcavity with $χ^{(2)}$ and $χ^{(3)}$ nonlinearities

Third-harmonic generation can be realized via both $χ^{(3)}$ and cascaded $χ^{(2)}$ nonlinear processes in a triply-resonant microcavity. It is still unknown how these processes interfere with each other and the optimization of the conversion efficiency still remains as a question. In this work, the interplay between the direct third-harmonic generation and the cascaded process combining of the second-harmonic generation and the sum-frequency generation are investigated. It is found that the interference effect between these two processes can be used to improve the conversion efficiency. By optimizing the cavity resonance and the external coupling conditions, the saturation of the nonlinear conversion is mitigated and the third-harmonic conversion efficiency is increased. A design rule is provided for achieving efficient third-harmonic generation in an optical microcavity, which can be generalized further to the high-order harmonic generations.

physics.optics↗

arXiv2018

Enhanced absorption microscopy with correlated photon pairs

By harnessing the quantum states of light for illumination, precise phase and absorption estimations can be achieved with precision beyond the standard quantum limit. Despite their significance for precision measurements, quantum states are fragile in noisy environments which leads to difficulties in revealing the quantum advantage. In this work, we propose a scheme to improve optical absorption estimation precision by using the correlated photon pairs from spontaneous parametric down-conversion as the illumination. This scheme performs better than clasical illumination when the loss is below a critical value. Experimentally, the scheme is demonstrated by a scanning transmission type microscope that uses correlated photon illumination. As a result, the signal-to-noise ratio (SNR) of a two-photon image shows a $1.36$-fold enhancement over that of single-photon image for a single-layer graphene with a $0.98$ transmittance. This enhancement factor will be larger when using multi-mode squeezed state as the illumination.

quant-ph↗

arXiv2018

Enhancement of the second-harmonic generation based on the cascaded second- and third-order nonlinear processes in a multimode optical microcavity

Optical microcavities are often used to realize enhanced nonlinear optical interactions for highly efficient second-harmonic generation. With increased pump power, the efficiency of nonlinear frequency conversion can be increased further, while some other unwanted nonlinear effects will also emerge, leading to complicated dynamics or instability. Here, we study the interplay between cascaded second- and third-order nonlinear processes and investigate their impact on the second-harmonic generation in microcavities. It is found that the non-degenerate optical parametric oscillation (OPO) appears and the presence of $χ^{(3)}$ process can modify the OPO threshold significantly when the multimode cavity is strongly pumped at the fundamental optical mode. One can even break the efficiency limitation of the second-harmonic mode restricted by the OPO by utilizing the interference between the OPO and the four-wave mixing. The present coherent interplay between nonlinear optical processes in microcavities is conducive to exploring new physics in the cavity nonlinear photonics.

physics.optics↗

arXiv2018

Control of Second Harmonic Generation in Doubly Resonant Aluminum Nitride Microrings to Address Rubidium Two-Photon Clock Transition

Nonlinear optical effects have been studied extensively in microresonators as more photonics applications transition to integrated on-chip platforms. Due to low optical losses and small mode volumes, microresonators are demonstrably the state-of-the-art platform for second harmonic generation (SHG). However, the working bandwidth of such microresonator-based devices are relatively small, presenting a challenge for applications where a specifically targeted wavelength needs to be addressed. In this work, we analyzed the phase-matching window and resonance wavelength with respect to varying microring width, radius and temperature. A chip with precise design parameters was fabricated with phase-matching realized at the exact wavelength of two-photon transition of 85-Rubidium. This procedure can be generalized to any target pump wavelength in the telecom-band with picometer precision.

physics.optics↗

arXiv2018

One way quantum repeaters with quantum Reed-Solomon codes

We show that quantum Reed-Solomon codes constructed from classical Reed-Solomon codes can approach the capacity on the quantum erasure channel of $d$-level systems for large dimension $d$. We study the performance of one-way quantum repeaters with these codes and obtain a significant improvement in key generation rate compared to previously investigated encoding schemes with quantum parity codes and quantum polynomial codes. We also compare the three generation of quantum repeaters using quantum Reed-Solomon codes and identify parameter regimes where each generation performs the best.

quant-ph↗

arXiv2018

Superconducting cavity electro-optics: a platform for coherent photon conversion between superconducting and photonic circuits

Leveraging the quantum information processing ability of superconducting circuits and long-distance distribution ability of optical photons promises the realization of complex and large-scale quantum networks. In such a scheme, a coherent and efficient quantum transducer between superconducting and photonic circuits is critical. However, such quantum transducer is still challenging since the use of intermediate excitations in current schemes introduces extra noise and limits bandwidth. Here we realize direct and coherent transduction between superconducting and photonic circuits based on triple-resonance electro-optics principle, with integrated devices incorporating both superconducting and optical cavities on the same chip. Electromagnetically induced transparency is observed, indicating the coherent interaction between microwave and optical photons. Internal conversion efficiency of 25.9\pm0.3\% has been achieved, with 2.05\pm0.04\% total efficiency. Superconducting cavity electro-optics offers broad transduction bandwidth and high scalability, and represents a significant step towards the integrated hybrid quantum circuits and distributed quantum computation.

physics.optics↗

arXiv2018

All-Optical control of linear and nonlinear energy transfer via Zeno effect

Microresonator-based nonlinear processes are fundamental to applications including microcomb generation, parametric frequency conversion, and harmonics generation. While nonlinear processes involving either second- ($χ^{(2)}$) or third- $χ^{(3)}$) order nonlinearity have been extensively studied, the interaction between these two basic nonlinear processes has seldom been reported. In this letter, we demonstrate a coherent interplay between second- and third- order nonlinear processes. The parametric ($χ^{(2)})$ coupling to a lossy ancillary mode shortens the lifetime of the target photonic mode and suppresses its density of states, preventing the photon emissions into the target photonic mode via Zeno effect. Such effect is then used to control the stimulated four-wave mixing process and realize a suppression ratio of $34.5$.

quant-ph↗

arXiv2018

Reconfigurable vortex beam generator based on the Fourier transformation principle

A method to generate the optical vortex beam with arbitrary superposition of different orders of orbital angular momentum (OAM) on a photonic chip is proposed. The distributed Fourier holographic gratings are proposed to convert the propagating wave in waveguides to a vortex beam in the free space, and the components of different OAMs can be controlled by the amplitude and phases of on-chip incident light based on the principle of Fourier transformation. As an example, we studied a typical device composed of nine Fourier holographic gratings on fan-shaped waveguides. By scalar diffraction calculation, the OAM of the optical beam from the reconfigurable vortex beam generator can be controlled on-demand from -2nd to 2nd by adjusting the phase of input light fields, which is demonstrated numerically with the fidelity of generated optical vortex beam above 0.69. The working bandwidth of the Fourier holographic grating is about 80 nm with a fidelity above 0.6. Our work provides an feasible method to manipulate the vortex beam or detect arbitrary superposition of OAMs, which can be used in integrated photonics structures for optical trapping, signal processing, and imaging.

physics.optics↗

arXiv2017

Phase sensitive imaging of 10 GHz vibrations in an AlN microdisk resonator

We demonstrate a high frequency phase-sensitive heterodyne vibrometer, operating up to 10 GHz. Using this heterodyne vibrometer, the amplitude and phase fields of the fundamental thickness mode, the radial fundamental and the 2nd-order modes of an AlN optomechanical microdisk resonator are mapped with a displacement sensitivity of around 0.36 picometer at 1 Hz resolution bandwidth. The simultaneous amplitude and phase measurement allows precise mode identification and characterization. The recorded modal frequencies and proles are consistent with numerical simulations. This vibrometer will be of great significance for the development of high frequency mechanical devices.

physics.ins-det↗

arXiv2017

Efficient Third Harmonic Generation in Composite Aluminum Nitride / Silicon Nitride Microrings

Aluminum nitride and silicon nitride have recently emerged as important nonlinear optical materials in integrated photonics respectively for their quadratic and cubic optical nonlinearity. A composite aluminum nitride and silicon nitride waveguide structure, if realized, will simultaneously allow highly efficient second and third harmonic generation on the same chip platform and therefore assists 2f-3f self-referenced frequency combs. On-chip third harmonic generation, being a higher order nonlinear optics effect, is more demanding than second harmonic generation due to the large frequency difference between the fundamental and third harmonic frequencies which implies large change of refractive indices and more strigent requirements on phase matching. In this work we demonstrate high-efficiency third harmonic generation in a high Q composite aluminum nitride / silicon nitide ring cavity. By carefully engineering the microring resonator geometry of the bilayer structure to optimize the quality factor, mode volume and modal overlap of the optical fields, we report a maximum conversion efficiency of $180\%\,\mathrm{W^{-2}}$. This composite photonic chip design provides a solution for efficient frequency conversion over a large wavelength span, broadband comb generation and self-referenced frequency combs.

physics.optics↗

arXiv2017

Reconfigurable optomechanical circulator and directional amplifier

Non-reciprocal devices, which allow the non-reciprocal signal routing, serve as the fundamental elements in photonic and microwave circuits and are crucial in both classical and quantum information processing. The radiation-pressure-induced coupling between light and mechanical motion in traveling wave resonators has been exploited to break the Lorentz reciprocity, realizing non-reciprocal devices without magnetic materials. Here, we experimentally demonstrate a reconfigurable nonreciprocal device with alternative functions of either a circulator or a directional amplifier via the optomechanically induced coherent photon-phonon conversion or gain. The demonstrated device exhibits considerable flexibility and offers exciting opportunities for combining reconfigurability, non-reciprocity and active properties in single photonic structures, which can also be generalized to microwave as well as acoustic circuits.

physics.optics↗

arXiv2017

Quantum transduction with adaptive control

Quantum transducers play a crucial role in hybrid quantum networks. A good quantum transducer can faithfully convert quantum signals from one mode to another with minimum decoherence. Most investigations of quantum transduction are based on the protocol of direct mode conversion. However, the direct protocol requires the matching condition, which in practice is not always feasible. Here we propose an adaptive protocol for quantum transducers, which can convert quantum signals without requiring the matching condition. The adaptive protocol only consists of Gaussian operations, feasible in various physical platforms. Moreover, we show that the adaptive protocol can be robust against imperfections associated with finite squeezing, thermal noise, and homodyne detection. It can be implemented to realize quantum state transfer between microwave and optical modes.

quant-ph↗

arXiv2017

Phase-Controlled Phonon Laser

A phase-controlled ultralow-threshold phonon laser is proposed by using tunable optical amplifiers in coupled-cavity-optomechanical system. Giant enhancement of coherent photon-phonon interactions is achieved by engineering the strengths and phases of external parametric driving. This in turn enables single-photon optomechanics and low-power phonon lasing, opening up novel prospects for applications, e.g. quantum phononics and ultrasensitive motion detection.

quant-ph↗

arXiv2017

Effect of unbalanced and common losses in quantum photonic integrated circuits

Loss is inevitable for the optical system due to absorption of materials, scattering caused by the defects and surface roughness. In quantum optical circuits, the loss can not only reduce the intensity of signal, but also affect the performance of quantum operations. In this work, we divide losses into unbalanced linear loss and shared common loss, and provide a detailed analysis on how loss affects the integrated linear optical quantum gates. It is found that the orthogonality of eigenmodes and the unitary phase relation of the coupled waveguide modes are destroyed by the loss. As a result, the fidelity of single- and two-qubit operations decrease significant as the shared loss becomes comparable to the coupling strength. Our results are important for the investigation of large-scale photonic integrated quantum information process.

physics.optics↗

arXiv2017

Efficient visible frequency comb generation via Cherenkov radiation from a Kerr microcomb

Optical frequency combs enable state-of-the-art applications including frequency metrology, optical clocks, astronomical measurements, and sensing. Recent demonstrations of microresonator-based Kerr frequency combs or microcombs pave the way to scalable and stable comb sources on a photonic chip. Generating microcombs in the visible wavelength range, however, has been limited by large material dispersion and optical loss. Here we demonstrate a scheme for efficiently generating visible microcomb in a high Q aluminum nitride microring resonator. Enhanced Pockels effect strongly couples infrared and visible modes into hybrid mode pairs, which participate in the Kerr microcomb generation process and lead to strong Cherenkov radiation in the visible band of an octave apart. A surprisingly high conversion efficiency of 22% is achieved from the pump laser to the visible comb. We further demonstrate a robust frequency tuning of the visible comb by more than one free spectral range and apply it to the absorption spectroscopy of a water-based dye molecule solution. Our work marks the first step towards high-efficiency visible microcomb generation and its utilization, and it also provides insights on the significance of Pockels effect and its strong coupling with Kerr nonlinearity in a single microcavity device.

physics.optics↗