A phonon laser operating at an exceptional point

Zhang, Jing; Peng, Bo; Özdemir, Şahin Kaya; Pichler, Kevin; Krimer, Dmitry O.; Zhao, Guangming; Nori, Franco; Liu, Yu-xi; Rotter, Stefan; Yang, Lan

doi:10.1038/s41566-018-0213-5

Cited by 342 publications

(169 citation statements)

References 40 publications

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“…Further increasing the pumping power, the coupled cavity system will exceed the threshold and enter the lasing phase. The EP, known as the  phase transition point, occurs at the point g 2 a = g¢ and ò=0 in the parametric space; when g 2 a g > ¢ , the system is in the  symmetric lasing phase, where both modes are lasing; whereas when g 2 a g < ¢ , the  symmetry breaks and the system is in the single mode lasing phase [9,[56][57][58]. In contrast to the cases below the lasing threshold, a nonequilibrium phase transition occurs at the EP.…”

Section: Active-passive Cavity Systemmentioning

confidence: 99%

Sensitivity of parameter estimation near the exceptional point of a non-Hermitian system

2019

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The exceptional points (EPs) of non-Hermitian systems, where n different energy eigenstates merge into an identical one, have many intriguing properties that have no counterparts in Hermitian systems. In particular, the n 1  dependence of the energy level splitting on a perturbative parameter ò near an nth order EP stimulates the idea of metrology with arbitrarily high sensitivity, since the susceptibility dò 1/ n /dò diverges at the EP. Here we theoretically study the sensitivity of parameter estimation near the EPs, using the exact formalism of quantum Fisher information (QFI). The QFI formalism allows the highest sensitivity to be determined without specifying a specific measurement approach. We find that the EP bears no dramatic enhancement of the sensitivity. Instead, the coalescence of the eigenstates exactly counteracts the eigenvalue susceptibility divergence and makes the sensitivity a smooth function of the perturbative parameter. between these eigenenergies can be excited to measure the eigenvalue susceptibility. However, non-Hermitian systems are fundamentally different. Because different eigenstates of non-Hermitian systems are in general nonorthogonal and even become identical at the EP, exciting the transitions between different eigenstates near the EP to measure the eigenvalue susceptibility is infeasible.In this paper, we study the sensitivity around the EP of a coupled cavity system for its immediate relevance to recent experimental studies [34,35]. Nonetheless, the theoretical formalism and the main conclusion-no dramatic sensitivity enhancement at the EP-are applicable to a broad range of systems, such as magnon-cavity systems [37,38] and opto-mechanical systems [39,40]. We use the exact formalism of quantum Fisher information (QFI) [41] to characterize the sensitivity of parameter estimation. The QFI formalism enables us to evaluate the sensitivity without referring to a specific measurement scheme-be it phase, intensity, or any other complicated measurements of the output from the system. We find that no sensitivity boost exists at the EP. The reason boils down to the coalescence of the eigenstates around the EP. Due to the indistinguishability of different eigenstates around the EP, not one but all eigenstates are equally excited by an arbitrary detection field. The average of all eigenstates exactly cancels out the singularity in the susceptibility divergence of the eigenenergies and makes the sensitivity normal around the EP. The cancellation may also be understood by the divergent Pertermann excess-noise factor at the EP (or critical point) [42,43].The article is organized as follows: in section 2, the basic concept of EPs is introduced using a simple coupled-cavity model; in section 3, we introduce the definition of sensitivity. Sensitivity analysis for general linear systems is presented in this section; In sections 4 and 5, two specific experimentally relevant schemes, namely, coupled passive-passive cavities and coupled active-passive cavities, are considered and the numerical simul...

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Section: Active-passive Cavity Systemmentioning

confidence: 99%

Sensitivity of parameter estimation near the exceptional point of a non-Hermitian system

2019

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“…In addition, by making use of the thermal effects, innovative photonic techniques have been developed. For example, the thermal tuning technique has been applied to adjust the resonator frequency in parity-time-symmetric resonator systems 20,61,62 and to accurately measure optothermal properties of resonators 63,64 . Furthermore, thermal sensing applications have also been demonstrated in many WGM microresonators using the thermo-optic effect and/or the thermal expansion effect.…”

Section: Introductionmentioning

confidence: 99%

Optothermal dynamics in whispering-gallery microresonators

2020

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Optical whispering-gallery-mode microresonators with ultrahigh quality factors and small mode volumes have played an important role in modern physics. They have been demonstrated as a diverse platform for a wide range of photonics applications, such as nonlinear optics, optomechanics, quantum optics, and information processing. Thermal behaviors induced by power buildup in resonators or environmental perturbations are ubiquitous in high-quality-factor whispering-gallery-mode resonators and have played an important role in their operation for various applications. Here in this review, we discuss the mechanisms of laser field induced thermal nonlinear effects, including thermal bistability and thermal oscillation. With the help of the thermal bistability effect, optothermal spectroscopy and optical non-reciprocity have been demonstrated. On the other hand, by tuning the temperature of the environment, the resonant mode frequency will shift, which could also be used for thermal sensing/tuning applications. Thermal locking technique and thermal imaging mechanisms are discussed briefly. Last, we review some techniques to realize thermal stability in a high-quality-factor resonator system.

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“…Phonon lasing have been demonstrated in the electromechanical resonator [47], the nanomechanical resonator [48], the vertical cavity structure [49], and the compound microcavity system [50], and some schemes are also proposed to realize phonon laser in the quantum-dot system [51,52]. In particular, the ultralow-threshold phonon laser [53][54][55] still gives rise to the broad interest and remains largely unexplored.…”

Section: Introductionmentioning

confidence: 99%

Phase-controlled phonon laser

et al. 2018

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A phase-controlled ultralow-threshold phonon laser is proposed by using tunable optical amplifiers in coupled-cavity-optomechanical system. The multiplicative behavior of the individual enhancements, by engineering the phases and strengths of external parametric driving, makes it possible to achieve the strong-coupling regime of optomechanics, where the switching among radiation-pressure, parametric amplification, and three-mode optomechanical couplings can be realized and ultralowthreshold phonon lasing is observable. This opens up novel prospects for applications in, e.g. quantum acoustics, nonlinear phonon devices, and ultrasensitive motion sensing.

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A phonon laser operating at an exceptional point

Cited by 342 publications

References 40 publications

Sensitivity of parameter estimation near the exceptional point of a non-Hermitian system

Sensitivity of parameter estimation near the exceptional point of a non-Hermitian system

Optothermal dynamics in whispering-gallery microresonators

Phase-controlled phonon laser

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