The interplay between interference and absorption leads to interesting phenomena like coherent perfect absorption and coherent perfect transparency (CPA and CPT), which can be exploited for fully optical modulation. While it is known that it is possible to harness CPA and CPT for switching a strong signal beam with a weak control beam, it is not immediate that this process suffers from a fundamental compromise between the device efficiency (quantified by device loss and modulation depth) and the asymmetry between signal and control intensity desired for operation. This article quantifies this compromise and outlines a possible way to overcome it by means of a combination of optical gain and loss in the same photonic component. A general formulation and a specific device realization are both discussed.
The interplay between interference and absorption leads to interesting phenomena like coherent perfect absorption and coherent perfect transparency (CPA and CPT), which can be exploited for fully optical modulation. While it is known that it is possible to harness CPA and CPT for switching a strong signal beam with a weak control beam, it is not immediate that this process suffers from a fundamental compromise between the device efficiency (quantified by device loss and modulation depth) and the asymmetry between signal and control intensity desired for operation. This article quantifies this compromise and outlines a possible way to overcome it by means of a combination of optical gain and loss in the same photonic component. A general formulation and a specific device realization are both discussed.
An experimental work [W. J. Wan, Y. D. Chong, L. Ge, H. Noh, A. D. Stone, and H. Cao, Science 331, 889 (2011)] showed that a resonator that contains a loss medium instead of a gain medium enables coherent perfect absorption (CPA) by interference. Here, we propose an alternative approach to realize such a CPA and coherent perfect transmission (CPT) as well as the switching between CPA and CPT in a cavity quantum electrodynamics (CQED) system by applying an external magnetic field. The proposed CPA and CPT scheme is based on the magnetically induced transparency (MIT) configuration, instead of the conventional electromagnetically induced transparency configuration, which offers a sensitive method to tune CPA and CPT and also is conducive to the flexible control of the CPA and CPT scheme. Under the linear and nonlinear excitation regimes, we derive the approximate analytical solutions of the cavity-output power and the CPA criteria of the CQED system, and find that the CPA can occur at different frequencies in both regimes. In the nonlinear excitation regime, the relationship between the cavity-output power and the cavity-input power can show a bistable characteristic by the control of the static magnetic field, and the CPA point is near the turning point of the cavity-input power on the bistable return hysteresis curve. Furthermore, the line shape and the threshold value for optical bistability can be flexibly controlled by varying the magnetic field under experimentally accessible conditions, thus the magnetic field can well tune the CPA. Also, we compare the analytical and numerical results of the cavity-output power in the nonlinear excitation regime, and they are in good agreement. Our results show that the CQED system based on the MIT configuration can be used as a perfect absorber or nearly perfect transmitter, which may have practical applications in optical logic and optical communication devices.
Abstract Coherent perfect absorption (CPA) and coherent perfect transmission (CPT) are two extreme states arising from the manipulation of optical fields. Generally, CPA and CPT occur under different input-field phases. Therefore, we propose a scheme to realize an all-optical switch based on phase-dependent CPA–CPT conversion. In our proposal, the CPT state and the CPA state are treated as the on state and the off state, respectively. Consequently, the efficiency of this all-optical switch can reach the maximum value of 1. With the introduction of an incoherent pump field, the CPA state can be achieved under a weaker input probe field or can be converted into a CPT state. The results show that the optical switch can operate with weaker fields and can be further optimized by the application of an incoherent field.
Coherent perfect absorption (CPA) or reflection (CPR) are methods to realize the extreme manipulation on an optical field. We propose a scheme to operate a bistable switch with convertible CPA and/or CPR. Generally, CPA and CPR occur with different input-field phases. For example, CPA is realized when two input probe beams are in phase; instead, CPR is achieved when they are out of phase. In this scheme, a CPA state can be converted to a CPR state by an incoherent field although two input fields are in phase. When we use the incoherent field as a switching field, the CPA (CPR) state is treated as the closed (open) state. As a result, the switching efficiency can theoretically reach a maximum value, i.e., η = 1. In addition, the switch can be operated in the linear regime with a weak input field, and in the nonlinear or bistable regime with a strong input field. Moreover, the efficiency of the bistable switch is sensitively dependent on the input-field intensity. It provides a potential application of this work on sensitive optical detecting.
We propose a multiple beam illumination scheme to control the intensity of the light emitted by a thin luminescent layer. The experiment is designed to get as close as possible to the condition of Coherent Perfect Absorption (CPA) at a wavelength at which the absorption coefficient of the luminescent layer is low, and it is realized by externally acting on the phase difference between the incident beams. We elucidate experimental limitations that prevent the achievement of CPA in these slabs. Nevertheless, we are able to demonstrate that when the two beams destructively interfere outside the luminescent layer, the incident light is more efficiently absorbed by the luminescent layer and the intensity of the emitted light is phase-modulated.
Perfect absorption of light critically affects light-matter interaction for various applications. Coherent perfect absorbers (CPA) gain the unique capability of controlling light with light in a linear fashion. Multi-color CPAs [Phys. Rev. Lett. 107, 033901] are highly desirable for broadband and nonlinear light-to-light coherent control, however, the experimental demonstration has still remained elusive. Here we experimentally observe a dual-color version of CPA (DC-CPA) through a second harmonic generation in a single whispering-gallery-mode microcavity. The DC-CPA enables simultaneous perfect absorption of both the incoming fundamental wave and its second harmonic. Similar to its linear counterpart, coherent control in the DC-CPA can be also realized by tuning the relative phase and intensity between the two-colored waves through nonlinear interference instead of the linear one. This scheme breaks the linear boundary of the traditional CPA into a multi-frequency domain and paves the way toward all-optically signal processing and quantum information.
本文提出一种广义的多模式腔光机械系统，其中两光学腔由一束较强的控制场和一束较弱的信号场驱动与同一个机械振子耦合。较弱的信号场将会被该系统完全吸收而不产生任何能量输出，定义该现象为相干完美吸收，并且当相干完美吸收产生时输入信号场的能量将由两个腔场和机械模所分担。改变参数条件，较弱的输入信号场将由一个腔传递到另一个腔而不产生任何的能量损耗，定义该现象为相干完美透射。上述两种现象可由两腔场之间的耦合所操控，并进一步分析了该现象产生的起源和条件。上述两种现象将在全光学领域中的量子信息方面有着潜在的应用。 We present a generalized multi-mode cavity optomechanical system, where two cavity modes with strong control fields and weak signal fields are coupled to a common mechanical resonator. The weak input signal fields will be entirely absorbed by the system without generating any energy output from each of the cavity modes termed coherent perfect absorption (CPA), and the two cavity modes and mechanical mode will share the input probe fields energy when CPA occurs under parameter regimes. With changing the parameter conditions, a weak input signal field will transmit from one cavity to the other cavity without undergoing any energy loss termed coherent perfect transmission (CPT). The above phenomena are dependent on the coupling strength between the two cavity modes in this optomechanical system. The origin and conditions that enable these phenomena to achieve are analyzed, and potential applications in quantum information may be realized in all-optical domain based on such phenomena.