Optomechanically Induced Absorption (OMIA)

• OMIA is a mechanically mediated absorption phenomenon in cavity optomechanics, characterized by a narrow dip arising when the pump–probe beat resonates with a mechanical mode.
• It is observed across diverse platforms including cryogenic microwave systems, room-temperature 3D cavities, and hybrid optical–microwave devices, highlighting its versatile applications in notch filtering and sensing.
• The effect relies on interference mechanisms and dressed susceptibilities in multi-mode interactions, allowing control over the transition between absorption and transparency regimes.

Optomechanically induced absorption (OMIA) is the absorptive counterpart of optomechanically induced transparency (OMIT) in driven cavity optomechanics. In its standard form, a strong control field and a weak probe interrogate a cavity whose resonance is coupled to mechanical motion, and the probe response develops a narrow mechanically mediated absorption feature when the pump–probe beat note is resonant with the mechanical mode. Depending on platform and readout convention, OMIA appears as a sharp dip or notch in transmission, a narrow dip in reflection, or a reduction of probe throughput relative to the bare cavity response (Kumar et al., 2021, Shevchuk et al., 2015). In hybrid settings it is also described as the optomechanical analog of electromagnetically induced absorption (EIA), including blue-sideband optical absorption in a common optical–microwave–mechanical device and absorption resonances embedded inside broader OMIT windows in double-cavity systems (Jiang et al., 2014, Qu et al., 2013).

1. Terminology, scope, and conceptual placement

OMIA belongs to the same interference-controlled linear-response family as OMIT. In microwave cavity optomechanics, OMIA is defined operationally as the regime in which mechanically mediated interference causes a reduction of probe transmission at the optomechanical resonance, producing a narrow absorption dip or notch in the measured $S_{21}$ spectrum (Kumar et al., 2021). In a single-port optical or microwave cavity probed in reflection, the same phenomenon is identified as a narrow dip in the reflection coefficient $|S_{11}|$ and is explicitly distinguished from optomechanically induced reflection (OMIR), which is a peak rather than a dip (Shevchuk et al., 2015).

The terminology is not entirely uniform across the literature. Hybrid double-cavity opto-electro-mechanical work from 2013 framed the effect as “electromagnetically induced absorption” in a three-oscillator system, but the same paper states that this is best understood in modern language as a hybrid double-cavity realization of OMIA-like physics, more precisely an absorption resonance embedded inside an OMIT transparency window (Qu et al., 2013). A later hybrid opto-electromechanical study made the identification more explicit by describing blue-sideband optical absorption as the analog of EIA and, in optomechanical language, as an OMIA-type response (Jiang et al., 2014).

A recurring source of confusion is the relation between optomechanical EIA and atomic EIA. The three-mode hybrid EIA discussed in double-cavity opto-electro-mechanics is explicitly stated to be different from the atomic EIA discovered by Lezama et al.; the hybrid effect is a classical or semiclassical coupled-mode interference phenomenon in damped oscillators rather than an atomic coherence effect based on optical pumping, excited-state degeneracy, or selection rules (Qu et al., 2013). A second distinction is between standard OMIA and inverse OMIT: the latter is a coherent-perfect-absorption effect requiring two coherent counter-propagating probes and vanishing output at both ports, rather than a single-probe absorption feature (Wu et al., 2015).

2. Linear-response formulation

The common theoretical structure is a strong-control, weak-probe linearization of radiation-pressure dynamics. In the microwave formulation, the cavity input–output relation and the linearized cavity–mechanical response give the probe transmission as

$$S_{21}(\omega_p)=1-\frac{\chi_c(\omega_p)\,\kappa_{\mathrm{ext}}/2}{1\mp g_0^2\,n_{\mathrm{cav}}\,\chi_c(\omega_p)\chi_m(\omega_p)},$$

with cavity and mechanical susceptibilities

$$\chi_c^{-1}(\omega_p)=\frac{\kappa}{2}-i(\Omega+\Delta), \qquad \chi_m^{-1}(\omega_p)=\frac{\Gamma_m}{2}-i(\Omega\pm\Omega_m),$$

where $\Omega=\omega_p-\omega_d$ and $\Delta=\omega_d-\omega_c$ (Kumar et al., 2021). The sign choice in the denominator distinguishes red and blue pumping. In this formulation OMIA, OMIT, and gain are different interference outcomes of the same dressed response.

In hybrid multi-mode systems the same logic appears as a nested susceptibility. For the red-red double-cavity opto-electro-mechanical configuration, the normalized optical response is

$$\mathcal{E}_L(x) = \cfrac{2\mathrm{i}\kappa_1} {(x+\mathrm{i}\kappa_1) - \cfrac{g_1^2|a_{10}|^2/2} {(x+\mathrm{i}\gamma_m/2) - \cfrac{g_2^2|a_{20}|^2/2}{(x+\mathrm{i}\kappa_2)}}},$$

with $x=\delta-\omega_m$ (Qu et al., 2013). The optical cavity denominator is corrected by a mechanical susceptibility, and the mechanical susceptibility is itself corrected by the second cavity. That nested denominator is the origin of the narrow absorption resonance inside the broader OMIT window.

The same dressed-susceptibility structure persists in later two-cavity and auxiliary-mode systems. In the two-cavity optomechanical model, the probe-sideband amplitude in the probed cavity contains a cavity denominator dressed by a mechanical denominator that is itself modified by the second cavity drive through a term proportional to $\beta_2/(\kappa_2-ix)$ (Qian et al., 2023). In the indirectly coupled auxiliary-mode microcavity, the red-sideband transmission coefficient $t_r$ contains a mixed interference term

$|S_{11}|$0

which encodes optical and optomechanical pathways on equal footing (Qin et al., 2019).

3. Interference mechanisms and detuning conventions

The physical mechanism is always sideband interference, but the sign of the observed feature depends on detuning convention, measured port, and which field amplitude is being added or subtracted. In the microwave transmission measurements, blue pumping means

$|S_{11}|$1

the probe is swept near

$|S_{11}|$2

and the lower sideband generated by the mechanically modulated pump interferes destructively with the probe, producing decreased transmission and therefore OMIA (Kumar et al., 2021). Because blue detuning also gives negative dynamical backaction damping, the OMIA linewidth narrows as pump power increases, until the system approaches the auto-oscillation threshold (Kumar et al., 2021).

The hybrid optical–microwave theory of 2014 uses a different output convention. There the OMIA regime is

$|S_{11}|$3

with the optical cavity blue detuned and the microwave cavity red detuned (Jiang et al., 2014). Under these conditions the resonantly generated Stokes field overlaps the near-resonant optical probe and interferes constructively with the intracavity probe pathway. The consequence is enhanced intracavity buildup and reduced through-port transmission, so the measured $|S_{11}|$4 shows an absorption feature even though the interference is described as constructive at the intracavity level (Jiang et al., 2014). In that same system OMIA is the intermediate regime between bare transmission and parametric amplification: for $|S_{11}|$5 the transmission is reduced below the bare-cavity value, while above about $|S_{11}|$6 the response crosses to $|S_{11}|$7, and at $|S_{11}|$8 amplification is observed (Jiang et al., 2014).

Single-port cavities introduce an additional distinction between OMIA and OMIR. In a Duffing-mechanical single-port cavity, an overcoupled cavity driven on the red sideband may exhibit either OMIA or OMIR depending on drive strength, whereas a blue-sideband drive gives only OMIR in the overcoupled case (Shevchuk et al., 2015). That result makes explicit that OMIA is not determined by detuning alone; coupling condition and measurement geometry are part of the definition.

4. Experimental realizations and representative parameter regimes

OMIA has been realized or predicted across cryogenic microwave devices, ambient-temperature microwave architectures, hybrid optical–microwave systems, and molecular cavity optomechanics. The measurements and models span both resolved-sideband and unresolved-sideband regimes, and the spectral signatures range from narrow absorptive notches to absorption valleys embedded in broader transparency windows.

Platform	OMIA manifestation	Representative conditions
Hybrid opto-electromechanical system (Jiang et al., 2014)	Optical through-port absorption for blue-optical/red-microwave pumping	$|S_{11}|$9 gives OMIA; $$S_{21}(\omega_p)=1-\frac{\chi_c(\omega_p)\,\kappa_{\mathrm{ext}}/2}{1\mp g_0^2\,n_{\mathrm{cav}}\,\chi_c(\omega_p)\chi_m(\omega_p)},$$0 marks crossover; $$S_{21}(\omega_p)=1-\frac{\chi_c(\omega_p)\,\kappa_{\mathrm{ext}}/2}{1\mp g_0^2\,n_{\mathrm{cav}}\,\chi_c(\omega_p)\chi_m(\omega_p)},$$1 gives amplification
Microwave cavity optomechanics at $$S_{21}(\omega_p)=1-\frac{\chi_c(\omega_p)\,\kappa_{\mathrm{ext}}/2}{1\mp g_0^2\,n_{\mathrm{cav}}\,\chi_c(\omega_p)\chi_m(\omega_p)},$$2–$$S_{21}(\omega_p)=1-\frac{\chi_c(\omega_p)\,\kappa_{\mathrm{ext}}/2}{1\mp g_0^2\,n_{\mathrm{cav}}\,\chi_c(\omega_p)\chi_m(\omega_p)},$$3 mK (Kumar et al., 2021)	Blue-pump transmission notch in $$S_{21}(\omega_p)=1-\frac{\chi_c(\omega_p)\,\kappa_{\mathrm{ext}}/2}{1\mp g_0^2\,n_{\mathrm{cav}}\,\chi_c(\omega_p)\chi_m(\omega_p)},$$4 with linewidth narrowing as pump power increases	$$S_{21}(\omega_p)=1-\frac{\chi_c(\omega_p)\,\kappa_{\mathrm{ext}}/2}{1\mp g_0^2\,n_{\mathrm{cav}}\,\chi_c(\omega_p)\chi_m(\omega_p)},$$5, $$S_{21}(\omega_p)=1-\frac{\chi_c(\omega_p)\,\kappa_{\mathrm{ext}}/2}{1\mp g_0^2\,n_{\mathrm{cav}}\,\chi_c(\omega_p)\chi_m(\omega_p)},$$6, $$S_{21}(\omega_p)=1-\frac{\chi_c(\omega_p)\,\kappa_{\mathrm{ext}}/2}{1\mp g_0^2\,n_{\mathrm{cav}}\,\chi_c(\omega_p)\chi_m(\omega_p)},$$7, $$S_{21}(\omega_p)=1-\frac{\chi_c(\omega_p)\,\kappa_{\mathrm{ext}}/2}{1\mp g_0^2\,n_{\mathrm{cav}}\,\chi_c(\omega_p)\chi_m(\omega_p)},$$8, maximum blue-pump $$S_{21}(\omega_p)=1-\frac{\chi_c(\omega_p)\,\kappa_{\mathrm{ext}}/2}{1\mp g_0^2\,n_{\mathrm{cav}}\,\chi_c(\omega_p)\chi_m(\omega_p)},$$9
3D microwave cavity at ambient temperature (Kumar et al., 2024)	Pump-on-resonance upper-sideband absorption dip, with attenuation-to-gain crossover	$$\chi_c^{-1}(\omega_p)=\frac{\kappa}{2}-i(\Omega+\Delta), \qquad \chi_m^{-1}(\omega_p)=\frac{\Gamma_m}{2}-i(\Omega\pm\Omega_m),$$0, $$\chi_c^{-1}(\omega_p)=\frac{\kappa}{2}-i(\Omega+\Delta), \qquad \chi_m^{-1}(\omega_p)=\frac{\Gamma_m}{2}-i(\Omega\pm\Omega_m),$$1, $$\chi_c^{-1}(\omega_p)=\frac{\kappa}{2}-i(\Omega+\Delta), \qquad \chi_m^{-1}(\omega_p)=\frac{\Gamma_m}{2}-i(\Omega\pm\Omega_m),$$2, up to $$\chi_c^{-1}(\omega_p)=\frac{\kappa}{2}-i(\Omega+\Delta), \qquad \chi_m^{-1}(\omega_p)=\frac{\Gamma_m}{2}-i(\Omega\pm\Omega_m),$$3 attenuation, $$\chi_c^{-1}(\omega_p)=\frac{\kappa}{2}-i(\Omega+\Delta), \qquad \chi_m^{-1}(\omega_p)=\frac{\Gamma_m}{2}-i(\Omega\pm\Omega_m),$$4 amplification, $$\chi_c^{-1}(\omega_p)=\frac{\kappa}{2}-i(\Omega+\Delta), \qquad \chi_m^{-1}(\omega_p)=\frac{\Gamma_m}{2}-i(\Omega\pm\Omega_m),$$5 notch width
Hybrid molecular cavity optomechanics (Yin et al., 8 Feb 2025)	Port-selective OMIA when probing through the microdisk-waveguide port	OMIA accompanied by $$\chi_c^{-1}(\omega_p)=\frac{\kappa}{2}-i(\Omega+\Delta), \qquad \chi_m^{-1}(\omega_p)=\frac{\Gamma_m}{2}-i(\Omega\pm\Omega_m),$$6 at $$\chi_c^{-1}(\omega_p)=\frac{\kappa}{2}-i(\Omega+\Delta), \qquad \chi_m^{-1}(\omega_p)=\frac{\Gamma_m}{2}-i(\Omega\pm\Omega_m),$$7; same device gives OMIT for plasmonic-port probing

The cryogenic microwave experiment provides the most direct validation of standard linear input–output theory over a large parameter space. It varies probe frequency, pump frequency, pumping scheme, probe power, pump power, and temperature from $$\chi_c^{-1}(\omega_p)=\frac{\kappa}{2}-i(\Omega+\Delta), \qquad \chi_m^{-1}(\omega_p)=\frac{\Gamma_m}{2}-i(\Omega\pm\Omega_m),$$8 to $$\chi_c^{-1}(\omega_p)=\frac{\kappa}{2}-i(\Omega+\Delta), \qquad \chi_m^{-1}(\omega_p)=\frac{\Gamma_m}{2}-i(\Omega\pm\Omega_m),$$9 mK, and reports excellent agreement with the susceptibility-based model using one $\Omega=\omega_p-\omega_d$0 and one $\Omega=\omega_p-\omega_d$1 per temperature, while allowing $\Omega=\omega_p-\omega_d$2 and $\Omega=\omega_p-\omega_d$3 to vary with temperature and probe power (Kumar et al., 2021). The main OMIA figure shows that the absorption dip becomes stronger and narrower as blue pump power increases, but that the simple theory fails near the blue-sideband auto-oscillation threshold (Kumar et al., 2021).

The room-temperature 3D microwave realization demonstrates that OMIA is not restricted to cryogenic microwave platforms. In a re-entrant cavity with a metallized $\Omega=\omega_p-\omega_d$4 membrane, the unresolved-sideband ratio is

$\Omega=\omega_p-\omega_d$5

the pump is kept on cavity resonance,

$\Omega=\omega_p-\omega_d$6

and OMIA appears at the upper motional sideband $\Omega=\omega_p-\omega_d$7 below an input pump threshold of $\Omega=\omega_p-\omega_d$8, corresponding to $\Omega=\omega_p-\omega_d$9 and $\Delta=\omega_d-\omega_c$0 (Kumar et al., 2024). At $\Delta=\omega_d-\omega_c$1, $\Delta=\omega_d-\omega_c$2, the experiment reports $\Delta=\omega_d-\omega_c$3 attenuation in an $\Delta=\omega_d-\omega_c$4 bandwidth, five times smaller than the bare mechanical linewidth $\Delta=\omega_d-\omega_c$5 (Kumar et al., 2024).

The molecular platform is distinctive because OMIA is selected by probe port rather than by changing the device itself. Probing through the plasmonic cavity yields OMIT, whereas probing through the microdisk waveguide yields an absorption dip once the pump turns on the molecular vibrational pathway, with the hierarchy

$\Delta=\omega_d-\omega_c$6

biasing the interference toward absorption through the lossy plasmonic channel (Yin et al., 8 Feb 2025).

5. Hybrid, multimode, nonlinear, and qubit-assisted generalizations

A major development in OMIA research is the transition from single-cavity, single-mechanical-mode models to nested and multi-path architectures. In the red-red double-cavity opto-electro-mechanical theory, the second driven cavity splits the narrow OMIT pole and inserts a narrow absorption peak of half-width

$\Delta=\omega_d-\omega_c$7

valid when

$\Delta=\omega_d-\omega_c$8

and the line-center response obeys

$\Delta=\omega_d-\omega_c$9

The paper identifies “perfect EIA” at $$\mathcal{E}_L(x) = \cfrac{2\mathrm{i}\kappa_1} {(x+\mathrm{i}\kappa_1) - \cfrac{g_1^2|a_{10}|^2/2} {(x+\mathrm{i}\gamma_m/2) - \cfrac{g_2^2|a_{20}|^2/2}{(x+\mathrm{i}\kappa_2)}}},$$0, where $$\mathcal{E}_L(x) = \cfrac{2\mathrm{i}\kappa_1} {(x+\mathrm{i}\kappa_1) - \cfrac{g_1^2|a_{10}|^2/2} {(x+\mathrm{i}\gamma_m/2) - \cfrac{g_2^2|a_{20}|^2/2}{(x+\mathrm{i}\kappa_2)}}},$$1 (Qu et al., 2013). This is a three-mode OMIA-like effect produced by the mechanical susceptibility being dressed by a second cavity rather than by a simple blue-detuned single-cavity pathway.

Two-cavity optical systems make the same control principle explicit in a different notation. In the mechanically shared two-cavity model, the response of cavity 1 can be switched from perfect OMIT to OMIA by increasing the drive strength of cavity 2, because OMIA becomes significant when the ratio $$\mathcal{E}_L(x) = \cfrac{2\mathrm{i}\kappa_1} {(x+\mathrm{i}\kappa_1) - \cfrac{g_1^2|a_{10}|^2/2} {(x+\mathrm{i}\gamma_m/2) - \cfrac{g_2^2|a_{20}|^2/2}{(x+\mathrm{i}\kappa_2)}}},$$2 is sufficiently large (Qian et al., 2023). With fixed $$\mathcal{E}_L(x) = \cfrac{2\mathrm{i}\kappa_1} {(x+\mathrm{i}\kappa_1) - \cfrac{g_1^2|a_{10}|^2/2} {(x+\mathrm{i}\gamma_m/2) - \cfrac{g_2^2|a_{20}|^2/2}{(x+\mathrm{i}\kappa_2)}}},$$3, reducing $$\mathcal{E}_L(x) = \cfrac{2\mathrm{i}\kappa_1} {(x+\mathrm{i}\kappa_1) - \cfrac{g_1^2|a_{10}|^2/2} {(x+\mathrm{i}\gamma_m/2) - \cfrac{g_2^2|a_{20}|^2/2}{(x+\mathrm{i}\kappa_2)}}},$$4 from $$\mathcal{E}_L(x) = \cfrac{2\mathrm{i}\kappa_1} {(x+\mathrm{i}\kappa_1) - \cfrac{g_1^2|a_{10}|^2/2} {(x+\mathrm{i}\gamma_m/2) - \cfrac{g_2^2|a_{20}|^2/2}{(x+\mathrm{i}\kappa_2)}}},$$5 to $$\mathcal{E}_L(x) = \cfrac{2\mathrm{i}\kappa_1} {(x+\mathrm{i}\kappa_1) - \cfrac{g_1^2|a_{10}|^2/2} {(x+\mathrm{i}\gamma_m/2) - \cfrac{g_2^2|a_{20}|^2/2}{(x+\mathrm{i}\kappa_2)}}},$$6 changes $$\mathcal{E}_L(x) = \cfrac{2\mathrm{i}\kappa_1} {(x+\mathrm{i}\kappa_1) - \cfrac{g_1^2|a_{10}|^2/2} {(x+\mathrm{i}\gamma_m/2) - \cfrac{g_2^2|a_{20}|^2/2}{(x+\mathrm{i}\kappa_2)}}},$$7 from about $$\mathcal{E}_L(x) = \cfrac{2\mathrm{i}\kappa_1} {(x+\mathrm{i}\kappa_1) - \cfrac{g_1^2|a_{10}|^2/2} {(x+\mathrm{i}\gamma_m/2) - \cfrac{g_2^2|a_{20}|^2/2}{(x+\mathrm{i}\kappa_2)}}},$$8 to about $$\mathcal{E}_L(x) = \cfrac{2\mathrm{i}\kappa_1} {(x+\mathrm{i}\kappa_1) - \cfrac{g_1^2|a_{10}|^2/2} {(x+\mathrm{i}\gamma_m/2) - \cfrac{g_2^2|a_{20}|^2/2}{(x+\mathrm{i}\kappa_2)}}},$$9, and with $x=\delta-\omega_m$0 the same structure that showed perfect OMIT for $x=\delta-\omega_m$1 exhibits OMIA at $x=\delta-\omega_m$2 with $x=\delta-\omega_m$3 (Qian et al., 2023).

Indirectly coupled auxiliary optical modes generate a closely related multi-path OMIA even in the red-sideband regime. In the single microcavity with an auxiliary cavity mode coupled only through the waveguide, three-pathway interference can induce an absorption dip within a transparent window when $x=\delta-\omega_m$4, and four-pathway interference can switch back and forth between OMIT and OMIA when $x=\delta-\omega_m$5 by tuning the relative amplitude and phase of the optical paths (Qin et al., 2019). This is significant because it shows that OMIA need not be tied to a separate physical cavity; an indirectly coupled auxiliary mode is sufficient to create the necessary interference structure.

Mechanical nonlinearity modifies OMIA without removing it. In the single-port Duffing system, the OMIA dip can broaden, shift, become asymmetric, and become hysteretic, yet the paper emphasizes that the cavity response is not simply the Duffing amplitude response because the mechanical phase as well as amplitude is imprinted on the cavity field (Shevchuk et al., 2015). The paper also states that nonlinearities beyond the Duffing model have little effect on the size of the OMIA dip though they affect its width (Shevchuk et al., 2015).

Hybrid qubit-assisted architectures produce multi-peak OMIA. In the electro-optomechanical system interacting with a qubit, the optical probe susceptibility contains a mechanical denominator dressed both by the microwave cavity and by a qubit term proportional to

$x=\delta-\omega_m$6

and the resolved-sideband regime yields a three-peak OMIA structure with two transparency windows between the peaks, whereas the nearly sideband-resolved regime yields double-OMIT (Kumar et al., 2021). A related double-cavity membrane system with a qubit embedded on the membrane also reports that OMIA shows three distinct peaks in both the linear and nonlinear qubit–mechanics cases, that removing the qubit converts OMIA to OMIT, and that increasing the qubit decay rate produces an OMIA-to-OMIT transition (Barbhuiya et al., 2020).

The generalized cross-Kerr extension pushes this further. In the two-mechanical-mode microwave circuit mapped from SCPTs and an $x=\delta-\omega_m$7 resonator, the cavity couples to the mechanical modes through radiation pressure, conventional CK, higher-order generalized CK, a three-mode CK term, and an induced CK between the two mechanical modes. The paper states that the higher-order nonlinear CK and three-mode CK couplings have remarkable impact on OMIT and OMIA, that they can give rise to gain in the absorption profile, and that the three-mode CK coupling is central to the appearance of OMIA and to the broadening of the windows in the two-mechanical-mode configuration (Bayati et al., 21 Aug 2025).

6. Related phenomena, applications, and distinctions

OMIA is technologically attractive because it is intrinsically narrowband and mechanically tunable. The microwave experiment at $x=\delta-\omega_m$8–$x=\delta-\omega_m$9 mK explicitly identifies OMIA as the basis for microwave notch filters and emphasizes extremely narrow bandwidths, pump-power-tunable attenuation, and compatibility with microwave optomechanical architectures that also support amplification (Kumar et al., 2021). The room-temperature 3D cavity work makes the same point in a more deployment-oriented form: the absorptive notch can reach $\beta_2/(\kappa_2-ix)$0 attenuation with $\beta_2/(\kappa_2-ix)$1 bandwidth at ambient temperature, and the authors argue that detecting a shift of about half that width, $\beta_2/(\kappa_2-ix)$2, would allow mass sensing around $\beta_2/(\kappa_2-ix)$3, an improvement by a factor of 5 over direct measurement limited by the bare mechanical linewidth (Kumar et al., 2024).

Hybrid OMIA-like structures also support routing and transduction functions. The three-mode double-cavity EIA paper emphasizes photon switching, routing, and optical-to-microwave transduction, and shows that when $\beta_2/(\kappa_2-ix)$4 the optical probe is effectively redirected from cavity 1 to cavity 2 (Qu et al., 2013). In the molecular system, the same device supports either OMIT-based slow light or OMIA-based fast light depending on the probe port, with a reported maximum delay of about $\beta_2/(\kappa_2-ix)$5 in the OMIT configuration at $\beta_2/(\kappa_2-ix)$6 and a minimum delay of about $\beta_2/(\kappa_2-ix)$7 in the OMIA configuration at $\beta_2/(\kappa_2-ix)$8 (Yin et al., 8 Feb 2025).

Several neighboring phenomena should not be conflated with standard OMIA. Inverse OMIT is a coherent-perfect-absorption limit realized in a double-sided cavity with two coherent probes. For identical resonators and red-sideband driving, the outputs vanish when

$\beta_2/(\kappa_2-ix)$9

leading to one-channel or three-channel coherent absorption at

$t_r$0

(Wu et al., 2015). This is closely related to OMIA in its interference structure, but it is a two-port coherent-absorption condition rather than a single-probe induced absorption line shape.

Loss-engineered transparency is another adjacent but distinct effect. In a compound two-resonator optomechanical system, added optical loss from a nanotip can produce a loss-induced revival of transparency in an otherwise strongly absorptive regime, especially near an exceptional point (Zhang et al., 2018). This suggests that absorption and transparency in optomechanical spectra are not controlled solely by dissipation magnitude but by how dissipation reshapes the non-Hermitian interference landscape.

Taken together, the literature portrays OMIA as a broad class of mechanically mediated absorptive responses rather than a single canonical lineshape. In some systems it is a blue-sideband microwave notch; in others it is a blue-optical hybrid through-port absorption, a narrow absorption spike carved inside a red-sideband transparency window, a red-sideband multi-path absorption dip generated by an auxiliary mode, or a qubit-assisted three-peak absorption spectrum. The unifying element is the same: a weak probe interrogates a cavity whose effective susceptibility has been dressed by coherent optomechanical scattering, and the dressed response enhances absorption rather than transparency under the relevant interference, coupling, and readout conditions (Kumar et al., 2021, Jiang et al., 2014).