Fundamental Distinction of Electromagnetically Induced Transparency and Autler–Townes Splitting in Breaking the Time‐Reversal Symmetry

Abstract

Despite the essential difference in underlying physics, electromagnetically induced transparency (EIT) and Autler–Townes splitting (ATS) are difficult to be discriminated because they cause resemble absorption and dispersion to a probe electromagnetic field. They are mainly discerned in the sense of absorption profile fitting. Here, the breakdown of the time‐reversal symmetry (TRS), namely optical nonreciprocity in the EIT and ATS configurations are experimentally observed by using warm rubidium atoms. The microscopic Doppler effect due to atomic thermal motion causes strong optical nonreciprocity to the probe field in the EIT configuration. In stark contrast, the propagation of the probe field is primarily reciprocal in the ATS configuration. The experimental observations in this study objectively distinguish the EIT and ATS effects in the fundamental physics of breaking the TRS. This experiment proves a concept of using the TRS as a testbed for discerning fundamental physical effects.

Optical Router and 4 × 1 Multiplexer of Coexisting Crystal Field and Non‐Hermitian Autler‐Townes Splitting Controlled by Photon–Phonon Dressing in Eu3+: BiPO4

“…Also, the ratio of dressing Rabi-frequency G and transverse de-phase rate 𝛾 can be tuned by changing the time gate, and this ratio of 𝛾 and G obeys parity-time (PT) symmetry. [30,31] The strong photon dressing effect is caused by laser excitation G, whereas transverse de-phase rate 𝛾 results from the parallel effect of weak photon dressing and strong phonon dressing. When the time gate is at 8 μs, the coexistence of SAT-splitting and crystal field splitting ( MJ = ±1 , MJ = 0 ) is observed in Figure 2a1 owing to weak photon dressing (G < 𝛾), which corresponds to the PT symmetry imaginary part (Figure 2c1,c2) and can be mathematically represented as imaginary part in table S3 (supporting information).…”

“…[10] The spectral degeneracies induced by PT symmetry are, however, very different from conventional ones: they are non-Hermitian and known as exceptional points (EPs). [11][12][13] The emission spectra of atomic-like media (Eu 3+ ions doped BiPO 4 crystal) exhibit the bands accompanying the electronic transitions 5 D 0 → 7 F 0 (J = 1, 2, 3, and 4) of Eu 3+ has been reported. [14] It is well known that bismuth phosphate (BiPO 4 ) exhibits three different crystal structures, namely the low-temperature monoclinic phase (LTMP, space group: P2 1 /n), the high-temperature monoclinic phase (HTMP, space group: P2 1 /m), and the hexagonal phase (HP, space group: P3 1 21).…”

“…[ 10 ] The spectral degeneracies induced by PT symmetry are, however, very different from conventional ones: they are non‐Hermitian and known as exceptional points (EPs). [ 11–13 ]…”

One‐Step Generation of Energy‐Time‐Polarization‐Hyper‐Entangled W‐Class Triphotons: Nonlinear and Linear Optical Responses

“…It is worth mentioning that when considering the actual situation, even degenerate Zeeman sublevels [ 52–54 ] of each hyperfine energy level are to some extent distributed at different heights. However, for simplicity, being similar to other work, [ 52–55 ] here, they are also plotted at the same height. The polarization of the S 1–3 photons follows those of the corresponding coupling and pump field in each incidence case.…”

Spectral non-hermitian quantization line shape controlled by phonon dressing in various phases of Eu3+:BiPO4

“…This can lead to more efficient and effective lasers for a variety of applications. [9][10][11][12] Phonons also play a vigorous role in the line shape change of rare-earth ion-doped crystals. Phonon properties have been studied to understand the thermodynamic behavior of materials under high-temperature conditions.…”