Faraday rotation is one of the most classical ways to realize nonreciprocal photonic devices like optical isolators. Recently, the temporal analog of Faraday rotation, achieved through time-interfaces, was introduced [Li et al., Phys. Rev. Lett. 128, 173901 (2022)]. Here, we extend this concept to the periodic switching regime by introducing nonreciprocal photonic time-crystals (NPTC), formed by switching material properties of a spatially homogeneous magnetoplasma medium periodically in time. Based on a temporal transfer matrix formalism, we study the NPTC band structure and show that temporal Faraday rotation can be achieved in both momentum bands and (partial) bandgaps. When combined with the bandgaps of the NPTCs, the temporal Faraday effect can enable a unidirectional wave amplifier by extracting energy from the modulation. Our study expands the catalog of photonic time-crystals (PTCs), forging a link between photonic nonreciprocity and parametric gain and shedding light on unexplored functionalities of PTCs in wave engineering.

1.
C.
Caloz
and
Z.-L.
Deck-Léger
, “
Spacetime metamaterials—Part I: General concepts
,”
IEEE Trans. Antennas Propag.
68
,
1569
(
2020
);
C.
Caloz
and
Z.-L.
Deck-Léger
Spacetime metamaterials—Part II: Theory and Applications
,”
IEEE Trans. Antennas Propag.
68
,
1583
(
2020
).
2.
N.
Engheta
, “
Metamaterials with high degrees of freedom: Space, time, and more
,”
Nanophotonics
10
,
639
(
2020
).
3.
E.
Galiffi
,
R.
Tirole
,
S.
Yin
,
H.
Li
,
S.
Vezzoli
,
P. A.
Huidobro
,
M. G.
Silveirinha
,
R.
Sapienza
,
A.
Alù
, and
J. B.
Pendry
, “
Photonics of time-varying media
,”
Adv. Photonics
4
,
014002
(
2022
).
4.
S.
Yin
,
E.
Galiffi
, and
A.
Alù
, “
Floquet metamaterials
,”
eLight
2
,
8
(
2022
).
5.
V.
Pacheco-Peña
,
D. M.
Solís
, and
N.
Engheta
, “
Time-varying electromagnetic media: Opinion
,”
Opt. Mater. Express
12
,
3829
(
2022
).
6.
Z.
Hayran
and
F.
Monticone
, “
Challenging fundamental limitations in electromagnetics with time-varying systems
,” arXiv:2205.07142 (
2022
).
7.
A.
Akbarzadeh
,
N.
Chamanara
, and
C.
Caloz
, “
Inverse prism based on temporal discontinuity and spatial dispersion
,”
Opt. Lett.
43
,
3297
(
2018
).
8.
V.
Pacheco-Peña
and
N.
Engheta
, “
Temporal aiming
,”
Light
9
,
129
(
2020
).
9.
H.
Li
,
S.
Yin
,
E.
Galiffi
, and
A.
Alù
, “
Temporal parity-time symmetry for extreme energy transformations
,”
Phys. Rev. Lett.
127
,
153903
(
2021
).
10.
M. S.
Mirmoosa
,
G. A.
Ptitcyn
,
V. S.
Asadchy
, and
S. A.
Tretyakov
, “
Time-varying reactive elements for extreme accumulation of electromagnetic energy
,”
Phys. Rev. Appl.
11
,
014024
(
2019
).
11.
E.
Galiffi
,
Y.-T.
Wang
,
Z.
Lim
,
J. B.
Pendry
,
A.
Alù
, and
P. A.
Huidobro
, “
Wood anomalies and surface-wave excitation with a time grating
,”
Phys. Rev. Lett.
125
,
127403
(
2020
).
12.
Y.
Sharabi
,
E.
Lustig
, and
M.
Segev
, “
Disordered photonic time crystals
,”
Phys. Rev. Lett.
126
,
163902
(
2021
).
13.
R.
Carminal
,
H.
Chen
,
R.
Pierrat
, and
B.
Shapiro
, “
Universal statistics of waves in a random time-varying medium
,”
Phys. Rev. Lett.
127
,
094101
(
2021
).
14.
B.
Apffel
,
S.
Wildeman
,
A.
Eddi
, and
E.
Fort
, “
Experimental implementation of wave propagation in disordered time-varying media
,”
Phys. Rev. Lett.
128
,
094503
(
2022
).
15.
J.
Kim
,
D.
Lee
,
S.
Yu
, and
N.
Park
, “
Unidirectional scattering with spatial homogeneity using photonic time disorder
,” arXiv:2208.11884 (
2022
).
16.
Y.
Hadad
,
J.
Soric
, and
A.
Alù
, “
Breaking temporal symmetries for emission and absorption
,”
Proc. Natl. Acad. Sci. U. S. A.
113
,
3471
(
2016
).
17.
A. V.
Maslov
and
M. I.
Bakunov
, “
Temporal scattering of a graphene plasmon by a rapid carrier density decrease
,”
Optica
5
,
1508
(
2018
).
18.
A.
Shlivinski
and
Y.
Hadad
, “
Beyond the Bode-Fano bound: Wideband impedance matching for short pulses using temporal switching of transmission-line parameters
,”
Phys. Rev. Lett.
121
,
204301
(
2018
).
19.
H.
Li
,
A.
Mekawy
, and
A.
Alù
, “
Beyond Chu's limit with Floquet impedance matching
,”
Phys. Rev. Lett.
123
,
164102
(
2019
).
20.
C.
Firestein
,
A.
Shlivinski
, and
Y.
Hadad
, “
Absorption and scattering by a temporally switched lossy layer: Going beyond the Rozanov bound
,”
Phys. Rev. Appl.
17
,
014017
(
2022
).
21.
M. R.
Shcherbakov
,
K.
Werner
,
Z.
Fan
,
N.
Talisa
,
E.
Chowdhury
, and
G.
Shvets
, “
Photon acceleration and tunable broadband harmonics generation in nonlinear time-dependent metasurfaces
,”
Nat. Commun.
10
,
1345
(
2019
).
22.
P. A.
Huidobro
,
E.
Galiffi
,
S.
Guenneau
,
R. V.
Craster
, and
J. B.
Pendry
, “
Fresnel drag in space–time-modulated metamaterials
,”
Proc. Natl. Acad. Sci.
116
,
24943
(
2019
).
23.
V.
Bruno
,
C.
DeVault
,
S.
Vezzoli
 et al, “
Negative refraction in time-varying, strongly-coupled plasmonic antenna-ENZ systems
,”
Phys. Rev. Lett.
124
,
043902
(
2020
).
24.
H.
Li
and
A.
Alù
, “
Temporal switching to extend the bandwidth of thin absorbers
,”
Optica
8
,
24
(
2021
).
25.
V.
Pacheco-Peña
and
N.
Engheta
, “
Antireflection temporal coatings
,”
Optica
7
,
323
(
2020
).
26.
H.
Li
,
H.
Moussa
,
D.
Sounas
, and
A.
Alù
, “
Parity-time symmetry based on time modulation
,”
Phys. Rev. Appl.
14
,
031002
(
2020
).
27.
X. G.
Zhang
,
Q.
Yu
,
W. X.
Jiang
,
Y. L.
Sun
,
L.
Bai
,
Q.
Wang
,
C. W.
Qiu
, and
T. J.
Cui
, “
Polarization-controlled dual-programmable metasurfaces
,”
Adv. Sci.
7
,
1903382
(
2020
).
28.
V.
Pacheco-Peña
and
N.
Engheta
, “
Temporal equivalent of the Brewster angle
,”
Phys. Rev. B
104
,
214308
(
2021
).
29.
D.
Ramaccia
,
A.
Alù
,
A.
Toscano
, and
F.
Bilotti
, “
Temporal multilayer structures for designing higher-order transfer functions using time-varying metamaterials
,”
Appl. Phys. Lett.
118
,
101901
(
2021
).
30.
Z.
Hayran
,
A.
Chen
, and
F.
Monticone
, “
Spectral causality and the scattering of waves
,”
Optica
8
,
1040
(
2021
).
31.
J.
Xu
,
W.
Mai
, and
D. H.
Werner
, “
Complete polarization conversion using anisotropic temporal slabs
,”
Opt. Lett.
46
,
1373
(
2021
).
32.
Z.
Hayran
and
F.
Monticone
, “
Capturing broadband light in a compact bound state in the continuum
,”
ACS Photonics
8
,
813
(
2021
).
33.
G.
Castaldi
,
V.
Pacheco-Peña
,
M.
Moccia
,
N.
Engheta
, and
V.
Galdi
, “
Exploiting space-time duality in the synthesis of impedance transformers via temporal metamaterials
,”
Nanophotonics
10
,
3687
(
2021
).
34.
J. R.
Zurita-Sánchez
,
P.
Halevi
, and
J. C.
Cervantes-González
, “
Reflection and transmission of a wave incident on a slab with a time-periodic dielectric function εt
,”
Phys. Rev. A
79
,
053821
(
2009
).
35.
J. S.
Martínez-Romero
,
O. M.
Becerra-Fuentes
, and
P.
Halevi
, “
Temporal photonic crystals with modulations of both permittivity and permeability
,”
Phys. Rev. A
93
,
063813
(
2016
).
36.
E.
Lustig
,
Y.
Sharabi
, and
M.
Segev
, “
Topological aspects of photonic time crystals
,”
Optica
5
,
1390
(
2018
).
37.
J. D.
Joannopoulos
,
S. G.
Johnson
,
J. N.
Winn
, and
R. D.
Meade
,
Photonic Crystals: Molding the Flow of Light
, 2nd ed. (
Princeton University Press
,
Princeton, NJ
,
2011
).
38.
A.
Dikopoltsev
,
Y.
Sharabi
,
M.
Lyubarov
,
Y.
Lumer
,
S.
Tsesses
,
E.
Lustig
,
I.
Kaminer
, and
M.
Segev
, “
Light emission by free electrons in photonic time-crystals
,”
Proc. Natl. Acad. Sci. U. S. A.
119
,
e2119705119
(
2021
).
39.
M.
Lyubarov
,
Y.
Lumer
,
A.
Dikopoltsev
,
E.
Lustig
,
Y.
Sharabi
, and
M.
Segev
, “
Amplified emission and lasing in photonic time crystals
,”
Science
377
,
425
(
2022
).
40.
H.
Li
,
S.
Yin
,
H.
He
,
J.
Xu
,
A.
Alù
, and
B.
Shapiro
, “
Stationary charge radiation in anisotropic photonic time crystals
,” arXiv:2209.10964 (
2022
).
41.
L.
Bi
,
J.
Hu
,
P.
Jiang
,
D. H.
Kim
,
G. F.
Dionne
,
L. C.
Kimerling
, and
C. A.
Ross
, “
On-chip optical isolation in monolithically integrated non-reciprocal optical resonators
,”
Nat. Photonics
5
,
758
(
2011
).
42.
Y.
Zhang
,
Q.
Du
,
C.
Wang
,
T.
Fakhrul
,
S.
Liu
,
L.
Deng
,
D.
Huang
,
P.
Pintus
,
J.
Bowers
,
C. A.
Ross
,
J.
Hu
, and
L.
Bi
, “
Monolithic integration of broadband optical isolators for polarization-diverse silicon photonics
,”
Optica
6
,
473
(
2019
).
43.
M. I.
Abdelrahman
and
F.
Monticone
, “
Broadband and giant nonreciprocity at the subwavelength scale in magnetoplasmonic materials
,”
Phys. Rev. B
102
,
155420
(
2020
).
44.
N.
Bender
,
S.
Factor
,
J. D.
Bodyfelt
,
H.
Ramezani
,
D. N.
Christodoulides
,
F. M.
Ellis
, and
T.
Kottos
, “
Observation of asymmetric transport in structures with active nonlinearities
,”
Phys. Rev. Lett.
110
,
234101
(
2013
).
45.
D. L.
Sounas
,
J.
Soric
, and
A.
Alù
, “
Broadband passive isolators based on coupled nonlinear resonances
,”
Nat. Electron.
1
,
113
(
2018
).
46.
M.
Cotrufo
,
S. A.
Mann
,
H.
Moussa
, and
A.
Alù
, “
Nonlinearity-induced nonreciprocity—Part I
,”
IEEE Trans. Microwave Theory Tech.
69
,
3569
(
2021
);
M.
Cotrufo
,
S. A.
Mann
,
H.
Moussa
, and
A.
Alù
Nonlinearity-induced nonreciprocity—Part II
,”
IEEE Trans. Microwave Theory Tech.
69
,
3584
(
2021
).
47.
Z.
Yu
and
S.
Fan
, “
Complete optical isolation created by indirect interband photonic transitions
,”
Nat. Photonics
3
,
91
(
2009
).
48.
N. A.
Estep
,
D. L.
Sounas
,
J.
Soric
, and
A.
Alù
, “
Magnetic-free non-reciprocity and isolation based on parametrically modulated coupled-resonator loops
,”
Nat. Phys.
10
,
923
(
2014
).
49.
F.
Ruesink
,
M.-A.
Miri
,
A.
Alù
, and
E.
Verhagen
, “
Nonreciprocity and magnetic-free isolation based on optomechanical interactions
,”
Nat. Commun.
7
,
13662
(
2016
).
50.
S.
Taravati
and
C.
Caloz
, “
Mixer-duplexer-antenna leaky-wave system based on periodic space-time modulation
,”
IEEE Trans. Antennas Propag.
65
,
442
(
2017
).
51.
J.
Kim
,
S.
Kim
, and
G.
Bahl
, “
Complete linear optical isolation at the microscale with ultralow loss
,”
Sci. Rep.
7
,
1647
(
2017
).
52.
D.
Sounas
and
A.
Alù
, “
Non-reciprocal photonics based on time modulation
,”
Nat. Photonics
11
,
774
(
2017
).
53.
H.
Li
,
T.
Kottos
, and
B.
Shapiro
, “
Floquet-network theory of nonreciprocal transport
,”
Phys. Rev. Appl.
9
,
044031
(
2018
).
54.
H.
Li
,
B.
Shapiro
, and
T.
Kottos
, “
Floquet scattering theory based on effective Hamiltonians of driven systems
,”
Phys. Rev. B
98
,
121101(R)
(
2018
).
55.
E.
Galiffi
,
P. A.
Huidobro
, and
J. B.
Pendry
, “
Broadband nonreciprocal amplification in luminal metamaterials
,”
Phys. Rev. Lett.
123
,
206101
(
2019
).
56.
X.
Wang
,
A.
Diaz-Rubio
,
H.
Li
,
S. A.
Tretyakov
, and
A.
Alù
, “
Theory and design of multifunctional space-time metasurfaces
,”
Phys. Rev. Appl.
13
,
044040
(
2020
).
57.
X.
Wang
,
G.
Ptitcyn
,
V. S.
Asadchy
,
A.
Díaz-Rubio
,
M. S.
Mirmoosa
,
S.
Fan
, and
S. A.
Tretyakov
, “
Nonreciprocity in bianisotropic systems with uniform time modulation
,”
Phys. Rev. Lett.
125
,
266102
(
2020
).
58.
H.
Li
,
S.
Yin
, and
A.
Alù
, “
Nonreciprocity and Faraday rotation at time interfaces
,”
Phys. Rev. Lett.
128
,
173901
(
2022
).
59.
A.
Ishimaru
,
Electromagnetic Wave Propagation, Radiation, and Scattering
(
John Wiley & Sons
,
Hoboken, NJ
,
2017
).
60.
K.
Shastri
,
M. I.
Abdelrahman
, and
F.
Monticone
, “
Nonreciprocal and topological plasmonics
,”
Photonics
8
,
133
(
2021
).
61.
C. J.
Joshi
,
C. E.
Clayton
,
K.
Marsh
,
D. B.
Hopkins
,
A.
Sessler
, and
D.
Whittum
, “
Demonstration of the frequency upshifting of microwave radiation by rapid plasma creation
,”
IEEE Trans. Plasma Sci.
18
,
814
(
1990
).
62.
Z.
Hayran
,
J. B.
Khurgin
, and
F.
Monticone
, “
ω Versus k: Dispersion and energy constraints on time-varying photonic materials and time crystals [invited]
,”
Opt. Mater. Express
12
,
3904
(
2022
).
63.
The temporal boundary conditions essentially follow from Maxwell's equations in time domain and the built-in material models for specific scenarios.64 To describe the time-varying magnetoplasma media in our case, the set of relevant equations are given as ×H=J+ϵ0E/t, ×E=μ0H/t, and J/t+γωctẑ×J=ϵ0ωp2tE, where ẑ denotes the unit vector.65 Based on the methods of distribution balance66 or Laplace transform,65 these equations can be used to determine the corresponding temporal boundary conditions to be the continuity of the physical quantities E,H and J across a time interface when the parameters ωp and ωc change abruptly, see also Ref. 58.
64.
M. I.
Bakunov
and
A. V.
Maslov
, “
Reflection and transmission of electromagnetic waves at a temporal boundary: Comment
,”
Opt. Lett.
39
,
6029
(
2014
).
65.
D. K.
Kalluri
,
Electromagnetics of Time Varying Complex Media: Frequency and Polarization Transformer
(
CRC Press
,
Boca Raton
,
2010
).
66.
J.
Gratus
,
R.
Seviour
,
P.
Kinsler
, and
D. A.
Jaroszynski
, “
Temporal boundaries in electromagnetic materials
,”
New J. Phys.
23
,
083032
(
2021
).
67.
The modes f2t and b2t at the final time t=tf are present in free space, which are associated with static magnetic fields and thus do not contribute to Faraday polarization rotation directly.
68.
T. T.
Koutserimpas
and
R.
Fleury
, “
Nonreciprocal gain in non-Hermitian time-Floquet systems
,”
Phys. Rev. Lett.
120
,
087401
(
2018
).

Supplementary Material

You do not currently have access to this content.