In-vacuum optical isolation changes by heating in a Faraday isolator.
We describe a model evaluating changes in the optical isolation of a Faraday isolator when passing from air to vacuum in terms of different thermal effects in the crystal. The changes are particularly significant in the crystal thermal lensing (refraction index and thermal expansion) and in its Verdet constant and can be ascribed to the less efficient convection cooling of the magneto-optic crystal of the Faraday isolator. An isolation decrease by a factor of 10 is experimentally observed in a Faraday isolator that is used in a gravitational wave experiment (Virgo) with a 10 W input laser when going from air to vacuum. A finite element model simulation reproduces with a great accuracy the experimental data measured on Virgo and on a test bench. A first set of measurements of the thermal lensing has been used to characterize the losses of the crystal, which depend on the sample. The isolation factor measured on Virgo confirms the simulation model and the absorption losses of 0.0016 +/- 0.0002/cm for the TGG magneto-optic crystal used in the Faraday isolator.
Acernese
Fausto
F
Alshourbagy
Mohamed
M
Amico
Paolo
P
Antonucci
Federica
F
Aoudia
S
S
Astone
P
P
Avino
Saverio
S
Ballardin
G
G
Baggio
L
L
Barone
Fabrizio
F
Barsotti
Lisa
L
Barsuglia
Matteo
M
Bauer
Th S
TS
Bigotta
Stefano
S
Birindelli
Simona
S
Bizouard
Marie-Anne
MA
Boccara
Albert-Claude
AC
Bondu
François
F
Bosi
Leone
L
Braccini
Stefano
S
Bradaschia
Carlo
C
Brillet
Alain
A
Brisson
Violette
V
Buskulic
Damir
D
Cagnoli
G
G
Calloni
Enrico
E
Campagna
Enrico
E
Carbognani
Franco
F
Carbone
L
L
Cavalier
Fabien
F
Cavalieri
R
R
Cella
G
G
Cesarini
E
E
Chassande-Mottin
E
E
Chatterji
S
S
Cleva
F
F
Coccia
E
E
Corda
C
C
Corsi
A
A
Cottone
F
F
Coulon
J-P
JP
Cuoco
E
E
D'Antonio
S
S
Dari
A
A
Dattilo
V
V
Davier
M
M
De Rosa
R
R
Del Prete
M
M
Di Fiore
L
L
Di Lieto
A
A
Di Paolo Emilio
M
M
Di Virgilio
A
A
Evans
M
M
Fafone
V
V
Ferrante
I
I
Fidecaro
F
F
Fiori
I
I
Flaminio
R
R
Fournier
J-D
JD
Frasca
S
S
Frasconi
F
F
Gammaitoni
L
L
Garufi
F
F
Genin
E
E
Gennai
A
A
Giazotto
A
A
Giordano
L
L
Granata
V
V
Greverie
C
C
Grosjean
D
D
Guidi
G
G
Hamdani
S
S
Hebri
S
S
Heitmann
H
H
Hello
P
P
Huet
D
D
La Penna
P
P
Laval
M
M
Leroy
N
N
Letendre
N
N
Lopez
B
B
Lorenzini
M
M
Loriette
V
V
Losurdo
G
G
Mackowski
J-M
JM
Majorana
E
E
Man
N
N
Mantovani
M
M
Marchesoni
F
F
Marion
F
F
Marque
J
J
Martelli
F
F
Masserot
A
A
Menzinger
F
F
Milano
L
L
Minenkov
Y
Y
Moins
C
C
Morgado
N
N
Mosca
S
S
Mours
B
B
Neri
I
I
Nocera
F
F
Pagliaroli
G
G
Palomba
C
C
Paoletti
F
F
Pardi
S
S
Pasqualetti
A
A
Passaquieti
R
R
Passuello
D
D
Persichetti
G
G
Piergiovanni
F
F
Pinard
L
L
Poggiani
R
R
Punturo
M
M
Puppo
P
P
Rabaste
O
O
Rapagnani
P
P
Regimbau
T
T
Remillieux
A
A
Ricci
F
F
Ricciardi
I
I
Rocchi
A
A
Rolland
L
L
Romano
R
R
Ruggi
P
P
Russo
G
G
Sentenac
D
D
Solimeno
S
S
Swinkels
B L
BL
Tarallo
M
M
Terenzi
R
R
Toncelli
A
A
Tonelli
M
M
Tournefier
E
E
Travasso
F
F
Vajente
G
G
van den Brand
J F J
JF
van der Putten
S
S
Verkindt
D
D
Vetrano
F
F
Viceré
A
A
Vinet
J-Y
JY
Vocca
H
H
Yvert
M
M