The authors fabricate rolled up microtubes consisting of Si/SiOx on Si substrate and analyze the possibility to use them as a refractometric sensor. An aqueous sugar solution is inserted into the microtube, which leads to a change in refractive index and, as a result, to a detectable spectral shift of the whispering gallery modes. Experimental results can fit well with finite-difference time-domain simulations, which are used to determine the sensitivity of this tube refractometer. The ratio of spectral sensitivity to channel cross-sectional area of the refractometer is particularly striking and allows analysis of fluid volumes in the range of femtoliters. A comparative discussion with other existing refractometer schemes concludes this work.

1.
D.
Psaltis
,
S. R.
Quake
, and
C.
Yang
,
Nature (London)
442
,
381
(
2006
).
2.
C.
Monat
,
P.
Domachuk
, and
B. J.
Eggleton
,
Nat. Photonics
1
,
106
(
2007
).
3.
D.
Erickson
,
S.
Mandal
,
A. H. J.
Yang
, and
B.
Cordovez
,
Microfluid. Nanofluid.
4
,
33
(
2008
).
4.
D.
Yin
,
D. W.
Deamer
,
H.
Schmidt
,
J. P.
Barber
, and
A. R.
Hawkins
,
Opt. Lett.
31
,
2136
(
2006
).
5.
A.
Datta
,
I. -Y.
Eom
,
A.
Dhar
,
P.
Kuban
,
R.
Manor
,
I.
Ahmad
,
S.
Gangopadhyay
,
T.
Dallas
,
M.
Holtz
,
H.
Temkin
, and
P. K.
Dasgupta
,
IEEE Sens. J.
3
,
788
(
2003
).
6.
D.
Erickson
,
T.
Rockwood
,
T.
Emery
,
A.
Scherer
, and
D.
Psaltis
,
Opt. Lett.
31
,
59
(
2006
).
7.
O. G.
Schmidt
and
K.
Eberl
,
Nature (London)
410
,
168
(
2001
).
8.
V. Ya.
Prinz
,
V. A.
Seleznev
,
A. K.
Gutakovsky
,
A. V.
Chehovskiy
,
V. V.
Preobrazhenskii
,
M. A.
Putyato
, and
T. A.
Gavrilova
,
Physica E (Amsterdam)
6
,
828
(
2000
).
9.
R.
Songmuang
,
Ch.
Deneke
, and
O. G.
Schmidt
,
Appl. Phys. Lett.
89
,
223109
(
2006
).
10.
S.
Mendach
,
R.
Songmuang
,
S.
Kiravittaya
,
A.
Rastelli
,
M.
Benyoucef
, and
O. G.
Schmidt
,
Appl. Phys. Lett.
88
,
111120
(
2006
).
11.
R.
Songmuang
,
A.
Rastelli
,
S.
Mendach
, and
O. G.
Schmidt
,
Appl. Phys. Lett.
90
,
091905
(
2007
).
12.
T.
Kipp
,
H.
Welsch
,
Ch.
Strelow
,
Ch.
Heyn
, and
D.
Heitmann
,
Phys. Rev. Lett.
96
,
077403
(
2006
).
13.
N. M.
Hanumegowda
,
C. J.
Stica
,
B. C.
Patel
,
I. M.
White
, and
X.
Fan
,
Appl. Phys. Lett.
87
,
201107
(
2005
).
14.
A. M.
Armani
and
K. J.
Vahala
,
Opt. Lett.
31
,
1896
(
2006
).
15.
I. M.
White
,
J.
Gohring
,
Y.
Sun
,
G.
Yang
,
S.
Lacey
, and
X.
Fan
,
Appl. Phys. Lett.
91
,
241104
(
2007
).
16.
R.
Songmuang
,
A.
Rastelli
,
S.
Mendach
,
Ch.
Deneke
, and
O. G.
Schmidt
,
Microelectron. Eng.
84
,
1427
(
2007
).
17.
Ch.
Deneke
and
O. G.
Schmidt
,
Appl. Phys. Lett.
85
,
2914
(
2004
).
18.
D. J.
Thurmer
,
Ch.
Deneke
,
Y.
Mei
, and
O. G.
Schmidt
,
Appl. Phys. Lett.
89
,
223507
(
2006
).
19.
Ch.
Strelow
,
C. M.
Schultz
,
H.
Rehberg
,
H.
Welsch
,
Ch.
Heyn
,
D.
Heitmann
, and
T.
Kipp
,
Phys. Rev. B
76
,
045303
(
2007
).
20.
F.
Xu
and
G.
Brambilla
,
Appl. Phys. Lett.
92
,
101126
(
2008
).
21.
I. M.
White
,
H.
Zhu
,
J. D.
Suter
,
N. M.
Hanumegowda
,
H.
Oveys
,
M.
Zourob
, and
X.
Fan
,
IEEE Sens. J.
7
,
28
(
2007
).
22.
V.
Zamora
,
A.
Díez
,
M. V.
Andrés
, and
B.
Gimeno
,
Opt. Express
15
,
12011
(
2007
).
23.
M.
Sumetsky
,
R. S.
Windeler
,
Y.
Dulashko
, and
X.
Fan
,
Opt. Express
15
,
14376
(
2007
).
24.
W.
Liang
,
Y.
Huang
,
Y.
Xu
,
R. K.
Lee
, and
A.
Yariv
,
Appl. Phys. Lett.
86
,
151122
(
2005
).
25.
Ó.
Esteban
,
N.
Díaz-Herrera
,
M. -C.
Navarrete
, and
A.
González-Cano
,
Appl. Opt.
45
,
7294
(
2006
).
26.
H. -J.
Moon
,
G. -W.
Park
,
S. -B.
Lee
,
K.
An
, and
J. -H.
Lee
,
Appl. Phys. Lett.
84
,
4547
(
2004
).
27.
M.
Adams
,
G. A.
DeRose
,
M.
Loncar
, and
A.
Scherer
,
J. Vac. Sci. Technol. B
23
,
3168
(
2005
).
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