Photonic crystals in biology

Poster Session, Tuesday, June 15
Theme A1 - B702
Terahertz Emission from Rectangular Mesa Structures of Superconducting Bi 2 Sr 2 CaCu 2 O 8+
Fulya Türkolu 1 , Lütfi Özyüzer 1 , Hasan Köseolu 1 , Yasemin Demirhan 1 , Ylmaz imsek 2
Sascha Preu 3 , Daniel Ploss 3 , Stefan Malzer 3 , Huabing Wang 4 , and Paul Müller 2
1 Department of Physics, Izmir Institute of Technology (IZTECH), 35430, Izmir, Turkey,
2 Physical Institute III, University of Erlangen-Nurnberg, Erlangen, Germany,
3 Max Planck Optics Group, University of Erlangen-Nurnberg, Erlangen, Germany,
4 National Institute for Materials Science, Tsukuba, Japan
Abstract— Rectangular intrinsic Josephson junction mesa structures of superconducting Bi 2 Sr 2 CaCu 2 O 8+ (Bi2212) can be used as a source of
continuous, coherent and polarized terahertz (THz) radiation. In this work, we obtained THz emission from 60x300 μm 2 rectangular mesa
structures. The frequency of the generated waves was determined as 0.537 THz by Michelson interferometer setup. The voltage per junction
satisfies the Josephson voltage-frequency relation.
Many people at science and technology are interested in the
electromagnetic waves in terahertz frequency range (0.1-10
THz) because of their wide-ranging applications including
security, medicine, quality control and environmental
monitoring [1]. The observation on generation of THz
radiation emitted from lateral dimension of high temperature
superconductor (HTS) Bi 2 Sr 2 CaCu 2 O 8+ (Bi2212) and
responses to THz waves increase the importance of these
HTSs [2]. Single crystal of HTS Bi2212 forms natural
superconductor-insulator-superconductor (SIS) layered
junctions, which are called intrinsic Josephson junctions (IJJ).
The stacks of IJJs in Bi2212 can be used such a voltagefrequency
converter and their large energy gap allows the
emissions at THz frequency range. Recently, it is
demonstrated that rectangular IJJ mesa structures of Bi2212
can be used as a source of continuous, coherent and polarized
THz radiation [2]. Strong THz-emission was observed when
the voltage across the mesa was adjusted in such a way that
the Josephson frequency of the IJJ matches the cavity
resonance [2]. It is shown that all THz emitting mesas are
below a certain underdoped level, which has relatively small
critical current in contrast to optimally doped and overdoped
Bi2212 [3]. Because of small critical current, large area mesas
fabricated from underdoped crystals cause less heating and
backbending occurs after the cavity resonance in voltage scale.
In this work, single crystals of Bi2212 grown by TSFZ
method were used. Mesa shaped photoresist mask was
patterned using optical photolithography process and the
rectangular mesa structures with required sizes (60x300 to
100x300 μm 2 ) were fabricated using Ar-ion beam etching as
explained in ref. [3]. Since it is known that thickness of an IJJ
is 1.5 nm as shown in figure 1, the number of IJJs in mesa is
calculated from mesa height. The heights of fabricated mesas
are about 800 nm, so we expect approximately 533 IJJs.
In order to characterize the Bi2212 mesas, c-axis resistance
versus temperature (R-T) and current-voltage behavior (I-V)
were measured in a He flow cryostat. During I-V
characterization, Si composite bolometer was used to detect
the THz emission. The c-axis R-T measurements of the mesas
exhibit underdoped behavior of Bi2212 single crystal. Some of
the hysteretic quasiparticle branches are observed in the I–V
characteristics. All of the curves show backbending above 1.5
V because of high doping level of Bi2212, number of
junctions and surface area of mesa. THz emission
characteristics of one of the 60x300 μm 2 mesa at 22 K shows
that bolometer signal is increasing at back bending region of I-
V curve. It indicates that local mesa temperature is increasing
and bolometer detects the heating of the mesa. THz emission
was obtained before heating severely affects the local mesa
temperature, near 0.61 V. Michelson interferometer setup was
used to form an interference pattern as in Figure 2. As shown
in figure, signals detected by bolometer indicate that
wavelength of the emission is 558 m and so the emission
frequency is 0.537 THz for 60 μm wide mesa. We observed
that the cavity resonance and applied voltage satisfies the
Josephson voltage-frequency relation.
Power (a.u.)
-3.4
-3.45
-3.5
-3.55
-3.6
-3.65
0.537 THz
-4 -2 0 2 4
Delay Stage Position/mm
Figure 2: Interference patterns detected by bolometer
This research is supported in part by the TUBITAK
(Scientic and Technical Council of Turkey) project no.
108T238.
*Corresponding author: fulyaturkoglu@iyte.edu.tr
Figure 1: Atomic view and crystal structure of Bi2212
[1] M. Tonouchi, Nature Photonics 1, 97-105 (2007)
[2] L. Ozyuzer et al., Science 318, 1291 (2007)
[3] L. Ozyuzer et al., Supercond. Sci. and Technol. 22,114009 (2009)
6th Nanoscience and Nanotechnology Conference, zmir, 2010 311