IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 21, NO. 17, SEPTEMBER 1, 2009
1163
Electromagnetic Source Azimuth Measurement
Using Electrooptical Electromagnetic Field Probe
Tsung-Hsin Lee, Wen-Tron Shay, and Ching-Ting Lee, Fellow, IEEE
Abstract—A new type electrooptical electromagnetic field probe
was fabricated by combining three magnetic field sensors, each of
which consists of a Mach–Zehnder modulator and an integrated
annular antenna. The frequency response was flat from 50 MHz to
2.2 GHz. The average minimum detectable electromagnetic field
intensity of the sensor is 2.22 mV/m. When the probe axis was
pointed toward the electromagnetic radiation source, the highest
sensitivity was obtained. The variation of the sensitivity is within
0.5 dB with rotating the probe around its axis. This result indi-
cates that the azimuth of the electromagnetic radiation source can
be measured.
Index Terms—Electromagnetic sensor, electromagnetic source
azimuth, field probe, Mach–Zehnder modulator.
I. INTRODUCTION
R ECENTLY, there has been a great interest in electromag-
netic field sensors to protect the biological and natural en-
vironment against unhealthy effects of the electromagnetic field.
Several kinds of electromagnetic field sensors have been devel-
oped to detect field intensity [1]–[3]. However, the sensitivity
of these sensors is always azimuth-dependent. In the real envi-
ronment, the polarizations of electromagnetic fields rarely show
any uniformity; consequently, an acute need to obtain an electro-
magnetic field probe with an isotropic response is always there.
To achieve this purpose, only recently, Tajima et al. [4] and Diba
and Trzaska [5] have developed optical isotropic electric field
probes by using three electric field sensors with a dipole ele-
ment.
In this work, we propose a new scheme of the electroop-
tical electromagnetic field probe. Our electromagnetic sensor
system integrated three magnetic filed sensors. The azimuth de-
pendence of the sensitivity of the fabricated probe was mea-
sured. It is demons