| dc.description.abstract | Today the era of the information explosion are rapid development, data
transportation increasingly more large, and because the development of network
of information exchanging between countries are more important, a large
number of undersea fiber transportation system have been built, and lithium
niobate with its excellent optical properties, and compared with telecom
transmission, it’s more difficult to stolen and tampered, with the low driving
energy required it’s in line with the policy of world energy trends and applies in
many regions. With the advent of optical communication era, none of countries
not to attach this regions.
Ultra‐fast electro‐optical modulator for optical communication industry is an
essential element, which is made by the advantages of titanium in:diffused
process, with low propagation loss, high bit rate, highly application, low driving
energy, and low signal to noise ratio, low ambient temperature affect being
adopted in the relevant countries, like Americas, Europe, Japan, etc....... the
island or cross‐border fiber‐optic network in submarine cables. And Taiwan has
also carried out related research and development by way of industry‐university
cooperation, achieved its related products can be developed independently,
keeping up with the world countries, wish to complete a variety upgrading and
development of related industries.
In this thesis using the 1550nm light source to produce a ultra‐fast electrooptic
modulator with 3Gbps bandwidth. We used a Z‐cut lithium niobate crystal,
using its high electro‐optic coefficient, and in accordance with the principles of
electro‐optic effect, Mach‐Zehnder interferometer waveguide is designed by
using commercial software R‐Soft, the type of waveguide was produced with
titanium in:diffused process, to design the waveguide width of 7μm, arm gap
width of 60μm, S‐Bend length of 6000μm single‐mode transported in Mach‐
Zehnder interferometer structure. Electrode design using a commercial software
“High Frequency Structure Simulator, HFSS” and layout the coplanar waveguide
electrode structure which suit on high‐frequency electrical signal transmission,
driving electrode of modulator was made by gold achieved the bandwidth(S21)
of electrical transmission to 40GHz or more, the reflection signal (S11) of
electrical transmission and less than ‐18dB. We use silicon dioxide as
conventional buffer layer on semiconductor industry with atomic vapor
deposition equipment, in order to reach our velocity matching conditions and
thickness of buffer layer is 1μm to suit the modulator design. And we try to reach
a better velocity matching conditions, we must use thicker electrodes structure,
so we developed the electroplating systems, using eco‐friendly gold plating
solution as material, successfully fabricated thickness of electrode up to 21μm
at ambient temperature at 35 ℃
Finally we achieved the total length of 3.4cm, the propagation loss of
straight waveguide under TM mode transmission is 0.8735dB / cm, while Mach‐
Zehnder interferometer propagation loss is 0.9911 dB / cm under TM mode, we
use Network Analyzer to measure the S‐parameter which bandwidth(S21) up to
21.3GHz and reflection(S21) signal are lower than ‐15dB, and achieved the
frequency response of 3Gbps bandwidth under driving voltage is 6V with the Eye‐
Diagram. | en_US |