An Interferometric Polymer Optical Waveguide Sensor (IPOWS) for intravascular optoacoustic signal detection has been
fabricated by UV-imprinting method. The sensor has been characterized in sensitivity, dynamic range and frequency
bandwidth. We have compared experimentally the performance of the IPOWS with a piezoelectric ultra wideband sensor
and other optical fiber sensors based on single-mode silica and polymer optical fibers. All sensors are designed for the
detection of optoacoustic wave sources with a frequency bandwidth that exceed 10MHz.
In this work, we investigate the usability of layered polymer - inorganic composite waveguides for label-free sensing of
surface bound bioreactions in an aqueous environment. The waveguide structure consists of a nanoimprint fabricated
polymeric inverted rib waveguide with a sputtered Ta<sub>2</sub>O<sub>5</sub> thin film on top. The interaction of the optical field with the
surface is increased as a consequence of the mode profile localization near the surface, when high-index coating is
deposited on a low-index waveguide. Young interferometer configuration with reference and sensors waveguide arms
was utilized in sensor chips. Light from a laser source was end-fire coupled into the chips and interference pattern
produced by the outcoupled light was investigated. External μ-fluidic pump was used to produce the analyte flow.
Ambient refractive index change was characterized by applying DI-water with varying glucose concentration on
waveguides. With the waveguide length of 1 cm a detection limit in the order of 10<sup>-7</sup> - 10<sup>-6</sup> refractive index unit (RIU)
was achieved. Specific binding reactions on the surface were investigated with C - reactive protein (CRP) antibodies and
An Interferometric Polymer Optical Waveguide Sensor (IPOWS) for optoacoustic signal detection has been fabricated
by UV-imprinting method. The sensor has been characterized in sensitivity, dynamic range and frequency bandwidth.
The noise equivalent pressure (NEP) of the sensor is around 100 Pa for a bandwidth range of 20 MHz. We have
compared experimentally the performance of the IPOWS with a piezoelectric ultra wideband sensor and other optical
fiber sensors based on single-mode silica and polymer optical fibers. All sensors are designed for the detection of
optoacoustic wave sources with a frequency bandwidth that exceed 10MHz.
Polymers are important materials in fabrication of photonics devices due to their good optical properties, such as, high
transmittivity, versatile processability also at low temperatures allowing potential for low-cost fabrication. A critical
requirement in the fabrication of integrated optical devices has been selecting a most suitable method for patterning the
ridge bounding the optical mode in the waveguide. In this paper, we discuss a UV-imprint fabrication of polymeric
single-mode waveguides with different configurations: ridge type, inverted rib type and layered composite waveguides.
A ridge waveguide type consists of a strip waveguide superimposed onto a slab waveguide made of the same material.
When patterning a ridge by imprinting technique, a residual layer is formed underneath the imprinted ridges. A too thick
residual layer might cause a loss of propagation mode due to power leakage to the slab guide, which might require a
subsequent etching step. In inverted rib waveguide structure, a groove of cladding material is patterned by imprinting.
This is followed by the filling of the groove with a core material. From the imprint fabrication point of view, the
fabrication tolerances can be relaxed because the residual slab layer underneath the waveguide can have arbitrary
thickness. Besides fabrication of above mentioned waveguide structures, we also investigate the possibility to produce
composite waveguide devices by depositing inorganic thin films with high-refractive index on UV-imprinted polymeric
structures with low-refractive. The purpose to use composite structures is to manipulate the optical field distribution in
The fabrication of polymer based waveguide devices by different methods is investigated in this work including
lithographic, imprinting and focused-ion-beam processing. Also, the combination of luminescent substance with
waveguide is evaluated to produce integrated optical micro system including both the light source and sensor structure
on a single platform.
We fabricated SU-8 based slab waveguides on surface-modified poly(dimethyl siloxane) PDMS lower claddings for
application in evanescent field sensing. In this application, higher sensitivity is obtained by generating stronger
penetrating power above the waveguide into the analyte. This can be achieved by reducing the refractive index of the
substrate. Compared with glass substrates that have a refractive index of 1.5, PDMS has a refractive index of 1.42 at 633
nm, thus serving as a better lower cladding material for high-sensitivity sensing with an evanescent field or as claddings
in multilayer waveguide applications. In order to increase the adhesion of PDMS surfaces for successful SU-8
application we treated PDMS thin films in low-frequency (40 kHz) oxygen plasma for varied length of exposure time.
The treatment process made PDMS hydrophilic and created nano-structures on the surfaces. The resultant surface
topography with different exposure time was studied by an interferometric profiler on PDMS lower claddings and the
later spin-coated SU-8 waveguides. Measurement results showed that longer plasma treatment on PDMS claddings
significantly improved the uniformity and waviness of the waveguides. Light propagation tests performed with a prism
coupler and an end-butt coupling setup proved that PDMS can be used as a proper material for SU-8 waveguides.
This paper presents a label-free optical biosensor based on a Young's interferometer configuration that uses a vertically
integrated dual-slab waveguide interferometer as sensing element. In this element, linearly polarized light is coupled into
a dual-slab waveguide chip from the input end-face, and the in-coupled zeroth order mode propagates in separated upper
and lower waveguides. At the output end-face, the two closely spaced coherent beams diffract out and produce an
interference fringe pattern. An evanescent wave field, generated on the surface of the upper waveguide, probes changes
in the refractive index of the studied sample, causing a phase shift in the fringe pattern. Compared to a conventional
integrated Young's interferometer utilizing a Y-junction as the beam splitter, the dual-slab waveguide Young's
interferometer has the advantage of easy fabrication and large tolerance to the input-coupling beam. This paper builds a
measurement system to investigate sensor performance using glucose solutions with various concentrations. These
glucose concentration measurements are performed within the physiological range of 30mg/dl ~ 500mg/dl. The results
indicate that a dual-slab waveguide interferometer yields an average phase resolution of 0.002 rad, which corresponds to
an effective refractive index change of 4×10<sup>-8</sup> with an interaction path length of 15 mm.
Doppler Optical Coherence Tomography (DOCT) is a useful technique for flow measurements. Its potential applications
include industrial suspension viscosity measurements and blood flow measurements. In this work, a flow velocity profile
of 1% Intralipid was measured in a capillary with an inner diameter of 0.8 mm and in a microfluidic channel with a
cross-section of 1000 μmx100 μm. Two different DOCT measurement systems were utilized in the experiments: a
commercial conventional OCT system and a laboratory-built DOCT system, intended particularly for flow velocity
measurements. In the laboratory-built DOCT system, depth scanning was achieved by moving the whole measurement
system with the reference mirror fixed. This modification from a conventional OCT system improves lateral resolution
during the scanning process. A syringe pump was used to induce flow in the capillary. Flow velocity was measured with
flow rates from 1 ml/min to 3.33 ml/min using both measurement systems. For a flow rate of 3.33 ml/min, both systems
gave reasonable results. For flow rates lower than 3.33 ml/min, however, the laboratory-built DOCT system gave much
better results. Its mean measurement error was as low as 0.8%, while that of the commercial OCT was 6.8%. Measured
with the laboratory-built DOCT system, capillary force-induced flow velocity in the microfluidic channel was around 2
mm/s. The commercial OCT system, on the other hand, proved unsuitable for flow measurements in the microfluidic
channel due to its high scanning speed.
This paper presents a novel method for detecting a change in the refractive index of samples. One of its major
applications is sensing molecular interaction in biological samples. In our study a self-mixing interferometer (SMI) was
chosen as the instrument for measuring the refractive index in free -space. A GaN blue laser diode was used as a light-emitting
source. Compared with traditional interferometric configurations, self-mixing interferometry combined with
the laser diode package has the advantage of a compact setup and high sensitivity.
Long-term stability issue was first concerned in our research. The results showed that in 15 minutes the movement of
the fringe pattern formed by the self-interfered laser beam is 13.6 nm. The measurement of the refractive index was
performed by adding a heating element to the external cavity of the SMI. The refractive index of the air in the external
cavity was varied by the atmospheric temperature. The change in the refractive index of the air was calculated using
both a modified Edlén equation and the recorded self-interfered signals. The results showed that the change in the
refractive index observed from the shift in the fringe pattern is compatible with that calculated with the modified Edlén
equation, or about 1×10<sup>-6</sup>/°C with optical path length of 5 cm. Theoretically, the smallest movement of the fringe pattern
that can be detected with our measurement setup is 1.6 nm, corresponding to a 10<sup>-8</sup> change in the refractive index in the
In the future fast, simple and reliable biosensors will be needed to detect various analytes from different biosamples. This is due to fact that the needs of traditional health care are changing. In the future homecare of patients and peoples' responsibility for their own health will increase. Also, different wellness applications need new parameters to be analysed, reducing costs of traditional health care, which are increasing rapidly.
One fascinating and promising sensor type for these applications is an integrated optical interferometric immunosensor, which is manufactured using organic materials. The use of organic materials opens up enormous possibilities to develop different biochemical functions. In label free biosensors the measurement is based on detecting changes in refractive index, which typically are in the range of 10<sup>-6</sup>-10<sup>-8</sup> .
In this research, theoretically generated interferograms are used to compare various signal processing methods. The goal is to develop an efficient method to analyse the interferogram. Different time domain signal processing methods are studied to determine the measuring resolution and efficiency of these methods. A low cost CCD -element is used in detecting the interferogram dynamics.
It was found that in most of the signal processing methods the measuring resolution was mainly limited by pixel size. With calculation of Pearson's correlation coefficient, subpixel resolution was achieved which means that nanometer range optical path differences can be measured. This results in the refractive index resolution of the order of 10<sup>-7</sup>.