This paper describes the implementation of a low-cost technology platform for fluorescence-based optochemical sensors
made up of arrays of multimode waveguides and coupling structures integrated onto a flexible substrate. Such a
configuration is ideal for multi-analyte detection owing to a possibility of future integration of different dyes in each
waveguides. The presence of light sources, fluorescent sensing elements and photodetectors in a foil platform makes it a
compact optochemical sensor, which has wide-range of applications in medical, biochemical, and environmental
diagnostics. Flexible lightguides fabricated using soft-lithography based replication techniques, are used in combination
with 45° micromirror coupling structures, having a loss of 0.5dB. Fluorescent dyes are incorporated with the lightguides
enabling a detection of shift in fluorescence-peaks in contact with gases, which are read-out at the detection. Initial
measurements yielded promising results of the waveguides mixed with fluorescent dyes showing response to toluene.
We present the design and fabrication of a complete optical interconnection scheme including the optoelectronic
package, containing driving Vertical Cavity Surface Emitting Lasers (VCSELs) and read-out photodiode (PDs), the
coupling scheme of the fiber or waveguide interconnect and the fabrication technology of the waveguide structures itself.
Both the optoelectronic package and the waveguide part are fabricated using polymer materials resulting in a low-cost,
flexible interconnection scheme.
The optoelectronic package consists of an ultra-thin (20 μm) chip embedded in a flexible polymer stack, connected
through metalized microvias using thin film deposition steps. A 45° deflecting micromirror is used to couple this
optoelectronic package to an optical fiber or an optical waveguide. The waveguiding structures can be integrated with the
coupling plug leading to a 1 step alignment process which significantly reduces the coupling losses. Flexible and
stretchable multimode polymer waveguides are also developed to end up with a fully flexible optical interconnect for
short (waveguide) or long distance (fiber) communication or for application in sensing.
This paper describes the development of a low-cost technology platform for fluorescence-based optochemical sensors.
These sensors were constructed by incorporating fluorescent sensing elements in the core of multimode waveguides or
lightguides, and have applications in medical, biochemical and environmental diagnostics. Flexible lightguides were
fabricated either with silsesquioxane-based or PDMS-type optical polymers using photolithography or soft-lithography
based replication techniques respectively. Spectral transmission characteristics were measured along with loss values
obtained by cut-back measurements for several wavelengths from visible to mid-IR. Propagation losses as low as
0.14dB/cm were measured for 50 x 50 μm<sup>2</sup> waveguides. For coupling light in and out of the waveguides, different types
of coupling structures, e.g. 45° micromirror plugs were investigated.
Fiber Bragg gratings can be used for monitoring different parameters in a wide variety of materials and constructions.
The interrogation of fiber Bragg gratings traditionally consists of an expensive and spacious peak tracking or spectrum
analyzing unit which needs to be deployed outside the monitored structure. We present a dynamic low-cost interrogation
system for fiber Bragg gratings which can be integrated with the fiber itself, limiting the fragile optical in- and outcoupling
interfaces and providing a compact, unobtrusive driving and read-out unit. The reported system is based on an
embedded Vertical Cavity Surface Emitting Laser (VCSEL) which is tuned dynamically at 1 kHz and an embedded
photodiode. Fiber coupling is provided through a dedicated 45° micromirror yielding a 90° in-the-plane coupling and
limiting the total thickness of the fiber coupled optoelectronic package to 550 μm. The red-shift of the VCSEL
wavelength is providing a full reconstruction of the spectrum with a range of 2.5 nm. A few-mode fiber with fiber Bragg
gratings at 850 nm is used to prove the feasibility of this low-cost and ultra-compact interrogation approach.
This paper reports on the latest trends and results on the integration of optical and opto-electronic devices and
interconnections inside flexible carrier materials. Electrical circuits on flexible substrates are a very fast growing
segment in electronics, but opto-electronics and optics should be able to follow these upcoming trends. This paper
presents the back-thinning and packaging of single opto-electronic devices resulting in highly flexible and reliable
packages. Optical waveguides and optical out-of-plane coupling structures are integrated inside the same layer stack,
resulting in complete VCSEL-to-PD links with low total optical losses and high resistance to heat cycling and moisture