Soft lithography molding of polymer integrated optical devices: Reduction of the background residue

Soft lithography molding is a promising technique for patterning polymer integrated optical devices, however the presence of a background residue has the potential to limit the usefulness of this technique. We present the soft lithography technique for fabricating polymer waveguides. Several effects of the background residue are investigated numerically, including the modal properties of an individual waveguide, the coupling ratio of a directional coupler, and the radiation loss in a waveguide bend. Experimentally, the residue is found to be reduced through dilution of the core polymer solution. We find that the force with which the soft mold is depressed on the substrate does not appreciably affect the waveguide thickness or the residue thickness. Optical microscope images show that the residue is thinnest next to the waveguide

Soft lithography replica molding of critically coupled polymer microring resonators

We use soft lithography replica molding to fabricate unclad polystyrene (PS) and clad SU-8 microring resonator filters. The PS resonator has an intrinsic quality factor of 1.0/spl times/10/sup 4/ at /spl lambda/=1.55 /spl mu/m, while that of the SU-8 resonator is 7100. The extinction ratios of the PS and SU-8 microring filters are -12 and -20 dB, respectively, with net insertion losses of 6.7 and 9.9 dB. The good quality factors and high extinction ratios of the microring resonator filters show the practicality of soft-lithography replica molding for the fabrication of integrated optical devices

Soft lithography replication of polymeric microring optical resonators

We have developed a soft lithography method to replicate polymeric integrated optical devices. In this method, the master device and the molded replica are made of the same materials, allowing direct comparison. To evaluate the quality of the replication, microring optical resonators are chosen as test devices because of their sensitivity to small fabrication errors. The master devices are precisely fabricated using direct electron beam lithography. The replicas are produced by the molding technique and subsequent ultraviolet curing. Compared with the master devices, the molded devices show minimal change in both physical shape and optical performance. This correspondence indicates the merits of soft lithographic methods for fabrication of precision integrated optical devices

Electroluminescent light sources via soft lithography

Purpose: Microcontact printing is a process used to print high resolution protein arrays for biosensors. We investigate using these techniques to print electrically conductive fine line structures for electroluminescent (E/L) light sources. Approach: The viability of using microcontact printing as a process for electronics fabrication is investigated. Polydimethylsiloxane (PDMS) stamps inked with alkanethiol compounds form Self Assembled Monolayers (SAM) on substrate surfaces, acting as the resist to subsequent etching processes. The printed lines are characterized with regard to their performance as high electric field generators in electroluminescent displays. Findings: It has been demonstrated that microcontact printing is a cheap, repeatable process for fabricating electronic devices. The results demonstrate the viability of the process to fabricate electric field generator structures for E/L light sources with reduced driving voltages. Value: It has been demonstrated that microcontact printing can produce electrically conductive fine-line structures with high resolution, confirming its viability in printed electronics manufacture

Soft lithographic fabrication of microresonators

Using ultra-high-Q toroid microcavity masters, soft lithography is applied to fabricate polymer microcavity arrays with Q factors in excess of 10^6. This technique produces resonators with material-limited quality factors

A microfluidic 2×2 optical switch

A 2×2 microfluidic-based optical switch is proposed and demonstrated. The switch is made of an optically clear silicon elastomer, Polydimethylsiloxane (PDMS), using soft lithography. It has insertion loss smaller than 1 dB and extinction ratio on the order of 20 dB. The device is switching between transmission (bypass) and reflection (exchange) modes within less than 20 m

All optically tunable wavelength-selective reflector consisting of coupled polymeric microring resonators

We present an all optically tunable wavelength-selective reflector for planar lightwave technology based on coupled microring resonators. By employing the Vernier effect, we demonstrate narrow-band reflection and strong side-lobe suppression in an optical polymer device fabricated by soft lithography. Wide and simple tuning of the reflection peak using an external control beam is demonstrated

High-resolution imprint and soft lithography for patterning self-assembling systems

This thesis contributes to the continuous development of patterning strategies in several different areas of unconventional nanofabrication. A series of soft lithography approaches (microcontact printing, nanomolding in capillaries), nanoimprint lithography (NIL), and capillary force lithography (CFL) combined with different surface chemistry have been used to pattern or process different self-assembling systems (e.g. self-assembled monolayers, nanoparticles, (bio)molecules, and polymers) on surfaces. A focus is on high resolution and high materials versatility. In Chapter 3, the formation of bifunctional, chemically patterned flat PDMS stamps improved the compatibility of the PDMS with polar inks by having hydrophilic patterns on the PDMS surface. In chapter 4 and 5, the combination of nanoimprint lithography or capillary force lithography with flat stamp concept opens new ways to fabricate chemical patterns on flat PDMS and improves the printing resolution down to sub-100 nm. In chapter 6 and 7, the use of a hybrid PDMS nanomold as a template for a wet lithography approach has created a simple but powerful tool to pattern different kinds of material at the nanoscale. These high-resolution soft lithography approaches developed in this thesis are ready to be used in normal research labs as tools to pattern different molecules or nanomaterials to functional nanostructures especially, when combined with the large chemical versatility of soft lithography. I also believe these tools are valuable to fabricate future nano-electronic or bio-sensing devices

Micro/Nano Patterning on Polymers Using Soft Lithography Technique

Microfabrication is essential in the field of science and technology. The development and innovations in this field are already prominent in the society through microelectronics and optoelectronics. The lithography or transfer of pattern to the substrate/surface of a layer is an important process step in microfabrication and is usually carried out with photolithography. Though photolithography is a well-established technique, it suffers from drawbacks such as limited feature size due to optical diffraction, requirement of high-energy radiation for small features, and high-cost involvement for sophisticated instruments. Also, it cannot be applied to nonplanar surfaces. Soft lithography is complement to photolithography which overcomes the above-mentioned drawbacks. Soft lithography is a simple and inexpensive method, and also, it suits to wide range of materials and very large surface areas. High-quality micropatterns or nanopatterns can be made using a patterned elastomeric stamp. This article briefly describes the various soft lithography techniques to obtain high-resolution structures for nanofabrication

Registration accuracy in multilevel soft lithography

We investigate the registration accuracy achievable by multilevel soft lithography. By a specifically designed soft lithography aligner, we obtain, for the average misalignment between two registered patterned organic layers, values decreasing from (4.96 ? 0.02) to (0.50 ? 0.01)??m upon increasing the Young's modulus of the stamp materials from 1.8 to 2600?MPa. This clearly identifies in the stamp distortions the main factor limiting the registration accuracy. The potentiality to achieve registration within 500?nm over areas of 50 ? 50??m2 is demonstrated, opening the way for soft lithographies with high overlay alignment accuracy