Kari Tukkiniemi

CMOS-Integrated Film Bulk Acoustic Resonators for Label-Free Biosensing

The throughput is an important parameter for label-free biosensors. Acoustic resonators like the quartz crystal microbalance have a low throughput because the number of sensors which can be used at the same time is limited. Here we present an array of 64 CMOS-integrated film bulk acoustic resonators. We compare the performance with surface plasmon resonance and the quartz crystal microbalance and demonstrate the performance of the sensor for multiplexed detection of DNA.

All-silicon monolithic Mach-Zehnder interferometer as a refractive index and bio-chemical sensor

A complete Mach-Zehnder interferometer monolithically integrated on silicon is presented and employed as a refractive index and bio-chemical sensor. The device consists of broad-band light sources optically coupled to photodetectors through monomodal waveguides forming arrays of Mach-Zehnder interferometers, all components being monolithically integrated on silicon through mainstream silicon technology. The interferometer is photonically engineered in a way that the phase difference of light travelling through the sensing and reference arms is approximately wavelength independent. Consequently, upon effective medium changes, it becomes feasible even with a broad-band source to induce sinusoidal-type of detector photocurrents similar to the classical monochromatic counterparts. The device is completed with its fluidic and interconnect components so that on chip interferometric measurements can be performed. Examples of refractive index and protein sensing are presented to establish the potential of the proposed device for real-time in situ monitoring applications. This is the only silicon device that has achieved complete on-chip interferometry.

Advances in miniature spectrometer and sensor development

Miniaturization and cost reduction of spectrometer and sensor technologies has great potential to open up new applications areas and business opportunities for analytical technology in hand held, mobile and on-line applications. Advances in microfabrication have resulted in high-performance MEMS and MOEMS devices for spectrometer applications. Many other enabling technologies are useful for miniature analytical solutions, such as silicon photonics, nanoimprint lithography (NIL), system-on-chip, system-on-package techniques for integration of electronics and photonics, 3D printing, powerful embedded computing platforms, networked solutions as well as advances in chemometrics modeling. This paper will summarize recent work on spectrometer and sensor miniaturization at VTT Technical Research Centre of Finland. Fabry-Perot interferometer (FPI) tunable filter technology has been developed in two technical versions: Piezoactuated FPIs have been applied in miniature hyperspectral imaging needs in light weight UAV and nanosatellite applications, chemical imaging as well as medical applications. Microfabricated MOEMS FPIs have been developed as cost-effective sensor platforms for visible, NIR and IR applications. Further examples of sensor miniaturization will be discussed, including system-on-package sensor head for mid-IR gas analyzer, roll-to-roll printed Surface Enhanced Raman Scattering (SERS) technology as well as UV imprinted waveguide sensor for formaldehyde detection.

Simulation of imaging system's performance

In this paper, an imaging system simulation tool is presented. With the tool, it is possible to simulate the performance (quality) of an imaging system. Furthermore, the system allows optimization of the lens system for a given image sensor. Experiments have shown that the tool is useful in actual lens design.

Inexpensive packaging techniques of fiber pigtailed laser diodes

Commercial single heterojunction GaAs laser diode chips have been fiber pigtailed with a 100/140 micrometers fiber. These lasers, producing 5 ... 10 W peak pulse power, are used in time-of-flight distance measurement instruments. The laser chips were purchased mounted on a coaxial TO-5 base. Two different types of packaging constructions were tested: a sleeve construction and a butt construction. In the sleeve construction the fiber was aligned with the laser chip using a loose sleeve and a fiber ferrule. In the butt construction the fiber ferrule was butt coupled to the laser submount. The fiber ferrule was actively aligned with the laser and fixed with an adhesive or with an adhesive and laser welding. Silicone gel potting was tested to improve the module stability in outdoor applications. The pigtailed laser modules and commercial laser modules were temperature cycled and results were compared. The measurements show that the properties of the adhesive are crucial to the temperature stability of the module. The tests show that optical output variation of the module was 6 dB in the temperature range of -20 ... 55 degree(s)C when the peak power was 3.7 W at room temperature. The stability of poor adhesive joints can be improved utilizing laser welding. However, the drawback is the high investment cost of equipment required. The results show that simple and inexpensive fiber pigtailed modules can be made using properly selected adhesives.

Packaging considerations of fiber-optic laser sources

The continuous progress in material and component technology has generated new laser-based applications that require special packaging techniques. Hybrid integration offers a flexible method to accomplish custom design needs. This paper discusses several aspects in fiber optic packaging including optical, thermal, and mechanical issues. Special emphasis is on optical coupling between a laser diode and a single-mode fiber.

Monolithic silicon interferometric optoelectronic devices for label-free multi-analyte biosensing applications

Miniaturized bioanalytical devices find wide applications ranging from blood tests to environmental monitoring. Such devices in the form of hand held personal laboratories can transform point-of-care monitoring provided miniaturization, multianalyte detection and sensitivity issues are successfully resolved. Optical detection in biosensors is superior in many respects to other types of sensing based on alternative signal transduction techniques, especially when both sensitivity and label free detection is sought. The main drawback of optical biosensing transducers relates to the unresolved manufacturability issues encountered when attempting monolithic integration of the light source. If the mature silicon processing technology could be used to monolithically integrate optical components, including light emitting devices, into complete photonic sensors, then the lab on a chip concept would materialize into a robust and affordable way. Here, we describe and demonstrate a bioanalytical device consisting of a monolithic silicon optocoupler properly engineered as a planar interferometric microchip. The optical microchip monolithically integrates silicon light emitting diodes and detectors optically coupled through silicon nitride waveguides designed to form Mach-Zehnder interferometers. Label free detection of proteins is demonstrated down to pM sensitivities.

All-optical fiber optic interface for sensors and actuators

The feasibility of an all-optical fiber optic interface for sensors and actuators is demonstrated. The interface module converts optical power to electrical power for the use of the sensor or the actuator. In addition, the module provides bidirectional optical data transmission be- tween the sensor or actuator and a control unit by using the power- feeding fiber as a data transmission media. Optical power and data is transmitted to the sensor or actuator via a single multimode fiber. The system comprises of a customized 10-cell photovoltaic array illuminated by the use of a customized 1310 integrated optics coupler. A 41% optical-to-electrical power conversion efficiency was obtained for the photovoltaic array, and a 27% total optical-to-electrical power conversion efficiency was attained for the system. When a single element in the array was biased as an LED, a 233 dBm optical power was coupled to the multimode fiber.

Laser profilometer module based on a low-temperature cofired ceramic substrate

We realized a laser profilometer module using low tempera- ture cofired ceramics technology. The device consists of a vertical-cavity surface-emitting laser as the light source and a complementary metal oxide semiconductor image sensor as the detector. The laser transmitter produces a thin light stripe on the measurable object, and the receiver calculates the distance profile using triangulation. Because the design of optoelectronic modules, such as the laser profilometer, is usually carried out using specialized software, its electronic compatibility is very impor- tant. We developed a data transmission network using commercial opti- cal, electrical, and mechanical design software, which enabled us to electronically transfer data between the designers. The module electron- ics were realized with multilayer ceramics technology that eases compo- nent assembly by providing precision alignment features in the sub- strate. The housing was manufactured from aluminum using electronic data transfer from the mechanical design software to the five-axis milling workstation. Target distance profiles were obtained from 100 points with an accuracy varying from 0.1 mm at a 5-cm distance to 2 cm at 1.5 m. The module has potential for distance measurement in portable devices where small size, light weight, and low power consumption are important.

Optical-To-Electrical Power Conversion and Data Transmission Module

Use of optical fiber to supply power for an electrical sensor or actuator is advantageous in applications where galvanic isolation between a control and remote unit is required or when immunity to electromagnetic interferences, intrinsic safety, small size, or light weight are needed. When a conventional sensor is equipped with an optical fiber, the sensor is called a fiber optic hybrid sensor (Gross, 1991; Ross, 1992); when the current conducting paths of a conventional system are replaced by optical fibers, the system is called a power-by-light (PBL) system (Landry et al., 1991). Optically powered sensors and actuators are advantageous, for example, in electric power plant instrumentation to provide galvanic isolation between a remote sensor or actuator unit and a control unit.