Krister Hammarling

Printed Write Once and Read Many Sensor Memories in Smart Packaging Applications

A horizontal printed Write-Once-Read-Many (WORM) resistive memory has been developed for use in wireless sensor tags targeting single-event detection in smart packaging applications. The WORM memory can be programmed using a 1.5-V printed battery. An alternative programming method is to use chemical sintering which allows the development of exposure-time triggered single event tags that can be accessed wirelessly. The new WORM memory has very low losses in the ON-state which allows direct integration into antenna structures. A sensor tag that utilizes the WORM memory functionality and the well established Electronic Article Surveillance (EAS) communication standard has been outlined. Both active and fully passive sensor tag solutions have been proposed. The role of printed electronics in smart packaging applications has been reviewed and discussed. Important enabling factors for the future development have been highlighted, such as the need for hierarchical design and test tools, better printed interconnect technologies as well as better components that allow communication with existing information and communication technology (ICT) standards. This is illustrated and underlined by the presented smart packaging concept demonstrators.

Strong excited state absorption (ESA) in Yb-doped fiber lasers

Excited state absorption (ESA) measurements performed on Yb-doped silica bers show the onset of a strong absorption band in the visible range. In this work, we perform experiments to investigate the possibility for ESA to be part of the induced optical losses (photodarkening) observed in Yb-doped ber lasers. Our results indicate that an ESA process, from the 2F5/2 excited state manifold in the Yb3+ ion to the charge-transfer state with absorption bands in the UV range, may constitute a transfer route for pump- and laser photons in the near-infrared range.

A combined glucose and pH sensor on a single optical fiber for continuous point-of-care testing (Conference Presentation)

Stress-induced hyperglycemia is very common for patients in intensive care units, which can become fatal if left uncontrolled. Blood glucose concentrations for patients at the intensive care units should therefore be monitored at all times. To be successful in monitoring the glucose concentrations of patients, the sensor needs to be fast, accurate and able to measure in real time. In addition, the pH level should be monitored, as a diagnostic parameter by itself, or to improve the reliability of the glucose measurement. To address this challenge, a fiber optic sensor for dual parameter measurement of glucose concentration and pH level for use in point-of-care testing has been developed. The sensor utilizes two stimuli responsive hydrogels to create two interferometers combined on one single mode fiber. The sensor is created by splicing a short section of thin-core fiber (SM450) coated with a pH-sensitive polymer, which constitutes a Mach-Zehnder type interferometer. The glucose is measured with a low finesse Fabry-Perot cavity made by polymerizing a glucose sensitive hydrogel hemisphere at the end face of the fiber. A versatile Fourier transform based, low pass filter was developed, which enable evaluation of the two signals independently. Our results show the feasibility of measuring glucose concentration and pH level by using a single fiber. This dual parameter and single point fiber optic biosensor is expected to be of great interest for in vivo measurements in medical applications where pH and glucose, as specific markers are monitored in real time, during or after surgery.

Dual parameter fiber optic sensor combining a Fabry-Perot and a Mach-Zehnder interferometer

A new concept for dual parameter fiber optic sensor has been developed and characterized, both in a two-fiber and single-fiber configuration. The liquid sensor measures ethanol concentration with a stimuli responsive hydrogel which constitutes a low finesse Fabry-Perot cavity, and refractive index with a Mach-Zehnder type fiber optic interferometer. The two-fiber configuration utilize a fiber optic 1310/1550 nm wavelength division multiplexer to separate the two parameters, while a versatile filtering algorithm extracts and separates the two parameters in the single-fiber configuration. No cross talk were observed for the measured parameters of free spectral range and refractive index for the two-fiber configurations, while for the single fiber configuration cross-talk were observed. The two configurations prove to be versatile dual parametric fiber optic sensor concepts for accurate detection of specific parameters, based on stimuli responsive hydrogels.

Blood pH optrode based on evanescent waves and refractive index change

Sensing pH in blood with an silica multimode optical fiber. This sensor is based on evanescent wave absorption and measures the change of the refractive index and absorption in a cladding made of a biocompatible Polymer. In contrast to many existing fiber optical sensors which are based upon different dyes or florescent material to sense the pH, here presents a solution where a part of the cladding is replaced with a Poly (β-amino ester) made of 1.4-Butanediol diacrylate, Piperazine, and Trimethylolpropane Triacrylate. Piperazine has the feature of changing its volume by swelling or shrinking in response to the pH level. This paper utilizes this dimension effect and measure the refractive index and the absorption of the cladding in respect to different pH-levels. The alteration of refractive index also causes a change in the absorption and therefore the output power changes as a function of the pH level. The sensor is sensitive to pH in a wide spectral range and light absorbency can be observed for wavelengths ranging from UV to far IR.

Fiber Bragg grating filter using evaporated induced self assembly of silica nano particles

In the present work we conduct a study of fiber filters produced by evaporation of silica particles upon a MM-fiber core. A band filter was designed and theoretically verified using a 2D Comsol simulation model of a 3D problem, and calculated in the frequency domain in respect to refractive index. The fiber filters were fabricated by stripping and chemically etching the middle part of an MM-fiber until the core was exposed. A mono layer of silica nano particles were evaporated on the core using an Evaporation Induced Self-Assembly (EISA) method. The experimental results indicated a broader bandwidth than indicated by the simulations which can be explained by the mismatch in the particle size distributions, uneven particle packing and finally by effects from multiple mode angles. Thus, there are several closely connected Bragg wavelengths that build up the broader bandwidth. The experimental part shows that it is possible by narrowing the particle size distributing and better control of the particle packing, the filter effectiveness can be greatly improved.

Surface state effects on N+P doped electron detector

Surface states and interface recombination velocity that exist between detector interfaces have always been known to affect the performance of a detector. This article describes how the detector performance varies when the doping profile is altered. When irradiated with electrons, the results show that while changes in the doping profile have an effect of the detector responsivity with respect to the interface recombination velocity vs, there is no visible effect with respect to fixed oxide charge Qf otherwise known as interface fixed charge density.