Micropelt develops and markets the world's smallest thermoelectric power generation devices. Due to the silicon-wafer
based MEMS-like production process elements with a total thickness of 1 mm and a footprint from less than 1 mm² to 25
mm2 can be realized. The fabrication process is based on standard semiconductor equipment and processes. Therefore
ramp-up schemes and economies-of-scale close to those of common chip devices apply to Micropelt products.
Micropelt thermogenerators produce much higher output voltages than conventional bulk devices which is due to the fact
that their micro-structuring technology produces near 8000 p-n thermo-couples per square centimeter, while
conventional thermogenerators typically have less than 10 such thermo-couples on the same area. Consequently
Micropelt generators are well suited as the core of an integrated power supply for energy-autonomous miniaturized smart
systems with average power consumptions of a few Milliwatts. Micropelt Engineering has proven readiness of their
devices for use in a multitude of wireless sensor and micro systems, including smart actuators
In this paper we will first introduce the Micropelt technology and further discuss energy harvesting opportunities for
novel low power devices and wireless applications based on given waste heat reservoirs.
Infrared breath analysis is used in diagnostics of respiratory diseases, pulmonary function testing, and for metabolic studies. With selective and highly sensitive instruments exhaled trace gas concentrations can be related to specific diseases.
For many applications also a time resolution below 0.1s is needed. Frequently, performance is limited by the IR source. New developments offer solutions even for compact instruments. Different setups employing quantum cascade lasers (QCL), VCSELs, and a new optically pumped IR emitter are compared focusing on CO2 measurements as an example.
Light emitting devices for the infrared spectral region are used in a lot of application fields. In the mid infrared (MIR) region, where a lot of gases show strong absorptions, the optical output power of inexpensive emitters in the relevant wavelength range is too low. An optically pumped emitter for the MIR region around 4 μm based on narrow gap semiconductors is demonstrated. The pumping takes place using inexpensive near-infrared (around 1 μm) high power continuous wave (cw) semiconductors laser. The radiation is converted by the narrow gap semiconductor into the MIR region as spontaneous emission. Molecular beam epitaxy (MBE) grown IV-VI lead chalcogenide-based compounds, especially PbSe, are applied for frequency conversion. The structural and optical quality of these thin film materials is characterized mainly by X-ray defraction measurements (XRD) and photo luminescence (PL) spectroscopy. For high radiation efficiency the outcoupling of the light is enhanced by surface structuring. Useful structures generating high photoluminescence intensity are characterized by IR imaging with an IR camera system being sensitive in the spectral region of interest. Due to the high pumping powers the device design-especially the thermal management of the active PbSe film-plays an important role. We will present a preparation technique for optically pumped, surface structured PbSe emitters in transmission geometry exploiting the transparency of the substrates and glues in the relevant wavelength region. The measured total emission power of the emitters exceeds 0.5 mW. Using an optimised design total emission powers up to 2 mW were achieved.
We present a novel hybrid light emitting device design based on a standard InAlGaAs/GaAs high-power laser diode array chip as a pump source and a narrow-gap PbSe-layer as active optical material. Maximum cw output powers of more than 1.1 mW and slope efficiencies of 0.4 mW/A are obtained at 25 °C. The external power efficiency amounts to 3.5×10-2 %. The emission wavelength is 4.2 μm, with a half width of 770 nm (50 meV). Details about the optimization of the emitter material and device design are discussed as well.
We report on the development of epitaxial thin film materials for optical pumped light emitting devices in the wavelength range of 4-5 μm. The active layers are lead selenide (PbSe) thin films grown by molecular-beam epitaxy (MBE) on single crystalline, infrared transparent BaF2 substrates. The electrical properties of the layers were determined by van der Pauw Hall measurements. A dependency of the PL intensity on the dopant type and carrier concentration was found. To increase the output power, layers with antireflection coatings were grown and characterized by Fourier-transform infrared (FTIR) spectroscopy and photoluminescence (PL) measurements. A further possibility to increase the extraction efficiency is surface texturing. Infrared imaging and PL measurements at samples with different surface structures, prepared by wet chemical etching, are presented. To improve the heat dissipation, which is a problem of optical pumped devices due to the small efficiency and pump densities up to some kW/cm2, the BaF2 substrates were removed and the active layers were transferred to different heat sinks with significantly higher thermal conductivities. Afterwards the PL intensities were compared among each other.
An optically pumped emitter for the mid-infrared region around 4 µm based on narrow gap semiconductors is demonstrated. The pumping takes place in the near-infrared around 1 μm and the radiation is converted by the narrow ap semiconductor into the MIR region as spontaneous emission. IV-VI lead chalcogenide-based compounds, especially PbSe and III-V InAsSb-based quantum well systems are applied for frequency conversion. These materials are grown by MBE and characterized mainly by photo luminescence spectroscopy. For a high radiation efficiency the outcoupling of the light is enhanced by surface structuring. Useful structures generating high photoluminescence intensity are characterized by IR imaging with an IR camera system being sensitive in the spectral region of interest.