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We present terahertz lenses made of polymeric compounds which provide a better focusing capability and an increased functionality than state of the art lenses made of pure base polymers. This is achieved by employing mixtures between polypropylene and alumina as well as polypropylene and zinc sulfide which allows for a significant increase of the refractive index of the lens base material.
Medical devices with embedded highly miniaturized microsystems are used as implants in the human body or as non-invasive devices for sensor applications outside the body. Those devices bear quite a lot of economic opportunities but they also do offer unique challenges compared to consumer or automotive applications. Medical applications need to provide biocompatibility, highest miniaturization, rough...
Polymers typically show only low absorption in the far-infrared or terahertz (THz) frequency range and are thus often used as window or lens materials for THz spectroscopy and imaging systems. A comprehensive study of the far-infrared properties of polymers yet reveals that THz spectroscopy is a very convenient technology for the investigation of various material properties including the morphology...
Polymer materials - mainly epoxy resins - are widely used in microelectronics packaging. They are established in printed circuit board manufacturing, for adhesives as die attach glues or for encapsulants as molding compounds, glob tops or underfill materials. Low cost and mass production capabilities are the main advantages of these materials. But like all polymers they cannot provide a hermetical...
We present photonic crystals exhibiting a pronounced form birefringence at terahertz frequencies. These crystals can be employed as volumetric birefringent elements for a broad frequency range. Along with a theoretical discussion we demonstrate measurement results of a polymeric crystal.
Understanding the interactions of the crystalline and the amorphous domains in semi-crystalline polymers, such as HDPE or PVDF, is a subject of ongoing research. Here, we apply terahertz time-domain spectroscopy to study the impact of the glass transition taking place in the amorphous phase on lattice modes associated with the crystalline domains.
We present a cost efficient delay technique for terahertz spectrometers based on discrete phase shifting of the THz wave. This can be achieved by using a polymer disc with segments of different thickness. The approach is demonstrated by measurements with a six segment disc placed in the THz beam.
This paper describes the potential of different nano- and micro-sized particles as additives for plastic packaging materials for enhanced humidity resistance/barrier enhancement within microelectronic packages as well testing methods for material characterization concerning their humidity diffusion and absorption properties. This topic is gaining increased importance when considering the trend towards...
The glass transition temperature Tg of polymers is identified by terahertz (THz) time-domain spectroscopy (TDS). The THz refractive index n of the investigated material changes significantly in the region of the glass transition. Hence, THz TDS offers the possibility for non-contact polymer analysis.
Decreasing the temperature leads to a blue shift of the B1u lattice mode in different types of polyethylene, which can be observed using terahertz time-domain spectroscopy. Moreover, the frequency shift reveals the glass transition of high-density polyethylene due to the semi-crystalline nature in this polymer. In addition, morphological factors on the B1u lattice mode of LDPE, LLDPE, and HDPE are...
The glass transition temperature Tg of polymers is identified by terahertz time-domain spectroscopy (TDS). The thermo-quasi-optic coefficient noticeably changes in the region of the glass transition. THz TDS can thus serve as a non-destructive and non-contact technique for polymer analysis.
We present two fiber-coupled terahertz (THz) time-domain transceiver heads that are well suited for zero degree reflection measurements and allow for flexible handling. One consists of only one photoconductive switch that is capable of emitting and detecting at the same time and the other operates with two antennas and a beam splitter made from a polypropylene-titanium (PP-TiO2) compound.
We present a sub-terahertz wave on-off switch based on a two-dimensional photonic crystal (PC). The PC consists of a triangular hole array in high density polyethylene (HDPE). The holes are infiltrated with the nematic liquid crystal 5CB. The transmission of sub-terahertz electromagnetic waves is controlled by an electric field-induced rotation of the nematic axis of the 5CB molecules. The measured...
We present non-destructive and contactless inline measurements on the molten polymer polypropylene and on the polymeric compound polypropylene-CaCO3 carried out with a THz spectrometer. The effect of temperature and pressure on the THz properties of the molten polymeric material is investigated. Additionally, we analyze the additive content of the compound during the extrusion processing and compare...
Polymer materials - mainly epoxy resins - are widely used in microelectronics packaging. They are established in printed circuit board manufacturing, for adhesives as die attach glues or for encapsulants as molding compounds, glob tops or underfill materials. Low cost and mass production capabilities are the main advantages of these materials. But like all polymers they can not provide a hermetical...
Terahertz technology holds a huge potential for a variety of applications in science and the industry, but still suffers from the lack of widely available system components. Not only active but also passive components like reflectors and filters are needed to advance the maturity of terahertz technology in general. Here, we present high quality, flexible, low-cost terahertz Bragg reflectors and filters...
We present terahertz time-domain spectroscopy measurements on compounds based on standard polymers. Concentrations of various additives are clearly distinguished. The results are encouraging for the industrial application of terahertz time-domain spectroscopy for polymer science, the control of compounding processes and for quality assurance.
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