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A hermetic fiber pigtailed laser module utilizing passive device alignment on a low-temperature cofired ceramics (LTCC) substrate is demonstrated. The 3-D shape of the laminated and cofired ceramic substrate provides the necessary alignment structures, including grooves and cavities, for the laser-to-fiber coupling. When the laser diode chip and component tolerances are tight enough, the passive alignment allows high coupling efficiency realizations of multimode fiber pigtailed laser modules. The ceramic substrate is intrinsically hermetic and it opens up the possibility to use the substrate as an integrated part of the hermetic module package. In our concept hermetic sealing is produced by utilizing a Kovar frame, which is soldered to an LTCC substrate. The Kovar frame has a hole for a fiber feed-through and a hermetic glass-metal seal between fiber and frame is processed using a glass preform. The module can be used as a transmitter in a laser pulse time-of-flight distance sensor and in this application it can be overdriven by a factor of 10. This means that the peak optical power in the pulses can be several dozen watts. The laser chip allows this kind of overdriving, due to the fact that the duty factor in the operation is only 0.0% at 2 kHz pulsing frequency, which leads to an average power of several milliwatts. The simulated nominal coupling efficiency between the 210 mum times 1 mum stripe laser and the 200/220 mum step index fiber (NA = 0.22) was 0.65. The measured coupling efficiency of the hermetically sealed prototypes varied from 0.14 to 0.64, where the average was 0.39. A leak rate of 1 times 10-7 . .. 8 times 10-7 [atm times cm3/s] was measured in the helium leak tests of the final operational prototypes, when the modules were tested according to MIL-STD-883F method 1014.9 specification. The rather high leak rate is mainly due to the helium absorbed by the fiber polymer buffer layer and rubber guard tube in the pressurization process. The leak rate for the dummy modules using a buffer stripped fiber without a rubber guard tube was 3 times 10-9 . .. 1 times 10-8 [atm times cm3/s]. The maximum allowed leak rate for this size of hermetic module is 1 times 10-7 [atm times cm3/s]. The background helium level before and after the tests was less than 3 times 10-10 [atm times cm3/s]. Measurements proved that the manufacturing procedure is capable of producing hermetic fiber pigtailed laser modules.

Autonomous systems are pursued in automotive and signage applications due to easy installation and achieved energy savings. In addition, reduction of cabling decreases system weight, which is especially pursued in automotive applications due to the decreased fuel consumption. Naturally, autonomous systems require some kind of energy harvesting and energy storing systems. In order to achieve required autonomy operation time of over 15 hours, four flexible Li-Ion batteries of 1200 mAh total capacity in automotive demonstrator and four flexible Li-Ion batteries of 3200 mAh total capacity in signage demonstrator were required. The dimensions of batteries were 295 mm × 29 mm and 295 mm × 119 mm. The energy harvesting for autonomous operation was based on flexible commercially available amorphous silicon solar cells, types MP3-25 and MPT6-150 manufactured by Power Film. The dimensions of the solar cells were 114 mm × 29 mm and 114 mm × 150 mm. The pursued autonomy time of demonstrators resulted to a large surface area requirement for the backplane substrates. The dimensions of the assembled automotive demonstrator were 2400 mm × 35 mm × 0.95 mm and the dimensions of the assembled signage demonstrator were 2550 mm × 144 mm × 0.95 mm. The large size of both the components and the substrates produced challenges for assembly and bonding processes. As the bonding method hot bar bonding or oven curing were used, the experimental procedure being compatible with the guidelines of the material suppliers. Daisy chain test structures were used to study the interconnections between the foils. Thermal humidity testing at 85°C/85%RH and thermal cycling between −40….+85°C were used as the environmental tests for the test structures processed before final selection of the bonding materials and processes for demonstrators manufacturing. Both manufactured demonstrators were operational after assembly and bonding processes. The energy produced by the solar cells was guided to the Li-Ion batteries by a specific charge regulator. Batteries were able to supply power to the automotive and signage LED elements so that the systems autonomous operation was successfully demonstrated.

An infrared (IR) temperature measurement system consists of not only a sensor module and electronics, but also an optomechanical system that guides IR radiation onto the sensor. The geometry and emissivity of the parts affects the reading, if the detector sees not only the target but parts of the measuring system itself. In normal industrial applications, the optics is designed so that the surfaces stabilize to the same temperature as the sensor. This allows the error caused by the device temperature to be easily calibrated away. The correction is valid for stationary conditions and usually near the calibration temperature, which is typically at room temperature. However, we show that if the sensor is embedded into a mobile (hand-held) device which has heat sources, such as power electronics, the normal conditions are no longer valid and the calibration fails. In order to improve infrared temperature sensing for mobile devices, the optics concept was studied and detailed design was performed. In addition, the optics performance was modelled and verified by measurement sensor prototyping. A calibration procedure noticing operational temperature variations was applied. The repeatability of the implemented IR temperature sensor using on a correct transferred calibration curve was better than plusmn0.5degC in an operational temperature range from +12.6 to +49.3degC and target range from +10 to +90degC.