Diode laser based light sources (implemented monolithically or in a hybrid configuration) offer various functionalities to meet the requirements of specific applications. This includes tuning or switching between different wavelengths, modulating the optical output power, or implemented frequency conversion. Such light sources often contain multisection diode lasers or several active elements. Their operation requires multiple individually adjustable current sources, galvanically isolated current sources, and temperature control. A suitable optical interface should be available for a subsequent integration of the turnkey into the addressed application. In this contribution, a versatile turnkey system meeting the above-mentioned requirements will be presented. Ten p-type current sources, each with currents up to 750 mA, and four galvanically decoupled current sources are implemented. The ten individual sources enable switching frequencies up to 1 kHz and can be combined to provide currents up to 7.5 A. A temperature control unit capable to remove 10 W thermal load using a Peltier element completes the system, which contains an internal microcontroller, trigger in- and outputs, and an USB interface for the integration into various environments. Moreover, fiber coupling and free space optics to transfer the laser emission are offered. Turnkey systems containing in-house developed light sources at 488 nm or 785 nm were implemented into portable Raman spectroscopic measurement systems. To separate Raman signals from background disturbances, shifted excitation Raman difference spectroscopy (SERDS) was applied using dual-wavelength light sources. Systems addressing the measurement of carotenoids under clinical conditions and soil properties in the field will be presented.
Recent advances in optimizing the efficiency and lifetime of far-UVC LEDs with emission wavelengths below 240 nm are presented. The design of the semiconductor heterostructure is considered as well as the chip layout. Cross-comparisons are used to draw general conclusions about degradation mechanisms in UV LEDs and to identify development strategies to minimize them. Furthermore, it is discussed which chip packaging is particularly suitable for a combination of far-UVC LEDs with spectral filters. Finally, far-UVC irradiation systems for skin-friendly irradiation of the human body are presented and their performance is illustrated with selected medical and biological data.
Far-UVC LEDs are interesting for applications such as skin-tolerant inactivation of multiresistant pathogens and gas sensing. We present the development of 233 nm AlGaN-based far-UVC LEDs with an emission power of 3 mW at 200 mA and L50 lifetime of more than 1000 h, after burn-in. Additionally, the design of a far-UVC LED-based irradiation system, with a spectral filter which supresses emission >240 nm, to study the inactivation of bacteria and skin compatibility of the radiation will be presented. The system can be used to homogeneously irradiate a target area of 70 mm diameter with a mean irradiance of 0.4 mW/cm².
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