Experimental analysis of spatial states in broad-area vertical-cavity surface-emitting lasers

In dieser Arbeit wird die spontane Musterbildung in der Emission von oberflächen-emittierenden Halbleiterlasern (englisch "Vertical-cavity surface-emitting lasers", kurz VCSEL) untersucht. Dabei handelt es sich um VCSEL mit großer quadratischer (30 30 µm² und 40 40 µm²) und runder (80 µm Durchmesser) Apertur. Diese Laser neigen aufgrund ihrer sehr hohen Fresnelzahl zu der Emission von stark divergenten Transversalmoden, welche sich in Form von Intensitätsmodulationen des Laserstrahls zeigen. Die Ergebnisse der Arbeit umfassen eine quantitative Untersuchung der Abhängigkeit der Musterlängenskalen von den Betriebsparametern, eine Erklärung der Entstehung der Emissionsmuster und deren komplexer Polarisationsverteilung, sowie eine Untersuchung der Kontrolle der Mustereigenschaften durch Rückkopplung

Mechanically Flexible Dielectric Waveguides and Bandstop Filters in Glass Technology at G-band

A novel mechanically flexible filter integrated in a glass dielectric waveguide is presented for sensor applications at G-band (140–220 GHz). The use of laser-induced deep etching (LIDE) technology enables the production of via holes and thus the local modulation of the effective permittivity in a dielectric waveguide. This approach enables the implementation of a filter without the use of metal structures. In addition, extraordinary mechanical flexibility is achieved through meandering slots, which simultaneously perform the permittivity modulation. The RF performance was studied in full-wave simulations and validated by measurements of the manufactured bandstop prototypes. The experimental results of the implemented filter element show good agreement with the simulated values. At the center frequency of 156 GHz a notch depth below −14 dB in the measured stop band is achieved. Additional measurements show a stable filter characteristic at up to 8◦ bend angle applicable for the use as a low-loss waveguide under harsh environmental condition

Hermetically sealed glass package for highly integrated MMICs

A novel hermetically sealed RF packaging concept based on glass is presented. Using the laser induced deep etching (LIDE) technology enables the fabrication of glass vias without degrading the mechanical stability as micro-cracks are completely avoided. Furthermore, aspect ratios of up to 1:10 make this technology superior over conventional packaging solutions for the upper millimeter wave regime beyond 150 GHz. As an initial design demonstration, this paper shows a vertical RF-transition through the glass substrate using Through-Glass Vias (TGVs) with an aspect ratio larger than 1:6. The realized prototypes intended for highly efficient LO/VCO distribution within the glass package show excellent reproducibility with a maximum insertion loss of 0.4 dB up to 40 GHz. In addition, a very compact RF-interconnection from PCB to the glass package using solder balls is presented. The simulation of the RF-transition is in good agreement with the measured reflection and transition coefficient not exceeding −15 dB and −1.5 dB up to 35 GHz, respectively