Bernd Maisenhölder

Quantum-well intermixing for fabrication of lasers and photonic integrated circuits

Various applications of quantum-well intermixing, ranging from multiwavelength lasers to complex photonic integrated circuits, are described. The fabrication of these GaAs-AlGaAs-based devices relies on the postgrowth definition of regions with varying bandgap, enabling the manufacture of wavelength shifted modulators and lasers, as well as the integration of transparent waveguides with absorbing lasers and detectors. The impurity-free vacancy-enhanced disordering technique employed, and its integration with existing process technologies, will be presented, and examples of multicolor lasers, wavelength shifted modulators and integrated optical interferometers are shown. These applications yield high-optical functionality using relatively simple process and integration technology.

A GaAs/AlGaAs-based refractometer platform for integrated optical sensing applications

Abstract We present a new type of integrated optical refractometer, based on a Mach-Zehnder interferometer using III–V semiconductor and TiO2 on SiO2 waveguides. We report on the design, optimized for high sensitivity in immunoassay sensing applications, and the fabrication of this sensor chip. Using a test liquid system of ethanol in water, we demonstrate a refractive-index resolution of 1× 10−5 for this refractometer. This device is a basic building block of a novel, monolithically integrated optical sensing circuit, which can be used for example in chemical or immunological sensing applications.

Sub-micron grating formation in Ta2O5-waveguides by femtosecond UV-laser ablation

Abstract Sub-micron-period surface gratings on Ta2O5 waveguide layers were produced by ablation with a sub-ps-UV-laser. The structure is generated by projection imaging of a primary transmission grating mask. A grating of 500 nm period with a surface modulation depth of 10 nm on a sample area of about 300 μm×300 μm can be produced with a single laser pulse of about 100 mJ/cm2 at 248 nm. Adjustment of the modulation depth to specific requirements can be accomplished by varying laser fluence or pulse number. The structures can be used as grating couplers.

Optical refractometry using a monolithically integrated Mach-Zehnder interferometer

Integrated optical sensors, based on evanescent wave sensing, are useful for numerous applications, including medical, environmental and food analysis. System miniaturization is a key issue in their further development. We present the design and fabrication of a novel refractometric transducer, where all optoelectronic components (laser, waveguide, modulators, detectors and sensor pads) are and report on its performance as a refractometer in a flow-through system.