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Single-mode diode lasers on an InP(001) substrate have been developed using InAs/In0.53Ga0.47As quantum dash (Qdash) active regions and etched lateral Bragg gratings. The lasers have been designed to operate at wavelengths near 2 lm and exhibit a threshold current of 65mA for a 600 lm long cavity, and a room temperature continuous wave output power per facet >5mW. Using our novel growth approach based on the low ternary In0.53Ga0.47As barriers, we also demonstrate ridge-waveguide lasers emitting up to 2.1 lm and underline the possibilities for further pushing the emission wavelength out towards longer wavelengths with this material system. By introducing experimentally the concept of high-duty-cycle lateral Bragg gratings, a side mode suppression ratio of >37 dB has been achieved, owing to an appreciably increased grating coupling coefficient of j~40 cm-1. These laterally coupled distributed feedback (LC-DFB) lasers combine the advantage of high and well-controlled coupling coefficients achieved in conventional DFB lasers, with the regrowth-free fabrication process of lateral gratings, and exhibit substantially lower optical losses compared to the conventional metal-based LC-DFB lasers. [ABSTRACT FROM AUTHOR]

We report on the fabrication and characterization of high-resolution gratings with high efficiency in the extreme ultraviolet (EUV) and soft x-ray ranges using spin-on-carbon (SOC) underlayers. We demonstrate the fabrication of diffraction gratings down to 20 nm half-pitch (HP) on Si3N4 membranes with a bilayer of hydrogen silsesquioxane (HSQ) and spin-on-carbon and show their performance as a grating mask for extreme ultraviolet interference lithography (EUV-IL). High-resolution patterning of HSQ is possible only for thin films due to pattern collapse. The combination of this high-resolution resist with SOC circumvents this problem and enables the fabrication of high aspect ratio nanostructures. Rigorous coupled-wave analysis shows that the bilayer gratings exhibit higher diffraction efficiency than what is feasible with a grating made of HSQ. We also demonstrate a simple and accurate method to experimentally measure the diffraction efficiency of high-resolution gratings by measuring the relative ratio of the dose-to-clear curves of the photoresist. The measured diffraction efficiencies are in good agreement with the theoretically predicted values. Furthermore, we verify our calculations and measurements by printing line/space patterns in chemically amplified resists down to 10 nm HP with both HSQ and bilayer grating masks using EUV-IL. The improved diffraction efficiency of the bilayers is expected to have applications not only in gratings for interference lithography, but also in Fresnel zone plates and gratings for spectroscopy in the EUV and soft x-ray ranges. [ABSTRACT FROM AUTHOR]