Nano-optical gratings for integrated laser interferometer arrays

In this contribution we show that binary nano-optical gratings in the resonance domain are ideal elements to build up such integrated interferometers. By means of symmetry considerations the grating's requirements for an ideal operation of the interferometer are determined. Utilizing the resonance behaviour of such nano-structures an interferometer operation close to the theoretical limits is reachable. A modal analysis reveals the basic effects causing the special responses of the gratings. The gratings are fabricated by electron-beam lithography and accompanied technology

Investigations on black silicon nanostructures fabricated by reactive ion etching on highly curved surfaces

A large amount of valuable research on black silicon (b-Si) nanostructures has pushed its use further into application in recent years. However, the research results to be found are all related to plane substrates. For an investigation of b-Si structures on curved surfaces, they were fabricated on hemispherical silicon lenses using inductively coupled plasma reactive ion etching. It was possible to achieve different structure morphologies according to the selected etching parameters, analogous to their fabrication on Si wafers. Scanning electron microscopy inspections of the structure morphology were carried out to study the homogeneity across the lens surface as well as the orientation of the structures. Simulations of the bent electric field within the etching chamber and the resulting ion trajectories explain the underlying etching process that creates structures approximately perpendicular to the curved lens surface. Optical reflectance measurements confirm the findings on homogeneity and orientation

Pixeliertes, diffraktives optisches Element mit zwei Hoehenstufen zur Erzeugung einer Phasenverteilung mit beliebigem Phasenhub

DE 102009037629 A1 UPAB: 20110302 NOVELTY - The diffractive optical element has an element section and multiple pixels for realizing an adjusting phase shift with a basis surface. A part of the pixels has a height profile with surfaces. An altitudinal belt is realized between the surfaces. The altitudinal belt is synchronized to an adjusted maximum phase shift of the diffractive optical element. The altitudinal belt has a constant height difference for the pixel with altitude profile. USE - Diffractive optical element for generating a phase distribution. ADVANTAGE - The diffractive optical element has an element section and multiple pixels for realizing an adjusting phase shift with a basis surface, and thus ensures improved diffractive optical element

Pointwise process proximity function calibration - PPFexplorer application results

The semiconductor industry and mask shops spend great efforts in order to keep pace with the requirements on pattern fidelity of the ITRS lithography roadmap. Even for e-beam lithography - often referred to as technology with "unlimited" resolution - the challenges increase with shrinking feature sizes in combination with applicable resist processes. The pattern fidelity, specifically CD control, is crucial for the application of e-beam lithography. One aspect in CD control is the intrinsic proximity effect of the electron beam. This together with other contributions like influences from resist process or beam generation which are summarized altogether under the term process proximity effect have to be corrected. An accurate e-beam process proximity effect correction is therefore a key component of e-beam lithography. Some process proximity effect correction algorithms provide not only accurate correction for the process proximity effect induced pattern deformation but also optimize pattern contrast by adjusting geometry and dose simultaneously. However, the quality of the process proximity effect correction is limited by the calibration accuracy of the used model, i.e., the accuracy of the utilized process proximity function (PPF). In a previous paper [R. Galler et al, "PPF - Explorer: Pointwise Proximity Function calibration using a new radialsymmetric calibration structure", BACUS 2011] the PPF-explorer - a new experimental method for pointwise process proximity function calibration - was introduced and some first promising calibration results were shown. This paper presents the progress of the PPFexplorer proximity function calibration. This progress, among others, comprises automatic generation of calibration patterns, including pre-correction with respect to a rough forecast of the process proximity function to be calibrated. This pre-correction approach significantly reduces the number of necessary calibration structures and the number of measurement sites, without sacrificing calibration accuracy. On the contrary, the pre-correction has positive impact on the calibration quality, since it allows unifying the pattern contrast at the measurement sites, which reduces the SEM measurement induced error. We present the results of a PPFexplorer calibration with special focus on minimizing the number of measurement sites. The results show that the PPFexplorer method can help to improve the proximity effect model calibration with controllable efforts

Table-top high-energy 7 μm OPCPA and 260 mJ Ho:YLF pump laser

International audienceWe present a state-of-the-art compact high-energy mid-infrared (mid-IR) laser system for TW-level eight-cycle pulses at 7 μm. This system consists of an Er:Tm:Ho:fiber MOPA which serves as the seeder for a ZGP-based optical parametric chirped pulse amplification (OPCPA) chain, in addition to a Ho:YLF amplifier which is Tm:fiber pumped. Featuring all-optical synchronization, the system delivers 260 mJ pump energy at 2052 nm and 16 ps duration at 100 Hz with a stability of 0.8% rms over 20 min. We show that chirp inversion in the OPCPA chain leads to excellent energy extraction and aids in compression of the 7 μm pulses to eight optical cycles (188 fs) in bulk BaF2 with 93.5% efficiency. Using 21.7 mJ of the available pump energy, we generate 0.75 mJ energy pulses at 7 μm due to increased efficiency with a chirp inversion scheme. The pulse quality of the system’s output is shown by generating high harmonics in ZnSe which span up to harmonic order 13 with excellent contrast. The combination of the passive carrier-envelope phase stable mid-IR seed pulses and the high-energy 2052 nm picosecond pulses makes this compact system a key enabling tool for the next generation of studies on extreme photonics, strong field physics, and table-top coherent X-ray science

Grating-Based Mid-Infrared Long-Pass Filter for High-Power Applications

We present a gold-coated silicon grating which provides efficient spatial separation of a broadband mid-infrared (MIR) beam from a collinear, 30W beam of broadband near-infrared (NIR) pulses in a power-scalable and chromatic dispersion-free manner

Watt-scale 50-MHz source of single-cycle waveform-stable pulses in the molecular fingerprint region

We report a coherent mid-infrared (MIR) source with a combination of broad spectral coverage (6–18 μm), high repetition rate (50 MHz), and high average power (0.5 W). The waveform-stable pulses emerge via intrapulse difference-frequency generation (IPDFG) in a GaSe crystal, driven by a 30-W-average-power train of 32-fs pulses spectrally centered at 2 μm, delivered by a fiber-laser system. Electro-optic sampling (EOS) of the waveform-stable MIR waveforms reveals their single-cycle nature, confirming the excellent phase matching both of IPDFG and of EOS with 2-μm pulses in GaSe