Direct electron beam patterning of electro-optically active PEDOT:PSS.

The optical and electronic tunability of the conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has enabled emerging applications as diverse as bioelectronics, flexible electronics, and micro- and nano-photonics. High-resolution spatial patterning of PEDOT:PSS opens up opportunities for novel active devices in a range of fields. However, typical lithographic processes require tedious indirect patterning and dry etch processes, while solution-processing methods such as ink-jet printing have limited spatial resolution.

Ultracompact wavefront characterization of femtosecond 3D printed microlenses using double-frequency Ronchi interferometry.

3D printed microoptics have become important tools for miniature endoscopy, novel CMOS-based on-chip sensors, OCT-fibers, among others. Until now, only image quality and spot diagrams were available for optical characterization. Here, we introduce Ronchi interferometry as ultracompact and quick quantitative analysis method for measuring the wavefront aberrations after propagating coherent light through the 3D printed miniature optics.

Limits of the detection of microplastics in fish tissue using stimulated Raman scattering microscopy.

We demonstrate the detection sensitivity of microplastic beads within fish tissue using stimulated Raman scattering (SRS) microscopy. The intrinsically provided chemical contrast distinguishes different types of plastic compounds within fish tissue. We study the size-dependent signal-to-noise ratio of the microplastic beads and determine a lower boundary for the detectable size.

Spectrally resolved ultrafast transient dynamics of a femtosecond fiber-feedback optical parametric oscillator.

We report on spectrotemporal transient dynamics in a femtosecond fiber-feedback optical parametric oscillator (FFOPO) system. Burst modulation of the pump beam in combination with dispersive Fourier transformation sampling allows to record single-pulse signal spectra at 41 MHz sampling rate. Therefore, each individual pulse of the signal transients can be spectrally resolved.

Electrically switchable metallic polymer metasurface device with gel polymer electrolyte.

We present an electrically switchable, compact metasurface device based on the metallic polymer PEDOT:PSS in combination with a gel polymer electrolyte. Applying square-wave voltages, we can reversibly switch the PEDOT:PSS from dielectric to metallic. Using this concept, we demonstrate a compact, standalone, and CMOS compatible metadevice.

3D stimulated Raman spectral imaging of water dynamics associated with pectin-glycocalyceal entanglement.

Pectin is a heteropolysaccharide responsible for the structural integrity of the cell walls of terrestrial plants. When applied to the surface of mammalian visceral organs, pectin films form a strong physical bond with the surface glycocalyx. A potential mechanism of pectin adhesion to the glycocalyx is the water-dependent entanglement of pectin polysaccharide chains with the glycocalyx.

Electro-active metaobjective from metalenses-on-demand.

Switchable metasurfaces can actively control the functionality of integrated metadevices with high efficiency and on ultra-small length scales. Such metadevices include active lenses, dynamic diffractive optical elements, or switchable holograms. Especially, for applications in emerging technologies such as AR (augmented reality) and VR (virtual reality) devices, sophisticated metaoptics with unique functionalities are crucially important.

Femtosecond tunable light source with variable repetition rate between 640 kHz and 41 MHz with a 130 dB temporal pulse contrast ratio.

We demonstrate a femtosecond tunable light source with a variable pulse repetition rate based on a synchronously pumped fiber-feedback optical parametric oscillator (FFOPO) that incorporates an extended-cavity design. The repetition rate can be reduced by an acousto-optical modulator in the FFOPO pump beam. The extended FFOPO cavity supports signal oscillation down to the 64 subharmonic.

Burst-mode femtosecond fiber-feedback optical parametric oscillator.

In multiphoton 3D direct laser writing and stimulated Raman scattering applications, rapid and arbitrary pulse modulation with an extremely high contrast ratio would be very beneficial. Here, we demonstrate a femtosecond fiber-feedback optical parametric oscillator (FFOPO) system in combination with pulse picking in the pump beam. This allows tunable signal output at variable burst rates from DC all the way up to 5 MHz.

Electrically switchable metallic polymer nanoantennas.

Electrical switching of a metal-to-insulator transition would provide a building block for integrated electro-optically active plasmonics. In this work, we realize plasmonic nanoantennas from metallic polymers, which show well-pronounced localized plasmon resonances in their metallic state. As a result of the electrochemically driven optical metal-to-insulator transition of the polymer, the plasmonic resonances can be electrically switched fully off and back on at video-rate frequencies of up to 30 hertz by applying alternating voltages of only ±1 volt.

Synchronization-free all-solid-state laser system for stimulated Raman scattering microscopy.

We introduce an extremely simple and highly stable system for stimulated Raman scattering (SRS) microscopy. An 8-W, 450-fs Yb:KGW bulk oscillator with 41 MHz repetition rate pumps an optical parametric amplifier, which is seeded by a cw tunable external cavity diode laser. The output radiation is frequency doubled in a long PPLN crystal and generates 1.

Low drift cw-seeded high-repetition-rate optical parametric amplifier for fingerprint coherent Raman spectroscopy.

We introduce a broadly tunable robust source for fingerprint (170 - 1620 cm) Raman spectroscopy. A cw thulium-doped fiber laser seeds an optical parametric amplifier, which is pumped by a 7-W, 450-fs Yb:KGW bulk mode-locked oscillator with 41 MHz repetition rate. The output radiation is frequency doubled in a MgO:PPLN crystal and generates 0.