EUROPHOTON 2022

In this lecture, I will give an introduction into the topic of integrated photonic quantum systems, revising the on-chip realization of quantum states and their integrated/fiber-based processing with dedicated application scenarios.

The revolution in optical frequency comb generation started in 1999. This lecture will give an introduction of modelocked frequency comb generation, noise characterization and single-cavity dual-comb generation. I will refer to my new textbook “Ultrafast Lasers” (Springer Verlag 2022) which provides a more comprehensive introduction to fundamental principles and applications.

A large fraction of STEM-graduates does not pursue an academic career, but takes up a position in the industrial sector. This talk will shed light on the points that should be considered for a successful transition into the industrial realm.

Solid-state lasers are attractive sources of coherent radiation. In the past 60 years different laser geometries have been developed to overcome challenges in power scaling conserving the beam quality. This contribution presents the physical and technical basics of solid-state lasers and their power scalability.

We introduce the fundamental principles and review experimental implementations of temporal compression setups based on self-phase modulation. For each platform, such as fibers, capillaries, multiplate setups or multipass cells, we try to outline the design principles, the advantages, and the limitations in terms of pulse parameters.

After a brief historical perspective on the field of harmonic generation in gases, an introduction to the physics of the process will be given covering the single atom response and phase matching. The presentation will also discuss laser-assisted photoionization, used both for measurement and application of attosecond pulses.

Since Burneika’s first demonstration in 1972 of a synchronously pumped optical parametric oscillator (OPO), this technology has evolved and matured considerably. I will introduce concepts underpinning femtosecond OPOs, typical architectures, modelling approaches, principles of phase control and several key applications in areas of sensing and metrology.

We present the first experimental demonstration of direct light waveform control over collective relativistic electron motion during ultra-high intensity laser-matter interactions driven by near-single-cycle laser transients.

We report on two efficient XUV out-coupling methods highly suitable for intra-oscillator HHG. We demonstrate for the first time XUV cavity out-coupling using a coated grazing-incidence plate. We further show a preliminary operation with a pierced mirror reaching 1-GW of intracavity peak power highly suitable for HHG.

We report on the recent progress in solid-state lasers emitting ultrashort pulses around 2 µm based on broadband-emitting gain media: disordered crystals (garnets and aluminates) and “mixed” transparent ceramics (sesquioxides) doped with Tm3+ and Tm3+/Ho3+ ions. The role of multiphonon-assisted long-wave emissions in reaching sub-50 fs pulse durations is discussed.

We demonstrate a silicon nitride waveguide-based optical parametric oscillator exploiting four-wave mixing (FWM), synchronously fiber-laser pumped at 40 MHz repetition rate and showing an idler tunability across 95 nm near 1150 nm with a output pulse energy up to 63 pJ and a bandwidth of about 10 nm.

A waveguide-based OPO (WOPO) exploiting four-wave mixing in the emerging tantalum pentoxide platform is investigated. The WOPO, pumped with 500 fs long pulses centered at 1.55 $\mu$m wavelength with 2 nJ energy, provided up to 6 pJ pulse energy at 1.46 $\mu$m wavelength. It shows potential to be fully integrated on a chip.

We demonstrate simple and efficient broadband mid-infrared generation via optical parametric amplification driven inside a dispersion-engineered nanophotonic waveguide. Using a commercially-available pulsed pump laser centered at 1045 nm and a CW telecom seed, we achieve up to 60% of conversion efficiency and 140 nm of mid-infrared spectral bandwidth.

We report on our recent developments on rare-earth-based gain and lasing directly on silicon photonic chips. We demonstrate laser emission around 1.8-1.9 $\mu$m in thulium-doped tellurium oxide coated silicon hybrid microdisks, with on-chip output powers of > 1 mW and sub-milliwatt threshold pump powers at 1.6 $\mu$m.

Latest developments in nanophotonics associated with advantageous use of surface plasmon polaritons, hybrid excitations involving free electron oscillationsin metals and electromagnetic fields in dielectrics, are overviewed. Special attention is given to the progress in ultra-compact photonic circuitry, including modulators and detectors, and plasmonic metasurfaces dynamically controlling propagation of light.

We report a compact ultrafast solid-state laser source with a tunable pulse repetition rate from 0.5 - 1.3GHz. The novel cavity design allows to vary the repetition rate by moving two mirrors, without realignment. The Yb:KYW crystal-based SESAM-modelocked laser emits 230fs pulses with 200mW average power around 1040nm.

An all-fiberized dissipative-soliton mode-locked thulium fiber laser operating at 1875 nm was demonstrated. Using an in-house fabricated thulium fiber as thegain medium, the laser provided ultrashort pulses with 12-ps pulse duration and 10.3-nJ pulse energy. The pulses could be compressed to 547 fs using a grating pair compressor.

Nanocrystalline LiYF4:Pr promises exciting design opportunities for composite photonic devices in the visible. Here, we present the spectroscopic properties of monodisperse colloidal LiYF4:Pr nanocrystals. We observed an unexpected yet intense emission with lifetimes comparable to bulk crystals. These results pave the way for applications in quantum optics and biomedicine.

We studied cryogenic laser operation of Tm: YLF using a modular setup pumped by a VBG stabilized diode. At 80K, a maximum output power of 6.50 W corresponding to a slope efficiency of 38% was achieved with excellent beam quality.

We compare a Ho$3+:YAG laser cavity that includes two crossed Porro prisms instead of cavity end mirrors with a conventional mirror resonator. While the Porro resonator shows a slightly lower slope efficiency of 67.4 % than the mirror resonator, it is superior in terms of beam quality and stability.

We studied the continuous-wave laser performance of Yb:Lu2O3 at cryogenic temperatures using a modular laser setup. A maximum output power of 15.23 W was achieved for 120 K corresponding to a slope efficiency of 63%.

High optical quality 3.5-at.% Nd:LGSB crystal with non-congruent melting wasgrown by the Czochralski method. The structural, the linear and nonlinear properties, as well as the laser emission characteristics in the near-infrared spectrum by direct emission and in the green visible range through self-frequency doubling were investigated.

The first subnanosecond pulse duration optical parametric generator (OPG) based on fan-out grating design MgO:PPLN crystal is demonstrated. Fan-out grating OPG enables quickly, widely, and continuously tunable, compact, and effective subnanosecond coherent light source covering near-infrared spectral region (1400 - 4400 nm) with OPG conversion efficiency up to 47 %.

Incongruent melting Pr-doped La0.678Gd0.572Sc2.75(BO3)4 (Pr:LGSB) crystals were grown by the Czochralski method, for the first time to our knowledge. The spectroscopic and nonlinear optical properties of the 2.5 at.% Pr:LGSB crystal shown that it can be a promising self-frequency doubling crystal in the UV range at ~301.5 nm.

We present the manufacturing of side-fused signal-pump combiners with 25/400-µm signal feed-through fibers and >90% pump coupling efficiency. On the basis of CO2-laser restructuring of the used optical fibers, the necessity of splice connection is avoided, which improves the pump coupling efficiency and thus overall laser efficiency.

The slow response time of semiconductor saturable absorbers significantly increases the noise of generated pulse train. We report a substantial improvement of amplitude and phase noise properties in a SESAM mode-locked Er:fiber oscillator via intracavity spectral filtering. We observed a 2.6-fold reduction of integrated timing jitter to 1.71 ps.

We demonstrate a spatially-resolved approach to simulating thin-disk lasers. The model supports exact phase profiles for cavity elements, allowing the impact of experimentally measured non-radially-symmetric aberrations of the thin-disk to be studied. Predicted stability zones, distorted fundamental mode and higher-order mode excitation are in good qualitative agreement with high-power experiments.

Many applications require tunable-wavelength laser radiation, which is provided by optical parametric amplifiers (OPAs) and optical parametric generators (OPGs). We report, to the best of our knowledge, the first dual-crystal LBO subnanosecond OPA system generating widely-tunable radiation in the visible spectrum range from roughly 460 nm to 680 nm.

We present a Mamyshev oscillator setup in which a fiber amplifier is split into two equal parts and placed before the filters. At low repetition rates this setup allows to produce pulses which are less affected by nonlinear distortions.

Methane-air mixtures were ignited in a constant-volume combustion chamber by a diode-pumped, passively Q-switched Nd:YAG/Cr4+:YAG laser with four beams, yielding single pulses or operating in burst mode with two pulses. A discussion of peak pressure, combustion time and of the ignition limits is made for each type of ignition.

Solution-processed nanoplatelets exhibit exciting optical properties which can be exploited for lasing in novel spectral ranges. Here, we incorporate these nanoplatelets in capillary fused silica fibers and investigate their optical properties. These results are the basis for a novel class of solution-processed nano-material fiber lasers.

A passively Q-switch Er:YAP laser, emitting 21.8 ns long (FWHM) pulses with energy 0.54 µJ and repetition rate 41.6 kHz at 2.9 µm is presented. In a free-running regime, the Er:YAP laser reached maximal output mean power of 200 mW with 25.5 % slope efficiency.

Cooling of Pr:YAP crystals close to liquid helium temperature allowed to significantly improve the Pr:YAP laser performances with respect to room temperature, which yielded in Watt-level laser outputs at all studied wavelengths (747 nm, 622 nm, 547 nm, and 493 nm) under 4W InGaN laser diode pumping.

Frequency-doubled 220 fs laser pulses at 515 nm are spectrally broadened and compressed in a multipass cell down to 38 fs using solid and gas as nonlinear media. The efficiency of this process is 90 %. This is the first demonstration of multipass spectral broadening and compression in green.

We present a Tm3+-doped actively Q-switched fiber laser providing pulse energies of 960 µJ with 20.5 kW peak power at a wavelength of 2050 nm and pulse energies of 720 µJ with 6.5 kW peak power at a wavelength of 2090 nm. The laser is ideally suited as a pump source for nonlinear frequency conversion.

We present a picosecond source use to characterise a PCF dispersive properties through Four Wave Mixing. We demonstate that the use of a stochastic pulse train obtain through an Amplified Spontaneous Emission seeder reduce the FWM threshold by several orders of magnitude as compared to a CW seeder.

Here, we report on a sub-30 fs Yb:YAP laser delivering soliton pulses as short as 24 fs at 1085 nm with an average output power of 186 mW and a pulse repetition rate of 87.8 MHz via soft-aperture Kerr-lens mode-locking (KLM).

We present two parallel all-PM-fiber Ytterbium amplifiers seeded by a single oscillator at 78.9 MHz repetition rate. An output power of 5 W is available at 7.5 or 50 ps pulse duration. The femtosecond part delivers 13.5 W output power at a compressed pulse duration below 60 fs.

We developed a high-speed S²-method-based device to monitor the modal content of a beam out of an optical fiber. The device is used to evaluate and optimize a CO2-laser-based fiber end cap manufacturing process.

Measurement of absorption and emission cross sections of the $~$790 nm and $~$1600-1900 nm thulium peaks relevant for high-power operation of cladding-pumped fiber lasers at 2-micrometers is reported. Up to 40% change of the respective peak values were observed while heating the fiber from -15 to 300°C.

The degenerate DROPO was stabilized by using a locking scheme which utilizes monitoring of a “parasitic” sum-frequency generation (SFG) of the signal and pump and together with the phase locked pump laser which can provide high intensities tailored two-color fields and benefit for THz generation.

The power dependence of a Nd:YVO4 laser amplifier beam wavefront was analyzed by Zernike polynomial decomposition. This analysis was performed experimentally and by simulations based on split-step Fourier propagation showing a good agreement. The simulations yield a base for the design of an aberration compensation system.

We demonstrate sub-7-fs pulses derived from a carrier-envelope-phase-stabilized Cr:ZnS mode-locked laser. These pulses drive cascaded intra-pulse difference-frequency mixing in a ZGP crystal, leading to multi-octave (0.9 - 12 $\mu$m) coherent pulse synthesis. The resultant single-cycle mid-infrared wave-forms can be shaped by varying the CEP of the driving pulses.

A mode-locked source operating at 1064 nm producing 13 ps pulses with a repetition rate of 276 MHz and output power of 102 mW is demonstrated. It is achieved by two Nd:YVO4 cavities operating at different wavelengths that interact in shared section through a PPRKTP crystal phase-matching for sum-frequency mixing.

We present a single-mode pumped SESAM-modelocked single-cavity GHz dual-comb laser with widely tunable repetition rate difference. This low noise free-running solid-state laser is applied for THz-TDS using photoconductive antennas. We show nanosecond scans with 36 kHz update rate, yielding a 40-dB dynamic range for an integration time of 2 seconds.

We generate mid-infrared ranging from 12 to 35 THz (9 - 25 $\mu$m) via IDFG. Theradiation is directly generated in GaSe by the pulses of an in-house developed KLM Cr:ZnS oscillator. The spectral coverage towards 30 $\mu$m is in reach, which is of interest for ultrafast spectroscopy of solids.

We investigate third harmonic generation (THG) in thin dielectric HfO2 gradient layers experimentally and theoretically. This method allows for the first time to quantify the third and fifth order susceptibility in dielectric layer materials.

We present the post compression of a thulium-doped fiber laser output in a gas-filled multi-pass cell, delivering 51W average power, 35fs pulse duration at 300kHz repetition rate centered at 1940nm wavelength. To the best of our knowledge, this is the highest average-power multi-pass cell post compression in the
short-wave-infrared reported.

We present a post compression of a thulium-doped fiber laser output in a hollow-core fiber, delivering 100W average power, 1mJ pulse energy and 17.6fs pulse duration at 100kHz repetition rate. It is, to the best of our knowledge, the highest average-power mJ-class few-cycle source in the SWIR reported.

We present a pulsed polarization-maintaining all-in-fiber MOPA setup based on Ho3+ and Tm3+ -doped silica fibers. By pumping a ZGP OPO an mid-IR output power of 8.1 W and a conversion efficiency of 44 % (slope 61 %) is obtained. M² factors of 2.2 (signal) and 2.0 (idler) are determined at maximum power.

We present our recent results in high-power laser emission from 2.1 to 2.2 µm, introducing the 79X nm pumped Tm3+:Ho3+ -codoped silica fiber laser as serious alternative when it comes to power scaling within this wavelength region. In particular, a record power of 145 W has been achieved at 2.2 µm.

We report on the generation of up to 12 nJ pulse energy with a compressed pulse duration of 156 fs by an ultrafast thulium-doped fiber Mamyshev oscillator. The oscillator incorporated double-clad fibers to provide a sufficient amplification with a high suppression of amplified spontaneous emission of 22 dB.

We present a high-power, highly efficient thulium-doped fiber amplifier which is cladding-pumped at 1692 nm. For the first time, a Tm-doped fiber suitable for ultrafast operation with considerable pulse energies provides slope efficiencies around 80% with 58 W output power. Using commercially available pump sources, this approach is highly scalable.

A simple method is presented for determining the quantum efficiency and back-ground core propagation loss in Thulium (Tm)-doped fibre lasers. Since the overall laser efficiency is typically limited by one of these two parameters, quantitatively determining their individual contributions is vital to informing the development of future Tm-doped fibres.

We present our latest results in power scaling in the 2 $\mu$m region. The all-fiber laser system is a simple MOPA configuration composed of a seed laser and a high power amplifier. More than 900 W of output power at 2036 nm are demonstrated with a diffraction limited beam quality.

Frequency-domain two-photon quantum interference between a thermal field and a heralded-state is studied theoretically and experimentally, revealing the dependency of visibility on the multiphoton components within the heralded-state.

We present an environmentally stable laser oscillator, mode-locked through nonlinear-polarisation evolution, that is entirely based on polarisation-maintaining fibres, except for the Yb-doped gain fibre. The laser is reliably operated at the fourth harmonic repetition rate, at 250 MHz, with output pulse energies of 1 nJ.

We report the compression of 1 ps duration, 112 muJ energy pulses from an YbYAG amplifier to 11 fs and the generation of an octave-spanning spectrum by two hybrid multi-pass multi-plate spectral broadening stages. Both, the compression factor and the output pulse duration set new records for bulk multi-pass cells.

We demonstrate nonlinear spectral broadening of 2.1-mJ, 670-fs pulses at 210 W of average power in a focus-free compact 61.5 cm distance, convex-concave MPC in ambient air. We show pulse broadening from 21 nm to 24.5 nm, and we demonstrate compressibility down to 134 fs with excellent spectral homogeneity.

We report on conical third harmonic generation that accompanies supercontinuum generation in fused silica using broadly tunable femtosecond pulses. Third harmonic radiation carries a broadband, octave-spanning spectrum, with propagation angles of individual spectral components precisely following the entire phase matching curve, as attested by the measurements of angle-resolved spectra.

We present a 108-fs Kerr-lens-modelocked, diode-pumped 1-GHz Tisapphire laser. Self-starting operation producing 103 mW was obtained for 1-Watt pumping with a single 520-nm laser diode. From 1 Hz1 MHz the relative intensity noise was 0.01 and the repetition rate was externally referenced with a phase error of 1.7 mrad.

Recent developments in two-micron thulium and thulium-holmium doped solid-state and fiber lasers allow for significant average-power and pulse-energy scaling, important for mid-IR OPO pumping, materials processing and communication. A focus is put on all-fiber designs and robust, if possible self-aligning, laser resonators, which allow for stable and ruggedized designs.

Highest peak powers pave new insights for fundamental research. The performance of laser beam lines is mainly determined by the quality of the optical components. This paper presents novel approaches to manufacture laser mirrors with optimized laser induced damage threshold applying ion beam sputtering up to substrate sizes of 550mm.

We present a platform for high-power dual comb sources from a single spatially-multiplexed oscillator cavity. We demonstrate femtosecond pulses and Watt-level average output powers with low-noise operation over short and long timescales. Our 80 MHz version is ideal for pump-probe measurements, while our 1 GHz version supports coherent dual-comb spectroscopy.

We designed and tested phase mirrors for intra and extra-cavity flat-top beam shaping of high energy Ytterbium systems. The concept can be applied as a new approach to perform spectrally homogeneous thin-plate post-compression of picosecond pulses from J-level Yb:YAG systems.

On the way to developing 100W and 10 mJ class laser we demonstrate a hybrid laser system based on fiber laser seed source and chirped pulse amplification in free-space Yb:YAG cascade. The system is capable of delivering 13 mJ energy 1 ps duration pulses at 20 Hz repetition rate.

A compact Kerr-lens mode-locked thin-disk oscillator delivering 110 MW output peak power, the highest among all oscillators, is reported. A pulse train with a repetition rate of 14 MHz carries 115 fs long, 14.5 uJ pulses resulting in 203 W of average power.

We present first results of our research towards ultra-short pulse generation in the sub-100 ps range based on cascaded gain-switched diode-pumped vertical-cavity surface-emitting semiconductor lasers. In particular, we focus on the surface emitters themselves and on the dependence of the output parameters on the pump wavelength and the pump fluence.

We report the first mode-locked operation of a bulk laser based on Ho:CALGO. The laser generates up to 8.7 W of average power and 369-fs pulses duration at 2118 nm, representing the highest avergae power achieved from a mode-locked bulk lasers in the 2-3 µm wavelength region.

The conversion of longitudinal mode-locked beam to a transversal mode-locked beam is equivalent to the conversion of temporal pulses to a spatiotemporal oscillation. This is achieved by matching the frequency spacing of incident phase-locked longitudinal modes and the transverse mode spacing of an optical cavity.

We report the developement of a sub-ps Yb:YAG thin disk regenerative amplifier delivering 50 mJ at 1 kHz with an optical-optical efficiency of 18%. We discuss how to address thermal issues in the BBO Pockel’s crystal to further increase the output energy up to 100 mJ.

With the advances in fundamental science such as gravitational wave detection, cold atom physics and quantum computing the need for single frequency high-power fiber lasers has been increasing. We will present several very low noise high power laser sources at different wavelengths and the potential applications.

A fiber-based light source with multi-color output and a fast wavelength tuning mechanism is presented. The combination of a frequency modulation scheme for pulse-to-pulse wavelength-switching and low-noise operation with a relative intensity noise of -153.7 dBc/Hz makes this light source well suited for nonlinear microscopy applications.

In this work, more than 5 W of output power is obtained between 616.5 nm and 630.8 nm using sum frequency generation of 1 $\mu$m and 1.5 $\mu$m laser sources in a PPLN crystal with a relative intensity noise lower than -157 dB/Hz at 5 MHz.

Thanks to the use of a new-gen UV hollow core fiber, we report here 2 orders of magnitude of gain on the current state of the art, with on a record single-mode delivery of 23.3W (155$\mu$J) with 89.1% transmission from a 343 nm, 10 ns, 150 kHz laser source.

We show an approach to effectively generate tunable vacuum and extreme ultra-violet light with both short (femtosecond) and long (nanosecond) pulses using four wave mixing of the fundamental and its second harmonic in hollow gas-filled capillaries. The particularly important application includes nuclear thorium clock with signal at 160 nm.

The flexibility of new laser sources and process-monitoring enables new possibilities in laser-based production technology, especially the combination of different laser processes with many adjustable parameters. The fusion of domain knowledge and probabilistic models in the form of hybrid models allows an efficient optimization of these processes with machine learning.

The team at Southampton are applying the deep learning technology that supports self-driving cars to the real-time control and optimisation of a wide range of light-matter interactions, including femtosecond laser machining. This presentation will provide an overview of recent activity at Southampton at this exciting interface.

We report a new technique for phase control of tiled array of lasers based on a specific quasi-reinforcement learning approach. Principle and experiments on a seven-fiber amplifier laser array will be presented. We will show the dynamic locking of the laser phase relationship, and on-demand wavefront shaping.

Precise control of lasers is of critical importance for particle accelerators and free electron lasers. We discuss our approach to leverage the power of data science and artificial intelligence to improve the performance (pulse parameters, fast set-point tuning, stability) of our photocathode and pump-probe lasers.

We will present an overview on our research on novel multi-core fibers towards lasers and amplifiers for telecommunication, sensing as well as for scaling of coherently combined high power and high energy laser systems. We will link the required properties for the fibers to the manufacturing and characterization process chain.

We demonstrated a yellow laser source emitting at 577nm externally pumped by 1029 nm Q-switched laser. With the proper combination of Raman and frequency doubling medium, a maximum output of 9mW is achieved.

Nanocrystalline LiYF4:Pr promises exciting design opportunities for composite photonic devices. Here, we present an in-depth spectroscopic investigation on monodispersed colloidal LiYF4:Pr nanocrystals of 10nm size. We observed an unexpected yet intense emission with comparably long lifetimes. These results
pave the way for applications in quantum optics or biomedicine.

A compact laser head emitting a linearly polarized radiation at wavelength 1342 nm was designed and constructed. This laser was based on a separate Nd:YAP gain part and V:YAG saturable absorber. Q-switched pulses 12 ns long with energy up to 0.1 mJ were generated with repetition rate 500 Hz.

The influence of the pump wavelength on the heat load and efficiency of Nd:YVO4 crystals is investigated with a specially designed crystal mount. The measurements indicate that the change in heat load in the crystal can be solely ascribed to the difference of quantum defects and no further non-radiative effects.

We report on the cryogenic laser performance of a new “mixed” Yb:LuYAG garnet crystal in the continuous-wave and pulsed regimes. We determined an optimum temperature of 140 K for efficient laser operation. A maximum output of 10.65 W with a slope efficiency of 56% was achieved.

A theoretical model is built for scattering loss from the planar waveguide with multilayer substrate and experimentally validated with good agreement. Our work shows that substrate layer interference can significantly suppress scattering loss.

We introduce a novel nonlinear multi-pass cell configuration comprising a concave-convex geometry. In a proof-of-principle experiment, 260 fs, 15 $\mu$J pulses are broadened and compressed to approximately 50 fs with 90 % efficiency with excellent spatio-spectral homogeneity. A compact design for 0.5 J and 1 ps laser is also presented.

We demonstrate enhanced spectral broadening in Nitrogen, Nitrous Oxide filled multipass cells. Contrast to atomic gases, molecular gases have stronger effective nonlinearity leading to red-shifted broadband spectrum. For comparison, the spectral span of Argon, Nitrogen and Nitrous Oxide recorded is 45, 106 and 265 nm at 15 $\mu$J input energy.

We have frequency doubled an entirely passive dual-comb thin-disk oscillator to perform spectroscopy of iodine at 515nm. Simultaneous measurement of iodine and acetylene (1034nm) helps to evaluate the jitter characteristics at both wavelengths. It indicates that the approach can be extended to higher harmonics in the deep UV spectral range.

A continuous-wave all-fibered single-oscillator thulium-doped fiber laser is developed. Taking advantage of a high absorption at 793 nm (8.42 dB/m), the source exhibits 260 W of maximum output power at 1.94 µm and a slope efficiency of 59 %. Rate equations are applied to numerically study the cavity.

Temperature measurements inside electrolysis cells pose a challenge for conventional sensors. Since up-conversion-nanocrystals exhibit a temperature dependent emission, we attached such nanocrystals to a fiber facet and applied it as nanothermometer in an electrolysis cell. This approach will yield new insights into the performance of these cells.

The phase transition in fully-connected, multimode equal-coupling photonic networks is studied via numerical simulations and by using methods from statistical mechanics. Finite-size scaling is used to estimate critical points and exponents, yielding a phase diagram in a relevant parameter plane, and confirming mean-field behavior as for the planar XY model.

An important aspect of optical satellite communication technology is the power consumption of the laser systems. We present a high-efficiency all-fiber amplifier for a WDM communication system. 10 channels combined in a polarization-
maintaining fiber can be efficiently amplified up to a total power level of 100W in the 1 $\mu$m wavelength-range.

We present a polarization-maintaining all-normal dispersion fiber with flat dispersion profile over the range of 1200-2100 nm. The fiber possesses the solid core of an elliptical shape that enables high birefringence (with polarization extinction ratio of > 22 dB) and also allows for low-loss fusion splicing to conventional Panda fiber.

We present a Mamyshev regenerator setup with electrically controlled acousto-optic switch. This setup allows the injection of
a long, poor quality pulse through one of the switch inputs. After a few tens of regeneration cycles occur the input pulse is shaped into high quality ultrashort light pulse.

The melanoma incidence is rising for all skin types. While being responsible for 75 % of deaths from skin cancer, melanoma is highly curable at early stages. We demonstrate a multimodal device for the early detection of melanoma that comprises non-contact dermoscopy, 3D measurement technology and Mueller matrix polarimetry.

We demonstrate high quality, short period QPM structures in KTP and RKTP, produced through coercive field engineering using a new ion exchange based on Ba2+ ion indiffusion. We show advantages of using this method over the previously established coercive field engineering method using Rb+ ions.

Tapered multicore fibers (MCFs) are numerically analyzed in the context of high power MCF lasers using Beam Propagation Method. These simulations facilitate taper design to avoid mode mixing and intercore crosstalk. MCF tapers with active fibers enable scalable fundamental-mode operation in large multimode waveguide cores.

We investigated inversion dependent fluorescence quenching of Tb3+ via a Z-scan technique. Analysis with an analytical model yielded parameters describing the strength of energy transfer upconversion and energy migration between Tb3+ ions. This allows optimizing the quantum efficiency of the emitting ^5𝐷_4-level in Tb3+-based lasers by optimized composition

Previously we have demonstrated an all-fiber-integrated, alignment-free NALM PM Yb: fiber oscillator with sub-fs timing jitter. Here we report on the next steps in engineering this all-fiber compact oscillator. We developed a method to repeatably assemble lasers at a repetition rate required by DESY’s FEL facilities.

An easily fabricated planar polymer optical waveguide sensor with metal-organic framework coating for carbon dioxide sensing is demonstrated. The proposed device exhibits good sensitivity, excellent reversibility and rapid response, which are significant towards the further development of gas sensing products for real-world applications such as environmental monitoring and gas detection.

A scalable fabrication approach for aperiodic and twisted multicore fibers is presented, which will enable next-generation lens-less endoscopy for 3D imaging deep inside tissue. Particularly, an aperiodic fiber with 1281 cores was developed, which is single-mode throughout the visible spectrum. The design process was supported by in-depth numerical design studies.

We study spectral broadening of sub-picosecond telecom wavelength pulses in periodically-poled thin-film lithium niobate waveguides that results from cascaded nonlinear interaction. We experimentally investigate the effect of phase mismatching on spectral broadening and compare the results with simulations based on a split-step Fourier method.

We report that the modulation of the heat-load in fibre laser systems significantly mitigates the transverse mode instability when carefully choosing the modulation parameters. It is possible to suppress the higher-order modes by inducing a permanent energy transfer from the higher-order modes to the fundamental
mode.

We demonstrate a design for a monolithic, multi-gigahertz soft-aperture Kerr-lens mode-locked Ti:Sa laser. First experiments did not show mode-locking but cw laser operation with power fluctuations of less than 0.04% rms. We discuss possible obstacles to mode-locking in monolithic lasers like spatial-hole burning or a standing-wave of the pump beam.

Here, the beat signal detection towards carrier-envelope phase stabilization of a 110 MW Kerr-lens mode-locked thin-disk oscillator delivering 140 fs-long pulses is presented. The implementation of an f-2f interferometer is demonstrated using an octave-spanning spectrum from a cascade with a multi-pass
cell and photonic-crystal fiber.

Ion traps are a promising platform for the realization of high-fidelity quantum information processors. To scale the systems to a large number of qubits, integrated photonic components are crucial for guiding and manipulating laser light on a chip-scale level. We will present our first design of surface-electrode ion-trap chips with integrated optics.

We investigate the suitability of vertical-cavity surface-emitting lasers (VCSEL) as highly sensitive distance sensors for topography measurement. The concept relies on the light reflected from a moving sample into the VSCEL resonator inducing a measurable change of operating current and emission wavelength to detect motion of a few nm only.

We demonstrate an agile high power Yb-fiber frequency comb laser system with long-term stable remote-controlled operation via digital feedbacks and user-friendly interfaces. A programmable, phase and amplitude filter allows optimization of the laser output pulse for driving a subsequent nonlinear process, such as nonlinear frequency shifting and XUV-comb generation.

We present here a new FROG retrieval algorithm which performs well under heavy noise conditions through a structured random search of the available input space. It can retrieve pulses from any FROG geometry, partial datasets, as well as blind FROG retrieval.

We report the very first demonstration of wavelength-tunable operation in the UV from a diode-pumped Alexandrite laser. 375-385nm continuous tuning is obtained using a high-power diode-pumped tunable Alexandrite laser and a Type I critically phase-matched BBO crystal. The use of PPLN waveguides for UV generation is also discussed.

We present a cavity-dumped Q-switched Alexandrite laser for LIDAR applications under CW double-pass diode pumping. A record pulse energy of >500 $\mu$J was achieved at 755 nm, 2.8 ns and 5 kHz. Furthermore, efficient laser operation at 10 – 20 kHz repetition rates is demonstrated for the first time.

We report a 7.5W Alexandrite (Cr-doped Chrysoberyl) ring laser operating at 757nm. Pumping is provided by a 200 𝜇m fibre-coupled red laser diode (640nm) with optical and slope efficiencies of 28% and 35%, respectively. This result shows potential for high-power single-longitudinal-mode operation across 720-800nm and 360-400nm by second-harmonic-generation.

We developed a cost-effective broadband SWIR-MIR mJ-level OPCPA pumped and seeded with 1.2 ps Yb:YAG laser. Pulses amplified to 2 mJ in the wavelength range 1900 – 2300 nm with a pump-to-signal record conversion efficiency of ~30% and compressed up to 50 fs in 3-stage OPCPA based on BiBO.

We present spectroscopic investigations and laser operation of a Czochralski-grown Tm3+:YScO3 mixed sesquioxide crystal. We observed broadband absorption and emission spectra, desirable for ultrafast 2 µm lasers. Continuous wave laser experiments were performed using a 780 nm laser diode, and a maximum slope efficiency of 40% was achieved.

Single-frequency operation of a diode-pumped praseodymium-doped YLF laser has been demonstrated using an elegant cavity design. Over 100 mW of single-frequency operation has been achieved from 687 nm to 705 nm with one cavity arrangement. This laser system targets use in neutral strontium optical clocks.

We report the fabrication and first demonstration of crystalline grating waveguide reflectors comprising a Sc2O3 waveguide grown on a sub-wavelength-patterned sapphire substrate. Operating in the 1- and 2-micron regime, distinct TE- and TM-polarisation resonances were obtained, with reflectance approaching 50% at ~7∘ incident angle from a single waveguide and GWS.

We introduce a novel wavelength shifting concept for ultrafast lasers. We demonstrate this concept by efficiently tuning the wavelength of a 80 W, 200 fs Ytterbium-fiber laser from 1000 nm to 1060 nm. Our method supports high peak and average power operation and excellent temporal pulse quality.

The generation of two-frequency compound states is challenging, since access to two incommensurable, group-velocity matched frequencies is required. For a possible experimental realization, we propose a self-generation scheme enabled by a spectral tunneling process. With this approach, we demonstrate the generation of a compound state from a single input pulse.

We highlight the potential of liquid-core fibers as nonlinear devices for adaptive fiber applications featuring low-coupling losses, full fiber-system connectivity, and picojoule pump energy requirements. We experimentally showcase this potential by controlling the soliton fission point, the soliton self-frequency shift, and the tuneable emission of cascaded dispersive waves.

We report on the recent developments regarding unidirectional lasing observed in a reciprocal fiber ring laser. In this talk we present how retardation of Stokes assisted broadening results in a considerable reduction of required threshold power accompanied by stabilization enhancement in terms of output power and directionality in unidirectional regime.

By using the dispersion scan technique based on tunable chirped fiber Bragg gratings, the 650 ps pulses can be compressed to ~650 fs with optimized pedestals. This method allows reliable pulse-characterization and optimization without movable parts and therefore improve the stability of a laser system used in 24/7 operation.

High repetition rates in fiber-based laser systems can be achieved through multiplication in asymmetric Mach-Zehnder interferometers. We utilize a spectral band-pass filter to reduce the asymmetric dispersion that is accumulated in the different paths to increase the compressibility of the pulses.

We present an agile novel laser source delivering clean and stabilized ultrashort pulses < 500 fs at different pulse repetition rates from 10 MHz to 100 MHz and 100 mW of average power. This laser source can be easily synchronized.

We demonstrate a spatially-multiplexed dual-comb 250-MHz OPO from a single linear cavity. The adjustable repetition-rate difference is 4.1 kHz. Each idler comb has >200 mW average power at 3.5 𝜇m with 30 nm bandwidth. The OPO is wavelength-tunable from 1.36 $\mu$m to 1.7 $\mu$m and 2.9 $\mu$m to 4.17 $\mu$m.

We present an inline mid-infrared source based on intrapulse-difference-frequency-generation and subsequent optical parametric amplification, with pump recycling. Driven by an Yb-doped-fiber amplifier at 1030 nm, at a repetition rate of 250 kHz, the source delivers 1 $\mu$J 73 fs pulses at 8 $\mu$m, corresponding to an unprecedented efficiency of 2%.

We present the concept and first results of a novel OPCPA system with highly-efficient, broadly-tunable UV conversion for XUV/VUV FEL seeding. The start-to-end simulation allows to predict the system performance regarding tunability, beam-quality, stability and pointing, depending on the measured input parameters and fluctuations of the high-power CPA pump laser.

The visible spectral range is difficult to cover by non-parametric laser gain media. Therefore, optical parametric oscillators offer a versatile solutions to this problem but have rather low tuning speeds. We demonstrate a quickly tunable, high power, femtosecond, noncollinear optical parametric oscillator which covers nearly the entire visible spectral range.

We present a LWIR OPCPA containing a fs Cr:ZnS laser as front-end. Sub-200 fs idler pulses at 11.4 µm with 50 µJ energy are generated in the 1 kHz pulse train.

The development of optical frequency combs, and notably self-referencing, has revolutionized precision measurements over the past decade, and enabled counting of the cycles of light. Frequency combs, have enabled dramatic advances in timekeeping, metrology and spectroscopy.

We report on a mid-infrared thulium laser operating on the 3H4 → 3H5 transition with a dual-wavelength pumping at 0.78 and 1.05 µm (direct and upconversion pumping schemes). The reciprocal interplay between the two pump is studied to evaluate the benefits in terms of the pump absorption and laser efficiency.

In the present work, we explored further reduction of the pulse duration in ML Tm,Ho:CALGO laser via soft-aperture Kerr-lens mode-locking (KLM).Pulses as short as 37 fs were generated from KLM Tm,Ho:CALGO laser at 2061.3 nm with an average output power of 55 mW and a repetition rate of 76 MHz.

We report our recent progress in power-scaling of short-wave infrared laser systems by demonstrating high-power SESAM-modelocked thin-disk Ho:YAG oscillator, delivering record average power of 50 W and more than 2 µJ of pulse energy at the central wavelength of 2092 nm.

We report on a SESAM mode-locked Tm:(Lu,Sc)2O3 ceramic laser in-band pumped by a Raman fiber laser at 1627 nm.An average output power up to 1.02 W at 2060 nm is achieved for transform-limited 280-fs pulses at a repetition rate of 86.5 MHz, giving an optical efficiency of 36.4%.

We have demonstrated an incoherent source centred at 2100nm with a bandwidth of 300nm. It is three times brighter spectrally than a blackbody and 10 times brighter than SWIR LEDs. This source consists of a cascade of luminescent concentrators with a Ce:YAG in first and a CTH:YAG in second.

In this work we present a highly accurate model for simulating laser resonators based on a beam propagation method algorithm including thermal effects in the laser. An experimental Ho3+:YAG resonator setup is used to validate the model, which shows excellent agreement in output power, resulting M2 and output field distribution.

We present an electro-optic comb seeded ultrafast nonlinear fiber amplifier at 1.03 $\mu$m. By tuning and dividing the driving radiofrequency of the EO comb, the system can deliver up to 200 W picosecond pulses compressible down to hundreds of femtoseconds at flexible GHz repetition rate.

We present a photocathode laser generating a train of 1030 nm, picosecond pulses with a repetition rate of 3 GHz, which is converted to 257 nm by two stages of second harmonic generation. The system is able to generate bursts of microsecond duration for the application of ultrafast electron diffraction.

We present a 17.5 GHz repetition rate, femtosecond fiber laser operating in the burst mode, achieved by nonlinearly shaping and amplifying a phase-only modulated electro-optic comb at 1.03 $\mu$m. The system delivers 1.2 W output pulses compressible down to <100 fs level.

A new versatile patent-pending method to generate ultra-high (>2 GHz) repetition rate bursts of ultrashort laser pulses containing any number of pulses within a burst with identical pulse separation and adjustable amplitude is introduced in industrial-grade 30 W-level average power ultrashort (sub-1 ps) pulse laser system.

Despite the importance of multi-pulsing modelocking as a nonlinear phenomenon and a potential source of high repetition-rate ultrashort pulses, it remains poorly controlled. Guided by the slaving principle in a hierarchy of timescales, we achieved excellent control of a multi-pulsing oscillator, allowing reliable and stable harmonic modelocking with superior characteristics.

An OPO pumped by femtosecond pulses delivered by a large-mode-area, ytterbium-doped, rod-type fiber laser mode locked at harmonic repetition rates. The repetition rate is changed by adjusting the pulse polarization inside the laser cavity. The OPO delivers femtosecond signal pulses that are tunable from 1450nm to 1700nm.