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As laser diodes replace LEDs in the remote phosphor configuration, a new class of lighting solutions is emerging. Laser-excited remote phosphor (LERP) systems, have advanced characteristics compared to their LED-based counterparts. The focus of this study is on Ce:YAG single-crystals that exhibit outstanding thermal stability and are therefore ideal for LERP applications. Although the quantum efficiency of these materials is stable for most operating temperatures of lighting systems, even for temperatures below the thermal quenching threshold the absorption and emission spectra of the phosphor are temperature-dependent. Furthermore, the ability to calculate the temperature profile of the phosphor layer is a prerequisite for the development of an effective thermal management system. For these reasons, a multi-physics simulation framework has been developed that couples the optical and thermal effects. This is achieved here by using the ray tracing software OpticStudio in conjunction with F.E.M. heat transfer calculations performed in ANSYS. In addition to the temperature-dependent quantum efficiency considered in the current state-of-the-art simulation schemes, temperature-dependent models for the mean free path for absorption and emission spectrum have been established. For modeling purposes the single-crystal Ce:YAG phosphor can be considered a bulk diffuser; the incident light is either down-converted and homogeneously scattered or refracted. A built-in bulk scattering model has been customized to simulate this behavior. After a ray tracing is performed, the absorbed flux is calculated from the ray data generated. The resulting heat generation rates are computed in such a way that they can be directly applied as element-wise loads to solve the steady-state heat equation. The experimental validation of the model has shown that the simulated and measured temperature profiles are in good accordance and will be presented here. As a consequence, the thermal response of the phosphor’s optical properties can be taken into account and optimized.

Ultrafast Thulium-doped fiber oscillators and amplifiers have become increasingly relevant over the past few years for applications like precise processing of polymers, as well as driving nonlinear frequency conversion stages to cover the fingerprint region in the mid-infrared and the soft X-ray spectral region [1] – [3] . Those applications require high peak powers or respective high pulse energies, which are usually generated by master oscillator power amplifier setups with several subsequent amplification stages. Reducing the number of amplification stagse would enable a more compact setup. Due to a higher tolerance for nonlinear phase accumulation compared to established pulse evolution schemes, Mamyshev oscillators (MO) are promising to omit one amplification stage in the future.

An advantage of using additive manufacturing (AM) processes as opposed to conventional fabrication methods is that the additional degrees of freedom in design allow compact and at the same time lightweight components to be manufactured. In addition, AM reduces the material consumption, resulting in a more cost efficient production. Among others, the field of laser development benefits from the progressive implementation of AM-related opportunities. However, this integration is mostly limited to single components. In contrast, we present a compact, lightweight solid-state laser oscillator system for low-power applications based on additively manufactured optomechanical components via Fused Filament Fabrication (FFF). The laser system is based on a Nd:YVO4-crystal pumped externally with a fiber-coupled laser diode at a wavelength of 808nm and a maximum output power of 3 W. The commercial optical components, such as lenses and the crystal, are firmly embedded via FFF in quasi-monolithic optomechanics. Thereby, they are fixed at their position and thus secured against misalignment. Furthermore, sensor technology for temperature monitoring is implemented into the structure. The possibility of the FFF process to work with different materials in parallel is used here. This multi-material printing approach enables the use of the appropriate polymer for the individual mechanical and thermal requirements for any structural part. The thermal stability of the printed structures is evaluated to ensure damage-free operation of the 3D-printed polymer optomechanics. Furthermore, output power, optical-to-optical efficiency, beam pointing, and spatial beam profile of the laser system are measured for several on- and off-switching cycles as well as for long-term operation.

The principle of a Mamyshev oscillator depends on alternating spectral filtering between sections of spectral broadening by self-phase modulation. In the 2 µm wavelength range, this concept faces the difficulty that standard fibers are anomalous dispersive which limits the possible pulse energy to the pJ-regime without proper dispersion management. We applied ultra-high numerical aperture fibers with normal dispersion in order to achieve up-chirped pulses in an anomalous dispersive Thulium-doped gain fiber. With that design, we achieved mode-locked pulses with energies of 6.4 nJ and a compressed autocorrelation duration of 195 fs at a repetition rate of 16 MHz.

Das Laser-Glass-Deposition Verfahren (LGD) ermoglicht eine laser- und glasfaserbasierte Additive Fertigung optischer Komponenten aus Glas im Makro- bis Mikrometerbereich bei gleichzeitig hoher Gestaltungsfreiheit. Die guten optischen Eigenschaften sowie Temperatur- und Umweltbestandigkeit von Glas fuhren dazu, dass diese Verfahrens-Werkstoffkombination insbesondere fur Anwendung in Hochleistungsbereichen interessant ist.

We report on two different concepts to generate µJ-level mid-infrared laser pulses with sub-10 ps pulse duration via nonlinear parametric generation at high pulse repetition rates. Both schemes rely on the recent development of compact and efficient CPA-free, Ho:YLF-based 2-µm laser sources pumping the highly nonlinear crystal ZnGeP

We present experimental results of the generation of ultrashort pulses in the 2 µm wavelength region by a fiber Mamyshev oscillator, along with the simulation of the pulse propagation in the cavity. The Mamyshev oscillator emitted pulses with energies of 3.55 nJ at a repetition rate of 15 MHz and optical spectra with bandwidths of 48 nm. The pulses propagated in anomalous dispersive Thulium-doped fiber sections with dispersion compensation sections of normal dispersive fibers.

Nowadays, customized optomechanics for complex optical setups are increasingly manufactured additively using the polymer-based process of fused filament fabrication. In this article, a kinematic polymer mirror holder is demonstrated, in which the mirror is imprinted and thus fixed against misalignment. Furthermore, the necessary spring system and ball joint are manufactured in a single printing process. This mirror holder can then be embedded into an also printed cage system. Mirror mounts made of different polymers are examined and compared with each other. The mechanical stress induced into the imprinted optic is determined. Regarding the 3D-printed spring system, the angular alignment range as well as the load limits are defined. The reproducibility of the mirror's angular position and the long-term stability together with the influence of thermal cycling is determined. The results will be compared with a conventional, subtractive manufactured metallic optomechanic.

We present a MgO:PPLN- and AgGaSe2-based, picosecond OPG/OPA scheme, enabling the generation of mid-to-long-infrared continuously tunable, microjoule energy pulses with a narrow spectral bandwidth of sub-8 cm-1 over the full tuning range. The approach combines a 1-µm-pumped, double-pass OPG setup with a 2-µm-pumped parametric booster amplifier stage. As pump laser is applied a CPA-free Ho:YLF laser delivering 32 µJ at 2051 nm wavelength and 20 kHz repetition rate. The OPG/OPA system specifications of µJ-level pulse energies in combination with narrowband and widely tunable, mid-to-long-IR spectra enable numerous possibilities for mid-IR spectroscopy and wavelength-specific mid-IR material processing.

The generation of ultrashort pulses in the mid-infrared (mid-IR) spectral region is highly demanded for a multitude of applications such as spectroscopy, materials processing, or biomolecular and chemical sensing. For many of the aforementioned applications a high pulse repetition frequency (PRF) is desirable, since it reduces measurement time and improves spectroscopic signal-to-noise ratio. However, most of the ultrafast mid-IR sources are limited to a PRF below 10 kHz as they rely on regenerative amplifier-based pump sources for optical parametric chirped pulse amplification (OPCPA) [1–3]. The herein applied Pockels cell represents a bottleneck for PRF tuning usually below 10 kHz. Just recently, we presented a 2-μm, sub-10 ps pulse laser system with millijoule-level pulse energy, which is in principle not limited by the PRF [4]. This laser system benefits from its simplified, compact CPA-free architecture and high efficiency.

The mid-to-long-infrared spectral range (3–15 μm) is of high interest for a multitude of material processing and spectroscopic applications due to wavelength-specific absorption features of many polymers and organic molecules in this spectral region. Especially narrowband, spectrally wide tunable mid-to-long-IR source reaching μΐ-level pulse energies are attractive due to their ability to address specific absorption bands of the target materials. Common sources for narrowband, wide spectral tunable pulse generation are pico- or nanosecond optical parametric oscillators (OPO) or parametric amplifier systems (OPA) combined with a subsequent difference frequency generation stage in order to reach the mid-to-long-infrared spectral region [1]. In contrast optical parametric generators (OPG) possess a much higher simplicity of the optical design compared to OPOs or OPAs due the absence of specifically designed optical cavities nor the requirement of an optical seed. On the downside, the spectra generated in OPG systems are typically only limited by phase-matching constraints and therefore the generated bandwidth can be very broad and can vary significantly over the full spectral tuning range.

We report on two different concepts to generate µJ-level mid-infrared laser pulses with sub-10 ps pulse duration via nonlinear parametric generation at high pulse repetition rates. Both schemes rely on the recent development of compact and efficient CPA-free, Ho:YLF-based 2-µm laser sources pumping the highly nonlinear crystal ZnGeP2 used for parametric amplification. The first concept comprises a simplified OPG/OPA scheme efficiently producing signal and idler radiation at fixed wavelengths of 3.0 and 6.5 µm, respectively. In the second concept, we demonstrate a wide spectral tunability of the picosecond, µJ pulses over the entire tuning range between 2.5 and 12 µm maintaining a constant bandwidth of sub-20 cm−1 by integrating a two-color pumping scheme and a spectral shaper into the setup. The presented compact and efficient mid-IR picosecond radiation sources offer a way towards low-cost mid-IR material processing and spectroscopic applications.

The generation of sub-10 ps pulses around a wavelength of 2 μm with pulse energy at millijoule-level in a compact CPA-free amplifier chain is presented. This laser source covers a broad range of pulse repetition frequencies from 1 to 100 kHz with a pulse peak power from 136 to 17MW, respectively. We used highly doped Ho:YLF crystals to achieve an overall amplification factor of almost 52 dB. A characterization of these crystals regarding upconversion losses and attainable small-signal gain supports this work.

We present a mode-locked holmium-doped all-fiber soliton laser operating in the 2052 nm wavelength range. The ultrashort pulse oscillator is simultaneously self-providing 1950-nm radiation for efficient in-band pumping in a subsequent thulium-/holmium-doped fiber tandem amplifier. More than 76 nJ-pulses for Ho:YLF or Ho:YVO4 amplifier seeding have been achieved.

Passively mode-locked, ultrafast and compact laser sources operating in the wavelength range beyond 2 μm have gained interest for several applications such as nonlinear frequency conversion into the mid-infrared and THz region, material processing, medicine etc. Typically, Ho-doped optical fibers (HDF) are used to directly address this spectral region in ultrafast mode-locked oscillators while Ho:YLF amplifier systems can boost the pulse energy to multi mJ-level, provided, the seed wavelength of the oscillator corresponds to the emission wavelength of the Ho:YLF crystal which is centered around 2051 nm with spectral bandwidth of about 5 nm.

The generation of millijoule-level ultrashort laser pulses at a wavelength of 2.05 μm in a compact chirped pulse amplification-free linear amplifier based on Holmium-doped YLF gain medium is presented. More than 100 MW of pulse peak power has been achieved. We show the capabilities of this laser amplifier from a 1 kHz to 100 kHz repetition rate. A detailed numerical description supports the experimental work and verifies the achieved results.

We demonstrate the manufacturing of embedded multimode optical waveguides through linking of polymethylmethacrylate (PMMA) foils and cyclic olefin polymer (COP) filaments based on a lamination process. Since the two polymeric materials cannot be fused together through interdiffusion of polymer chains, we utilize a reactive lamination agent based on PMMA copolymers containing photoreactive 2-acryloyloxyanthraquinone units, which allows the creation of monolithic PMMA-COP substrates through C-H insertion reactions across the interface between the two materials. We elucidate the lamination process and evaluate the chemical link between filament and foils by carrying out extraction tests with a custom-built tensile testing machine. We also show attenuation measurements of the manufactured waveguides for different manufacturing parameters. The lamination process is in particular suited for large-scale and low-cost fabrication of board-level devices with optical waveguides or other micro-optical structures, e.g., optofluidic devices. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE). DFG/SFB/TRR 123