This PDF file contains the front matter associated with SPIE Proceedings Volume 12866, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

In this contribution, we show for the first time to our knowledge the realization of a high power 1.94 µm triple clad fiber combiner with low insertion losses, thanks to the implementation in the component of a low-index glass capillary. Moreover, in this contribution we discuss the power scalability of a 2.1 µm Ho3+-doped fiber laser architecture integrating the above mentioned triple clad fiber combiner and pumped at 1.94 µm using Tm3+-doped fiber lasers developed at ISL.

The latest technology silica/silica, step-index multimode fiber bundle end treatment technology shows outstanding transmission all over the spectral range of silica material transparency. Fibers are fused in a honeycomb-like structure with a fill factor close to one while the fused end of the bundle is surrounded by a low refractive index medium. This allows us to consider the utility of new fiber bundles for low-loss, high-power applications where all until now-known fiber bundle end treatment technologies would fail. Large active area bundles remain flexible as they are loose along the longitudinal axis and only the tip of bundled fibers at the length are fused a few centimeters. Active areas can be shaped mixing curvatures, positive and negative angles with high repeatability and negligible deformations of individual fibers to fit the output of the source giving an advantage of expensive silica material economy. Furthermore, mirroring the shape of the light source output to bundle input benefits coupling efficiency especially for high NA (Numerical Aperture) coupling. This can increase output power density while the construction of the fused fiber bundle end allows designs with good heat management options. There are continued studies of Clad Fused Bundle (CFB) end treatment technology in this paper focusing on destructive tests and laser power threshold values at NIR (Near Infrared) with CW (Continuous Wave) sources. During the tests laser power is gradually increased to several kW and fiber bundle temperature changes are observed.

In this work we report a -24dB LP11 mode suppression in a 7+1 to 1 Backward Pump-Signal Combiner. The mode content is measured using the S² -Measurement technique. The high signal beam quality is attributed to a low overlap splice loss between the Tapered Fiber Bundle and the output fiber. The combiner output fiber is large mode area with a LP01 mode effective area of 584 um².

With the rapid advancement of kW-class fiber laser sources in recent years, taper-fused side pump and signal combiners have been confirmed as the essential tool for further power scaling these laser sources. The taper-fused side-pump coupler involves direct fusion splices between several tapered multi-mode pump fibers and a double-clad signal fiber. In this research, we present the design and fabrication of a (6+1) x1 taper-fused side pump and signal combiner specifically tailored for high-power fiber laser application. Notably, this combiner has six pump arms, surpassing previous research in this area. For numerical simulations, a commercial beam propagation method software, Rsoft BeamPROP, is utilized for the 3D simulations of laser propagation and higher-order modal characteristics in optical waveguides. We have successfully optimized the device design to achieve high coupling efficiency, minimal signal loss, and exceptional high backward pump isolation. By avoiding the need for bridging fibers, the tapered side-coupler eliminates fusion-splice points, thus enabling low signal insertion loss and maintaining excellent spatial beam quality. The combiner experimentally demonstrates an impressive total pump efficiency of 97.98% while carrying a pump power of 2230 W. Furthermore, the measured signal insertion loss is approximately -0.11dB. The numerical and experimental results agree with each other and successfully confirm the outstanding performance of the combiners and validate their suitability for kW-class fiber laser applications. Moving forward, we anticipate that the integration of these side-pumping combiners into kW-class fiber lasers will further unlock the advantages of side-pumping technology and facilitate advancements in high-power laser applications.

Fiber-based laser and amplifier systems provide high output power, excellent beam quality and easy handling by utilizing a setup consisting of fiber components like signal-pump combiners and cladding-light strippers. Large-mode-area fibers are used in these systems to improve the performance while maintaining single-mode operation. Compared to pure single-mode fibers, these fibers always guide higher order modes, which can have an impact on the system’s performance. An instrument was developed based on the S²-method, which is able to perform high-speed, in-line measurements of the modal composition and polarization extinction ratio. This device is used to monitor the fiber component manufacturing process using large-mode-area fibers in real-time, enabling us to improve critical process steps and, thereby, optimize the manufactured components, namely signal-pump combiners and fiber endcaps.

We designed and constructed two novel fiber optic devices that have never been revealed before. One is a wavelength-selective optical router, and the other is a wavelength-selective retroreflector with a bypass fiber channel. They find usefulness in many applications, especially in fiber amplifier, fiber-optic communication, and fiber sensing. To prove their effectiveness, we built a single-stage, two-pass fiber amplifier system composed of these two components. The fiber amplifier yielded an unprecedent 47 dB gain with less than - 23 dB amplified spontaneous emission. The amplifier also possesses a very wide input signal dynamic range and very high output saturation limit. It can be operated in either CW mode or pulse modes.

The optical position of optical glasses is fixed by its chemical composition but also by the temperature history of the glass. Therefore, fine annealing of optical glass is an important part in the production process. The temperature profile during cooling of the optical glass from glass transition temperature down to room temperature generates thermomechanical stress in the material. The thermomechanical stress is translated into stress birefringence by means of the stress optical coefficient. The stress birefringence is a measure of the difference in refractive index as a function of the polarization direction. Stress optical coefficient is a function of the wavelength and varies among different glass compositions. For polarization sensitive applications the knowledge of the stress optical coefficient as a function of the wavelength is essential. In this publication a new method of measurement of the stress optical coefficient based on the ASTM C770 procedure C is presented. The new method enables spectral measurements from 245 nm up to 1670 nm. Results of the stress optical coefficient as a function of wavelength for a variety of optical glasses are discussed and compared to measurements from the past based on ISO 10345-2.

12kw fiber laser has become the new industrial laser standard being widely used in sheet metal cutting, laser cladding, laser welding and many other industrial applications. The most common failure associated with such high-power fiber laser is the thermally induced component failure, including the laser chip failure resulting in power degradation, the high-power pump diode failure from insufficient cooling to fiber component failure from overheat, etc. Here we present an innovative active air cooled 12kw fiber laser system with the build-in closed-loop- controlled waterless cooling system, not only improve the component and the overall laser reliability but also improve the overall system electric-optical efficiency by as much as 30%.

JAXA’s Martian Moons eXploration (MMX) mission is a project to explore the two moons of Mars, with the launch currently being scheduled for 2024. Part of the project is raman spectroscopy to investigate fingerprints of organic compounds. The green 532 nm laser is an adaption from EXOMARS’ raman laser, providing ⪆100 mW in a singlemode fiber at a spectral bandwidth ⪅10 pm. Solderjet bumping as a laser-based soldering and thus optics bonding technology has been employed for the attachment of all miniaturized components of the two-channel DPSS configuration with intra-cavity frequency conversion by means of a BBO crystal. The integration platform is a DCB substrate for thermal connection, the system including fiber-coupling fits into a butterfly-alike housing ⪅10e5 mm³ volume, and ⪅10 g mass. Stability of the soldered optics in the <10 arcsec range was proven also during thermal vacuum, mechanical and radiation testing for space conditions.

Feasibility of various illumination sources for a SWIR sensor was explored: Edge Emitting Laser (EEL), Vertical Cavity Surface Emitting Laser (VCSEL), and Light Emitting Diode (LED) were evaluated in terms of level of optical power, optical power variation over temperature and image quality. The highest optical power was measured from the EEL, while the LED showed the best images quality: LED ⪆ VCSEL ⪆ EEL, because of the spatial incoherency of LED as well as the lack of optimization of the EEL diffuser. Emission wavelength variation with temperature requires the use of long pass filtering of the illumination sources. If an application needs a narrow band pass filter, the temperature should be controlled. A combination of numerical, graphical, and actual images will be presented to compare the performance of the devices under study.

In this paper, a kind of electrodeless millimeter diameter micro xenon lamp was developed. The micro xenon lamp was driven by inductive coupling. The experimental investigation of the discharge characteristics and laser pump performance of the developed micro xenon lamp have been carried out. The energy coupling efficiency of the drive scheme is between 22.4% and 24.2%. The fluorescent spectrum of micro xenon lamp is composed of line spectrum and continuous spectrum, which is well matched with Nd3+ absorption spectrum. Because of its small size and flexible layout, it is suitable to be used as the pump light source of fiber laser. The fluorescence radiation of fiber can be improved by using multiple micro xenon lamps. Four micro xenon lamps can improve the fluorescence radiation power by 80.5% compared with only one. The results indicate a complete set of micro xenon lamps can be applied in the field of fiber lasers.

We report on an External Cavity Diode Laser (ECDL) in a hermetically sealed 14-pin butterfly package with a collimated output beam. The laser emits more than 50 mW at a drive current of 165 mA and the emission wavelength can be tuned between 460.74 nm and 460.97 nm. The maximum mode-hop-free tuning range measures 26 GHz. The laser consists of a GaN-based gain chip, which is collimated by an aspheric lens. Behind the lens, a Volume Bragg Grating (VBG) stabilizes the laser emission to the target wavelength of around 460.8 nm, which can therefore be used for laser cooling or trapping of strontium without the need for frequency-doubling. Inside the butterfly package, the laser diode is soldered on a ceramic submount and mounted on an optical work bench together with the aspheric lens and the VBG. The optical work bench is temperature stabilized by a Thermoelectric Cooler (TEC) in combination with a thermistor. In frequency noise measurements of the packaged laser, we measured a white noise level of 1.29 MHz. This demonstrates a reasonable stabilization of the emission wavelength of the gain chip via the VBG. By further improvements of the ECDL we expect that a linewidth ⪅ 1 MHz can be achieved. This development paves the way for compact, blue laser diodes with a narrow linewidth for quantum technology, spectroscopy, and sensing.

808nm Quasi-Continuous Wave (QCW) Laser Diode arrays (LDAs) have found a wide range of applications in medical, scientific research, defense, surveillance and solid-state laser pumping, printing and others. As a result, the design varieties and upgrades of such products have emerged as prominent topics in the current discourse. Through a compact structural design and optional independent bar beam shaping, we achieve high-power, high emission density, narrow spectral width, excellent uniformity, and consistent pulsed laser output. The entire product series, namely G-stack and C-stack, allowing for customization of pitch, number and type of bars, output power, wavelength range, overall dimensions, and beam profile according to customer requirements. This product features a highly reliable gold-tin bonding packaging, which ensures the stability and durability of the laser system over a long service life. These products demonstrate reliable operation up to 20% duty cycle. This article primarily focuses on a sandwich structure as the basic building block for further packaging. Here, eight sandwiches with a pitch of 1.7mm form one subunit, and three units are vertically arranged in a 3×8, 24-bar array configuration. Under a 3% duty cycle test, by bar selection, the output wavelength could be achieved within a range of 808nm±1nm, with a FWHM of less than 3.5nm and peak power exceeding 11 kW pulsed. Additionally, this design showcases exceptional reliability, accumulating over 7000 hours of reliability test data under various conditions. Optically, precise collimation is achieved by employing not only best collimation alignment to the specified divergence using from simple fibers to aspheric cylinder lenses, but also specific pointing angles for each bar's fast axis, resulting in outstanding beam uniformity of 95%. These high-power and high-uniformity array products find significant applications in scientific research fields, where the uniform laser output yields substantial benefits in crystal absorption and pumping efficiency. This design holds also great potential and benefits in the field of hair removal, serving to the increasing demand and widespread acceptance of laser-based epilation.

Rogers Micro-Channel Coolers (MCC) cover a wide range of thermal management applications, such as laser diode heat sinks and CPU coolers. Apart from top-of-the-line thermal performance, some applications require a particularly homogeneous temperature distribution. In this paper, we present Finite-Element-Method (FEM) simulation results of a new MCC stack setup for single emitter laser diodes and a solid copper heatsink reference with variable heat transfer coefficient (α) on the bottom side. Characteristic curves for temperature (T), temperature difference (ΔT) between optical components and pressure drop are shown as a function of α and flow rate. We find a ΔT of less than 2 K between the semiconductor elements and a total T reduction of ⪆20 K compared to the reference heatsink.

For compact spectrometers with high resolution and especially for Quantum Technology (QT) of the second generation, compact, portable, and long-term stable systems are a prerequisite for the breakthrough of the technology. In this paper, we demonstrate a miniaturized external-cavity diode laser (miniECL), which is frequency stabilized with a Volume Bragg Grating (VBG), and a miniaturized fiber-coupled tapered amplifier (miniTA). Both devices feature a collimated output beam and are integrated in a hermetically sealed 14-pin butterfly module. Due to the external cavity design and a robust packaging process, the miniECL has a linewidth below 350 kHz with an output power ⪆ 80 mW at 670 nm, 770 nm, 780 nm, 852 nm, and 894 nm. These wavelengths correspond to the D1 and D2 transitions of Li, the D1 transition of K, the D2 transition of Rb and the D2 and D1 transition of Cs, respectively. Hence, the miniECL is perfectly suited to excite atomic transitions. In addition, the miniECL can be used as a seed laser for the miniTA, which amplifies its output power to 1.5 W - 3.0 W with excellent beam quality (M² between 1.3 and 1.7 and beam divergence ⪅ 3 mrad), while maintaining the narrow linewidth of the seed laser. The amplification bandwidth of the miniTA matches with the emission wavelength of the miniECL, which enables extremely compact Master Oscillator Power Amplifier (MOPA) setups.

Semiconductor Master-Oscillator Power-Amplifiers (MOPAs) are versatile tools for various applications. We will present high-power (P ⪆ 5 W), high-coherence length (L_c ⪆ 100 m), small-sized (L ≤ 25 mm), hybrid semiconductor MOPAs at 920 nm, 976 nm, 1030 nm, 1064 nm, 1120 nm, and 1154 nm. We compare their performance to corresponding distributed Bragg reflector tapered laser and discuss strategies to extend the wavelength range.

This study presents an innovative method for analyzing spatiotemporal couplings induced by an optical element, using a scanning white-light interferometer. This study, which measured the induced spatiotemporal couplings through a novel analysis method of an interferogram of the white-light interferometer, emphasizes that commonly used optics, such as simple lenses, can generate spatiotemporal couplings that degrades spatiotemporal focal intensity, and quantifies it through experimental measurements rather than theoretical analysis. The analysis method involves the Fourier transformation at each transverse position along the scanning axis and frequency-resolved unwrapping in the transverse plane to obtain frequency-resolved wavefronts and dispersion. From the results of frequency-resolved wavefronts and dispersion, the spatiotemporal couplings induced by the optical elements can be reconstructed. The reconstructed results, validated against theoretical simulations, confirm the precision of the technique. This approach offers significant contributions to ultrafast high-power laser systems by providing an improved technique for characterizing spatiotemporal couplings induced by optical systems and for selecting appropriate optical components suitable for the laser’s specifications.

The rectangular diffraction grating on single crystal diamond was fabricated with the wavelength of 10.6 μm. A novel method called bi-layer lift-off technology was used to form the hard mask. This approach simplified the patterning process of the thick Al film and made the deep etching on single crystal diamond achievable according to our requirement. The fabrication steps and the bi-layer lift-off technology are demonstrated in detail. We characterized the diamond grating and found that the angles of its sidewalls were almost vertical (within 3°), with a mean roughness of Ra = 3.01 nm on the bottom and 12.4 nm on the top.