Faraday rotator design for 266nm, 343nm and 355nm lasersMelzer, Volker; Gabler, Werner; Anders, Matthias
doi: 10.1117/12.3045427pmid: N/A
The continuous lasing process of a laser is sensitive to back reflected laser light, because it is disturbing the intrinsic stimulated emission process in the laser material. Faraday Isolators and Rotators are therefore commonly used to separate back reflected light from entering the laser cavity or the resonator. We present a new design of a Faraday Rotator for UV lasers with laser wavelengths of 343 and 355nm. This Faraday Rotator is suited for CW or pulsed UV lasers with typically averaged laser power up to few 10W range. In addition, we demonstrate the design option and feasibility of a 266nm Faraday Isolator.
Miniaturized wavelength stabilized laser module emitting at 619nmMauerhoff, Felix; Senel, Oktay; Feise, David; Sahm, Alexander; Schröder, Tim; Paschke, Katrin
doi: 10.1117/12.3041600pmid: N/A
We present the development and experimental verification of a wavelength stabilized fiber coupled diode laser module emitting at 619nm at ambient room temperature. Furthermore, we focus on wavelength stabilization to achieve stable operation and narrow laser linewidth at the target wavelength. The miniaturized module is based on an external cavity diode laser setup stabilized by a fiber Bragg grating. The resonator is housed in a 14-pin butterfly package. We use FC/APC connectors for the optical output of a single mode polarization maintaining fiber. The gain material is optimized for room temperature operation at 626nm. The module inlay can be operated at temperatures as low as -25C to shift the gain peak beyond 619nm. We measure peak output powers over 10mW ex fiber at 619nm.
A novel high-gain, ASE-suppressed, and highly efficient fiber amplifierHe, Chun
doi: 10.1117/12.3040854pmid: N/A
We present a novel high-gain fiber amplifier incorporating recently developed advanced fiber optic devices. The amplifier achieves an unprecedented gain of 45–50dB with background suppression exceeding 25dB, effectively mitigating amplified spontaneous emission (ASE) and nonlinear effects commonly observed in fiber-based lasers and amplifiers. Additionally, the device demonstrates compatibility with a wide input signal dynamic range and a remarkably high output saturation threshold. It operates seamlessly in continuous-wave (CW) mode as well as in pulsed modes, accommodating millisecond to picosecond pulse durations. Experimental results are provided for nanosecond 1550nm erbium-doped fibers, nanosecond 1064nm ytterbium-doped fibers, and mode-locked picosecond 1064nm ytterbium-doped fibers.
Enhancing stability and radiation resilience of phase-shifted fiber Bragg gratings for high-power and space applicationsLablonde, Laurent; Pinsard, Emmanuel; Le Grand, Catherine; Le Masson, Ronan; Boiron, Hugo; Robin, Thierry; Boutillier, Mathieu
doi: 10.1117/12.3042384pmid: N/A
Narrowband filtering using phase-shifted fiber Bragg gratings (PS-FBGs) is gaining attention across various applications including laser line filtering, optical communications, optical fiber sensing, and other fields requiring high sensitivity, accuracy, and stability. When employed in transmission, PS-FBGs with a bandpass of a few gigahertz or less are particularly sensitive to input power and radiation. The stability of the central wavelength of PS-FBGs becomes problematic at typical power levels exceeding a few milliwatts when fabricated using conventional methods. Introducing a phase shift in the Bragg grating creates an optical cavity where optical intensity concentrates around the phase shift, causing significant temperature variations along the grating due to absorption. This photothermal effect, influenced by the fiber's thermo-optic coefficient and thermal expansion, leads to a shift in wavelength and consequent power loss at the filter output. In this study, we present stable 1GHz and 4GHz filters UV-written in polarization-maintaining (PM) and single-mode (SM) fibers respectively, operating around 1.55m. By reducing non-resonant absorption during grating photo-inscription, minimizing intensity factor, and enhancing fiber thermal dissipation, we demonstrate stability up to 100mW, corresponding to a sensitivity reduction by a factor of 10 to 20. Investigating the radiation response of optimized, unpackaged PS-FBGs, we observe a wavelength shift induced by irradiation of less than 15pm and no spectral distortion up to an accumulated X-ray dose of 8.5kGy (SiO2), with a dose rate of 40mGy/s at room temperature. This work showcases state-of-the-art performance in stability to input power and paves the way for narrowband filters compatible with space applications.
High-power InP diode lasers operating under long-pulse condition with high reliabilityFan, Yingmin; Li, Wenwei; Tian, Xiaoyu; Hong, Fei; Hou, Lin; He, Chun; Liu, Xingsheng
doi: 10.1117/12.3041005pmid: N/A
In comparison to 8xx–9xx nm semiconductor lasers fabricated on GaAs substrates, the development of high-power 13xx–15xx nm semiconductor lasers on InP substrates faces fundamental challenges. The electro-optical (EO) conversion efficiency of InP-based lasers is significantly lower than that of GaAs-based lasers. Moreover, their EO conversion efficiency degrades substantially with increasing temperature. The conventional approach of increasing laser output power by raising pump current proves ineffective and often results in early thermal rollover. Additionally, the mechanical properties of InP-based lasers, which are critical for reliable high-power packaging, are less favorable compared to GaAs-based lasers. The considerably lower thermal expansion coefficient (CTE) of InP compared to commonly used heatsink materials can generate increased packaging stress within the lasers. This stress is exacerbated by the lower Young’s modulus and fracture toughness of InP, leading to reliability issues and reduced device lifetime. We present here InP-based 1470nm laser bar devices with passively conduction-cooled heatsinks designed to minimize bonding stress and thermal resistance. These devices are fabricated using an innovative packaging process. For laser diode (LD) chips with a 2mm cavity length, the thermal resistance of the devices is approximately 0.27C/W, and the thermal rollover power achieves 60W at 150A under continuous wave (CW) conditions. Furthermore, these LD devices demonstrate high reliability under hard-pulse operating conditions.
Automated assembly and alignment of NIR and MIR external cavity diode laser systemsErfle, Denis; Assmann, Christian; Schmidtmann, Sebastian; Honsberg, Martin; Sacher, Joachim
doi: 10.1117/12.3042948pmid: N/A
Laser systems operating in the near-infrared (NIR) and mid-infrared (MIR) spectral regimes have become indispensable tools for a wide range of applications, including spectroscopy, metrology, and emerging quantum technologies. However, high manufacturing costs and variability due to manual assembly remain significant barriers to widespread adoption. This work introduces an automated assembly and alignment approach for NIR and MIR external cavity diode laser systems, leveraging robotic systems and artificial intelligence in the vision system for edge detection to enhance precision, reproducibility, and efficiency while significantly reducing production costs and time. The automation process achieves positioning accuracy better than 100nm across all three translational degrees of freedom and angular accuracy exceeding 0.6 arcminutes. Continuous in-situ monitoring of optical and spectral performance during each alignment step ensures high reproducibility and optimal laser performance. A key focus of this approach is achieving symmetrical laser beams with well-defined divergence angles, which are crucial for effective cavity alignment. The method is demonstrated through the alignment of external cavity lasers with Volume-Bragg-Grating components, showcasing examples of NIR VBG lasers with varying cavity lengths. This automated production concept represents a significant advancement in industrial laser manufacturing by addressing challenges associated with manual processes, such as variability and inefficiency. It provides a scalable solution for producing high-performance laser systems at reduced costs while maintaining stringent quality standards.
High power diode laser development using advanced bonding technology and innovative structure designHou, Dong; He, Chun; Fu, Tuanwei; Liang, Xuejie; Liu, Jindou; Li, Changxuan; Li, Zhi; Fan, Yingmin; Yuan, Ke; Zah, Chung-en; Liu, Xingsheng
doi: 10.1117/12.3041774pmid: N/A
High power diode lasers, operating in long pulse width mode, require high reliability and extended lifetime in the medical aesthetic application. Traditionally diode laser bars are bonded on microchannel cooling plates (MCCs) using Indium soft solder or packaged through AuSn hard solder and coefficient of thermal expansion (CTE) matched sub-mount. It presents a design challenge for achieving higher output power and reliable operation in long pulse width operation mode. In this study, we have developed a sophisticated high performance large channel cooling plate (LCC) diode laser, which utilizes advanced bonding technology and dual side heat dissipation structure design. For diode laser (DL) chips with a 1.5mm cavity length at 808nm wavelength, the thermal resistance achieved is 0.3K/W. The thermal rollover power in continuous wave (CW) mode reaches 267.7W, marking a 25% improvement over the comparable diode lasers packaged in conventional MCCs with direct chip bonding. Under quasi continuous wave (QCW) mode with working condition of 20ms pulse width and 10Hz repetition frequency, the thermal rollover power increases to 345.9W, representing a 34% enhancement over hard soldered microchannel cooling plates (HMCCs). Additionally, a 10-bar vertical stack was assembled using the new LCC and bonding process. The optical power achieved 2417W under QCW working condition of 20ms 10Hz and passed an 852-hour lifetime test.
New results on the temperature coefficient of the refractive index for various optical materialsJedamzik, Ralf; Petzold, Uwe; Kaufmann, Henning
doi: 10.1117/12.3039110pmid: N/A
The refractive index, a property of optical materials, fluctuates with changes in temperature. This means that any temperature variations in a lens, whether it’s made from optical glass, infrared material, or even a filter, can cause changes in the refractive index. This, in turn, leads to distortions in the wavefront that are dependent on temperature in the application. However, these temperature-dependent variations in the refractive index can be offset by thermal expansion, which allows us to define what we call athermal glass behavior. A crucial element for designing athermal optics is a dependable database that contains the thermal coefficient of the refractive index for the optical materials. ISO has released two standards, ISO 6760-1 and 6760-2, which focus on measuring the temperature coefficient of the refractive index. For many years, reliable data on these temperature coefficients have been a key component of the data sheets for optical glass. More and more applications need broadband dn/dT evaluations up to 2325nm. Current measurement capabilities are limited to 1060nm wavelength. This paper addresses the question if extrapolation of dn/dT data from 1060nm to 2325nm is a valid approach.
Front Matter: Volume 13344doi: 10.1117/12.3068601pmid: N/A
This PDF file contains the front matter associated with SPIE Proceedings Volume 13344, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.