Components and Packaging for Laser Systems XI

Quantum computers based on neutral-atoms have achieved large-scale and high-fidelity operation on hundreds of qubits. High-fidelity photonic integrated circuits (PICs), particularly in the visible spectrum, will be crucial for the fundamental operation and scaling roadmap of error-corrected quantum computers. We present our multi-channel PIC solution operating in the visible-NIR with high-speed switching, ultrahigh extinction ratios and low channel crosstalk. We describe its operation in a neutral-atom quantum computer and discuss our scaling roadmap.

Infleqtion is a leader in neutral atom quantum systems, with a long history in quantum research (as ColdQuanta), and now a pioneer in commercializing quantum products; optical atomic clock, ‘Tiqker’, Rydberg-atom Quantum-RF sensing, ‘SqyWire’, and Quantum Computer, ‘Sqorpius’. Future Infleqtion quantum products will incorporate advanced photonic integrated circuits (PICs) for miniaturization, cost reduction, and ruggedization. These will replace the large and expensive laser systems, frequency control, and beam-steering in current systems with advanced PICs, providing 10x to 10,000x reduction in cost, size, weight and power (C-SWaP). Infleqtions advanced PIC technologies, brought into the company through acquisitions of Morton Photonics and SiNoptiQ, will be described, as well as how these will be used in Infleqtion products. PIC devices include III-V semiconductor gain based single wavelength and ultra-wideband tunable lasers with world leading noise performance, ultra-low thermo-refractive noise (TRN) coil resonators for frequency control, and stimulated Brillouin scattering (SBS) lasers for the ultimate in phase noise performance.

Integrated Photonic Circuits (PIC) combine active semiconductors generating single frequency radiation and photodetectors with photonic integrated circuits (PIC) for routing the photons and active components for modulating the photons. This enables highly integrated and miniaturized devices. We will review the packaging requirements associated with Sensing applications, such as Lidar and quantum technology. We will review the state of the art for design and execution of integrated photonic packages, which encompasses low loss optical interfaces, high density, high bandwidth electrical interfaces, efficient cooling and reliable packaging. High efficiency optical coupling between semiconductors and fiber arrays (FAU) or PIC includes butt coupling, integrated spot size converters made by ion exchange and nanoimprinted lenses that also enable surface coupling. The routing of electrical DC and RF drive current as well as low level RF currents must be laid out for minimal interference and bandwidths reaching 100 GHz.

Narrowband spectral filters, based on volume Bragg gratings (VBGs) in photo-thermo-refractive glass, were recently deployed in a wide variety of applications. This material allows recording of VBGs in the visible and near IR spectral regions with high efficiency, narrow bandwidth, high suppression, and large dispersion. Recent advances in VBG technology enabled fabrication of various holographic components well suited for quantum optics applications such as single photon detection, atomic clocks, quantum computing and networks. VBG-based diffractive elements are used for beam combining, signal separation, pump suppression, and as dispersive elements. In this paper we demonstrate manufacturing of high efficiency (>90%) reflecting VBG filters with enhanced suppression of side bands. Such elements provide suppression of background or pump by more than 25 dB for all spectral components shifted from the signal by 70 GHz or higher.

Mastering the journey from R&D to reality in photonics module development demands precision, innovation, and strategic foresight. In this guest lecture, I will share insights on expediting the design, development, and build processes for photonics modules within constrained timelines. The discussion will highlight key considerations for derisking optical link budgets and optimizing module architecture. Additionally, I will delve into strategies to address challenges related to die attachment reliability and thermal management, ensuring system robustness. Attendees will gain actionable techniques for mitigating risks and enhancing performance, paving the way for successful commercialization of advanced photonics technologies.

We optimise the packaging of Watt-power tapered amplifiers in order to offer high coupling efficiency into single mode fibre. The conclusions of a lab study were used to inform the build and manufacturing procedure for integration inside a 14-pin butterfly module, seeded with an input fibre. Careful thermal management and robust alignment is critical for reliable operation. We demonstrate devices with the output externally coupled into PM fibre with efficiencies exceeding 60% and powers above 1 W at 780 nm. The devices are currently being used to drive a rubidium magneto-optic trap.

Intel has developed a high-volume active alignment for eight channel coupling of a fiber array to photonic integrated circuit (PIC) though a lens array. The fiber array itself has mixed polarization maintaining (PM) fibers and single mode (SM) fibers. The PM fibers are utilized to induce external narrow linewidth laser diodes, while the SM fibers are utilized as both for functional channel and assisting of active alignment. On PIC chip, there are assisting edge channels either incorporated with a integrated laser diode or monitoring photodiode (MPD) to assist the active alignment. Upon completion, all of PM fiber channels are introduced with external laser sources and the coupling and real time monitoring can be realized via MPDs. We have realized that low coupling loss and fast processing for high volume active alignment.

We demonstrate a novel and ultra-compact SLED transceiver module realized in a standard 14-pin Butterfly module where a broadband 1550nm superluminescent diode is integrated alongside a 3-channel beam divider, a 3-channel optical circulator and three receiver photodiodes on a temperature-controlled, free-space, micro-optical bench architecture. The integrated transceiver module provides an ultra-stable light output through a PM fiber array with high polarization extinction.

Within an European Space Agency (ESA) Basic Technology Research Programme (TRP) funded project a laser-based soldering technology was evaluated for a low-stress bonding of large (>100 mm diameter) lenses within mounts. Objective of the activity was to overcome limitations of traditional clamping and adhesive bonding technologies with respect to stress and long-term stability in harsh and high power environments, by applying a anorganic-metallic bonding agent, and a localized, minimal impact laser-based soldering technology, the so-called Solderjet Bumping (SJB). Fused Silica, N-LAK9 and CaF2 lens dummies were processed, respective mounts in CTE-matching materials incorporated flexures to minimize operational and non-operation environmental conditions thermo-mechanical stress. Throughout the whole process chain of assembly and testing surface P-V deviations <100 nm, birefringence changes <10 nm, and position changes <1 micron where measured. The results enable applications of the technology for high power systems e.g. in laser material processing and fusion energy creation.

A holographic video microscopy system for counting and characterizing suspended particles is presented. The basic optical system and system-level functionality are introduced. Application examples for detecting different particles are presented.

Diode lasers are vital in applications like telecommunications, medical devices, and industrial manufacturing due to their high efficiency and optical output. Combined, they are used as pump sources in fibre laser systems or solid state laser systems, enhancing performance and reliability. Combining multiple diode lasers to a high-power pump source requires specialized adhesives that ensure precision and stability of integrated optical components. Key requirements include minimal outgassing, low shrinkage, and active alignment capabilities during curing. Additionally, dual curing options (thermal and UV) increase manufacturing flexibility. These adhesives do not only bond optical components but also secure other assemblies, maintaining overall system integrity and performance.

The development of an innovative hyperspectral imaging camera system and the design and process for its manufacture are presented. These imagers capture high-spatial resolution image data-cubes over wide wavelength bands in seconds. Wavelength ranges depend on the camera model in spectral windows from 250 nm to 2100 nm. Each imager can be programmed to scan subsets of bands. Imaging resolutions range from 4 nm FWHM in the visible to 15 nm in the Extended SWIR. The fundamental working principle and some of the challenges in realizing it as a product, are described and application examples are presented.

LiDAR based on line-beam is increasingly becoming the mainstream solution for laser radar because of its simple architecture, high reliability, regular point cloud, and smaller size. We report on an EEL chip-based line beam module packaged with GS technology. Compared to conventional COB packaging, the peak power is increased by 25%, while the junction temperature decreases by approximately 10.4°C. The module shows excellent optical performance including small SMILE resulting from the symmetrical structure and light emission from the center of a PCB.

Since the groundbreaking achievement of ignition and self-sustaining fuel burn at the U.S. National Ignition Facility (NIF), the field of fusion, specifically laser inertial fusion energy (IFE), has rapidly accelerated and transformed. Numerous countries are investing more heavily or initiating new fusion programs, with significant collaborative efforts from international research institutions and the private sector accelerating the path to practical fusion energy. The implications for the photonics market include an increased demand for lasers, optics, optical materials, diagnostics, and other key technologies, creating new opportunities for photonics companies and shifting market dynamics. Future challenges and strategies for achieving higher energy yields and commercial viability are outlined, emphasizing the critical role of photonics in enabling the next generation of fusion energy solutions.

The interaction of light and matter can create bonding structural and morphological changes in nano/micro-scale from the surfaces of diverse materials, sometimes even deep within them. This feature has been utilized in laser processing to produce new value for both science and industry. Recent advances in high-power, ultrashort pulsed laser and fast beam delivery technologies are rapidly expanding the possibilities of laser processing. At the same time, the number of parameters to be controlled has become enormous, which is why we have introduced Data Science. In this talk, we will discuss new data-driven laser processing utilizing high-speed data acquisition and AI data optimization for higher throughput and quality. We also aim for this technology to contribute to sustainable manufacturing and society in the future.

Optical frequency combs have revolutionized time and frequency metrology by providing rulers in frequency space that measure large optical frequency differences and/or straightforwardly link microwave and optical frequencies. One of the most successful uses of frequency combs beyond their original purpose has been dual-comb interferometry. An interferometer can be formed using two frequency combs of slightly different line spacing. Dual-comb interferometers without moving parts have no geometric limitations to resolution, therefore miniaturized devices using integrated optics can be envisioned. Dual-comb interferometers outperform state-of-the-art devices in an increasing number of fields including spectroscopy and holography, offering unique features such as direct frequency measurements, accuracy, precision, and speed.

Today, approximately 12,000 satellites orbit Earth. By 2030, estimates show numbers above 60,000. Today, we service spacecraft when absolutely necessary. By 2030’s, in-space services will be routine; refueling, repair, relocation, assembly, and manufacturing. Advances are underway to realizing this future, enabling a sustainable version will require photonics technologies.

I review the recent investigation results of our group’s on the design and fabrication of a cladding light stripper (CLS) with ultra-low backward scattering. The relationship between the roughness of the cladding surface and the backscattering of cladding light for the periodically grooved CLSs was investigated using a ray tracing method. A periodically grooved CLS structure with multiple unetched sections of a suitable length was found to efficiently suppress backscattering and verify its efficacy through numerical simulations. A CLS with 6-cm length of an LMA DCF with core and cladding diameters of 10 and 125 um was fabricated by using a hydrogen fluoride (HF)-free chemical etching technique considering fabrication and environmental safety. It was shown that the cladding attenuation was ~21 dB and the backward beam scattering level was much lower than that of commercially available CLSs.

Fiber bundles can transmit light effectively, and our clad fused bundle (CFB) technology allows high-power transmission (up to 6 kW) with low losses and flexible end shapes. However, for deep UV light, existing technologies degrade over time and have lower transmission. To address this, Lightguide has developed a new fiber bundle technology using carbon-coated hydrogen-loaded fibers, which resist solarization and maintain high transmission and durability in deep UV light. This technology is ideal for medicine, quality control, and UV curing applications. The presentation will cover spectral transmission, solarization, recovery characteristics, and manufacturing challenges.

We report an 8+1 to 1 pump-signal combiner (PSC) designed for backward pumping with higher-order mode content 19 dB lower than the fundamental mode in the output pigtail. The mode content is measured using the S2 measurement technique. The output beam M2 was near diffraction limited at M2 X of 1.23 and M2 Y of 1.21. The high signal beam quality is attributed to a high-quality taper and low overlap splice loss between the tapered fiber bundle and the output fiber. The combiner output fiber is large mode area with an LP01 mode field diameter of 33 µm at 1064 nm and mode effective area of 854 µm2. The large effective area of the output pigtail is ideal for low nonlinearity and high-power delivery. The additional pump ports allow for lower system weight by eliminating the additional layer of pump combiners (PC) in a PC+PSC tree of combiners and using higher power low brightness pump diode sources.

Delivering high power via fibers, and scaling the power level via arrays of such fibers is a crucial topic in many field of high power applications, in particular for materials processing, but also for long range energy delivery and others. Monolithic fiber connections to end caps, already known from freespace to fiber coupling of kW of optical power, can be expanded to 1D or even 2D fiber arrays, using a CO2-laser to splice each fiber sequential to an end cap substrate. As the CO2 laser radiation melts the glass at its surface, it realizes a monolithic glass-to-glass bond, enabling kW levels of power transmission through this interface without catastrophic damage. We report about an axicon setup for a ring-shaped CO2 laser focus illumination of local areas on an end cap substrate, to bond single or multimode fibers with a pitch of down to 250 micron in 1D or even 2D arrays to the substrate, at a lateral positioning tolerance <10 micron. A structured illumination of the ring allows for not damaging the previously assembled fibers, and the quality of bond enables high power transmission at lowest wavefront deformations.

The amplifier achieved a record gain of 47dB, meanwhile the ASE has been effectively suppressed to -40 dB below the laser signal. It shows wide dynamic range and can be operated with input as low as 10pW. Experiments have been performed by applying this novel design in Er-doped fiber amplifies at 1.5um and Yb-doped amplifier at 1.0um wavelength ranges, with running conditions of cw, directly driven 2ns laser pulses, model-locked 10ps fiber lasers, and mode-locked, dispersion-compensated 100fs soliton fiber lasers. The amplifiers especially outperform the traditional fiber amplifiers when operating at lower repetition rates where the ASEs are strongly competing with stimulated emissions.

Phase-shifted fiber Bragg gratings (PS-FBGs) are increasingly important in laser line filtering, optical communications, and fiber sensing due to their sensitivity and stability needs. In transmission, PS-FBGs with narrow bandwidths are sensitive to input power, affecting central wavelength stability. This study introduces stable 1 GHz and 4 GHz filters UV-written in polarization-maintaining and single-mode fibers at 1.55 µm. Using an optimized technique to reduce non-resonant absorption and improve thermal dissipation allow to achieve stability up to 100 mW, reducing sensitivity by 10 to 20 times. Radiation tests show minimal wavelength shift and no spectral distortion up to 8.5 kGy X-ray exposure, affirming suitability for space applications.

We have developed a Faraday isolator for high-power lasers using magneto-optical glass. The thermally induced depolarization of the glass was evaluated, and it was found that the depolarization ratio was lower than that of TGG. Furthermore, we fabricate an optical isolator with a φ12 mm aperture and evaluated its characteristics. Since glass has significant advantages in homogeneity and mass production, it can greatly contribute to quality stabilization of optical isolators.

The refractive index of optical materials varies with changes in temperature. This, in turn, leads to temperature dependent wavefront distortions in the application. However, temperature-dependent variations in the refractive index can be offset by the thermal expansion coefficient, which leads to what is called athermal glass behavior. A crucial element for designing athermal optics is a dependable database of the thermal coefficients of the refractive index for the optical materials.For many years, reliable data on these temperature coefficients have been a key component of the data sheets for optical glass. ISO has released two standards, ISO 6760-1 and 6760-2, focused on measuring the temperature coefficient of the refractive index. More and more applications need broadband dn/dT evaluations up to 2325 nm. Current measurement capabilities are limited to 1060 nm wavelength. Questions arise if extrapolation of dn/dT data from 1060 nm to 2325 nm is a valid approach. This presentation showcases measurement results between 1060 nm and 2325 nm in comparison to datasheet extrapolations for several different glasstypes.

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.

Interband cascade lasers (ICLs) are promising light sources for mid-infrared (MIR) sensing applications in the 3-6 μm range. Since their first room temperature continuous-wave (cw) operation in 2008, achieving a 0.7% wall-plug efficiency (WPE), significant advancements have been made to increase output power. Improvements include intrinsic modifications, such as optimizing the active region design and balancing carrier densities, and extrinsic optimizations in chip design and fabrication. Combining these strategies has resulted in the creation of single-mode GaSb-based ICLs that deliver over 50 mW of output power and achieve a 9% wall-plug efficiency (WPE) in continuous-wave (cw) operation at an emission wavelength of 3.3 µm. These advancements position ICLs as strong contenders for mid-infrared (MIR) sensing applications, providing both high efficiency and reliable performance at room temperature.

High power diode lasers, operating in long pulse width mode, require high reliability in the medical aesthetic application. In this study, we have developed a sophisticated high-performance diode laser device. For diode laser (LD) chips with a 1.5 mm cavity length at a wavelength of 808 nm, the thermal resistance is approximately 0.3 K/W. The thermal rollover power in continuous mode reaches 268 W, which is 40% higher than conventional MCCs with direct chip bonding. In quasi-continuous mode with 20 ms at 10 Hz, the maximum power reaches 345 W, marking a 15% enhancement compared to MCCs with direct chip bonding.

State-of-the-Art manufacturing processes are carried out using manual operators, which results into significant variations in the manufacturing process. This has negative effects on reproducibility and quality. A solution suitable for industrial use is a fully automated production concept using assembly robots. This high-precision assembly technology approach applied on the alignment of collimation lenses and on external cavity components provides sufficient precision as required for the best performance of the laser system. The presented solution provides positioning accuracy better than 100 nm in all three translation degrees of freedom and angle accuracy better than 1/100°. In-situ monitoring of the optical and spectral performance of each of the assembly and alignment process steps allows to make use of the alignment accuracy and results into the best possible reproducibility and performance. Application of this technology like alignment of external cavity lasers with Volume-Bragg-Grating or MEMS-Actuator as cavity mirror element are presented.

In this paper, we present the results of development of high power (30W) narrowband (10-50 GHz) laser system suitable for large area remote Raman application. The laser system was successfully used for detection of foodborne contaminants in variety of powder materials at the wavelength of 785 nm.

For semiconductor laser bars based on InP substrate, which has different physical properties from that of GaAs, it is necessary to develop packaging technologies with low thermal resistance and low packaging stress to achieve high reliability and high-power performance. We report here InP-based 1470 nm laser bar devices with passively conduction-cooled heatsink that feature low bonding stress and low thermal resistance, made through an innovative packaging process. For laser diode (LD) chips with a 2 mm cavity length, the thermal resistance of the devices is about 0.27°C/W, and the thermal rollover power can reach 60 W at 150 A under continuous wave (CW) conditions. Moreover, these LD devices demonstrate high reliability under hard-pulse operating conditions.

Phase-shifted Bragg gratings operate as a Fabry-Perot cavity to facilitate a narrow-band transmission line within the diffraction band of the grating. Such elements, when holographically encoded into a volume element, enable a host of technologies to become available in free-space regimes. Recent advances in PTR glass, a high-resolution medium used for the recording of volume Bragg gratings, have realized higher transmission efficiencies, allowing these elements to be used as a cost-effective laser-locking solution. Here, such a system is investigated, and future configurations are considered.

Ultrashort laser pulses and the phase mask scanning technique enable the inscription of VBGs in fused silica with low intrinsic absorption. These VBGs have improved the performance of stabilized laser diodes in high power applications in the NIR. To extend their application to the low VIS to near UV wavelength range, we are investigating their performance at higher Bragg orders. The dependence on inscription parameters and grating period is analysed.

We successfully designed and manufactured a semiconductor based miniaturized laser module operating at ambient room temperature at 619 nm to improve research and scaling of tin-diamond colour centres-based quantum repeaters. As design models we used thermal and optical simulations. An externally stabilized semiconductor laser is used. The wavelength stabilization is performed by a fibre Bragg grating, written into a single mode polarization maintaining FC/APC-fibre. We used a 14-pin butterfly module with an internal temperature of -20ºC. We demonstrated more than 10 mW at 619 nm ex fibre.

Volume Bragg Gratings (VBGs) in photo-thermo-refractive glass enable unmatched filter performance for ultra-low frequency Raman spectroscopy. High diffraction efficiency, combined with ultra-narrow bandwidth, provides simultaneous access to Stokes and anti-Stokes Raman modes with frequencies as low as 5cm-1. Recent advances in the VBG-based filter technology enabled fabrication of Bragg Notch Filters (BNFs) with an optical density of OD>7 in the 500-2500 nm spectral range with transmittance exceeding 95%. Maximal optical density of OD≥8 was achieved at the near IR spectral region. Such filters can be manufactured with standard (5cm-1) and reduced (2cm 1) spectral bandwidth. The new generation of BNFs significantly improves performance and simplifies the design of Raman spectroscopy systems.

In this paper,Short-term stabilization of Ti:sapphire laser was developed using µ-TEC water cooling system. It was observed that the output of laser changes periodically, similar to the crystal temperature change cycle. This is believed to be due to the heat exchange cycle of the crystal and the cooler. Firstly, the resonator with specification of 1 W, 100 fs, 80 MHz and 800 nm-center wavelength was developed. The oscillator is typical X-cavity and consists of gain medium, a half wave-plate, two concave mirror, three chirped mirror and two prism pairs for compensation of GVD.Then, we have designed, simulated using Ansys fluent and manufactured a water cooling system applied with µ-TEC devices. The experiment was conducted by comparing output efficiency between the µ-TEC cooling system we developed and the general water cooling chiller.

Titanium sapphire shows characteristics of poor output stability due to different laser cavity length due to thermal expansion of the gain medium. In this study, we have improved the problem of poor output stability. A Kerr lens mode locking titanium sapphire laser resonator with a specification of 1 W, 100 fs, and 800 nm-center wavelength was developed. The laser system was designed with a continuous light laser structure using titanium sapphire crystals as a gain medium, then distributed correction was performed by inserting a prism pair, and a manual mode locking pulse laser based on the Kerr lens effect was produced. Then, a water cooling system applied with a Peltier device was designed and applied to the laser system we developed. The experiment was conducted by comparing the cooling efficiency between the water cooling system to which the Peltier device was applied and the general water cooling chiller. Through the water cooling system to which the Peltier device was applied, the thermal properties of titanium sapphires with poor output stability could be improved. In addition, short term stability could also be improved.