Cryogenic Laser Research Articles

Single-fundamental-mode cryogenic (3.6 K) 850-nm oxide-confined VCSEL

Cryogenic oxide-confined vertical-cavity surface-emitting laser (VCSEL) has promising application in cryogenic optical interconnect for cryogenic computing. In this paper, we demonstrate a cryogenic 850-nm oxide-confined VCSEL at around 4 K. The cryogenic VCSEL with an optical oxide aperture of 6.5 μm in diameter can operate in single fundamental mode with a side-mode suppression-ratio of 36 dB at 3.6 K, and the fiber-coupled output power reaches 1 mW at 5 mA. The small signal modulation measurements at 298 and 292 K show the fabricated VCSEL has the potential to achieve a high modulation bandwidth at cryogenic temperature.

Synergistic Effects of Surface Texture and Cryogenic Treatment on the Tribological Performance of Aluminum Alloy Surfaces

In order to improve the tribological properties of the 7075-T6 aluminum alloy used on the rotor surface, a combined method of cryogenic treatment and laser surface texture treatment was applied. Various tests, including metallographic microscopy, scanning electron microscopy, elemental analysis, microhardness measurements, were conducted to examine the wear morphology and modification mechanism of the treated 7075-T6 aluminum alloy surface. A numerical simulation model of surface texture was established using computational fluid dynamics to analyze the lubrication characteristics of V-shaped texture. The research finding that the 7075-T6 aluminum alloy experienced grain refinement during the cryogenic treatment process, enhancing the wear resistance of the V-shaped textures. This improvement delayed the progression of fatigue wear, abrasive wear, and oxidative wear, thereby reducing friction losses. The designed V-shaped texture contributes to reducing contact area, facilitating the capture and retention of abrasives, and enhancing oil film load-bearing capacity, thereby improving tribological performance. The synergistic effect of cryogenic treatment reduced the friction coefficient by 24.8% and the wear loss by 66.4%. Thus, the combination of surface texture and cryogenic treatment significantly improved the tribological properties of the 7075-T6 aluminum alloy.

Optical bias and cryogenic laser readout of a multipixel superconducting nanowire single photon detector

Optical bias and cryogenic laser readout of a multipixel superconducting nanowire single photon detector

Impact of temperature on optical properties of Tm3+-doped disordered oxide crystals for cryogenic lasers emitting near 1.9 μm: a comparative study

Impact of temperature on optical properties of Tm3+-doped disordered oxide crystals for cryogenic lasers emitting near 1.9 μm: a comparative study

Fractional thermal load in cryogenically cooled Yb:YLF and Yb:YAG lasers

We present a method for the direct measurement of the fractional thermal load (FTL) in cryogenically cooled laser crystals. The experimental methodology involves characterizing the liquid nitrogen evaporation rate in a dewar containing the laser crystals, allowing for the accurate determination of FTL. The FTL is measured to be 1.7 × quantum defect (QD) for Yb:YLF and 1.5 × QD for Yb:YAG under continuous wave lasing conditions. The measured FTL values are then used to calculate the temperature distribution inside the crystals as a function of pump power, and the simulation results are found to be in very good agreement with the in-situ temperature measurements using contactless optical luminescence thermometry. The method and findings presented in this work hold great potential to benefit laser engineers and scientists working with cryogenic lasers to address and overcome temperature-dependent handicaps.

Surface integrity analysis of Si3N4 under cryogenic assisted femtosecond laser ablation

Femtosecond laser is suitable to process Si3N4, but heat effect forming during machining process could degrade the performance of specimen. To reduce heat damage, in this study, the effects of cryogenic assisted laser machining on the surface quality and micro-structures of Si3N4 was investigated. The femtosecond laser was employed to ablate Si3N4 at various low temperatures, accompanied with comprehensive analysis of the surface roughness, material removal rate and SEM topography. To further illustrate the formation mechanism of surface structure, finite element analysis was conducted. Results indicated that while low temperature exerted negligible effects in single-layer ablation, multi-layer laser machining benefits from improved surface quality. Low temperature mitigated thermal effects and reduced the recast layer area, resulting in decreased surface roughness. The lowest surface roughness was obtained during the machining of the specimen at −60 °C of 1.072 μm, representing a 54.6 % reduction compared to ambient air machining. However, further decreasing the temperature below −60 °C led to an increase in surface roughness. This was attributed to the combined effects of Gaussian beam energy distribution and low temperature, resulting in incomplete ablation of the surface region between two scanning pitches, thereby decreasing surface quality. This research provides valuable insights into the cryogenic assisted femtosecond laser machining.

Cryogenic assisted femtosecond laser ablation of polycrystalline diamond

Polycrystalline diamond (PCD) tools have gained popularity in machining industry ascribed to superior surface quality and durability at elevated temperature and abrasive forces. A major obstacle for high-speed PCD machining is the excessive heat production that transcend the heat dissipation capacity, resulting in reduced tool life and performance. Surface microstructures on PCD tools can improve thermal performance by increasing the heat transfer area and reducing the thermal contact resistance, therefore enhancement in durability and operation. Femtosecond laser processing is a non-contact, high precision and low thermal effect technique for creating superior quality microstructures. This study investigates the effects of cryogenic-assisted femtosecond laser processing in improvement of diamond microstructures quality. Initially the effects of different laser settings on the performance of the process were investigated by conducting single-factor experiments at ambient conditions. Later, the effects of cryogenic assistance on diamond irradiation, surface quality and chemical changes were investigated utilizing laser confocal scanning microscopy (LCSM), scanning electron microscopy (SEM) and Raman spectroscopy. Cryogenic laser ablation had no effect on the diamond removal rate, on contrary improved the surface quality by reducing the surface roughness and graphite disorderliness. This study reports superior surface quality finish for cryogenic assisted laser ablation than ambient conditions therefore it is recommended to irradiate PCD at low temperatures.

U(VI) sorption on illite in the presence of carbonate studied by cryogenic time-resolved laser fluorescence spectroscopy and parallel factor analysis

Identification of sorption species of uranium (U) on clay minerals by spectroscopic techniques would consolidate the reliability of predicted sorption models. However, it is still challenging, especially, under complex environmental conditions, where the surface loading is low, and quenching elements for spectroscopic analyses hamper the application. In light of this, the sorption of U(VI) on illite at different pH and dissolved inorganic carbon (DIC) levels was investigated by using batch experiments, surface complexation modeling, and cryogenic time-resolved laser fluorescence spectroscopy (cryo-TRLFS) combined with parallel factor analysis (PARAFAC). The inhibiting effect of DIC on U(VI) sorption was revealed by the macroscopic batch experimental results. However, there was still sorption of U(VI) on illite even at a high DIC (19 mM), validating certain retention capacities of illitic clay minerals for U(VI) even from pore waters with high DIC. An updated 2-site protolysis non-electrostatic surface complexation and cation exchange model considering the formation of two uranyl-carbonate sorption complexes was able to reproduce the experimental results well. Based on the PARAFAC analysis on the cryo-TRLFS spectra, there was clear correspondence in the variation trend of the derived components with the sorption species from the modeling results, validating the formation of ternary uranyl-carbonate sorption species. The results imply that ternary uranyl-carbonate sorption species need particular consideration in the modeling of U(VI) sorption on clay minerals at high DIC levels. Identifying the sorption species adds more credibility to the predictive sorption model, which provides more confidence in the safety assessment of deep geological disposal. In addition, these results help better understand the fate of uranium during transport in geological disposal-related environments.

67.5% Efficient InP-Based Laser Power Converters at 1470 nm at 77 K

Recent developments in long wavelength and cryogenic laser power converters have unlocked record performances in both areas. Here, devices for an optical input at ~1470 nm are studied for cryogenic applications, combining these cryogenic and long-wavelength attributes. Multijunction laser power converters are demonstrated to have a high-efficiency operation at 77 K. The photovoltaic-power-converting III-V semiconductor devices are designed with InGaAs-absorbing layers, here with 10 thin subcells (PT10), connected by transparent tunnel junctions. Unprecedented conversion efficiencies of up to 67.5% are measured at liquid nitrogen temperatures with an output power of Pmpp = 1.35 W at an average optical input intensity of ~62 W/cm2. A remarkably low bandgap voltage offset value of Woc~50 mV is obtained at an average optical input intensity of ~31 W/cm2.

Grain structure and intermetallic evolution of Nb-containing FeCrAl alloy treated by cryogenic laser quenching

Thin-walled FeCrAl alloy tubes emerge as significant contenders for substituting zirconium alloy cladding tubes. Enhancing the surface strength and corrosion resistance of these tubes is essential for their industrial utilization. Cryogenic laser treatment emerges as a promising technique for enhancing the surface corrosion resistance of Nb-containing FeCrAl alloy. A comprehensive investigation was carried out to study the evolution of solidification structure in a Nb-containing FeCrAl alloy subsequent to cryogenic laser quenching, with the intention of augmenting the mechanical characteristics of the alloy surface. A refined composite structure, consisting of planar-columnar-equiaxed crystals, was identified on the surface of the sample. We have made observation of an amorphous precipitated phase, which is recognized as the intermediate phase found between the Laves phase and ferrite phase. The presence of amorphous precipitates exerts a beneficial influence on the surface hardness and strength of the alloy. Our study delves into the exploration of the causes for the amorphous phase and conducts an analysis of the structural evolution during its recrystallization.

Tracking and imaging nano-plastics in fresh plant using cryogenic laser ablation inductively coupled plasma mass spectrometry

Tracking and imaging of nano-plastics are extremely challenging, especially in fresh biological samples. Here, we propose a new strategy in which polystyrene (PS) was doped with the europium chelate Eu (DBM)3bpy to quantify, track, and in situ image nano-plastics in fresh cucumber based on inherent metals using cryogenic laser ablation inductively coupled plasma mass spectrometry (cryo-LA-ICP-MS). The cryogenic conditions provide a stable condition for imaging fresh cucumber, suppressing the evaporation of water in fresh plants, and maintaining the original structure of plants with respect to room temperature imaging in LA-ICP-MS. The plants were cultivated in two types of nano-plastics solutions with low (50 mg/L) and high (200 mg/L) concentrations for 9 days. The results showed that nano-plastics mainly enrich the roots and have negative effects, which decrease the trace elements of Zn, Mn, and Cu in cucumber. Smaller PS particles are able to penetrate the plant more easily and inflict serious damage. Novel imaging method provides a novel insight into the tracking and imaging of nano-plastics in fresh plant samples. The results illustrated that nano-plastics deposition on plants has the potential to have direct ecological effects as well as consequences for potential health.

Identification and Localization of Labile Molecules in Broccoli Cell by CLA-ICP-MS and Single-Cell Nanospray HRMS.

Although molecular analysis and imaging by mass spectrometry are emerging as tools to identify metabolites and determine their distribution in cells and tissues, it is difficult to directly analyze the labile molecules at the single-cell level. Glucosinolate (GL) is a plant-active substance with much attention as a chemical defense mechanism known as a "mustard oil bomb" in broccoli. When tissue is damaged, these substances undergo rapid degradation, making them unsuitable for conventional mass spectrometry (MS), particularly for surface MS imaging analysis methods that necessitate intricate preprocessing. Herein, a strategy combining cryogenic laser ablation inductively coupled mass spectrometry (CLA-ICP-MS) and capillary microsampling nanospray high-resolution mass spectrometry (HRMS) was developed. The sulfur-rich microzone in tissue which was thought as a suspect GL-rich cell population was located via CLA-ICP-MS. Three GLs in single cells were accurately identified by nanospray HRMS with a hydrogen/deuterium exchange reaction. Subsequently, cell-by-cell imaging by nanospray HRMS showed that the GL-rich cells were below the stalk surface by approximately 30 μm. This proposed strategy can also be applied to rapidly identify labile compounds and localize molecule-rich cells in tissues.

Cryogenic slab RF discharge CO laser with hybrid waveguide-unstable resonators

Dependences of a cryogenic slab radio-frequency discharge CO laser output power on a distance between mirrors of a hybrid negative-branch waveguide-unstable resonator were experimentally studied. The maximum output power was observed at the resonator length longer than the one calculated by taking into account the mirrors radii of curvature. Optimization of the resonator length made it possible to get the output power increase up to 20%–25%. The results obtained can be used for designing not only slab laser systems with hybrid waveguide-unstable resonators, but also for high-power lasers with full-sized negative-branch unstable ones.

High energy, high pulse rate laser operation using crystalline adhesive-free bonded Yb:YAG slabs.

We report on the successful amplification of 10 ns pulses to 10 J energy at 10 Hz in a DiPOLE laser amplifier using crystalline Yb:YAG/Cr:YAG composite slabs manufactured using adhesive-free bonding (AFB) technology. We demonstrate that bonded slabs are suitable for operation in high energy cryogenic laser amplifiers. We also report on frequency doubling of the beam amplified in the bonded slabs. When the pulse energy of the output infrared beam is set to 5 J, a pulse energy of 3.9 J is achieved in the green (corresponding to 78% conversion efficiency). Results demonstrate that AFB technology is suitable for producing large-sized gain material slabs and can overcome current limitations in the manufacture of large-aperture gain material pieces. We believe this work will facilitate energy scaling of high energy lasers where aperture scaling of optical elements is not achievable via conventional manufacturing techniques.

Evaluation of Lithium Metal Anode Volumetric Expansion through Laser Plasma Focused Ion Beam Cross-Sectional Imaging

Lithium metal is an ideal anode for high energy density batteries, however the implementation of lithium metal anodes remains challenging. Beyond the development of highly efficient electrolytes, degradation processes restrict cycle life and reduce practical energy density. Herein lithium volumetric expansion and degradation pathways are studied in half cells through coupling electrochemical analysis with cross-sectional imaging of the intact electrode stack using a cryogenic laser plasma focused ion beam and scanning electron microscope. We find that the volumetric capacity is compromised as early as the first cycle, at best reaching values only half the theoretical capacity (1033 vs 2045 mAh cm−3). By the 101st electrodeposition, the practical volumetric capacity decreases to values ranging from 143 to 343 mAh cm−3.

Effect of cryogenic laser surface modification on the microstructure evolution and corrosion resistance of accident-tolerant FeCrAl alloys

Accident-tolerant FeCrAl alloys require a thinner cladding wall than zirconium cladding to overcome the extra neutron loss, thus requiring enhanced corrosion resistance. Surface treatment was used in this study to address this issue via cryogenic laser surface modification. A finite element model based on heat-transfer theory was raised to reveal the temperature field change during cryogenic laser treatment. The relationship between the laser processing parameters and surface morphology was studied with various characterizations to better understand the process mechanism and verify the correctness of the model. Hydrothermal corrosion test was proceeded in an autoclave at 290 °C and 7.5 MPa for 150 h to examine the enhancing corrosion resistance. STEM observations were used to study the microstructure evolution by cryogenic laser processing and corrosion. Electrochemical tests were performed to analyze the relationship between processing parameters and corrosion resistance before and after corrosion. The oxide film thickness and corrosion rate of the cryogenic laser-modified sample were 66 % and 80 % smaller than the as-received sample. The enhanced corrosion resistance was attributed to the microcrystalline layer and the thin duplex passive film that formed during the cryogenic laser process.

Ultra-stable cryogenic sapphire cavity laser with an instability reaching 2 × 10-16 based on a low vibration level cryostat.

Cryogenic ultra-stable lasers have extremely low thermal noise limits and frequency drifts, but they are more seriously affected by vibration noise from cryostats. Main material candidates for cryogenic ultra-stable cavities include silicon and sapphire. Although sapphire has many excellent properties at low temperature, the development of sapphire-based cavities is less advanced than that of silicon-based. Using a homemade cryogenic sapphire cavity, we develop an ultra-stable laser source with a frequency instability of 2(1) × 10-16. This is the best frequency instability level among similar systems using cryogenic sapphire cavities reported so far. Low vibration performance of the cryostat is demonstrated with a two-stage vibration isolation, and the vibration suppression is optimized by tuning the mixing ratio of the gas-liquid-helium. With this technique, the linear power spectral densities of vibrations at certain frequencies higher than tens of hertz are suppressed by two orders of magnitude in all directions.

Exploring Structure-Sensitive Factors Relevant to Cryogenic Laser Operation in Oxide Crystals Doped with Er3+ Ions.

Crystals of Gd3Al2.5Ga2.5O12:Er3+, (Lu0.3Gd0.7)2SiO5:Er3+ and LiNbO3:Er3+ compounds differing in origin and the nature of their inherent structural disorder were crystalized. Optical absorption and luminescence spectra for transitions between the 4I15/2 and the 4I13/2 multiplets of Er3+ ions for the crystal samples were recorded versus temperatures in the region of 80-300 K. Gathered data were analyzed thoroughly providing the in-depth knowledge of the effects of temperature on intensities, wavelengths and bandwidths of Er3+ transitions. The information acquired together with the knowledge of significant structural dissimilarities of the host crystals chosen made it possible to propose an interpretation of the impact of a structural disorder in Er3+-doped crystals on their spectroscopic properties, and to determine their lasing ability at cryogenic temperatures upon resonant (in-band) optical pumping.

Quantitative imaging of fluorine in human teeth by cryogenic laser ionization time-of-flight mass spectrometry

Cryogenic laser ionization time-of-flight mass spectrometry provides a new quantitative imaging technique to reveal F distribution in human teeth.

Direct Quantitative Analysis of Fluorine in Solid Samples by Cryogenic Laser Ablation and Ionization Time-of-Flight Mass Spectrometry.

The determination of fluorine, the lightest element in halogens, suffers from high ionization potential and spectral interference from water molecules in mass spectrometry. Herein, we introduced a liquid nitrogen cooling unit into the laser ablation and ionization source for the first time to construct a cryogenic laser ablation and ionization time-of-flight mass spectrometry (Cryo-LAI-TOFMS) system. With this system, the interference of water-related species at m/z 19 was effectively eliminated, and fluorine atomization and ionization efficiency could reach 6.3%. A direct quantitative analysis method was developed to determine fluorine contents in phosphate rock, copper ore, industrial byproduct gypsum, stream sediment, and soil. Considering the simplicity, high sensitivity, and low spectral interference of this technique, it can be extended to the determination of fluorine content as low as μg/g in complex solid samples.