Laser-ablated Surface Research Articles

Three-dimensional surface analysis of iron-based materials using synchrotron Mössbauer source

A novel three-dimensional surface analysis system for iron-based solid materials has been developed. This system is composed of a synchrotron Mössbauer source, an X-ray focusing device, a precision stage, a gas flow proportional counter for conversion electron measurements, and multiple multichannel scalers. The performance was evidenced by determining the spatial distribution of the iron oxide abundance on a laser-ablated iron foil surface. This system can be widely utilized as a powerful analytical tool in steel science for corrosion, welding, and laser surface modification.

Experimental investigation on microstructure, mechanical and optical properties of RB-SiC ablated by nanosecond pulsed laser in nitrogen atmosphere

Reaction-bonded silicon carbide (RB-SiC) has gained significant attention owing to its exceptional physical and chemical properties. Improving the photovoltaic efficiency and mechanical properties of RB-SiC is conducive to further enhancing its applicability. Laser gas nitriding is an effective strategy to simultaneously reduce the surface reflectivity and enhance the surface hardness of materials. Accordingly, the evolution of microstructure, mechanical and optical properties of RB-SiC composite ablated by nanosecond pulsed laser in nitrogen atmosphere was comprehensively investigated. After laser gas nitriding, the surface hardness of RB-SiC composite was increased by 10.6–44.6 %. The chemical composition analysis indicated that Si-based nitride was formed on the laser-ablated surface, which was mainly responsible for the hardness enhancement. Additionally, the reflectivity of the laser-ablated surface was reduced by up to 95.2 % compared to the original RB-SiC composite. This study provides a straightforward and effective method to simultaneously improve the mechanical and optical properties of RB-SiC composites.

Experimental study of nucleate boiling heat transfer of refrigerant-oil mixture on various modified surfaces

As a crucial component of refrigeration and heat pump system, the evaporator performance directly affects system efficiency. Due to the lubricating oil in the compressor circulating into the evaporator, studying the nucleate boiling heat transfer (NBHT) of refrigerant-oil mixture is of greater practical and guiding significance. Surface modification technology has opened up a new avenue for enhancing NBHT of refrigerant-oil mixture. Therefore, experimental study was conducted on NBHT characteristics of R134a-POE mixture and R1234ze(E)-POE mixture on smooth surface, initial laser-ablated surface, stabilized laser-ablated surface, machined surface, and composite processed surface. The effects of oil concentration (ω), surface microstructure and surface wettability on NBHT of refrigerant were discussed and analyzed, and the underlying heat transfer mechanisms were elucidated. The research indicates that for NBHT of refrigerant-oil mixture, surface microstructure has a greater impact than surface wettability. To enhance heat transfer coefficient (HTC), it is crucial to establish a surface pattern comprising alternating regions of high and low nucleation sites to mitigate bubble interaction and coalescence. Once this objective is attained, enhancing surface wettability can be contemplated. The addition of oil promotes foaming and induces tornado-shaped bubble group, which facilitate heat transfer. However, the rise in mixture viscosity and surface tension exerts a more pronounced adverse effect on heat transfer, outweighing the positive impacts of foaming and tornado-shaped bubble group. Consequently, the presence of oil diminishes HTC. And as ω and heat flux increase, HTC further decreases. Additionally, the increase in vaporization nuclei on modified surface leads to a higher local ω, the increase in ω further weakens the enhanced heat transfer effect of modified surface, and thus narrows the difference in HTC among various modified surfaces. The research results aim to uncover the mechanisms by which surface wettability, surface microstructure, and lubricating oil affect NBHT of refrigerant.

Experimental investigation on wettability of refrigerants on laser-ablated surfaces

Due to the refrigerant's low surface tension, it is difficult to increase its static contact angle (SCA) on the surface. Existing studies all employed the method of low surface energy coating to increase the SCA of the refrigerant on the surface, but this method has the drawback of coating peeling. In this study, the SCAs of R134a and R1234ze(E) refrigerants on the surface were increased using a simple and reliable laser surface texturing technique. The results showed that the SCAs of R134a and R1234ze(E) on the polished surface were 6.2° and 6.4°, respectively, indicating that the surface was superhydrophilic. Immediately after laser ablation, the surface hydrophilicity was improved with SCA approaching 1° due to the increase in surface roughness and the oxidation effect of the surface. However, over time, the laser-ablated surface adsorbed substances containing hydrophobic C-C(H) groups, resulting in a gradual increase in SCA. The steady-state SCAs of R134a and R1234ze(E) on the laser-ablated surface were 12.2° and 12.7°, respectively, which were about twice the SCAs of the refrigerants on the polished surface. In terms of the increased percentage of SCA, the laser surface texturing technique is effective in increasing the hydrophobicity of the refrigerant on the surface.

Inert ambiance-assisted laser ablation of CVD diamond leads to enhanced surface quality and grindability

Diamond is a versatile ultimate engineering material that has been recommended for numerous purposes, especially micro mills. Laser-assisted precision grinding is substantiated to be a promising approach for fabricating diamond micro tools. Yet, in practice, the short pulses that render express elimination will deteriorate the flatness of the tool surfaces, bringing about a boost in the risk of edge collapse and a shrink in yield during the subsequent precision grinding. The tactic of ambiance-assisted laser ablation, which introduces an auxiliary gas during the irradiation to promote the ablated domain quality, is proposed in this investigation. Specifically, a raster scanning-based transient temperature distribution simulation is erected to comprehend the ablation mechanism of the chemical vapor deposition (CVD) diamond. Additionally, it can be deduced that the inert nitrogen with high cohesive energy curbs the instantaneous deflagration of oxidation on the Knudsen layer and the activity of dangling bonds that are desorbed at high temperatures. The nitrogen-assisted laser ablation of the diamond sample leads to a maximum dwindling in surface roughness of 33% compared to that with non-ambiance-assisted. Subsequently, the laser-ablated surface optimized by an inert atmosphere is precisely ground with a fine abrasive grinding wheel. The detection of the sharp cutting edge ( r β = 1.74 μm) with almost no notch and the ground flank surface with the roughness of 168 nm indicates that accessing the inert auxiliary atmosphere during ablation can enhance the surface quality of the machined diamond and the corresponding grindability.

Hierarchical composite structure to simultaneously realize superior superhydrophobicity and anti-reflection

Superhydrophobicity and anti-reflection of metallic surfaces have potential applications, and obtaining superhydrophobicity on metallic surfaces by simple methods is still a challenge. The composite microstructure consisting of micro-protrusions, micro-lumps and particles was fabricated on aluminum surface by laser ablation. A layer of hydrophobic species that can prevent the surface from being wetted formed on the microstructure through organic adsorption. In particular, laser ablation parameters were optimized to achieve better superhydrophobicity and anti-reflection. The fabricated superhydrophobic surfaces showed contact angles > 165° for water and contact angles > 160° for high-concentration solutions and high-viscosity solutions. Conventional bounce contact time < 10 ms was exhibited for water droplets impacting on fabricated surfaces, especially, the shortest contact time reaching 9.4 ms. anti-reflection was also realized on the laser-ablated aluminum surface, and specular reflections were almost completely avoided by laser ablation structures. The mechanism of the transition from superhydrophilic to superhydrophobic on fabricated surfaces was discussed. Superhydrophobic aluminum surfaces with anti-reflection could be efficiently manufactured in a few hours without special equipment and harsh condition through the proposed two-step method.

Real-Time (iOCT) Guided Epiretinal Membrane Surgery Using a Novel Forceps with Laser-Ablated Microstructure Tip Surface.

Purpose: We investigated intraoperative OCT (iOCT)—guided epiretinal membrane (ERM) and internal limiting membrane (ILM) removal using a novel forceps with a laser-ablated tip surface; it was designed to help prevent indentation force, shear stress, or tractional trauma when grasping very fine membranes. Patients and Methods: This retrospective study included patients who underwent 23- and 25-gauge pars plana vitrectomy (PPV) for vitreoretinal interface disorders. ERM and ILM peeling was performed under guidance with microscope-integrated iOCT using novel ILM forceps with laser-ablated tip surfaces. These forceps were engineered to enhance friction when grasping tissue. Evaluation of ERM/ILM manipulation included postoperative slow-motion video analysis of the number of grasping attempts, initial ILM mobilization, and observed damage to retinal tissue. Results: ERM/ILM removal was successfully performed in all patients, with an average of four grasp actions to initial membrane mobilization (91%). Additional use of a diamond-dusted membrane scraper was used in two cases (9%). Mean best-recorded visual acuity (BRVA) logMAR improved from 0.5 ± 0.34 to 0.33 ± 0.36 (p = 0.05) and mean central retinal thickness (CRT) improved from 462 ± 146 µm to 359 ± 78 µm (p = 0.002). Postoperative iOCT video analysis demonstrated hyper-reflectivity of the inner retinal layers associated with retinal hemorrhage in five eyes (22%), but no grasping-related retinal breaks. Conclusions: The texturized surface on the tips of the ILM forceps were found to be helpful for mobilizing ILM edges from the retinal surface. iOCT-guided ERM surgery also allowed for improved intraoperative tissue visualization. We believe that these two technologies helped reduce both unnecessary surgical maneuvers and retinal damage.

Long-term osseointegration of laser-ablated hearing implants in sheep cranial bone.

Osseointegration, the ability for an implant to be anchored in bone tissue with direct bone-implant contact and allowing for continuous adaptive remodelling, is clinically used in different reconstructive fields, such as dentistry, orthopedics and otology. The latter uses a bone conducting sound processor connected to a skin-penetrating abutment that is mounted on a titanium implant placed in the temporal bone, thereby acting as a path for transmission of the vibrations generated by the sound processor. The success of the treatment relies on bone healing and osseointegration, which could be improved by surface modifications. The aim of this study was to evaluate the long-term osseointegration in a sheep skull model and compare a laser-ablated implant surface with a machined implant. Commercially available 4 mm titanium implants, either with a machined (Wide Ponto) or a laser-ablated surface (Ponto BHX, Oticon Medical, Sweden), were used in the current study. The surfaces were evaluated by scanning electron microscopy. The implantation was performed with a full soft tissue flap and the osteotomy was prepared using the MIPS drill kit (Oticon Medical, Sweden) prior to installation of the implants in the frontal bone of eight female sheep. After five months, biopsies including the implant and surrounding bone tissue obtained, processed and analysed using histology, histomorphometry, scanning electron microscopy and Raman spectroscopy. The animals healed well, without signs of adverse events. Histomorphometry showed a large amount of bone tissue around both implant types, with 75% of the threaded area occupied by bone for both implant types. A large amount of bone-implant contact was observed for both implant types, with 67%–71% of the surface covered by bone. Both implant types were surrounded by mature remodelled lamellar bone with high mineral content, corroborating the histological observations. The current results show that the laser-ablated surface induces healing similar to the well-known clinically used machined surface in ovine cranial bone. In conclusion, the present long-term experimental results indicate that a laser-ablated implant performs equally well as a clinically used implant with a machined surface. This, together with previously reported, improved early biomechanical anchorage, suggests future, safe and efficient clinical potential.

Achieving Superhydrophobicity of Zr-Based Metallic Glass Surfaces with Tunable Adhesion by Nanosecond Laser Ablation and Annealing.

Tuning the surface wettability and adhesion of metallic glasses (MGs) is a promising approach to enrich their engineering applications. In this study, using nanosecond laser ablation in air, hierarchical micro/nanostructures were directly fabricated on a Zr-based MG surface. Following subsequent annealing, the surface exhibited superhydrophobicity (maximum contact angle: 166°, minimum sliding angle: 2°). Furthermore, the superhydrophobic surface could be tuned from low to high surface adhesion force by controlling the laser-ablated spot interval. By analyzing the laser-ablated structures and surface chemical compositions, the superhydrophobicity was related to the formation of hierarchical micro/nanostructures and the absorption of organic compounds with low surface free energy in air, and the change in surface adhesion force was attributed to the difference in surface roughness. The experimental results showed that the superhydrophobic surface with low adhesion force could be used in self-cleaning applications, while the superhydrophobic surfaces with different adhesion forces could be used in no-loss liquid transportation. This study provides an efficient and low-cost way to fabricate superhydrophobic MG surfaces with tunable adhesion, which will broaden the functional applications of MGs.

Laser-Induced Slippery Liquid-Infused Surfaces with Anticorrosion and Wear Resistance Properties on Aluminum Alloy Substrates.

Slippery liquid-infused surfaces (SLISs) are developed as a potential alternative to superhydrophobic surfaces (SHSs) to resolve the issues of poor durability in corrosion protection and wear resistance. In this work, we used a simple laser processing technology to prepare a SLIS on the aluminum alloy (7075) surface. The superhydrophobicities of the modified surface and the oil film formed by liquid injection make the corrosive medium difficult to directly contact the surface and thus have a significant effect on corrosion resistance. The water and oil repellent SLIS exhibits durable corrosion resistance and excellent tribological properties compared with the SHS. The anticorrosion and wear resistance performances provided by the composite film have been assessed by multiple methods including the electrochemical test, immersion test, and friction wear test. The results indicate that compared to the bare surface, laser-ablated surface (LAS), and fluoroalkyl silane-modified SHS, the SLIS composite coating has better corrosion resistance and wear resistance, which is of great significance to expand the potential applications of 7075 aluminum alloys. The work provides a research basis for expanding the practical application of SLISs in complex environments.

Femtosecond Laser Treatment for Improving the Corrosion Resistance of Selective Laser Melted 17-4PH Stainless Steel.

Currently, laser surface treatment (LST) is considered the most promising method available within the industry. It delivers precise control over surface topography, morphology, wettability, and chemistry, making the technique suitable for regulating the corrosion behavior of alloys. In this paper, femtosecond laser texturing with different parameters and atmosphere environments was adopted to clarify the effect of surface treatment on the corrosion resistance of selective laser melted (SLM-ed) 17-4PH stainless steel (SS) in a NaCl solution. The experimental results show that, after the heat treatment, the corrosion resistance of the laser-treated samples was enhanced. With the further laser treatment in an argon atmosphere, the oxidation of nanostructural surfaces was avoided. The Cr, Cu, and other alloying elements precipitated on the laser-ablated surface were beneficial to the formation of a passivation film, leading to an improved corrosion resistance performance.

Femtosecond Laser-Ablated Copper Surface as a Substrate for a MoS2-Based Hydrogen Evolution Reaction Electrocatalyst.

One of the methods to improve the performance of a heterogeneous electrocatalyst is the dispersion of a catalytic material on a suitable substrate. In this study, femtosecond laser ablation was used to prepare very rough but also ordered copper surfaces consisting of vertical, parallel ridges. Then, a molybdenum sulfide coating was electrochemically deposited onto these surfaces. It was observed by profilometry that the average roughness of the surface after coating with MoS2 had decreased, but the developed surface area still remained significantly larger than the projected surface area. The electrodes were then used as an electrocatalyst for the hydrogen evolution reaction in acidic media. These were highly efficient, reaching 10 mA cm−2 of HER current at a −181 mV overpotential and a Tafel slope of ~39 mV dec−1. Additionally, scanning electrochemical microscopy was used to observe whether hydrogen evolution would preferentially occur in certain spots, for example, on the peaks, but the obtained results suggest that the entire surface is active. Finally, the electrochemical impedance spectroscopy data showed the difference in the double-layer capacitance between the ablated and non-ablated surfaces (up to five times larger) as well as the parameters that describe the improved catalytic activity of fs-Cu/MoS2 electrodes.

UV laser-ablated Cu superwetting surface with improved anti-icing and antibacterial properties

Ultraviolet laser-ablated technique was used to improve the anti-icing and antibacterial properties of copper (Cu) with the objective of achieving efficient heat exchange performance. The laser scanning space interval exhibited a critical influence on the surface topography. SEM observation showed that nano-villi-like products appeared on the surface, which resulted in the formation of a micro/nano-hierarchical structure when the scanning interval was below 40 µm. When the scanning space interval was above 40 µm, the surface presented only a micron-level papilla/groove pattern without any nano-villi-like product. Combined analysis of XRD, TEM, and XPS results indicated that the nano-villi products were partially crystallized copper oxide particles with 5–10 nm size. It was speculated that nano-oxide was obtained by vapor deposition of Cu caused by laser ablation. Furthermore, after modification with FAS-17, the hydrophobicity of the nano-villi-like surface became significantly higher than that of the papilla/groove surface. The highest water contact angle reached 156.30 ± 0.53° and the water sliding angle was as low as 1.57 ± 0.99°. In the anti-icing test at − 10 °C, the delayed freezing time of this superhydrophobic surface reached 9923 s. This excellent anti-icing property can be attributed to the improvement in critical activation energy for ice nucleation and reduction in interfacial thermal conductivity caused by superhydrophobic surface. Finally, the inhibition zone test proved that laser ablation could significantly improve the antibacterial activity of Cu against E. coli and S. aureus.

Microstructures and mechanical properties of Zr-based metallic glass ablated by nanosecond pulsed laser in various gas atmospheres

The surface with micro-convex prepared by laser ablation is beneficial to improving the functional properties of metallic glasses (MGs). However, accompanied by the formation of micro-convex, surface hardness of the ablated area generally decreases due to the softening effect caused by laser thermal shock. Previous studies have shown that the mechanical properties of laser-ablated MG surface are significantly different when using different gas atmospheres. In this study, a comparative investigation was performed to analyze the influence of gas atmosphere (i.e. argon, nitrogen, and air) on the formation of micro-convex as well as its surface characteristics and mechanical properties. Experimental results showed that the atmosphere type did not affect the formation of micro-convex, but significantly affected the surface morphology and element composition of the laser-ablated area. The element analysis and Raman spectral measurements indicated that laser ablation in nitrogen or air atmosphere resulted in local nitridation or oxidation. The results of nanoindentation tests demonstrated that laser ablation in nitrogen or air atmosphere also resulted in surface hardness inhomogeneity, i.e., softening and hardening effects coexist in the ablated area, which could be attributed to the combined influence of laser thermal shock, the introduction of secondary phase as well as laser ablation induced loose structure.

Investigation of the influence of the scanning speed and step in laser marking and engraving of aluminum

Marking and engraving of aluminum was carried out by a CuBr (copper bromide) laser operating at the wavelength of 511 nm with a pulse duration of 30 ns. The reflection was investigated of the laser-ablated aluminum surface depending on the laser beam scanning speed and the distance between the laser lines. The changes of the aluminum surface were observed before and after laser processing by an optical microscope and visually. The laser marking quality was estimated by measuring the reflection of the irradiated aluminum surface by an optical spectrometer. The dependence was analyzed of the contrast on the speed for different steps in laser marking of areas of the surface of aluminum samples. Marking by a CuBr laser shows a potential for good quality marking of barcodes and QR codes on aluminum products.

Transient boiling of a droplet stream quenching microstructured surfaces

We experimentally investigate the transient flow boiling that takes place when a stream of ethanol droplets starts impinging on a heated copper plate. If the initial surface temperature is sufficiently high, the flow boiling develops from film boiling, to transition boiling and then nucleate boiling, while the flow behavior development shows repelling, contacting, and pooling stages. Copper plates with laser-ablated surface microstructures are used in the tests to investigate the effects of surface microstructures on the boiling regimes. It is found that film boiling can be achieved on microstructured surfaces with lower initial temperatures as compared to the smooth surface. This observation is supported by boiling curve analysis, which noticeably shows the Leidenfrost temperature decreases with increasing surface roughness. It is also found that surface microstructures slightly reduce the Nukiyama temperature. This work is relevant to two-phase spray cooling in high temperature boiling regimes.

Femtosecond laser preparing patternable liquid-metal-repellent surface for flexible electronics

HypothesisControlling the wetting behaviour of gallium-based liquid metal is highly desired for soft electronics applications. Currently, achieving durable and patternable liquid-metal-repellent surfaces by a simple and flexible method is challenging. The femtosecond laser has a remarkable ability to modify the morphology and wettability of a solid surface. It can also potentially be applied to control the wettability of liquid metal and achieve complete liquid-metal patterns. ExperimentsFemtosecond laser processing was used to form a microstructure on a polydimethylsiloxane (PDMS) surface. With regard to the laser-ablated surface, its morphology was observed by a scanning electron microscope, and its wettability to liquid metal was characterized by measuring the contact angle, sliding angle, and adhesive force. Finally, its potential applications in soft electronics were demonstrated. FindingsA layer of micro/nanostructures was directly prepared on the PDMS surface by laser ablation, presenting excellent liquid-metal repellence. Without expensive masks and complex operation processes, programmable liquid-metal-repellent patterns were easily obtained by femtosecond laser selectively treating the PDMS surface, enabling EGaIn to be patterned on the textured surface. The as-prepared liquid-metal patterns can be used as a flexible microheater and a microstrip patch antenna. It is believed that laser-patterned liquid-metal-repellent surfaces will have significant applications in soft electronics, such as antennas, microcircuits, lab on chips, and wearable electronic devices.

Rapid laser fabrication of long-term stable superhydrophilic aluminum surface

A simple method for fabricating stable superhydrophilic aluminum surface is reported in this paper. Controllable micro-nanostructures were prepared on the surface of aluminum plate by nanosecond laser and then soaked in boiled 45% ethanol solution for 2 h as the post-treatment. It is demonstrated that the laser-ablated aluminum plate surface is hydrophilic and then switch to superhydrophilic after a 45% ethanol solution post-treatment. The treated superhydrophilic structure has good hydrophilic stability in a certain period of time. The mechanism of superhydrophilic behavior of aluminum surface treated with laser and ethanol solution was discussed. A new method for preparing stable superhydrophilic surface is proposed in this paper, which is of great significance for the preparation of superhydrophilic surface and the application of superhydrophilic surface in industrial production.

Laser ablation of silicon in water at different temperatures

Underwater laser machining process is an alternative method to cut materials with less thermal damage due to the water cooling of workpiece during the ablation. However, the rapid cooling induced by water can instantly solidify the laser-molten material rather than expel it to form a cut. To understand the roles of processing temperature on ablation performance in water, this paper presents the influences of water temperature on cut width, depth, and surface morphology in the underwater laser grooving of silicon. The effects of laser power, laser traverse speed, and number of laser passes on the groove characteristics were also examined in this work. The results revealed that using high water temperature can increase the groove aspect ratio, particularly when high laser power, slow traverse speed, and multiple laser passes were employed. However, debris deposition and oxides were found on the laser-ablated surface when processing at high water temperature. The implication of this study could enhance the ablation rate for the underwater laser as well as low-power laser cutting systems.

Optical coherence tomography characterizes the roughness and thickness of the heterogeneous layer on cortical bone surface induced by Er:YAG laser ablation at different moisture contents.

As an innovative bone ablation tool, pulsed erbium: yttrium-aluminum-garnet (Er:YAG) laser is being used in clinical practice. It faces the same problems as traditional tools: the water content of bone usually changes with the position, while the amount of water spray in the process of laser irradiation is also uncertain. Real-time monitoring of the effects of laser bone ablation is necessary, but effective tools are still lacking. In this study, we examined the feasibility of rapidly and non-destructively evaluating the surface properties of bone after Er:YAG laser irradiation at different moisture contents by optical coherence tomography (OCT). Bone specimens (n=90) collected from pig cortical bone were used in this study. All bone specimens had similar volume and surface characteristics after machining. To display the baseline level before Er:YAG laser ablation, a control group (n=10) without dehydration or Er:YAG laser ablation was examined with OCT, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy. The remaining specimens were randomly divided into four groups (n=20/group) with different moisture content: dried (Group 2 and Group 4) or not dried (Group 1 and Group 3). Pulsed Er:YAG laser (120 mJ/pulse, 20 Hz, 100 µs) was used for perpendicular irradiation with (Group 1 and Group 2) or without (Group 3 and Group 4) water spray. The treated specimens were subjected to SEM, EDX spectroscopy, OCT, and then processed for histological evaluation. After Er:YAG laser ablation, the melting effect was obvious in the SEM results of the dry groups and non-sprayed groups (Groups 2-4). EDX spectroscopy showed that the content of calcium and phosphorus and their ratios remained unchanged in the undried and with water spray group (Group 1) were the closest to the control group. Three-dimensional (3D) OCT could evaluate the depth and shape of ablation grooves. The roughness of the laser-ablated surface could be visualized by extracting the surface lines from cross-sectional OCT images. The results illustrated that the laser ablation with water spray could achieve a smoother surface. Furthermore, OCT results demonstrated that a layer with high image intensity was generated on the bone surface after laser irradiation. The thickness of these layers showed a correlation with whether or not the laser irradiation was sprayed with water. Histology showed that thin eosin-stained layers were created in all experimental groups, which matched well with OCT results of the layers with high image intensity. No denatured layer was observed in the non-irradiated areas of bone tissues. OCT could rapidly and non-destructively visualize the bone surface before and after Er:YAG laser ablation at four different moisture contents. The morphology of ablation grooves, as well as the roughness and thickness of the heterogeneous layer on the bone surface, could be characterized quantitatively with good correlation with SEM and histology. This study will promote the development of OCT as an efficient and accurate tool for evaluating laser ablation of bone.