CO2 Laser Frequency Research Articles

Unraveling the parameters and biological mechanisms of CO2 laser therapy for acute pain relief.

Acute pain-related pathology is a significant challenge in clinical practice, and the limitations of traditional pain-relief drugs have made it necessary to explore alternative approaches. Photobiomodulation (PBM) therapy using CO2 laser has emerged as a promising option. In this study, we aimed to identify the optimal parameters of CO2 laser irradiation for acute pain relief through in vivo and in vitro experiments. First, we validated the laser intensity used in this study through bone marrow mesenchymal stem cells (BMSCs) experiments to ensure it will not adversely affect stem cell viability and morphology. Then we conducted a detailed evaluation of the duty cycle and frequency of CO2 laser by the hot plate and formalin test. Results showed a duty cycle of 3% and a frequency of 25 kHz produced the best outcomes. Additionally, we investigated the potential mechanisms underlying the effects of CO2 laser by immunohistochemical staining, and found evidence to suggest that the opioid receptor may be involved in its analgesic effect. In conclusion, this study provides insights into the optimal parameters and underlying mechanisms of CO2 laser therapy for effective pain relief, thereby paving the way for future clinical applications.

A Prospective, Nonrandomized, Open-label Study, Comparing the Efficacy, Safety, and Tolerability of Fractional CO2 Laser versus Fractional Microneedling Radio Frequency in Acne Scars.

Background:Acne scar is a distressing psychosocial problem, and it has a negative effect on the quality of life. Although variety of approaches are available, demand of less invasive and more effective ways for their treatment is needed.Objective:This study aimed to assess and compare the clinical safety, efficacy, and tolerability of fractional carbon dioxide (FCO2) laser versus fractional microneedling radio frequency (MNRF) in the management of acne scars.Materials and Methods:This study was a prospective, observational, nonrandomized, open-labeled study of total 50 patients selected according to Goodman and Baron global qualitative acne scar grading, and they were divided into two groups of 25 each, having Fitzpatrick skin type III–V. A total of four sessions were given for both the groups at an interval of 2 months. The assessment was done by the treating physician as well as by the blinded physician. Both the subjective and the objective assessment was done at the last follow up given at second month of the fourth session.Results:The mean score of 25 patients in each group of FCO2 and fractional MNRF, decreased from 29.24 to 10.7 (i.e., 63.41%) and from 33.24 to 13.04 (i.e., 60.72%), respectively, as calculated by Goodman and Baron quantitative grading assessed by the treating physician (P = 0.0001). Grade 4 (>75%) improvement was shown by four patients and Grade 3 improvement (51%–75%) was shown by 14 patients among FCO2 group, and similarly Grade 4 (>75%) improvement was shown by three patients and Grade 3 improvement (51%–75%) was shown by 12 patients among MNRF group, as observed by a blinded physician (P = 0.689).Conclusion:Both modalities are equally effective in the treatment of acne scars; however, fractional MNRF having lesser down time and Post inflammatory hyperpigmentation (PIH) among darker skin shades, with good patient satisfaction score, makes it an efficient and safer treatment option as compared to FCO2.

Highly sensitive torsion sensor based on triangular-prism-shaped long-period fiber gratings

We propose and investigate a compact optical fiber sensor that aims to measure the torsion in both amount and direction with high sensitivity. This sensor is configured by a triangular-prism-shaped long-period fiber grating, which is fabricated by the high frequency CO2 laser polished method. The unique design of the triangular-shaped structure breaks the rotational symmetry of the optical fiber and provides high sensitivity for torsion measurement. In preliminary experiments, the torsion response of the sensor achieves a good stability and linearity. The torsion sensitivity is 0.54 nm/(rad/m), which renders the proposed structure a highly sensitive torsion sensor.

Comparative study of efficacy and safety of fractional CO2 laser and microneedling fractional radiofrequency (MnRF) in the treatment of striae distensae

Striae Distensae (SD) are common disfiguring skin conditions having significant psychological impact on affected patients, especially in young healthy women. Management of striae poses a therapeutic challenge. Recently, fractional CO2 laser and microneedling radio frequency have shown to be efficacious in the treatment of SD. However, there is paucity of such studies in Indian population. Hence, we intend to conduct the present comparative study. To compare the efficacy and safety of fractional CO2 laser and Microneedling fractional radiofrequency (MnRF) in the treatment of SD. A total of 30 patients (18-40 years) having SD, attending the out-patient department at the Department Of Dermatology, Venereology and Leprosy, Adichunchanagiri Hospital and Research Centre, B.G. Nagara were alternately allocated into group-A (fractional CO2 group) and group-B (MnRF group). Patients in both the groups received four sequential treatments with an interval of 4 weeks between each session. Clinical assessment of the improvement of striae was done based on Global Improvement Scale (GIS) at the end of 1 month after the last session, by a Side-by-side comparison of Pre-operative photographs. In addition, patients were asked to provide their opinion on improvement of striae using the patient satisfaction Visual Analogue Score (VAS). In our study, at the end of 1 month after the last treatment session, according to GIS, clinical improvement of SD was better in Group B when compared to Group A (p=0.000023), which was statistically significant. Patients in Group B were more satisfied with their treatment than the patients in Group A, according to the patient satisfaction VAS score, which was again found to be statistically significant (p=0.00086).Five patients (33.33%) in Group-A had post-inflammatory hyperpigmentation. In the present study, MnRF was found to be more efficacious and safe than fractional CO2 laser in clinical improvement of striae distensae.

A new strain sensor based on depth-modulated long-period fiber grating

In this paper, a novel strain sensor based on Depth-Modulated Long Period Fiber Grating (DM-LPFG) is presented and demonstrated. One side polished deformations with different milling depth are fabricated by a high frequency CO2 laser, so the DM-LPFG possesses a staircase-shaped structure. This kind of structure provides the high strain sensitivity of DM-LPFG. Experimental results clearly demonstrate that the structure has excellent mechanicalcapacity and repeatability. The sensor has a considerable strain sensitivity, which can reach up to 27.4 pm/με with the range of 0–450 με, it is an order of magnitude higher than conventional CO2 laser induced LPFG. The temperature characteristic is 49 pm/°C with the range of 30–170 °C. Furthermore, the strain sensor possesses a compact structure, with a total length of 9 mm.

Compact fiber strain sensor fabricated by a CO2 laser.

In this Letter, a novel, to the best of our knowledge, parallel inclined planes long period fiber grating (PIP-LPFG) for strain measurement is proposed. This structure is fabricated by a high frequency CO2 laser, which has polished periodic parallel inclined planes on a single mode fiber (SMF). Refractive index modulation (RIM) over a large area on the surface of the SMF significantly shortens the total length of the grating, and the structure of parallel inclined planes efficiently enhance the strain sensitivity of PIP-LPFG. Experimental results show that this LPFG with a miniature length of 3.9 mm has a good repeatability and stability of strain response, which can reach to 116 pm/µε in the dynamic range of 0-425 µε. Meanwhile, the temperature sensitivity of PIP-LPFG is 54.7 pm/°C in the dynamic range of 30-170°C.

An integrated wavelength selective coupler based on long period grating written in twin-core fiber

Wavelength selective couplers (WSC) are demonstrated theoretically and experimentally by writing long period gratings (LPGs) in a twin-core fiber (TCF). The coupling characteristics of the wavelength selective coupler are analyzed for different conditions based on the coupled-mode theory. Two LPGs with nearly the same resonant wavelength are written in each core of the TCF by using a high frequency CO2 laser. The experimental results show that the LPGs in the TCF can couple the light from one core to the other and a peak coupling efficiency of 42% has been achieved. Our results prove the viability of realizing an integrated wavelength selective coupler by using the configuration of TCF with LPFs.

高重频CO2激光干扰技术研究

本文针对高重频CO2激光干扰技术展开分析和研究。首先，概述了激光对抗武器的概念、分类和特点，以及激光对抗武器的干扰与破坏的主要目标对象。其次，分析了红外探测器激光干扰损伤效果的检测方法。再次，分析了光学元件激光变形损伤效果的检测方法以及光学薄膜的激光损伤检测方法。按照上述检测方法进行实验，分别对红外单元探测器、光学元件、光学薄膜和其他材料的激光损伤阈值实验数据进行分析与讨论。最后，总结了全文并且展望了激光干扰技术的发展。

Long period fiber grating in two-core hollow eccentric fiber.

Long period fiber gratings (LPGs) in a two-core hollow eccentric fiber (TCHF) have been demonstrated experimentally. Two LPGs have been fabricated into the respective core of the TCHF by a high frequency CO2 laser. The coupling characteristics in the TCHF-LPG have been studied using the coupling mode theory (CMT). The resonant peak is mainly caused by the coupling between the core mode LP01 and cladding mode LP81. The experimental results agree well with the simulation results. Furthermore, the sensing properties of the TCHF-LPG have been investigated with respect to bending, temperature and axial strain. Compared with the LPG in the single mode fiber (SMF), the experimental results indicate that the sensitivity of the TCHF-LPGs to bending curvature is low and even very small at some bending directions. In addition, TCHF-LPGs are insensitive to the axial strain while sensitive to the temperature. Therefore, the proposed TCHF-LPGs can efficiently sense the changing temperature that is independent of the strain. Moreover, the TCHF-LPGs can also be applied to two-channel filters without signal crosstalk between two cores.

Stabilization of 48- and 57-μ m CH3OD lasers for plasma diagnostics

Simultaneously oscillated 48-μ m and 57-μ m CH3OD lasers pumped by a 9R(8) CO2 laser have been developed as optical sources of interferometer and polarimeter for fusion plasma diagnostics. The objective of this paper is to present a method for stabilizing the two-color far-infrared (FIR) laser outputs. A stable FIR laser requires a stable pump CO2 laser and a prevention of a back reflection from the FIR laser cavity. The frequency of the pump CO2 laser has been stabilized by an external Stark-cell modulation. The back reflection has been reduced by an optical isolator using a quarter-wave plate and an absorbing thin-film reflector. The two-color FIR laser outputs have been stabilized by controlling the cavity length. As a result of these measures, we have achieved output stabilities of ± 1.2%/h at the 48-μ m laser and ± 1.3%/h at the 57-μ m laser.

CO2 Laser irradiation of GeO2 planar waveguide fabricated by rf-sputtering

We present a fabrication protocol combining radio frequency sputtering technique and CO2 laser annealing for GeO2 based planar optical waveguides. The effects of pulsed CO2 laser irradiation on the optical and structural properties of pure GeO2 planar waveguide are evaluated by different techniques as m-line and micro-Raman spectroscopy and AFM measurements. Amorphous GeO2 planar waveguide was fabricated by Radio Frequency magnetron sputtering system on v-SiO2 substrate. An increase of the refractive index of approximately 0.04 at 1.5 μm and a decreasing of the attenuation coefficient from 0.9 to 0.5 dB/cm at 1.5 μm have been observed after pulsed CO2 laser annealing. Raman spectroscopy and AFM results showed that after an adapted pulsed CO2 laser annealing, the resulting materials showed a crystalline environment in which the phase of the crystalline GeO2 varies with varying irradiation time.

准位相匹配砷化镓晶体制备工艺及脉冲CO2激光倍频研究

准位相匹配砷化镓晶体制备工艺及脉冲CO₂激光倍频研究

Tunable infrared laser desorption and ionization of fullerene films

Infrared laser excitation/desorption of thin film samples or powders containing fullerenes was observed to produce efficient ionization of both the fullerene and other molecules mixed into the sample. Both cations and anions were produced. The ions produced by this IR laser desorption ionization (IR-LDI) process were detected with a time-of-flight mass spectrometer. The mechanism of this IR-LDI process was investigated with mass spectra under different conditions, delayed pulse acceleration experiments, and IR wavelength dependence studies, employing either a fixed frequency CO2 laser (10.6μm) or an IR optical parametric oscillator (2000–4500cm−1; 5.0–2.2μm). The mechanism of fullerene IR-LDI was found to involve both direct emission of electrons from alkali-fulleride impurities in the sample and multiple photon-induced thermionic (delayed) emission of electrons from hot fullerenes. In both cases, the electrons produced are accelerated by the source fields resulting in electron impact ionization of, or electron attachment to, neutral species in the outgoing plume of desorbed material. The IR-LDI process is enhanced on resonance with fullerene vibrations, suggesting the possibility of a new kind of laser-thin film spectroscopy.

Fabrication of twisted long period fiber gratings with high frequency CO2 laser pulses and its bend sensing

We experimentally demonstrated a simple and effective method to write long period fiber gratings (LPFGs) with low fiber grating birefringence using high frequency CO2 laser pulses. Such LPFGs were fabricated by introducing twist strains to the fiber and then exposing the fiber to the laser. We theoretically analyzed the influence of the twist strains on the spectra of the LPFGs, and examined bend characteristics of twisted long period fiber gratings (T-LPFGs). Experimental results showed that T-LPFGs exhibited clear spectra, low insertion loss, and low polarization-dependent loss (PDL) compared with conventional LPFGs exposed to a single-side CO2 laser beam. The slope of the linear equation of the distance between the two split resonance peaks in the bending experiment is 20.55 nm/m−1, which makes T-LPFGs sensitive bending sensors.

Temperature characteristics of fusion splicing Hollow Core Photonic Crystal Fiber by sinusoidal modulation CO2 laser

During the fusion splicing Hollow Core Photonic Crystal Fiber (HC-PCF), the air-holes collapse easily due to the improper fusion duration time and optical power. To analyze the temperature characteristics of fusion splicing HC-PCF, a heating method by sinusoidal modulation CO2 laser has been proposed. In the sinusoidal modulation, the variation relationships among laser power, temperature difference and angular frequency are analyzed. The results show that the theoretical simulation is basically in accordance with the experimental data. Therefore, a low-loss fusion splicing can be achieved by modulating the CO2 laser frequency to avoid the air-holes collapse of HC-PCF. Further, the errors are also given.

高重频CO2激光损伤HgCdTe晶体的数值分析

To obtain thermal damage characteristics of the HgCdTe crystal irradiated by a CO2 laser,the theoretical model of Hg0. 784Cd0. 216Te crystal damaged by the high repetition frequency CO2 laser was developed,and then the damage thresholds of Hg0. 784Cd0. 216Te crystal irradiated by a single pulse laser and a high repetition frequency laser were calculated based on the finite element method. Finally,the effect of irradiation time and laser repetition frequency on the damage thresholds was analyzed. The results show that the damage threshold of the crystal radiated by a single pulse laser is 64. 5 J / cm2. In the high repetition frequency( f 1 kHz) CO2laser irradiation,the damage threshold of the crystal mainly depends on the laser average power density and irradiation time,and is independent of the laser repetition frequency. With the increase of irradiation time,the damage threshold can effectively be reduced. When the laser average power density is less than1. 95 kW / cm2,the crystal damage will not occur. The conclusions have a reference value for laser processing and protection.

Long-Period Fiber Grating Within D-Shaped Fiber Using Magnetic Fluid for Magnetic-Field Detection

A magnetic sensor utilizing long-period fiber grating (LPFG) written by high frequency CO2 laser pulses in a D-shaped fiber and the magneto-optical effect of magnetic fluid is proposed. Because of the high evanescent field of the grating structure in D-shaped fiber, by immersing the LPFG with a period of 685 μm into a water-based magnetic fluid within a capillary tube, the redshift as high as 33.5 nm of the resonant wavelength of the grating is observed when the external magnetic-field intensity is 189.7 mT, resulting in a sensitivity of 176.4 pm/mT. The hysteresis effect is observed and explained by the characters of magnetic fluid. Such kind of sensors would find potential applications in magnetic sensing fields.

CO激光在非线性晶体ZnGeP2和GaSe中的混频效应

The CO laser frequency mixing in high-quality ZnGeP2 and GaSe crystals is studied to obtain the 2.15-1 500 μm coherent sources.Secondary Harmonic Generation(SHG),sum-and difference frequency generations are considered as a method for the CO laser frequency mixing and the mode-locking as an efficient way to improve the mixing efficiency.Results show that the internal SHG efficiency of Q-switched multiline CO laser radiation has exceeded by 0.3% for GaSe crystal and has reached by 1.1 % for ZnGeP2 crystal.When the SHG is in ZnGeP2,the internal efficiency of electron beam sustained discharge frequency-tunable mode-locking CO laser is up to 12.5 %.Simultaneous SHG and sum frequency generation show the same output spectrum.It is shown by modeling that the sum and difference frequency generations of neighboring lines of both fundamental and first overtone bands can allow one to get the oscillation,respectively,at 4.0-5.0 μm and 100-≥1 200 μm(THz).In conclusions,the frequency mixing of mode-locked CO laser emission lines in ZnGeP2 crystals allows some one to design 2.15-≥1 500 μm coherent sources with the power frequency conversion efficiency up to or over 12.5%.

Laser induced surface modification of clay-PAN composite nanofibers

In this study a newly laser treatment method for surface modification of nanofibers is introduced. The new method is based on different infrared absorption of materials. Surface modification of Clay-PAN composite nanofibers was performed using selective laser etching approach with CO2 pulsed laser in order to increase surface area of nanofibers. The surface structure of resulted nanofibers is characterized using field emission scanning electron microscope and the results show characteristic modification of the surface topography of laser treated nanofibers. The modified surface structure of nanofibers was studied and analyzed for different laser pulse numbers and laser fluence. The results show that nanofiber surface modification strongly depends on the number of CO2 laser pulses and frequency of modified sites on the surface of nanofibers increasing with increasing the pulse fluence. This new technique is highly selective and can also compete with conventional techniques for nanofibers surface modification.

Relativistic four- and two-component calculations of parity violation effects in chiral tungsten molecules of the form NWXYZ (X, Y, Z=H, F, Cl, Br, or I)

Parity violation (PV) effects to the electronic ground state structure for a series of chiral tungsten molecules of the type NWXYZ (X, Y, Z = H, F, Cl, Br, or I) are compared using four- (Dirac) and two- (X2C) component relativistic Hartree-Fock and density functional theories. The results show the computationally more affordable two-component X2C approach yields accurate results for all molecules investigated. The PV energy differences between the two enantiomers range from as little as 0.4 Hz for NWClBrI to 140 Hz for NWHClI using a generalized gradient approximation including exact exchange (B3LYP). The W-N stretching mode in these molecules lies in the experimentally favorable CO(2) laser frequency range, and we therefore investigated PV effects in vibrational transitions using a single normal mode analysis. Here the PV frequency shift between the two enantiomers ranges from 1.6 mHz for NWFBrI to 710 mHz for NWHClI. Thus these types of molecules could be useful for the future detection of PV effects in chiral molecules.