Near-infrared Diode Laser Research Articles

2D tomographic terahertz imaging using a single pixel detector.

A 2D tomographic terahertz imaging set-up using a single pixel imaging approach is realized, where a liquid helium cooled bolometer is utilized as a bucket detector and a mercury-arc lamp serves as a broadband terahertz source. The different patterns of the terahertz radiation, which are necessary for the single pixel imaging approach, are realized by spatially addressed photodoping of a high resistivity float zone silicon window, employing a near-infrared laser diode, which is spatially modulated by a digital micromirror device. The two investigated sample objects have cylindrical and cuboid shapes and consist of polypropylene. Both sample shapes cause strong influences of refraction, reflection and diffraction, which distort the measured projections and thus have to be considered in the tomographic reconstruction. In order to consider these effects, a model is developed which combines refraction and diffraction effects by a hybrid approach using ray tracing and scalar diffraction theory yielding finally projections of the sample objects. These simulated projections are compared to the measured projections and show a good agreement between the experimental results and the developed model. In accordance with this result, an optimization problem is formulated, which offers an approach for tomographic reconstruction using the developed model.

Effects of high-frequency near-infrared diode laser irradiation on the proliferation and migration of mouse calvarial osteoblasts.

Laser irradiation activates a range of cellular processes and can promote tissue repair. Here, we examined the effects of high-frequency near-infrared (NIR) diode laser irradiation on the proliferation and migration of mouse calvarial osteoblastic cells (MC3T3-E1). MC3T3-E1 cells were cultured and exposed to high-frequency (30kHz) 910-nm diode laser irradiation at a dose of 0, 1.42, 2.85, 5.7, or 17.1J/cm2. Cell proliferation was evaluated with BrdU and ATP concentration assays. Cell migration was analyzed by quantitative assessment of wound healing using the Incucyt® ZOOM system. In addition, phosphorylation of mitogen-activated protein kinase (MAPK) family members including p38 mitogen-activated protein kinase (p38), stress-activated protein kinase/Jun-amino-terminal kinase (SAPK/JNK), and extracellular signal-regulated protein kinase (ERK)1/2) after laser irradiation was examined with western blotting. Compared to the control, cell proliferation was significantly increased by laser irradiation at a dose of 2.85, 5.7, or 17.1J/cm2. Laser irradiation at a dose of 2.85J/cm2 induced MC3T3-E1 cells to migrate more rapidly than non-irradiated control cells. Irradiation with the high-frequency 910-nm diode laser at a dose of 2.85J/cm2 induced phosphorylation of MAPK/ERK1/2 15 and 30min later. However, phosphorylation of p38 MAPK and SAPK/JNK was not changed by NIR diode laser irradiation at a dose of 2.85J/cm2. Irradiation with a high-frequency NIR diode laser increased cell division and migration of MT3T3-E1 cells, possibly via MAPK/ERK signaling. These observations may be important for enhancing proliferation and migration of osteoblasts to improve regeneration of bone tissues.

Photoacoustic Measurement of Ethane with Near-Infrared DFB Diode Laser

A compact resonant photoacoustic sensor based on a near-infrared distributed-feedback (DFB) diode laser was developed for detection of ethane (C2H6). A DFB laser emission at 5937.25 cm−1 with a power of ∼5 mW was used as an excitation light source for generating the photoacoustic signal. Wavelength modulation and second harmonic detection scheme were employed. Modulation frequency and modulation amplitude were optimized for getting optimum performance. Performance evaluation based on the linearity response of the PAS sensor system with respect to C2H6 concentration levels was performed, and a good linear dependence of the PAS signal on the C2H6 concentration was obtained. A minimum detectable concentration of 9 ppmv was achieved for detection of C2H6 with a lock-in time constant of 10 ms.

Hydrogen peroxide vapor cross sections: A flow cell study using laser absorption in the near infrared

The absorption spectra of vapors of concentrated hydrogen peroxide/water mixtures (without a carrier gas) were characterized at wavelengths from 1390 to 1470 nm utilizing a near-infrared diode laser. Low pressures were employed to examine these spectral features near the Doppler-broadened limit. An advantageous portion of the spectra near 1420 nm containing several distinct H2O2 peaks and one well-known H2O peak (for calibration) was identified and the cross-sections of these peaks determined. These cross section values can be employed to measure vapor-phase concentrations of H2O2 in propulsion, atmospheric chemistry, and sterilization applications.

Dispersion of near-infrared laser energy through radicular dentine when using plain or conical tips.

The aim of this study was to investigate the influence of tip design on patterns of laser energy dispersion through the dentine of tooth roots when using near-infrared diode lasers. Diode laser emissions of 810 or 940nm were used in combination with optical fiber tips with either conventional plain ends or conical ends, to irradiate tooth roots of oval or round cross-sectional shapes. The lasers were operated in continuous wave mode at 0.5W for 5s with the distal end of the fiber tip placed in the apical or coronal third of the root canal at preset positions. Laser light exiting through the roots and apical foramen was imaged, and the extent of lateral spread calculated. There was a significant difference in infrared light exiting the root canal apex between plain and conical fiber tips for both laser wavelengths, with more forward transmission of laser energy through the apex for plain tips. For both laser wavelengths, there were no significant differences in emission patterns when the variable of canal shape was used and all other variables were kept the same (plain vs conical tip, tip position). To ensure optimal treatment effect and to prevent the risks of inadvertent laser effects on the adjacent periapical tissues, it is important to have a good understanding of laser transmission characteristics of the root canal and root dentine. Importantly, it is also essential to understand transmission characteristics of plain and conical fibers tips.

Ultraviolet and Visible Upconversion Emissions in Er3+-Yb3+ Doped Titanium Dioxide Nanopowder under the 980 nm Laser Diode Excitation

Er3+-Yb3+ co-doped titanium dioxide upconversion nanoparticles were synthesized by Sol-gel method. White upconversion emissions were observed after excitation of nanoparticles with 980 nm Near-Infrared laser diode. Upconversion emissions consist of red (640-690 nm), green (520-570 nm) and blue (408 nm) emissions. Ultraviolet upconversion emissions were also detected with wavelength about 210 nm. Ultraviolet emissions are probably the results of relaxation from 2I13/2 (220 nm) and 2L15/2 (210 nm) states to 4I15/2. Visible and ultraviolet emissions of these nanoparticles can be used in photodynamic therapy. High penetration of Near-Infrared light into the body tissue makes these nanoparticles appropriate for aiming tumors in deeper tissues in comparison with older methods of photodynamic therapy.

An open-path tunable diode laser absorption spectrometer for detection of carbon dioxide at the Bonanza Creek Long-Term Ecological Research Site near Fairbanks, Alaska

We have developed a low-power, open-path, near-infrared (NIR) tunable diode laser sensor for the measurement of near ground-level concentrations of greenhouse gases. Here, we report on instrument design, characterization, and initial measurements of carbon dioxide concentrations during deployment to a thermokarst collapse scar bog near Fairbanks, AK (USA). The optics “launch-box” portion of the instrument couples radiation from an NIR, distributed feedback diode laser operating near 1572 nm with a visible laser for alignment purposes. The outgoing beam is directed through a 3.2-mm hole in a parabolic mirror and the launch-box is oriented using a two axis, altitude-azimuth telescope mount such that the beam strikes a retroreflector target at a set distance downfield. The beam then retraces the path back to the launch-box where the light is collected on the surface of the parabolic mirror and focused onto a multimode fiber that transfers the radiation to an InGaAs detector. Sweeps over a ~1.6 cm−1 spectral region were collected at a rate of 500 scans per second and were typically stored as 10 s sweep averages. These averaged sweeps could be individually spectrally fit for CO2 concentration or averaged into a single spectrum for fitting (after correction for slight frequency drift). Field data reported here was averaged for 2.5 min and was found to follow trends in diurnal cycles of CO2 concentration cycles reported by sensors located nearby in the field site.

Biofunctionalized Hybrid Magnetic Gold Nanoparticles as Catalysts for Photothermal Ablation of Colorectal Liver Metastases.

Purpose To demonstrate that anti-MG1 conjugated hybrid magnetic gold nanoparticles (HNPs) act as a catalyst during photothermal ablation (PTA) of colorectal liver metastases, and thus increase ablation zones. Materials and Methods All experiments were performed with approval of the institutional animal care and use committee. Therapeutic and diagnostic multifunctional HNPs conjugated with anti-MG1 monoclonal antibodies were synthesized, and the coupling efficiency was determined. Livers of 19 Wistar rats were implanted with 5 × 106 rat colorectal liver metastasis cell line cells. The rats were divided into three groups according to injection: anti-MG1-coupled HNPs (n = 6), HNPs only (n = 6), and cells only (control group, n = 7). Voxel-wise R2 and R2* magnetic resonance (MR) imaging measurements were obtained before, immediately after, and 24 hours after injection. PTA was then performed with a fiber-coupled near-infrared (808 nm) diode laser with laser power of 0.56 W/cm2 for 3 minutes, while temperature changes were measured. Tumors were assessed for necrosis with hematoxylin-eosin staining. Organs were analyzed with inductively coupled plasma mass spectrometry to assess biodistribution. Therapeutic efficacy and tumor necrosis area were compared by using a one-way analysis of variance with post hoc analysis for statistically significant differences. Results The coupling efficiency was 22 μg/mg (55%). Significant differences were found between preinfusion and 24-hour postinfusion measurements of both T2 (repeated measures analysis of variance, P = .025) and T2* (P < .001). Significant differences also existed for T2* measurements between the anti-MG1 HNP and HNP-only groups (P = .034). Mean temperature ± standard deviation with PTA in the anti-MG1-coated HNP, HNP, and control groups was 50.2°C ± 7.8, 51°C ± 4.4, and 39.5°C ± 2.0, respectively. Inductively coupled plasma mass spectrometry revealed significant tumor targeting and splenic sequestration. Mean percentages of tumor necrosis in the anti-MG1-coated HNP, HNP, and control groups were 38% ± 29, 14% ± 17, and 7% ± 8, respectively (P = .043). Conclusion Targeted monoclonal antibody-conjugated HNPs can serve as a catalyst for photothermal ablation of colorectal liver metastases by increasing ablation zones. © RSNA, 2017.

A Novel Multi-Pass Cell System for Measurements of Methane Carbon Isotopes Using a Near-Infrared Tunable Diode Laser

A novel multi-pass cell laser absorption spectrometer to measure δ13C diluted with nitrogen using a 1.658 μm nearinfrared distributed-feedback laser was developed. The system temperature and pressure were measured with an accuracy of ±11 mK and ±3.2 Pa, respectively. The spectrometer is small, reliable, and compact. To minimize the temperature effect in absorbance ratio measurements, we used two appropriate absorption line pairs with nearly the same temperature dependences. The absorption spectrometer demonstrated high precision (a repetitive precision (reproducibility) of ~0.9‰ (1σ) is obtained at 300 ppmv methane concentrations). This concentration ratio is adequate for most CH4 source characterization studies.

Optical sensitisation of energetic crystals with gold nanoparticles for laser ignition

The laser ignition of explosives is safer and more environmentally beneficial than electric ignition systems, but optical sensitisers must be present to facilitate heating by optical absorption. We investigated, for the first time, the optical sensitisation of cyclotrimethylenetrinitramine (RDX) crystals by doping them with gold nanoparticles to enhance laser ignitibility using a near-infrared diode laser. RDX crystals physically coated with gold nanoparticles or recrystallised from a solution containing gold nanoparticles were tested for optical sensitisation by micro-imaging with a scanning electron microscope, and high-speed video was used to experimentally observe the enhanced laser ignitibility. The gold nanoparticles achieved effective optical sensitisation and significantly enhanced the laser ignitibility of RDX, reducing the laser ignition threshold power from more than 45W to as little as 1W. Our results show that gold nanoparticles are effective as optical sensitisers for the ignition of energetic materials using a small, low-power diode laser.

Tomographic imaging of reacting flows in 3D by laser absorption spectroscopy

This paper describes the development of an infrared laser absorption tomography system for the 3D volumetric imaging of chemical species and temperature in reacting flows. The system is based on high-resolution near-infrared tunable diode laser absorption spectroscopy (TDLAS) for the measurement of water vapour above twin, mixed fuel gas burners arranged with an asymmetrical output. Four parallel laser beams pass through the sample region and are rotated rapidly in a plane to produce a wide range of projection angles. A rotation of 180° with 0.5° sampling was achieved in 3.6 s. The effects of changes to the burner fuel flow were monitored in real time for the 2D distributions. The monitoring plane was then moved vertically relative to the burners enabling a stack of 2D images to be produced which were then interpolated to form a 3D volumetric image of the temperature and water concentrations above the burners. The optical transmission of each beam was rapidly scanned around 1392 nm and the spectrum was fitted to find the integrated absorbance of the water transitions and although several are probed in each scan, two of these transitions possess opposite temperature dependencies. The projections of the integrated absorbances at each angle form the sinogram from which the 2D image of integrated absorbance of each line can be reconstructed by the direct Fourier reconstruction based on the Fourier slice theorem. The ratio of the integrated absorbances of the two lines can then be related to temperature alone in a method termed, two-line thermometry. The 2D temperature distribution obtained was validated for pattern and accuracy by thermocouple measurements. With the reconstructed temperature distribution, the temperature-dependent line strengths could be determined and subsequently the concentration distribution of water across the 2D plane whilst variations in burner condition were carried out. These results show that the measurement system based on TDLAS can be used for 2D temporal or 3D volume imaging of temperature and chemical species concentration in reacting flows.

Laser and light-based therapy for cutaneous and soft-tissue metastases of malignant melanoma: a systematic review.

Invasive cutaneous melanoma is a growing health concern. Although surgical excision can effectively treat in situ tumors, use for metastatic melanoma is limited. Laser and light-based therapies may be a valuable palliative treatment option for patients with stage III and stage IV cutaneous metastatic melanoma. Our goal is to review the published literature and provide evidence-based recommendations on laser and light-based palliative therapies for metastatic melanoma. A search of the databases Pubmed, EMBASE, Web of Science, and CINAHL was performed on March 10, 2016. Key search terms were related to melanoma, laser, and light-based modalities. Our search initially identified 13,923 articles and 27 original articles met inclusion criteria for our review. Grade of recommendation: C for non-fractionated carbon dioxide laser, Grade of recommendation: D for fractionated carbon dioxide laser, ruby laser, neodymium laser, near-infrared diode laser, and photodynamic therapy. Non-fractionated carbon dioxide laser had the best palliative efficacy of the reviewed laser and light-based therapies, while other treatment modalities may have potential as adjunctive therapy to standard of care.

Self-assembled photoadditives in polyester films allow stop and go chemical release.

Upconverting nanoparticles and zinc oxide nanorods were found to spontaneously self-assemble into submicron particles in organic solvents. Exposure of the submicron particles to near-infrared light allows stop and go chemical release from biocompatible polymers. Sample preparation of thin films is done with ease through physical mixing of the photoadditives followed by air-dried knife casting. A colloidal ZnO variant that does not self-assemble with upconverting nanoparticles had slower chemical release, suggesting that synergistic chemical release is brought upon by highly efficient energy transfer mechanisms when the nanoparticles are less than 10nm apart. Never before seen composite particles of UCNP/ZnO are displayed, which shows the close interaction of the photoadditives within the polymer matrix.

Frequency comb assisted two-photon vibrational spectroscopy.

We report a setup for high-resolution two-photon spectroscopy using a mid-infrared continuous wave optical parametric oscillator (CW-OPO) and a near-infrared diode laser as the excitation sources, both of which are locked to fully stabilized optical frequency combs. The diode laser is directly locked to a commercial near-infrared optical frequency comb using an optical phase-locked loop. The near-infrared frequency comb is also used to synchronously pump a degenerate femtosecond optical parametric oscillator to produce a fully stabilized mid-infrared frequency comb. The beat frequency between the mid-infrared comb and the CW-OPO is then stabilized through frequency locking. We used the setup to measure a double resonant two-photon transition to a symmetric vibrational state of acetylene with a sub-Doppler resolution and high signal-to-noise ratio.

Methane-based in situ temperature rise measurement in a diode-pumped rubidium laser.

We measured active zone temperature rise of an operational diode-pumped rubidium laser non-perturbatively with methane-based near-infrared tunable diode laser spectroscopy (TDLAS). For a Rb+ methane diode-pumped alkali laser (DPAL), the temperature rise was obtained. Especially, the temperature differences (∼10 K) between lasing and un-lasing cases were well identified, which demonstrated a high sensitivity of the method. To our knowledge, this is the first demonstration of extending the methane-based TDLAS method to DPAL study.

Grazing-incidence optical magnetic recording with super-resolution.

Heat-assisted magnetic recording (HAMR) is often considered the next major step in the storage industry: it is predicted to increase the storage capacity, the read/write speed and the data lifetime of future hard disk drives. However, despite more than a decade of development work, the reliability is still a prime concern. Featuring an inherently fragile surface-plasmon resonator as a highly localized heat source, as part of a near-field transducer (NFT), the current industry concepts still fail to deliver drives with sufficient lifetime. This study presents a method to aid conventional NFT-designs by additional grazing-incidence laser illumination, which may open an alternative route to high-durability HAMR. Magnetic switching is demonstrated on consumer-grade CoCrPt perpendicular magnetic recording media using a green and a near-infrared diode laser. Sub-500 nm magnetic features are written in the absence of a NFT in a moderate bias field of only μ0H = 0.3 T with individual laser pulses of 40 mW power and 50 ns duration with a laser spot size of 3 μm (short axis) at the sample surface – six times larger than the magnetic features. Herein, the presence of a nanoscopic object, i.e., the tip of an atomic force microscope in the focus of the laser at the sample surface, has no impact on the recorded magnetic features – thus suggesting full compatibility with NFT-HAMR.

2f-wavelength modulation Fabry-Perot photothermal interferometry.

Trace gas detection was performed by the principle of photothermal interferometry using a Fabry-Perot interferometer combined with wavelength modulation and second harmonic detection. The sensor employed a compact, low-volume gas cell in an overall robust set-up without the use of any moveable part. A quantum cascade laser was used as powerful mid-infrared excitation source to induce refractive index changes in the sample, whereas a near-infrared laser diode served as probe source to monitor the photo-induced variations. The functional principle of the selective sensor was investigated by detection of sulfur dioxide. For the targeted absorption band centered at 1379.78 cm-1 a 1 σ minimum detection limit of about 1 parts per million by volume was achieved. The work demonstrates high potential for further sensor miniaturization down to a sample volume of only a few mm3. Limitations and possible improvements of the sensor regarding sensitivity are discussed.

Antimicrobial photodynamic therapy using Indocyanine green and near-infrared diode laser in reducing Entrerococcus faecalis

BackgroundThe use of Antimicrobial Photodynamic Therapy (aPDT) has been suggested as an adjuvant method to eliminate facultative bacteria during root canal disinfection. The purpose of this preliminary in vitro study was to determine whether the light-activated antimicrobial agent, Indocyanine green (ICG), could be used as photosensitizer and kill Enterococcus faecalis strain under planktonic conditions when irradiated with near-infared (NIR) diode laser emitting in 810nm wavelength. MethodsPlanktonic suspension containing Enterococcus faecalis strain was divided into nine experimental groups: (1) aPDT with ICG and laser (medium energy fluence), (2) aPDT with ICG and laser (high energy fluence), (3) only ICG without laser activation, (4) only laser emission without ICG (5) 2.5% Sodium hypochlorite (NaOCl) as irrigant, (6) 2.5% NaOCl and aPDT with ICG and laser, (7) 2.0% Chlorhexidine gluconate (CHX) as irrigant (8) No treatment (positive control), (9) No bacterial biofilm growth (negative control). The samples were incubated for 7days and colony-forming units (CFUs) were determined to evaluate bacterial viability. ResultsThe microbiological test revealed that aPDT groups, regardless the overall power, showed significant lower mean log10 CFU levels, than groups 3, 4 and 7 (p<0.01). The irrigation with 2.5% NaOCl and the combination of PDT and NaOCl achieved total elimination of bacteria. ConclusionThese preliminary in vitro findings imply that the combination of ICG and NIR diode laser may be a novel supplement in aPDT and provide better disinfection during endodontic treatment.

Portable Device for Measuring Breath Acetone Based on Sample Preconcentration and Cavity Enhanced Spectroscopy.

A portable and compact device is demonstrated for measuring acetone in breath samples. The device features a 7 cm long high finesse optical cavity as an optical sensor that is coupled to a miniature adsorption preconcentrator containing 0.5 g of polymer material. Acetone is trapped out of breath and released into the optical cavity where it is probed by a near-infrared diode laser operating at ∼1670 nm. With an optical cavity mirror reflectivity of 99.994%, a limit of detection of 159 ppbv (1σ) is demonstrated on samples from breath bags. Initial results on direct breath sampling are presented with a precision of 100 ppbv. The method is validated with measurements made using an ion-molecule reaction mass spectrometer. Data are presented on elevated breath acetone from two individuals following an overnight fast and exercise, and from a third individual during several days of routine behavior.

Laser ignition of elastomer-modified cast double-base (EMCDB) propellant using a diode laser

An experimental study was conducted to investigate laser ignition using a diode laser for elastomer-modified cast double-base (EMCDB) propellant in order to develop more liable and greener laser ignitors for direct initiation of the propellant. Samples of the propellant were ignited using a 974nm near-infrared diode laser. Laser beam parameters including laser power, beam width and pulse width were investigated to determine their effects on the ignition performance in terms of delay time, rise time and burn time of the propellant which was arranged in several different configurations. The results have shown that the smaller beam widths, longer pulse widths and higher laser powers resulted in shorter ignition delay times and overall burn times, however, there came a point at which increasing the amount of laser energy transferred to the material resulted in no significant reduction in either delay time or overall burn time. The propellant tested responded well to laser ignition, a discovery which supports continued research into the development of laser-based propellant ignitors.