SignificanceAn integrated cellular-resolution optical coherence tomography (OCT) module with near-infrared Raman spectroscopy was developed on the discrimination of various skin cancer cells and normal cells. Micron-level three-dimensional (3D) spatial resolution and the spectroscopic capability on chemical component determination can be obtained simultaneously.AimWe experimentally verified the effectiveness of morphology, intensity, and spectroscopy features for discriminating skin cells.ApproachBoth spatial and spectroscopic features were employed for the discrimination of five types of skin cells, including keratinocytes (HaCaT), the cell line of squamous cell carcinoma (A431), the cell line of basal cell carcinoma (BCC-1/KMC), primary melanocytes, and the cell line of melanoma (A375). The cell volume, compactness, surface roughness, average intensity, and internal intensity standard deviation were extracted from the 3D OCT images. After removing the fluorescence components from the acquired Raman spectra, the entire spectra (600 to 2100 cm − 1) were used.ResultsAn accuracy of 85% in classifying five types of skin cells was achieved. The cellular-resolution OCT images effectively differentiate cancer and normal cells, whereas Raman spectroscopy can distinguish the cancer cells with nearly 100% accuracy.ConclusionsAmong the OCT image features, cell surface roughness, internal average intensity, and standard deviation of internal intensity distribution effectively differentiate the cancerous and normal cells. The three features also worked well in sorting the keratinocyte and melanocyte. Using the full Raman spectra, the melanoma and keratinocyte-based cell carcinoma cancer cells can be discriminated effectively.
We demonstrate a record gain of 11.4-dB for 300-nm broadband single-mode Cr-doped crystalline core fibers (SMCDCCFs) employing a novel growth of smaller core. The gain-per-unit-length efficiency of the SMCDCCF is 38-dB/m, which is much higher than current Er and Bi-doped fibers of 0.3 dB/m. The record gain achieved is mainly due to constantly maintain conical molten-zone shape in growth process to fabricate a smaller core of 15-µm and a longer fiber length of 30-cm.
An in-vivo anterior-segment optical coherence tomography with sub-micron isotropic resolutions is demonstrated on rat cornea. The opacity of the layered cornea was quantitatively analyzed. The morphology of corneal layers was well-depicted by the en-face image.
A random rayburst sampling (RRBS) framework was developed to detect the nucleus and cell membrane boundaries in three-dimensional (3-D) space. Raw images were acquired through a full-field optical coherence tomography system with submicron resolution—i.e., 0.8 μm in lateral and 0.9 μm in axial directions. The near-isometric resolution enables 3-D segmentation of a nucleus and cell membrane for determining the volumetric nuclear-to-cytoplasmic (N/C) ratio of a single cell. The RRBS framework was insensitive to the selection of seeds and image pixel noise. The robustness of the RRBS framework was verified through the convergence of the N/C ratio searching algorithm. The relative standard deviation of the N/C ratio between different randomly selected seed sets was only 2%. This technique is useful for various in vitro assays on single-cell analyses.
Full-Field Optical Coherence Tomography (FF-OCT) is a high resolution instrument in 3 dimensional (3D) space, including lateral and longitudinal direction. With FF-OCT, we can perform 3D scanning for excised biopsy or cell culture sample to obtain cellular information. In this work, we have set up a high resolution FF-OCT scanning instrument that can perform cellular resolution tomography scanning of skin tissue for histopathology study. In a scan range of 1cm(x), 1cm(y), 106μm(z), for example, digital data occupies 253 GB capacity. Copying these materials is time consuming, not to mention efficient browsing and analyzing of these data. To solve the problem of information delivery, we have established a network service to browse and analyze the huge volume data.
High-efficiency fiber-based extreme ultraviolet driver in the alignment-free configuration has been experimentally achieved with a maximum intensity of 6.4×1010 W/cm2 on target at a repetition rate of 20 kHz. The output EUV signal within 10~20 nm in wavelength was confirmed with a Si/Zr-coated x-ray photodiode by varying numbers of Be and Al foil filters. The measured spectral range is consistent with that obtained by the weighted oscillator strengths of Sn8+ to Sn+13 ions using an one-dimensional hydrodynamic code coupled with the ionization model of collisional-radiative equilibrium. The driver is based on a 1064-nm nanosecond coiled ytterbium all-fiber laser system in diode-seeded master oscillator power amplification. With an overall optical efficiency up to 56%, it can deliver a 1.16-mJ, 117-kW, 6.1-ns laser pulses with a FWHM linewidth of 10 nm and beam propagation factor of M2~1.55. The full advantages of using fiber laser for a movable LPP EUV metrology source are revealed.
High power fiber laser amplifier cascade can be simplified using double-pass scheme due to improvement of overall efficiency, especially for amplifiers with small input seed or high stored energy. The yield of stimulated Raman scattering (SRS) in the double-pass scheme is comparable to the level in amplifiers using counter-directional-pumped single-pass scheme if the pumping configuration is appropriate, even though the interaction length becomes twice for double pass scheme. In the study, insertions of Raman strippers along the active fiber with double-pass scheme is proved to be another choice to effectively suppress SRS besides the utilization of photonic band-gap fibers.
Intense nanosecond emission with spectral broadening from 980 to 1600 nm was generated with peak power up to 117 kW, close to the damage threshold of fiber fuse. Both laser amplification and nonlinear conversion were simultaneously employed in a fiber power amplifier giving power scaling free from significant depletion. In a diode-seeded all-PM-fiber master oscillation power amplifier system under all normal dispersion, a core-pumped preamplifier using double-pass scheme can significantly improve the energy extraction. This produced the pulse energy of 1.2 mJ and duration of 6 ns with a conversion efficiency of 66% at the moderate repetition of 20 kHz, which is consistent with the coupled laser rate equations including the stimulated Raman scattering. For the comparable nonlinear strength in each stage from single to few modes, the onset and interplay of four kinds of fiber nonlinearities can be addressed.
Based on single-objective construction utilizing high brightness Ce3+:YAG single-clad crystal fiber light source, this
Mirau-based full-field time-domain optical coherence tomography with circular polarization incident light represents
deeper penetration in scattering medium. Using objective-changeable ability of home-designed Mirau objective, this
system provides different applications, like biological tissue and single cells, by different spatial resolution with
corresponding dynamics. High quality image relying on less ghost image and near common-path interference was
demonstrated under this compact and power-stable system.
By limiting the core diameter of 15 μm at maximum with NA=0.07±0.01 for the near-diffraction-limited output (V <3.6), we successfully generate the pulse with the peak power of 36 kW and the duration of 4.6 ns in FWHM at the repetition rate of 20 kHz. To the best of our knowledge, the signal pulse energy corresponding to 264 μJ is the highest to date in the diode-seeded 15-μm all-fiber MOPA system with the efficiency of 35%. The success in the energy/power scaling is attributed to the further raise of input energy for more extracted energy, the tradeoff between the Raman-limited signal energy and the amplifier slope efficiency for more signal energy ratio, and the proper adjustment of both pump wavelength and power for avoiding coat damage without forced cooling.
In this paper we attempted to simulate the macroscopic light scattering phenomenon of optical coherence
tomography. Numerical solutions of Maxwell’s equations were computed to accurately account for phase and
amplitude of light. According to the simulation results, the qualitative and quantitative characterization may provide
important information for future development of this technique, especially on the index mapping of biological cells.
Yttrium aluminium garnet (YAG) has been widely used as a solid-state laser host because of its superior optical, thermal,
mechanical properties, as well as its plurality in hosting active ions with a wide range of ionic radii. Drawing YAG into
single crystalline fiber has the potential to further scale up the attainable power level with high mode quality. The recent
advancement on the codrawing laser-heated pedestal growth (CDLHPG) technique can produce glass-clad YAG
crystalline fibers for laser applications. The drawing speed can reach 10 cm/min for mass production. The CDLHPG
technique has shown advantages on transition-metal ion doped YAG and short-fluorescent-lifetime ion doped YAG host.
Compared to silica fiber lasers, the crystalline core offers high emission cross section for transition metal ions because of
the unique local matrix. The challenges on the development of
glass-clad YAG fibers, including core crystallinity,
diameter uniformity, dopant segregation, residual strain, post-growth thermal treatment, and the thermal expansion
coefficient mismatch between the crystalline core and glass clad are discussed. Chromium, ytterbium, and neodymium
ions doped YAG fiber lasers have been successfully achieved with high efficiency and low threshold power. Power
scaling with a clad-pump/side-coupling scheme using single clad or double clad YAG fibers is also discussed.
Cr:forsterite (Cr:Mg2SiO4) single crystal fibers of diameter less than 100 μm were made for the first time to our knowledge. This novel fiber material will be used to make fiber light sources such as fiber lasers and broadband light sources for applications in biophotonics and optical communications. Cr:forsterite crystal has a broad emission spectrum ranging from 1.1 to 1.4 μm that traditional glass fibers or semiconductor light sources cannot offer. And fiber light sources are compact, efficient, maintenance-free and compatible with fiber-optic components potentially leading to new performance and functions. In this work, bulk Cr:forsterite crystal was melted, pulled and re-grown into a long fiber using laser heated pedestal growth (LHPG) technique. Single crystal rhombic structure was preserved and verified by Xray diffractometer. By using electron probe micro-analyzer, change in Cr dopant concentration and distribution profile for various fiber diameters and growth conditions was studied.
In this study, epilayers of packaged indium gallium nitride light emitting diodes (LED's) are characterized by optical beam induced current (OBIC) and photoluminescence laser scanning microscopy through two-photon excitation. OBIC reveals spatial and electrical characteristics of LED's which can not be distinguished by photoluminescence. When compared with single- photon OBIC, two-photon OBIC imaging not only exhibits superior image quality but also reveals more clearly the characteristics of the epilayers that are being focused on. The uniformity of these LED's OBIC images can also be related to their light emitting efficiency.
In this study, we have developed a high performance microscopic system to perform second-harmonic (SH)imaging on a tooth. The high sensitivity of the system allows an acquisition rate of 300 seconds/frame with a resolution at 512x512 pixels. The surface SH signal generated from the tooth is also carefully verified through micro-spectroscopy, polarization rotation, and wavelength tuning. In this way, we can ensure the authenticity of the signal. The enamel that encapsulates the dentine is known to possess highly ordered structures. The anisotrophy of the structure is revealed in the microscopic SH images of the tooth sample.
We have observed the poly(p-phenylene vinylene) (PPV) thin film based light emitting devices with a multifunction laser scanning microscope. The spatial distribution of PPV thin film's reflectivity, photoluminescence, and photocurrent are imaged. In addition, site dependent optical density and photocurrent spectra are also measured, which reveal the nature of optical excitations within PPV. The contrast between photoluminescence and photocurrent images is attributed to field induced luminescence quenching under exciton model.
The on-resistance of a GaAs coplanar waveguide-photoconductive switch was characterized as a function of laser photon energy, switch temperature, and applied dc electric field. An electric-field-dependent resonance at photon energies near the GaAs energy band-gap edge has been observed. This resonant behavior is believed to be caused by a competition between carrier recombination in the switch bulk and carrier sweep-out effects near the switch surface. This field-induced resonance was verified with 5, 10 and 20 micrometers switch gaps that were fabricated on three separate semi-insulating GaAs wafers. For fixed-wavelength laser sources, it has been shown that one can optimize the optical coupling by varying the switch temperature. The switch resistance decreased by a factor of three as a result of an increase in the switch temperature of 20 degree(s)C at photon energies near the absorption edge. A conductive-mode plasma model has been developed that adequately predicts the nonresonant switch behavior.
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