Coherent and incoherent beam combination technologies of laser arrays are absolutely imperative for high power and intensity scaling. Coherent beam combining method classifi ed into two classes; active (tiled-aperture and fi lled-aperture) and passive phase control and incoherent method is a multi-channel, spectrally beam-combination technique. This paper reviewed an overview of progress in beam combination techniques. Recently, the output power of fi ber laser has been signifi cantly increased using beam combination techniques. Total output power of 8.2 kW is generated by wavelength combination of four fi ber amplifi ers and near-diffraction-limited 4 kW is obtained by coherent combination of 8 fi ber lasers.

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We propose the one-shot-type spectroscopic-tomography for medical-patient-condition monitoring systems in daily-life environment, such as non-invasive blood-glucose sensor. We proposed the 2-dimensional imaging-type Fourier-spectroscopy that can limit the measuring depth into focal plane and is a near common-path interferometer with high robustness for mechanical vibration. Because the proposed 2-dimensional imaging-type Fourier-spectroscopy is a wavefront-division-type interferometer, we could acquire the spectroscopic tomography by scanning focal plane into depth direction. To improve the time resolution for living tissues, we develop the time-domain phase-shift method into a spatial phase-shift interferometer by installing the transmission-type relativeinclined phase-shifter into optical Fourier transform plane. In this report, we demonstrate the feasibility of the one-shot-type spectroscopic-tomography.

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The diagnosis of tissue mechanical properties, e.g. vulnerability and viscoelasticity, has been being required clinically and cosmetically. Especially, the rupture of unstable plaque on coronary artery should cause acute coronary syndromes. Optical Coherence Straingraphy (OCSA) was proposed, which can visualize tissue mechanical information, e.g. strain tensor distribution, from speckle deformation between synthetic 3-dementional images obtained by Optical Coherence Tomography. This is basically constructed by Recursive 2- or 3-dementional cross-correlation as well as an image deformation technique which take account of linear deformation of interrogation volume. In this study, OCSA was in/ex vivo applied to finger pad of human skin and atherosclerotic plaque in WHHL rabbit aorta, respectively. Consequently, residual strain distributions identifi ed according to the mechanical boundary conditions of fingerprints and the accumulation of lipid tissue having low elastic modulus. It was concluded that 3D-OCSA could be highly effective to clinical tissue assessment as “Micro Mechanical Biopsy”.

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To visualize the optical properties in cerebral cortex of in vivo rat brain, we investigated a spectral refl ectance images estimated by the Wiener estimation method form a digital RGB camera. The reduced scattering coeffi cient and absorption coeffi cient were successfully estimated by the diffuse refl ectance spectroscopy with the Monte Carlo simulation for light transport. In order to confi rm the possibility of the method, we performed in vivo experiments for exposed brain of rats during cortical spreading depression. The sequential images of total hemoglobin indicated the hemodynamic change in cerebral cortex. On the other hand, increases in μ s’ was observed before the profound increase in total hemoglobin, which is indicative of changes in light scattering by tissue. The results indicate potential of the method to evaluate the pathophysiological conditions of in vivo brain.

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Polarization-resolved second-harmonic-generation (SHG) microscopy is useful to visualize orientation in dermal collagen fi ber. Using this microscopy, we investigated the relation between wrinkle direction and collagen orientation in photoaged mouse skin. A polarization anisotropic image of the SHG light indicated that wrinkle direction in photoaged skin is predominantly parallel to the orientation of dermal collagen fi bers. Furthermore, collagen orientation in wrinkle-disappeared skin was between photoaged skin and non-photoaged one. This microscopy has the potential to become a powerful non-invasive tool for assessment of cutaneous photoaging.

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Photoacoustic imaging is a unique modality that overcomes the resolution and depth limitations of optical imaging of tissues while maintaining relatively high contrast. In this article, we review the biomedical applications of photoacoustic imaging for cancer diagnosis. Representative endogenous photoabsorbers include melanin and hemoglobin, whereas exogenous photoabsorbers include dyes, metal nanoparticles, and other constructs that absorb strongly in the near-infrared band of the optical spectrum and generate strong photoacoustic responses. These photoabsorbers, which can be specifi cally targeted to molecules or cells, have been coupled with photoacoustic imaging for preclinical and clinical applications including detection of cancer cells, sentinel lymph nodes, micrometastases, and monitoring of angiogenesis. Overall, photoacoustic imaging has significant potential to assist in diagnosis, therapeutic planning, and monitoring of treatment outcome for cancers and other pathologies.

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In turbid media such as biological tissues and living organisms, light is scattered randomly so that it is very diffi cult to obtain useful information inside the area of interest. Even in such situation, wavefront shaping can be used to focus and manipulate the spatial and temporal properties of light by controlling the many degrees of freedom of the optical phase in the incident beam. In this review, we explain the principle of the wavefront shaping and describe a couple of the previous studies to demonstrate the viability of this method. We also discuss potential application to control the temporal properties of ultrafast laser pulses both in spatial and temporal domain. This approach will open many new ways for biological imaging and photonics by combining with nonlinear optical effects.

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We developed a laser-scanning stimulated Raman scattering microscope using a fiber-based pulse source, which is comprised of second-harmonic Er-doped and Yb-doped fi ber lasers. The intensity noise of the former was decreased by the collinear balanced detection technique using a fi ber-based delay-andadd line. We successfully imaged polymer beads with 200 × 200 pixels in only 0.4 s.

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Amyotrophic lateral sclerosis (ALS) patients in a completely locked-in state are unable to move any part of their body and have no usual means of communication. A near infrared light spectroscopy-based YES/NO judgment devise is one successful user interface for such patients. However, several remaining problems must be solved. In this paper, we propose a noise reduction method using a two-point detection measurement technique to improve the rate of correct detections. Our experiment results show that this method is useful for ALS patients who have a small signal amplitude caused by mental tasks. We also propose a brain switch technique using Optical Topography. Our experiment results show that the proposed brain switch can be used to control the cursor for auto-scanned cursor character boards.

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