Manabu Shiozawa

Compact light source for ultrabroadband coherent anti-Stoke Raman scattering (CARS) microscopy

A compact light source module for ultrabroadband coherent anti-Stoke Raman scattering (CARS) microscopy was developed. It mainly consists of a nanosecond microchip laser, a photonic crystal fiber for Stokes light generation, and a single mode polarization maintaining fiber for pump light propagation. It is alignment-free and relatively low-cost compared with previous light sources of CARS microscopy. By using an assembled module, we successfully observed an ultrabroadband CARS spectrum and a CARS image of a murine adipocyte. The module is expected to greatly spread the CARS microscopy to various fields by its extreme easiness to handle.

Compact and fully collinear light source for broadband multiplex CARS microscopy covering the fingerprint region.

Compact and fully collinear light source for multiplex coherent anti-Stokes Raman scattering (CARS) microscopy was proposed and demonstrated. It consists of only a microchip laser, a short photonic crystal fiber, and a longpass filter. It offers performance of sensitivity, bandwidth, and spectral resolution suitable for biomedical applications, especially covering the entire fingerprint region (500-1800 cm(-1)). It can be readily implemented by a commercially available microchip laser and a photonic crystal fiber. It has great potential to expand the utility of CARS microscopy to a wide variety of fields such as endoscopy.

Simultaneous Multi-Bit Recording in Fused Silica for Permanent Storage

In recent years, optical discs and hard disc drives have been widely used as storage media. However, the lifetime of recorded data in these media is about 100 years. On the other hand, a permanent storage system that can store data for more than 1,000 years is strongly required, especially for historically valuable data. One candidate system for permanent storage is a system using fused silica, which is thermally and chemically stable. In this paper, we reported simultaneous multi-bit recording in fused silica with a femtosecond laser and a spatial light modulator. The recording quality was evaluated using signal-to-noise ratio with an optical microscope. We recorded a four-layer sample with a dot pitch of 2.8 µm and obtained a signal-to-noise ratio greater than 15 dB. Furthermore, we confirmed that the sample had good thermal resistance at 1,000 °C for 120 min, which indicates a lifetime of over 319 million years.

100-Layer recording in fused silica for semi permanent data storage

Data storage using fused silica is a candidate archival medium for long-term preservation of important data such as official documents and cultural heritages. It is highly resistant to high temperature and chemical damage, and the Arrhenius law suggests that it would have a semi permanent lifetime. In order to improve the recording density of this type of storage, we increased the number of recording layers to 100 and achieved a recording density of 1.5 Gbyte/in.2 without the use of an error correction code. The total bit error rate of all 100 layers was 2.3 × 10−4, which is acceptable for practical use. The analysis of the experimental results suggests that a further increase in the number of recording layers is possible by the correction of the spherical aberration induced by a mismatch in the refractive index at the surface of a medium.

A Driveless Read System for Permanently Recorded Data in Fused Silica

A driveless, multilayer read system was demonstrated as applicable to a permanent digital-storage using fused silica. The combination of a low-magnification microscope and signal processing were simple enough to be emulated in the distant future. Test data were recorded in a 2-mm-thick fused-silica plate by a femtosecond laser to form four layers with dot pitch of 2.8 µm and interlayer distance of 60 µm. The total recording density was 40 Mbytes/in.2, which is as high as that of a conventional compact disc. This system achieved a bit-error rate in the order of 10-3 when reading the test data (without error-correction code) from images taken at a 19.5-times-magnification. Signal processing using unsharp masking and subtraction of images at different focal points effectively contribute to read data from blurred image with the low bit-error rate.

Quantitative index of arbitrary molar concentration for coherent anti-Stoke Raman scattering (CARS) spectroscopy and microscopy

We propose a simple quantitative index for coherent anti-Stoke Raman scattering (CARS) spectroscopy and microscopy. Unlike previous similar indices, it can be applied to samples with arbitrary molar concentration, and it is robust against environmental change. Concentrations of aqueous hydrogen peroxide solution and lipid concentration distribution in a live murine adipocyte were successfully quantified by the new index. The index can be obtained in a broad range of CARS setups and it is readily applicable to quantitative CARS microscopy for deep inspection of samples such as biological specimens.

CARS hyperspectral imaging of cartilage aiming for state discrimination of cell

Non-invasive cell analyses are increasingly important for medical field. A CARS microscope is one of the non-invasive imaging equipments and enables to obtain images indicating molecular distribution. Some studies on discrimination of cell state by using CARS images of lipid are reported. However, due to low signal intensity, it is still challenging to obtain images of the fingerprint region (800~1800 cm-1), in which many spectrum peaks correspond to compositions of a cell. Here, to identify cell differentiation by using multiplex CARS, we investigated hyperspectral imaging of fingerprint region of living cells. To perform multiplex CARS, we used a prototype of a compact light source, which consists of a microchip laser, a single-mode fiber, and a photonic crystal fiber to generate supercontinuum light. Assuming application to regenerative medicine, we chose a cartilage cell, whose differentiation is difficult to be identified by change of the cell morphology. Because one of the major components of cartilage is collagen, we focused on distribution of proline, which accounts for approximately 20% of collagen in general. The spectrum quality was improved by optical adjustments about power branching ratio and divergence of broadband Stokes light. Hyperspectral images were successfully obtained by the improvement. Periphery of a cartilage cell was highlighted in CARS image of proline, and this result suggests correspondence with collagen generated as extracellular matrix. A possibility of cell analyses by using CARS hyperspectral imaging was indicated.

Coherent anti-Stokes Raman scattering hyperspectral imaging of cartilage aiming for state discrimination of cell.

Abstract. Noninvasive cell analyses are increasingly important in the medical field. A coherent anti-Stokes Raman scattering (CARS) microscope is the noninvasive imaging equipment and enables to obtain images indicating molecular distribution. However, due to low-signal intensity, it is still challenging to obtain images of the fingerprint region, in which many spectrum peaks correspond to compositions of a cell. Here, to identify cell differentiation by using multiplex CARS, we investigated hyperspectral imaging of the fingerprint region of living cells. To perform multiplex CARS, we used a prototype of a compact light source generating both pump light and broadband Stokes light. Assuming application to regenerative medicine, we chose a cartilage cell, whose differentiation is difficult to be identified by change of the cell morphology. Because one of the major components of cartilage is collagen, we focused on distribution of proline, which accounts for approximately 20% of collagen. The spectrum quality was improved by optical adjustments of the power branching ratio and divergence of Stokes light. Periphery of a cartilage cell was highlighted in a CARS image of proline, and this result suggests correspondence with collagen generated as an extracellular matrix. The possibility of noninvasive analyses by using CARS hyperspectral imaging was indicated.