We synthesized Cr3+, Cr4+-codoped Mg2SiO4 phosphors and studied their optical properties for application as a novel wideband near-infrared (NIR) light-source. The phosphors have an ultra-wideband NIR luminescence spectrum of 650–1400 nm. The origin should be the transition of Cr3+ and the transition of Cr4+. The luminescence spectrum spans over one octave range and covers the “optical window in biological tissues”. We successfully achieved an ultra-wideband luminescence of 650–1400 nm with a maximum output power of 367.5 μW by combining a blue LED with Cr3+ and Cr4+-codoped Mg2SiO4 phosphors in a single package.

We have fabricated a novel near-infrared light source for optical coherence tomography (OCT) using a glass phosphor and a light emitting diode (LED) as the excitation source. We used 1.glass as the phosphor to obtain wideband light emission around 1000 nm. We observed a full-width at half-maximum (FWHM) as wide as 98 nm with an output power as high as 1 mW. The interference signal showed a coherence length of 4.6 m. This value indicates that the depth resolution of the OCT is twice as high as that of conventional LEDs and super luminescent diodes (SLDs). #

We have synthesized 0.3Sm2O3–0.12Pr2O3–10Bi2O3–45Sb2O3–45B2O3 glass as an ultrawide-band near-infrared phosphor for LED-based light sources. We have achieved an ultrawide-band luminescence from 760 to 1100 nm with an output power of over 1 mW by combining a blue LED with Sm3+,Pr3+-codoped borate glass in one package. Absorption bands corresponding to C–H and O–H stretchings in aqueous solutions of glucose have been observed using this light source and a multichannel spectrometer. These results indicate that the Sm3+,Pr3+-codoped borate glass combined with the blue LED is a useful novel light source for absorption spectrometry.

Pr, Nd, and Sm L1-edge and L3-edge X-ray absorption near edge structure (XANES) spectra of their complex oxides were measured to investigate the relationship between the characteristic feature of the spectra and the local structure around the Pr, Nd, and Sm atoms. The pre-edge peak area of the L1-edge and the full width at half-maximum (fwhm) of the white line of the L3-edge XANES spectra are extracted by curve fitting analyses with one Gaussian and one cubic spline function as a background or with one arctangent and one pseudo-Voigt function, respectively. As a result, a clear correlation between the pre-edge peak area and the fwhm is found with another correlation with abstract physical parameters defined by bond angles formed with Pr, Nd, or Sm and two adjacent oxygen atoms, which represent an indicator of disorder of local configuration of the target element. This finding will open a way to estimate an average local structure of lanthanide elements by means of XANES spectroscopy.

We have investigated the spectroscopic properties of Bi 2 O 3 -B 2 O 3 glasses doped with Nd 3þ and Yb 3þ separately, and doubly doped with the same ions, in order to search for appropriate phosphors for an optical coherence tomography (OCT) light source. The effects of Yb 3þ and Nd 3þ co-doping and varying Yb 3þ concentration on the spectrum shape were studied to obtain an optimum line shape for OCT. We successfully obtained a Gaussian-like shape spectrum from 5.0Yb 2 O 3 -1.0Nd 2 O 3 -46.0Bi 2 O 3 -46.0B 2 O 3 (in nominal molar composition) with a full-width-at-half-maximum (FWHM) of 101 nm in the wavelength region around 1000 nm. This FWHM corresponds to a depth resolution of 4.5 mm, which is about twice that of conventional light emitting diodes (LEDs) and super luminescent diodes (SLDs). The Gaussian-like line shape is very important to suppress ghost images in OCT. These results indicate that a Yb 3þ , Nd 3þ co-doped Bi 2 O 3 -B 2 O 3 glass phosphor can indeed be applied as a new type of OCT light source.