Satoshi Makio

GROWTH AND CHARACTERIZATION OF K3LI2(TAXNB1-X)5O15 CRYSTALS FOR BLUE SECOND-HARMONIC-GENERATION APPLICATIONS

Potassium lithium tantalate niobate, K3Li2(TaxNb1−x)5O15, or KLTN single crystals were grown by spontaneous crystallization method, and it has been demonstrated that the KLTN crystal has high potential as a nonlinear crystal for blue second‐harmonic‐generation (SHG) applications. Ta substitution for Nb site in K3Li2Nb5O15 crystal improves the transparency in the blue light region and decolorizes the material. Compared with K3Li2Nb5O15, the K3Li2Ta5O15 crystal exhibits a 60 nm blueshift of the absorption edge from 376 to 316 nm, and decreases its absorption coefficient from 2.3 to 0.3 cm−1 at 400 nm. The phase‐matched frequency doubling of the Ti:sapphire infrared laser for blue SHG at room temperature has been demonstrated with the KLTN bulk crystal.

Fabrication of periodically inverted domain structures in LiTaO3 and LiNbO3 using proton exchange

We report on the fabrication of a first‐order periodically inverted domain structure in LiTaO3 and LiNbO3 for quasi‐phase‐matched devices using proton exchange with one‐directional heating. First‐order periodically inverted domains with a 3.2 μm period and more than 40 μm depth were formed beyond the proton exchanged region. This domain inversion took place during the proton exchange process, far below the Curie temperatures. Taking advantage of these deep domains, we demonstrated second‐harmonic generation without fabricating a channel waveguide.

Increased optical damage resistance and transparency in MgO-doped LiTaO3 single crystals

Clear and transparent 2-inch diameter undoped and MgO-doped LiTaO3 single crystals with few Fe impurities have been grown by the conventional Czochralski method from a congruent melt. The optical damage resistance of undoped LiTaO3 has been characterized by the measurement of photoinduced birefringence change and is lower than that of commercially available LiNbO3, which is not consistent with the previously reported data in the literature. In addition, doping of a few mol% MgO further improved the optical damage resistance, transmission in the visible light region, and crystal decolorization, and produced a favorable shift of absorption edge toward shorter wavelengths for lithium tantalate. These are important advantages when considering shorter- wavelength accessibility and high conversion efficiency in second-harmonic- generation devices.

67-mW Continuous-Wave Blue Light Generation by Intracavity Frequency Doubling of a Diode Pumped Cr:LiSrAlF6 Laser

We report a new configuration for an intracavity frequency-doubled Cr-doped LiSrAlF6 (Cr:LiSAF) solid state laser, by inserting a nonlinear crystal of LiB3O5 (LBO) for second harmonic generation (SHG). By applying a highiy reflective coating on LBO crystal, blue light of 67.8 mW was obtained. The slope efficiency of the Cr:LiSAF laser was 39.2% and the continuously tunable wavelength range by a birefringent filter was 113 nm.

Valency control of iron in Y3Fe5O12 single crystals grown by the floating zone method

Doping of Y3Fe5O12 (YIG) single crystals with various elements, such as Si, Ca, Mg, Mn, Mo, and V, has shown that Mn is the most appropriate dopant for improving the transparency in the near infrared. Mn doping does not show any additional absorption (wavelength range 0.8 to 2μm), and results in YIG crystals with very high transparency. By determination and optimization the ratio of the Cs/Cf(Cs dopant concentration in the flux rod; Cf: that in the feed rod) as a function of the distribution coefficient k, even the k value is not unity, YIG crystals were grown by the floating zone method with the variation of transparency along the growth direction exceedingly small.

High-Power, Continuous-wave and Blue Light Generation by Intracavity Frequency Doubling of a Cr:LiSrAlF6 Laser

Thermal quenching phenomena in a Cr doped LiSrAlF6 (Cr:LiSAF) laser pumped by a laser diode (LD) was studied to improve the second harmonic generation (SHG). The second harmonic to obtain blue light was generated by an intracavity frequency doubled solid state laser where LiB3O5 (LBO) crystal was inserted in the cavity. A circular pumping beam profile was essential to suppress thermal quenching, which was realized by the arrangement of horizontal and vertical two LD pumping or bundled fiber pumping. In particular for the latter case, blue light of 120 mW was obtained with pump power of 1200 mW.

Low noise CW 355 nm generation by simple single pass configuration with PPMgSLTs from fiber based laser

Low noise CW 355nm with more than 50 mW was generated by frequency conversion of 1064 nm fiber based laser with simple cascaded single pass configuration using two PPMgSLTs.

Surface acoustic wave convolver using multiple waveguide

A new elastic convolver is proposed in which a nonlinear interaction of surface acoustic waves (SAW) on multiple waveguides is used. Theoretical and experimental investigations are carried out. When two SAWs with angular frequency of ω and wavenumber of β, and with ω and-β propagate in opposite directions on N waveguides, the parametric mixing phenomenon generates a SAW with a sum frequency traveling in the direction normal to the waveguide. The generation efficiency increases: (i) when the width of one of the waveguides is one-half the wavelength of the sum frequency SAW; (ii) with the number N of the waveguides with the maximum occurring at N = 8 ∼ 10; and (iii) with the larger velocity difference (ΔV/V). Generation of the sum frequency SAW is possible only with the guided mode of SAW. The present convolver can be matched easily with the external circuit, because the convolution output is extracted with an interdigital electrode (IDT).

Demonstration of 40-Gb/s Low-Group-Delay-Ripple Tunable Dispersion Compensator Using Angled Etalon With Multiple Reflections

We experimentally demonstrated a high-performance tunable dispersion compensator with a simple configuration using an angled etalon with multiple reflections. We developed a group-delay model of the compensator and designed to suppress the group-delay ripple (GDR). A tunable dispersion range of plusmn250ps/nm and a low <2.0-ps GDR were shown

Novel control methods to enlarge dispersion range of tunable dispersion compensator using angled etalons with multiple reflections

We propose some novel control methods for 40-Gbps etalon based tunable dispersion compensators. We developed two compensators; one with a low 3.2-dB loss (no circulator required) and the one with a wide 620 ps/nm tunable range