Tetsumi Sumiyoshi

Efficient optical parametric oscillation based on periodically poled 1.0 mol % MgO-doped stoichiometric LiTaO3

Effective optical parametric oscillation (OPO) at room temperature was demonstrated by a periodically poled 1.0 mol% MgO-doped stoichiometric lithium tantalate (Mg:SLT) crystal. The slope conversion efficiency of total output power was ∼65% and the maximum output power was 655 mW at 1.3 W pumping without photorefraction. The difference of the OPO performance was investigated between 0.5 and 1.0 molu2009% Mg:SLT crystals, and a 1.0 molu2009% MgO-doped device exhibited better OPO performance and high resistance of photorefraction. The effective nonlinear coefficient of deff was found to be 10pm∕V by single-pass first-order quasiphase matched second-harmonic generation at 1064 nm.

Efficient ablation of organic polymers polyether sulphone and polyether ether ketone by a TEA CO2 laser with high perforation ability

Organic polymer (PES: PolyEther Sulphone and PEEK: PolyEther Ether Ketone) ablation with oscillation-line selected TEA CO2 lasers is successfully demonstrated. With different irradiation conditions the ablative etch-rate slopes were varied, which means that the ablation process is dependent on the ablation conditions such as incident laser intensity and ambient gas. In perforation processing of the PEEK film, the TEA CO2 laser had a higher etch rate of 42 μm/pulse at a fluence of 70 J/cm2 in vacuum than the XeCl laser.

High-power CW deep-UV coherent light sources around 200 nm based on external resonant sum-frequency mixing

We report pure continuous-wave (CW) high-power (>100 mW) deep-ultraviolet (DUV) light sources emitting around 200-nm spectral region based on singly resonant sum-frequency mixing (SRSFM). Efficient DUV generation is made possible by use of a Brewster-cut CsLiB/sub 6/O/sub 10/ (CLBO) crystal near noncritically phase-matched (NCPM) condition for the SFM of 1-/spl mu/m output of neodymium lasers. The CW radiation of fifth-harmonic wavelength of a neodymium laser at 213 nm was generated by the SFM of enhanced 1064-nm radiation with single-passing 266-nm radiation produced by external-resonant frequency doubling of a 532-nm green laser. With 1.8 W of 266-nm radiation incident upon a CLBO crystal, as much as 180 mW of CW 213-nm power has been produced. The sub-200-nm CW radiation with 140-mW power has also been achieved by SFM of 1064 nm with 244-nm radiation from a frequency-doubled Argon-ion laser in the CLBO crystal operated near the NCPM condition.

Stable long-life 1-W femtosecond laser for industrial and biomedical applications

We have successfully developed a highly-stable commercial femtosecond laser. We achieved continuous operation of femtosecond laser over 4,000 hours.

Effects of wavelength on boron nitride ablation by a transversely excited atmospheric CO2 laser

Laser ablation processing for a reaction sintered cubic boron nitride (cBN) by a transversely excited atmospheric CO2 laser was found to be strongly affected by the laser wavelength. The ablation threshold of the cBN was 3 J/cm2 at 9.3 μm for the 9R(10) branch but 18 J/cm2 at 10.8 μm for the 10P(38) branch since the 9.3 μm laser pulse is resonantly absorbed by the transverse optical phonons. Although the reflectance of the cBN surface is very high, it was efficiently ablated by the 9.3 μm laser irradiation. Hot pressed hexagonal BN samples were also ablated by a 9 μm band laser as well as a 10 μm laser, however, a boron rich layer was left on the ablated surface.

Selective ablation of a hydrogenated amorphous silicon thin layer by the second‐harmonic radiation of a transversely excited atmospheric CO2 laser

The second‐harmonic radiation of the transversely excited atmospheric CO2 laser generated by a AgGaSe2 nonlinear crystal is used for the selective ablation of a hydrogenated amorphous silicon (a‐Si:H) thin layer on a quartz substrate. The vibrational energy of the Si—H bonds contained in a‐Si:H at 10 at.u2009% coincides with the photon energy of the 5 μm light and absorbed the laser photons to sufficiently ablate the layer without damage on the quartz substrate.

CW DUV light sources for inspection tools

We describe true continuous-wave (CW), high-power, line-narrowed, deep-ultraviolet (DUV) light sources for the high-resolution metrology tools such as wafer inspection and mask inspection systems. The 198.5-nm CW radiation with 300-mW power has also been achieved by sum-frequency mixing (SFM) of 1064-nm output from a single-frequency Yb3+ fiber amplifier with the 244-nm radiation from a frequency-doubled argon-ion laser. The 266-nm CW DUV radiation with 5 W of maximum power has been generated by frequency doubling of 532-nm green laser output. Both sources utilize Brewster-cut CsLiB6O10 (CLBO) crystal for efficient and stable DUV light generation.

Direct writing of conductive aluminum line on aluminum nitride ceramics by transversely excited atmospheric CO2 laser

The fabrication of very low resistance aluminum conductor line on the aluminum nitride (AlN) by transversely excited atmospheric (TEA) CO2 laser writing was demonstrated. A minimum electrical resistance was measured to be less than 0.1 Ω/mm with a linewidth of 500 μm. The electrical resistance measured is lower than those of conventional conductor lines used for electronic circuits. The x-ray photoelectron spectroscopy depth profile analysis of aluminum layers can explain the resistance of the metallic aluminum layer formed. Compared to the experimental data by KrF laser, TEA CO2 laser writing is found to be a more effective process for fabricating a low resistance conductor line on AlN than the KrF excimer laser.

Kerr lens mode-locked Yb:Lu2O3 bulk ceramic oscillator pumped by a multimode laser diode

We report a Kerr lens mode-locked Yb:Lu₂O₃ ceramic oscillator with a pulse energy of 23.5 nJ, which is the highest value in bulk Yb:Lu₂O₃ ceramic oscillators, to the best of our knowledge.

High-Pulse-Energy Yb:YAG Thin Disk Mode-Locked Oscillator for Intra-Cavity High Harmonic Generation

We have generated 1-mJ pulses with a pulse duration of 520 fs at a repetition rate of 2.85 MHz in a mode-locked oscillator cavity. These pulses can be used for generating high-harmonics in the cavity.