Hiroyoshi Yajima

Hole Drilling of Glass-Foam Substrates with Laser

Using 10 - 100 msec pulses and a 10.6 micrometers wavelength CO2 laser, focused to a spot size 200 micrometers , we have produced holes into glass-foam substrates. We examine the effect of pulse width on the hole structure and the pile-up around the hole in single-pulse drilling. The height of the pile-up increases 7 - 30 micrometers with increasing the pulse width. The residual melting layer is under 0.5 (mu) m in the hole walls. It seems that the glass-foam substrate is suitable for laser beam machining.

Guided-Wave EO Intensity Modulator Using Coupled Microstrip Line Electrode of Higher-Order Harmonic Resonance Combined with Polarization-Reversed Structure

A novel structure of a resonator type guided-wave electrooptic intensity modulator is introduced that uses a higher-order harmonic resonant electrode of coupled microstrip lines combined with polarization-reversed structure. The light modulation cancellation caused by the light transit-time effect in the resonant electrode, which is longer than the wavelength of the standing wave, is compensated for to enhance modulation efficiency. The modulator for 26 GHz operation was designed and fabricated with a LiTaO 3 substrate. The modulation electrode is 9.03 mm long for seventh order harmonic resonance by RF signal. The workability of the modulator was confirmed by experiments with 1.3 μm wavelength light.

Guided-Wave Electro-Optic Modulators Using Novel Electrode Structure of Coupled Microstrip Line Resonator

A novel structure of guided-wave electro-optic modulators is proposed and their operation of the optical intensity modulation is successfully confirmed. The modulators use a newly developed modulation electrode consisting of coupled microstrip lines. A high voltage can be induced by the resonance of the odd propagation mode to realize efficient electro-optic modulation in spite of the microstrip-line configuration. The properties of the coupled microstrip lines were analytically evaluated by using the method of conformal transformations and the effectiveness as a modulation electrode was presented. The modulation electrodes of the half-wavelength coupled microstrip line resonator were designed at 10 GHz and 26 GHz, where the electrode lengths were 3 mm and 1.2 mm, respectively. The modulators using these electrodes with the Mach-Zehnder interferometer of LiTaO 3 waveguides were fabricated. The measured modulation coefficient of the 26 GHz modulator normalized at 100 mW signal input was 0.13 rad.

60 GHz guided-wave electro-optic modulator using novel electrode structure of coupled microstrip line resonator

A guided-wave electro-optic modulator is proposed and its operation of optical intensity modulation by 60 GHz millimeter-wave signals is successfully confirmed. The modulator uses a newly developed electrode structure consisting of coupled microstrip lines. A high voltage can be induced by the resonance of the odd propagation mode to realize efficient electro-optic modulation even at millimeter-wave frequencies. The properties of the coupled microstrip lines were evaluated to show the effectiveness as a modulation electrode. The modulator designed at 60 GHz was fabricated with LiNbO/sub 3/ waveguides. The measured modulation coefficient normalized at 1 cm electrode length and 100 mW signal input was 2.4 rad.

Hole drilling of glass substrates with a slab waveguide CO2 laser

Using 30-1000 (mu) s pulses and 9.3 (mu) m wavelength from a CO2 slab waveguide laser, focused to a spot size of 130 (mu) m, we have produced holes in synthetic quartz, soda-lime glass, and Pyrex glass substrates. In the three types of substrates, the mass removal per pulse increases almost linearly with the pulse energy used to vary the pulse interval. The removal rates of the three substrates are almost the same. We examine the effect of the pulse interval on the hole structure and the pile-up around the hole in single- and multiple-pulse hole drilling. The deformation on the pile-up region can be accounted by the melting walls of the hole. Moreover, we examine the effect of pulse energy on the inclination of the hole walls. A multiple-pulse hole shaping technique is effective in decreasing the height coefficient of the pile-up region and the angle of inclination.