Jungo Kondo

High-speed and low-driving-Voltage thin-sheet X-cut LiNbO/sub 3/ Modulator with laminated low-dielectric-constant adhesive

We present a novel thin-sheet X-cut LiNbO/sub 3/ optical modulator structure which can be fabricated by precise polishing and lapping to obtain a thinner LiNbO/sub 3/ substrate for a lower driving voltage in addition to velocity matching and impedance matching. We demonstrated that the fabricated modulator had a driving voltage V/spl pi/ of 2 V and zero chirp for 40-Gb/s operation and had a high potential for suppressed dc drift, and long-term reliability.

40-Gb/s X-cut LiNbO/sub 3/ optical modulator with two-step back-slot structure

We propose a newly designed X-cut lithium niobate (LiNbO/sub 3/) optical modulator. It has a two-step back-slot structure to satisfy the velocity-matching condition without the buffer layer of silicon dioxide (SiO/sub 2/). Accordingly, this modulator can achieve low drive voltage and low optical insertion loss. In addition, the dc-drift phenomena due to the buffer layer can be suppressed. This structure is fabricated with micromachining technology using excimer laser ablation. The optical 3-dB bandwidth of the fabricated modulator reaches 30 GHz, and the drive voltage is less than 3 V at 1 kHz. From the measurement of the optical eye diagram at 43.5-Gb/s, clear eye openings were obtained. This modulator is sufficient for 40-Gb/s optical transmission systems.

High-performance optical modulator with a wide center electrode and thin x-cut LiNbO/sub 3/ substrate

We propose an excellent large-bandwidth back-slot lithium niobate (LN) modulator with a wide center electrode of typically 50 /spl mu/m or wider and relatively thin electrodes. From the calculation, a modulator with a 3-dBe bandwidth of 34 GHz and a half-wave voltage of 2.0 V for a 50-/spl Omega/ characteristic impedance system was realized theoretically. This means when their half-wave voltages are identical, by applying a wider electrode, the modulator bandwidth becomes 2.6 times larger than that of a conventional one. We also confirmed experimentally that the wide center electrode structure is effective for back-slot LN modulators.

Single-drive X-cut thin-sheet LiNbO/sub 3/ optical modulator with chirp adjusted using asymmetric CPW electrode

The authors propose a prechirped X-cut thin-sheet lithium niobate modulator. In this modulator, the /spl alpha/-chirp characteristic can be adjusted in the range of 0 to 0.8 by making coplanar waveguide electrodes asymmetric. In addition, a low-driving-voltage operation is achieved to make use of the thin-sheet structure without a SiO/sub 2/ buffer layer. We fabricated such a modulator with an /spl alpha/-chirp parameter of 0.65, a low half-wave voltage of 2.5 V, and a large bandwidth of 20 GHz. We also confirmed 10 Gb/s error-free transmission over an 80 km normal fiber (1.3 /spl mu/m zero-dispersion fiber) at a wavelength of 1.55 /spl mu/m by utilizing the modulator.

Low Half-Wave Voltage X-Cut Thin LiNbO

We present a novel X-cut lithium niobate optical phase modulator. Low driving voltage was realized by adopting both an X-cut thin LN sheet structure and an asymmetric coplanar waveguide electrode. A low half-wave voltage of 2.9 V in 20-GHz operation was obtained.

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We propose a small-footprint X-cut thin-sheet lithium niobate optical modulator with high-speed and low-driving-voltage characteristics. Since an optical waveguide is folded by a mirror placed at one edge of the modulation chip, the chip can be shortened by about half. In addition, a wide modulation bandwidth can be achieved, because the path-length difference between the optical waveguide and the coplanar-waveguide (CPW) electrode is decreased to as short as possible by placing the CPW electrode as far as possible along the optical waveguide in the folded portion, and the microwave effective index is set to realize effective velocity matching between the lightwave and the microwave. A small footprint of 1.78 times 29 mm, a low half-wave voltage of 2.0 V at dc, and a 3-dBe modulation bandwidth of 20 GHz were obtained.

Sheet Optical Phase Modulator With Asymmetric Coplanar Waveguide Electrode

A 40 Gb/s X-cut LiNbO/sub 3/ modulator based on a two-step back-slot structure provides low drive voltage of 2.8 V. No DC drift phenomena are observed during more than 100 hours of operation at 100 degree C. These performances indicate high potential for 40 Gb/s transmission system application.

High-Speed X-Cut Thin-Sheet

We examined a Ti-diffused optical waveguide formed on a thin X-cut LiNbO 3 substrate for a lower-drive-voltage modulator. Under the single-mode condition, optical mode-size decreases with LiNbO 3 substrate thickness below 10μm. A thin-sheet LiNbO 3 modulator could achieve a low-drive-voltage of 1.3 V with a bandwidth of 15 GHz by adopting a narrow electrode-gap.

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We proposed an X-cut thin LiNbO3 sheet modulator with a folded Mach-Zehnder waveguide. A small footprint of 1.78×29mm, a low half-wave voltage of 2.4V@DC, and a 3dBe modulation bandwidth of 14GHz were achieved.

Optical Modulator With Folded Structure

We propose a newly designed X-cut lithium niobate (LiNbO3) optical modulator. It has a two-step back-slot structure to satisfy the velocity matching condition without the buffer layer of silicon dioxide (Si02). Accordingly, this modulator can achieve low drive voltage and low optical insertion loss. In addition, dc-drift phenomena due to the buffer layer can be suppressed This structure is fabricated with micro-machining technology using excimer laser ablation. The optical 3-dBe bandwidth of fabricated modulator reaches 30GHz and the drive voltage is less than 3V at 1kHz. From the measurement of optical eye diagram at 43.5-Gb/s, the RF-extinction-ratio resulted in 12dB with the drive voltage of 4.lVp-p. This modulator has the sufficient capability for 40-Gb/s optical transmission systems.