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

Thin-Film Mach-Zehnder Lithium Niobate Optical Modulator on Silicon Substrates with VpL of 4 V·cm

“…As can be seen from the figure, the V π of the device is 6.8 V. Since the electrodes of the device are 6 mm long, the measured V π ·L is equal to ~ 4 V·cm. This record value of V π ·L is lower by at least a factor of 3 compared to the best optimized diffusion-based lithium niobate modulators 3 . As mentioned, with more optimized design and higher fabrication tolerance, V π ·L smaller than 1.2 V is feasible in future, which will be 10 times lower than diffusion-based devices.…”

“…Radiofrequency (RF) electrodes are then placed in close proximity of the optical waveguide to achieve modulation via the EO effect. These modulators are usually several centimeters long since the modulation half-voltage length-product or V π ·L of more than 12 V-cm is typical in these devices 3 .…”

Ultra-high-speed LiNbO3 modulators

“…In this case, TE-mode optical signals are launched into the optical waveguide and the lateral component of the electrical field is used for modulation. Since there is no need for a buffer layer, it is possible to suppress the dc-drift in the modulator [9,14,15].…”

“…Using this structure, they examined the modulation response up to 110 GHz, as described in the next section [33]. Kondo et al reported an X-cut modulator with a two-step back-slot structure [9,15] as shown in Fig. 12.…”

“…These modulators have been used in advanced transmission experiments demonstrating large capacity optical transmission systems [1,2], an optical-time-division-multiplexing (OTDM) system [3], and carrier suppressed return-to-zero (CS-RZ) systems [4,5]. With the recent development of low-drive voltage capability [8][9][10][11], the modulators have become strong candidate for 40-Gbit/s systems of the next generation.…”