4 research outputs found
ThinâFilm Lithium Niobate Optical Modulators with an Extrapolated Bandwidth of 170âGHz
Highâspeed modulators with low driving voltage, low loss, and compact size are essential for future optical communication systems. Thinâfilm lithium niobate modulators have met each of these criteria separately, but simultaneous achievement of all of them has been challenging on this platform. Low driving voltage electroâoptic modulators necessitate either a narrow gap between the electrodes or an elongated MachâZehnder arms, both of which adversely affect the microwave loss, hence the bandwidth. Herein, this tradeâoff is alleviated by placing the optical waveguides nonsymmetrically with respect to the electrodes and by including a dielectric buffer layer beneath the electrodes. Exploiting this novel design yields a modulator with a measured rollâoff of only 2âdB from low frequencies up to 100âGHz, and with an extrapolated 3âdB bandwidth of 170âGHz. The measured voltageâlength product of this subterahertz device is 3.3âVâcm. Another device, optimized for a lower voltageâlength product of 2.2âVâcm, exhibits a 3âdB electroâoptic bandwidth of 84âGHz. The devices are also tested for eightâlevel pulseâamplitude modulation (PAMâ8) and demonstrate data rates of up to 240âGbâsâ1 at 80âGbaud, validating that the modulators are a propitious candidate for nextâgeneration optical communication systems