Traveling wave GaAs electrooptic waveguide modulators at a wavelength of 1.3 mu m with bandwidth in excess of 20 GHz have been developed and characterized. The design and characteristics of both p-i-n modulators in microstrip configuration and Schottky barrier on n/sup -/-GaAs/semi-insulating (SI) GaAs in the coplanar strip configuration modulators are discussed. It is shown that microwave loss and slowing on n/sup +/ GaAs substrates will limit the bandwidth of the microstrip modulator to less than 10 GHz for a device 8 mm in length. Modulators with bandwidths in excess of 10 GHz are fabricated on SI GaAs substrates. >

High speed III-V electrooptic waveguide modulators at lambda -1.3 mu m

A one-to-four optical switch was fabricated by integrating three interferometric modulators on a z -cut LiNbO 3 substrate. Each of three modulators consists of a symmetric Y-junction and an asymmetric X-junction as 3-dB input and output couplers, respectively, to function as a one-to-two light switching element. They are arranged so that the input light is switched at the first stage into two intermediate guides which are connected to two second stage elements where light signals are further divided into the final four output ports. The measured switching voltages were 6.6 and 13.3 V for the first- and second-stage elements respectively, for TE -mode at a 633-nm wayelength, and the maximum crosstalk ratio was -18 dB. The device was driven by a 1-GHz signal and the transmission characteristics for four output ports were measured. The device performs the function of demultiplexing an optical signal from 4 to 1 Gbit.

An integrated 1 &#215; 4 high-speed optical switch and its applications to a time demultiplexer

The polarization reversal techniques of ferroelectric optical crystals enable us to construct new high-speed microwave signal processing devices with advanced functions; wireless microwave signal discrimination for space-division-multiplexing systems, pre-equalization for signal distortion caused by fiber dispersion in long haul optical fiber communications, and so on. In this paper, potential of these new functional devices for microwave photonic systems is discussed.

High-Speed Signal Processing Utilizing Polarization-Reversed Electro-Optic Devices

Since the concept of optical guided-wave devices was introduced, remarkable progress has been made in the characteristics of opto-electronic devices. One of the most important features of waveguide-type components is the possibility of realizing higher performances compared with the bulk type counterpart. It is of great interest in applications like ultrafast signal processing, communication, and sensors.

Ultrafast Traveling-Wave Light Modulators with Reduced Velocity Mismatch

Integrated electro-optic devices serve the functions of rapid light modulation, time-multiplexing, signal routing, tunable filtering, and polarization conversion. They are attractive devices due to their potential applications for wide-band optical communication, optical signal processing, and sensors. Today, most interest is given to electro-optic devices on LiNbO3 because of the known technology for fabricating optical strip waveguides, their large modulation bandwidth B beyond 10 GHz and their relatively low driving power of about 100 mW. The growing interest in semiconductor-based integrated optics resulted in various examples of electrooptic modulators on GaAs- and InP-substrates. We compare both technologies. However, emphasis is given here to the operational principles, the configurations, and properties of LiNbO3 modulators with titanium indiffused strip waveguides.

Integrated Electro-optic Devices

Picosecond pulse operation of the guided-wave light modulator is reported in this paper. First, we analyze the time responses of phase and intensity modulators of the traveling-wave type, and the modulated output waveforms related to the modulating pulses are discussed. It is shown that there is an optimum interaction (or electrode) length of the modulator whereby the drive voltage is minimized for a desired output pulse width. The traveling-wave push-pull light intensity modulator of Ti-diffused LiNbO 3 waveguides was modulated by a pulse train of 1 GHz repetition frequency, and the modulated output was observed by the image tube streak camera modified for sinusoidal scan at the same frequency. The duration of the modulated light pulses was less than 45 ps, which shows good agreement with the predicted one.

T. Sueta

Papers

Picosecond pulse response of broad-band guided-wave interferometric light modulators