High-speed Electro-optic Modulator Research Articles

High-speed electrooptic phase modulators using InGaAs/InAlAs multiple quantum well waveguides

High-speed phase modulation of waveguided InGaAs/InAlAs multiple-quantum-well optical modulators operating at 1.55 mu m is described. The modulator requires a low voltage for pi -phase-shift (V/sub pi /=2.5 V) as well as a small intensity modulation depth of 1 dB. The measured electrical 3-dB bandwidth is 10 GHz, giving a bandwidth-to-voltage ratio of 4 GHz/V.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

High-speed electrooptic modulation in GaAs/GaAlAs waveguide devices

A figure of merit is constructed for broad-band electrooptic modulators which compares bandwidth with launched generator voltage standardized to a common wavelength. Comparison of various published results in terms of this figure shows that a lumped-element III-V semiconductor device performance may be no more than a factor of two below that of typical (i.e., LiNbO 3 ) traveling wave devices and are probably easier to implement-especially in an integrated format. Accurate modeling, which incorporates all transit time and velocity match effects, is described and found to agree well with experimental results. Experimental GaAs/GaAlAs modulators have been made, using a Mach-Zehnder interferometer configuration. At a wavelength of 1.15 μm and with unterminated drive a bandwidth of 6.5 GHz was obtained with V pi of 17.3 V. A shorter (34.6-v) device was ∼ 1.25-dB down at 8.4 GHz. The corresponding figures of merit are close to the maximum expected for the configurations used.

High-speed waveguide electro-optic polarization modulator

By careful electrode design we have achieved a 1.7-GHz modulation bandwidth for a Ti:LiNbO(3) integrated-optic TE ? TM mode-converter modulator. Because of the wavelength selectivity of this modulator, it is an attractive device for simultaneously providing multiplexing and signal encoding in future wavelength-multiplexed single-mode light-wave systems.

Electro-optic diffraction modulator using out-diffused waveguiding layer in LiNbO3

A high-speed Bragg-type electro-optic modulator with modified interdigital electrodes has been constructed using a Li out-diffused waveguide layer in LiNbO3. The thickness of the layer is about 7 μm and only two modes, TE0 and TE1, are supported. For the TE0 mode, a maximum modulation index of about 70% is obtained up to 900 MHz with an applied voltage of 18 V.

Growth of single crystals of meta-nitroaniline and the evaluation of its electro-optic properties

Single crystal boules of meta-nitroaniline of good optical quality have been grown. Metanitroaniline exhibits a strong linear electro-optic effect, has a low refractive index and low permittivity, making it attractive for use in high-speed electro-optic modulators and deflectors.

High-speed electro-optic diffraction modulator for baseband operation

A new kind of laser-beam modulator is described. An interdigital electrode structure deposited on an electro-optic crystal is used to produce a spatially periodic electric field which diffracts the laser beam within the crystal. Baseband operation is possible, and optical-pulse risetimes of 1.5 ns have been observed. The required drive power is only 7.5 nJ per pulse at 25 V, but this could be improved by scaling. The measured extinction ratio is 25 dB and this varies by less than ±1dB for a 10 K temperature change. The form of the modulator lends itself to inclusion in thin-film optical circuits.