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We report continuous frequency shifting of a train of mode-locked pulses of light by up to /spl plusmn/400 GHz using electrooptic frequency shifting (EOFS). Dynamic, continuous, and accurate shifting of the optical pulses is achieved by controlling the phase and power of a single frequency microwave signal in a traveling wave phase modulator structure. Operation of the device under different microwave power and optical pulse length settings was investigated in order to study spectral distortion predicted to occur at high levels of frequency shifting and when using long pulses. Possible techniques for future device improvement were proposed and preliminary tests were performed. The use of a second-harmonic component of the microwave drive signal leads to a longer region of constant amplitude gradient and results in reduced distortion.

In this paper, we present a semiclassical wave equation analysis using a coupled-mode expansion formalism to study the effect of a microwave field on a train of short optical pulses co-propagating in a traveling-wave modulator structure. This device can continuously shift the central frequency of light pulses. We demonstrate the effect of the applied field on the light spectrum, the dependence on the relation between microwave wavelength and pulse length, and the effect of changing the interaction length or the power of the applied microwave field. The results of the calculation of these effects are presented.

Optical wavelength shifting of 1.054-nm laser pulses in excess of +or- 10 wavenumbers (+or- 300 GHz) was demonstrated. The wavelength shifter consists of synchronous microwave and optical waveguides fabricated monolithically on LiNbO/sub 3/. An optical pulse experiences a constant refractive index gradient that travels with the pulse and causes the wavelength shift. >

We develop analytical models for the operation of gain-expanded transverse gradient wigglers in the low, medium, and high optical intensity regimes. The first two are Raman regimes in which the optical wave and transverse betatron oscillations grow simultaneously. They differ from one another only in the nature of the saturation mechanism. The third or high intensity regime is a trapped particle regime physically very similar to the regime of high extraction variable parameter wigglers.