Stephen E. Ralph

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In this paper, we present integrated circuit solutions that enable high-speed data transmission over legacy systems such as short reach optics and electrical backplanes. These circuits compensate for the most critical signal impairments, intersymbol interference and crosstalk. The finite impulse response (FIR) filter is the cornerstone of our architecture,(More)
We demonstrate near-transform-limited pulse generation through spectral compression arising from nonlinear propagation of negatively chirped pulses in optical fiber. The output pulse intensity and phase were quantified by use of second-harmonic generation frequency-resolved optical gating. Spectral compression from 8.4 to 2.4 nm was obtained. Furthermore,(More)
The unique dispersive and nonlinear properties of air-silica microstructure fibers lead to supercontinuum generation at modest pulse energies. We report the results of a comprehensive experimental and numerical study of the initial stages of supercontinuum generation. The influence of initial peak power on the development of a Raman soliton is quantified.(More)
Ultra-high-speed optical communication systems which can support ≥ 1Tb/s per channel transmission will soon be required to meet the increasing capacity demand. However, 1Tb/s over a single carrier requires either or both a high-level modulation format (i.e. 1024QAM) and a high baud rate. Alternatively, grouping a number of tightly spaced "sub-carriers" to(More)
We report significant improvement in terahertz (THz) power and efficiency using photoconductive sources by use of a spatially extended line source excitation and the trap enhanced field effect that occurs in sources made on semi-insulating GaAs. The combination of high electric fields and reduced screening effects allows 10 microW of THz power to be(More)
We propose a new passive optical thresholding device that combines the principles of multimode interference (MMI) with self-guiding. The multimode region is composed of a nonlinear optical material that will support a self-guided beam (i.e., a material with a positive Kerr nonlinearity). The device operates by switching between the MMI mode of operation and(More)
Performance-limiting asymmetric distortion is observed in the spectra of fundamental pulses transmitted through GaAs-Al(0.9)Ga(0.1)As multilayer waveguides designed for surface-emitted second-harmonic generation. This behavior is attributed to refractive-index changes resulting from the accumulation of free carriers created by two-photon absorption in the(More)