Mode-discriminating electrooptic sampling for separating guided and unguided modes on coplanar waveguide

Abstract

Abstuact-Mode-discriminating electrooptic sampling (MEOS) of coplanar waveguides was shown to discriminate between the symmetric quasi-TEM guided mode and asymmetric field distributions including unguided electromagnetic radiation. Radiation generated in a photoconductive switch and reflected from the back of the substrate was unambiguously identified. Ultrafast sampling of devices showed features in the transmitted pulse due to multiple substrate reflections. These features are removed using MEOS, leading to increased accuracy in determination of s-parameters. J. Allam is with the

Guided surface waves in photoconductive excitation

“…In addition, the relative arrival of the surface-wave mode would be expected to depend on substrate thickness but be independent of sampling location. This is not in accord with the CPW observations [6]. Furthermore, while it is difficult from our measurements to quantitatively determine the power propagating in the surface-wave signal, the large amplitudes we see suggest that it is substantial.…”

“…2(c), where the 650-pm sample being tested is placed on another unpattemed substrate of equal thickness. In this case the sampling location was 1.5 mm from the photoconductive switch and located on-reflected from the backside of the substrate [6]. Using this rayoptics picture, the relative delay between the two signals can be estimated using the quasistatic dielectric constant ( E , + 1)/2 for the CPS mode, and eT for the surface wave.…”

“…Paulter has described a feature observed by photoconductive sampling that was attributed to a reflection from the back surface of the substrate [5]; Baynes has made similar observations in photoconductive excitation of coplanar waveguides [6]. The presence of surface-wave signals in the characterization of electronic devices can complicate the interpretation of such measurements; from this point of view their presence is problematic.…”

Comparison of the noise and jitter characteristics of harmonic injection-locked and mode-locked erbium-doped fiber lasers

“…Actively modelocked EDFL's have been emerged to generate short and high repetition-rate optical pulse trains [2][3][4] for application in high-speed optical time division multiplexed (OTDM) transmission system [5] and electro-optical sampling [6]. However, EDFL's are sensitive to environmental perturbation such as temperature fluctuations and mechanical vibration due to their relatively long cavity length and a large number of cavity modes are associated with the main longitudinal modes.…”

<title>Delay-time tunable mode-locked erbium-doped fiber ring laser</title>

“…[1] On the other hand, active harmonically mode-locking has been considered as one of the promising techniques to construct the ultrafast lasers with high-repetitive optical pulse-train [2][3][4] and ultrashort pulsewidth. Based on this technique, the mode-locked erbium-doped fiber (ML-EDF) ring laser which provides stable, nearly transform-limited, picosecond optical pulses with low timing jitter [3] has been developed and found its application in ultrahigh bit-rate optical communication, high-speed optical time division multiplexed (OTDM) transmission [5], and electro-optical sampling [6] systems. The typical optical pulsewidth of these lasers operated at frequencies of 10 GHz is about picosecond [7] or subpicosecond pulsewidth and can be obtained by using a dual-modulator scheme [8] or by external pulse compression techniques.…”