Pulse-coupling measurement of coupled microstrip lines using a micromachined picosecond optical near-field probe

By measuring the transverse electric-field distributions using a newly deve loped micromachined optical near-field mapping probe, pulse-coupling phenom ena on coupled microstrip lines are reported for the first time. The measur ed field distribution of the propagating coupled pulse provides useful info rmation to aid understanding of the coupling phenomena; this cannot be obta ined by conventional external-port access test instruments. The measurement is performed based on the picosecond photoconductivity of low-temperature- grown GaAs (LT-GaAs). A system for the measurement of the internal electric field distribution using the optical near-field probe is described and cha racterized. It is capable of measuring independent orthogonal components of free-space electric fields with less than 2-ps temporal resolution and wit h minimal loading effects. The loading effects of the probe are minimized b y adopting a micromachining technique for the use of a I-Mm-thick LT-GaAs e pilayer as a substrate, and by using silver-paint-coated optical fibers for electrical connections.