The use of linear photoconductive switches rather than nonlinear switches for the generation of Ultra-Wide-Band (UWB) pulses provides advantages such as jitter-free operation, low losses, and a reduction of the electrical and mechanical stresses in the switch. These advantages lead to the operation of many switches in series and/or parallel, higher average powers and longer lifetimes. Energy Compression Research Corporation (ECR) has demonstrated an advanced UWB source based on light activated silicon switches (LASS). The UWB source consists of a single LASS device mounted on a low impedance (< 0.5 (Omega) ) microstrip transmission line and a high fidelity impedance transformer connected to a 50 (Omega) coaxial connection. The voltage was measured at low impedance and 50 (Omega) to verify the efficiency and fidelity of the impedance transformer. After a transformation of 110:1 in impedance, the measurement at the end of the transformer verified that pulse rise-time was less than 100 ps and the overall efficiency was 50%. The system was tested up to 10 kV into 50 (Omega) before connector breakdown limited further increase. Larger powers can be radiated if the transformer is directly connected to the antenna.
We report on the application of new electro-optic modulators which are controlled by photoconductive switches. Various configurations of modulator are presented and are applied to several applications. Experimental results are presented in which a photoconductively controlled modulator is used to Q-switch and cavity dump a Nd:YAG laser, utilizing only a single external trigger. The same modulator is also used to Q-switch, mode-lock and cavity dump the same laser. The use of the modulator results in a single laser being able to generate pulses in three duration ranges, i.e., approximately 20 ns, approximately 2 ns and approximately 70 ps. A similar modulator is used to suppress the pre-pulse generated by a regenerative amplifier and help attain a 105 contrast ratio between signal and pre-pulse. Other modulators and applications are presented, including an approximately 30 ps Pockels cell for use as an optical gate.
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