A thyristor will stay conducting until the current through the device is zero (“current zero”) or perhaps slightly negative. LLNL’s approach is to use the opticondistor (“OTV”) to force this current zero in order to force the device into an “off” state. By combining a light-activated thyristor with an OTV, a noise-immune, high efficiency, high-power switching device can be constructed. The…
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- (-) Photoconductive Semiconductor Switches (PCSS) (9)
![A cross-sectional schematic of a diffused Ga2O3 photoconductive semiconductor switch (PCSS)](/sites/default/files/styles/scale_exact_400x400_/public/2024-02/a%20cross-sectional%20schematic%20of%20a%20diffused%20beta-Ga2O3%20PCSS.png?itok=Z41s0FbO)
The researchers’ approach leverages the concept that dopants have high diffusivities in Ga2O3; the key lies in the selection of the appropriate dopant. This LLNL invention describes two device types that employ this design:
![Samples of optimized diamond switches](/sites/default/files/styles/scale_exact_400x400_/public/2024-01/Samples%20of%20optimized%20diamond%20switches.png?itok=5syzdD0q)
Design and construction of a photoconductive switch requires a diamond photoconductor illuminated by light of a certain excitation wavelength.
Characteristics of the LLNL-developed switch are as follows:
![Custom PCB design of a PCSS Laser Diode Driver](/sites/default/files/styles/scale_exact_400x400_/public/2023-11/PCSS%20Laser%20Diode%20Driver.png?itok=WQ2FNHQF)
LLNL researchers have invented an ultrafast PCSS to drive a high-power laser diode with arbitrary pulse widths. These devices operate by supplying a high voltage (>10 kV) to one side of the switch. A short pulse of light illuminates the semiconductor, instantly turning it from highly resistive to highly conductive.
![twister oven component with reflective inner cylinder surface](/sites/default/files/styles/scale_exact_400x400_/public/2023-06/twister%20oven%20component.png?itok=v3jlzm2V)
U.S. Patent No. 11,555,965 describes LLNL’s invention of “Illumination Frustums” for photoconductive switches to capture and “frustrate” the light from leaving the frustum. LLNL researcher’s latest novel invention, “Twister Oven”, achieves this by encouraging laser light absorption in a photo conductor material. Light enters the oven twisting and reflecting, making near normal incident multi…
![A photoconductive switch made from a synthetic, chemical vapor deposition diamond under test](/sites/default/files/styles/scale_exact_400x400_/public/2023-06/Photoconductive%20switch.jpg?itok=xC1O7vXg)
Design and construction of a photoconductive switch requires a diamond photoconductor illuminated by light of a certain excitation wavelength. The diamond material is chosen to be doped with substitutional nitrogen to act as a source of electrons. The device architecture allows maximum light entering the aperture. The top and bottom electrodes are made of ultra-wide bandgap (UWBG)…
![schematic of LLNL’s field emission photocathode device architecture with examples of tunable SiC surface micro- and nanostructures fabricated at LLNL](/sites/default/files/styles/scale_exact_400x400_/public/2023-05/FE%20photocathode%20device.png?itok=z-1Om9v8)
LLNL researchers faced this challenge by bridging the gap between VEDs and solid-state electronics (SSE). Their approach was to create a hybrid vacuum microelectronic device (VMD) architecture that combines the properties of vacuum as the electronic medium and the compact form factor and manufacturing scalability of semiconductor microelectronic chips.
![Segments of transmission line lengths can be switched to open circuit (as shown) or shorted to the ground (not shown)](/sites/default/files/styles/scale_exact_400x400_/public/2023-05/Segments%20of%20tranmission%20line%20lengths.png?itok=FF0qaBGw)
Design and construction of a photoconductive switch requires a diamond photoconductor illuminated by light of a certain excitation wavelength. The diamond material is specifically doped with substitutional nitrogen, which act as a source of electrons. The device architecture allows maximum light entering the aperture. The top and bottom electrodes are made of ultra wide band gap (UWBG)…
![Annular illumination on photo conductor by Conical Total Internal Reflection “CTIR” endcap](/sites/default/files/styles/scale_exact_400x400_/public/2023-05/CONIFR.png?itok=L4wSanXF)
The approach is to use a custom-designed frustrum and attach it to the optical fiber that connects to the PCSS. Light from the fiber enters the frustrum, spreads out, and enters the PCSS. Any unabsorbed light re-enters the frustrum and, because of its geometry, reflects back into the PCSS itself with only a negligible fraction escaping from the fiber. The shape of the novel frustrum is…