Electronic – Photoelectric effect vacuum tube

physicsvacuum-tube

It occurred to me that it ought to be possible to make a vacuum tube which, instead of a heater, uses an intense light source, such as a laser, to kick electrons off of the cathode through the photoelectric effect instead of them being excited using a heated filament. I am aware that two terminal evacuated tubes have been made, using the photoelectric effect to sense light and its wavelength too (as in Einstein's experiment). However, this device would have one or more grids, a plate (anode), and a cathode just like a typical amplifying vacuum tube, the only difference being a light source in place of a heater. Would this:

A. Be possible?

B. Be practical? (at least to the extent to which a vacuum tube is practical at all)

And…

C. Has it been done?

I cannot find anything about this using Google, some lab equipment is taking precedence over the results I am looking for, if they exist.

EDIT:

Here is a functional diagram:Laser Excited Photoelectric Effect Vacuum Tube Amplifier Functional Diagram

Here are the first drawings I made of the device. The scans aren't so great, but it shows my original concept and a proposed Class B amplifier, as an example of an application which almost certainly would never work. Connections points A and B are an incoming audio signal. C is a connection to voltage supply. D is power for the lasers. I suspect that the laser diodes ought not be connected in parallel as is shown, but I didn't think of that while drawing this. Perhaps it is okay.Drawings of Photoelectric Effect Amplifier Tubes and a Class B Amplifier

Best Answer

These were common before the transistor and called "Phototubes". Every 16mm sound projector in the US schools had one to read the sound track on the film.

With higher voltage and multiple plates - one designed to emit electron when struck by light. The others are meant to kick out more electrons when they are hit by an energetic electron and you get a cascade. These are "Photomultipliers" and are still used extensively for photon counting and any very low light application like fluorescence spectroscopy or phosphorescence lifetime measurement.

There is a very fast and sensitive star tracking application that uses a spinning mask in the optical path to a photomultiplier. I have not seen one in decades even though they have a much faster response than CCD based tracking.

Hamamatsu is one maker of both devices in many forms.