Electron source designs are disclosed. The emitter structure, which may be silicon, has a layer on it. The layer may be graphene or a photoemissive material, such as an alkali halide. An additional layer between the emitter structure and the layer or a protective layer on the layer can be included. Methods of operation and methods of manufacturing also are disclosed.

A photocathode can include a body fabricated of a wide bandgap semiconductor material, a metal layer, and an alkali halide photocathode emitter. The body may have a thickness of less than 100 nm and the alkali halide photocathode may have a thickness less than 10 nm. The photocathode can be illuminated with a dual wavelength scheme.

A photocathode can include a body fabricated of a wide bandgap semiconductor material, a metal layer, and an alkali halide photocathode emitter. The body may have a thickness of less than 100 nm and the alkali halide photocathode may have a thickness less than 10 nm. The photocathode can be illuminated with a dual wavelength scheme.

Disclosed herein is a method comprising: emitting electrons from an electron ejector in response to an incident photon; driving the electrons through a hole toward a detector configured to collect the electrons and provide an output signal representative of the incident photon; driving the electrons away from sidewalls of the hole, using an electric field.

Disclosed herein is a method comprising: emitting electrons from an electron ejector in response to an incident photon; driving the electrons through a hole toward a detector configured to collect the electrons and provide an output signal representative of the incident photon; driving the electrons away from sidewalls of the hole, using an electric field.

A flat top laser beam is used to generate an electron beam with a photocathode that can include an alkali halide. The flat top profile can be generated using an optical array. The laser beam can be split into multiple laser beams or beamlets, each of which can have the flat top profile. A phosphor screen can be imaged to determine space charge effects or electron energy of the electron beam.

Exemplary metamaterial photocathodes enable detection of light from visible through long wave infrared wavelengths. Metamaterial stacks, comprising gold, silicon, and cesium-oxide, coupled to a semiconductor allow hot electrons to efficiently enter a vacuum. The hot electrons are multiplied in a multichannel plate and directly through another vacuum towards a phosphorus screen.

Exemplary metamaterial photocathodes enable detection of light from visible through long wave infrared wavelengths. Metamaterial stacks, comprising gold, silicon, and cesium-oxide, coupled to a semiconductor allow hot electrons to efficiently enter a vacuum. The hot electrons are multiplied in a multichannel plate and directly through another vacuum towards a phosphorus screen.

The invention relates to a photocathode including an input window (210) suitable for receiving a flow of incident photons, and an active layer (230), the active layer consisting of a plurality of elementary layers (2301, 2302) made of semiconductor materials having decreasing forbidden bandwidths in the direction of the flow of incident photons. The surface of the photocathode opposite the input window is structured so that each elementary layer of the active layer has its own photoelectric emission surface (2401, 2402). By choosing the semiconductor materials of the elementary layers, it is possible to obtain an image which has high sensitivity in both the visible spectrum and the near infrared.

The invention relates to a photocathode including an input window (210) suitable for receiving a flow of incident photons, and an active layer (230), the active layer consisting of a plurality of elementary layers (2301, 2302) made of semiconductor materials having decreasing forbidden bandwidths in the direction of the flow of incident photons. The surface of the photocathode opposite the input window is structured so that each elementary layer of the active layer has its own photoelectric emission surface (2401, 2402). By choosing the semiconductor materials of the elementary layers, it is possible to obtain an image which has high sensitivity in both the visible spectrum and the near infrared.