Electron beam generating apparatus and optical sampling apparatus using the same

1. An optical sampling apparatus comprising:

a cathode for generating an electron beam in accordance with an optical signal applied to the cathode;

a deflection electrode for deflecting the generated electron beam;

a sampling slit for transmitting a part of the deflected electron beam; and

a charge detection section that detects a quantity of charges or accumulated current of the transmitted electron beam, further comprising:

a first substrate and a second substrates that are brought into tight contact with each other,

wherein the cathode, the deflection electrode and the sampling slit are disposed in a recess portion formed in at least one of the first and second substrates and are sealed in the recess portion under vacuum with the first and second substrates.

2. The optical sampling generating apparatus according to claim 1 ,

wherein an optical window is formed near a side edge portion of the second substrate, and wherein said optical beam is irradiated onto said cathode through the window.

3. An electron beam generating apparatus comprising:

a source of an optical signal,

a cathode irradiated with said optical signal,

wherein the cathode generates said electron beam in accordance with the optical signal, wherein the cathode is disposed within a package having a window, and

wherein said optical beam is irradiated onto said cathode through the window.

4. The electron beam generating apparatus according to claim 3 , wherein the cathode comprises a carbon nanotube.