PHOTOELECTRIC CATHODE

PROBLEM TO BE SOLVED: To provide a photoelectric cathode superior in detection sensitivity of light. SOLUTION: When detecting light enters a support substrate 2 side of a photoelectric cathode E1, an optical absorption layer 3 absorbs this detecting light and generates a photoelectron. However, dependent on the thickness or the like of the optical absorption layer 3, the detecting light is not absorbed sufficiently by the optical absorption layer and occasionally transmitted through the optical absorption layer 3. In this case, the detecting light transmitted through the optical absorption layer 3 reaches an electron emitting layer 4. A part of the detecting light reaching the electron emitting layer 4 advances toward a through hole 5a of a contact layer 5. The length d1 of the diagonal line of the through hole 5a is shorter than the wavelength of the detected light, thereby, emission of the detected light to the outside by passing through the through hole 5a is certainly suppressed. The detecting light suppressed from emitting to the outside is reflected by the exposed surface of the electron emitting layer 4 and enters the optical absorption layer 3 again and is absorbed. COPYRIGHT: (C)2009,JPO&INPIT