OPTICAL MASS MEMORY EMPLOYING AMORPHOUS THIN FILMS

• US 3,696,344 A
• Filed: 02/19/1970
• Issued: 10/03/1972
• Est. Priority Date: 02/19/1970
• Status: Expired due to Term

• Current Assignee: Julius Feinleib, Robert F. Shaw
• Original Assignee: Julius Feinleib, Robert F. Shaw
• Inventors: Feinleib, Julius, Shaw, Robert F.
• Primary Examiner(s): Konick, Bernard
• Assistant Examiner(s): Hecker, Stuart
• Application Number:
  US05/012,622
• Time in Patent Office: 957 Days
• Field of Search: 340/173LS,173LT,173LM,173CC 350/16R
• US Class Current: 365/127
• CPC Class Codes: G11B 2007/24316 group 16 elements (i.e. chalcogenides, Se, Te)
• CPC Class Codes: G11B 7/00454 involving phase-change effects
• CPC Class Codes: G11B 7/0062 Overwriting strategies, e.g. recording pulse sequences with erasing level used for phase-change media
• CPC Class Codes: G11B 7/2433 Metals or elements of Groups 13, 14, 15 or 16 of the Periodic Table, e.g. B, Si, Ge, As, Sb, Bi, Se or Te
• CPC Class Codes: G11C 13/048 using other optical storage elements

Abstract

This optical mass memory utilizes an amorphous semiconductor thin film which can be switched between a generally amorphous or disordered state and a crystalline or more ordered state by applying a laser beam. The laser beam is modulated and scanned across the amorphous film to record and erase information by switching the state of certain regions of the film. The same laser beam modulator and scanner can be used to read the information stored on the film by detecting whether the film is in the amorphous or crystalline state at any given location. The laser beam is composed of at least two frequencies, one of which is absorbed by the amorphous film and is used to write and also erase information on the film. The amorphous film is transparent to the other frequency and the transmission of this frequency is used to determine whether the film is in the crystalline or amorphous state at any given location thereby reading out the information recorded therein.

Claims

1. A system for storing and retrievinG information comprising:

a source for the provision of radiant electromagnetic energy in the form of a single beam comprising energy of at least a first frequency and energy of a second frequency;

a layer of semiconductor memory material capable of being reversibly switched between two stable structure states in response to the amount of energy applied thereto of said first frequency, and which material produces a different detectable effect upon energy of said second frequency applied thereto, depending upon the stable structure state in which said material resides;

one of said stable structure states being a generally amorphous or disordered state and the other stable structure state being a crystalline or more ordered state;

beam directing means for applying said single beam of electromagnetic radiation from said source to certain regions of said memory material;

control means for varying the amount of energy of said first frequency applied to said memory material by said beam directing means into at least three levels, a highest level sufficient to switch said memory material into one of said two stable structure states, an intermediate level sufficient to switch said memory material into the other of said two stable structure states, and a low level insufficient to switch said memory material; and

detecting means, responsive to the effect said memory material produces upon energy of said second frequency applied to certain regions of said memory material by said beam directing means, for detecting the stable structure state of said memory material at said certain regions whereby the information stored in said memory material is retrieved.

2. The system as defined in claim 1 wherein said control means varies the amount of energy at said second frequency applied to said memory material by said beam directing means in a manner relatively proportional to the manner in which said control means varies said first frequency, and with sufficient energy of said second frequency in all three of said levels to permit said detecting means to detect the stable structure state of said memory material.