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Silicon as a Bleachable Absorber for Q Switching of a Laser

IP.com Disclosure Number: IPCOM000096105D
Original Publication Date: 1964-Dec-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 21K

Publishing Venue

IBM

Related People

Armstrong, JA: AUTHOR [+2]

Abstract

Laser crystal 2 is an active medium or a negative temperature medium and, in one example, is formed of glass doped with neodymium. Crystal 2 is prepared with totally reflecting surfaces 4 and 6 at one end and an anti-reflecting coating 8 at its other end. Mirror 10 is substantially 99% reflective and 1% transmissive of wave lengths of light in the region of 1.06 mu. Interposed between layer 10 and ruby crystal 2 is single crystal silicon slab 12. Its band gap is chosen so as to give a small absorption at the neodymium laser wave length, namely, 1.06 microns.

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Silicon as a Bleachable Absorber for Q Switching of a Laser

Laser crystal 2 is an active medium or a negative temperature medium and, in one example, is formed of glass doped with neodymium. Crystal 2 is prepared with totally reflecting surfaces 4 and 6 at one end and an anti-reflecting coating 8 at its other end. Mirror 10 is substantially 99% reflective and 1% transmissive of wave lengths of light in the region of 1.06 mu. Interposed between layer 10 and ruby crystal 2 is single crystal silicon slab 12. Its band gap is chosen so as to give a small absorption at the neodymium laser wave length, namely, 1.06 microns.

When pumping energy from source 14 is applied to the neodymium glass laser 2, the initial loss in slab 12 necessitates a large pump power for the production of laser action. Such large pump power results in a relatively large inverted population. At some point during the pumping of laser 2, the silicon bleaches, permitting laser 2 fire. Since the population inversion has been kept in excess of the normal threshold of laser 2 due to the absorption characteristics of the silicon in its unbleached state, the resulting firing of laser 2 during bleaching produces a giant pulse. Such giant pulse can be sensed by a detector.

Other semiconductors can be used as bleachable absorbers in the infrared so long as the semiconductor employed, either pure or alloyed, has the proper band gaps. As an example, the uranium laser, whose wave length is 2.5 microns, can be...