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Feedback Stabilized Scanlaser

IP.com Disclosure Number: IPCOM000091370D
Original Publication Date: 1968-Jan-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 3 page(s) / 69K

Publishing Venue

IBM

Related People

Myers, RA: AUTHOR

Abstract

A scanlaser is a light-scanning device which utilizes the nonlinear properties of the laser. In the scanlaser, no deflection of laser light actually occurs. Instead, the laser is so controlled as to emit only from one selected point on its output mirror at any given time. A scanlaser is a laser device which consists of an optical resonator capable of supporting a large number of transverse modes and of electrical devices for selecting those modes which are to lase at any given time.

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Feedback Stabilized Scanlaser

A scanlaser is a light-scanning device which utilizes the nonlinear properties of the laser. In the scanlaser, no deflection of laser light actually occurs. Instead, the laser is so controlled as to emit only from one selected point on its output mirror at any given time. A scanlaser is a laser device which consists of an optical resonator capable of supporting a large number of transverse modes and of electrical devices for selecting those modes which are to lase at any given time.

The two basic components of a scanlaser are its multimode cavity or resonator and its mode selector. There are electron beam type scanlasers and digital type scanlasers. One type of digital scanlaser uses Nd:YAG, neodymium yttrium aluminum garnet, as the active medium. The YAG laser is subject to both short and long term output fluctuations. This describes a method by which the fluctuations can be suppressed. Such method is not restricted to the particular scanlaser device considered.

The digital scanlaser consists of an active element YAG and a mode selector of some type. The resonator is so constructed that it can support a large number of nearly degenerate transverse modes. Scanning is then accomplished by selecting one of the modes and spoiling the Q for all others. One of the modes of the scanlaser is maintained above threshold at all times. There is derived from the output of this mode an error signal with which to correct the fluctuations in other modes.

Two fundamentally different methods of feedback control can be used. In one, the output of the reference mode is detected photoelectrically and compared with an electrical reference signal. The difference between the two is then amplified and used to control the electrical input to the laser pump, e.g., to the lamps. This system is shown in drawing 1.

A second method, which is much better suited to the scanlaser and is, in addition, much faster, takes the error signal as before, but uses it to control the intracavity loss for all modes. This...