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Phase Locked Digital Scanlaser

IP.com Disclosure Number: IPCOM000092246D
Original Publication Date: 1968-Oct-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 3 page(s) / 32K

Publishing Venue

IBM

Related People

Pole, RV: AUTHOR

Abstract

The digital scanlaser is a device employing a multimode conjugate laser cavity in which one cavity mirror is in the form of separate horizontal stripes and the other cavity mirror is in the form of separate vertical stripes. Modes are selected by applying voltage to selected horizontal and vertical stripes.

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Phase Locked Digital Scanlaser

The digital scanlaser is a device employing a multimode conjugate laser cavity in which one cavity mirror is in the form of separate horizontal stripes and the other cavity mirror is in the form of separate vertical stripes. Modes are selected by applying voltage to selected horizontal and vertical stripes.

In this digital scanlaser, the switching speed of the device is considerably increased by phase-locking the modes. The principle is applicable to any version of the digital scanlaser, however, this relates to the particular version shown.

The active medium 10 is Nd:YAG. Switching is accomplished on KDP crystals 12 and 14 covered with striped mirrors. The horizontal one is mirror 12, the vertical one is mirror 14. Also included in the system is a phase modulator 16, either electro-optic or acousto-optic, capable of modulating the internal laser light at exactly the frequency of the longitudinal mode separations, i.e., with the frequency v = c/2L. L is the optical length of the resonator and c the velocity of light. Then the laser, if in lasing conditions, is phased-locked. Thus, all its longitudinal modes are in phase and the lasing light consists of periodic short pulses, due to the interference of all longitudinal modes. These pulses appear with a period T = (1/v) = 2L/c. Their width t is of the order of t approximately = (1/ delta v(osc))=0.3 x 10/-11/ sec. which is the oscillating line width of the lasing transition. These are extremely short pulses.

A pair of striped mirrors, one horizontal and one vertical, is selected or a pair of specially circular mutually conjugated mirrors, not shown, can be provided which have very high reflectivity. The laser can then be made to continuously oscillate between these two mirrors, regardless of whether any other pair is despoiled for scanning or not. The phase modulator has to be constantly on, working at the frequency v.

The scanlaser cavity is a degenerate one and all other possible spatially different modes belong to the same set of longitudinal modes. Furthermore, due to the fact that all th...