# US 5,351,261 A · Integrated optics

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- Number: US 5,351,261 A
- Document ID: US5351261A
- Status: Granted
- Kind: A
- Application number: 08/048,533
- Filed: 1993-04-14
- Granted: 1994-09-27
- Earliest claimed: 1993-04-14
- Assignees: AT&T Bell Laboratories
- Inventors: Louis D. Lanzerotti; Samuel L. McCall; Bernard Yurke
- Web page: https://patentgrep.com/patent/US5351261A

## CPC

- H01S 5/1075: {Disk lasers with special modes, e.g. whispering gallery lasers}
- H01S 5/4025: {Array arrangements, e.g. constituted by discrete laser diodes or laser bar (H01S5/42 takes precedence)}
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL

## Abstract

Lasing threshold for a whispering mode laser is reduced by appropriate placement of a reflector. A reflector parallel to, and within a wavelength distance of, the disk decreases radiation loss due to imperfect internal reflection. Enhancement is calculable on the basis of destructive interference between reflected and direct radiation.

## Claims

### Claim 1

Apparatus including at least one element including a path for an electromagnetic wave within a body of high refractive index for such energy relative to refractive index of surrounding ambient, at least some portion of the path being curved to a curvature defined by a local radius as bounded at an interface between such body and ambient, the interface defining a convex surface of the high index material, retention of energy within such path being at least partially due to small angle incidence of the energy at the interface, relative refractive indices and curvature at incidence being such as to result in loss by direct radiation from the body, po1 CHARACTERIZED IN THAT
an interfering mirror is provided as spaced from the body and of such extent that a portion of the radiation is reflected, thereby increasing the path length for reflected radiation, so that it destructively interferes with direct radiation and thereby decreases radiation loss.

### Claim 2 (depends on 1)

Apparatus of claim 1 in which the element is a non-resonant waveguide.

### Claim 3 (depends on 1)

Apparatus of claim 1 in which the element is a resonant cavity for a peripheral path of at least three wavelengths in length.

### Claim 4 (depends on 3)

Apparatus of claim 3 in which the element is of regular shape, and in which the path defines a regular polygon.

### Claim 5 (depends on 4)

Apparatus of claim 4 in which the element is a disk defining a modal path of at least five wavelengths.

### Claim 6 (depends on 1)

Apparatus of claim 1 in which the interfering mirror is planar, is spaced from the body by a distance .ltoreq. the wavelength, .lambda., of the electromagnetic wave, and in which the mirror extends to a distance at least twice as great as the radius defining the curved path.

### Claim 7 (depends on 6)

Apparatus of claim 6 in which the element is a peripheral mode resonant disk of regular shape, so that the mirror extends to a distance at least as great as the diameter of the disk.

### Claim 8 (depends on 7)

Apparatus of claim 7 in which the element is a whispering mode laser.

### Claim 9 (depends on 8)

Apparatus of claim 8 in which the laser mode is TM.

### Claim 10 (depends on 8)

Apparatus of claim 8 in which the laser mode is TE.

### Claim 11 (depends on 6)

Apparatus of claim 6 in which the interfering mirror consists essentially of a gold layer.

### Claim 12 (depends on 6)

Apparatus of claim 6 including a second interfering mirror as defined in that claim, the first and second mirrors sandwiching the body.

### Claim 13 (depends on 6)

Apparatus of claim 6 in which spacing corresponds with the height of a supporting pedestal.

### Claim 14 (depends on 6)

Apparatus of claim 6 in which spacing corresponds with interposed material of low dielectric constant relative to that of the body.

### Claim 15 (depends on 14)

Apparatus of claim 14 in which the interposed material consists essentially of SiO.sub.2.

### Claim 16 (depends on 6)

Apparatus of claim 6 including a plurality of elements as defined.

### Claim 17 (depends on 16)

Apparatus of claim 16 including at least one whispering mode laser.

### Claim 18 (depends on 17)

Apparatus of claim 17 including at least one two-port element.

### Claim 19 (depends on 17)

Apparatus of claim 17 including at least one three-port element.

### Claim 20 (depends on 1)

Apparatus of claim 1 in which interfering mirror is provided about substantially the entirety of the convex surface.

### Claim 21 (depends on 20)

Apparatus of claim 20 in which interfering mirror is omitted about a region of the convex surface to permit emission from that region to define an emitting region.

### Claim 22 (depends on 21)

Apparatus of claim 21 in which the element is a disk laser.

### Claim 23 (depends on 22)

Apparatus of claim 22 in which the emitting region is further provided with means for increasing intensity of emission by constructive interference with reflected radiation.