JPS59121027A - Optical device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical amplifier for amplifying the light intensity of a total optical image.

BACKGROUND OF THE INVENTION Conventionally, optical amplifiers are configured to receive an unmodulated human-powered spot beam and an intensity-modulated signal spot beam to produce an amplified, intensity-modulated output spot beam. It is something that

In television images, the entire image is transmitted over one cycle. 2. Conventional optical amplifiers, used to amplify television images, must amplify small individual segments, tiny spots, of the image individually at different time periods over a cycle. Must be. The disadvantage is that before these image segments can be amplified, the entire image has to be segmented and, as a result, reconstructed into an image using complex electronic circuitry.

A problem with conventional optical amplifiers is that they require complex and expensive optoelectronic equipment to segment, amplify, and reconstruct images.

SUMMARY OF THE INVENTION This problem can be solved by an optical image amplifier configured to receive an unmodulated light beam and an input image beam. The image intensifier according to the invention instantly produces a fully optically amplified image with a spatially modulated light intensity distribution that depends on the spatially modulated light intensity distribution of the input image beam. It includes a non-linear optical device.

DETAILED DESCRIPTION 1. Referring to FIG. 1, receiving an unmodulated input beam 20,
Optical image amplifier 16 receiving input optical image beam 22
is the indication. Both person beams 20.22 include a region large enough to span the associated input images. In response to these input source beams, an optical image intensifier 16
produces an optically amplified output image beam 24 that is dependent on the input image beam 22. Output image beam 24 also includes a sufficient area to contain the relevant images.

In the amplifier 16, an input image beam 22, having a spatially modulated light intensity distribution 23 to represent the image, is received by a beam splitter 25, which has a partially reflective coating. A beam splitter 25 is positioned at an angle to reflect the rays of the input image beam 22 into the Fabry-Perot resonator 28 in a direction perpendicular to the input plane. An unmodulated input beam 20 is transmitted through a beam splitter to a resonator 28 in a direction perpendicular to the input surface of the beam splitter. The light intensity of input beam 20 is not modulated in time and is substantially uniform across the area of input image beam 22.

The amplifier 16 also includes partially transparent mirrors 29 facing each other on a common optical axis, which is perpendicular to the mirror surface and forming a Fabry-Perot cavity 28. .

The input beam 20.22 is incident on the left-most mirror 29 in the direction of the common element axis. A thin slab of nonlinear optical material 30 is contained inside the cavity between mirrors 29.

An important parameter of an optical material is its optical path length, ie its physical length multiplied by its refractive index. The nonlinear material 30 must exhibit an (8) optical Kell effect in effect, in which its refractive index is a function of the light intensity inside the material. The refractive index of a nonlinear material is n = n(, -4-n2I
where n(1 is the refractive index for low-intensity light, n2 is the optical Kel constant, and ■ is the intensity of light inside the material. An increase in the intensity of will increase the refractive index once the input light from the unmodulated beam is beam diffused.

It is transmitted to the cavity 28 via the Litter and the left mirror, which oscillates between the mirrors 29 inside the nonlinear optical material 30 . In the light from inside the resonator 28,
It leaks out through the right mirror in output beam 24 and is thereby transmitted.

The intensity of light in the resonator depends on the optical path length of the resonator 28. If the optical path length of the resonator corresponds to an integer number of half wavelengths of the incident light, the sequentially emitted waves are in phase.

The waves constructively interfere with each other to produce a powerful output beam 24. This condition corresponds to the peak value, or maximum value, of the light intensity inside the device,
called resonance. At frequencies away from resonance, destructive interference occurs inside the cavity, reducing the light intensity transmitted within and through the device.

In FIG. 2, a resonator transmission curve 33 (output light intensity/input light intensity versus optical wavelength) for the resonator 28 in FIG. 1 is shown.
is the indication. Resonance occurs at peak value 35 shown in FIG. As shown on the vertical axis, the transmission at the peak value is equal to 2. The horizontal scale is the optical wavelength of the resonator, referred to as the incident optical wavelength. At frequencies away from the resonator, the destructive interference reduces the resonator transmission, creating a valley 36 between the resonant peaks in FIG.

Because of the nonlinear optical material 30, the optical length in the resonator 28 is proportional to the light intensity in the resonator, which in turn is proportional to the output light intensity. This relationship is represented in FIG. 2 by a set of straight lines. The slopes of these straight lines are inversely proportional to the input light intensity. The lines all pass through a common point 40, corresponding to the length of the resonator at zero light intensity in the resonator.

The position of this common point 40 can be adjusted by changing the tuning of the resonator. For a given input light intensity, the points where the -set of straight lines intersect the resonator transmission curve 33 represent possible steady-state operating points A, B, C, .D, E.

From the simple graph configuration of FIG. 2, the basic output light intensity can be easily obtained for the input source intensity characteristics of the device, as shown in FIG. At low input source strengths, such as that corresponding to point A in both Figures 2 and 3,
There are negligible nonlinear effects and therefore the resonator transmission is low. As the input source intensity increases, the light intensity and transmission in the resonator begins to increase. As the input light intensity further increases, the tuning of the resonator approaches the operating points B, C, and D, and the transmission rapidly increases accordingly (11).

Physically, light in a resonator changes its refractive index inside the nonlinear material to tune the resonator to a value close to the resonance point, thereby increasing the light intensity within the resonator and creating positive feedback. It gives an effect. Furthermore, an increase in the input light intensity, corresponding to point E, causes the resonator to tune away from the resonance point, thereby reducing the light intensity inside the resonator and applying negative feedback that stabilizes the output light intensity. There is.

Journal of the American Society of Applied Physics, by R. C. Miller et al.
Volume 47, No. 10, pages 4509-4517 (1976, Publication 1), as well as materials such as those reported in J. Hegarty et al., American Applied Physics Essays, Volume 40, No. 2, pages 132-134. Page (198
Materials with multiple quantum wells, such as those reported in 2007, published in 1, provide suitable nonlinear optical properties for use with unmodulated input beams from Gouiot tracer sources operating at room temperature (12). . (R.C., Miller et al., Jo
urnal of Applied Physics,
Vol, 47. Nα10. pP.

4509-4517 (1976): J, H
Egarty et al.

Applied Physics Letters,
Vol, 40. Nα2゜pp, 132
-134 (1982)) The multiple quantum well material is Ga
It has an As/Ga1-XAtxAs structure. In the specific material example, a GaAs layer of 102 A and a G of 107
ao, 7□A16.28As layers are alternately included. The total thickness of the material is 2.4 microns. These layers must be perpendicular to the direction of light propagation, as shown in FIG. The nonlinear refractive coefficient n2 is described by D.N.B. Miller et al. in American Applied Physics Essays, Vol. 41, No. 8, pp. 679-681.
page (2×lO as reported in 1982 Publishing 1)
``It is close to the value of i/W. (D, A, B.

Miller et al, Applied Phys.
sics Letters.

Vol, 41. t@8. pp, 679-681
(1982) ) A light intensity signal source, such as the Gouioto laser described above, providing an unmodulated input light beam 20 has an optical axis oriented perpendicular to the surface of the partially transparent mirror 29 of the resonator. The beam is made to travel straight along the beam through a beam splitter 25 and a resonator 28. As previously discussed, this monochromatic source of unmodulated light is arranged to have a relatively uniform intensity across the surface portion of the resonator that receives the input image beam. The strength of this unmodulated signal source does not change over time.

The image source of the input image beam 22 is the reflection of the beam from a beam splitter 25 along an optical axis perpendicular to the surface of a partially transparent mirror 29 of the resonator 28 . The input image beam includes a spatially modulated intensity distribution, as shown in image 23. Different spatial elements of the input image will have different intensities. The strength of elements can change over time. Thus, either a fixed image or a moving image can be used as an input to the image amplifier 16.

The light of unmodulated beam 20 as well as input source image beam 22 effectively covers the same surface area on a thin slab of nonlinear optical material 30. Since the unmodulated beam and the input image beam are incident on the area of the effective surface of the resonator, the entire image is instantly amplified. For conceptual reasons, the surface of the resonator can be thought of as an array of subareas, or segments, each corresponding to an element of the entire image. These individual segments of resonators function as individual optical amplifiers within the array. Each of these optical amplifiers operates on a corresponding element of the image. Each optical amplifier is responsive to the light intensity of an input image element incident thereon to produce an associated element of an output image. The intensity of the relevant segment of the output image is amplified according to the characteristics of FIG. Each different element of the output image can change over time depending on changes in related elements of the input image. Thus, the optically (15) amplified output image can be a still image or a moving image. In either case, all elements of the instantaneous value input image 23 are amplified simultaneously to produce a similar but optically amplified associated instantaneous output image 31. The output image beam 24 therefore has a spatially modulated intensity distribution that is dependent on the spatially modulated intensity distribution of the input image beam 22.

At a point such as point 40 near the peak of resonance in FIG.
The wavelength of the input beam is selected such that all segments of the resonator are activated.

For one segment of the resonator, each straight line drawn through the operating point 40, as shown at point 40 on the horizontal axis in FIG. This operating point is close enough to the resonance peak so that only the output light intensity/input source intensity curve is crossed.

As previously explained, the straight lines represent behavior at different input source strengths.

(16) The curve in FIG. 3 is a nonlinear, two-level transfer characteristic curve. The substantially linear operating region 46 of the curve has a steep slope, interconnecting the lower and higher regions of the curve. Amplification of the image elements is effectively accomplished within the linear operating region of the associated segment of amplifier 16. As shown in FIG. 3, a time-varying input image element 47 having a light intensity with a relatively small amplitude has a corresponding time-varying output image element 47 having a relatively large amplitude depending on the amplitude change in the input image intensity. 48. Each area segment of resonator 28 operates with a transfer characteristic curve as shown in FIG.

Considering the output as a whole, the entire input image is instantly optically amplified by all segments of the image intensifier, as explained above.

Referring now to FIG. 4, unmodulated optical beam 6 is directed through beam splitter 57 toward surface region 61.
An optical image amplifier 56 is shown for receiving 0 and an input optical image beam 62. As previously discussed with respect to input beam 23 of FIG. 1, the input optical image beam has a spatially modulated light intensity distribution 64.

In FIG. 4, unmodulated beam 60 traverses beam splitter 57, which is shown as a partially mirrored transparent glass plate. This unmodulated beam passes through a beam splitter and transmits the elements of the unmodulated beam to a lens 65, an array of fly eyepieces, which focuses the elements of the unmodulated beam into an array of small area beams of small cross-section, i.e. spot beams 66. . This array of focused small area beams is applied perpendicular to the surface of a self-focusing imaging material 68, such as sodium vapor.

In self-focusing materials, a small area beam 66
are respectively J.E., Joecomb et al.
Each small-area beam 66 is arranged such that the refractive index is The self-focusing image is focused on the surface of the profile depending on the light intensity.

The refractive index increases with increasing light intensity. The input source power Pin of each incident small area beam, that is, the spot beam, is adjusted so that the critical power per is equal to Y so that the beam penetrates the material without changing the spot size. This is referred to as self-capture. If the input optical power of spot beam 66 is much less than the critical power, the beam will diverge significantly through self-focusing imaging profile 68. If the input source power of the spot beam is greater than the critical power, the beam will converge through this material.

The array of spot beams generated on the face 63 of the self-focusing imaging profile passes through an array of apertures 70 to another lens 72 on a partially transparent mirror 75, an array of fly eye lenses. passing through. This mirror (
19) is vertically aligned to the array of unmodulated beams to provide optical feedback.

The transmitted light forms an optically amplified image beam 77.

The open lower 0 allows substantially all of the light from each self-focusing imaged beam to pass through mirror 75, and causes substantially all of the light reflected from mirror 75 to pass along the same self-focusing optical path. It is large enough that it can be done.

Open lower 0 is small enough to allow only a small portion of the beam that is not self-focused to pass through.

5, there is shown an operating characteristic curve 80 representing the output power relative to the total input power for each segment of the array of optical amplifiers shown in FIG. For total input power less than the self-focusing imaging power, the output power transmitted through mirror 75 is weak, as shown near the origin of FIG. If the total input power is somewhat high,
The output power gradually rises until the input power approaches the self-heating (20) point imaging power. When the total input power is greater than the self-focusing imaging power, the output power rises directly with the input power. At the self-focusing point, the output power becomes very steep.
Moreover, it rises in a straight line. There is a range in which the image amplifier of FIG. 4 operates linearly.

The input power of the unmodulated beam is selected such that each optical segment of the array of FIG. 4 operates in this linear region.

In this region of linear operating characteristics, each element of the array operates as an optical amplifier.

At the same time, the input optical image beam 62 is transferred to the beam splitter 5
7 is reflected onto a lens array 65 which images a small area, or element, of the input image into an array of input image elements. This array of input image elements is applied perpendicular to the surface 61 of the self-focusing imaging profile 68 along with an array of unmodulated manual spot beams. Both arrays of small area beams traverse the self-focusing imaging profile. Since each segment of the amplifier is operating in the linear part of the characteristic curve, each beam retains its small cross section.

Amplify the power of each input image element. The input image element is the waveform 81 superimposed on the operating characteristic curve 80 in FIG.
It is represented by The corresponding element of the output optical image 85 of FIG. 4 is represented in FIG. 5 by an optically amplified power waveform 82 that is dependent on the power of the associated input image element waveform 81.

Optically amplified image beam 77 of FIG. 4 is an array of amplified image elements, each element represented by a waveform such as waveform 82.

Overall, depending on the spatially modulated input beam 2, the optically amplified image beam contains an amplified image, since each element of the image may be different.

Optically amplified image beam 77 therefore has a spatially modulated light intensity distribution that is dependent on the spatially modulated light intensity distribution of input image beam 62.

Referring to FIG. 6, an optical image intensifier for receiving an unmodulated optical beam 90 and an input image beam 93 is shown. Unmodulated optical beam 90 is transmitted through linear optical material 91 to optical interface region 92 . The unmodulated input beam 90 may be considered to include a plurality of spot beams, or segments, each of which is described by P. W. Smith and W. G. Tomlinson, Journal of the Institute of Electrical and Electronics Engineers, June 1981, 2.
This interferes with the interface described by the authors on pages 6 to 33.

(P, W, Sm1th and W, J, T
omlinson, IEEE Spectrum, p.
ages 26-33. June 1981) An input image beam 93 is transmitted to the same interface region 92 via a nonlinear optical medium 94.

As noted for beam 23 in FIG. 1 (23), input image beam 93 has a spatially modulated light intensity distribution. Beam 93 thus includes an array of image elements.

Interface region 92 is an optical interface between linear optical material 91 and nonlinear optical material 94. Linear optical materials have a refractive index n. It is a common dielectric material such as glass with a Nonlinear optical materials are materials such as carbon disulfide, which have an optical intensity-dependent refractive index that causes the optical Kell effect.

The refractive index of the nonlinear medium is of the form n = nQ - △n2■. The refractive index when the intensity is zero is the refractive index n of a linear medium where Δ is extremely small.

be equivalent to. Its optical Kel coefficient n2 is a positive value. Input image beam 93 is introduced along input beam 90 either through a nonlinear optical material 94 as shown in FIG. 6 or by a beam splitter as shown in FIG.

Referring briefly to FIG. 7, unmodulated input beam 90 and input image beam 93 are transmitted along the axis of beam (24) 90 by beam splitter 95. The resulting composite beam 96 is continuous along the axis of beam 90 shown in the configuration of FIG. beam 90
Using a beam splitter 95 that combines and 93,
The resulting composite beam is oriented such that it enters the interface region 92 of FIG. 6 at an angle less than the critical angle on the low power side of the interface region 92. Such critical angles must be stated directly.

The reflectance of the interface region 920 is light intensity dependent. When the light intensity is low in a linear material, the critical angle Wc-('-)'/2.

If the angle of incidence is too small, all of the beam will be internally reflected at the interface relative to the input beam. In nonlinear materials, the beam is not transmitted, but an evanescent field
) exists there.

Because of the positive Kel effect, the annihilation field reduces the difference in refractive index across the interface, reducing the effective critical angle. By changing the effective critical angle close to the angle of incidence, the extinction field is increased. This gives a positive feedback effect; an increase in the incident light intensity increases the annihilation field, decreasing the effective critical angle and increasing the annihilation field.

At a critical input light intensity, total internal reflection suddenly causes almost all of the beam to be transmitted through interface region 92 and into nonlinear material 94 .

Referring to FIG. 8, there is shown a total input light intensity versus output light intensity operating characteristic curve 100, which is a curve representative of the operation of the array of segments of the image intensification device of FIG.

For an input beam with a low input source, the output light intensity is all equal to the input source intensity along an upward slope to a peak value. The peak value of ``:'' and the critical input light intensity 10
3, the output light intensity drops very steeply. For high input light intensity, somewhat above the critical light intensity, the output light intensity is relatively low. 1 Within the devices of FIGS. 6 and 7, the unmodulated input beam 900 intensity is
All segments of the region of boundary 92 between linear and non-linear materials operate steeply and also in the relatively linear portion of the operating characteristic curve of FIG. As shown in FIG. 8, when there is a relatively small change in light intensity in a component of input image beam 93, as represented by waveform 101, there is an associated amplified output component, as represented by waveform 102. This results in a relatively large amplitude change in the output light intensity.

Because each segment of amplifier 86 operates in the manner described above, differences in source intensity between different elements of the input image are optically amplified by different regions of the amplifier of FIGS. 6 and 7. Depending on the spatially modulated light intensity distribution of the input image beam, the overall result obtained from the total amplifier 86 of either FIG. 6 or FIG.
An optically amplified output (27) force surface image with a spatially modulated light intensity distribution.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an embodiment of an optical image amplifier including a resonator; FIG. 2 is a resonance characteristic diagram of the resonator included in the optical image amplifier of FIG. 1; 3 is a characteristic diagram of the output light intensity with respect to the input light intensity in the optical image amplifier of FIG. 1, and FIG. 4 is a system diagram of an embodiment of the optical image amplifier including a self-focusing optical material, FIG. 5 is a characteristic curve diagram of output power with respect to total input power in an optical image amplifier; FIG. 6 is a system diagram of an embodiment of an optical image amplifier using a nonlinear optical interface; FIG. 8 shows a system diagram of a variation of the embodiment shown in FIG. 6, in which the input beam is incident through a beam splitter (28). FIG. 8 is a characteristic curve diagram of the output intensity with respect to the total input intensity of the optical image amplifier shown in FIG. 7. FIG. Applicant: Western Electric Company, Inc. Total Input Light Intensity -178-

Claims (1)

Claims: (1) An optical device responsive to an input image beam, wherein the image amplifier includes an unmodulated optical beam and an input device for receiving the input image beam having a spatially modulated light intensity distribution. and an amplification comprising a spatially modulated light intensity distribution in response to the unmodulated optical beam and the spatially modulated light intensity distribution of the human image beam in response to the input image beam. 1. An optical device comprising non-linear optical means for producing an image beam. (2. The optical device according to claim 1, wherein the spatially modulated light intensity distribution of the input image beam changes with time, and the device (1) 1p. An optical device characterized in that it generates an amplified image beam having a spatially modulated light intensity distribution that depends on and synchronously changes the temporal variation of the spatially modulated light intensity distribution. (3) An optical device according to claim 1 or 2, wherein the input image beam includes an input array of multiple elements, and the device adjusts the optical intensity of the input array of multiple elements. An optical device characterized in that it simultaneously amplifies an input array of said plurality of elements so as to produce a light intensity amplifying array of said plurality of elements dependently. ft listed in one of the terms,
An optical device, characterized in that the image intensifier comprises a Fabry-Perot resonator with a nonlinear optical material inserted between opposing mirrors. 1 (2) (5) Claims: An optical device according to one of the preceding claims, characterized in that the unmodulated light beam has a virtually uniform light intensity distribution function. (6) The optical device according to claim 4, wherein the nonlinear optical material is a multi-quantum well semiconductor material. (7) The optical device of claim 1, wherein the image intensifier includes a self-focusing imaging profile and an aperture array inserted between a first and second lens array, and wherein each through a self-focusing imaging profile in which the lenses of the array are configured to amplify a portion of said input image beam representing one of an array of different elements of said input image beam; An optical device characterized by (3) being placed with an aperture and an optical path. 8. The optical device of claim 7, wherein the first lens array is configured to split the unmodulated light beam into an array of spot beams. (9) The optical device of claim 1, wherein the image intensifier includes a boundary between a linear optical material and a nonlinear optical material, and the unmodulated light beam is capable of being transmitted through the linear optical material. and can be incident on the boundary at an angle of incidence smaller than the critical angle for low optical power, and such that the input image beam can be incident perpendicularly on the boundary through the nonlinear optical material. An optical device comprising: 00 The optical device (4) according to claim 1, wherein the image intensifier comprises a boundary between a linear optical material and a non-linear optical material and a beam splitter, and the non-modulated optical beam and the an input image beam can be transmitted using the beam splitter and the linear optical material, and both beams can be incident on the boundary at an angle of incidence less than a critical angle for low optical power. An optical device comprising: