Phase conjugated miror system and method

Abstract

An optical system and method are disclosed for generating a phase-conjugated output beam. The system includes at least one phase conjugated mirror (PCM) configured to receive input signals and emit output signals with conjugated phase patterns. An optical arrangement directs an input beam, splits it into two or more beam portions, and transmits the portions to the PCM. The PCM produces corresponding phase-conjugated output signals, which are recombined to form a common output beam exhibiting phase conjugation of the original input.

Description

[0001] PHASE CONJUGATED MIROR SYSTEM AND METHOD

[0002] TECHNOLOGICAL FIELD

[0003] The present disclosure relates phase conjugated mirror and optical arrangement using phase conjugated mirrors.

[0004] BACKGROUND

[0005] Phase conjugation, and phase conjugated mirrors (PCM), relate to a physical phenomenon and elements providing transformation of a wave resulting in reverse propagation while reversing phase of the incoming wave.

[0006] Phase conjugated mirrors typically utilize holographic or nonlinear phenomena for reflecting incoming wave. The reflected wave usually propagates in reverse direction to the incoming wave, as in a retro-reflector, while providing a reverse wavefront pattern.

[0007] PCMs and phase conjugated optical elements can be used in various applications and are often used to compensate for phase distortion and enable signal reconstructions. For example, turbulence or thermal induced refractive index variations may result in phase distortion of a signal. Reconstruction of such distorted signal can utilize reflection of the distorted signal using a PCM and providing an additional passage through the distorting medium. As the phase properties of the collected signal are reversed, the distortion may reverse itself providing the original signal.

[0008] To date there have been several technical approaches that can efficiently produce the backward phase-conjugate beam, some of these approaches are based on the degenerate (or partially degenerate) four-wave mixing processes, others are based on various backward stimulated scattering processes, such as Brillouin, Raman, or Rayleighwing scattering. Among the different approaches, there is a common physical mechanism that plays the same essential role in generating a backward phase-conjugate beam, which is the formation of the induced holographic grating and the subsequent wavefront restoration via a backward reading beam. The momentum of OPC studies has recently become even stronger because there are more prospective potentials and achievements for applications. OPC-associated techniques can be successfully utilized in many different application areas: such as high- brightness laser oscillator / amplifier systems, cavity-less lasing devices, laser targetaiming systems, aberration correction for coherent-light transmission and reflection through disturbing media, long distance optical fiber communications with ultra-high bitrate, optical phase locking and coupling systems, and novel optical data storage and processing systems.

[0009] US 4,880,295 indicates that the output of an optical device which involves a stimulated Brillouin scattering (SBS) gain medium is enhanced over a range of input beam intensities by providing a gain medium which has a given SBS gain for a given input beam intensity, and modifying the gain medium to reduce its SBS gain coefficient. By lowering the SBS gain coefficient, SBS dominance and suppression of stimulated Raman scattering (SRS) can be mitigated, and the output fidelity of a phase conjugation system with respect to its input can be significantly enhanced. Mechanisms for reducing the SBS gain coefficient include increasing the medium viscosity, thermal conductivity and / or diffusion coefficient, or causing the medium relaxation zone to coincide with the frequency of the phonons involved in the SBS process. Two different media can be mixed together in varying proportions to progressively modify the overall medium SBS gain as the input beam intensity is progressively changed.

[0010] GENERAL DESCRIPTION

[0011] As indicated above, a phase conjugated mirror (PCM) is an optical element configured to receive an input beam and emit a reverse beam having wavefront that is phase conjugated with respect to the input beam. Phase conjugation is a nonlinear phenomenon, which is typically characterized by a relatively sharp threshold gain to initiate the stimulated process. In this connection the terms threshold gain, and breakthrough threshold are used herein interchangeably, indicating an amplitude or intensity limit, where input signal below the limit does not result with proper phase conjugated output signal. As a result, typical PCM devices are limited in dynamic range, and do not properly reconstruct signal portions of low intensity, due to nonlinearity of the process. Further, various PCM techniques, and specifically PCM elements based on stimulated scattering effects, may experience saturation in response to input beam portions having high intensity or even breakdown, which limits its ability to emit an output beam having a conjugated phase.

[0012] To overcome these issues, the present disclosure provides an optical system configured for receiving an input beam, splitting the input beam into two or more beam portions having different intensities between them, while having the same (or equal) spatial shape and phase, and input the two or more beam portions separately to be reflected by one or more PCM elements. The optical system may further be configured to receive two or more conjugate beam portions being output from the one or more PCM elements, and to combine the two or more conjugate beam portions to provide an output conjugate beam transmitted in reverse direction with respect to the input beam. The benefit of such optical system is enhancement of dynamic range and improving the fidelity of the reflected beam with respect to conventional PCM systems.

[0013] The present technique may typically relate to PCM elements based on stimulated scattering effects but may also be useful for PCM elements utilizing four wave mixing.

[0014] Thus, according to a first broad aspect, the present disclosure provides an optical system comprising: at least one phase conjugated mirror (PCM) configured for receiving one or more input signals and in response emitting one or more corresponding output signals having conjugated phase pattern; an optical arrangement configured to receive an input beam, split the input beam to two or more beam portions, transmit the two or more beam portions as two or more input signals to the at least one PCM, to receive respective two or more output signal from the phase conjugated mirror, and to combine the two or more output signals providing a phase conjugated output beam.

[0015] According to some embodiments, the optical system may be configured to provide a single phase-conjugated output beam.

[0016] According to some embodiments, the optical system may comprise a single PCM configured for receiving the two or more beam portions as two or more input signals. The single PCM element may be configured for receiving the two or more input signals and generate in response two or more output signals. According to some embodiments, the at least one PCM comprises at least two PCM elements. The two PCM elements are configured with different optical parameters associated with or affecting breakthrough threshold and saturation intensity to be different between the PCM elements. Each one of the two or more beam portions is directed toward a respective one of the at least two PCM elements, in some embodiments, variation in optical parameters may be associated with variation in parameters of optical elements focusing the two or more beam portions into the respective PCM elements, associated with e.g., lens power.

[0017] According to some embodiments, the two or more beam portions having two or more different intensities.

[0018] According to some embodiments, the optical arrangement is configured to transmit the output beam in a reverse direction with respect to direction of propagation of the input beam.

[0019] According to some embodiments, the at least one PCM comprises at least two PCM units, wherein one PCM is positioned to receive input signal associated with one beam portion having high intensity, and a second PCM is positioned to receive input signal associated with a second beam portion having lower intensity.

[0020] According to some embodiments, the intensity ratio between the two or more beam portions is in a range between 1 : 1 and 1 :200.

[0021] According to some embodiments, the optical arrangement comprises: a first input beam splitter partially transmitting the input beam and reflecting output beam, at least one second beam splitter configured for unequal splitting of the input beam for generating the two or more beam portions having different intensities, and for directing the two or more beam positions toward the respective PCM elements.

[0022] In some embodiments, the optical system may further comprise one or more additional optical elements for directing and focusing the two or more beam portions toward the respective PCM elements. The additional optical elements may comprise one or more reflecting elements (e.g., mirrors), and one or more lenses having selected optical power for focusing the two or more beam portions toward the respective PCM elements.

[0023] According to some embodiments, the at least one PCM utilizes Stimulated Brillouin Scattering (SBS) or Stimulated Ramman Scattering (SRS). Typically, when two or more PCM elements are used, the Two or more PCM elements may be of similar and / or equal physical structure to provide similar or equal phase conjugated signal and avoid frequency shifts.

[0024] According to some embodiments, at least one PCM comprises a chamber comprising at least one of solid material, liquid material, or a high-pressure gas.

[0025] According to some embodiments, the optical arrangement comprises at least one attenuator positioned and configured to adjust intensity of at least one of the two or more beam portions.

[0026] According to some embodiments, the optical arrangement is configured to provide equal optical path for the incoming and reflected beam and respective signals.

[0027] According to on other broad aspect, the present disclosure provides a method for generating phase conjugated reflection of an optical signal, the method comprising: receiving an input beam; splitting the input beam into two or more beam portions; inputting each of the two or more beam portions into at least one phase conjugated mirror (PCM) element, and obtaining respective two or more output signals having conjugated phase with respect to the two or more beam portions; combining the two or more output signals into a common output beam, thereby providing phase conjugated output beam.

[0028] According to some embodiments, the method may further comprise transmitting the output beam in a reverse direction with respect to direction of propagation of the input beam.

[0029] According to some embodiments, the method may further comprise using least two PCM elements, e.g. comprising at least a first PCM and a second PCM, wherein the first PCM is positioned to receive input signal associated with a first beam portion having high intensity, and the second PCM is positioned to receive input signal associated with a second beam portion having lower intensity. It should be noted that the terms “first” and “second”, here and throughout the description below, relates to general naming of the PCM elements and have no relation to temporal order.

[0030] According to some embodiments, the method may further comprise using a common PCM element configured for receiving the two or more beam portions.

[0031] According to some embodiments, said splitting the input beam into two or more beam portions comprises splitting the input beam into two or more beam portions having different intensity levels. According to some embodiments, the method may further comprise splitting the input beam into two or more beam portions having wherein intensity ratio in a range between 1 : 1.1 and 1 :200.

[0032] According to some embodiments, the at least one PCM utilizes Stimulated Brillouin Scattering (SBS) or Stimulated Ramman Scattering (SRS).

[0033] According to some embodiments, the at least one PCM comprises at least one of solid material, liquid material, or a high-pressure gas.

[0034] According to some embodiments, the method may further comprise inputting each of the two or more beam portions into at least one phase conjugated mirror (PCM) element while applying two or more different optical parameters, thereby affecting response of the at least one PCM element with respect to breakthrough and saturation thresholds in accordance with focusing level of the respective beam portions. This may be associated with using optical elements comprising one or more lenses having different optical parameters selected from optical power, f-number, etc.

[0035] BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

[0037] Fig- 1 illustrates the operation concept of conjugate phase mirror;

[0038] Fig. 2 schematically illustrates an optical system according to some embodiments of the present disclosure;

[0039] Fig- 3 illustrates an exemplary optical system according to some embodiments of the present disclosure;

[0040] Fig- 4 illustrates an additional example of an optical system according to some embodiments of the present disclosure including an attenuator and optical isolators; and

[0041] Figs. 5A and 5B exemplify path of input (Fig. 5A) and output (Fig. 5B) beams within an optical system according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF EMBODIMENTS

[0042] Phase conjugated mirrors (PCMs) are specialized optical devices that reflect light in a unique way. They are often used in laser systems to correct wavefront distortions, effectively reversing the path of the light and undoing the effects of aberrations. Fig. 1 exemplifies general concept of operation of a PCM element 10 in response to an input beam IB having wavefront 12. More specifically, given an input beam having certain electric field: where Eo is amplitude of the wave for each point (x,y,z), 0 is the wave frequency, and c.c. relates to complex conjugate. The phase conjugate beam has the same wavefront, where the sign of the spatial phase is inverted providing:

[0043] Accordingly, output beam OB emitted from the PCM 10 has complex conjugate phase with respect to input beam IB. This results in a beam having reverse propagation direction while maintaining orientation of the wavefront 12* as illustrated in Fig. 1.

[0044] Typically, PCMs utilize one or more selected nonlinear optical processes generating the desired output beam. Such nonlinear processes may include stimulated scattering, e.g., stimulates Brillouin, Raman, or Rayleigh-wing. Certain other techniques utilize Degenerated four wave mixing.

[0045] Certain PCM elements, typically utilizing stimulated scattering effects, are formed by solid, liquid or high-pressure gas within a selected container. In response to input beam being focused into the PCM element, the input beam causes nonlinear interaction of the electromagnetic field with the medium of the PCM, which leads to generation of output beam of conjugate phase.

[0046] A major issue with PCM elements often relates to a relatively narrow dynamic range with respect to input beam amplitude. As a result from the nonlinear nature of the optical process, amplitude of the input beam, and of any portion thereof, affects that process efficiency. This may be presented by certain breakthrough threshold, as well as by a saturation threshold. More specifically, signal portions having amplitude below the breakthrough threshold along the interaction length may be insufficient to provide conjugate phase output signal. Additionally, signal portions having amplitude above the saturation threshold may reduce the reflection efficiency of the output beam. The dynamic range limitation may result in failure in generating high fidelity conjugated beam, generating an output beam having intensity pattern that deviates from intensity pattern of the input beam. In this connection, it should be noted that the terms breakthrough threshold and saturation threshold are to be interpreted broadly, as relating to beam profile intensity that fits within dynamic range of the PCM. Generally, the nonlinear interaction occurring within the PCM is not instantaneous, and the output conjugated signal may be generated along certain propagation path of the input signal through the PCM.

[0047] For example, in response to an input beam having wavefront pattern that includes regions of intensity below breakthrough threshold and regions above the breakthrough threshold, the PCM element may efficiently generate conjugate signal for the beam portion having sufficiently high intensity, while fail to emit conjugate beam portions for the low intensity regions. The resulting output beam may be distorted with respect to the input beam, preventing the PCM ability to be used for correcting distortions.

[0048] The present disclosure provides an optical system utilizing at least one PCM element and configured to receive an input beam and reflect a respective output beam having conjugate phase with respect to the input beam, while enhancing dynamic range of the one or more PCM elements. The optical system of the present disclosure may be used to reconstruct conjugate phase beam based on input beams having general beam intensity profile and wavefront, and specifically for input beams of low quality having varying amplitude or speckled pattern.

[0049] Reference is made to Fig. 2 exemplifying an optical system 100 according to some embodiments of the present disclosure. Optical system 100 includes one or more PCM elements 10 and an optical arrangement 50 configured to receive an input beam IB, split the input beam into two or more signal portions SI and S2 and transmit the signal portions into the PCM elements 10. The optical arrangement 50 is also configured to receive reflected output signal portions S*1 and S*2 from the PCM element 10 and to combine the signal portions and generate an output beam OB. Optical arrangement 50 is configured to provide signal portions SI and S2 (optionally including additional signal portions) having different intensities, e.g., signal portions SI having high intensity and signal portion S2 having lower intensity. The beam combining process may utilize one or more beam splitters with adequate loss ratio between S*1 and S*2 or use polarization related elements, including polarizers, rotators and waveplates. Typically, optical elements and their placement is optimized for best beam restoration. Additionally, the optical arrangement 50 may include one or more optical lenses for focusing the signal portions into the one or more PCM elements 10 for generating respective conjugate phase output signals S*1 and S*2.

[0050] The PCM element 10 may be formed by a chamber holding liquid or gas phase material selected to provide Stimulated Brillouin Scattering (SBS) or Stimulated Ramman Scattering (SRS) or using a solid material having desired nonlinear properties. In accordance with parameters of the PCM element 10, it may be characterized by certain breakthrough and saturation thresholds. Accordingly, in some cases, the first, stronger, signal portion SI may be within dynamic range of the PCM 10, while the second, weaker, signal portion S2 may be below breakthrough threshold. As a result, the second signal portion does not cause generation of a conjugate output signal S*2, but the PCM 10 does emit output conjugate signal S*l. In another case, first signal portion SI may be above saturation threshold, and second signal portions S2 may be within operation range of the PCM 10. As a result, output signal S*2 may be properly emitted, while emit output signal S*1 may be distorted due to saturation of the PCM, which may fail to preserve beam profile.

[0051] In a general case, the input beam may have varying intensity pattern, causing signal portions SI and S2, and optionally additional signal portions, to have corresponding variation in intensity pattern thereof. Accordingly, regions of the signal portions that are within dynamic range of the PCM are properly reflected generating partial conjugate output signal, and regions of the signal portions that are either above or below operation dynamic range may not be properly reflected. The combined output beam OB, being a combination of the conjugate signal portions S*1 and S*2 (and optically additional signal portions) may efficiently reconstruct the wavefront providing a conjugate output beam OB with respect to input beam IB. Thus, enabling enhanced dynamic range of the PCM element 10.

[0052] Generally, in some embodiments, optical arrangement 50 may include one or more lens units configured for focusing signal portions SI, S2, and optionally additional signal portions, into the PCM elements to enhance efficiency of the PCM element 10. Additionally, the optical arrangement 50 may include one or more attenuators or variable attenuators positioned and configured to adjust relative intensity of the first SI, second S2 and optionally additional signal portions. Optical arrangement 50 may also include elements that match the intensity ratio between the output signal portions S*1 and S*2 to provide a smooth combined output beam OB with best shape reconstruction.

[0053] Figs. 3 and 4 illustrate more detailed configurations of the optical system 100 according to some embodiments of the present disclosure. Fig. 3 exemplifies the optical arrangement 50 and a general description of its operation, and Fig. 4 further exemplifies additional optical elements such as optical isolator, dump and attenuator defining path of input beam and first and second signal portions.

[0054] More specifically, Fig. 3 illustrates optical system 100 including optical arrangement 50 and one or more PCM elements illustrated by PCM 10a and 10b. The optical arrangement includes a beam splitter BS, which may be configured as an unequal beam splitter (e.g., 90 / 10, 80 / 20, 70 / 30 or any other uneven intensity ratio). The optical arrangement also includes reflecting element, or mirror, Ml generally configured with maximal reflection. In some embodiments beam splitter BS may be configured to any other ratio, including e.g., 50 / 50 ratio, while the PCM elements 10a and 10b are configured to operate with different properties defining their respective breakthrough threshold and saturation level. For example, the optical arrangement may include one or more optical elements, such as lenses providing selected focusing conditions to the first and second signal portions resulting in variation in breakthrough and / or saturation thresholds. For example, by using lenses with different f-number that focuses the light into the PCM cell. Smaller f-number may reduce PCM threshold but also the saturation level.

[0055] Optical arrangement 50 is configured to receive an input beam IB and to split the input beam into at least first 14 and second 16 signal portions. The split signal portions 14 and 16 are directed to impinge onto one or more PCM elements 10a and 10b in this example. In some embodiments the system may utilize a common PCM chamber / cell for receiving the two or more signal portions. In some other embodiments, as exemplified in Fig- 3, the optical system may include two or more PCM elements configured to each receive a respective signal portion. As indicated above, in some embodiments, beam splitter BS is configured as an uneven beam splitter, providing that intensities of signal portions 14 and 16 are different. Specifically, in some embodiment the total input intensity may be split between first 14 and second 16 signal portions in intensity ratio 90: 10, 80:20, 70:30 or any other selected intensity ratio. Further, in some other embodiments, the PCM elements 10a and 10b may have different phase conjugation properties. More specifically, the optical arrangement may split the input beam into at least two signal portions (e.g., signal portions 14 and 16) having any selected intensity ratio, including 50 / 50 ratio. The optical arrangement may include one or more optical elements configured to provide different parameters, such as spot size, to the different signal portions when impinging on the respective PCM elements 10a and / or 10b.

[0056] In response to input signal portions 14 and 16, respective PCM elements 10a and 10b may generate output signal portions 24 and 26. The output signal portions 24 and 26 are combined using the beam splitter BS providing output beam OB having conjugate phase with respect to input beam IB.

[0057] In accordance with operation of the PCM elements 10a and 10b, signal portions 24 and 26 have conjugate phase with respect to signal portions 14 and 16, up to limitation of dynamic range of the PCM elements. The optical system 100 utilizes intensity difference, difference in optical signal spot / focusing size, and / or difference in PCM parameters, between the first and second signal portions to enhance dynamic range and improve the ability of PCM elements 10a and 10b to provide phase conjugate beam. More specifically, if parts of the higher intensity signal portion exceed saturation threshold of the PCM element, the conjugate reflection of the lower intensity signal portion can provide proper phase conjugated signal. Alternatively, elements of the lower intensity signal having intensity below breakthrough threshold may not result in reflected conjugate signal, while the respective parts of the higher intensity signal portion are efficiently reflected.

[0058] Generally, to properly obtain increase in dynamic range, PCM elements 10a and 10b may be configured with different properties. Such properties may affect breakthrough and saturation thresholds. For example, in some embodiments, where PCM elements 10a and 10b utilize high pressure gas of liquid directed to support stimulated scattering (such as Brillouin, Raman, Rayleigh-wing, or others), one or more of focusing properties and pressure of the input signals into the PCM elements 10a and 10b may be suitable adjusted with respect to variation in intensity between the respective signal portions.

[0059] Fig. 4 provides a more detailed illustration of system 100 according to some embodiments of the present disclosure. Fig. 4 exemplifies the use of first beam splitter BS1 separating paths of input 12 and output 22 signals. In some configurations, the first beam splitter may be configured to provide even splitting of the input beam. Additionally, the optical arrangement is illustrated including first and second isolators 32 and 34 configured to isolate paths of incoming beam portion 12 and outgoing combined signal 22, making the path of the beam portions and internal signals unidirectional and preventing unwanted paths. Fig. 4 also utilizes variable attenuator 36 configured to selectively vary intensity of at least one of the signal portions, exemplified operating on signal portion 16 in this example, and dump (e.g., absorber or deflector) 38 configured to removed elements of the internal combined signal 22 that are transmitted by beam splitter BS1. It should be noted that dump 38 is illustrated herein for clarity and may be a part of isolator 32 and / or 34, preventing internal reflections within the system. More specifically, isolators 32 and / or 34 may divert light portions out of the optical system. In some embodiments dump 38 may also be configured to prevent reflections from reaching beam splitter BS1.

[0060] Isolators 32 and 34 enable transmission of optical signals in one direction, marked by directions of beam 12 and signal 22 in Fig. 4, while preventing transmission of optical signals in the opposite directions. There are various types of optical isolators known in the art, including for example Faraday isolators or, as well as various other isolator types that can be used in the system according to the present disclosure. Dump 38, when used, may be configured as a light blocking element, an absorbing element, or a light deflector configured to direct undesired beam portions away from the system.

[0061] In this connection, reference is further made to Figs. 5A and 5B exemplifying path of input (Fig. 5A) and output (Fig. 5B) beams within the optical system 100 according to some embodiments of the present disclosure. Figs. 5A and 5B show generally similar system configuration and path of input and output signals as shown in Fig. 4 and add indications of loss beam potions 12’ and 22’ in the input and output paths respectively. Typically, system 100 may be configured to operate receiving polarization input beam IB, simplifying the use of isolators 32 and 34 for removing beam portions 12’ and 22’ to prevent internal reflections from interfering with output conjugate beam OB.

[0062] Accordingly, the present disclosure provides an optical system utilizing one or more phase conjugate mirror (PCM) elements and an optical arrangement. The present disclosure provides splitting of an input beam into two or more signal portions having different intensities, using the one or more PCM elements to generate phase conjugated output signal portions, and combining the output signal portions to an output signal beam being phase conjugated with respect to the input beam. This configuration enables increase of dynamic range of the PCM elements and maintaining better similarity between incident and reflected beam in terms of spatial intensity distribution.

[0063] It is to be noted that the various features described in the various embodiments can be combined according to all possible technical combinations. It is to be understood that the invention is not limited in its application to the details set forth in the description contained herein or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Hence, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will appreciate that the conception upon which this disclosure is based can readily be utilized as a basis for designing other structures, methods, and systems for carrying out the several purposes of the presently disclosed subject matter.

[0064] Those skilled in the art will readily appreciate that various modifications and changes can be applied to the embodiments of the invention as hereinbefore described without departing from its scope, defined in and by the appended claims.

Claims

CLAIMS:

1. An optical system comprising: at least one phase conjugated mirror (PCM) configured for receiving one or more input signals and in response emitting one or more corresponding output signals having conjugated phase pattern; an optical arrangement configured to receive an input beam, split the input beam to two or more beam portions, transmit the two or more beam portions as two or more input signals to the at least one PCM, to receive respective two or more output signal from the phase conjugated mirror, and to combine the two or more output signals providing a phase conjugated output beam.

2. The optical system of claim 1, configured to provide a single conjugated phase output beam.

3. The optical system of claim 1 or 2, comprising a single PCM configured for receiving the two or more beam portions as two or more input signals.

4. The optical system of claim 1 or 2, wherein said at least one PCM comprises at least first and second PCM elements configured to operate with respective first and second optical parameters comprising breakthrough different threshold and saturation intensity respective, and where each one of the two or more beam portions is directed toward a respective one of the at least first and second PCM elements.

5. The optical system of claim 4, wherein the optical arrangement comprises one or more lenses configure to focus the two or more beam portions onto the at least first and second PCM elements with respective different optical parameters selected from optical power.

6. The optical system of any one of claims 1 to 5, wherein said the two or more beam portions having two or more different intensities.

7. The optical system of any one of claims 1 to 6, wherein the optical arrangement is configured to transmit the output beam in a reverse direction with respect to direction of propagation of the input beam.

8. The optical system of any one of claims 1 to 7, wherein the at least one PCM comprises at least a first PCM and a second PCM, wherein the first PCM is positioned to receive input signal associated with a first beam portion having high intensity, and the second PCM is positioned to receive input signal associated with a second beam portion having lower intensity.

9. The optical system of any one of claims 1 to 8, wherein intensity ratio between the two or more beam portions is in a range between 1 : 1 and 1 :200.

10. The optical system of any one of claims 1 to 9, wherein the optical arrangement comprises: a first input beam splitter for receiving input beam and transmitting output beam, at least one second beam splitter configured for unequal splitting of the input beam for generating the two or more beam portions having different intensities, and for directing the two or more beam positions toward the respective PCM elements.

11. The optical system of claim 10, wherein the optical arrangement further comprises one or more additional optical elements for directing and focusing the two or more beam portions toward the respective PCM elements; the one or more additional optical elements being selected from one or more reflecting elements, and one or more lenses having selected optical powers for focusing the two or more beam portions toward the respective PCM elements.

12. The optical system of any one of claims 1 to 11, wherein the optical arrangement comprises one or more Polarizing elements selected from a group consisting of: polarizers beam splitters, polarization rotators and waveplates.

13. The optical system of any one of claims 1 to 12, wherein the at least one PCM utilizes Stimulated Brillouin Scattering (SBS) or Stimulated Ramman Scattering (SRS).

14. The optical system of any one of claims 1 to 13, wherein the at least one PCM comprises a chamber comprising at least one of solid material, liquid material, or a high- pressure gas.

15. The optical system of any one of claims 1 to 14, wherein the optical arrangement comprises at least one attenuator positioned and configured to adjust intensity of at least one of the two or more beam portions.

16. The optical system of any one of claims 1 to 15, where the optical arrangement is configured to provide equal optical path for each of the two or more beam portions, [the beam portions are defined in claims 1 as between the splitting and combining]17. A method for generating phase conjugated reflection of an optical signal, the method comprising:(a) receiving an input beam;(b) splitting the input beam into two or more beam portions;(c) inputting each of the two or more beam portions into at least one phase conjugated mirror (PCM) element, and obtaining respective two or more output signals having conjugated phase with respect to the two or more beam portions;(d) combining the two or more output signals into a common output beam, thereby providing phase conjugated output beam.

18. The method of claim 17, further comprising transmitting the output beam in a reverse direction with respect to direction of propagation of the input beam.

19. The method of claim 17 or 18, comprising using least a first PCM and a second PCM, wherein the first PCM is positioned to receive input signal associated with a first beam portion having high intensity, and the second PCM is positioned to receive input signal associated with a second beam portion having lower intensity.

20. The method of claim 17 or 18, comprising using a common PCM element configured for receiving the two or more beam portions.

21. The method of any one of claims 17 to 20, wherein said splitting the input beam into two or more beam portions comprises splitting the input beam into two or more beam portions having different intensity levels.

22. The method of claim 21, comprising splitting the input beam into two or more beam portions having wherein intensity ratio in a range between 1 : 1.1 and 1 :200.

23. The method of any one of claims 17 to 22, wherein the at least one PCM utilizes Stimulated Brillouin Scattering (SBS) or Stimulated Raman Scattering (SRS).

24. The method of any one of claims 16 to 23, wherein the at least one PCM comprises at least one of solid material, liquid material, or a high-pressure gas.

Images