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A bi-directional pulsed ring laser that produces bi-directional light pulses that interact in such a way that they are phase conjugated. A nonlinear substance, such as a nonlinear crystal or fluid, that has an index of refraction that is dependent upon light intensity is located near a beam waist of

A bi-directional pulsed ring laser that produces bi-directional light pulses that interact in such a way that they are phase conjugated. A nonlinear substance, such as a nonlinear crystal or fluid, that has an index of refraction that is dependent upon light intensity is located near a beam waist of the laser cavity to provide a self-lensing effect. Methods for reducing dead band beyond observable limits are also provided. The increased sensitivity of the bi-directional pulsed ring laser provides application in detecting magnetic susceptibility by detecting the change in phase between the arrival times of the bi-directional pulses at a modulator and the electrical signal of the modulator to determine the change in frequency of a coil that has magnetic susceptibility.

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A bi-directional pulsed ring laser that produces bi-directional light pulses that interact in such a way that they are phase conjugated. A nonlinear substance, such as a nonlinear crystal or fluid, that has an index of refraction that is dependent upon light intensity is located near a beam waist of

A bi-directional pulsed ring laser that produces bi-directional light pulses that interact in such a way that they are phase conjugated. A nonlinear substance, such as a nonlinear crystal or fluid, that has an index of refraction that is dependent upon light intensity is located near a beam waist of the laser cavity to provide a self-lensing effect. Methods for reducing dead band beyond observable limits are also provided. The increased sensitivity of the bi-directional pulsed ring laser provides application in detecting magnetic susceptibility by detecting the change in phase between the arrival times of the bi-directional pulses at a modulator and the electrical signal of the modulator to determine the change in frequency of a coil that has magnetic susceptibility. assive picocell: a new concept in wireless network infrastructure, Electronic Letters, vol. 33, No. 5, pp. 404-406 (Feb. 1997). Smith et al., Full-Duplex Fiber-Wireless System Using Electrical and Optical SSB Modulation For Efficient Broadband Millimeter-Wave Transport, Proc. Microwave Photonics Workshop 1997, Duisburg, FR 2-2, pp. 223-226, (1997). (no month). Shiomi et al., Optical Pulse Modulation of HMIC Oscillator used Illuminated MESFET, The Institute of Electronics, Information and Communication Engineers, SC-3-3, p. 367, (1996). (no month). Nishikawa et al., Millimeter-Wave Photonic Passive Base Station Employing the Nonlinear Photdetection Scheme, The Institute of Electronics, Information and Communication Engineers, MWP97-18, pp. 52-58, (1998). (no month). onds to picoseconds. 12. A source as defined in claim 1 wherein first and second DFB lasers comprise one of the gain coupled and loss coupled DFB lasers. 13. A source as defined in claim 12 wherein the active medium includes a multiple quantum well structure. 14. A source as defined in claim 13 wherein the first and second gratings are formed by etching grooves directly through the multiple quantum well structure. 15. A source as defined in claim 14 wherein each grating has a period comprising a first section and a second section with substantially all quantum wells being etched away from the second section, thus providing no substantial photon emission in the second section and ensuring no substantial interaction between the lasers. 16. A source as defined in claim 1 further comprising means for stabilizing the frequency of one of the first and second lasers. 17. A source radiation as defined in claim 10 further comprising means for stabilizing the frequencies of both lasers. 18. A source as defined in claim 1 further comprising means for tuning frequencies of the first and second lasers. 19. A source as defined in claim 1 further comprising means for modulating light generated by one of the first and second lasers. 20. A source as defined in claim 19 wherein the modulation is provided at a frequency which is subharmonic to the beat frequency. 21. A source as defined in claim 1 further comprising means for modulating light generated by the lasers simultaneously. 22. A source defined in claim 1 wherein pumping of the active medium is provided by current injection into the active medium. 23. A source defined in claim 1 wherein pumping of the active medium is provided by an external optical pumping source. 24. A source as defined in claim 1 wherein the first and second gratings have same periods. 25. A source as defined in claim 24 wherein the first and second lasers generate light at the same side of stopband. 26. A source as defined in claim 25 wherein the difference between the first and second frequencies is provided by different current injection into the first and second lasers. 27. A source as defined in claim 25 wherein the difference between the first and second frequencies is provided by different width of the active medium in the first and second lasers. 28. A source as defined in claim 25 wherein the difference between the first and second frequencies is provided by difference in temperatures at which the first and second lasers are maintained. 29. A source as defined in claim 24 wherein the first and second lasers generate light at different sides of stopband. 30. A source as defined in claim 1 wherein the first and second gratings have different periods. 31. A source as defined in claim 30 wherein the frequency of one of the lasers which is remote from an output facet does not fall within a stopband of the other laser which is closer to the output facet so that light emitted by the remote laser can pass through the shared optical path to the output facet. 32. A source as defined in claim 1 wherein the first and second gratings comprise one of the uniform and chirped gratings. 33. A source as defined in claim 1 wherein the first and second gratings are first order gratings. 34. A source as defined in claim 1 wherein the first and second gratings are formed by one of the holographic writing and electron beam writing onto the active medium. 35. An optical pulse source, comprising: a first single mode DFB semiconductor laser having a first grating for generating light at a first frequency; a second single mode DFB semiconductor laser having a second grating for generating light at a second frequency; the lasers having a common active medium and shared optical path, the lasers providing light injection of light imposed on each other resulting in generation of a beat signal at a difference frequency of two lasers; a saturable absorber disposed for receiving the beat signal and providing an initial time compression