Abstract: The phase sensitive amplifier according to the present invention is a phase sensitive amplifier that uses the optical mixing using a nonlinear optical effect to amplify the signal light. The phase sensitive amplifier according to the present invention includes: the first second-order nonlinear optical element; and the second second-order nonlinear optical element. The first second-order nonlinear optical element causes the fundamental wave light to generate second harmonic light used as pump light and separates only the second harmonic light. The second second-order nonlinear optical element includes a multiplexer to multiplex the signal light with the second harmonic light and spectrally separates only the amplified signal light. The multiplexed signal light and second harmonic light are used subjected to parametric amplification.

Abstract: The phase sensitive amplifier according to the present invention is a phase sensitive amplifier that uses the optical mixing using a nonlinear optical effect to amplify the signal light. The phase sensitive amplifier according to the present invention includes: the first second-order nonlinear optical element; and the second second-order nonlinear optical element. The first second-order nonlinear optical element causes the fundamental wave light to generate second harmonic light used as pump light and separates only the second harmonic light. The second second-order nonlinear optical element includes a multiplexer to multiplex the signal light with the second harmonic light and spectrally separates only the amplified signal light. The multiplexed signal light and second harmonic light are used subjected to parametric amplification.

Abstract: A wavelength converter which performs simultaneously wavelength conversion for a plurality of input light wavelengths that are unequally intervals, is provided. The nonlinear material of the wavelength converter has a modulation structure which has modulation of a nonlinear optical constant at a period ?0 in a propagating direction of light, a phase being continuously changed each period ?0 and a continuous phase modulation for a different period ?ph being added to the modulation structure. The nonlinear material has a modulation structure obtained by changing a modulation curve for the phase modulation, wherein a phase mismatch ?? is represented by ??=2?(n3/?3?n2/?2?n1/?1), and at least three peaks at unequally intervals within a plurality of peaks for conversion efficiency represented by 2?/?0+2?i/?f (i=m, m+1, . . . , n: where m and n are positive or negative integers) have highest conversion efficiency.

Abstract: A light source apparatus with modulation function has a wavelength conversion module (75) composed of a nonlinear optical material with a structure having a nonlinear constant modulated periodically. It outputs a difference frequency or sum frequency produced by multiplexing pumping light from semiconductor laser light sources (71) and (72) with different wavelengths through a WDM coupler (74) and by launching the multiplexed light into the optical waveguide. The semiconductor laser light source (72) includes a diffraction grating. The semiconductor laser light source (71) includes a section for modulating output light emitted from its semiconductor laser, and is connected to an external FBG (73) which has a reflection band narrower than a resonance wavelength spacing determined by the device length of the semiconductor laser. The FBG (73) is supplied with the modulated output.

Abstract: A light source apparatus with modulation function has a wavelength conversion module (75) composed of a nonlinear optical material with a structure having a nonlinear constant modulated periodically. It outputs a difference frequency or sum frequency produced by multiplexing pumping light from semiconductor laser light sources (71) and (72) with different wavelengths through a WDM coupler (74) and by launching the multiplexed light into the optical waveguide. The semiconductor laser light source (72) includes a diffraction grating. The semiconductor laser light source (71) includes a section for modulating output light emitted from its semiconductor laser, and is connected to an external FBG (73) which has a reflection band narrower than a resonance wavelength spacing determined by the device length of the semiconductor laser. The FBG (73) is supplied with the modulated output.

Abstract: A wavelength converter which performs simultaneously wavelength conversion for a plurality of input light wavelengths that are unequally intervals, is provided. The nonlinear material of the wavelength converter has a modulation structure which has modulation of a nonlinear optical constant at a period ?0 in a propagating direction of light, a phase being continuously changed each period ?0 and a continuous phase modulation for a different period ?ph being added to the modulation structure. The nonlinear material has a modulation structure obtained by changing a modulation curve for the phase modulation, wherein a phase mismatch ?? is represented by ??=2?(n3/?3?n2/?2?n1/?1), and at least three peaks at unequally intervals within a plurality of peaks for conversion efficiency represented by 2?/?0+2?i/?f (i=m, m+1, . . . , n: where m and n are positive or negative integers) have highest conversion efficiency.

Abstract: A light source is provided that realizes a single spectral linewidth having a half value width of 1 MHz or less and that is not influenced by the ambient temperature. A light source includes first laser (71) generating first laser light, second laser (12) generating second laser light, and nonlinear optical crystal (13) wherein the first laser light and the second laser light are injected into the nonlinear optical crystal to generate coherent light by the generation of a difference frequency or a sum frequency. The second laser (12) is a wavelength-tunable light source that includes therein a diffraction grating and that can sweep the wavelength of the second laser light. The first laser (71) is composed of semiconductor laser and a fiber grating that has a reflection bandwidth narrower than a resonance wavelength spacing determined by the laser chip length of the semiconductor laser.

Abstract: A laser light source is disclosed consisting of first and second lasers that respectively generate laser beams of wavelengths ?1 and ?2. Wavelength ?1 is in the range of 0.9-1.0 ?m. A nonlinear optical crystal uses the laser beams of wavelengths ?1 and ?2 as inputs, and outputs a coherent beam having a wavelength ?3 of a difference frequency that satisfies a relationship of 1/?1?1/?2=1/?3. The nonlinear optical crystal has a periodically poled structure of a single period. The wavelength ?3 of the difference frequency varies between 3.1 ?m and 2.0 ?m when the wavelength ?2 varies between 1.3 ?m and 1.8 ?m.

Abstract: The present invention provides a periodically-poled structure with high conversion efficiency and improved manufacturing yield. The method for manufacturing a periodically-poled structure in a second order nonlinear optical crystal having a single domain structure (31) includes the steps of forming a resist pattern (32) which matches a polarization-inverted period on a ?Z surface of the second order nonlinear optical crystal (31), and applying voltage to the ?Z surface as a negative voltage where the resist pattern (32) is formed, and a +Z surface as a positive voltage so as to apply an electric field in the second order nonlinear optical crystal (31), wherein the second order nonlinear optical crystal (31) contains at least one element as a dopant which compensate for the crystal defects.

Abstract: The invention provides a compact laser light source whose wavelength can be designed freely in a wavelength band in which the semiconductor laser has not been put to practical use by combining an efficient nonlinear optical crystal and high-power semiconductor lasers for optical communication. In one embodiment, the laser light source includes: a first laser for generating a laser beam of a wavelength ?1; a second laser for generating a laser beam of a wavelength ?2; and a nonlinear optical crystal that allows the laser beam of wavelength ?1 and the laser beam of wavelength ?2 as inputs and outputs a coherent beam having a wavelength ?3 of a sum frequency that satisfies a relationship of 1/?1+1/?2=1/?3. The wavelength ?3 of the sum frequency is 589.3±2 nm that is equivalent to the sodium D line.

Abstract: A laser light source is disclosed consisting of first and second lasers that respectively generate laser beams of wavelengths ?1 and ?2. Wavelength ?1 is in the range of 0.9-1.0 ?m. A nonlinear optical crystal uses the laser beams of wavelengths ?1 and ?2 as inputs, and outputs a coherent beam having a wavelength ?3 of a difference frequency that satisfies a relationship of 1/?1?1/?2=1/?3. The nonlinear optical crystal has a periodically poled structure of a single period. The wavelength ?3 of the difference frequency varies between 3.1 ?m and 2.0 ?m when the wavelength ?2 varies between 1.3 ?m and 1.8 ?m.

Abstract: The invention provides a compact laser light source whose wavelength can be designed freely in a wavelength band in which the semiconductor laser has not been put to practical use by combining an efficient nonlinear optical crystal and high-power semiconductor lasers for optical communication. In one embodiment, the laser light source includes: a first laser for generating a laser beam of a wavelength ?1; a second laser for generating a laser beam of a wavelength ?2; and a nonlinear optical crystal that allows the laser beam of wavelength ?1 and the laser beam of wavelength ?2 as inputs and outputs a coherent beam having a wavelength ?3 of a sum frequency that satisfies a relationship of 1/?1+1/?2=1/?3. The wavelength ?3 of the sum frequency is 589.3±2 nm that is equivalent to the sodium D line.

Abstract: A wavelength converter has a phase modulated periodically modulated structure, where a nonlinear optical coefficient is periodically modulated at a fundamental period &Lgr;0 and the phase of the modulation varies nearly continuously, and the phase variation of the modulation unit structure is repeated at a period &Lgr;ph (>&Lgr;0). A conversion efficiency is made maximum when a phase mismatch amount &Dgr;&bgr; equals 2&pgr;/&Lgr;0±2&pgr;i/&Lgr;ph (i=0, 1, . . . , n, where n is a positive integer), 2&pgr;/&Lgr;0±2&pgr;(2i+1)/&Lgr;ph (i=0, 1, . . . , n), or 2&pgr;/&Lgr;0+2&pgr;i/&Lgr;f (i=m, m+1, . . . .

Abstract: An optical transmitter for realizing a high tolerance with respect to the group velocity dispersion of the optical fibers, a small receiver sensitivity degradation, and an improved stability that is hardly affected by the group velocity dispersion even in the case of network scale expansion, is constructed by a light source section for generating optical clock pulses synchronized with a signal bit rate while maintaining a duty ratio of the optical clock pulses constant, which is capable of variably setting the duty ratio, and an encoding section for encoding the optical clock pulses by using electric signals synchronized with the optical clock pulses while setting a relative optical phase difference between the optical clock pulses in adjacent time-slots to be an odd integer multiple of &pgr;.

Abstract: A wavelength converter has a phase modulated periodically modulated structure, where a nonlinear optical coefficient is periodically modulated at a fundamental period &Lgr;0 and the phase of the modulation varies nearly continuously, and the phase variation of the modulation unit structure is repeated at a period &Lgr;ph (>&Lgr;0). A conversion efficiency is made maximum when a phase mismatch amount &Dgr;&bgr; equals 2&pgr;/&Lgr;0±2&pgr;i/&Lgr;ph (i=0, 1, . . . , n, where n is a positive integer), 2&pgr;/&Lgr;0±2&pgr;(2i+1)/&Lgr;ph (i=0, 1, . . . , n), or 2&pgr;/&Lgr;0+2&pgr;i/&Lgr;f (i=m, m+1, . . . .