JP4521538B2 - Laser light generator - Google Patents

Description

  The present invention provides an injection locking method that obtains a high output with a narrow line width by combining a master oscillator with low output but good frequency purity and oscillation light of a power oscillator that has high output but is not specifically controlled. The present invention relates to an applied laser beam generator.

  In recent years, optical soliton transmission technology has attracted attention as a transmission technology that enables next-generation large-capacity and long-distance transmission. The optical soliton transmission technology is a transmission technology for performing long-distance communication of 1200 km or more without relay using a stable optical pulse called an optical soliton (isolated wave).

  In order to realize this optical soliton transmission technology, development of communication lasers using injection locking and an external resonator method has been actively promoted. Here, the injection locking method means that the output from a master oscillator (also referred to as a seed laser) with low output but high frequency purity is injected into a power oscillator with low frequency purity but high output, and the power oscillator of the power oscillator is injected into the master oscillator. In this method, laser light having high frequency purity and high output is obtained with high stability by dragging oscillation light.

  The master oscillator used here is generally a laser device that outputs a single longitudinal mode wavelength. In order to obtain an output having a desired characteristic using this apparatus, it is necessary to match the single longitudinal mode wavelength with at least one of the single longitudinal mode wavelengths of the power oscillator.

  When a laser beam generator with the above conditions is used, it has a transform limit spectrum width (several to several tens of MHz) almost completely for a pulse width of several nano to several hundred nanoseconds, and further has a peak of MW. An output having characteristics such as wavelength variability over several tens of nanometers with intensity and MHz accuracy can be obtained. A laser beam generator having such characteristics is expected to be used as, for example, an experimental instrument for nonlinear optics that requires high peak intensity and high adjustment accuracy in the frequency domain.

By the way, as a technique using the above-described injection locking method, Patent Document 1 discloses a master oscillator capable of outputting two or more types of frequency spectra from one laser device (corresponding to injection light in Patent Document 1). ), And the wavelength distribution of the master oscillator and the resonator mode of the power oscillator (corresponding to the Q-switched laser in Patent Document 1) are selected so that the power oscillator oscillates in a plurality of modes. It is disclosed.
Japanese Patent Laid-Open No. 10-294517

  By the way, the technique described in Patent Document 1 uses a device that outputs a plurality of spectra from a single laser device as a master oscillator. However, in general, the output of a laser beam is sensitive to minute fluctuations in the environment. The multiple spectrum and power oscillator of the master oscillator drift independently, and one wavelength can be stabilized. However, it is very difficult to stabilize other wavelengths for a long time.

  On the other hand, since such a master oscillator that outputs a plurality of single longitudinal mode wavelengths outputs an equally spaced frequency, the output of the injection-locked power oscillator is also equally spaced. Accordingly, the output obtained is a frequency spectrum with equal intervals, and a wavelength spectrum with non-equal intervals cannot be obtained.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a laser beam generator capable of easily obtaining a spectrum having high wavelength selectivity, high output, and high stability. is there.

In order to solve the above-mentioned problem, the present invention according to claim 1 synthesizes at least two seed light generating means for outputting a single longitudinal mode wavelength and the seed light output from the seed light generating means. and combining means, said combined seed light is synchronized to a specific wavelength, and the laser beam generating means for frequency purity outputs the well and light intensity high laser light generated for each seed light, the laser beam in advance and discriminating means for discriminating for each wavelength to determine converts discriminated laser light into an electric signal, as compared with the predetermined reference signal, when the difference occurs in the electrical signal and the reference signal, various optical Based on the value of either the wavelength of the generating means or the effective resonator length of the laser light generating means, so that the values of the wavelengths of the various light generating means or the effective resonator length of the laser light generating means have a predetermined relationship Values other than the reference are corrected Te calculated, further comprising a drive control means for driving and controlling the cavity length of the seed light generating means or the seed light generating means outputs a correction value obtained in the laser beam generating means or the laser beam generating means The gist.

According to a second aspect of the present invention, at least two or more seed light generating means for outputting a single longitudinal mode wavelength, a combining means for combining the seed light output from the seed light generating means, and the synthesized light Laser light generating means for synchronizing seed light with a specific wavelength, outputting laser light with good frequency purity and high light intensity generated for each seed light, and photoelectric conversion means for converting the laser light into an electrical signal; The electric signal discriminating means for discriminating the electric signal for each electric signal having a predetermined frequency, and comparing the discriminated electric signal with a preset reference signal, thereby producing a difference between the reference signal and the electric signal. In this case, the values of the wavelengths of the various light generating means or the effective resonator length of the laser light generating means are used as a reference, and the values of the wavelengths of the various light generating means or the effective resonator length of the laser light generating means are To be in a predetermined relationship Obtains a value other than the reference as a correction value, driving and controlling the cavity length of each of said seed light generating means or the seed light generating means outputs a correction value obtained in the laser beam generating means or the laser beam generating means The gist of the invention is that it comprises drive control means and modulation signal generation means for outputting a modulation signal to be superimposed on the laser light on the seed light generation means to the seed light generation means .

  According to a third aspect of the present invention, in the laser light generation device according to the first or second aspect, when the correction value is output to the seed light generation unit, the drive control unit is provided for each seed light generation unit. This is the gist.

The gist of the present invention described in claim 4 is the laser light generator according to claim 1 , further comprising modulation signal generation means for outputting a modulation signal to the seed light generation means.

  According to a fifth aspect of the present invention, in the laser light generation device according to the first or second aspect, the drive control unit calculates a correction value based on a displacement direction and a displacement amount of the electrical signal with respect to the reference signal, The gist is to output a correction signal including the correction value to the resonator length.

  According to a sixth aspect of the present invention, in the laser light generator according to the first aspect, the discriminating means includes a spectroscopic means for splitting the laser light output from the laser light generating means for each wavelength, and the split light. The gist of the invention is to have photoelectric conversion means for converting the signal into an electric signal.

  The gist of the present invention described in claim 7 is that, in the laser light generator according to claim 2, the modulation signal generating means is provided for each seed light generating means.

The present invention according to claim 8 is characterized in that at least two or more seed light generating means for outputting a single longitudinal mode wavelength, a combining means for combining the seed light output from the seed light generating means, and the synthesized light. A nonlinear medium that forms an optical soliton array based on the seed light, harmonic generation means for matching the laser light output from the nonlinear medium to the amplification frequency region of the power oscillator, optical solitons or harmonics thereof A laser light generating means for generating a high output optical soliton array in synchronization with a specific wavelength, a discrimination means for discriminating the laser light according to a predetermined wavelength, and a photoelectric for converting the discriminated laser light into an electrical signal conversion means, as compared with a preset reference signal and the electrical signal, when the difference occurs in the electrical signal and the reference signal, the wavelength or the laser beam generating means various light generating means Using any value of the effective resonator length as a reference, obtain a value other than the reference as a correction value so that each value of the wavelength of various light generation means or the effective resonance length of the laser light generation means has a predetermined relationship, And a means for outputting a correction value obtained to the seed light generating means or the laser light generating means to drive and control the resonator length of the seed light generating means or the laser light generating means.

The invention according to claim 9 is characterized in that at least two or more seed light generating means for outputting a single longitudinal mode wavelength, a combining means for combining the seed light output from the seed light generating means, and the synthesized light. A nonlinear medium that forms an optical soliton array based on the seed light, harmonic generation means for matching the laser light output from the nonlinear medium to the amplification frequency region of the power oscillator, optical solitons or harmonics thereof A laser light generating means for generating a high output optical soliton array synchronized with a specific wavelength, a photoelectric conversion means for converting the laser light into an electric signal, and the electric signal for each electric signal of a predetermined frequency electrical signal discrimination means for discriminating, as compared with a preset reference signal and the electrical signal, when the difference occurs in the electrical signal and the reference signal, the wavelength of various light generating means or rate -Using any value of the effective resonator length of the light generating means as a reference, set a value other than the reference so that the wavelengths of the various light generating means or the effective resonator length of the laser light generating means have a predetermined relationship. calculated as a correction value, and means for driving and controlling the cavity length of each of said seed light generating means or the seed light generating means or laser beam generating means have outputs a correction value obtained in the laser beam generating means, said seed The gist of the present invention is to provide a modulation signal generating means for outputting a modulation signal to be superimposed on the laser beam on the light generating means to the seed light generating means .

  According to the present invention, at least two or more master oscillators that output a single longitudinal mode wavelength, an optical system that includes an optical element that combines seed light output from these master oscillators, and a combined seed A power oscillator that synchronizes the light with a specific wavelength and outputs laser light with high frequency purity and high light intensity generated for each type of light, a spectrometer that discriminates the laser light by wavelength, and discriminated laser light Is converted into an electrical signal, and when a difference occurs between the electrical signal and the reference signal compared with a preset reference signal, a correction signal for correcting the resonator length corresponding to the difference is mastered. A laser beam generator equipped with a drive controller that drives back and controls the resonator length of the master oscillator or power oscillator by returning to the oscillator or power oscillator. The by providing a high wavelength selectivity, and high output, a spectrum having a high stability can be easily obtained.

  Hereinafter, the best mode for carrying out the present invention will be described.

  This laser beam generator functions as, for example, a master oscillator that functions as at least two or more seed beam generators that output light in a single longitudinal mode, and a combiner that synthesizes the seed beams output from the master oscillator. An optical system composed of optical elements such as a total reflection mirror and a partial reflection or transmission mirror, and a frequency generated for each seed light by injecting the seed light into a laser beam that outputs a wavelength region synchronized with the seed light. For example, a power oscillator that functions as a laser beam generating unit that outputs laser light with high purity and high light intensity, and a spectral unit that functions as a discriminating unit that discriminates laser light output from the power oscillator by wavelength. The converted laser light is converted into an electrical signal and compared with a preset reference signal. In the case where a difference occurs, a drive control unit that outputs a correction signal for correcting the resonator length corresponding to the difference to the master oscillator or the power oscillator and drives and controls the resonator length of the master oscillator or the power oscillator. It has.

  With reference to FIG. 1, the structure of the laser beam generator 1 which concerns on embodiment of this invention is demonstrated concretely.

  As shown in the figure, the laser light generator 1 includes a power oscillator 3, a power oscillator drive control unit 7 that drives and controls the power oscillator 3, and a plurality of different oscillation frequencies injected into the power oscillator 3. 1, 2,... N master oscillators 5 a, 5 b... 5 n and first, second,..., N master oscillator control drive units 11 a, 11 b that drive and control each of these master oscillators. 11n, a modulation oscillator 13 that modulates each master oscillator control drive unit, a spectroscopic unit that splits the output of the power oscillator 3 according to wavelength, and a first that receives these lights and outputs an electrical signal. The second,..., Nth light receiving means and the output electric signals are converted into first, second,..., Nth master oscillators, respectively. The control drive units 11a, 11b,... 11n are fed back to the first, second,..., Nth feedback circuits, and outputs from the n master oscillators are provided between the master oscillator and the power oscillator. The mirrors 17a, 17b,... To be combined and the half mirrors 15a, 15b,. A partial transmission mirror 15 c for obtaining output light from the power oscillator 3 is provided between the power oscillator 3 and the spectroscopic means 19.

  In the present embodiment, the spectroscopic means 19 divides the laser light output from the power oscillator 3 for each wavelength, and includes, for example, a diffraction grating and a prism. An example of photoelectric conversion means for converting the dispersed light into an electrical signal is an optical photodetector (PD).

  The first feature of the laser beam generator 1 includes a detection mechanism and a correction mechanism for detecting a correction signal (error signal) corresponding to each master oscillator 5 in order to feed back n master oscillators 5. There is in point. In order to realize this, a modulation signal is superimposed on the power oscillator 3, the light output from the power oscillator 3 is dispersed by the spectroscopic means, and the dispersed light is further detected by the photoelectric conversion means and superimposed on each light. A correction signal is acquired by passing through a phase sensitive detector corresponding to the modulated signal.

  The second feature of the present laser beam generator 1 is that a conventional laser device using an injection locking method uses only one master oscillator, whereas a master oscillator with low output intensity but good frequency purity. Is that at least two of them are used. In addition, in accordance with this, each spectrum of the master oscillator used at least two or more is synchronized so as to coincide with the longitudinal mode and the transverse mode of the resonator of the power oscillator.

In order to match the longitudinal mode of the resonator in this way, for example, when two master oscillators are used, it is necessary to apply feedback so as to satisfy the following formula (1).

  In this case, since the degree of freedom is determined by three parameters of the wavelength ν1, the wavelength ν2, and the effective resonator length L of the power oscillator, it is necessary to feed back two of these variables in order to obtain synchronization. There is.

  In view of this, in this laser light generation apparatus 1, considering that the resonator length drifts due to the influence of heat generation and ambient heat during oscillation, feedback to wavelengths ν1 and ν2 based on the resonator length L in advance. multiply. The reference is not limited to the resonator length L, and may be the wavelength ν1 or ν2.

  Furthermore, the third feature of the laser beam generator 1 is that a modulation signal is superimposed on either or both of the output light of the master oscillator and the power oscillator.

  The fourth feature of the laser beam generator 1 is that, for the purpose of the present invention, a plurality of master oscillators are used to obtain non-equally spaced spectra, but the same standard lock-in amplifier is used for each master oscillator. It is in. This eliminates the need to provide a dedicated lock-in amplifier for each master oscillator, thereby improving the yield of the laser beam generator.

  Furthermore, the fifth feature of the laser beam generator 1 is that the alignment of the resonator (adjustment of the optical path) is facilitated because a plurality of seed lights are independently detected. As a result, when an abnormality occurs in the seed light, this abnormality can be found instantly.

(First embodiment)
Next, an example of the laser beam generator according to the first embodiment will be described with reference to FIG.

  This laser beam generator is roughly divided into a master oscillator unit 21, a power oscillator unit 23, and a feedback circuit 25.

  In the master oscillator unit 21, a titanium sapphire laser (oscillation wavelength 757.8749 [nm]) 211 is applied as a first master oscillator, and an LD (oscillation wavelength 784.9494 [nm]) 213 is used as a second master oscillator. Applied. Here, the titanium sapphire laser 211 is a reference laser device in this embodiment, and the LD (retro type external resonator semiconductor laser) 213 is a master oscillator that receives feedback of the oscillation wavelength.

this is,
The seed light output from the LD 213 passes through the anamorphic prism 221 and the isolator 223a, and is then combined with the seed light from the titanium sapphire laser 211 that has passed through the λ / 2 plate 225a by the coupling mirror 227a. The synthesized seed light passes through the two convex lenses 215c and 215d connected via the optical fiber 217b, then passes through the isolator 223b and enters the power oscillator unit 23.

  The power oscillator unit 23 is a ring resonator in which mirrors are arranged in a triangle. This triangular ring resonator includes an output coupling mirror 227b and mirrors 229c and 227c, and a PZT (piezo element) is attached to the mirror 229c as a piezoelectric element. A power oscillator excitation laser Q-YAG laser (oscillation wavelength 532 [nm]) 233 that is transmitted through the mirror 227c and introduced into the triangular ring resonator excites the titanium sapphire crystal 231. Further, a titanium sapphire crystal 231 for branching feedback laser light is disposed between the half mirror 227c and the half mirror 227d.

  The feedback circuit 25 includes a diffraction grating 253 that splits the weak seed light partially reflected by the end face of the titanium sapphire crystal 231 and a split laser beam (hereinafter referred to as a first detection signal and a second detection signal). 1) and 2nd PDs 255a and 255b for receiving light respectively. The first and second detection signals output from the first and second PDs 255a and 255b are input to the phase sensitive detectors 259a and 259b. The first detection signal detected by the phase sensitive detector 259a is compared with the modulation oscillator (5 kHz) 263 by the PZT driver 261, and a correction signal based on the comparison result is output to the PZT 265. On the other hand, the second detection signal detected by the phase sensitive detector 259b passes through the PZT driver 261 and is input to the LD 213.

  Here, the frequency of the modulation oscillator is 5 kHz, but the frequency is not limited to this and may be other frequencies.

  Next, the operation of this laser beam generator will be described.

  First, the intensity adjustment of the seed light of the LD 213 incident on the power oscillator is set by turning the polarized light with the λ / 2 plate 225a provided in the master oscillator unit 21, and the intensity of the titanium sapphire laser 211 is set to be the titanium sapphire laser 211. This is set by rotating the polarized light with the λ / 2 plate 225b on the line.

  Next, the weak seed light reflected by the end face of the titanium sapphire crystal 231 disposed in the triangular resonator is extracted as detection light. The detection light is split by the diffraction grating 253 and input to the first and second PDs 255a and 255b, respectively. The light detected by the first and second PDs 255a and 255b is further extracted as a detection signal by a phase sensitive detector using 5 [kHz] as a reference signal.

  Thereafter, the first detection signal is returned to the PZT 265 that controls the resonator length, and the other is returned to the LD 213. As a result, the two seed lights and the longitudinal mode of the power oscillator can be consistently matched over a long period of time. Laser light with high output and high frequency accuracy can be obtained.

  Since the oscillation light is dragged by the seed light, a laser beam having high frequency purity and high output is generated and output from the triangular resonator. The center wavelength of one spectrum output at this time is 757.8749 [nm], which is the same as that of the titanium sapphire laser 211, and the center wavelength of the other spectrum is 784.9494 [nm], which is the same as that of the LD 213.

  Next, with reference to FIG. 3, the experimental result of the said laser beam generator is demonstrated. In the spectrum shown in FIG. 3, the horizontal axis represents wavelength [nm] and the vertical axis represents relative intensity (logarithmic display).

  In FIG. 3, spectrum (1) is an oscillation spectrum obtained by injecting and locking seed light of 757.88749 [nm], and spectrum (2) is injecting and locking seed light of 784.9487 [nm]. It is an oscillation spectrum obtained in this way. Spectrum (3) is a spectrum in a free-run state (a state in which seed light is not injected).

  In this experimental condition, the energy of the excitation light (Q-YAG laser (532 [nm])) is 40 [mJ], the wavelength of the titanium sapphire laser is 757.88749 [nm], and the intensity is 1.4 after the output coupling mirror. [mW] On the other hand, the result is obtained when the LD wavelength is 784.9498 [nm] and the intensity is 97 [μW] after the output coupler. The output energy was divided into components by a prism and measured with a power meter, both of which were 4.1 [mJ].

  As shown in the experimental results of FIG. 3, the free-run component is completely drawn into the wavelengths of the two seed lights, and the free-run component is suppressed to at least 1/1000 or less.

(Modification of the first embodiment)
Next, with reference to FIG. 4, the modification of the laser beam generator 1 which concerns on 1st Embodiment is demonstrated.

  The laser beam generator 30 functions as at least two or more seed beam generators that output a single longitudinal mode wavelength. For example, the first, second, and nth master oscillators 55a, 35b,. Consists of optical elements of total reflection mirrors 47a and 47b and half mirrors 45a and 45b that function as a combining means for combining the seed lights output from the first, second, and n-th master oscillators 55a and 35b,. For example, a power oscillator 33 that functions as laser light generation means that synchronizes the synthesized seed light with a specific wavelength and outputs laser light with high frequency purity and high light intensity generated for each seed light. And, for example, an optical photodetector (PD) 39 that functions as a photoelectric conversion means for converting the laser light into an electrical signal, For example, a frequency discrimination filter (electric circuit) 31 having a frequency filter that functions as an electric signal discrimination means for discriminating each length is compared with the discriminated electric signal with a preset reference signal, and the electric signal and the reference A correction signal corresponding to the signal difference is fed back to the master oscillator or the power oscillator, and the first, second, and nth drive control units 41a, 41b,. 41n. The first, second,... N master oscillators 35a, 35b,... 35n are connected to first, second, nth modulation oscillators 43a, 43b,. The modulation signals m1, m2,... Mn from the respective modulation oscillators are input to the respective master oscillators.

  In the present embodiment, the difference from the first embodiment is that in the first embodiment, the laser light output from the power oscillator 3 is separated for each wavelength using the spectroscopic means. In the embodiment, the laser light output from the power oscillator is converted into an electric signal by a photoelectric conversion element and then separated through a frequency discrimination filter. Thereby, even if each wavelength difference of several seed light is made small, it can isolate | separate reliably.

    That is, in the first embodiment, since the light is directly divided for each wavelength, the separation accuracy depends on the resolution of the spectroscopic element. However, according to the present invention, separation is performed after conversion into an electric signal, so that the high accuracy is achieved. Separation becomes possible. However, in the present invention, it is necessary to select a frequency that does not compete with the modulation signal to be superimposed on the laser beam.

  In the first embodiment, the number of light receiving elements is the same as the number of master oscillators. However, according to the present embodiment, the number of light receiving elements can be realized by one light receiving element, so that the yield can be improved. .

(Second Embodiment)
Next, the configuration of the laser beam generator according to the second embodiment of the present invention will be described. FIG. 5 is a configuration diagram of a laser beam generator 50 according to the second embodiment.

  The laser beam generator 50 functions as at least two or more seed beam generators that output a single longitudinal mode wavelength, for example, first and second master oscillators 55a and 55b, and first and second master oscillators. Optical fibers 63a and 63b that function as a combining unit that combines the seed lights output from 55a and 55b, a nonlinear medium 51 that forms an optical soliton array based on the combined seed light, and an output from the nonlinear medium 51 The harmonic generator 57 for matching the laser beam to the amplification frequency region of the power oscillator and the optical soliton column, or the high-frequency optical soliton column is generated by synchronizing the high-frequency laser beam with a specific wavelength. For example, a power oscillator 53 that functions as laser light generation means, and discrimination means for discriminating the laser light according to wavelength In comparison with a reference signal set in advance, a spectroscopic means that functions as a spectroscopic means, a photoelectric conversion means that converts the discriminated laser light into an electrical signal, and when a difference occurs between this electrical signal and this reference signal, A correction signal for correcting the resonator length corresponding to the difference is output to the master oscillator or the power oscillator, and the first and second drive control units 61a and 61b for driving and controlling the resonator length of the master oscillator or the power oscillator are provided. I have.

  In the present embodiment, the spectroscopic means is for splitting the laser light output from the power oscillator 53 for each wavelength, and examples thereof include a diffraction grating and a prism. An example of photoelectric conversion means for converting the dispersed light into an electrical signal is an optical photodetector (PD). The nonlinear medium 51 may be a combination of a highly nonlinear fiber and a dispersion compensating fiber, a photonic crystal fiber, a taper fiber, or the like.

  This laser beam generator 5 generates a large number of frequency combs through a nonlinear optical process (four-wave optical process) based on two independent continuous wave laser beams that oscillate at two different wavelengths close to each other. This is a method of increasing the output as light by the injection locking method.

  Here, the longitudinal mode interval of the frequency comb is determined by the oscillation wavelength of the two continuous-wave lasers of the seed light. Therefore, the longitudinal mode is matched between the three independent lasers including the master oscillator and the power oscillator. Just take it. The frequency difference between the two wavelengths is generally about several hundred MHz to several THz.

  As a modification of the present embodiment, the frequency difference may be continuously swept with injection locking applied. Moreover, the generated frequency comb may be used as it is, or its harmonics may be used. Furthermore, the power oscillator 53 is not limited to continuous wave oscillation, and pulse oscillation may be used.

  Next, the process of changing the frequency spectrum of the laser beam generator 50 according to the second embodiment will be described with reference to FIGS.

  6 shows the spectrum of the portion indicated by arrow A in FIG. 5, FIG. 7 shows the spectrum of the portion indicated by arrow B, and FIG. 7 shows the spectrum when the power oscillator of the portion indicated by arrow C is pulse oscillated. Yes.

  6A shows an oscillation spectrum when the horizontal axis is the frequency ν and the vertical axis is the light intensity I, and FIG. 6B is the case where the horizontal axis is the time and the vertical axis is the light intensity I. It is a time waveform. As shown in FIGS. 6A and 6B, different frequencies ν1 and ν2 are output from the first and second master oscillators 55a and 55b, respectively. The light intensity of each laser beam at this time is kept constant.

  Similarly to FIG. 6A, FIG. 7A also shows an oscillation spectrum when the horizontal axis is the frequency ν and the vertical axis is the light intensity I, and FIG. Is a time waveform when the light intensity is I. As shown in FIGS. 7A and 7B, the oscillation spectrum forms a frequency comb having an equal frequency interval Δν = | ν2−ν1 |, and an optical soliton train having a constant peak intensity is formed in the time domain.

  FIG. 8A also shows the oscillation spectrum when the horizontal axis is the wavelength ν and the vertical axis is the light intensity I, as in FIG. 6A, and FIG. Is a time waveform when the light intensity is I. As shown in FIGS. 8A and 8B, the oscillation spectrum retains the same shape as in FIG. 7A, and its peak intensity is high, and the time waveform is the envelope curve of the time waveform of the pulse oscillation of the power oscillator. The optical soliton array in FIG. 7B is formed therein.

  Next, with reference to FIG. 9, the Example of the laser beam generator 50 which concerns on 2nd Embodiment is demonstrated.

  The laser beam generator 70 is a so-called triangular ring resonator composed of three mirrors 85a, 79d, and 85b. The pump light uses a Nd: YAG laser double wave, a repetition frequency of 10 Hz, and a wavelength of 532 nm. An optical soliton having a repetition frequency of 160 GHz, a center wavelength of 1.55 μm, and a pulse width (full width at half maximum) of 500 fs generates a two-wavelength beat signal using two first and second DFBLDs (wavelength variable laser light sources) 71a and 71b. It is generated using a highly nonlinear fiber CDPF (Comb Like Dispersion Profiled Fiber) 73.

  In order to use this optical soliton as seed light, the titanium sapphire crystal 89 has a gain in the wavelength region of 600 to 900 nm, so here it is necessary to generate a double wave using PPNL (Periodically Poled Lithium Niobate) 77. is there.

  Further, since the semiconductor laser is weak to the return light and easily broken, the isolator 83 is inserted so that the crystal of the PPLN 77 is not damaged by the return light.

  The weak reflected light from the end face of the titanium sapphire crystal 89 is separated by the diffraction grating 93 and detected by the first and second PDs 95a and 95b, respectively, and modulated at 5 kHz, one for the resonator length and the other for the wavelength. By applying feedback to, injection locking can be performed simultaneously on a frequency comb composed of a number of longitudinal modes. As a result, an output with a repetition frequency of 160 GHz, a center wavelength of 775 nm, a pulse width of 500 fs, and a pulse envelope width of 6 ns and 10 mJ can be obtained.

  Next, the process of changing the frequency spectrum of the laser beam generator 70 according to the second embodiment will be described with reference to FIGS.

  10 shows the spectrum of the portion indicated by arrow D in FIG. 9, FIG. 11 shows the spectrum of the portion indicated by arrow E, and FIG. 12 shows the spectrum of the portion indicated by arrow F.

  10A shows an oscillation spectrum when the horizontal axis is the wavelength ν and the vertical axis is the light intensity I, and FIG. 10B shows the case where the horizontal axis is the time and the vertical axis is the light intensity I. It is a time waveform. As shown in FIGS. 10A and 10B, different frequencies ν1 and ν2 are output from the first and second DFBLDs 71a and 71b, respectively. The light intensity of each laser beam at this time is kept constant.

  Similarly to FIG. 10A, FIG. 11A is an oscillation spectrum in which the horizontal axis is the wavelength ν and the vertical axis is the light intensity I, and FIG. Is a time waveform when the light intensity is I. As shown in FIGS. 11A and 11B, the oscillation spectrum forms a frequency comb having an equal frequency interval Δν = | ν2−ν1 |, and an optical soliton train having a constant peak intensity is formed in the time domain.

  Similarly to FIG. 10A, FIG. 12A is an oscillation spectrum in which the horizontal axis is the wavelength ν and the vertical axis is the light intensity I, and FIG. Is a time waveform when the light intensity is I. As shown in FIGS. 12A and 12B, the oscillation spectrum retains the same shape as in FIG. 11A, and its peak intensity is high, and the time waveform is an envelope curve of the time waveform of the pulse oscillation of the power oscillator ( The optical soliton array in FIG. 11B is formed in the full width at half maximum (6 ns).

1 is a configuration diagram of a laser beam generator 1 according to a first embodiment of the present invention. It is a figure explaining the Example of the laser beam generator 1 which concerns on the 1st Embodiment of this invention. It is a spectrum figure which shows the experimental result of the laser beam generator 1 which concerns on the 1st Embodiment of this invention. It is a figure which shows the modification of the laser beam generator 30 which concerns on the 1st Embodiment of this invention. It is a block diagram of the laser beam generator 50 which concerns on the 2nd Embodiment of this invention. It is a wave form diagram of the position shown with arrow A in laser beam generator 50 concerning a 2nd embodiment of the present invention. It is a wave form diagram of the position shown by arrow B in laser beam generator 50 concerning a 2nd embodiment of the present invention. It is a wave form diagram of the position shown by arrow C in laser beam generator 50 concerning a 2nd embodiment of the present invention. It is a figure explaining the Example of the laser beam generator 70 which concerns on the 2nd Embodiment of this invention. It is a wave form chart of the position shown by arrow D in the example of laser beam generator 70 concerning a 2nd embodiment of the present invention. It is a wave form chart of the position shown by arrow E in the example of laser beam generator 70 concerning a 2nd embodiment of the present invention. It is a wave form diagram of the position shown by arrow F in the Example of the laser beam generator 70 which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser beam generator 3 ... Power oscillator 5a, 5b, ... 5n ... Master oscillator 7 ... Power oscillator drive control part 11a, 11b, ... 11n ... Master oscillator control drive part 13 ... Oscillator for modulation 15a, 15b, 15c ... half mirrors 17a, 17b ... mirror 19 ... spectroscopic means 21 ... master oscillator part 23 ... power oscillator part 25 ... feedback circuit 33 ... power oscillators 35a, 35b, ... 35c ... master oscillators 41a, 41b, ... 41n ... drive control 43a, 43b,... 43n ... Modulator oscillator 45a ... Half mirror 47a ... Total reflection mirror 51 ... Non-linear medium 53 ... Power oscillator 55a ... Second master oscillator 57 ... Harmonic wave generator 61a ... Second drive controller 63a …light Aiba 71a, 71b ... DFBLD
77 ... PPLN
83 ... Isolator 85a ... Mirror 89 ... Titanium sapphire crystal 93 ... Diffraction gratings 95a, 95b ... PD
211 ... Titanium sapphire laser 213 ... LD
215c ... convex lens 217b ... optical fiber 221 ... anamorphic prism 223a ... isolator 223b ... isolator 225a, 225b ... λ / 2 plate 227a, 227b, 227c, 227d ... coupling mirror 229c ... mirror 231 ... titanium sapphire crystal 253 ... diffraction grating 255a, 255b ... PD
259a, 259b ... phase sensitive detector 261 ... PZT driver 265 ... PZT

Claims (9)

At least two seed light generating means for outputting a single longitudinal mode wavelength;
Combining means for combining the seed light output from the seed light generating means;
Laser light generating means for synchronizing the synthesized seed light with a specific wavelength and outputting laser light with high frequency purity and high light intensity generated for each seed light;
Discriminating means for discriminating the laser beam according to a predetermined wavelength;
When the discriminated laser beam is converted into an electrical signal and compared with a preset reference signal, if there is a difference between the electrical signal and the reference signal, the wavelength of the various light generating units or the laser beam generating unit Based on one of the effective cavity length values, a value other than the reference is obtained as a correction value so that the wavelengths of the various light generating means or the effective resonator length of the laser light generating means have a predetermined relationship. Driving control means for driving and controlling a resonator length of the seed light generating means or the laser light generating means by outputting a correction value obtained to the seed light generating means or the laser light generating means;
A laser light generator comprising: At least two seed light generating means for outputting a single longitudinal mode wavelength;
Combining means for combining the seed light output from the seed light generating means;
Laser light generating means for synchronizing the synthesized seed light with a specific wavelength and outputting laser light with high frequency purity and high light intensity generated for each seed light;
Photoelectric conversion means for converting the laser light into an electrical signal;
An electric signal discriminating means for discriminating the electric signal for each electric signal having a predetermined frequency ;
When the discriminated electrical signal is compared with a preset reference signal, and there is a difference between the reference signal and the electrical signal, the wavelength of various light generating means or the effective resonator length of the laser light generating means A value other than the reference is obtained as a correction value so that each value of the wavelength of the various light generating means or the effective resonator length of the laser light generating means has a predetermined relationship, and each of the seed lights A drive control means for driving and controlling a resonator length of the seed light generating means or the laser light generating means by outputting a correction value obtained to the generating means or the laser light generating means;
Modulation signal generating means for outputting to the seed light generating means a modulation signal to be superimposed on laser light on the seed light generating means;
A laser light generator comprising:   3. The laser light generator according to claim 1, wherein when the correction value is output to the seed light generating means, the drive control means is provided for each seed light generating means. 2. The laser beam generator according to claim 1, further comprising a modulation signal generator that outputs a modulation signal to the seed light generator.   The drive control means calculates a correction value based on a displacement direction and a displacement amount of the electrical signal with respect to the reference signal, and outputs a correction signal including the correction value to the resonator length. Or the laser beam generator of 2.   2. The discriminating means includes: a spectroscopic means for splitting the laser light output from the laser light generating means for each wavelength; and a photoelectric conversion means for converting the split light into an electric signal. Laser light generator.   3. The laser beam generator according to claim 2, wherein the modulation signal generator is provided for each seed light generator. At least two or more seed light generating means for outputting a single longitudinal mode wavelength, a combining means for combining the seed light output from the seed light generating means, and an optical soliton based on the combined seed light A nonlinear medium forming a row, a harmonic generation means for matching the laser light output from the nonlinear medium with the amplification frequency region of the power oscillator, and a high output by synchronizing the optical soliton or its harmonic with a specific wavelength Laser light generating means for generating the optical soliton train, discrimination means for discriminating the laser light according to a predetermined wavelength, photoelectric conversion means for converting the discriminated laser light into an electric signal, and the electric signal compared to a predetermined reference signal, when the difference occurs in the electrical signal and the reference signal, one of the effective resonator length of the wavelength or the laser beam generating means various light generating means Using the value as a reference, a value other than the reference is obtained as a correction value so that the values of the wavelengths of the various light generating means or the effective resonance length of the laser light generating means have a predetermined relationship, and the seed light generating means or the laser light is obtained. And a means for driving and controlling the cavity length of the seed light generating means or the laser light generating means by outputting the correction value obtained to the generating means. At least two or more seed light generating means for outputting a single longitudinal mode wavelength, a combining means for combining the seed light output from the seed light generating means, and an optical soliton based on the combined seed light A nonlinear medium forming a row, a harmonic generation means for matching the laser light output from the nonlinear medium with the amplification frequency region of the power oscillator, and a high output by synchronizing the optical soliton or its harmonic with a specific wavelength Laser light generating means for generating a generated optical soliton array;
Photoelectric conversion means for converting the laser light into an electrical signal;
An electric signal discriminating means for discriminating the electric signal for each electric signal having a predetermined frequency ;
When there is a difference between the electrical signal and the reference signal set in advance , either the wavelength of the various light generation means or the effective resonator length of the laser light generation means As a reference, a value other than the reference is obtained as a correction value so that each value of the wavelength of various light generating means or the effective resonator length of the laser light generating means has a predetermined relationship, and each seed light generating means or Outputting a correction value obtained to the laser light generating means to drive and control the resonator length of the seed light generating means or the laser light generating means; and a modulation signal to be superimposed on the laser light on the seed light generating means. A laser light generation apparatus comprising: modulation signal generation means for outputting to seed light generation means .

Images