JP2007193231A - Light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source device that can vary the power of a SC (super continuum) optical pulse train while keeping the spectral waveform of SC light to be emitted. <P>SOLUTION: A light source device 1a is equipped with a pulse light source 2 that emits an optical pulse train P1 of ultrashort pulse light having a pulse width of several femtoseconds, an optical fiber 11 optically coupled with the pulse light source 2 and receiving the optical pulse train P1 to emit SC light P2, and a time-division multiplexing unit 3 as a power varying means optically coupled between the pulse light source 2 and the optical fiber 11. The time-division multiplexing unit 3 varies the power of the SC light P2 by varying the repetition frequency of the optical pulse train P1 emitting from the pulse light source 2 and thereby, varying the repetition frequency of the SC light P2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light source device for outputting super continuum light (SC light).

  The SC light source, which is one of the broadband light sources, is expected as an important light source for various application fields because of its high output power, wide bandwidth, and spectral flatness. Although various types of SC light source devices have been proposed, the configuration generated in the optical fiber is simple, the interaction length can be easily increased, and spectrum control is easy. Generally, it is widely used.

Examples of such an SC light source device include a coherent broadband light source described in Patent Document 1 and a broadband near-infrared pulsed laser light source described in Non-Patent Document 1.
JP-A-11-160744 Okuno et al., “Broadband near-infrared pulsed laser light source applying non-linearity of optical fiber”, Proceedings of the 21st Near-Infrared Forum Lecture, Near-Infrared Study Group, November 2005, p. 173

  Depending on the application field of such an SC light source, it may be desired to use it while adjusting the power of the SC light. For example, when the object to be measured is a low scatterer in infrared spectroscopic measurement, it may be desired to increase the power of the SC light applied to the object to be measured in order to accurately measure scattered light. On the other hand, in order to avoid deterioration or alteration of the measurement target object due to the interaction between the SC light and the measurement target object, it may be desired to reduce the power of the SC light applied to the measurement target object. In addition, when adjusting the power of the SC light, it is desirable that the power can be adjusted while maintaining the spectrum waveform of the SC light in order to maintain measurement accuracy.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a light source device that can vary the power of SC light while maintaining the spectrum waveform of the emitted SC light.

  In order to solve the above-described problems, a first light source device of the present invention includes a seed light source that emits an optical pulse train, and light that is optically coupled to the seed light source and emits supercontinuum light (SC light) upon receiving the optical pulse train. A fiber and power varying means for varying the power of the SC light, and the power varying means is an SC emitted from the light source device in a part or all of the wavelength range included in the spectrum band of the SC light. It is characterized in that the power of the SC light is changed in a state where the spectrum waveform of the light is maintained. According to this light source device, the power of the SC light in the wavelength range can be made variable while maintaining the spectrum waveform of the SC light in the wavelength range necessary for measurement by the power variable means. The spectral waveform of the SC light here refers to a undulation state along the wavelength axis in the spectral intensity characteristic of the SC light. In addition, the fact that the spectrum waveform is maintained means that the ratio of the spectrum intensity before and after the change in each wavelength is substantially uniform over the wavelength range.

  Further, the first light source device may be characterized in that the power variable means changes the power of the SC light by changing the peak value of the power waveform of each pulse included in the optical pulse train. Thereby, the power of the SC light can be changed to a desired intensity while suitably maintaining the spectrum waveform of the SC light.

  In the first light source device, the power variable means changes the peak value of the power waveform of each pulse included in the optical pulse train by changing the output power of the excitation laser light source included in the seed light source. May be a feature. The output power of the excitation laser light source can be easily controlled by the amount of current supplied to the excitation laser light source. Therefore, according to this light source device, the peak value of the power waveform of each pulse included in the optical pulse train can be easily changed using one parameter such as the amount of current of the excitation laser light source.

  Further, the first light source device may be characterized in that the power variable means is a variable gain optical amplifier optically coupled between the seed light source and the optical fiber. By increasing the peak value of the power waveform of each pulse included in the optical pulse train by an optical amplifier and making the amplification factor variable, the power of the SC light can be easily controlled to a desired intensity. In this case, since the output power of the seed light source may be constant, an optical pulse train can be obtained stably. In this case, the spectral shape of the light incident on the optical amplifier may be different from the spectral shape of the light emitted from the optical amplifier. In addition to the peak value of the power waveform of each pulse of the optical pulse train incident on the optical fiber, by taking into account the change in the spectral shape of the optical pulse train in the optical amplifier, while maintaining the spectral waveform of the SC light suitably, The power of the SC light can be made close to the desired intensity with high accuracy.

  Further, the first light source device may be characterized in that the power variable means is a variable attenuation factor optical attenuator optically coupled between the seed light source and the optical fiber. By attenuating the power of each pulse included in the optical pulse train with an optical attenuator and making the attenuation factor variable, each noise of the optical pulse train is not affected without affecting the noise characteristics, time waveform, and spectrum shape of the optical pulse train. The peak value of the power waveform of the pulse can be controlled. Therefore, according to this light source device, the power of the SC light can be brought closer to the desired intensity with high accuracy.

  Further, in the first light source device, the power variable means changes the optical coupling efficiency between the seed light source and the optical fiber by using the optical axis shift between the seed light source and the optical fiber, thereby changing the optical pulse train. The peak value of the power waveform of each included pulse may be changed. As a result, the power of the SC light can be suitably controlled, and the optical loss can be suppressed as compared with the case where an optical amplifier or an optical attenuator is used.

  Further, the first light source device may be characterized in that the power varying means maintains the spectrum waveform of the SC light by changing the time waveform of each pulse included in the optical pulse train incident on the optical fiber. Thereby, the power of the SC light can be changed while suitably maintaining the spectrum waveform of the SC light.

  The first light source device may be characterized in that the power variable means maintains the spectrum waveform of the SC light by changing the center wavelength of the optical pulse train incident on the optical fiber. The spectral waveform of SC light is affected by the dispersion characteristics of the optical fiber and the center wavelength of the optical pulse train. Therefore, according to this light source device, it is possible to change the power of the SC light while suitably maintaining the spectrum waveform of the SC light.

  Further, the first light source device may be characterized in that the power varying means maintains the spectrum waveform of the SC light by changing the spectrum shape of the optical pulse train incident on the optical fiber. Thereby, the power of the SC light can be changed while suitably maintaining the spectrum waveform of the SC light.

  The first light source device may be characterized in that the power variable means maintains the spectrum waveform of the SC light by changing the polarization direction of the optical pulse train incident on the optical fiber. The spectrum waveform of SC light is affected by the polarization of the optical pulse train and the polarization dependence of the optical fiber. Therefore, according to this light source device, it is possible to change the power of the SC light while suitably maintaining the spectrum waveform of the SC light.

  In addition, a second light source device according to the present invention includes a seed light source that emits continuous light, an optical fiber that is optically coupled to the seed light source and receives continuous light and emits supercontinuum light (SC light), and SC light. Power varying means for varying the power of the SC light, and the power varying means has a spectral waveform of the SC light emitted from the light source device in a part or all of the wavelength range included in the spectral band of the SC light. The power of the SC light is changed in a maintained state. Even if the light incident on the optical fiber is continuous light, SC light can be generated in the optical fiber if the continuous light has a relatively high power. According to this light source device, the power of the SC light in the wavelength range can be made variable while maintaining the spectrum waveform of the SC light in the wavelength range necessary for the measurement by the power variable means.

  The second light source device may be characterized in that the power of continuous light incident on the optical fiber is 100 mW or more. Thereby, SC light can be suitably generated in the optical fiber.

  Further, the first or second light source device may be characterized in that a wavelength of 1550 nm is included in a wavelength range of an optical pulse train or continuous light incident on an optical fiber. Thereby, SC light can be efficiently generated in a low-loss region of the optical fiber.

  The first or second light source device may further include a temperature control unit that controls the temperature of the optical fiber. As a result, the dispersion characteristic of the optical fiber can be suitably changed, so that the power of the SC light can be brought closer to a desired value with high accuracy while the spectral waveform of the SC light emitted from the light source device is more preferably maintained. . In this case, the temperature control means preferably includes a temperature control element provided in contact with the optical fiber. Thereby, the temperature of the optical fiber can be easily controlled.

  Further, the first or second light source device may be characterized in that the power varying means is a curved portion having a variable curvature formed in an optical waveguide for emitting SC light to the outside of the device. Since the SC optical waveguide has such a curved portion, it is possible to give an arbitrary bending loss to the SC light and to change the power of the SC light while suitably maintaining the spectrum waveform of the SC light.

  Further, the first or second light source device may be characterized in that the power varying means is a variable attenuation factor optical attenuator optically coupled to the output end of the optical fiber. According to this light source device, for example, the SC light is attenuated by using an optical attenuator having a sufficiently low wavelength dependency of the attenuation rate, thereby changing the power of the SC light while suitably maintaining the spectrum waveform of the SC light. be able to. In this case, the difference between the maximum attenuation rate and the minimum attenuation rate of the optical attenuator in the wavelength region is preferably 20 dB or less. This is because it is not easy to keep the wavelength dependency of the loss constant for a variable attenuation amount of 20 dB or more. If such a thing is obtained, the attenuator becomes expensive. Also, for normal applications, a 20 dB change in strength is sufficient.

  The first or second light source device may be characterized in that the power variable means is a variable gain optical amplifier optically coupled to the output end of the optical fiber. According to this light source device, for example, by amplifying the SC light by using an optical amplifier having a sufficiently low wavelength dependency of the amplification factor, the power of the SC light can be changed while favorably maintaining the spectrum waveform of the SC light. Can do.

  The first or second light source device may be characterized in that the power varying means changes the power of the SC light by changing the repetition frequency of the SC light. Thereby, the power of the SC light can be changed while suitably maintaining the spectrum waveform of the SC light.

  In the first or second light source device, the seed light source emits the optical pulse train, and the power variable means changes the repetition frequency of the optical pulse train incident on the optical fiber, thereby changing the SC light repetition frequency. It is good also as making it feature. Thereby, the repetition frequency of SC light can be changed, maintaining the spectrum waveform of SC light suitably. In this case, it is preferable to change the repetition frequency of the optical pulse train while maintaining the peak value of the power waveform of each optical pulse included in the optical pulse train incident on the optical fiber.

  The first or second light source device may further include detection means that is optically coupled to the output end of the optical fiber and detects at least one of the power and spectral shape of the SC light. By detecting at least one of the power and spectrum shape of the SC light by this detection means, it becomes possible to feedback-control the power variable means using this detection result, maintaining the spectrum waveform of the SC light, and SC Light power control can be performed with high accuracy and stability.

  Further, the first or second light source device may be characterized in that the spectrum width of the SC light is 10 times or more of the optical pulse train incident on the optical fiber or the spectrum width of the continuous light. When the spectrum width of the SC light becomes 10 times or more of the spectrum width of the optical pulse train (or continuous light), the deformation of the spectral shape of the SC light due to fluctuations in the characteristics (nonlinearity) of the optical pulse train or optical fiber becomes significant. . Therefore, in such a case, it is desirable that the power of the SC light in the wavelength range necessary for measurement can be arbitrarily changed by the power variable means.

  According to the light source device of the present invention, the power of the SC light can be varied while maintaining the spectrum waveform of the emitted SC light.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a light source device according to the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

  FIGS. 1A and 1B are diagrams respectively showing configurations of light source devices 1a and 1b according to the embodiment of the present invention. Referring to FIG. 1A, the light source device 1 a includes a pulse light source 2, a time division multiplexing processing unit 3, and an optical fiber 11. The pulse light source 2 is a seed light source in the present embodiment, and emits an optical pulse train P1 upon receiving power supply from a power supply device (not shown).

  The optical fiber 11 is optically coupled to the pulse light source 2 via the time division multiplex processing unit 3, receives the optical pulse train P1, and receives pulsed SC light P2 including supercontinuum (SC) light. Is emitted. Specifically, the optical fiber 11 generates SC light P2 having a gentle spectral shape over a wide band by expanding the spectral width of the optical pulse train P1 to, for example, twice or more. The center wavelength of the optical pulse train P1 is preferably in the vicinity of 1550 nm. Thereby, the SC light can be efficiently generated in the low loss region of the optical fiber 11.

  The time division multiplex processing unit 3 is power variable means for changing the power of the SC light P2. The time division multiplexing processing unit 3 changes the repetition frequency of the SC light P2 by changing the repetition frequency of the optical pulse train P1, and as a result, changes the time average power of the SC light P2.

  The time division multiplex processing unit 3 is optically coupled between the pulse light source 2 and the optical fiber 11, and includes a duplexer 31, a plurality of optical waveguides 32 and 33, a delay unit 34, a multiplexer 35, Have The demultiplexer 31 is a demultiplexing unit for demultiplexing the optical pulse train P <b> 1 from the pulse light source 2 into the optical waveguides 32 and 33. The delay unit 34 is a delay unit for delaying the optical pulse train P1 in terms of time. The delay device 34 is provided in one of the optical waveguides 32 and 33 (in this embodiment, the optical waveguide 32) or both. The multiplexer 35 is a multiplexing unit for multiplexing the optical pulse train P <b> 1 from the optical waveguides 32 and 33. Whether the optical pulse train P1 is demultiplexed into the optical waveguides 32 and 33, or the optical pulse train P1 is guided only to the optical waveguide (optical waveguide 33) not provided with the delay device 34. An optical switch for selection is provided. In this case, the frequency can be changed repeatedly while the average power output from the multiplexer 35 is kept constant. Further, an optical shutter, an optical switch, an optical variable attenuator or the like that effectively blocks light may be inserted into the optical waveguide 32 or 33. In this case, the frequency can be changed repeatedly without changing the energy of the pulsed light output from the multiplexer 35.

  Referring to FIG. 1B, the light source device 1 b includes a pulse light source 2, a time division multiplex processing unit 4, and an optical fiber 11. Among these, the configurations and functions of the pulse light source 2 and the optical fiber 11 are the same as those of the light source device 1a.

  The time division multiplex processing unit 4 is a power variable means for changing the power of the SC light P2. The time division multiplex processing unit 4 changes the repetition frequency of the SC light P2 by changing the repetition frequency of the optical pulse train P1, similarly to the time division multiplex processing unit 3 of FIG. The time average power of the light P2 is changed.

  The time division multiplex processing unit 4 is optically coupled between the pulse light source 2 and the optical fiber 11, and includes a duplexer 41, a plurality of optical waveguides 42 to 44, and a multiplexer 45. The demultiplexer 41 is a demultiplexing unit for demultiplexing the optical pulse train P <b> 1 from the pulse light source 2 into the optical waveguides 42 to 44. The multiplexer 45 is a multiplexing unit for multiplexing the optical pulse train P <b> 1 from the optical waveguides 42 to 44.

  Some of the optical waveguides 42 to 44 have delay paths 42a and 43a, respectively. The delay paths 42a and 43a are portions for delaying the optical pulse train P1 passing through the optical waveguides 42 and 43 in time, and constitute a delay section in the time division multiplex processing section 4. The delay path 42a is longer than the delay path 43a, and the delay time of the optical pulse train P1 is longer in the order of the optical waveguides 42, 43, and 44. The duplexer 41 selects whether to split the optical pulse train P1 into the optical waveguides 42 to 44, or to guide the optical pulse train P1 only to the optical waveguide (optical waveguide 44) in which no delay path is provided. An optical switch is provided. In this case, the frequency can be changed repeatedly while the average power output from the multiplexer 45 is kept constant. In addition, an optical shutter, an optical switch, an optical variable attenuator, or the like that effectively blocks light may be inserted into the optical waveguide 42, 43, or 44. In this case, the frequency can be changed repeatedly without changing the energy of the pulsed light output from the multiplexer 45.

  FIG. 2 is a diagram illustrating a configuration of a pulse light source 2 a as an example of the pulse light source 2. The pulsed light source 2a is a so-called active mode-locked ultrashort pulsed light source, and is composed of a ring resonator. That is, the pulse light source 2a includes a semiconductor laser element 21, an LN modulator 22a, a signal generator 22b that drives the LN modulator 22a, and a ring-shaped cavity (optical waveguide) 23. The semiconductor laser element 21 is optically coupled to the ring-shaped portion of the cavity 23 through a coupler 23a. The ring-shaped portion of the cavity 23 is optically coupled to the output optical waveguide 23d through the coupler 23c. An erbium-doped optical fiber (EDF) 23 b and an LN modulator 22 a are optically coupled in series to the ring-shaped portion of the cavity 23.

  When the signal generator 22b sends an electrical pulse signal of a certain frequency to the LN modulator 22a, the optical loss in the LN modulator 22a decreases at a period corresponding to the frequency. Excitation light is incident on the ring-shaped portion of the cavity 23 from the semiconductor laser element 21. If the LN modulator 22a is controlled so that oscillation occurs when the phases of the modes contained in the light pumped by the pump light are synchronized, an ultrashort pulse laser beam having a pulse width of about several femtoseconds can be obtained. It is generated and periodically emitted from the output optical waveguide 23d to the outside. In the light source devices 1a and 1b shown in FIGS. 1A and 1B, this periodic ultrashort pulse light is used as the optical pulse train P1. At this time, the repetition frequency of the optical pulse train P1 matches the frequency of the electrical pulse signal sent from the signal generator 22b to the LN modulator 22a.

  FIG. 3 is a diagram showing a configuration of a pulse light source 2b as another example of the pulse light source 2. The pulse light source 2b is a so-called passive mode-locked ultrashort pulsed light source, and is constituted by a ring resonator. That is, the pulse light source 2b includes a semiconductor laser element 21, a ring-shaped cavity (optical waveguide) 23, a reflection mirror 24a, a piezo motor 24b attached to the reflection mirror 24a, and a signal generator 24c for driving the piezo motor 24b. Have The point that the semiconductor laser element 21 is optically coupled to the cavity 23, the point that the cavity 23 has the output optical waveguide 23d, and the point that the EDF 23b is optically coupled to the ring-shaped portion of the cavity 23 are the above-mentioned pulses. This is the same as the light source 2a (FIG. 2).

  In the pulse light source 2b, a reflection mirror 24a is provided in place of the LN modulator 22a of the pulse light source 2a. The reflection mirror 24a constitutes a part of the ring-shaped portion of the cavity 23, and the length of the ring-shaped portion of the cavity 23 changes periodically as the position of the reflection mirror 24a vibrates. The vibration of the reflection mirror 24a is given by the piezo motor 24b. The vibration frequency is controlled by a signal generator 24c that drives the piezo motor 24b.

  When the signal generator 24c sends an electrical pulse signal having a certain frequency to the piezo motor 24b, the length of the cavity 23 varies in a cycle corresponding to the frequency. Excitation light is incident on the ring-shaped portion of the cavity 23 from the semiconductor laser element 21. Then, at the moment when the length of the cavity 23 satisfies the soliton condition, ultrashort pulse laser light having a pulse width of about several femtoseconds is generated. The ultrashort pulse light is periodically emitted from the output optical waveguide 23d to the outside as an optical pulse train P1. At this time, the repetition frequency of the optical pulse train P1 matches the frequency of the electrical pulse signal sent from the signal generator 24c to the piezo motor 24b. In the pulsed light source 2b, periodic ultrashort pulsed light is generated by mechanically driving the reflection mirror 24a. Therefore, the pulsed light source 2b is compared with the pulsed light source 2a configured to electrically drive the LN modulator 22a. Thus, the repetition frequency of the optical pulse train P1 tends to decrease.

  FIG. 4 is a diagram showing a configuration of a pulse light source 2 c as another example of the pulse light source 2. The pulsed light source 2c is a so-called passive mode-locked ultrashort pulsed light source, and is composed of a solid-state laser made of Er: Yb co-doped glass. That is, the pulse light source 2c includes a semiconductor laser element 21, a saturable absorber mirror 25 in which a saturable absorber and a reflector are integrally formed, a collimator lens 26a, prisms 26b and 26c, an output coupler 26d, Mirrors 27a to 27c, an Er: Yb co-added glass plate 28, and a transparent medium 29 are included. Among these components, components other than the semiconductor laser element 21 and the collimator lens 26a constitute a cavity CA for laser oscillation. The transparent medium 29 is provided as necessary.

  Excitation light emitted from the semiconductor laser element 21 reaches the Er: Yb co-doped glass plate 28 via the collimator lens 26a and the mirror 27a, and excites the Er: Yb co-doped glass plate 28. The Er: Yb co-doped glass plate 28 is disposed on a cavity CA including the saturable absorbing mirror 25, prisms 26b and 26c, an output coupler 26d, and mirrors 27a to 27c. The light traveling through the cavity CA reciprocates between the saturable absorber mirror 25 and the output coupler 26d while being amplified by the Er: Yb co-doped glass plate 28.

  The saturable absorbing mirror 25 has a property of absorbing weak light and reflecting strong light. Since the intensity of the light becomes maximum when the phases of the modes included in the light reaching the saturable absorber mirror 25 are synchronized, the saturable absorber mirror 25 functions as a reflecting mirror only at this moment and laser oscillation occurs. . Therefore, this laser light becomes ultrashort pulse light having a pulse width of about several femtoseconds, and is emitted to the outside from the output coupler 26d as an optical pulse train P1. At this time, the repetition frequency of the optical pulse train P1 is a value corresponding to the length of the cavity CA.

  Of the light source devices 1a and 1b having the above configuration, the operation of the light source device 1a will be described. The operation of the light source device 1b is almost the same as the operation of the light source device 1a.

The pulse light source 2 having any one of the pulse light sources 2 a to 2 c shown in FIGS. 2 to 4 emits the optical pulse train P <b> 1 to the time division multiplex processing unit 3. The optical pulse train P1 is composed of ultrashort pulse lights having a pulse width of about several femtoseconds arranged periodically (period T ₁ ). At this time, in the time division multiplexing processing unit 3, when the demultiplexer 31 is set so that the optical pulse train P 1 is demultiplexed into the optical waveguides 32 and 33, the optical pulse train P 1 is transmitted to the optical waveguides 32 and 33. It is demultiplexed. Then, the optical pulse train P1 that advances toward one optical waveguide 32, only the delay unit 34 for example (T _1/2) seconds delay. Thereafter, the optical pulse train P1 that has advanced to each of the optical waveguides 32 and 33 is multiplexed again by the multiplexer 35. In the time division multiplex processing unit 3, when the demultiplexer 31 is set so that the optical pulse train P <b> 1 is not demultiplexed into the optical waveguide 32, the optical pulse train P <b> 1 travels through the optical waveguide 33.

Here, FIG. 5 (a) and (b) an output waveform P _A and from division multiplexing processing section 3 in each case when the optical pulse train P1 in the demultiplexer 31 is the case and demultiplexed not demultiplexed it is a graph showing a P _B. When the optical pulse train P1 is not demultiplexed at the demultiplexer 31, from FIG. 5 as the output waveform P _A shown in (a), when the optical pulse train P1 emitted from the pulse light source 2 is directly division multiplexing processing section 3 It becomes the output waveform, a waveform aligned optical pulse with a period T _1. If, on the other hand, the optical pulse train P1 in the demultiplexer 31 is demultiplexed, as the output waveform P _B shown in FIG. 5 (b), half the period T ₁ of the optical pulse train P1 emitted from the pulse light source 2 optical pulse a waveform aligned with the period _{T 2 (= T 1/2} ).

Further, in this case, the intensity decrease of each pulse caused by demultiplexing by the demultiplexer 31 may be compensated by increasing the amount of current supplied to the semiconductor laser element 21 (see FIGS. 2 to 4), for example. As a result, as shown in FIGS. 5A and 5B, the peak value of each optical pulse in the output waveform P _B is equivalent to the peak value of each optical pulse in the output waveform P _A (PW). . As described above, it is preferable to change the repetition frequency of the optical pulse train P1 while maintaining the peak value of the power waveform of each optical pulse included in the optical pulse train P1 incident on the optical fiber 11.

The peak value PW of each optical pulse of the output waveforms P _A and P _B is a value such as 80 kW, for example. Further, the repetition frequency of the output waveform P _A (that is, the reciprocal of the period T ₁ of the optical pulse train P1) is a value such as 25 MHz, and the repetition frequency of the output waveform P _B is a value such as 50 MHz. The pulse width of the output waveform _{P A} and _{P B} are values of, for example 200 femtoseconds. The time average power of the output waveform P _A is a value such as 40 mW, and the time average power of the output waveform P _B is a value such as 80 mW.

  Such an output waveform from the time division multiplex processing unit 3 enters the optical fiber 11. Then, the spectral bandwidth of each optical pulse is expanded more than twice by the non-linear optical effect (adiabatic soliton compression effect) in the optical fiber 11, and the SC light P2 having a gentle spectral shape over the wide band is generated. The repetition frequency of the SC light P2 generated at this time coincides with the repetition frequency of the optical pulse train P1 incident on the optical fiber 11. The SC light P2 is emitted from the light emitting end of the light source device 1a to the outside. The length (interaction length) of the nonlinear portion of the optical fiber 11 is preferably 2 m, for example.

Here, FIG. 6 is a graph showing an example of the spectrum shape of the SC light P2 generated in the optical fiber 11. In FIG. 6, graph SP1 is the spectral shape of the SC light P2 that corresponds to the output waveform _{P A} shown in FIG. 5 (a), the graph SP2 corresponds to the output waveform _{P B} shown in FIG. 5 (b) SC It is the spectrum shape of the light P2. In FIG. 6, the value of the spectral intensity on the vertical axis is normalized.

  As shown in graphs SP1 and SP2 in FIG. 6, the SC light P2 has a gentle spectral shape over a wide band. Then, comparing the graph SP1 and the graph SP2, it can be seen that the total power (time average power) of the SC light P2 increases in proportion to the value of the repetition frequency of the optical pulse train P1 incident on the optical fiber 11. . Further, the spectrum waveforms (the undulation state along the wavelength axis) of the graphs SP1 and SP2 are substantially the same. That is, it can be seen that the ratio of the spectral intensity before and after the change is substantially equal over the entire band, and the spectral waveform is suitably maintained.

  That is, in this embodiment, the spectral shapes of the individual optical pulses included in the SC light P2 are the same regardless of the change in the repetition frequency of the SC light P2. Therefore, the time average power and the spectrum waveform of the SC light P2 are superposed of individual spectrum intensities corresponding to the repetition frequency of the SC light P2. Thereby, the power of the SC light P2 can be changed in proportion to the repetition frequency while maintaining the spectrum waveform of the SC light P2.

  Thus, according to the light source device 1a (or 1b) of the present embodiment, the time division multiplexing processing unit 3 (or 4) maintains the spectrum waveform of the SC light P2 emitted from the light source device 1a while maintaining the SC waveform. The power (time average power) of the light P2 can be made variable. Thereby, for example, when the measurement object is a low scatterer in infrared spectroscopy, the time average power of the SC light P2 irradiated to the measurement object is increased while maintaining the spectrum waveform of the SC light P2. Therefore, the measurement accuracy can be increased. In addition, since the time average power of the SC light P2 irradiated to the object to be measured can be suitably weakened while maintaining the spectrum waveform of the SC light, the object to be measured due to the interaction between the SC light P2 and the object to be measured. Deterioration and alteration of things can be avoided.

(First modification)
Fig.7 (a) is a figure which shows the structure of the light source device 1c which concerns on the 1st modification of the said embodiment. Referring to FIG. 7A, the light source device 1 c of this modification includes a pulse light source 2, a pulse extraction unit 5, and an optical fiber 11. Among these, since the configurations of the pulse light source 2 and the optical fiber 11 are the same as those in the above-described embodiment, detailed description thereof is omitted.

  The pulse extraction unit 5 is a power varying means for varying the power of the SC light P2. The pulse extraction unit 5 changes the repetition frequency of the SC light P2 by changing the repetition frequency of the optical pulse train P1, and as a result, changes the time average power of the SC light P2.

  Specifically, the pulse extraction unit 5 is optically coupled between the pulse light source 2 and the optical fiber 11 and includes an optical switch 51 and a signal generator 52. The optical switch 51 is a component for periodically taking out optical pulses from the optical pulse train P <b> 1 emitted from the pulse light source 2. The signal generator 52 is a component for driving the optical switch 51.

  The signal generator 52 sends to the optical switch 51 an electrical pulse signal having a cycle that is an integral multiple of the repetition cycle of the optical pulse train P1. As a result, among the optical pulses included in the optical pulse train P <b> 1, an optical pulse that matches the timing of the electrical pulse signal is emitted from the pulse extraction unit 5. In this manner, the pulse extraction unit 5 periodically extracts the optical pulse from the optical pulse train P1 emitted from the pulse light source 2, thereby changing the repetition frequency of the optical pulse train P1 incident on the optical fiber 11.

  At this time, the repetition frequency of the SC light P2 emitted from the optical fiber 11 coincides with the repetition frequency of the optical pulse train P1 incident on the optical fiber 11. Therefore, according to the light source device 1c, since the repetition frequency of the SC light P2 can be suitably changed, the SC light P2 emitted from the light source device 1c is similar to the light source devices 1a and 1b of the above embodiment. The time average power of the SC light P2 can be changed while suitably maintaining the spectral waveform. The signal generator 52 may be provided outside the light source device 1c. In addition, the pulse extraction period in the pulse extraction unit 5 is preferably variable, which increases the degree of freedom in changing the time average power of the SC light P2.

(Second modification)
FIG.7 (b) is a figure which shows the structure of the light source device 1d which concerns on the 2nd modification of the said embodiment. Referring to FIG. 7B, the light source device 1 d of this modification includes a pulse light source 2, a signal generator 6, an optical fiber 11, and an optical amplifier 12. Among these, the configurations of the pulse light source 2 and the optical fiber 11 are the same as those in the above embodiment.

  The signal generator 6 is a power variable means for changing the power of the SC light P2. The signal generator 6 changes the repetition frequency of the SC light P2 by changing the repetition frequency of the optical pulse train P1, and as a result, changes the time average power of the SC light P2.

  Specifically, the signal generator 6 changes the repetition frequency when the pulse light source 2 emits the optical pulse train P1. For example, when the pulse light source 2 is the pulse light source 2a shown in FIG. 2, the signal generator 6 corresponds to the signal generator 22b. When the pulse light source 2 is the pulse light source 2b shown in FIG. 3, the signal generator 6 corresponds to the signal generator 24c. In this way, the signal generator 6 directly controls the pulse light source 2 to change the repetition frequency of the optical pulse train P1, thereby changing the repetition frequency of the SC light P2 with a simple configuration, and thereby the SC light P2. The time average power can be changed.

  The optical amplifier 12 is optically coupled between the pulse light source 2 and the optical fiber 11. The optical amplifier 12 is a component for amplifying the optical pulse train P1 emitted from the pulse light source 2, and is configured by, for example, an erbium-doped optical fiber (EDF). The optical amplifier 12 is used, for example, to control the peak value of the power waveform of each pulse to be substantially constant even when the repetition frequency of the optical pulse train P1 incident on the optical fiber 11 changes.

(Third Modification)
FIG. 8A is a diagram illustrating a configuration of a light source device 1e according to a third modification of the embodiment. Referring to FIG. 8A, the light source device 1 e of this modification includes a pulse light source 2, a variable attenuation factor optical attenuator 7, and an optical fiber 11. Among these, the configurations of the pulse light source 2 and the optical fiber 11 are the same as those in the above embodiment.

  The optical attenuator 7 is power varying means for varying the power of the SC light P2. In this modification, the power variable means changes the power of the SC light P2 by changing the peak value of the power waveform of each pulse included in the optical pulse train P1. Specifically, the optical attenuator 7 is optically coupled between the pulse light source 2 and the optical fiber 11, and the peak value of the power waveform of each pulse included in the optical pulse train P <b> 1 emitted from the pulse light source 2. Decrease. Further, the attenuation factor of the optical attenuator 7 is variable, and the peak value of the power waveform of each pulse included in the optical pulse train P1 can be reduced with an arbitrary attenuation factor.

  In addition to changing the repetition frequency of the optical pulse train P1 as in the above embodiment, for example, by changing the peak value of the power waveform of each pulse included in the optical pulse train P1 as in this modification, the light source device 1e The power of the SC light can be changed to a desired intensity while suitably maintaining the spectrum waveform of the SC light emitted from the light source. Further, as in this modification, by reducing the peak value of the power waveform of each pulse included in the optical pulse train P1 by the optical attenuator 7 and making the attenuation factor variable, the noise characteristics of the optical pulse train P1, The peak value of the power waveform of each pulse of the optical pulse train P1 can be controlled without affecting the time waveform and the spectrum shape. Therefore, according to the light source device 1e, the time average power of the SC light P2 can be brought closer to the desired intensity with high accuracy.

(Fourth modification)
FIG. 8B is a diagram illustrating a configuration of a light source device 1f according to a fourth modification of the embodiment. Referring to FIG. 8B, the light source device 1f of the present modification includes a pulse light source 2, an optical axis adjustment unit 8, an optical fiber 11, a collimator lens 13a, and a condenser lens 13b. Among these, the configurations of the pulse light source 2 and the optical fiber 11 are the same as those in the above embodiment. The collimator lens 13 a and the condenser lens 13 b are disposed between the pulse light source 2 and the optical fiber 11. The optical pulse train P1 is collimated by the collimator lens 13a and then condensed by the condenser lens 13b.

  The optical axis adjustment unit 8 is a power variable unit for changing the power of the SC light P2. The optical axis adjustment unit 8 changes the optical coupling efficiency between the pulse light source 2 and the optical fiber 11 by using the optical axis shift between the pulse light source 2 and the optical fiber 11, and each pulse included in the optical pulse train P1. The power of the SC light P2 is changed by changing the peak value of the power waveform. The optical axis adjustment unit 8 of the present modification includes a first drive unit 81 that displaces the condenser lens 13 b and a second drive unit 82 that displaces the light incident end of the optical fiber 11. The first drive unit 81 changes the optical coupling efficiency between the pulse light source 2 and the optical fiber 11 by displacing the condenser lens 13b in the optical axis direction and the direction intersecting the optical axis direction. The second drive unit 82 changes the optical coupling efficiency between the pulse light source 2 and the optical fiber 11 by displacing the light incident end of the optical fiber 11 in a direction crossing the optical axis direction.

  As in this modification, the power variable means (optical axis adjustment unit 8) uses the optical axis shift between the pulse light source 2 and the optical fiber 11 to make optical coupling efficiency between the pulse light source 2 and the optical fiber 11. The peak value of the power waveform of each pulse included in the optical pulse train P1 may be changed by changing. As a result, the time average power of the SC light P2 can be changed while favorably maintaining the spectrum waveform of the SC light P2 emitted from the light source device 1f. Compared with Example), the optical loss can be suppressed low.

(Fifth modification)
Fig.9 (a) is a figure which shows the structure of the light source device 1g which concerns on the 5th modification of the said embodiment. Referring to FIG. 9A, the light source device 1 g of this modification includes a pulse light source 2, a variable attenuation factor optical attenuator 7, a pulse compression / expansion unit 9, and an optical fiber 11. Among these, the configurations of the pulse light source 2 and the optical fiber 11 are the same as those in the above embodiment. The configuration of the optical attenuator 7 is the same as that of the third modified example (FIG. 8A).

  The pulse compressor / expander 9 constitutes a power variable means together with the optical attenuator 7. Specifically, the pulse compression / expansion unit 9 is optically coupled in series with the optical attenuator 7 between the pulse light source 2 and the optical fiber 11, and the time waveform of each optical pulse included in the optical pulse train P1 is obtained. By changing, the spectrum waveform of the SC light P2 is suitably maintained. As the pulse compressor / expander 9, a dispersion device such as a variable dispersion compensator is preferably used.

  As in the present modification, the power variable means further includes the pulse compression / expansion unit 9, whereby the spectral waveform of the SC light P2 emitted from the light source device 1g can be more suitably maintained.

(Sixth Modification)
FIG. 9B is a diagram illustrating a configuration of a light source device 1h according to a sixth modification of the embodiment. Referring to FIG. 9B, the light source device 1 h of the present modification includes a continuous light source 20, an optical amplifier 10 with a variable gain, and an optical fiber 11. Among these, about the structure of the optical fiber 11, it is the same as that of the said embodiment.

  The continuous light source 20 of this modification is a seed light source that emits continuous light P3. The continuous light source 20 provides continuous light P3 to the optical fiber 11 via the optical amplifier 10. Even if the light incident on the optical fiber 11 is continuous light, the SC light P2 can be generated in the optical fiber 11 if the continuous light has a relatively high power. At this time, it is preferable that the power of the continuous light P3 incident on the optical fiber 11 is 100 mW or more. Thereby, the SC light P2 can be suitably generated in the optical fiber 11.

  The optical amplifier 10 is power varying means for varying the power of the SC light P2. The optical amplifier 10 changes the power of the SC light P2 to a desired value by changing the power of the continuous light P3. That is, when the power of the continuous light P3 incident on the optical fiber 11 is changed, the generation condition of the pulsed SC light P2 in the optical fiber 11 changes, so the repetition frequency of the pulsed SC light P2 also changes. It will be. Thus, according to this modification, the repetition frequency of the SC light P2 can be changed by the power means (optical amplifier 10), so that the spectrum of the SC light P2 emitted from the light source device 1h is the same as in the above embodiment. The time average power of the SC light P2 can be changed while maintaining the waveform suitably.

(Seventh Modification)
FIG. 10 is a diagram illustrating a configuration of a light source device 1i according to a seventh modification of the embodiment. Referring to FIG. 10, the light source device 1 i of the present modification includes a pulse light source 2 (or continuous light source 20), an optical fiber 11, a collimator lens 13 a, a condenser lens 13 b, and a variable attenuation factor optical attenuator 14. With. Among these, about the structure of the pulse light source 2 (continuous light source 20) and the optical fiber 11, it is the same as that of the said embodiment. The configurations of the collimator lens 13a and the condenser lens 13b are the same as those in the fourth modification (FIG. 8B).

  The optical attenuator 14 is power varying means for varying the power of the SC light P2. The optical attenuator 14 is optically coupled to the light emitting end of the optical fiber 11 and attenuates the time average power of the SC light P2 while substantially maintaining the spectrum waveform of the SC light P2 emitted from the optical fiber 11. Specifically, the optical attenuator 14 maintains the spectrum waveform of the SC light P2 in the entire wavelength range or a part of the wavelength range used for measurement in the spectral band of the SC light P2, while maintaining almost the spectrum waveform of the SC light P2. The peak value of the power waveform of the optical pulse consisting of is attenuated.

  In this modification, the wavelength dependence of the attenuation factor of the optical attenuator 14 in the entire spectral wavelength range of the SC light P2 or in a part of the spectral range of the SC light P2 used for measurement is ignored. It is preferable to be sufficiently small as possible. For example, the difference between the maximum attenuation rate and the minimum attenuation rate of the optical attenuator 14 in the wavelength range is preferably 20 dB or less. Moreover, it is preferable that the wavelength dependence of the attenuation rate in the change range (for example, 10 dB) of the attenuation rate necessary for measurement is small enough to be ignored in a desired wavelength band. The optical attenuator 14 having a small wavelength dependency of the attenuation rate in a part of the wavelength band of the SC light P2 includes, for example, a filter type optical attenuator that blocks light outside the band.

  Here, FIG. 11A shows an example of the spectral shape of the output light from the optical attenuator 14 when the wavelength dependence of the attenuation factor of the optical attenuator 14 is sufficiently small in the entire spectral band of the SC light P2. It is a graph which shows. FIG. 11B shows the output light from the optical attenuator 14 when the wavelength dependency of the attenuation factor of the optical attenuator 14 is sufficiently small in a part of the spectrum band of the SC light P2. It is a graph which shows an example of a spectrum shape. In FIGS. 11A and 11B, graphs SP3 and SP6 indicate the spectrum shape of the SC light P2 before entering the optical attenuator 14, and graphs SP4 and SP7 are in the optical attenuator 14. The spectrum shape of the output light when the attenuation factor is 2 dB is shown, and the graphs SP5 and SP8 show the spectrum shape of the output light when the attenuation factor in the optical attenuator 14 is 6 dB. In addition, in FIGS. 11A and 11B, the value of the spectral intensity on the vertical axis is normalized.

  As shown in FIG. 11 (a) (or FIG. 11 (b)), according to the light source device 1i of this modification, the spectrum waveform of the output light after attenuation in all or part of the spectrum band of the SC light P2 is obtained. It can be seen that the wavelength dependency is favorably maintained regardless of the attenuation rate. Thus, according to the light source device 1i of the present modification, the light intensity (that is, the time average) of the SC light P2 is preferably maintained while suitably maintaining all or part of the spectrum waveform of the SC light P2 emitted from the light source device 1i. (Power) can be changed.

(Eighth modification)
FIG. 12A is a diagram illustrating a configuration of a light source device 1j according to an eighth modification of the embodiment. Referring to FIG. 12A, a light source device 1j according to this modification includes a pulse light source 2 (or a continuous light source 20), an optical fiber 11, and an optical amplifier 15 having a variable gain. Among these, about the structure of the pulse light source 2 (continuous light source 20) and the optical fiber 11, it is the same as that of the said embodiment.

  The optical amplifier 15 is power varying means for varying the power of the SC light P2. The optical amplifier 15 is optically coupled to the light emitting end of the optical fiber 11 and amplifies the time average power of the SC light P2 while substantially maintaining the spectrum waveform of the SC light P2 emitted from the optical fiber 11. Specifically, the optical amplifier 15 maintains the spectrum waveform of the SC light P2 within the wavelength band amplified by the optical amplifier 15 in the spectral band of the SC light P2, while maintaining the optical pulse composed of the SC light P2. The peak value of the power waveform is amplified in the band. As such an optical amplifier 15, for example, an erbium-doped optical fiber (EDFA) capable of amplification in a wide wavelength range (1535 to 1605 nm) extending from the C band to the L band is preferably used.

  Here, FIG. 12B is a graph showing an example of the spectrum shape of the output light from the optical amplifier 15. In FIG. 12B, the graph SP9 shows the spectrum shape of the SC light P2 before entering the optical amplifier 15, and the graph SP10 shows the output light when the amplification factor in the optical amplifier 15 is 2.5 dB. A spectrum shape is shown, and a graph SP11 shows the spectrum shape of the output light when the amplification factor in the optical amplifier 15 is 6 dB. In FIG. 12B, the value of the spectral intensity on the vertical axis is normalized.

  As shown in FIG. 12B, according to the light source device 1j of the present modification, the wavelength dependence of the spectrum waveform of the output light after amplification in the band (band A in the figure) amplified by the optical amplifier 15 is increased. It can be seen that it is favorably maintained regardless of the amplification factor. Thus, according to the light source device 1j of the present modification, the light intensity (that is, the time average) of the SC light P2 is preferably maintained while favorably maintaining all or part of the spectrum waveform of the SC light P2 emitted from the light source device 1j. (Power) can be changed.

(Ninth Modification)
FIG. 13A is a block diagram illustrating a configuration of a light source device 1k according to a ninth modification of the embodiment. Referring to FIG. 13A, the light source device 1k of the present modification includes a pulse light source 2, an optical fiber 11, a pulse variable unit 16, and a control unit 17a. Among these, the configurations of the pulse light source 2 and the optical fiber 11 are the same as those in the above embodiment.

  The pulse variable unit 16 is a power variable means for changing the power of the SC light P 2, and is optically coupled between the pulse light source 2 and the optical fiber 11. The pulse variable unit 16 includes, for example, the time division multiplexing processing units 3 and 4 of the above-described embodiment illustrated in FIGS. 1A and 1B, and the pulse extraction unit 5 of the first modification illustrated in FIG. The optical attenuator 7 of the third modification shown in FIG. 8A, the optical axis adjustment unit 8 of the fourth modification shown in FIG. 8B, or the fifth modification shown in FIG. 9A. The example pulse compression / expansion unit 9 can be applied.

  In addition to the above-described configuration, for example, a band variable filter or the like is applied to the pulse variable unit 16 to change the spectral shape (particularly the center wavelength) of the optical pulse train P1 incident on the optical fiber 11, thereby changing the spectral waveform of the SC light P2. May be maintained. The spectral shape of the SC light P2 is affected by the dispersion characteristics of the optical fiber 11 and the spectral shape of the optical pulse train P1, particularly the center wavelength. Therefore, by adding a band-variable filter between the pulse light source 2 and the optical fiber 11, the time average power of the SC light P2 is maintained while maintaining the spectral waveform of the SC light P2 emitted from the light source device 1k more suitably. Can be changed.

  In addition to the above configuration, the pulse varying unit 16 may change the power of the SC light P2 by changing the polarization direction of the optical pulse train P1 incident on the optical fiber 11. The spectrum shape of the SC light P2 is affected by the polarization of the optical pulse train P1 and the polarization dependence of the optical fiber 11. Therefore, according to this configuration, it is possible to change the time average power of the SC light P2 while further suitably maintaining the spectrum waveform of the SC light P2 emitted from the light source device 1k.

The control unit 17a of the present modification also functions as a power variable unit for changing the power of the SC light P2. That is, the control unit 17 a supplies an electrical control signal S ₁ for controlling the output power of the excitation laser light source (for example, the semiconductor laser element 21 shown in FIGS. 2 to 4) of the pulse light source 2 to the pulse light source 2. The peak value of the power waveform of each pulse included in the optical pulse train P1 is changed by changing the output power of the pumping laser light source. For example, in the third modified example (see FIG. 8A), the peak value of the power waveform of each pulse of the optical pulse train P1 is changed using the optical attenuator 7, but the output of the excitation laser light source is changed. The peak value of the power waveform of each pulse of the optical pulse train P1 can be easily changed by changing the power. In addition, the output power of the excitation laser light source can be easily controlled by the amount of current supplied to the excitation laser light source. Therefore, with this configuration, the peak value of the power waveform of each pulse of the optical pulse train P1 can be easily changed using one parameter such as the amount of current of the excitation laser light source, so that the light is emitted from the light source device 1k. It is possible to easily change the time average power of the SC light P2 while suitably maintaining the spectrum waveform of the SC light P2.

The controller 17a can also change the power of the SC light P2 by changing the repetition frequency of the optical pulse train P1. That is, the control unit 17 a sends a control signal S ₁ for changing the cavity length of the pulse light source 2 to the pulse light source 2. Thereby, since the repetition frequency of the optical pulse train P1 emitted from the pulse light source 2 changes, the repetition frequency of the SC light P2 changes, and as a result, the time average power of the SC light P2 changes. Control signals S ₁ is fed for example FIG. 4 shows a pulse light source 2c of the saturable absorber mirror 25 and a signal generator for controlling the position of the mirror 27c (not shown) to the like. By the saturable absorber mirror 25 and the mirror 27c is repositioned in accordance with the control signal S _1, it is possible to change the length of the cavity CA. Thereby, the repetition frequency of SC light P2 can be changed suitably, and the time average power of SC light P2 can be changed easily, maintaining the spectrum waveform of SC light P2 emitted from the light source device 1k.

Moreover, the control part 17a maintains the spectrum waveform of SC light P2 radiate | emitted from the light source device 1k more suitably by controlling the temperature of the optical fiber 11. FIG. That is, the control unit 17a sends an electric control signal S ₂ for controlling the temperature of the optical fiber 11, the temperature control device 11a, such as a Peltier element provided in contact with the optical fiber 11. As a result, the dispersion characteristics of the optical fiber 11 can be suitably changed, so that the spectral waveform of the SC light P2 emitted from the light source device 1k is more suitably maintained, and the power of the SC light P2 is accurately adjusted to a desired value. You can get closer. In addition, it is preferable that the temperature of the temperature control element 11a is easily conducted by winding the optical fiber 11 in a coil shape.

Further, the control unit 17a electrically controls the pulse variable unit 16 in order to obtain a desired power while maintaining the spectrum waveform of the SC light P2. For example, when the pulse variable unit 16 includes time division multiplex processing units 3 and 4 (FIGS. 1A and 1B), a control signal S for controlling the optical switches provided in the duplexers 31 and 41 is used. ₃ is sent to the pulse variable section 16. When the pulse varying unit 16 includes the pulse extracting unit 5 (FIG. 7A), a control signal S ₃ for controlling the signal generator 52 is sent to the pulse varying unit 16. When the pulse variable unit 16 includes the optical attenuator 7 (FIG. 8A) and the pulse compressor / expander 9 (FIG. 9A), the control unit 17a performs control for controlling them. The signal S ₃ is sent to the pulse variable unit 16. When the pulse variable unit 16 includes the optical axis adjustment unit 8 (FIG. 8B), the control unit 17a outputs a drive signal for driving the first and second drive units 81 and 82 as a control signal. sent as S ₃ to the pulse changing unit 16.

  As described above, by including the control unit 17a that electrically controls the pulse varying unit 16, the spectrum waveform and the time average power of the SC light P2 emitted from the light source device 1k can be automatically controlled or remotely controlled. In addition, it is possible to easily adjust the time average power of the SC light P2 to a desired value without replacing parts. Further, even when adjusting to different power for each part to be measured, the adjustment can be performed in a short time.

(10th modification)
FIG. 13B is a block diagram illustrating a configuration of a light source device 1m according to a tenth modification of the embodiment. Referring to FIG. 13B, the light source device 1m of the present modification includes a pulse light source 2 (or continuous light source 20), an optical fiber 11, a control unit 17b, an optical amplifier 18, and a power variable unit 19. Prepare. Among these, about the structure of the pulse light source 2 (continuous light source 20) and the optical fiber 11, it is the same as that of the said embodiment.

The optical amplifier 18 is power varying means for varying the power of the SC light P2, and the time average power of the SC light P2 is changed by changing the peak value of the power waveform of each pulse included in the optical pulse train P1. Change. The optical amplifier 18 has a gain variable, light from the control signal S ₄ for controlling the amplification factor received from the control unit 17a, the pulse light source 2 with an amplification factor in accordance with the control signal S ₄ The pulse train P1 (or continuous light P3 from the continuous light source 20) is amplified.

  As in the present modification, the power variable means may be a variable gain optical amplifier 18 optically coupled between the pulse light source 2 (continuous light source 20) and the optical fiber 11. Thereby, the power of the SC light P2 can be easily controlled to a desired intensity. In this case, since the output power of the pulse light source 2 (continuous light source 20) may be constant, the optical pulse train P1 can be obtained stably. In this case, the spectral shape of the light incident on the optical amplifier 18 and the spectral shape of the light emitted from the optical amplifier 18 may be different from each other. In addition to the peak value of the power waveform of each pulse of the optical pulse train P1 incident on the optical fiber, the SC light emitted from the light source device 1m is also considered by taking into account the change in the spectral shape of the optical pulse train P1 in the optical amplifier 18. While suitably maintaining the spectral waveform of P2, the power of the SC light P2 can be made closer to the desired intensity with high accuracy.

The power variable unit 19 is another power variable means for changing the power of the SC light P2. For example, the optical attenuator 14 of the seventh modified example shown in FIG. 10 or the optical amplifier 15 of the eighth modified example shown in FIG. Further, the power variable section 19 may be a curved section having a variable curvature formed in an optical waveguide for emitting the SC light P2 to the outside of the apparatus. Since the optical waveguide for emitting the SC light P2 has such a curved portion, an arbitrary bending loss is given to the SC light P2, and the power of the SC light P2 is increased while favorably maintaining the spectrum waveform of the SC light P2. Can be changed. Power variable unit 19 receives the control signal S ₅ to control the spectral waveform and temporal average power of the SC light P2 from the control unit 17b, so that the spectral waveform and temporal average power corresponding to the control signal S ₅ The amplification factor or attenuation factor is changed, or the curvature of the optical waveguide is changed.

Control unit 17b, in addition to the control signal S ₄ and S ₅ described above, similarly to the control section 17a of the ninth modification, for controlling the output power of the excitation laser light source of the pulse light source 2 (continuous light source 20) sends the control signals S ₁ to the pulse light source 2 (continuous light source 20), by changing the output power of the excitation laser light source, changing the peak value of the power waveform of the optical pulse train P1 (maximum power of the continuous light P3) . The control unit 17b, a control signal S ₂ for controlling the temperature of the optical fiber 11, by sending to the temperature control device 11a provided in contact with the optical fiber 11, to change the dispersion characteristic of the optical fiber 11 .

(Eleventh modification)
FIG. 14 is a block diagram showing a configuration of a light source device 1n according to the eleventh modification of the embodiment. Referring to FIG. 14, the light source device 1 n of the present modification includes a pulse light source 2, an optical fiber 11, a pulse variable unit 16, a control unit 17 c, and a detector 30. Among these, the configurations of the pulse light source 2, the optical fiber 11, and the pulse variable unit 16 are the same as those in the above embodiment.

  The detector 30 is a detecting means for detecting at least one of the time average power and the spectral shape of the SC light P2. The detector 30 is optically coupled to the output end of the optical fiber 11 via the branching filter 11b, and takes in part of the SC light P2. The detector 30 includes a wavelength tunable filter 30a, a light detection element 30b, and a signal processing unit 30c. A part of the SC light P2 taken into the detector 30 passes through the wavelength tunable filter 30a, and then is photoelectrically converted by the light detection element 30b to become a periodic electrical signal. Based on this electric signal, at least one of the time average power and the spectrum shape is detected by the signal processing unit 30c. The detection result is sent to the control unit 17c.

Based on the detection result from the detector 30, the control unit 17 c controls the control signal S ₁ for changing the output power of the excitation laser light source of the pulse light source 2 and the control signal S for controlling the temperature of the optical fiber 11. ₂ , and a control signal S ₃ for controlling the pulse variable unit 16 are generated and sent to the pulse light source 2, the temperature adjustment element 11 a, and the pulse variable unit 16, respectively. In this way, by detecting at least one of the time average power and the spectrum shape of the SC light P2 by the detector 30, the power variable means (pulse variable unit 16, control unit 17c) is feedback controlled using the detection result. Therefore, it is possible to maintain the spectrum waveform of the SC light P2 and control the power of the SC light P2 with high accuracy and stability.

  The light source device according to the present invention described above is not limited to the above-described embodiments and modifications, and various modifications and additions of components are possible. For example, in the above-described embodiments and modifications, various aspects of the power variable unit according to the present invention have been described. However, the light source device according to the present invention combines a plurality of arbitrary units among the above-described power variable units. May be configured.

FIGS. 1A and 1B are diagrams each showing a configuration of a light source device according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration of a pulse light source as an example of the pulse light source. FIG. 3 is a diagram illustrating a configuration of a pulse light source as another example of the pulse light source. FIG. 4 is a diagram illustrating a configuration of a pulse light source as another example of the pulse light source. FIGS. 5A and 5B are graphs showing output waveforms from the time division multiplex processing unit when the optical pulse train is not demultiplexed and when demultiplexed in the demultiplexer. FIG. 6 is a graph showing an example of the spectrum shape of the SC light generated in the optical fiber. Fig.7 (a) is a figure which shows the structure of the light source device which concerns on a 1st modification. FIG. 7B is a diagram illustrating a configuration of the light source device according to the second modification. FIG. 8A is a diagram illustrating a configuration of a light source device according to a third modification. FIG. 8B is a diagram illustrating a configuration of a light source device according to a fourth modification. Fig.9 (a) is a figure which shows the structure of the light source device which concerns on a 5th modification. FIG. 9B is a diagram illustrating a configuration of a light source device according to a sixth modification. FIG. 10 is a diagram illustrating a configuration of a light source device according to a seventh modification. FIG. 11A is a graph showing an example of the spectral shape of the output light from the optical attenuator when the wavelength dependence of the attenuation factor of the optical attenuator is sufficiently small in the entire spectral band of SC light. FIG. 11B shows the spectral shape of the output light from the optical attenuator when the wavelength dependence of the attenuation factor of the optical attenuator is sufficiently small in some of the spectral bands of the SC light. It is a graph which shows an example. FIG. 12A is a diagram illustrating a configuration of a light source device according to an eighth modification. FIG. 12B is a graph showing an example of the spectral shape of the output light from the optical amplifier. FIG. 13A is a block diagram illustrating a configuration of a light source device according to a ninth modification. FIG. 13B is a block diagram illustrating a configuration of the light source device according to the tenth modification. FIG. 14 is a block diagram illustrating a configuration of a light source device according to an eleventh modification.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1a-1n ... Light source device, 2, 2a-2c ... Pulse light source, 3, 4 ... Time division multiplex process part, 5 ... Pulse extraction part, 6 ... Signal generator, 7 ... Optical attenuator, 8 ... Optical axis adjustment part , 9 ... Pulse compression / expansion device, 10 ... Optical amplifier, 11 ... Optical fiber, 11a ... Temperature control element, 12, 15, 18 ... Optical amplifier, 14 ... Optical attenuator, 16 ... Pulse variable section, 17a-17c ... Control unit, 19 ... power variable unit, 20 ... continuous light source, 21 ... semiconductor laser element, 22a ... LN modulator, 22b, 24c, 52 ... signal generator, 23 ... cavity, 24a ... reflection mirror, 24b ... piezo motor, 25 ... saturable absorption mirror, 28 ... Er: Yb co-doped glass plate, 30 ... detector, 31, 41 ... demultiplexer, 32, 33, 42-44 ... optical waveguide, 34 ... delay device, 35, 45 ... combined Waver, 42a, 43a ... delay path, 51 ... Switch, 52 ... signal generator, 81 ... first driving unit, 82 ... second driving unit, P1 ... optical pulse train, P2 ... SC light, P3 ... continuous light.

Claims (21)

A seed light source that emits an optical pulse train;
An optical fiber optically coupled to the seed light source and receiving the optical pulse train and emitting supercontinuum light (SC light);
Power varying means for changing the power of the SC light in a state where the spectral waveform of the SC light emitted from the light source device is maintained in a part or all of the wavelength range included in the spectral band of the SC light. A light source device comprising:   The power variable means changes the power of the SC light while maintaining the spectrum waveform of the SC light by changing the peak value of the power waveform of each pulse included in the optical pulse train. The light source device according to claim 1.   The power variable means changes a peak value of a power waveform of each pulse included in the optical pulse train by changing an output power of an excitation laser light source included in the seed light source. Item 3. The light source device according to Item 2.   3. The light source device according to claim 2, wherein the power varying means is a variable gain optical amplifier optically coupled between the seed light source and the optical fiber.   3. The light source device according to claim 2, wherein the power varying means is a variable attenuation factor optical attenuator optically coupled between the seed light source and the optical fiber.   The power varying means changes the optical coupling efficiency between the seed light source and the optical fiber by utilizing the deviation of the optical axis between the seed light source and the optical fiber. The light source device according to claim 2, wherein the peak value of the power waveform of the pulse is changed.   The power variable means changes the power of the SC light while maintaining the spectrum waveform of the SC light by changing the time waveform of each pulse included in the optical pulse train incident on the optical fiber. The light source device according to claim 1, wherein:   The power variable means changes the power of the SC light while maintaining the spectrum waveform of the SC light by changing the center wavelength of the optical pulse train incident on the optical fiber. The light source device according to any one of claims 1 to 7.   The power variable means changes the power of the SC light in a state in which the spectrum waveform of the SC light is maintained by changing a spectral shape of the optical pulse train incident on the optical fiber. The light source device according to claim 1.   The power variable means changes the power of the SC light while maintaining the spectrum waveform of the SC light by changing the polarization direction of the optical pulse train incident on the optical fiber. The light source device according to any one of claims 1 to 9. A seed light source that emits continuous light;
An optical fiber optically coupled to the seed light source and receiving the continuous light and emitting supercontinuum light (SC light);
Power varying means for changing the power of the SC light in a state where the spectral waveform of the SC light emitted from the light source device is maintained in a part or all of the wavelength range included in the spectral band of the SC light. A light source device comprising:   The light source device according to claim 1, wherein a wavelength of 1550 nm is included in a wavelength range of the optical pulse train or the continuous light incident on the optical fiber.   The light source device according to claim 1, further comprising temperature control means for controlling a temperature of the optical fiber.   The light source device according to claim 13, wherein the temperature control unit includes a temperature control element provided in contact with the optical fiber.   The light source device according to claim 1, wherein the power varying means is a curved portion having a variable curvature formed in an optical waveguide for emitting the SC light to the outside of the device.   The light source device according to claim 1, wherein the power varying unit is a variable attenuation factor optical attenuator optically coupled to an output end of the optical fiber.   The light source device according to claim 1, wherein the power varying unit is a variable gain optical amplifier optically coupled to an output end of the optical fiber.   12. The power varying unit according to claim 1, wherein the power of the SC light is changed in a state where a spectrum waveform of the SC light is maintained by changing a repetition frequency of the SC light. Light source device.   The power variable means changes the repetition frequency of the optical pulse train incident on the optical fiber to change the repetition frequency of the SC light, whereby the SC light is maintained in a state in which the spectrum waveform of the SC light is maintained. The light source device according to claim 1, wherein the power of the light source is changed.   The light source device according to claim 19, wherein a repetition frequency of the optical pulse train is changed while maintaining a peak value of a power waveform of each optical pulse included in the optical pulse train incident on the optical fiber. .   21. The light source according to any one of claims 1 to 20, further comprising detection means that is optically coupled to an output end of the optical fiber and detects at least one of power and spectral shape of the SC light. apparatus.

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