JP2015119012A - Solid state laser device and nonlinear measuring device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that the excitation efficiency cannot be enhanced sufficiently, because the beam waists of excitation light beams cross at an angle θ(0<θ) in the condensing position, in a solid-state laser device configured to excite a gain medium with a plurality of excitation light sources.SOLUTION: In a nonlinear measuring device where a solid-state laser device includes: a light source for emitting the output light including first light and second light having a wavelength different from that of the first light and modulated for the first light; a condensing optical system for condensing the output light and irradiating a subject therewith; and a detector for detecting the first light passed through the subject, the light source includes a solid state laser device described in any one of claims 1-8.

Description

  The present invention relates to a solid-state laser apparatus including a crystal gain medium and a plurality of excitation light sources, and a nonlinear measurement apparatus using the solid-state laser apparatus.

  In recent years, attention has been focused on nonlinear measuring apparatuses that identify or observe substances using nonlinear effects such as stimulated Raman scattering, fluorescence due to two-photon absorption, anti-Stokes Raman scattering, and the like that occur in an object by irradiation light. Since the nonlinear effect becomes stronger as the peak power of the irradiation light is higher, a higher output is required for the light source of the nonlinear measuring apparatus.

  A solid-state laser device is known as one of high-output light sources. The solid-state laser device outputs a laser beam generated by irradiating a gain medium disposed in a resonator with an excitation light beam, stimulated emission and oscillation.

  Non-Patent Document 1 discloses a solid-state laser device (mode-locked laser) using a plurality of excitation light sources. FIG. 9A is a schematic diagram illustrating the configuration of the solid-state laser device described in Non-Patent Document 1. FIG. In the solid-state laser device of FIG. 9A, a titanium sapphire crystal 904 is disposed in a resonator composed of a plurality of high reflection mirrors 901, and two excitation light sources for exciting the titanium sapphire crystal 904 are provided. (Blue laser diode) 905 and 906 are provided. Excitation light beams 911 and 912 emitted from each excitation light source are collimated by a collimator lens 907 and guided to a condenser lens 909 by a mirror 910. FIG. 9B shows the distribution of the excitation light beams 911 and 912 on the plane perpendicular to the optical axis of the condenser lens when entering the condenser lens.

  The excitation light beams 911 and 912 that have passed through the condenser lens 909 form beam waists at the condensing position of the condenser lens 909, respectively. FIG. 9C shows beam waists 1002 and 1003 of the excitation light beams 911 and 912, respectively. At the condensing position, the excitation intensity is high in the hatched portion 1005 in the figure where the beam waist 1002 of the excitation light beam 911 and the beam waist 1003 of the excitation light beam 912 intersect and overlap each other. When the gain medium 904 is arranged so that the hatched portion 1005 is irradiated, excitation is performed with high excitation intensity and high output can be obtained. The light generated in the gain medium 904 oscillates in a resonator composed of a plurality of high reflection mirrors 901, and part of the light is emitted from the partial reflection mirror 902 as an output.

Charles G. Durfee “Direct diode-pumped Kerr-lens mode-locked Ti: sapphjre laser” OPTICS EXPRESS 18 June 2012 / Vol. 20, no. 13 13677-13683

  However, as described in Non-Patent Document 1, when the excitation light beam 911 and the excitation light beam 912 intersect at an angle θ (0 ° <θ) at the condensing position, the beam waist of each excitation light beam Since the overlap is narrow, the excitation efficiency cannot be sufficiently increased.

  This problem will be described with reference to FIG. Since the excitation beam 911 and the excitation beam 912 are output from separate excitation light sources, there is no interference between them, and beam waists 1002 and 1003 are formed independently of each other. Dotted lines 1006 and 1007 in FIG. 10 represent central axes (hereinafter simply referred to as central axes) of beam waists in the traveling direction of the excitation light beams 911 and 912, respectively. The dotted line 1006 and the dotted line 1007 intersect at an angle θ (0 ° <θ). Therefore, the overlap of the beam waists of the excitation light beams is limited to the hatched portion 1005 in the drawing.

Since the absorption coefficient of the excitation beam in the titanium sapphire crystal is about several cm ⁻¹ , the distance that the excitation beam can propagate in the crystal is about several mm. For example, when the diameter of the beam waist of the excitation beam is 30 μm and the angle θ at which the excitation light beams intersect is 30 °, the overlap length ΔS can be estimated to be about 115 μm. Since ΔS is as short as several tenths of the distance that the excitation beam can propagate in the crystal, much of the energy of the excitation beam is absorbed outside the hatched portion 1005 in FIG. 9B.

  A dotted line 1004 in FIG. 9B indicates the oscillated laser beam. The excitation light beam absorbed outside the beam represented by the dotted line 1004 does not contribute to the oscillation of the laser beam. For this reason, the solid-state laser device of FIG. 9 cannot sufficiently increase the pumping efficiency even though it uses two laser diodes.

In view of the above problems, a solid-state laser device according to the present invention includes a plurality of excitation light sources that emit an excitation light beam, a plurality of mirrors that form a resonator, a gain medium disposed in the resonator, and the plurality of the plurality of excitation light sources. A condensing lens that condenses a plurality of excitation light beams emitted from an excitation light source and irradiates the gain medium,
Each of the excitation light beams emitted from the plurality of light sources is incident on the condenser lens to be rotated with respect to the optical axis of the condenser lens.

  In addition, the nonlinear measurement apparatus according to the present invention includes an output including first light and second light having a wavelength different from that of the first light and modulated with respect to the first light. A non-linear measurement apparatus comprising: a light source unit that emits light; a condensing optical system that collects the output light and irradiates the subject; and a detection unit that detects the first light that has passed through the subject. The solid-state laser device is provided.

  According to the present invention, in a solid-state laser device including a plurality of pumping light sources, the central axes of the beam waists of the plurality of pumping light beams coincide with each other, so that the pumping intensity can be increased over a wide range in the gain medium. it can. As a result, it is possible to increase the excitation efficiency of the gain medium.

1 is a schematic diagram illustrating a solid-state laser device according to the present invention. Schematic explaining the solid-state laser apparatus which concerns on 1st Embodiment. The figure for demonstrating the condensing characteristic of a multi mode edge-emitting laser diode. The figure showing the relationship between the distribution in the surface perpendicular | vertical to the optical axis of the condensing lens of the excitation light beam at the time of injecting into a condensing lens, and the intensity distribution of the slow axis direction in a condensing position. Schematic explaining the solid-state laser apparatus which concerns on 2nd Embodiment. The figure showing the relationship between the separation distance of the excitation light beam which injects into a condensing lens, and the intensity distribution of the slow axis direction in a condensing position. The distribution diagram in the surface perpendicular | vertical to the optical axis of the condensing lens of the excitation light beam at the time of injecting into the condensing lens illustrated in 3rd Embodiment. Schematic explaining the solid-state laser apparatus which concerns on 4th Embodiment. Schematic explaining the conventional solid-state laser apparatus. Schematic explaining the structural example of a beam splitting member. 1 is a schematic diagram of a non-linear measurement device using a solid-state laser device according to the present invention.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In the drawings, the same or corresponding members are denoted by the same reference numerals. Moreover, the point which is not demonstrated in particular is a case where description overlaps or a well-known technique is employable.

  FIG. 1 is a diagram for explaining a solid-state laser device according to the present invention. FIG. 1A shows an outline of the configuration of the solid-state laser device. The solid-state laser device according to the present embodiment includes a plurality of excitation light sources 105 and 106, and a resonator including a high reflection mirror 101, a partial reflection mirror 102, and a pump mirror 103. A gain medium 104 is disposed in the resonator. At this time, depending on the crystal material used for the gain medium, the beam diameter of the laser beam oscillated by the resonator is reduced to about several tens of μm, so that the light intensity irradiated to the gain medium 104 is increased and the Kerr lens effect is produced. Mode-lock oscillation can be performed.

  The solid-state laser device includes a collimating lens 107 for each excitation light source, which collimates light emitted from the excitation light source to generate an excitation light beam. Furthermore, a beam splitting member 108 that splits the excitation light beam 111 emitted from one excitation light source and a high reflection mirror 110 that folds the excitation light beam 112 emitted from the other excitation light source are provided.

The beam splitting member 108 is composed of, for example, two prisms, and splits the excitation light beam 111 emitted from the light source 105 into two beams 111A and 111B. The beam splitting member 108 is arranged so that the split excitation light beams 111 </ b> A and 111 </ b> B are incident on the condensing lens 109 in two-fold symmetry with respect to the optical axis of the condensing lens 109.
Here, a case where the excitation light beam is divided into two is shown, but the present invention is not limited to this. The beam splitting member may be arranged so as to be incident on the condensing lens so that the pumping light beam is divided into N beams and the divided pumping light beam is N times symmetrical with respect to the optical axis of the condensing lens. Good. However, in order to divide the excitation light beam into three or more, the structure of the beam splitting member becomes complicated, so that the splitting into two beams is the most preferable mode.

  The excitation light beam 112 emitted from the excitation light source 106 is reflected by the mirror 110 and then enters the condenser lens 109 so that the center of the beam coincides with the optical axis of the condenser lens 109. FIG. 1B shows the distribution of the excitation light beams 111A, 111B, and 112 in a plane perpendicular to the condenser lens when entering the condenser lens 109. FIG.

  Here, the expressions “rotationally symmetric with respect to the optical axis” or “coincident with the optical axis” allow a slight deviation. The allowable range of deviation may be a range in which the effect of the present invention can be obtained, and can be determined according to the configuration of the solid-state laser device and required characteristics. The same applies to the following.

  FIG. 1C shows the beam waist of the excitation light beam at the condensing position at this time.

  Since the excitation light beams 111A and 111B are light emitted from the same excitation light source, they interfere with each other to form one beam waste. Further, since the excitation light beams 111A and 111B are two-fold symmetrical with respect to the optical axis 121 of the condenser lens, the central axis of the obtained beam waist (that is, the beam waist of the excitation light beam 111) is the condenser lens. Coincides with the optical axis 121. A dotted line 124 in FIG. 1C represents an oscillating laser beam. The central axis of the laser beam 124 coincides with the central axes of the excitation light beam 111 and the excitation light beam 112.

  Accordingly, the beam waists of the excitation light beams emitted from the two excitation light sources 105 and 106 in FIG. 1 overlap with each other in a state where the central axes coincide with each other, and also overlap with the central axis of the oscillating laser beam. Therefore, in the high excitation intensity region where the beam waists of the excitation light beams 111 and 112 overlap, most of the excitation light beam absorbed by the gain medium 104 can contribute to the oscillation of the laser beam, and the excitation efficiency can be improved more than before. It becomes possible to raise.

  The excitation light source of the present invention can be appropriately selected from known light sources such as a laser diode, a semiconductor excitation solid (DPSS) laser, and a fiber laser, but has a wavelength spectrum that can oscillate the gain medium efficiently. It is preferable to use a light source with high intensity. In addition, since a non-linear measuring apparatus requires a small light source, it is particularly preferable to use a laser diode in terms of downsizing the excitation light source.

  As the gain medium, Nd: YAG crystal, alexandrite crystal, glass and the like can be used in addition to the titanium sapphire crystal. Among these, a titanium sapphire mode-locked laser using a titanium sapphire crystal as a gain medium can realize pulsed laser light having a pulse width of nanoseconds or less and a high peak power reaching megawatts.

  Since the nonlinear measuring device requires pulse laser light having a pulse width of about several nanoseconds, a solid-state laser device using a titanium sapphire crystal as a gain medium is particularly preferable as a light source of the nonlinear measuring device.

  In FIG. 1, a member combining two prisms is used as the beam splitting member 108, but other members such as the member of FIG. 10 combining the half mirror 130, the high reflection mirrors 131 and 132, and the prism 133 are used. It can also be used.

  In FIG. 1, the light beam from one of the plurality of excitation light sources is divided and incident on the condenser lens. However, the present invention is not limited to this. As shown in FIG. 5, a configuration in which the beam lights emitted from both of the plurality of excitation light sources are respectively divided and incident on the condenser lens is also preferable.

  Further, three or more excitation light sources may be provided as shown in FIG. In this case, the advantage of downsizing the apparatus is reduced, but the gain medium can be excited with a stronger excitation intensity.

  The excitation light beams from a plurality of light sources do not necessarily have to be irradiated from one direction to the gain medium as shown in FIG. 1, and a configuration of irradiation from a plurality of directions as shown in FIG. 8 can be adopted.

  A λ / 2 wavelength plate for controlling the polarization direction is inserted between the excitation light source and the condenser lens so that the absorptivity of the gain medium depends on the polarization dependency or the polarization dependency of the optical surface of the gain medium. Also good.

  As described above, when the solid-state laser device described above is used in a non-linear measurement device, since the excitation efficiency is high, an output having a peak power equal to or higher than that of a conventional power can be obtained. As a result, power saving or high-precision observation becomes possible.

(First embodiment)
FIG. 2 is a configuration diagram of the solid-state laser device according to the first embodiment, and laser diodes are used for the excitation light sources 105 and 106. Hereinafter, a case where the laser diode is a multimode edge-emitting laser diode capable of obtaining a high output will be described as an example.

  FIG. 3A shows a part of the configuration of FIG. 2A extracted in order to explain the condensing characteristics of the multimode edge-emitting laser diode. FIG. 3B is an enlarged view of the diode substrate 403.

  The laser beam of the multimode edge-emitting laser diode has a slow axis with a small divergence angle and a fast axis with a large divergence angle. The edge-emitting laser diode used here oscillates in multimode in the slow axis direction parallel to the slow axis and in single mode in the fast axis direction parallel to the fast axis.

  In general, an axis parallel to the active layer 410 of the diode substrate 403 is a slow axis, and an axis orthogonal to the active layer 410 is a fast axis. Therefore, the distribution 405 of the beam collimated by the collimator lens 404 in the plane perpendicular to the optical axis of the collimator lens is a long ellipse in the fast axis direction 402 as shown in FIG. Become.

  The collimated beam is adjusted to a circular distribution 407 by passing through a beam adjusting member 406 having different magnifications in the slow axis direction 401 and the fast axis direction 402. The beam adjusting member 406 is a member that adjusts the distribution in a cross section perpendicular to the traveling direction of the beam, and a known optical member such as a telescope or an anamorphic prism pair can be used.

  The beam having a circular distribution 407 in the cross section perpendicular to the traveling direction is incident on the condenser lens 408. The beam waist diameter ds in the slow axis direction 401 and the beam waist diameter in the fast axis direction of the distribution (cross section distribution of the beam waist) 409 in the cross section perpendicular to the traveling direction at the condensing position of the beam condensed by the condenser lens 408. Each df is expressed as in equation (1).

  Here, dgs and dgf are the diameter in the slow axis direction and the diameter in the fast axis direction of the beam waist at the condensing point of the Gaussian beam, respectively. dgs and dgf are expressed by Equation (2) using the wavelength λ, the diameter Ds of the beam incident on the condenser lens 408 in the slow axis direction 401, the diameter Df in the fast axis direction 402, and the focal length f of the condenser lens, respectively. expressed.

Ms ² and Mf ² are parameters representing the condensing characteristic of the laser diode called Msquare. The value of Msquare is 1 when the ideal Gaussian beam is 1, and the value increases as the intensity distribution of the beam cross-section distribution deviates from the Gaussian distribution.

Since it oscillates as a single mode in the fast axis direction, it is generally Mf ² to 1. Therefore, the beam waist diameter df substantially coincides with dgf. On the other hand, Ms ² generally has a value of 3 or more in the slow axis direction that oscillates as a multimode. If a high-power edge-emitting laser diode that performs high-order multimode oscillation in the slow axis direction is used as the excitation light source, the value of Ms ² may be a large value of 10 or more.

  When ds and df when the beam whose cross-sectional distribution is adjusted to be circular by the beam adjusting member 406 are condensed by the condensing lens are calculated using the equations (1) and (2), as shown in FIG. In addition, the cross section of the beam at the condensing position becomes an ellipse that is long in the slow axis direction.

  The cross section of the laser beam oscillated in the solid-state laser device is determined by the configuration of the resonator, the shape of the gain medium, etc., regardless of the cross sectional shape of the excitation light beam. In general, the cross-sectional distribution of an oscillating laser beam is designed to be substantially circular. Therefore, if the cross-sectional distribution at the beam waist of the excitation light beam is elliptical, a region that does not overlap with the circular cross-sectional distribution of the oscillating laser beam is generated, and the excitation efficiency is lowered.

  FIG. 4 is a diagram illustrating the cross-sectional distribution of the beam incident on the condensing lens and the intensity distribution in the slow axis direction at the condensing position. In the diagram showing the intensity distribution in the slow axis direction at the condensing position, the beam diameter in the slow axis direction is indicated by an arrow. FIG. 4A shows a case where a beam having the same beam diameter Ds in the slow axis direction and the beam diameter Df in the fast axis direction is incident. FIG. 4B shows a case where a beam having a beam diameter Ds in the slow axis direction longer than a beam diameter Df in the fast axis direction is incident by dividing the excitation light beam emitted from one light source in the slow axis direction. It is. FIG. 4C shows a case where an elliptical beam having a beam diameter Ds in the slow axis direction longer than a beam diameter Df in the fast axis direction is incident. Comparing the respective cases, the beam diameter in the slow axis direction at the condensing position in FIGS. 4B and 4C is smaller than the beam diameter in the slow axis direction at the beam waist in FIG. I understand that.

  That is, as shown in FIGS. 4B and 4C, when the beam diameter Ds in the slow axis direction of the beam incident on the condenser lens is longer than the beam diameter Df in the fast axis direction, the condensing characteristic in the slow axis direction. Is improved. As a result, the difference in beam diameter between the slow axis direction and the fast axis direction of the beam at the condensing position becomes small, and the cross-sectional distribution of the beam waist approaches a circle. When the beam waist of the excitation light beam approaches a circle, the overlap with the circular cross-sectional distribution of the oscillating laser beam increases, and the excitation efficiency of the solid-state laser device can be improved.

  From the above, in this embodiment, the excitation light beam 111 emitted from the light source 105 is split into two in the slow axis direction 401-1 and is incident on the condenser lens 109. At this time, the split excitation light beams 111 </ b> A and 111 </ b> B are incident on the condensing lens so as to be symmetrical with respect to the optical axis of the condensing lens 109.

  The excitation light beam 112 emitted from the excitation light source 106 is beamed by the beam diameter adjusting member 114 placed on the optical path so that the beam diameter in the direction of the slow axis 401-2 is larger than the beam diameter in the fast axis direction. Adjust the diameter. Then, the light is incident so that the center axis of the beam and the optical axis of the condenser lens 109 coincide with each other. FIG. 2B shows cross-sectional distributions of the excitation light beam 111 and the excitation light beam 112 on the surface of the condensing lens 109.

In order to make the cross-sectional distribution of the beam waist at the condensing position almost circular, the beam diameter Ds in the slow axis direction and the beam diameter Df in the fast axis direction are expressed as Ds / Df = Ms ² / It can be derived that Mf ² should be satisfied. When the excitation light beam is divided, the beam diameter Ds may be defined for the length including the divided excitation light beam, as defined in FIG.

Based on the above examination results, in FIG. 2, the excitation light beam 111 is divided in the slow axis direction and incident on the condenser lens, and the excitation light beam 112 is adjusted to have an elliptical cross-sectional distribution that is long in the slow axis direction. The light is incident on the lens 109. When the cross-sectional distribution of the beam waist at the condensing position is almost circular, the excitation efficiency of the solid-state laser device is the highest, so it is preferable to adjust the beam shape so that Ds / Df = Ms ² / Mf ² is satisfied. .

  Here, the edge-emitting laser diode that oscillates in the multimode in the slow axis direction and in the single mode in the fast axis direction has been described. However, the present invention is not limited to this, and when oscillating in the single mode in the slow axis direction and in the multi mode in the fast axis direction, the same effect can be obtained by replacing the slow axis in the above-described contents with the fast axis. .

(Second Embodiment)
FIG. 5 is a schematic diagram for explaining the second embodiment. In the present embodiment, not only the excitation light beam 111 but also the excitation light beam 112 is divided into two in the direction of the slow axis, and is a two-fold symmetry with respect to the optical axis of the condenser lens 109. 109 is different from the first embodiment in that it is made incident on 109.

  FIG. 6 shows the intensity distribution in the slow axis direction of the beam at the condensing position when the separation distance L between the divided excitation light beams is changed. As shown in FIG. 6, the side intensity peak 701 decreases as the separation distance L between the excitation light beams decreases. In general, the light having the side intensity peak 701 is outside the beam diameter of the laser beam considered in the present invention, and therefore hardly contributes to the oscillation of the laser beam. Therefore, the smaller the side intensity peak 701 is, the less energy is wasted.

  In FIG. 5, the excitation light beam 111 is divided into 111A and 111B, and the excitation light beam 112 is divided into 112A and 112B, respectively, and are incident twice symmetrically with respect to the optical axis of the condenser lens. The division of the excitation light beam may be performed in the same manner as in the first embodiment.

  As can be seen from a comparison between FIG. 5B and FIG. 2B, the separation distance L between the excitation light beams 111A and 111B is obtained by dividing not only the excitation light beam 111 but also the excitation light beam 112. Can be shortened compared to the first embodiment. As a result, the influence of the side peak can be reduced and the excitation efficiency can be increased.

(Third embodiment)
In the present embodiment, an example will be described in which the cross-sectional distribution of an excitation light beam emitted from an edge emitting laser diode having a large value of Ms ² is adjusted to improve the condensing characteristic in the slow axis direction.

As described above, the diameter of the beam waist in the slow axis direction and the fast axis direction at the condensing position can be controlled by the diameter Ds in the slow axis direction and the diameter Df in the fast axis direction of the excitation light beam, respectively. Therefore, when an edge-emitting laser diode having a large value of Ms ² is used, the condensing characteristic in the slow axis direction can be further improved by extending the diameter of the divided excitation light beam 111 in the slow axis direction.

  For example, in FIG. 2, it is more preferable to adjust the beam cross-sectional distribution of the excitation light beams 111A and 111B to an elliptical shape that is long in the slow axis direction as shown in FIG. In FIG. 5, when the beam cross-sectional distributions of the excitation light beams 111 </ b> A and B, 112 </ b> A and B are adjusted to elliptical shapes that are long in the slow axis direction and are incident on the condenser lens, as shown in FIG. 7B. More preferred.

  The cross-sectional distribution of the excitation light beam can be formed into a desired shape by adjusting the magnification of the beam diameter adjusting member 114 in the slow axis direction and the fast axis direction.

(Fourth embodiment)
In the present embodiment, a configuration in which the gain medium is irradiated with the excitation light beam from two directions will be described.

  FIG. 8A shows an outline of the configuration of the solid-state laser device according to the present embodiment, and FIG. 8B shows a cross-sectional distribution of the beam when entering the condenser lens 109.

  The solid-state laser apparatus of FIG. 8A has four excitation light sources 105, 106, 205, and 206, and the two condensing lenses 109-1 and 109-2 have their optical axes and condensing positions. Are arranged so that the gain medium 104 is sandwiched therebetween.

  The excitation light beam 111 emitted from the excitation light source 105 and the excitation light source 112 emitted from the excitation light source 106 irradiate the gain medium 104 in the same manner as in the first embodiment. That is, the excitation light beams 111A and 111B emitted from the excitation light source 105 and divided in the slow axis direction are incident on the condenser lens two times symmetrically with respect to the optical axis of the condenser lens 109-1. The excitation light beam 112 emitted from the excitation light source 106 is adjusted so that the beam diameter in the slow axis direction is larger than the beam diameter in the fast axis direction, and the center axis of the beam coincides with the optical axis of the condenser lens 109-1. The light is incident on the condenser lens 109-1. The excitation light beams emitted from the excitation light sources 205 and 206 are incident in the same manner from the side opposite to the surface on which the excitation light beams emitted from the excitation light sources 105 and 106 are incident on the gain medium. In other words, the excitation light beams 211A and 211B emitted from the excitation light source 205 and divided into two in the direction of the slow axis 401-1 are condensed symmetrically twice with respect to the optical axis of the condenser lens 109-2. Make it incident on the lens. The excitation light beam 212 emitted from the excitation light source 206 is adjusted so that the beam diameter in the direction of the slow axis 401-2 is larger than the beam diameter in the fast axis direction, and coincides with the optical axis of the condenser lens 109-1. So that it is incident. By adopting such a configuration, the central axis of the beam waist of the excitation light beam from each excitation light source coincides with the optical axis of the condenser lens and also coincides with the central axis of the oscillating laser beam. Therefore, in the region where the excitation light beams overlap each other and the excitation intensity is high, most of the excitation light beams absorbed by the gain medium 104 can contribute to the oscillation of the laser beam, and the excitation efficiency can be increased as compared with the conventional case. Become.

  In this embodiment, since four excitation light sources are used, the output from the solid-state laser device can be further increased.

(Fifth embodiment)
A nonlinear measuring apparatus using the solid-state laser device according to the present invention as a light source will be described. FIG. 12 is a schematic diagram of a stimulated Raman scattering microscope which is an example of a nonlinear measurement apparatus.

The light source unit 150 includes light sources 151-1 and 151-2 having the same frequency, and the mode-locked solid-state laser device according to the present invention was used as the light sources 151-1 and 151-2. Here, output light having a wavelength λ _p emitted from the light source unit 151-1 is used as excitation light, and output light having a wavelength λ _s output from the light source 151-2 and different from the wavelength λ _p is output by the modulator 152. Modulated and used as Stokes light.

  The output light emitted from each of the light sources 151-1 and 151-2 is aligned by the dichroic mirror 153 by the pulse adjusting unit (not shown), and is combined from the light source unit 150. Emitted. The pulse adjustment unit may be configured to adjust the optical path length, or a synchronization circuit that synchronizes the light sources 151-1 and 151-2 may be employed.

  The output light emitted from the light source unit 150 is condensed by the condensing optical system 154 and irradiated on the subject 155. At the condensing point of the output light, stimulated Raman scattering based on molecular vibrations of the molecules occurs due to the excitation light and Stokes light. Excitation light that has received an intensity change due to stimulated Raman scattering generated in the subject passes through the light condensing optical system 156 and a bandpass filter 157 that transmits the wavelength region of the excitation light, and then passes to the detection unit (light receiving element) 158. Detected. The light detected by the detection unit 158 is acquired as an image signal by the information acquisition unit 519 and displayed on the display unit 160 as necessary.

  Although not shown in the figure, the light output from the light source unit 150 can be scanned two-dimensionally within the subject 156 by the scanning means to obtain two-dimensional information or three-dimensional information of the subject. it can.

  In this embodiment, since the excitation efficiency of the solid-state laser device included in the light source unit is high, it is possible to reduce the power consumption of the entire nonlinear measurement device. In addition, when the same power is applied, it is possible to irradiate output light with higher peak power than before, so that strong signal light can be obtained, and it is possible to acquire highly accurate information about the subject. Become.

DESCRIPTION OF SYMBOLS 101,110 High reflection mirror 102 Partial reflection mirror 103 Pump mirror 104 Gain medium 105,106,205,206 Excitation light source 107 Collimating lens 108 Laser split member 109 Condensing lens 111,112, 211,212 Excitation light beam 114 Beam adjustment member 401 Slow axis direction 402 Fast axis direction

Claims (14)

A plurality of pumping light sources that emit pumping light beams, a plurality of mirrors that form a resonator, a gain medium disposed in the resonator, and a plurality of pumping light beams that are emitted from the pumping light sources are collected. A solid-state laser device comprising a condensing lens that irradiates and irradiates the gain medium,
A beam splitting member for splitting the excitation light beam is disposed on an optical path from the excitation light beam emitted from at least one of the plurality of excitation light sources to the condenser lens;
The solid-state laser device characterized in that the excitation light beams divided into N (N ≧ 2) by the dividing means are incident on the condenser lens N times symmetrically with respect to the optical axis of the condenser lens. .   The plurality of excitation light sources include an excitation light source that emits an excitation light beam that is not split by the beam splitting member. The excitation light beam that is not split is centered on the optical axis of the condenser lens. The solid-state laser device according to claim 1, wherein the light enters the condenser lens.   3. The solid-state laser device according to claim 1, wherein N = 2.   The solid-state laser device according to any one of claims 1 to 3, wherein the excitation light source is an edge-emitting laser diode.   5. The solid-state laser device according to claim 4, wherein the edge-emitting laser diode is an edge-emitting laser diode that emits light in a multimode in either the fast axis direction or the slow axis direction.   The solid-state laser device according to claim 5, wherein the excitation light beam is split in an axial direction in which multi-mode light emission is performed by the beam splitting member.   The distribution of the excitation light beam in the plane perpendicular to the optical axis of the condenser lens when entering the condenser lens is such that the beam diameter in the axial direction for emitting light in multimode is larger than the beam diameter in the other axial direction. The solid-state laser device according to claim 5, wherein the solid-state laser device is large.   The ratio of the axial beam diameter emitted in the multimode to the other axial beam diameter is such that the axial M square emitting in the multimode of the edge-emitting laser diode and the other square M square. The solid-state laser device according to claim 5, wherein the ratio is equal to the ratio of   9. The solid-state laser device according to claim 1, wherein the beam splitting member is a prism pair.   The solid-state laser device according to claim 1, wherein the gain medium is a titanium sapphire crystal.   The solid-state laser apparatus according to claim 1, wherein the solid-state laser apparatus performs mode-lock oscillation. A light source unit that emits output light including first light and second light having a wavelength different from that of the first light and modulated with respect to the first light; and the output light A non-linear measurement apparatus comprising: a condensing optical system that collects and irradiates a subject; and a detection unit that detects the first light that has passed through the subject,
The non-linear measuring device, wherein the light source unit includes the solid-state laser device according to claim 1.   The nonlinear measuring apparatus according to claim 11, wherein the nonlinear measuring apparatus is a stimulated Raman scattering microscope that detects stimulated Raman scattering generated in the subject by the detection unit.   The nonlinear measurement apparatus according to claim 12, wherein the light source unit includes a gain medium made of a titanium sapphire crystal.