JPH01214079A - Laser light source - Google Patents

Abstract

PURPOSE:To obtain a laser light source which can provide a further high power output laser beam with a high quality single lateral mode by using the constitution of an end pump type laser light source by a method wherein exciting laser beams are supplied to both ends of a laser medium. CONSTITUTION:In a laser light source 11, an oscillated light passage PTH through a laser medium 12 is formed by the oscillating operation of a basic wave laser beam LA12 generated in the laser medium 12 and an output laser beam 14 is emitted in accordance with the basic wave laser team A12. First and second exciting laser beam LA11 and LA13 are supplied to the first and second end planes 12A and 12B of the laser medium 12 at which the oscillated light passage PTH crosses the laser medium 12. For instance, the exciting laser beam LA11 from an exciting semiconductor laser 13 is applied to the incident plane 12A of the rod type laser medium 12 through a condensing lens system 14 and, further, the exciting laser beam LA13 a second exciting semiconductor laser 15 is applied to the emitting plane 12B of the laser medium 12 through a condensing lens system 16 and a polarization type beam spritter 17.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a laser light source, and is particularly adapted to obtain a high power output laser light.

B Summary of the Invention The present invention provides a laser light source configured to obtain an output laser beam by exciting a laser medium with an excitation laser beam, in which the excitation laser beam is supplied from both end faces of the laser medium. As a result, it is possible to obtain an output laser beam with a single transverse mode having good optical characteristics and high power.

C. Prior art A light source has been proposed that uses a solid-state laser as the laser medium constituting a resonator and a semiconductor laser as the excitation light source, which is a so-called semiconductor laser pumped solid-state laser. There are two types: one with a side pump type and one with a side pump type.

Problems to be Solved by the Invention First, as shown in FIG. The laser beam LAI from the excitation semiconductor laser 3 is incident through the condensing lens system 4 as the incident surface 2A, thereby generating fundamental laser beam LA2 in the laser medium 2 and sending it out from the other end surface 2B.

This fundamental wave laser beam LA2 is transmitted to the incident surface 5A of the output mirror 5.
and is reflected at a predetermined reflectance (for example, 95%). The entrance surface 2A of the laser medium 2 receives the fundamental laser beam LA.
2, thus having a reflectance of 100% for the entrance surface 2
A resonator CAV is formed by the fundamental wave laser beam LA2 resonating between A and 5A.

The fundamental wave laser beam LA2 that has passed through the incident surface 5A of the output mirror 5 (transmittance 5%) is emitted from the output surface 5B of the output mirror 5 as an output laser beam LA3.

The laser light source with this configuration has the advantage that the excitation laser light LAl can be focused into a narrow beam spot by the condensing lens system 4, and a beam with a good single transverse mode can be emitted as the output laser light LA3.

However, the excitation laser beam LA incident from the incident surface 2A
Since I quickly diffuses after passing a predetermined absorption region,
There is a problem that a large power cannot be obtained as the fundamental laser beam LA2.

Second, as shown in FIG.
Excitation laser beams LA4A and LA4B of a plurality of, for example, three excitation semiconductor lasers 8A, 8B, and 8G arranged along the longitudinal direction.

By irradiating LA4G, fundamental wave laser light LA5 is generated in the laser medium 7.

In this case, a mirror is formed on one end surface 7B of the laser medium 7 to have a 100% reflectance for the fundamental laser beam LA5, and a mirror is formed on the other end surface 7C to have a 95% reflectance. Thus, a resonator CAV in which the fundamental wave laser beam LA5 operates resonantly is formed between the end surfaces 7B and 70, and the fundamental wave laser beam LA5 is transmitted from the end surface 7C at a transmittance of 5%. Output laser light LA6 is emitted.

This side pump type laser light source includes excitation laser beams LA4A-LA4 of a plurality of excitation semiconductor lasers 8A to 8C.
By being able to irradiate the excitation laser light over a relatively wide area from C, the output laser light LA6 with a large power can be emitted as the output laser light LA6.

However, according to the configuration shown in FIG. 2, the excitation laser beam LA4A
- Since LA4C is irradiated laterally, it is difficult to obtain a high quality single transverse mode output laser beam LA6.

The present invention has been made in consideration of the above points, and it is possible to obtain an output laser beam having a high-quality single transverse mode and a higher power by using an end-pump laser light source configuration. This is an attempt to IX a laser light source.

E Means for Solving Problem E To solve this problem, in the present invention, the fundamental wave laser beam LA12 generated in the laser medium 12 performs an oscillation operation, so that the oscillation optical path PTH passing through the laser medium 2 is In the laser light source 11 that is formed and sends out the output laser beam LAI4 based on the fundamental laser beam LA12, a first
and the first and second excitation laser beams (LAII, LAI3), (LAII, L
AI3, LA31), (LAILLA13, LA31.
LA41).

Excitation laser light (LAI 1.L
AI 3), (LAII, LAI3, LA31), (L
AII, LAI3, LA31, LA41), the length of the effective absorption region formed in the laser medium 12 can be doubled, and this spectroscopic fundamental wave laser beam LA12, therefore Output laser beam L
The power of AI4 can be increased.

G example An embodiment of the present invention will be described in detail below with reference to the drawings.

(G1) First embodiment In FIG. 1, 11 indicates a laser light source as a whole;
For example, it has a rod-shaped laser medium 12 using a solid-state laser made of YAG, and the excitation laser beam LAII of the excitation semiconductor laser 13 is focused into a narrow beam and incident on the incident surface 12A through a condensing lens system 14. As a result, a fundamental laser beam LA12 is generated in the absorption region ERI (FIG. 2) formed within the laser medium 12.

In addition to this, the exit surface 12B of the laser medium 12 has a second
After the excitation laser beam LA13 of the excitation semiconductor laser 15 is condensed into a narrow beam by the condenser lens system 16, it enters the polarizing beam splitter 17 through the p-wave transmission direction, and is thus formed into a laser ring 1t12. A fundamental laser beam LA12 is generated in the absorption region ER2 (FIG. 2).

In this embodiment, the polarizing beam splitter 17 has an optical characteristic of reflecting S-polarized light and transmitting p-polarized light among the intrinsic polarized lights of the fundamental laser beam LA12. Among the unique polarizations of the fundamental laser beam LA12 emitted from the laser beam LA12, the S-polarized light is reflected laterally at the polarizing beam splitter 17 and is incident on the output mirror 18.

Here, the incident surface 18A of the output mirror 18 forms a reflective surface with a reflectance of 95%, and the incident surface 18A of the laser medium 12 forms a reflective surface with a reflectance of 95%.
A reflecting surface having a reflectance of 100% with respect to the fundamental laser beam LA12 is formed.

In this way, from the incident surface 12A of the laser ring 1t12, it passes through the polarization type beam splitter 17 to the output mirror 180 incident surface 1.
8A, the laser beam LA consisting of S polarization among the fundamental laser beam LA12 generated in the laser medium 12
12. forms a resonant optical path PTH through resonant operation, and the laser beam L A 121 consisting of S polarization that performs resonant operation on this resonant optical path PTH is emitted through the incident surface of the output mirror 18 having a transmittance of 5%. The output laser beam LA14 is emitted from the surface 18B.

In the configuration shown in FIG. 1, the incident surface 12 of the laser ring f12
The excitation laser beam LAII incident from A through the condensing lens system 14 is condensed into a narrow beam by the condensing lens system 14, so that a first absorption region ERI (see FIG. 2) is formed on the incident surface 12A side. ), and the fundamental laser beam LA12 can be generated in the absorption region ERI.

In addition, from the exit surface 12B side of the laser ring f12, the excitation laser beam LA13 is incident from the excitation semiconductor laser 15 through the condenser lens system 16 while being condensed into a narrow beam by the condenser lens system 16. As a result, a second absorption region ER2 (FIG. 2) is formed on the exit surface 12B side,
Also in the second absorption region ER2, the fundamental laser beam L
A12 can be generated.

Thus, according to the configuration of FIG. 1, the length of the effective absorption region formed inside the laser medium 12 can be doubled compared to the conventional case described above with reference to FIG. By doing so, the power of the output laser beam LA14 can be doubled compared to the conventional case. Therefore, the excitation method for the laser medium 12 can be an end-pump method similar to that described above with reference to FIG. can.

(G2) Second Embodiment FIG. 3 shows a second embodiment of the present invention. As shown by assigning the same reference numerals to corresponding parts as in FIG. 1, a second excitation semiconductor laser is used. 15 excitation laser beams LA13 are incident on the polarizing beam splitter 17 from the S-wave reflection direction, thereby being reflected by the polarizing beam splitter 17 and made to enter the exit surface 12B of the laser medium 12.

At the same time, the output laser beam LA12 is composed of p-polarized light transmitted through the polarizing beam splitter 17 among the unique polarized light of the fundamental laser beam LA12 generated in the laser ring f12.
．． is incident on the incident surface 18A of the output mirror 18 to obtain an output laser beam LA14.

If configured as shown in FIG. 3, the output laser beam LA14 is
By obtaining , it is possible to obtain the same effect as described above with respect to FIG.

(G3) Third Embodiment FIG. 4 shows a third embodiment of the present invention. As shown by assigning the same reference numerals to corresponding parts as in FIG. 1, in the case of FIG. The configuration is similar to that in which a wavelength selective beam splitter 21 is used in place of the polarizing beam splitter 17.

In this case, the wavelength selective beam splitter 21 transmits the excitation laser beam LA13 (for example, having a wavelength λ13 = 0.810 Cμm) of the second excitation semiconductor laser 15, and at the same time transmits the excitation laser beam LA13 (having a wavelength λ13 = 0.810 Cμm) of the second excitation semiconductor laser 15, and at the same time Fundamental laser beam LA12 (for example, wavelength λ1χ=1.06
0 Cμm]).

In the configuration shown in FIG. 4, the second excitation semiconductor laser 15
The excitation laser beam LA13 passes through the wavelength selective beam splitter 21 and enters the exit surface 12B of the laser medium 12.

Thus, the laser medium 12 is the first excitation semiconductor laser 1
Together with the excitation laser beam LAII of No. 3, a fundamental laser beam LA12 is generated in the absorption regions ERI and ER2 on the side of the entrance surface 12A and the exit surface 12B.

This fundamental laser beam LA12 is reflected by the wavelength selective beam splitter 21, passes through the output mirror 18, and is emitted as an output laser beam LA21.

Even in this case, the same effect as described above with respect to FIG. 1 can be obtained.

(G4) Fourth Embodiment FIG. 5 shows a fourth embodiment of the present invention. As shown by assigning the same reference numerals to corresponding parts as in FIG. 4, in FIG. The configuration is similar to that in which a wavelength selective beam splitter 22 having different wavelength selection characteristics is used in place of the beam splitter 21.

That is, the wavelength selective beam splitter 22 in FIG.
Wavelength λ of fundamental laser beam LA12, t (=1.060
(μm)) at the same time, the wavelength λ+s of the excitation laser beam LA13 of the second excitation semiconductor laser 15
(=0.810 (μff)) has optical properties that reflect light.

In the configuration shown in FIG. 5, the excitation laser beam LAI3 enters from the S-wave reflection direction, is reflected by the wavelength selective beam splitter 22, and is supplied to the exit surface 12B of the laser medium 12.

The fundamental laser beam LA12 thus generated in the laser medium 12 enters from the p-wave transmission direction, passes through the wavelength selective beam splitter 22, and is sent to the output mirror 1.
Thus, this fundamental wave laser beam LA12 is emitted as an output laser beam LA21.

Even with the configuration as shown in FIG. 5, the same effect as in the case of FIG. 4 can be obtained.

(G5) Fifth Embodiment FIG. 6 shows a fifth embodiment of the present invention. As shown by assigning the same reference numerals to corresponding parts as in FIG. 1, the first and second excitation In addition to the semiconductor lasers 13 and 15 for excitation, a third semiconductor laser 31 for excitation is provided.

Excitation laser beam LAI of the first excitation semiconductor laser 13
A polarizing beam splitter 32 is inserted to cause the excitation laser beam LA11 to enter from the p-wave transmission direction into the optical path where the excitation laser beam LA11 enters the incident surface 12A of the laser medium 12 while being condensed by the condensing lens system 14.

To this polarizing beam splitter 32, the excitation laser beam LA31 from the third excitation semiconductor laser 31 passes through a condensing lens system 33 and is condensed into a narrow beam from the S wave reflection direction to the polarizing beam splitter 32. It is incident. At this time, the polarizing beam splitter 32 uses the excitation laser beam L.
A31 is reflected and enters the incident surface 12A of the laser medium 12.

In the configuration of FIG. 6, the first, second, and third excitation semiconductor lasers 13, 15, and 31 generally emit laser light LA40 of elliptically polarized light, as indicated by reference numeral 41 in FIG.

In other words, the semiconductor laser 41 (13, 15, 31) has a structure in which the inert layer 41A is sandwiched between the cladding layer 41B and the front cleavage plane 41CF and the rear cleavage plane 41CR which face each other. A stripe-shaped laser oscillation region 41D is formed in the active layer 41A using the reflective surface as a reflecting surface.

Thus, the laser oscillation region 41D exposed to the front cleavage plane 41CF generates a near-field image 42 having a light intensity distribution in a direction parallel to the PN junction, and the near-field image 42 effectively arranges the light sources in a linear manner. The laser beam LA thus emitted from the laser oscillation region 41D has a horizontal transverse mode similar to
41 forms a far-field image 43 having a light intensity distribution corresponding to the horizontal transverse mode.

Here, the far-field image 43 has a lateral width d□ of the near-field image 42
It has a width aW* in the short axis direction corresponding to , and a width dV in the long axis direction corresponding to the vertical direction aVt of the near-field image 42.
It has an elliptical shape with t.

In this way, the excitation laser beams LA11 and LA31 in the case of FIG. In practice, the emitted excitation laser beam LA32 has a shape close to a circular cross section, and thus the laser medium 1 as shown in FIG.
At t12, the same absorption regions ER3 are excited so as to have a substantially circular cross-sectional shape so as to overlap each other.

Therefore, the spot shape of the fundamental wave laser beam LA12 generated in the laser medium 12 becomes approximately circular, and thus is emitted from the laser medium 12 as a laser beam with practically good optical characteristics.

The fundamental laser beam LA12 generated in the laser medium 12 in this manner is incident on the polarizing beam splitter 17 provided on the exit surface 12B side from the S wave reflection direction, and is reflected at the polarizing beam splitter 17. and enters the nonlinear optical crystal element 34.

This nonlinear optical crystal element 34 has a fundamental wave laser beam LA1.
It has optical characteristics such that it is phase-matched to the second harmonic laser beam having a wavelength of 1/2 compared to 2, and thus, while the fundamental wave laser beam LA12 is transmitted through the nonlinear optical crystal element 34, the second harmonic laser beam is Light LA33 is generated and sent out via output mirror 18 as output laser light LA34.

According to the configuration shown in FIG. 6, three excitation semiconductor lasers 13
．． 15.31 excitation laser beam LAII.

By being able to excite the laser medium 12 using LA13, L, and A31, the fundamental wave laser beam LA
12 power can be increased.

In addition, the first and second excitation semiconductor lasers 13 and 31 are used to generate excitation laser beam LA3 having a substantially circular cross section.
2 can be supplied to the laser medium 12, it is possible to generate an output laser beam LA34 which has a nearly circular cross section and is therefore good for practical use.

(G6) Sixth Embodiment FIG. 9 shows a sixth embodiment of the present invention. As shown by assigning the same reference numerals to corresponding parts as in FIG. 6, a second excitation semiconductor laser is used. A polarizing beam splitter 51 and a wavelength selective beam splitter 52 are sequentially inserted into the optical path in which the 15 excitation laser beams LA13 are focused by the condensing lens system 16 and incident on the exit surface 12B of the laser medium 12. .

The polarizing beam splitter 51 receives the excitation laser beam LA1.
3 is transmitted from the p-wave transmission direction, and the excitation laser beam LA41 of the fourth excitation semiconductor laser 53 is reflected from the S-wave reflection direction through the condenser lens system 54, and combined with the polarization laser beam LA13 to obtain the wavelength. Selective beam splitter 5
2.

In this embodiment, the wavelength λ41 of the excitation laser beam LA41 of the excitation semiconductor laser 53 is selected to be the wavelength λ13 of the excitation laser beam LA13 (a value equal to -0,810(un)), and the wavelength selective beam splitter 52 is the wavelength λ of the fundamental laser light LA12 that is generated in the laser medium [12] at the same time that the light with the wavelength λ13=λ41 (=0.813 (um)) is transmitted.

(-1,060 (μm)).

Thus, the excitation laser beam LA42 having a substantially circular cross section is emitted from the polarizing beam splitter 51 onto the exit surface 12B of the laser medium 12 in the same manner as described above for the polarizing beam splitter 32 in FIG. can be input into the laser medium 12.

Further, the wavelength selective beam splitter 52 includes excitation laser beams LA generated from the excitation semiconductor lasers 15 and 53.
13 and LA41, and the fundamental wave laser beam L generated in the laser medium 12 at the same time.
The fundamental wave laser beam LA12 emitted from the laser medium f12 is converted into a second harmonic laser beam LA through the nonlinear optical crystal element 34.
The second harmonic laser beam LA33 that is incident on the output mirror 18 together with the second harmonic laser beam LA33 and transmitted therethrough is sent out as an output laser beam LA34.

According to the configuration of FIG. 9, it is possible to irradiate the excitation laser beam LA32, which is a light beam with a circular cross section, onto the incident surface 12A of the laser medium 12 in the same manner as described above with respect to FIG. The excitation laser beam LA42, which is a light beam with a circular cross section obtained on the output side of the polarizing beam splitter 51, can be supplied to the exit surface 12B of the laser medium 12 through the wavelength selective beam splitter 52.

Thus, the four excitation semiconductor lasers 13.15.315
3 can excite the laser medium 12, thereby making it possible to further increase the power of the output laser beam LA34.

(G7) Other embodiments (1) In the embodiments shown in FIGS. 1 and 3, the polarizing beam splitter 17 is designed to reflect light polarized in the S-wave direction and transmit light in the P-wave direction. Although we have described the case where this is the case, conversely, it is also possible to apply a device with optical characteristics that reflects light in the p-wave direction.
At this time, the excitation semiconductor laser 15 may be configured to emit excitation laser light LA13 having polarization in the p-wave direction.

(2) In the embodiments shown in FIGS. 1, 3, 4, and 5, the fundamental laser beam LA12 generated in the laser medium 12 is emitted as the output laser beams LA14 and LA21. As described above, based on this fundamental laser beam LA12, for example, a second
Even if a harmonic laser beam is generated and the second harmonic laser beam is emitted from the output mirror 18 as the output laser beams LA14 and LA21, the same effect as in the above case can be obtained.

(3) In the embodiments shown in FIGS. 6 and 9, the fundamental laser beam LA1 generated in the laser medium 1t12
2 is supplied to the nonlinear optical crystal element 34 to emit the second harmonic laser beam LA33 as the output laser beam LA34, but the nonlinear optical crystal element 34 is omitted,
The fundamental laser beam LA12 may be directly emitted as the output laser beam LA34.

Effects of the Invention As described above, according to the present invention, in an end-pump type laser medium, by supplying excitation laser light from both end faces, a single transverse mode is good as an optical property and further improved. It is possible to obtain output laser light with high power.

[Brief explanation of the drawing]

FIG. 1 is an optical path diagram showing one embodiment of the present invention, FIG. 2 is a route diagram for explaining the absorption region within the laser medium, and FIGS. Optical path diagrams showing the second, third, fourth, and fifth embodiments of the invention; FIG. 7 is a route diagram for explaining the absorption region of the laser medium in FIG. 6; FIG. FIG. 9 is an optical path diagram showing a sixth embodiment of the present invention, and FIGS. 10 and 11 are optical path diagrams showing a conventional configuration. 11... Laser light source, 12... Laser medium, 13.15.3153... Laser light source for excitation, 17.51... Polarizing beam splitter, 21.22.52... Wavelength selective beam splitter, 18... Output mirror, 34...
・Nonlinear optical crystal element.

Claims (1)

[Claims] A laser light source that forms an oscillation optical path passing through the laser medium by oscillating the fundamental laser light generated in the laser medium, and sends out an output laser light based on the fundamental laser light. in which the oscillation optical path intersects the laser medium;
A laser light source characterized in that first and second excitation laser lights are supplied from an end face of the laser light source.