JPH04291779A - Solid laser unit - Google Patents

Abstract

PURPOSE:To provide a compact solid laser unit requiring small number of components in which second higher harmonic and sum frequency wave can be outputted simultaneously on a same axis and alignment thereof can be carried out easily. CONSTITUTION:Both nonlinear optical elements 15, 13 generating second higher harmonic and sum frequency, respectively, are arranged in the laser resonator of a solid laser unit so that second higher harmonic and sum frequency are generated simultaneously on a same axis from a single laser resonator.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state laser device that converts the wavelength of fundamental laser light generated by a laser medium using a nonlinear optical element to generate harmonics.

0002

2. Description of the Related Art An example of a conventional solid-state laser device for generating second harmonics is shown in FIG.

[0003] The solid-state laser for second harmonic generation has an optical axis 50
A semiconductor laser (hereinafter referred to as LD) 51 arranged above
, condensing lens 52, solid-state laser rod 53, second harmonic generation nonlinear optical element (hereinafter referred to as SHG element) 5
4 and an output mirror 55. Further, the end face of the solid-state laser rod 53 on the LD 51 side is coated with a coating that highly reflects the solid-state laser fundamental wave, and forms an optical resonator 56 together with the output mirror 55 . LD51
The solid-state laser rod 53 is excited by the output light 501 and generates a fundamental wave 502. Generated fundamental wave 502
operates in resonance so as to pass through the SHG element 54, and the second
It is converted into harmonics 503. The second harmonic 503 passes through the output mirror 55 and is output to the outside. In this conventional example, if Nd:YAG is used for the solid-state laser rod 53 and KTiO4PO4 (hereinafter referred to as KTP) is used for the SHG element, green laser light with a wavelength of 532 nm can be obtained as the second harmonic. be able to.

Next, an example of a conventional solid-state laser device for generating a sum frequency is shown in FIG.

The solid-state laser device for generating a sum frequency has an optical axis 60
LD 61, condensing lens 62, nonlinear optical element for sum frequency generation (hereinafter referred to as SFG element) 63, arranged above.
It is composed of a solid-state laser rod 64 and an output mirror 65. Further, the end face of the SFG element 63 on the LD 61 side is coated with a coating that highly reflects the solid-state laser fundamental wave, and forms an optical resonator 66 with the output mirror 65. Output light 601 from the LD 61 passes through the SFG element 63 and excites the solid-state laser rod 64. The fundamental wave 602 generated from the solid-state laser rod 64 is transmitted to the SFG element 6
3, the output light of LD61 and S
Sum frequency mixing is performed within the FG element element 63. SFG element 6
The sum frequency 603 generated within the solid-state laser rod 64
The light passes through the output mirror 65 and is output to the outside. In this conventional example, for example, the solid-state laser rod 64 is made of Nd.
: If KTP is used for the YAG or SFG element 63, blue laser light with a wavelength of 459 nm is obtained as a sum frequency. In addition,
The KTP used in the solid-state laser device for generating a sum frequency wave is different from the KTP for generating a second harmonic wave in the crystal direction in which the fundamental wave is incident.

[0006]

[Problem to be Solved by the Invention] However, when both the second harmonic and the sum frequency are required, a solid-state laser device for generating the second harmonic and a solid-state laser device for generating the sum frequency must be prepared. did not become. As a result, the number of parts increases, leading to an increase in the size and cost of the device. Furthermore, it was necessary to adjust the alignment of the solid-state laser device for generating the second harmonic and the solid-state laser device for generating the sum frequency.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a solid-state laser device with a reduced number of parts, easy alignment, and high reliability.

[0008]

[Means for Solving the Problems] In order to achieve this object, the solid-state laser device of the present invention converts the wavelength of fundamental laser light generated by a laser medium using a nonlinear optical element, and generates harmonics. In the apparatus, a second harmonic generation nonlinear optical element and a sum frequency generation nonlinear optical element were arranged in a laser resonator.

Furthermore, in a solid-state laser device that converts the wavelength of fundamental laser light generated by a laser medium using a nonlinear optical element to generate harmonics, the functions of the nonlinear optical element and the laser medium are combined in the laser resonator. A nonlinear optical element for second harmonic generation or a nonlinear optical element for sum frequency generation is arranged.

Note that the laser medium may be excited by a semiconductor laser. In addition, KTiO4 is added to the second harmonic generation nonlinear optical element and the sum frequency generation nonlinear optical element.
PO4 may also be used.

[0011]

[Operation] In the solid-state laser device of the present invention having the above structure, the second harmonic and the sum frequency are simultaneously generated on the same axis by one laser resonator.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying the present invention will be described below with reference to the drawings.

First, the structure of the solid-state laser device of the first embodiment will be explained with reference to FIG. The solid-state laser device of the first embodiment includes an LD 11 on the optical axis 10 and an LD 1 on the optical axis 10.
1, the condenser lens system 12, the KTP 13 for sum frequency generation, and the Nd:YA
A G crystal 14, a KTP 15 for second harmonic generation, and an output mirror 16 are arranged. In addition, KTP13 for sum frequency generation
, Nd:YAG crystal 14, KTP15 for second harmonic generation
Both end faces of the optical resonator are coated to reduce loss within the optical resonator.

The coating specifications of each element are summarized below, with the end face on the LD 11 side as A and the end face on the output mirror 16 side as B. KTP13 end face A for sum frequency generation is 808 nm
High transmission for 1064nm, 459nm, 532n
The end face B of KTP13 for sum frequency generation and the end face A of Nd:YAG crystal 14 are 808 nm, 10
Highly transparent for 64 nm, 459 nm, and 532 nm, Nd:YAG crystal 14 end face B, second harmonic generation K
The TP15 end face A and the KTP15 end face B for second harmonic generation have high transmission at 1064 nm, 459 nm, and 532 nm, and the output mirror 16 has high reflection at 1064 nm and high transmission at 459 nm and 532 nm. In this way, the end face A of the sum frequency generating KTP 13 and the output mirror 16 form an optical resonator 17 since both have high reflection for the wavelength of 1064 nm. The KTP13 for second harmonic generation and the KTP15 for sum frequency generation are as follows:
Although the composition is the same, the direction of the crystal axis with respect to the optical axis is different.

Next, the operation of the solid-state laser device having this configuration will be explained step by step with reference to FIG.

The first fundamental wave (wavelength 8
08 nm) 101 is condensed by the condenser lens system 12, transmitted through the KTP 13 for sum frequency generation, and absorbed by the Nd:YAG crystal 14. The Nd:YAG crystal 14 is excited by absorbing a first fundamental wave (wavelength: 808 nm) 101, and generates a second fundamental wave (wavelength: 1064 nm) 102. The generated second fundamental wave (wavelength 1064 nm) 102
KTP13 for sum frequency generation, KTP for second harmonic generation
15. Resonant operation occurs within the optical resonator 17 so as to transmit through the Nd:YAG crystal 14. At this time, K for second harmonic generation
Within TP15, the second fundamental wave (wavelength 1064 nm) 102
A part of the wavelength is converted into the second harmonic (wavelength 532 nm).
)103 occurs. The generated second harmonic (wavelength 532
nm) 103 is transmitted through the output mirror 16 and output to the outside.

At the same time, in the sum frequency generation KTP 13, the first fundamental wave (wavelength 808 nm) 101 and the second fundamental wave (
1064 nm) 102 is subjected to sum frequency mixing to generate a sum frequency (wavelength 459 nm) 104. The generated sum frequency (wavelength 459 nm) 104 is transmitted to the solid-state laser rod 14, the second
It passes through the harmonic generation KTP 15 and the output mirror 16 and is output to the outside. That is, from the output mirror, the optical axis 10
Along the line, green laser light with a wavelength of 532 nm and blue laser light with a wavelength of 459 nm are simultaneously output.

Next, a second embodiment will be explained with reference to FIG. In the description, the same parts as in the previous embodiment are given the same reference numerals.

In the second embodiment, a NYAB crystal 21 is used in place of the Nd:YAG crystal 14 used in the previous embodiment and the second harmonic generation KTP 15, but the structure is similar. . NYAB crystal has a composition of NdXY
1-XAl3(BO3)4; x=0.04 to 0.08, and functions as both a laser material and a nonlinear optical element.

Here, the specifications of the coating applied to the NYAB crystal 21 and other optical elements are summarized below, with the LD side end face being A and the output mirror side end face being B, as in the previous embodiment. KTP13 end face A for sum frequency generation is 8
High transmission for 04nm, 1062nm, 458nm,
Highly reflective at 531 nm, KTP for sum frequency generation
13 end face B, NYAB crystal 21 end face A is 804 nm,
It has high transmittance at 1062 nm, 458 nm, and 531 nm, and the end surface B of NYAB crystal 21 is 1062 nm, 458 nm, and 531 nm.
58 nm, 531 nm, the output mirror 16 has high reflection at 1062 nm, 458 nm,
High transmission at 531 nm. In this way, both the end face A of the KTP 13 for sum frequency generation and the output mirror 16 are highly reflective for the wavelength of 1062 nm, so the optical resonator 17
is formed. Regarding the coating specifications for each optical component, the wavelength of the second fundamental wave generated by NYAB crystal 21 is 1062 nm, and the peak wavelength of absorption is 804 nm, which is slightly different from Nd:YAG, so the changed values are shown. . In addition, the phase matching direction of the KTP 13 for sum frequency generation also requires some changes.

Next, the operation of the solid-state laser device having this configuration will be explained.

The first fundamental wave (wavelength: 804 nm) 201 outputted from the LD 11 is focused by the condensing lens system 12, transmitted through the KTP 13 for sum frequency generation, and absorbed by the NYAB crystal 21. The NYAB crystal 21 is excited by absorbing a fundamental wave (wavelength: 804 nm) 201, and generates a second fundamental wave (wavelength: 1062 nm) 202. The generated second fundamental wave (wavelength: 1064 nm) 202 resonates within the optical resonator 17 so as to pass through the KTP 13 and NYAB crystal 21 for sum frequency generation. At this time, within the NYAB crystal 21, a part of the second fundamental wave (wavelength 1062 nm) 202 is converted into a second harmonic wave (wavelength 531 nm).
203 occurs. The generated second harmonic (wavelength 531n
m) 203 is transmitted through the output mirror 16 and output to the outside.

At the same time, the first fundamental wave (wavelength 804 nm) 201 and the second fundamental wave (wavelength 804 nm) are generated in the KTP 13 for sum frequency generation.
1062 nm) 202 is subjected to sum frequency mixing to generate a sum frequency wave (wavelength 458 nm) 204, which is transmitted through the NYAB crystal 21 and the output mirror 16 and output to the outside. That is,
As in the first embodiment, a green laser beam with a wavelength of 531 nm and a green laser beam with a wavelength of 4 nm are emitted from the output mirror 16 along the optical axis 10.
A 58 nm blue laser beam is output at the same time.

Next, a third embodiment will be explained with reference to FIG. In the description, the same parts as in the first embodiment will be given the same symbols.

In the first embodiment, one LD serves both for excitation of the Nd:YAG crystal 14 and for supplying the first fundamental wave (wavelength 808 nm) to the KTP 13 for sum frequency generation. In the example, as shown in FIG. 3, the LD 11 is used exclusively for supplying the first fundamental wave (wavelength: 808 nm), and the LD 31 is used separately for exciting the solid-state laser material. Here, the polarization directions of the first fundamental wave (wavelength 808 nm) 101 from the LD 11 and the excitation light 105 (wavelength 808 nm) from the LD 31 are perpendicular to each other. The output lights of these two LDs are combined by a polarizing beam splitter 32,
After being focused by the focusing lens system 12, the light enters the KTP 13 for sum frequency generation and the Nd:YAG laser rod 14. The Nd:YAG crystal 14 receives excitation light (wavelength: 808 nm).
) 105, the second fundamental wave (
A wavelength of 1064 nm) 102 is generated.

[0026] Second fundamental wave generated (wavelength 1064 nm)
102 is so as to pass through the KTP 13 for sum frequency generation, the KTP 15 for second harmonic generation, and the Nd:YAG crystal 14.
It operates resonantly within the optical resonator 17. At this time, the second fundamental wave (wavelength 1064 nm) is generated within the second harmonic generation KTP15.
102 is converted into a second harmonic (wavelength 53
2nm) 103 is generated. The generated second harmonic (wavelength: 532 nm) 103 is transmitted through the output mirror 16 and output to the outside. At the same time, the first fundamental wave (wavelength 808 nm) 101 and the second fundamental wave (1064 nm) 102 are sum-frequency mixed in the KTP 13 for sum frequency generation, and the sum frequency (
Wavelength: 459 nm) 104 is generated. The generated sum frequency (
The wavelength 459 nm) 104 is transmitted through the solid-state laser rod 14, the second harmonic generation KTP 15, and the output mirror 16, and is output to the outside. That is, from the output mirror to the optical axis 1
0, a green laser beam with a wavelength of 532 nm and a blue laser beam with a wavelength of 459 nm are simultaneously output.

The configuration using two LDs as described above can be similarly applied to the second embodiment.

Various other changes can be made without departing from the spirit of the invention. For example, in the first embodiment, Nd:YAG is used as the solid-state laser material.
Although we used crystals, other solid-state laser materials such as N
d: YVO4 crystal may be used. Furthermore, in this example, KTP was used for the second harmonic generation nonlinear optical element and the sum frequency generation nonlinear optical element, but other suitable nonlinear optical materials such as KNbO3 or organic nonlinear optical materials could be used. Alternatively, different materials may be used for the second harmonic generation nonlinear optical element and the sum frequency generation nonlinear optical element.

[0029]

[Effects of the Invention] As is clear from the above explanation, according to the solid-state laser device of the present invention, the second harmonic and the sum frequency can be generated simultaneously on the same axis by one solid-state laser device. . Therefore, even if two wavelengths of laser light are required, there is no need to prepare both a solid-state laser device for second harmonic generation and a solid-state laser device for sum frequency generation, as in the past, and the number of parts is significantly reduced. This makes it possible to provide a highly reliable and compact solid-state laser device.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a solid-state laser device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a solid-state laser device according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a solid-state laser device according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional solid-state laser device for second harmonic generation.

FIG. 5 is a configuration diagram of a conventional solid-state laser device for generating a sum frequency.

[Explanation of symbols]

11 Semiconductor laser 13 KTP for sum frequency generation 14 Nd:YAG crystal 15 KTP for second harmonic generation 17 Optical resonator 21 NYAB crystal

Claims (4)

[Claims] Claim 1: In a solid-state laser device that wavelength-converts a fundamental laser beam generated by a laser medium using a nonlinear optical element, the laser resonator includes a nonlinear optical element for second harmonic generation and a sum frequency generator. A solid-state laser device characterized by having a nonlinear optical element arranged therein. [Claim 2] In a solid-state laser device in which a fundamental laser beam generated by a laser medium is wavelength-converted by a nonlinear optical element, an element having the functions of both the nonlinear optical element and the laser medium is provided in the laser resonator. and a nonlinear optical element for generating a second harmonic or a nonlinear optical element for generating a sum frequency. 3. The solid-state laser device according to claim 1, wherein the laser medium is excited by a semiconductor laser. 4. The solid-state laser device according to claim 1, claim 2, or claim 3, wherein the second harmonic generation nonlinear optical element and the sum frequency generation nonlinear optical element include K.
A solid-state laser device using TiO4PO4 and simultaneously generating green laser light that is the second harmonic of the solid-state laser and blue laser light that is the sum frequency of the semiconductor laser and the solid-state laser.