KR20200011271A - Solid state laser apparatus having saturable absorber for suppressing amplified spontaneous emission - Google Patents

Abstract

The present invention relates to a solid-state laser apparatus having a saturable absorber for suppressing amplified spontaneous emission. The solid-state laser apparatus comprises: a first amplification medium storing pumping energy supplied by a pumping source, and amplifying and transmitting the laser input from the outside; a second amplification medium storing pumping energy supplied by the pumping source, spaced apart from one side of the first amplification medium, and amplifying and transmitting again the laser introduced from the first amplification medium; a saturable absorber spaced apart from one side of the second amplification medium to suppress amplified spontaneous emission components generated in the first and second amplification media, and transmitting the laser introduced from the second amplification medium; and a reflective mirror spaced apart from one side of the saturable absorber and reflecting again the laser introduced from the saturable absorber. The reflected laser is re-amplified while being sequentially transmitted through the saturable absorber, the second amplification medium, and the first amplification medium so as to be output to the outside. According to the present invention, the amplified spontaneous emission components generated in the amplification media can be effectively suppressed by using the saturable absorber added between the amplification media and the reflective mirror. Therefore, the output of the laser can be increased by increasing the maximum energy capacity of the pumping energy which can be stored in the amplification media.

Description

Solid state laser apparatus having saturable absorber for suppressing amplified spontaneous emission

The present invention relates to a solid state laser device having a saturable absorber for suppressing spontaneous amplification emission, and more particularly, by utilizing a saturable absorber to suppress spontaneous amplification emission components naturally occurring in the amplification medium and thereby laser output performance and operational stability. It relates to a solid state laser device that can improve the.

With the development of the electronics industry, high specifications of lasers are required. In particular, when amplifying the seed laser (Seed Laser) can be used to implement a high power laser system.

The solid state laser system outputs a laser beam using a solid medium amplification medium (Gain Medium). The amplification medium stores energy pumped by a pumping source (eg, flash lamp), and when a seed laser is input to the pumped amplification medium, a high power laser may be output. Here, higher laser power can be obtained when the pumping energy is increased or the power of the pumping source and the seed laser is increased.

However, when the amount of energy accumulation in the amplification medium is higher than a certain level, light is naturally emitted in the amplification medium, and amplified spontaneous emission (ASE) is generated in which the accumulated energy is absorbed and emitted. In addition, the higher the energy accumulation, the greater the loss due to natural amplification emission, which slows down the increase in gain of the amplification medium.

1 is a diagram for explaining a relationship between energy accumulated in an amplification medium of a laser device and an amplification gain.

1 is the magnitude of the pumping energy stored in the amplification medium, and the vertical axis is the gain of the amplification medium. In Fig. 1, the dotted line represents the gain of the amplification medium in an ideal situation and the real line represents the gain of the actual amplification medium.

As shown in FIG. 1, in an ideal situation, as the energy accumulated in the amplification medium increases, the gain also increases and the gain increase gradually increases.

However, in real situations, when the energy capacity accumulated in the amplification medium is above a certain level, the loss due to natural amplification emission occurs and the gain increase starts to slow down, especially as the energy capacity increases. Become. In other words, the gain increase gradually slows down after the inflection point occurs in the gain graph.

Therefore, the energy must be stored until the point of spontaneous amplification emission and it is not meaningful to store above the limit energy.

Conventionally, in order to reduce the influence of natural amplification emission, a method of increasing the distance between the amplification media or adding a spatial filter, an optical rectifier, a reflector, etc. is used. However, these conventional methods increase the complexity of the structure or the natural amplification emission. There was a limit to suppressing the ingredients.

The background technology of the present invention is disclosed in Korea Patent Registration No. 10-0789278 (2008.01.02 notification).

The present invention provides a solid state laser device having a saturated absorber for suppressing a natural amplification emission, which can effectively suppress a natural amplified emission component generated in an amplification medium by utilizing a saturated absorber, thereby improving output performance and operational stability of the laser. There is a purpose.

The present invention relates to a solid state laser device for suppressing Amplified Spontaneous Emission (ASE), comprising: a first amplification medium storing pumping energy supplied by a pumping source and amplifying and transmitting a laser input from the outside; And a second amplifying medium which stores pumping energy supplied by a pumping source, is spaced apart from one side of the first amplifying medium, and amplifies and transmits the laser introduced from the first amplifying medium again. And a saturable absorber spaced apart from one side of the second amplification medium so as to suppress a natural amplification emission component generated in the second amplification medium, and a saturable absorber for transmitting the laser introduced from the second amplification medium, and a side of the saturated absorber. And a reflecting mirror installed to reflect back the laser introduced from the saturated absorber, wherein the reflected laser comprises: Provided is a solid-state laser device that is amplified and sequentially output while passing through a saturated absorber, the second amplification medium, and the first amplification medium.

In addition, the solid state laser device may suppress the spontaneous amplified emission component by the saturable absorber, thereby increasing the maximum capacity of the pumping energy that can be stored in the first and second amplification media.

In addition, the laser input from the outside may be a pulsed laser signal.

The solid state laser device may further include a quartz rotator (QR) disposed between the first and second amplifying media, and a λ / 4 polarizing plate disposed between the saturable absorber and the reflecting mirror. Can be.

In addition, the saturated absorber is Cr: YAG, Cr: ZnS, Cr: ZnSe, V: YAG, Co: MgAl2O4, GaAs, Carbon nanotube, Graphene, Cr: YAG, Cr: ZnS , Cr: ZnSe, V: YAG, Co: MgAl 2 O 4, GaAs, carbon nanotubes, carbonene, graphene, and at least one material selected from optical materials added with rare earth ions.

In addition, the saturated absorber may be made of Cr: YAG, and the first and second amplification media may be made of Nd: YAG.

In addition, the ion concentration of the Cr contained in the saturated absorbent, the ion concentration of the Nd contained in the first and second amplifying media, the length of the saturated absorbent, and the length of each of the first and second amplifying media, respectively. May be determined by the following equation.

Where A is the ion concentration of Cr, B is the ion concentration of Nd, C is the length of the saturated absorber, and D is the length of the first and second amplification media.

According to the present invention, a saturated absorber added between the amplifying medium and the reflecting mirror can be used to effectively suppress the natural amplified emission component generated in the amplifying medium, and thereby the maximum energy capacity of the pumping energy that can be stored in the amplifying medium. Increasing the result, the result is that the output performance of the laser can be improved while at the same time ensuring the stable operation of the laser.

1 is a diagram for explaining a relationship between energy accumulated in an amplification medium of a laser device and an amplification gain.
2 is a diagram showing the configuration of a solid state laser device having a saturated absorber according to an embodiment of the present invention.
3 is a view showing a configuration excluding the saturated absorber in FIG.
4 is a diagram in which the number of each point is given on the laser path of FIG. 3.
FIG. 5 is a diagram illustrating the number of each point on the laser path of FIG. 2.
6 and 7 are diagrams showing the results of simulation of the laser intensity observed at each point of FIGS. 4 and 5, respectively.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present disclosure.

2 is a diagram showing the configuration of a solid state laser device having a saturated absorber according to an embodiment of the present invention.

As shown in FIG. 2, the solid state laser device 100 according to an exemplary embodiment of the present invention may include a first amplifying medium 110, a second amplifying medium 120, a saturated absorber 130, a reflective mirror 140, and quartz. It includes a rotator 150, and a polarizing plate 160, and receives a seed laser (hereinafter referred to as a laser) output from an external oscillator to amplify it and output it.

The first and second amplification media 110 and 120 store pumping energy supplied by a pumping source, respectively, and amplify the input laser signal to a larger size.

The pumping source may be a flash ramp that provides light to each amplification medium 110, 120, and other known means may be used. The pumping source may be provided separately for each amplification medium 110, 120 and may be included as a component in the laser device.

The first and second amplification media 110 and 120 may be configured as Nd: YAG, respectively, and may be implemented in the form of Nd: YAG rods having a long longitudinal direction, as shown in FIG. 2.

The first amplification medium 110 receives a laser output from a resonator (not shown) and amplifies and transmits the laser. Here, the laser provided by the resonator may be a pulsed laser signal. The first amplification medium 110 amplifies and outputs the pulsed laser signal input from the resonator using pumping energy.

The second amplification medium 120 is spaced apart from one side of the first amplification medium 110, and amplifies and transmits the seed laser introduced from the first amplification medium 110 again. The second amplification medium 120 also amplifies and outputs the pulsed laser signal input from the second amplification medium using pumping energy. Accordingly, amplification is performed twice before the laser signal is transmitted to the reflection mirror 140.

A saturable absorber 130 (SA) is installed on one side of the second amplification medium 120 to provide amplified spontaneous emission (ASE) component generated in the first and second amplification medium (110,120). Suppress it. As such, the saturated absorber 130 serves to absorb the natural amplified emission signal and may be made of a material such as Cr: YAG.

Natural Amplified Release (ASE) is a naturally occurring (self-induced release) when a certain amount of pumping energy is stored in the amplification medium, as described in the background art, and substantially slows the increase in the amplification gain of the amplification medium. It must be suppressed because it becomes a factor.

In an exemplary embodiment of the present invention, the first and second amplifying mediums may be added by adding a saturated absorber 130 to one side of the second amplifying medium 120 corresponding to the second amplifying medium 120 and the reflecting mirror 140. It can be suppressed by effectively absorbing the natural amplified emission (ASE) component generated in the 110,120.

In terms of the laser's ingress path, the pulsed laser signal passes through the first and second amplification media 110, 120 in turn, so that the saturable absorber in order to suppress both the effects of spontaneous amplification emission (ASE) by the two amplification media 110, 120. 130 is preferably added between the second amplification medium 120 and the reflecting mirror 140.

The saturable absorber 130 transmits the laser amplified by the first and second amplification media 110 and 120 toward the reflective mirror 140. At this time, since the saturable absorber 130 has the property of absorbing the signal as described above, it does not transmit all of the laser, but transmits the remaining part of the absorbed portion to the reflective mirror 140. This principle applies equally to the laser reflected back from the reflecting mirror 140 later. Data relating to this will be described later.

Of course, when the saturated absorber 130 absorbs the natural amplified emission (ASE) component, it absorbs at a high absorption rate and transmits the laser beam at a relatively high transmittance. This is also related to the absorption rate gradually lowering when energy is absorbed and saturated.

The reflective mirror 140 is spaced apart from one side of the saturable absorber 130, and reflects the laser introduced from the saturable absorber 130 to almost 100% again. The reflected laser is re-amplified and transmitted through the saturable absorber 130, the second amplification medium 120, and the first amplification medium 110, as shown in FIG. 2, to be output to the outside.

The λ / 4 polarizing plate 160 corresponds to the λ / 4 plate and is disposed between the saturable absorber 130 and the reflecting mirror 140. A quartz rotator 150 (QR) is disposed between the first and second amplification media 110 and 120 to cancel polarization distortion. Since the λ / 4 polarization plate 160 and the quartz rotator 150 correspond to known elements, detailed description thereof will be omitted.

In this embodiment of the present invention, the ion concentration of Cr included in the saturated absorber 130, the ion concentration of Nd included in the first and second amplifying media 110 and 120, respectively, the length of the saturated absorber 130, and the first And the length of each of the second amplification media 110 and 120 may be determined by Equation 1 below.

Here, A is the ion concentration of Cr, B is the ion concentration of Nd, C is the length of the saturated absorber 130, D is the length of the first and second amplification medium (110, 120). Here, the length may mean the length of the left and right of each element shown in FIG.

Of course, the optimum efficiency of the laser device may vary depending on the type of medium, the operating voltage and the like.

In addition, in the embodiment of the present invention, the saturated absorber 130 is not necessarily limited to Cr: YAG material, Cr: YAG, Cr: ZnS, Cr: ZnSe, V: YAG, Co: MgAl 2 O 4, GaAs, carbon nanotubes ( Carbon nanotube), graphene (Graphene), may comprise at least one material selected from the added optical material rare earth ions.

In this embodiment of the present invention, after the seed laser introduced into the solid state laser device 100 is amplified twice while sequentially passing through the first amplification medium 110 and the second amplification medium 120, the amplified laser signal is Attenuation was slightly attenuated twice via the saturable absorber 130 before and after reflection by the reflecting mirror 140, and then added twice, in turn via the second amplification medium 120 and the first amplification medium 110 in turn. Is amplified. As a result, a high power laser can be output as a result.

In particular, in the embodiment of the present invention, the natural amplified emission (ASE) component is suppressed by the saturable absorber 130, thereby increasing the maximum capacity of pumping energy that can be stored in the first and second amplification media 110, 120, respectively. Increasing the capacity of the pumping energy means improving the output size of the laser.

In the exemplary embodiment of the present invention, Nd: YAG rods having a diameter of 0.5 inch and a length of 85 mm were used as amplification media, respectively, and Nd: YAG rods of the corresponding specification were used in a state in which a saturated absorber 130 was added. As a result, pumping energy of up to 1.82 J was found to be measurable. However, when there is no saturated absorber as shown in FIG. 3, only 1.55 J of pumping energy can be stored.

3 is a view showing a configuration excluding the saturated absorber in FIG. In the case of Figure 3, as a result of operating the flash lamp of the same conditions in the Nd: YAG rod of the same specification in the state where the saturable absorber 130 is removed, it was shown that up to 1.55 J of pumping energy is stored.

When the saturable absorber 130 is added, the inflection point as shown in FIG. 1 may occur later while the natural amplification emission (ASE) component is suppressed, and a larger amount of pumping energy may be stored.

As such, the embodiment of the present invention increases the maximum storage capacity of the pumping energy by inserting the saturable absorber 130, thereby storing more capacity of the pumping energy in the amplification medium than before. Since the increase in the capacity of the pumping energy stored in the amplification medium leads to an increase in the gain of the amplification medium, it is possible to provide a higher power laser signal than the conventional one.

Of course, when a saturated absorber is added to the solid state laser device based on the same output performance (output energy), the natural amplified emission (ASE) component can be suppressed unlike the case where the solid state laser device is more stable. This also provides the effect.

Hereinafter, the result of simulating the laser output performance before and after insertion of a saturated absorber is compared and demonstrated.

4 is a diagram illustrating the number of each point on the laser path of FIG. 3, and FIG. 5 is a diagram illustrating the number of each point on the laser path of FIG. 2.

In FIG. 4 and FIG. 5, the seed laser applied through point ① is internally amplified, reflected, and again amplified and then output through point ⑥.

As described above, up to 1.55 J of pumping energy is stored for FIG. 4 without a saturable absorber. However, in the structure of FIG. 5 according to the present embodiment in which the saturated absorber is present, it can be seen that pumping energy of up to 1.82 J, which is about 20% higher capacity, is stored.

FIG. 6 is a diagram illustrating a result of simulation of laser intensity observed at each point of FIG. 4.

The graph included in FIG. 6 is an intensity value according to time t, and the laser intensity in J units can be obtained by using the area of the lower portion of the graph.

Referring to FIG. 6, the seed laser of 1 mJ input at point ① is amplified to 6 mJ (②) through the first amplification medium and then amplified to 40 mJ (③) through the second amplification medium. Subsequently, the 40 mJ (④) laser reflected from the mirror and returned as it is is amplified to 245 mJ (⑤) through the second amplification medium, and then amplified to 1 J (⑥) through the first amplification medium and finally output.

Thus, in the structure of FIG. 4 without a saturated absorber, 1 mJ laser is input and 1 J laser is output.

FIG. 7 is a diagram illustrating a result of simulation of laser intensity observed at each point of FIG. 5. Here, the notation in parentheses next to each numerical value at the top of FIG. 7 indicates the results of FIG. 6 for ease of comparison.

First, the 1 mJ seed laser input at point ① is amplified to 8.26 mJ (②) through the first amplification medium 110 and then amplified to 74.6 mJ (③) through the second amplification medium 120. .

The amplified laser passes through the saturable absorber 130 and enters the reflecting mirror 140 and then is reflected again, passing through the saturable absorber 130 again, so that two attenuation (signal absorption) processes occur. It can be seen that mJ (④) has decreased.

From the point ④, it can be seen that the case where no saturated absorber is inserted shows a higher signal strength than when the saturated absorber is inserted. However, after the point ④, while passing through the second amplification medium 120, the effect of substantial amplification gain improvement due to the increase in pumping energy capacity in the amplification medium (1.55-> 1.82 J) occurs.

That is, the 38 mJ (④) laser passing through the saturated absorber 130 is amplified to 307 mJ while passing through the second amplification medium 120, and then 1.39 J (⑥) while passing through the first amplification medium 110. Amplified to the final output. 1.39 J represents about 40% higher intensity than 1 J.

As a result, in the structure of FIG. 4 without the saturable absorber, the laser of 1 mJ is input and output 1 J laser, whereas in the structure of FIG. 5 according to the present embodiment with the saturable absorber, due to the increase of the maximum pumping energy capacity. We can see that the laser outputs 1.39 J much higher than 1 J.

This means that the gain increase effect due to the increase in the maximum pumping energy capacity of the amplification medium is much greater than the signal attenuation and loss effects of the insertion of the saturated absorber 130.

From these results, it can be seen that the saturated absorber 130 absorbs and suppresses at a high absorption rate when absorbing the natural amplified emission (ASE) component, and transmits the laser beam at a relatively high transmittance.

The embodiment of the present invention mainly uses the generation of high energy pulses through the suppression of spontaneous amplified emission (ASE), but may be used for the stable operation of the laser as needed. For example, pulse generation with 1 J of energy is possible without a saturable absorber (SA), but this is close to the limit of spontaneous amplification emission (ASE), resulting in less stable output and instantaneous spontaneous amplification due to external factors. Rash of the ASE) component may appear. However, when the saturated absorber SA is inserted, energy of 1 J can be stably oscillated without concern about the above-described natural amplification emission (ASE).

According to the present invention as described above, by using a saturated absorber added between the amplification medium and the reflection mirror, it is possible to effectively suppress the natural amplification emission component generated in the amplification medium, and through this, the maximum of the pumping energy that can be stored in the amplification medium. By increasing the energy capacity, it is possible to improve the laser's output performance as a result and to ensure the stable operation of the laser.

Although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

100: solid state laser device 110: first amplification medium
120: second amplification medium 130: saturated absorber
140: reflection mirror 150: quartz rotator
160: polarizing plate

Claims (7)

A solid state laser device that suppresses spontaneous amplified emission (ASE),
A first amplification medium that stores the pumping energy supplied by the pumping source and amplifies and transmits the laser input from the outside;
A second amplifying medium that stores pumping energy supplied by a pumping source, is spaced apart from one side of the first amplifying medium, and amplifies and transmits the laser introduced from the first amplifying medium again;
A saturated absorber installed at one side of the second amplifying medium to suppress the natural amplifying emission component generated in the first and second amplifying media and transmitting a laser beam introduced from the second amplifying medium; And
It is installed on one side of the saturable absorber and includes a reflecting mirror to reflect back the laser flowing from the saturable absorber,
The reflected laser,
And amplified through the saturable absorber, the second amplification medium, and the first amplification medium in order to be re-amplified and output to the outside. The method according to claim 1,
And the natural amplified emission component is inhibited by the saturable absorber so that the maximum capacity of the pumping energy that can be stored in the first and second amplification media is increased. The method according to claim 1,
The laser input from the outside,
Solid state laser device that is a pulsed laser signal. The method according to claim 1,
A quartz rotator (QR) disposed between the first and second amplification media; And
And a λ / 4 polarizing plate disposed between the saturable absorber and the reflecting mirror. The method according to claim 1,
The saturated absorber,
Cr: YAG, Cr: ZnS, Cr: ZnSe, V: YAG, Co: MgAl2O4, GaAs, Carbon nanotube, Graphene, Cr: YAG, Cr: ZnS, Cr: ZnSe, V: A solid state laser device comprising at least one material selected from YAG, Co: MgAl 2 O 4, GaAs, carbon nanotubes, graphene, and optical materials added with rare earth ions. The method according to claim 1,
The saturable absorber is made of Cr: YAG, and the first and second amplification media are made of Nd: YAG. The method according to claim 6,
The ion concentration of the Cr contained in the saturated absorbent, the ion concentration of the Nd contained in the first and second amplifying media, the length of the saturated absorbent, and the length of each of the first and second amplifying media are Solid state laser device determined by the equation:

Where A is the ion concentration of Cr, B is the ion concentration of Nd, C is the length of the saturated absorber, and D is the length of the first and second amplification media.

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