KR20150078940A - Q-switched Yb:KYW planar waveguide laser Device by evanescent-field-interaction with carbon nanotubes and method of manufacturing the same - Google Patents

Abstract

The present invention relates to an Yb:KYW planar waveguide laser device Q-switched by evanescent-field-interaction with a carbon nanotube and a manufacturing method thereof and, more specifically, to a laser device and a manufacturing method thereof, capable of directly manufacturing a carbon-nanotube-based SWCNT-SA on a planar waveguide, and forming a nanosecond pulse by being Q-switched by evanescent-field-interaction with a carbon nanotube. To achieve the purpose, the Yb:KYW planar waveguide laser device Q-switched by evanescent-field-interaction with a carbon nanotube is a laser device using a single wall carbon nanotube. The device includes a planar waveguide formed on a KYW substrate and having an Yb:KYW material as a gain medium; the carbon-nanotube-based SWCNT-SA; a single mode laser diode; at least one aspheric lens; at least one mirror; a faraday isolator for preventing damage to a pumping light source, caused by retro-reflection from the mirror and the gain medium; and a half-wave plate for setting P-polarization.

Description

Q-Switched Yb: KYW Planar Waveguide Laser Device and its Fabrication Method by Interaction of Carbon Nanotubes with Destructive Fields same}

More particularly, the present invention relates to a Q-switched Yb: KYW plane waveguide laser device and a method of manufacturing the same. More particularly, the present invention relates to a carbon nanotube-based saturable absorber (SWCNT-SA) To a laser device that directly forms on a waveguide and thus forms a nanosecond pulse by Q-switching through an extinction field interaction with a carbon nanotube, and a manufacturing method thereof.

The present invention was derived from a research carried out by the Ministry of Education and the Korea Research Foundation as part of a project to support a large researcher [project assignment number: 2011-0017494 Title: Low-Dimensional Carbon Nanostructured Photonics: Synthesis and Control, Broadband Optical Characteristic Analysis and Understanding, Photonics Device Development and Application].

A pulsed laser refers to a laser capable of obtaining a pulsed output in contrast to a continuous wave laser. Among pulse lasers, the development of ultra-high speed pulse lasers has greatly contributed to many fields such as large-capacity optical signal processing, high-speed sensing, fine processing, and nondestructive inspection.

In order to generate a pulse train having a short pulse width and a high repetition rate in a pulse laser, it is impossible to insert a mechanical switch for on / off in the laser resonator. To achieve this, mode-locking ) Technology was developed.

Mode - locking technology is largely divided into active mode - locking and passive mode - locking method.

The active mode locking method includes a forced mode locking mode in which a modulator is provided in a laser to the same frequency as an external modulation signal and a magnetic mode locking mode occurs spontaneously due to nonlinearity of the laser medium. There is a method of using a saturable absorber (SA), in which the saturable absorber serves to match the starting points of the various modes so that the phases of the modes start to match each other Thereby generating an ultrashort pulse.

The saturable absorber refers to an optical element having a different absorption rate of light depending on the intensity of an incident beam. In general, a saturable absorber has a property of decreasing the absorption rate as the intensity of light becomes stronger, .

Therefore, a method of fabricating the above-mentioned saturated absorber using various materials can be easily achieved by inserting a saturated absorber having such characteristics into a laser to induce passive mode-locking or Q-switching.

On the other hand, waveguide laser refers to a laser having a gain medium of an optical waveguide structure. Since it can obtain high gain efficiency from efficient beam superimposition, it is suitable for use of a low gain gain medium and a laser capable of operating with a low pump. However, since the fabrication of the waveguide gain medium is not easy until now, the contents related to the laser operation have been mainly reported.

Accordingly, various attempts have been made to develop a laser device which can cope with various gain mediums with respect to a waveguide laser, achieve high efficiency at low cost, and cope with various operation modes.

In particular, solid waveguide pulsed laser with a neodymium-doped glass as a gain medium was first reported in 1994 for a solid-state waveguide laser with a resonator in the form of a Fabry-Perot. After that, Yb: YAG, Yb: KYW , Tm: KYW, and so on.

However, since most lasers operate in a direct coupling manner with a laser beam by using a saturable absorber mirror (SESAM), which is the most widely used saturable absorber, in the case of a waveguide laser having a small beam size, Damage problems frequently occur.

In particular, although the saturable absorption mirror is widely used as a light switching device for a laser because of its ability to control the characteristics of the device, the manufacturing process is complicated and requires expensive equipment.

In the case of a solid waveguide laser in which the resonator is formed in the form of a Fabry-Perot type, since the saturated absorption mirror is generally in the form of a mirror, there is a problem in limiting the configuration of the resonator of the Fabry-Perot type, which is difficult to apply to a solid waveguide laser.

As an alternative to this, an indirect coupling type with a laser beam is proposed based on the extinction field interaction, which can avoid the disadvantages of the above-mentioned direct coupling type saturated absorber, that is, frequent damage.

In the study of pulse laser oscillation using extinction field interactions, there is a case where a saturated absorber based on BDN dye is used in the development of pulsed solid waveguide lasers, but the dye saturable absorber itself is harmful to the human body, And the damage threshold is low. Since the reported laser itself uses the polished waveguide surface as the output light, related development studies are still rare.

Single-walled carbon nanotubes (SWCNTs) are known to operate as saturable absorbers in fiber lasers for the first time in 2004, and are now available in a smaller nano-size than other devices, ultra-fast recovery times of 1-2 ps In this study, we have investigated the effect of high-power lasers on the performance of lasers. In this study, we have investigated the effect of high-power lasers And a drawback that durability and stability are deteriorated due to weak mechanical strength in itself, so that the solid-state laser-related research is still difficult.

Korean Patent No. 1091159 entitled " Ultra-fast carbon nanotube saturable absorber for mode locking of a solid laser oscillated in a 1 mu m area " discloses that a single walled carbon nanotube (SWCNT) produced by an electric discharge method is dissolved in dichlorobenzene Forming a SWCNT / PMMA composite by mixing the carbon nanotube solution with PMMA (polymethyl methacrylate), and then forming the SWCNT / PMMA composite on the substrate through a spin coating method to form a thin film To obtain a saturated absorber.

However, the prior art has shown that carbon nanotube saturation (SESAM), which can replace saturated absorption mirrors (SESAM) to make ultra-fast pulse emitting solid state lasers, Since the saturable absorber manufactured by the prior art operates in a direct coupling manner with the laser beam in the same manner as the conventional saturated absorption mirror (SESAM), a waveguide laser having a small beam size In this case, the problem of damage to the device may frequently occur. Moreover, since it is a mirror shape similar to that of a saturated absorption mirror, it is difficult to apply it to a solid waveguide laser because there is a problem of limiting the configuration of a resonator of a Fabry- The prior art also introduces a mode-locked technique through the fabricated saturated absorber, which has the disadvantage that it can not implement pulses with large energies such as Q-switching techniques.

In the case of a laser device, control of characteristics of the device plays an important role according to purposes, and in particular, in the case of a laser for mode-locked and a laser for Q-switching, The characteristics are different. It is generally known that the larger the modulation depth, the more Q-switching occurs. However, since the modulation depth of the device manufactured in the above-described prior art is not large, it does not operate properly when applied to a laser for Q-switching purpose.

Therefore, it is required to develop a laser device capable of achieving high efficiency at low cost, meeting the purpose of use, and minimizing damage to the device even if it is continuously used.

Korean Registered Patent No. 1091159 (Registered on December 1, 2011)

The present invention aims at inducing a Q-switching operation through a single walled carbon nanotube-based saturable absorber (SWCNT-SA) in a Yb: KYW plane solid waveguide laser.

The present invention aims at performing nanosecond Q-switching oscillation by extinction field interaction in a solid plane waveguide laser.

It is an object of the present invention to develop a very small planar waveguide pulsed laser through a single-walled carbon nanotube-based saturated absorber directly formed on a planar waveguide capable of extinction field interaction and a lens positioned in the resonator.

The present invention aims at presenting a structure of a new Q-switched plane waveguide laser.

The present invention aims at independently controlling the laser components.

In order to achieve the above object, a Q-switched Yb: KYW plane waveguide laser device having a Fabry-Perot structure due to the extinction field interactions with carbon nanotubes according to the present invention includes a KYW substrate A planar waveguide formed on the planar waveguide and having a Yb: KYW material as a gain medium, and a saturable absorber formed by coating a single-walled carbon nanotube-based dispersion solution on one side of the planar waveguide, Is a Yb: KYW plane waveguide laser device that interacts with the evanescent field in the vicinity to cause the Q-switching operation of the laser device.

At this time, the single-walled carbon nanotube as a base of the dispersion solution is prepared by an arc discharge method (or an electric discharge method), and the dispersed solution is prepared by dispersing the produced single-walled carbon nanotube in dichlorobenzene Centrifuging, and then mixing a part of the separated solution with PMMA (polymethyl methacrylate). In addition, the saturated absorber is prepared by coating the prepared dispersion solution on the planar waveguide and then drying it on a hot plate.

In addition, the Q-switched Yb: KYW plane waveguide laser device using a single-walled carbon nanotube, which is formed on a KYW substrate by a quenching field interaction with a carbon nanotube according to the present invention, A planar waveguide as a medium, an optical nonlinear saturable absorber formed by coating a dispersion solution prepared using the single-walled carbon nanotube on the planar waveguide and inducing Q-switching by extinction interaction, At least one aspheric lens, at least one mirror, a gain medium and a Faraday diaphragm to prevent damage to the pumping light source due to retroreflection in the mirror. ≪ RTI ID = 0.0 > A faraday isolator, and a half-wave plate for aligning the p-polarized light.

At this time, the saturable absorber controls the concentration of the carbon nanotubes used for producing the dispersion solution and the ratio of at least one solvent substance (DCB or PMMA, etc.) mixed in the dispersion solution production process, The characteristics can be controlled by adjusting the number of times of coating on the planar waveguide.

Meanwhile, a Q-switched Yb: KYW plane waveguide laser is produced by a liquid phase deposition method on a KYW substrate by using a planar waveguide having a Yb: KYW material as a gain medium, Preparing a single-walled carbon nanotube by using an arc discharge method, preparing a dispersion solution by using the single-walled carbon nanotube prepared above, and dispersing the dispersed solution on the planar waveguide Coating a carbon nanotube-based saturated absorber.

The step of fabricating the saturable absorber may include coating the planar waveguide with the planar waveguide so that the saturable absorber interacts with the evanescent field around the planar waveguide to induce a Q- And is integrally formed.

The step of preparing the dispersion solution may be performed by dispersing the prepared single-walled carbon nanotube in dichlorobenzene, centrifuging the separated single-walled carbon nanotube, and mixing a part of the separated solution into PMMA (polymethyl methacrylate) , And the step of preparing the saturated absorber can be produced by coating the dispersed solution on the planar waveguide and then drying it on a hot plate.

According to the present invention, a Q-switching operation can be induced through a single-wall carbon nanotube-based saturable absorber (SWCNT-SA) for the first time in a Yb: KYW plane solid waveguide laser.

The giant medium / Q-switching optical device integrated structure based on the excellent optical characteristics and the extinction field interactions of the carbon nanotube adopted in the present invention can be similarly applied to various other waveguide structures.

(SWCNT-SA) based on single-walled carbon nanotubes (SWCNT-SA) on a waveguide and enables pulse oscillation through extinction field interactions, thereby overcoming the problems of low structural constraints and low fracture thresholds .

The present invention has the effect of developing a very small flat waveguide pulse laser through a single-walled carbon nanotube-based saturated absorber fabricated directly on a gain medium capable of extinction field interaction and a lens positioned in the resonator.

The present invention has the effect of independently controlling the laser components such as the type and position of the saturated absorber, the pulse oscillation due to the extinction field interaction, and the type of the output beam.

The present invention can be applied to the development of a new concept ultra-small pulse laser light source operating in a 1 μm wavelength band and various optical measurement and measurement devices based on the same. Pulse light source technology which can be directly manufactured in an integrated circuit, It can be applied as a key element in the industry.

Since the present invention induces the Q-switching technique due to the extinction field interaction, the energy per pulse is largely realized in the laser operation, and thus it is applicable to various fields such as laser surgery / treatment.

It is believed that the present invention can be used in a wide range of optical characteristics because it is compatible with a comparatively inexpensive general-purpose photodiode.

FIG. 1 is a schematic view of a Q-switched Yb: KYW plane waveguide laser device due to the extinction field interactions with carbon nanotubes according to an embodiment of the present invention.
FIG. 2 is a view for explaining an extinguishing field interaction in a Q-switching operation according to an embodiment of the present invention.
3 is a schematic flow diagram of a method for fabricating a gain medium / saturated absorber integrated structure according to an embodiment of the present invention.
4 is a flowchart of step S320 of FIG. 3 according to an embodiment of the present invention.
5 is a graph illustrating a characteristic of a single-walled carbon nanotube according to an embodiment of the present invention.
6 is a graph showing an experimental result in a continuous oscillation state according to an embodiment of the present invention.
7 is a diagram illustrating experimental results in a Q-switching operation according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. In the following description of the embodiments of the present invention, specific values are only examples.

More particularly, the present invention relates to a Q-switched Yb: KYW plane waveguide laser device and a method of manufacturing the same. More particularly, the present invention relates to a carbon nanotube-based saturable absorber (SWCNT-SA) To a laser device that directly forms on a waveguide and thus forms a nanosecond pulse by Q-switching through an extinction field interaction with a carbon nanotube, and a manufacturing method thereof.

The Q-switching technique to be implemented in the present invention is advantageous in that it can implement a pulse having a larger energy than a mode-locked technique. In addition, Q-switching technology can be applied to various fields such as laser surgery / treatment because the energy per pulse is realized large in laser operation. On the other hand, since the mode-locking technique determines the pulse cycle according to the length of the waveguide, It is useful.

On the other hand, the optical characteristics of the saturated absorber that can lead to the Q-switching operation should match well with the type of light source and gain medium to obtain the desired effect. In particular, the present invention can reduce the manufacturing cost by using an inexpensive photodiode because the absorption wavelength band of the Yb: KYW gain medium matches the wavelength of the photodiode, and in the case of the SWCNT-based saturable absorber operation, the emission of the Yb: KYW gain medium The wavelength band is well matched to the absorption wavelength band of SWCNT, and thus the range of utilization can be wide.

Meanwhile, the Q-switched Yb: KYW plane waveguide laser device can be realized in a Fabry-Perot type resonator structure due to the extinction field interaction with the carbon nanotube according to the present invention.

The Fabry-Perot resonator refers to a highly resonant optical resonator with two highly reflective facets placed in front of it. Fabry-Perot resonators using spherical reflective mirrors are most commonly used in many lasers, and confocal Fabry-Perot resonators are formed by a pair of equivalent spherical reflective mirrors that share a focus on the optical axis, and are used for observing laser oscillators and output spectra. Used a lot.

Therefore, the present invention describes a Yb: KYW plane solid waveguide laser device having a Fabry-Perot structure and a manufacturing method thereof.

FIG. 1 is a schematic view of a Q-switched Yb: KYW plane waveguide laser device due to the extinction field interactions with carbon nanotubes according to an embodiment of the present invention.

First, the components of the present invention will be briefly described with reference to FIG. 1, and the manufacturing method will be described in detail.

Referring to FIG. 1, WG represents a Yb: KYW plane waveguide formed on a KYW substrate as a gain medium. The Yb: KYW; means a KYW with a Yb ^{3 +} doped. The WG more specifically refers to a KYW substrate and a Yb: KYW plane waveguide produced by doping Yb ^{3 +} on the KYW substrate. SWCNT-SA means a single-walled carbon nanotube-based saturated absorber thin film directly manufactured by the present invention, which is formed by coating on a Yb: KYW plane waveguide of a gain medium.

KYW is an abbreviation for Potassium Yttrium Tungstate. In 2006, KYW was founded by the Ecole Polytechnique Federale de Lausanne in Switzerland and the Max-Born-Institute for Germany An example of using Yb: KYW waveguide structure with yb (Yb) added to a KYW material with KY (WO4) 2 as a laser waveguide is shown by the researchers of Nonlinear Optics and Ultrafast Spectroscopy. It will be apparent to those skilled in the art that there will be no difficulty in understanding the waveguide structure of the Yb: KYW material from the description of the present invention.

At this time, the singular point of the present invention is that the saturated absorber (SWCNT-SA) is manufactured on the gain medium (WG), so that the saturated absorber and the gain medium are formed into an integral structure, and Q- . In other words, the present invention has the significance of the present invention in inducing the Q-switching through the extinction field interaction with the carbon nanotubes by forming the gain medium and the saturated absorber into an integral structure. The integrally formed structure is represented by a gain medium / saturated absorber integrated structure, a gain medium / Q-switching photonic integrated structure, a gain medium / optical switching element monolithic structure, and a WG / SWCNT-SA monolithic structure. Meanings are all equivalent.

Next, L1 and L2 are aspheric lenses, M is a total reflection mirror, and OC is the output diameter. In addition, the length of the entire resonator is 2.5 cm, and the 980 nm pump means that the laser pumping light source of the present invention uses a single mode laser diode that oscillates at 980 nm and emits a maximum power of 750 mW.

The present invention relates to a carbon nanotube-based waveguide using a Yb: KYW plane waveguide of Yb: KY (WO ₄ ) ₂ as a gain medium and a carbon nanotube (SWCNT) (SWCNT-SA), and then forms a pulse through extinction field interaction. This is important for inducing the Q-switching phenomenon through extinction field interactions. Therefore, the following description will explain in detail a method for manufacturing a gain medium / saturated absorber integrated structure, which is a singular point of the present invention.

3 is a schematic flow diagram illustrating a method of fabricating a gain medium / saturated absorber integral structure in accordance with an embodiment of the present invention.

3, the Yb: KYW plane waveguide is obtained by growing Yb: KYW on a 1 mm thick KYW substrate by a liquid phase epitaxy method. The Yb: KYW plane waveguide has a Yb ^{3 +} atomic ratio (Yb: KYW planar waveguide) having a thickness of 26.4 μm is fabricated by doping the first planar waveguide (first planar waveguide) with 1.7 at.%. The present invention did not deposit additional KYW for the symmetry of the guided beam because it intends the extinction field interaction with the carbon nanotubes in the process of manufacturing the Yb: KYW plane waveguide (gain medium). Then, both surfaces of the Yb: KYW plane waveguide fabricated in step S300 are polished well and then cut to a length of 6 mm, thereby completing fabrication of a gain medium (WG) having a Yb: KYW material, that is, a Yb: KYW plane waveguide formed on the KYW substrate (S310).

Then, a carbon nanotube-based saturable absorber (SWCNT-SA) is fabricated on the Yb: KYW plane waveguide (S320), which is one side surface of the gain medium manufactured in step S310 (S320) Will be described in detail with reference to FIG. Therefore, when the step S320 is completed, the fabrication of the gain medium / saturated absorber integrated structure capable of Q-switching induction is completed (S330).

4 is a flowchart of step S320 of FIG. 3 according to an embodiment of the present invention.

Referring to FIG. 4, in the method of manufacturing the carbon nanotube-based saturated absorber (SWCNT-SA), a single-walled carbon nanotube is manufactured by an arc discharge method (S400). The arc discharge method refers to a method in which a current of about 100 A flows between two carbon rods to vaporize carbon to re-condense into a nanotube form. When carbon nanotubes are manufactured using this method, can do.

According to an embodiment of the present invention, the single-walled carbon nanotube may be a HiPco SWCNT or a single-walled carbon nanotube (SWNT) synthesized under a high-pressure carbon monoxide (CO) condition . The HiPco SWCNT has the effect of forming a uniform and small size distribution of the material during synthesis.

Thereafter, the single-walled carbon nanotube (SWCNT) produced by the arc discharge method was dispersed in 1,2-dichlorobenzene (DCB) and centrifuged at 20000 g for 30 minutes. Then, about 70% Is mixed with polymethyl methacrylate (PMMA) to prepare a dispersion solution (S410).

Then, the dispersed solution prepared in step S410 is coated on the Yb: KYW plane waveguide manufactured in step S310, and then dried on a hot plate to produce a carbon nanotube-based saturated absorber (SWCNT-SA) on the gain medium (S420). At this time, when the dispersion solution is coated on the Yb: KYW plane waveguide corresponding to the gain medium, the edge portions are not coated to prevent damage due to beam focusing at the edge of the Yb: KYW waveguide.

Accordingly, the gain medium / saturated absorber integrated structure is manufactured through the process of steps S300 to S330. In the following experiment, the concentration of the carbon nanotubes (SWCNT) used for preparing the dispersion solution and the ratio of at least one solvent substance (DCB or PMMA, etc.) mixed in the dispersion solution production process are controlled, The number of times of coating on the gain medium, and the like were controlled to control the characteristics of the saturated absorber.

The following description explains the structure of the ultra-small laser device of the Fabry-Perot type based on the integrated gain / saturable absorber structure formed through the above process. This further describes the present invention based on the contents of FIG. 1 described above.

The Q-switched Yb: KYW plane waveguide laser device is a laser pumping light source that oscillates at 980 nm and emits a maximum output of 750 mW due to the extinction field interaction with the carbon nanotube according to an embodiment of the present invention. I used a laser diode. And a Faraday isolator was placed after the single mode laser diode to prevent damage to the pumping light source due to the retroreflection in the mirror or gain medium and a half wave plate was placed after the Faraday polarizing plate to align the p- Respectively.

The pump beam focusing on the Yb: KYW plane waveguide was performed through an 18 mm aspheric lens, which was an aspherical lens (L1). The focused beam passed through the total reflection mirror (M) at 980 nm high- Plane waveguide. Here, the Yb: KYW plane waveguide means a waveguide in a gain medium / saturable absorber integrated structure.

Then, a resonator was constructed by disposing an 11 mm aspheric lens (aspherical lens L2) and an output light (OC) having a transmittance of 2.4% for laser oscillation. The total length of the resonator, that is, the length between the total reflection mirror (M) and the output light (OC), was 2.5 cm. Each of the optical components of the present invention can be independently moved, thereby making it possible to manufacture a stable laser by optimizing each position after the oscillation.

FIG. 2 is a view for explaining an extinguishing field interaction in a Q-switching operation according to an embodiment of the present invention.

Referring to FIG. 2, the cross-section of the integrated gain / saturable absorber structure manufactured through the process of steps S300 to S330 of FIG. 3 can be confirmed. That is, a carbon nanotube-based saturated absorber (SWCNT) was fabricated by forming a Yb: KYW planar waveguide on a KYW substrate and coating a dispersion solution of the single-walled carbon nanotube on the Yb: KYW planar waveguide -SA) is formed in the gaseous medium / saturated absorber integrated structure.

Referring to this, most of the laser beam oscillated along the Yb: KYW doped layer (or Yb: KYW plane waveguide) travels along the Yb: KYW doping layer. In the case of some beams, Tube-based saturable absorber (SWCNT-SA) thin film. At this time, the part of the beam causes an evanescent field interaction with the carbon nanotubes, which causes non-linear absorption and Q-switching operation. This can be understood with reference to FIG.

5 is a graph illustrating a characteristic of a single-walled carbon nanotube according to an embodiment of the present invention.

Referring to FIG. 5, it can be seen that a single-walled carbon nanotube exhibits a non-linear relationship between light intensity and absorption rate. That is, a single-walled carbon nanotube has a high absorption rate when the intensity of light is weak, and thus the energy is staying for a long time. In the present invention, the extinction field interaction is formed by a small amount of beams of the oscillated laser, so that the energy is weak and the absorption rate is high. As the time elapses, the amount of energy absorbed in the saturable absorber gradually increases, so that the extinction field interaction becomes strong. When the accumulated amount of energy gradually increases, the absorptivity and the intensity of light become equal to each other, ) Will not come up. That is, when a certain critical point (a) is reached, the absorption rate is reduced and the accumulated energy is released to the outside, which can be referred to as a Q-switching operation.

This Q-switched laser has the advantage that it can implement a pulse with a large energy compared to a mode-locked laser. Accordingly, the present invention can be applied to various fields such as laser surgery / therapy by implementing a large energy per pulse in a laser operation.

6 is a graph showing an experimental result in a continuous oscillation state according to an embodiment of the present invention.

Referring to Fig. 6, the output (Fig. 6 (a)) and the spectrum (Fig. 6 (b)) appearing in the continuous oscillation state can be confirmed. It is confirmed that the transmittance at the output wavelength is 2.4% and the maximum power is 62 mW when the beam intensity entering the Yb: KYW plane waveguide of the integrated structure of the gain medium / saturable absorber is 617 mW and continuous oscillation occurs at around 1026 nm . In this case, the laser operates in multiple modes because the waveguide thickness is larger than the wavelength, and the position of the lens and the position of the output mirror can be adjusted in the range of cm when the continuous oscillation operation is performed.

Also, according to the output of FIG. 6 (a), as the pump intensity increases, the output intensity becomes large in proportion to the direct proportion relationship.

7 is a diagram illustrating experimental results in a Q-switching operation according to an embodiment of the present invention.

7 (a)), the oscillation spectrum (Fig. 7 (b)), the pulse train measurement result from the laser (Fig. 7 (c)), the laser repetition rate (FIG. 7D), the pulse width (FIG. 7E), and the pulse energy (FIG. 7F)

The Q-switching operation can be easily obtained by adjusting the position of the aspheric lens in the resonator in the state of performing the continuous oscillation operation.

The resonator was operated at a maximum output of 30 mW when the length of the resonator was adjusted to 2.5 cm (see FIG. 7 (a)), and Q-switching operation was started even at a low output at which the laser was initially oscillated. At this time, the center wavelength was 1030 nm, and the central wavelength was somewhat longer than that in the continuous oscillation operation (see FIG. 7 (b)). This is indirect evidence of the Q-switching phenomenon due to the extinction interaction with carbon nanotubes.

In addition, the laser repetition rate at the Q-switching oscillation increased as the pump intensity increased, and the maximum repetition rate was found to be 241 kHz (see FIG. 7 (d)). As in the case of a conventional Q-switching laser, the pulse width was asymptotically decreased with increasing pump intensity. The pulse width at the oscillation was 804 ns and the minimum pulse width was 433 ns (Fig. 7 ) Reference). In addition, it was confirmed that the pulse energy intensity according to the pump intensity exhibits a maintenance relationship (Fig. 7 (f)), and the pulse train change from the laser can be confirmed (Fig. 7 (c)).

In the present invention, Q-switching operation is induced by using a single-walled carbon nanotube-based saturable absorber in a Yb: KYW plane solid waveguide laser. At this time, the gain medium, which is an integrated structure of a gain medium and a Q- / In the structure of the saturated absorber integral, pulse formation is proposed through extinction field interaction. The gain medium / saturable absorber integrated structure of the present invention can be similarly applied to various other waveguide structures in the future, so that the scalability is very high.

In the present invention, the characteristics of the optical device, that is, the characteristics of the saturated absorber, are such that the concentration of the carbon nanotubes used for producing the dispersion solution, the mixing ratio of the solvent material (DCB or PMMA, It is possible to control the characteristics of the device (such as the thickness of the radius).

Also, the present invention is a carbon nanotube-based saturable absorber capable of replacing a conventional saturated absorption mirror (SESAM), which can manufacture a ultra-short-pulse-emission solid-state laser in a 1-μm band at a lower cost and easily, It is possible to mass-produce and produce laser devices with superior quality and durability over conventional methods.

More particularly, the present invention relates to a method and apparatus for the production of a saturable absorber by means of an inexpensive price from a commercialized laser diode pumping, a gain medium / saturable absorber integrated structure, autonomy of a stable resonator configuration using a lens in the resonator, High breakdown thresholds, different types of single-wall carbon nanotubes and fabrication methods, scalability to other types of waveguide lasers, and a new planar waveguide-based pulse laser structure.

As described above, the present invention has been described with reference to the specific details such as specific numerical values, the limited embodiments, and the drawings. However, the present invention is not limited to the above embodiments, Various modifications and variations may be made thereto by those skilled in the art to which the present invention pertains.

Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

WG: Yb: KYW plane waveguide formed as a gain medium on a KYW substrate
SWCNT-SA: Single-walled carbon nanotube-based saturated absorber
L1, L2: aspheric lens
M: Total Mirror
OC: Output light

Claims (10)

In a laser device having a Fabry-Perot structure,
A planar waveguide formed on a KYW (potassium-yttrium tungstate) substrate and having a Yb: KYW material as a gain medium; And
A saturable absorber formed by coating a single-walled carbon nanotube-based dispersion solution on one side of the planar waveguide;
Lt; / RTI >
Wherein the saturable absorber interacts with an evanescent field around the planar waveguide to cause a Q-switching operation of the laser device. The method according to claim 1,
Wherein the single-walled carbon nanotube as a base of the dispersion solution is manufactured by an arc discharge method. 3. The method of claim 2,
The dispersion solution
The Yb: KYW plane waveguide laser device is produced by dispersing the prepared single-walled carbon nanotube in dichlorobenzene, centrifuging the separated single-walled carbon nanotube, and mixing a part of the separated solution into PMMA (polymethyl methacrylate). The method of claim 3,
The saturable absorber
Coating the prepared dispersed solution on the planar waveguide, and then drying the dispersion solution on a hot plate to form a Yb: KYW plane waveguide laser device. As a laser using single wall carbon nanotubes,
A planar waveguide formed on a KYW (potassium-yttrium tungstate) substrate and having a Yb: KYW material as a gain medium;
An optical nonlinear saturable absorber formed by coating a dispersion solution prepared using the single-walled carbon nanotubes on the planar waveguide and inducing Q-switching by extinction interaction;
A single mode laser diode oscillating in the 980 nm wavelength band and emitting up to 750 mW;
At least one aspheric lens;
At least one mirror;
A faraday isolator for preventing damage to the pumping light source due to the gain medium and retroreflection in the mirror; And
half-wave plate for p-polarizing;
Yb: KYW plane waveguide laser device. 6. The method of claim 5,
The saturable absorber
The concentration of the carbon nanotubes used to produce the dispersion solution and the ratio of at least one solvent material mixed in the dispersion solution production process are controlled and the number of times the dispersion solution is coated on the planar waveguide is controlled Characterized in that the characteristics of the Yb: KYW plane waveguide laser device are controlled. A step of preparing a planar waveguide on which a Yb: KYW material acts as a gain medium on a KYW (potassium-yttrium tungstate) substrate by liquid phase deposition;
Preparing single-walled carbon nanotubes by an arc discharge method;
Preparing a dispersion solution using the prepared single-walled carbon nanotubes; And
Preparing a carbon nanotube-based saturated absorber by coating the dispersed solution on the planar waveguide;
Wherein the Yb: KYW planar waveguide laser is fabricated. 8. The method of claim 7,
The step of producing the saturated absorbent comprises
Wherein the saturable absorber is coated on the planar waveguide and integrated with the planar waveguide so that the saturable absorber interacts with an evanescent field around the planar waveguide to induce a Q-switching operation. Fabrication method of planar waveguide laser. 8. The method of claim 7,
The step of preparing the dispersion solution
The single-walled carbon nanotube thus prepared is dispersed in dichlorobenzene, centrifuged, and a part of the separated solution is mixed with PMMA (polymethyl methacrylate)
Wherein the Yb: KYW plane waveguide laser is fabricated. 10. The method of claim 9,
The step of producing the saturated absorbent comprises
Coating the above-prepared dispersed solution on the planar waveguide, and then drying it on a hot plate
Wherein the Yb: KYW plane waveguide laser is fabricated.

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