KR102357576B1 - Stretched pulse mode locking wavelength swept laser device and operation method thereof - Google Patents

Abstract

Disclosed are a stretch pulse mode locked wavelength sweeping laser device and an operating method thereof. According to an embodiment, the laser device comprises: an optical modulator for generating optical pulses; and a beam splitter configured to emit some of a plurality of dispersive media for dispersing an optical pulse for each wavelength or compressing an optical pulse into a single wavelength, a gain medium for amplifying the dispersed optical pulse, and the amplified optical pulse.

Description

STRETCHED PULSE MODE LOCKING WAVELENGTH SWEPT LASER DEVICE AND OPERATION METHOD THEREOF

The following embodiments relate to a stretch pulse mode-locked wavelength sweeping laser device and an operating method thereof.

Optical coherence tomography (OCT) is a technology capable of obtaining a high-resolution three-dimensional image by non-invasively photographing a sample using light interference. In particular, the Fourier domain OCT can obtain an image having a higher signal-to-noise ratio using a wavelength swept laser or a spectrometer, unlike the conventional time domain OCT.

The most important component that determines the performance of a Fourier domain OCT system that provides high-quality and high-speed images may be a wavelength swept laser. That is, the high-speed broadband wavelength-sweeping characteristic of the laser can greatly affect the performance of the Fourier domain OCT system.

For wavelength conversion lasers used in Fourier domain OCT, it is most common to use a mechanical wavelength conversion filter, such as a method of changing the wavelength by changing the voltage applied to the wavelength adjustment filter using the principle of Fabry-Perot interferometer. A method of changing the wavelength without mechanical movement has been proposed recently.

As a related prior art, there is Korean Patent Registration No. 10-1510584 (Title of the Invention: Wavelength Swept Pulse Laser Device).

The embodiments stabilize the laser by minimizing the effects of polarization rotation and polarization mode dispersion (PMD) due to birefringence in the resonator of the laser device, and the net dispersion of light generated during one rotation of the resonator of the laser device By minimizing (Net dispersion), it is possible to provide a wavelength-swept laser generation technology having a wide oscillation wavelength.

In addition, embodiments may provide a technique for adjusting the wavelength sweep repetition rate in a wide range while minimizing the resonator loss.

However, the technical tasks are not limited to the above-described technical tasks, and other technical tasks may exist.

A laser device according to an embodiment includes an optical modulator for generating an optical pulse, a plurality of dispersive media for dispersing the optical pulse for each wavelength or compressing the optical pulse into a single wavelength, and the dispersed It includes a gain medium for amplifying an optical pulse, and a beam splitter for emitting a portion of the amplified optical pulse.

The light modulator may be an optical intensity modulator that divides light into a plurality of paths and generates a light pulse by generating a phase difference between the light passing through the plurality of paths.

The light modulator, the dispersion medium, the gain medium, and the beam splitter may drive only light of one of two perpendicular optical axes.

In the laser device, the wavelength sweeping repetition rate of the emitted laser may be controlled by adjusting the length of the dispersion medium.

The plurality of dispersion media may include a plurality of chirped fiber Bragg gratings that reflect light pulses at different positions for each wavelength.

The plurality of chirped fiber Bragg gratings may include a first chirped fiber Bragg grating for dispersing an optical pulse for each wavelength and a second chirped fiber Bragg grating for compressing an optical pulse dispersed for each wavelength into a single wavelength.

The first chirped optical fiber Bragg grating disperses the optical pulse output from the optical modulator to output it to the gain medium, and the second chirped optical fiber Bragg grating compresses the optical pulse not emitted from the beam splitter to compress the optical pulse. It can be output with a modulator.

The number of the plurality of chirped fiber Bragg gratings may be adjusted to control the wavelength sweeping repetition rate of the emitted laser.

The light modulator, the dispersion medium, the gain medium and the beam splitter may be connected using a polarization maintaining fiber.

The plurality of dispersion media may include a chirped optical fiber Bragg grating for adjusting at least one of a wavelength sweeping range and a wavelength sweeping repetition rate of a laser that receives the optical pulse emitted by the beam splitter and emits it.

A method of operating a laser device according to an embodiment includes the steps of: generating an optical pulse; dispersing the optical pulse for each wavelength using a first chirped optical fiber Bragg grating; and amplifying the dispersed optical pulse; and emitting a portion of the amplified optical pulse, and compressing a non-emitted optical pulse among the amplified optical pulses into a single wavelength using a second chirped optical fiber Bragg grating.

The generating may include dividing light into a plurality of paths and generating a light pulse by generating a phase difference between the light passing through the plurality of paths.

The dispersing includes reflecting the light pulses at different positions for each wavelength.

The method of operating the laser device may include controlling the wavelength sweeping repetition rate of the emitted laser by adjusting the length of the first chirped fiber Bragg grating.

A method of operating a laser device according to another embodiment includes generating an optical pulse;

Dispersing the optical pulses for each wavelength using a plurality of chirped optical fiber Bragg gratings, amplifying the dispersed optical pulses, emitting a part of the amplified optical pulses, and the plurality of chirped optical fiber Bragg gratings and compressing a non-emitted optical pulse among the amplified optical pulses into a single wavelength by using the amplified optical pulse.

The method of operating the laser device may include controlling the wavelength sweeping repetition rate of the emitted laser by adjusting the number of the plurality of chirped fiber Bragg gratings.

A method of operating a laser device according to another embodiment includes generating an optical pulse, dispersing the optical pulse for each wavelength, amplifying the dispersed optical pulse, and emitting a portion of the amplified optical pulse The steps of: compressing a non-emitted optical pulse among the amplified optical pulses to a single wavelength; include

The adjusting may include adjusting at least one of the range and the repetition rate using at least one or more chirped fiber Bragg gratings.

1 is a view showing a conventional stretching pulse mode-locked laser device.
2A and 2B are diagrams for explaining the operation of the light intensity modulator.
3 is a diagram for explaining a chirped optical fiber Bragg grating.
4 and 5 are diagrams for explaining the problems of the conventional stretching pulse mode-locked laser device.
6 is a diagram illustrating a stretching pulse mode-locked laser device according to an embodiment.
7A and 7B are diagrams for explaining another example of a stretch pulse mode-locked laser device.
8A and 8B are diagrams for explaining another example of the stretching pulse mode locking laser device.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. However, since various changes may be made to the embodiments, the scope of the patent application is not limited or limited by these embodiments. It should be understood that all modifications, equivalents and substitutes for the embodiments are included in the scope of the rights.

The terms used in the examples are used for the purpose of description only, and should not be construed as limiting. The singular expression includes the plural expression unless the context clearly dictates otherwise. In this specification, terms such as "comprise" or "have" are intended to designate that a feature, number, step, operation, component, part, or a combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiment belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

In addition, in the description with reference to the accompanying drawings, the same components are given the same reference numerals regardless of the reference numerals, and the overlapping description thereof will be omitted. In describing the embodiment, if it is determined that a detailed description of a related known technology may unnecessarily obscure the gist of the embodiment, the detailed description thereof will be omitted.

In addition, in describing the components of the embodiment, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only for distinguishing the elements from other elements, and the essence, order, or order of the elements are not limited by the terms. When it is described that a component is "connected", "coupled" or "connected" to another component, the component may be directly connected or connected to the other component, but another component is between each component. It will be understood that may also be "connected", "coupled" or "connected".

Components included in one embodiment and components having a common function will be described using the same names in other embodiments. Unless otherwise stated, descriptions described in one embodiment may be applied to other embodiments as well, and detailed descriptions within the overlapping range will be omitted.

1 is a view showing a conventional stretching pulse mode-locked laser device.

The Stretched Pulse Mode Locking (SPML) laser device 100 may generate a wavelength swept laser. That is, the stretch pulse mode-locked laser device 100 may be a laser light source that emits a wavelength sweeping laser whose wavelength changes with time in a wide wavelength band. In this case, the wavelength sweeping laser may be a wavelength conversion laser.

The stretch pulse mode-locked laser device 100 may generate a wavelength sweeping laser by passively changing a wavelength without mechanical movement.

The stretching pulse mode-locked laser device 100 can generate a wavelength sweeping laser by inserting a dispersive medium 130 that causes large dispersion inside the resonator to change the wavelength.

The stretch pulse mode-locked laser device 100 may be used for swept source-optical coherence tomography (SS-OCT).

The stretching pulse mode lock laser device 100 may include an optical modulator 110 , a dispersive medium 130 , a gain medium 150 , and a beam splitter 170 . have.

A path through which light travels in the stretch pulse mode-locked laser device 100 may be a resonator. For example, the resonator may include an optical intensity modulator 110 , a dispersion medium 130 , a gain medium 150 , a beam splitter 170 , and an optical fiber connecting them.

The light modulator 110 may be an optical intensity modulator 110 that adjusts the intensity of light using the principle of a Mach-Zehnder interferometer.

The light intensity modulator 110 may divide the incoming light into a plurality of paths and generate a phase difference between the light passing through the plurality of paths to generate an optical pulse. For example, the light intensity modulator 110 applies a voltage to at least one path among the plurality of paths to change the refractive index of the material by an electro-optic effect, thereby generating a phase difference between the light passing through the plurality of paths to increase the intensity of the light. can be tampered with.

The dispersion medium 130 may change the wavelength of light passively without mechanical movement. The dispersion medium 130 may be a medium that greatly scatters light inside the resonator.

The dispersion medium 130 may disperse the light pulse for each wavelength or compress the light pulse to a single wavelength. For example, the dispersion medium 130 may disperse the light pulse transmitted from the light intensity modulator 110 according to the wavelength, and may compress the light pulse not emitted from the beam splitter 170 back to a single wavelength. . That is, the dispersion medium 130 may change the wavelength of the laser emitted over time by generating a time difference for each wavelength in the optical pulse, and on the contrary, the dispersion medium 130 removes the time difference for each wavelength of the optical pulse dispersed for each wavelength. Thus, it is possible to compress optical pulses of all wavelengths into one optical pulse.

The gain medium 150 may amplify the intensity of light. For example, the gain medium 150 may amplify an optical pulse dispersed according to a wavelength through the dispersion medium 130 .

Beam splitter 170 may emit some of the amplified light pulses through gain medium 150 . The beam splitter 170 may deliver a portion of the non-emitted light pulse back to the dispersion medium 130 .

The light emitted through the beam splitter 170 may be a wavelength-switched laser whose wavelength changes with time.

2A and 2B are diagrams for explaining the operation of the light intensity modulator.

Specifically, FIG. 2A is a graph showing the relationship between the phase difference between two paths and the intensity of light passing through the light intensity modulator 110 , and FIG. 2B is a graph illustrating the relationship between the voltage applied to the light intensity modulator 110 and the two paths. It is a graph showing the relationship between the phase differences.

The light intensity modulator 110 may generate a light pulse. For example, the light intensity modulator 110 divides light into two paths using the principle of a Mach-Zehnder interferometer, applies a voltage to one path, and adjusts the refractive index of the material by an electro-optical effect. By changing it, it is possible to modulate the intensity of light by generating a phase difference between the two paths.

The relationship between the phase difference of light passing through the two paths of the light intensity modulator 110 and the intensity of the light passing through the light intensity modulator 110 may be expressed as Equation (1).

는 두 경로를 지나는 빛의 위상차를 나타낸다.In Equation 1, I is the intensity of light that has passed through the light intensity modulator 110, I _max and I _min are the maximum and minimum values of the intensity that the light that has passed through the light intensity modulator 110 can have,

represents the phase difference of light passing through the two paths.

According to Equation 1, when the refractive index is changed so that the phase difference becomes an odd integer multiple of π, the intensity of the passing light is the weakest, and when the refractive index is changed so that the phase difference becomes an integer multiple of 2π, the intensity of the passing light can be the strongest.

The light intensity modulator 110 basically applies a voltage having a phase difference of π, and when a pulsed voltage having an amplitude sufficient to generate a phase difference of π is applied, light is emitted only during a time range as narrow as the width of the pulse. can pass

That is, the light intensity modulator 110 may generate an optical pulse by passing light only during a narrow time range.

3 is a diagram for explaining a chirped optical fiber Bragg grating.

The dispersion medium 130 may be a Chirped Fiber Bragg Grating (CFBG) 130 .

The chirped fiber Bragg grating 130 may be a type of fiber Bragg grating (FBG) in which a grating is engraved on an optical fiber to reflect or pass only light of a specific single wavelength according to the spacing between the gratings.

The chirped fiber Bragg grating 130 is engraved with gratings at different intervals at different positions of the optical fiber to reflect all the light of the wavelength band on which the grating is engraved. That is, the chirped optical fiber Bragg grating 130 may disperse an incident light pulse according to a wavelength.

,

, 및

인 광 펄스를 각각의 파장대역에 대응되는 격자의 위치에서 반사할 수 있다. 즉, 처프 광섬유 브래그 격자(130)는 파장이 각각

,

, 및

인 광 펄스를 서로 다른 위치에서 반사하므로, 파장이 각각

,

, 및

인 광 펄스는 서로 시간차를 가지도록 분산될 수 있다. 이때, 처프 광섬유 브래그 격자(130)의 좌측에서 입사된 광 펄스는 파장이 각각

,

, 및

인 순서로 반사되고, 우측에서 입사된 광 펄스는 파장이 각각

,

, 및

인 순서로 반사될 수 있다.Taking the chirped fiber Bragg grating 130 shown in FIG. 3 as an example, the chirped fiber Bragg grating 130 has a wavelength among incident light pulses, respectively.

,

, and

The phosphorescent light pulse may be reflected at a position of the grating corresponding to each wavelength band. That is, the chirped fiber Bragg grating 130 has a wavelength of each

,

, and

Because the light pulses are reflected at different locations, the wavelengths

,

, and

The phosphorescent light pulses may be dispersed to have a time difference from each other. At this time, the wavelengths of the optical pulses incident from the left side of the chirped optical fiber Bragg grating 130 are respectively.

,

, and

is reflected in the order of , and the light pulses incident from the right have

,

, and

can be reflected in the order of

4 and 5 are diagrams for explaining the problems of the conventional stretching pulse mode-locked laser device.

4 is a diagram illustrating a movement path of light passing through the chirped optical fiber Bragg grating 130 .

The stretch pulse mode-locked laser device 100 should be driven only when the optical pulse stretched (or dispersed) through the chirped fiber Bragg grating 130 passes through the gain medium 150 . When light passing through the chirped fiber Bragg grating 130 passes through the gain medium 150, there is a risk that unwanted light is predominantly amplified.

The stretch pulse mode-locked laser device 100 drives the gain medium 150 at a duty cycle of up to 50%, and blocks the light passing through the chirped fiber Bragg grating 130 in the gain medium 150 . It may be possible.

FIG. 5 is a diagram for explaining a phenomenon in which a wavelength sweeping width is narrowed due to dispersion in the stretch pulse mode-locked laser device 100 .

Since the stretch pulse mode-locked laser device 100 does not have a mechanical movement element compared to the annular wavelength conversion laser, the phase stability may be high and there may be fewer restrictions on the sweeping speed of the laser.

Since the repetition rate of the stretching pulse mode-locked laser device 100 is the same as the speed at which the pulse revolves around the inside of the resonator, the repetition rate of the laser may be determined by the length of the entire resonator. In this case, the repetition rate may mean the number of pulses repeated per second.

The stretch pulse mode-locked laser device 100 may adjust the overall length of the resonator to be short in order to increase the repetition rate of the wavelength sweeping laser, and conversely may increase the length of the resonator to slow the repetition rate.

Regardless of the repetition rate of the stretch pulse mode-locked laser device 100 , the wavelength sweeping speed may be determined by the amount of dispersion of the dispersion medium 130 that disperses the light transmitted through the light intensity modulator 110 into the wavelength sweeping light.

When the chirped fiber Bragg grating 130 is used as the dispersion medium 130, the length of the chirped fiber Bragg grating determines the wavelength sweeping speed. That is, the stretch pulse mode-locked laser device 100 may use a short-length chirped optical fiber Bragg grating 130 for high-speed wavelength sweeping, and a relatively long chirped optical fiber Bragg grating 130 for relatively low-speed wavelength sweeping. ) can be used.

) 수학식 2과 같이 나타낼 수 있다.In optical coherence tomography using a wavelength sweeping laser, axial resolution may be determined by the center wavelength of the light source and the wavelength sweeping width. Axial resolution;

) can be expressed as Equation (2).

는 파장 스위핑 레이저의 중심 파장이고

은 파장 스위핑 폭을 의미한다.in Equation 2

is the center wavelength of the wavelength sweeping laser and

is the wavelength sweeping width.

According to Equation 2, if the wavelength sweeping width becomes narrow, the resolution in the optical axis direction deteriorates.

In the case of a single mode fiber (SMF), dispersion may be zero at a wavelength of 1310 nm. Therefore, when the wavelength of light passing through the single-mode optical fiber is near 1310 nm, dispersion hardly occurs in the optical fiber, and greater dispersion may occur as it moves away from 1310 nm.

Optical coherence tomography mainly uses light having a center wavelength of 1050 nm, 1310 nm, and 1550 nm. Additional dispersion may occur with optical fiber based devices.

Referring to FIG. 5 , when an optical pulse dispersed according to a wavelength passes through the optical intensity modulator 110 , it can be seen that the intensity of the optical pulse varies according to the wavelength of the optical pulse.

In the stretch pulse mode-locked laser device 100, when the net dispersion inside the resonator does not become zero, the optical pulse may be distorted as shown in FIG. 5 due to additional dispersion by optical fibers or optical fiber-based elements. For example, the stretching pulse mode-locked laser device 100 may increase the overall length of the resonator in order to lower the sweep speed of the emitted laser. Additional dispersion is generated by the elements, so that the optical pulse may be distorted as shown in FIG. 5 .

The stretching pulse mode-locked laser device 100 uses one chirped optical fiber Bragg grating 130 in both stretching (forward) and compression (reverse) directions. Dispersion occurring in parts other than the chirped optical fiber Bragg grating 130 Since it cannot compensate, the mode locking condition may not be satisfied in a wide wavelength range.

If the stretching pulse mode lock laser device 100 fails to compensate for dispersion occurring in portions other than the chirped fiber Bragg grating 130 , the wide wavelength sweeping width cannot be used even if the wavelength width of the chirped fiber Bragg grating 130 is widened. can

6 is a diagram illustrating a stretching pulse mode-locked laser device according to an embodiment.

The stretching pulse mode-locked laser device 100 uses a plurality of dispersion media 130 to cancel the dispersion amount of dispersion generated by other optical and optical fiber elements inside the resonator, thereby achieving net dispersion of the wavelength sweeping laser in a wide wavelength band. can be minimized

The stretch pulse mode-locked laser device 100 may include a plurality of chirped optical fiber Bragg gratings 130 - 1 and 130 - 2 . For example, the deep pulse mode-locked laser device 100 may include a first chirped fiber Bragg grating 130-1 and a second chirped fiber Bragg grating 130-2.

The first chirped fiber Bragg grating 130 - 1 may be a stretched chirped fiber Bragg grating. The first chirped optical fiber Bragg grating may disperse the optical pulse output from the optical intensity modulator 110 for each wavelength and output it to the gain medium 150 .

The second chirped fiber Bragg grating 130 - 2 may be a compressed chirped fiber Bragg grating. The second chirped fiber Bragg grating may compress an optical pulse not emitted from the beam splitter 9170 and output it to the optical intensity modulator 110 .

The second chirped fiber Bragg grating 130 - 2 may be used in the opposite direction to the first chirped fiber Bragg grating 130 - 1 to collect the scattered optical pulses again. For example, the second chirped fiber Bragg grating 130 - 2 may be manufactured to compensate for all dispersion occurring inside the resonator as well as the first chirped fiber Bragg grating 130 - 1 .

The stretching pulse mode-locked laser device 100 may separately implement a first chirped optical fiber Bragg grating 130-1 for dispersing an optical pulse and a second chirped optical fiber Bragg grating 130-2 for compressing the dispersed optical pulse. have.

Since the stretch pulse mode-locked laser device 100 can perfectly combine optical pulses at all wavelengths using the second chirped optical fiber Bragg grating 130-2, there may be no limitation in the wavelength sweeping width.

Polarization mode dispersion is a phenomenon in which the birefringence experienced by light varies according to the wavelength of the light passing through the single-mode optical fiber.

In a laser device using a single-mode optical fiber, polarization mode dispersion, a phenomenon in which the birefringence experienced by light varies depending on the wavelength of light passing through the single-mode optical fiber, may occur. Therefore, in the case of a laser device using a single-mode optical fiber, a plurality of polarization controllers (PC) are used in the resonator of the laser device to minimize polarization mode dispersion and the polarization of all wavelengths has different transmittance depending on the polarization. It should be adjusted so that the maximum transmitted polarization of the elements in the resonator is obtained.

In a laser device using a single-mode optical fiber, if the polarization controller is used, the polarization mode dispersion cannot be completely eliminated. should be regulated

In the stretch pulse mode-locked laser device 100, all elements are driven only by light of one of two perpendicular optical axes, thereby eliminating the effects of birefringence and polarization mode dispersion.

The stretching pulse mode-locked laser device 100 can minimize birefringence and polarization mode dispersion in the resonator by configuring all constituent elements of a polarization maintaining fiber (PMF).

The stretching pulse mode-locked laser device 100 uses a polarization-maintaining optical fiber in which the polarization of the incident light is maintained while passing through the optical fiber, so that a polarization controller is not required, and the laser performance is achieved by birefringence and polarization mode dispersion and changes in these values. This degrading effect can be eliminated.

7A and 7B are diagrams for explaining another example of a stretch pulse mode-locked laser device.

The stretch pulse mode-locked laser device 100 may include a plurality of dispersion media 130 - 1 and 130 - 2 .

7A shows a conventional stretching pulse mode-locked laser device 100, and FIG. 7B shows a stretching pulse mode-locked laser device 100 including a plurality of dispersion media 130-1 and 130-2. Although only two dispersion media 130 - 1 and 130 - 2 are shown in FIG. 7B , the present invention is not limited thereto, and the stretch pulse mode-locked laser device 100 may include three or more dispersion media 130 .

The stretch pulse mode-locked laser device 100 may adjust the wavelength sweep repetition rate by adjusting the length and number of the dispersion media 130-1 and 130-2.

The wavelength sweeping repetition rate of the stretch pulse mode-locked laser device 100 may be inversely proportional to the length of the resonator, and the wavelength sweeping speed may be inversely proportional to the length of the chirped optical fiber Bragg grating 130_.

In the stretch pulse mode-locked laser device 100 , the wavelength sweeping speed may also need to be reduced in order to obtain a usage rate close to 100% while lowering the wavelength sweeping repetition rate. Accordingly, the stretch pulse mode-locked laser device 100 may use a long-length chirped optical fiber Bragg grating 130 to lower the wavelength sweeping repetition rate if necessary.

The chirped fiber Bragg grating 130 can be manufactured to a maximum length of about 10 m, and when using the chirped fiber Bragg grating 130 with a length of 10 m, the stretch pulse mode-locked laser device 100 can obtain a wavelength sweeping repetition rate of about 10 MHz. have.

The stretch pulse mode-locked laser device 100 may require a wavelength sweeping repetition rate lower than 10 MHz due to the speed limit of electronic equipment such as a photodetector and a data acquisition module. In this case, the laser resonator There may be limits to arbitrarily increasing the length of .

The stretch pulse mode-locked laser device 100 may reduce the wavelength sweeping repetition rate by providing a plurality of chirped Bragg gratings 130 - 1 and 130 - 2 in the resonator. For example, the stretch pulse mode-locked laser device 100 may use two 10 m-long chirped fiber Bragg gratings 130 to obtain a 5 MHz wavelength sweeping repetition rate, and a 10 m long chirped optical fiber to obtain a 2 MHz wavelength sweeping repetition rate. Five Bragg gratings 130 can be used.

8A and 8B are diagrams for explaining another example of the stretching pulse mode locking laser device.

The stretch pulse mode-locked laser device 100 may include a chirped fiber Bragg grating 130 that is additionally used outside the resonator. For example, the stretching pulse assortment lock laser device 100 may include a chirped fiber Bragg grating 130 connected to a laser output unit. In this case, the laser output unit may mean a position where the light pulse divided by the beam splitter 170 is emitted.

FIG. 7A shows one chirped fiber Bragg grating 130-2 implemented outside the resonator of the stretch pulse mode-locked laser device 100, and FIG. 7B shows a chirped fiber Bragg grating 130-2 implemented outside the resonator. 130-3), but is not limited thereto, and the stretch pulse mode-locked laser device 100 may include three or more chirped optical fiber Bragg gratings 130 implemented outside the resonator.

In the stretch pulse mode-locked laser device 100, when a plurality of chirped optical fiber Bragg gratings 130 are used in the resonator, optical loss in the resonator due to the increased chirped optical fiber Bragg grating 130 may increase, and the chirped optical fiber Bragg grating 130 may increase. 130), light loss of an optical circulator (not shown) used together with each chirped Bragg grating may occur in order to use the reflected light, and thus performance may be degraded.

The stretching pulse mode-locked laser device 100 minimizes the optical loss of the resonator by not using or using only one chirped fiber Bragg grating 130-1 in the resonator, and the required number of chirped fiber Bragg gratings ( 130-2 and 130-3) can be used.

The stretching pulse mode-locked laser device 100 lowers the wavelength sweeping speed by using the chirped fiber Bragg gratings 130-2 and 130-3 installed in the laser output unit, and then uses an optical amplifier (not shown) to control the wavelength sweeping laser. The intensity can be amplified to obtain the required wavelength sweep repetition rate, wavelength sweep width, and light output intensity.

The stretch pulse mode-locked laser device 100 may generate a wavelength sweeping laser having a utilization rate of close to 100% by using the chirped fiber Bragg grating 130-2 implemented outside the resonator.

As described above, although the embodiments have been described with reference to the limited drawings, those skilled in the art may apply various technical modifications and variations based on the above. For example, the described techniques are performed in an order different from the described method, and/or the described components of the system, structure, apparatus, circuit, etc. are combined or combined in a different form than the described method, or other components Or substituted or substituted by equivalents may achieve an appropriate result. Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

Claims (18)

an optical modulator for generating optical pulses;
A plurality of dispersive medium (dispersive medium) including a plurality of chirped fiber Bragg grating (Chirped Fiber Bragg Grating) for reflecting the light pulse at different positions for each wavelength;
a gain medium for amplifying the dispersed light pulses; and
A beam splitter that emits a portion of an amplified light pulse
including,
The chirped fiber Bragg grating,
a first chirped fiber Bragg grating for dispersing an optical pulse for each wavelength and positioned between the optical modulator and the gain medium; and
A second chirped optical fiber Bragg grating is located between the beam splitter and the optical modulator, which compresses the dispersed optical pulses for each wavelength into a single optical pulse.
comprising, a laser device.
According to claim 1,
The light modulator is
A laser device as an optical intensity modulator that divides light into a plurality of paths and generates a light pulse by generating a phase difference between the light passing through the plurality of paths.
According to claim 1,
The light modulator, the dispersion medium, the gain medium and the beam splitter are
It drives only the light of one of the two perpendicular optical axes.
laser device.
According to claim 1,
The wavelength sweeping repetition rate of the emitted laser is controlled by adjusting the length of the dispersion medium.
laser device.
delete delete According to claim 1,
The first chirped fiber Bragg grating,
Dispersing the optical pulse output from the optical modulator and outputting it to the gain medium,
The second chirped fiber Bragg grating,
Compressing an optical pulse not emitted from the beam splitter and outputting it to the optical modulator
laser device.
According to claim 1,
The number of the plurality of chirped fiber Bragg gratings is adjusted so that the wavelength sweeping repetition rate of the emitted laser is controlled.
laser device.
According to claim 1,
The light modulator, the dispersion medium, the gain medium and the beam splitter are connected using a polarization maintaining fiber.
laser device.
According to claim 1,
The plurality of dispersion media,
A chirped optical fiber Bragg grating that receives the optical pulse emitted by the beam splitter and adjusts at least one of a wavelength sweeping range and a wavelength sweeping repetition rate of the emitted laser
A laser device comprising a.
generating light pulses;
dispersing the optical pulses for each wavelength using a first chirped fiber Bragg grating;
amplifying the scattered light pulses;
emitting a portion of the amplified light pulse; and
Compressing a non-emitted optical pulse among the amplified optical pulses into a single wavelength using a second chirped optical fiber Bragg grating
A method of operating a laser device comprising a.
12. The method of claim 11,
The generating step is
dividing light into a plurality of paths and generating a light pulse by generating a phase difference between the light passing through the plurality of paths
A method of operating a laser device comprising a.
12. The method of claim 11,
The dispersing step is
Reflecting the light pulses at different positions for each wavelength
A method of operating a laser device comprising a.
12. The method of claim 11,
controlling the wavelength sweeping repetition rate of the emitted laser by adjusting the length of the first chirped fiber Bragg grating
A method of operating a laser device further comprising a.
generating light pulses;
dispersing the optical pulses for each wavelength using a plurality of chirped optical fiber Bragg gratings;
amplifying the scattered light pulses;
emitting a portion of the amplified light pulse; and
compressing a non-emitted optical pulse among the amplified optical pulses into a single wavelength using the plurality of chirped optical fiber Bragg gratings
A method of operating a laser device comprising a.
16. The method of claim 15,
controlling the wavelength sweeping repetition rate of the emitted laser by adjusting the number of the plurality of chirped fiber Bragg gratings
A method of operating a laser device further comprising a.
generating light pulses;
dispersing the light pulses for each wavelength;
amplifying the scattered light pulses;
emitting a portion of the amplified light pulse;
compressing a non-emitted optical pulse among the amplified optical pulses into a single wavelength; and
Adjusting at least one of a wavelength sweeping range and a wavelength sweeping repetition rate of the emitted laser by receiving the emitted light pulse as an input
A method of operating a laser device comprising a.
18. The method of claim 17,
The adjusting step is
adjusting at least one of the range and the repetition rate using at least one chirped fiber Bragg grating.
A method of operating a laser device comprising a.

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