KR101127153B1 - Dual mode optical fiber laser module - Google Patents

Abstract

The present invention provides a dual mode fiber laser module. The dual mode fiber laser module includes a fiber laser, a first injection locking portion for providing a first injection locking to the fiber laser, and a second injection locking portion for providing a second injection locking to the optical fiber laser, the first injection locking portion The first wavelength and the second wavelength of the second injection locking part are different from each other, and the first injection locking part and the second injection locking part oscillate the dual mode in the fiber laser.

Terahertz Wave, Injection Locking, Frequency Domain, Frequency Variable

Description

Dual Mode Fiber Laser Module {DUAL MODE OPTICAL FIBER LASER MODULE}

The present invention relates to a fiber laser module, and more particularly to a dual mode fiber laser module for generating a wideband frequency variable terahertz wave.

Terahertz wave generation methods currently in use include frequency doubling, backward wave oscillating method, photomixing method, CO ₂ pumping gas laser method, and quantum cascade laser. ), Or a free electron laser method.

One technical problem to be solved of the present invention is to provide a dual mode photonic oil laser provided in a portable, high-power, low-cost frequency variable terahertz wave source.

A dual mode fiber laser module according to an embodiment of the present invention includes a fiber laser, a first injection locking unit for providing a first injection lock to the fiber laser, and amplified spontaneous emission or oscillated light of the fiber laser. A first circulator provided in a locking unit, a second injection locking unit providing a second injection locking to the optical fiber laser, and providing the amplified spontaneous emission or the oscillated light of the optical fiber laser to the second injection locking unit And a second circulator, wherein the first wavelength of the first injection locking part and the second wavelength of the second injection locking part are different from each other, and the first injection locking part and the second injection locking part are doubled in the optical fiber laser. To trigger the mode.

In one embodiment of the present invention, the optical fiber laser may include an optical fiber laser resonator, an excitation light source for supplying energy to the optical fiber laser resonator, and an input optical fiber coupler coupling the excitation light source to the optical fiber laser resonator.

In one embodiment of the present invention, the excitation light source may be a laser diode of 980 nm.

In one embodiment of the present invention, the optical fiber laser resonator may be doped with at least one of erbium (Er) and ytterbium (Yb).

In one embodiment of the present invention, the optical fiber laser may further include an optical isolator for laser oscillation in one direction.

In one embodiment of the present invention, at least one of the first injection locking portion and the second injection locking portion may include a frequency variable heater or cooler.

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In one embodiment of the present invention, the first injection locking portion and the second injection locking portion may act as a filter and an external locking light source.

In one embodiment of the present invention, the first injection locking portion and the second injection locking portion may be a Fabry Ferret (FP) laser.

In one embodiment of the present invention, the optical fiber laser may include an optical fiber laser resonator including a semiconductor optical amplifier, and an excitation power supply for supplying energy to the optical fiber laser resonator.

A dual mode fiber laser module according to an embodiment of the present invention comprises a first injection locking unit which is locked by an optical fiber laser, Amplified spontaneous emission (ASE) light in the optical fiber laser; And a first circulator for providing amplified spontaneous emission light from the optical fiber laser to the first injection locking unit. A second injection locking part locked by the amplified spontaneous emission light in the optical fiber laser; And a second circulator for providing the amplified spontaneous emission light from the optical fiber laser to the second injection locking unit, wherein the first wavelength of the first injection locking and the second wavelength of the second injection locking are mutually different. The output light of the first injection locking part and the output light of the second injection locking part may be provided again by the optical fiber laser.

The dual mode fiber laser according to the exemplary embodiment of the present invention may adjust two oscillation wavelengths by an injection locking method in the fiber laser resonator. Accordingly, the dual mode fiber laser can provide two stable oscillation wavelengths.

The dual mode optical fiber laser module according to an embodiment of the present invention may be provided for terahertz wave generation by photomixing. The dual mode fiber laser module may include two Fabry-Perot (FP) lasers that inject light into the fiber laser resonator. Accordingly, the FP lasers can be locked by amplified spontaneous emission (ASE) in the fiber laser resonator. Alternatively, the FP lasers can induce injection locking in a dual mode fiber laser. The FP lasers can induce a predominant mode oscillation in the fiber laser resonator to provide a very stable and narrow oscillation spectrum.

The 0.1 THz to 3 THz (1 THz: 10 ¹² Hz) terahertz wave region may have permeation characteristics of nonmetallic and nonpolar materials. In addition, resonant frequencies of various molecules may be distributed in the terahertz wave region. Terahertz wave technology can provide real-time identification of molecules by nondestructive, unopened, and noncontact methods. The terahertz wave technology can provide a new concept of analysis technology in medical, medical, agricultural food, environmental measurement, bio, advanced materials evaluation and the like. The terahertz wave technology can be rapidly extended to other application areas. The terahertz wave region has very low energy of a few meV levels and has little effect on the human body. Therefore, the terahertz wave technology is rapidly increasing demand as an essential core technology in realizing a human-centered ubiquitous society.

The dual mode fiber laser module according to an embodiment of the present invention may be provided in a continuous oscillation frequency variable terahertz wave generator in a high efficiency, low cost, and portable concept. The dual mode fiber laser module may provide a high power light source. Much research is being conducted on the development of wave sources operating in the 0.1 to 10 THz frequency band, also known as the THz gap region.

The dual mode fiber laser module may be provided for molecular fingerprint analysis in the 0.1 to 3 THz region. The dual mode fiber laser module may provide real-time measurement of molecular fingerprints in the frequency domain (FP). The typical terahertz wave generation method utilizes a TDS (Time Domain Spectroscopy) based photomixing method that generates THz waves by irradiating a femto elementary ultra-short pulsed laser to a semiconductor having a super fast response speed. It is a terahertz wave system composed of femto-grade high power pulsed laser and photomix, and has the advantage of providing high signal-to-noise ratio (SNR).

The dual mode fiber laser module according to an embodiment of the present invention may include two FP lasers whose oscillation wavelengths are varied by temperature change. Light of the two FP lasers may be injected into the fiber laser resonator through a circulator. The two FP lasers may have different frequencies. In this case, the FP lasers may be locked by Amplified spontaneous emission (ASE) in the fiber laser resonator. Alternatively, the FP lasers may provide injection locking to the fiber laser. Accordingly, the fiber laser can be oscillated in dual mode. Accordingly, the dual mode fiber laser can have a narrow spectrum and vary the oscillation wavelength.

The dual mode fiber laser module may have a dual mode oscillation characteristic because only two dominant modes in the fiber laser resonator reach a critical gain by varying the oscillation center wavelength and varying the oscillation center wavelength. The wavelength difference between the two modes may correspond to the frequency of the terahertz wave. The frequency variation may be performed by controlling the wavelength of the injection locked FP lasers in the fiber laser resonator. The control of the wavelength of the FP lasers can be performed by adjusting the drive temperature.

The dual mode fiber laser module may adjust wavelength intervals corresponding to two modes. Accordingly, the dual mode fiber laser module may be used as a low frequency, portable variable frequency terahertz wave source. The dual mode fiber laser module may be provided to a wide variety of fields such as optical modules related to terahertz wave sources, terahertz wave generation and detection, and application technologies.

1A and 1B illustrate a terahertz optical device according to the prior art. FIG. 1B is a diagram illustrating data obtained by using the optical device of FIG. 1A.

1A and 1B, the optical apparatus 10 may generate and / or detect terahertz waves using the ultra-short pulse laser 110. The optical device 10 may be a time domain spectroscopy (FDS) system. The optical device 10 has an advantage of obtaining a high signal to noise ratio (SNR) by using a homodyne detection method that acquires data only during a gating time of femto beginners.

The path of the output light of the ultra-short pulse laser 110 may be changed by the first mirror 112. The output light of the ultra-short pulse laser 110 reflected from the first mirror 112 may be divided into two using a beam splitter (BS) 114. One ultrashort pulse may be incident on the terahertz wave generator THz Tx 130a through the second mirror 116 to generate the terahertz wave. The other short pulse can be used to sample the data by entering the terahertz wave detector (THz Dx, 130b) with an appropriate time delay. The terahertz wave generator 130a and the terahertz wave detector 130b may be a photomix having the same structure. The time delay may be performed using a delayed line 118 (DL). The output light of the delayed line 118 may be provided to the terahertz wave detector 130b through the third mirror 122 and the fourth mirror 124.

The terahertz wave generated by the terahertz wave generator 130a may be focused on the sample 146 through the first focusing lens 142. The terahertz wave passing through the sample 146 may be incident on the terahertz wave detector 130b through the second focusing lens 144.

The terahertz wave generator 130a and / or the terahertz wave detector 130b may be a photomix. The terahertz wave generated by the terahertz wave generator 130a may be focused by a silicon lens. The terahertz wave detector 130b may generate an electrical signal through the photomix structure by light incident and collected through the Fresnel lens.

The terahertz wave detector 130b may generate an electric signal depending on time according to a time delay. The electrical signal may be obtained by the sampler 148. The sampler 148 may be a high speed A / D converter or a high speed oscilloscope.

Referring to FIG. 1B, the electrical signal may be FFT (Fast Fourier Transform) transformed to provide a spectrum of terahertz waves.

As such, the photomix used in the optical electronic conversion may include a pulse method and a beating method. The beating method may generate terahertz waves by irradiating two lasers having different wavelengths of high power to the photomix. The photomix may include an antenna integrated on a semiconductor substrate having an ultra high speed response speed. The antenna may be applied with a high voltage.

Optical devices for generating and detecting TDS-based terahertz waves can generate terahertz waves relatively easily due to the generation of electromagnetic waves due to the acceleration of the carrier generated by irradiating ultra-short femtosecond pulsed lasers to semiconductor or nonlinear materials. The optical device for generating and detecting the TDS-based terahertz wave has been widely used for research as an advantage of securing a high SNR by using the same homodyne detection method for the gating time of the femto elementary class. The femto-element ultra-short pulse laser of 800nm band is divided into two and one is inputted to THz Tx (Transmitter) marked photomix and used to generate terahertz wave.The other ultra-short pulse has a proper time delay Is incident on (THz Dx). It is possible to obtain a terahertz wave spectrum by taking data depending on the delay time and transforming it by fast Fourier transform (FFT). For the practical application of terahertz wave, it is necessary to collect the information corresponding to each delay time in each pixel, and it is impossible to avoid the time delay in data processing by FFT the information. Development of terahertz sources is limited.

Frequency domain (Frequency) is expected to increase gradually in various areas such as TDS-based terahertz wave source generation and detection system and overcomes the disadvantages of extracting harmful substances through molecular fingerprint analysis, measuring new material characteristics, and measuring freshness of agricultural and marine products. Domain: FD) based terahertz wave source is required.

In order to generate a tunable continuous oscillation terahertz wave using a photomix, two independent light sources are essential. The light source may be a high power tunable laser. The oscillation frequency difference of the tunable lasers may correspond to the frequency of the terahertz wave. In the generation of frequency domain (FD) based variable frequency terahertz waves, the characteristics of different oscillation wavelengths can directly affect the noise characteristics of terahertz waves.

In the frequency domain (FD) -based method, two lasers having different wavelengths of high power are generated by integrating an antenna on a semiconductor substrate having a super fast response speed and irradiating a voltage applied photomixer to generate terahertz waves. The photoelectric conversion efficiency is as follows.

The photomix may have the following optical eletrical conversion efficiency.

Where P ₁ and P ₂ are the light outputs of two lasers with different wavelengths, P ₀ average power, I _o is the DC photocurrent, R _A is the radiation resistance of the antenna, and c is the capacitance of the photomix. where τ is the life time of the photomix and m is the mixing ratio of the two beams.

For high efficiency terahertz wave generation, it is necessary to adjust variables affecting photoelectric conversion efficiency of photomix with high power light source. The photoelectric conversion efficiency of the photomix may be affected by the high response speed or life time of the photomix, the antenna resistance, and the mixing ratio of the two light sources.

In the terahertz wave generation and detection system using the photomix method, methods for utilizing the wavelength of the excitation light source in the range of 1.5 μm and 1.3 μm have been proposed. The reason is low cost by utilizing optical parts developed for optical communication, and most core technologies such as ultra-small modular technology and high speed signal processing technology have been developed and can be used relatively easily. Well-developed, semiconductor optical amplifier in the 1.3㎛ band is also well developed, and has a high photoelectric conversion efficiency according to the long wavelength utilization compared to the short wavelength.

In the continuously variable terahertz wave source, the difference between the frequency f of the terahertz wave and the two oscillation wavelengths of the excitation light has a relationship of f = cΔλ / λ ² . The wavelength characteristics of the two excitation light can directly affect the generation of terahertz waves. The frequency f of the terahertz wave can be determined by the difference between the frequencies f ₁ = c / λ ₁ and f ₂ = c / λ ₂ corresponding to the respective oscillation wavelengths λ ₁ and λ ₂ . In other words, the variable wavelength characteristic of the excitation light source becomes very important in the frequency variable terahertz wave source. In order to change the 1THz frequency, it is necessary to secure the characteristics of the variable wavelength spacing between two modes of 8 nm in the 1.5 탆 wavelength region and about 6 nm in the 1.3 탆 wavelength region. Therefore, it is necessary to develop a tunable laser for this purpose. Due to the importance and the high price of the tunable laser in a wavelength division multiplexer (WDM) based optical communication system, the terahertz wave source using the wavelength division multiplexer may have many difficulties.

However, the dual mode optical fiber laser module according to the embodiment of the present invention can provide a very narrow oscillation wavelength line width with wideband wavelength tunable characteristics.

Typically, two independent wavelength tunable lasers having a full width half maximum (FWHM) of the oscillation wavelength of about kHz may be provided to the terahertz wave source. However, independently oscillating tunable lasers can have disadvantages such as destabilization of wavelengths and control of polarization between wavelengths, and high system cost.

The dual mode fiber laser may be provided for generating a frequency variable continuous oscillation terahertz wave. The dual mode fiber laser is fabricated based on an optical fiber and can be easily combined with an erbium optical amplifier or an optical fiber mounted semiconductor optical amplifier. The dual mode fiber laser can easily increase the light output. The dual mode fiber laser may be manufactured as a portable module. In addition, the output of the dual mode fiber laser can be provided integrally to the photomix. Thus, the dual mode fiber laser can provide a high efficiency and low cost terahertz wave generation module.

Dual-mode fiber laser module according to an embodiment of the present invention can extend the wavelength variable range by using a low-cost semiconductor laser, and can reduce the half width (FWHM) of the oscillation wavelength.

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

2A and 2B are views illustrating characteristics of an injection locking unit used in a dual mode fiber laser module according to an embodiment of the present invention. Simulation diagrams showing an oscillation spectrum of the injection locking part.

Referring to FIG. 2A, the injection locking unit may be an FP laser. The spectrum of the injection locking part may have a plurality of longitudinal modes formed by the resonator length. The center wavelength of the injection locking part may be 1550 nm, 1300 nm, 1060 nm, or 850 nm, depending on the composition.

Referring to FIG. 2B, the injection lock of the injection locking part shows the simulation result of the injection when the injection lock is performed by external injection light having a very narrow oscillation spectrum from the outside in the oscillation state. The external injection light may be 1545 nm. Accordingly, the line width is narrowed and locked by external injection light of a predetermined size or more, the center wavelength of the injection locking portion can move to 1545 nm, and the slave modes other than the main mode can be attenuated.

Referring to FIG. 2B, the wavelength of the external injection light may be about several nm before and after the increasing wavelength of the injection locking part according to the composition. Accordingly, the line width is narrowed and locked by the external injection light of a predetermined size or more, so that the center wavelength of the injection locking part can move to the wavelength of the external injection light, and the vertical modes other than the main mode can be attenuated.

3 is a view for explaining the operation principle of a dual mode fiber laser module according to an embodiment of the present invention.

Referring to FIG. 3, external injection light of the mast laser 32 may be provided to the slave laser 34 through the circulator 36. The mast laser 32 provides external injection light. The slave laser 34 may be locked by external injection light of the mast laser 32. The external injection light is for injection locking. The external injection light may be provided by a light source having excellent spectral characteristics, such as a distributed feedback laser diode (DFB LD). Alternatively, the external injection light may be provided by a light source having a constant spectral line width. The external injection light of the mast laser may have a center wavelength λ ₀ . When the slave laser 34 is locked, a locked light source may be provided depending on the wavelength of the external injection light, the output, the characteristics of the locking laser, and the like.

The slave laser 34 may be an LD having a plurality of longitudinal modes and having a broad spectrum. The center wavelength of the slave laser 34 may be λ ₁ . The slave laser 34 may include an antireflection film AR and / or a high reflection film HR formed in a resonator for smooth injection of the external injection light and easy extraction of locked light. The antireflection film and the high reflection film may be formed of a dielectric film.

The circulator 36 may have three input porters. The first port 36a may be connected to the mast laser 32, and the external injection light may be injected into the first port 36a. The second port 36b may be connected to the slave laser 34. Injection light injected into the first port 36a may be provided to the slave laser 34 through the second port 36b.

The slave laser 34 may be locked to the wavelength of the external injection light. The locked light of the slave laser 34 provided to the second port may be output through the third port 36c. When the slave laser 34 is not locked by external injection light, the center wavelength λ ₁ of the slave laser 34 may be different from the wavelength λ ₀ of the external injection light.

The wavelength λ ₀ of the external injection light of the mast laser 32 may shift the main mode of the slave laser 34. When the external injection light of the mast laser 32 locks the slave laser 34, the slave laser 34 may oscillate at the wavelength λ ₀ of the external injection light.

4A to 4C are diagrams illustrating a dual mode fiber laser module according to an embodiment of the present invention. 4B is a view illustrating oscillation characteristics of the fiber laser when there is no injection locking in both of the fiber laser of FIG. 4A. FIG. 4C is a view illustrating oscillation characteristics of the fiber laser when injection locking is present in both of the fiber lasers of FIG. 4A.

4A to 4C, the dual mode fiber laser module 200 includes a fiber laser 210, a first injection locking unit 222 for providing a first injection lock to the fiber laser 210, and the A second injection locking unit 224 for providing a second injection locking to the optical fiber laser 210, wherein the first injection locking unit 222 has a first wavelength λ ₁ and the second injection locking unit 222. The second wavelength λ ₂ of 224 may be different from each other, and the first injection locking unit 222 and the second injection locking unit 222 may oscillate the dual mode in the optical fiber laser 210.

The optical fiber laser 210 couples the optical fiber laser resonator 202, the excitation light source 212 to supply energy to the optical fiber laser resonator 202, and the excitation light source 212 to the optical fiber laser resonator 202. It may include an input fiber coupler 214. The excitation light source 212 may be a laser diode of 980 nm.

The fiber laser resonator 202 may be doped with erbium (Er), ytterbium (yb), or ytterbium (Yb) and erbium (Er) simultaneously. The doped material may function as an amplifier. The optical fiber laser 210 may oscillate in a band of 1550 nm and 1060 nm.

According to a modified embodiment of the present invention, the fiber laser resonator 202 may include a semiconductor optical amplifier. The fiber laser resonator 202 may include a semiconductor optical amplifier instead of a doped fiber amplifier. In this case, the excitation light source may be removed from the fiber laser laser 210. The fiber laser 210 may oscillate in a band of 1550 nm, 1300 nm, and 850 nm. The excitation power source (not shown) may supply energy to the semiconductor optical amplifier. The semiconductor optical amplifier may have a structure in which cross-sectional reflection of the semiconductor laser is removed to prevent resonance. The semiconductor optical amplifier can gain by current injection. The central wavelength of the semiconductor optical amplifier may be 1.55um, 1.3um, or 850nm band.

The input fiber coupler 214 may be a 980 / 1550nm, 980 / 1060nm WDM fiber coupler. The fiber laser 210 may include an optical isolator 216 for laser oscillation in one direction. The optical fiber laser 210 may be erbium, ytterbium, or erbium and ytterbium simultaneously.

Alternatively, the optical fiber laser 210 may be used by continuously connecting semiconductor optical fiber amplifiers having different center gains to enlarge the gain area. The fiber laser 210 may include an output fiber coupler 218. The output fiber coupler 218 may provide 10 percent of output externally.

At least one of the first injection locking unit 222 and the second injection locking unit 224 may include a thermo electric cooler (TEC) or a micro cooler. The first injection locking unit 222 and the second injection locking unit 224 may be Fabry Ferret (FP) lasers. The first wavelength of the first injection locking unit 222 and the second wavelength of the second injection locking unit 224 may be varied. The oscillation wavelength of the first injection locking unit 222 and the second injection locking unit 224 may vary according to temperature. The oscillation wavelength of the fiber laser 210 may be varied by a TEC and / or a micro heater mounted on the first injection locking unit 222 or the second injection locking unit 224. That is, the first injection locking unit 222 or the second injection locking unit 224 may have a frequency variable characteristic according to temperature. In the optical fiber laser 210, only two predominant modes in the optical fiber laser resonator 202 may reach a critical gain, thereby exhibiting dual mode oscillation characteristics. That is, the wavelength difference between the two modes may correspond to the frequency of the terahertz wave. The wavelength difference between the two modes may be controlled according to driving temperatures of the first injection locking unit 222 and / or the second injection locking unit 224.

The first injection locking unit 222 and the second injection locking unit 224 may act as a filter and an external locking light source. The output light of the first injection locking unit 224 may be injected into the optical fiber laser resonator 202 through the first circulator 223. The fiber laser 210 may oscillate at a first wavelength of the first injection locking unit 222. The output light of the second injection locking unit 224 may be injected into the fiber laser resonator 202 through the second circulator 225. The fiber laser 202 may oscillate at a second wavelength of the second injection locking unit 224. Accordingly, the fiber laser 210 may be injected locked by the first injection locking unit 222 and the second injection locking unit 224 to be oscillated in two modes. The wavelengths of the two modes may substantially match the first wavelength of the first injection locking unit 222 and the second wavelength of the second injection locking unit 224.

According to a modified embodiment of the present invention, the first circulator 223 may provide the ASE or oscillated light of the optical fiber laser 210 to the first injection locking unit 222. The first injection locking unit 222 may be locked by the AMP (Amplified Spontaneous Emission) light in the optical fiber laser resonator. The first circulator 223 may provide the locked light of the first injection locking unit 222 to the optical fiber laser 210 again.

The second circulator 225 may provide the ASE or oscillated light of the optical fiber laser 202 to the second injection locking unit 224. The second injection locking unit 224 may be locked by Amplified spontaneous emission (ASE) light in the optical fiber laser resonator 202. The second circulator 225 may provide the locked second light of the second injection locking unit 224 to the optical fiber laser 202.

The first wavelength of the first injection locking unit 222 and the second wavelength of the second injection locking unit 224 may be different from each other. The difference between the wavelengths of the first injection locking unit 222 and the second injection locking unit 224 may be due to the driving temperatures of the first injection locking unit 222 and the second injection locking unit 224. have.

Conventional DFB lasers can include a diffraction grating on the active layer. The DFB laser can be difficult to provide wavelength variability at levels of 0.01 mA / mA and 0.1 mA / ° C. For wavelength tunability, semiconductor lasers can adopt a distributed bragg reflector (DBR) structure. The semiconductor laser of the DBR structure may be difficult to apply to a continuous frequency oscillation wavelength tunable laser.

The first injection locking unit 222 and the second injection locking unit 224 may be FP lasers. The FP laser 224 may have a very wide oscillation wavelength variable characteristic of 0.8 nm / ℃ level. Two FP lasers having different oscillation frequencies may be provided to utilize injection locking in one optical fiber laser resonator 202.

According to a modified embodiment of the present invention, the first injection locking portion 222 and the second injection second injection locking portion 224 may be connected to the fiber laser 210 in various ways.

FIG. 5 is a diagram illustrating a side-mode suppression ratio (SMSR) between a main mode and a neighbor mode of an oscillation spectrum of an injection locking unit of a dual mode fiber laser module according to an exemplary embodiment of the present invention.

Referring to FIG. 5, when locking by the ASE of the fiber laser is dominant, the fiber laser may be difficult to secure a desired line width due to a structure that does not utilize a very narrow filter. However, as the difference between the main mode and the neighbor mode of the injection locking unit locks the fiber laser, the FM side-mode suppression ratio (FM _SMSR ) may gradually increase. Accordingly, a closed loop reaching a very narrow spectrum can be formed to provide a stable dual mode optical fiber laser. In addition, by adjusting the wavelength difference between the modes can be directly utilized in the generation of broadband terahertz wave.

The oscillation state of the fiber laser may be greatly influenced by the states of the two injection locking portions. When the injection current of the injection locking unit is lower than the oscillation threshold current, it may act as a semiconductor optical amplifier to provide a gain difference between the optical fiber laser modes. In addition, when the injection current of the injection locking unit is higher than the oscillation threshold current, the mode selectivity of the optical fiber laser can be increased because the influence of the ASE locking of the optical fiber laser and the optical fiber laser locking of the FP laser dominate.

6 is a diagram illustrating a dual mode fiber laser module according to another embodiment of the present invention. Descriptions overlapping with those described in FIGS. 4A to 4C will be omitted.

The output light of the first injection locking unit 222 may be injected into the optical fiber laser resonator 202 through the first optical fiber coupler 223a. The fiber laser 210 may oscillate at a first wavelength λ ₁ of the first injection locking unit 222. Output light of the second injection locking unit 224 may be injected into the optical fiber laser resonator 202 through the second optical fiber coupler 225a. The fiber laser 210 may oscillate at the second wavelength λ ₂ of the second injection locking unit 224. Accordingly, the fiber laser 210 may be injected locked by the first injection locking unit 224 and the second injection locking unit 224 to oscillate in two narrow spectrums of two modes. The wavelengths of the two modes may substantially match the first wavelength of the first injection locking unit 222 and the second wavelength of the second injection locking unit 224.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be defined by the equivalents of the claims of the present invention as well as the following claims.

1A and 1B illustrate a terahertz optical device according to the prior art.

2A and 2B are views illustrating characteristics of an injection locking unit used in a dual mode fiber laser module according to an embodiment of the present invention.

3 is a view for explaining the operation principle of a dual mode fiber laser module according to an embodiment of the present invention.

4A to 4C are diagrams illustrating a dual mode r optical fiber laser module according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating a side-mode suppression ratio (SMSR) between a main mode and a neighbor mode of an oscillation spectrum of an injection locking unit of a dual mode fiber laser module according to an exemplary embodiment of the present invention.

6 is a diagram illustrating a dual mode fiber laser module according to another embodiment of the present invention.

Claims (11)

Fiber lasers; A first injection locking unit providing a first injection locking to the fiber laser; A first circulator for providing an amplified spontaneous emission (ASE) or oscillated light of the optical fiber laser to the first injection locking unit; A second injection locking unit providing a second injection locking to the fiber laser; And A second circulator for providing the amplified spontaneous emission or the oscillated light of the optical fiber laser to the second injection locking part, The first wavelength of the first injection locking portion and the second wavelength of the second injection locking portion are different from each other, And the first injection locking part and the second injection locking part oscillate a duplex mode in the optical fiber laser. The method according to claim 1, The fiber laser is: Fiber laser resonators; An excitation light source for supplying energy to the fiber laser resonator; and And an input fiber coupler for coupling the excitation light source to the fiber laser resonator. The method of claim 2, Wherein the excitation light source is a 980 nm laser diode. The method of claim 2, And the fiber laser resonator is doped with at least one of erbium and ytterbium. The method according to claim 1, The optical fiber laser module of claim 1, further comprising an optical isolator for laser oscillation in one direction. The method according to claim 1, And at least one of the first injection locking unit and the second injection locking unit includes a frequency variable heater or cooler. delete The method of claim 1, And the first injection locking part and the second injection locking part act as filters and external locking light sources. The method of claim 1, And the first injection locking part and the second injection locking part are Fabry Ferret (FP) lasers. The method according to claim 1, The fiber laser is: A fiber laser resonator including a semiconductor optical amplifier; And And an excitation power supplying energy to the fiber laser resonator. Fiber lasers; A first injection locking unit locked by an amplified spontaneous emission (ASE) light in the optical fiber laser; And A first circulator for providing amplified spontaneous emission light from the optical fiber laser to the first injection locking unit; A second injection locking part locked by the amplified spontaneous emission light in the optical fiber laser; And A second circulator for providing the amplified spontaneous emission light from the optical fiber laser to the second injection locking part, The first wavelength of the first injection locking and the second wavelength of the second injection locking are different from each other, And the output light of the first injection locking part and the output light of the second injection locking part are provided again by the optical fiber laser.

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