KR20120075340A - Apparatus for generating mid-wavelength infrared fiber laser with separated wavelength conversion head - Google Patents

Abstract

PURPOSE: An apparatus for generating a mid infrared optical fiber laser source with a separated wavelength conversion head is provided to form of a light and miniature structure by separating an Yb(Ytterbium) added optical fiber laser module part and a PPLN(Periodically Poled Lithium Niobate) light medium oscillation part. CONSTITUTION: An optical fiber laser module part(210) generates laser beams by pre-amplifying and amplifying generated seed beams. A wavelength conversion head part(220) is composed of a PPLN(Periodically Poled Lithium Niobate) light medium oscillator generating laser beams by changing the generated laser beam into a mid infrared wavelength within the wavelength band of 2-5um. An optical fiber(214) for transmission transmits the laser beams without loss by connecting the optical fiber laser module part to the wavelength conversion head part. The optical fiber laser module part comprises a seed beam generating part(211), a pre-amplifying part(212), and a main amplification part(213).

Description

Wavelength conversion head separated mid-infrared fiber laser generator {APPARATUS FOR GENERATING MID-WAVELENGTH INFRARED FIBER LASER WITH SEPARATED WAVELENGTH CONVERSION HEAD}

The present invention relates to an optical fiber laser generating apparatus, and more particularly, to a wavelength converting head-separated mid-infrared optical fiber laser generating apparatus which transmits a long distance efficiently by minimizing the loss of mid-infrared laser light.

Conventionally, countermeasures for deceiving infrared guided missiles in the military field have been developed according to the performance improvement of infrared guided missiles, and band I, II, and II in the 2 ~ 5um mid-infrared wavelength band according to the type of detector applied to the missile. Oscillation of a multi-band mid-infrared laser light source corresponding to IV is required. These bands I, II, and IV are divided according to the wavelength. It also requires a high power mid-infrared laser to deceive the tracking of infrared guided missiles. In addition, in order to equip the system with countermeasures against threats, the volume and weight of the device must be small and light, and the generated mid-infrared laser light loss is minimized and transmitted.

Reflecting this trend, there is a need for a device capable of simultaneously generating high-power, mid-infrared light sources in the 2-5 um wavelength band, easily modulating the pulses, minimizing loss to a long distance, and transmitting a device. In addition, mechanical fabrication is required to facilitate installation in systems such as aircraft and helicopters.

Conventionally, there is no optical fiber laser device that directly oscillates the mid-infrared light source of 2 to 5 um wavelength band, and nonlinear wavelength conversion material such as PPLN (Periodically Poled Lithium Niobate) from Yb-doped fiber laser that directly oscillates 1 um wavelength band. A mid-infrared light source was generated by converting the wavelength into a wavelength band of 2 to 5 um using. High-power fiber lasers are relatively stronger than semiconductor lasers against external impacts, and can be manufactured smaller and lighter than solid-state lasers. In addition, when directly modulating the seed laser, the line width and repetition rate can be easily controlled, and code jamming required by the directional infrared deception equipment can be implemented. Among wavelength conversion technologies, wavelength conversion technology using an optical mediated oscillator (OPO) is mainly used because of its high wavelength conversion efficiency to the mid-infrared region and easy wavelength variability.

1 is a block diagram showing a conventional laser generator.

As shown in the drawing, a conventional laser generator generates a laser beam, and converts the high power fiber laser unit 110 to amplify the generated laser beam, and the laser output from the high power fiber laser unit 110 into mid-infrared wavelengths. The optical medium oscillation unit 130, and the transmission optical fiber 120 for connecting the high power optical fiber laser unit 110 and the optical medium oscillation unit 130.

The high power optical fiber laser unit 110 includes an external optical modulator 111 for modulating pulsed light, reflectors 112 and 114 for reflecting the generated light source, and an active optical fiber for amplifying a beam between respective reflection surfaces. 113, a pump laser diode 116 for generating a light source, a coupling mechanism 115 for connecting the pump light and a resonator for generating a low output signal light, a preamplifier 117 for amplifying the generated low output light pulse to high output, It consists of a main amplifier 118 that amplifies the first amplified light generated by the preamplifier 118 to a higher high output.

In such a structure of the conventional laser generating apparatus, the connecting portion is bulk type. The bulk type refers to a structure in which a process of amplifying laser light by absorbing light of a pump laser diode into a core of an active optical fiber is performed by external bulk optical systems. Due to this structural feature, the bulk type requires precise alignment of the active optical fiber and external bulk optical systems, and is not only affected by external shocks but also affected by dust.

In addition, there is no form in which the high power fiber laser unit 110 and the optical medium oscillator 130 are mechanically separated, and the laser generating apparatus 100 generating a mid-infrared laser light source having a wavelength range of 2 to 5 um. There was also no mid-infrared optical fiber for transmitting all high-power mid-infrared laser light in the 2-5 um wavelength range from 4m to more than 4m. In addition, even if there is a mid-infrared transmission optical fiber that can transmit some wavelength bands, there is a problem that a lot of losses occur in the transmission process of the mid-infrared laser light.

Accordingly, the present invention provides a wavelength conversion head-separated mid-infrared optical fiber laser generating apparatus for efficiently transmitting a long distance by minimizing the loss of mid-infrared laser light in order to solve the above problems.

According to the present invention for achieving the above-mentioned object, in the mid-infrared fiber laser generating apparatus, generating a temporally modulated pulsed seed beam by the input modulation signal, and generating a laser beam by multi-stage amplifying the generated seed beam A fiber laser module unit to which Yb of a master oscillator power amplifier (MOPA) structure is added, a wavelength conversion head unit converting the generated laser beam into mid-infrared wavelengths and generating mid-infrared laser wavelengths in all wavelength bands, and generating The laser beam is transmitted to the wavelength conversion head unit, and includes a transmission optical fiber connecting the optical fiber laser module unit and the wavelength conversion head unit, wherein the optical fiber laser module unit includes a seed beam generator, a preamplifier, and a main amplifier. Comprising an all-fiber structure that is connected to each optical fiber, the seed beam generating unit Generates a pulsed seed beam modulated temporally by the input modulation signal, and is equipped with a DFB seed laser diode, and the DFB seed laser diode is driven by a direct modulation method to generate several nanoseconds ( ns) pulse width of the laser can be output, the wavelength conversion head portion is produced at three different intervals, the wavelength conversion according to each channel, the band in the 2 ~ 5um wavelength range A QPM PSI (Quasi-Phase Matching Periodically Poled Lithium Niobate) device that oscillates wavelengths corresponding to I, II, and IV is included.

According to the present invention, by separating the Yb-added fiber laser module unit and the PPLN optical development development unit at least 4 m or more from the optical fiber for transmission, many mid-infrared light loss problems occurring during the transmission of the mid-infrared laser light within the 2 to 5 um wavelength band can be solved. Rather, the wavelength can be converted to all wavelengths within the wavelength range of 2 ~ 5um.

In addition, the present invention can be manufactured in a small size, light weight by separating the Yb-added fiber laser module unit and the PPLN photo-mediated oscillation unit, there is an effect that can be improved in the mounting system with space constraints such as aircraft.

In addition, since the fiber laser module of the present invention controls the seed beam generator by a direct modulation method, since each amplification stage and the connection of the pump light and the signal light are all connected in an all-fiber type, they are resistant to external shocks and require no external optical alignment. It is not affected by dust and dirt.

1 is a block diagram showing a conventional laser generator.
Figure 2 is a block diagram showing a laser generating apparatus according to an embodiment of the present invention.
3 is a configuration diagram showing in detail the pre-amplification unit of the fiber laser module unit according to an embodiment of the present invention.
4 is a configuration diagram showing in detail the main amplifier of the optical fiber laser module unit according to an embodiment of the present invention.
5 is a configuration diagram showing in detail the wavelength conversion head of the laser generating apparatus according to the embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the preferred embodiment of the present invention. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to a user, a user's intention or custom. Therefore, the definition should be based on the contents throughout this specification.

The present invention provides an all-fiber type laser generator of a direct modulation method that generates mid-infrared wavelengths including all wavelength bands to which the detector of the infrared guided missile required by the directional infrared based equipment responds.

The present invention also provides a wavelength conversion head-separated mid-infrared optical fiber laser generating apparatus and method capable of generating mid-infrared laser light at a distance from a high power pump fiber laser.

2 is a block diagram illustrating a laser generating apparatus according to an exemplary embodiment of the present invention.

As shown, the laser generating apparatus according to the embodiment of the present invention generates a temporally modulated pulsed seed beam by the input modulation signal when the direct modulation signal is input, and pre-amplifies and generates the seed seed beam. Optical fiber laser module 210 for amplifying and generating a laser beam, and PPLN (Periodically Poled Lithium Niobate) photo-mediated oscillator for converting the generated laser beam into mid-infrared wavelength within a wavelength band of 2 to 5um It comprises a transmission optical fiber 214 for connecting the wavelength conversion head 220, the optical fiber laser module 210 and the wavelength conversion head 220 and transmits the laser without loss.

When the direct modulation signal is input, the optical fiber laser module 210 generates a seed beam generator 211 and a seed beam generator 211 that generate a pulsed seed beam modulated in time by the input modulation signal. A preamplifier 212 for amplifying the low output light pulses to a high output, and a main amplifier 213 for amplifying the light amplified first in the preamplifier 212 to a higher high output.

Hereinafter, a laser generating apparatus according to an embodiment of the present invention will be described in detail with reference to FIG. 2.

The optical fiber laser module 210 is composed of a Yb-added optical fiber laser having a master oscillator power amplifier (MOPA) structure, and the Yb-added optical fiber laser includes a seed beam generator 211, a preamplifier 212, and a main amplifier. 213. The DFB laser diode of the seed beam generator 211 is driven by a direct modulation method to produce a high peak output at a pulse width of several ns, and to control parameters such as pulse width and pulse shape. Can be. The seed laser diode of the Yb-doped fiber laser employs a laser diode that oscillates in the 1064 nm wavelength band. The seed beam, which can control the pulse width of about ns by the direct modulation method, amplifies the optical fiber based on the Yb-added optical fiber of the designed MOPA structure, and generates a high output pump light of 30W.

When the jamming code for deceiving the infrared guided missile to the optical fiber laser module 210 is directly modulated by the modulator 202 and multiplied by a pulse current, the seed beam of the optical fiber laser module 210 is input. The generator 211 generates a pulsed seed beam. The seed beam generator 211 is configured in an on-board form in which a DFB seed laser diode is mounted on a driving board. The drive board is composed of a pulse current generator, a microcomputer for control, a temperature control circuit, an interface for communication and power, and the like. The pulse current generator generates a pulse current in a differential switching method according to the signal of the microcomputer to pulse drive the laser diode. The microcomputer analyzes parameters according to the signals of the laser system and performs control functions such as laser pulse generation and temperature control. The temperature control circuit stabilizes the temperature of the laser diode for stable laser driving, and the interface is supplied with DC power for communication and driving with the laser system.

When the seed beam generated through the seed beam generator 211 is input to the preamplifier 212, the preamplifier 212 is composed of two stages of a single mode optical fiber and a single mode dual clad optical fiber, and the seed beam The low power optical pulse generated by the generator 211 is amplified to a high output and input to the main amplifier 213. The preamplifier 220 is composed of an isolator, a spectral filter, a pump laser diode, a wavelength division multiplexer, and an optical combiner. The isolator blocks the amplified spontaneous emission light in the reverse direction to prevent laser damage, and the spectral filter suppresses the amplified spontaneous emission light generated inside the amplifier, and the wavelength division multiplexer and the optical combiner are pumped light. And to combine the signal light. A more detailed description of the preamplifier 212 will be described later with reference to FIG. 3.

In addition, the main amplifier 213 serves to amplify the high output light pulse input from the seed beam generator 211, that is, the first amplified light to a higher high output. The main amplifier 213 is composed of an isolator, a spectral filter, a pump striper, a large diameter double clad optical fiber, an optical combiner, pump laser diodes, and a silica end-cap. More detailed description of the main amplifier 213 will be described later with reference to FIG. 4.

As described above, the laser beam output through the optical fiber laser module 210 generates a high output laser pulse 310 having a wavelength of 1064nm. The pulsed laser beam is input to the wavelength conversion head 220 through the optical fiber 214 for transmission.

The wavelength conversion head unit 220 receives the high power pump laser beam from the optical fiber laser module unit 210 having a master oscillator power amplifier (MOPA) structure from the optical fiber channel 214 for transmission. Conversion to wavelength produces a laser having mid-infrared laser wavelength 222 in all wavelength bands (eg, Band I, II, IV). The wavelength conversion head 220 has a PPLN photo-mediated oscillator structure, and includes a QPM Pasi-Phase Matching Periodically Poled Lithium Niobate (PPLN) element, a temperature controlled oven, and a photo-mediated oscillator reflector. The PPLN device is a nonlinear wavelength converting material having a high nonlinear coefficient in the infrared region, and photo-mediated oscillator reflectors are configured to control the temperature of the PPLN using an oven and increase the wavelength conversion efficiency. Such a detailed description of the wavelength conversion head unit 220 will be described later with reference to FIG. 5.

In addition, the transmission optical fiber 214 connecting the optical fiber laser module 210 and the wavelength conversion head 220 has a distance of 4 m or more from the optical fiber laser module 210 to the amplified pump light of the optical fiber laser module 210. The wavelength conversion head 220 in the role of transmitting without loss. By separating the optical fiber laser module 210 and the wavelength conversion head 220 at a distance of 4 m or more, the wavelength conversion head 220 at a distance of 4 m or more from the optical fiber laser module 210 is required by the directional infrared deception equipment. The wavelength conversion is possible to all wavelength bands (eg Band I, II, IV), and minimizes the optical loss of the mid-infrared laser wavelength in the converted 2 ~ 5um wavelength band.

3 is a configuration diagram showing in detail the pre-amplification unit of the fiber laser module unit according to an embodiment of the present invention.

As shown, the preamplifier 212 of the optical fiber laser module unit according to the embodiment of the present invention isolator (302, 312) to block the amplified spontaneous emission light and the reflected signal in the reverse direction to prevent the laser damage, Spectral filters 304 and 314 for suppressing the amplified spontaneous emission light generated inside the amplifier, optical combiners 308 and 318 for coupling the pump light and the signal light, and a specific wavelength. Pump laser diodes 306 and 316 for pumping a laser having a single mode active fiber or a single mode dual clad active fiber.

The preamplifier 212 may include at least one stage, and each stage includes an isolator, a spectral filter, a wavelength division multiplexer, a combiner, a pump laser diode, and an optical fiber. If the preamplifier 212 is composed of two or more stages, one end of the optical fiber is configured as a single mode active optical fiber, and the other end is composed of a single mode dual clad active optical fiber.

Hereinafter, the preamplification unit of the optical fiber laser module unit according to the embodiment of the present invention will be described in detail with reference to FIG. 3.

First, the preamplifier 212 according to the present invention is composed of at least two or more stages. For example, each stage is composed of a single mode active optical fiber 310 and a single mode dual clad active optical fiber 320. do

The single mode active optical fiber 310 is an isolator 302 for blocking the amplified spontaneous emission and reflected light in the reverse direction when outputting the input high output light pulse, that is, the first amplified light, and wavelength filtering around the center wavelength A spectral filter 304 for removing side wavelengths caused by nonlinear phenomena such as Raman, a pump laser diode 306 for pumping a laser of 915 nm or 975 nm, and an optical comb that combines the input high-output signal light and pumped light. And a single mode active optical fiber 310 which amplifies the signal light output by the pumping from the pumping light.

In addition, the single mode dual clad active optical fiber 320 has a structure similar to the single mode active optical fiber 310, but the single mode dual clad active optical fiber 320 is different.

The above-described optical combiners 308 and 318 are coupled to each other so that pump laser diode light having a wavelength of 915 nm or 975 nm can be absorbed by the Yb-doped optical fiber to emit pump laser light having a band of 1 to 1.1 um.

4 is a configuration diagram showing in detail the main amplifier of the optical fiber laser module according to an embodiment of the present invention.

As shown, the main amplifier 213 of the optical fiber laser module unit according to an embodiment of the present invention is a high output isolator 402 suitable for the first amplified high output pump light, a high output spectrum filter 404, a pump A streber 406, a large diameter double clad active optical fiber 408, a wavelength division multiplexer 410, 915 nm or 975 nm pump laser diodes 412a-412f, and an end cap 414.

The main amplifier 213 secondly amplifies the pump laser light that has passed through the preamplifier 212 to finally generate a high output pump light of 30 W class.

The first amplified light in the preamplifier 212 is free from limitation due to the nonlinear phenomenon by performing high absorption and amplification even with a short length for light pumping from the pump laser diode in the active optical fiber to which the large-diameter double clad Yb is added. . Coupling of optical fibers of different core sizes can result in loss and reflection in the mating surface, thereby reducing optical loss and reflection between heterogeneous fiber couplings through proper mode matching technology between heterogeneous optical fibers. The first amplified light is amplified to 30W high output light 416 through six pump laser diodes 412a to 412f and the wavelength division multiplexer 410. In addition, in order to increase the conversion efficiency in the wavelength conversion head 40, all components constitute a polarization sustaining optical fiber connected to the polarization maintaining optical fiber to maintain the linear polarization characteristics of the seed laser diode. The output end of the fiber laser module 210 is coupled to the inclined silica end cap 414 to be incident on the optical fiber 214 for transmission in order to prevent damage to the laser due to high peak output and back reflection of the output.

The transmission optical fiber 214 transmits the incident high power pump laser light to the wavelength conversion head 220 at a distance of 4 m or more from the optical fiber laser module 210 without light loss. By separating the optical fiber laser module 210 and the wavelength conversion head 220 more than 4m in this way it facilitates the system mountability which is regarded as a problem of the existing integrated mid-infrared fiber laser. In addition, by converting the wavelength at a distance of 4m, the loss of the mid-infrared laser light 222 in the band I, II, and IV areas is minimized.

5 is a configuration diagram showing in detail the wavelength conversion head of the laser generating apparatus according to the embodiment of the present invention.

The wavelength conversion head 220 of the laser generating apparatus according to the embodiment of the present invention has a PPLN photo-mediated oscillator 221 structure, the focus lens 502, the first reflector 504, the second reflector 510, Temperature control oven 506, PPLN non-linear element 508.

Hereinafter, the wavelength conversion head of the laser generating apparatus according to the exemplary embodiment of the present invention will be described in detail with reference to FIG. 5.

The wavelength conversion head 220 has a wavelength of 30W amplified by the transmission optical fiber 214 collimated to the QPM PPLN element 508 by the focus lens 502 to a wavelength corresponding to the band I, II, IV region. Is converted. The mid-infrared light converted by the first reflector 504 and the second reflector 510 is resonated and amplified and output to the second reflector, and has a waveform of the mid-infrared laser light 222.

The light output through the second reflector corresponds to bands I, II, and IV in a 2 to 5 um wavelength band, and is output as a waveform of high power mid-infrared laser light of at least 1 Watt.

Then, the PPLN optical medium development oscillator 221 resonates the laser beam of the amplified 1064 nm waveform 416 incident from the Yb-added fiber laser in the PPLN optical medium oscillator. The QPM PPLN device 508 is fabricated in three different main periods, and can convert wavelengths according to each channel and oscillate wavelengths 222 corresponding to bands I, II, and IV in a 2 to 5 um wavelength region. . The 1 W or higher high power mid-infrared laser light 222 oscillated by the PPLN photo-mediated oscillator 221 of the wavelength conversion head 220 is finally output as parallel light through a collimator.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

210: fiber laser module unit 211: seed beam generator
212: preamplifier 213: main amplifier
214: transmission optical fiber 220: wavelength conversion head
221: PPLN photomediated oscillator

Claims (5)

In the mid-infrared fiber laser generator,
A fiber laser module unit to which Yb of a MOPA (Master Oscillator Power Amplifier) structure for generating a temporally modulated pulsed seed beam by the input modulation signal and generating a laser beam by multi-stage amplifying the generated seed beam; ,
A wavelength conversion head unit converting the generated laser beam into mid-infrared wavelengths to generate mid-infrared laser wavelengths in all wavelength bands;
A transmission optical fiber which transmits the generated laser beam to the wavelength conversion head part and connects the optical fiber laser module part and the wavelength conversion head part,
The fiber laser module unit
It consists of a seed beam generator, a preamplifier, and a main amplifier, each having an all-fiber structure connected by optical fibers,
The seed beam generator
Generates a pulsed seed beam modulated in time by the input modulation signal, and is equipped with a DFB seed laser diode,
The DFB seed laser diode
Driven by a direct modulation method, it is possible to output a laser of a pulse width of several nanoseconds (ns),
The wavelength conversion head portion
QPM PPLN (Quasi-Phase Matching Periodically Poled Lithium), which is manufactured at three different periodic intervals, differs in wavelength conversion according to each channel, and oscillates wavelengths corresponding to Band I, II, and IV in a 2 ~ 5um wavelength range. A mid-infrared optical fiber laser generating device comprising a niobate) element.
According to claim 1, wherein the fiber laser module unit
A preamplifier configured to amplify the generated pulsed seed beam with high power, and comprising a single mode optical fiber and a single mode dual clad optical fiber;
And a main amplifier for amplifying the pulsed seed beam amplified by the high power again.
3. The preamplifier of claim 2, wherein the preamplifier is
It is composed of at least two stages, each stage isolator to prevent damage to the laser amplifier by blocking the spontaneous emission light, the reflected signal that the seed beam amplified by the high power proceeds in the reverse direction,
A spectral filter for suppressing spontaneous emission light generated inside the preamplifier;
An optical combiner for coupling the signal light and the pump light output from the spectral filter;
A pump laser diode for generating the pump light;
A mid-infrared optical fiber laser generation device comprising a single mode active optical fiber that amplifies the signal light output by pumping from the pump light.
According to claim 1, wherein the optical fiber for transmission
And generating the laser beam without loss to the wavelength conversion head part a few meters away from the optical fiber laser module part.
The method of claim 2, wherein the main amplifier
A mid-infrared fiber laser generator comprising a high power isolator, a high power spectral filter, a pump striper, a large diameter double clad active fiber, an optical combiner, 915 nm or 975 nm pump laser diodes, and an end cap.

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