CN101303452A - Bundled fiber optic pulse delay superposition shaper - Google Patents

Abstract

The invention discloses a bundled optical fiber pulse delay superposition shaper, which belongs to the field of laser technology. The device consists of a single high-power pulsed laser, an aspheric collimating beam expander or microlens array, a clustered single-mode fiber retarder, an aspheric focusing lens or a microlens array and multiple single-mode fibers. The flat-top type large-mode field laser beam is coupled into the cluster type single-mode fiber delayer after being collimated and beam-expanded. The beam splitting pulse forms a pulse sequence with a fixed time delay and the same pulse energy. The pulse sequence is focused by the aspheric surface of the converging lens The lens is coupled to a single-mode fiber, superimposed and shaped into a rectangular pulse output on the order of nanoseconds. The invention has the advantages that: the pulse superposition shaper has the advantages of small volume, low cost, high stability, multiple beam splitting, uniform pulse energy and the like.

Description

Bundled fiber optic pulse delay superposition shaper

technical field

The invention relates to a bundled optical fiber pulse delay superposition shaper, which belongs to the technical field of lasers.

Background technique

In the field of optical communication and laser inertial confinement nuclear fusion, there are special requirements for the shape of the seed laser pulse, and a rectangular pulse with a long duration (ns order) is often required. The methods used mainly include: frequency domain filtering method, time domain delay superposition method.

At present, there are two relatively mature technologies in the time-domain delay-and-addition method: one is to introduce a time delay from the picosecond-level pulses output by multiple fiber lasers in parallel through different time delay lines, and then superimpose them to form nanosecond-level pulses. The second is to use a single laser output to perform multiple beam splits in series and then superimpose them to form nanosecond-level rectangular pulses.

There is an obvious shortcoming in the above technique, that is, it is impossible to separate more pulses (generally<10). This is because: in method 1, the parallel output technology of multiple fiber lasers is used, and every time a superimposed pulse is added, a laser will be added, which will lead to a rapid increase in the cost, power consumption, complexity, and volume of the entire system; in method 2, although the laser The number does not increase, but the pulse energy after serial beam splitting is attenuated, that is, the beam splitting pulse energy decreases step by step, which brings difficulties to the superposition and synthesis process.

Contents of the invention

The present invention aims to propose a bundled optical fiber pulse delay superposition shaper, which has the advantages of small size, low cost, high stability, multiple beam splitting, uniform pulse energy, etc. High pulse quality.

The present invention is realized through the following technical scheme, a bundled optical fiber pulse delay superposition shaper, characterized in that the device includes a single high-power large-mode-field photonic crystal fiber mode-locked laser or a single high-power solid-state pulse laser or A single high-power semiconductor pulsed laser 1, an aspheric collimating beam expander or microlens array I2, a clustered single-mode fiber retarder 3, an aspheric focusing lens or microlens array II4 and multi-headed single-mode fiber 5, The connection relationship of the various components in the device is that the laser beam output by the laser with a flat top-shaped spatial distribution is collimated and expanded by the aspheric collimator beam expander shaping system, and then coupled into the cluster type single-mode fiber delay device. The beam-split pulses after the bundled single-mode fiber delayer form a pulse sequence with a fixed time delay and the same pulse energy, and then all the pulse sequences are coupled into a single-mode fiber through a converging lens aspherical focusing lens, superimposed and shaped into a nanometer Second level rectangular pulse output.

The above-mentioned high-power large-mode field photonic crystal fiber mode-locked laser is composed of an oscillation stage and an amplification stage and a polarization Faraday isolator between the oscillation stage and the amplification stage. Coated photonic crystal gain fiber, semiconductor saturable absorbing mirror and polarization rotation (NPE) hybrid mode locker, oscillation level grating pair or large negative dispersion fiber dispersion compensator, wherein the core diameter of photonic crystal gain fiber is 10-50 Micron, numerical aperture (NA) of 0.02-0.06, outer cladding diameter of 200-400 microns, numerical aperture (NA) of 0.4-0.8, length of 1-10m, cladding pump source of 5-30W high-power laser diode ; The amplification stage comprises a double-coated photonic crystal gain fiber of ytterbium-doped ions or erbium-doped ions in a large mode field, an amplification stage grating pair or a large negative dispersion fiber dispersion compensator, wherein the core diameter of the photonic crystal gain fiber is 20- 70 microns, the numerical aperture (NA) is 0.02-0.06, the outer cladding diameter is 200-400 microns, the numerical aperture (NA) is 0.4-0.8, the length is 1-10m, and the cladding pump source is 20-100W high-power laser diode .

The above-mentioned aspherical collimating beam expander is a Galileo telescope system, and the beam expansion ratio is 1:2-10 relative to the effective mode field diameter of the small-core bundled photonic crystal fiber, or the focal length is a microlens array on the order of millimeters Array.

The above-mentioned bundled single-mode fiber delayer is a bundle of ordinary single-mode fibers (SMF) or other types of transmission fibers of different lengths. One end of the bundled fibers is aligned and then fixed, and the length of the other end of the bundled fibers is selected according to the required time delay. And according to the length from the central optical fiber to the outer optical fiber of the optical fiber bundle, it is arranged in descending order.

The above-mentioned aspherical converging lens is a microscopic objective lens with a focal length of 5-20 mm, or a microlens array with a focal length of millimeter order.

The present invention has the advantages of: (1) a single high-power large-mode-field photonic crystal fiber-locked laser is used as the seed pulse source, which is better than the current parallel output mode of multiple low-power common single-mode fiber lasers regardless of operating costs, The power consumption, complexity and volume are all significantly reduced; (2) The bundled fiber optic pulse delayer is used to delay the incident pulse in parallel, which is simpler in structure and smaller in pulse decay than the original technology; (3) The long optical fiber is placed in the In the middle part of the bundle, the bundled fiber-type pulse delay line is constructed in a way that gradually shortens from the inside to the outside, which can easily correct the energy of the pulse splitting introduced by the stronger distribution of the seed pulse space; (4) The bundled fiber-optic pulse delay line can be used repeatedly, that is, the output pulse of each fiber in the first-level bundled fiber-optic pulse delay line is coupled to the second-stage bundled fiber-type pulse delay line to form a parallel cascaded dendritic structure, which increases rapidly Split the number of beams without adding complexity.

Description of drawings

Fig. 1 is a structural block diagram of the bundled optical fiber pulse delay superposition shaper of the present invention.

In the figure: 1 is a high-power pulsed laser; 2 is an aspheric collimating beam expander or microlens array I; 3 is a clustered single-mode fiber retarder; 4 is an aspheric focusing lens or microlens array II; 5 is multi-head single-mode fiber.

FIG. 2 is a schematic structural diagram of the bundled single-mode fiber delayer 3 in FIG. 1 .

FIG. 3 is a schematic structural diagram of a high-power large-mode-field photonic crystal fiber mode-locked laser used in the high-power pulsed laser in FIG. 1 .

In the figure: 1-1 is an oscillation-level pump source; 1-2 is an oscillation-level large-mode-field photonic crystal gain fiber; 1-3 is a semiconductor saturable absorber mirror and a polarization rotation (NPE) hybrid mode-locker; 1-4 1-5 are polarization Faraday isolators; 1-6 are amplification-level large-mode-field photonic crystal gain fibers; 1-7 are amplification-level grating pairs or large negative dispersion fibers Dispersion compensator; 1-8 are the pumping sources of the amplification stage.

Detailed ways

The integrated optical fiber pulse delay superposition shaper of the present invention is as shown in accompanying drawing 1, and specific embodiment is as follows:

The high-power pulsed laser adopts the high-power large-mode-field photonic crystal fiber mode-locked laser shown in Figure 3, and the gain medium of the oscillation stage adopts Yb-doped large-mode-field double-clad polarization-maintaining photonic crystal fiber 1-2, the core diameter 25 microns, NA is 0.03, the outer cladding diameter is 250 microns, NA is 0.5, and the length is 3.5m. Both ends are collapsed and polished to beveled angles to directly pump the cladding, or weld SMF of appropriate length, and pump by WDM pump; the oscillation stage uses 10W LD1-1 for single-sided or double-clad pumping, and one end of the resonant cavity adopts semiconductor saturable absorbing mirror and polarization rotation mixer mode-locking 1-3 as the output port, in the resonant cavity The other end adopts grating pair or large negative dispersion fiber dispersion compensator 1-4 to perform dispersion compensation and pulse compression; the gain medium of the amplification stage adopts Yb-doped large mode field double-clad polarization-maintaining photonic crystal fiber 1-6, the core diameter 40 microns, NA is 0.03, outer cladding diameter is 270 microns, NA is 0.6, and the length is 1.5m. Both ends are collapsed and polished to beveled angles to directly pump the cladding, or welded with SMF of appropriate length, pumped by WDM Pump; use high-power 30W LD1-8 for single-sided or double-clad pumping, place a polarization Faraday isolator 1-5 at the input of the resonator to prevent the laser from returning to the oscillation stage, and place it at the output of the resonator A grating pair or a large negative dispersion fiber dispersion compensator 1-7 is used to perform dispersion compensation and pulse compression; the high-power pulse laser 1 can also be any other high-power pulse laser. Aspherical collimation beam expander or microlens array I2 selects aspheric lens to form a Galileo telescope system with a beam expansion ratio of 1:5; or uses microlens array to directly focus the output of 1 into a bundled single-mode fiber delay in each fiber core of the device. The bundled single-mode fiber delayer 3 is shown in Figure 2, 19 SMFs are integrated into one bundle, the shortest single SMF takes 20mm, and the remaining SMFs are increased by 11mm in turn, single-ended parallel bundles, and the incident 1550nm band It is divided into 19 pulse sequences with a time delay interval of about 56ps; and a bundled optical fiber pulse delayer is constructed by placing a long optical fiber in the middle of the bundle and gradually shortening from the inside to the outside. The aspherical focusing lens II4 is a microscopic objective lens composed of aspheric lenses with a focal length of 10-20 mm, or a microlens array with a focal length of millimeters corresponding to the core of the bundled single-mode optical fiber retarder. The multi-head single-mode fiber 5 is bundled with ordinary single-mode fiber with multiple heads (corresponding to 3 output ports), the fiber length is 0.2m, and the output pulse is a rectangular pulse of ns magnitude synthesized by 19 ultrashort pulses. If the process of the bundled single-mode fiber delayer 3 is repeated for the output pulses of each fiber after passing through the bundled single-mode fiber delayer 3 , the number of pulse splits can be rapidly increased in a branch-weighted manner.

Claims (5)

1. A bundled optical fiber pulse delay superimposition shaper is characterized in that the device comprises a single high-power large-mode field photonic crystal fiber mode-locked laser or a single high-power solid-state pulsed laser or a single high-power semiconductor pulsed laser (1 ), aspheric collimating beam expander or microlens array I (2), bundled single-mode fiber retarder (3), aspheric focusing lens or microlens array II (4) and multi-headed single-mode fiber (5 ) structure, the connection relationship of each component in the device is that the spatial distribution of the laser output is a flat-top type large-mode field laser beam is collimated by the aspheric collimator beam expander shaping system and then coupled into the clustered single-mode fiber delay The beam splitting pulse after passing through the bundled single-mode fiber delayer forms a pulse sequence with a fixed time delay and the same pulse energy, and then all the pulse sequences are coupled into a single-mode fiber through a converging lens aspheric focusing lens, superimposed Shaped into a rectangular pulse output on the order of nanoseconds. 2. by the bundled optical fiber pulse delay superposition shaper according to claim 1, it is characterized in that, the high-power large-mode field photonic crystal fiber mode-locked laser is separated by polarization Faraday between the oscillation stage and the amplification stage and the oscillation stage and the amplification stage The oscillator consists of large mode field yttrium-doped or erbium-doped double-coated photonic crystal gain fiber, semiconductor saturable absorption mirror and polarization rotation hybrid mode-locker, oscillation stage grating pair or large negative dispersion fiber dispersion compensation The photonic crystal gain fiber has a core diameter of 10-50 microns, a numerical aperture of 0.02-0.06, an outer cladding diameter of 200-400 microns, a numerical aperture of 0.4-0.8, and a length of 1-10m. It is a high-power laser diode of 5-30W; the amplification stage includes a double-coated photonic crystal gain fiber with a large mode field of ytterbium-doped ions or erbium-doped ions, a pair of amplifier-level gratings, or a large negative dispersion fiber dispersion compensator. The core diameter of crystal gain fiber is 20-70 microns, the numerical aperture is 0.02-0.06, the outer cladding diameter is 200-400 microns, the numerical aperture is 0.4-0.8, the length is 1-10m, and the cladding pump is 20-100W high power laser diode. 3. by the described bundled optical fiber pulse delay superposition shaper of claim 1, it is characterized in that, the aspheric collimated beam expander is a Galileo telescope system, and the beam expansion ratio is relative to the small core diameter bundled photonic crystal fiber effective mode field 1:2-10 of the diameter, or the focal length is on the order of millimeters is a microlens array. 4. The bundled optical fiber pulse delay superposition shaper according to claim 1, wherein the bundled single-mode fiber delay device is a bundle of common single-mode optical fibers of different lengths or other types of transmission fibers, and one end of the bundled optical fibers is aligned After fixing, the length of the other end of the bundled optical fiber is selected according to the required time delay, and is arranged in descending order according to the length from the central optical fiber to the outer optical fiber of the optical fiber bundle. 5. The bundled optical fiber pulse delay superposition shaper according to claim 1, wherein the aspheric converging lens is a microscopic objective lens with a focal length of 5-20 mm, or a microlens array with a focal length of millimeter order.

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