CN202454888U - Single longitudinal mode narrow line width fiber laser of single-point injection type active parallel-connection subsidiary cavity - Google Patents

Abstract

The utility model discloses a single longitudinal mode narrow line width fiber laser of a single-point injection type active parallel-connection subsidiary cavity. The single longitudinal mode narrow line width fiber laser comprises a star coupler provided with an N*N port, an optical active subsidiary cavity, N-1 optical passive subsidiary cavities, a 1*2 coupler and a subsidiary laser. Two ends of the optical active subsidiary cavity are respectively connected with two ends of a branch circuit of the star coupler to form a closed loop circuit, two ends of each optical passive subsidiary cavity are respectively connected with two ends of one of surplus branch circuit of the star coupler form a closed loop circuit respectively, a gain amplification unit and a mode selection unit are sequentially connected in one closed loop circuit, the input end of the 1*2 coupler and one output end are respectively connected in the closed loop circuit where the 1*2 coupler is, and the other output end serves as the output end of the fiber laser. The output ends is connected with the optical active subsidiary cavity through a coupling unit of the subsidiary laser. The single longitudinal mode narrow line width fiber laser is simple and compact in structure, flexible in adjustment, capable of achieving single longitudinal mode, narrow line width and high stable output.

Description

The single longitudinal mode narrow cable and wide optical fiber laser in the sub-chamber of single-point injection active parallel connection

Technical field

The utility model relates to a kind of fiber laser, relates in particular to the single longitudinal mode narrow cable and wide optical fiber laser in the sub-chamber of a kind of single-point injection active parallel connection, belongs to laser technology field.

Background technology

The single mode narrow linewidth fiber laser has high temporal coherence and low phase noise characteristic, has in civil and military fields such as superhigh precision long-distance optical fiber sensing system, high speed optical communication system, coherent optical communication, laser radar, microwave photon widely to use.

The key that realizes the single longitudinal mode output of laser is to obtain the single longitudinal mode running of laser and suppress multimode oscillation and mode hopping phenomenon through model selection and stabilization technique; Especially for having high power continuous wave output optical fibre laser, long playing stability has determined laser performance good and bad.The filtering technique that the realization single longitudinal mode that adopts is at present selected mainly comprises the method for laser cavity structure and chamber inner fiber filter modeling.The former comprises annular chamber or linear cavity; The latter comprises according to the filter effect classification: based on the Fiber Bragg Grating FBG filter of Light Diffraction Effect; Fabry-fabry-perot filter, multilayer thin-film-filter and Mach-Zehnder interference filter etc. based on interference effect.The centre wavelength filtering spectral width that the filter modeling can obtain has the above spectrum width of GHz generally greater than 0.01nm, and the laser output mode depends on chamber inner fiber device and stability of filter, is subject to such environmental effects.How, acquisition to guarantee that the operation stability of fiber laser becomes the technical barrier of restriction fiber laser performance boost when reaching the single longitudinal mode output of kHz narrow linewidth.

The utility model content

The utility model technical problem to be solved is to overcome the deficiency of prior art, and the single longitudinal mode narrow cable and wide optical fiber laser in the sub-chamber of a kind of single-point injection active parallel connection is provided, and can realize single longitudinal mode, narrow linewidth, high stable output.

The single longitudinal mode narrow cable and wide optical fiber laser in the sub-chamber of the single-point injection active of the utility model parallel connection comprises: a star-type coupler, have the port of N * N, and N is the integer greater than 1;

The sub-chamber of one optical active fiber, its two ends are connected with one of them two ends along separate routes of said star-type coupler respectively, form the closed-loop path;

N-1 the sub-chamber of optical fiber passive, the two ends in each sub-chamber of optical fiber passive are connected with the two ends of along separate routes one of them of said star-type coupler residue respectively, form the closed-loop path respectively; Be connected with gain amplifying unit, modeling unit in one of them closed-loop path in turn, and one 1 * 2 couplers; The input of said 1 * 2 coupler inserts its closed-loop path, place respectively with one of them output, and the another one output is as the output of fiber laser;

One seed laser, its output is connected with the sub-chamber of said optical active fiber through the seed laser coupling unit.

Further, except that the sub-chamber of the optical fiber passive that is connected with 1 * 2 coupler, also have one in the sub-chamber of remaining N-2 optical fiber passive at least and be connected with gain amplifying unit, modeling unit.Preferably, said gain amplifying unit comprises multistage structure for amplifying.

Preferably, said seed laser coupling unit comprises optical isolator and optical fiber circulator; The input of optical isolator is connected with the output of seed laser, and output is connected with a port of optical fiber circulator; Two other port of optical fiber circulator is connected with the sub-chamber of said optical active fiber respectively with respectively.

Said seed laser optimal wavelength and the humorous laser of adjustable power.

Preferably, said gain amplifying unit comprises first pumping, second pumping, first gain fibre, second gain fibre, first pumping coupler, second pumping coupler, optical isolator; The output of first pumping is connected with short wavelength's input of first pumping coupler; The output of first pumping coupler is connected with long wavelength's input of second pumping coupler through first gain fibre, optical isolator, second gain fibre successively; Short wavelength's input of second pumping coupler is connected with the input of second pumping, and the output of second pumping coupler is connected with long wavelength's input of first pumping coupler through said star-type coupler.

Preferably, said first pumping is that single mode 980nm is semiconductor pumped, and said second pumping is the multiple die semiconductor pumping.

Preferably, said first gain fibre is the single mode Er-doped fiber, and said second gain fibre is the double clad rare earth doped fiber.

Compare prior art, the utlity model has following beneficial effect:

1, adopts sub-chamber parallel-connection structure, increased the fineness of whole laser resonant cavity model selection, improved the laser delivery efficiency, improved output optical mode noise characteristic.Can in the different sub chamber, carry out filtering and Stability Control, increase the stability of laser output;

2, the seed source that injects in the active cavity has locked laser output wavelength, has compressed laser spectrum width, has improved laser output coherence;

3, employing has been compressed laser spectrum width with the method and parallelly connected sub-chamber acting in conjunction in the sub-chamber of MHz seed source laser injection fibre, has improved laser output coherence;

3, adopt multistage light amplification structure in single subcavities, increased the laser interacvity gain, improved laser output power;

5, adopt all optical fiber cavity structure, coupling loss is little, compact conformation, and delivery efficiency is high, and environmental interference immunity is high to external world.

Description of drawings

Fig. 1 is the structural principle sketch map of the single longitudinal mode narrow cable and wide optical fiber laser in the sub-chamber of the utility model single-point injection active parallel connection;

Fig. 2 is the structural representation of embodiment described in the embodiment; Wherein, 1,7 is semiconductor pumped, and 2,6 is pumping coupler; 3,5 is gain fibre, and 4,9,14 is optical isolator, and 8 is 1 * 2 optical coupler; 10 is 2 * 2 optical couplers, and 11 is Polarization Controller, and 12 is optical filter; 13 is seed laser, and 15 is optical fiber circulator, and a, b, c are three ports of optical fiber circulator 15;

Fig. 3 is the sketch map that concerns of the off resonance amount between seed injection operating frequency ' locked ' zone and seed laser and the passive sub-chamber optical maser wavelength;

The laser single longitudinal mode continuous wave output spectrum figure of Fig. 4 for recording with spectrometer;

The laser pulse output time-domain diagram that Fig. 5 realizes for seed laser being adopted pulse external modulation light mode;

The utility model laser continuous wave single-frequency output of Fig. 6 for utilizing time-delay self-heterodyne method to record.

Embodiment

Be elaborated below in conjunction with the technical scheme of accompanying drawing to the utility model:

The thinking of the utility model is to utilize coupler that the sub-chamber of optical active fiber is parallelly connected with the sub-chamber of one or more optical fiber passives; Thereby form the resonant tank of sub-chamber parallel connection; In the sub-chamber of optical active fiber, inject seed light source through seed laser then, thereby improve laser output characteristic.Following elder generation carries out brief description to the utility model principle of the utility model.

When light transmitted in the structure of the sub-chamber of a plurality of optical fiber through the coupler parallel connection, the light in the sub-chamber of different fibers can carry out the coherent superposition effect through coupler, thereby has improved whole laser cavity structure output spectrum characteristic.Every subcavities in N sub-chamber of optical fiber forms the harmonic oscillator loop of a laser, and is equipped with the gain amplifying unit, can know that by vernier (Vernier) effect the optical maser wavelength that is produced should satisfy the hunting of frequency condition of all resonant tanks, that is:

$f=\frac{{\mathrm{<figure-callout\; id="1"\; label="cm"\; filenames="DEST\_PATH\_120702142807.png,DEST\_PATH\_120702142813.png"\; state="\{\{state\}\}">cm</figure-callout>}}_1}{{\mathrm{<figure-callout\; id="1"\; label="cL"\; filenames="DEST\_PATH\_120702142807.png,DEST\_PATH\_120702142813.png"\; state="\{\{state\}\}">cL</figure-callout>}}_1}=\frac{{\mathrm{cm}}_2}{\mathrm{<figure-callout\; id="2"\; label="n\; L"\; filenames="DEST\_PATH\_120702142754.png,DEST\_PATH\_120702142800.png"\; state="\{\{state\}\}">n</figure-callout>}{L}_{}{}_2}=...=\frac{{\mathrm{cm}}_i}{n{L}_i}i=\mathrm{1,2}...N---\left(1\right)$

Wherein n is an optical fibre refractivity, m _iBe any positive integer, c is an optical maser wavelength, L _iBe the length of i subcavities

By the laser resonance frequency interval in the long sub-chamber of single optical fiber that determines, chamber, promptly so-called Free Spectral Range (Free spectrum resolution, expression formula FSR) is:

${\mathrm{FSR}}_i=\frac{c}{{\mathrm{nL}}_i}(i=\mathrm{1,2}...N)---\left(2\right)$

For the situation of N subcavities parallel connection, the long highest common divisor length in all chambeies is L, and L _i=j*L, wherein j is a positive integer, corresponding FSR is:

$\mathrm{FSR}=\frac{c}{\mathrm{nL}}=\frac{c*j}{L_i}(i=\mathrm{1,2}...N)---\left(3\right)$

Can increase the FSR of laser through parallelly connected number N that increases the sub-chamber of optical fiber and the length that shortens the sub-chamber of any single optical fiber, thereby increase the laser cavity internal schema at interval, improve the mode stability of laser output, help realizing the single longitudinal mode modeling.In addition, in passive sub-chamber, insert gain unit and can solve the contradiction between logical peak value of pattern filter response band in the Vernier effect and the side mode suppression ratio, and improve the power output of laser.

The basic structure of the fiber laser of the utility model is as shown in Figure 1, can be made up of a sub-chamber of optical active fiber and the sub-chamber parallel connection of one or more optical fiber passive.For ease of explanation, be example only below with the simplest sub-chamber of optical active fiber and an optical fiber passive chamber parallel connection, come the technical scheme of the utility model is elaborated.

Fiber laser among this embodiment, as shown in Figure 2, comprising: semiconductor pumped 1; Pumping coupler 2; Gain fibre 3, being used to sub-chamber provides the luminous power one-level to amplify; Optical isolator 4, level is amplified the reverberation of light path after being used to prevent; Gain fibre 5, being used to sub-chamber provides the luminous power secondary to amplify; Pumping coupler 6; Semiconductor pumped 7; 1 * 2 optical coupler 8, an one of which output is as the output of whole laser; Optical isolator 9 is used to control sub-endovenous laser one-way transmission; 2 * 2 optical couplers 10; Polarization Controller 11 is used to control polarization state in the laser cavity; Optical filter 12 is used for the mould of roughly selecting in the sub-chamber of passive fiber; Seed laser 13; Optical isolator 14; Optical fiber circulator 15.

Semiconductor pumped 1 output is connected with short wavelength's input of pumping coupler 2; The output of pumping coupler 2 is connected with long wavelength's input of pumping coupler 6 through gain fibre 3, optical isolator 4, gain fibre 5 successively; Short wavelength's input of pumping coupler 6 is connected with semiconductor pumped 7 input; The output of pumping coupler 6 input through optical coupler 8, optical isolator 9,2 * 2 couplers 10, Polarization Controller 11, optical filter 12 successively is connected with long wavelength's input of pumping coupler 2, and an output of optical coupler 8 is as laser output; The output of seed laser 13 links to each other with the input of optical fiber circulator 15 through optical isolator 14; Another input of optical fiber circulator 15 links to each other respectively with output with the input of 2 * 2 couplers 10 with output.Laser cavity forms the parallelly connected structure of two ring cavities through 2 * 2 couplers, and one of them sub-chamber is the sub-chamber of optical active fiber, is used to inject seed light; The sub-chamber of another one is the sub-chamber of optical fiber passive, is used to the coupling output that whole laser provides gain, roughly selects mould and laser.

Wherein semiconductor pumped 1 preferred single mode 980nm is semiconductor pumped; Semiconductor pumped 7 preferred multiple die semiconductor pumpings; Gain fibre 3 preferred single mode Er-doped fibers, gain fibre 5 preferred double clad rare earth doped fiber, seed laser 13 optimal wavelength and the humorous Distributed Feedback Lasers of adjustable power.

Realize that through the active method for implanting of single-point the frequency lock and the live width compression process of laser are following:

Seed laser gets in the sub-chamber of Active Optical Fiber through optical fiber circulator, and its power and wavelength-tunable joint are through carrying out mutual effect like 2 * 2 couplers among Fig. 2 and passive sub-endovenous laser.Passive sub-endovenous laser intensity depends on the summation of two stage gains, and its representative value is 30-40dB.The wavelength of seed light source and passive lasertron chamber optical maser wavelength are divided into non-off resonance and two kinds of situation of off resonance; The former is through the form unit of roughly selecting in the passive sub-chamber; It is filter cell; Centre wavelength is positioned near the seed laser, makes that active cavity and passive cavity interior resonance wavelength are basic identical, and the latter injects the seed laser that wavelength is different from passive lasertron chamber in the chamber.Seed laser gets in the active sub-chamber, carries out mutual effect through the laser in coupler and other the sub-chambeies.Typical light is injected (OIL) rate equation asks steady state solution to obtain:

$\mathrm{\&Delta;f}=-\mathrm{\&kappa;}\sqrt{1+{\mathrm{\&alpha;}}^2}\sqrt{I_{\mathrm{in}}/I_0}\sin ({\mathrm{\&phi;}}_0+{\tan }^{-1}\mathrm{\&alpha;})---\left(4\right)$

Wherein Δ f does not have the frequency-splitting that injects laser for injecting in laser and the chamber, and κ is the coupling coefficient of the two mutual effect, I _In/ I ₀Be the light intensity ratio of the two, φ ₀For there not being when injection chamber interior resonance phase factor, when injection laser is identical with the resonance wavelength of nothing injection laser in the chamber, φ ₀Be 0.It is as shown in Figure 3 that the seed of the laser that is characterized by this formula injects the relation of the off resonance amount between operating frequency ' locked ' zone and seed laser and the passive sub-chamber optical maser wavelength; Wherein inject the ratio that intensity is seed laser power and passive cavity laser power; With dB is unit; Frequency detuning is measured the normalization into the seed laser frequency, and the positive number scope is represented seed laser greater than passive laser output frequency, and negative is opposite.When passive interacvity gain is bigger, and seed laser power hour, and the frequency lock operation that obtains laser need be adjusted to the wavelength of seed laser and passive laser output wavelength consistent, and this can pass through modeling unit realization in the sub-chamber of passive fiber.

The fiber laser of the utility model inserts the modeling unit in the sub-chamber of optical fiber passive; Filters such as film filter, Fabry-Perot and fiber grating for example; Except realizing the mould of roughly selecting in the sub-chamber of passive fiber; Also be used to avoid the frequency detuning of seed laser and passive sub-endovenous laser, make laser move and ' locked ' zone, thereby near the laser of seed laser wavelength that is positioned at that obtains frequency lock is exported.

The utility model laser single longitudinal mode continuous wave output spectrum figure of Fig. 4 for recording with spectrometer; The laser pulse output time-domain diagram that Fig. 5 realizes for seed laser being adopted pulse external modulation light mode, wherein the width of pulse and repetition rate depend on the pulse modulation mode that seed laser is adopted; The laser linewidth that the utility model laser continuous wave single-frequency output of Fig. 6 for utilizing time-delay self-heterodyne method to record, the Distributed Feedback Laser of the MHz live width of employing obtain during for seed source laser is 21kHz; The long-time running stability test result of the utility model laser shows: its 2 hours run durations, laser output power and wavelength variations are 0.1dB and 0.01nm, when guaranteeing narrow linewidth output, have guaranteed the stability of laser operation.

Claims (9)

1. the single longitudinal mode narrow cable and wide optical fiber laser in the sub-chamber of single-point injection active parallel connection is characterized in that, comprising:

One star-type coupler has the port of N * N, and N is the integer greater than 1;

The sub-chamber of one optical active fiber, its two ends are connected with one of them two ends along separate routes of said star-type coupler respectively, form the closed-loop path;

N-1 the sub-chamber of optical fiber passive, the two ends in each sub-chamber of optical fiber passive are connected with the two ends of along separate routes one of them of said star-type coupler residue respectively, form the closed-loop path respectively; Be connected with gain amplifying unit, modeling unit in one of them closed-loop path in turn, and one 1 * 2 couplers; The input of said 1 * 2 coupler inserts its closed-loop path, place respectively with one of them output, and the another one output is as the output of fiber laser;

One seed laser, its output is connected with the sub-chamber of said optical active fiber through the seed laser coupling unit.

2. the single longitudinal mode narrow cable and wide optical fiber laser in the sub-chamber of single-point injection active parallel connection according to claim 1; It is characterized in that; Except that the sub-chamber of the optical fiber passive that is connected with 1 * 2 coupler, also have one in the sub-chamber of remaining N-2 optical fiber passive at least and be connected with gain amplifying unit, modeling unit.

3. the single longitudinal mode narrow cable and wide optical fiber laser in the sub-chamber of single-point injection active parallel connection according to claim 1 or claim 2 is characterized in that said gain amplifying unit comprises multistage structure for amplifying.

4. like the single longitudinal mode narrow cable and wide optical fiber laser in the sub-chamber of the said single-point injection active of claim 3 parallel connection; It is characterized in that said gain amplifying unit comprises first pumping, second pumping, first gain fibre, second gain fibre, first pumping coupler, second pumping coupler, optical isolator; The output of first pumping is connected with short wavelength's input of first pumping coupler; The output of first pumping coupler is connected with long wavelength's input of second pumping coupler through first gain fibre, optical isolator, second gain fibre successively; Short wavelength's input of second pumping coupler is connected with the input of second pumping, and the output of second pumping coupler is connected with long wavelength's input of first pumping coupler through said star-type coupler.

5. like the single longitudinal mode narrow cable and wide optical fiber laser in the sub-chamber of the said single-point injection active parallel connection of claim 4, it is characterized in that said first pumping is that single mode 980nm is semiconductor pumped, said second pumping is the multiple die semiconductor pumping.

6. like the single longitudinal mode narrow cable and wide optical fiber laser in the sub-chamber of the said single-point injection active parallel connection of claim 4, it is characterized in that said first gain fibre is the single mode Er-doped fiber, said second gain fibre is the double clad rare earth doped fiber.

7. the single longitudinal mode narrow cable and wide optical fiber laser in the sub-chamber of single-point injection active parallel connection according to claim 1 or claim 2 is characterized in that said seed laser coupling unit comprises optical isolator and optical fiber circulator; The input of optical isolator is connected with the output of seed laser, and output is connected with a port of optical fiber circulator; Two other port of optical fiber circulator is connected with the sub-chamber of said optical active fiber respectively with respectively.

8. the single longitudinal mode narrow cable and wide optical fiber laser in the sub-chamber of single-point injection active parallel connection according to claim 1 or claim 2 is characterized in that said seed laser is wavelength and the humorous laser of adjustable power.

9. the single longitudinal mode narrow cable and wide optical fiber laser in the sub-chamber of single-point injection active parallel connection according to claim 1 or claim 2 is characterized in that said modeling unit is film filter, fabry-perot filter or fiber grating filter.

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