Embodiment
Picopulse optical fiber laser of the present invention, its preferable embodiment are to comprise main resonance cavity, exocoel feedback fraction.
Wherein, the exocoel feedback fraction comprises AOM (acousto-optic modulator), AOM adopt Raman-Nath (diffraction of Raman-Nai Si), in the diffraction light that is produced, zero order light output, the arbitrary level in the senior light feeds back in the main resonance cavity.The laser of main resonance cavity output can impinge perpendicularly on the plane of crystal of AOM behind the collimating lens collimation.Senior light can be the arbitrary level in 2 grades of light, 3 laser to the 5 grade light, also can be more senior time diffraction light.The modulating frequency of AOM can be more than or equal to 40MHz.
As shown in Figure 1, main resonance cavity can comprisedichroscope 3, yb-doped double-clad fiber 4.
In the specific embodiment, main resonance cavity can comprise semiconductor laser 1, coupledsystem 2,dichroscope 3 and yb-doped double-clad fiber 4 from left to right successively.Semiconductor laser 1 is a pumping source, and excitation wavelength can be 975nm.
A chamber mirror of main resonance cavity is adichroscope 3, the tail end vertical cut end face A that another chamber mirror is a yb-doped double-clad fiber 4, the feedback that the Fresnel reflection of tail end vertical cut end face A provides can make semiconductor laser 1 starting of oscillation, anddichroscope 3 and double clad Yb dosed optical fiber 4 itself have just constituted resonant cavity like this.Pump light enters in the resonant cavity through coupledsystem 2.
The length of yb-doped double-clad fiber 4 can be 20m, and doping content can be 0.65mol%, and the absorption coefficient at the 975nm place can be 5dB/m.Yb-doped double-clad fiber can be single transverse mode optical fiber.
The parameter ofdichroscope 3 is: the reflectivity at the 975nm place can be 97%, and the reflectivity at the 1064nm place can be 0.2%.
As shown in Figure 2, the exocoel feedback fraction can comprise balzed grating, 7, and balzed grating, 7 is used for the diffraction light of feedback and output AOM (acousto-optic modulator 6) generation.
In the specific embodiment, the exocoel feedback fraction can comprise collimatinglens 5, acousto-optic modulator 6 (AOM) and reflective balzed grating, 7 from left to right successively.The laser of main resonance cavity output outputs to the exocoel feedback fraction through yb-doped double-clad fiber 4, becomes directional light behind collimatinglens 5 collimations, incides on the balzed grating, 7 through acousto-optic modulator 6.7 pairs of corresponding excitation wavelengths of balzed grating, produce reflective diffraction, and the horizontal rotatio direction of regulating balzed grating, 7 makes zero order light export, and the arbitrary level in the senior light feeds back in the described main resonance cavity.Among the present invention, because acousto-optic modulator AOM adopts this diffraction of Raman-how, in the diffraction light that is produced, zero order light output, one or more in the senior light feed back in the main resonance cavity, can export the more psec light pulse of high repetition frequency.
Balzed grating, 7 can be reflective balzed grating,, by accommodation reflex formula balzed grating, 7, can realize the tuning of output laser and pressure narrow linewidth.The centre wavelength of reflective balzed grating, 7 can be 1064nm, and senior diffraction of light efficient can be 35%.
Concrete reflective balzed grating, 7 can be provided with the whirligig of arrangement for adjusting height and horizontal direction.On the workbench of the rotation that reflective balzed grating, 7 also can be fixed on highly and can regulate, horizontal direction is passable, by height and horizontal direction realization broad tuning, narrow linewidth and the stable laser pulse output of accommodation reflex formula balzed grating, 7.
In the specific embodiments of the invention, the chamber length of main resonance cavity can for the long positive integer in the chamber of exocoel feedback fraction doubly.The long distance of the tail end vertical cut end face A of yb-doped double-clad fiber 4 that promptly refer in the chamber of exocoel feedback fraction to balzed grating, 7; The chamber length of main resonance cavity refers to the distance ofdichroscope 3 to the tail end vertical cut end face A of yb-doped double-clad fiber 4.
The chamber length of frequency displacement feedback cavity and the product of the frequency displacement in the chamber can equal π, and the chamber length of frequency displacement feedback cavity refers to the distance ofdichroscope 3 to balzed grating, 7.
In the prior art, AOM adopts the Bragg diffraction, plane of crystal and the non-normal incidence of incident laser and AOM when the Bragg diffraction phenomena takes place.Zero order light and one-level light only occur through behind the AOM, one-level light feeds back in the chamber via grating, zero order light output, and pulse period this moment is depended on the radio frequency operation frequency of AOM.
Among the present invention, laser vertical incides plane of crystal in the AOM, the Raman-Nath diffraction takes place through laser behind the crystal, zero order light, one-level light are not only arranged, even there are other senior time light (4,5 grades light etc.) also can outgoing, a certain senior time light is fed back in the chamber, zero order light output, the frequency shift amount between incident light and the diffraction light no longer has been the frequency of AOM radiofrequency signal at this moment.Equal π according to the chamber length of frequency displacement feedback and the frequency displacement product in the chamber again, can produce picopulse equally.If when the main resonance cavity chamber is long when covering with the certain positive integer proportionate relationship of foot with outer cavity, the repetition rate of generation pulse is the product of this positive integer and senior optical frequency shift amount.
Therefore, can obtain the more output psec light pulse of high repetition frequency, and the off resonance scope that allows is bigger, can in the scope of broad, carries out tuningly, generally can reach tens nanometers.Simple in structure, cost performance is high, can realize broad tuning, narrow linewidth, stable picosecond pulse laser output.Can be widely used in fields such as laser processing, laser medicine, laser marking, seed light source.
As shown in Figure 3, be the pulse energy of the output laser of specific embodiments of the invention and the relation between the tuning wavelength.Therefrom tuning range broad has as can be seen reached 60nm.
As shown in Figure 4, the repetition 1GHz that obtains for Picopulse optical fiber laser of the present invention running, the time domain specification of pulsewidth 40ps laser can obtain stable picosecond pulse laser.
The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.