CN1200494C - Laser Q-switching and tuning device - Google Patents

Abstract

The present invention relates to a laser Q regulation and tuning device, particularly to a laser Q regulation and tuning device composed of a single electrooptic crystal. The present invention is characterized in that the electrooptic crystal has two light through surfaces, two reflecting surfaces and two electrode surfaces, normal lines of the light through surfaces and the reflecting surfaces are in the same plane surface with a light axis of the electrooptic crystal, and the plane surface is perpendicular to a main axis beyond the light axis of the electrooptic crystal; simultaneously, the two electrode surfaces are parallel to the plane surface. The two light through surfaces, the two reflecting surfaces and the light axis of the electrooptic crystal all have specific acute included angles. Thus, after light with different wavelengths at the same incidence angle passes through the crystal, the propagation directions of the light are different on the basis of the dispersion characteristic of the electrooptic crystal. The characteristic is used for realizing tuning a laser device, the output wavelength of a tunable laser device can be controlled, and simultaneously, the laser device has the function of generating giant pulse output.

Description

Laser Q-switching and tuner

Technical field

The present invention relates to a kind of laser and transfer Q and tuner, what belong to optical property with the electrooptic crystal material and be feature transfers Q and tuning device to laser.

Background technology

Tunable laser need be carried out tuning when transferring Q in order to produce the output of different wavelength of laser giant pulse.

Adopting electro-optical Q-switch is the present known effective ways that can be used to produce the laser giant pulse, electro-optical Q-switch can be changed its open and close state by the variation of external control voltage rapidly, thereby make laser cavity be in high Q value, low reactance-resistance ratio state, the Q value of laser cavity can be changed rapidly controllably be that to produce the output of laser giant pulse necessary.

Utilize the chromatic dispersion device to insert in the chamber of tunable laser, can make that the oscillation light of different wave length has different losses in the chamber, can make the oscillation light of specific wavelength have minimum loss by the state that changes laser cavity, thereby reach the purpose that changes output optical maser wavelength, this also is the method for known realization laser tuning.

Existing tunable laser often adopts two independent device in order to produce the giant pulse output of different wave length, realizes the accent Q of laser and tuning respectively, thereby makes the complex structure of laser.U.S. Pat 5583877 discloses a kind of device that produces the output of tunable laser giant pulse, and the device that wherein produces tunning effect is distinct with the device that produces accent Q effect.(basket letter hard iron etc. is write " laser technology ", Science Press's in August, 2000 front page) introduced a kind of known method of making two 45 ° of electric-optically Q-switched devices with the monolithic lithium columbate crystal for the 79th page～the 81st page, but this Q-modulating device can only be used for the accent Q of laser, does not have tunable laser is carried out tuning function.

Summary of the invention

The purpose of this invention is to provide a kind of simple mechanism that can be used for laser Q-switching and laser tuning simultaneously, it can control the output wavelength of tunable laser, and has the effect that makes the output of laser generation giant pulse simultaneously.

In order to achieve the above object, the present invention adopts an electrooptic crystal, utilizes its cross electro-optical effect to realize the accent Q of laser, utilizes the dispersion characteristics of this crystal and specially designed contour structures to realize the tuning of laser simultaneously.

Concrete technical scheme is:

A kind of accent Q and tuner of the laser that is made of electrooptic crystal it is characterized in that said laser Q-switching and tuner are made of the monolithic electrooptic crystal, and electrooptic crystal have two logical light faces, two reflectings surface, two electrode surfaces;

The normal of logical light face, reflecting surface and the optical axis of electrooptic crystal are all in same plane; Electrode surface and this plane parallel, and vertical with electrooptic crystal optical axis another main shaft in addition;

Between the optical axis of logical light face and electrooptic crystal sharp angle i is arranged ₂, between the optical axis of another logical light face and electrooptic crystal sharp angle i is arranged ₇, and satisfy following relationship:

$i_2=i_7=\mathrm{arcSin}\left(\frac{\mathrm{Sin}{i}_b}{n_e}\right)$

Between the optical axis of reflecting surface and electrooptic crystal sharp angle i is arranged ₃, sharp angle i is arranged between the optical axis of another reflecting surface and electrooptic crystal ₆, and satisfy following relationship:

$i_3=i_6=\mathrm{arctg}\left(\frac{n_o}{n_e}\right)$

Wherein: i _bBe Brewster's angle,

n _oBe the ordinary refraction index of electrooptic crystal at laser central task wavelength place,

n _eBe the extraordinary ray refractive index of electrooptic crystal at laser central task wavelength place.

Electrooptic crystal is lithium niobate LiNbO ₃Crystal.

The normal of the logical light face of electrooptic crystal and the angle between the incident light are Brewster's angle.

Two electrode surfaces of electrooptic crystal are coated with metal electrode, receive the positive pole and the negative pole of driver respectively by cable, and provide accent Q voltage by driver.

The angle setting of two logical light faces of crystal, make the linearly polarized light of polarization direction in the plane of incidence with near the incident angle of Brewster's angle during from the outside incident of crystal, this linearly polarized light is to propagate in crystal along the direction approximately perpendicular to the optical axis of crystal after reflecting by above-mentioned logical light face, and the approximate optical axis that is parallel to of the direction of polarization, then this light can successively experience the reflex of two above-mentioned reflectings surface at crystals, leave crystal through the refraction of the above-mentioned logical light face of another one at last, and the refraction angle is near Brewster's angle.Wherein, the angle setting of described two reflectings surface should make that above-mentioned linearly polarized light is that approximate optical axis along crystal is propagated when propagating into the another one reflecting surface by a reflecting surface in crystal.

Based on the dispersion characteristics of electrooptic crystal, with same angle incident but the light of different wave length by above-mentioned crystal after the direction of propagation difference of light, promptly difference is departed from the angle of light, utilizes these characteristics can realize tuning to laser.

Simultaneously, utilize the cross electro-optical effect of crystal, by changing the voltage that between above-mentioned electrode surface, applies, can make the linear polarization incident ray in optical loss generation obvious variation, utilize this point can make above-mentioned crystal become the electro-optical Q-switch of laser through being experienced behind the above-mentioned electrooptic crystal.

Such simple mechanism is inserted in the laser cavity, not only can control the output wavelength of tunable laser, also have the effect that makes the output of laser generation giant pulse simultaneously.

Description of drawings

Fig. 1 is the perspective view of embodiment of the present invention.

Fig. 2 is the plane graph of Fig. 1.

Fig. 3 is the fundamental diagram of execution mode shown in Figure 1 when being applied to tunable laser.

Embodiment

In perspective view shown in Figure 1, the lithium columbate crystal 2 of monolithic has optics to lead to light face 11 and 14, two optical reflection faces 12 and 13, the normal of these four faces all is in the same plane, and the some main shaft x outside the optical axis 10 of this plane and crystal 2 are vertical, between the optical axis 10 of logical light face 11 and crystal 2 sharp angle i arranged ₂, between logical light face 14 and the optical axis 10 sharp angle i is arranged ₇, between reflecting surface 12 and the optical axis 10 sharp angle i is arranged ₃, between reflecting surface 13 and the optical axis 10 sharp angle i is arranged ₆, they satisfy following relationship:

$i_2=i_7=\arcsin \left(\frac{\sin \left(i_b\right)}{n_e}\right)$

$i_b=\mathrm{arctg}\left(\frac{n_e}{n_1}\right)$

$i_b={\mathrm{<figure-callout\; id="6"\; label="i"\; filenames="C0311318900101.png"\; state="\{\{state\}\}">i</figure-callout>}}_6=\mathrm{arctg}\left(\frac{n_o}{n_e}\right)$

Wherein, n _eExtraordinary ray refractive index for lithium columbate crystal; n _oOrdinary refraction index for lithium columbate crystal; n ₁Be the refractive index of crystal medium of living in, medium is under the situation of air around, generally gets it and is vacuum refractive index value 1; i _bBe Brewster's angle.Because crystal 2 is dispersive medium, the refractive index of its ordinary light and extraordinary ray diminishes with the increase of propagation light wavelength, and each refractive index all is in the refractive index value at the central task wavelength place of tunable laser by lithium columbate crystal here.Such as, for the central task wavelength be the lamp pump of 2.01 μ m mix the chromium thulium and yttrium aluminum garnet (value of all angles is for Cr, Tm:YAG) laser:

i ₂＝i ₇＝25°12′

i _b＝64°48′

i ₃＝i ₆＝45°57′

Crystal 2 also has two parallel planes 15 and 16, the plane parallel that normal constituted of they and optical axis 10 and above-mentioned four optical surfaces 11,12,13,14, also vertical with main shaft x recited above, plane 15 and plane 16 all are coated with metallic film to constitute the electrode of crystal 2.

In order to further specify embodiments of the present invention, the consideration wavelength is that the linearly polarized light 17 of laser centre wavelength incides logical light face 11, and light 17 is Brewster's angle i with the angle of the normal on plane 11 _b, promptly incidence angle is a Brewster's angle, the polarization direction of light 17 is to be in the plane of incidence that normal constituted of light 17 and logical light face 11, is the meridian direction polarization.Light 17 becomes light 18 after reflecting through logical light face 11, and the polarization direction of light 18 is parallel to optical axis 10, and the direction of propagation of light 18 is perpendicular to optical axis 10.Light 18 becomes the light of propagating along optical axis 10 19 after reflecting surface 12 reflections, the polarization direction of light 19 is perpendicular to optical axis 10 and be parallel to parallel plane 15,16.Light 19 is reflected and becomes after face 13 reflection along perpendicular to optical axis 10 and be parallel to the light 20 that the direction on plane 15,16 is propagated, and the polarization direction of light 20 is parallel to optical axis 10.Light 20 leaves crystal 2 after logical light face 14 refractions become light 21, the angle of the normal of light 21 and logical light face 14, and promptly the refraction angle is Brewster's angle i _bIn fact, the above-mentioned communication process of light is all finished in same plane, this plane is exactly the plane of incidence of light 17 and the exit plane of light 21, Fig. 2 is the plane graph of crystal 2 on this plane, therefrom can more be clear that the angular relationship that light is propagated between each optical surface, clearly, light 19 all is vertical with light 18, light 20.Wavelength departure centre wavelength when light 17, such as wavelength during greater than centre wavelength, refraction by logical light face 11, original direction can slightly be departed from the direction of propagation of light becomes light 18`, in follow-up communication process, light becomes 19`, 20` successively, 21`, emergent ray 21` at this moment has less refraction angle than original light 21.In like manner, if the wavelength of light 17 less than centre wavelength, the refraction angle of emergent ray can be bigger than the refraction angle of light 21.

Continue to consider that above-mentioned linearly polarized light 17 incides the situation of crystal 2, between the electrode surface 15 of crystal 2 and electrode surface 16, be applied in half-wave voltage V _λ/2The time, since light in crystal when reflecting surface 12 is transmitted to reflecting surface 13 polarization direction 90 ° deflection can take place, be that the polarization direction is parallel with above-mentioned optical main axis x, the optical loss during by logical light face 14 will be much larger than not loading half-wave voltage V in the face of being reflected 13 reflection back for this light _λ/2The time loss, thereby make the laser cavity at place be in the low reactance-resistance ratio state.After the above-mentioned voltage that applies is removed fully, light in crystal when reflecting surface 12 is transmitted to reflecting surface 13 polarization direction remain unchanged, the optical loss that the linearly polarized light after face 13 reflection of being reflected is experienced during by logical light face 14 is very little, can make residing laser cavity have much higher Q value.

Can the method for work that embodiments of the present invention are applied to laser be described further by Fig. 3.After tunable laser working media 5 is encouraged by pumping system 4, the laser system that constitutes with reflecting cavity mirror 1 and output cavity mirror 6 can produce laser, crystal 2 of the present invention places in the laser cavity according to illustrated mode, and provide by cable 7 by driver 3 and to transfer Q voltage, wherein the positive pole of driver 3 and negative pole are received the upper surface that is coated with metal electrode 15 and the lower surface 16 of crystal 2 respectively by cable 7,8 is the opticpath of laser in laser cavity of centre wavelength, and 9 is the output light of laser.During tuning work, when making laser output Wavelength of Laser longer than centre wavelength such as needs, can be by rotating mirror 1 to 1` orientation, chamber, the reflecting cavity mirror that at this moment is positioned at the 1` orientation just in time can go back light 21` normal reflection, thereby forces laser works in selected wavelength.When transferring Q work, select the operation wavelength of the orientation of chamber mirror 1 earlier, apply half-wave voltage V by driver 3 and cable 7 to crystal 2 again with the setting laser device _λ/2, make laser cavity be in the low reactance-resistance ratio state, remove the voltage that is applied then suddenly, make laser cavity moment become high Q state of value, at this moment laser just has giant pulse output.The laser that is propagation in output laser or the chamber all is linear polarization, and the polarization direction is positioned at plane shown in Figure 3, this plane and shown in Figure 2 be same plane.

Claims (4)

1, a kind of accent Q and tuner of the laser that is made of electrooptic crystal it is characterized in that said laser Q-switching and tuner are made of the monolithic electrooptic crystal, and electrooptic crystal have two logical light faces, two reflectings surface, two electrode surfaces;

The normal of logical light face, reflecting surface and the optical axis of electrooptic crystal are all in same plane; Electrode surface and this plane parallel, and vertical with the optical axis main shaft in addition of electrooptic crystal;

Between the optical axis of logical light face and electrooptic crystal sharp angle i is arranged ₂, between the optical axis of another logical light face and electrooptic crystal sharp angle i is arranged ₇, and satisfy following relationship:

$i_2=i_7=\mathrm{arcSin}\left(\frac{{\mathrm{Sini}}_b}{n_e}\right)$

Between the optical axis of reflecting surface and electrooptic crystal sharp angle i is arranged ₃, sharp angle i is arranged between the optical axis of another reflecting surface and electrooptic crystal ₆, and satisfy following relationship:

$i_3=i_6=\mathrm{arctg}\left(\frac{n_o}{n_e}\right)$

Wherein: i _bBe Brewster's angle,

n _oBe the ordinary refraction index of electrooptic crystal at laser central task wavelength place,

n _eBe the extraordinary ray refractive index of electrooptic crystal at laser central task wavelength place.

2. according to claim 1 said accent Q and tuner, it is characterized in that electrooptic crystal is lithium niobate LiNbO ₃Crystal.

3. according to claim 1 said accent Q and tuner, it is characterized in that the normal and the angle between the incident light of the logical light face of electrooptic crystal is Brewster's angle.

4. according to claim 1 said accent Q and tuner, it is characterized in that two electrode surfaces of electrooptic crystal are coated with metal electrode, receive the positive pole and the negative pole of driver respectively by cable, and provide accent Q voltage by driver.

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