CN103995362A - Method and device for continuously adjusting pulse interval - Google Patents

Abstract

The invention discloses a method and a device for continuously adjusting the pulse interval. The method comprises the following steps: an ultra-short laser pulse passes through a right-triangle birefringent crystal and is split into two equal-energy sub pulses of which the polarization directions are mutually perpendicular; the optical path difference of the two sub pulses is adjusted by adjusting the effective thickness of an isosceles-triangle birefringent crystal with three wedge-shaped structures; and the adjusted sub pulses are combined through the right-triangle birefringent crystal to obtain an ultra-short laser pulse with adjusted pulse interval. Therefore, the pulse interval can be continuously adjusted, no additional pulse is generated, and the influence to measuring results is avoided.

Description

The method and apparatus at a kind of continuous regulating impulse interval

Technical field

The present invention relates to pulse interval modulation technology, refer to especially the method and apparatus at a kind of continuous regulating impulse interval.

Background technology

In order to carry out to the change procedure of ultrafast transient phenomenon the detection of adjustable exposure interval, need continuously adjustable multiple direct impulses of recurrent interval.In continuously adjustable beam-splitting method of existing recurrent interval, although had by birefringece crystal and realized continuously adjustable method of recurrent interval, but realize and adjust difficulty, physical construction and complicated movement, poor stability, and adjacent crystal requires close contact, causes producing between adjacent crystal stress and air layer, produce thus extra-pulse, affect measurement result.Therefore, there is no at present that can to realize the recurrent interval continuously adjustable and be easy to the method realizing.

Summary of the invention

In view of this, the fundamental purpose of the embodiment of the present invention is to provide the method and apparatus at a kind of continuous regulating impulse interval, can regulate continuously at paired pulses interval, and can not produce extra-pulse, avoids affecting measurement result.

For achieving the above object, the technical scheme of the embodiment of the present invention is achieved in that

The method and apparatus that the invention provides a kind of continuous regulating impulse interval, described method comprises:

A branch of ultrashort laser pulse is through the birefringece crystal of right-angle triangle, and beam splitting is the subpulse of the two orthogonal homenergics in bundle polarization direction;

By regulating the net thickness of birefringece crystal of isosceles triangle three wedge structures, the optical path difference of two bundle subpulses is regulated;

Subpulse after regulating is closed to bundle through the birefringece crystal of right-angle triangle, obtain the ultrashort laser pulse of recurrent interval through overregulating.

Wherein, described a branch of ultrashort laser pulse is through the birefringece crystal of right-angle triangle, beam splitting is the two orthogonal subpulses in bundle polarization direction, be specially: a branch of ultrashort laser pulse is incided in the birefringent wedge crystal of right-angle triangle, the optical axis of described birefringent wedge crystal is vertical with ultrashort laser pulse incident direction, and ultrashort laser pulse polarization direction and optical axis of crystal angle are 45 °.

Wherein, the net thickness of the birefringece crystal of described adjusting isosceles triangle three wedge structures, is specially: the height that regulates in vertical direction the birefringece crystal of described isosceles triangle.

Wherein, the described birefringece crystal by the subpulse process right-angle triangle after regulating closes bundle, obtain the ultrashort laser pulse of recurrent interval through overregulating, be specially: the birefringece crystal of the right-angle triangle of utilization and ultrashort laser pulse incident, the refracting crystal of the right-angle triangle that mirror image is placed, two bundle subpulses after regulating are closed to bundle, obtain the ultrashort laser pulse of recurrent interval through overregulating.

The present invention also provides the device at a kind of continuous regulating impulse interval, and described device comprises:

The birefringece crystal of incident birefringece crystal, isosceles triangle three wedge structures and outgoing birefringece crystal, wherein, incident birefringece crystal is that right-angle triangle and mirror image are placed, shape is identical with outgoing birefringece crystal;

Described incident birefringece crystal, for being the subpulse of the two orthogonal homenergics in bundle polarization direction by a branch of ultrashort laser pulse beam splitting;

The birefringece crystal of described isosceles triangle three wedge structures, for the net thickness of the birefringece crystal by regulating described isosceles triangle three wedge structures, regulates the optical path difference of two bundle subpulses;

Described outgoing birefringece crystal, for the subpulse after regulating is closed to bundle, obtains the ultrashort laser pulse of recurrent interval through overregulating.

Wherein, described incident birefringece crystal, be the two orthogonal subpulses in bundle polarization direction by a branch of ultrashort laser pulse beam splitting, be specially: a branch of ultrashort laser pulse is incided in the birefringent wedge crystal of right-angle triangle, the optical axis of described birefringent wedge crystal is vertical with ultrashort laser pulse incident direction, and ultrashort laser pulse polarization direction and optical axis of crystal angle are 45 °.

Wherein, the net thickness of the birefringece crystal of described adjusting isosceles triangle three wedge structures, is specially: the height that regulates in vertical direction the birefringece crystal of described isosceles triangle three wedge structures.

Wherein, the subpulse after regulating is closed bundle by described outgoing birefringece crystal, obtain the ultrashort laser pulse of recurrent interval through overregulating, be specially: the birefringece crystal of the right-angle triangle of utilization and ultrashort laser pulse incident, the birefringece crystal of the right-angle triangle that mirror image is placed, two bundle subpulses after regulating are closed to bundle, obtain the ultrashort laser pulse of recurrent interval through overregulating.

The method and apparatus at a kind of continuous regulating impulse interval that the embodiment of the present invention provides, described method comprises: a branch of ultrashort laser pulse is through the birefringece crystal of right-angle triangle, and beam splitting is the subpulse of the two orthogonal homenergics in bundle polarization direction; By regulating the net thickness of birefringece crystal of isosceles triangle three wedge structures, the optical path difference of two bundle subpulses is regulated; Subpulse after regulating is closed to bundle through the birefringece crystal of right-angle triangle, obtain the ultrashort laser pulse of recurrent interval through overregulating, can regulate continuously at paired pulses interval like this, and can not produce extra-pulse, avoid affecting measurement result.

Brief description of the drawings

Fig. 1 is the method flow schematic diagram at a kind of continuous regulating impulse of the present invention interval;

Fig. 2 is the apparatus structure schematic diagram at a kind of continuous regulating impulse of the present invention interval;

Fig. 3 is the structural representation of device during the present invention tests.

Embodiment

Below by drawings and the specific embodiments, the embodiment of the present invention is described in further detail again.

The embodiment of the present invention provides the method at a kind of continuous regulating impulse interval, and Fig. 1 is the method flow schematic diagram at a kind of continuous regulating impulse of the present invention interval, and as shown in Figure 1, described method comprises:

Step 101, a branch of ultrashort laser pulse is through the birefringece crystal of right-angle triangle, and beam splitting is the subpulse of the two orthogonal homenergics in bundle polarization direction;

Concrete, described a branch of ultrashort laser pulse is through the birefringece crystal of right-angle triangle, beam splitting is the two orthogonal subpulses in bundle polarization direction, be specially: a branch of ultrashort laser pulse is incided in the birefringent wedge crystal of right-angle triangle, the optical axis of described birefringent wedge crystal is vertical with ultrashort laser pulse incident direction, and ultrashort laser pulse polarization direction and optical axis of crystal angle are 45 °.

Step 102, by regulating the net thickness of birefringece crystal of isosceles triangle three wedge structures, regulates the optical path difference of two bundle subpulses;

Wherein, the thickness that only need carry out the middle isosceles triangle of structure in this process is realized the adjusting of three wedge structure crystal net thickness, and in this process, between the variable quantity of the net thickness of isosceles triangle and the variable quantity in recurrent interval, be continuous linear relationship.

Concrete, the net thickness of the birefringece crystal of described adjusting isosceles triangle three wedge structures, is specially: the height that regulates in vertical direction the birefringece crystal of described isosceles triangle.So just can realize and regulate the net thickness of two bundle subpulses through three cumeat structures, to reach, the optical path difference of two bundle subpulses is regulated, and in this process, between the variable quantity of the net thickness of isosceles triangle and the variable quantity in recurrent interval, be continuous linear relationship.

Step 103, closes bundle by the subpulse after regulating through the birefringece crystal of right-angle triangle, obtains the ultrashort laser pulse of recurrent interval through overregulating.

Concrete, the described birefringece crystal by the subpulse process right-angle triangle after regulating closes bundle, obtain the ultrashort laser pulse of recurrent interval through overregulating, be specially: the birefringece crystal of the right-angle triangle of utilization and ultrashort laser pulse incident, the birefringece crystal of the right-angle triangle that mirror image is placed, two bundle subpulses after regulating are closed to bundle, obtain the ultrashort laser pulse of recurrent interval through overregulating.

Fig. 2 is the apparatus structure schematic diagram at a kind of continuous regulating impulse of the present invention interval, as shown in Figure 2, described device comprises: birefringece crystal 22 and the outgoing birefringece crystal 23 of incident birefringece crystal 21, isosceles triangle three wedge structures, wherein, incident birefringece crystal 21 is that right-angle triangle and mirror image are placed, shape is identical with outgoing birefringece crystal 23;

Described incident birefringece crystal 21, for being the subpulse of the two orthogonal homenergics in bundle polarization direction by a branch of ultrashort laser pulse beam splitting;

Concrete, described incident birefringece crystal 21, be the two orthogonal subpulses in bundle polarization direction by a branch of ultrashort laser pulse beam splitting, be specially: a branch of ultrashort laser pulse is incided in the birefringent wedge crystal of right-angle triangle, the optical axis of described birefringent wedge crystal is vertical with ultrashort laser pulse incident direction, and ultrashort laser pulse polarization direction and optical axis of crystal angle are 45 °.

The birefringece crystal 22 of described isosceles triangle three wedge structures, for the net thickness of the birefringece crystal 22 by regulating described isosceles triangle three wedge structures, regulates the optical path difference of two bundle subpulses;

Concrete, the net thickness of the birefringece crystal 22 of described adjusting isosceles triangle three wedge structures, is specially: the height that regulates in vertical direction the birefringece crystal 22 of described isosceles triangle three wedge structures.

Described outgoing birefringece crystal 23, for the subpulse after regulating is closed to bundle, obtains the ultrashort laser pulse of recurrent interval through overregulating.

Concrete, the subpulse after regulating is closed bundle by described outgoing birefringece crystal 23, obtain the ultrashort laser pulse of recurrent interval through overregulating, be specially: the birefringece crystal of the right-angle triangle of utilization and ultrashort laser pulse incident, the birefringece crystal of the right-angle triangle that mirror image is placed, two bundle subpulses after regulating are closed to bundle, obtain the ultrashort laser pulse of recurrent interval through overregulating.

The ultimate principle of device provided by the present invention is the birefringent characteristic according to birefringece crystal, light beam incides birefringece crystal, be decomposed into the two mutually perpendicular linearly polarized lights in bundle polarization direction, wherein, Ray Of Light, in the plane of incidence, is observed common refraction law, be called ordinary light (o light), Ray Of Light is not observed common refraction law in addition, and not necessarily in the plane of incidence, is called special ray (e light).Light is by birefringece crystal, and when incident direction is during perpendicular to optical axis of crystal direction, o light is identical with e optical propagation direction, but in intracrystalline transmission speed difference, therefore two-beam is from the asynchronism(-nization) of crystal outgoing.

Fig. 3 is the structural representation of device during the present invention tests, in test, as shown in Figure 3, this device is divided into identical fixed part 1 and 3, and adjustable part 2, three part optical axis of crystal directions are consistent, by regulating 2 parts to change the net thickness of crystal, thereby realize the adjustable continuously of the subpulse time interval.Wherein, the process that 2 parts move to dotted line position by solid line position shown in figure is that crystal net thickness is minimum to maximum change procedure.S1, S2, S3, S4, S5, S6 are the workplaces of beam splitter, and S2 and S3, S4 and S5 are parallel to each other respectively, and θ is the structure angle of crystal, and D is the thickness of 1 part crystal, and H is the height of 2 part crystal, and l is the half width of device.When light beam is from S1 surface vertical incidence (incident ray is perpendicular to the optical axis of crystal), through 1,2 and 3 parts, and clearance between them, from S6 surface outgoing, because this apparatus structure symmetry, from light splitting optical path, o light and e light after outgoing are propagated in same direction.

In adjustment process, θ ₁and θ ₂be respectively o light and the e light deflection angle with respect to incident light when by S2 surface.From refraction law, θ ₁and θ ₂can be expressed as:

θ ₁＝arcsin(n _osinθ) (1)

θ ₂＝arcsin(n _esinθ) (2)

In beam splitting arrangement, total optical path Δ 1 and the Δ 2 of o light and e light are respectively:

$\mathrm{\Δ}1=2(n_o\frac{D}{2}+\frac{d}{{\cos \mathrm{\θ}}_1}+n_o(C_1+x\tan \mathrm{\θ}))---\left(3\right)$

$\mathrm{\Δ}2=2(n_e\frac{D}{2}+\frac{d}{{\cos \mathrm{\θ}}_2}+n_e(C_2+x\tan \mathrm{\θ}))---\left(4\right)$

In formula (3) (4): d is the thickness of clearance between crystal 1,2 (or crystal 2,3), can be showed by θ, D and L:

d＝cosθ(L-D-xtanθ) (5)

$C_1=(H-\frac{D}{2\tan \mathrm{\θ}})\tan \mathrm{\θ}-(L-D)\cos \mathrm{\θ}\sin (\tan \mathrm{\θ}-\tan {\mathrm{\θ}}_1)$

$C_2=(H-\frac{D}{2\tan \mathrm{\θ}})\tan \mathrm{\θ}-(L-D)\cos \mathrm{\θ}\sin (\tan \mathrm{\θ}-\tan {\mathrm{\θ}}_2)$

The optical path difference Δ of o light and e light is so:

Δ＝Δ1-Δ 2(6)

Through beam splitting arrangement beam splitting, the o photon pulse after outgoing and the time interval of e photon pulse are:

$\mathrm{\Δt}=\frac{\mathrm{\Δ}}{c}---\left(7\right)$

Wherein, c=3*10 ⁸ms.

The relation that formula (1)～(6) substitution formula (7) can be obtained to pulse interval after beam splitting and crystal displacement x meets: Δ t=kx+b (8)

Wherein,

$k=2(n_o-n_e)\tan \mathrm{\θ}+2\sin \mathrm{\θ}(\frac{1}{\cos {\mathrm{\θ}}_2}-\frac{1}{\cos {\mathrm{\θ}}_1})---\left(9\right)$

$b=D(n_o-n_e)+2(n_0{C}_1-n_e{C}_2)+2(\frac{1}{\cos {\mathrm{\θ}}_1}-\frac{1}{\cos {\mathrm{\θ}}_2})(L-D)\cos \mathrm{\θ}---\left(10\right)$

From formula (8)～(10), (l), and 2 part crystal displacement x are relevant for the thickness D of 1 part crystal and device half width for the structure angle θ of pulse interval Δ t and crystal and the size of device.

The above, be only preferred embodiment of the present invention, is not intended to limit protection scope of the present invention, all any amendments of doing within the spirit and principles in the present invention, is equal to and replaces and improvement etc., within all should being included in protection scope of the present invention.

Claims (8)

1. the method at continuous regulating impulse interval, is characterized in that, described method comprises:

A branch of ultrashort laser pulse is through the birefringece crystal of right-angle triangle, and beam splitting is the subpulse of the two orthogonal homenergics in bundle polarization direction;

By regulating the net thickness of birefringece crystal of isosceles triangle three wedge structures, the optical path difference of two bundle subpulses is regulated;

Subpulse after regulating is closed to bundle through the birefringece crystal of right-angle triangle, obtain the ultrashort laser pulse of recurrent interval through overregulating.

2. method according to claim 1, it is characterized in that, described a branch of ultrashort laser pulse is through the birefringece crystal of right-angle triangle, beam splitting is the two orthogonal subpulses in bundle polarization direction, be specially: a branch of ultrashort laser pulse is incided in the birefringent wedge crystal of right-angle triangle, the optical axis of described birefringent wedge crystal is vertical with ultrashort laser pulse incident direction, and ultrashort laser pulse polarization direction and optical axis of crystal angle are 45 °.

3. method according to claim 1 and 2, is characterized in that, the net thickness of the birefringece crystal of described adjusting isosceles triangle three wedge structures, is specially: the height that regulates in vertical direction the birefringece crystal of described isosceles triangle.

4. method according to claim 1 and 2, it is characterized in that, the described birefringece crystal by the subpulse process right-angle triangle after regulating closes bundle, obtain the ultrashort laser pulse of recurrent interval through overregulating, be specially: the birefringece crystal of the right-angle triangle of utilization and ultrashort laser pulse incident, the refracting crystal of the right-angle triangle that mirror image is placed, closes bundle by two bundle subpulses after regulating, and obtains the ultrashort laser pulse of recurrent interval through overregulating.

5. the device at a continuous regulating impulse interval, it is characterized in that, described device comprises: birefringece crystal and the outgoing birefringece crystal of incident birefringece crystal, isosceles triangle three wedge structures, wherein, incident birefringece crystal is that right-angle triangle and mirror image are placed, shape is identical with outgoing birefringece crystal;

Described incident birefringece crystal, for being the subpulse of the two orthogonal homenergics in bundle polarization direction by a branch of ultrashort laser pulse beam splitting;

The birefringece crystal of described isosceles triangle three wedge structures, for the net thickness of the birefringece crystal by regulating described isosceles triangle three wedge structures, regulates the optical path difference of two bundle subpulses;

Described outgoing birefringece crystal, for the subpulse after regulating is closed to bundle, obtains the ultrashort laser pulse of recurrent interval through overregulating.

6. device according to claim 5, it is characterized in that, described incident birefringece crystal, be the two orthogonal subpulses in bundle polarization direction by a branch of ultrashort laser pulse beam splitting, be specially: a branch of ultrashort laser pulse is incided in the birefringent wedge crystal of right-angle triangle, the optical axis of described birefringent wedge crystal is vertical with ultrashort laser pulse incident direction, and ultrashort laser pulse polarization direction and optical axis of crystal angle are 45 °.

7. according to the device described in claim 5 or 6, it is characterized in that, the net thickness of the birefringece crystal of described adjusting isosceles triangle three wedge structures, is specially: the height that regulates in vertical direction the birefringece crystal of described isosceles triangle three wedge structures.

8. according to the device described in claim 5 or 6, it is characterized in that, the subpulse after regulating is closed bundle by described outgoing birefringece crystal, obtain the ultrashort laser pulse of recurrent interval through overregulating, be specially: the birefringece crystal of the right-angle triangle of utilization and ultrashort laser pulse incident, the birefringece crystal of the right-angle triangle that mirror image is placed, closes bundle by two bundle subpulses after regulating, and obtains the ultrashort laser pulse of recurrent interval through overregulating.