CN102980739A - Pulse gas laser intracavity flow field measurement device based on four-quadrant detector - Google Patents

Abstract

The invention discloses a pulse gas laser intracavity flow field measurement device based on a four-quadrant detector. The pulse gas laser intracavity flow field measurement device comprises a detection light source, a detection light receiving system and a signal processing system. A light beam sent out by the detection light source is parallel to the optical axis direction of a pulse gas laser. The detection light receiving system comprises a four-quadrant photoelectric detector, a photosensitive face faces towards a detection area and is perpendicular to a detection light beam to be used for receiving the detection laser light beam, and signals of the four-quadrant photoelectric detector can be processed by a signal processing system to obtain laser wave transmission characteristic parameters. The pulse gas laser intracavity flow field measurement device is simple in structure and convenient to operate. The four-quadrant photosensitive sensor simplifies an experiment device. Laser wave disturbance and transmission direction of the laser wave can be judged according to movement of the center of a light spot of the four-quadrant photosensitive detector to improve detection flexibility. Simultaneously, a dichroic mirror is used to separate the detection light beam form laser of the pulse gas laser. The laser oscillation can simultaneously obtain real-time test results to overcome the defect that thermal deposition in non-laser resonant cavity test discharging area is high.

Description

Pulsed gas laser chamber flow field measurement mechanism based on 4 quadrant detector

Technical field

The invention belongs to field of optical measuring technologies, what relate to is the device of measuring the flow field fluctuation, particularly a kind ofly measure the device of the shock propagation characteristic in the flow field based on four-quadrant photo detector, utilize all quadrants exporting change of four-quadrant photo detector to realize the direction of propagation of shock wave and the measurement of disturbance size thereof.The method is particularly useful for the measurement of gas flowfield disturbance in the pulsed gas laser.

Background technology

Adopt the pulsed gas laser of pulsed discharge pumping to have repetition rate height, energy and reach greatly the low characteristics of cost and obtain a wide range of applications industrial, such as integrated circuit (IC) etching, laser medicine and industrial processes etc.In the pulsed gas laser course of work, since in the finite space moment Implantation Energy larger, thereby can produce the shock wave of each different directions development, these shock waves can move back and forth in laser cavity, can bring the variation of density in the communication process, the homogeneity of chamber underexcitation medium is changed, so the disturbance size of shock wave has characterized the homogeneity in flow field.Because the unevenness of laser cavity flow field can directly affect Uniform discharge, and then affect the beam quality of Laser output and the stability of output power, therefore the measurement of Shock Wave Characteristics parameter (size and the direction of propagation that comprise shock wave) seemed particularly important.

The measuring method of traditional flow field fluctuation often can adopt pressure probe method (O.Uteza; Ph.Delaporte; B.Fontaine; B.Forestier, M. Sentis, I. Tassy; J.P.Truong:Appl.Phys.B 64; 531 (1997)), the method adopts piezoelectric transducer that the pressure surge in the flow field is converted to electric signal output, the disturbance size in can the Real-Time Monitoring flow field.The method belongs to a kind of contact type measurement, need to be installed on the laser cavity inwall, can't arbitrarily move, and relatively be difficult to during measurement realize accurate location, and the method can't be judged source and the propagation characteristic of disturbance.

Interferometric method and schlieren method are two kinds of non-contact measurement methods commonly used, be used for observing the evolution (P.Delaporte of pulsed gas laser shock wave, B.Fontaine, B.Forestier, M. Sentis, J.P.Truong, O.Uteza, D.Zeitoun, D.Tarabelli:Proc.18th Int.Symp.Shock Waves2,1301 (1991)).The variation of interferometric method optical system by the interference fringe on the receiving screen obtains that shock wave causes the change information of gas density in the flow field in communication process, thereby judges size and the direction of propagation of shock-wave disturbance.Similarly, the density perturbation information that the schlieren method optical system can cause shock wave is converted into the variation of intensity on the receiving screen, changes to judge position and the direction of propagation of shock wave by power.These two kinds of methods can both obtain situation in the flow field intuitively by photodistributed change information on the receiving screen, judge origin and the evolution thereof of shock wave.But these two kinds of methods all are the methods by sequential, take the different flow fields constantly of different pulses and develop, and the evolutionary process of shock wave can not obtain real-time signal in the flow field that its combination is obtained; And these two kinds of system and devices are more complicated and the more precision optics equipment of needs all, and operation and data are processed all cumbersome.The human single-point schlieren methods such as Wingate come that the shock strength in the flow field has carried out measuring (F.Wingate, J.T.Lee, AIAAPaper81-1286 (1981)) after the pulsed discharge of paired pulses gas laser.Although utilize this device can obtain the disturbance of shock wave in the flow field, the direction of propagation that the method can't the accurate detection shock wave.

Summary of the invention

The object of the present invention is to provide the measurement mechanism of shock wave in a kind of pulsed gas laser flow field, this device is shock-wave disturbance size and the direction of propagation in the ranging pulse gas laser flow field simply and exactly, and the subsequent treatment of signal is also relatively simple.

A kind of pulsed gas laser chamber flow field measurement mechanism based on 4 quadrant detector provided by the invention, comprise probe source, survey optical receiver system and signal processing system, it is characterized in that: the light beam that probe source sends is parallel with the optical axis direction of pulsed gas laser; Described detection optical receiver system comprises four-quadrant photo detector, and wherein the photosurface of four-quadrant photo detector is used for receiving the exploring laser light light beam that probe source sends towards search coverage and vertical with detecting light beam; The signal of four-quadrant photo detector obtains the propagation characteristic parameter of shock wave after signal processing system is processed.

A kind of improvement as technique scheme, described detection optical receiver system also comprises dichroic mirror, laser rays optical filter, described double-colored minute surface becomes 45 degree with detecting light beam, filter plate and four-quadrant photo detector are over against detecting light beam, and probe source, dichroic mirror, laser rays optical filter and four-quadrant photo detector are positioned on the same light path successively.

Another kind as technique scheme improves, described detection optical receiver system also comprises dichroic mirror, laser rays optical filter and spectroscope, described light splitting minute surface, double-colored minute surface become miter angle with detecting light beam, described laser rays filter plate is vertical with detecting light beam, described detecting light beam passes through respectively the center of light splitting minute surface and double-colored minute surface, and via again passing through the center of double-colored minute surface and light splitting minute surface and the center of laser rays filter plate after the reflection of measured laser device reflecting surface, received by 4 quadrant detector at last.

The present invention has overcome the shortcomings such as traditional measurement apparatus system complexity, apparatus expensive, has improved simultaneously precision and the sensitivity of measuring, and can obtain in real time disturbance size and the direction of propagation of the shock wave in the flow field.During pulsed gas laser work, behind each discharge excitation in the flow field moment inject larger energy, and in the flow field, form various shock waves, there is the wave front of a high-density region in these shock waves, can make detecting light beam generation deviation, the variation that all quadrants that utilizes four-quadrant photo detector to obtain is exported, by data acquisition circuit facula deviation information is transferred to computing machine and process and display, the particular kind of relationship that utilizes the propagation characteristic of the side-play amount of spot center and shock wave to exist obtains disturbance size and the direction of propagation of shock wave.

The present invention is simple in structure, and is easy to operate, adopts four-quadrant photo detector greatly to simplify experimental provision, judges by the movement of four-quadrant photo detector spot center and disturbance size and the direction of propagation of shock wave improved the sensitivity of surveying; Adopt simultaneously dichroic mirror that the laser of detecting light beam and pulsed gas laser is separated, laser generation obtains real-time test result simultaneously, the higher defective of region of discharge heat deposition when having avoided testing without laserresonator.

Description of drawings

Fig. 1 is structural representation of the present invention;

Fig. 2 is that the present invention is applied to detecting light beam and pulsed gas laser light direction a kind of example in the same way;

Fig. 3 is a kind of example that the present invention is applied to the pulsed gas laser that rear anti-mirror is all-trans;

Fig. 4 is the sectional view of the four-quadrant photo detector that adopts among the present invention;

Fig. 5 is workflow diagram of the present invention;

Fig. 6 is the experimental result with the Matlab software simulation.

Embodiment

The wave front that the high-density region that the various shock waves that form during pulsed gas laser work are corresponding forms in its communication process forms a density perturbation zone to propagating all around; Can be toward the high regional deviation of density when light beam is propagated in nonhomogeneous media, the size of deviation is directly proportional with density gradient, the deviation direction is identical with the shock front normal direction, therefore can characterize with the size of facula deviation the density perturbation size that shock wave causes, and the angle of facula deviation is judged the direction of propagation of shock wave.Utilize skew that four-quadrant photo detector can real time record surveys the spot center position over time, disturbance size and the direction of propagation that size and the angle by skew can obtain shock wave in the pulsed gas laser flow field.

The present invention is based on above-mentioned principle design and form, below in conjunction with accompanying drawing the specific embodiment of the present invention is described further.Need to prove at this, understand the present invention for the explanation of these embodiments for helping, but do not consist of limitation of the invention.In addition, below in each embodiment of described the present invention involved technical characterictic just can mutually not make up as long as consist of each other conflict.

As shown in Figure 1, the measurement mechanism of shock wave mainly comprises probe source 1, dichroic mirror 2, laser rays optical filter 3, four-quadrant photo detector 4, data acquisition circuit 5 and computing machine 6 in the pulsed gas laser provided by the invention chamber.Wherein dichroic mirror 2, laser rays optical filter 3 and four-quadrant photo detector 4 consist of the photoelectricity receiving unit, data acquisition circuit 5 is transferred to the output signal in the four-quadrant photo detector 4 on the computing machine 6 and is processed and displayed, and obtains size and the direction of propagation of shock wave.

Probe source 1 sends the direction of light beam and the optical axis direction keeping parallelism that pulsed gas laser produces, as shown in Figure 2, select the optical maser wavelength of probe source 1, can see through rear anti-mirror 11 and the output window 12 of pulsed gas laser 10, should see through the laser generation that light beam can the paired pulses gas laser and exert an influence; The spot diameter of light beam and the angle of divergence should be less, guarantee that spot diameter in search coverage less than 1mm, improves detection accuracy; Probe source 1 can be by two-dimension translational platform control with four-quadrant photo detector 4, thus the real-time disturbance of shock wave that can direct impulse gas laser flow field diverse location.Fig. 2 is described to be that rear anti-mirror 11 and output window 12 are all transparent to detecting light beam, if the rear anti-mirror of pulsed gas laser 20 21 is opaque, but output window 22 is transparent, then device can be changed into device as shown in Figure 3, and wherein the effect of spectroscope 23 is semi-transparent semi-reflecting to detecting light beam; Detecting light beam can enter from output window 22, through after after 21 reflections of anti-mirror, still left by output window 22, by dichroic mirror 2, and behind the spectroscope 23, shine four-quadrant photo detector 4 through laser rays optical filter 3.

Dichroic mirror 2 is at 45 ° with the optical axis of pulsed gas laser, and dichroic mirror 2 is narrowband reflection filters, and the centre wavelength of reflection is the output wavelength of laser instrument, and half peak value overall with (FWHM) of its reflection is less than 10nm; It only makes the laser beam reflection and other wavelength light beam is passed through, the laser emission that is the paired pulses gas laser has very high reflection, but the beam reflection to the probe source emission is lower, this so that this measurement mechanism can the paired pulses gas laser in test process duty and light path exert an influence, also avoid the laser emission of pulsed gas laser to the destruction of 4 quadrant detector; Laser rays optical filter 3 is the arrowband transmission filter, and its centre wavelength that sees through is the wavelength that probe source sends, and the half peak value overall with (FWHM) that sees through is less than 5nm, and namely it can only pass through the laser of probe source 1 emission, and the light of other wavelength of filtering; Thereby further reduce other factors to the impact of detector.

Four-quadrant photo detector 4 has four symmetric photosurfaces, as shown in Figure 4.Before measuring, need position and the angle of fine setting four-quadrant photo detector 4, make the hot spot of probe source 1 emission be evenly distributed in four quadrants.The response frequency of four-quadrant photo detector 4 can reach tens megahertzes, and the shock-wave disturbance cycle in several microseconds, therefore can satisfy the demand of real-time detection.Optical filter described in the light path only makes to be surveyed light and passes through, and can prevent that the laser etc. of pulsed gas laser from causing damage to four-quadrant photo detector.

Data acquisition circuit 5 comprises preposition amplification, and A/D change-over circuit etc. is input to computing machine 6 with photosignal and processs and displays, and obtains the spot center offset information; Utilize the light beam deviation rule that causes in the shock propagation process further to obtain the size and Orientation of shock-wave disturbance, wherein the size of side-play amount has characterized the intensity of shock wave, and the angle of side-play amount can be judged the direction of propagation of shock wave.

The below illustrates the workflow of pulsed gas laser of the present invention flow field shock wave measurement device according to Fig. 5.

Before the pulse gas work, mobile probe source 1 is placed on the position of required detection, the position of corresponding adjustment four-quadrant photo detector 4 makes the hot spot of probe source 1 emission through behind the flow field of pulsed gas laser, is evenly distributed in four quadrants of four-quadrant photo detector 4.Can produce the strong electromagnetic of tens nanoseconds after the pulsed gas laser pulse excitation, this electromagnetic interference (EMI) is as the trigger pip of four-quadrant photo detector 4.

Pulse excitation is accompanied by a large amount of energy depositions, in the flow field of pulsed gas laser, produce a lot of shock waves, these shock waves are propagated to diffusion all around, can make it that deviation occurs through surveying the light time, spot center is moved, and the output of four quadrants of four-quadrant photo detector 4 changes.Make a voltage that produces to four-quadrant be respectively U ₁, U ₂, U ₃, U ₄, then hot spot is respectively in horizontal and vertical side-play amount:

$\left\{\begin{array}{c}{\mathrm{\&rho;}}_x=k_x\frac{(U_1+U_2)-({\mathrm{<figure-callout\; id="3"\; label="U"\; filenames="HDA00002329861100011.png,HDA00002329861100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_3+U_4)}{U_1+{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HDA00002329861100011.png,HDA00002329861100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_2+{\mathrm{<figure-callout\; id="3"\; label="U"\; filenames="HDA00002329861100011.png,HDA00002329861100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_3+{\mathrm{<figure-callout\; id="4"\; label="U"\; filenames="HDA00002329861100011.png,HDA00002329861100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_4}\\ {\mathrm{\&rho;}}_y=k_y\frac{(U_1+U_4)-({\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HDA00002329861100011.png,HDA00002329861100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_2+U_3)}{U_1+{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HDA00002329861100011.png,HDA00002329861100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_2+{\mathrm{<figure-callout\; id="3"\; label="U"\; filenames="HDA00002329861100011.png,HDA00002329861100021.png"\; state="\{\{state\}\}">U</figure-callout>}}_3+U_4}\end{array}\right.---\left(1\right)$

Wherein k is the preset parameter of four-quadrant photodetection, has reflected that the variable quantity of light intensity and facula position move the relationship between quantities, can be by detector is demarcated acquisition.(1) formula of utilization can obtain facula deviation size ρ and deviation angle θ:

$\left\{\begin{array}{c}\mathrm{\&rho;}=\sqrt{{{\mathrm{\&rho;}}_x}^2+{{\mathrm{\&rho;}}_{\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="HDA00002329861100011.png,HDA00002329861100021.png"\; state="\{\{state\}\}">y</figure-callout>}}}^2}\\ \mathrm{\&theta;}=\arctan \left(\frac{{\mathrm{\&rho;}}_y}{{\mathrm{\&rho;}}_x}\right)\end{array}\right.---\left(2\right)$

Shock wave is when the detecting light beam, and detecting light beam can be towards the shock wave deviation, offset direction and wave front normal opposite direction and when shock wave passed detecting light beam, detecting light beam was equally towards the shock wave deviation, and the deviation direction is identical with wave front normal direction at this moment.Therefore at shock wave during through detecting light beam, the deflection of light size remains constant, but shock wave near and away from the time deflection of light degree can differ 180 °, and the direction of shock propagation and shock wave away from the time hot spot deflection angle that causes equate.Because the high density wave front of Shock wave has certain width, what can detect is the output signal of Temporal Evolution, and what therefore obtain is the real-time information of facula deviation.When shock wave passes through detecting light beam, the different constantly facula deviation amount ρ of t _(t)(t) can be expressed from the next with the hot spot deflection angle theta:

$\left\{\begin{array}{c}{\mathrm{\&rho;}}_{\left(t\right)}=\sqrt{{{\mathrm{\&rho;}}_{x,\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HDA00002329861100011.png,HDA00002329861100021.png"\; state="\{\{state\}\}">t</figure-callout>}}}^2+{{\mathrm{\&rho;}}_{y,\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HDA00002329861100011.png,HDA00002329861100021.png"\; state="\{\{state\}\}">t</figure-callout>}}}^2}\\ {\mathrm{\&theta;}}_{\left(t\right)}=\arctan \left(\frac{y_{\left(t\right)}}{x_{\left(t\right)}}\right)\end{array}\right.---\left(3\right)$

Figure 6 shows that the facula deviation amount size that causes when shock wave that the Matlab software simulation propagates toward 45 ° of directions is through detecting light beam and the real-time change information of hot spot deflection angle size, wherein the size of shock-wave disturbance is ρ _{(t) max}, and the angle of shock propagation direction when leaving detecting light beam with shock wave is identical, namely the latter half with hot spot angular deflection result is identical, propagates toward 45 ° of directions.Because four-quadrant photo detector 4 has higher look-in frequency, therefore can reflect in real time the evolution of shock wave in the flow field, the shock-wave disturbance size and Orientation in the observation flow field.

The series of advantages such as the present invention can well detect shock wave in the laser chamber, can accurately judge size and the direction of propagation of shock wave, and has higher sensitivity, and measurement mechanism is simple, method is easy.

The above is preferred embodiment of the present invention, but the present invention should not be confined to the disclosed content of this embodiment and accompanying drawing.So everyly do not break away from the equivalence of finishing under the spirit disclosed in this invention or revise, all fall into the scope of protection of the invention.

Claims (7)

1. pulsed gas laser chamber flow field measurement mechanism based on 4 quadrant detector, comprise probe source, survey optical receiver system and signal processing system, it is characterized in that: the light beam that probe source sends is parallel with the optical axis direction of pulsed gas laser; Described detection optical receiver system comprises four-quadrant photo detector, and wherein the photosurface of four-quadrant photo detector is used for receiving the exploring laser light light beam that probe source sends towards search coverage and vertical with detecting light beam; The signal of four-quadrant photo detector obtains the propagation characteristic parameter of shock wave after signal processing system is processed.

2. the pulsed gas laser chamber flow field measurement mechanism based on 4 quadrant detector according to claim 1, it is characterized in that, described detection optical receiver system also comprises dichroic mirror, laser rays optical filter, described dichroic mirror plane becomes 45 degree with detecting light beam, filter plate and four-quadrant photo detector are over against detecting light beam, and probe source, dichroic mirror, laser rays optical filter and four-quadrant photo detector are positioned on the same light path successively.

3. the pulsed gas laser chamber flow field measurement mechanism based on 4 quadrant detector according to claim 1, it is characterized in that, described detection optical receiver system also comprises dichroic mirror, laser rays optical filter and spectroscope, described light splitting minute surface, double-colored minute surface becomes miter angle with detecting light beam, described laser rays filter plate is vertical with detecting light beam, described detecting light beam passes through respectively the center of light splitting minute surface and double-colored minute surface, and via again passing through the center of double-colored minute surface and light splitting minute surface and the center of laser rays filter plate after the reflection of measured laser device reflecting surface, received by 4 quadrant detector at last.

4. according to claim 2 or 3 described pulsed gas laser chamber flow field measurement mechanisms based on 4 quadrant detector, it is characterized in that the laser rays optical filter is to the high saturating arrowband transmission filter of exploring laser light bundle.

5. according to claim 2 or 3 described pulsed gas laser chamber flow field measurement mechanisms based on 4 quadrant detector, it is characterized in that dichroic mirror is the high anti-narrowband reflection filter of paired pulses laser beam.

6. the pulsed gas laser chamber flow field measurement mechanism based on 4 quadrant detector according to claim 4 is characterized in that, dichroic mirror is the high anti-narrowband reflection filter of paired pulses laser beam.

7. according to claim 2 or 3 described pulsed gas laser chamber flow field measurement mechanisms based on 4 quadrant detector, it is characterized in that spectroscope is to surveying the semi-transparent semi-reflecting optical filter of light.

Images