CN100595537C - Femtosecond laser burst self-correlation tester and method thereof - Google Patents
Femtosecond laser burst self-correlation tester and method thereof Download PDFInfo
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- CN100595537C CN100595537C CN200810057363A CN200810057363A CN100595537C CN 100595537 C CN100595537 C CN 100595537C CN 200810057363 A CN200810057363 A CN 200810057363A CN 200810057363 A CN200810057363 A CN 200810057363A CN 100595537 C CN100595537 C CN 100595537C
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Abstract
The invention relates to a femtosecond laser pulse autocorrelation tester and a method thereof, and belongs to the photoelectron field. The prior products have the deficiencies of complicated opticaldesign and regulating process, large size and high cost. The invention subsequently includes two same sheet materials (FS1) and (FS2) which are transparent relatively to the laser to be tested and with thickness in mm, a concave mirror (CM1), a non-linear crystal (NL), a pinhole diaphragm (PA), a concave mirror (CM2), a photodetector (PD), and an autocorrelation characteristic curve display devicefor incident light pulse (OSC); two beams of the laser to be tested which pass the sheet materials are in parallel but not the same high, incidence to the concave mirror (CM1) to focus, and put the non-linear crystal on the focus and generate sum-frequency light; the pinhole diaphragm is only collimated by the other concave mirror (CM2) through the sum-frequency light, incidence to the photodetector to convert the optical signal into electric signal and input to the autocorrelation characteristic curve display device for incident light pulse (OSC), so as to obtain the autocorrelation characteristic curve of the incident light pulse. The invention has high integration degree, is convenient in operation and has high performance-price ratio.
Description
Technical field
The present invention is a kind of integrated degree height, easy and simple to handle, femtosecond laser burst self-correlation tester device with high performance price ratio, belongs to photoelectron technology and devices field.
Background technology
Femtosecond laser technology and device are the most important and most active scientific research of present laser technology and application, hi-tech industry field.Femtosecond pulse has been widely used in scientific research fields such as biology, chemistry, nanomaterial science, condensed state physics, industrial circles such as the exploitation of new pattern laser device and Laser Micro-Machining, and military field etc.Correspondingly ultra-intense laser device, ultrafast laser spectroscopy technology have become research tool indispensable in present scientific research and the new technology development.
The outstanding feature of femto-second laser pulse is its transient state high-strength characteristic.Generally below 200 femtoseconds, promptly its duration is shorter than 200 * 10 to the width of the femto-second laser pulse of our common indication
-15Second.So short light pulse is that the testing apparatus used always (as ondograph etc.) institute can't directly respond and differentiate, therefore can only be by means of indirect measurement scheme, and common scheme is the measurement that the measurement of time is converted to the space.Measuring method commonly used at present has: correlation method, frequency resolution optical shoulder rotation (FROG), the relevant electric field reconstruction method (SPIDER) of self-reference spectrum phase.FROG and SPIDER can provide the intensity and the phase place of pulse in detail, but need comparatively complicated optical system and just can obtain relevant ultrashort pulse information through after the loaded down with trivial details data processing.But under normal conditions, we are concerned about and need most the width that is appreciated that pulse most.Correlation method can or directly provide the width of pulse in real time with the fastest speed, is the testing tool and the characterization tool of ultrafast laser laboratory indispensability therefore.Based on the auto-correlation ratio juris, present existing multiple product on the international market, but optical design and adjustment process complexity, test process technical requirement height, cycle are long, and volume is greatly the main drawback of these products.Because its know-why and device architecture complexity, the auto-correlation testing tool on the international market costs an arm and a leg at present, is difficult to as breadboard daily Instrument purchase, use.
Summary of the invention
The problems referred to above at existing femtosecond pulse autocorrelation function analyzer, the invention provides a kind of simple in structure, novel, easy to adjust, volume is little, the femtosecond laser burst self-correlation tester device that cost is low, for femto-second laser pulse provides a kind of advantages of simplicity and high efficiency pulse width measure device, have important practical value and and economic benefit.
The invention provides a kind of femtosecond laser burst self-correlation tester, it is characterized in that, comprise successively:
Two be transparent for testing laser and thickness at the identical flaky material FS1 of millimeter magnitude, the autocorrelation characteristic graph display devices OSC of FS2, concave mirror CM1, nonlinear crystal NL, pinhole diaphragm PA, concave mirror CM2, photoelectric detector PD, incident light pulse;
Wherein flaky material FS1 and FS2 are orthogonal and be fixed on up and down on the rotor, and rotor connects direct current generator and drives, and flaky material FS1 and FS2 are rotating in the plane that flaky material FS1 and FS2 determine under the drive of direct current generator;
Testing laser is parallel to plane that flaky material FS1 and FS2 determine and is centering adjustment incident with the intersection point of flaky material FS1 and FS2, and by flaky material FS1, FS2, is divided into two bundles up and down.When flaky material FS1 and FS2 planar periodically rotated, two-beam was because different through the light path of FS1 and FS2 up and down, and its time-delay also presents periodic variation, thereby realizes the scanning of time-delay.Flaky material FS1 is parallel but highly different with the two-beam that FS2 passes through, when being incident to, they will intersect in the focus of concave mirror CM1 when concave mirror CM1 focuses on, focus at concave mirror CM1 is placed nonlinear crystal NL, makes two-beam to produce in nonlinear crystal NL and frequency; Via nonlinear crystal NL emitting laser, comprise first-harmonic, separately frequency doubled light with and light frequently;
Adopt pinhole diaphragm PA with first-harmonic and frequency doubled light filtering separately, only see through and frequency light, collimate through another concave mirror CM2, be incident to photoelectric detector PD, photoelectric detector PD is converted into light signal electric signal and input and display device OSC is carried out processes and displays, promptly obtains the autocorrelation characteristic curve of incident light pulse.
Use the method that above-mentioned femtosecond laser burst self-correlation tester is tested, it is characterized in that, may further comprise the steps:
1) determines the time interval Δ t at half-peak value place in the auto-correlation waveform according to the autocorrelation characteristic curve of incident light pulse; And two autocorrelative time interval T, thereby the angular velocity that obtains direct current generator is ω=2 π/T; 2) obtain angle θ=ω * Δ t/2 that direct current generator turns over by Δ t and angular velocity omega;
3) the following formula of angle θ substitution that direct current generator is turned over obtains real time-delay Δ τ;
N is the refractive index of fused quartz, and c is the light velocity, and d is the thickness of flaky material FS1 and FS2.
Compare with traditional autocorrelation function analyzer, principal feature of the present invention has:
1, do not need the complicated adjusting process, total optical path length can contract to 15cm, easy operating, and the antijamming capability of system is strong, signal contrast height, good reliability;
2, the time of measuring has greatly been simplified and shortened to realization to the scanning that laser pulse postpones automatically;
3, optics and mechanical components and parts are few, compact conformation, and volume is little, is easy to carry and moves; Simultaneously, greatly reduce optical loss, improved system effectiveness and sensitivity;
4, with low cost, be suitable as the conventionally test instrument of ultrafast optical laboratory.
Main performance index of the present invention
Measure wave band: the test spectral scope can cover from the femto-second laser pulse of 450nm to 3 mu m waveband;
Measure pulse width: 20fs to 500fs;
Test result: oscillograph shows the intensity autocorrelator trace, and time shaft is demarcated the back and obtained pulse width.
Description of drawings:
Fig. 1 is the structure principle chart of auto-correlation tester among the present invention;
Fig. 2 for laser beam incident to by the fused quartz thin slice time by the schematic diagram of beam splitting;
Fig. 3 a be bbo crystal obtain when being in 800nm basic frequency beam focus with frequently and frequency multiplication hot spot pattern;
Fig. 3 b is the frequency multiplication hot spot pattern that bbo crystal obtains during away from 800nm basic frequency beam focus;
The intensity autocorrelator trace that Fig. 4 a records for experiment;
Fig. 4 b is the measurement result in a plurality of cycles, and wherein each spike is represented autocorrelation process one time;
The intensity autocorrelator trace that Fig. 5 demarcates for the elapsed time axle, the halfwidth that therefrom can determine pulse is 232fs.
Embodiment
Below be a specific embodiment of the present invention, the autocorrelation function analyzer structure as shown in Figure 1.But the present invention is not limited to following examples, so long as the variation that those skilled in the art carry out in principle of the present invention should belong to protection scope of the present invention.
The core of its optical system comprises:
1, two fused quartz thin slices (FS1, FS2): thickness 1mm, long 20mm, wide 8mm;
2, the concave mirror of two metal-plated membranes (CM1, CM2): radius-of-curvature is 75mm, bore 12.7mm;
3, a BBO nonlinear crystal (NL): thickness 2mm, clear aperture 5 * 5mm
2
4, a pinhole diaphragm (PA): diameter 0.5mm;
5, a silicon photoelectric diode (PD);
6, direct-drive motor: 3000 rev/mins of rotating speeds.
Wherein FS1 and FS2 are orthogonal and be fixed on up and down on the rotor, drive by direct current generator, and the rotation by FS1 and FS2 realizes through the delayed sweep between the two-beam of FS1 and FS2.
The principle of work of autocorrelation function analyzer:
Testing laser is center incident and passes through FS1, FS2 that with the intersection point of flaky material FS1 and FS2 be divided into two bundles up and down, its space structure as shown in Figure 2.Laser beam is different with the angle of flaky material FS1 and FS2, then Jing Li time-delay difference.Two fused quartz thin slices high speed rotating under the drive of direct current generator, thereby the continuous sweep of the interpulse time delay of realization two-beam.It is highly different because the two-beam that the fused quartz thin slice passes through is parallel, when being incident to, they will intersect in the focus of concave mirror when concave mirror CM1 focuses on, place nonlinear crystal NL in the focus of concave mirror CM1 this moment, makes two-beam to produce in BBO and frequency.Via the BBO emitting laser, comprise first-harmonic, separately frequency doubled light with and light frequently, but their shooting angle difference and light is in the centre frequently, fundamental frequency light and frequency doubled light apportion separately be both sides up and down.The relevant information of two-beam that it has neutralized optical recording frequently.Employing pin hole PA only sees through first-harmonic and frequency doubled light filtering separately and frequency light, through another concave mirror CM2 collimation, is incident to photodetector (for example photodiode or photomultiplier etc.) PD.Photodetector is converted into electric signal with light signal and imports oscillograph and carry out processes and displays, promptly obtains the autocorrelation characteristic curve of incident light pulse.
1, tested object: continuous light pumping titanium jewel mode-locked laser oscillator output optical pulse;
2, test result: the intensity autocorrelator trace that directly reads from the oscillograph as shown in Figure 4;
3, calibrated intensity autocorrelator trace: the calibrated intensity autocorrelator trace of time shaft as shown in Figure 5;
4, pulse width measuring result:, determine the pulse width at halfwidth place according to the physical relation of intensity auto-correlation and pulse width:
The time shaft of autocorrelator trace is demarcated:
The ultimate principle of autocorrelation function analyzer in according to the present invention, in the rotor rotation process, because two-beam, causes the variation of its time-delay Δ τ generating period by the time-delay difference of the experience of fused quartz thin slice, the concrete numerical value of Δ τ is decided by the angle of incident light and thin slice.Derivation according to how much can be through the light path P1 of two thin slice two-beams, and P2 is respectively:
It wherein is the corner that rotor is ordered with respect to O.O point position corresponding to the time incident light along the angular bisector direction incident (as shown in Figure 2) of two fused quartz thin slices; α, β are respectively the refraction angle of two-beam in two thin slices; N is the refractive index of fused quartz.The time-delay that can be obtained two-beam by light path is:
When leveling off to, time-delay Δ τ can be reduced to:
∵θ＝ωt [2]
Wherein ω is the angular velocity of motor rotation,
Can get:
By [3] as seen, Δ τ is the amount that changes of cycle in time, thereby the cycle of realizing the two-beam time-delay changes.Further as can be known, the rate of change of Δ τ and the thickness d of thin slice, the angular velocity omega of motor is relevant.
Because the time of the auto-correlation waveform that oscillograph the is shown real time-delay Δ τ (shown in Fig. 4 a) that is not two-beam, so be necessary oscillographic time scale is demarcated, obtaining auto-correlation waveform, thereby further obtain pulse width corresponding to true time delay Δ τ.The demarcation of autocorrelation function analyzer is performed such: the time interval Δ t that 1. determines half-peak value place in the auto-correlation waveform; 2. determine the angular velocity omega of direct current generator according to the repetition frequency of auto-correlation waveform, shown in Fig. 4 b.For example the two autocorrelative time intervals were T=47.6ms among the figure, and then the angular velocity of motor is ω=2 π/T=132rad/s; 3. according to formula [2], obtain angle θ=ω * Δ t/2 that motor turns over,, obtain real time-delay Δ τ 4. with θ substitution formula [1] by Δ t and angular velocity.
In fact, for femtosecond pulse, because very little (θ concerning our example=1.36 ° of motor turns in the Δ t time angle, therefore time scale and the actual time delay that can regard as on the oscillograph is directly proportional (shown in formula [3]), like this as long as just can obtain time-delay to the oscillographic time divided by a calibration factor.This calibration factor and n, d, ω is relevant.Because theoretical calculating often has error,, after this just the pulsewidth of various femto-second laser pulses can have been measured so before correlator dispatches from the factory, can calibration factor be determined by a known pulsewidth.
In addition, the full width at half maximum of intensity auto-correlation waveform is not real pulse width, need be divided by a factor, and for Gauss pulse, pulse width is to demarcate the full width at half maximum (FWHM) of back intensity auto-correlation waveform divided by 1.414; And for the hyperbolic secant pulse, pulse width is to demarcate the full width at half maximum (FWHM) of back intensity auto-correlation waveform divided by 1.543.
The present invention overcomes the guardian technique difficult point, develops a kind of novel femto-second laser pulse auto-correlation test Instrument. It is optical principle and mentality of designing cleverly, and extremely easy optics and electronics system is having Under the stability that effect assurance femtosecond laser pulse width is measured and the prerequisite of reliability, greatly simplified loaded down with trivial details System and optical path adjusting, have simultaneously little, the lightweight distinguishing feature of volume. This just falls greatly Low instrument cost. Its price only be equal performance indications the commercialization instrument 20%.
Claims (2)
1. a femtosecond laser burst self-correlation tester is characterized in that, comprises successively:
Two be transparent for testing laser and thickness at the identical flaky material FS1 of millimeter magnitude, the autocorrelation characteristic graph display devices (OSC) of FS2, concave mirror CM1, nonlinear crystal (NL), pinhole diaphragm (PA), concave mirror CM2, photodetector (PD), incident light pulse;
Wherein flaky material FS1 and flaky material FS2 are orthogonal and be fixed on up and down on the rotor, rotor connects direct current generator and drives, and flaky material FS1 and flaky material FS2 are rotating in the plane that flaky material FS1 and flaky material FS2 determine under the drive of direct current generator;
Testing laser is parallel to plane that flaky material FS1 and flaky material FS2 determine and is centering adjustment incident with the intersection point of flaky material FS1 and flaky material FS2, and by flaky material FS1 and flaky material FS2, is divided into two bundles up and down; When flaky material FS1 and flaky material FS2 planar periodically rotated, two-beam was because different with the light path of flaky material FS2 through flaky material FS1 up and down, and its time-delay also presents periodic variation, thereby realizes the scanning of time-delay;
Flaky material FS1 is parallel but highly different with the two-beam that flaky material FS2 passes through, when being incident to, they will intersect in the focus of concave mirror CM1 when concave mirror CM1 focuses on, focus at concave mirror CM1 is placed nonlinear crystal (NL), makes two-beam produce in nonlinear crystal (NL) and frequency; Via nonlinear crystal (NL) emitting laser, comprise first-harmonic, separately frequency doubled light with and light frequently; Adopt pinhole diaphragm (PA) with first-harmonic and frequency doubled light filtering separately, only see through and frequency light, collimate through concave mirror CM2, be incident to photodetector (PD), photodetector (PD) is converted into light signal electric signal and electric signal input and display device (OSC) is carried out processes and displays, obtain the autocorrelation characteristic curve of incident light pulse, described flaky material is the fused quartz thin slice.
2, application rights requires the method that 1 described femtosecond laser burst self-correlation tester is tested, and it is characterized in that, may further comprise the steps:
1) determines the time interval Δ t at half-peak value place in the auto-correlation waveform according to the autocorrelation characteristic curve of the incident light pulse that obtains; And two autocorrelative time interval T, thereby the angular velocity omega that obtains direct current generator is ω=2 π/T;
2) obtain angle θ=ω * Δ t/2 that direct current generator turns over by Δ t and angular velocity omega;
3) the following formula of angle θ substitution that direct current generator is turned over, Δ τ obtains delaying time;
N is the refractive index of fused quartz, and c is the light velocity, and d is the thickness of flaky material FS1 and flaky material FS2.
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| CN108775966B (en) * | 2018-09-05 | 2023-06-09 | 中国工程物理研究院激光聚变研究中心 | Double-delay third-order correlator |
| CN111091989B (en) * | 2020-03-23 | 2020-06-26 | 北京波量科技有限公司 | High-field laser laboratory safety interlocking device and control method thereof |
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| US6057919A (en) * | 1996-07-16 | 2000-05-02 | Japan Science And Technology Corporation | Apparatus and method for measuring characteristics of optical pulses |
| CN2519256Y (en) * | 2002-01-29 | 2002-10-30 | 中国科学院物理研究所 | Double-function small-sized ultrashort laser pulse self-correlation measuring instrument |
| JP2004283873A (en) * | 2003-03-24 | 2004-10-14 | Nippon Steel Corp | Laser beam machining head |
| EP1681542A1 (en) * | 2005-01-17 | 2006-07-19 | Fujitsu Limited | Optical waveform measuring apparatus and optical waveform measuring method |
| CN201173826Y (en) * | 2008-02-01 | 2008-12-31 | 北京工业大学 | Ultrashort pulse width tester |
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2008
- 2008-02-01 CN CN200810057363A patent/CN100595537C/en not_active Expired - Fee Related
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6057919A (en) * | 1996-07-16 | 2000-05-02 | Japan Science And Technology Corporation | Apparatus and method for measuring characteristics of optical pulses |
| CN2519256Y (en) * | 2002-01-29 | 2002-10-30 | 中国科学院物理研究所 | Double-function small-sized ultrashort laser pulse self-correlation measuring instrument |
| JP2004283873A (en) * | 2003-03-24 | 2004-10-14 | Nippon Steel Corp | Laser beam machining head |
| EP1681542A1 (en) * | 2005-01-17 | 2006-07-19 | Fujitsu Limited | Optical waveform measuring apparatus and optical waveform measuring method |
| CN201173826Y (en) * | 2008-02-01 | 2008-12-31 | 北京工业大学 | Ultrashort pulse width tester |
Non-Patent Citations (2)
| Title |
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| 基于啁啾镜色散补偿技术的超宽带飞秒激光脉冲. 田金荣等.物理学报，第55卷第9期. 2006 |
| 基于啁啾镜色散补偿技术的超宽带飞秒激光脉冲. 田金荣等.物理学报，第55卷第9期. 2006 * |
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