CN2861993Y - Ultrashort pulse measuring device using reflection type Dammann grating - Google Patents

Abstract

An ultrashort laser pulse measuring device using a reflective Dammann grating includes a beam splitter and time delay device, a converging mirror, a nonlinear crystal, an aperture and a spectrometer, wherein the beam splitter and time delay device is a reflective Dammann grating beam splitter and time delay device composed of three fast 1×2 reflective Dammann gratings and two light shielding plates in a three-dimensional configuration, and the converging mirror is a reflective converging mirror. The utility model is a fully reflective ultrashort laser pulse measuring device, which solves the problem of ultrashort pulse broadening caused by the light beam passing through a medium during the ultrashort laser pulse measurement process, and has the characteristics of simplified structure, convenient adjustment and low instrument cost.

Description

Utilize the ultrashort pulse measuring device of reflective dammann grating

Technical field

The utility model relates to ultrashort laser pulse, particularly a kind of ultrashort laser pulse measurement mechanism that utilizes reflective dammann grating.

Background technology

Since nineteen nineties ultrashort pulse particularly femtosecond (fs 10 ^-15Second) laser technology has obtained development fast, because femto-second laser pulse has the ultrashort characteristic of time domain, can carry out the research of ultrafast phenomena to fields such as physics, chemistry, biology, medical science.Simultaneously, femto-second laser pulse also has high peak power, is the strong instrument that carries out various non-linear phenomena researchs.

The research of the various phenomenons under the femto-second laser pulse effect realizes by the femtosecond pulse measuring technique, obtains the physical essence of femtosecond dynamic system response by the measurement to the characteristics such as time domain, frequency domain and transmission of femtosecond light.Simultaneously, the development of measuring technique also has huge impetus to the development of femtosecond laser technology itself, and the light pulse that produces the shorter duration is had huge directive function.

The femto-second laser pulse measurement has a variety of methods, frequency resolution optical shoulder rotation (frequency-resolved optical gating wherein, abbreviate FROG as) [referring to technology 1 " Frequency-Resolved optical Gating:The Measurement of Ultrashort LaserPulses " Rick Trebino formerly, 2002 Kluwer Academic Publishers] with relevant electric field reconstruct method (the spectral phase interferometry for direct electric-fieldreconstruction in spectrum position, SPIDER) [referring to technology 2 " Spectral phaseinterferometryfor direct electric-field reconstructionof ultrashort opticalpulses " C.Iaconis formerly, A.Walmsley, Optics Letters, Vol.23 Issue 10 1998], be the two kinds of more methods that adopt at present.

The basic structure of existing frequency resolution optical shoulder rotation measurement mechanism as shown in Figure 1, among Fig. 12 the expression be the beam splitting delayer.Femtosecond pulse light 1 is divided into two light beams by beam splitter 21: switching pulse light beam and direct impulse light beam, the switching pulse light beam reflects along opposite direction through corner cube mirror 22.Wherein corner cube mirror 22 is fixed on the computer-controlled micropositioner 23.The direct impulse light beam by 25 reflections of corner cube mirror 24 and catoptron and with the switching pulse parallel beam.Two beam pulse light beams are focused on the nonlinear crystal 5 by lens 4 then, produce frequency inverted, flashlight is received by spectrometer 7 by shadow shield 6 and measures, the delay inequality that changes two-beams by micropositioner 23 obtains the two-dimensional map (FROG Trace) of intensity with respect to time and frequency, collection of illustrative plates using iterative algorithm [participating in technology 1 formerly] is obtained the amplitude of femtosecond pulse and mutually.What yet the beam splitter in present most of ultrashort pulse measuring device adopted all is semi-transparent semi-reflecting lens, femto-second laser pulse is very short pulse, have very wide frequency spectrum, therefore must produce the broadening influence, cause measurement result inaccurate the ultrashort pulse of transmission; It can also be seen that by Fig. 1 also adopted more catoptron in this measurement mechanism, this has not only increased the adjusting difficulty, and has increased cost.

Summary of the invention

The technical problems to be solved in the utility model is to overcome the shortcoming of above-mentioned prior art, a kind of ultrashort laser pulse measurement mechanism that utilizes reflective dammann grating is provided, this invention should reduce the ultra-short pulse-width expansion influence that produces owing to transmission process as far as possible, further simplified structure reduces and regulates difficulty and lowering apparatus cost.

Technical solution of the present utility model is as follows:

A kind of ultrashort laser pulse measurement mechanism that utilizes reflective dammann grating, comprise the beam splitting chronotron, convergent mirror, nonlinear crystal, diaphragm and spectrometer, it is characterized in that described beam splitting chronotron is by the one 1 * 2 reflective dammann grating, the 21 * 2 reflective dammann grating, the 31 * 2 reflective dammann grating, computer-controlled micropositioner, first baffle plate and second baffle stereoscopic configurations and the reflective dammann grating beam splitting chronotron that constitutes, described the 21 * 2 reflective dammann grating places on the computer-controlled micropositioner, described convergent mirror is a reflective convergent mirror, its position relation is: when a branch of femtosecond pulse light incides first reflective 1 * 2 Darman raster (31) in perpendicular and with a low-angle α, in surface level, be divided into-1 grade of P light beam and+1 grade of G bundle light, this two-beam is placed on distance L place, back respectively and at conplane second reflective 1 * 2 Darman raster and three-mirror reflective 1 * 2 Darman raster institute diffraction, produce the P-1 level again respectively, P+1 level two-beam and G-1 level, G+1 level two-beam, wherein the P+1 level light beam of second reflective 1 * 2 Darman raster diffraction is covered by first baffle plate, the G-1 level light of three-mirror reflective 1 * 2 Darman raster institute diffraction is covered by second baffle, and the G light+1 grade parallel beam ground outgoing of the P-1 level light beam of second reflective 1 * 2 Darman raster diffraction and three-mirror reflective 1 * 2 Darman raster institute diffraction, converge at nonlinear crystal through reflective convergent mirror reflection, received by spectrometer by diaphragm and measure.

The structure of described reflective 1 * 2 Darman raster is identical, and the cycle is d, and the degree of depth is λ _c/ 4, wherein λ c is the centre wavelength of described ultra-short pulse laser.

Described low-angle α≤2 °.

Described second reflective 1 * 2 Darman raster and three-mirror reflective 1 * 2 Darman raster and distance L between first reflective 1 * 2 Darman raster should guarantee by first reflective 1 * 2 Darman raster produce+1 grade of light can spatially separate with-1 grade of light.

Darman raster is [referring to technology 3 " Numerical study of Dammann arrayilluminators " Changhe Zhou formerly, and Liren Liu Applied Optics, Vol.34, No.261995] be a kind of diffraction optical device, be widely used in matrix lamp at present.Position and position by the flex point in the control Darman raster one-period are worth the control that realizes incident beam mutually, and Darman raster can easily be beamed into a branch of incident light m * n (m, n are integer) bundle.

When a branch of centre wavelength is the laser vertical of λ when to incide aperture efficiency be 1: 2 the grating of reflective dammann, reflected light can be divided into the identical two-beam of intensity, and the angle of emergent light and grating normal is

θ＝sin ^-1(λ/d) (1)

Grating degree of depth h is relevant with catoptrical diffraction efficiency

$\mathrm{\η}=I_{+1}=I_{-1}=I_0\frac{4}{{\mathrm{\π}}^2}{\sin }^2\frac{\mathrm{\φ}}{2}---\left(2a\right)$

$\mathrm{\φ}=\frac{4\mathrm{\π}}{\mathrm{\λ}}h---\left(2b\right)$

I wherein _{+ 1}, I _-1Be respectively+1 grade and-1 grade of catoptrical intensity I ₀Be the incident pulse light intensity, h is the degree of depth of grating.Can be drawn by formula 2 that every bundle reflected light has the highest diffraction efficiency 40.5% when the h=λ/4, total diffraction efficiency is 81%.

Technique effect of the present utility model:

Because the utility model utilizes reflective dammann grating to make the ultrashort pulse measuring device of the no transmission device of beam splitting chronotron and concave mirror focusing, what promptly adopt is the total-reflection type structure, avoided the femtosecond ultra-short pulse laser owing to the problem that penetrates the pulse strenching that medium produces in the transmission course effectively, can eliminate the broadening of hosqt media femtosecond pulse.The reflective coating of Darman raster adopts the metallic diaphragm of high reflectance, wide spectrum, easily processing.Because the manufacturing technology of Darman raster and microelectronic processing technique be compatibility mutually, have easy processing, advantage that cost is low.The core of this device has only three Darman rasters in addition, is easy to realize the aplanatism of pulse, has compact conformation, the advantage that light path is easy to adjust.

Description of drawings

Fig. 1 is the ultrashort pulse FROG measurement mechanism of existing standard.

Fig. 2 is the ultrashort pulse measuring device vertical view that the utility model utilizes reflective dammann grating.

Fig. 3 is the side view that the utility model utilizes beam splitting delayer in the reflective dammann grating ultrashort pulse measuring device.

The amplitude of Fig. 4 ultrashort laser pulse time domain that to be the utility model come out according to experimental result and technology 1 reconstruct formerly and the position figure that compares.

Among the figure: 1-femto-second laser pulse light beam;

2-beam splitting delayer; The 21-beam splitter; 22-rigging-angle cone catoptron; The computer-controlled micropositioner of 23-; 24-rigging-angle cone catoptron; The 25-catoptron;

3-Damman raster splitting beam delayer; 31-the one 1 * 2 reflective dammann grating; 32-the 21 * 2 reflective dammann grating, 33-the 31 * 2 reflective dammann grating; The computer-controlled micropositioner of 34-; 35-first shadow shield, 36-second shadow shield;

The 4-convergent mirror; The 5-nonlinear crystal; The 6-diaphragm; The 7-spectrometer.

Embodiment

The utility model is described in further detail below in conjunction with embodiment and accompanying drawing, but should not limit protection domain of the present utility model with this.

See also Fig. 2 and Fig. 3 earlier, as seen from the figure, the utility model utilizes the ultrashort laser pulse measurement mechanism of reflective dammann grating, comprise the beam splitting chronotron, convergent mirror 4, nonlinear crystal 5, diaphragm 6 and spectrometer 7, it is characterized in that described beam splitting chronotron 3 is by the one 1 * 2 reflective dammann grating 31, the 21 * 2 reflective dammann grating 32, the 31 * 2 reflective dammann grating 33, computer-controlled micropositioner 34, first baffle plate 35 and second baffle 36 stereoscopic configurations and the reflective dammann grating beam splitting chronotron that constitutes, described the 21 * 2 reflective dammann grating 32 places on the computer-controlled micropositioner 34, described convergent mirror 4 is reflective convergent mirrors, its position relation is: when a femto-second laser pulse light beam 1 incides on first reflective 1 * 2 Darman raster 31 in perpendicular and with a low-angle, in surface level, be divided into-1 grade of P light beam and+1 grade of G light beam, this two-beam is placed on distance L place, back respectively and at conplane second reflective 1 * 2 Darman raster 32 and 33 diffraction of three-mirror reflective 1 * 2 Darman raster, produce the P-1 level again respectively, P+1 level two-beam and G-1 level, G+1 level two-beam, wherein the P+1 level light beam of second reflective 1 * 2 Darman raster, 32 diffraction is covered by first baffle plate 35, the G-1 level light of 33 diffraction of three-mirror reflective 1 * 2 Darman raster is covered by second baffle 36, and the G light+1 grade parallel beam ground outgoing of the P-1 level light beam of second reflective 1 * 2 Darman raster, 32 diffraction and 33 diffraction of three-mirror reflective 1 * 2 Darman raster, converge at nonlinear crystal 5 through described reflective convergent mirror 4, received by spectrometer 7 by diaphragm 6 and measure.

The structure of described reflective 1 * 2 Darman raster is identical, and the cycle is d, and the degree of depth is λ _c/ 4, wherein λ c is the centre wavelength of described ultra-short pulse laser.

Described low-angle α≤2 °.

Described second reflective 1 * 2 Darman raster 32 and three-mirror reflective 1 * 2 Darman raster 33 and the distance L of first reflective 1 * 2 Darman raster 31 should guarantee by first reflective 1 * 2 Darman raster 31 produce+1 grade of light can spatially separate with-1 grade of light.

A branch of centre wavelength is λ _c, width is τ ₀ Femtosecond pulse light 1 in perpendicular along with a low-angle α (α less than the 2 degree) cycle of inciding be d (d＞＞λ _c), the degree of depth is λ _cOn/4 reflective 1 * 2 Darman raster 31, in surface level, be divided into-1 grade of P and+1 grade of G two-beam, this two-beam is placed on respectively that back L (should guarantee+1 grade of light can spatially separate with-1 grade of light) locates and at conplane synperiodic reflective 1 * 2 Darman raster 32,33 diffraction, produce two-beam respectively, wherein grating 32 is placed on the computer-controlled micropositioner 34, and micropositioner can be regulated the position of grating 32, thereby can change the optical path difference of two pulses.Utilize baffle plate 35 and 36 respectively with light beam P+1 grade of light ,-1 grade of light of G covers, according to grating equation as can be known-1 grade of light of light beam P and G+1 only parallel.In addition according to [technology 4 GuoweiLi formerly, Changhe Zhou, and Enwen Dai, " Splitting of femtosecond laser pulses byusing a Dammann grating and compensation gratings ", J.Opt.Soc.Am.A, 22 (2005)] can draw pulsed light through the pulse width behind the grating pair.

$\mathrm{\τ}=\sqrt{{\mathrm{\τ}}_0^2+\frac{{\left({2\mathrm{k\β}}^{2}L\right)}^2}{{\mathrm{\τ}}_0^2}}---\left(3\right)$

Wherein ${\mathrm{\β}=\mathrm{\λ}}_c^2/\left(2\mathrm{\πcd}\right),$ K=2 π/λ _c, c is the light velocity.

Two-beam is focused in the nonlinear crystal 5 by concave mirror 4 and produces flashlight, and flashlight is received by spectrometer 7 by shadow shield 6 and produces frequency discrimination, utilizes micropositioner to change delay inequality and realizes optical switch, can obtain the FROG collection of illustrative plates.

In sum, the utility model has been realized the ultrashort pulse photo measure of total-reflection type with three reflection Darman rasters, thereby eliminated the influence of traditional saturating/reflecting light beam splitter paired pulses light, simultaneously the manufacturing technology of Darman raster is compatible mutually with microelectronic processing technique, so has easy processing, advantage that cost is low

The centre wavelength 800nm that utilized this measurement of installing our success, the ultrashort pulse of 11.7 femtoseconds of pulse width, the cycle d=100 μ m of reflective dammann grating wherein, etching depth is 0.2 μ m, surface gold-plating.The focal length of concave mirror is 300mm.What nonlinear crystal adopted is the bbo crystal of 30 micron thickness, α=1.5 °.Become light path and obtain the FROG collection of illustrative plates by computer-controlled micropositioner 34 with spectrometer 7 amounts and frequency light.Fig. 4 be the ultrashort laser pulse time domain of coming out according to experimental result and technology 1 reconstruct formerly amplitude and position mutually, the result is as shown in the table.

	The time domain full width at half maximum	Spectrum width	Error
				FROG	11.7fs	94.5nm	0.005

Reconstructed error is very little as can be seen, has proved the practicability and effectiveness of this device.

Claims (4)

1. A device for measuring ultrashort laser pulses utilizing reflective Damman gratings, comprising beam splitters, converging mirrors (4), nonlinear crystals (5), apertures (6) and spectrometers (7), which It is characterized in that the beam splitting delay device (3) is composed of a first 1×2 reflective Damman grating (31), a second 1×2 reflective Damman grating (32), a third 1×2 reflective Damman grating (33), computer-controlled micro-motion table (34), first baffle plate (35) and second baffle plate (36) three-dimensional configuration constitute the reflective Damman grating beam splitting delay device, said The second 1×2 reflective Damman grating (32) is placed on the micro-movement stage (34) controlled by the computer, and the described converging mirror (4) is a reflective converging mirror, and its positional relationship is: when a flying The second laser pulse beam (1) is incident on the first reflective 1×2 Damman grating (31) at a small angle α in the vertical plane, and is divided into -1-level P beam and +1-level G beam in the horizontal plane light beams, the two light beams are respectively placed at the back distance L and diffracted by the second reflective 1×2 Damman grating (32) and the third reflective 1×2 Damman grating (33) on the same plane, respectively Two beams of P-1 and P+1 beams and two beams of G-1 and G+1 are generated, wherein the P+1 beam diffracted by the second reflective 1×2 Damman grating (32) is captured by the first Covered by a baffle (35), the G-1 order light diffracted by the third reflective 1×2 Damman grating (33) is covered by the second baffle (36), while the second reflective 1×2 Daman grating The P-1 order beam diffracted by the Mann grating (32) exits in parallel with the G light+1 order beam diffracted by the third reflective 1×2 Damman grating (33), and passes through the reflective converging mirror (4) Converging on the nonlinear crystal (5), it is received and measured by the spectrometer (7) through the diaphragm (6). 2. The ultra-short laser pulse measuring device of reflective Damman grating according to claim 1, characterized in that the structure of the reflective 1×2 Damman grating is the same, the period is d, and the depth is λ _c /4 , where λc is the central wavelength of the ultrashort pulse laser (1). 3. The ultrashort laser pulse measuring device of reflective Damman grating according to claim 1, characterized in that said small angle α≤2°. 4. The ultrashort laser pulse measuring device of reflective Damman grating according to claim 1, characterized in that the second reflective 1×2 Daman grating (32) and the third reflective 1×2 Daman grating The distance L between the Mann grating (33) and the first reflective 1×2 Damman grating (31) should ensure that the +1-order beam and the -1-order light beam produced by the first reflective 1×2 Damman grating (31) The beams can be spatially separated.

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