CN101752778A - Double-cavity resonating device and method for generating self-synchronizing femtosecond pulse and picosecond pulse - Google Patents
Double-cavity resonating device and method for generating self-synchronizing femtosecond pulse and picosecond pulse Download PDFInfo
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Abstract
The invention discloses a double-cavity resonating device, comprising a focusing lens, a sphere reflection cavity lens a, a titanium sapphire laser crystal and a sphere reflection cavity lens b. The incident light side of the focusing lens is provided with a beam splitter; the reflected light side of the sphere reflection cavity lens b is provided with an output coupling lens a and an output coupling lens b which is provided with a piezoelectric sensor a; the reflected light side of the sphere reflection cavity lens a has two reflected light paths one of which includes a planar reflection cavity lens b, an acoustic optical modulator, a slit a and a planar reflection cavity lens a sequentially arranged, and the other one of which includes a quartz prism a, a quartz prism b, a slit b and a planar reflection cavity lens c sequentially arranged; and the planar reflection cavity lens is provided with a piezoelectric sensor b. Self-synchronizing output femtosecond pulse and picosecond pulse can be generated by different dispersion compensation and accurate cavity length matching. In the device and method, the self-synchronizing output femtosecond pulse and picosecond pulse are particularly suitable for research and application of a selective pumping-detecting test.
Description
Technical field
The invention belongs to the ultrashort laser technical field, be specifically related to a kind of double-cavity resonating device, the invention still further relates to and utilize this device to produce the method for self-synchronizing femtosecond pulse and picopulse.
Background technology
At present, the development of double-wavelength short pulse laser has obtained significant progress, can produce the two row femtosecond pulse of output synchronously from single-cavity resonance structure and double-cavity resonating structure.But, in the research and application of ultrafast optics and ultrafast spectroscopy, be to realize the selectivity pumping-detection, often need synchronous femtosecond of exporting and psec light pulse as light source.Existing dual wavelength femtosecond pulse laser can not satisfy the needs of the research and the application of selectivity pumping-detection.Mainly show:
1, the restriction of spectral width
The selectivity pumping-detection requires to adopt the laser pulse of narrow spectrum to excite or pumping, surveys with the laser pulse of wide spectrum.And existing dual wavelength femtosecond pulse laser is merely able to export the femto-second laser pulse of two col width spectrum, therefore can't carry out the selectivity pumping-detection.
2, the influence of chromatic dispersion paired pulses characteristic
In the pumping-detection experiment, the optical element in specimen material, the light path all can exert an influence to laser pulse, mainly shows as the generation of warbling.When laser pulse width reaches the femtosecond magnitude, this influence is particularly remarkable.The femto-second laser pulse of two col width spectrum of existing dual wavelength femtosecond pulse laser output all produces significantly in the pumping-detection experiment and warbles, and directly has influence on measurement result.
3, the restriction of Pulse tuning scope
Though, utilize the single-cavity resonance structure to obtain the passive and synchronous output of femtosecond and picopulse, but, because femtosecond and picopulse degree of coupling in laser crystal can't effectively be controlled in the single-cavity resonance structure, the tuning range mutual restriction of femtosecond and picopulse, tuning range is restricted.
Summary of the invention
The purpose of this invention is to provide a kind of double-cavity resonating device, solved existing resonant structure because the restriction of the influence of the restriction of spectral width, chromatic dispersion paired pulses characteristic and Pulse tuning scope can't be satisfied the problem that produces self-synchronizing femtosecond and picopulse.
Another object of the present invention provides a kind of method of utilizing said apparatus to produce self-synchronizing femtosecond pulse and picopulse.
The technical solution adopted in the present invention is, a kind of double-cavity resonating device, comprise the condenser lens that places successively on the same precise guide rail, spheric reflection chamber mirror a, Ti doped saphire and spheric reflection chamber mirror b, the incident light side of condenser lens is provided with beam splitter, the reverberation side of spheric reflection chamber mirror b is provided with output coupling mirror a and output coupling mirror b, output coupling mirror b is provided with piezoelectric transducer a, the reverberation side of spheric reflection chamber mirror a is provided with two reflected light paths, one the tunnel is the plane reflection chamber mirror b that sets gradually, acousto-optic modulator, slit a, plane reflection chamber mirror a, another road is the quartz prism a that sets gradually, quartz prism b, slit b, plane reflection chamber mirror c, plane reflection chamber mirror c is provided with piezoelectric transducer b, spheric reflection chamber mirror a, spheric reflection chamber mirror b, quartz prism a, quartz prism b, plane reflection chamber mirror c and output coupling mirror b constitute femtosecond laser chamber, spheric reflection chamber mirror a, spheric reflection chamber mirror b, plane reflection chamber mirror b, plane reflection chamber mirror a and output coupling mirror a constitute the picosecond laser chamber.
Another technical scheme of the present invention is, a kind of method of utilizing double-cavity resonating device to produce self-synchronizing femtosecond pulse and picopulse is specifically implemented according to following steps:
Step 1: open argon ion laser, laser power is transferred to 2-3W, the pump beam of incident is divided into parallel two-beam by beam splitter;
Step 2: the distance that is provided with between condenser lens and the Ti doped saphire surface is 99-99.5mm, the spacing of spheric reflection chamber mirror a and spheric reflection chamber mirror b is 99.8-100.3mm, angle between the axis of the axis of spheric reflection chamber mirror a and spheric reflection chamber mirror b is 16 °-26 °, adjust Ti doped saphire normal to a surface direction, make two bundle directional lights that step 1 obtains with brewster angle incidence;
Step 3: determine the pumping light of argon ion laser with two diaphragms, close argon ion laser, do the collimated light source, the pump beam that argon ion laser sends in its light that sends and the step 1 is overlapped with a He-Ne laser;
Step 4: take away the He-Ne laser, open argon ion laser, power transfers to 7-8W, obtains kermesinus fluorescence at plane reflection chamber mirror b, plane reflection chamber mirror c and output coupling mirror a, output coupling mirror b on the surface;
Step 5: regulate position and the axis direction of plane reflection chamber mirror b, the kermesinus fluorescence that step 4 is obtained is penetrated on the surface of plane reflection chamber mirror a, regulates position and the axis direction of plane reflection chamber mirror a then, and kermesinus fluorescence is returned along original optical path; Regulate position and the axis direction of output coupling mirror a, kermesinus fluorescence is returned along original optical path; Further alternately regulate the axis direction of plane reflection chamber mirror a and output coupling mirror a, kermesinus fluorescence is all returned along original optical path on plane reflection chamber mirror a and output coupling mirror a, in the picosecond laser chamber, produce the output of continuous laser; Continue to regulate the axis direction of plane reflection chamber mirror a and output coupling mirror a, the position and the direction of regulating condenser lens, Ti doped saphire, spheric reflection chamber mirror a, spheric reflection chamber mirror b simultaneously make picosecond laser chamber power output maximum; Regulate position and the drift angle direction of quartz prism a, quartz prism b, the kermesinus fluorescence that step 4 is obtained is penetrated on the surface of plane reflection chamber mirror c, regulates position and the axis direction of plane reflection chamber mirror c then, and kermesinus fluorescence is returned along original optical path; Regulate position and the axis direction of output coupling mirror b, bolarious fluorescence is returned along original optical path; Further alternately regulate the axis direction of plane reflection chamber mirror c and output coupling mirror b, kermesinus fluorescence is all returned along original optical path on plane reflection chamber mirror c and output coupling mirror b, in the femtosecond laser chamber, produce the output of continuous laser, continue to regulate the axis direction of plane reflection chamber mirror c and output coupling mirror b, make femtosecond laser chamber power output maximum;
Step 6: close argon ion laser, laser power is adjusted to 9-10W, open acousto-optic modulator, the modulating frequency of acousto-optic modulator is transferred to 78-80MHz, and it is long to regulate chamber, picosecond laser chamber, reaches locked mode, close acousto-optic modulator, the picosecond laser chamber maintains the self mode locking state; Vibration quartz prism b makes the femtosecond laser chamber reach self mode locking;
Step 7: measure the repetition rate of picosecond laser chamber output pulse and the repetition rate of femtosecond laser chamber output pulse with frequency counter, it is long to regulate chamber, femtosecond laser chamber, makes the femtosecond laser chamber consistent with the repetition rate of picosecond laser chamber output pulse;
Step 8: mobile focusing lens, plane reflection chamber mirror c and output coupling mirror b vertically, simultaneously, keep the repetition rate of femtosecond laser chamber output pulse constant, the spectrum of exporting pulse until femtosecond laser chamber and picosecond laser chamber changes;
Step 9: open piezoelectric transducer a and piezoelectric transducer b, regulation voltage, the front and back position of fine setting plane reflection chamber mirror c and output coupling mirror b makes the picosecond laser chamber export the spectrum widening maximum of pulse;
Step 10: along the direction travelling slit a and the slit b that propagate perpendicular to light, the seam of regulating slit a and slit b is wide, makes the wavelength tuning of picopulse and femtosecond pulse;
Step 11: mobile focusing lens, reflecting cavity mirror c and output coupling mirror b vertically, make the long accurately coupling in chamber in picosecond laser chamber and femtosecond laser chamber, it is consistent and export synchronously to reach the wavelength tuning range of picopulse and femtosecond pulse.
Characteristics of the present invention also are, half metal-plated membrane of the upper surface of beam splitter wherein is to the light half reflection of 450-540nm; Second half metal-plated membrane of upper surface is to the whole transmissions of the light of 450-540nm; The lower surface metal-plated membrane all reflects the light of 450-540nm.
The invention has the beneficial effects as follows, utilize the long coupling in different dispersion compensations and accurate chamber, adopt rational gain allocation, in the double-cavity resonating structure, produce the femtosecond and the picopulse of motor synchronizing output; Control the degree that intercouples between femtosecond and the picopulse on the laser crystal surface, widened the tuning range of femtosecond and picopulse.Wherein, warbling that the picosecond laser pulse produces after by the optical element in specimen material, the light path is smaller, and be less to the influence of experimental result.The femtosecond of motor synchronizing output and picopulse are very suitable for the research and the application of selectivity pumping-detection experiment.
Description of drawings
Fig. 1 is the structural representation of double-cavity resonating device of the present invention;
Fig. 2 is the structural representation of pump beam beam splitter in the double-cavity resonating device of the present invention;
Fig. 3 utilizes the femtosecond pulse of apparatus of the present invention generation and the schematic diagram of picopulse coupling regime;
Fig. 4 is the second order autocorrelator trace of picopulse during independent self mode locking in the embodiment of the invention 1;
Fig. 5 is the spectrogram of picopulse during independent self mode locking in the embodiment of the invention 1;
Fig. 6 is the second order autocorrelator trace of femtosecond pulse during independent self mode locking in the embodiment of the invention 1;
Fig. 7 is the spectrogram of femtosecond pulse during independent self mode locking in the embodiment of the invention 1;
Fig. 8 is the second order autocorrelator trace of picopulse when intersecting locked mode in the embodiment of the invention 1;
Fig. 9 is the spectrogram of picopulse when intersecting locked mode in the embodiment of the invention 1;
Figure 10 is the second order autocorrelator trace of femtosecond pulse when intersecting locked mode in the embodiment of the invention 1;
Figure 11 is the spectrogram of femtosecond pulse when intersecting locked mode in the embodiment of the invention 1;
Figure 12 is the crosscorrelation curve of psec and femtosecond pulse when intersecting locked mode in the embodiment of the invention 1;
Figure 13 is total spectrogram of psec and femtosecond pulse when intersecting locked mode in the embodiment of the invention 1;
Figure 14 is the structural representation of the embodiment of the invention 1 double-cavity resonating device.
Among the figure, 1. beam splitter, 2. condenser lens, 3. spheric reflection chamber mirror a, 4. Ti doped saphire, 5. spheric reflection chamber mirror b, 6. output coupling mirror a, 7. piezoelectric transducer a, 8. output coupling mirror b, 9. plane reflection chamber mirror a, 10. slit a, 11. acousto-optic modulators, 12. plane reflection chamber mirror b, 13. quartz prism a, 14. quartz prism b, 15. slit b, 16. plane reflection chamber mirror c, 17. piezoelectric transducer b.
Embodiment
The present invention is described in detail below in conjunction with the drawings and specific embodiments.
The structure of double-cavity resonating device of the present invention, as shown in Figure 1, comprise the condenser lens 2 that places successively on the same precise guide rail, spheric reflection chamber mirror a3, Ti doped saphire 4 and spheric reflection chamber mirror b5, the incident light side of condenser lens 2 is provided with beam splitter 1, the reverberation side of spheric reflection chamber mirror b5 is provided with output coupling mirror a6 and output coupling mirror b8, output coupling mirror b8 is provided with piezoelectric transducer a7, the reverberation side of spheric reflection chamber mirror a3 is provided with two reflected light paths, one the tunnel is the plane reflection chamber mirror b12 that sets gradually, acousto-optic modulator 11, slit a10, plane reflection chamber mirror a9, another road is the quartz prism a13 that sets gradually, quartz prism b14, slit b15, plane reflection chamber mirror c16, plane reflection chamber mirror c16 is provided with piezoelectric transducer b17.Spheric reflection chamber mirror a3, spheric reflection chamber mirror b5, quartz prism a13, quartz prism b14, plane reflection chamber mirror c16 and output coupling mirror b8 constitute a laser cavity, be called the femtosecond laser chamber, spheric reflection chamber mirror a3, spheric reflection chamber mirror b5, plane reflection chamber mirror b12, plane reflection chamber mirror a9 and output coupling mirror a6 constitute another laser cavity, are called the picosecond laser chamber.
Ti doped saphire 4 is used to produce laser pulse;
Spheric reflection chamber mirror a3 and spheric reflection chamber mirror b5 are used to make up stable laser oscillation cavity;
Plane reflection chamber mirror a9, plane reflection chamber mirror b12 and plane reflecting cavity mirror c16 are used for the reflection of laser generation endovenous laser;
Output coupling mirror a6 and output coupling mirror b8 are used for the coupling output of laser oscillation cavity;
Slit a10 and slit b15 are used for the wavelength of pulse in the tuning laser vibration chamber;
Quartz prism a13 and quartz prism b14 are used to compensate the chromatic dispersion of laser generation endovenous laser pulse;
Acousto-optic modulator 11 is used for the startup of picosecond laser locked mode;
Piezoelectric transducer a7 and piezoelectric transducer b17, the chamber that is used to regulate laser oscillation cavity is long.
The structure of beam splitter 1 as shown in Figure 2, beam splitter 1 is positive for diameter is 2 inches a circle, thickness is 4mm.Half metal-plated membrane of upper surface (AE part), to the light half reflection of 450-540nm, second half is metal-plated membrane (ED part) also, to the whole transmissions of the light of 450-540nm; Lower surface metal-plated membrane (BC part) all reflects the light of 450-540nm.The pump light incidence angle is 45 °, and pump light is divided into parallel two-beam behind beam splitter 1, and the power ratio of two-beam can be controlled by the reflectivity that changes metal film, and the distance between the two-beam can be controlled by the thickness that changes beam splitter 1.
Femtosecond pulse and picopulse coupling regime are as shown in Figure 3, after two row mode-locked laser pulses form, when the length of two laser cavities is accurately mated, two row mode-locked laser pulse meetings are met in laser crystal, its stiffness of coupling and their interactional distance dependents, the position of change laser crystal makes their interactional zones 0.1-0.5mm under the surface of laser crystal, just can control its stiffness of coupling, further reach the purpose of control laser pulse tuning range.
The present invention utilizes double-cavity resonating device to produce the method for self-synchronizing femtosecond pulse and picopulse, specifically implements according to following steps:
Step 1: open argon ion laser, laser power is transferred to 2-3W, the pump beam of incident is divided into parallel two-beam by beam splitter 1;
Step 2: the distance that is provided with between condenser lens 2 and Ti doped saphire 4 surfaces is 99-99.5mm, the spacing of spheric reflection chamber mirror a3 and spheric reflection chamber mirror b5 is 99.8-100.3mm, sharp angle between the axis of spheric reflection chamber mirror a3 and spheric reflection chamber mirror b5 is between 16 °-26 °, adjust Ti doped saphire 4 normal to a surface directions, make two bundle directional lights that step 1 obtains with brewster angle incidence;
Step 3: determine the pumping light of argon ion laser with two diaphragms, close argon ion laser, do the collimated light source, the pump beam that argon ion laser sends in its light that sends and the step 1 is overlapped with a He-Ne laser.Argon laser brightness height, intensity are big, easily eyes are damaged.So, adopt the He-Ne laser that brightness is low, intensity is low to do the collimated light source, make the adjusting of light path become relatively easy.In addition, the wavelength of He-Ne laser and titanium precious stone laser wavelength are approaching, help the adjusting and the collimation of light path;
Step 4: take away the He-Ne laser, argon ion laser is opened, power transfers to 7-8W.Obtain bolarious fluorescence at plane reflection chamber mirror b12, plane reflection chamber mirror c16 and output coupling mirror a6, output coupling mirror b8 on the surface;
Step 5: position and the axis direction of regulating plane reflection chamber mirror b12, the kermesinus fluorescence that step 4 is obtained is penetrated on the surface of plane reflection chamber mirror a9, regulate position and the axis direction of plane reflection chamber mirror a9 then, kermesinus fluorescence is returned along original optical path.Regulate position and the axis direction of output coupling mirror a6, kermesinus fluorescence is returned along original optical path.Further alternately regulate the axis direction of plane reflection chamber mirror a9 and output coupling mirror a6, kermesinus fluorescence is all returned along original optical path on two minute surfaces.After repeatedly regulating, the output that just can in the picosecond laser chamber, produce continuous laser.Continue to regulate the axis direction of plane reflection chamber mirror a9 and output coupling mirror a6, the position and the direction of regulating condenser lens 2, Ti doped saphire 4, spheric reflection chamber mirror a3, spheric reflection chamber mirror b5 simultaneously make picosecond laser chamber power output maximum; Regulate position and the drift angle direction of quartz prism a13, quartz prism b14, the kermesinus fluorescence that step 4 is obtained is penetrated on the surface of plane reflection chamber mirror c16, regulate position and the axis direction of plane reflection chamber mirror c16 then, kermesinus fluorescence is returned along original optical path.Regulate position and the axis direction of output coupling mirror b8, bolarious fluorescence is returned along original optical path.Further alternately regulate the axis direction of plane reflection chamber mirror c16 and output coupling mirror b8, kermesinus fluorescence is all returned along original optical path on two minute surfaces.After repeatedly regulating, the output that just can in the femtosecond laser chamber, produce continuous laser.Continue to regulate the axis direction of plane reflection chamber mirror c16 and output coupling mirror b8, make femtosecond laser chamber power output maximum;
Step 6: close argon ion laser, laser power is adjusted to 9-10W.Open acousto-optic modulator 11, the modulating frequency of acousto-optic modulator 11 is transferred to 78-80MHz, it is long to regulate chamber, picosecond laser chamber, reach locked mode, close acousto-optic modulator 11, the picosecond laser chamber can maintain self mode locking (kerr lens mode locking) state, at this moment, measure the auto-correlation and the spectrum of picopulse; Vibrate quartz prism b14 simultaneously and make the femtosecond laser chamber reach self mode locking (kerr lens mode locking), measure the auto-correlation and the spectrum of femtosecond pulse;
Step 7: measure the repetition rate of picosecond laser chamber output pulse and the repetition rate of femtosecond laser chamber output pulse with frequency counter.It is long to regulate chamber, femtosecond laser chamber, makes the femtosecond laser chamber consistent with the repetition rate of picosecond laser chamber output pulse;
Step 8: mobile focusing lens 2, plane reflection chamber mirror c16 and output coupling mirror b8 vertically, simultaneously, keep the repetition rate of femtosecond laser chamber output pulse constant, the spectrum of exporting pulse until femtosecond laser chamber and picosecond laser chamber changes;
Step 9: open piezoelectric transducer a7 and piezoelectric transducer b17, regulation voltage, the front and back position of fine setting plane reflection chamber mirror c16 and output coupling mirror b8 makes the picosecond laser chamber export the spectrum widening maximum of pulse; Measure the auto-correlation of picopulse and the auto-correlation and the spectrum of spectrum and femtosecond pulse once more; Measure the crosscorrelation of picopulse and femtosecond pulse, simultaneously, measure total spectrum of picopulse and femtosecond pulse;
Step 10: along the direction travelling slit a10 and the slit b15 that propagate perpendicular to light, the seam of regulating slit a10 and slit b15 is wide, realizes the wavelength tuning of picopulse and femtosecond pulse;
Step 11: mobile focusing lens 2, reflecting cavity mirror c16 and output coupling mirror b8 vertically, make the long accurately coupling in chamber in picosecond laser chamber and femtosecond laser chamber, it is consistent and export synchronously to reach the wavelength tuning range of picopulse and femtosecond pulse.
Theoretical foundation and beneficial effect that double-cavity resonating device of the present invention and motor synchronizing produce the method for femtosecond and picopulse are:
1, theoretical foundation
The locked mode that intersects relates to two bundles or the above laser of two bundles, each Shu Jiguang not only is subjected to gaining and loss, from the effect of phase modulated, group velocity disperse, and also have coupling each other.Self-focusing effect has been strengthened in coupling, thereby has strengthened phase modulated, that is to say, has produced the cross-phase modulation.In the double-wavelength short pulse laser, two bundle laser are forming the intersection locked mode under phase modulated, group velocity disperse, gain and loss, cross-linked acting in conjunction, and wherein each effect is all most important to the formation of ultrashort pulse.
The classical locked mode equation of dual wavelength intersection locked mode femto-second laser is:
Wherein Φ (z x) is light field envelope operator in the time domain,
β
1, β
2Be respectively the total group velocity disperse in two light beam loops in the optical cavity, ε
1, ε
2Be respectively its Kerr function coefficient, k is a coupling coefficient, and α is a gain by one path, and γ is the loss of one way cavity total, and g is a gain bandwidth, and z is for being the normalized length of unit with chamber length.
The 3rd the expression cross-phase modulation on equation the right.If formula (1) and (2) are represented the locked mode equation in femtosecond and picosecond laser chamber respectively, second of the middle the right of formula (1) so
In the expression femtosecond laser chamber from phase modulated, the 3rd of the right
Cross-phase modulation in the expression femtosecond laser chamber.Because the light field amplitude of femto-second laser pulse is far longer than the light field amplitude of picosecond laser pulse, therefore, cross-phase modulation in the femtosecond chamber is far smaller than from phase modulated, and the intersection locked mode that the cross-phase modulation causes is less to the influence of pulse time domain and frequency domain characteristic in the femtosecond chamber.In the formula (2) second of the right
In the expression picosecond laser chamber from phase modulated, the 3rd of the right
Cross-phase modulation in the expression picosecond laser chamber.Because the light field amplitude of femto-second laser pulse is far longer than the light field amplitude of picosecond laser pulse, therefore, cross-phase modulation in the psec chamber is far longer than from phase modulated, and the intersection locked mode that the cross-phase modulation causes is to the highly significant that influences of pulse time domain and frequency domain characteristic in the femtosecond chamber.
When the locked mode that intersects took place, the phase modulated of laser cavity total was by forming from phase modulated and cross-phase modulation two parts.Because the intersection locked mode that the cross-phase modulation causes is to the highly significant that influences of pulse time domain and frequency domain characteristic in the psec chamber, therefore, we observe the remarkable broadening of picopulse spectrum in this case.And, show that on this basis the intersection locked mode takes place for femtosecond and picopulse.
2, beneficial effect
Utilize the long coupling in different dispersion compensations and accurate chamber, adopt rational gain allocation, in the double-cavity resonating structure, produce the femtosecond pulse and the picopulse of motor synchronizing output, control the degree that intercouples between femtosecond pulse and the picopulse on the laser crystal surface, widened the tuning range of femtosecond pulse and picopulse.And warbling that the picosecond laser pulse produces after by the optical element in specimen material, the light path is smaller, and be less to the influence of experimental result.The femtosecond pulse of motor synchronizing output and picopulse are very suitable for the research and the application of selectivity pumping-detection experiment.
As shown in figure 14, it is 10W that the argon laser power output is set, and beam diameter is 3mm, is incident on the beam splitter M1 with 45.Half metal-plated membrane of beam splitter M1 upper surface has 65% reflectivity to the light of 450-540nm, and second half is metal-plated membrane also, and the light of 450-540nm is had 99% transmitance; The lower surface metal-plated membrane has 99% reflectivity to the light of 450-540nm.The power of light beam 1 is 6.5W, and the power of light beam 2 is 3.5W, and the distance at two-beam edge is 2mm.By focal length is that (CVI BICX-25.4-102.4-UV) focuses on (EKSMA OPTICS) in the Ti doped saphire rod, and Ti doped saphire is pressed Brewster's angle cutting for the lens L of 100mm, optical axis C is perpendicular to the rod axle, mix concentration 0.12wt%, long 4mm, diameter 5mm.The wave vector of pump light is perpendicular to Ti doped saphire optical axis C, and the electric vector of pump light is parallel to optical axis C, forms the π polarized pump, 60.4 ° of incidence angles.Chamber mirror M2 and M3 (CVI, radius of curvature LPK-12.5-25.9-C) is 100mm, to the reflection of light rate of 740-860nm wavelength greater than 99%.Planar cavity mirror M4 to M6 (CVI, TLMB-800-0-2506M) to the reflection of light rate of 740-860nm wavelength greater than 99%.M7 and M8 are that transmitance is 3% plane output coupling mirror.P1 and P2 are quartz prism (IB-12.4-69.1-UV), spacing 56cm.P3 and P4 are piezoelectric transducer (17BPC102).AOM is acousto-optic modulator (12080-3-BR-TE).Condenser lens L, Ti doped saphire Ti:S, reflecting cavity mirror M4 and output coupling mirror M7 place (GCM-72114M) on the precise guide rail.M2, M3, M4, M7 and quartz prism P1 and P2 constitute a laser cavity, are called the femtosecond chamber, and its pump power is 3.5W.M2, M3, M5, M6, M8 constitute another laser cavity, are called the psec chamber, and the chamber is long to be 1906mm, and its pump power is 6.5W.The autocorrelator trace of femtosecond and psec light pulse is measured by the frequency-doubled signal of pulse in bbo crystal respectively, and crosscorrelation is measuring with the frequency signal in bbo crystal by femtosecond pulse and picopulse.The spectrum of pulse comes record by spectrometer.
Experimental result
(1) independent self mode locking
In the psec chamber, realize laser mode locking.Close acousto-optic modulator, locked mode still can be kept in the psec chamber, shows that self mode locking (kerr lens mode locking) finishes.Measure the auto-correlation and the spectrum of picopulse, as Fig. 4 and shown in Figure 5.The full width at half maximum of pulse second order autocorrelator trace is 7.31ps in the psec chamber, and the centre wavelength of pulse spectrum is 786.7nm, and full width at half maximum is 0.23nm, and power output is 373mW.Make femto-second laser reach self mode locking.Measure the auto-correlation and the spectrum of femtosecond pulse, as Figure 6 and Figure 7, the full width at half maximum of pulse second order autocorrelator trace is 47fs in the femtosecond chamber, and the centre wavelength of pulse spectrum is 801nm, and full width at half maximum is 34nm, and power output is 238mW.
(2) intersection locked mode
Measure the repetition rate of picosecond laser output pulse with frequency counter, the result is 78696116Hz.It is long to utilize precise guide rail to regulate chamber, femtosecond laser chamber, makes femto-second laser consistent with the repetition rate of picosecond laser output pulse.Utilize precise guide rail mobile focusing lens L, reflecting cavity mirror M4 and output coupling mirror M7 vertically, simultaneously, keep the repetition rate of femto-second laser output pulse constant, the spectrum of exporting pulse until femto-second laser and picosecond laser changes.Open piezoelectric transducer P3 and P4, regulation voltage, the front and back position of fine setting reflecting cavity mirror M4 and output coupling mirror M7 makes picosecond laser export the spectrum widening maximum of pulse.Measure the auto-correlation and the spectrum of picopulse once more, as Fig. 8 and shown in Figure 9.The full width at half maximum of pulse second order autocorrelator trace is 1.26ps, and the centre wavelength of pulse spectrum is 781.3nm, and full width at half maximum is 1.24nm, and power output is 319mW.Simultaneously, measure the auto-correlation and the spectrum of femtosecond pulse once more, as Figure 10 and shown in Figure 11.The full width at half maximum of pulse second order autocorrelator trace is 53fs, and the centre wavelength of pulse spectrum is 800nm, and full width at half maximum is 33nm, and power output is 212mW.Fig. 8, Fig. 9, Figure 10 and Figure 11 show that the time domain and the frequency domain characteristic of two interior pulses of laser cavity all change.Measure the crosscorrelation of picopulse and femtosecond pulse, simultaneously, measure total spectrum of picopulse and femtosecond pulse, as shown in Figure 12 and Figure 13.Along the direction travelling slit S1 and the S2 that propagate perpendicular to light, simultaneously, the seam of control slit S1 and S2 is wide, can realize the wavelength tuning of laser pulse.When under the surface of coupling regime at laser crystal of picopulse and femtosecond pulse during 0.18mm, the tuning range of the picopulse of output and femtosecond pulse reaches maximum synchronously, is respectively 38nm and 46nm.
Comparison diagram 4, Fig. 5, Fig. 8 and Fig. 9, Fig. 6, Fig. 7, Figure 10 and Figure 11 can find to intersect that marked change has taken place pulse characteristic under the locked mode mode of operation.Variation has taken place in the frequency spectrum and the time width of pulse in femtosecond and the psec chamber.The time width of femtosecond pulse becomes greatly slightly in the femtosecond chamber, and spectral width diminishes slightly, and the time width of picopulse obviously reduces in the psec chamber, and spectral width significantly increases.The variation of femtosecond and picopulse characteristic results from the group velocity disperse, from phase modulated, and the comprehensive function of cross-phase modulation and gain competition.When the locked mode that intersects took place, the phase modulated of laser cavity total was by forming from phase modulated and cross-phase modulation two parts.Cross-phase modulation in the femtosecond chamber is far smaller than from phase modulated, so the intersection locked mode that the cross-phase modulation causes is less to the influence of pulse time domain and frequency domain characteristic in the femtosecond chamber.Yet the modulation of cross-phase in the psec chamber is far longer than from phase modulated, thus the intersection locked mode that causes of cross-phase modulation to the influence of pulse time domain and frequency domain characteristic in the psec chamber with regard to highly significant.
(3) time jitter
Time jitter is to weigh the important indicator of double-wavelength short pulse laser quality, and respectively as pumping with survey the light time, time jitter has determined the temporal resolution of pumping-detection device to a great extent when dipulse.We calculate time jitter between femtosecond and the picopulse by the crosscorrelation curve of measuring femtosecond and picopulse.Utilize that nonlinear optical crystal BBO measures two row pulses with the frequency signal, obtain the crosscorrelation curve, compare with two row pulses autocorrelator trace separately then, thereby the result of calculating.Figure 12 has provided the intensity crosscorrelation curve of two row intersection mode locking pulses, and Figure 13 is total spectrum of femtosecond and picopulse.
To being the laser pulse of gaussian intensity profile in the time domain, time jitter can be expressed as
Wherein τ is the full width at half maximum of crosscorrelation curve, τ
1Be the full width at half maximum of a pulse, τ
2It is the full width at half maximum of another pulse.Suppose that the pulse of measuring in the experiment is a Gaussian pulse, according to Fig. 8, Fig. 9, Figure 10 and Figure 11, the full width at half maximum τ=1.031ps of crosscorrelation curve, femtosecond pulse full width at half maximum τ
1=53 * 0.707=37.5fs, picopulse full width at half maximum τ
2=1.26 * 0.707=0.891ps.Calculating time jitter is τ
j=517fs.
Claims (4)
1. double-cavity resonating device, it is characterized in that, comprise the condenser lens (2) that places successively on the same precise guide rail, spheric reflection chamber mirror a (3), Ti doped saphire (4) and spheric reflection chamber mirror b (5), the incident light side of condenser lens (2) is provided with beam splitter (1), the reverberation side of spheric reflection chamber mirror b (5) is provided with output coupling mirror a (6) and output coupling mirror b (8), output coupling mirror b (8) is provided with piezoelectric transducer a (7), the reverberation side of spheric reflection chamber mirror a (3) is provided with two reflected light paths, one the tunnel is the plane reflection chamber mirror b (12) that sets gradually, acousto-optic modulator (11), slit a (10), plane reflection chamber mirror a (9), another road is the quartz prism a (13) that sets gradually, quartz prism b (14), slit b (15), plane reflection chamber mirror c (16), plane reflection chamber mirror c (16) is provided with piezoelectric transducer b (17), spheric reflection chamber mirror a (3), spheric reflection chamber mirror b (5), quartz prism a (13), quartz prism b (14), plane reflection chamber mirror c (16) and output coupling mirror b (8) constitute femtosecond laser chamber, spheric reflection chamber mirror a (3), spheric reflection chamber mirror b (5), plane reflection chamber mirror b (12), plane reflection chamber mirror a (9) and output coupling mirror a (6) constitute the picosecond laser chamber.
2. double-cavity resonating device according to claim 1 is characterized in that, half metal-plated membrane of upper surface of described beam splitter (1) is to the light half reflection of 450-540nm; Second half metal-plated membrane of upper surface is to the whole transmissions of the light of 450-540nm; The lower surface metal-plated membrane all reflects the light of 450-540nm.
3. method of utilizing the described double-cavity resonating device of claim 1 to produce self-synchronizing femtosecond pulse and picopulse, it is characterized in that, adopt a kind of double-cavity resonating device, comprise the condenser lens (2) that places successively on the same precise guide rail, spheric reflection chamber mirror a (3), Ti doped saphire (4) and spheric reflection chamber mirror b (5), the incident light side of condenser lens (2) is provided with beam splitter (1), the reverberation side of spheric reflection chamber mirror b (5) is provided with output coupling mirror a (6) and output coupling mirror b (8), output coupling mirror b (8) is provided with piezoelectric transducer a (7), the reverberation side of spheric reflection chamber mirror a (3) is provided with two reflected light paths, one the tunnel is the plane reflection chamber mirror b (12) that sets gradually, acousto-optic modulator (11), slit a (10), plane reflection chamber mirror a (9), another road is the quartz prism a (13) that sets gradually, quartz prism b (14), slit b (15), plane reflection chamber mirror c (16), plane reflection chamber mirror c (16) is provided with piezoelectric transducer b (17), spheric reflection chamber mirror a (3), spheric reflection chamber mirror b (5), quartz prism a (13), quartz prism b (14), plane reflection chamber mirror c (16) and output coupling mirror b (8) constitute the femtosecond laser chamber, spheric reflection chamber mirror a (3), spheric reflection chamber mirror b (5), plane reflection chamber mirror b (12), plane reflection chamber mirror a (9) and output coupling mirror a (6) constitute the picosecond laser chamber
Specifically implement according to following steps:
Step 1: open argon ion laser, laser power is transferred to 2-3W, the pump beam of incident is divided into parallel two-beam by beam splitter (1);
Step 2: the distance that is provided with between condenser lens (2) and Ti doped saphire (4) surface is 99-99.5mm, the spacing of spheric reflection chamber mirror a (3) and spheric reflection chamber mirror b (5) is 99.8-100.3mm, angle between the axis of the axis of spheric reflection chamber mirror a (3) and spheric reflection chamber mirror b (5) is 16 °-26 °, adjust Ti doped saphire (4) normal to a surface direction, make two bundle directional lights that step 1 obtains with brewster angle incidence;
Step 3: determine the pumping light of argon ion laser with two diaphragms, close argon ion laser, do the collimated light source, the pump beam that argon ion laser sends in its light that sends and the step 1 is overlapped with a He-Ne laser;
Step 4: take away the He-Ne laser, open argon ion laser, power transfers to 7-8W, obtains kermesinus fluorescence at plane reflection chamber mirror b (12), plane reflection chamber mirror c (16) and output coupling mirror a (6), output coupling mirror b (8) on the surface;
Step 5: position and the axis direction of regulating plane reflection chamber mirror b (12), the kermesinus fluorescence that step 4 is obtained is penetrated on the surface of plane reflection chamber mirror a (9), regulate position and the axis direction of plane reflection chamber mirror a (9) then, kermesinus fluorescence is returned along original optical path; Regulate position and the axis direction of output coupling mirror a (6), kermesinus fluorescence is returned along original optical path; Further alternately regulate the axis direction of plane reflection chamber mirror a (9) and output coupling mirror a (6), kermesinus fluorescence is all returned along original optical path on plane reflection chamber mirror a (9) and output coupling mirror a (6), in the picosecond laser chamber, produce the output of continuous laser; Continue to regulate the axis direction of plane reflection chamber mirror a (9) and output coupling mirror a (6), regulate position and the direction of condenser lens (2), Ti doped saphire (4), spheric reflection chamber mirror a (3), spheric reflection chamber mirror b (5) simultaneously, make picosecond laser chamber power output maximum; Regulate position and the drift angle direction of quartz prism a (13), quartz prism b (14), the kermesinus fluorescence that step 4 is obtained is penetrated on the surface of plane reflection chamber mirror c (16), regulate position and the axis direction of plane reflection chamber mirror c (16) then, kermesinus fluorescence is returned along original optical path; Regulate position and the axis direction of output coupling mirror b (8), bolarious fluorescence is returned along original optical path; Further alternately regulate the axis direction of plane reflection chamber mirror c (16) and output coupling mirror b (8), kermesinus fluorescence is all returned along original optical path on plane reflection chamber mirror c (16) and output coupling mirror b (8), in the femtosecond laser chamber, produce the output of continuous laser, continue to regulate the axis direction of plane reflection chamber mirror c (16) and output coupling mirror b (8), make femtosecond laser chamber power output maximum;
Step 6: close argon ion laser, laser power is adjusted to 9-10W, open acousto-optic modulator (11), the modulating frequency of acousto-optic modulator (11) is transferred to 78-80MHz, it is long to regulate chamber, picosecond laser chamber, reach locked mode, close acousto-optic modulator (11), the picosecond laser chamber maintains the self mode locking state; Vibration quartz prism b (14) makes the femtosecond laser chamber reach self mode locking;
Step 7: measure the repetition rate of picosecond laser chamber output pulse and the repetition rate of femtosecond laser chamber output pulse with frequency counter, it is long to regulate chamber, femtosecond laser chamber, makes the femtosecond laser chamber consistent with the repetition rate of picosecond laser chamber output pulse;
Step 8: mobile focusing lens (2), plane reflection chamber mirror c (16) and output coupling mirror b (8) vertically, simultaneously, keep the repetition rate of femtosecond laser chamber output pulse constant, the spectrum of exporting pulse until femtosecond laser chamber and picosecond laser chamber changes;
Step 9: open piezoelectric transducer a (7) and piezoelectric transducer b (17), regulation voltage, the front and back position of fine setting plane reflection chamber mirror c (16) and output coupling mirror b (8) makes the picosecond laser chamber export the spectrum widening maximum of pulse;
Step 10: along the direction travelling slit a (10) and the slit b (15) that propagate perpendicular to light, the seam of adjusting slit a (10) and slit b (15) is wide, makes the wavelength tuning of picopulse and femtosecond pulse;
Step 11: mobile focusing lens (2), reflecting cavity mirror c (16) and output coupling mirror b (8) vertically, make the long accurately coupling in chamber in picosecond laser chamber and femtosecond laser chamber, it is consistent and export synchronously to reach the wavelength tuning range of picopulse and femtosecond pulse.
4. the method for utilizing double-cavity resonating device to produce self-synchronizing femtosecond pulse and picopulse according to claim 3 is characterized in that half metal-plated membrane of upper surface of described beam splitter (1) is to the light half reflection of 450-540nm; Second half metal-plated membrane of upper surface is to the whole transmissions of the light of 450-540nm; The lower surface metal-plated membrane all reflects the light of 450-540nm.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102570258A (en) * | 2011-02-25 | 2012-07-11 | 北京国科世纪激光技术有限公司 | Laser resonator cavity |
| CN104677510A (en) * | 2015-01-28 | 2015-06-03 | 西安工程大学 | Multi-high-frequency quantum beat dynamics detecting device and detecting method thereof |
| CN106129800A (en) * | 2016-08-23 | 2016-11-16 | 天水师范学院 | A kind of based on single pumping or the dual wavelength tunable laser of double pumping action |
| CN109489838A (en) * | 2018-10-25 | 2019-03-19 | 北京无线电计量测试研究所 | A kind of high-precision pulse Jitter characteristic measurement method |
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2009
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102570258A (en) * | 2011-02-25 | 2012-07-11 | 北京国科世纪激光技术有限公司 | Laser resonator cavity |
| CN104677510A (en) * | 2015-01-28 | 2015-06-03 | 西安工程大学 | Multi-high-frequency quantum beat dynamics detecting device and detecting method thereof |
| CN106129800A (en) * | 2016-08-23 | 2016-11-16 | 天水师范学院 | A kind of based on single pumping or the dual wavelength tunable laser of double pumping action |
| CN106129800B (en) * | 2016-08-23 | 2022-11-15 | 天水师范学院 | Dual-wavelength tunable laser based on single pump or double pumps |
| CN109489838A (en) * | 2018-10-25 | 2019-03-19 | 北京无线电计量测试研究所 | A kind of high-precision pulse Jitter characteristic measurement method |
| CN109489838B (en) * | 2018-10-25 | 2020-01-31 | 北京无线电计量测试研究所 | high-precision pulse time domain jitter characteristic measuring method |
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