CN101593933A - Saturation absorption frequency discrimination device - Google Patents
Saturation absorption frequency discrimination device Download PDFInfo
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- CN101593933A CN101593933A CNA2009100534239A CN200910053423A CN101593933A CN 101593933 A CN101593933 A CN 101593933A CN A2009100534239 A CNA2009100534239 A CN A2009100534239A CN 200910053423 A CN200910053423 A CN 200910053423A CN 101593933 A CN101593933 A CN 101593933A
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Abstract
A kind of saturation absorption frequency discrimination device, formation is: is λ/2 wave plates along the laser beam input direction successively with optical axis ground, polarization beam splitter prism, λ/4 wave plates, the saturated absorption pond, the wedge shape quartz glass plate, the front surface of described wedge shape quartz glass plate is perpendicular to described laser beam, described incident beam is through front surface and rear surface reflection formation respectively detecting light beam and the reference beam of described wedge shape quartz glass plate, reflection direction at the detecting light beam of described polarization beam splitter prism is provided with photodetector, and described detecting light beam and reference beam are received by described photodetector.Light path of the present invention is simplified, and it is little to take up room, easy to use, also realizes Zeemen effect frequency discrimination or shift frequency easily, can not occur being in the light.
Description
Technical field
The present invention relates to a kind of saturation absorption frequency discrimination device, be used for frequency stabilization of semiconductor laser, belong to non-linear laser spectral technique, precise laser spectral technique field.
Background technology
At present, utilize saturated absorption effect stable laser frequency very general in the cold atom physics laboratory.Utilize the saturated absorption effect can obtain atom or the molecular absorption line that not widened by Doppler effect, for example some hyperfine structure spectral lines.The spectral line live width is very narrow, can reach the magnitude of natural linewidth (MHz).These spectral lines can provide a kind of stable extraneous reference frequency, make laser frequency be stabilized to 1MHz or following.
Saturated absorption is a kind of nonlinear optical effect.Light laser (for the saturated light intensity of absorbing medium) is when inciding on the absorbing medium, and the absorption coefficient of medium can reduce greatly with the change of light intensity, occurs saturated.When laser frequency swept, owing to there is Doppler effect, laser only was satisfied ω
c-kv
z=ω
0Atom or molecule absorb.ω in the formula
cBe laser frequency, v
zBe atom or the molecular thermalmotion speed component (supposition laser is along the incident of z axle) on the laser incident direction, ω
0Be atom or molecular entergy level transition centre frequency.V in the absorbing medium
z=0 atom or molecule Probability Distribution maximum, so ω
c=ω
0Locate greatlyyer than other frequency place degrees of absorption, i.e. population inversion degree is bigger, and a depression can appear in absorption line herein.With a branch of weak light detection (generally being correlation), transmitted light can be at ω at this moment
c=ω
0A spike appears in the position.
Common absorbing medium is one and is filled with hypobaric atom (or molecule) absorption cell (cell), the collision of absorption line is widened with the pressure displacement and can be ignored, there is not discharge process in the absorption cell yet, the position of saturated absorption spectral line is highly stable like this, narrower in width, most suitable as the extraneous reference frequency of frequency stabilization of semiconductor laser.
Generally can add three-beam on the saturated absorption basis, be called reference light, incide in the absorption cell with surveying parallel light, light intensity is identical, but does not intersect in absorption cell with pump light.The purpose that adds reference light is to remove Doppler's background of surveying on the light signal, makes that the saturated absorption signal is more obvious, is convenient to follow-up signal processing.
The saturated absorption effect also can combine with Zeemen effect.Zeemen effect is the phenomenon that occurs division in the spectrum line outside magnetic field of atom.External magnetic field makes atomic energy level division occur, and energy level splitting shows as the splitting of spectral lines of atom, and split separation is directly proportional with magnetic field intensity.In the saturated absorption structure on the absorption cell around one group of coil, feed electric current, the different operating mode according to electric current can realize Zeeman frequency discrimination or shift frequency.If electric current is modulated (normally triangular wave), atomic energy level transition centre frequency can change (being equivalent in the saturated absorption laser diode current to be modulated the laser frequency that causes changes) thereupon, detector can obtain a peak signal at the current zero place, atomic energy level transition centre frequency position when representative does not have external magnetic field.If electric current remains unchanged, a fixing frequency displacement takes place in atomic energy level transition centre frequency so, and the frequency displacement size is relevant with the magnetic field that electric current produces.
λ of common saturated absorption optical routing/2 wave plates, a polarization beam splitter prism (being called for short PBS), a saturated absorption pond (cell), a quartz glass plate, two speculums, a photodetector (to tubular construction) constitutes.As shown in Figure 1.The light that laser 1 comes out is divided into two bundles through λ/2 wave plates 2 on polarization beam splitter prism 3, reverberation forms two bundle reverberation through quartz glass plate 4 in front and rear surfaces, and its light intensity is roughly the same, and wherein a branch of as surveying light, another Shu Ze is a reference light.The transmitted light of quartz glass plate 4 incides in the absorption cell after through two secondary reflections (speculum 5 and 7), and surveys light and intersects in the pond.Surveying light and reference light is received by photodetector 7 at last.Photodetector 7 is to tubular construction, and two photodiodes are arranged, and its both positive and negative polarity reversal connection will be surveyed light signal and reference optical signal and subtract each other the back amplification.
Because each optical element of this kind saturated absorption light path is on same optical axis, and need to regulate make pump light with survey the angle of light degree near 180 degree, the intersection region in absorption cell is big, otherwise the saturated absorption signal can be relatively poor.When laser power a little less than, perhaps spectrum also need be by other auxiliary observe or sniffer be regulated light path when human eye visible range edge.Concerning the beginner, regulate to get up to acquire a certain degree of difficulty.From stability of layout, need two speculums on the pump light light path, be unfavorable for that light path is stable.If want to utilize Zeemen effect shift frequency or frequency discrimination, need on absorption cell, add one group of coil, absorption cell is taken up room become big, might block pump light or need readjust light path, saturated absorption signal possible deviation.The shared volume of this kind light path is also bigger in addition, is unfavorable for compressing light path.
Summary of the invention
The objective of the invention is to overcome above-mentioned the deficiencies in the prior art, propose a kind of saturation absorption frequency discrimination device, the light path of this device is simplified, and it is little to take up room, easy to use, also realizes Zeemen effect frequency discrimination or shift frequency easily, can not occur being in the light.
Technical solution of the present invention is as follows:
A kind of saturation absorption frequency discrimination device, be characterised in that its formation is, is λ/2 wave plates along the laser beam input direction successively with optical axis ground, polarization beam splitter prism, λ/4 wave plates, the saturated absorption pond, the wedge shape quartz glass plate, the front surface of described wedge shape quartz glass plate is perpendicular to described laser beam, described incident beam is through front surface and rear surface reflection formation respectively detecting light beam and the reference beam of described wedge shape quartz glass plate, reflection direction at the detecting light beam of described polarization beam splitter prism is provided with photodetector, and described detecting light beam and reference beam are received by described photodetector.
Around one group of coil, keep this coil current constant during work on the described saturated absorption pond.
The angle of wedge of described wedge shape quartz glass plate is 3～5 degree.
Before described λ/2 wave plates with optical axis first aperture is set, after described wedge shape quartz glass plate with optical axis second aperture and laser diode be set.
Technique effect of the present invention:
The present invention has inserted a λ/4 wave plates between PBS and absorption cell, allow reference light and detection light reflex on the photodetector through PBS on the one hand, and rotation λ/4 wave plates can change its reflective light intensity; Can form σ on the other hand
+, σ
-Circularly polarized light so just can be realized the Zeemen effect frequency discrimination, only need the electric current of coil be modulated around one group of coil on absorption cell.If the hold-in winding current constant just can shift frequency.
The present invention has added two apertures before and after the main body light path, and utilizes a laser diode, allows the user at an easy rate whole device be joined existing light path.
Optical element is few among the present invention, and main optical element is coaxial, and device takes up room little, builds and regulate all to be easy to, and also realizes Zeemen effect frequency discrimination or shift frequency easily.These advantages make the easy miniaturization of this kind saturated absorption device, modularization, practicability.
Description of drawings
The present invention is further described below in conjunction with drawings and Examples.
Fig. 1 is the basic light path of existing saturated absorption principle.
Fig. 2 is the light path principle figure that the embodiment of the invention 1 is used for saturation absorption frequency discrimination, and the part in the dotted line is a contrive equipment.
Fig. 3 is the light path principle figure (absorption cell belt coil) that the embodiment of the invention 2 is used for Zeemen effect frequency discrimination or shift frequency, and the part in the dotted line is a contrive equipment.
Fig. 4 is a photodetector typical case amplifying circuit schematic diagram.
Among the figure: 1-semiconductor laser, 2-λ/2 wave plates, 3-polarization beam splitter prism, the 4-quartz glass plate, 5-45 ° of speculum, 6-absorption cell, 7-45 ° of speculum, 8-be to the tubular construction photodetector, 9-λ/4 wave plates, 10-wedge shape quartz glass plate, 11-first aperture, 12-second aperture, 13-laser diode, the coil of 14-absorption cell, the 15-current source, 16-photodiode (S2386-18L), 17-photodiode (S2386-18L), 18-resistance (500K), 19-resistance (1M), 20-resistance (2M), 21-electric capacity (5nF), the 22-switch, 23-integrated transporting discharging (LF356).
Embodiment
The invention will be further described below in conjunction with embodiment and accompanying drawing, but should not limit excursion of the present invention with this.
For example rubidium (Rb) nonmagnetic atom ligh trap again pumping light (repump light) frequency should be stabilized to
87Rb hyperfine structure F1 → F2 jump frequency place.Usually need take a saturated absorption light path and obtain a frequency discrimination signal.
See also Fig. 2, Fig. 2 is the light path principle figure that the embodiment of the invention 1 is used for saturation absorption frequency discrimination, and the part in the dotted line is a contrive equipment.As seen from the figure, the formation of saturation absorption frequency discrimination device of the present invention is, along the laser beam input direction is λ/2 wave plates 2 successively, polarization beam splitter prism 3, λ/4 wave plates 9, saturated absorption pond 6, wedge shape quartz glass plate 10, the front surface of described wedge shape quartz glass plate 10 is perpendicular to described laser beam, described incident beam is through front surface and rear surface reflection formation respectively detecting light beam and the reference beam of described wedge shape quartz glass plate 10, reflection direction at the detecting light beam of described polarization beam splitter prism 3 is provided with photodetector 8, described detecting light beam and reference beam are received by described photodetector 8, before described λ/2 wave plates 2 with optical axis first aperture 11 is set, after described wedge shape quartz glass plate 10 with optical axis second aperture 12 and laser diode 13 be set.
The laser that semiconductor laser 1 emits among Fig. 2 at first through a λ/2 wave plates 2, then incides on the polarization beam splitter prism 3.Through behind the polarization beam splitter prism 3, laser can be divided into transmitted light and reverberation (not drawing among the reverberation figure), by rotation λ/2 wave plates 2, can change the power of the transmitted light of polarization beam splitter prism 3.Transmitted light through polarization beam splitter prism 3 is linear polarization (a P ripple), is placed on λ/4 wave plates 9 between polarization beam splitter prism 3 and the absorption cell 5, and the light that reflects through wedge shape quartz glass plate 11 is reflexed on the photodetector 8 by polarization beam splitter prism 3.Can be reflected into two-beam by the front and rear surfaces of wedge of glass plate 10 through the light that incides wedge shape quartz glass plate 10 behind the absorption cell 6, intensity is basic identical.Described photodetector 8 typical amplifying circuits as shown in Figure 4, first photodiode 16 and second photodiode 17 are reversal connections, when detection light and reference light incide on two pipes respectively, photoelectric current is done subtraction earlier, then by switch 22 controls, flow through feedback resistance 18 or 19 or 20 on the integrated transporting discharging 23 obtains the voltage signal of an amplification at output.This voltage signal is exactly the frequency discrimination signal.Described feedback resistance resistance is represented enlargement ratio, can only single conducting.
Apparatus of the present invention are built and regulate very simple, and are convenient.
Each element of apparatus of the present invention is installed on the one flat plate.In adjustment, it should be noted that the incidence surface of absorption cell 6 and light path will have an angle, make reverberation can not interfere with and survey light and reference light.λ/4 wave plates 9 should rotate to and make the strong position of polarization beam splitter prism 3 reverberation, could guarantee to enter into the only circular polarization of absorption cell 6 like this, and are extremely important when this carries out the Zeeman frequency discrimination to utilizing this device.Vertical as for the plane of incidence of regulating wedge shape quartz glass plate 10 with light path, can place an Amici prism (BS) at λ/2 wave plates, 2 places, regulate wedge shape quartz glass plate 10, make the reverberation and the laser of front surface of wedge shape quartz glass plate 10 be overlapped at far place by the reverberation of BS.After main optical element adjustment finishes, place first aperture 11 and second aperture 12 at the two ends of apparatus of the present invention, make light beam can just pass through aperture.Regulate laser diode 13 (this kind laser diode does not all require power and pattern very common on the market), the outgoing luminous energy that makes laser diode 13 is by first aperture 11 and second aperture 12.First aperture 11, second aperture 12 and laser diode 13 can greatly make things convenient for the user that the whole device of the present invention is joined to rarely have in the light path.
Concerning the user, had after apparatus of the present invention, can apparatus of the present invention be added in the existing light path by following method.At first open laser diode 13, make its emergent light, from device, transmit by first aperture 11 and second aperture 12.Afterwards, between the two, place two speculums (not drawing among Fig. 2), make the wide access to plant light path that causes that user's laser branches away according to user's laser and the position of apparatus of the present invention.At last, by regulating the angle of pitch of two speculums, make laser diode 13 collimate through the spot center of light on two speculums that transmitted light and user's laser of device branches away.Through above-mentioned steps, the user need not the optical element of adjusting device inside, just can obtain good beam path alignment effect.Above-mentioned regulating step is that the supposition device is different with user's laser emitting light optical axis, and situation about using with reality is consistent.
Fig. 3 is the light path principle figure (absorption cell belt coil) that the embodiment of the invention 2 is used for Zeemen effect frequency discrimination or shift frequency, and the part in the dotted line is a contrive equipment.The difference of embodiment 2 and embodiment 1 is that described saturated absorption pond 6 has coil 14, can be used for Zeemen effect frequency discrimination or shift frequency, and the number of turn of coil and the size of electric current or modulating frequency are decided according to concrete purposes.As shown in Figure 3, device is not had too much influence, do not have the problem that may be in the light.
Apparatus of the present invention experiment shows that effect is fine.
Claims (4)
1, a kind of saturation absorption frequency discrimination device, be characterised in that its formation is, along the laser beam input direction is λ/2 wave plates (2) successively, polarization beam splitter prism (3), λ/4 wave plates (9), saturated absorption pond (6) and wedge shape quartz glass plate (10), the front surface of described wedge shape quartz glass plate (10) is perpendicular to described laser beam, described incident beam is through front surface and rear surface reflection formation respectively detecting light beam and the reference beam of described wedge shape quartz glass plate (10), reflection direction at the detecting light beam of described polarization beam splitter prism (3) is provided with photodetector (8), and described detecting light beam and reference beam are received by described photodetector (8).
2, saturated absorption frequency stabilization device according to claim 1 is characterized in that described saturated absorption pond (10) upward around one group of coil (14), keeps this coil current constant during work.
3, saturated absorption frequency stabilization device according to claim 1, the angle of wedge that it is characterized in that described wedge shape quartz glass plate (10) are 3～5 degree.
4, according to claim 1 or 2 or 3 described saturated absorption frequency stabilization devices, it is characterized in that described λ/2 wave plates (2) before with optical axis first aperture (11) is set, described wedge shape quartz glass plate (10) afterwards with optical axis second aperture (12) and laser diode (13) be set.
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| CN2009100534239A CN101593933B (en) | 2009-06-19 | 2009-06-19 | Saturation absorption frequency discrimination device |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101995384A (en) * | 2010-09-27 | 2011-03-30 | 浙江大学 | Saturated absorption spectrum method and device based on internal surface reflection of atomic gas sample cell |
| CN103986062A (en) * | 2014-05-04 | 2014-08-13 | 中国科学院上海光学精密机械研究所 | Single-beam saturated absorption frequency stabilization optical device |
| CN107192536A (en) * | 2017-04-19 | 2017-09-22 | 华中光电技术研究所（中国船舶重工集团公司第七七研究所） | One kind is without burnt conjugated optical channels MTF test devices and method of testing |
| CN108088766A (en) * | 2016-11-23 | 2018-05-29 | 北京自动化控制设备研究所 | A kind of alkali metal atom transfer method |
| CN109378697A (en) * | 2018-12-19 | 2019-02-22 | 北京航天控制仪器研究所 | A kind of integrating device for external modulation saturation-absorption spectrum |
| CN113410754A (en) * | 2021-05-28 | 2021-09-17 | 华东理工大学 | Micro-power-consumption miniaturized saturated absorption spectrum device for semiconductor laser |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1016916B (en) * | 1988-09-08 | 1992-06-03 | 清华大学 | Dual-isotope zeeman laser and its freq-stabilizing method |
| US7289544B2 (en) * | 2001-09-20 | 2007-10-30 | Sumitomo Electric Industries, Ltd. | Optical module |
| CN100585967C (en) * | 2008-09-10 | 2010-01-27 | 哈尔滨工业大学 | Based on accurate vertical zeeman laser frequency-stabilizing method and the device that separates of luminous power |
-
2009
- 2009-06-19 CN CN2009100534239A patent/CN101593933B/en not_active Expired - Fee Related
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101995384A (en) * | 2010-09-27 | 2011-03-30 | 浙江大学 | Saturated absorption spectrum method and device based on internal surface reflection of atomic gas sample cell |
| CN103986062A (en) * | 2014-05-04 | 2014-08-13 | 中国科学院上海光学精密机械研究所 | Single-beam saturated absorption frequency stabilization optical device |
| CN108088766A (en) * | 2016-11-23 | 2018-05-29 | 北京自动化控制设备研究所 | A kind of alkali metal atom transfer method |
| CN107192536A (en) * | 2017-04-19 | 2017-09-22 | 华中光电技术研究所（中国船舶重工集团公司第七七研究所） | One kind is without burnt conjugated optical channels MTF test devices and method of testing |
| CN107192536B (en) * | 2017-04-19 | 2019-06-07 | 华中光电技术研究所（中国船舶重工集团公司第七一七研究所） | It is a kind of without burnt conjugated optical channels MTF test device and test method |
| CN109378697A (en) * | 2018-12-19 | 2019-02-22 | 北京航天控制仪器研究所 | A kind of integrating device for external modulation saturation-absorption spectrum |
| CN113410754A (en) * | 2021-05-28 | 2021-09-17 | 华东理工大学 | Micro-power-consumption miniaturized saturated absorption spectrum device for semiconductor laser |
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