CN1091317C - Polarizing double reflecting film two-frequency laser - Google Patents
Polarizing double reflecting film two-frequency laser Download PDFInfo
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- CN1091317C CN1091317C CN99123748A CN99123748A CN1091317C CN 1091317 C CN1091317 C CN 1091317C CN 99123748 A CN99123748 A CN 99123748A CN 99123748 A CN99123748 A CN 99123748A CN 1091317 C CN1091317 C CN 1091317C
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- laser
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- reflecting film
- magnetic field
- double reflecting
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Abstract
The present invention belongs to the technical field of a laser technology. The present invention comprises a full inner cavity He-Ne laser device and a transverse magnetic field, wherein the full inner cavity He-Ne laser is composed of a laser cavity body and two reflectors which are hermetically connected with both ends of the laser cavity body; the transverse magnetic field is arranged outside the laser cavity body. At least one reflector is a polarized reflector with two reflection films; the direction of the magnetic field is approximately parallel to the direction of o or e output by the laser device. The present invention has the advantage of simple structure, good beam property, proper frequency difference, good frequency stability, good frequency difference stability, etc.; TEMOO films are adopted, lasers with two different frequencies are linearly polarized lasers which are mutually vertical. The present invention is suitable for manufacturing high-speed heterodyne interferometers.
Description
Technical field
The invention belongs to laser technology field, particularly the structural design of two-frequency laser.
Technical background
The double-frequency laser heterodyne measurement has tangible advantage: antijamming capability is strong, can carry out phase measurement and multi-channel measurement.Thereby interferometer not only can be realized multi-functional but also can improve resolution.This is that the single-frequency interferometer is incomparable.The measuring speed that heterodyne ineterferometer is surveyed long function is subjected to a restriction: Doppler frequency shift must not be higher than the heterodyne beat frequency difference, that is:
Δ f
d=υ/(λ/2)＜Δ ν such as Δ ν are 1MHz, and surveying long speed υ just can only be less than 300mm/s, otherwise interferometer can't be worked.Frequency difference as U.S. HP5527 is 2MHz, and the speed limit that allows to measure is 0.45m/s, and the frequency difference of HP5529 is 3MHz, and the speed limit that allows to measure is 0.7m/s.The speed of service of lathe and measuring machine has been brought up to 1m/s now, and this just requires the beat frequency frequency difference to be higher than 4.5MHz.
The method that improves heterodyne ineterferometer beat frequency frequency difference has two kinds: a kind of is to produce shift frequency with acoustooptic modulation, is representative with U.S. ZYGO company.This method can produce the frequency difference of 20MHz easily, and its shortcoming is that laser is a single frequency laser, and with the frequency stabilization of isocandela method, precision frequency stabilization can not be very high; In addition, the light of laser output must separate, with being combined into a light beams behind the acousto-optic shift frequency again.Do making the optical system complexity like this, cost strengthens.Another kind method is to utilize the birefringence effect of birefringece crystal to produce double frequency.The Zhang Shulian of relevant birefringence double-frequency laser Tsing-Hua University has done many work, and document is also reported a lot.But the problem that also has some application: in the laser cavity birefringence device must be arranged, this complicates laser structure, and the structure of nearest this laser is the outside that the high-reflecting film of laser is plated in laser mirror, produces birefringence with the method that adds stress.Adopt this structure, a series of problem such as stable of the life-span of laser, stress all requires study.
Summary of the invention
The objective of the invention is for overcoming the weak point of prior art, design a kind of polarizing double reflecting film two-frequency laser, utilize special laminated reflective film different to the reflection coefficient phase transition when the vertical incidence of different polarization light, thereby and utilize horizontal Zeeman effect enabled stage division to reduce Mode Coupling, thereby export the laser of two different frequencies.Have simple in structure, advantage such as beam characteristics is good, is the TEMOO mould, and the light of two different frequencies is orthogonal linearly polarized light, and its frequency difference is suitable, and frequency stability and frequency difference stability are all fine.Be applicable to and make the high speed heterodyne ineterferometer.
The present invention proposes a kind of method of making polarizing double reflecting film, it is characterized in that may further comprise the steps: stress application on the circular glass sheet of preparing the plating highly reflecting films at first, plate highly reflecting films then, remove sheet glass stress, thereby on reflective coating, form overstrain; Simultaneously, form new strain in the process of speculum sealing-in, the synergy result of the two constitutes the reflected phase will transition on the laser mirror, adopts ellipsometer or half-intracavity laser and detector, and frequency meter is measured, and obtains reflected phase will transition value.
The present invention also proposes to state above a kind of the employing two-frequency laser of the polarizing double reflecting film that method makes, comprise the full inner chamber He-Ne laser of forming by two speculums of laser cavity and two ends sealing-in thereof, be arranged on the transverse magnetic field in the laser cavity outside, it is characterized in that, have at least one to be the polarizing double reflecting film speculum in the said speculum, approximate o direction or the e direction that is parallel to this laser output of said magnetic direction.
The intensity of said transverse magnetic field can be 0.01 ~ 0.02T.
Polarizing double reflecting film two-frequency laser principle of the present invention is described as follows:
The said double reflecting film of the present invention is meant the laminated reflective film of making of the specific technology of the present invention, and polarizing double reflecting film is to form by means of the overstrain on the rete.When vertical incidence, it has two reflection coefficients:
R wherein
oAnd r
eIt is complex reflection coefficient to o light and e light.r
o' and r
e' be the mould of reflection coefficient, φ
oAnd φ
eIt is the phase jump of reflex time.In polarizing double reflecting film two-frequency laser, r
o≈ r
e≈ 1, and the main distinction is φ
o≠ φ
e
Definition Δ φ=φ
o-φ
e, be called the transition of double reflecting film reflected phase will and differ.
Polarizing double reflecting film two-frequency laser
The output frequency of laser satisfies condition:
Wherein L is that the chamber is long, and n is the active medium refractive index, and ν is the frequency of laser, and c is the light velocity in the vacuum, φ
1And φ
2Be the phase jump of light at two chamber mirrors, m is an integer.The frequency interval of two adjacent laser longitudinal modules:
If laser tube (is φ by a common speculum
o=φ
e) and a double reflecting film speculum composition, because reflex time phase jump difference will satisfy equation (3), ν
oAnd ν
eFrequency just must be different.So just can constitute a two-frequency laser, its frequency difference with a normal mirror and a double reflecting film speculum:
Because Δ ν
cCan be up to 1000MHz, so as long as very little Δ φ just can obtain very high frequency difference.
When frequency difference was higher than 40MHz, the result that (5) formula provides was correct.But the frequency difference that is higher than 40MHz is had higher requirement to electronic system, and general TTL element operating frequency is about 30MHz, and in a foreseeable future mechanical measurement does not need high like this frequency difference yet.
When the frequency difference that is provided by (5) formula was lower than 40MHz, because frequency locking takes place the coupling of the optical mode of two frequencies, the result had only the light output of a frequency probably.And theoretical frequency difference reduction, Mode Coupling strengthens, and does not almost have possibility to obtain being lower than the following frequency difference of 20MHz.So when Δ φ was very little, the light of the light of this laser output and the output of common intracavity laser was almost as broad as long.
The light of two frequencies can be exported when making Δ φ very little, Mode Coupling must be reduced.Specific practice is to add the energy level splitting that a transverse magnetic field makes active medium.It should be noted that:, can not reduce Mode Coupling, so this laser can not be used longitudinal magnetic field though longitudinal magnetic field also can enabled stage divide.Moreover, transverse magnetic field neither be in any direction can.
The present invention is the laterally difference of Zeeman laser together:
Though from the structure appearance, the present invention is with laterally the Zeeman laser is almost completely the same, they belong to the laser of two kinds of different principle, and its difference is as follows:
(1) operation principle and frequency difference vary in size.Energy level splitting and mode pulling effect decision that the frequency difference of Zeeman laser is caused by transverse magnetic field, frequency difference is difficult to be higher than 1MHz usually.The frequency difference of polarizing double reflecting film two-frequency laser is mainly determined by formula (5).Promptly mainly by double reflecting film reflex time o light and the decision of e light phase transition difference.The effect of energy level splitting mainly is to reduce Mode Coupling.Mode pulling effect is very little to the contribution of frequency difference.Thereby the output optical frequency difference of this laser in theory can be up to hundreds of MHz, and our experiment has obtained the frequency difference (we are only interested in little Δ φ) of 5 ~ 6MHz, and, magnetic field intensity is reduced to original half, frequency difference changes considerably less.
(2) structural relation has particular requirement.Laterally the magnetic direction of Zeeman laser is only required perpendicular to discharge tube and is got final product, and laser tube can rotate to the optional position in magnetic field.The laser tube of polarizing double reflecting film two-frequency laser and magnetic direction have a specific relation: because reflection coefficient r
oAnd r
eDifferent, this is equivalent to define an xy direction, and transverse magnetic field has defined a direction simultaneously, and this both direction should overlap or differ 90 ° in theory, and 180 °, 270 °.There is a matching relationship in the placement of laser and magnetic field in other words.
When Δ φ hour, if matching relationship is fine, also can go out double frequency even Δ φ is very little, if matching relationship bad (is 45 ° as xy direction and magnetic direction angle), do not go out double frequency in Δ φ hour.But it is very not strict that this matching relationship requires, and franchise is in the scope of tens degree.Because the existence of this relation, polarisation of light is more near ideal situation.
When Δ φ is big, because mode pulling effect is little, does not add magnetic field and high frequency difference frequency can occur yet, there are not above-mentioned relation in laser tube and magnetic field.
The present invention has obvious difference with birefringence double-frequency laser: the crystal that the crystal that polarizing double reflecting film two-frequency laser of the present invention does not have crystal or other effects to cause between two speculums, birefringence double-frequency laser have a crystal or other effects to produce between two speculums.
Characteristics of the present invention:
(1) the invention provides a kind of novel He-Ne laser-polarizing double reflecting film two-frequency laser.Its beat frequency frequency difference is higher than the Zeeman laser, and output mode is the TEMOO mould.The only linear polarization of two frequencies, and orthogonal, this laser is applicable to the making high-speed interferometer.
(2) polarizing double reflecting film two-frequency laser is formed intracavity laser by a slice polarizing double reflecting film speculum at least.
(3) the polarizing double reflecting film speculum is meant: when vertical incidence, laminated reflective film has two different complex reflection coefficients, and it is relevant with the polarization of incident light direction.Especially the phase jump of digital reflex light is inconsistent, and its phase jump difference is represented with Δ φ.
(4) the invention provides a kind of working as Δ φ hour, reduce Mode Coupling, solve the frequency locking problem, make laser still can export the method for two frequencies of light: to add transverse magnetic field.And point out that transverse magnetic field and laser tube relative position have particular kind of relationship, have provided method of adjustment.
Description of drawings
Fig. 1 is a polarizing double reflecting film two-frequency laser example structure schematic diagram of the present invention
Embodiment
A kind of polarizing double reflecting film two-frequency laser example structure of the present invention as shown in Figure 1, wherein,
(1) mirror M 1 and M2 have at least one to be the polarizing double reflecting film speculum
(2) constitute inner chamber He-Ne laser 1 by M1 and M2
(3) add transverse magnetic field 2, magnetic field intensity is about 0.01 ~ 0.02T
(4) rotary laser makes the o direction of its decision or e direction approximate parallel with magnetic direction.The parameter that adopts is:
The long L=150mm of laser tube chamber, double reflecting film phase jump Δ φ=0.675 ° is when magnetic field intensity is about 0.01 ~ 0.02T, the about 5M of frequency difference Δ ν, light velocity c=299792458m/s in the vacuum makes frequency difference remain on 5.375 ± 1KHz with frequency locking method, and the actual measurement precision frequency stabilization is better than 10
-9
Claims (3)
1, a kind of method of making polarizing double reflecting film is characterized in that may further comprise the steps: stress application on the circular glass sheet of preparing the plating highly reflecting films at first, plate highly reflecting films then, and remove sheet glass stress, thereby on reflective coating, form overstrain; Simultaneously, form new strain in the process of speculum sealing-in, the synergy result of the two constitutes the reflected phase will transition on the laser mirror, adopts ellipsometer or half-intracavity laser and detector, and frequency meter is measured, and obtains reflected phase will transition value.
2, a kind of employing two-frequency laser of the polarizing double reflecting film made of method according to claim 1, comprise the full inner chamber He-Ne laser of forming by two speculums of laser cavity and two ends sealing-in thereof, be arranged on the transverse magnetic field in the laser cavity outside, it is characterized in that, have at least one to be the polarizing double reflecting film speculum in the said speculum, approximate o direction or the e direction that is parallel to this laser output of said magnetic direction.
3, polarizing double reflecting film two-frequency laser as claimed in claim 2 is characterized in that, the intensity of said transverse magnetic field is 0.01 ~ 0.02T.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN99123748A CN1091317C (en) | 1999-11-19 | 1999-11-19 | Polarizing double reflecting film two-frequency laser |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN99123748A CN1091317C (en) | 1999-11-19 | 1999-11-19 | Polarizing double reflecting film two-frequency laser |
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| Publication Number | Publication Date |
|---|---|
| CN1254212A CN1254212A (en) | 2000-05-24 |
| CN1091317C true CN1091317C (en) | 2002-09-18 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN99123748A Expired - Fee Related CN1091317C (en) | 1999-11-19 | 1999-11-19 | Polarizing double reflecting film two-frequency laser |
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|---|---|
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4858240A (en) * | 1986-01-09 | 1989-08-15 | Veb Kombinat Feinmechanische Werke Halle | Arrangement for the generation of CO2 laser pulses of high power |
| CN2053386U (en) * | 1988-12-31 | 1990-02-21 | 清华大学 | He-ne dual-frequency laser with quartz crystal tuning |
| US5150370A (en) * | 1989-06-14 | 1992-09-22 | Matsushita Electric Industrial Co., Ltd. | Narrow-band laser apparatus |
-
1999
- 1999-11-19 CN CN99123748A patent/CN1091317C/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4858240A (en) * | 1986-01-09 | 1989-08-15 | Veb Kombinat Feinmechanische Werke Halle | Arrangement for the generation of CO2 laser pulses of high power |
| CN2053386U (en) * | 1988-12-31 | 1990-02-21 | 清华大学 | He-ne dual-frequency laser with quartz crystal tuning |
| US5150370A (en) * | 1989-06-14 | 1992-09-22 | Matsushita Electric Industrial Co., Ltd. | Narrow-band laser apparatus |
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| Publication number | Publication date |
|---|---|
| CN1254212A (en) | 2000-05-24 |
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