CN102928094A - Absolute wave calibration instrument - Google Patents

Abstract

Absolute wave calibration instrument includes a calibrating light source, a to-be-measured light source, a first optical fiber, a second optical fiber, an optical fiber coupler, a third optical fiber, a small hole, a paraboloid high reflective mirror, a grating, an imaging lens, a linear photoelectric detector and a computer. According to the invention, the calibrating light source and the to-be-measured light source are input to a measurement system through the optical fiber coupler, the problems of spatial alignment and coaxial optical paths are effectively solved, and the spatial size of the wave length calibration instrument is reduced; the absolute wave length of the to-be-measured light source can be obtained as per the imaging distance of the to-be-measured light source and the calibrating light source on the linear photoelectric detector, the focal length of the imaging lens and the grating constant; and the absolute wave calibration instrument can be used for accurately and conveniently calibrating the wave length of the wavemeter or a spectrograph.

Description

The absolute wavelength calibration instrument

Technical field

The present invention relates to a kind of absolute wavelength calibration instrument, mainly be applicable to wavemeter and spectrometer.

Background technology

Absolute wavelength is a basic optical parameter of laser.Have important effect in laser is used, for example imaging aberration, the raising design accuracy in order to revise projection objective in the litho machine need to be known absolute optical maser wavelength.In laser spectrum tech, in order to improve the stability of Laser output, need to measure in real time laser output wavelength, and come the elements tune optical maser wavelengths such as tuning grating according to the drift value of output wavelength and target wavelength, thereby realize the stable control of optical maser wavelength.Therefore, to the demarcation of laser absolute wavelength with measure significant.

First in technology, adopt a plurality of etalons and come the calibration laser wavelength with iterative algorithm, referring to document P.S.Bhatia, C.W.McCluskey, and J.W.Keto, " Calibration of aComputer-Controlled Precision Wavemeter for Use with Pulsed Lasers, " Appl.Opt.38,2486 (1999).Adopt iterative algorithm in this technology, and iterative algorithm is a kind of approximate data in essence, not only its precision is difficult to guarantee but also calculating process is time-consuming.In addition, the mode that this technology adopts Space Coupling only has a port when being coupled to regulation light source and light source to be measured in the measuring system, and two kinds of light sources need to be connected to the purpose that just can realize in the system calibrating dividually.

Summary of the invention

The object of the present invention is to provide a kind of absolute wavelength calibration instrument, this absolute wavelength calibration instrument can be accurately, at a high speed, calibration laser absolute wavelength easily.

Technical solution of the present invention is as follows:

A kind of absolute wavelength calibration instrument, it is characterized in that this absolute wavelength calibration instrument is comprised of regulation light source, light source to be measured, the first optical fiber, the second optical fiber, fiber coupler, the 3rd optical fiber, aperture, parabolic high reflective mirror, grating, imaging len, linear photoconductor detector and computer, the position relationship of each part mentioned above is as follows:

Regulation light source warp and light source to be measured respectively through the first optical fiber and the second coupling fiber to fiber coupler, light beam arrives the aperture place through the 3rd Optical Fiber Transmission, the light beam of dispersing incides and incides grating after parabolic high reflective mirror expands and collimates, diffraction light focuses on the linear photoconductor detector through imaging len, computer reads respectively and record the location of pixels of hot spot imaging on linear photodetector of regulation light source and light source to be measured, and to data analysis and processing.

Described regulation light source is the known narrow linewidth light source of wavelength, and has preferably wavelength stability.

Described the first optical fiber, the second optical fiber and the 3rd optical fiber are radiation-resistant fiber, and have preferably transmissivity in wider spectral range.

The curved surface of described parabolic high reflective mirror plating broadband highly reflecting films, guaranteeing all has higher reflectivity to the spectrum that regulation light source and light source to be measured comprise.

Grating is reflective blazed grating, and it is inferior high that this grating has the order of diffraction, and dispersive power is large, the characteristics that spectrophotometric result is good.

The material of imaging len is ultraviolet fused quartz or calcium fluoride crystal, to guarantee all have preferably transmissivity in wider spectral range.

Described linear photoconductor detector is linear diode array or linear CCD.

Described computer comprises data collecting card and DAP, can the picture of linear photoconductor detector be read, record and data process.Described data are processed namely and are carried out the data processing by following formula, and the absolute wavelength that obtains light source to be measured is λ _x:

${\mathrm{\λ}}_x={\mathrm{\λ}}_r+\mathrm{\Δ\λ}={\mathrm{\λ}}_r+\frac{2\mathrm{dh}\cos \mathrm{\α}}{\mathrm{kf}}(P_x-P_r).$

Wherein: λ _rBe regulation light source absolute wavelength, P _rAnd P _xBe respectively the location of pixels of regulation light source and light source to be measured imaging on linear photodetector, h is the unit picture element width, and d, α and k are respectively grating constant, blaze of grating angle and the order of diffraction time of grating, and f is the focal length of imaging len.

Technique effect of the present invention is as follows:

The same fiber-optic output of fiber coupler is coupled to regulation light source and light source to be measured by the mode of fiber coupler in the present invention, need to two repeated multiple times measuring systems that are connected to respectively of light source, repeatability and difficulty that light path is aimed at have effectively been reduced when having solved the prior art spatial coupling.On the other hand, the present invention adopts and measures because the method for the relative distance on the line detector that the deviation of the angle of diffraction of different wave length causes is directly calibrated wavelength, avoided iterative algorithm, have the high and advantage efficiently of calibration accuracy, can be used for simultaneously the measurement of the centre wavelength of pulse laser and continuous laser.

Description of drawings

Fig. 1 is the structured flowchart of absolute wavelength calibration instrument of the present invention.

Embodiment

See also Fig. 1, Fig. 1 is the structured flowchart of absolute wavelength calibration instrument of the present invention.As seen from the figure, absolute wavelength calibration instrument of the present invention is comprised of regulation light source 1, light source to be measured 2, the first optical fiber 3, the second optical fiber 4, fiber coupler 5, the 3rd optical fiber 6, aperture 7, parabolic high reflective mirror 8, grating 9, imaging len 10, linear photoconductor detector 11 and computer 12, and the position relationship of each part mentioned above is as follows:

Regulation light source 1 links to each other with the input end of described fiber coupler 5 with the second optical fiber 4 through the first optical fiber 3 respectively with light source 2 to be measured, the light beam of the output terminal output of this fiber coupler 5 is transferred to aperture 7 places through the 3rd optical fiber 6, the light beam of dispersing incides parabolic high reflective mirror 8 and incide described grating 9 behind collimation, diffraction light focuses on the linear photoconductor detector 11 through imaging len 10, the location of pixels of hot spot imaging on linear photodetector 11 of 12 pairs of regulation light sources 1 of computer and light source to be measured 2 reads respectively and record, and to data analysis and processing.

The known narrow linewidth light source of described regulation light source 1 wavelength, and have preferably wavelength stability.

Described the first optical fiber 3, the second optical fiber 4 and the 3rd optical fiber 6 are radiation-resistant fiber, have preferably transmissivity in wider spectral range.

The curved surface of described parabolic high reflective mirror 8 plating broadband highly reflecting films, guaranteeing all has higher reflectivity to the spectrum that regulation light source 1 and light source to be measured 2 comprise.

Described grating 8 is reflective blazed grating, and it is inferior high that this grating has the order of diffraction, and dispersive power is large, the characteristics that spectrophotometric result is good.

The material of described imaging len (10) is ultraviolet fused quartz or calcium fluoride crystal, to guarantee all have preferably transmissivity in wider spectral range.

Described linear photoconductor detector 11 is linear diode array or linear CCD.

Described computer 12 comprises data collecting card and DAP, can read linear photoconductor detector 11, record and data analysis.

Regulation light source 1 and light source to be measured 2 are coupled to fiber coupler 5 through the first optical fiber 3 and the second optical fiber 4 respectively, be transferred to aperture 7 places through the 3rd optical fiber 6, the light beam of dispersing incides and incides grating 9 after parabolic high reflective mirror 8 expands and collimates, when incident beam and grating 9 were in Littrow (Littrow) structure, grating equation can be written as

2dsinα＝kλ， [1]

Wherein: d is grating constant, and α is blaze of grating angle, and k is the order of diffraction time, and is time identical in order to guarantee optical maser wavelength order of diffraction when grating (9) diffraction, requires the optical maser wavelength of regulation light source (1) and light source to be measured (2) close.

Grating equation [1] differential is had:

2dcosαΔα＝kΔλ， [2]

When being f such as the focal length of imaging len (10), the relative distance of different wave length spot on linear photodetector (11) is:

ΔL＝fΔα. [3]

Regulation light source (1) λ _rWith light source to be measured (2) λ _xLocation of pixels in the upper imaging of linear photodetector (11) is respectively P _rAnd P _x, be h such as the unit picture element width, then the distance of the hot spot of two wavelength on imaging surface is

ΔL＝h(P _x-P _r). [4]

Can obtain two diffraction angular differences that wavelength is corresponding according to formula [3] and formula [4] $\mathrm{\Δ\α}=\frac{h}{f}(P_x-P_r).$ [5]

Formula [5] substitution formula [2] can be obtained wavelength to be measured and the wavelength difference of calibration between the wavelength, $\mathrm{\Δ\λ}=\frac{2\mathrm{dh}\cos \mathrm{\α}}{\mathrm{kf}}(P_x-P_r).$ [6]

Then the absolute optical maser wavelength of light source to be measured (2) is ${\mathrm{\λ}}_x={\mathrm{\λ}}_r+\mathrm{\Δ\λ}={\mathrm{\λ}}_r+\frac{2\mathrm{dh}\cos \mathrm{\α}}{\mathrm{kf}}(P_x-P_r).$ [7]

Therefore, the image-forming range on linear photodetector (11) according to regulation light source (1) and light source to be measured (2) can realize treating the absolute wavelength calibration of photometry source (2).

Claims (8)

1. absolute wavelength calibration instrument, it is characterized in that this prover is by regulation light source (1), light source to be measured (2), the first optical fiber (3), the second optical fiber (4), fiber coupler (5), the 3rd optical fiber (6), aperture (7), parabolic high reflective mirror (8), grating (9), imaging len (10), linear photoconductor detector (11) and computer (12) form, the position relationship of each part mentioned above is as follows: described regulation light source (1) links to each other with the input end of the second optical fiber (4) with described fiber coupler (5) through the first optical fiber (3) respectively with light source to be measured (2), the coupled light beam of the output of this fiber coupler (5) is transferred to described aperture (7) through the 3rd optical fiber (6) and locates, the light beam of being dispersed by this aperture (7) incides described grating (9) after described parabolic high reflection mirror (8) expands and collimates, described regulation light source (1) and light source to be measured (2) are imaged on the described linear photoconductor detector (11) by described imaging len (10) through the diffraction of this grating (9), described computer (12) reads respectively and record at the location of pixels of the upper imaging of linear photodetector (11) the hot spot of regulation light source (1) and light source to be measured (2), carry out data and process, obtain the absolute wavelength of light source to be measured (2).

2. absolute wavelength calibration instrument according to claim 1 is characterized in that described regulation light source (1) is the known narrow linewidth light source of wavelength, and has preferably wavelength stability.

3. wavelength calibration instrument according to claim 1 is characterized in that described the first optical fiber (3), the second optical fiber (4) and the 3rd optical fiber (6) are radiation-resistant fiber, has preferably transmissivity in wider spectral range.

4. absolute wavelength calibration instrument according to claim 1 is characterized in that the curved surface plating broadband highly reflecting films of described parabolic high reflective mirror (8), and guaranteeing all has higher reflectivity to the spectrum that regulation light source (1) and light source to be measured (2) comprise.

5. absolute wavelength calibration instrument according to claim 1 is characterized in that described grating (8) is reflective blazed grating, and it is inferior high that this grating has the order of diffraction, and dispersive power is large, the characteristics that spectrophotometric result is good.

6. absolute wavelength calibration instrument according to claim 1 is characterized in that described imaging len (10) made by ultraviolet fused quartz or calcium fluoride crystal, to guarantee all have preferably transmissivity in wider spectral range.

7. absolute wavelength calibration instrument according to claim 1 is characterized in that described linear photoconductor detector (11) is linear diode array or linear CCD.

8. absolute wavelength calibration instrument according to claim 1 is characterized in that the data processing of described computer (12) is namely carried out the data processing by following formula, and the absolute wavelength that obtains light source to be measured (2) is λ _x:

${\mathrm{\λ}}_x={\mathrm{\λ}}_r+\mathrm{\Δ\λ}={\mathrm{\λ}}_r+\frac{2\mathrm{dh}\cos \mathrm{\α}}{\mathrm{kf}}(P_x-P_r).$

Wherein: λ _rBe regulation light source (1) absolute wavelength, P _rAnd P _xBe respectively regulation light source (1) and light source to be measured (2) at the location of pixels of the upper imaging of linear photodetector (11), h is the unit picture element width, d, α and k are respectively grating constant, blaze of grating angle and the order of diffraction time of grating (9), and f is the focal length of imaging len (10).

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