CN102508364B - Broadband wave plate, method for realizing equality of phase delay and polarization controller - Google Patents

Abstract

The invention discloses a broadband wave plate, a method for realizing equality of phase delay and a polarization controller. The broadband wave plate is formed by sequentially attaching a first dispersion element, a wedged birefringence wave plate and a second dispersion element, wherein the first dispersion element sequentially unfolds input broadband waves according to a sequence of the sizes of wavelengths so as to output dispersion waves with the corresponding wavelengths; the wedged birefringence wave plate outputs delay waves with the corresponding wavelengths according to the same phase delay generated by the dispersion waves with the corresponding wavelengths; and the second dispersion element gathers the delay waves with the corresponding wavelengths into a broadband wave. According to the invention, the dispersion elements are used for separating a broadband spectrum spatially, and the equal phase delay is obtained in a broadband range through the wedged wave plate. By the polarization controller combined by the broadband wave plate, the bandwidth is up to a hundreds nanometer scale.

Description

Broadband waveplate and realize method and the Polarization Controller that phase delay is equal

Technical field

The present invention relates to optical device, be specifically related to broadband waveplate and Polarization Controller.

Background technology

Polarization Controller is a kind of important optical device, in optical fiber communication and sensory field, all has a wide range of applications.Particularly, in optical fiber telecommunications system, utilize Polarization Controller to control exactly the polarization state of fiber middle light signal, to improving the stability of optical fiber telecommunications system, play a part crucial with the bit error rate that reduces data transmission.

The typical structure of Polarization Controller is comprised of three rotatable wave plates, and one of them λ/2 (HWP) wave plate is positioned in the middle of the wave plate of two λ/4 (QWP), and each wave plate can freely rotate with respect to other wave plate along optical axis.The effect of first λ/4 wave plate is to change the polarized light of input arbitrarily into linearly polarized light, then by λ/2 wave plate, this linearly polarized light is rotated to the polarization direction that arbitrary hope obtains, finally by second λ/4 wave plate, change this polarized light into output polarization state that any hope obtains.

In Polarization Controller, the phase change of input beam is that the phase delay by HWP wave plate and QWP wave plate realizes.Because the phase delay of wave plate is fixed, therefore, when the wavelength of input beam is fixed value, the polarized light that output is wanted is easy to accomplish.But well-known, phase delay is that the variation with wavelength changes, when input beam is the larger broadband ripple of wavelength coverage, because the phase delay of different wave length is different, therefore, can not export whole broadband wave polarization light simultaneously.

Known through above analysis, common wave plate has certain limitation to the bandwidth of input beam, and therefore, common wave plate is very restricted on to the processing of broadband ripple.At present, the method for solution wave plate limit bandwidth problem mainly contains two kinds:

(1), utilize total internal reflection principle to manufacture wave plate, make two polarized components phase changing capacity phase difference of pi when total reflection of light beam, to realize the function of quarter wave plate or 1/2 wave plate, the achromatism quarter wave plate that third-class girdle prism as disclosed in Chinese invention patent CN1258849 forms.Tantalum is, this wave plate utilizes the mode of total reflection prism to produce phase delay, and bandwidth range is narrower, cannot meet wider wave band and high-precision requirement.

(2), utilize combined type wave plate color difference eliminating (Chinese laser, Vol.31, No.3,2004, " development of infrared composite broadband wave plate ").Yet, the composite wave plate that in this technical scheme, requirement is comprised of three wave plates, three wave plates are necessary for zero-th order waveplates, and zero-th order waveplates is very thin, even if use quartzy (refringence of o, e light is little) to make, zero level half-wave plate also only has 81um left and right.Three compound thickness are altogether about 0.24mm.The optical element of this thickness, is processed with difficulty, and yield rate is lower.

In sum, the broadband waveplate that prior art is manufactured, or bandwidth range is narrower, or be processed with that difficulty is large, yield rate is low, and be badly in need of the simple broadband waveplate of a kind of production and processing, be suitable for the wider light beam of wavelength coverage to carry out phase delay.

Summary of the invention

Technical matters to be solved by this invention is that solution broadband waveplate or bandwidth range are narrower, or is processed with the problem that difficulty is large, yield rate is low.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is to provide a kind of broadband waveplate and realizes the method that phase delay is equal, by the first dispersion element, the broadband ripple of glancing incidence is launched to export the dispersive wave of respective wavelength successively by the order of wavelength size, the dispersive wave of described respective wavelength produces the delay ripple of identical phase delay output respective wavelength through birefringent wedge wave plate, the delay ripple of described respective wavelength is converged as broadband ripple by described the second dispersion element.

The present invention also provides a kind of broadband waveplate, by the first dispersion element, birefringent wedge wave plate and the laminating of the second dispersion element, formed successively, described the first dispersion element launches to export the dispersive wave of respective wavelength successively by the broadband ripple of input by the order of wavelength size, described birefringent wedge wave plate produces the dispersive wave of described respective wavelength in the delay ripple of identical phase delay output respective wavelength, and described the second dispersion element converges the delay ripple of described respective wavelength into broadband ripple.

In above-mentioned broadband waveplate, described first, second dispersion element is prism or diffraction grating.In above-mentioned band wave plate, the angle of wedge of described birefringent wedge wave plate is

wherein a is maximum wavelength and minimum wavelength skew of the position on prism exiting surface through prism dispersion in wideband spectrum, and l is the thickness difference of the wave plate at the same level of the interior maximum wavelength of wideband spectrum and minimum wavelength.

In above-mentioned band wave plate, maximum wavelength and the minimum wavelength skew of the position on prism exiting surface through prism dispersion in wideband spectrum

$a=\sqrt{{\left(\frac{A\×\tan \mathrm{\α}}{\sin ({\mathrm{\θ}}_2-\mathrm{\α})}\right)}^2+{\left(\frac{A\×\tan \mathrm{\α}}{\sin ({\mathrm{\θ}}_1-\mathrm{\α})}\right)}^2-2\left(\frac{A\×\tan \mathrm{\α}}{\sin ({\mathrm{\θ}}_2-\mathrm{\α})}\right)\left(\frac{A\×\tan \mathrm{\α}}{\sin ({\mathrm{\θ}}_1-\mathrm{\α})}\right)\cos ({\mathrm{\θ}}_2-{\mathrm{\θ}}_1)}$

Wherein θ 2 and θ 1 represent respectively the refraction angle of the light that wavelength is different, the refraction angle that θ 1 is short wavelength light, and θ 2 is the refraction angle of long wavelength's light, the drift angle that α is prism, A is the logical light face size of prism.

In above-mentioned band wave plate, described broadband waveplate is half-wave plate, and described prism is made by pure silicon material, and abbe number is 4.522 * 10 ^-5/ nm, drift angle is 16.7 °, and logical light face is of a size of 5mm, and described birefringent wedge wave plate adopts Pyatyi HWP quartz wave-plate, and the angle of wedge is 17 °.

The present invention also provides a kind of Polarization Controller, comprises the broadband waveplate of said structure.

The present invention, utilizes dispersion element that wideband spectrum is spatially separated and passes through wedge shape wave plate, realizes and in broad frequency range, obtains equal phase delay.Utilize the Polarization Controller of this wide wave plate combined, bandwidth can reach hundreds of nanoscales.

Accompanying drawing explanation

Fig. 1 is its wavelength of wave plate that phase delay is equal and the graph of a relation of thickness;

Fig. 2 is the dispersion of prism;

Fig. 3 is broadband waveplate structural representation provided by the invention;

Fig. 4 is Polarization Controller structural representation provided by the invention.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in detail.

As shown in Figure 3, broadband waveplate provided by the invention is fitted tightly and is formed by the first dispersion element 102, birefringent wedge wave plate 103 and the second dispersion element 104 successively.

First, second dispersion element 102,104 is prism or diffraction grating, the first dispersion element 102 launches to export the dispersive wave of respective wavelength successively by the broadband ripple of input by the order of wavelength size, birefringent wedge wave plate 103 produces the dispersive wave of described respective wavelength in the delay ripple of identical phase delay output respective wavelength, and the second dispersion element 104 converges the delay ripple of described respective wavelength into the output of broadband ripple.

Innovative point of the present invention is: utilize dispersion element that wideband spectrum is spatially separated and pass through wedge shape wave plate, realizing and in broad frequency range, obtain equal phase delay.; broadband ripple is after the first dispersion element 102; because the refraction angle of different wave length is different; so each wavelength spatially separates; pass through again birefringent wedge wave plate 103; make the long light beam of ripple through longer light path; and the short light beam of wavelength is through shorter light path; by selecting the drift angle of the first dispersing prism 102 and the angle of wedge of birefringent wedge wave plate 103; make the phase of light wave delay of all wavelengths identical, finally by the second dispersion element 104, the light beam of different wave length is converged to output again again.

Below in conjunction with Figure of description, the principle that realizes of the present invention is described in detail.

As everyone knows, the phase delay Φ of optical wave plate is:

$\mathrm{\φ}=\frac{2\mathrm{\π}}{\mathrm{\λ}}\·\mathrm{\Δn}\·d---\left(1\right)$

Wherein, Δ n is the refringence of o light and e light, the thickness that d is optical wave plate, and λ is wavelength.Therefore, the thickness of wave plate is:

$d=\frac{\mathrm{\φ}\·\mathrm{\λ}}{\mathrm{\Δn}\·2\mathrm{\π}}---\left(2\right)$

The o light of quartz material and the refractive index equation of e light are: the light vibration of incident is resolved into perpendicular to optical axis (o vibration) and is parallel to two components of optical axis (e vibration), the o light in their corresponding wafers and e light.

$n_o\left(\mathrm{\λ}\right)=\sqrt{a_0+a_1\·{\mathrm{\λ}}^2+a_2\·{\mathrm{\λ}}^{-2}+a_3\·{\mathrm{\λ}}^{-4}+a_4\·{\mathrm{\λ}}^{-6}+a_5\·{\mathrm{\λ}}^{-8}}---\left(3\right)$

$n_e\left(\mathrm{\&lambda;}\right)=\sqrt{A_0+{\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="HDA0000105425440000011.png"\; state="\{\{state\}\}">A</figure-callout>}}_1\&CenterDot;{\mathrm{\&lambda;}}^2+A_2\&CenterDot;{\mathrm{\&lambda;}}^{-2}+A_3\&CenterDot;{\mathrm{\&lambda;}}^{-4}+A_4\&CenterDot;{\mathrm{\&lambda;}}^{-6}+A_5\&CenterDot;{\mathrm{\&lambda;}}^{-8}}---\left(4\right)$

Wherein, λ is wavelength, a0 ... a5, A0 ... A5 is constant, and measured value is as follows:

$\left\{\begin{array}{c}{a}_0=2.35676495\\ {\mathrm{<figure-callout\; id="1"\; label="a"\; filenames="HDA0000105425440000011.png"\; state="\{\{state\}\}">a</figure-callout>}}_1=-1.13996924\&times;{10}^{-2}\\ a_2=1.08741656\&times;{10}^{-2}\\ a_3=3.32066914\&times;{10}^{-5}\\ a_4=1.0860934\&times;{10}^{-5}\\ a_5=-3.10123984\&times;{10}^{-7}\end{array}\right.$ $\left\{\begin{array}{c}{A}_0=2.38421862\\ {\mathrm{<figure-callout\; id="1"\; label="A"\; filenames="HDA0000105425440000011.png"\; state="\{\{state\}\}">A</figure-callout>}}_1=-1.20653449\&times;{10}^{-2}\\ A_2=1.10138430\&times;{10}^{-2}\\ A_3=1.28863130\&times;{10}^{-4}\\ A_4=1.68747314\&times;{10}^{-7}\\ A_5=4.92022338\&times;{10}^{-8}\end{array}\right.$

By calculating, learn Δ n=n _o(λ)-n _e(λ) at wavelength 1450nm, within the scope of 1650nm, be constant 0.0085, like this, can draw, at wavelength 1450nm, within the scope of 1650nm, the refractive index of quartz material is approximate linear with wavelength, as shown in Figure 1.

Known based on above-mentioned analysis, if wave plate is processed into wedge shape wave plate, by the selection to the angle of wedge, just can utilize the thickness of wave plate to increase at short transverse Linear, make broadband ripple in its wavelength band, obtain identical phase delay.

Referring to Fig. 2, the different wave length in broad band light beam reflects after prism again, and refraction angle is different, by refraction law, can be derived, and the skew a that the light of different wave length produces is:

$a=\sqrt{{\left(\frac{A\&times;\tan \mathrm{\&alpha;}}{\sin ({\mathrm{\&theta;}}_2-\mathrm{\&alpha;})}\right)}^2+{\left(\frac{A\&times;\tan \mathrm{\&alpha;}}{\sin ({\mathrm{\&theta;}}_1-\mathrm{\&alpha;})}\right)}^2-2\left(\frac{A\&times;\tan \mathrm{\&alpha;}}{\sin ({\mathrm{\&theta;}}_2-\mathrm{\&alpha;})}\right)\left(\frac{A\&times;\tan \mathrm{\&alpha;}}{\sin ({\mathrm{\&theta;}}_1-\mathrm{\&alpha;})}\right)\cos ({\mathrm{\&theta;}}_2-{\mathrm{\&theta;}}_1)}---\left(5\right)$

Wherein θ 2 and θ 1 represent respectively the refraction angle of the light that wavelength is different, the refraction angle that θ 1 is short wavelength light, and θ 2 is the refraction angle of long wavelength's light, the drift angle that α is prism, A is the logical light face size of prism.

The wave plate thickness at the same level of supposing different wave length differs as l, and for the phase delay of all wavelengths is equated, the angle of wedge of wedge shape wave plate (angle on side and base) should be:

$a\tan \left(\frac{l}{a}\right)---\left(6\right)$

Make the optional following material of material of dispersing prism 102:

Material	Material dispersion value dn/d λ (/nm)
		SiO2	1.195×10 -5

Si	4.522×10 -5
		YVO4	3.193×10 -5
CaF2	4.841×10 -6
		MgF2	5.339×10 -6
TiO2	6.206×10 -5
		Icelandspar	1.727×10 -5

Below by specific embodiment, illustrate the angle of wedge of how selecting birefringent wedge wave plate 103 according to the drift angle of dispersing prism 102, the present embodiment is HWP wave plate.

Dispersing prism 102 is selected pure silicon material, and abbe number (dn/d λ) is 4.522 * 10 ^-5/ nm, broadband ripple is with 88 ° of angle glancing incidences, wavelength is the refraction angle θ 1=16.509 of the light beam of 1530nm and 1630nm, θ 2=16.485, the two differs θ 2-θ 1=0.024 °, if apex angle α=16.7 ° of dispersing prism 102, size A=5mm on logical light face, by formula (5), calculated, ripple two wavelength after prism in broadband separate a=228um.Birefringent wedge wave plate 103 adopts Pyatyi HWP quartz wave-plate, the wave plate thickness that is calculated 1530nm and 1630nm by formula (2) differs d=1017.5 μ m-947.8 μ m=69.7 μ m, so the angle of wedge of birefringent wedge wave plate 103 is: atan (69.7/228)=17 °.

The present invention also provides a kind of Polarization Controller that adopts above-mentioned broadband waveplate.Its structure as shown in Figure 4.The light of optical fiber output is inputted successively wide band lambda/4 (QWP) wave plate 202 after collimation lens 201 collimations, wide band lambda/2 (HWP) wave plate 203, and wide band lambda/4 (QWP) wave plate 204, through coupled lens 205, input in optical fiber, wave plate 202,203 and 204 adopts the broadband waveplate of said structure again.

The present invention is not limited to above-mentioned preferred forms, and anyone should learn the structural change of making under enlightenment of the present invention, and every have identical or close technical scheme with the present invention, within all falling into protection scope of the present invention.

Claims (5)

1. broadband waveplate is realized the method that phase delay is equal, it is characterized in that, by the first dispersion element, the broadband ripple of glancing incidence is launched to export the dispersive wave of respective wavelength successively by the order of wavelength size, the dispersive wave of described respective wavelength produces the delay ripple of identical phase delay output respective wavelength through birefringent wedge wave plate, the delay ripple of described respective wavelength is converged as broadband ripple by described the second dispersion element; The angle of wedge of described birefringent wedge wave plate is

wherein a is maximum wavelength and minimum wavelength skew of the position on prism exiting surface through prism dispersion in wideband spectrum, and l is the thickness difference of the wave plate at the same level of the interior maximum wavelength of wideband spectrum and minimum wavelength.

2. broadband waveplate, it is characterized in that, by the first dispersion element, birefringent wedge wave plate and the laminating of the second dispersion element, formed successively, described the first dispersion element launches to export the dispersive wave of respective wavelength successively by the broadband ripple of input by the order of wavelength size, described birefringent wedge wave plate produces the dispersive wave of described respective wavelength in the delay ripple of identical phase delay output respective wavelength, described the second dispersion element converges the delay ripple of described respective wavelength into broadband ripple, and the angle of wedge of described birefringent wedge wave plate is

wherein a is maximum wavelength and minimum wavelength skew of the position on prism exiting surface through prism dispersion in wideband spectrum, and l is the thickness difference of the wave plate at the same level of the interior maximum wavelength of wideband spectrum and minimum wavelength.

3. broadband waveplate as claimed in claim 2, is characterized in that, maximum wavelength and the minimum wavelength skew of the position on prism exiting surface through prism dispersion in wideband spectrum

$a=\sqrt{{\left(\frac{A\&times;\tan \mathrm{\&alpha;}}{\sin ({\mathrm{\&theta;}}_2-\mathrm{\&alpha;})}\right)}^2+{\left(\frac{A\&times;\tan \mathrm{\&alpha;}}{\sin ({\mathrm{\&theta;}}_1-\mathrm{\&alpha;})}\right)}^2-2\left(\frac{A\&times;\tan \mathrm{\&alpha;}}{\sin ({\mathrm{\&theta;}}_2-\mathrm{\&alpha;})}\right)\left(\frac{A\&times;\tan \mathrm{\&alpha;}}{\sin ({\mathrm{\&theta;}}_1-\mathrm{\&alpha;})}\right)\cos ({\mathrm{\&theta;}}_2-{\mathrm{\&theta;}}_1)}$

Wherein θ 2 and θ 1 represent respectively the refraction angle of the light that wavelength is different, the refraction angle that θ 1 is short wavelength light, and θ 2 is the refraction angle of long wavelength's light, the drift angle that α is prism, A is the logical light face size of prism.

4. broadband waveplate as claimed in claim 3, is characterized in that, described broadband waveplate is half-wave plate, and described prism is made by pure silicon material, and abbe number is 4.522 * 10 ^-5/ nm, drift angle is 16.7 °, and logical light face is of a size of 5mm, and described birefringent wedge wave plate adopts Pyatyi HWP quartz wave-plate, and the angle of wedge is 17 °.

5. Polarization Controller, is characterized in that comprising the broadband waveplate described in claim 2-4 item any one.

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