CN203825317U - Broadband polarizing-dependent free space isolator - Google Patents

Abstract

The utility model provides a broadband polarizing-dependent free space isolator which is characterized by being composed of a broadband polarizing film and a lambda/4 rhombic phase delay device. The broadband polarizing film and the lambda/4 rhombic phase delay device are spliced to form a whole. The lambda/4 rhombic phase delay device is a parallelepiped made of glass materials. The polarizing axis of the polarizing film is parallel to the light transmitting face. A 45-degree included angle is formed between the polarizing axis of the polarizing film and the fully-reflecting surface of the lambda/4 rhombic phase delay device. Linearly-polarized light passes through the polarizing film to enter a rhombus, total reflection is generated twice, the phase of the linearly-polarized light is delayed by lambda/4, and the linearly-polarized light is changed into rotary polarizing light to exit. The bandwidth, with the isolation larger than 30 dB, of the broadband polarizing-dependent free space isolator is larger than 400 nm, and the broadband polarizing-dependent free space isolator is suitable for isolating broadband transmission reflection light; the use materials are common glass, crystals are replaced, and therefore the broadband polarizing dependent free space isolator is quite low in cost and high in performance cost ratio.

Description

A kind of wideband polarization free space isolator of being correlated with

Technical field

The utility model relates to the optical passive component of optical fiber telecommunications system, relates in particular to the relevant free space isolator of a kind of wideband polarization.

Background technology

Isolator is that a kind of permission forward light passes through and isolation reflected light, thereby the optical passive component that makes light source not disturbed by reflected light, it can be divided into the online isolator of polarization irrelevant free space isolator relevant to polarization by polarization state and applicable cases, wherein the online isolator of polarization irrelevant is generally used in fiber optic communication network, and the relevant free space isolator of polarization mainly comprises Faraday rotation sheet type isolator and crystal wave-plate type isolator, be generally used in semiconductor laser.Conventional Faraday rotation sheet type isolator is comprised of the first polaroid, 45 degree Faraday rotation sheets and the second polaroid successively, and wherein the polarization axle of the polarization axle of the second polaroid and first polaroid in angle of 45 degrees.When light positive is to when transmission, incident light passes through polaroid with the parallel part in first polaroid polarization direction, the part vertical with polarization direction is absorbed, after entering Faraday polarization apparatus, light by polaroid under Faraday effect effect, rotates 45 degree, just in time parallel with the polarization direction of second polaroid, therefore can pass through the second polaroid losslessly.When light reverse transfer, the part vertical with second polaroid polarization direction is directly polarized sheet and absorbs, parallel part is lossless to be seen through, then enter Faraday polarization apparatus, direction rotation 45 degree the same while then continuing again to transmit along forward arrive the first polaroid, now polarisation of light state is vertical with the polarization direction of the first polaroid, thereby light is absorbed to produce, isolates.Due to Faraday rotation sheet, the polarized light anglec of rotation changed with wavelength variations and to the coefficient of temperature very greatly, make it at isolation, be greater than smaller bandwidth more than 30dB, being generally not more than 40nm, thereby not being suitable for the catoptrical isolation of wideband transmit.And conventional crystal wave-plate type isolator is comprised of a slice polaroid and a slice 1/4th crystal wave-plates.When light positive is to when transmission, incident light enters polaroid and forms linearly polarized light, then enter quarter-wave plate and become circularly polarized light, emergent light becomes circularly polarized light again after the end face reflection of optical fiber collimator, then enter quarter-wave plate and again become the linearly polarized light vertical with polaroid polarization axle, thereby reach buffer action.Its isolation is greater than that more than 30dB bandwidth compares with Faraday rotation sheet type isolator can be relative wider, but be generally also not more than 60nm, is not also suitable for the catoptrical isolation of wideband transmit.And above two kinds of isolator material therefors are crystal, its cost is comparatively expensive, and cost performance is lower.

Utility model content

The technical problems to be solved in the utility model, be to provide a kind of wideband polarization free space isolator of being correlated with, its sensitivity to wavelength is low, increased isolation bandwidth, and replace crystalline material with glass material, reduce cost, improved cost performance, thereby overcome the little and high shortcoming of material cost of prior art isolation bandwidth.

The utility model is achieved in that a kind of wideband polarization free space isolator of being correlated with, and a slice wideband polarization sheet and a slice λ/4 rhombohedreon type phase delay device, consists of; The logical light face of the logical light face of described wideband polarization sheet and described λ/4 rhombohedreon type phase delay device is bonding and form an integral body.

Further, described λ/4 rhombohedreon type phase delay device is the parallelepipedon of being made by glass material, the polarization direction linearly polarized light identical with described wideband polarization sheet is after described wideband polarization sheet, incide in the rhombohedreon type phase delay device of described λ/4 and at two parallel fully reflecting surfaces of λ/4 rhombohedreon type phase delay device, twice total reflection occur, its angle of total reflection β meets following formula:

$\mathrm{\δ}(\mathrm{\β},\mathrm{\λ}):=2(2\·a\tan \left(\frac{\cos \left(\mathrm{\β}\right)\·\sqrt{n{\left(\mathrm{\λ}\right)}^2\·\sin {\left(\mathrm{\β}\right)}^2-1}}{n\left(\mathrm{\λ}\right)\·\sin {\left(\mathrm{\β}\right)}^2}\right))$

In formula, δ (β, λ) is pi/2, and n (λ) is the refractive index in af at wavelength lambda of rhombohedreon material.

Further, the polarization axle of described wideband polarization sheet be parallel to logical light face and with the fully reflecting surface of described λ/4 rhombohedreon type phase delay device in angle of 45 degrees.

Further, described bonding method is gummed, optical cement, in-depth optical cement or chemical bonding.

The utlity model has following advantage: the wideband polarization of the present utility model free space isolator of being correlated with, the band that its isolation is greater than 30dB is wider than 400nm, far away higher than the bandwidth (being generally not more than 40nm) of Faraday rotation sheet isolator and the bandwidth (being generally not more than 60nm) of other Retardation Sheets isolators, be applicable to the catoptrical isolation of wideband transmit, and material therefor is simple glass, replaced crystal, made its cost very cheap, cost performance is high.

Accompanying drawing explanation

The present invention is further illustrated in conjunction with the embodiments with reference to the accompanying drawings.

Fig. 1 is the structural representation of the relevant free space isolator of wideband polarization.

Fig. 2 is that the relevant free space isolator forward loss of wideband polarization and reverse isolation degree are with the curve map of wavelength.

Embodiment

As shown in Figure 1, a kind of wideband polarization of the present utility model free space isolator of being correlated with, is comprised of a slice wideband polarization sheet 1 and a slice λ/4 rhombohedreon type phase delay device 2; One logical light face 12 of described wideband polarization sheet 1 is bonding and form an integral body with a logical light face 21 of described λ/4 rhombohedreon type phase delay device 2, and described bonding method can be gummed, optical cement, in-depth optical cement or chemical bonding.

Described λ/4 rhombohedreon type phase delay device 2 is by being the parallelepipedon that glass material is made.The polarization direction linearly polarized light identical with wideband polarization sheet 1 is after described wideband polarization sheet 1, incide in described λ/4 rhombohedreon type phase delay device 2 and in the side (being fully reflecting surface 23,24) of two parallel polishings of λ/4 rhombohedreon type phase delay device 2, twice total reflection occur, its angle of total reflection β meets following formula:

$\mathrm{\δ}(\mathrm{\β},\mathrm{\λ}):=2(2\·a\tan \left(\frac{\cos \left(\mathrm{\β}\right)\·\sqrt{n{\left(\mathrm{\λ}\right)}^2\·\sin {\left(\mathrm{\β}\right)}^2-1}}{n\left(\mathrm{\λ}\right)\·\sin {\left(\mathrm{\β}\right)}^2}\right))$

In formula, δ (β, λ) is pi/2, and n (λ) is the refractive index in af at wavelength lambda of rhombohedreon material.

The polarization axle of described wideband polarization sheet 1 be parallel to logical light face 11 (12) and with the fully reflecting surface 23 (24) of described λ/4 rhombohedreon type phase delay device 2 in angle of 45 degrees.

Wherein, in the present embodiment, wideband polarization sheet 1 Shi You Corning Incorporated provides, its polarization extinction ratio is all greater than 50dB between 1275nm-1635nm, and logical light face 11 plating anti-reflection films in this wave band, rete reflectivity R<0.2%, logical light face 12 is plated film not.λ/4 rhombohedreon type phase delay device 2 is parallelepipedons of being made by H-K9L glass material, and its two logical light face 21,22 respectively with fully reflecting surface 23,24 one-tenths 53.5 angles of spending, and logical light face 21 is plated film not, logical light face 22 is coated with anti-reflection film, rete reflectivity R<0.2% in 1275nm-1635nm wave band.And the polarization axle of wideband polarization sheet 1 is parallel to logical light face 11,12,21,22, and with two fully reflecting surfaces 23,24 one-tenths 45 angles of spending.

The concrete principle of work of the utility model is as follows:

The polarization direction linearly polarized light identical with wideband polarization sheet 1 is after wideband polarization sheet 1, incide in described λ/4 rhombohedreon type phase delay device 2 and after twice total reflection of two fully reflecting surfaces, 23,24 generations of described λ/4 rhombohedreon type phase delay device 2, then from rear logical light face 22 outgoing.Now, there are two polarized components in reflected light, p light and s light, and its phase differential is λ/4.Therefore, linearly polarized light before becomes circularly polarized light after λ/4 rhombohedreon type phase delay device 2, emergent light is again through optical element reflection below, again enter λ/4 rhombohedreon type phase delay device 2, phase place postpones λ/4 again, its polarization state becomes polarization direction and the orthogonal line polarisation of described wideband polarization sheet 1 plane of polarization direction from rotatory polarization, therefore plays buffer action.

Being calculated as follows of its forward optical transmission loss and backlight transmission isolation:

The matrix of incident light:

$\mathrm{Ein}\left(\mathrm{\&theta;}\right):=\left(\begin{array}{c}\cos \left(\mathrm{\&theta;}\right)\\ \sin \left(\mathrm{\&theta;}\right)\end{array}\right)$

Wherein, θ is the angle of linearly polarized light and x axle, in this utility model, and θ=45 degree;

The transmission matrix of wideband polarization sheet 1:

$P\left(\mathrm{\&theta;}\right):=\sqrt{1p}\&CenterDot;\left(\begin{array}{cc}\cos {\left(\mathrm{\&theta;}\right)}^2& \frac{\sin \left(2\mathrm{\&theta;}\right)}{2}\\ \frac{\sin \left(2\mathrm{\&theta;}\right)}{2}& \sin {\left(\mathrm{\&theta;}\right)}^2\end{array}\right)+\sqrt{1p\&CenterDot;\mathrm{ep}}\&CenterDot;\left(\begin{array}{cc}\sin {\left(\mathrm{\&theta;}\right)}^2& -\frac{\sin \left(2\mathrm{\&theta;}\right)}{2}\\ -\frac{\sin \left(2\mathrm{\&theta;}\right)}{2}& \cos {\left(\mathrm{\&theta;}\right)}^2\end{array}\right)$

Wherein, lp is the loss factor of wideband polarization sheet 1, and ep is the extinction ratio of wideband polarization sheet 1, and θ is the polarizing axis of wideband polarization sheet 1 and the angle of x axle, in this utility model, and θ=45 degree;

The transmission matrix of λ/4 rhombohedreon type phase delay device 2:

$R(\mathrm{\&alpha;},\mathrm{\&beta;}):=\sqrt{1w}\&CenterDot;\left(\begin{array}{cc}\cos (-a)& \sin (-a)\\ -\sin (-a)& \cos (-a)\end{array}\right)\&CenterDot;\left(\begin{array}{cc}{e}^{\frac{i\&CenterDot;\mathrm{\&delta;}}{2}}& 0\\ 0& e^{-\frac{i\&CenterDot;\mathrm{\&delta;}}{2}}\end{array}\right)\&CenterDot;\left(\begin{array}{cc}\cos \left(\mathrm{\&alpha;}\right)& \sin \left(\mathrm{\&alpha;}\right)\\ -\sin \left(\mathrm{\&alpha;}\right)& \cos \left(\mathrm{\&alpha;}\right)\end{array}\right)$

Wherein, lw is the loss factor of λ/4 rhombohedreon type phase delay device 2, and α is described λ/4 rhombohedreon type phase delay device 2 fully reflecting surfaces 23,24 and x axle clamp angle, and δ is the phase-delay quantity of λ/4 rhombohedreon type phase delay device 2, by following formula, is determined:

$\mathrm{\&delta;}(\mathrm{\&beta;},\mathrm{\&lambda;}):=2(2\&CenterDot;a\tan \left(\frac{\cos \left(\mathrm{\&beta;}\right)\&CenterDot;\sqrt{n{\left(\mathrm{\&lambda;}\right)}^2\&CenterDot;\sin {\left(\mathrm{\&beta;}\right)}^2-1}}{n\left(\mathrm{\&lambda;}\right)\&CenterDot;\sin {\left(\mathrm{\&beta;}\right)}^2}\right))$

In formula, n (λ) is the refractive index in af at wavelength lambda of the rhombohedreon material of λ/4 rhombohedreon type phase delay device 2.

The transmission matrix of catoptron:

$\mathrm{Jm}:=\left(\begin{array}{cc}1& 0\\ 0& -1\end{array}\right)$

Thus, during the transmission of forward light, its transmission matrix is:

Eout(θ,α,β,λ):=R(α,β(β,λ))·P(θ)·Ein(θ)

Forward optical transmission loss is:

$\mathrm{IL}(\mathrm{\&theta;},\mathrm{\&alpha;},\mathrm{\&beta;},\mathrm{\&lambda;}):=-10\&CenterDot;\log [\frac{{\left(\right|\mathrm{Eout}(\mathrm{\&theta;},\mathrm{\&alpha;},\mathrm{\&beta;},\mathrm{\&lambda;})\left|\right)}^2}{{\left(\right|\mathrm{Ein}\left(\mathrm{\&theta;}\right)\left|\right)}^2},10]$

Thus, during backlight transmission, its transmission matrix is:

Eout(θ,α,β,λ)：=P(π-θ)·Ｒ(π-α,δ(β,λ))·Ｊm·R(α,δ(β,λ))·P(θ)·Ｅin(θ)

Backlight transmission isolation is:

$\mathrm{ISO}(\mathrm{\&theta;},\mathrm{\&alpha;},\mathrm{\&beta;},\mathrm{\&lambda;}):=-10\&CenterDot;\log [\frac{{\left(\right|\mathrm{Eout}(\mathrm{\&theta;},\mathrm{\&alpha;},\mathrm{\&beta;},\mathrm{\&lambda;})\left|\right)}^2}{{\left(\right|\mathrm{Ein}\left(\mathrm{\&theta;}\right)\left|\right)}^2},10]$

Wherein, getting H-K9L is the material of λ/4 rhombohedreon type phase delay device 2, and by above computing formula, its forward loss and reverse isolation degree are shown in Fig. 2 with the change curve of wavelength.

As shown in Figure 2, the wavelength coverage that the utility model adopts is 1200nm-1700nm, and forward light when transmission, forward optical transmission loss is a straight line stably in this wavelength coverage, and its loss value is 0.10dB; During backlight transmission, backlight transmission isolation is the para-curve that Open Side Down slowly changes in this wavelength coverage, and its isolation is all more than 40dB, and visible, the broadband that isolation of the present utility model is greater than 30dB is greater than 400nm; And for the isolator of crystal wave-plate type, its backlight transmission isolation first increases fast and reduces fast in this wavelength coverage, isolation is greater than smaller bandwidth more than 30dB, is generally not more than 60nm.

Although more than described embodiment of the present utility model; but being familiar with those skilled in the art is to be understood that; our described specific embodiment is illustrative; rather than for the restriction to scope of the present invention; those of ordinary skill in the art are in equivalent modification and the variation done according to spirit of the present invention, all should be encompassed in the scope that claim of the present invention protects.

Claims (4)

1. the relevant free space isolator of wideband polarization, is characterized in that: a slice wideband polarization sheet and a slice λ/4 rhombohedreon type phase delay device, consist of; Bonding and the integral body of formation of one logical light face of one logical light face of described wideband polarization sheet and described λ/4 rhombohedreon type phase delay device.

2. the relevant free space isolator of a kind of wideband polarization as claimed in claim 1, it is characterized in that: described λ/4 rhombohedreon type phase delay device is the parallelepipedon of being made by glass material, the polarization direction linearly polarized light identical with described wideband polarization sheet is after described wideband polarization sheet, incide in the rhombohedreon type phase delay device of described λ/4 and at two parallel fully reflecting surfaces of λ/4 rhombohedreon type phase delay device, twice total reflection occur, its angle of total reflection β meets following formula:

$\mathrm{\&delta;}(\mathrm{\&beta;},\mathrm{\&lambda;}):=2(2\&CenterDot;a\tan \left(\frac{\cos \left(\mathrm{\&beta;}\right)\&CenterDot;\sqrt{n{\left(\mathrm{\&lambda;}\right)}^2\&CenterDot;\sin {\left(\mathrm{\&beta;}\right)}^2-1}}{n\left(\mathrm{\&lambda;}\right)\&CenterDot;\sin {\left(\mathrm{\&beta;}\right)}^2}\right))$

In formula, δ (β, λ) is pi/2, and n (λ) is the refractive index in af at wavelength lambda of rhombohedreon material.

3. the relevant free space isolator of a kind of wideband polarization as claimed in claim 1 or 2, is characterized in that: the polarization axle of described wideband polarization sheet be parallel to logical light face and with the fully reflecting surface of described λ/4 rhombohedreon type phase delay device in angle of 45 degrees.

4. the relevant free space isolator of a kind of wideband polarization as claimed in claim 1, is characterized in that: described bonding method is gummed, optical cement, in-depth optical cement or chemical bonding.