CN201097026Y - A polarization related separator for free space - Google Patents

Abstract

The utility model discloses a polarization related type isolating device with free space. The isolating device is composed of a birefringent crystal and a quarter wave plate, wherein an optical axis of the birefringent crystal is parallel to an incident plane, and forms an acute angle with the incident surface of the birefringent crystal, the polarized status between the optical axis direction of the quarter wave plate and an emergent Omicron light of the vertical incident light on the birefringent crystal presents a 45 degrees angle, when the above structure is adopted, the polarized status rotates with a 90 degrees angle after an initial polarized light passing the quarter wave plate twice in the direction where the polarized direction and the optical axis of the quarter wave plate present a 45 degrees angle, then an included angle is formed between the transmission direction and the original direction after the initial polarized light passing a polarized beam splitting device which is formed of the birefringent crystal with an included angle being presented between the optical axis of the birefringent crystal and the surface of the birefringent crystal, to ensure the returned light and the incident light to perform a certain transversal displacement, the returned light can not enter the inner part of a luminous element, and thus the function of the isolating device is performed. The isolating device has the advantages that the free space is large, the structure is simple, the volume is small, the isolating device can be easily integrated in a light receiving and shooting module, the influence of the isolating returned light over the luminous element is ensured, therefore the cost of the light receiving and shooting device is reduced, and the performance-price ratio is improved.

Description

A kind of polarization relationship type isolator of free space

Technical field

The utility model relates to the optical fiber communication technology field, relates in particular to the polarization relationship type isolator of a kind of free space that is applied in the optical transceiver module.

Background technology

Optoisolator is one of micro-optical device that is applied to the earliest optical communication, and it mainly acts on is that the light of forward transmitted is passed through, and the light of reverse transfer is isolated.Isolator is divided in line style and free space type two big classes as if the environment by its use; Isolator also can be by polarization relevant and polarization irrelevant classify, all have for two kinds at line style and free space type to comprise that the polarization relationship type isolator of general free space type is used more, mainly is used in the encapsulation of active device.

At present, the general principle of polarization relationship type isolator can be described below: primary structure (generally adopts LN angle of wedge sheet or YV04 angle of wedge sheet by polarizer, optical axis position is vertical), (material is identical with the preceding paragraph polarizer with another polarizer for 45 ° of Faraday rotators (generally adopting BIG or yig crystal), optical axis position is 45 ° relatively), its ultimate principle is: during forward transmitted, light is launched by entering another polarizer behind preceding paragraph polarizer and 45 ° of Faraday rotators from the incident collimating apparatus, since the optical axis of another polarizer just be 45 ° oppositely, polarized light is just as entering the reception collimating apparatus through a flat board; Effect owing to Faraday rotator when the light reverse transfer makes by polarization state direction behind the Faraday rotator vertical with preceding paragraph polarizer optical axis, therefore during reverse transfer, light is just as passing through a Wo Nasidun prism, make o light separate certain angle with e light, light can not enter collimating apparatus, plays the effect that light is isolated.This structure has complexity of free space isolator structure, and volume is big, is not easy to be integrated in the optical transceiver module defectives such as cost height.

Utility model content the purpose of this utility model provides the polarization relationship type isolator of the free space that a kind of volume is little and cost is low.

The scheme that the above technical matters that solves the utility model adopts is: isolator is made up of birefringece crystal and quarter-wave plate, wherein the optical axis of birefringece crystal is parallel to the plane of incidence, and form acute angle with the incidence surface of birefringece crystal, the optical axis direction of quarter-wave plate and the o polarization state of light at 45 angle of light when outgoing that impinges perpendicularly on the birefringece crystal.

Described birefringece crystal and quarter-wave plate are combined into an optical body by optics contact or the gluing mode that connects between the two.

The angle that the optical axis of birefringece crystal and birefringece crystal surface form is greater than 0 ° and less than 90 °, and wherein best angle is 45 °.

After adopting said structure, initial polarized light is understood half-twist with twice in polarization direction and quarter-wave plate optical axis direction at 45 through its polarization state behind the quarter-wave plate, (being that the polarization direction can be vertical with original polarization direction), again behind the polarization beam apparatus through the optical axis of birefringece crystal and the birefringece crystal formation that the birefringece crystal surface forms an angle, its direction of propagation and former direction have certain angle, make return light and incident light that certain transversal displacement take place, return light can not enter light-emitting component inside, play the effect of isolator, the linearly polarized light forward that promptly makes light-emitting component send passes through, oppositely by.

The optical axis direction that the utility model can be by adjusting birefringece crystal and the thickness of crystal are controlled return light and depart from laterally walking to off normal and moving of forward light when the outgoing crystal, effect with polarization beam apparatus, change optical axis of crystal direction, can change the deviation angle of e light, when the incident light vertical incidence, when the angle of optical axis and plane of crystal is θ, corresponding deviation angle is α, law of refraction according to uniaxial crystal, formula (1) is arranged, and the transversal displacement of e light and o light is d * tg α, and d is the thickness of crystal optical direction; As tg θ=n _e/ n _oThe time, there is maximal value at the α angle: ${\mathrm{\&alpha;}}_{\max }=\arctan \frac{{n_e}^2-{{\mathrm{<figure-callout\; id="2"\; label="n\; o"\; filenames="Y20072000736300061.png,Y20072000736300064.png"\; state="\{\{state\}\}">n</figure-callout>}}_o}^2}{2n_e{n}_o}.$ For θ angle easy to process is selected 45 °, incident ray is selected vertical incidence, also can oblique incidence, $\mathrm{tg\&alpha;}\frac{\frac{1}{2}({n_e}^2-{n_o}^2)}{{n_o}^2{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="Y20072000736300061.png,Y20072000736300064.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\mathrm{\&theta;}+{{\mathrm{<figure-callout\; id="2"\; label="n\; e"\; filenames="Y20072000736300061.png,Y20072000736300064.png"\; state="\{\{state\}\}">n</figure-callout>}}_e}^2{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="Y20072000736300061.png,Y20072000736300064.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2\mathrm{\&theta;}}\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="Y20072000736300061.png,Y20072000736300064.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&theta;}.$

The beneficial effects of the utility model are: because the optical axis of birefringece crystal of the present utility model can be in the plane of incidence and had angle with the surface of crystal, make the light incide intracrystalline different polarization states take place laterally to walk from other angles, form the polarization isolator of free space.This isolator has free space characteristics big and simple in structure, that volume is little compared with the prior art, is easy to be integrated in the optical transceiver module, guarantees the influence of isolated return light to light-emitting component, makes that the cost of optical transceiver is low, cost performance improves.

Description of drawings

The utility model will be further described below in conjunction with accompanying drawing:

Fig. 1 is the main TV structure synoptic diagram of the utility model isolator;

Fig. 2 is that the light path synoptic diagram is looked on the left side of the utility model isolator;

Fig. 3 is the utility model light path principle synoptic diagram.

Fig. 4 is a kind of concrete embodiment structural representation of the present utility model.

Embodiment

Shown in Fig. 1 or 2, the utility model isolator 2 is made up of birefringece crystal 21 and quarter-wave plate 22, can be combined into an optical body by optics contact or the gluing mode that connects between the two.Wherein the optical axis 211 of birefringece crystal 21 is parallel to the plane of incidence, and forms acute angle with the incidence surface of birefringece crystal 21, and its angle is the 45 the best of getting easy to process greater than 0 ° and less than 90 °.Optical axis 221 directions of quarter-wave plate 22 with impinge perpendicularly on the polarization state angle at 45 of the o of light when outgoing on the birefringece crystal, optical axis 211 directions that can get optical axis 221 directions of quarter-wave plate 22 and birefringece crystal 21 simultaneously are at 45.

As shown in Figure 3, c is the optical axis of quarter-wave plate, and the p direction is the polarisation of light direction that incides quarter-wave plate.After entering quarter-wave plate, the polarized light of p direction is decomposed into o light and e light, quarter-wave plate makes the line polarisation become rotatory polarization, when reverse light passes through quarter-wave plate once more, become the line polarisation by rotatory polarization again, and the polarization direction is vertical with p direction before, propagates with e light after entering birefringece crystal once more.

As shown in Figure 4, the utility model is installed in the optical transmitting set, and the utility model isolator 2 is arranged between LD light source 1 and the coupled system 3, and the other end of coupled system 3 is an optical fiber 4.After LD light source 1 output polarization light impinges perpendicularly on birefringece crystal 21 surfaces, in crystal, propagate with o light, behind quarter-wave plate 22, it is (left-handed that the line polarisation becomes rotatory polarization, or dextrorotation), after the subsequent element reflection, (the left-handed change dextrorotation that changes during than forward of the precession direction of the rotatory polarization of return light, or dextrorotation becomes left-handed), again through behind quarter-wave plate 22,90 ° deflection has taken place in return polarization state of light direction when transmitting than forward, enter birefringece crystal 21 backs and propagate with e light, and there is a deviation angle degree its direction of propagation than the direction of propagation in forward time, because birefringece crystal 21 has certain thickness, light is propagated lateral excursion behind the segment distance like this, and return light can not be back to light-emitting component along former road again, has played buffer action.

Claims (4)

1. the polarization relationship type isolator of a free space, form by birefringece crystal and quarter-wave plate, it is characterized in that: the optical axis of birefringece crystal is parallel to the plane of incidence, and form acute angle with the incidence surface of birefringece crystal, the optical axis direction of quarter-wave plate and the o polarization state of light at 45 angle of light when outgoing that impinges perpendicularly on the birefringece crystal.

2. the polarization relationship type isolator of a kind of free space according to claim 1 is characterized in that: the optical axis of its birefringece crystal and birefringece crystal surface angulation are greater than 0 ° and less than 90 °.

3. the polarization relationship type isolator of a kind of free space according to claim 2 is characterized in that: it is 45 ° that the optical axis of its birefringece crystal becomes best angle with birefringece crystal surface institute.

4. according to the polarization relationship type isolator of claim 1,2 or 3 described a kind of free spaces, it is characterized in that: its birefringece crystal is contacted by optics with quarter-wave plate or gluing connecing forms one.

Images