DE1928665C3 - Optical resonance reflector with periodic characteristics - Google Patents

Description

is. .

4. Optical resonance reflector according to one of the preceding claims, characterized in that the mutual distances (Zi ₁ ) between the plates (1) are determined by a preferably vapor-deposited nngformige or frame-shaped, thin intermediate layer (2) of well-adhering material applied to the plates are.

5. Optical resonance reflector according to one of claims 2 to 4, characterized by se.ne Use as a mode-selective decoupling level with a very high load capacity for an optical Resonator of a giant pulse laser to which the optical length of the distance (ft, between two adjacent plates (I) of the reflector is set for a value em optimal Reflectivity of the giant pulse laser

^Wl 6. ^ application of an optical ₍ Resonanzreflek sector according to one of claims 1 to 4 as a filter with a periodic structure, in particular for channel separation in an optical multi-channel communication system.

The desired stimulated radiation S is obtained within an optical resonator by the fact that this can also be stimulated? H "in the energy of a Pumpcnencrgiequelle thereby the emjaiun for the excitation of stimuu _h ^u, ,,. Ford variable inversion its Eiicr-» ~ _{s herb} is eigeführt, m general, ytnive · s _Rcsonator a plurality of axial

"^^., icn fashions. The _requirements for this multitude of fashions & fa ^ _crhc b1ich are restricted. 5ί5 at least one of the optical resonators ^ ",! LA _n both mirrors is designed as a modcnselcktiver ReJ2" _reflector . ,. son "m * _{upc from} nihrungsrorm an optical"*;_{"nzrcflcktors} is the so-called dielectric« ■ »» n _{of mehrerC} aiii a Glaslriigcr Open l ^ _'{tcn layers of transparent material ζ ~ 7 \ _[Durcn the number of.. Layers, the Brerhimas index of the layer material used as well as cnuug ^. ^ ^ _{Layerscn) asscn s} , _c h such aur di jili Gb

40

g ^^ ^ _{layercn) assc} g

aur ^. ^ limits to the respective given subject ■ adapt. However, they have the proof _that ^H _{quickly destroys them} under greater loads [""'. _{bw their} reflective properties in JJjJjJ ^ _{Wcisc ündcr} „.

u ™ iwu ^^. ^ _bckannt- Rcsonanzreflcktorcn with "" rinrlischer characteristic by the fact that pen "ι ^^ _p i _anpara il _c | c glass plates of the kind zwc. _{ketes while} maintaining the same

S " _Abs To be merged with _dc . Such

^s _p ^e "fe _n . _Resonanzre fl _c laoren also hold BcIana« en ^^ ^ ^^ _{Aurircffen ejncs from cinom}

Giant pulse laser generated light pulse occur. ^ J " _e inscht ^: iaiec studies show wise sol ^ ' ^e ^". " _a reflection behavior as well

«Jriodic structure extraordinarily multifaceted in the penodiscnc. _{ring down the frequency}

Mine successive reflection maxima

"" ^, ' _{undesirable ingenuity} notices limit the »1 · _you , _hr pianen-Rcsonanzreflektorcn so-application so, _c modenselective reflector,

probably Her as a _{Riescnirnpulslasei} ·. considerably nsbusondcru De. . mode-selective

] ^ Storage arrangement _{sets namely}

it peak reflectivity at Jj P ^ _Su . _{ahlu ahead}

of the waves for a long time

55

gens ^ be ^

onanzrc lets

_{Bmlenmg des Spil} .

The invention time regards, is au _(a oplischen * fK ^ ^ be based on y _b particularly high

^ _{c ne} \ another solution to indicate the a

g ^ _c ^P _nrormigcr periodic structure and also gives the possibility to choose the peak reflectivity continuously within wide limits.

Utilizing coherent optical waves 6 _{5 of} equal mutual distances together
What do you think you have to do with this kind of feedback? If this feature is born according to the invention, it has gained increased practical importance. This means that with a thickness of the plates that is very much known, a laser consists of an active one is greater than the wavelength of the coherent radiation.

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the optical length of the distance between two adjacent plates to an area within the limits of a fraction of a wavelength and a few wavelengths of coherent radiation. with preferred values of a quarter of the wavelength or an odd multiple thereof, is shortened.

The invention is based on the knowledge that by measuring the optical length of the distance between two adjacent ones Plates to a maximum of several odd-numbered quarters of the wavelength of the coherent radiation the diversity of the period of reflectivity in this sense is much clearer and simpler than the Rcflexionsmaxima between two successive maximum reflection peaks on the frequency axis to a practically negligible Waviness can be reduced and also the successive equidistant maxima the reflection peaks have the same height in a wide range of wavelengths. This structure of the Reflectivity gives the advantageous possibility of an optical dimensioned in this way To use a resonance reflector as an optical filter with a periodic structure, for example for channel separation in an optical communication system.

In this connection, the ratios are particularly favorable if the optical length the distance between two adjacent 3c Plates equal to a quarter of the wavelength of coherent radiation or several odd ones Multiples of it is chosen. With this dimensioning of the distance between the plates, the ratio between the blocking range (reflection peak) and the transmission range (minimum reflection) a maximum.

How further extensive investigations on which the invention is based have shown can be the height of the reflection maxima, which are equidistant in a wide range of wavelengths, within wide limits, while maintaining the same height, adjust that the optical length of the distance between two adjacent plates of a quarter of the wavelength of the coherent radiation or several odd multiples thereof is selected to be different. This comes to mind insofar as it is of particular importance when using such a resonance reflector as Mode selector, especially in the case of a giant pulse laser, what matters is that its peak reflectivity at the wavelength of the coherent Radiation is optimally adaptable for the laser system in question.

It is particularly useful in this context that the optical length of the distance between two adjacent plates less than a quarter of the wavelength of the coherent radiation is chosen.

In a preferred embodiment according to the invention, the mutual distances are between two the plates by an applied, preferably vapor-deposited, annular or Frame-shaped thin intermediate layer of well-adhering material set.

On the basis of an embodiment shown in the drawing, the invention is intended in the following will be explained in more detail. In the drawing means

F i g. 1 is a side view of an optical resonance reflector according to the invention,

Fig. 2 is the end view of a plate of the optical resonance reflector according to Fig. I,

F i g. 3 a diagram of the periodic curve plotted against the change in length * of the reflection behavior of the resonance reflector according to Fig. I,

F i g. 4 shows a diagram of the maxi plotted against the refractive index 11 of the plate material paint peak reflectivity depending on the number of plates,

F i g. 5 is a diagram of the plotted against the distance between two adjacent plates Peak reflectivity for a resonance reflector according to Fig. I at various Refractive index of the plate material.

The optical resonance reflector according to FIG. 1 consists of three circular glass panes I with plane-parallel end faces. The glass plates 1, which are arranged one behind the other, adjoin one another with their end faces via annular layers 2, the thickness of which is at most several odd multiples of a quarter of the wavelength of the coherent radiation. In this way, an air gap of a corresponding width is created between the adjacent glass plates 1, which air gap is shown in FIG. 1 to be much wider than in reality with regard to a reasonable graphic representation. The ratio of the air gap width / 1 to the optical thickness of the glass panes 1, which is given by the product of their geometric width / i ₂ and the refractive index / 1 of the glass material, is about a thousandth and less.

The in F i g. The plan view shown in FIG. 2 of the end face of the left glass plate 1 corresponding to the section line AB illustrates the air gap 3 that forms between the adjacent end faces of two glass plates I due to the annular intermediate layer 2.

As already stated in the introduction, the inventive dimensioning of the distances / 1 between two adjacent glass plates leads to an almost uniform periodic structure of the reflection behavior. In FIG. 3, this reflection behavior is plotted against the change in wavelength I /. applied. The reflectivity given on the ordinate is denoted by R. First of all: only consider the curve drawn in solid lines, which is at a distance / i, equal to a fourth! The distance between the reflection maxima depends on the optical thickness of the glass plates 1 and in the selected example is about 1.5 A. The maxima have a constant height over a relatively wide range of change in wavelength. Only a slight ripple can be detected in the transmission areas between the reflection peaks. The curve / I ₁ = ^ - yields for a given number k dci

glass plates used, in the present case k = 3 maximum height of the reflection peaks.

In general, the periodicity of the reflection behavior arises from the fact that the maximum peak reflectivity of a resonance reflector consisting of k glass plates with the refractive index / 1 is achieved for all such wavelengths! becomes, for which both the distance / i, between two

glass plates adjacent to one another and the optical thickness η · h _{2 of} a glass plate is equal to an odd multiple of a quarter of the wavelength A ₀ .

As can be shown, the maximum peak reflectivity R _{mux of} an optical periodic resonance reflector of the type underlying the present invention is given by the relationship

R = ί - ^ ΐ

^ly inux I j ι "2 Ii

given. This maximum peak reflectivity is therefore only dependent on the number of plates k and on the refractive index η of the plate material used.

As the diagram of FIG. 4 shows, in which the maximum peak reflectivity R _{imx is plotted} against the refractive index η , * o theoretically a resonance reflector with any peak reflectivity can be realized by suitable choice of the number of plates k and the refractive index η of the selected plate material. In practice, however, the situation looks much less favorable, since suitable types of glass, such as those required in particular for the use of the resonance reflector according to the invention in laser arrangements, are not available in a range of the refractive index η of 1 to 2. For example, as the diagram of FIG. 4 shows that a maximum peak reflectivity of 0.3 to be required requires a glass type whose refractive index is either less than 1.4 or greater than 1.8. However, the refractive index of suitable types of glass customary in the trade is in the range between 1.4 and 1.8.

Due to the teaching given according to the hamlet of the invention of the dimensioning of the distance between two adjacent plates different from a quarter of the wavelength / _{0 of} the coherent radiation or several odd multiples thereof, however, the peak reflectivity of a plate resonance reflector can be adjusted within wide limits without that here the almost uniform periodic structure of the tip reflection changes significantly. In the diagram of FIG. 5, the change in the peak reflectivity R, _{is plotted against the distance between two plates, based on a quarter of the wavelength A 0.} plotted for different refractive indices η of the types of glass used within the limits of 1.4 to 1.8, namely for a resonance reflector with a number of plates Zc = 3. B. shows the curve π = 1.5, the tip reflection R, _{p can be changed} in a ratio of 3.5: 1 _{when the distance Zi 1 changes} within the limits between - ^ and ^.

In the diagram of FIG. 3, in addition to the solid curve indicating the course of the reflectivity R over the change in wavelength for the case in which the distance Zi ₁ between two plates = ^ - is selected, the course for the case is also shown Zi ₁ = ^ (broken line) and the case Zi ₁ = || (dash-dotted line) indicated. The comparison of the curve Zi ₁ = j- with the curves

Zi, = γ and Zi ₁ = ^ l shows that in the example chosen, as the distance / i | below the value of a quarter of the wavelength A _{0 of} the coherent radiation, the maxima of the reflection peaks shift somewhat towards lower wavelengths, and the ripple in the intermediate areas to be addressed as transmission areas increases slightly. The character of the reflection structure is, however, retained in a desired manner with a continuously decreasing amplitude of the reflection _{peaks with decreasing distance Zi 1 with good approximation.} This also applies in particular to an amplitude of the equidistant reflection maxima that is constant over a wide range of wavelengths as a function of the change in wavelength IA.

For this purpose 4 sheets of drawings

Claims (3)

io 15 20 claims: 1. Optical resonance reflector with periodic characteristic door coherent radiation, consisting of two or more plane-parallel translucent plates, preferably glass plates which are assembled like a plate package while maintaining equal mutual distances, characterized in that with a thickness (A,) of the plates (1 ), which is much greater than the wavelength (/ ") of the coherent radiation, the optical length of the distance (Zi ₁ ) between two adjacent plates to a range within the limits of a fraction of a wavelength and a few wavelengths of the coherent radiation, with preferred values of a quarter of the wavelength or an odd multiple thereof. 2. Optical resonance reflector according to claim 1, characterized in that the optical length of the distance (Zj ₁ ) between two adjacent plates (1) of a quarter of the wavelength U ₀ ) of the coherent radiation or several odd multiples thereof different in the sense of a predetermined desired peak Zenreflectivity (R) is chosen. 3. Optical resonance reflector according to claim 2, characterized in that the optical length of the distance (Zi ₁ ) between two adjacent plates (1) is selected to be less than a quarter of the wavelength (X ₀ ) of the coherent radiation