DE1174903B - Light transmitter or amplifier for as monochromatic emission as possible by means of selective fluorescence - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Boarding school Kl .: H Ol r;

Number:
File number:
Registration date:
Display day:

H05b

German class: 2If-90

April 4, 1960

July 30, 1964

The invention relates to light amplification devices made according to similar aspects work as they do in a molecular amplifier or maser (Microwave Amplification by Stimulated Emission of Radiation) can be applied, and to various arrangements using such devices built-in included. In particular, the invention relates to the amplification of light by excited Photoemission from ions, atoms or molecules in gases, liquids or solids. In some embodiments of the invention, this is done in a "cavity" or other environment carried out, from where the light energy cannot escape freely, but prompts it to do so will increase its intensity. _

The light amplified in such a device is characterized by spatial or temporal coherence and is therefore emitted in phase and polarized.

To explain the essence of the invention, it seems appropriate to briefly refer to the basis of the invention underlying physical laws.

It is known that atoms, ions or molecules (for the sake of simplicity and in the following only the designation Molecule selected) usually in so-called "stationary" states with more or less exactness certain energy. In such a state, a molecule shows neither an electrical nor an magnetic moment. However, since a molecule is made up of charged particles, each one gets it vibrating electric or magnetic field in which it is disturbed. Such a disorder occurs a, then a molecule that was originally with certainty in the steady state "a" has a certain probability that it was hit with different energies in state "b" will. If it is in such a "mixed state," then it can be electrical or magnetic Have moment (i.e. it appears as a system of oscillating charges or charges in alternating tracks). A molecule will make a transition from state "a" to state "b" (i.e. it will have a greater probability of being in state "b"), when the induced electric or magnetic moment has almost the same frequency as that of the own electric or magnetic field oscillates, and if polarization and phases of the oscillations to match. The frequency of the oscillation moment is given by Einstein's equation:

AE = hv

Light transmitter or amplifier for as possible
monochromatic appearance by means of
selective fluorescence

Applicant:

TRG, Incorporated, Syosset, Long Island, N.Y.

(V. St. A.)

Representative:

Dr.-Ing. E. Liebau, patent attorney,
Göggingen via Augsburg,
Von-Eichendorff-Str. 10

Named as inventor:

Gordon Gould, Bronx, N.Y. (V. St. A.)

Claimed priority:

V. St. ν. America April 6, 1959 (804 539) -

given. Thereby means

ν = vibration frequency,
h = Planck's quantum of action,
AE = energy difference between two molecular states.

The same equation AE = h ν gives the energy of the photons associated with the electromagnetic field. The photon density is proportional to the energy density of the field. During a transition, a photon or "quantum" of electromagnetic energy is either emitted or absorbed by the field, depending on whether the molecule changes from a higher to a lower energy state or vice versa. But even if no radiation energy density with the correct frequency is directly observable in the molecule, spontaneous transitions from higher to lower states occur with simultaneous emission of photons. These transitions are actually caused by random fluctuations in the electromagnetic field of so-called "empty space".

The photons emitted during an induced transition are in phase with the excitation wave and have the same polarization, i. i.e., they are with

So you "coherent". A single atom can put photons in radiate in any direction. However, many atoms are distributed over a finite volume and send

409 638/164

3 4

coherent radiation, then they work together If the condition for the oscillation is not exact and form a wave whose speed of propagation is given, but energy from the outside into the cavity radiation vector with that of the excitation wave inside, then the excited or »highly certain scattering limits coincide . That is, they pumped “molecules to amplify the signal. Because by amplifying the excitation wave. The radiation of the 5 the output coupling energy loss occurs, is considered to be induced emission has a spectral distribution, condition for infinite amplification, at optimal which corresponds to that of the inducing radiation and output variable that
can exist in a very sharp line. _H

Spontaneously emitted photons have due to the Nj ₁ - N, ^>
Irregularity of the zero point fluctuations neither ok

fixed phase still polarization. Because the zero point is.

Fluctuations include all frequencies, which has this gain only adds to the amplified signal Spontaneously emitted radiation has a finite bandwidth, plus very little random noise. Of the the minimum noise level, which is at least characterized by a Lorentz line width, is characterized by thermal fluctuations is. 15 effects in the radiation field or by irregular

In the thermal equilibrium is the occupation spontaneous emission, with the proportion of the latter

determined by two states E ₂ (high) and E ₁ (low) which is always greater.

Boltzmann's distribution factor with each other in Various methods have been proposed,

Relationship. The band occupation ratio is an excess of the occupation of the higher of

give by the quotient of the occupation numbers N ₂ ao two molecular energy states of a gas, which

and N ₁ to be loaded in a resonance molecular amplifier cavity

pf egg ^ e ₁ hv finds maintain. An apprenticeship as a

? - e ^kT = t ^kT . beaten molecular amplifier achieves »the optical

¹ Pumping up «with the help of unpolarized light.

From this it follows that in equilibrium, the 35 The discussion of this kind of "optical elevation a state of higher energy is smaller "is supposed to be at the thermal baths of rubidium atoms than before that of the state of deeper energy. In particular are taken, but also applies accordingly to the occupation is different at ordinary temperatures. Light that for different spontaneous a state which is characteristic of transitions in Rb from the lowest energy state becomes in a 30 discharge lamp generated separately by excitation by means of optical frequency and ghost through a filter, practically zero. Send in under these conditions. This filter removes all frequencies except Guided transitions must be photons from the line component, the transitions from the F-8-l-Hy radiation field absorb. perfect state of the electronic basic state

The foregoing laws can induce any excellent higher electron design of a device for microwave amplification. Spontaneous decay back on both kung by excited radiation emission serve, the hyperfine ground states leads to a transition as molecular amplifier is called. Is changed by the Rb atoms from F = 1 to F - 2.
suitable precautions the occupation of a higher To maintain an excess of occupation in the F = 2 energy state greater than that of a lower energy state compared to F = 1, the optical state, then the induced transitions 40 "pump" speed, is solely necessary in the emission of photons in the speed of the extinguishing shocks, which is up to 10 per radiation field. As a result, a molecule can spontaneously decrease, exceed, emit a photon, which in turn triggers coherent Naturally this causes minimal "pump" speed emissions of neighboring molecules, which add a correspondingly small energy yield of the total radiant energy. Find 45 Molecular Enhancers.

the transition takes place at a microwave frequency. On the other hand, the light amplifier makes the

then the arrangement in a cavity resonance-negligible thermal occupation of higher

Tor the same frequency included and the Ent-electron states and the high speed

the photons are prevented. Is the spontaneous emissions produced by these states

Energy loss of the cavity is smaller than that emanating from the 50, a significantly higher "pump" speed

Molecules emitted energy, then the dizziness oscillates. Generally these close

System with a frequency whose fluctuation effects the operation of a light amplifier between

much smaller than the (Lorentz) range of a higher and a ground state.

Transition is. In general there must be a transition between two

The condition for the occurrence of an oscillation 55 higher electron states can be used

of the molecular enhancer in a gas is that the corresponding to the molecular enhancer for short

The mode of operation of the light-molecular-

. Amplifier based on the principle of induced more suitable

Nu - N _e > . _{a 2} transitions from a higher energy state in

ΐ, π ρ rQ _{6o e} j _nen lower energy state, its occupation

is when the gas fills the cavity. is less.

This means: This frequency range is used for the present

Fall through the limit of the permeability of the material

T = T ₁ = T ₂ relaxation time or states in the infrared and ultraviolet defined in

lifetime, 65 practice to approximate

Θ = quality factor of the cavity, _{t (VV} .,

ρ = electrical or magnetic oscillation ^{lü mm} > ^{λ> ltXX) A}

moment that marks the transition. 3 · 10 ¹² Hz <ν <3 · 10 ¹⁵ Hz.

5 6

Another limitation that becomes important in the distant ultra-high energy state, which becomes an electromagnetic violet, lies in the amount of energy, wave within a certain frequency range, which is spontaneously emitted by activated atoms. can amplify. The fact that this energy emission increases with v ⁴ and must be reached or exceeded by the desired property of amplification of an electrical or input energy. Beil = 1000 Å of the molecules with the higher energy state before an input energy of the order of magnitude must be assumed, but this known device requires 1 kilowatt. At this wavelength, the process is cumbersome and complicated. Expenditure on the necessary input energy to One was also already aware of the fact that large, in order to be meaningful. Otherwise, it is possible to excite the atoms, the much shorter wavelengths and higher ions or molecules in the manner of a fluorescence frequency of light with the useful properties of radiation in the same space, of the light amplifier qualitatively from those of the molecule from which the radiation to be generated emanates. The lar amplifier for shortwave different. The invention is based specifically on a known prior art. The above explanation has been given in relation to a device of this type, namely a light intensifier and amplification, but the transmitter or amplifier should be toned as monochrome as possible, that if sufficient Vertical radiation can be achieved by means of selective fluorescence, strengthening the light-amplifying effect in which atoms, ions and molecules can be converted into a "self-oscillating" device effect with photons or particles in the way by changing devices. Accordingly, one understands when stimulated that a short-term overcrowding includes "amplification" in a sense, the "oscillation" of a higher energy level in the selectively fluorescent medium. A controlled light amplifier can therefore be created, the excitation of which can also be used as a light transmitter. Atoms, ions or molecules in the form of a fluo-A form of the light amplifier, which takes place as resonance radiation in the same space, of the non-resonance form, can be described as 25 from which the radiation to be generated emanates, the transmitter can be used to generate light waves, which, in the case of the light transmitter, lie above the spontaneous stimuli of a narrow frequency bandwidth and form lating radiation, for which, to compensate for the thermodynamic imbalance, they are only supposed to have an extremely constant mean frequency. The light of such a transmitter, independent return to normal energy, especially when short-term frequency interference by division is decisive, whereas in the case of averaging over a finite period of time, the return to normal energy is effectively switched off by light amplifiers, represents a light frequency distribution by means of an externally acting to standard represent an accuracy that is triggered with the stimulating accuracy of any known frequency radiation matched to the energy jump, so that these stimulating standards can be compared. Obvious radiation is in any case largely monochromatic areas of application of such a light source and is coherently amplified, with the reaction, time measurement, frequency measurement and especially space of the selectively fluorescent medium, partly for distance measurement with the help of interference collecting optical energy, partly for training. standing waves between opposing reflective surfaces. The known device has somewhat different properties. The reaction space has somewhat different properties and can be used for different and very different elongated shapes with partially reflective forehead-like applications. It is characteristic and either completely or little or not of such a resonance light amplifier that reflective side walls. Due to the above-mentioned output variable in the form of a wave, the two parallel reflecting end faces should be approximately a plane wave if the input sharp focus of the output from the reaction space is also a plane wave. This means that the emerging light beam can be reached. The disadvantage is that the divergence of this wave can be very small, but that light rays that are not exactly perpendicular so that the energy of the wave essentially run within a very small solid angle of the magnitude 50 within the two parallel end-face reflection surfaces by the side walls of the reaction order of 10 ~ ⁸ or even less is included. lost space.

The corresponding device has its own The invention has the task of this ability to amplify light coherently, at least to eliminate it at a disadvantage. To this end is in accordance with with respect to frequency, phase and in some cases of the invention the preferably hollow one also with respect to the direction of propagation and 55 reaction space only partially with reflective Polarization axis. For the development of such a device, the radiation is an inwardly converging Rezu notice that flexion was found a long time ago, this reaction space being closed that the current in a discharge has at least one exit window for the stimulated beam lamp has been influenced from outside by irradiation with light. One has the advantage here that can be flowed. Furthermore, one has a Vorrich- because of this special surface design of the device created in which ammonia molecules in the reaction space or the reflective layers can easily introduce stimulating light to an electric field in a limited space. It is there be subjected in such a way that a segregation is also favorable that in the manner mentioned of those molecules with the higher energy state 65 arranged by reflective surfaces those molecules with the lower passing light at premature exit from the Energy state results. In this way one obtains the chamber and preserves it, so to speak. In a Set of molecules with relative consequences is also the correct alignment of the

opposing parallel mirror surfaces less critical than in the known known Construction.

The device according to the invention is suitable for emitting an almost flat wave as an output variable. Accordingly, the device is also suitable for communication systems in which the output light energy is concentrated within a very small solid angle. The output beam of such a The wall 17 of the hollow body 11 is provided with a reflective coating 20. This surface can either from a specular reflector, such as. B. polished metal, or a diffuse reflector exist. For visible light, the best reflection is with a diffuse reflector, such as z. B. magnesium oxide powder achieved.

Generally, therefore, such a reflective surface is used as a reflective coating 20

powerful transmission system only needs io turns. A gas atmosphere inside the hollow

an information to be transmitted is modulated and received and demodulated by a receiver operating by a conventional photoelectric or other suitable method. Except the mentioned arrangements, there are other possible applications, such. B. TV projection, Short-term photography, precision measurements of lengths and speeds, lighting, control systems for various plants, production of X-rays etc.

Further details and advantages of the invention emerge from the following description some embodiments with reference to the drawings. Herein shows

F i g. 1 shows a partially schematically illustrated cross section of a non-resonance light amplifier which is arranged so that it is excited by an external light source,

F i g. 2 a diagram of the energy states of the space 16 can be obtained from a storage vessel 18 which is via a pipe 19 is connected to the cavity.

A heating coil 21, which is controlled by a temperature controller 22, can be used to maintain of the desired vapor pressure inside the cavity can be used. A temperature control furnace 23, which can surround the cavity 11, serves to raise the temperature of the cavity to a higher value than that of the storage vessel 18 in order to prevent condensation in the cavity 11 and pressure control by means of a temperature controller 22 regardless of the temperature change to secure the environment of the hollow body.

Light emanates from a light source 24 serving for excitation and passes through the window 15 in the inside of the cavity 11.

In a specific example, the light source 24 consists of a gas discharge lamp, the filling gas of which

Sodium, which for an understanding of the invention 30 has a similar composition as the atmospheric light intensifiers is shown, sphere in the interior 16 of the cavity 11.

F i g. 3 shows a partially schematic, albeit solid or liquid fluorescent substance

Cross-section of a resonance light amplifier which, for certain purposes, is better than a gas-incoherent one Light is excited and with an optically shaped medium in the cavity 11 of FIG. Be 1 If flat, parallel mirrors can be used as reflective surfaces, the processes in gases are more complete

researched, and for the explanation of the invention this more easily surveyable form of training is primarily used used.

is permitted

F i g. 4 a diagram of the energy states of the iodine molecule, which is used to understand an education of the subject matter of the invention is shown, in which the coincidence of spectral lines to excite a Working medium is used in a light amplifier,

F i g. 5 shows a diagram of the energy states of ionized europium Eu ⁺ ++, which is used in one embodiment of the subject matter of the invention with a non-gaseous working medium.

How a light amplifier works without geometric resonance

Light amplifier without due to the geometric dimensions of the reaction space

Cavity Resonance The operation of the light amplifier of FIG. 1 is intended first with reference to a relatively simple form of excitation, namely excitation by Resonance radiation can be explained. It should be noted, however, that other forms of excitation occur which will be discussed below, are preferred to the simpler resonance radiation in many cases.

Sodium vapor provides a good example of this type of excitation. It is therefore supposed to be adopted for explanation be that the interior 16 of the cavity is filled with sodium vapor and the excitation The light source 24 used is a sodium vapor lamp. F i g. 2 shows a diagram of some higher ones Electronic states of sodium without the hyperfine structures.

The vacuum wavelengths emitted during transitions between certain pairs of states

55

F i g. Fig. 1 shows a spherical cavity 11, the main part of the non-resonance light amplifier. Even though In the case of a hollow sphere, the ratio of volume to surface area is optimal, the hollow space can be made from cylindrical, rectilinear, or any other desired shape. In the cavity 11 are Openings 12 and 13 are provided for the output and input of the light used for excitation.

Suitable windows 14 and 15 close the openings and 60 electromagnetic radiation are shown in the diagram of FIG gen 12 and 13 and consist of material with a F i g. 2 drawn. Also are the measured

or estimated rates of spontaneous emission of these transitions. Selection rules of the electric dipole radiation only allow transitions between states in adjacent ones Rows of the diagram. Therefore, there are no transitions between states with the same letter designation (same orbital angular momentum). Atoms in

high transmission coefficient for the frequency range of the light in question, as is e.g. B. Glass or the like.

The interior 16 of the cavity 11 is in the exemplary embodiment with an excited working medium filled. The type and mode of action of this working medium are discussed in detail below.

9 10

Ground state (3 ² S _1/2 ) can be mutually opposite due to resonance parts of the hollow body

radiation from a sodium lamp only applies to the various places on the surface of the amplifier housing,

which P-states are excited. Will take up a considerable part of the total area of the

First of all, the aim is to have a stronger occupation of the hollow body from the window surface for light stimulation

any higher state compared to a lower 5 is required, one can preferably use the amplifier

To achieve state. ' The transitions to the deeper one have a different shape, e.g. B. give a cylindrical shape.

State can be caused by the presence of light- This form can in so far be particularly suitable

energy of a suitable frequency are excited. Are considered to be the curved parts of the set

the case that only the 6 ² P-states directly from the cylindrical surface for the initiation of the

Ground state are excitable, then can be permeable by io excitation light while

suitable optical filters all light, the other at the same time made the cylinder ends diffusely reflective

States would encourage to be fed away. Can be on it. With such an arrangement can

through spontaneous emission, a large amount of light energy is conveniently introduced into the

deeper states occupied to a certain extent. Cavity are transferred. It is true that a

The occupation in dynamic equilibrium can reduce the mean effective 15 to a certain extent

However, reflection coefficients can be connected from the speed of the spontaneous transitions

be calculated. this, as other considerations show, can be remedied.

Assuming that the 6 ² P-states have a non-unit occupation of the cylindrical non-unit occupation described above, the occupations of the resonance amplifiers are designed in a longitudinal form, then other lower states are calculated and from the 2 ° only light can be within a narrow angle diagram refer to. For example, the range of the direction of propagation is to be reinforced. Occupation of the 4 ² S _1/2 state only 0.0067 of that of the This means that the noise level is caused by the spontaneous 6 ² P state. Therefore, in a suitable emission can be reduced and a narrower bandwidth of the space transitions that the 8660 Å infrared lines output size achieved. The output of a produce to be expected. 25 elongated cylindrical non-resonance amplifiers

From the diagram of FIG. 2 and what has been said kers can largely be limited to an angle of magnitude that is limited by the excitation of the medium in orderly approximately 6 °. This the cavity 1.1. with the light of the light source 24 is much cheaper and can be considerably more effective (wavelength 2680 Å) a condition created for it to be aligned more closely than the diffuse output is that the occupation of a higher energy state 30 size of a spherical amplifier or transmitter. (6 ² P) is much greater than that of a deeper state The occurrence of resonance phenomena can (4 ² S _1/2 ), so that the irradiation of stimulating at the non-resonance light amplifier in the form of a light of a frequency equal to the difference between these elongated cylinders be avoided by the fact that both energy states correspond (wavelength the light paths between the reflectors completely different), a transition from the higher energy 35 have different lengths. If necessary, the state can stimulate the lower energy state, the shape of the reflectors can be chosen so that they are emitted with the light of this same frequency amplified difference of the optical light paths between the. Reflectors is still enlarged.

Accordingly, if the pumping except sodium can also be used for the production

speed by the excitation of the light source 24 40 of a non-resonance amplifier various others

is so great that there is a great difference in the cast elements used, especially the elements

between these two states, in favor of the I. and III. Group of the periodic table,

of the higher state is maintained and However, the properties of sodium are that

when the losses in the cavity due to reaching other elements are particularly favorable.

Achieving a maximum reflectivity of the 45 _light amplifiers without geometric resonance

flat 20 can be made sufficiently small that the bedm- ⁶

conditions for an undamped oscillation. The above-described light amplifier of the

are, the arrangement of the F i g. 2 as a non-resonant F i g. 1 is referred to as a non-resonance light amplifier.

Light transmitter works. net, since the frequency of the light output is relative

Obviously, in the event that the Schwin 50 is constant, but essentially independent of the

conditions is only approximate, but not exactly the dimensions of the cavity in which the vibration

present, the light of the corresponding frequency generation is generated.

(8660 Å), which is radiated into the cavity, by the following is another embodiment

amplifies the excited radiation emission, and described that of a light amplifier in which the »Reso-

The output variable of the cavity is to a large extent for this frequency 55 nance frequency «of the arrangement

be larger than the input variable and thus one of the dimensions of the cavity is dependent. Of the

Amplification can be achieved, however, no resonance amplifiers will also have others

self-excited vibrations occur. significant differences, but the reso-

The non-resonance light amplifier of FIG. 1, the display property is shown as an essential feature of the sub-schematic with a relatively small window to distinguish it from the previously described non-introduction of the excitation light. Used in real-resonance light amplifiers,
In general, it will be advantageous to have a _T. , ..,. ..,. ,. ,
essential part of the surface of the hollow body as a light amplifier with additional geometric
To use windows for light stimulation. Thereby resonance by means of a mirror arrangement
however, requires an enlargement of the window area 65 F i g. 3 shows a light resonance amplifier, a reduction of the available for reflection standing out of a cavity 101 with a radiation surface. The effective reflection coefficient can be made of transmissive sidewalls, which can be made relatively large at its ends by adding reflective flat mirrors 102 and 103 to completion.

Il

The interior 104 of the hollow body 101 is with an excited working medium, such as. B. sodium vapor filled. A hollow cylindrical discharge lamp 105 runs concentrically around the hollow body 101. The surface 106 can be provided with a reflective coating in order to be able to fully utilize the light, while the inner wall 107 of the discharge lamp 105 is permeable to the desired line of the light generated in the discharge lamp.

Electrodes 108 in discharge lamp 105 are supplied with voltage from an energy source 109 via supply lines 111.

In the case of the in FIG. 3, the gas discharge lamp 105 is also filled with sodium.

Storage vessels, ovens and other aids for maintaining suitable gas conditions in the discharge lamp 105 and the hollow body 101 are omitted from the drawing for the sake of simplicity. These tools for the in F i g. Apparatus shown in FIG. 3 may be the same as shown in the other drawings or may consist of any other suitable means of maintaining a suitable atmosphere.

How the resonance light amplifier works

As already mentioned, the induced emission of the atoms is coherent with the excitation radiation, i.e. h., they is in phase and has the same frequency and polarization. Emit many atoms in the area the exciting wave, then the emitted radiation also consists of an essentially flat one Wave with the same propagation vector with the exception of very small diffraction effects. From this it follows that the resonance light amplifier of the F i g. 3 despite its in comparison with the entire inner surface only small reflective surfaces effectively limit the amplification process due to the fact that now light energy within a very narrow frequency range and angular range to the direction of propagation is amplified, and that this energy has a vector of reproduction in such a Direction has that it is contained substantially between the two reflective surfaces.

There are low energy losses at the edge of the reflectors, those from small angular deviations to the direction of propagation of the rays to be amplified. However, this loss of energy is too insignificant than that it could prevent proper functioning in a well-trained device. Within its frequency and angle limitations imposed by the dimensions and the loss coefficient are given due to the reflection, the resonance light amplifier amplifies plane waves in a continuously variable manner in direction and frequency.

If the input shaft is flat, the output shaft is almost flat. The finite extent of a wavelength causes the wavefront to spread during its propagation. At a great distance from a circular end plate takes the wavefront, instead of a circle of constant diameter, the shape of the intensity distribution of Fraunhofer diffraction.

In this diffraction pattern, approximately 98% of the light falls in a cone of half the solid angle and more than half of the light lies within a cone of half the solid angle ¹ I ₂ Ad. If the wave is focused on a nearby plane, one observes the same diffraction image instead of a point. The Rayleigh equation for the angular resolution of two plane waves that are focused in a telescope states that they form an angle with one another which is equal to ΔΘ . This means that the maximum of one wave is reduced to the first minimum of the

ίο the diffraction pattern of the other wave falls. Hence can plane waves emanating from different places on a distant object are coherent amplified with the help of the resonance light amplifier and then on a screen or a front panel a TV camera tube to be focused. The resulting image can then be scanned or otherwise be used.

If a plane wave passes through a circular opening, the wave begins for a short time

ao spread out behind the opening and forms a diffraction pattern according to Fresnel.

When a "plane" wave reflects back and forth inside the tube, light escapes through it cylindrical space between the two reflectors.

as The proportion of light loss when passing through a

Distance / = is approximately given by

= Share of loss

(L XY (2Rf

where L is the traversing distance between the reflectors and R is the effective reflector radius.

Go uiff. - * ■ 1, then the effective loss due to reflection is greatly increased. This sets a lower limit for the radius of the reflector.
is

L = 100 cm,

λ = 5- ICh ⁵ Cm = 5000A,

2 rows = 1 cm,

then Φ mg. ^ 0.001. This means that the loss fraction is less than the absorption loss.

A typical absorption coefficient is a = 0.01.

The mirrors 102 and 103 can be either metallized or multi-layer interference reflectors. The latter are almost loss-free (ie the transmission component plus the reflection component result in almost 100%). Interference reflectors can have a very high reflectivity for a given wavelength. This depends on the number of layers present. In practice, 98% is achieved in the visible range with a six-layer reflector. Flat surfaces with a tolerance smaller than approximately V ₅₀ A are not commonly available, so that in the event that no better surfaces are available, an even better reflectivity is not necessary in a resonance system. Another advantage of the interference reflectors is that photons that originate from a transition other than the intended one are not reflected (a consequence of the frequency selection), and thus undesired ones are excited

Ö5 transitions held.

From FIG. 3 it is clear that a plane wave which is perpendicular to the mirror surface divergent direction propagates through the

Boundary leaks and its energy faster than that normal wave loses. The spatial shift per reflection is:

χ = L sin Θ m L Θ.

The energy loss for each reflection is approximate

χ ΣΘ

2R 2R

The effective loss coefficient due to reflection is thus

If the bandwidth Af is limited in a subsequent electronic amplifier, then it can be shown that the following expression for the noise

-AvAf

TC

AvAf

Λ - dabs + diff. H

ΣΘ

or the energy loss component is given by

E at

2R

if χ increases , then the gain of the light amplifier decreases, proportionally in the range of the linear gain.

As a practical measure for a critical angle for which there is still effective reinforcement, the angle given is for which = 2ocai, _s .

30th

2R L

2aR

Θ, =

35

The maximum can be reached if 6> ₂ ~ 0.10 angular units; for the sizes listed above, Θ is ₂ ^ 5 · 10 ~ ⁴ angular units.

The fact that the loss coefficient decreases with increasing angle Θ determines the most important property for the resonance light oscillator output variable, namely a very limited beam.

One can calculate that in the ideal case 0 = 0 the entire emerging beam falls into the Fraunhofer diffraction pattern. It can also be shown that with P _out = 1 watt at λ - 1 μ the frequency bandwidth of the output beam will be less than 100 Hz. This remaining bandwidth is based on the noise floor that has yet to be dealt with.

As already emphasized, corresponding to the due to the random field fluctuations as a base existing spontaneous emissions in the visible area transitions, which are induced by thermal radiation at a temperature of 30000 K ^0. However, this is not as high as it initially appears, since a resonance light amplifier has a possibility of separating from all signals that lie outside an optical band and from all directions of propagation that lie outside the Fraunhofer cone. One can estimate that the input noise corresponding to the minimum in a Fraunhofer cone is given by

Pmin «a 1.5 x 10 ¹¹ watts

in the visible area.

is.

So the minimum of the noise depends on the square root of the bandwidth, but not on the area of the reflectors 102, 103 at the pipe ends. The in FIG. The device shown in FIG. 3 can be used as an amplifier, which differs from a self-excitable transmitter, if the gain is limited. This is achieved in that the proportion of the light energy which is introduced by the discharge lamp 105 remains limited, so that no self-excitation oscillations are generated. A signal can therefore enter through the mirror 103, as indicated in the drawing by the arrow 112 , since the mirrors 103 and 102 are partially transparent.

The light beam, denoted by 112, causes stimulated emission of light energy in the hollow body 101, which is coherent with the input signal with regard to its phase, frequency and direction of propagation. The amplification within the cavity is largely selective with regard to the direction of propagation and frequency, so that only a relatively narrow area exists in which the input signal is amplified in the device.

The light output of the light amplifier passes through the mirrors 103 and 102, as indicated by the arrows 113 and 115. Either or both outputs can be used, depending on the particular application or system in which the light amplifier is used.

As in the light amplifier discussed above, the one shown in FIG. 3 can be used as a transmitter arrangement. All that is necessary is to increase the effectiveness of the process or the gain of the amplifier to the point at which self-excited vibrations are generated. In some areas of application it may be desirable to use the same device both as a transmitter and as an amplifier, for example alternating over time. This can be achieved in that, for example, the light energy generated in the discharge lamp 105 increases periodically in order to generate brief, self-exciting oscillations. Of course, the optical system can be replaced by other optical systems, and other excitation processes than those in FIG. 3 can be used.

Since that is shown in FIG. 3 does not differ significantly from the previously described cylindrical non-resonance amplifier, the resonance amplifier according to FIG. 3 can be converted into a non-resonance amplifier by installing diffuse reflectors in place of mirrors 102 and 103 .

Excitation through overlapping spectral lines

So far, the excitation of atoms by resonance radiation has been dealt with.

The spectral lines emitted by a lamp necessarily overlap with frequencies that are strongly are absorbed by like atoms in a light amplifier. However, as with the Treatment of the excitation of sodium was mentioned during the intensities of the lamp of the decay of higher states, lines emitted spontaneously are very weak. One way, one strong To obtain excitation for higher electron states, there is a random overlap of bright emission ίο lines of another atom.

The coincidence probability of two suitable atomic lines is small. Within the visible and in the near ultraviolet area there is space for about three hundred thousand spectral lines of Doppler width, there is only a slight overlap. There are at most a thousand useful resonance transitions suitable atoms and approximately thirty bright atomic lines to excite them. With that lies the Probability of a good coincidence around 10% · At least three are moderately close overlaps known.

Overlapping atomic spectral lines

H ₆ (3 P ³ -> 2 ³ S) 3889 Ä * Cs (8 P ³ _3/2 - 6 ³ S _{l / 2)} 3889 Ä Zn 3303JÄ "* Na (P 4 ² _1/2 ~ 3 ² ₁ S , *) 3303 Ä

A 8521.4 Ä ^ Cs (6 ² P _3/2 - 6 ² S _{l / 2} ) 8521.2 Ä

35

But in none of the cases is the overlap so good that a high excitation effect is achieved. On the other hand, numerous examples of excitation of molecules by neighboring atomic lines have been observed been.

There are few reports of fluorescence from

Molecules with more than 2 atoms. Therefore only the diatomic molecules will be considered here.

Every electron state of a 2-atom molecule

is split into about fifty vibrations. 30 Torr pressure absorbs the greater part of the sodium states and each vibrational state turns into
nearly two hundred rotational states.

Therefore, on average, one can see more than a hundred thousand absorption transitions from occupied states expect in every molecule.

As expected, there is generally at least one bright atomic spectral line match with any resonance transition of a molecule present. For the same reason, the emission is one Discharge in a molecular gas divided into many faint lines. In general, these cannot be excited from the outside by a lamp.

Materials that are transparent to ultraviolet radiation below 2000 Å are not available. Therefore the above-described light amplification process cannot be used; h, the suggestion from a high electron state by means of the emission of the light amplifier to an intermediate state, whose occupation is kept low is due to rapid spontaneous disintegration into one Basic state not possible. On the other hand, there is a different mechanism due to the properties of the molecules required and also possible so that the occupation of the lower state is less than the occupation of a higher state can be maintained. This mechanism consists in the cancellation of the occupation of the deep states due to shocks.

To illustrate this process, _{consider the molecule J 2} (see Fig. 4).

The first line of the main sodium series at 5893 Å coincides with one of the numerous absorption lines of the iodine molecule. The transition in question runs from a rotational sub -state of the ν = 2 vibrational state of the electronic ground state [Eg)

of the [Eg j states are well populated in thermal equilibrium at room temperature (see lower right-hand part of FIG. 4), while ν = 7 of the [Eg ) state has less than 1% of the population

and ν = 17 of the (3 πο) -state is completely empty.

A 1 cm thick layer of I ₂ vapor on some: the greater part of the sodium light and lifts the I ₂ molecules into the higher state at one speed

available at _ P

at ~~ Tv '

where Pavailable is the intensity of an external lamp that excites the medium.

In the absence of light amplification, the atoms decay at one rate

d «= tih [γc + EA (all other states)] where

EA = spontaneous rate of radiation decay, Yc = rate of decrease due to extinguishing collisions with other Jj molecules (extinguishing collisions).

The cross-section for these collisions is very large, since many J ₂ states are energetically close together. About 5% of the molecules decay after ν = 7 of the [Eg ) state.

Following the same disintegration process, the rates of change in occupation are the higher or lower energy levels in dynamic equilibrium

45

55 German

dm
"dT

available

Ti

- «A (ye + ΣA),

and

«A =

^ available

to the sub -state ν = 17 of the (s ^ oj-state of the iodine molecule J = 30. The ν - 2

It should be emphasized that the atoms of ν = 7 of the) -state only through collisions with extinguishing after others

Sub-states of the electronic ground state can be brought. Because when the J ₂ vapor pressure (5 Torr) is such that

on the other hand, the required illumination intensity Iavailable for an externally excited resonance light amplifier increases.

aR - hvlA

Σι A _h f * t 20 A Qi -> /) * v 107 see,

20> 1,

then
rih
m

and that is necessary for light amplification.

The further analysis largely corresponds to that for the light amplification transition of Na (6P -> 4S).

The values included are not very different, as is the case with a light amplification tube 1 cm in diameter and 100 cm in length, the required Na (5893 Å) intensity of the tube enveloping discharge lamp.

/> ΙΟ- ³ watt / cm ² solid angle,

where the solid angle starting from a plane is 2π . As already said, the intensity of the first line of the main series of sodium can easily be greater than 0.1 watt per square centimeter of solid angle, saving a factor of 100.

From the above explanation it can be seen that although a light amplifier according to the invention thereby Can be constructed that the light energy of a substance to excite another substance with an adjacent spectral line is used, the known combinations of monoatomic substances obvious coincidences are not promising.

On the other hand, they enable a large degree of correspondence between an atomic line and a resonance transition of a molecule very often has a high degree of correspondence that is suitable as To find excitation process in a light amplifier according to the invention application.

An example of such an overlap, which can be used as an excitation process, is the overlap of the first line of the main series of sodium at λ s >> 5893 Å with one of the absorption lines of the iodine molecule.

The construction of a light amplifier based on this excitation principle is essentially similar to the already described except for the difference that the excitation lamp is a sodium discharge lamp while iodine vapor is used as the working medium in the hollow body.

Liquid or solid working substances

The line width A ν of radiation transitions from ions, atoms or molecules in liquids or solids is generally quite wide because of the constant strong interaction with neighboring atoms. The continuous live life is

π Av

2 ■ ΙΟ- ¹³ sec

in a special case, while the time of the spontaneous radiation decay is long: T ₁ > 10 ~ ⁸ see.

The success is that the density of excited atoms, ions, etc., which are required for the oscillation of the light amplifier, increases. This his- 'available-

where L is the mean distance between the reflectors for the special case of a spherical cavity. The line factor / (v ₀ ) measures the ease of initiation of the transition for a fluorescence line of width Av.
The line factor is

/ (V ₀ ) =

π Δ ν

for a Lorentz line and is approximately the same for other lines. The most densely packed systems require high energy input to stimulate light amplification.

Another difficulty is that the excitations in solids or liquids in general can be deleted by "non-radiating" processes. Accordingly, one should use substances which fluoresce with a high quantum yield. Some substances that have the high-energy Na (5893 Ä) line absorb and fluoresce effectively are merveyamine colors, fluorescein, meld or blue and rhodamine "B". Certain substances in which the electrons that participate in the excitation are in are better inner electron shells of the atoms or ions in question and oppose external interference are shielded. Such substances, e.g. B. Porphyrins, rubies and rare earths, have essential narrower lines.

The use of polycrystalline solids has refraction and reflection of a light wave at the Crystal interfaces result in the lossless repeated reflection of a wave between the Amplifier reflectors prevented. To avoid this, one could use a ruby single crystal.

The induced by the use of solids and liquids as a working medium difficulties can be alleviated by the use of, for example, ions of the rare-earth Eu ⁺ ++ in a liquid solution. The sub-states of the torque of the first two electron states are shown in FIG. 5 shown.

The J sub-states are split into further states, and a component of the J '= 0 -> J "= 1 transition covers the Na-5893-line. The higher J-states go quickly into the two deepest J- States (y sa 1.5 · 10 ¹² / sec) by deletion over, but transitions between the higher and lower electron states occur only with radiation emission at the slow "forbidden" speed} / sa 10 ³ / sec in the case of europium sulfate in water .

The ions can be excited by the radiation of sodium in J '= 0 and decay according to one of the J "states. The two strongest fluorescence transitions at X = 8110 Å and 6881 Å are suitable for a light amplifier with a liquid working medium.

The J-cancellation interaction causes a line width of Av ^ S- 10 ¹¹ Hz or Al & 6 Å. The line width is much smaller than that of other condensate

■ ^ 409 638/164

ized fluorescent substances, but very broad compared to the spectral lines of atoms when discharged under low pressure (Δλ ^ 0.01 Å). Therefore, one can artificially increase the energy of the Na discharge lamp in order to obtain the necessary energy without having to worry about changing the line width.

The required illumination intensity is given by the above equation _ver fügbar I and is between 0.1 and 1.0 watts per centimeter solid angle.

A commercial lamp with broadened and inverted sodium lines emits just with this Intensity.

If, for special purposes, a compressed working medium, such as. B. a liquid is to be used, such a working substance can be placed in a hollow body according to FIG. 3 used will. An example of such a working substance is europium sulfate in water. The excitation can be by means of a sodium discharge lamp, similar to one of the commercially available types a broadening of the sodium line occurs and that with an intensity between 0.1 and 1.0 watts each Square centimeter solid angle shines.

It should be emphasized that the discussed conditions forms of stimulation such as B. by resonance radiation etc. in general both in non-resonance as can also be used with resonance light amplifiers. The same also applies to the working media mentioned.

Claims (7)

30 claims: 1. Light transmitter or amplifier for as monochromatic radiation as possible by means of selective fluorescence, in which atoms, ions and molecules are excited by interaction with photons or particles in such a way that a brief translation of higher energy levels occurs in the selectively fluorescent medium, with the excitation of the Atoms, ions or molecules in the manner of fluorescent radiation takes place in the same space from which the radiation to be generated emanates, which in the case of the light transmitter is formed via the spontaneous stimulating radiation, for which only the independent return into one to compensate for the thermodynamic imbalance normal power distribution is essential, whereas in the case of the optical amplifier back to the normal energy distribution by means of a force acting from the outside, to the energy gap tuned stimulating radiation is initiated, so that this stimulating radiation in any case, far-i continuously monochromatisc h and is coherently amplified, the reaction space of the selectively fluorescent medium being used partly to collect optical energy and partly to form standing waves between opposing reflective surfaces, characterized in that the preferably hollow reaction chamber is only partially provided with reflective surfaces (11) which result in an inwardly converging reflection for the purpose of combining the radiation, this reaction space having at least one exit window (14) for the stimulated radiation. 2. Light transmitter or amplifier according to claim 1, characterized in that the reaction space is limited by a concave spherical surface (11) surrounding it, the at least one outlet opening (14) for the stimulated radiation and preferably a separate inlet opening (15) for the stimulating Owns light. 3. Light transmitter or amplifier according to claim 1 or 2, characterized in that the selective fluorescent medium contains rare earth ions. 4. light transmitter or amplifier according to claim 2, characterized in that as a rare earth Europium is used. 5. Light transmitter or amplifier according to one of claims 1 and 2, characterized in that a molecular gas is used as the selectively fluorescent medium and the excitation light radiated into the reaction chamber comes from a gas discharge lamp (24, 105) which contains monatomic vapor. 6. Light transmitter or amplifier according to claim 1 or 2, characterized in that the selective The fluorescent medium of the reaction space is a ruby crystal. 7. Light transmitter and amplifier according to claim 4, characterized in that the selectively fluorescent medium in the reaction chamber consists of a solution containing europium, the excitation light radiated into the reaction chamber originating from a discharge lamp (24, 105) containing sodium vapor. Considered publications: Austrian Patent No. 132 192; U.S. Patent No. 2,851,652; Journal of Applied Physics, Vol. 10, 1958, .480 to 488; Physical Review, Vol. 112, No. 6 of December 15, 1958,. 1940 to 1949. 1 sheet of drawings 409 638/164 7.64 © Bundesdruckerei Berlin