DE1514087C - Optical transmitter - Google Patents

Description

1 2

The invention relates to an optical medium 10 shown. Which is surrounded by a helical transmitter with control of the quality factor of its optical discharge flash lamp 11, which is made up of a resonator (β-circuit), in which a suitable energy source 12 is fed in dependent. The light emanating from the end mirror 13 limiting the stimulable medium, the optical resonator within the optical resonator 5 and 14 are used for feedback of the optical sensor arranged absorber can be bleached, which can be bleached in the case of the embodiment shown here, interruption of the incident light In the im these mirrors are 100% or 85% reflective, essentially opaque state in reverse Storage of a higher amount of energy in the stimu- io chemical substance 16 is included. In the case of this lubricatable medium, the time delay is required when the chemical substance is active. 16 for example from a reversibly bleachable. Such an optical transmitter is already known organic dye, such as kryptocyanine dissolved in methyl alcohol (cf. IBM Journal of Research and Development. The concentration of crypto-Vol. 8, No. 2, April 1964 , Pp. 182 to 184). With the 15 eyanins, in the range of 10 ¹⁵ moles known optical transmitters, phthalocyanine molecules per cm ^{3 of} methyl alcohol in a cell with 1 cm molecules in solution are used as absorbers. Be phthalic length.

cyanine colors, however, in the excited state. In this embodiment, the stimu-

a relatively long lifespan, which is why lable medium 10 made of a ruby crystal from

the Q-circuit when using such an ab- 20 about 10 cm in length and about 9.5 mm in diameter,

sorbers takes place comparatively slowly. doped with 0.05 percent by weight chromium. By

The invention is based on the object of defining a certain wavelength of the stimulated emission ^{in Cr 3+}

an optical transmitter of the type mentioned sion B of this optical transmitter is 6943 Å; at

a particularly fast control of the quality - this wavelength is offered by the cryptocyanine

factor of its optical resonator to enable 25 large absorption cross-section. The cell is

and in this way a short-term laser - thus practically dark or opaque and

radiation impulse (giant impulse) of very special- prevents any stimulated emission in the optimal

This high energy content to enable the two resonators during the initial excitation

for example, is suitable for distance measurement. of the stimulable medium.

According to the invention, this object is achieved by 30 If the light control cell 15 is not present, that the absorber from a reversible bleach gives a threshold of about 900 joules a bar solution of cryptocyanine with one for the coherent radiance. When arranging the light wavelength the stimulated emission high Ab control cell in the optical resonator is an absorption cross section consists. output energy of about 3000 joules is required

35 Giant laser pulses of around 20 MW peak

dissolved cryptocyanine is used as an absorber. to generate power.

Kryptocyanin has a particularly short The way in which the light control cell "recovery time", which is an extraordinarily short 15 from FIG. 1, delays the triggering until a duration of the switching process is possible. With another exceptionally high amount of energy in the stimu-words: the fallback time for the excited mole- 40 lable medium is pent up, and the kind and küle in their original inert state, ie the way in which this energy is then released from the translucent in the opaque can be seen on the basis of FIG. 2 understand even better, gen state, is extremely short. It is in FIG. 2 shows a graph, the order of which is, for example, in the order of magnitude of 10 ~ ¹⁰ s. Nate 17 qualitatively the measure of the light transmission This switching time is at least one full size or transparency of the organic color in the order more favorable compared to the solution cell 15 of FIG. 1 and its lower, dashed phthalcyanine molecules of the known abscissa 18 the measure of the luminous flux of a light-optical transmitter. source illustrates that linear and separate from

The consequence of this is that a short-term laser- the laser from FIG. 1 can be varied. The GE-

Radiation pulse of exceptionally high energy 50 dashed curve 19 is with reference to the ordinate 17

Energy content can be brought about, the at- and the abscissa 18 drawn and illustrated

For example, to measure the distance in a radar, qualitatively the degree of permeability of the cell 15

system in which the laser energy is harnessed according to an evenly distributed from zero to

is usable with very good success. a maximum value of changing luminous flux.

In addition, cryptocyanine also has particularly good 55 As shown, the light transmission of the

Solubility properties compared to phthalic cells are initially greater when the

cyanine. A cryptocyanine solution is more stable and molecules are borne by the incident light.

therefore, in this respect too, it is more advantageous than phthalate stimulation. The speed of change in

cyanine solutions. Light transmission over time is initially relative

In the following the invention with reference to the 60 slowly and then increases, so that an approximately

Drawing explained in more detail, for example. S-shaped curve that follows the state of the

Fig. 1 shows a very schematic representation of light transmission running asymptotically,
a giant pulse laser with a Lichtsteucrein- The abscissa 20 represents the time and the full direction according to the invention; plotted curve the change in transmittance

Fig. 2 shows a qualitative representation of the character 65 of the cell 15 when installed in the giant pulse laser

Characteristic of the light control device for explaining the system shown in FIG. 1. In this case, the

the operation of the establishment of Fig. 1. Light intensity not increased evenly; much more

In Fig. 1 a crystal is located as a stimulable measurement when the optical excitation is a

Reversal of settlement in the stimulable medium 10 causes practically no light in the optical resonator. Thus, the cell remains practically dark or opaque, as was the case with the initial one horizontal part 21 of the fully distinguished curve is indicated. It can have a low level of opacity be present, creating a slight incline of the line 21 towards the permeability is effected.

At a given time T1, when a considerable amount of energy is absorbed by the stimulable medium, a first release of coherent quanta is initiated. The cell 21 is not so opaque that some feedback between the end mirrors 13 and 14 cannot take place. This feedback increases any small amount of light incident from the cell 15 considerably, with the result that a rapid excitation and saturation of the absorber molecules of the cell to a second energy level takes place. When this second energy level experiences an increase in occupancy, the cell becomes more transparent, and this increased transparency immediately allows an increased release of the energy stored in the stimulable medium, so that this leads to a further bleaching of the absorber and a further increase in the incident light. The combination of cell and stimulable medium thus has the character of a feedback, so that an extremely rapid switching from a practically opaque to a practically transparent state of the cell is the result, as is the case with 22 and 23 or between times T1 and T 2 is specified.

When the molecules in the cell have been "bleached" or have all reached the stage of excitation, can the stimulated emission of radiation take place in the optical resonator in the same way as when the cell 15 would not be present at all with the consequence of the release of a giant pulse.

When the optical excitation pulse stops or a short period of time later when it stops the giant impulse returns the cell to its normal, opaque, dark state, as indicated by line 24.

If the excitation pulse is of longer duration, the stimulable medium can again reverse the population and one more, possibly even several giant impulses during one build up a single excitation pulse, with the cell, as described, automatically responding to the incident Light responds to alternately delay the release of the stored energy and to act on it Way to enable the formation of giant impulses.

If the concentration of cryptocyanine in cell 15 is decreased, there will be less incident Light required to change the state of the cell from the state of opacity to that of the Bring permeability; as a result, even more can be used for a given optical excitation pulse width Giant pulses are generated for each excitation pulse. Conveniently takes when the focus is still further reduced, the number of giant pulses in their repetition frequency to until one Point is reached at which only a usual coherent broadcast takes place.

In the particular one shown in FIG. The system described in Fig. 1 has been found to result in approximately 100 giant pulse events practically no deterioration

ίο the bleachable color appeared, neither visually nor spectrophotometrically. Furthermore, a measurement of the wide-field pattern of beam B did not reveal any significant differences between the giant pulse and normal operation; Both modes of operation resulted in radiation angles of 5 · 10 ^-3 radians. Furthermore, it has been found that the spectral line width of the coherent emission is in fact narrower than is normally the case with ordinary coherent radiation and that it is also narrower than has ever been achieved with giant pulse lasers.

In the arrangement described here as an exemplary embodiment, the system was not yet optimized, to get the highest possible performances or the most desirable pulse widths. the As already mentioned, the figures shown are intended to explain the invention using only one example.

The amount of color concentration and the path length of the optical resonator can vary depending on the Gain of the stimulable crystal medium and the Q-value of the optical resonator selected to give values of the product of cell length and absorption coefficient between 0.01 and 100 receive.

Different members of the family of cyanine dyes can be chosen to be used in special cases to allow absorption to take place at the desired wavelengths. It can be assumed that many others Families or groups of dyes behave similarly to the cyanines.

Claims (2)

Patent claims: 1. Optical transmitter with control of the quality factor of its optical resonator (Q-circuit), in the case of which, depending on the light emanating from the stimulated medium, a light is arranged inside the optical resonator Absorber can be bleached, which when the incidence of light is interrupted again in the essentially opaque state falls back in a reversible manner and the one for accumulation a higher amount of energy in the stimulable medium causes the time delay required, characterized in that the absorber consists of a reversibly bleachable solution of cryptocyanine with a high absorption cross-section for the wavelength of the stimulated emission consists. 2. Optical transmitter according to claim 1, characterized in that dissolved in methyl alcohol Cryptocyanine is used as an absorber. 1 sheet of drawings