Patent
1986-05-05
1988-04-05
Punter, William H.
350388, G02F 103
Patent
active
047354909
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION AND DESCRIPTION OF THE PRIOR ART
The invention relates to an optically serially connected electro-optical light modulator put together from modulator crystals which are dimensioned for the reduction of the optical effects arising from the electrical control in a piezo-optical manner, which enables a considerably increased reduction of the disturbing piezo-optical effects disturbing the light modulators during operation and which reduction is proportional with the number of the employed modulator crystals.
For the formation of a laser beam within the resonator, or for the control of the phase, frequency and the polarization of the coherent beam emitted from the resonator, or for the control of the amplitude, or of the intensity of the laser radiation now mainly electro-optical light modulators are used. Such electro-optical light modulators are, for example, described in detail in the corresponding literature by E. D. Mustjel, V. N. Parugin: "Methodi Modulacija i skanirowania sweta", Nauka, Moskau 1970. The operation of electro-optical light modulator is based as known on the double refraction of the electro-optical material which is controllable by an electric field. The essential advantage of the electro-optical light modulators resides in the quick electro-optical effect and in the electrical controllability of the electro-optical effect, which enable a switching of the light with a high speed and also a light modulation having a wide band. The electrically controllable modulator crystal which is split-off from the electro-optical single crystal, modulates with double refraction the phase and the phase difference and also the delay, or the polarization as well as the ellipticity of the components of the passed and linearly polarized light. The light which has been modulated as to its phase or its polarization can be transformed with an appropriate optical system into an intensity modulated or amplitude modulated light. An intensity modulated light may be produced in the simplest fashion by a modulator crystal which is placed between pair of polarizers. In the generally strong piezo-electric linear electro-optical modulator crystals the acoustic waves which are produced by the electrical control in a piezo-electric fashion will influence the operation of the electro-optical light modulator. The technological complexity of the methods employed for the reduction of the piezo-optical effects, and the very high electronic requirements which are made to the controls as well as the damaging consequences to which the modulator parameters are exposed in the known solutions, prompted us to set our task to provide a new electro-optical light modulator having a reduced piezo-optical effect, which at a relatively simple construction will considerably reduce the damaging piezo-optical effects of the acoustic waves.
SUMMARY OF THE INVENTION
The invention rests on the recognition that the piezo-optical effects produced in the individual modulator crystals of an electro-optical light modulator put together from several elements can be separated space-wise in the case of a pulse control (light blocking operation) and in the case of a periodic control (modulator type of operation) according to their frequency by appropriate dimensioning of the outer dimensions.
The said object has been solved with an electro-optical light modulator having a reduced piezo-optical effect, and which comprises several modulator crystals connected in series optically and arranged between polarizers. Such light modulator became further improved according to the invention in that in the case of a pulse control the overlapping of the acoustical transients produced in the individual modulator crystals became dimensioned along the light path with different magnitude for each individual modulator crystal, and in the case of a periodic control the overlapping of the piezo-electric resonant frequencies of the individual modulator crystals became dimensioned exclusive different in the frequency and the modulator crystals
REFERENCES:
patent: 1670757 (1928-05-01), Bronk
patent: 2024737 (1935-12-01), Klingsporn
patent: 3572897 (1971-03-01), Bousky
Carpenter, R. O'B., "The Electro-Optic Effect in Uniaxial Crystals of the Dihydrogen Phosphate Type. III Measurements of Coefficients", Jr. Optical Soc. America, vol. 40, 4-1950, pp. 225-229.
Tada et al., "Electrically Controlled Optical Switch", Sumitomo Electric Tech. Review, #19, 1-1980, pp. 47-56.
Kalymnios et al., "Optimisation of 45.degree. y' cut Modulators", Electronics Letters, vol. 6, 11-26-70, pp. 771-773.
Bakos Jozsef
Juhasz Tibor
Kalman Peter
Kuti Csaba
Vannay Lao
Budapesti Muszaki Egyetem
Punter William H.
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