Generator of short light pulses

The invention relates to the field of quantum electronics, namely, pulsed-adjustable lasers using forced light backscattering, and can be applied to the development of laser locators, materials science, various technologies, etc.

There is a swinging laser that emits pulses of adjustable ripple light, which has an optical pulse laser, a rotating mirror, a polarizer, a Pokels cage and a fully reflecting mirror arranged in one optical axis and optically coupled, as well as a polarization rotating unit electrode assembly with electrically coupled photodiode, high-speed comparator, emitter repeater, an adjustable delay line and electrically associated therewith two high-voltage keys connected to said Pokels cage electrodes. The pulse duration in the generator is varied by varying the delay between high-torque key opening moments (U.S. Patent No. 4483005, H01S 3 / 10,1984).

The closest to the present invention is a laser with pulse compression laser having a fully reflective mirror arranged in one optical axis and optically coupled, a quality modulator, a polarizer, an active medium with a storage device, a phase shifting element, a positive focal pancreatic lens, assembled from two positive lenses, one fixed and the other mounted, and filled with Brillouin active medium cuvettes. (USSR Invention No. 1795851 H01S 3 / 00,1992) Disadvantages of a known laser include:

- there is no possibility to accurately synchronize the laser pulse with an external event;

- high storage energy;

- change of impulse power at the output is possible only by replacement of optical elements of the laser or introduction of additional losses, ie, reduction of laser efficiency;

- high depolarizing background;

- unstable output pulse characteristics.

The object of the invention is to increase the accuracy of the synchronization of the generated short pulses with an external event, ie to obtain a minimum passage of the optical pulse in time with respect to the electric 'synchronous pulse, while obtaining maximum laser efficiency and parameter stability.

The essence of the problem is that a short-light pulse generator having a fully reflecting mirror, a quality modulator, a first polarizer, an active medium with a storage device, a diaphragm and an output mirror, positioned further on a single optical axis, and a phase-shifting element, and Brillouin active medium, additionally equipped with a polarization control unit, a high-speed photo receiver and an electrical pulse generator, electrically coupled to the storage device, said quality modulator being controlled by a signal from a polarization control unit, the control inputs of which are respectively electrically coupled to the outputs of the pulse generator and the fast photoelectric, wherein said photoelectric input is optically coupled to the first polarizer the first quarter-wave plate is placed in the active medium, and a second quarter-wave wafer is located behind the active medium, a spectrum narrowing element is placed in front of the exit mirror, a second polarizer is placed behind the optical axis of the exit mirror, and the lens is a variable or fixed focal point.

The control of the quality modulator in the optical axis from the synchronization pulse from the oscillator increases the accuracy of the synchronization of the generated short light pulses with the external event, ie, allows the optical pulse to travel in time with respect to the electrical synchronization pulse. Additional control of the light generated by a signal from a high-speed photo receiver, combined with a spectrum narrowing element and two phase plates, ensures smooth light pulse generation while achieving maximum laser efficiency and parametric stability during Brillouin scattering.

The controlled quality modulator consists of first and second electro-optical crystals disposed on the optical axis between the fully reflecting mirror and the first polarizer, and the polarization control unit consists of two separate polarization control units, the output of the first polarization control unit electrically coupled to the first , and the output of the second polarization control unit is electrically coupled to the second electro-optical crystal, and the inputs respectively to a pulse generator and a high-speed photo receiver having an input optically coupled to said first polarizer.

Thus, in addition to the conventional quality control of an electro-optical resonator, which functions as the first electro-optical crystal with a polarization control unit, the quality control of the resonator in proportion to the amount of light hitting the high-speed photo receiver is added. This control is performed by a second electro-optic crystal and a second polarization control unit which maintains the light energy in the resonator at a low level for a longer time than the conventional resonator and, by complex operation of the narrowband and a pair of quarter-wavelength phase plates. When the first electro-optical crystal and polarization control unit is activated, the weak single-frequency contamination is amplified and the pulse of the smooth envelope is emitted. This pulse is sent to Brillouin's active medium and compressed in time.

The controlled quality modulator consists of one multielectrode electro-optical crystal controlled from a single polarization control unit, the first input electrically coupled to the pulse generator output directly and the second input electrically coupled to the pulse generator via an additional polarization control unit and directly to a high speed photoelectric input coupled to the first polarizer.

This technical solution simplifies the construction of the generator.

The spectrum narrowing element is placed in the thermostat. This ensures long-term laser stability.

The spectrum narrowing element and the output mirror comprise a single output mirror having spectrum narrowing properties. This simplifies the construction of the laser.

The invention is further explained in the drawings, wherein:

FIG. 1 is a general schematic diagram of the proposed laser;

FIG. Fig. 2 is a schematic of Fig. 1 of the proposed schematic diagram of a laser; FIG. Fig. 3 is a schematic view of the second embodiment of the proposed laser principle scheme; FIG. 4 is a diagram of the laser (Fig. 2);

FIG. 5 is a working diagram of the laser (Fig. 3).

The short-pulse laser consists of a fully reflective mirror 1, aligned on an optical axis, and controlled by a quality modulator 2, a polarizer 3, a diaphragm 4, a quarter-wavelength phase plate 5, an active medium 6 with a storage device 7, a quarter-wavelength phase plate 8 a tapering element 9, an output mirror 10, followed by a polarizer 11, a quarter-wavelength phase plate 12, a positive variable focal lens 13, a cuvette with a Brillouin active medium 14. The polarizer 3 is optically coupled to the input of the quick-shot receiver 15, the output of which is electrically coupled to the first input of the polarization control unit 16. The second input of the polarization control unit 16 is coupled to the output of the pulse generator 17, the other output of which is coupled to the storage device 7 (excitation element).

FIG. The laser pulse quality controlled modulator 2 of Fig. 2 consists of two electro-optical crystals 18 and 19 disposed in the optical axis between the fully reflecting mirror 1 and the polarizer 3, and the polarization control unit 20 comprises two polarization control units 20 and 21, respectively. One output of the generator 17 via the polarization control unit 20 is electrically connected to the control input of the electro-optical crystal 18 and the other output of the generator 17 via the polarization control unit 21 to the control input of the electro-optical crystal 19. The other input of the polarization control unit 21 is electrically coupled to the output of the fast photo receiver 15.

FIG. 3 the short-pulse laser-controlled quality modulator 2 shown in FIG. 2 comprises a multi-electrode electro-optical crystal 22 disposed in the optical axis between the fully reflecting mirror 1 and the polarizer 3 and controlled by a single polarization control unit 23 having one input electrically coupled to the respective output of generator 17, and its other input is electrically coupled to the output of the high-speed photo receiver 15 and via the additional polarization control unit 24 to the other output of the generator 17.

The short-pulse laser operates as follows. At the time point ti (Fig. 4), the accumulator 7 starts accumulating the active medium 6. The current I l i, flowing through the pulse lamp of the accumulator 7, is shown in the top diagram of Fig. 4. At the same time instant tj, a voltage Ui is applied to the electrodes of the first electro-optic crystal 18 (Fig. 4), and the resonator quality is reduced to such a level that generation begins only at maximum inversion of the active medium 6 (time t_2> FIG. 4). At the onset of generation, a portion of the light reflected from the polarizer 3 enters the fast photo camera 15, which, through the polarization control unit 21, transmits a voltage proportional to the generation to the second electro-optical crystal 19, resulting in increased resonator losses (time diagram U2, Fig. 4). . During the amplification of the active medium 6 and under the influence of the loss controlled by the photoelectric, the generation of the resonator stabilizes (diagram E, t₂-t₃₎ Fig.4). With such a generation and operation of the spectral selector 9, it is possible to generate only one eigenfrequency of the resonator. At the time instant t₃ the voltages Ui, U of the first and second electro-optical crystals 18 and 19 are removed₂ (in diagrams Ulir U2, Fig. 4). Losses in the resonator are reduced to zero and a powerful single-frequency pulse with a smooth envelope develops. Upon exiting the resonator, this powerful pulse passes the polarizer 11, the quarter-wavelength phase plate 12, and the lens 13 is focused on Brillouin's active medium 14. In the case of Brillouin forced scattering, the impulse shortened by about 20 times returns through the lens 13, a quarter-wavelength phase plate that reverses polarization and is reflected from polarizer 11. Since all generation and control processes are synchronized with generator 17, the laser pulse emitted from the polarizer is accurately synchronized with synchro-pulse t₃ (Gen chart, Fig.4).

The short pulse generator is illustrated in Fig. 3, in which the quality modulator functions are controlled by a single multi-electrode electro-optical crystal 22 controlled by a single polarization control unit 23. An additional polarization control unit 24 is provided to maintain a constant generation development time t₂-t₃ (Fig. 4), provides long-term stability. The working time diagram of this generator is shown in Fig.5. At the time instant ti, the accumulator 7 starts accumulating the active medium 6. The current Iil flowing through the impulse lamp of the accumulator is shown in the top diagram of Fig. 5. At the same time, voltage U (FIG. 5 ) which reduces the quality of the resonator to such an extent that the generation only begins at maximum inversion in the active medium 6 (time t₂, In diagram E, FIG. 5). At the beginning of the generation, the light reflected from the polarizer 3 passes into the light¹ a high-speed photo receiver 15 which transmits a voltage U to the electro-optic crystal 22 through the polarization control unit 23, which is controlled in proportion to time t₂-t₃. As time goes by, t₂-t₃.The voltage is increased and decreased when shortened (AU in diagram U, Fig.5). This ensures a constant time t₂-t₃, which is very important for good energy stability of the generated pulses.