JPH0567829A - Laser pulse compressor - Google Patents

Abstract

PURPOSE:To provide a laser pulse compressor for producing short pulses, which includes pulse-compressing prisms that are easy to handle and control. CONSTITUTION:A pair of prisms 2a and 2b are opposed to each other in the path of incident laser pulses. The two prisms are provided with electrodes (4a1 and 4a2) and (4b1 and 4b2), respectively, for applying the electric field to control reflectivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser pulse compression element for generating short wavelength pulses.

In recent years, in the fields of optical computers, optical communications, etc., researches on basic elements such as high-speed optical switches for light-to-light conversion have been advanced, and the relaxation time of the target electronic level, the spread of energy, etc. have been investigated. A tunable short pulse light source is used for the measurement. This short pulse is also expected in physical property research. Therefore, it is necessary to generate a stable short pulse.

[0003]

2. Description of the Related Art Generally, shortening a pulse of a laser beam is to compress a laser pulse in order to increase a speed and an energy, and the pulse width is adjusted according to a target pulse width such as compression by a saturable absorber. There are various compression methods. Among them, when a pulse width of 100 fs (femtosecond) is targeted, compression by a prism pair inside the optical resonator and compression by an optical fiber and prism pair outside the optical resonator are available.

FIG. 3 shows a configuration diagram of a conventional laser pulse compression. 3A shows an example of pulse compression inside the optical resonator, and FIG. 3B shows an example of pulse compression outside the optical resonator.

The pulse compression shown in FIG.
The laser medium 22 and the pair of prisms 23 and 2 are provided in the optical path between the output mirrors 1a to 21c and the output mirror (half mirror) 21d.
4 is arranged in the opposite direction. In this case, pulse compression is performed by the prism pair 23, 24 between the reflection mirrors 21a, 21b, optical resonance is performed between the reflection mirrors 21a, 21d, and a short pulse is taken out from the output mirror 21d.

The pulse width to be compressed is mechanically adjusted while rotating the pair of prisms 23 and 24 and observing with a measuring instrument.

The optical resonator between the reflection mirrors 21a and 21d is such that when a laser pulse reciprocates between the reflection mirrors 21a and 21d, it is gradually amplified in the laser medium 22 by the excitation light to resonate.

Next, pulse compression outside the optical resonator is shown in FIG.
As shown in (B), the laser pulse passes through the optical fiber 25 and is pulse-compressed by the pair of prisms 27 and 28 via the lens 26. This pair of prisms 27, 28
Are arranged in the opposite direction as in FIG. 3A, and the principle of compression and adjustment are the same as in FIG.

Here, the pulse compression by the prism pair 27, 28 will be described. Since the phase velocity of the rising edge of the pulse is delayed due to the non-linear optical effect with respect to the laser beam having a high peak intensity, the pulse shifts to the low frequency side in the first half and shifts to the high frequency side in the second half. When this pulse enters a pair of prisms 27 and 28 having anomalous dispersion, the latter half of the pulse catches up with the first half of the pulse due to the difference in optical path length depending on the frequency, and the pulse width is compressed. In this case, the optical fiber 25 is a non-linear optical medium and prevents the pulse from spreading. On the other hand, since the nonlinear optical medium does not exist in the optical resonator shown in FIG. 3A, the short pulse of the incident pumping light spreads in the normal dispersion medium in the resonator to become a long pulse. This is prevented by the abnormal dispersion medium of the prisms 23 and 24.

[0010]

However, as described above, the prisms 23, 24, 27 and 28 are displaced by the reflection mirrors 21c and 21d due to the influence of temperature and light intensity.
Fine adjustments must be made and readjustments must be made in the case of wavelength changes. Prism 23, 24, 2
Since the adjustment of Nos. 7 and 28 mechanically adjusts the rotation angle, it is difficult to electrically control.

Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a laser pulse compression element which improves the operability and controllability of a prism for performing pulse compression.

[0012]

Means for Solving the Problems The above-mentioned problem is solved in a pulse compression element for performing pulse compression of an incident laser pulse by a pair of prisms arranged in opposite directions in the optical path.
This is solved by providing an electrode for applying an electric field for controlling the refractive index to each of the pair of prisms.

[0013]

As described above, the electrodes are provided on each of the pair of prisms. By applying a voltage to this electrode, an electro-optical effect in which the refractive index is changed by the action of an electric field is generated in the prism.

That is, the adjustment of the optical path difference for each wavelength, which is conventionally performed by rotating the prism, is performed by adjusting the refractive index by the electro-optical effect.

As a result, the prism can be easily adjusted and the operability and controllability can be improved.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a block diagram of an embodiment of the present invention.
In FIG. 1, the laser pulse compression element 1 is configured by arranging a pair of prisms 2a and 2b in opposite directions.

The prisms 2a and 2b are, for example, quartz prisms cut at Brewster's angle, and buffer layers 3a ₁ , 3a ₂ , 3b ₁ and 3b ₂ are formed on both side surfaces thereof. For the buffer layers 3a ₁ , 3a ₂ , 3b ₁ , 3b ₂ , a material having a smaller refractive index than the prisms 2a, 2b is selected.

Buffer layer 3a₁, 3a₂, 3b₁, 3b
₂Electrode 4a on top₁, 4a₂, 4b ₁, 4b₂Is vapor deposition, etc.
Although not shown, it is connected to a power source
Pressure is applied.

The laser pulse compression element 1 is arranged on the optical path inside or outside the optical resonator as shown in FIGS. 3 (A) and 3 (B).

The laser pulse compression element 1 as described above compresses a laser pulse into a predetermined pulse width (frequency) as described with reference to FIG. In this case, the electrodes 4a ₁ , 4a ₂ , 4
When a voltage is applied to b ₁ and 4b ₂ , an electric field E corresponding to the voltage is applied.
(Voltage / distance between electrodes) acts on the prisms 2a and 2b.

As a result, the effective refractive index changes in the prisms 2a and 2b, and the electro-optical effect is produced. Therefore,
The laser pulse passing through the prism 2a (the laser pulse is first incident on the prism 2a, but the reverse may be the case) causes a difference in the optical path length for each wavelength, and the longer the wavelength is, the smaller the original refractive index is. It produces a large optical path difference.
That is, the optical path lengths of the respective wavelengths are set to the electrodes 4a ₁ , 4a ₂ , 4
It is controlled by the voltage applied to b ₁ and 4b ₂ .

Therefore, by feeding back the voltage corresponding to the compressed pulse, the prism 2 can be easily
It is possible to adjust a and 2b, and it is possible to easily correct the influence of temperature change and light intensity.

For example, when the laser pulse compression element 1 is arranged in the optical resonator, the pulse broadening due to the group velocity dispersion of the laser medium (22, see FIG. 3A) generated in the optical resonator is compensated for. Pulse compression can be performed.

Further, when the optical fiber is arranged outside the optical resonator, the pulse whose frequency is shifted by the optical fiber (25, see FIG. 3B) is passed through the laser pulse compression element 1 to easily perform pulse compression. It can be performed.

The buffer layers 3a ₁ , 3a ₂ , 3
b ₁ and 3b ₂ have electrodes 4a ₁ , 4a ₂ , 4b ₁ and 4 in the peripheral part of the central part of the pulse passing through the prisms 2a and 2b.
It serves to reduce absorption by b ₂ .

Next, FIG. 2 shows a block diagram of another embodiment of the present invention. In FIG. 2, the laser pulse compression element 1 is
Buffer layers 6a and 6b are formed on both side surfaces of the plate-shaped prism 5, and triangular electrodes 7a ₁ , 7a ₂ , 7b ₁ and 7b ₂ in opposite directions are formed on both ends of the buffer layers 6a and 6b by vapor deposition or the like. It was formed. That is, corresponding to FIG. 1, the medium 8 is interposed between the pair of prisms 2a and 2b to be integrated. In this case, the prism 5 is made of a material having a large electro-optical effect.

Explaining in comparison with FIG. 1, the prism 2a
Since the pulse has a property of being diffused by the prism 2a between the positions 2 and 2b as described above, the loss in this portion can be reduced by the medium 8.

Further, by converting the optical path other than the laser pulse compression element 1 in FIG. 2 into a waveguide with low loss, the electro-optical effect in the element 1 can be effectively utilized.

[0029]

As described above, according to the present invention, by providing an electrode for applying an electric field for controlling the refractive index to each of the pair of prisms, it becomes easy to adjust the prism for pulse compression. Operability and controllability can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of another embodiment of the present invention.

FIG. 3 is a configuration diagram of conventional laser pulse compression.

[Explanation of symbols]

1 laser pulse compression element 2a, 2b prisms _{3a 1, 3a 2, 3b 1} , 3b 2 buffer layer _{4a 1, 4a 2, 4b 1} , 4b 2 electrode 8 medium

Claims (2)

[Claims] 1. A pulse compression element for performing pulse compression of an incident laser pulse by a pair of prisms (2a, 2b) arranged in opposite directions in an optical path, wherein each of the pair of prisms (2a, 2b) is provided. , Electrodes (4a ₁ , 4a) for applying an electric field for controlling the refractive index
₂ , 4b ₁ , 4b ₂ ) is provided. 2. A medium (8) is interposed between the pair of prisms (2a, 2b) to form a pair of prisms (2).
2. The laser pulse compression element according to claim 1, wherein a and 2b) are integrated.