JP2591003B2 - Pulse multiplex optical system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse multiplexing optical system, and more particularly to a pulse multiplexing optical system that converts a light pulse periodically output by a laser device or the like into a light pulse having a higher repetition frequency. About.

[Conventional technology]

When performing heavy metal isotope separation by the laser method, it is necessary to irradiate heavy metal vapor with light pulses generated by a high-power laser device. In order to perform isotope separation efficiently, the repetition frequency of light pulses must be about several MHz, but the repetition frequency of light pulses in high-power laser equipment for such applications is several kHz.
It is about. Therefore, it is necessary to convert an optical pulse generated by the high-power laser device into an optical pulse having a repetition frequency higher by about three digits.

FIG. 3 is an optical path diagram for explaining an operation principle of an example of a conventional pulse multiplexing optical system used for the conversion of the optical pulse, and FIG. 4 is a timing diagram of the same. In FIG. 3, the light path in the left-right direction is shown in an enlarged manner as compared with the light path in the up-down direction.

In FIG. 3, it is assumed that the propagation time in the direct optical path between the half mirrors is negligibly small. The light pulse incident on the half mirror 11 at the repetition period T ₀ is divided into two equal parts, one of which is directly incident on the half mirror 14, and the other is reflected on the reflecting mirrors 12 and 13 before being incident on the half mirror 14. Half mirror 14 from half mirror 11 via reflecting mirrors 12 and 13
Reflectors 12 and 13 as the propagation time of the optical path becomes T _0/2 to
Is arranged, the light pulse 2 is incident on the half mirror 14 from the top to the bottom with a time T _0/2 delayed from the light pulse incident from the left to the right. Each of these two light pulses is a half mirror
Divide by 14 into two. Therefore, as shown in FIG. 4, the repetition frequency of the light pulse output from the half mirror 14 is twice that of the light pulse output from the half mirror 11, and the peak power is halved.

1/2 of the repetition period T _0/2 of the light pulse to output the propagation time of the optical path from the half mirror 14 from the half mirror 14 to the half mirror 17 via the reflecting mirror 15 and 16, i.e. when the T _0/4 In the same manner as described above, the repetition frequency and the peak power of the optical pulse output from the half mirror 17 are twice and 1/2 that of the optical pulse output from the half mirror 14,
4 times the light pulse output from the half mirror 11 and
It becomes 1/4.

Each of the half mirror 11 to the half mirror 14, the half mirror 14 to the half mirror 17, the half mirror 17 to the half mirror 20,... Has one stage, and the propagation time of the optical path through two reflecting mirrors at each stage. To T _{0
^{/ 2, T 0/2 2}} , T 0/2 3 if ..., 2 of the repetition frequency of the optical pulse repetition frequency of the optical pulses incident on the half mirror 11 to be output from the last half mirror m-th stage ^m times.

As described above, for example, to convert an optical pulse having a repetition frequency of 5 kHz to an optical pulse having a repetition frequency of about 5 MHz,
The above number of stages becomes 10 stages (2 ¹⁰ = 1024), half mirror 1
The optical path length from 1 to the half mirror 14 via the reflecting mirrors 12 and 13 is
15 km, the number of required half mirrors and reflectors will be 11 and 20, respectively.

[Problems to be solved by the invention]

The conventional pulse multiplexing optical system described above has a disadvantage that the mechanical structure is complicated because a large number of half mirrors and reflecting mirrors are required to increase the change ratio of the repetition frequency of the light pulse. The optical path length from one half mirror to the next half mirror via two reflecting mirrors is extremely large because the input light pulse has a low repetition frequency and a long repetition frequency.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pulse multiplexing optical system having a simple structure and a small size and capable of increasing a repetition frequency conversion ratio.

[Means for solving the problem]

The pulse multiplexing optical system according to the present invention includes a first polarizing plate that receives input pulse light having a predetermined repetition period, and a polarization direction of light that is input after receiving pulse light transmitted through the first polarizing plate. The first and second electro-optical elements are arranged in a series that changes accordingly, and the first and second electro-optical elements output the first polarized light component while reflecting the first polarized light component and transmitting the second polarized light component. A second polarizing plate that outputs one of the two polarized components as an external output, and a second polarizing plate that outputs the other polarized component of the output of the second polarizing plate that is not output as an external output, and receives a second one of the repetition periods of the input pulse light. An optical delay element that delays by an integral time and feeds back to the first polarizing plate, and synchronizes with the timing of the input pulse light so as to guide the input pulse light to the optical delay element through the second polarizing plate. The first electro-optical element with the applied control voltage And controlling the second electro-optical element with a control voltage that changes gradually during the period of the input pulsed light in order to generate a polarization component output as an external output through the second polarizing plate. It is characterized by.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

 FIG. 1 is a block diagram showing one embodiment of the present invention.

The embodiment shown in FIG. 1 is a Pockels cell.
ll) 1, 2, polarizing plate 3, optical delay cell 4, polarizing plate 5
And the plane mirrors 61 and 62 and the control signals CS1 and CS2 in the Pockels cell
And a control signal generator 7 for outputting to the control signals 1 and 2. The mutual arrangement of these components will be described later.

FIG. 2 is a waveform chart for explaining the operation of the embodiment shown in FIG.

A polarizing plate 5 is disposed so that a directly polarized light pulse L1 having a repetition period T2 from a high-power laser device (not shown) is input as a P component obliquely in the signal direction, passed therethrough, and output to the Pockels 1. I do.

As is well known, the Pockels cell outputs linearly polarized light input in a specific polarization direction as it is unless a control voltage is applied, and applies a polarization direction component (hereinafter referred to as a parallel component) of the input linearly polarized light when a control voltage is applied. In addition, a component in the orthogonal polarization direction (hereinafter referred to as an orthogonal component) is also output. The power ratio of the orthogonal component to the parallel component increases with the applied voltage,
The voltage becomes infinite at a certain voltage value, and only the orthogonal component is output.

When the control signals CS1 and CS2 are not input to the Pockels cells 1 and 2, the light pulse L1 that has passed through the polarizing plate 5 passes through the Pockels cell 1 and further passes through the Pockels cell 2 and
Pockels cell obliquely incident as a P component
1, 2 and the polarizing plate 3 are arranged.

At the timing when the light pulse L1 that has passed through the polarizing plate 5 reaches the Pockels cell 1, the control signal generator 7 generates a pulse-like control signal CS1 having a voltage value such that the Pockels cell 1 outputs only the orthogonal component. As a result, the light pulse L1 output from the Pockels cell 1 becomes only the S component for the polarizing plate 3.

The control signal generator 7 generates a control signal CS2 having a repetition period T2 of the waveform shown in FIG. As a result, the light pulse L1 output from the Pockels cell 2 contains the P component and the S component for the polarizing plate 3, and the P component is passed through the polarizing plate 3 and extracted outside as a light pulse L2. S
The components are reflected by the polarizing plate 3, reflected by the plane mirror 61, input to the optical delay cell 4, output from the optical delay cell 4, reflected by the reflecting mirror 62, and incident on the polarizing plate 5.

The light pulse reflected by the plane mirror 62 enters the polarizing plate 5 as an S component and is reflected by the Pockels cell 1 by a plane mirror.
61, 62 and the optical delay cell 4 are arranged. Further, a required repetition period of the light pulse L2 is T1 (T2 / T1 is an integer n).
Then, the propagation time in an optical path (hereinafter referred to as a cyclic optical path) output from the polarizing plate 5 and returned to the polarizing plate 5 again via the Pockels cell 1, the Pockels cell 2, the polarizing plate 3, the plane mirror 61, the optical delay cell 4, and the plane mirror 62 is shown. The delay time of the optical delay cell 4 is set so as to be T1.

As a result of the above arrangements and settings, one pulse of the light pulse L1 passes through the Pockels cells 1 and 2 and a part thereof
And all the reflected components return to the Pockels cell 1 through a part of the traveling optical path. At this time, since the control signal CS1 is not applied to the Pockels cell 1, the light pulse input to the Pockels cell 2 has only the S component for the polarizing plate 3, and a part of the light pulse becomes an orthogonal component in the Pockels cell 2, and the polarizing plate 3 , And becomes a light pulse L2, and the remaining parallel components are reflected by the polarizing plate 3 again. The same is repeated thereafter, and one pulse of the light pulse L1 is changed to the light pulse by setting the waveform of the control signal CS2 as shown in FIG.
The peak power of each pulse can be converted to n pulses of L2 equal to each other, and the pulse can be converted without loss except for the loss of each component.

Each time the light pulse L1 is input, the control signal CS1
, The repetition period of the control signal CS1 also becomes T2.

〔The invention's effect〕

As described above, in the present invention, the pulse multiplexing optical system is configured with a small number of components that are not related to the change ratio of the repetition frequency of the optical pulse, and the optical path length of the required optical delay element is used to output the optical pulse. Since the high repetition frequency is relatively short, there is an effect that the structure of the pulse multiplexing optical system can be made simple and small, and the repetition period of the output optical pulse can be changed only by changing the optical path length of only one optical delay element. First
In addition, there is an effect that it is possible to cope with the change of the repetition period of the input optical pulse only by changing the repetition period of the second control voltage, and further, the conversion ratio of the repetition frequency of the optical pulse is set to not only 2 ^m but any integer. There is an effect that can be done.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the embodiment shown in FIG. 1, and FIG. 3 is an operation of an example of a conventional pulse multiplexing optical system. FIG. 4 is an optical path diagram for explaining the principle, and FIG. 1,2 ... Pockels cell, 3,5 ... polarizer, 4 ... optical delay cell, 7 ... control signal generator, 61,62 ... plane mirror.

Claims (1)

(57) [Claims] 1. A series comprising: a first polarizing plate for receiving an input pulse light having a predetermined repetition period; and a series for changing the polarization direction of the input light by receiving the pulse light transmitted through the first polarizing plate according to a control voltage. The first and second electro-optical elements are arranged in a matrix, and the first and second polarization components of the output of the second electro-optical element reflect the first polarization component and transmit the second polarization component. And a second polarizing plate that outputs one of the polarized light components as an external output, and receives the other polarized light component that is not output as an external output among the outputs of the second polarizing plate, and receives an integer fraction of the repetition period of the input pulse light. And an optical delay element for delaying the input pulse light through the second polarizer to the optical delay element with a control voltage synchronized with the timing of the input pulse light. To control the first electro-optical element The second electro-optical element is controlled by a control voltage gradually changing between the periods of the input pulse light in order to generate a polarization component output as an external output through the second polarizing plate. Pulse multiplexing optical system.