JPH04192582A - Control circuit for laser frequency sweeping - Google Patents

Abstract

PURPOSE:To easily perform the sharp sweeping operation of a frequency by providing the following: an electro-optic element in which the input face and the output face of a laser beam are not parallel; a means used to control an electric field inside the electro-optic element; and a means used to change the input point of the laser beam to the electro-optic element. CONSTITUTION:In order to exert an electric field on an electro-optic element 2A, a power amplifier 3A is connected electrically; the power amplifier 3A together with an oscillator 4 controls the electric field inside the electro-optic element 2A. The input part P of a laser beam La radiated from a laser-beam generation source 1 to the electro-optic element 2A is moved. Consequently, a distance l through which a laser beam is passed inside the electro-optic element 2A is changed. When the distance l is changed, a frequency sweeping amount can be changed. Thereby, the frequency sweeping amount of the laser beam is increased sharply, and a power amplifier for high-speed control use is not required.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a laser frequency sweep control circuit that controls frequency sweep of laser light.

[Prior Art] FIG. 6 is a block diagram showing a conventional laser frequency sweep control circuit disclosed in, for example, U.S. Pat. No. 4,636,287.

In Fig. 6, (1) is a laser beam generation source such as an Alcon laser, La is the laser beam output from this laser beam generator #(1), and (2) is the laser beam for sweeping the frequency of this laser beam La. The electro-optical element, Lb is this electro-optical element (2
), the frequency-swept laser output light is output from (
3) is a power amplifier for high-voltage high-speed control that is electrically connected to the electro-optical element (2) and applies an electric field to the electro-optical element (2), and (4) is this power amplifier (3).
This is an oscillator electrically connected to the power amplifier (3) for providing a control signal to the power amplifier (3).

The conventional laser frequency sweep control circuit is configured as described above, and the laser light La generated by the laser light generation source (1) is input to the electro-optical element (2). At this time, the output ~'X of the power amplifier (3) controlled by the output ~'0 of the oscillator (4) changes the electric field in the electro-optical element (2) over time. ), and as a result, the refractive index of the laser light passing through the electro-optical element (2) changes over time.

The amount of change △n in the refractive index within the electro-optical element (2) is △n=
It is expressed as -(n3/2) ・E -41). Here, K is a constant, n is the refractive index, and E is the electric field. When an electric field E, a temporally varying voltage vx, or a power amplifier (3) is applied, the frequency sweep amount △f of the laser La becomes △f=, d (△n)/dt-( -,・dE/dt−C −to*・d Vx/d t ) ・ff −(2
). Here K,,K! +K3 is a constant,
a is the distance within the electro-optical element (2) through which the laser beam La passes. That is, by controlling the amount of change over time of the voltage VX applied from the power amplifier (3), it is possible to obtain the laser output light Lb in which the frequency of the laser light La is swept.

:Problems to be Solved by the Invention] In conventional laser frequency sweep control circuits, it is necessary to increase dV, /dt in order to significantly change the amount of frequency sweep, and power amplifiers have to control high voltage at high speed. There was a question of whether it was necessary.

This invention was made to solve these problems, and even if the frequency sweep amount of the laser beam is changed significantly,
It is an object of the present invention to provide a laser frequency sweep control circuit that does not require a high-speed control power amplifier to obtain high dVx/di and can easily perform a wide frequency sweep.

[Means for Solving the Problems 2] The laser frequency sweep control circuit according to the present invention is provided in at least one electro-optical element whose input surface and output surface of the laser beam are not parallel to each other.

7 Effect 2 In this invention, the distance ρ in equation (2) can be changed by changing the input point of the laser beam to the electro-optical element or by moving a plurality of electro-optic elements relatively. , As a result, the sweep amount Δf can be changed.

:Example: An embodiment of the present invention will be described below with reference to the drawings.

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

In FIG. 1, (1) and (4) are the same as described with respect to FIG. (2 people) is an electro-optical element whose input surface of laser beam La and output surface of laser output beam Lb are not parallel. For example, is the input surface perpendicular to laser beam La, or is the output surface relative to laser output beam Lb? The surface is an electro-optical element that forms an angle. P is the point where the laser beam La is input to the electro-optic element (2A), and a is the point where the laser beam La is input to the electro-optic element (2A) or the electro-optical element (2A).
). (3A) is a power amplifier not for high-speed control. (5) is, as shown in Figure 2,
These electrodes sandwich the electro-optical element (2A) between its sides, and are electrically connected to the power amplifier (3A) in order to apply an electric field to the electro-optical element (2N). Note that the power amplifier (3A) and the oscillator (4) constitute means for controlling the electric field within the electro-optical elements (two).

In the laser frequency sweep control circuit of the present invention configured as described above, the input point P of the laser beam La emitted from the laser beam generation source (1) to the electro-optical element (two)
When is moved, the distance C that the laser beam passes through the electro-optical element (2A) changes.

As can be seen from equation (2), the frequency sweep amount Δf can be changed by changing the distance a.

As shown in FIG. 3(A), the input point P to the electro-optical element (2A) can be easily changed by reflecting the laser light La output from the laser light generation source (1) on the mirror (6). can be done. Furthermore, as shown in FIG. 3(B), by placing the electro-optical element (2A) on a fine movement table (7) and moving this fine movement table (7) perpendicularly to the laser beam La, By changing the input point P and thereby changing the passing distance p of the laser beam, the frequency sweep amount △f
can be changed. Furthermore, as shown in FIG. 3(C), by swinging the fine movement table (7) or by swinging the electro-optical element (2A) itself, the laser beam can be controlled in the electro-optical element (2A). It is possible to change the frequency sweep amount Δf by changing the passing distance a. Therefore, the mirror (6) and fine movement table (7) shown in FIG. 3 constitute means for changing the input point P of the laser element to the electro-optic element (2A).

In the above-mentioned embodiments, an electro-optic element is used in which the output surface forms an angle with respect to the laser beam. elements may also be used.

FIG. 4 is a block diagram showing another embodiment of the invention. Figure 4 shows an example of using an electro-optical element (2B) whose output surface forms an angle with respect to the laser beam, and an electro-optical element (2C) whose input surface forms an angle with respect to the laser beam. It is possible to make the shapes of the optical elements (2B) and (2C) the same. In addition, P,,P.

and C, , 122 are each electro-optical element (2B), (2
C) is the input point and passing distance of the laser beam.

In the laser frequency sweep control circuit configured in this way, the laser beam La irradiated from the laser beam generation source (1)
is incident on the electro-optical element (2B) at its input point P1,
It moves through the electro-optical element (2B) over a distance of Q, enters the electro-optical element (2C) arranged in a point pair manner at its input point P, and moves through the electro-optical element (2C) over a distance of C7. Then, it is output as laser output light Lb. At this time, by changing the input points P, , P of the laser beam La to the electro-optic elements (2B) and (2C), respectively, or by changing the relative position of the electro-optic elements (2B) and (2C). 2 Therefore, electro-optical elements (2B), (2C)
By moving B, the length of the distance c+ + I2t changes, and the frequency sweep amount Δf in equation (2) changes. Furthermore, by symmetrically arranging two or more electro-optical elements, the laser beams travel in the same direction.

In addition to the electro-optical elements (2B) and (2C),
By arranging the electro-optical element (2D) with both the input surface and the output surface forming an angle as shown in FIG. 5, it is possible to obtain the laser output light Lb without changing the optical axis of the laser light La. I can do it.

[Effects of the Invention] As explained in detail above, the present invention includes at least one electro-optical element whose input surface and output surface of the laser beam are non-parallel, and where the input point of the laser beam to the electro-optical element is By changing the relative position of the electro-optical element, the frequency sweep amount of the laser beam can be greatly increased, and a power amplifier for high-speed control is not required.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a sectional view showing an electro-optical element used in this invention together with an electrode, and FIG. 3 is a block diagram showing an example of a laser beam used in this invention. FIG. 4 is a block diagram showing another embodiment of the present invention; FIG. 5 is a block diagram showing a modification of FIG. 4;
FIG. 6 is a block diagram showing a conventional laser frequency sweep control circuit. In the figure, (1)...laser light generation source, (2A) to (
2D)...Electro-optical element, (3A)...Power amplifier, (
4)...oscillator, (6)...mirror, (7)...fine movement table. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] (1) a laser beam generation source that generates a laser beam; an electro-optical element that allows the laser beam irradiated from the laser beam generation source to pass through and whose input surface and output surface of the laser beam are nonparallel;
A laser frequency sweep control circuit comprising: means for controlling an electric field within the electro-optical element; and means for changing an input point of the laser light to the electro-optical element. (2) a laser light generation source that generates laser light; a plurality of electro-optical elements that allow the laser light irradiated from the laser light generation source to pass through and whose input and output surfaces of the laser light are nonparallel; A laser frequency sweep control circuit comprising: means for controlling electric fields within these electro-optical elements, and relatively moving the plurality of electro-optical elements.